Flexor pollicis longus dysfunction after volar plate fixation of distal radius fractures.

PURPOSE To evaluate the natural history and etiology of decreased thumb interphalangeal (IP) joint flexion after volar plate fixation of distal radius fractures. METHODS A total of 46 patients who underwent volar plating of 48 distal radius fractures by a single surgeon were retrospectively studied. Of those patients, 24 (24 wrists) exhibited loss of thumb IP joint flexion (group 1) and 22 (24 wrists) retained thumb IP joint flexion (group 2) with attempted thumb opposition to the small finger after surgery. All patients were seen at regular intervals until IP joint flexion returned and fracture healing was confirmed radiographically. Patient demographics, fracture patterns, surgical variables, and final radiographs were compared between groups. Twenty patients in group 1 were seen after a mean of 6.5 months (range, 5-12 mo) for specific outcome measurements. Eight cadaveric specimens were used to replicate the flexor carpi radialis approach to the distal radius and evaluate flexor pollicis longus tendon excursion. RESULTS There were no significant differences in fracture pattern, patient age or sex, injured extremity dominance, time to surgery, incision length, plate composition, plate length, tourniquet time, or final wrist radiographs between groups. In group 1, active thumb IP joint flexion returned on average 52 days (range, 19-143 d) postoperatively. At final evaluation in this group, mean IP joint flexion was 11° less than the contralateral thumb IP joint; however, patient-determined outcomes were favorable in most cases. In the cadaveric specimens, excursion of the flexor pollicis longus tendon decreased with sequential soft tissue dissection and retraction. CONCLUSIONS Loss of thumb IP joint flexion after volar plating of distal radius fractures was common, and motion returned to near normal in most cases within 2 months. Partial stripping of the flexor pollicis longus muscle from investing fascia and bone and retraction of soft tissues are likely etiological factors.