periprosthetic fractures of knee

PERIPROSTHETIC FRACTURES OF KNEE

Dr. A.SUPRAJA Post graduate

Department of orthopaedicsGandhi Medical College

PERIPROSTHETIC FRACTURES AROUND KNEEIncidence:Primary TKA – 0.3-2.5%Revision TKA- 1.6-38%

RISK FACTORS

Patient relatedAge RA( inflammatory arthropathy)Osteoporosis/osteopenia/osteolysisChronic steroid therapyNeurological disordersMetabolic bone disordersInfectionAxial mal alignmentFemale gender

TKA periprosthetic fractures

S.C # TIBIA # PATELLA #

SURGERY RELATED

• Press fit in non cemented stems with sharp edges results in increased interfacial stress• Supracondylar fractures• Anterior femoral notching weakens the anterior femur at the base component interface• Tibial fractures• Tibial broaching and punch instrumentation for keeled implants ,removal of well fixed

implants and cement, aggressive retraction , osteotomy of tibial tubercle.• Keeled pressfit long stemmed tibial components• P.O.- Varus positioning and malrotation of the tibial component

• Patellar fractures:• Axial extremity deformities or malalignment of the prosthesis• Extensive resection of patella < 15mm- compromises the mechanical strength• Metal backed noncemented patella and components with large central pegs• Heat necrosis

Preop evaluation

• Age: geriatric giants– instability, immobility, incontinence,intellectual decline, iatrogenic problems, isolation,inappetance.

• Rule out – anaemia, platelets/ coagulation / metabolic disorders, cardiovascular/ pulmonary diseases, DM,renal insufficiency, malnutrition, parkinsons, neurological disorders, polymedication.

• Fragility syndrome- increased vulnerability to external and internal stress factors

• Sarcopenia-age related muscle loss and its devastating effects on physical activity and independence in elderly

• Osteoporosis- FRAX (WHO Fracture Risk Assesment Tool)- fast screening tool

• Bone density measured both at the level of lumbar spine and femoral neck < threshold provided by the referance value.

• Osteopenia- T-SCORE- 1.0-2.5• Osteoporosis- T-SCORE >2.5

ASSESSMENT

• Clinical suspision• Prosthesis is stable or not• ASA score-• Infection- CRP/ ESR• Implants to be extracted• DEXA- gold standard- singhs index is obsolute• SUSPECT A FRACTURE UNTIL PROVEN

OTHERWISE

• Diagnostic imaging• Plain x-rays• CT• MRI

CLASSIFICATION

Femoral fractures

UNIFIED CLASSIFICATION SYSTEM

• DISTAL FEMUR V.3

• Type A: varus/valgus injuries

• A1 -lateral condyle fracture• A2- medial condyle fracture• Mx- conservative brace – fixation if displaced

• Type B• B1- femoral component well fixed and functioning before

injury Mx- fixation devices- depending on position and configuration

of fracture & design of femoral component• B2-implant loose- bone stock good Mx- stemmed femoral revision/ +/- additional osteosynthesis• B3-loose implant and bone loss Mx- structural allografts, augments, sleeves, modular

oncology implants

• Type C Proximal to implant or stem Mx- principalas of osteosyntheis• Type D- Interprosthetic or intercalary Mx- fracture should be analysed separately in each context and managed

accordingly• Type E Involve 3 or more implant bearing bones Mx- fracture should be analysed separately in each context and managed

accordingly• Type F Does not pertain to distal femur as not a part off standard orthopaedic practice

Tibial fractures

FELIX CLASSIFICATION

PROXIMAL TIBIA(UCS)• Type A Avulsion injuries of tibial tubercle Mx- conservative brace – fixation if displaced/ extensor mechanism is displaced• Type B

• B1-implant well fixed and functioning before injury Mx-rigid cast immobilisation- non displaced / minimally displaced Medial tibial plateaue fractures –mc +/_ trauma Undisplaced- nonsurgical I.O.- ORIF

• B2- implant loose and good bone stock Mx- stemmed tibial revision

• B3- loose implant , bone loss Mx- complex reconstruction

• Type C Distal to implant or stem Due to trauma , stress fractures, tibial tubercle osteotomy, improper implant orientation Mx- closed manipulation/ ORIF + bone grafting

