According to the research team at Rigshospitalet-Copenhagen University Hospital, patellofemoral arthroplasty has clearly demonstrated advantages over total knee arthroplasty (TKA) in the short run, but, they wondered, can those advantages be sustained over the medium term—six years, specifically?
The results of this impressive six-year follow-up study, “Patellofemoral Arthroplasty Results in Better Time-weighted Patient-reported Outcomes After 6 Years than TKA: A Randomized Controlled Trial,” has been published in the September 2022 edition of Clinical Orthopaedics and Related Research.
Anders Odgaard, DMSc, FRCS (Eng), professor and consultant orthopaedic surgeon at Rigshospitalet – Copenhagen University Hospital described the background of the study to OTW, “We initiated this randomized clinical trial in 2007, at a time when there was debate over which implant would give the better results for isolated patellofemoral osteoarthritis: total knee replacement or a partial knee replacement for the patellofemoral joint.”
“My colleagues and I were intrigued by the large discrepancy between register results and our own results from using patellofemoral arthroplasty. To provide good scientific data to improve decision making, we decided to design a study to answer our research question of ‘Which implant is the better?’”
The researchers found that patients in the patellofemoral arthroplasty group experienced more improvements in the 36-Item Short Form Health Survey (SF-36) bodily pain score during the first six years than those in the TKA group; the same was true for SF-36 physical, Knee Injury and Osteoarthritis Outcome Score (KOOS) symptoms, KOOS Sport/recreation, and Oxford Knee Score.
“There are three important findings,” stated Dr Odgaard to OTW.
- “First, we have proven that patients with patellofemoral arthroplasty recover faster than patients operated with a TKA.”
- “Second, patellofemoral arthroplasty and TKA patients appear to obtain the same level of quality after some years.”
- “Third, there is no deterioration of quality of life during the first six years. Thus, the 50 patients who were operated with a patellofemoral arthroplasty have had a higher overall quality of life improvement than the 50 patients operated with a TKA.”
“If one looks at the result at six years only, without considering the early advantage of patellofemoral arthroplasty, there appears to be no real difference between the implant types. To some, the latter may be taken as an argument that it does not matter which implant is used, but this would ignore the months to years with a better knee-specific quality of life in the patellofemoral arthroplasty group.”
Quality of Patient Life or Higher Risk of Revision?
“We have found a six-year revision rate of 10% and 4% for the patellofemoral arthroplasty and TKA patients, respectively. Although this difference is not statistically significant, it is likely that the patellofemoral arthroplasty patients will have a higher revision rate over the years to come. Nevertheless, we believe that the right measure of outcome should be the quality of life and not revision rates, and it should be noted that we follow our patients and analyze their results irrespective of a possible later revision (intention-to-treat analysis).”
“Another important conclusion is that register data that aims at comparing different implant types should be interpreted with caution. Patients treated with different implant types may be treated for different conditions, and they may more importantly be revised for different reasons.”
Strong Scientific Evidence and Caveats
“Our study is the best scientific evidence for the relative merits of patellofemoral arthroplasty over TKA, and we hope that this will have the effect that patellofemoral arthroplasty rather than TKA is considered for patients with severe symptoms caused by isolated patellofemoral osteoarthritis when conservative measures have been unsuccessful. But we also warn that indications should not be taken lightly.”
“Patellofemoral arthroplasty should generally not be performed for chondromalacia or patellofemoral pain. We also believe that the patellofemoral arthroplasty procedure should only be performed by surgeons, who have a special interest in the patellofemoral joint, and who do a fair number of these procedures.”
