Association of hospital and surgeon procedure volume with patient-centered outcomes of total knee replacement in a population-based cohort of patients age 65 years and older.

Objective: To study the association between procedure volume and patient-centered outcomes such as functional status.

Methods: We performed an observational study of a stratified random sample of Medicare beneficiaries who underwent primary total knee replacement (TKR) in 2000. Low-volume surgeons were defined as surgeons performing < or =6 TKRs per year in the Medicare population, and low-volume centers were defined as those in which < or =25 TKRs per year were performed. The primary outcome was the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) functional status score (0-100 scale; 100 = best) 2 years after TKR. We defined a WOMAC functional status score of <60 as a poor functional outcome. Analyses were adjusted for sociodemographic factors, preoperative functional status, and comorbidities.

Results: Fifty-eight percent of 1,597 eligible patients agreed to participate. Twelve percent of participating patients had a WOMAC score <60 2 years following TKR. Patients operated upon by low-volume surgeons in low-volume hospitals were twice as likely to have a poor WOMAC functional status score as patients operated upon by higher volume surgeons and in higher volume hospitals (odds ratio 2.1, 95% confidence interval 1.1-4.2).

Conclusion: Patients operated upon in low-volume hospitals by low-volume surgeons had worse functional outcomes 2 years after TKR. These findings add a new and important dimension to the discussion of whether to promote selective referral of procedures such as TKR to high-volume centers.