Review Question - QID 4398

The failure of this patient's fixation post-operatively is caused by failure to support the lunate-facet fragment noted on the injury radiographs.

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 distal volar lunate fragment is the site of origin of the strong volar radiolunate ligaments which insert onto the lunate, and so displacement of this small piece volarly will allow the lunate and the rest of the carpus to subluxate volarly. The unique anatomy of this fragment may prevent standard fixation devices for distal radial fractures from supporting the entire volar surface effectively, as a standard volar plate cannot capture this small distal piece without risking injury to the flexor tendons. Fragment specific fixation of the volar lunate facet fragment with commercially available small plates, or with a tension-band construct or augmentation with K-wires may be required to reduce and stabilize this fragment.

Harness et al. reported on a cohort of 7 patients with a volar shearing fracture of the distal radius who lost fixation of a volar lunate facet fragment with subsequent carpal displacement after open reduction and internal fixation. Five patients underwent revision surgery with adequate results. The authors concluded that with regards to lunate facet fracture fragments, it is preferable to recognize the complexity of the injury prior to the initial surgical intervention and to plan accordingly to prevent early post-operative failure.

Taylor et al. compared the biomechanical stability of a fixed-angle volar plate versus a fragment specific fixation system in the treatment of an intra-articular, dorsally comminuted distal radius fracture model. They found that both fixed-angle volar plate and fragment-specific fixation systems performed comparably in a simulated early postoperative motion protocol. Fragment-specific fixation had improved stiffness characteristics only with respect to the smaller ulnar-sided fragment.

Figures A and B show a shearing radiocarpal-fracture subluxation with small lunate-facet fracture. Figure C shows an immediate post-operative radiograph. Figure D shows subluxation of the radiocarpal joint caused by failure to support lunate-facet fragment. Figure E shows the clinical appearance of a volarly subluxated wrist.

Incorrect Answers:
Answer 2: The use of a non-locking plate in this situation did not directly lead to the failure of fixation, and applying a similar construct with locking fixation would not have prevented volar subluxation of the lunate facet fragment.
Answer 3: Volar tilt was grossly restored post-operatively.
Answer 4: Radial styloid plating would not have prevented volar subluxation of the lunate facet fragment.
Answer 5: Three bicortical screws in the intact radial shaft proximally is adequate fixation.