CORR Insights®: How do knee implants perform past the second decade? Nineteen- to 25-year followup of the Press-fit Condylar design TKA.

Abstract

Where Are We Now? In the last three decades, TKA has established its position as the gold standard surgical treatment for severe, symptomatic knee osteoarthritis (OA). Although TKA is common procedure, published studies with long-term clinical and radiological followup are few [2, 6]. In register studies, there has been a constant reduction in risk of revision over time [8]. For example, a patient who had an operation in 2000 has a lower risk for revision than the patient who had a similar operation in 1990 with a similar followup time. Challenges with TKA — perhaps even more than THA — are more related to function and patient satisfaction [10]. The number of of TKAs are increasing in developed countries, especially among young patients with primary knee OA [5, 7]. Therefore, there is a clear need for publications with long-term clinical and radiological followup. Where Do We Need To Go? In the current study, Papil el al. report the results of the Press-fit Condylar TKA system (DePuy Orthopaedics, Warsaw, IN, USA) in 160 TKAs performed between 1986 and 1989. The authors noted an 87% survivorship for revision for any reason (95% CI, 80%-92%), and a 98% Kaplan-Meier survivorship for revision for aseptic loosening (95% CI, 93%-99%) at the mean 20-year followup (range, 19-25 years). The Knee Society Score did not seem to provide useful information regarding long-term outcome in older patients, since, as expected, the score decreased over time as occurs with normal aging. Also, there was substantial loss to radiographic followup in this report, and more detailed radiological analysis would have provided useful information on polyethylene wear and subsequent osteolysis. In their study, Papil el al. found aseptic loosening to be uncommon, justifying the continued use of cemented TKAs. Additionally, the number of revisions from polyethylene wear was also low. Currently, use of new designs such as uncemented TKA implants and crosslinked polyethylene inserts is increasing [1, 8]. However, polyethylene wear and aseptic loosening seem to be uncommon. On the other hand, there is a need to improve functional outcome after TKA. Moving forward, we must provide more scientific data to support the use of new TKA innovations. How Do We Get There? Further prospective, randomized clinical studies are needed to compare uncemented and cemented TKA implants with similar polyethylene characteristics. In addition, there is a need for prospective randomized clinical studies comparing conventional polyethylene inserts with crosslinked polyethylene liners used in same implant in order to avoid bias caused differences in the implant geometry. Long-term studies providing data on patient reported outcome measures such as the WOMAC [4], Oxford Knee Score [3], and Short Form-12 (SF-12) [9] would also be useful. In the future, we should focus on maximizing knee function and patient satisfaction by improving the function of TKA implants.