Pain after orthopaedic surgery: differences in patient reported outcomes in the United States vs internationally. An observational study from the PAIN OUT dataset.

<bold>Background: </bold>A previous PAIN OUT study found that American orthopaedic-surgical patients rated 'worst pain' higher than did similar European patients. This study aims to confirm these findings in a larger, international patient sample, explore whether risk factors for greater postoperative pain exist disproportionately in the American population, and confirm the findings for one procedure.<bold>Methods: </bold>Surveyors collected patient reported outcomes (PROs) and perioperative pain management practices using PAIN OUT methodology. Most PROs used 11-point numerical rating scales (0=null, 10=worst possible). Risk factors included: female gender, younger age, high BMI, chronic pain, and opioid use before surgery. Initial analysis used a mixed patient cohort. A secondary analysis used only patients undergoing total knee replacement (TKR). Inference was based primarily on effect size using Cohen's d.<bold>Results: </bold>13,770 patients in 13 European and non-European countries (international ) and 564 patients from the United States (US) contributed data on the 1st postoperative day. Three of 11 PROs differed between the cohorts: 'worst pain' {US 7.5 (2.5) vs international 5.6 (2.8); d=0.66 [confidence interval (CI) 0.58-0.75]}; proportion 'receiving information about treatment options' [US 0.86 vs international 0.66; d=0.53 (CI 0.39-0.66)]; reporting adverse effects and their severity [US 0.87 vs international 0.73; d=0.52 (CI 0.38-0.66)]. Risk factors did not differ between the two cohorts. PROs and management patterns in TKR patients were similar to the mixed cohort.<bold>Conclusions: </bold>Three PROs differed between international and US patients, with higher 'worst pain' for US patients. Neither risk factors, nor patient mix accounted for the observed differences for 'worst pain'.<bold>Clinical Trial Registration: </bold>NCT 02083835. [ABSTRACT FROM AUTHOR]