Cancellous bone thickness in the distal fragment affects the severity of dorsal angulated distal radius fractures

Abstract

Introduction A fall with an extended wrist leads to distal radius fractures (DRFs). The sharing force between the carpus and the volar cortex causes volar-sharing fractures. Therefore, a sharing force between the carpus and the dorsal cortex could be generated in dorsally angulated DRFs. In cases of trauma, a moderate force may cause a non-articular fracture, while a stronger force could result in an articular fracture. We speculate that maintaining a thick cancellous bone in the distal fragment could help dissipate the force and potentially prevent articular fractures. We hypothesized that the cancellous thickness of the subchondral bone affects the development of intra-articular fractures. This study thus investigated the radiological parameters of DRFs to verify the development of intra-articular fractures. Materials and Methods We retrospectively reviewed 199 patients with dorsally angulated DRFs for whom reconstructed computed tomography images were available. Articular fracture patterns were evaluated in the axial planes. We measured cancellous thickness under the subchondral bone in the sagittal plane. Moreover, we compared the radial inclination, volar tilt, ulnar variance, and cancellous thickness among groups with types A, C1/2, and C3 DRFs. Results A fracture line running from the sigmoid notch to the dorsal extensor compartment accounted for approximately 80% of DRF cases. Ulnar variance was significantly larger in the type C3 group than in the type A group. Cancerous thickness was significantly smaller in the type C than in the type A group. Conclusions The sharing force between the carpus and the proximal dorsal cortex is one of the main causes of intra-articular fractures in dorsally angulated DRFs. Thicker cancellous bone in distal fragments protects the articular cartilage from the load.