Failure Analysis of Patellofemoral Arthroplasty

Study Overview
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Brief Summary
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The purpose of the retrospective cohort study is 1) to determine preoperative risk factors for revision af patellofemoral arthroplasty, and 2) to provide a detailed description of indications for revision after patellofemoral arthroplasty. All patients operated with patellofemoral arthroplasty in Denmark from January 1, 2008 to December 31, 2015, will be included in the cohort.

Detailed Description
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Approx. 11,000 operations with the insertion of a knee arthroplasty (knee prosthesis) are performed annually DK. The durability and quality of the treatment are assessed with prosthesis survival, that expresses the proportion of prostheses that are still functional after a given number of years (eg the 10-year prosthesis survival for all types of knee prostheses in DK is approximately 94%). Unicompartmental implants are increasingly used, so that only the worn part of the knee is replaced. Especially for osteoarthritis between the patella and the femur, a patellofemoral prosthesis (PFA - patellofemoral alloplasty) can be inserted, which is much smaller than the traditional full prosthesis (TKA - total knee arthroplasty). PFA operations are controversial. A recently published Danish study (double-blind RCT) comparing TKA and PFA has shown that PFA patients achieve greater satisfaction, better knee function and greater quality of life than TKA patients. A recent study has also demonstrated that the cost of a PFA procedure is less than that of a TKA. As a paradox to this clear RCT finding, all national implant registers (Sweden, England, New Zealand, Denmark, etc.) show a significantly poorer prosthesis survival for PFA compared with TKA. It is important for the future treatment of patients with severe osteoarthritis between the patella and femur to understand the cause of the discrepancy between RCT and registry results. The discrepancy gives rise to a number of questions regarding. indications, techniques, competences, postoperative regimens etc. The divergence between the RCT and registry studies can only be clarified by a study that 1) examines the influence of preperative factors (patient history, physical findings, radiology etc.) on outcome, and that 2) attempts a causal analysis for each reoperation. The investigators intend to do this though a cohort study including all cases of patellofemoral arthroplasty performed in Denmark from January 1, 2008 until December 31, 2015. The purpose is to determine preoperative risk factors for revision after PFA and to provide a detailed description of indications for revision after PFA.

Official Title
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Failure Analysis of Patellofemoral Arthroplasty

Conditions
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Patellofemoral Osteoarthritis, Arthroplasty Complications, Knee Osteoarthritis

Intervention / Treatment
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* Device: Patellofemoral arthroplasty


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Patellofemoral arthroplasty Primary procedure performed between Jan 1 2008 and Dec 31 2015 Primary procedure performed in Denmark Exclusion Criteria: Patella-nail syndrome Dislocating tendon following patellectomy.
Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| PFA<br>The cohort consists of all patients operated with patellofemoral arthroplasty for isolated patellofemoral osteoarthritis in Denmark from Jan 1 2008 to Dec 31 2015. The number of patients is expected to be around 500. A patellofemoral arthroplasty is defined as an arthroplasty consisting of a metal trochlear component and a polyethylene patella component. The definition of isolated patellofemoral osteoarthritis in the study is pragmatic and given by the operating surgeon. | Device: Patellofemoral arthroplasty<br>* Insertion of an artificial joint between the front of the femur and the back of the patella. The femoral component consists of a metal implant, and the patellar component is a polyethylene implant. The two components replace the original articular cartilage of the patellofemoral joint.<br>* Other names: Artificial joint between knee cap and thigh bone;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Implant revision and reoperation rates | The proportion of revised and reoperated patients | 10-year | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| The 6-year cumulative revision rate | The 6-year cumulative revision rate of patellofemoral arthroplasties in a target trial comparing two groups of surgeons: 1) those surgeons, who were a part of a randomised clinical trial comparing PFA and TKA, and 2) other surgeons. In addition to this, the 6-year cumulative reoperation rate (other than revision) and the 6-year cumulative mortality rate will also be reported. | 6 years | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Patellofemoral arthroplasty, Knee revision surgery, Indication