Purpose: Restoration of joint congruity has been shown to be an important factor in the prevention of arthritis in patients with Bennett's fracture. It is for this reason that surgical management is generally recommended for displaced intra-articular fractures of the base of the thumb metacarpal. Adequacy of closed reduction after pinning of Bennett's fracture is usually evaluated by fluoroscopic examination. The purpose of this study is to determine the accuracy of fluoroscopic examination compared to plain radiographs and direct visualization in closed reduction and percutaneous pin fixation of simulated Bennett's fractures.
Methods: In 8 fresh-frozen cadaveric hands, Bennett's fractures were created and the incisions were closed. Under fluoroscopic visualization the fractures were close reduced and pinned using 1.14-mm (0.045-in) K-wires. These reductions were all judged to be acceptably aligned with fracture stepoff and displacement less than 1.5 mm under fluoroscopy. Anteroposterior and lateral plain radiographic films were then taken to assess the reduction. Finally, the carpometacarpal joint was opened and visualized to directly assess the reduction for fracture stepoff, displacement, and gap.
Results: After percutaneous fixation, all closed reductions were deemed acceptable. Examination with plain radiographs demonstrated an average anteroposterior view displacement of 0 mm, lateral view gap of 0.1 mm, and articular stepoff of 1.1 mm. Direct examination of the joints showed an average articular gap of 0.9 mm, stepoff of 2.1 mm, and displacement of 3.1 mm. The values for stepoff and displacement were significantly different when the direct measurements were compared to the fluoroscopic measurements. Radiographic measurements were significantly different from direct measurements for displacement of the fracture fragments.
Conclusions: After closed reduction and percutaneous pinning of simulated Bennett's fractures in a cadaver model, the assessment of the articular gap, stepoff, and displacement as detected by fluoroscopy is often in error compared to that detected by plain radiographs and direct examination.