Validation of a second-generation appropriateness classification system for total knee arthroplasty: a prospective cohort study

BACKGROUND: To test the validity of a second-generation appropriateness system in a cohort of patients undergoing total knee arthroplasty (TKA). METHODS: We applied the RAND/UCLA Appropriateness Method to derive our second-generation system and conducted a prospective study of patients diagnosed with knee osteoarthritis in eight public hospitals in Spain. Main outcome questionnaires were the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Short-Form-12 (SF-12), and the Knee Society Score satisfaction scale (KSS), completed before and 6 months after TKA. Baseline, changes from baseline to 6 months (journey outcome), and 6-month scores (destination outcome) were compared according to appropriateness category. Percentage of patients attaining the minimal clinically important difference (MCID) and responders according to Outcome Measures in Rheumatology-Osteoarthritis Research Society (OMERACT-OARSI) criteria were also reported. RESULTS: A total of 282 patients completed baseline and 6-month questionnaires. Of these, 142 (50.4%) were classified as Appropriate, 90 (31.9%) as Uncertain, and 50 (17.7%) as Inappropriate. Patients classified as Appropriate had worse preoperative pain, function, and satisfaction (p < 0.001) and had greater improvements (i.e., journey scores) than those classified as Inappropriate (p < 0.001). At 6 months, destination scores for pain, function, or satisfaction were not significantly different across appropriateness categories. The percentage of patients meeting responder criteria (p < 0.001) and attaining MCID was statistically higher in Appropriate versus Inappropriate groups in pain (p = 0.04) and function (p = 0.004). CONCLUSIONS: The validity of our second-generation appropriateness system was generally supported. The findings highlight a critical issue in TKA healthcare: whether TKA appropriateness should be driven by the extent of improvement, by patient final state, or by both. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13018-021-02371-z.