DRUJ Instability / Dislocation
synonyms:Distal Radioulnar Joint dislocation, DRUJ instability
DRUJ Instability ICD-9
- 833.01(closed), 833.11(open)
DRUJ Instability Etiology / Epidemiology / Natural History
DRUJ Instability Anatomy
- DRUJ static restraints = sigmoid notch of the distal radius, dorsal and palmar radioulnar ligaments, the interosseous membrance and the dorsal retinaculum.
- DRUJ dynamic restaints = pronator quadratus, extensor carpi ulnaris and the flexor carpi ulnaris.
- Extensor carpi ulnaris with the attached TFCC and styloid fragment may prevent closed reduction. After the ECU has been detached from the distal part of the ulna together with the TFCC and the ulnar styloid process, it slips around either the radial or ulnar boarder of the distal part of the ulna to lie volar to it, Consequently, the joint cannot be reduced until the tendon with the attached TFCC and styloid fragment has been returned to it’s anatomical position. (Hanel DP, CORR 1988;234:56)
- Sigmoid notch of radius has a radius of curvature of 15mm. Ulnar head has a radius of curvature of 10mm.
- The ulnar head translates 5.4mm volarly in supination and 2.8mm dorsally in pronation. (Pirela-Cruz MA, J Hand Surg 1991;16A:75).
- Dorsal radioulnar ligaments are tight in pronation; lax is supination. Dorsal capsule imbrication prevents volar translation of the radius.
- Palmar radioulnar ligaments are tight in supination and lax in pronation. Palmar capsule imbrication prevents dorsal translation of the radius.
DRUJ Instability Clinical Evaluation
- Pain +/- snapping localized to the radioulnar joint exacerbated by forearm rotation.
- The ulnar head is prominent dorsal, with the forearm in pronation, as compared to the normal side.
- Piano key sign=patient actively tries to force pisiform into the table using entire extremity. Distal ulna moves dorsally like a piano key. Compare to uninjured side.
- TFC tenderness=with forearm in neutral palpate area proximal to pisiform between FCU and ulna styloid. Pain indicates TFC injury.
- Shuck test: With the patient’s forearm in supination, the examiner should holds the distal part of the ulna between the thumb and index finger and tests for dorsal and volar displacement of the distal part of the ulna. Increased laxity as compared to the normal side indicates DRUJ instability/peripheral TFCC tears.
- Acute dislocation: pronation is blocked in volar dislocations; supination is blocked in dorsal dislocations of the DRUJ.
DRUJ Instability Xray / Diagnositc Tests
- P/A, lateral and oblique views of both wrists. Subluxation or dislocation can be seen on a true lateral xray with the arm in neutral rotation. Consider lateral views of both wrists taken with the forearm in pronation. Measure ulnar variance.
- Signs of DRUJ injury: fracture at the base of the ulnar styloid, widening of the DRUJ space seen on the P/A xray, >20° of dorsal radial angulation, and >5 mm of proximal displacement of the distal part of the radius. (Szabo RM, JBJS 2006;88A:884).
- CT indicated if diagnosis is in question or pain / deformity limits the ability to obtain true lateral xray. (Mino DE, JBJS 1985;67A:247)
- MRI: useful to evaluate for TFCC injury and to assess DRUJ subluxation. DRUJ subluxation can be quanified using the radiolulnar ratio (Lo IK, J Hand Surg 2001;26A:236).
DRUJ Instability Classification / Treatment
- Acute dorsal, reducible: reduced with digital pressure on the distal part of the ulna and forceful supination. LAC in suppination for 6wks. Consider varifying reduction with CT scan.
- Acute volar, reducible: reduced with digital pressure on the distal part of the ulna in a dorsal direction combined with forceful pronation. LAC in slight pronation for 6 wks.
- Acute unreducible: Can be due to interposition of the TFCC, EDM, ECU, or the ring or little finger extensors. Treatment = open reduction and repair of injured structures.
- Chronic = DRUJ reconstruction, any osseous malalignment must be corrected. Pre-operative MRI is useful to determine integrity of TFCC.
- Adams BD, J Hand Surg 2002;27Am:243
- DRUJ Reconstruction Technique
DRUJ Instability Associated Injuries / Differential Diagnosis
DRUJ Instability Complications
DRUJ Instability Follow-up Care
DRUJ Instability Review References