Abstract
PurposeThe purpose of this study is to analyse long-term unicompartmental knee arthroplasty (UKA) focusing on survivorship, causes of failure and revision strategy.MethodsThis study is a retrospective analysis of data from a regional arthroplasty registry for cases performed between 2000 and 2017. A total of 6453 UKAs were identified and the following information was analysed: demographic data, diagnosis leading to primary implant, survivorship, complication rate, causes of failure, revision strategies. UKA registry data were compared with total knee arthroplasty (TKA) registry data of 54,012 prostheses, which were implanted in the same time period.Results6453 UKAs were included in the study: the vast majority of them (84.4%) were implanted due to primary osteoarthritis followed by deformity (7.1%) and necrosis of the condyle (5.1%). When compared to TKA, UKA showed lower perioperative complication rate (0.3% compared to 0.6%) but higher revision rate (18.2% at 15 years, compared to 6.2% for TKA). No correlation was found between diagnosis leading to primary implant and prosthesis survival. The most frequent cause of failure was total aseptic loosening (37.4%), followed by pain without loosening (19.8%). Of the 620 UKAs requiring revision, 485 were revised with a TKA and 61 of them required a re-revision; on the other hand, of the 35 cases where another UKA was implanted, 16 required a re-revision.ConclusionUKA is associated with fewer perioperative complications but higher revision rates when compared to TKA. Its survivorship is not affected by the diagnosis leading to primary implant. Revision surgery of a failed UKA should be performed implanting a TKA, which is associated with a lower re-revision rate when compared to another UKA.Level of evidenceLevel 3, therapeutic study.
Highlights
Unicompartmental knee arthroplasty (UKA) was introduced in the 1970s as an alternative to total knee arthroplasty (TKA) for single-compartment osteoarthritis (OA) of the knee [24]
UKA registry data were compared with total knee arthroplasty (TKA) registry data of 54,012 prostheses, which were implanted in the same time period
UKA surgery showed lower perioperative complication rate when compared to TKA (Table 1); both intraoperative and postoperative complications were more frequent in TKA (321/54,012 procedures; 0.6%) compared to UKA (20/6,453 procedures; 0.3%), p = 0.004
Summary
Unicompartmental knee arthroplasty (UKA) was introduced in the 1970s as an alternative to total knee arthroplasty (TKA) for single-compartment osteoarthritis (OA) of the knee [24]. The well-known advantages of this type of implant over TKA include bone stock and soft tissue preservation, central pivot retaining, earlier recovery, and better functional outcome [1, 37]; patients report a subjective feeling of a more natural knee when compared to TKA [36, 37]. In the last two decades, there has been a growing interest in the use of UKA implants [13, 37]. Despite the overall encouraging results, UKAs still show a relatively higher revision rate compared to TKA implants. The type and incidence of perioperative complications depend on the type and design of implants, in the follow-up period, and on the expertise of the surgeon performing the procedure [14, 15]
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