Measuring appropriate need for unicompartmental knee arthroplasty: results of the MANUKA study

PURPOSE: Indications for unicompartmental knee arthroplasty (UKA) are controversial. Studies based solely on radiographic criteria suggest up to 49% of patients with knee osteoarthritis (OA) are suitable for UKA. In contrast, the ‘Appropriate use criteria’ (AUC), developed by the AAOS, apply clinical and radiographic criteria to guide surgical treatment of knee OA. The aim of this study was to analyze patient suitability for TKA, UKA and osteotomy using both radiographic criteria and AUC in a cohort of 300 consecutive knee OA patients. METHODS: Included were consecutive patients with clinical and radiographic signs of knee OA referred to a specialist clinic. Collected were demographic data, radiographic wear patterns and clinical findings that were analyzed using the AUC. A comparison of the radiographic wear patterns with the treatment suggested by the AUC as well as the Surgeon Treatment Decision was performed. RESULTS: There were 397 knees in 300 patients available for analysis. Median age was 68 [IQR 15], BMI 30 [6] with 55% females. Excellent consistency for both the radiographic criteria and the AUC criteria was found. Based on radiological criteria, 41% of knees were suitable for UKA. However, when using the AUC criteria, UKA was the appropriate treatment in only 13.3% of knees. In 19.1% of knees, no surgical treatment was appropriate at the visit, based on the collected data. CONCLUSION: Application of isolated radiologic criteria in patients with knee OA results in a UKA candidacy is misleadingly high. AUC that are based on both radiological and clinical criteria suggest UKA is appropriate in less than 15% of patients. LEVEL OF EVIDENCE: III retrospective study.