A Biomechanical Perspective on Distal Radioulnar Joint Instability

Abstract

The distal radioulnar joint (DRUJ) is inherently unstable, and the curvature of the sigmoid notch of the radius (radius of curvature: 18 mm) is twice as large as that of the ulnar head (8 mm).1 During forearm rotation, both dorsal-palmar and proximal-distal translation occurs between the joint surfaces. Although there is considerable variation between individuals, the osseous architecture of the sigmoid notch is a dorsally open wedge (10 degrees) and its dorsal length (10 mm) is greater than its volar length (6 mm). has been demonstrated between the obliquity of the DRUJ and ulnar variance. 1,4The deep ligamentous portions of the triangular fibrocartilage complex (TFCC) provide the primary intrinsic stabilization of the DRUJ. These fibers, which attach at the ulnar fovea and lie on the axis of forearm rotation, are the most isometric and undergo the least length changes during pronosupination movement. The palmar deep fibers of the RULs may be taut in pronation to prevent dorsal ulnar head subluxation, and the dorsal deep fibers may be taut in supination to restrain the ulna from palmar migration relative to the radius.5 Supplemental stability is provided by superficial fibers of the RUL, which may have a checkrein effect during forearm rotation. The ulnocarpal ligament (UCL) complex and the floor of the extensor carpi ulnaris (ECU) tendon sheath, including the ulnar collateral ligament, are the other components of the TFCC and also stabilize the AbstractBackground The purpose of this article was to review the anatomy, kinematics of the distal radioulnar joint (DRUJ), and to discuss definition, classification, and diagnosis of DRUJ instability. Methods A biomechanical perspective on physical examination of DRUJ ballottement test was documented. Physiological dynamic DRUJ translation and differences of the translation following sequential ligament sectioning and changes in different forearm and wrist positions were demonstrated. The clinical significance of each ligament's contribution to joint stability in specific wrist positions was addressed. Conclusion Each ligament stabilizing the DRUJ contributed to joint stability depending on the direction (palmer or dorsal) and different positions of the wrist and forearm. DRUJ ballottement test in each wrist and forearm position may detect tears of specific ligament stabilizing the DRUJ.

Contribution of a distal radioulnar joint stabilizer on forearm stability: A modeling study

“…The injury to the IOM can be detected with magnetic resonance imaging and ultrasound. [8][9][10] In patients with gross radioulnar instability associated with RH fractures, the ''radius pull test'' can be used to assess signs of IOM and TFCC disruption. 2 Once the diagnosis is established, various surgical treatments can be used to treat forearm instability, ranging from a repair of the IOM or the TFCC, RH replacement, or ligament reconstructions.…”