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Diploma Thesis
Allograft versus Allograft with Internal Bracing in Anterior Cruciate Ligament Reconstruction in Revision
Cases after ACL re-tear
Submitted by
Andrea Baltic
In partial Fulfilment of the Requirements for the Degree
Doctor of Medicine
(Dr. med. univ.)
At the
Medical University of Graz
Conducted at the
Department of Orthopaedics and Trauma
Under Supervision of
Priv.-Doz. Dr.med.univ. Gerwin A. Bernhardt, MBA and
Priv.-Doz. Dr.med.univ. Gerald Gruber, MBA Graz, 07.11.2019
i
Statutory Declaration
I hereby declare that this thesis is my own original work and that I have fully acknowledged by name all of those individuals and organizations that have contributed to the research for this thesis. Due acknowledgements have been made in the text to all other material used. Throughout this thesis and in all related publications I followed the guidelines of “Good Scientific Practice”. Graz, 07.11.2019 Andrea Baltic eh
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Danksagungen
Zuallererst möchte ich mich hiermit bei PD Dr. Gerwin A. Bernhardt und PD Dr. Gerald
Gruber für die Möglichkeit bedanken, bei dieser Studie mitzuarbeiten. Ein großes
Dankeschön gilt dabei Dr. Bernhardt, der mir als Ansprechperson stets zur Seite stand und
mir mit seinem Wissen und Ratschlägen von Anfang bis zum Ende immer weitergeholfen
hat. Ein weiterer Dank gilt dem Klinikvorstand der Universitätsklinik für Orthopädie und
Traumatologie Univ.-Prof. Dr. Andreas Leithner für die Möglichkeit, an der Studie
mitgearbeitet und beim internationalen SICOT Kongress in Montreal vorgestellt zu haben.
Der größte Dank gilt jedoch meinen Eltern und Geschwistern, welche schon immer an mich
geglaubt und mich in allen Lebenslagen unterstützt haben. Ohne sie wäre mein
Studienabschluss niemals möglich gewesen.
Ein großer Dank gilt auch meinen zahlreichen Freunden, von denen jeder einzelne für mein
geistiges Wohl während der langen Studienzeit gesorgt hat. Besonders erwähnen möchte ich
meine Mädels, welche seit der Schulzeit an meiner Seite stehen, sowie meine zwei
Freundinnen Sandra und Isabella, durch die die Studienzeit erst so schön geworden ist, wie
sie letztendlich war.
Meinem guten Freund Tobias möchte ich noch danke sagen, da er mir bei allem Freud und
Leid die Diplomarbeit (und auch andere Lebensereignisse) betreffend zur Seite stand und
diesen doch recht langen Weg mit mir gegangen ist.
Mein allerherzlichster Dank gilt auch meinem Freund Jan, der immer für mich da ist und
immer an mich glaubt.
Vielen Dank!
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Abstract
Introduction:
Anterior cruciate ligament (ACL) ruptures are one of the most common sports-associated
injuries. Increasing numbers of ACL reconstructions result in higher re-tear rates after
return-to-sport and in a higher number of revisions. Allograft transplants may be a good
alternative in complex revision cases. The use of so-called internal brace augmentation might
help graft ingrowth by providing higher primary stability. This study aimed to investigate
the outcome of patients with versus patients without internal brace augmentation in ACL
revision cases with allografts.
Material and Methods:
This is a blinded, randomized controlled pilot study with 30 patients planned. All patients
were treated with Achilles tendon allografts with bone blocks either with or without internal
brace. Data (clinical outcomes, 6- and 13-month MRI scan, SF-36, VAS, IKDC, Lysholm
Knee questionnaire, TAS and KOOS) were collected preoperatively as well as 6, 12 weeks,
6 and 13 months after surgery. Data of the 12-week follow-up results were included in this
thesis.
Results:
There were 18 patients included in the study (16,7% female). Eight patients were treated
with internal bracing (44.4%). The mean age was 29.4±7.8. There was no graft-failure in
either group. The outcome scores did not differ between the two groups after 12 weeks,
except for the IKDC being significantly better in the group without IB. The results of the
scores were KOOS 82.6±9.8, IKDC 74.7±8.8 and a median Lysholm score of 94 (65-100)
for the group without internal bracing versus KOOS 74.8±6.3, IKDC 63.9±8.7 and median
Lysholm score of 67 (62-100) in the bracing group.
Discussion:
The results show satisfactory short-term outcomes in both groups. There were no re-
ruptures or other complications in either group. There were no relevant clinical differences
between the two groups. If internal bracing might support the allograft healing process and
reduce re-ruptures has to be examined in the long term of this pilot study. Future studies then
iv
need to confirm the results in a larger cohort with adequate power and sample size
calculation.
v
Zusammenfassung
Einleitung:
Mit zunehmend steigenden Fallzahlen und guten return-to-sport Ergebnissen steigt auch die
Häufigkeit von neuerlichen Verletzungen des vorderen Kreuzbands. Die Revisionsoperation
nach einer Re-ruptur stellt jedoch häufig eine erhebliche Herausforderung für
Chirurgin/Chirurg und Patientin/Patient dar. Aufgrund der zum Teil limitierten
Entnahmemöglichkeiten von körpereigenen Sehnen sind Allografttransplantate in der
Revision von besonderem Interesse. Eine vorübergehende Fixierung (‚internal bracing‘) des
frisch transplantierten Allografts könnte durch Verminderung des Belastungsstresses zu
einer besseren Einheilung führen und somit zu einer Reduktion der Re-rupturraten.
Material und Methoden:
Bei dieser Studie handelt es sich um eine prospektiv, randomisiert, kontrollierte Pilotstudie.
Insgesamt 30 Patientinnen/Patienten wurden in eine Gruppe mit Augmentation durch
internal-bracing und ohne Augmentation randomisiert. Alle Patientinnen/Patienten wurden
mit einem Achillessehnenallograft mit Knochenblock in gleicher Operationstechnik
versorgt. Die Daten der Patientinnen/Patienten (Klinische Untersuchung, 6- und 13-Monats
MRT, SF-36, VAS, IKDC, Lysholm Knee questionnaire, TAS, KOOS) wurden präoperativ
und im Rahmen von Nachuntersuchungen (nach 6 und 12 Wochen, 6 und 13 Monaten)
prospektiv erhoben und ausgewertet. Die folgende Arbeit behandelt die 12-Wochen
Ergebnisse der ersten 18 Patientinnen/Patienten.
Ergebnisse:
Es wurden 18 Patientinnen/Patienten in die Studie eingeschlossen (16.7% weiblich). Acht
wurden mit internal bracing versorgt (44.4%). Das Durchschnittsalter der
Patientinnen/Patienten lag bei 29.4±7.8. Es gab in beiden Gruppen keine Reruptur.
Hinsichtlich des Outcomes unterscheiden sich die beiden Gruppen nach 12 Wochen nicht
signifikant, bis auf den IKDC, welcher in der Gruppe ohne internal brace signifikant besser
war. In der Gruppe ohne Internal-Brace zeigten sich 12 Wochen postoperativ für KOOS
82.6±9.8; IKDC 74.7±8.8 und im Lysholm Score 94 im Median (65-100). Die Gruppe mit
Internal-Brace zeigte mit KOOS 74.8±6.3, IKDC 63.9±8.7 und Lysholm 67 im Median (62-
100) sehr ähnliche Werte.
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Diskussion:
Die ersten Kurzzeitergebnisse zeigen für die verwendeten Techniken in komplizierten
Revisionssituationen in beiden Studiengruppen sehr zufriedenstellende Ergebnisse. Es gab
keine Re-rupturen oder andere Komplikationen in keiner der zwei Gruppen. Es gab auch
keine relevanten klinischen Unterschiede zwischen den beiden Gruppen. Ob das Internal-
Brace die Einheilung verbessern oder die Re-rupturraten verringern kann, kann erst nach
längerem Follow-up gesagt werden und muss in zukünftigen Studien mit größeren
Populationen evaluiert werden.
vii
Table of Contents
List of Figures ................................................................................................................. VIII
List of Tables ...................................................................................................................... X
Abbreviations .................................................................................................................... XI 1 Introduction ..................................................................................................................... 1
2 Theoretical Background.................................................................................................. 3 2.1 Anatomy of the knee joint ........................................................................................... 3
2.1.1 Bones / Articulating Surfaces............................................................................... 3 2.1.2 Menisci ................................................................................................................. 4
2.1.3 Joint Capsule ........................................................................................................ 6
2.1.4 Bursae ................................................................................................................... 7
2.1.5 Ligaments ............................................................................................................. 7 2.1.5.1 Patellar ligament ......................................................................................... 8
2.1.5.2 Fibular collateral ligament (FCL) .............................................................. 8
2.1.5.3 Tibial collateral ligament (TCL) ................................................................ 8
2.1.5.4 Oblique popliteal ligament ....................................................................... 8 2.1.5.5 Arcuate popliteal ligament ......................................................................... 8
2.1.5.6 Anterior cruciate ligament (ACL) .............................................................. 9
2.1.5.7 Posterior cruciate ligament (PCL) ............................................................ 10
2.1.6 Vascular supply and Innervation ........................................................................ 10
2.1.7 Movement .......................................................................................................... 11 2.2 Pathophysiology ........................................................................................................ 13
2.2.1 Injury mechanism ............................................................................................... 13
2.2.2 Injury Consequences .......................................................................................... 13
2.2.3 ACL Healing ...................................................................................................... 14 2.3 Risk Factors for ACL rupture ................................................................................... 15
2.3.1 Gender ................................................................................................................ 15
2.3.2 Sport ................................................................................................................... 16
2.4 Diagnostic Methods .................................................................................................. 16 2.4.1 Anamnesis .......................................................................................................... 16
2.4.2 Physical Examination ......................................................................................... 16
2.4.2.1 Lachman Test ........................................................................................... 17
2.4.2.2 Pivot Shift Test ......................................................................................... 17 2.4.2.3 Anterior Drawer Test ............................................................................... 18
2.4.2.4 Lever Sign Test ......................................................................................... 19
viii
2.4.3 Radiology ........................................................................................................... 19
2.4.3.1 Radiography ............................................................................................. 19 2.4.3.2 Magnetic Resonance Imaging (MRI) ....................................................... 20
2.5 Treatment ................................................................................................................. 21
2.5.1 Conservative Management ................................................................................. 21
2.5.2 Surgical Treatment ............................................................................................. 22 2.5.3 Alternative Treatment ........................................................................................ 23
2.6 Grafts ........................................................................................................................ 23
2.6.1 Autografts .......................................................................................................... 23
2.6.2 Allografts ........................................................................................................... 24 2.6.3 Synthetic Grafts .................................................................................................. 25
2.7 Complications .......................................................................................................... 25
2.7.1 Osteoarthritis (OA)............................................................................................. 26
2.7.2 Graft Failure ...................................................................................................... 27 2.8 Revision ................................................................................................................... 27
2.9 Rehabilitation ........................................................................................................... 28
3 Material and Methods ................................................................................................... 29 3.1 Hypothesis of the Study ........................................................................................... 29
3.2 Study Population ...................................................................................................... 30 3.2.1 Inclusion Criteria ............................................................................................... 30
3.2.2 Exclusion Criteria .............................................................................................. 30
3.3 Study Design ............................................................................................................. 31
3.3.1 General Information .......................................................................................... 31 3.3.2 Ethics ................................................................................................................. 31
3.3.3. Data Protection ................................................................................................. 32
3.3.4 Revision ACL Reconstruction Surgery ............................................................. 32
3.3.5 Allografts ........................................................................................................... 32 3.3.6 Internal Brace (Arthrex ©) ................................................................................. 33
3.3.7 Rehabilitation .................................................................................................... 34
3.4 Questionnaires .......................................................................................................... 35
3.4.1 Case Report Form (CRF) .................................................................................. 35 3.4.2 International Knee Documentation Committee (IKDC) .................................... 35
3.4.3 Knee Osteoarthritis Outcome Score (KOOS) .................................................... 35
3.4.4 Lysholm Knee Scoring Scale ............................................................................. 36
3.4.5 Tegner Activity Scale (TAS) ............................................................................ 36 3.4.6 Short Form-36 (SF-36) ...................................................................................... 36
ix
3.5 Statistical Analysis ................................................................................................... 37