• Type D Between knee and ankle replacement Mx- fracture should be analysed separately in each context and managed accordingly

• Type E Tibia/ patella/ femur Mx- fracture should be analysed separately in each context and managed accordingly

• Type F Does not pertain to tibia as femoral hemiarthoplasty is not a part off standard

orthopaedic practice

Patellar fractures

PATELLA V 3.4• Type A Proximal or distal pole of patella Mx- integrity of extensor mechanism Repair +/_ partial patellectomy Locking stich / TBW• Type B B1 Implant well fixed , extensor mechanism intact Mx- cylindrical cast / locked knee brace in extension – 6weeks with immediate weight bearing < 2mm displacement transverse fracture- non operative Vertical stable- rarly effects extensor mechanism B2 Platellar component loose Mx- remove implant , repair of extensor mechanism B3- Bone loss Mx- resection arthroplasty

• Type C Small size – does not pertain to patella Poles or apophysis- type A• Type D does not pertain to patella Bone can support only one implant• Type E Tibia/ patella/ femur• Type F Fracture of patella after partial replacement of knee

without surface replacement of patella Prior intervention could be patellofemoral

hemiarthoplasty, unicompartmental / bicompartmental replacement

Management

• Decision making Non operative Internal fixation Revision arthroplasty Alternative complex fixation texhniques

• Preopertive planning Careful general assesment Multidisciplinary approach Pheripheral neurogical status DVT prophylaxis I.O. – embolisation Image intensifier- mandatory

Post op management

• Geriatric consultants• Early mobilisation• Success of rehabilitation efforts depend upon

quality of surgical procedure

Operative/ nonoperative management

• Fracture type , location and degree of displacement• Stability of fracture& prosthetic implant• Soft tissue condition• Neurovascular status• Fracture pattern(short oblique or transverse)• Risk of secondary displacement• Risk of damaging surrounding soft tissue• Risk of damaging surrounding neurovascular

structures

• Patient related General health status Functional demand Anticipated level of post op compliance Joint function Concommitant neurological injuries BONE RELATED Quality of bone stock Cortical thinning – excessive reaming of medial cortex /

osteolysis

Management

Femoral fractures• Surgery main option for peri& interprosthetic

fracture Undisplaced- conservative• Implant status to be evaluated- Loose implant – revision• History of long standing pain and discomfort• Prosthetic implant to be identified and

operative report of the index operation

• Strong bone – laterally placed blade plate with Locking screw plate device

• Fragile – additional medial plate , bone strut , bone cement

• Degree of osteoporosis – influence fixation technique

• Locked screws and fixed angle blade plates

INTRAMEDULLARY NAIL

• Biomechanaically ideal- comminuted supracondylar fracture with poor possibility of buttresing and mediocre bone quality

• Locked- proximally and distally with bicortical screws or distally with a spiral blade

• At the level of femoral component- nail should reach as far as middle of diaphysis

• Possible with open design• Exceptional cases – antegrade nail• Not procedure of choice with closed box implants and

proximal intramedullary device in place

• Approach• Supine- bolsters to prop up

knee• Midline skin incision with

parapatellar arthrotomy• Lateral incision with tibial

tuberosity osteotomy - rarely

• Best- go through the same approach < 1 year after primary surgery

Plate osteosynthesis

• Well fixed prosthesis- long bridging plate with LHS

• Open/ MIPO• PRINCIPALS: Restoring anatomical axes(roataions) Rigid fixation of articular segments Relative stability for bridging of diaphyseal

communication Atraumatic soft tissue handling

• Length of LISS communited fractures- 2-3 times length of fracture

zone Transverse / short oblique- 8-10 times

• Lateral LCP- medial buttresing is to be addressed• Low distal femoral prosthetic fractures/ posteriorly

stabilised component design just above the central box- arthroplasty

Basic principal

• Plate must be as long as the entire femur inorder to overlap the exsisting intramedullary implants

• Overlap should be at least half the length of the entire intramedullary implant

• proximal (Short )stem – plate may be solidly fixed with multiple bicortical screws in diaphysis before it overlaps with implanted stem

• long stem- monocortical screws, augmented by cerclage wires, cables,or the new locking-attachment plate (LAP)

REVISION ARTHROPLASTY

• MODULAR REVISION PROSTHESES with long intramedullary stems that will allow early movement and (partial) weight bearing- Depending on the extent of the fracture and the quality of the bone.

