Over the past 40 years we have collected data on the Oxford Knee. This chapter should have provided the reader with an overview of the current and past results of UKA and a comparison with TKA.
The data from joint registers confirms that whilst patients undergoing TKA, in general, had lower revision rates, they had higher rates of morbidity and mortality, longer hospital stays, and inferior PROMs compared to UKA. Surgeons with a higher UKA caseload had significantly lower revision rates and superior patient-reported outcomes. Increasing usage (offering UKR to a greater proportion of knee replacement patients) appears to be a viable method of increasing caseload and therefore of improving results. Surgeons with optimal usage (20% to 50% of knee replacements) achieved revision/reoperation rates similar to matched patients undergoing TKA up to eight years postoperatively.
Cohort studies of the cemented OUKA have demonstrated that high levels of function and excellent long term survival can be achieved. In an independent study the 20+ year survival was similar to the best TKA. The proposed general contraindications for UKA (youth, obesity, activity, PFJ damage, chondrocalcinosis) did not compromise the outcome. This suggests that if patients have AMOA, these proposed contraindications can be ignored. AMOA is present in about 50% of patients needing knee replacement. The importance of surgeons using the OUKA in a high proportion of patients is demonstrated by nine studies of the Phase 3, including 6000 patients, with 10 year survival of about 95% in which surgeons used the OUKA in 20% to 50% of their knee replacements.
Although the best 10 and 20-year results for mobile and fixed are similar, it is clear that, to achieve good long term results with the mobile, surgeons need a large usage, ideally somewhere between 20 and 50%. There is little evidence as to the optimal usage with the fixed but the evidence that exists would suggest that the usage should be much lower with much narrower indications. This is primarily due to problems with wear and progression of disease in the patellofemoral joint. The main conclusion of Argenson’s 20-year study was that the fixed bearing should not be used with significant patellofemoral joint problems (Argenson et al, 2013). This is opposite to the evidence for the Oxford which suggests that, apart from very rare cases with severe damage to the lateral side patellofemoral joint with bone loss, it can be ignored.
Although the results of the cemented OUKA are good, there can be problems particularly in the hands of inexperienced surgeons. Cementing errors are common and even if there are no errors, radiolucent lines are often present. These may be misinterpreted and lead to unnecessary revisions. To address these problems the cementless OUKA was introduced. This appears to be at least as good as the cemented. There is some evidence to suggest that it has better fixation, better function and better survival than the cemented.