3.5.1 Software Tools ...................................................................................................... 37
4 Results ............................................................................................................................. 37 4.1 Patient Demographics .............................................................................................. 38
4.2 Preoperative Data ..................................................................................................... 38
4.2.1 Physical Examination ......................................................................................... 38 4.2.2 Radiographic Evaluation .................................................................................... 39
4.2.3 Clinical Scoring Systems ................................................................................... 40
4.2.4 Short-Form 36 Health Survey ........................................................................... 40
4.3 Surgical Data ............................................................................................................ 42 4.4 12-Week-Follow-Up Data ....................................................................................... 43
4.4.1 Physical Examination ......................................................................................... 43
4.4.2 Clinical Scoring Systems ................................................................................... 43
4.4.3 Short-Form 36 Health Survey ............................................................................ 44 4.5 Case Presentation ..................................................................................................... 47
4.5.1 Patient without internal bracing ......................................................................... 47
4.5.2 Patient with internal bracing .............................................................................. 51
5 Discussion ....................................................................................................................... 54 5.1. Limitations and Strengths ....................................................................................... 57 5.2. Conclusion .............................................................................................................. 57
6 References....................................................................................................................... 58
7 Appendix – Informed Consent, Case Report Form, Questionnaires ....................... 64
x
List of Figures
Figure 1: Knee Injuries ........................................................................................................ 1
Figure 2: Ligament Injuries .................................................................................................. 2 Figure 3: Bones of the knee joint.......................................................................................... 3
Figure 4: Femoral articular surface ...................................................................................... 4
Figure 5: Tibial articular surface ......................................................................................... 4
Figure 6: Menisci .................................................................................................................. 4 Figure 7: Meniscal movements in a: extension and b: flexion ............................................. 5
Figure 8: Meniscal movements in a: neutral position, b: external rotation, and c: internal rotation .................................................................................................................................. 6
Figure 9: Joint Capsule ......................................................................................................... 6
Figure 10: Ligaments of the knee joint, a: medial view, b: lateral view .............................. 7
Figure 11: Cruciate Ligaments ............................................................................................. 9 Figure 12: Vascular supply of the knee joint ...................................................................... 10
Figure 13: Innervation of the knee joint ............................................................................. 11
Figure 14: Moving axis during flexion and extension ........................................................ 12
Figure 15: Range of motion (ROM): a: flexion and extension, b: internal and external rotation ................................................................................................................................ 12 Figure 16: Dynamic Valgus ................................................................................................ 15
Figure 17: Lachman Test .................................................................................................... 17
Figure 18: Pivot Shift Test ................................................................................................. 17
Figure 19: Anterior Drawer Test ........................................................................................ 18 Figure 20: Lever Sign Test ................................................................................................. 19
Figure 21: Frontal and sagittal radiograph of a 23-year old patient with recent ACL re-rupture, drill holes from previous ACL surgery can be seen.............................................. 20
Figure 22: Sagittal T2 weighted MRI of a 22-year old patient with recent ACL rupture .. 20
Figure 23: Unpacked Achilles Tendon Allograft ............................................................... 33
Figure 24: Finished Graft ................................................................................................... 33 Figure 25: Internal Brace integrated into the graft ............................................................. 34
Figure 26: Overview of Follow-Up Periods ....................................................................... 37
Figure 27: Preoperative ap / lateral X-ray of a patient in the group without IB ................. 39
Figure 28: Preoperative SF-36 Subscales ........................................................................... 41 Figure 29: Preoperative SF-36 Summary Scores ............................................................... 42
Figure 30: 12-Week Follow-Up Data ................................................................................. 44
Figure 31: 12-Week Follow-Up SF-36 Subscales .............................................................. 46
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Figure 32: 12-Week Follow-Up SF-36 Summary Scores .................................................. 46
Figure 33: SF-36 Comparison With US Normal Population .............................................. 47 Figure 34: Preoperative X-Ray Case I ................................................................................ 48
Figure 35: 6-Week Follow-Up X-Ray Case I ..................................................................... 48
Figure 36: 6-Month Follow-Up MRI Case I ...................................................................... 49
Figure 37: 13-Month Follow-Up MRI Case I .................................................................... 49 Figure 38: Preoperative X-Ray Case II .............................................................................. 51
Figure 39: 6-Week Follow-Up X-Ray Case II ................................................................... 52
Figure 40: 6-Month Follow-Up MRI Case II ..................................................................... 52
Figure 41: 13-Month Follow-Up MRI Case II ................................................................... 53
xii
List of Tables
Table 1: Muscles producing movement.............................................................................. 13
Table 2: Sensitivity and Specificity of ACL Tests ............................................................. 17 Table 3: Indications for conservative and surgical treatment of ACL ruptures ................. 21
Table 4: Advantages and disadvantages of available autografts ........................................ 23
Table 5: Advantages and disadvantages of allografts ........................................................ 25
Table 6: Complications associated with ACL reconstruction ............................................ 25 Table 7: Total patient population, total group without IB and total group with IB .......... 30
Table 8: Follow-Up Time and Performed Evaluations ...................................................... 31
Table 9: Patient demographics ........................................................................................... 38
Table 10: Preoperative Physical Examination .................................................................... 39 Table 11: Preoperative Questionnaire Data ........................................................................ 40
Table 12: Preoperative SF-36 Results ................................................................................ 40
Table 13: Surgical Data ...................................................................................................... 42
Table 14: 12-Week Physical Examination ......................................................................... 43 Table 15: Range Of Motion ................................................................................................ 43
Table 16: 12-Week Questionnaire Data ............................................................................. 44
Table 17: 12-Week Follow-Up SF-36 Results ................................................................... 45
Table 18: Questionnaire Results Case I .............................................................................. 50
Table 19: SF-36 Summary Scores Case I ........................................................................... 50 Table 20: Questionnaire Results Case II ............................................................................ 53
Table 21: SF-36 Summary Scores Case II ......................................................................... 53
xiii
Abbreviations
ACL Anterior Cruciate Ligament
AP Anterior-Posterior
AWMF The Association of the Scientific Medical Societies in Germany
BP Bodily Pain
CM Centimeter
CRF Case Report Form
FCL Fibular Collateral Ligament
GH General Health
HRQOL Health-Related Quality Of Life
IB Internal Brace
IKDC International Knee Documentation Committee
ITT Iliotibial Tract
KG Kilogram
KOOS Knee Injury and Osteoarthritis Outcome Score
LARS Ligament Advanced Reinforcement System
MAX Maximum
MH Mental Health
MIN Minimum
MM Millimeter
MRI Magnetic Resonance Imaging
MCS Mental Component Summary (SF-36)
OA Osteoarthritis
OC Oral Contraceptives
PCL Posterior Cruciate Ligament
PCS Physical Component Summary (SF-36)
PF Physical Functioning
PPI Proton Pump Inhibitor
PRP Platelet-Rich Plasma
QOL Quality of Life
RE Role Emotional
ROM Range of Motion
RP Role Physical
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RR Relative Risk
RTS Return-To-Sports
SF Social Functioning
SF-36 Short Form – 36
TAS Tegner Activity Score
TCL Tibial Collateral Ligament
VAS Visual Analog Scale
VT Vitality
1
1 Introduction
Nowadays sports are a very important part of most people’s lives, despite the benefits
however, this change in western lifestyle also brings an increased rate of injuries.
Anterior cruciate ligament (ACL) ruptures are one of the most common injuries related to
sports. The ACL is involved in approximately two-thirds of all ligamentous injuries, which
make up about 40 % of all knee traumas. (1)
This also leads to an increase in ACL reconstruction surgery. Reconstruction is indicated in
patients who suffer from complex knee injuries (combination of ligament, meniscal and
chondral damages) or instability and meniscal lesions (in case of meniscal resection joint
instability increases). Likewise, patients who want to maintain their activity level and still
have athletic ambitions are considered for reconstruction. (2) These facts simultaneously
lead to an increase in additional ACL injuries after return-to-sport and therefore a higher
number of revisions. These present a particularly challenging situation for the surgeon as
they display higher complication rates than first-time reconstructions. (3) In these situations,
allografts may be a good alternative to the usually used autografts. Further muscle and tissue
damage due to tendon harvest could be avoided. In Central Europe, allografts are less
commonly used than in Anglo-American countries, similarly in primary ACL
reconstructions.
Studies comparing autografts and allografts have shown different results depending on study
design and number of patients. The majority show that autografts and allografts have no
differences in rupture rates and clinical outcomes. (4, 5) Some show that autografts display
an earlier functional recovery and lower rates of graft failure, at least compared to irradiated
allografts. (6-8) Young and active patients have the highest risk of requiring revisional
ACL47%
Complex6%
ACL + MCL12%
MCL29%
PCL4%
LCL2%
Ligament injuries
Ligament injury40%
Meniscus injury11%
Patella injury24%
Miscellaneous25%
Knee injuries
Figure 1: Knee injuries, adopted from (1) Figure 2: Ligament injuries, adopted from (1)
2
surgery. To improve allograft outcome in these cases there have been attempts to strengthen
the allogenic tissue using internal brace augmentation with a polyethylene tape which is
integrated seamlessly into the graft construct. (9) This technique was successfully used in
primary ACL repairs using the polyethylene bridging to maintain the ruptured ACL tissue.
(10)
To the best of our knowledge so far no one performed a study investigating if allografts with
additional internal bracing improve the outcome of patients compared to those using
allografts alone.
3
2 Theoretical Background
2.1 Anatomy of the knee joint The knee joint is the largest synovial joint in the human body. It allows a wide range of
motion and is composed of a complex construct of bones, muscles, soft tissue and cartilage.
(11)
2.1.1 Bones / Articulating Surfaces The knee joint is formed by three bones – the femur, tibia, and patella (the fibula is not
involved). The articulating surfaces are characterized by their incongruent shapes which
make the joint comparatively weak in a mechanical way. Therefore the stability depends on
the muscles and ligaments surrounding and strengthening the joint. (12, 13)
Figure 3: Bones of the knee joint (14)
4
Femur and tibia form the tibiofemoral joint. The proximal tibial surface (also tibial plateau)
slopes posteriorly 3 to 7° and its lateral and medial articular surfaces, which are slightly
concave, interact with the corresponding femoral condyles, which are almost completely
convex. The area between the articular surfaces of the tibia displays an eminence with medial
and lateral tubercles in the center. (14) This joint can be considered a trocho-ginglymus joint.
(16)
The second component of the knee joint is the patellofemoral joint, which is formed by the
posterior surface of the patella and the anterior surface of the femur. During flexion and
extension, the patella glides on the femoral surface, however, in full extension, only the
lowest patellar facets are in contact with the femur. (14)
2.1.2 Menisci The two menisci are C- or rather semilunar-shaped fibrocartilaginous discs that equalize the
incongruence between the femur and tibia. (11)
Figure 4: Femoral articular surface (15) Figure 5: Tibial articular surface (15)
Figure 6: Menisci (16)
5
The meniscal horns are attached to the intercondylar area of the tibia, while the peripheral
borders are fixed on the joint capsule. Sometimes there is a transversal ligament between the
two front horns of the menisci. The medial meniscus is also fixed to the medial collateral
ligament and its insertion points are further apart than those of the lateral meniscus, resulting
in it being less movable (and therefore more at risk of ruptures).
