Does the orientation of the distal radioulnar joint influence the force in the joint and the tension in the interosseous membrane?

Objective. To investigate the effect of change in the orientation of the distal radioulnar joint on the force in the joint and the strain in the interosseous membrane. Design. Biomechanical study in fresh frozen cadavers. Background. The articular surfaces of the distal radioulnar joint may be orientated in parallel with the long axis of the forearm (a Type I joint) or at an oblique angle opening distally to the ulnar side (a Type II joint). Methods. Three cadaveric upper limbs were held on a custom built frame allowing measured rotation and axial loading across the wrist. Measurements of force in the distal radioulnar joint and strain in the interosseous membrane were taken and repeated after replacement of the distal radioulnar joint with prosthetic Type I and Type II joints. Findings. The force in the joint and the strain in the interosseous membrane increased with increasing load across the wrist ( P < 0.0001). The force in the Type I joint was reduced compared to the normal or Type II joint. This difference was greater with increasing load and was significant at 8 kg ( P < 0.001). The strain in the interosseous membrane was maximal at neutral forearm rotation and decreased with increasing pronation and supination. Interpretation. The force in the joint is greater with the Type II distal radioulnar joint. We believe this compressive force increases joint stability and this orientation of the articular surfaces should be considered in the design of a total distal radioulnar joint arthroplasty.