Reconstruction of the Interosseous Ligament Unloads Metallic Radial Head Arthroplasty and the Distal Ulna in Cadavers

Abstract

Longitudinal radioulnar dissociation may result when a compressive load to the hand results in excessive proximal migration of the radius with interosseous ligament (IOL) disruption and radial head fracture. Interosseous ligament reconstruction has been proposed to restore more normal forearm mechanics. The objective of this study was to evaluate the effect of IOL reconstruction on compressive load transfer through the forearm after excision and metallic replacement of the radial head in cadavers. In 8 cadaveric forearms, 138 N of compressive load was applied to the hand in neutral forearm rotation and neutral elbow varus-valgus alignment. We measured proximal radial migration and 3-dimensional force vectors acting on the distal radius, distal ulna, IOL, proximal radius, and proximal ulna. The experiment was repeated in order for 5 conditions: (1) with the IOL intact, (2) with the IOL reconstructed with a double-bundle flexor carpi radialis construct, (3) with the radial head excised, (4) after metallic radial head arthroplasty, and (5) after cutting the IOL reconstruction. Analysis of variance was used for statistical comparisons. With the IOL intact the resultant load in the distal radius was 94% +/- 3% of hand load, with 75% +/- 2% transmitted to the proximal radius. Double-bundle flexor carpi radialis reconstruction effectively restored this relationship. After radial head excision the resultant distal radius load decreased whereas great increases were seen in the resultant distal ulna load, the resultant load in the IOL reconstruction, the resultant load in the proximal ulna, and proximal radial migration. Force continued to transfer through the proximal radius transversely, with a 400% increase in transverse force, a consequence of abutment of the radial stump caused by proximal radioulnar convergence (there was no contact at the capitellum). After radial head arthroplasty loads transferred across the wrist remained closer to intact but the resultant load on the distal ulna and proximal radius remained increased. With cutting of the IOL reconstruction transverse forces in the forearm became negligible, the resultant distal ulna load increased by 50%, and the resultant radial head load increased by 25%. Proximal migration of the radius was small and was increased by 4.6 mm with radial head excision and by 1 mm after radial head replacement compared with the IOL-reconstructed, radial head-intact state. Interosseous ligament reconstruction may help improve treatment of longitudinal radioulnar dissociation but remains an experimental procedure.