The peripheries are vascularized by capillaries from the medial knee artery, while the inner
regions are nourished through diffusion from the synovia. (11)
The menisci increase the contact area between the two corresponding bones, spreading the
load on bones and cartilage and acting as shock absorbers. In extension, the contact area is
relatively big and in the flexed knee it is rather small, allowing rotational movements. (11)
The menisci slide on the tibial surface during movement, creating a moving articular cavity,
as they follow the femoral condyles. (11, 14)
Figure 7: Meniscal movement in a: extension and b: flexion (14) Figure 7: Meniscal movement in a: extension and b: flexion (14)
6
2.1.3 Joint Capsule The joint capsule of the knee joint consists of two layers. An external fibrous capsule and an
internal synovial membrane that covers all surfaces in the cavity which are not covered with
cartilage. (11)
Figure 8: Meniscal movement in a: neutral position, b: external rotation and c:internal rotation (14) Figure 8: Meniscal movement in a: neutral position, b: external rotation, and c: internal rotation (14)
Figure 9: Joint capsule (14)
7
The fibrous layer is thickened in the front by the quadriceps tendon and the patella, and in
the back by the oblique popliteal ligament. It is fixed on the tibia 1 centimeter (cm) below
the cartilage border, and on the femur, it runs lateral of the condyles, along the intercondylar
line in the back and merges with the patella and the quadriceps tendon in the front. (11)
The synovial membrane lines the articular cavity, which contains the synovial fluid. It runs
along the anterior intercondylar area and covers the cruciate ligaments (excluded from cavity
but within the capsule). In the front, it merges into the suprapatellar bursa which extends the
joint cavity approximately 5 cm superior to the patella. Under the patella, the synovial
membrane covers the infrapatellar fat body (Hoffa’s fat pad). (11, 12)
2.1.4 Bursae There are a lot of bursae around the knee joint because most of the tendons run parallel to
the bones. (11)
The prepatellar bursae have no connection to the joint cavity and are merely there to allow
the skin to move freely during movements. There are four bursae that communicate with the
synovial cavity: suprapatellar bursa, popliteus bursa, anserine bursa, and gastrocnemius
bursa. This is important to know because an inflammation of these bursae can extend into
the cavity and cause inflammation of the whole joint. (12)
2.1.5 Ligaments There are extracapsular ligaments such as the patellar ligament, the collateral ligaments and
the oblique popliteal ligament which strengthen the joint capsule. The cruciate ligaments are
found intra-articularly. (11)
Figure 10: Ligaments of the knee joint, a: medial view, b: lateral view (14)
8
2.1.5.1 Patellar ligament
The patellar ligament is formed by the distal end of the quadriceps tendon. It is a strong,
fibrous band inserting at the tibial tuberosity. Laterally, it receives the medial and lateral
patellar retinacula (aponeurosis of the medial and lateral vastus and deep fascia) which are
part of the joint capsule and maintain the patella in place. (12)
2.1.5.2 Fibular collateral ligament (FCL)
The lateral collateral ligament extends from the lateral epicondyle of the femur to the fibular
head. It crosses the popliteal tendon which separates it from the lateral meniscus and it splits
the tendon of the biceps femoris in two parts. In connection with the short posterior genual
ligament (a lateral ligament of the joint capsule) and the TCL, it stabilizes the knee in
extension. (11, 12)
2.1.5.3 Tibial collateral ligament (TCL)
The medial collateral ligament extends from the medial epicondyle of the femur and runs
flat to the medial condyle and medial surface of the tibia. It is crossed by the tendons of the
superficial pes anserinus, separated from them by the anserine bursa. It has an anterior,
parallel running part, and a posterior fan-shaped part which is firmly attached to the medial
meniscus. The TCL is weaker than the FCL, and therefore more often damaged. (11, 12)
2.1.5.4 Oblique popliteal ligament
The oblique popliteal ligament is an expansion of the semimembranosus tendon that
reinforces the posterior joint capsule. It expends from distal medial to proximal lateral
toward the lateral femoral condyle. (12)
2.1.5.5 Arcuate popliteal ligament
This ligament also strengthens the posterior joint capsule on the lateral side. It arises from
the posterior aspect of the fibular head and forms the “short posterior genual ligament”,
which inserts at the lateral epicondyle of the femur. (see also 2.1.5.2). Sometimes it involves
a fabella, in which case it would also be known as the fabellofibular ligament. (11)
9
2.1.5.6 Anterior cruciate ligament (ACL)
The ACL is attached to the anterior intercondylar area of the tibia and ascends up to the
medial surface of the lateral medial condyle. The tibial insertion site shows a high variation,
with three possible types of shapes: elliptical (51%), triangular (33%) and C-shaped (16%).
(15) Also, there is a large difference between the tibial and femoral footprint area, the tibial
being significantly smaller. (16)
The average length and width of an ACL in adults are 38 millimeters (mm) and 11mm. (14)
Numerous studies (16, 17) showed that the ACL consists of three functional bundles: the
anteromedial, posterolateral, and intermediate bundle. Each of them playing a slightly
different role during knee movement. The posterolateral bundle is mainly stretched in
extension, and the anteromedial in flexion, especially if there is additional inner rotation.
The ligament twists around itself, the isthmus being located approximately half the distance
between the insertions and making up less than half their diameter. (18) The configuration
of the ACL two millimeters from its direct femoral insertion to mid substance is flat. (19)
The histological structures of the ACL are also particularly interesting, differencing the ACL
from other ligaments and tendons. (20) It is mostly made up of wavy collagen fiber bundles
which are arranged in various directions, most of them around the ligament axis, but also a
few running parallel to it. Also, there are fibroblasts which appear elongated in the bundle
direction. The elastic system consists of elastic and oxytalon fibers. This special
Figure 11: Cruciate ligaments (14)
10
microscopical architecture provides the ligament with the ability to withstand the multiaxial
stresses and varying tensile strains that it is exposed to. (20)
Nonetheless, the ACL is the weaker of the cruciate ligaments and more often involved in
ruptures than the PCL.(12)
2.1.5.7 Posterior cruciate ligament (PCL)
The PCL is thicker and stronger than the ACL. The average dimensions are 38 mm in length
and 13 mm in width. It expands from the lateral surface of the medial femoral condyle up to
the posterior intercondylar area and the backside of the tibia. (14)
Anterolateral and posteromedial bundles have been defined (named according to femoral
attachments). The anterolateral bundle, making up the biggest part of the PCL, tightens in
flexion while the posteromedial bundle tightens in extension. In the weight-bearing flexed
knee (for example when walking downhill) the PCL is the main stabilizer of the femur. It is
not isometric during movement as the distance between attachments varies with knee
position. (12, 14)
2.1.6 Vascular supply and Innervation The arteries supplying the knee joint
are 10 vessels forming the genicular
anastomoses: the genicular branches
of the femoral and popliteal arteries
and the anterior and posterior
branches of the anterior tibial
recurrent and circumflex fibular
arteries. The middle genicular
branches of the popliteal artery
penetrate the fibrous capsule and
supply the cruciate ligaments,
synovial membrane, and the menisci.
(12, 21)
Figure 12: Vascular supply of the knee joint (21)
11
Due to Hilton’s law (22), the nerves
innervating the muscles moving the
joint also supply the joint itself.
Therefore, the articular branches from
the femoral, tibial, and common fibular
nerves supply the knee joint.
Additionally, the obturator and
saphenous nerves also supply articular
branches to the joint’s medial aspects.
(12)
2.1.7 Movement The movements of the knee are flexion and extension, and internal and external rotation in
the flexed knee, but abduction and adduction are not possible due to the collateral ligaments.
(11)
During flexion and extension, the axis also moves, because of the complex geometry of the
articular surfaces of the femur and tibia, and the disposition of the ligaments associated
(shown in Figure 14). The motion in the medial and lateral tibiofemoral parts differ. (11)
Laterally, the displacement of the femur on the tibia is greater leading to rolling as well as
sliding on the joint surface. Medially, the motion of femur and tibia is relatively small and
shows only minimal sliding. In full flexion, the lateral femoral condyle is close to posterior
subluxation, as it comes to a stop at the edge of the tibial articular surface. (14)
Figure 13: Innervation of the knee joint (21)
12
The range of extension is 5-10° beyond the “straight position”, which can only be achieved
passively. Newborns are not able to reach the “straight position” because of the greater
retroversion of the tibia. Active flexion is approximately 120° to 140° and passive flexion
up to 160°. In the right-angled knee, an external rotation up to 40° and an inner rotation up
to 10° is possible. During inner rotation, the cruciate ligaments are twisted and tightened
around each other, and during external rotation they untangle. In reverse, the collateral
ligaments are tightened during external rotation and loosen up during internal rotation. (11)
In addition, there is also an obligatory rotational mechanism during the later stages of
extension called the “screw-home” movement. It is initiated by the tension of the ACL and
the shape of the articular surfaces and causes a 5-10° internal rotation of the femur when the
foot is standing on the ground (when the foot is not on the ground the movement is reversed
Figure 14: Moving axis during extension and flexion (created by author)
Figure 15: Range of motion (ROM) a: flexion and extension, b: internal and external rotation (14, modified from the original)
13
in terms of an external rotation of the tibia). Due to this mechanism the knee passively
“locks”, making the lower limb more stable and allowing the thigh and leg muscles to relax.
This enables us to stand for long periods without rapid exhaustion. (11, 12)
Many muscles are involved in the movements of the knee, the most important are shown in
Table 1.
Movement Primary Muscles Producing Movement Limiting Factors Extension Quadriceps femoris Anterior edge of lateral meniscus,
cruciate ligaments, collateral ligaments
Flexion Hamstrings (semitendinosus, semimembranosus, long head of biceps), short head of biceps
Soft tissue (thigh), length of hamstrings, cruciate ligaments
Internal Rotation
Semitendinosus and semimembranosus Cruciate ligaments
External Rotation
Biceps femoris Collateral ligaments, Cruciate ligaments
Table 1 : Muscles producing movement (13, 16)
2.2 Pathophysiology The ACL is a complex ligament concerning structure, function and dynamics. Analogically
multiplex are its healing process and the effects an injury has on the ligament.
2.2.1 Injury Mechanism Most ACL injuries result from a non-contact event. The injury mechanism is a flexion and
external rotation, a flexion and internal rotation, a forced external rotation or a
hyperextension movement. (23) An anterior tibial translation also significantly increases
ACL strain, therefore being a risk factor for ruptures. (24, 25) Multiplanar external forces
significantly raise loading on the ACL compared to uniplanar forces. (24, 25)
The primary internal rotation restraint from 30 to 90 degrees of flexion is not the ACL, but
the iliotibial tract (ITT). (26) Therefore, it is not surprising that damage of the ITT correlated
with functionally unstable knees and the grade of pivot shift, whereas an ACL damage did
not. For this reason, the ACL is particularly involved and at risk during rotational movements
in extension. (26)
2.2.2 Injury consequences Information about limb position and movements are brought together by visual, vestibular,
cutaneous, muscular, tendinous and joint receptors. After an ACL injury, a reduction in
14
afferent information may cause a decrease in limb function. However, visual control seems
to be more important than local receptors. When deprived of it, the remaining afferent
information is not enough for full motor performance even in healthy patients. (27)
Kinematic differences in previously injured knees show less flexed, more externally rotated
and medially translated landings. These changes in knee kinematics are believed to be the
cause of early osteoarthritic onset, which is often seen after ACL ruptures, due to joint
loading alterations. Not only do kinematic changes occur in the injured knee, but also in the
contralateral ACL-intact ones, which is believed to be on the basis of reducing the kinematic
asymmetry. (28)
2.2.3 ACL Healing The native ACL’s direct insertion shows four histological zones: ligament – uncalcified
fibrocartilage – calcified fibrocartilage – bone. This natural structure is never found in a
graft. (23)
ACL healing is a complex process and much more difficult than e.g. an MCL rupture
treatment, which usually mends spontaneously. This is probably due to the differences in
blood supply and articular environment, as well as the structural and cellular differences and
the different biomechanical demands. ACL and PCL ruptures often acquire reconstruction,
because successful healing is prohibited by lack of contact between the two ruptured ends.
