Can cast immobilization successfully treat scapholunate dissociation associated with distal radius fractures?

During a 3.5-year period, 20 of 424 consecutive patients with fractures of the distal radius presented with evidence of scapholunate dissociation upon x-ray films and traction view fluoroscopy. The sequential changes of x-ray abnormalities of the scapholunate joint were consistently observed over a 1-year period, and wrist functions were evaluated 1 year after injury. The scapholunate gaps were 3.5 +/- 0.5 mm at the time of injury, 3.2 +/- 0.4 mm immediately after closed reduction of the fracture, 3.4 +/- 0.5 mm at the time after removal of fixation, and 3.8 +/- 0.4 mm 1 year after injury. By the modified clinical scoring system of Green and O'Brien, of these 20 patients, none had excellent, 2 had good, 14 had fair, and 4 had poor wrist function 1 year after injury. The wrists with scapholunate dissociation had significantly worse function as compared to a selected subgroup of 228 wrists with no signs of intercarpal ligament disruption. All 20 patients with signs of scapholunate dissociation on x-ray examination at the time of injury had clinical signs in the scapholunate joint and positive x-rays findings of dissociation 1 year later. After 1 year, 8 of the 20 patients underwent surgery for relief of symptoms and to stabilize the joint. Arthrography in the patients with persistent symptoms showed disruption in scapholunate interosseous ligaments. This study indicates that scapholunate dissociation with concomitant fractures of the distal radius cannot be cured by cast immobilization of the fracture. Early operative treatment should be instituted for the concomitant scapholunate dissociation.