Background: Few studies have combined preoperative patient-reported and objective outcome measures to predict outcomes after total hip arthroplasty (THA).

Purpose / Aim of Study: to identify predictors of outcome 3 and 12 months after THA

Materials and Methods: A cohort of 107 consecutive patients with primary hip osteoarthritis responded to Hip dysfunction and Osteoarthritis Outcome Score (HOOS) questionnaires prior to and 3 and 12 months after THA. Preoperative pain intensity; joint space width (JSW), age, gender, and body mass index (BMI) were used to predict changes in pain and physical function after surgery. Preoperative pain level scores were categorized into; none (76-100, reference), mild (51-75), moderate (26- 50) and severe (0-25). Single and multilevel repeated measures random effects linear regression models (MLM) were used

Findings / Results: Preoperative pain levels predicted improvement in postoperative pain in such a way that patients with mild pain improved; 20 points (95% CI: 2.5 to 36.8), while patients with moderate and severe pain improved; 32 (95% CI: 15.5 to 48.7) and 47 (95% CI: 29.3 to 64.3), points, respectively. Preoperative pain also predicted improvements in postoperative physical function scores; mild improved; 18 (-2.6 to 38.3), moderate 26 (6.7 to 46.2) and severe 44 points (23.2 to 64.9), respectively. Age, gender, BMI, and JSW had no predictive value. The patients achieved the same postoperative level of pain and function irrespective of pre- operative score.

Conclusions: Preoperative pain predicted changes in pain and physical function up to one year after THA. Such knowledge should be taken into consideration, when assessing OA patients prior to surgery. This study provides useful insight for clinicians, regarding the overall improvement patients can expect to achieve following their total hip arthroplasty