(29)
After implantation, a graft processes different phases of integration: first there is acute
inflammation showing mesenchymal cell recruitment, matrix proliferation, cytokine release
and neutrophil recruitment. This is followed by a chronic phase in which fibroblasts
synthesize new extracellular matrix (tissue scar) and then a remodeling phase in which
collagen is produced and re-organized. Osteointegration between tendon and bone occurs in
six to 15 weeks after surgery and tight contact between bone and graft (for example achieved
by an interference screw) is crucial for graft integration. The process of the graft turning into
an adapted ligamentous structure appears to take place within the first three years following
reconstruction. (23)
The ACL graft develops no recognizable blood supply during the first two years of
implantation, which leads to the assumption that revascularization is not required for graft
stabilization and function, leaving synovial diffusion as the main nourishment source. (30)
However, in contrast, the periligamentous soft tissue is highly vascularized and covers the
graft. (30)
15
In summary, the success of graft integration is determined by the balance between resorption
of local blood clots, removal of cellular debris by the synovial fluid, collagen production and
growth factor expression from both, graft and host tissue. (23)
2.3 Risk Factors for ACL rupture Many genetic and lifestyle factors have been investigated with regards to a first time ACL
rupture, but only two relate to the risk of injury: gender and sport. Other risk factors such as
young age, meniscal and chondral injuries and tendon harvest are either consequential
because of other factors or not proven to have an impact. (31, 32)
2.3.1 Gender The risk of suffering an ACL injury in high-risk sports is three to six times greater for female
than for male athletes. (31, 32)
One reason for this may be the slightly different geometry seen in female knees. A decreased
femoral intercondylar notch width, decreased height of the posterior medial meniscus,
increased quadriceps angle and increased posterior tibial slope could predispose women for
ACL injuries. (32, 33)
Knee motion and loading is also a predicting factor concerning ACL injury. Landing in
inadequate flexion and increased valgus (“dynamic valgus”) and external rotation, as is often
seen in female athletes, leads to increased ACL strain and therefore higher risk of future
ACL ruptures. (31, 32)
Figure 16: Dynamic Valgus (30)
16
However, these movement biomechanics as well as lower-extremity muscle strength and
recruitment are possible to be positively adjusted applying neuromuscular training. 15
minutes of neuromuscular warm-up program twice a week significantly reduces ACL injury
rate by targeting core stability, balance, and proper knee alignment. (31, 34)
The ACL is an estrogen targeted tissue. (35) Collagen synthesis is reduced in the presence
of high estrogen levels, therefore the ligament matrix is affected. There is a protective
association between the use of oral contraceptives (OC) and the risk of sustaining an ACL
injury. However, prophylactic use of OCs to minimize injury risk in at-risk women is not
recommended until further studies have investigated the relationship between estrogen level
and ACL injuries. (35)
2.3.2 Sport ACL ruptures commonly occur during non-contact movements, usually while participating
in sports. An athlete’s risk of having a first-time ACL injury is influenced by level of
competition, gender, and type of sport. Especially knee demanding sports such as soccer,
volleyball, handball, judo etc., including stop-and-go and rotational movements during
flexion are associated with a higher injury risk. (36, 37)
2.4 Diagnostic Methods In case of an acute trauma or chronic complaints regarding the knee, there are several steps
needed to determine the right diagnosis. (2)
2.4.1 Anamnesis Asking about previous traumas or knee pathologies is essential to exclude differential
diagnoses and to distinguish acute from chronic complaints. Also, letting the patient explain
in which situations pain or instability occur, and what quality of pain is experienced, helps
gaining a lot of information before even examining the knee. Special attention should be
paid to activity level, type of sport practiced and current occupation. (2)
2.4.2 Physical Examination Diagnosing an ACL rupture based on a physical examination remains a challenge. There are
3 physical examination tests commonly used to evaluate the ACL, and a new one showing
promising results: the Lachman test, the pivot-shift test, the anterior drawer test and the
Lever sign test. (38)
17
Sensitivity Specificity
Lachman Test 81-86 % 81-94 % Pivot Shift Test 18-48 % 81-99 % Anterior Drawer Test 38-82 % 67-91 % Lever Sign Test 86-100 % 91 %
Table 2: Sensitivity and Specificity of ACL Tests (36)
2.4.2.1 Lachman Test The Lachman Test is the most valid test of the following to determine an ACL rupture. It
has a high sensitivity and specificity especially in acute injury cases and is not dependent in
other associated ligamentous or meniscal injuries being present. (39, 40)
The Lachman Test is performed by holding the knee between full extension and 15 degrees
of flexion. One hand is stabilizing the femur, while applying anterior pressure with the other
hand, holding the proximal tibia. The test is positive if an anterior translation of the tibia
with a “soft” end point is seen or felt. (40)
2.4.2.2 Pivot Shift Test Specificity of the Pivot Shift Test is very high (particularly under anesthesia), but sensitivity
rather poor. A positive Pivot Shift Test result is associated with a clinical “giving way”
symptomatology. (39, 40)
Figure 17: Lachman Test (picture taken by author)
Figure 18: Pivot Shift Test (pictures taken by author)
18
For the Pivot Shift Test, the examiner picks up the leg at the ankle and places the other hand
behind the fibula. Under a strong valgus force of the upper hand and an internal rotation of
the tibia, the knee is slowly flexed. If the ACL is torn, this position subluxates the tibia
anteriorly. At about 30 degrees of flexion the tibia suddenly reduces back to its normal
position due to tightening of the ITT. This reduction is seen and felt by patient and examiner
and indicates a positive test. (40)
2.4.2.3 Anterior Drawer Test The Anterior Drawer Test shows low sensitivity especially in acute settings. There are many
reasons for a possible false negative result:
- Due to hemarthrosis and reactive synovitis, knee flexion may be prevented.
- Joint pain may cause protective muscle action of the hamstrings which leads to an
alternate force.
- The posterior horn of the medial meniscus could be pressed against the posterior
margin of the medial femoral condyle and inhibits anterior translation of the tibia.
Also, false positive results are possible if a PCL insufficiency exists, which leads to a
posterior sagging of the tibia simulating a false neutral position. (39, 40)
For the Anterior Drawer Test the hip needs to be flexed to 45° and the knee to 90°. The
examiner sits on the patient’s foot with both hands around the proximal tibia, thumbs on the
tibial tuberosities. Then anterior force is applied. If increased tibial displacement (compared
to the other side) is seen, an ACL tear is likely.(40)
Figure 19: Anterior Drawer Test (picture taken by author)
19
2.4.2.4 Lever Sign Test The Lever Sign Test is a relatively new clinical test designed by Alessandro Lelli. The Lever
Sign Test is as sensitive as the three clinical tests presented before (2.4.2.1 – 2.4.2.3),
concerning chronic and total ACL tears. (41) But, different to the other common manual
tests, the Lever Sign Test also shows a high sensitivity regarding both acute and partial tears
of the ACL, which makes it a better alternative in these situations than the usually used
clinical tests.(41)
To perform the Lever Sign Test, a point of leverage, e.g. the examiners fist, is placed under
the supine patient’s calf and a downward force is applied on the quadriceps with the other
hand. If the ACL is intact, the patient’s heel will rise off the table, as seen in Figure 20 – a.
If the ACL is insufficient, the patient’s heel will remain on the examination table as seen in
Figure 20 – b. (41)
2.4.3 Radiology
2.4.3.1 Radiography Anterior-posterior (AP) and sagittal knee radiographs are easily available and obtained. They
are important to identify fractures or dislocations requiring emergent care. However, if only
an ACL rupture was sustained, the radiograph shows no pathologies. Nonetheless, it is an
important diagnostic tool to rule out some differential diagnosis. (42)
Figure 20: Lever Sign Test (39)
20
2.4.3.2 Magnetic Resonance Imaging (MRI) MRI is the only non-invasive diagnostic tool which can provide guaranteed certainty of an
ACL rupture and it can help to identify concomitant ligament, meniscal and/or cartilage
injuries. (42)
Figure 21: Frontal and sagittal radiograph of a 23-year old patient with recent ACL re-rupture, drill holes (white arrows) from previous ACL surgery can be seen (LKH Universitätsklinikum Graz)
Figure 22: Sagittal T2 weighted MRI of a 22-year old patient with recent ACL rupture (white arrow) (Diagnostikzentrum Graz für Computertomographie und Magnetresonanztomographie)
21
However, MRI is not only helpful with diagnosing an ACL tear, but also with verifying graft
healing after operative reconstruction. Graft volume combined with median signal intensity
of the graft, measured using MR-images, can predict clinical tests and also correlate with
common questionnaires used to analyze patient’s outcome. (43) These findings suggest, that
with the help of MRI, in combination with other follow-up methods, clinicians could better
determine the appropriate timing for patients to return to sport. (43)
2.5 Treatment There are various treatment options for ACL ruptures. The choice depends on type of injury,
patient factors, symptoms, and patient’s expectation. Some indications whether to pick a
conservative or surgical treatment are shown in Table 2. (2)
Conservative Management Surgical Treatment
• Contraindication for surgery
• Minimal knee instability
• No high activity ambitions
• Pre-existing arthrosis
• No concomitant injuries, isolated
ACL injury
• Complex concomitant injuries
(collateral ligament injuries,
meniscal injuries)
• Objective and subjective knee
instability (“giving-way”)
• Recurrent swelling
• Knee-demanding sports, activities Table 3: Indications for conservative and surgical treatment of ACL ruptures (2)
2.5.1 Conservative Management According to the current guidelines put out by the Association of the Scientific Medical
Societies in Germany (AWMF) (2), there are some individual aspects which point to
conservative management rather than surgical reconstruction. For instance, a nonsurgical
approach is suggested in patients who have other health issues making them not fit for an
operation, as well as patients who show minimal knee instability and have no high activity
ambitions. Also, pre-existing arthrosis and a lack of concomitant injuries endorses a
nonsurgical treatment. Either way, if conservative management is chosen, this does not mean
that the patient is left on their own. Muscle strengthening, physiotherapy, as well as the use
of walking aids in combination with increasing loads and clinical follow-up examinations
are essential. (2)
22
The views on conservative management of an ACL injury show broad variation, but if
patients are willing to lower their activity level, nonsurgical treatment can lead to
comparable clinical results to surgical reconstruction. (44) In moderately active patients (not
athletes), the clinical results between early or late surgically reconstructed knees or those
treated with rehabilitation alone, do not differ at all.(45, 46) The overall exception are
children and adolescents. Within this cohort, early surgical stabilization is preferred.
Nonoperative treatment in these patients results in a persistently unstable knee and therefore
further intra-articular damage. Also, the inability to return to previous activity levels,
especially in young patients, has a great impact in everyday-life. (47)
2.5.2 Surgical Treatment Surgical treatment is indicated if patients report “giving-way”-sensations in daily living or
if they want to resume knee-straining activities/sports such as football, basketball, volleyball,
tennis, and skiing. (48) Other indications can be seen in Table 2.
There is no guaranteed report of the right time for a surgical intervention after an ACL
rupture. (2) However, moderate evidence supports reconstruction within five months after
surgery, to avoid cartilage and meniscal damage. (42) The official guideline by the AWMF
favors surgery 48 hours within injury or after the acute inflammatory phase passes and ROM
is regained. (2) Early (<two weeks) and late (four to six weeks after injury) reconstruction
lead to a similar clinical and functional outcome. (49)
If surgery is not performed immediately, injury management should focus on the reduction
of hemarthrosis with rest, ice, compression, and elevation. Sometimes the administration of
nonsteroidal anti-inflammatory agents can be helpful. (48)
There is no age limitation for a surgical approach. Patients older than 40 years even achieve
comparable clinical outcomes to younger patients. (50)
ACL reconstruction is an arthroscopically performed procedure. The ruptured ACL is
replaced by a suitable graft, which is anatomically implanted in the original femoral and
tibial footprint area. (2) In children and adolescents traditional reconstruction techniques
may disrupt the growth plates, leading to leg-length discrepancies, axis disturbances or
physeal disruptions. In these cases, special procedures sparing or avoiding the physis must
be considered. (47)
23
2.5.3 Alternative Treatment Besides these two most common approaches to treat a ruptured ACL, there are also other
procedures being investigated at the moment.
