PURPOSE: Longitudinal radioulnar dissociation occurs when traumatic axial loading through the wrist disrupts the interosseous membrane (IOM) of the forearm and fractures the radial head (Essex-Lopresti injury). Proximal migration of the radius results in a wrist with a positive ulnar variance, which leads ultimately to painful ulnar-sided wrist degeneration and wrist pain during grasping activities that involve axial loading or ulnar deviation of the wrist. In theory reconstruction of the IOM with a graft substitute can limit proximal migration of the radius, thereby preserving wrist function. The objective of this study was to measure the abilities of 3 graft tissues to limit proximal radial displacement compared with the native IOM in a radial head-deficient cadaver model.METHODS: Sixteen fresh-frozen cadaveric forearms were loaded axially to 134 N through the potted central 3 metacarpals; the elbow was flexed to 90 degrees with the wrist in neutral rotation. Proximal displacement of the radius relative to the capitellum was measured. With the radial head excised specimens were first tested with the IOM intact. The IOM was then sectioned and central band IOM reconstructions were performed on each specimen using the following tissues: palmaris longus tendon, flexor carpi radialis (FCR) tendon, and a 1-cm- wide bone-patellar tendon-bone (BPTB) onlay allograft. Ten loading cycles were performed with each test configuration. Proximal radial displacement between 13.4 N and 134 N of applied wrist force was analyzed for the 10th loading cycle. The increase in proximal displacement between the first and 10th loading cycles (recorded at 134 N of wrist force) represented permanent elongation of the graft.RESULTS: Mean cross-sectional areas were 5.11 mm2 for the palmaris longus tendon, 15.23 mm2 for the FCR tendon, and 51.59 mm2 for the BPTB allograft. Mean proximal radial displacements were 3.04 mm (intact IOM), 4.37 mm (BPTB), 4.92 mm (FCR tendon), and 6.43 mm (palmaris tendon); all means were significantly different from each other. Mean permanent graft elongations were 0.06 mm (IOM), 0.36 mm (BPTB), 1.25 mm (FCR tendon), and 1.80 mm (palmaris tendon); all means were significantly different from each other with the exception of means for palmaris longus vs FCR and BPTB vs IOM.CONCLUSIONS: No graft reconstruction limited proximal radial displacement as effectively as the native IOM. Of the 3 graft tissues tested the BPTB allograft had the greatest cross-sectional area, allowed the least proximal radial displacement, and displayed the least permanent elongation after 10 cycles of loading. The relatively thin and narrow palmaris longus tendon appears to be the least desirable choice for IOM reconstruction because of its relatively low stiffness and tendency to elongate permanently after cyclic loading. When the radial head is absent rupture of the IOM allows unopposed proximal displacement of the radius relative to the ulna as the wrist is loaded axially. In the present tests all 3 graft tissues used to reconstruct the IOM limited proximal radial displacement. The choice of graft material is an important variable if IOM reconstruction is considered for treatment of an Essex-Lopresti injury.
Adult Aged