[Primary hip replacement: first year results and predictive factors of poor outcome].

OBJECTIVE To evaluate the results of total hip arthroplasty in patients with osteoarthritis and to identify predictors of poor functional outcome. MATERIAL AND METHODS A prospective observational study in patients operated on in 2006 with total hip arthroplasty in 4 hospitals in Guipúzcoa, followed up for 1 year. OUTCOME VARIABLES pain, physical function, complications, mortality, quality of life by WOMAC and SF-12 (at 0, 3, 6 and 12 months) and «Poor functional outcome» at one year (last quartile of the WOMAC in function area). Logistic regression was performed to examine predictors of poor functional outcome. RESULTS A total of 166 patients were followed up. The incidence of systemic and local complications was 6.3% and 14.5%, respectively, 4.3% readmissions and no deaths related to surgery. Close to 40 points improvement in pain, stiffness and WOMAC functional limitation, mainly in the first 3 months after surgery. A similar trend was seen, but lower in the physical and mental component of the SF12 (12 and 8 points, respectively). The previous score on the WOMAC function area and the physical component of SF-12, and the existence of any complications, are predictors of poor functional recovery. DISCUSSION The improvement experienced after the surgery is already very important before the third month. The functional and physical status before surgery and possible complications of surgery are significant determinants of the results.