Currently, there is no attempt to repair the torn ligament because isolated repair has met only
moderate success in history. (10) The main inhibitor of intrinsic ACL healing being the lack
of clot formation between the two torn ends of the ACL.(51) However, in most cases,
sufficient tissue remains for a repair to be considered. (10) Using an Internal Brace
Augmentation system to protect ACL repair may offer an advantage over previous ACL
repair techniques. (10)
On the other side, there has been growing interest on regenerative approaches to stimulate
ACL healing during procedures of reconstruction or repair, using platelet-rich plasma (PLP)
or stem cells. (52) Although some studies showed promising short-term outcomes, there is
still insufficient evidence to support the use of these biological agents systematically. (52,
53)
2.6 Grafts There are a lot of options when it comes to graft choice in ACL reconstruction. There is no
such thing as the ideal graft that fits every patient in every situation. Deciding on which graft
to use is always an individual patient (activity level, comorbidities, tissue availability, prior
surgeries, preference) and surgeon-dependent (experience, preference) choice. (54)
The ideal graft should have structural and biomechanical qualities similar to those of the
native ligament, allow secure fixation and rapid biologic incorporation, and limit donor site
morbidity. (54)
2.6.1 Autografts Autografts are most commonly used when it comes to primary ACL reconstructions.
However, there is no ‘gold standard’ graft in these procedures, as none has clearly shown a
faster return-to-sports than the other ones. (54) The individual advantages and disadvantages
of the available autograft choices can be seen in Table 3. (55)
Bone – Patellar Tendon-
Bone
+ bone-to-bone
healing in both
tunnels
- risk of anterior
kneeling pain
- invasive, large
incision
24
+ comparable stiffness
to native ACL
- risk of patellar
fracture
- fixed length
- weaker than native
ACL
Hamstring Tendon + easy to harvest
+ cosmetics
+ minimal donor site
morbidity
+ comparable strength
to native ACL
- soft tissue healing
- unpredictable graft
size
- not for athletes who
rely on their
hamstring muscles
- less stiffness than
native ACL
Quadriceps Tendon + large graft
+ option of a one-sided
bone block
- invasive, large
incision
- risk of patellar
fracture Table 4: Advantages and disadvantages of available autografts (53)
2.6.2 Allografts Another option besides autologous grafts are allografts. At first mostly used in revision or
multiple ligament rupture cases, primary use of allografts is getting more common.
Particularly when the native tissue is insufficient for repair or donor site morbidity presents
a problem, allografts are a suitable choice. (56)
Regarding the clinical outcome of allograft in comparison to reconstruction with autografts,
there is no clear opinion. A lot of studies show poorer clinical outcome and higher failure
and revision rates regarding allografts, but mostly in irradiated grafts. (57, 58) When
comparing autografts and non-irradiated allografts there is no significant difference in
results. (59)
The most often mentioned disadvantage of allografts is the commonly known inferior
remodeling and healing process. Autografts show a more advanced remodeling progress at
early stages of recovery than allografts. However, after one year both groups return to an
ACL-similar structure. (60) Despite the disadvantages, there are also a lot of positive aspects
regarding allograft use, which can be found in Table 4. (56)
25
Advantages and disadvantages of allografts
+ faster postoperative recovery
+ less postoperative pain
+ no graft harvest needed shorter surgery
time
+ no donor site morbidity
+ length and diameter available as needed
- lower stability rate
- higher graft failure rate
- slower graft incorporation
- concerns of disease transmission
Table 5: Advantages and disadvantages of allografts (54)
2.6.3 Synthetic Grafts Artificial grafts have long been under consideration as they represent a type of graft which
is easily available and would simplify the surgery as there is no preparation time involved
as in allografts or even graft harvesting as in autografts. However, most of them have showed
high failure rates in the past. (61) The new generation synthetic ‘Ligament Advanced
Reinforcement System’ (LARS) has gained more popularity than its predecessors and
showed comparable complication rates to traditional surgical techniques in short-term follow
up. (62) Nevertheless, first long-term results indicate that the LARS system should not be
considered as a potential graft for ACL reconstruction in a primary setting, because of high
failure rates and poor patient satisfaction. (63)
2.7 Complications A list of general and ACL-Reconstruction-specific complications associated with ACL
reconstruction can be found in Table 6. (64)
Complications associated with ACL reconstruction
General Complications
Vascular Damage Rare
Nerve Damage Occurs in 8.2% of arthroscopic knee
surgeries (64)
Infection Occurs in 0.8% of ACL reconstructions
(64)
26
Thrombosis and Embolism Occurs in 1.5-17.9% of arthroscopic knee
surgeries without thromboembolic
prophylaxis (64)
Osteoarthritis See 2.7.1
ACL-Reconstruction-Specific Complications
Graft Damage Not reported
Wrong Drill Hole Placement Not reported, leads to Graft Failure
Graft Failure See 2.7.2 Table 6: Complications associated with ACL reconstruction (64)
The general complications mentioned in Table 6 occur in every arthroscopic knee surgery.
Vascular damages can be avoided by properly flexing the knee while drilling the femoral
and tibial tunnels to protect the popliteal vessels. Nerve damages are one of the most
common intraoperative complications. They occur mostly during graft harvest and
arthroscopic portal incisions and result in paresthesia and dysesthesia. However, the sensory
deficit most commonly regresses a short time after the procedure. Infections occur only in
rare cases. Additional procedures such as meniscal-resection or sutures increase the risk of
intraarticular infections, as well as previous knee surgeries. An infection occurs most
commonly 3-5 days after surgery and should be treated with arthroscopic rinses,
synovectomy, debridement and intra venous antibiotics. To prevent postoperative
thrombosis and embolism, a prophylaxis using low molecular weight heparin should be
administered until full loading. (64)
An ACL reconstruction specific complication is graft damage. It occurs mostly during graft
harvest or graft fixation. The preparation and harvest of the hamstring-graft showed to be
more complicated and riskier than the patellar-tendon graft. However, harvesting of the
patellar tendon with a proximal and distal bone block can, in rare cases, lead to patella
fracture. Another cause for complications can be the drill hole placement. Wrong placement
of the femoral drill hole is considered the most common cause for reconstruction failure. In
most cases the drill hole is placed more anterior then it should, leading to graft laxity. (64)
2.7.1 Osteoarthritis (OA) OA in injured joints is caused by pathogenic processes initiated at the time of injury, and
long-term changes in biomechanical joint loading. (65) At 10 to 20 years after diagnosis,
about 50% of those with a diagnosed ACL tear have OA with associated pain and functional
impairment. (65) ACL injury predisposes to OA, while ACL reconstruction surgery reduces
the risk of developing degenerative changes. (66) The relative risk (RR) of developing OA
27
in nonoperatively treated ACL injuries is significantly higher (4.98) compared with those
treated with reconstruction (3.62). (66) However, even after reconstruction surgery, patients
with ACL injuries in the past show a three-fold increased prevalence of OA compared with
the contralateral healthy knee. (67)
2.7.2 Graft Failure Graft failure is a rare, but dreaded complication after ACL reconstruction. Estimated revision
rates vary from three to nine percent depending on source and follow-up. (68-70)
There are many possible reasons for an ACL re-tear after reconstruction. The graft may fail
as a result of traumatic overload, poor surgical technique, untreated concurrent knee injuries,
or poor biological incorporation of the graft. (69) Possible predictors of revision surgery are
young age at time of reconstruction and competitive activity level, especially in soccer
players. (70) There are no associations regarding sex, height, weight, or body mass index.
(71)
2.8 Revision Up to 20% of patients experience complications like knee laxity and/or instability during
athletic activities or daily life after primary reconstruction due to graft failure. (72) Revision
surgery is performed in order to stabilize the knee joint, prevent further cartilage and menisci
damage, and allow the patient to resume normal daily and/or sports activities. (72)
Revision surgery poses several diagnostic and technical challenges compared to primary
reconstructions. Due to the complexity of this procedure, preoperative planning is essential.
It begins with determining the cause of failure for the primary reconstruction. Furthermore,
a thorough history regarding the initial surgery, associated injuries, used graft type, fixation
method, as well as other prior procedures performed are necessary to obtain. (73)
Widening of the tibial and femoral tunnels presents a substantial obstacle during revision
surgery because of the bone loss and poor graft fixation leading to delayed graft
incorporation and decreased stability. There are many mechanical and biologic factors
responsible for tunnel widening, including graft position, fixation method, graft type, graft
donor, synovial fluid, and implant material and preparation. (74) Sometimes, a two-stage
procedure with initial tunnel bone grafting followed by ACL reconstruction four to six
months later is necessary. (73) Another solution would be the use of an allograft with large
bone block, which can be constructed and tailored to the specific deficit. (74) Radiography,
28
CT, and MRI can be used to determine the extent of widening, which should be about 10
Millimeters in diameter normally, but often exceeds 15 Millimeters. (74)
Another unique problem in revision reconstruction is preexisting hardware. Biodegradable
hardware is prone to fragmentation and cannot be removed easily. Therefore, it should be
left in place. In contrast, metal interference screws must be removed when interfering with
proper tunnel placement. (73)
The outcome of revision reconstructions is worse compared with primary reconstruction.
The failure rate is nearly three to four times higher. (3) Return-To-Sport (RTS) rates after
revision are similar to those after primary reconstruction in individual patients, but still lower
than those of patients who did not need revision surgery in the first place. (75) Patients need
to know, that a return to their previous level of performance before their first ACL
reconstruction cannot be expected. (73)
2.9 Rehabilitation Numerous factors have an impact on an optimum return to function after ACL reconstructive
surgery, one of them being the impact of external and internal forces over the course of the
postsurgical period. Precisely, the degree of joint force that rehabilitation exercises produce,
the nature of performed exercises in terms of intensity, mode, frequency, and duration; and
their impact on knee joint proprioception are very important. One cause for graft failure may
involve overloading of the reconstructed knee as a result of inappropriate dosage or
performance of various exercises. (76)
Movements applied to the knee joint postoperatively extending 30° of knee flexion increase
joint swelling, but if performed in the final degrees of extension, there is a noted decrease in
quadriceps inhibition, as well as an improved healing rate. (76)
Appropriate initiation of non-weightbearing exercises designed to reduce knee extensor
muscle atrophy is the primary goal of a lot of ACL rehabilitation programs. However,
anatomical research has shown that when the knee extensors contract, they can cause anterior
tibial displacement, especially if performed in an ‘open’ kinetic chain mode. When
performed in a ‘closed’ kinetic chain mode ACL stress is minimized and additionally, more
specific and sensory feedback is stimulated. (76)
The quantity of exercises an individual performs in a given period after ACL reconstruction
surgery similarly impacts recovery. For example, even low workload exercises can increase
the anterior laxity of both normal and ACL reconstructed knees.
29
On the other side, an inappropriate exercise dosage that results in muscle atrophy may not
only lead to knee joint instability, it also may prevent appropriate healing of the newly
constructed graft. (76)
One important factor of rehabilitation after ACL reconstruction is RTS. A return to the
preinjury level of activity is commonly assumed to take between 6 and 12 months. However,
only one third of active patients make it by this time. After two years, two out of three
patients return to their preinjury level sport. This suggests that some patients simply need
more time to recover than initially suggested. (77)
Unlike previously expected, RTS does not depend exclusively on physical function, but is
multifactorial. A lot of psychological factors like fear of reinjury or pain, recovery
expectations, and the feeling of uncontrollability during sports predict RTS outcomes. Male
and young patients are more likely to return to their previous level of sport than older patients
and women. (77)
The second important part of rehabilitation presents the Quality of Life (QOL) level after
surgery. Measured with the Short Form-36 (SF-36) ACL reconstruction resulted in a
relatively high gain of quality-adjusted life years. In the physical component summary (PCS)
score large improvements were noted at two years and maintained at six years after ACL
reconstruction, showing that physical benefits are durable throughout many years. The
mental component summary (MCS) score, as well as the general health subscale are both
well above population norm in patients undergoing ACL reconstruction and do not change
dramatically over time. (78)
3 Material and Methods
3.1 Hypothesis of the Study The hypothesis of this study was that the clinical outcome of patients with internal brace
(IB) augmentation in ACL revision cases is better than without, because of improved healing
conditions. Furthermore, we wanted to evaluate the difference in QOL and RTS.
