The Mid- to Long-Term Outcomes of the Lateral Domed Oxford Unicompartmental Knee Replacement: An Analysis From the National Joint Registry for England, Wales, Northern Ireland, and the Isle of Man

Abstract

Background: Lateral unicompartmental knee replacement (UKR) is an alternative to total knee replacement for isolated lateral unicompartmental knee arthritis. The geometry and mechanics of the lateral compartment differ to the medial compartment with the Lateral Domed Oxford UKR designed to address this. We used National Joint Registry (NJR) data to report the mid to long term outcomes of this device. Methods:We performed a retrospective observational study using NJR data on 992 Lateral Domed Oxford UKRs implanted between 1 st January 2005 and 31 st December 2017.Outcomes of interest were implant survival and revision indications. Results:The 10 year cumulative implant survival rates were 88.6% (CI 85.3-91.2). When compared to <55 year age group, the 55-64, 65-74 and ≥75 groups had significantly lower revision rates (Hazard Ratio (HR)=0.56 (CI 0.32-0.98, p=0.04), HR 0.40 (CI 0.22-0.72, p=0.003) and HR 0.27 (CI 0.12-0.58, p=0.001) respectively). The obese group had significantly (p=0.04) increased revision risk compared to normal BMI (HR 2.33, CI 1.06-5.12). The commonest reasons for revision surgery were dislocation (n=23, 2.3%), pain (n=15, 1.5%) and aseptic loosening (n=14, 1.4%). Conclusion:The Lateral Domed Oxford UKR provides a good option for isolated lateral compartment osteoarthritis. However dislocation of the mobile bearing remains a problem, occurring in 2.3% of the patients and accounting for 30% of the revisions. To help prevent dislocation it is now possible to assess bearing stability intra-operatively and if very unstable to implant a compatible fixed bearing tibial component, without the need for further bone preparation.

Disease progression, aseptic loosening and bearing dislocations are the main revision indications after lateral unicompartmental knee arthroplasty: a systematic review

“…Following the removal of duplicates and screening, a total of 117 full-text records were obtained and assessed for eligibility. A total of 29 cohort [8,14,18,, 3 registry studies [51][52][53] and one registry [54], which included 7,668 UKAs, were selected for analysis (Table 1). Whilst a further seven studies met the inclusion and exclusion criteria, these were found to be overlapping reports of the same study cohort and were excluded.…”

“…Data from 32 studies were available to compare mobile-bearing vs. fixed-bearing implants; 10 studies (n ¼ 2,268) with mobile-bearing implants [14,18,28,32,33,37,38,41,50,53], 18 studies (n ¼ 1,469) with fixed-bearing [8,26,[42][43][44][45][46][47][48][49]27,30,31,[34][35][36]39,40] and 4 additional studies that reported outcomes for both (n ¼ 1,743 mobile-bearing, n ¼ 790 fixed-bearing) [25,29,46,51]. 18 studies had a moderate risk of bias [8,18,[44][45][46][47][48][49][50]53,26,31,33,34,37,39,42,…”

“…Data from 15 studies reported the use of all-PE vs. metal-backed fixedbearing implants; 5 studies (n ¼ 267) with all-PE implants [25,34,36,40,53]; 10 studies (n ¼ 660) with metal-baked implants [8,26,27,29,39,[42][43][44][45][46]. Nine studies had a moderate risk of bias [8,26,34,39,[42][43][44][45][46] and six studies had a serious risk of bias [25,27,29,30,36,40].…”

Midterm Outcomes in Lateral Unicompartment Knee Replacement: The Effect of Patient Age and Bearing Choice

“…In the review of the current literature, there are seven series reporting on lateral UKA survivorship of 10 years or more with survival ranging from 83 to 100%. 5,6,[15][16][17] While these published rates are certainly lower than those reported for TKA, it is critical when reviewing published reports because the readers take into account the age of the cohort and length of follow-up in various studies. Our median follow-up was close to 9 years with a median age of 55 years, both factors consistent with higher revision rates.…”

Survival of lateral unicompartmental knee arthroplasty at short‐, mid‐, and long‐term follow‐up: a systematic review and meta‐analysis

“…A majority of included papers (85%) were Europebased, with 3 conducted in the USA and one in China. There were two registry-based studies 17,28 without providing surgical details; three papers 7,8,37 were multiple-centered and the remaining were single-institution studies. Regarding surgeries, most lateral UKAs were performed using the lateral approach and 702 lateral UKAs from 10 papers (38.5%) were performed by one surgeon.…”