Rupture Site Location of Surgically Treated Thumb Metacarpophalangeal Ulnar and Radial Collateral Ligaments.

Purpose: Thumb metacarpophalangeal collateral ligament injuries occur in 50 per 100,000 people. The most frequent rupture site locations that are often cited are the thumb ulnar collateral ligament (UCL) occurring distally from the proximal phalanx and the radial collateral ligament (RCL) occurring proximally from the metacarpal head. Methods: A retrospective analysis of 1,004 consecutive finger collateral ligament surgeries performed at a single academic institution over 17 years was conducted. The inclusion criteria were any patient who underwent either a thumb UCL or RCL surgical repair. Patients were excluded if the rupture etiology was secondary to a laceration or a congenital or chronic deformity. Descriptive statistics were presented. Results: Three hundred forty-seven patients were included in this study, including 288 thumb UCL injuries and 59 thumb RCL injuries. The rupture site location for the thumb UCL was proximal in 5.9% (n = 17) of the cases, distal in 92.7% (n = 267), and midsubstance in 1.4% (n = 4). Fifty-three (18.4%) Stener lesions were noted. The rupture site location for the thumb RCL was proximal in 69.5% (n = 41) of the cases, distal in 25.4% (n = 15), and midsubstance in 5.1% (n = 3). Conclusions: In thumb UCL ruptures, the rupture site occurred most often at the proximal phalanx, whereas RCL injuries occurred most often at the metacarpal head. Overall, there was greater heterogeneity of RCL rupture site location frequency. Careful surgical exposure should be performed when repairing either the UCL or RCL. Further studies will determine if differences in rupture site location portend a difference in prognosis. Type of study/level of evidence: Prognostic III.