Therefore, the study objectives were:
• Visual Analog Scale (VAS) for Pain in patients treated without and with IB
augmentation
• Knee specific clinical scores in patients treated without and with IB augmentation
• QOL in patients treated without and with IB augmentation
• RTS in patients treated without and with IB augmentation
30
3.2 Study Population
3.2.1 Inclusion Criteria All patients (n=18) who underwent ACL revision reconstruction while this study took place
at the University Hospital of Graz (Austria) and who matched following criteria were
included in the study:
• MRI verified re-tear of the ACL and
• Clinical and patient-reported instability of the knee joint and
• Signed informed consent
Table 7 gives an overview of the patients’ characteristics of the total study population.
Gender Total Without IB With IB
Patients (n)
All 18 10 8
Male 15 10 5
Female 3 0 3
Age (years, mean ± SD)
All 29.4 ± 7.8 28.2 ± 7.7 30.9 ± 8.3
Male 28.6 ± 7.4 28.2 ± 7.7 29.4 ± 7.6
Female 33.3 ± 10.5 / 33.3 ± 10.5
BMI (mean ± SD)
All 24.83 ± 2.0 25.1 ± 1.8 23.3 ± 1.8
Male 24.5 ± 2.0 25.1 ± 1.8 23.3 ± 1.9
Female 23.1 ± 2.0 / 23.1 ± 2.0 Table 7: Total patient population, total group without IB and total group with IB, SD= standard deviation
3.2.2 Exclusion Criteria Patients were excluded if they:
• suffered from an advanced stage of OA
• had an ongoing infection
• had cancer
• suffered from any immunosuppressant disease
• had a diagnosed neuromuscular disease
• suffered from a psychiatric disease, which made them unfit to consent
• had a writing and/or reading disability
• could not speak German or English and there was no interpreter available
31
3.3 Study Design
3.3.1 General Information This study was designed as a prospective, randomized pilot study starting on the 14th
February, 2017 (date of ethic votum). Various questionnaires, physical examination and
imaging evaluations at different study timepoints were planned (Table 8). We collected
general information using a self-designed Case Report Form (CRF). The data collection was
performed by the operators of the survey.
Before
Surgery
After 6
weeks
After 12
weeks
After 6
months
After 13
months
Clinical
Examination X X X X X
VAS of Pain X X X X X
IKDC X X X X X
KOOS X X X X X
Lysholm Knee
Scoring Scale X X X X X
TAS X X X X X
SF-36 X X X X X
Radiography X X X X X
MR-Imaging X X X Table 8: Follow-Up Time and Performed Evaluations
The patients were blinded and randomly categorized into two groups (with and without IB
augmentation), The surgeon and the survey staff were unblended. The study was planned as
a single-surgeon study.
30 patients have been planned to be included, 15 in each group, over the course of three
years. In this diploma thesis the patients included until 31st January, 2019 and their
preliminary results are analyzed.
3.3.2 Ethics All participants of the study had to sign an informed consent before inclusion, confirming
their approval of usage of their data. The informed consent can be found in the appendix of
this thesis (see chapter: 8. Appendix - Informed Consent, Case Report Form, Questionnaire).
32
The ethics committee of the medical university of Graz authorized this study with the project
number 29-136 ex 16/17.
3.3.3 Data Protection For this survey, protected medical information was needed: patients’ names, dates of birth,
phone numbers, addresses, operation dates, and other personal information. This data is
available in the hospital information system openMEDOCS (KAGES group).
The collected data is registered in a Microsoft Excel datasheet. The datasheet is password
protected, only members of the study staff have access to it. For the statistical analysis and
publication, patient sensitive data is anonymized.
3.3.4 Revision ACL Reconstruction Surgery We used a modified all-inside technique for our revision ACL reconstruction. (79) In
primary ACL repairs this technique shows the advantage of lower bone loss and
determination of tunnel length even before drilling. Therefore, length of the graft must not
be too long, because this would lead to increased laxity of the graft construct. (79, 80) The
femoral tunnel is drilled approximately 2 cm proximal and 1 cm anterior of the epicondylus
lateralis, stopping 1 cm before reaching the cortex. The tibial tunnel is drilled starting from
the ACL insertion point up until 40 mm before reaching the cortex. With a shuttle-thread the
graft is inserted femorally through the anteromedial portal, and then tibially. In a nearly-
extension position the graft is then tightened. (79, 81) In revision cases the tibial tunnel is
drilled from the outside and the emerging bone defect is preoperatively measured and filled
with the achilles tendon bone block. In 8 patients (44%) an additional tibial screw was used
to add stability.
3.3.5 Allografts We obtained our allografts from LifeNet Health ©, a non-profit provider of allograft bio-
implants and organs for transplantation stationed in Virgina, USA. The allografts were
imported and distributed by AlloTiss Gemeinnützige Gewebebank GmbH in Austria and
thereafter by LifeNet Health © Europe, Vienna. The actual sales process and appropriate
usage of the products is supported by Arthrex ©, a global medical device company.
LifeNet Health © uses a patented and validated washing process called Allowash XG. It
provides a Sterility Assurance Level of 10-6, while still maintaining biomechanical and
biochemical properties of the tissue. Since 1995, there has been no record of disease
transmission. The Allowash XG process ends with a controlled dose of gamma irradiation,
33
administered at low temperatures after the tissue is packaged. Studies have shown no
difference in outcomes to non-irradiated autograft tendons. (82)
In the donor screening process information like cause of death, demographics, and any
contraindications to donation such as malignancy or infectious diseases are considered. After
the organ recovery is completed, the eyes and soft tissues of the donor are recovered in a
surgical procedure that is much like any standard operation. (82) In all patients we used an
achilles tendon with bone block, available in different dimensions (see Figure 23).
Figure 23: Unpacked Achilles Tendon Allograft (image taken by author)
Bone and tendons were shaped and adapted intraoperatively, depending on the bone defect
of the previous operation using an Arthrex Graft Prep Station © (see Figure 24).
Figure 24: Finished Graft (image taken by author)
3.3.6 Internal Brace (Arthrex ©) To protect the allograft during the revascularization and remodeling phase, which was shown
to be slower than in autografts, an internal brace was added in one study group. This
polyethylene/polyester fibre tape (Arthrex ©) is integrated seamlessly into the tendon graft
construct (see Figure 25). It is tensioned and fixed independently from the graft and always
at full hyperextension so it won’t lead to an overconstraining of the joint and therefor to a
loss of motion.(9)
34
3.3.7 Rehabilitation After surgery the patients received analgetic medication in addition to PPI (proton pump
inhibitor) therapy upon need.
During the first three weeks postoperatively, patients were allowed half body weight-bearing
in combination with crutches. During this period, they received thrombembolic prophylaxis
until full weight-bearing. In the first two weeks they wore a brace locked at 0/0/30. In the
four following weeks the brace was locked at 0/0/90. During this time period patients
performed physiotherapy with passive, isometric muscle-exercises and received lymphatic
drainage. After six weeks they were allowed full weight-bearing without a brace and active
exercise guided by a physiotherapist. Particular attention was paid to increase quadriceps
strength. A return to ACL-demanding sports was advised not to take place in the first 12
months after reconstruction.
Figure 25: Internal Brace (Arrow) integrated into the graft (Arthrex ©)
35
3.4 Questionnaires
3.4.1 Case Report Form (CRF) The questions were divided into general information (gender, age, affected side, BMI,
occupation, and activity level before injury), patient’s history (pre-existing conditions,
allergies, medication, consumption of alcohol, packyears), VAS of Pain, and clinical
examination. For further information the whole questionnaire is available in the Appendix
(see chapter: 8. Appendix - Informed Consent, Case Report Form, Questionnaire)
3.4.2 International Knee Documentation Committee (IKDC) The IKDC questionnaire helps to detect improvement or worsening in symptoms, function,
and sports activities due to knee impairment. It was developed in 1997 and has undergone
several minor revisions since its publication in 2001. (83)
It is divided into three domains:
1) Symptoms, pain, stiffness, swelling, locking/catching, and giving way
2) Sports and daily activities
3) Current knee function and knee function prior to knee injury (not included in the total
score)
The total score is calculated as (sum of items) / (maximum possible score) x 100, to give a
total score of 100. The usefulness of the IKDC has been shown, as it is responsive to change
following surgical interventions. (83)
3.4.3 Knee Osteoarthritis Outcome Score (KOOS) The KOOS questionnaire is used to measure patients’ opinions about their knee and
associated problems over short- and long-term follow-up. The original KOOS remains
unchanged up to now. (83)
It consists of five domains:
1) Pain frequency and severity during functional activities
2) Symptoms such as the severity of knee stiffness and the presence of swelling,
grinding or clicking, catching, and range of motion restriction
3) Difficulty experienced during activities of daily living
4) Difficulty experienced with sport and recreational activities
5) Knee-related QOL
The score ranges from 0 to 100, 100 meaning that there are no problems present. The KOOS
appears to be responsive to change in patients with a variety of conditions that have been
treated with nonsurgical and surgical interventions. (83)
36
3.4.4 Lysholm Knee Scoring Scale The Lysholm Knee Scoring Scale was developed to evaluate outcomes of knee ligament
surgery, particularly symptoms of instability. It was first published in 1982 and revised in
1985. There are only 8 items, making up a possible score of 100. The scores are categorized
as excellent (95-100), good (84-94), fair (65-83), and poor (<63). I was reported to be very
responsive to change following ACL reconstruction. (83)
3.4.5 Tegner Activity Scale (TAS) The TAS provides a standardized method of grading work and sport activities. It was
intended for use with the Lysholm Knee Scoring Scale, in patients with ACL injury. It
contains a graduated list of activities of daily living, recreation, and competitive sports.
Patients select the level that best describes their current level of activity. The possible score
ranges from 0 to 10, levels 6 to 10 can only be achieved if the person participated in
recreational or competitive sport. (83)
3.4.6 Short Form – 36 (SF-36) The 36-Item Short Form Health Survey questionnaire is a very popular instrument used to
evaluate health-related quality of life (HRQOL). It was not developed to measure QOL in
patients with a specific disorder, but rather in order to have a generic measurement of QOL
in all patients. It was first published in 1992, and revised in 1996 when a second version was
introduced. (84) There are 36 items to be answered, which are subdivided into eight scales:
• Physical Functioning (PF)
• Role Physical (RP)
• Bodily Pain (BP)
• General Health (GH)
• Vitality (VT)
• Social Functioning (SF)
• Role Emotional (RE)
• Mental Health (MH)
These subscales are subordinate to two main scales, and contribute in different proportions
to the scoring of these:
- Physical Component Summary (PCS)
- Made up from PF, RP, BP, GH
- Mental Component Summary (MCS)
- Made up from VT, RE, SF, MH
37
The SF-36 does not provide a single measure of health-related QOL. For the analysis a
manual and an interpretation guide is needed. The calculated data can be compared with data
from an age- and sex matched normal population. (84) The whole questionnaire can be found
in the appendix of this thesis (see chapter: 8. Appendix - Informed Consent, Case Report
Form, Questionnaire).
3.5 Statistical Analysis Standard descriptive statistics (tables, diagrams, graphics, etc.) were used for the description
of all baseline and follow-up parameters. T-test was used for parametric distributions, the
Mann-Whitney-U test for non-parametric distributions.
All analyses were performed per protocol. A p-value of <0,05 was determined as significant
for all tests. Parametric data is stated with mean and standard deviation, non-parametric data
with median and range.
3.5.1 Software Tools The basic data collection was done with the spreadsheet program Microsoft Excel
(Microsoft, v16.0, 2015). For the statistical analysis, we used the software SPSS Statistics
(IBM, v25, 2015). For the compilation of the text document, we used the program Microsoft
Word (Microsoft, v16.0, 2015).
Quotations were made with the citation management software EndNote (Clarivate Analytics,
X8.2, 2018). For the literature search, we used the search engine PubMed (National Center
for Biotechnology Information). Additionally, we used the books available in the library of
the Medical University of Graz.
