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New surgical instrumentation reduces the revision rate of Unicompartmental Knee Replacement: A propensity score matched comparison of 15,906 knees from the National Joint Registry

Research output: Contribution to journalArticle

Original languageEnglish
DateAccepted/In press - 13 Feb 2020


Background: Unicompartmental knee replacement (UKR) offers advantages over total knee replacement but has higher revision rates. New instrumentation known as Microplasty was introduced to address this. The aim was to compare the revision rates of UKRs implanted with Microplasty and traditional instrumentation (Non-Microplasty).

Methods: National Joint Registry (NJR) data was used to propensity score match 15,906 UKRs (7,953 Microplasty and 7,953 Non-Microplasty) for important patient, implant and surgical factors. Implant survival rates were determined using the Kaplan-Meier method and compared using Cox regression models in a multilevel model.

Results: The 5 year implant survival for Microplasty and Non-Microplasty UKRs were 96.7% (95% CI 96.0%-97.2%) and 94.5% (CI 93.8-95.1%) respectively. The revision rate for Microplasty UKR was significantly lower than that of Non-Microplasty UKRs (Hazard ratio 45 (HR)=0.77, p=0.008). Compared with Non-Microplasty UKRs, the revision rate of Microplasty UKRs implanted during the year after introduction of Microplasty was lower but the difference was not significant (HR 0.86, CI 0.67-1.10, p=0.23), whereas for those implanted more than a year after introduction the difference was significant (HR 0.69, CI 0.54-0.89, p=0.004).

Conclusion: The use of Microplasty instrumentation has resulted in an improved 5 year UKR survival. Microplasty UKR implanted during the first year after introduction had a small, non-significant decrease in revision rate. As the revision rate did not increase this suggests that there is no adverse learning curve effect. Microplasty UKRs implanted after this transition period had a revision rate 31% lower than the Non-Microplasty group.

    Research areas

  • microplasty, non microplasty, unicompartmental knee arthroplasty



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