Distal Radioulnar Joint Instability and Associated Injuries: A Literature Review

Abstract

The distal radioulnar joint (DRUJ) allows supination and pronation of the distal forearm and wrist, an integral motion in everyday human activity. DRUJ injury and chronic instability can be a significant source of morbidity in patients' lives. Although often linked with distal radius fractures, DRUJ injury may occur in a variety of other upper extremity injuries, as well as an isolated pathology. Diagnosis of this injury requires the clinician to have a high index of suspicion and low threshold for clinical testing and further imaging of the DRUJ. The purpose of this article is to provide a review on DRUJ anatomy and biomechanics, to discuss common diagnostic and treatment modalities, and to identify common injuries associated with DRUJ instability.

Keywords: DRUJ; anatomy; biomechanics; instability.

Fig. 1

Distal radioulnar joint anatomy. ECU, extensor carpi ulnaris.

Fig. 2

Sigmoid notch shapes. ( a ) “C” type sigmoid. ( b ) “S” type sigmoid. ( c ) Flat face sigmoid. ( d ) Ski-slope sigmoid.

Fig. 3

Deep and superficial radioulnar ligaments.

Fig. 4

( A ) With the patient’s forearm in neutral, the radius is stabilized and the distal ulna is shifted volar and dorsal to assess the amount of translation. ( B ) The examiner pulls the radius–carpus toward him/herself while also pressing the distal ulna volarly (toward the patient). ( C ) The examiner pulls the dorsal distal radius–carpus toward him/herself and presses the distal ulna dorsally (toward the patient).

Fig. 5

Ulnar fovea sign—One of the examiner’s hands supports the patient’s hand dorsally, and the opposite hand’s thumb tip is pressed deep into the ulnar fovea. The fovea is the “soft spot” between the ulnar styloid process and the flexor carpi ulnaris tendon.

Fig. 6

Passive ulnar wrist deviation. If pain is elicited, this is a positive exam.

Fig. 7

Ulnocarpal stress test—With the patient’s wrist in maximal ulnar deviation, an axial stress is applied with both examiner’s hands while the wrist is passively ranged through pronation–supination.

Fig. 8

Piano key sign—With the patient’s palm flat on the table and wrist in full pronation, a dorsal to volar load is applied across the distal ulna. Pain should be reproduced at the distal radioulnar joint level and ulnar motion may be produced. The patient can also be asked to push the ulna into the exam table with the hand flat on the table and in full pronation. A positive exam will also induce pain and ulnar motion.

Fig. 9

Bilateral test—The examiner bilaterally places the index finger on the distal radioulnar joint and the middle finger on the ulnar head, ranging the wrists from pronation ( A ) to supination ( B ) several times to provoke potential subluxation.

Fig. 10

( A ) Mino et al method for determining distal radioulnar joint (DRUJ) congruity—draw a line through the volar ulnar/radial borders of the radius as well as one through the dorsal ulnar/radial borders of the radius. The ulnar head should lie between these two lines in a stable DRUJ. ( B ) The radioulnar ratio (RUR) method. The center of the ulnar head is found using concentric circles. A line similar to that used in the epicenter method is drawn from the dorsal and volar margins of the sigmoid notch. A line perpendicular to this line is drawn to the center of the ulnar head. The AB:AC ratio is the radioulnar ratio (RUR). ( C ) Two lines are drawn from the volar and dorsal margins of the sigmoid notch, connecting perpendicularly to a line connecting the volar and dorsal margins of the sigmoid notch. The amount of the ulnar head that was either volar or dorsal to these lines is measured, and the ratio of this distance to the length of the sigmoid notch is calculated.