A 35-year-old female was referred to the Orthopaedics Clinic of our institution for complaints of right ulnar wrist pain. The patient had a known history of previous homolateral forearm fracture.
A 35-year-old female was referred to the Orthopedics Clinic of our institution for complaints of right ulnar wrist pain. The patient had a history of previous homolateral forearm fracture. At physical exam distal radioulnar joint (DRUJ) instability was suspected.
Computed tomography (CT) scans of the distal radioulnar joint, in extreme pronation (Figure 1a), neutral, and extreme supination (Figure 1b) were obtained for both wrists.
The modified radioulnar line method was applied (Figure 2). In extreme supination, significant incongruence between the right sigmoid notch and the ulnar head with volar displacement of the ulnar head was observed, compatible with volar DRUJ instability.
Notice also the presence of a posttraumatic exuberant bony prominence deforming the styloid apophysis of the right ulna (Figures 3 a - and b - arrow).
Subluxation and dislocation of the distal radioulnar joint (DRUJ) is a frequent cause of ulnar wrist pain and mechanical symptoms, remaining challenging both diagnostically and therapeutically.
DRUJ instability has multiple aetiologies and a wide spectrum of severity. It can result from an isolated ligament injury or be part of a complex lesion such as Colles fracture, or Galleazi or Essex-Lopresti fracture-dislocation. The Essex-Lopresti fracture-dislocation consists of a massive axial radioulnar traumatic derangement with longitudinal DRUJ instability, rupture of the interosseous membrane, and impaction fracture of the radial head.
Standard lateral wrist radiographs can only confirm DRUJ instability if a true lateral neutral view is acquired, which has shown to be consistently difficult. Additionally, in most cases DRUJ subluxation is not obvious in the neutral position, and radiographs do not appreciate the dynamic instability observed during active pronation and supination. Cross-sectional imaging with CT can overcome these limitations. A suggested protocol scans both wrists in extreme supination, neutral position, and extreme pronation.
The convex articular surface of lateral distal ulna should be congruent with the sigmoid notch regardless of wrist position. There are several proposed CT diagnostic criteria for DRUJ instability (figure 4). The radioulnar line method was modified by Nakamura et al. (1996) to include within normal limits of congruency, the dorsal displacement of the ulna in the pronation arc (neutral to maximum pronation) and its volar displacement in the supination arc (neutral to maximum supination) of less than one fourth the diameter of the sigmoid notch (figure 5).
The modified radioulnar line method due to its simplicity, low false positive results, and good interobserver agreement, is commonly used. The modification introduced expresses the main difficulty of evaluating DRUJ instability with CT - the large normal variation in the DRUJ translation, related to interindividual differences in the laxity of the ligaments and of others stabilizing soft-tissue structures. Comparison with the unaffected contralateral wrist and correlation with the physical exam findings are quite helpful in this behalf. The provocation of symptoms by a stress test is considered an essential step in differentiating an unstable joint from a normal lax joint.
Dorsal DRUJ instability is the most common form, whereby the distal ulna is dorsally displaced with respect to the distal radius and usually is exacerbated by pronation. Volar dislocation is rarer, usually after a hypersupination injury to the wrist and complete tear of the dorsal radioulnar ligament. This results in a prominent ulnar head on the volar aspect of the wrist and is most pronounced in full supination. Anatomical studies have shown that the isolated division of the dorsal radioulnar ligament produces volar dislocation of the ulna when the forearm is supinated. The dislocation can usually be reduced by pronation.
The treatment of chronic volar DRUJ instability is mainly surgical, mostly by using the techniques employed to treat dorsal DRUJ instability. Recently, as the awareness of the importance of the radioulnar ligaments and joint capsule stabilizing action grows, more specific surgical procedures are being developed.
Volar distal radioulnar joint instability
The patient’s right wrist CT scans in extreme supination, neutral position, and extreme pronation all indicate abnormal morphology of the distal radioulnar joint. Especially in extreme supination, the distal ulna is noticeably displaced toward the palmar side, no longer in normal alignment with the distal radial articular surface. Coronal and axial reconstruction images suggest that the distal ulna does not maintain a normal cylindrical alignment with the sigmoid notch, with visible palmar displacement. This indicates potential palmar distal radioulnar joint (DRUJ) instability or subluxation.
Considering the patient’s history of same-side forearm fracture, current right ulnar-sided wrist pain, and DRUJ instability, the following differential diagnoses should be considered:
Based on the current symptoms (ulnar-sided wrist pain), radiological observations (significant palmar subluxation of the distal ulna in extreme supination), and the history of a forearm fracture, the most likely diagnosis is:
For further clarification of soft tissue structures (e.g., ligaments, joint capsule) and detailed bony evaluation, arthroscopic examination or higher-resolution MRI could be considered.
For chronic palmar DRUJ instability confirmed through imaging and repeated clinical examination, surgical intervention is often required to repair or reconstruct the damaged ligamentous structures and restore joint stability. Conservative management can be attempted in cases of mild symptoms, acceptable stability, or when surgery is contraindicated. This includes:
If there is clear radiological and clinical instability that affects daily function or causes persistent pain, early surgical intervention should be considered, including:
Rehabilitation should follow a gradual and individualized approach, adhering to the “FITT-VP” principle (Frequency, Intensity, Time, Type, Volume, Progression):
Throughout the rehabilitation process, pain, swelling, and functional improvement must be closely monitored. If new pain or a decline in function appears, promptly seek re-evaluation.
Disclaimer: This report is a reference-based analysis derived from the provided medical history and radiological data, and it is not a substitute for an in-person consultation or professional diagnosis by a qualified physician. The actual treatment plan should be determined by a specialist at a formal medical institution according to the patient’s individual condition.
Volar distal radioulnar joint instability
