Radial collateral ligament injuries of the thumb metacarpophalangeal joint: Epidemiology in a military population

Purpose: The reasons for variation in the reported incidence rates between thumb metacarpophalangeal joint radial collateral ligament (RCL) and ulnar collateral ligament (UCL) injuries are unclear. Delay in diagnosis of injury to the RCL leads to greater time of patient disability. The purpose of this study was to define the demographics and presentation of patients with RCL injuries in a military health care system. Methods: We performed a retrospective review of electronic medical records over a 5-year period to determine the incidence and epidemiology related to patients with instability of the thumb metacarpophalangeal joint resulting from injury of the radial or ulnar collateral ligaments. Results: A total of 56 patients presented with thumb metacarpophalangeal joint instability. Of these, 18 (32%) had an RCL injury. Patients with an RCL injury were, on average, younger than those with UCL injuries. Those with RCL injuries were more likely to require surgery than were those with UCL injuries (67% vs 40%). With regard to time to presentation, most patients with UCL injuries presented 2 to 10 weeks after injury, whereas nearly all patients with RCL injuries presented greater than 10 weeks after injury. Radial collateral ligament injuries were more likely than UCL injuries to have resulted from an axial load (56% vs 16%), whereas UCL injuries were more likely to have been caused by an abduction-adduction moment (50% vs 22%). Conclusions: In this series, patients sustaining injuries to the RCL were younger and presented later than their counterparts with UCL instability. Close attention to subtle or frank instability presenting as pain in younger patients with axial loading injury mechanisms may allow early diagnosis and appropriate treatment of this injury. Type of study/level of evidence: Prognostic III.