Trapezial Fractures and Associated Fractures of the Ulnar Carpus: A Ring-Bone Model

Fractures of the trapezium are rare; however, the incidence may be under-reported in the literature. The incidence of ulnar-sided carpal body fractures as a concomitant injury has not been reported. Our study aimed to evaluate the incidence of trapezium fractures in conjunction with ulnar-sided carpal body fractures. METHODS: Over a five-year period, our electronic records were queried and charts reporting carpal bone fractures were reviewed. All cases of trapezium fracture were evaluated further and presented. RESULTS: Eight trapezial fractures were identified, representing 8% of all carpal fractures and 26% of all nonscaphoid carpal fractures. Of the eight trapezium fractures identified, five (62.5%) were associated with Bennett fracture and four (50%) were associated with ulnar-sided carpal fractures. CONCLUSION: Our study demonstrates a higher incidence of trapezial fractures than previously reported. Previously unreported concomitant ulnar-sided carpal body fractures are reported at a frequency nearly equal to that of concomitant Bennett fractures in our series. We propose a mechanism of injury where the carpal canal and overlying transverse carpal ligament function as a ring-bone construct similar to the pelvis. When a trapezium fracture is identified, we recommend additional evaluation for ulnar-sided injuries of the carpus.