Association of ulnar variance with primary distal radio-ulnar joint arthritis: a matched case-control study

Knowledge regarding risk factors for primary distal radioulnar joint (DRUJ) arthritis is limited. This study evaluated the association between ulnar variance (UV) and the development of primary DRUJ arthritis in a matched case-control cohort.

Patients with symptomatic DRUJ arthritis were identified from those attending an orthopaedic outpatient clinic between January 2017 and April 2023. The control group comprised individuals without radiographic evidence of DRUJ arthritis. Propensity score matching was performed, aiming for a 1:3 ratio with an age difference limit of five years or less. UV and grade of DRUJ arthritis were assessed using a previously described method. Differences in UV between the case and control groups, and the association between ulnocarpal joint (UCJ) and DRUJ arthritis, were analysed. Receiver operating characteristic (ROC) analysis was used to determine the UV cut-off value for predicting symptomatic DRUJ arthritis.

The case group comprised 49 wrists from 44 patients, while the control group included 147 wrists from 132 individuals. The mean ages of the case and control groups were 69.6 and 67.5 years, respectively. UV was significantly higher in the case group (3.5 ± 2.9 vs. 1.6 ± 1.5 mm). The prevalence of UCJ arthritis increased with higher DRUJ arthritis grades. ROC curve analysis revealed a UV cut-off of 2.9 mm, with a sensitivity of 0.612 and specificity of 0.816.

A UV greater than 2.9 mm was associated with symptomatic primary DRUJ arthritis. Patients with more advanced DRUJ arthritis were also more likely to have concomitant UCJ arthritis.