Background: The purpose of the present study is to report on a cohort of patients with a volar shearing fracture of the distal end of the radius in whom the unique anatomy of the distal cortical rim of the radius led to failure of support of a volar ulnar lunate facet fracture fragment.

Methods: Seven patients with a volar shearing fracture of the distal part of the radius who lost fixation of a volar lunate facet fragment with subsequent carpal displacement after open reduction and internal fixation were evaluated at an average of twenty-four months after surgery. One fracture was classified as B3.2 and six were classified as B3.3 according to the AO comprehensive classification system. All seven fractures initially were deemed to have an adequate reduction and internal fixation. Four patients required repeat open reduction and internal fixation, and one underwent a radiocarpal arthrodesis. At the time of the final follow-up, all patients were assessed with regard to their self-reported level of functioning and with use of Sarmiento's modification of the system of Gartland and Werley.

Results: At a mean of two years after the injury, six patients had returned to their previous level of function. The result was considered to be excellent for one patient, good for four, and fair for two. The average wrist extension was 48°, or 75% of that of the uninjured extremity. The average wrist flexion was 37°, or 64% of that of the uninjured extremity. The one patient who underwent radiocarpal arthrodesis had achievement of a solid union. The four patients who underwent repeat internal fixation had maintenance of reduction of the lunate facet fragment. The two patients who declined additional operative intervention had persistent dislocation of the carpus with the volar lunate facet fragment.

Conclusions: The stability of comminuted fractures of the distal part of the radius with volar fragmentation is determined not only by the reduction of the major fragments but also by the reduction of the small volar lunate fragment. The unique anatomy of this region may prevent standard fixation devices for distal radial fractures from supporting the entire volar surface effectively. It is preferable to recognize the complexity of the injury prior to the initial surgical intervention and to plan accordingly.

Level of Evidence: Therapeutic study, Level IV (case series [no, or historical, control group]). See Instructions to Authors for a complete description of levels of evidence.