4 Results The first 18 patients and their preliminary results were included in the statistical analysis of
this diploma thesis. Ten in the group without IB and 8 in the group with IB. Figure 26 gives
an overview of the different follow-up periods in the two groups.
n=18Revision ACL
reconstruction
n=10without IB
n=1012 weeks follow-up
n=86 months follow-up
n=413 months follow-up
n=8with IB
n=812 weeks follow-up
n=66 months follow-up
n=413 months follow-up
Figure 26: Overview of Follow-Up Periods
38
The following results focus on preoperative data and the 12-month follow-up.
4.1 Patient demographics The final study population of 18 patients (16.7% female) had a mean age of 29.4 ± 7.8 years
at the day of surgery (Table 9).
4.2 Preoperative Data
4.2.1 Physical Examination During clinical examination the patients showed a mean total ROM of 133 ± 11 degrees.
None of them showed signs of inflammation, only 4 (22%) reported mild pain during
palpation. There were no abnormalities detected in motor activity, circulation or sensitivity.
All patients showed positive Lachman, Anterior Drawer and Lever sign tests and complained
about instability in the affected knee (Table 10).
Without IB With IB p-value
Patients (n) 10 8
Side, left/right (n) 4 / 6 5 / 3
Meniscal Lesion (n, (%))
7 (70) 7 (88)
Injury Mechanism (n, contact sport/
non-contact sport
/accident/unknown)
1 / 2 / 2 / 5 1 / 3 / 2 / 2
Sport-Level before
injury
(TAS, mean ± SD)
8.3 ± 1.0 7.1 ± 2.0 0.281
Smoking Habits
(packyears, mean ±
SD)
3.1 ± 3.5 6.5 ± 8.9 0.573
Table 9: Patient demographics, n=number, SD= standard deviation
39
4.2.2 Radiographic Evaluation Preoperative MRI scans and radiographs were performed in all patients. Preoperative
planning regarding graft size, bone block diameter, position of previously used graft, and
any structural damages were performed. A preoperative radiograph example can be seen in
Figure 27.
Without IB With IB p-value
Patients (n) 10 8
ROM
(degrees, mean ±
SD)
132.5 ± 10.3 134.3 ± 12.7 0.762
Pain during
palpation (n) 1 3
Table 10: Preoperative Physical Examination, n=number, ROM=Range of Motion, SD=standard deviation
Figure 27: Preoperative ap / lateral X-ray of a patient (LKH Universitätsklinikum Graz)
40
4.2.3 Clinical Scoring Systems The mean preoperative scores for the used questionnaires in both groups can be seen in Table
11.
Preoperatively, none of the evaluated scores showed any significant difference between the
two groups.
4.2.4 Short-Form 36 Health Survey The outcome variables of the eight subscales and the two summary scores were compared
between the two groups. There were no significant differences between the two groups in
five of the eight subscales, the PCS or the MCS (see Table 12). There were significant
differences between the two groups in the VT, RE, and MH subscale, showing better results
in the group without IB preoperatively, however without clinical relevance.
Without IB With IB p - Value
Patients (n) 10 8
VAS
(median/range)
1 /
0-7
1 /
0-5 0.696
Lysholm Knee Questionnaire
(mean ± SD) 3.3 ± 1.2 3.4 ± 2.1 0.923
TAS (mean ± SD)
3.4 ± 2.0 3.3 ± 1.0 0.848
KOOS (days, mean ± SD)
73.5 ± 9.1 64.6 ± 16.2 0.191
IKDC (days, mean ± SD)
60.0 ± 16.1 53.5 ± 17.3 0.419
Table 11: Preoperative Questionnaire Data, n=number, min=Minimum, max= Maximum, SD=standard deviation
Without IB With IB p - Value
Patients (n) 10 8
Physical Functioning (mean ± SD)
75.5 ± 13.8 67.5 ± 20.9 0.343
Role-Physical (mean ± SD)
63.8 ± 29.0 61.0 ± 33.9 0.851
41
Figure 28 shows the eight subscales, and Figure 29 presents the two summary scores of the
SF-36 comparing the two study groups.
Figure 28: Preoperative SF-36 Subscales
0102030405060708090
100
PF RP BP GH VT SF RE MH
Preoperative SF-36 Subscales
Without Internal Brace With Internal Brace
Bodily Pain (mean ± SD)
61.6 ± 24.8 52.5 ± 23.2 0.437
General Health (mean ± SD)
85.9 ± 9.2 81.0 ± 11.9 0.360
Vitality (mean ± SD) 72.5 ± 11.9 57.1 ± 18.7 0.049*
Social Functioning (mean ± SD)
88.8 ± 19.0 90.6 ± 17.4 0.897
Role-Emotional (mean ± SD)
95.0 ± 10.5 72.9 ± 20.3 0.027*
Mental Health (mean ± SD)
85.5 ± 8.0 71.9 ± 17.5 0.043*
Physical Component
Summary (mean ± SD) 44.7 ± 8.1 44.5 ± 8.6 0.964
Mental Component
Summary (mean ± SD) 62.2 ± 11.2 57.1 ± 11.8 0.362
Table 12: Preoperative SF-36 Results, ‘ = non-parametric data, * = statistically significant, SD=standard deviation
p=0.049*
p=0.027* p=0.043*
p=0.343 p=0.851 p=0.437
p=0.360 p=0.897
42
Figure 29: Preoperative SF-36 Summary Scores
4.3 Surgical Data Data regarding surgery and hospital stay can be seen in Table 13. In some cases, a Push Lock
Anchor (Arthrex ©) was used, to additionally secure the allograft on the tibial footprint area.
The results show no statistically significant difference regarding surgery data and hospital
stay between the two groups.
0
10
20
30
40
50
60
70
PCS MCS
Preoperative SF-36 Summary Scores
Without Internal Brace With Internal Brace
Without IB With IB p - Value
Patients (n) 10 8
Surgical Time (minutes, mean ± SD)
115.9 ± 27.5 117.6 ± 31.7 0.903
Allograft Diameter (mm, mean ± SD)
9.8 ± 0.6 9.5 ± 1.1 0.633
Pushlock (n (%)) 7 (70%) 5 (63%)
Hospital Stay (days, median / range)
5 / 4-7 5.5 / 4-6 0.315
Table 13: Surgical Data, SD=standard deviation, ‘ = non-parametric data
p=0.964
p=0.362
43
4.4 12-Week Follow-Up Data
4.4.1 Physical Examination During the clinical examination the patients showed a mean total ROM of 138 ± 7 degrees.
There was no statistical significance between the two groups (see Table 14).
None of them showed signs of inflammation, only 3 (17%) reported mild pain during
palpation. All patients had a good condition of scars. There were no abnormalities detected
in motor activity, circulation or sensitivity. All patients, except one in the group without IB,
showed negative Lachman, Anterior Drawer and Lever sign tests and had not experienced
any giving-way symptoms since surgery.
ROM is better 12 weeks after surgery compared to preoperative data, but the difference is
not statistically significant (see Table 15).
4.4.2 Clinical Scoring Systems The mean scores for the used questionnaires in both groups can be seen in Table 16.
Without IB With IB p – Value
Patients (n) 10 8
ROM
(degrees, mean ± SD) 139.5 ± 6.9 135.7 ± 7.9 0.315
Pain during palpation (n/%)
1/10 2/25
Table 14: 12-Week Physical Examination
ROM (degrees, mean ± SD)
Preoperatively After 12 Weeks p – Value
Without IB 132.5 ± 10.3 139.5 ± 6.9 0.221
With IB 134.3 ± 12.7 135.7 ± 7.9 0.785
Table 15: ROM=Range Of Motion
44
Twelve weeks after surgery the IKDC score in the group without IB was significantly better
than in the group with IB. The other applied scores showed no significant difference.
A graphic presentation of the data can be seen in Figure 30.
4.4.3 Short-Form 36 Health Survey There were no significant differences between the two groups in seven of the eight subscales,
the PCS or the MCS after 12 Weeks. There was one significant difference between the two
Without IB With IB p - Value
Patients (n) 10 8
VAS (median/
range)
1 /
0-3
1.5 /
0-5 0.145
Lysholm K.Q. (median /
min-max) 94 / 65-100 67 / 62-100 0.109
TAS (median / min-max)
4 / 3-4 3 / 3-4 0.315
KOOS (days, mean ± SD)
82.6 ± 9.8 74.8 ± 6.3 0.090
IKDC (days, mean ± SD)
74.7 ± 8.8 63.9 ± 8.7 0.024*
Table 16: 12-Week Questionnaire Data, *= statistically significant
0102030405060708090
KOOS IKDC
12-Week-Follow-Up-Data
Without IB With IB
p=0.024*p=0.090
Figure 31: 12-Week Follow-Up Data Figure 30: 12-Week Follow-Up Data
45
groups in the subscale Physical Functioning (PF), which showed better results for the group
without IB (see Table 17).
Without IB With IB p - Value
Patients (n) 10 8
Physical Functioning (mean ± SD)
88.0 ± 10.1 75.0 ± 14.1 0.042*
Role-Physical (mean ± SD)
72.5 ±30.8 66.1 ± 18.0 0.629
Bodily Pain (mean ± SD)
85.1 ± 18.7 64.9 ± 23.1 0.065
General Health (mean ± SD)
84.3 ± 12.5 72.1 ± 10.5 0.053
Vitality (mean ± SD)
78.2 ± 9.0 69.7 ± 11.7 0.133
Social Functioning (mean ± SD)
100.0 ± 0.0 85.7 ± 13.4 0.055
Role-Emotional (mean ± SD)
96.7 ± 10.5 86.9 ± 17.3 0.315
Mental Health (mean ± SD)
86.5 ± 5.3 81.4 ± 8.0 0.133
Physical Component
Summary (mean ± SD) 50.9 ± 6.4 45.0 ± 7.2 0.093
Mental Component
Summary (mean ± SD) 53.5 ± 7.4 57.4 ± 11.4 0.396
Table 17: 12-Week Follow-Up SF-36 Results, ‘ = non-parametric data, * = statistically significant
46
Figure 31 shows the eight subscales, and Figure 32 presents the two summary scores of the
SF-36 comparing the two study groups.
Figure 33 shows the comparison of the two study groups 12 weeks after surgery with the
score of the US normal population.
0
20
40
60
80
100
120
PF RP BP GH VT SF RE MH
12-Week Follow-Up SF-36 Subscales
Without IB With IB
p=0.042*
Figure 31: 12-Week Follow-Up SF-36 Subscales
0
10
20
30
40
50
60
PCS MCS
12-Week Follow-Up SF-36 Summary Scores
Without IB With IB
Figure 32: 12-Week Follow-Up SF-36 Summary Scores
p=0.629 p=0.065 p=0.053
p=0.133
p=0.055 p=0.315 p=0.133
p=0.093 p=0.396
Figure 32: 12-Week Follow-Up SF-36 Summary Scores
47
Figure 33: SF-36 Comparison With US Normal Population (red line shows US norm value)
Both groups had better results in five out of eight subscales (GH, VT, SF, RE, MH) 12 weeks
after surgery compared to the US norm population. In one subscale (RP) the US norm
population had a better result than both groups, and in two subscales (PF, BP) the group
without IB showed a better result than the US norm, whereas the group with IB showed
worse results than the US norm.
4.5 Case Presentation
4.5.1 Patient without internal bracing A 28-year old male patient presented himself with permanent pain and increasing instability
in the right knee existing for a few weeks. Several years ago, he had an ACL, TCL (tibial
collateral ligament), and medial meniscus rupture in the same knee and got an ACL
reconstruction with a hamstring autograft. Afterwards he was able to continue sports like
football and skiing, up until now. He played football in a hobby league and was working as
a technical employee. The first ACL rupture occurred during a football match, the second
time he could not determine the exact time or context of the re-rupture.
A MRI scan of the right knee, performed three months before consultation, showed an ACL
re-rupture, and in the physical examination the Lachman and Anterior Drawer tests were
positive.
0
10
20
30
40
50
60
70
PF RP BP GH VT SF RE MH
SF-36 Comparison With US Normal Population
Without IB With IB
48
With conservative therapy methods the patient was not able to decrease instability or pain or
to continue playing football.
After a stay of 5 days the patient was discharged. The rehabilitation proceeded uneventful
and as described in 3.3.7. After six weeks he was allowed to move the knee without using a
restrictive brace.
