REVISION TOTAL KNEE ARTHROPLASTY

Abstract

Total knee arthroplasty is a predictable operation. Unfortunately, there is a subset of patients who do not well and require revision surgery. The surgical objective of revision total knee arthroplasty is the same as primary total knee arthroplasty: restore the original anatomy, restore function and provide a stable joint. The operation technique itself is a decisive for the success of arthroplasty as any type of malalignment may result in pain, instability or loosening of the implant.

1. REASONS OF FAILURE

The most important reason for revision total knee arthroplasty include aseptic loosening of one or both components. Early loosenings occur frequently as failures of ingrowth of a porous coated implant, while late loosenings mainly concentrate on cemented components, predominantly the tibial part. Another major reason for knee arthroplasties to fail is instability between the femur and tibia, caused by incorrect alignment or laxacity of the ligaments. Wear and osteolysis are the result of abnormally increased abrasion and plastic deformation of the polyethylene inlay. Usually this is a sequela of overloading through subluxation or deformity. It generally happens when the weight-bearing contact surfaces are small.

Pain around the patella may occur due to anterior displacmenet of the patellofemoral joint and is not related whether the patella remains natural or is totally replaced.

Rare complications are fatigue fractures of metallic components, femoral or tibial fractures around the implant, extreme limitation of motion or hyperextension of the joint.

The most severe complication is periprosthetic infection, which in most of the cases requires a one or two-stage revision procedure to replace the implant.

2. GOALS OF REVISION SURGERY

Correct axial and rotational alignment including the restoration of the right joint line is mandatory for the success of a revision total knee arthroplasty. Especially joint line elevation can result in functional disorders, therefore the use of distal femoral augmentation in revision has given more attention.

Balance of soft tissues to create equal flexion and extension spaces is another mandatory goal for revisions. Soft tissue releases can usually correct fixed angular deformities. Concerning balance by additional cuts of femoral or tibial bone one has to remember that adjustments on the femoral side can effect the knee in flexion or extension, whereas any adjustment on the tibial side will effect both. Minimize bone resection and achieving stability by stable fixation of all components of the implant are further prerequisits for the success of revision surgery.

Another criteria for success is correct patella tracking, which can on the one hand be solved by soft tissue procedures or by revising the implant. Even one has to change the femoral and tibial component, retaining a well fixed patella component appears to be a suitable option.

One of the most important criteria in revision total knee arthroplasty is implant selection. Recent publications have demonstrated that the implant-related failure rate was 25% when using implants designed for primary total knee arthroplasty, the failure rate of modified primary components was 14% and if components were used specially designed for revision the implant-related failure rate dropped to 6%. It was evident that revision implants exhibited superior performance and durability despite their use in more difficult reconstructions.

Concerning wear and osteolysis one should consider that an isolated revision of an polyethylene insert should not be performed when there is accelerated wear of the insert with severe delamination and radiographically under surface osteolysis.

The major objectives of bone grafting or augmentation blocks are filling in bony defects with biomechanically stable components to allow weight bearing and functional motion, to create an equal flexion and extension space for ligamentous stability and to restore a nearly anatomic joint line.

The use of intramedullary stems at revision surgery provides fixation of components into diaphyseal bone leading to increased stability for reconstruction. It produces axial alignment, the stems also partially relieve stresses on the deficient metaphyseal bone or allograft.

3. TREATMENT OF INFECTION

The incidence of periprosthetic infections is rather low. In early infections antibiotic treatment combined with open arthrotomy including debridement and exchange of inlay are the treatments of choice.

Late infections are best treated combining antibiotics and two stage exchange arthroplasty. Arthrodeses or amputations are extremely rare to indicate.

4. REVISIONS WITHOUT REPLACING THE IMPLANT

Many of these procedures belong to the patella including the removal of osteophytes, secondary release of the lateral patella retinaculum, secondary replacing the patella with an implant, or patellectomy.

The replacement of a worn tibial inlay is often combined with secondary synovectomy, sometimes heterotopic ossifications need to be removed for the improvement of mobility. In infected knees the placement of an inflow/outflow drain in an attempt to manage an acute periprosthetic infection or to provide relief of pain in the presence of sepsis.