Distal radioulnar joint instability
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Distal radioulnar joint (DRUJ) instability refers to excessive painful mobility in the distal radioulnar joint usually as a result of a previous traumatic injury or bony malunion.
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Distal radioulnar joint instability is common but often misdiagnosed 1.
Distal radioulnar joint instability is associated with the following 1-4:
- acute distal radioulnar joint dislocation
- distal radial fractures
- triangular fibrocartilage complex injuries
- fracture malunion
Patients will usually present with acute or chronic ulnar sided wrist pain. The clinical examination might reveal restricted supination or pronation, a snap during wrist rotation or a prominent ulnar head in pronation 1-4. Clinical testing as the ballotement test, clunk-test, ulnar fovea sign, press-test or extensor carpi ulnaris test might be abnormal and/or associated with pain 1-4.
Distal radioulnar joint instability can be caused by the following conditions 2,4:
- traumatic injuries
- Galeazzi fracture-dislocation
- Essex-Lopresti fracture-dislocation
- distal radius fracture
- ulnar head fracture or foveal avulsion
- radioulnar ligament tears
Distal radioulnar joint instability can be categorized into dorsal, palmar or multidirectional instability 2.
Radiographic signs that might indicate distal radioulnar joint instability include the following 2,3:
- ulnar styloid base fracture
- ulnar foveal avulsion fracture
- >20° of dorsal radial angulation
- >5 mm of radial shortening
Should be done with the forearm in a neutral position including a true lateral radiograph. This might reveal widening or displacement of the distal radioulnar joint 1,2.
A radioulnar distance of >6 mm between the most dorsal cortices on a true lateral radiograph indicates distal radioulnar instability 1,3. However, rotation as little as >10° of rotation can cause false results 2.
Another option is to obtain bilateral clenched-fist radiographs for comparative evaluation of the distal radioulnar gap distance 4.
Subluxation of the distal radioulnar joint can be evaluated with different methods including 1,5:
- radioulnar line (Mino) method
- subluxation ratio method
- congruency method
- epicenter method
- radioulnar ratio method
However, some of them are associated with a high amount of false positives 1,5 such as the Mino and congruency method. The epicenter method is considered the most reliable but there is a high variation in normal ulnar translation, which have to be taken into account 5. CT assessment of both wrists is a good option to increase specificity and reduce false positives.
MRI can be used for the evaluation of the triangular fibrocartilage complex (varying sensitivity and specificity) and the evaluation of the volar and dorsal radioulnar ligament.
A description of the following features should be included in the radiology report:
- ulnar subluxation and evaluation method
- presence of distal fractures or dislocations
- fracture malunion
- presence of triangular fibrocartilage complex injuries especially radioulnar ligament injury
- a distal radioulnar joint incongruency
- inflammatory, neoplastic or congenital lesions
Treatment and prognosis
Management will depend on the etiology, the congruity of the distal radioulnar joint and includes conservative therapy in dorsal subluxations in a congruent joint, or operative methods in almost all other settings including Galeazzi fractures, Essex-Lopresti injuries, triangular fibrocartilage injury and/or fractures through the base of the ulnar styloid 1. Surgical approaches include repair or reconstruction of the triangular fibrocartilage complex or open reduction and internal fixation of fractures 2,3.
The main differential diagnosis of implant migration include the following 1:
- ulnar impaction
- distal radioulnar joint incongruity
- distal radioulnar joint arthritis
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- 4. Omokawa S, Iida A, Kawamura K et al. A Biomechanical Perspective on Distal Radioulnar Joint Instability. J Wrist Surg. 2017;6(2):88-96. doi:10.1055/s-0037-1601367 - Pubmed
- 5. Wijffels M, Stomp W, Krijnen P, Reijnierse M, Schipper I. Computed Tomography for the Detection of Distal Radioulnar Joint Instability: Normal Variation and Reliability of Four CT Scoring Systems in 46 Patients. Skeletal Radiol. 2016;45(11):1487-93. doi:10.1007/s00256-016-2455-y - Pubmed