Relationship between distal radius fracture malunion and arm-related disability: A prospective population-based cohort study with 1-year follow-up

BACKGROUND Distal radius fracture is a common injury and may result in substantial dysfunction and pain. The purpose was to investigate the relationship between distal radius fracture malunion and arm-related disability. METHODS The prospective population-based cohort study included 143 consecutive patients above 18 years with an acute distal radius fracture treated with closed reduction and either cast (55 patients) or external and/or percutaneous pin fixation (88 patients). The patients were evaluated with the disabilities of the arm, shoulder and hand (DASH) questionnaire at baseline (concerning disabilities before fracture) and one year after fracture. The 1-year follow-up included the SF-12 health status questionnaire and clinical and radiographic examinations. Patients were classified into three hypothesized severity categories based on fracture malunion; no malunion, malunion involving either dorsal tilt (>10 degrees) or ulnar variance (≥ 1 mm), and combined malunion involving both dorsal tilt and ulnar variance. Multivariate regression analyses were performed to determine the relationship between the 1-year DASH score and malunion and the relative risk (RR) of obtaining DASH score ≥ 15 and the number needed to harm (NNH) were calculated. RESULTS The mean DASH score at one year after fracture was significantly higher by a minimum of 10 points with each malunion severity category. The RR for persistent disability was 2.5 if the fracture healed with malunion involving either dorsal tilt or ulnar variance and 3.7 if the fracture healed with combined malunion. The NNH was 2.5 (95% CI 1.8-5.4). Malunion had a statistically significant relationship with worse SF-12 score (physical health) and grip strength. CONCLUSION Malunion after distal radius fracture was associated with higher arm-related disability regardless of age.