The Effect of Elbow Extension on the Biomechanics of the Osseoligamentous Structures of the Forearm

Purpose To investigate the hypothesis that elbow extension alters the biomechanics of forearm rotation including force transmission in the distal and proximal radioulnar joints (DRUJ and PRUJ) and the interosseous ligament (IOL). Methods A cadaver model with a custom-designed jig was used to measure forearm pronosupination ranges, transmitted forces and contact areas across the PRUJ and DRUJ, and tension in the 3 main components of the IOL's central band. Testing with applied loads was undertaken throughout pronosupination with the elbow fully flexed (n = 15) and fully extended (n = 11). Results Elbow extension-flexion affected the range of forearm pronosupination, shifting the arc of rotation such that the forearm supinated maximally with the elbow flexed and pronated maximally with the elbow extended. Elbow extension also increased transmitted forces across the DRUJ and PRUJ while also increasing contact areas within the DRUJ and PRUJ. Elbow extension significantly increased tension in the central band of the IOL when the forearm was maximally pronated. Conclusions Maximum supination occurred with the elbow flexed. Maximum pronation occurred with it extended. Elbow position altered forearm biomechanics, including force transmission across the PRUJ and DRUJ and transmitted tension in the IOL. Clinical relevance The interplay of osseoligamentous forearm structures is such that we would anticipate surgical alteration of any one of them to have effects upon function of the others.