Fractures of the distal radius with small marginal fragments are unstable and can be difficult to manage. The volar lunate facet fragment has received attention over the last decade due to the potential for loss of fixation and carpal subluxation. The volar lunate facet may fracture in isolation or more commonly is associated with volar shearing fractures as well as severe comminuted fractures of the distal radius. Stable fixation of the volar lunate facet is critical because failure to do so results in volar carpal subluxation or dislocation and subsequent impaired function, pain, and posttraumatic arthritis.Despite the fact that surgeons are aware of this potential pitfall, loss of fixation continues to occur.
Jupiter et al observed that the vast majority of volar shearing fractures of the distal radius have two or more small marginal articular components. The scaphoid and lunate portions of the volar articular surface shear off of the distal radius as a unit but can fragment into separate pieces in the sagittal plane. The volar lunate facet fragment is the most difficult to stabilize because it projects volar to the axis of the palmer surface of the radius, making it inherently unstable and difficult to capture with a standard volar locking plate.
Beck et al found that the size of the volar lunate facet fragment and the amount of initial displacement determined whether a volar plate alone can maintain fracture reduction. More than 5 mm of initial lunate facet subsidence and lunate facets less than 15 mm in length were more likely to displace after adequate fixation with a volar plate.
The treatment of volar shearing fractures of the distal radius with comminution of the volar rim is challenging but loss of fixation and malunion can be avoided by the use of a fragment-specific fixation in addition to volar locking plates. Techniques that have been described for stabilization of the lunate facet include tension band wire constructs,Kirschner wires with external fixator, pin plates,Kirschner wire constructs,arthroscopic reduction and pinning,screw and washer fixation, 2.4-mm T- and L-plates, and more recently volar hook plate fixation.