tkr by dr. saumya agarwal
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TRANSCRIPT
TOTAL KNEE REPLACEMENT
Presenter : Dr. Saumya Agarwal
Junior resident Dept of Orthopaedics J.N .Medical College and Dr. Prabhakar
Kore Hospital and MRC, Belgaum
INDEX
• Anatomy of the knee joint
• Common conditions leading to TKR
• Evolution of TKR
• Total knee replacement
• Approaches
• Procedure
• Complications
• Computer assisted technology
• Questions
Anatomy Of The Knee Joint
• Three bones and three compartment
Knee Stabilizers
• Medial • Lateral • Anterior • Posterior • Rotatory
Osteokinematics Gross movements of bones at joints
Flexion / extension Abduction / adduction Internal rotation / external rotation
Arthrokinematics Small amplitude motions of bones at joint surface
Roll Glide (or slide) Spin
INTRODUCTION
Arthroplasty is the surgical reconstruction of a joint which aims to relieve pain , correct deformities and retain movements of a joint.
Total Knee Arthroplasty(TKA) is the surgical procedure to replace the weight-bearing surfaces of the knee joint.
Common Conditions That Lead To TKR
• OSTEOARTHRITIS Primary (idiopathic)Secondary
Post traumatic arthritis
• RHEUMATOID ARTHRITIS
Evolution of TKR
• Fergussen(1860) resection arthroplasty
• Verneuil performed first interposition arthroplasty
• 1940s- first artificial implants were tried when molds were fitted in the femoral condyle
• 1950s- combined femoral and tibial articular surface replacement appeared as simple hinges
Evolution ….
• Frank Gunston(1971), developed a metal on plastic knee replacement
• John Insall(1973), designed what has become the prototype for current total knee replacements. This was a prosthesis made of three components which would resurface all 3 surfaces of knee - the femur, tibia and patella
Classification of Implants Design
• Unconstrained – Cruciate retaining– Cruciate substituting– Mobile bearing knees
• Constrained (Hinged)
• Unicondylar Prosthesis
• Total Condylar Prosthesis
Prosthetic Design
Femoral rollback
– Posterior translation femur with flexion
– Controlled by PCL
– Improves Quad function and knee flexion
Unconstrained TKR
Cruciate retaining
Intact PCL Varus < 10 Valgus < 15
• Advantage1. Avoid post cam impingement/ dislocation2. More closely resembles knee kinematics3. Bone preserving4. Improved proprioception
• Disadvantage 1. Tight PCL – Increased poly wear2. Rupture PCL – flexion instability
Cruciate stabilized
• Cam and post mechanism• Insert more congruent / dished
AdvantagesEasier to balance kneeMore range of motion
DisadvantagesCam jumpPost wearPatellar clunk syndromeAdditional cut from distal femur
ABSOLUTE INDICATION•Previous patellectomy
•Inflammatory arthritis
•Deficient PCL
Cruciate sacrifice / retain - Evidence
PS increased ROM – No functional improvement
No difference in ROM between PS and CR
PCL does not work in CR knees
Increased wear Ps knee – cam & post
Cochrane review – No difference in function whether cruciate retained
or sacrificed
Mobile Bearing Design
• Poly Rotates over tibial base plate
• Reduced poly wear
• Bearing spin out
Fixed Bearing or mobile bearing - Evidence
• No advantage of mobile bearing over fixed bearing
• Increased wear in undersurface of mobile bearing
Constrained TKR
Constraint
– Ability of prosthesis to provide varus – valgus and flexion –extension stability in presence of ligamentous laxity / bone loss
Constrained Hinged design
• Linked femoral and tibial components
• Tibial bearing rotates around yoke
Aseptic looseningLarge amount bone
resection
INDICATIONGlobal ligamentous deficiencyHyperextension instability
Hi Flex Design
• Cultural / pt expectation
• Cut more posterior condyle
Preop flexion - most significant - Gatha etal 2008No difference in ROM - Mehin JBJS 2010
No difference in ROM Sumino Int Ortho 2010
Uni condylar TKR
Advantages of Unicondylar TKR
• Shorter rehabilitation time
• Greater average post-op range of movement
• Preservation of proprioception function of cruciate ligaments
CONTRA-INDICATIONS
a) Inflammatory conditions
b) Damage to articular cartilage
c) Flexion contracture of 5° or more
d) Preoperative arc of motion less than 90°
e) Angular deformity of more than 15°
f) ACL deficiency
Total Knee Replacement Today
• Large variety is available
• Majority of TKR today are condylar replacements which consist of the following– Cobalt-chrome alloy femoral component– Cobalt-chrome alloy or titanium tibial tray– UHMWPE tibial bearing component– UHMWPE patella component
Who Is A Candidate For TKR
