Treatment of scapholunate dissociation with a bioresorbable polymer plate: a biomechanical study.

PURPOSE: Untreated scapholunate dissociation can lead to pain and eventually arthritis. There has been minimal limited success of soft tissue surgical procedures to repair or functionally replicate the torn structures. In this study, we evaluated a new surgical repair for scapholunate dissociation using a bioresorbable polymer approved for human applications.

METHODS: Eight cadaver wrists were tested in a wrist joint motion simulator. Each wrist was moved in continuous cycles of flexion-extension and radioulnar deviation. Kinematic data for the scaphoid and lunate were recorded for each wrist in the intact state; after the scapholunate interosseous, dorsal radiocarpal, and dorsal intercarpal ligaments were sectioned; after repair using a 4-hole bioresorbable plate; and after 1,000 cycles of wrist motion to mimic continued use after surgery.

RESULTS: Sectioning of these 3 wrist ligaments resulted in static scapholunate dissociation. Application of the polymer plate statistically restored the scaphoid and lunate kinematics to that of the intact specimen. Scapholunate instability and any gap between the bones was eliminated. After 1,000 cycles of motion, the plate maintained intact kinematics in 5 of 8 arms. During cyclic motion, either the plate failed or the screws pulled out in the remaining 3 arms. This occurred in the smallest and most osteoporotic cadavers in which positioning a sensor post and the 2 screws for the plate in the small lunate compromised the pullout strength of the screws.

CONCLUSIONS: Use of a resorbable polymer plate in restoring normal kinematics in patients with scapholunate dissociation is supported by this study.