Which patients are most likely to benefit from total joint arthroplasty?

Objective — To evaluate patient predictors of 'good outcome' following total joint arthroplasty (TJA).

Methods — A population cohort with hip/knee arthritis (osteoarthritis, OA; inflammatory arthritis, IA) aged 55+ years was recruited (1996-98; baseline) and assessed annually (demographics, troublesome joints, health status and overall hip/knee arthritis severity [WOMAC]). Survey data were linked with administrative databases to identify primary TJAs. Good outcome was defined as a WOMAC summary score improvement ≥ the Minimal Important Difference (MID = 0.5 SD mean change). Logistic regression and Akaike's Information Criterion determined the optimal number of predictors and the best model of that size. Log Poisson regression determined relative risk for good outcome.

Results — 202 individuals received a primary TJA (mean age 71.0 years; 79.7% female; 82.7% > 1 troublesome hip/knee; 65.8% knee replacement). Mean WOMAC summary score improvement was 10.2 points (SD 18.05 = MID 9 points). 53.5% experienced a good outcome. Four predictors were optimal; the best four-variable model included pre-TJA WOMAC, comorbidity, number of joints, and arthritis type (c-statistic 0.80). The probability of a good outcome was greater with worse (higher) pre-TJA WOMAC summary scores (adjusted RR 1.32 per 10-point increase, p<0.0001), fewer troublesome hips/knees (adjusted RR 0.82 per joint, p=0.002), OA (adjusted RR for RA 0.33, p=0.009), and fewer comorbidities (adjusted RR per condition 0.88, p=0.01).

Conclusions — In an OA cohort with high prevalence of multiple troublesome joints and comorbidity, only half achieved a good TJA outcome, defined as improved pain and disability. A more comprehensive assessment of the benefits and risks of TJA is warranted.