The Effect of Volarly Angulated Distal Radius Fractures on Forearm Rotation: In Vitro Biomechanical Study

Introduction To examine the effects of volar angulation deformities of the distal radius with and without triangular fibrocartilage complex (TFCC) rupture on the magnitude of forearm rotation.

Materials and Methods Eight fresh-frozen cadaveric upper extremities were mounted in a forearm simulator that produced active forearm rotation. Volar angulation deformities of the distal radius with 0°, 10°, and 20° angulation from the original volar tilt were created. Active supination was simulated by displacing the biceps tendon at a constant velocity, while applying 33% of this load simultaneously to the supinator. Similarly, active pronation was simulated by motion control of the pronator teres, while 44% of the load was apportioned to the pronator quadratus. Testing was peformed initially with the TFCC intact and repeated after sectioning of the TFCC at its ulnar insertion. A two-way repeated measures analysis of variance with Greenhouse-Geisser correction was used to analyze the effects of volar angulation deformities and TFCC status on the magnitude of forearm supination and pronation.

Results Increasing volar angulation decreased forearm supination (p = 0.01) (Fig. 1). Significant reduction in supination was found in 20° of volar angulation (p = 0.02). Pronation was not affected by the magnitude of volar angulation (p = 0.32) (Fig. 2). There was no significant effect of TFCC status on the range of supination (p = 0.20) or pronation (p = 0.35).

Conclusion Volar angulation deformities of the distal radius should be corrected to less than 20° from the original tilt to resore the range of supination.

Fig. 1 Range of supination in 0°, 10°, and 20° of volar angulation deformities of the distal radius in the intact and sectioned TFCC.

Fig. 2 Range of pronation in 0°, 10°, and 20° of volar angulation deformities of the distal radius in the intact and sectioned TFCC.