Comparison of 2 forearm reconstructions for longitudinal radioulnar dissociation: a cadaver study.

PURPOSE: We present the results of a cadaveric study of 2 forearm reconstructions with radial head replacement for longitudinal radioulnar dissociation injuries.

METHODS: We created a simulated longitudinal radioulnar dissociation injury in 8 cadaver forearms. Two reconstructions were performed alternately on each arm: patellar tendon interosseous ligament complex reconstruction and the Herbert sling extensor retinaculum plication. We performed mechanical testing in a materials testing machine with and without a radial head replacement, and measured ulnocarpal impaction force through 2 distal ulna strain gauges. We determined relative radioulnar displacement using live fluoroscopic analysis of implanted stainless-steel beads.

RESULTS: Relative radioulnar longitudinal displacement in the destabilized forearms was 10.7 compared with 0.7 mm before creating the injury. A prosthetic radial head replacement alone decreased the displacement by 75% to 2.7 mm. Interosseous ligament reconstruction alone reduced the displacement to 5.1 mm and to 1.3 mm when combined with a radial head implant. The Herbert sling alone did not improve longitudinal stability. The distal ulna force in the native arm was 17 N, or 17% of the force across the wrist. The interosseous ligament reconstruction restored the force to 21 N, whereas the Herbert sling only marginally decreased the ulna impaction force to 45 N. Adding a radial head decreased the distal ulna force to 7 N for the patellar tendon interosseous ligament reconstruction, and 2 N for the Herbert sling.

CONCLUSIONS: In longitudinal radioulnar dissociation injuries, the radial head is an important stabilizer and should be repaired or replaced to minimize radial shortening and ulnar impaction force. Patellar tendon interosseous ligament reconstruction effectively restores the ulnocarpal force distribution and markedly reduces longitudinal instability at the distal radioulnar joint. Combined with radial head arthroplasty, the construct has stability similar to an intact forearm. The Herbert sling did not improve longitudinal stability in this testing construct.

CLINICAL RELEVANCE: Treatment of longitudinal radioulnar dissociation may benefit from radial head replacement and interosseous ligament reconstruction using a patellar tendon graft.