A Biomechanical Comparison of Three Current Scapholunate Reconstruction Methods

Disruption of the scapholunate (SL) ligament and secondary stabilizers impacts carpal kinematics, leading to instability and arthritis. There is no consensus on the most effective reconstruction technique for irreparable scapholunate dissociation. The purpose of this biomechanical study was to compare three scapholunate reconstruction techniques in a cadaveric model.

Eighteen cadaveric upper extremities without prior scapholunate disruption or degenerative changes were used. Markers were affixed to the scaphoid, lunate, and Lister's tubercle. After transection of primary and secondary scapholunate stabilizers, specimens were randomized to three reconstruction techniques: Modified Brunelli tenodesis (MBT); Reduction/Association of the Scaphoid, Lunate (RASL); or scapholunate interosseous reconstruction with suture-tape augmentation (IB). Specimens underwent cyclic loading by an actuator with static loads applied via pulley system. Postreconstruction stability was assessed using radiographic, digitizer, and caliper measurements at 0, 1,000, and 5,000 cycles.

There were no significant differences in radiographic SL interval at any postreconstructive timepoint. Radiographic SL angle increased significantly in the MBT group compared with RASL after 1,000 and 5,000 cycles. By digitizer, RASL exhibited significantly less SL widening than MBT, IB, and the native wrist. By caliper, MBT developed significantly more widening than both RASL and IB at 1,000 and 5,000 cycles. There were two failures during loading, both in the MBT group.

All three techniques were successful in restoring stability in the immediate postreconstruction state. IB most closely approximated the native state, whereas RASL over-reduced the SL interval. Both IB and RASL were durable throughout cyclic loading, whereas MBT demonstrated progressive attenuation and had the only two failures. Our findings support the use of adjunct measurement methods (caliper, digitizer) in future biomechanical studies.

Both interosseous reconstruction with suture-tape augmentation and RASL may achieve more durable long-term scapholunate stability compared to MBT. Radiographic evaluation alone may underestimate carpal instability.