• Quality of life severely affected
• Daily pain
• Restriction of ordinary activities
• Evidence of significant radiographic changes of the knee
INDICATIONS• Severe arthritis
• Young pts with systemic arthritis with multiple joint involvement
• Osteonecrosis with subchondral collapse of a femoral condyle
• Severe pain from chondrocalcinosis and pseudogout in elderly
• Severe patello femoral arthritis rarely
CONTRA-INDICATIONS
• Recent/current knee sepsis
• Remote source of ongoing infection
• Extensor mechanism discontinuity
• Recurvatum deformity secondary to muscle weakness
• Presence of painless, well functioning knee arthrodesis
What Is The Time For Replacement
• Old age with more sedentary life style
• Young patients who have limited function
• Progressive deformity
• Other treatment modalities have failed
TKR should be done before things get out of hand and the patient experiences a severe decrease in ROM, deformity, contracture, joint instability or muscle atrophy
Evaluation Of Patient Before Surgery
• A Complete Medical History
• Thorough Physical Examination
• Laboratory Work-up
• Anesthesia Assessment
34
Recommended Preoperative Radiographs in Knee Replacement Surgery
1. Standing full-length anteroposterior radiographfrom hip to ankle
2. Lateral knee x ray
3. Merchant’s view
Radiographs
• Standing Ap & Lateral• Sunrise – Merchant view
• Hip to ankle x- rays – Bony deformity– Short stature ( < 150 cm)– Very tall ( > 190 cm)
Radiographs
• Femoral and tibial cut• Position of femoral canal entry• Bone defects• Joint subluxation• Ligament stretch out – Varus Thrust • Ligament release• Constraint needed
Goal of TKR
• Pain relief
• Restoration of normal limb alignment
• Restoration of a functional range of motion
Successful Results Depends upon:
• Precise surgical technique
• Sound implant design
• Appropriate material
• Patient compliance with rehabilitation
Technical Goals Of Knee Replacement Surgery
1. The restoration of mechanical alignment
2. Preservation (or restoration) of the joint line
3. Balanced Ligaments
4. Maintaining or restoring a normal Q angle
Mechanical Alignment
TKA aims at restoring the mechanical axis of the lower limb by:Sequential soft tissue
releases
Correction of bone defects by grafts or prosthetic augments
Ligament Balancing
a. Coronal Plane– For varus deformities– For valgus deformities
b. Sagittal Plane– Flexion contractures– Extension contractures
Surgical Procedure
Procedure
Procedure
Procedure
Procedure
Procedure
Procedure
Procedure
VIDEO
APPROACHES
Medial parapatellar approach
• Most common• Surgeon are familiar
Lateral parapatellar approach
• Valgus knee• Allows access to lateral
side
• Technically demanding• Medial patellar eversion
difficult
Midvastus approach
• Spares VMO insertion
AdvantagesAccelerated rehab.Improved patellar tracking
DisadvantagesLess extensileDifficult in obese & flex
contracture
Subvastus approach• Vastus medialis lifted off
Lateral intermuscular septum
AdvantagesIntact quadPreserved vascularity of patella
DisadvantageLeast extensileDenervation of VMO possible
Femoral Cut
• Valgus cut angle• AAF – MAF
• Between 5 – 7 deg
• Intramedullary guide
Tibial Cut
• Angle between AAT – MAT
• Tibial cut angle- Zero
• Tibial deformity – cut perpendicular to MAT
• Intra or extramedullary guide
Joint line preservation• Inserting prosthesis same size as removed bone and
cartilage
Elevate joint line - mid flexion instabilityAbnormal patellofemoral trackingEquivalent to Patella Baja
Lowering joint line - Lack of full extension
Knee Balancing
• Balance in Coronal and saggital plane
• Concave side – ligaments contracted – release
• Convex side – ligaments stretched – Fill gap
Varus Knees
HenriK Schroeder – Boesch – Ligament balancing in TKR
Grade 1 release
Grade 2a release
Grade 2A
Grade 2b release
• Grade 2b release
Posterior part tight in
extensionAnterior part
tight in flexion
Grade 3 release
• Grade 2a + 2b
Grade 4 release
Valgus deformity• Osteophytes
• Lateral capsule
• Iliotibial band - Tight in extension
• Popliteus – Tight in flexion
• LCL
Pie crusting
Flexion contracture
• Osteophytes
• Posterior capsule
• Gastrocnemius ( Medial and lateral head)
• Inreased distal femoral cut
Saggital plane balancing
• Mc Pherson’s rule
Symmetric gap – address tibia
Asymmetric gap – address femur
Tight in Extension Tight in flexion
Symmetric gap Cut more tibia
Loose in Extension Loose in Flexion Symmetric gap
•Thicker poly •Tibial Metal augmentation
Extension good
Loose in flexion
Asymmetric gap
1. Increase size femoral component
