Cadaveric study to analyse the influence of distal radial malunion on muscle control of carpal rotational alignment.

Extra-articular distal radial malunion may result in poor functional outcome. This biomechanical study aims to investigate whether changes in the shape of distal radius (length and/or inclination) may influence the muscle control of carpal rotational alignment. Nine cryopreserved cadaveric specimens were used to reproduce six distal radius conditions: (1) unaltered anatomy; (2) 20° dorsal tilt; (3) 20° anterior tilt; (4) 4 mm shortening; (5) 20° anterior tilt and 4 mm shortening; and (6) 20° dorsal tilt and 4 mm shortening. Combined shortening and dorsal tilting of the radius reduced the supination effect of abductor pollicis longus and extensor carpi radialis longus on the distal carpal row, whereas combined shortening and anterior tilting prompted pronation of the distal row when all muscles were contracted. This study provides evidence that distal radial malunion may alter muscular control of carpal rotational alignment.