Figure 34: Preoperative X-Ray Case I
Figure 35: 6-Week follow-up X-Ray Case I (LKH Universitätsklinikum Graz)
49
Six months after surgery a MRI scan was performed, which showed a normally running ACL
graft (see Figure 36).
The MRI scan performed 13 months after surgery showed an intact ACL graft (see Figure
37).
Figure 36: 6-Month Follow-Up MRI Case I ((Diagnostikzentrum Graz für Computertomographie und Magnetresonanztomographie)
Figure 37: 13-Month Follow-Up MRI Case I (Diagnostikzentrum Graz für Computertomographie und Magnetresonanztomographie
50
The patient’s physical results increased over time and he felt very satisfied with the
postoperative progress. The questionnaire results were also constantly increasing (see Table
18).
The summary scores of the SF-36 over time can be seen in Table 19. After a postoperative
drop, the PCS was constantly increasing, after 13-months being higher than preoperatively.
The MCS shows a similar course, the score being lower after 13-months than preoperatively,
probably due to the fear of hurting the ACL again.
PCS MCS
Preoperative 52.5 50.8
After 6 Weeks 35.8 36.4
After 12 Weeks 56.3 47.3
After 6 Months 58.2 49.3
After 13 Months 59.5 45.3 Table 19: SF-36 Summary Scores Case I
Thirteen months after surgery the patient had no pain or instability in the affected knee and
was satisfied with the overall course. All clinical tests for ACL ruptures were negative and
VAS Lysholm K. Q. TAS KOOS IKDC
Preoperative 1 62 5 65.5 35.6
After 6 Weeks 1 62 2 62.8 54.0
After 12 Weeks 1 77 4 80.4 78.2
After 6 Months 1 100 5 95.8 86.2
After 13 Months 0 95 6 95.3 95.4
Table 18: Questionnaire Results Case I
51
his mobility unrestricted. He showed no signs of inflammation. Although he was allowed to
perform knee-strenuous sports, he was advised against stop-and-go movements and skiing
the following winter season.
4.5.2 Patient with internal bracing A 37-year old male patient presented himself with permanent instability in the left knee. A
few years back he ruptured his ACL and medial meniscus in the same knee and received
reconstruction surgery. The hamstring tendons of his left knee were used as an ACL graft.
A few days after surgery he developed a postoperative infection. He was treated with
intravenous antibiotics and his knee eventually healed without removing the implemented
graft. A few months ago he injured his left knee again while running. A performed MRI scan
showed a total re-rupture of the ACL graft. The patient demanded another surgery as he
wasn’t able to run long distances with an unstable knee.
After a stay of 4 days the patient could be discharged without any signs of inflammation.
The rehabilitation proceeded satisfactory, at the 6-week follow up his pain level was already
lower than before surgery.
Figure 38: Preoperative X-Ray Case II (LKH Universitätsklinikum Graz)
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The MRI scan performed 6 months after surgery showed a slightly thickened, but normally
running ACL graft (see Figure 40).
Figure 39: 6-Week Follow-Up X-Ray Case II (LKH Universitätsklinikum Graz)
Figure 40: 6-Month Follow-Up Case II (Diagnostikzentrum Graz für Computertomographie und Magnetresonanztomographie)
53
After 13 months the performed MRI scan showed no changes (see Figure 41).
The results of the applied questionnaires and their course over time can be seen in Table 20.
The summary scores of the SF-36 show both a better result after 13 months compared to the
preoperative score (see Table 21).
PCS MCS
Preoperative 45.1 40.9
VAS Lysholm K. Q. TAS KOOS IKDC
Preoperative 4 48 4 62.5 48.3
After 6 Weeks 3 35 3 51.2 40.2
After 12 Weeks 3 66 4 69.6 65.5
After 6 Months 2 85 4 85.7 79.3
After 13 Months 0 94 5 85.5 82.8
Table 20: Questionnaire Results Case II
Figure 41: 13-Month Follow-Up MRI Case II (Diagnostikzentrum Graz für Computertomographie und Magnetresonanztomographie)
54
After 6 Weeks 32.7 52.4
After 12 Weeks 49.3 47.5
After 6 Months 51.9 44.1
After 13 Months 55.3 47.0 Table 21: SF-36 Summary Scores Case II
After 13 months the patient was free of pain. He had not experienced any instability since
surgery and was very satisfied with the result. All clinical ACL tests were negative and his
mobility unrestricted.
5 Discussion This study presents the first-time results of revision ACL reconstruction using an internal
brace in allografts. Previous published studies have only shown results regarding internal
bracing used in ACL repairs (85-88) or reconstructions with autografts (89).
The use of allografts in ACL reconstructions has been well-reviewed in the past.(4, 5, 56,
59) Despite the availability of a limited number of prospective, randomized, controlled
studies regarding this topic, there are a lot of meta-analyses.(58, 90-95) Most of them show
a small advantage of autografts compared to highly irradiated allografts (90, 91, 93, 94),
however, this difference disappears when comparing autografts with non-irradiated
allografts (90, 94). Grassi et al. (90) performed a meta-analysis of 32 studies regarding
revision ACL reconstruction with a minimum 2-year follow up. They showed that autografts
had better outcomes concerning laxity, complications, and re-operations when compared to
irradiated allografts, but that results no longer differed when compared to non-irradiated
grafts (90). Condello et al. (96) also found that allografts had no disadvantages compared to
autografts, provided that the tissue was not irradiated, or any radiation was minimal. High-
dose irradiation has been shown to impair mechanical strength of the graft. (96)
These findings support the use of non- or low-irradiated allografts in primary ACL
reconstructions and revision cases. However, they are mostly used in revision ACL
reconstruction. Bait et al. (97) recently published a consensus statement developed by Italian
orthopedic surgeons stating that allografts should be used as first-line graft in revision
55
situations, but not in primary reconstruction unless autografts are not available. This
recommendation is based on the overall inferior results of irradiated allografts and does not
consider non-irradiated allografts (97). Another reason for preferring reconstruction using
autografts are higher costs along with allografts. Mistry et al. (98) stated the costs of an ACL
reconstruction surgery using autografts with approximately 2250 pounds, including the
operation itself, pre- and aftercare. The costs for an allograft procedure reached 4400 pounds,
including the allograft with approximately 2250 pounds. (98)
Internal Brace (IB) fibre tape (Arthrex ©) is supposed to strengthen the whole graft construct
and protect it during the first healing phase.(9) It was tested in the repair of other ligaments
like the deltoid ligament (99), or the talofibular ligament (100), where it showed good results
and higher maximum load values than native ligaments and no significant difference in
ROM. (99, 100)
In primary ACL ruptures the Internal Brace was used to repair the native ACL. A report was
published by Arthrex © (85) showing that patients whose ACL had been repaired using an
IB, showed less pain and improved function two years postoperatively. However, due to the
lack of a control group it is not possible to say if the results of a possible reconstruction
surgery would have been better. (85) Jonkergouw et al. (87) conducted a study comparing
ACL repair with IB and without IB. They found no significant differences in outcomes
between the two groups and no failures related to the hardware. There were also no clinical
benefits, but they stated that the use of an IB could possibly be beneficial and larger cohorts
are needed to clearly answer this question. (87) In an animal study Seitz et al. (88)
demonstrated, that an augmented repair led to superior biomechanical results 16 weeks
postoperatively compared to a primary repair. (88) IB was also used in pediatric patients as
a temporary augmentation when performing an ACL repair. Smith et al. (86) used it in three
children with an ACL rupture, and removed the IB after 3 months. They reported complete
healing and stability in all three patients two years postoperatively. (86)
To our knowledge no study examining the effects of an IB augmentation in allografts used
in a revision ACL reconstruction was yet conducted. Our results show overall satisfactory
outcomes in both groups, with no relevant clinical difference. We used Achilles tendons in
both groups. The advantage of using the Achilles tendon is the availability of a bone block.
Compared to other allografts the failure rate is lower (101), it shows lower displacement,
and higher stiffness. (102) Further, the use of a bone block made a two-time approach with
56
previous bone building redundant, and the osseous fixation of the graft in the femoral tunnel
increased the overall stability of the graft. (103)
The use of an additional IB did not interfere with surgery time, being 115.9 minutes without
IB and 117.6 minutes with IB. The length of hospital stay did also not differ between the
two groups, being 5 days without IB and 5.5 days with IB. So, the use of an IB did not
lengthen surgery time or shorten hospital stay.
The lower IKDC and SF-36 subscale score for Physical Functioning in the group with IB
compared to the group without IB could be attributed to over-constriction of the graft. Smith
et al. (9) already described this phenomenon, which ultimately leads to loss of motion if the
IB is fixed too tight. (9) However, ROM in our study population was 139.5 degrees without
IB and 135.7 degrees with IB, and no patient showed relevant flexion or extension deficits
in the physical examination. No patient-reported signs of constriction of the affected knee.
The lower IKDC result in the IB group could, therefore, be just coincidental and disappear
with longer follow-up.
Our results show a mean Lysholm score of 94 without IB and 67 with IB. In current
literature, Lysholm scores ranged from 89 to 91 in autografts (92, 93) and 84.7 to 99 in
allografts (91). Respectively, these outcomes were reported after a minimum follow-up of
2-years in much larger cohorts. Although the results of the IB group seem lower, they were
not statistically significant and are likely to increase over time.
Similar results can be seen regarding the Tegner Activity Scale, ranging from 4.8 to 7.9 in
autografts and from 4.5 to 7.8 in allografts published in the meta-analysis of Wang et al.
(93). The mean TAS scores in our study were 4 in the group without IB and 3 in the group
with IB. The lower results can be easily explained, as the patients are not capable to return
to sport after just three months.
The IKDC ranges from 77.2 to 90 in autografts and 73.7 to 90 in allografts as described by
Wang et al. (93), compared to 74.7 without IB and 63.9 with IB in our study population. As
the IKDC mainly focuses on symptoms, function and sports activities (83), the low scores
after 12 weeks are not surprising. Respectively, all of our results evaluated after three months
are likely to increase over time. (see 4.5 Case Presentation).
The overall good SF-36 results in both groups could be explained by our study group being
generally healthier and younger than the compared US norm population. Considering that
the majority of ACL injuries occur to a young athletic population, and the SF-36 addresses
topics such as tiredness, sadness, and nervousness, which are more often found in a less
57
active population, these results should be viewed with caution and only be compared to
similar cohorts. (104)
5.1 Limitations and Strengths One drawback of our study is the short follow-up period of three months. The 13-month
follow-up of all included patients is supposed to deliver more detailed results. Another
drawback is the relatively small size of the study population, however this is due to the study
design of a pilot study. After sample size calculation based on our results further adequately
powered RCT will be planned. Still, based on the limited data regarding internal bracing in
current literature and lack of similar studies, our study cohort is still one of the largest.
Lifestyle factors have not been taken into consideration when forming the two study groups,
one of them being smoking habits. There was no statistically significant difference between
the two groups regarding packyears, but smoking itself interferes with healing processes,
making the study results impressionable. The activity level was also not considered during
the inclusion of the patients. Even though the difference in activity level was not statistically
significant, and there were no professional athletes included, the inter-patient differences
could affect the results.
The most prominent strength of this study is that it is the first prospective, randomized, and
blinded study regarding the use of internal braces in allografts in revision cases in current
literature. There are just a few other prospective, randomized, and blinded studies regarding
the use of allografts in revision cases, and none regarding the use of internal bracing in
allografts. Another strength is that we used the same allograft with the same processing in
all patients. Most other studies used differently processed allografts, thus making the data
hard to compare. Also, the relatively similar population in the two compared groups
regarding age and BMI strengthens the informative value of the study.
5.2 Conclusion This study provides the first HRQOL data and clinical results in patients treated with IB in
revision ACL reconstructions using allografts.
Revision ACL reconstruction using allografts with, as well as without IB, show good results
in short-term follow-up. There were no graft failures after 12 weeks in any of the groups.
The advantage of IB regarding outcome and failure rate could not yet be proven in this short
period of time. Prospective studies with larger cohorts and longer follow-up are needed.
58
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