• Ipsilateral hip prosthesis-long stem can lead to stress risers• stem of the revision endo prosthesis should bridge

the fracture zone by at least two widths of the diaphysis

• stem of the prosthesis shouldbe inserted without cement, thereby preventing the risk of cement leaking into the fracture gaps

• Osteoporotic- cement to be used• fracture is unstable-explore the fracture during

the revision surgery, reducing the fragments and fixing them with a temporary external-fixator frame supplemented by an adequately positioned plate that is held in place by Verbrugge forceps

• insufficient bone stock-morselized allograft bone, implant sleeves, tumor prostheses (megaprosthesis), or structural allografts

• Tumor prostheses for distal femoral replacement and/or proximal tibial replacement usually show higher rates of loosening, especially in young. physically active patients,which makes this type of prosthesis more suitable for treating peri prosthetic fractures in older patients with lower levels of activity

PATELLAR FRACTURES

• Goal- restore the extensor mechanism• Simple fractures- TBW• 2 staged revision arthroplasty- as remaining

bone stock is often too poor for reimplantation• 1. resection arthroplasty with smoothing of the

contact surfaces of the old retropatellar replacement and fracture fixation

• 2. secondary retropatellar replacement after fracture healing

Open fractures of patella

• 2 stage • 1. aggressive algorithm consisting of

explantation of the arthroplasty, debridement, placement of an antibiotic spacer, and

osteosynthesis of the patella• 2. after fracture healing of the patella-revision

arthroplasty

• Results- poor• Non- union extensor lag

PROXIMAL TIBIA• most challenging and difficult to treat as the proximal

fragment is often small and of poor bone quality• least common• RISK FACTORS:• • Malpositioning of the prosthesis in varus or valgus

position• • Noncemented implants• • Poor knee function due to ligamentous imbalance• • Previous revision arthroplasty• • Joint stiffness• • Inflammation or infection.

• typically fatigue fractures resulting in an impaction or depression. or a split of the tibial plateau and involve the interface between the

tibial tray component and bone• fractures heal with increasing varus deformity and

knee pain• metallic or bony augmentation- insufficient bone

quality• rare complication-fracture of the tibial plateau during

or after surgery with subsidence of the prosthesis

• lateral ligaments – stable- unconstrained surface replacement prosthesis with a lengthened stem of the tibial component

• Lateral ligaments- UNSTABLE- semiconstrained prostheses with an appropriate stem and

spacers• large segmental bone defects, stem prostheses

with sleeves and/or structural allografts

• Injuries that involve the extensor mechanism or fractures of the tibial tuberosity (type A2) frequently occur after extensive dissection- goal is the restoration of the extensor mechanism.

IMPLANT EXTRACTION

• Femoral- first better clerance for tibial component

extraction chances of femoral condyle fracture cemented- osteotome is directed at prosthesis

cement interface rather than cement bone interface

cement easily extracted from surface ofbone

• SLAP HAMMER- longitudinal force is delivered• Never tilt the component by pheripheral

blows- fracture of condyle• If prosthesis is still not coming- osteotome

TIBIAL COMPONENT

• Polyethylene tibial component- oscillating saw cuts through the stem allowing acess to bone cement interface

• Metal backed tibial components-freeing the undersurface of tibial base plate allows component extraction without bone loss

• Long stem/ extensive cement fixation/ porous ingrowth surface- long tibial tubercle osteotomy

• Tibial base plate- cot with diamond tipped saw

Patellar componenet• Tear of patellofemoral interface- removal• Bone cement- oscillating saw

• Remaining fixation pegs- small curette/ burr• Metal backed- difficult to remove

• Small osteotome to fit between fixation lugs• Base plate- cut with a Diamond Tipped Saw