Scapholunate dissociation: an experimental kinematic study of two types of indirect soft tissue repairs

Indirect soft tissue repairs of scapholunate dissociation (SLD) address the pathophysiology but have been criticized for significantly limiting wrist flexion and altering wrist kinematics. This study was designed to analyze and compare the kinematics of a normal cadaveric wrist to those of 2 types of soft tissue repairs performed for SLD. Ten uninjured fresh cadaver arms were evaluated by cineradiography and standard x-rays. The average scapholunate (SL) gap was 0.9 mm, with a SL angle of 50 degrees. A model of SLD was produced by sectioning the SL ligaments resulting in an average SL gap of 3.9 mm and SL angle of 66 degrees. The wrists were randomized to a dorsal capsulodesis repair and a distally based split extensor carpi radialis longus (ECRL) repair. The average SL gap after repair was 1.0 mm and the average SL angle was 47 degrees. The split ECRL repair and dorsal capsulodesis reduced scaphoid flexion with only a 10 degree and 18 degree decrease in wrist flexion, respectively. Both repairs reduced the SLD and restored normal wrist kinematics.