2. Translate femoral component posterior
3. Use thicker poly and readdress as tight extension gap
Extension Tight
Flexion Good
Asymmetric Gap 1. Cut more distal femur
2. Release posterior capsule
Extension Good
Flexion Tight
Asymmetric gap 1. Decrease femoral component size
2. Recess PCL
3. Check slope of tibia
Extension Loose
Flexion Good
Asymmetric gap 1. Distal femoral augmentation
2. Decrease femoral component size and thicker poly
Patellofemoral Alignment
• Most common complication
• Maintain Q angle
• Proper component rotation
• Maintain normal patellofemoral tension
• Maintain Q angle
Avoid 1. Int rotn fem
component2. Medial rotn fem
component3. Int rotn tibia4. Patella prosthesis
lateral rotn
Femoral component rotation
• Ap Axis ( whiteside line)• Transepicondylar axis• Post condylar axis• Tibial alignment axis• Gap balance
Tibial component
• Int rotn tibia – increased Q angle
Patellar component
• Centre or medialized
• Avoid lateralizing
• Increases Q angle and cause patella maltracking
Patella Baja
• Patellar component superior
• Lower joint line
• Transfer tibial tubercle cephalad
• Patellectomy
Patella resurfacing vs non resurfacing
• Resurfacing
– Component loosening– Clunk– Fracture– AVN
• Non resurfacing
– Anterior knee pain– May require second
resurfacing
Patellar resurfacing Vs non resurfacing - Evidence
• Metal backed patella higher complications
• Patellar replacement does not gurantee painless Patellofemoral joint
• No significant benefit of patellar replacement
Complication
• Femoral notch
Saw cuts into anterior femoral cortexIncreases chance of periprosthetic fracture
Femoral stem extension
Complication
Peroneal Nerve palsy ( .3 to 2 %)
Pre op Flexion and Valgus Tourniquete time > 120 min.Epidural anaesthesia post opAberrant retractor placement
EMG & NCV at 3 months
Nerve decompression at 3 months
Complication
• Vascular complication ( <.17% - .2%)
• Risk factor– Sharp dissection– Posterior retractor placement– Pre existing vascular disease
– Immediate vascular repair
Complication
• Extensor mechanism rupture ( .17% - 2.5% )
– Direct repair with suture - < 30 % avulsion
– Primary repair and augment with graft
– Allograft repair
Complication
• Stiffness– Flexion contracture 10 – 15 % deg– Flexion < 90 deg
• Treatment– Manipulation under Anaesthesia– Arthroscopic lysis of adhesion– Revision TKR
Complication
• Hypersensitivity Rare ( nickel)
• Patch testing • Lymphocyte transformation test
• Revise to non allergic metal prosthesis
Summary
• Choose correct pt
• Plan properly
• Adequate exposure
• Follow principles to align and balance knee
• Meticulous closure
Hope for the best because 20 % of pt. with well performed TKR are not happy !!
Post Operative Rehabilitation– Rapid post-operative mobilization
• Range of motion exercises started• CPM• Passive extension by placing pillow under foot• Flexion- by dangling the legs over the side of
bed• Muscle strengthening exercises• Weight bearing is allowed on first post op day
Prosthesis Survival
Different studies shows different results
• Ranawat et al (Clin Orthop Relat Res ) 95% at 15 years
91% at 21 years• Gill and Joshi (Am J Knee Surg) 96% at 15 years 82% at 23 years• Font-Rodriguez (Clin Orthop Relat Res )
98% at 14 years
• The technique involves the attachment of active or passive trackers on femur and tibia, which are then tracked by a computer-assisted camera.
• Computer gives real-time feedback about alignment of bony cuts in all three anatomic planes, which allows surgeon to make changes and to measure the accuracy of the bony cuts.
• Computer navigation systems also can aid in determin ing the proper implant size as well as alignment. Soft tissue balancing and measurement of flexion and extension gaps during the procedure are other significant advantages to computer-assisted TKA.
• Objective measurement of the gaps ensures proper soft tissue balancing and gaps that will provide a stable joint throughout a range of motion.
• Another advantage of computer navigation is avoidance of violation of the femoral intramedullary canal, which may reduce blood loss and cardiac-related complications because fewer emboli are placed into the venous system than with placement of an intramedullary alignment rod.
Questions in exams ??Long Question?1) Describe in detail about the kinematics of knee and
enumerate the indications, procedure and complications of TKR
Short Questions? 1) Approaches for TKR 2) Hi flexion type implant in TKR 3) Computer assisted technology for TKR 4) Complications post TKR