Distal Radioulnar Joint (DRUJ) Dislocation: Causes, Symptoms, Diagnosis, and Treatment

What is DRUJ Dislocation?

A Distal Radioulnar Joint (DRUJ) dislocation is a significant orthopedic injury involving the complete separation of the articulating surfaces of the radius and ulna bones at the wrist, profoundly impacting forearm rotation and wrist stability.

Understanding the DRUJ: Anatomy and Function

The Distal Radioulnar Joint (DRUJ) is a critical pivot joint located at the wrist, facilitating the complex movements of the forearm and hand. It is formed by the articulation of the distal end of the ulna and the ulnar notch of the radius. Unlike many joints, its primary role is not in wrist flexion/extension but in pronation (turning the palm downwards) and supination (turning the palm upwards) of the forearm.

Key anatomical components of the DRUJ include:

• Radius: The larger of the two forearm bones, located on the thumb side. Its distal end forms the larger part of the wrist joint and articulates with the ulna at the DRUJ.
• Ulna: The smaller, longer forearm bone, located on the pinky finger side. Its distal end, specifically the ulnar head, articulates with the radius.
• Triangular Fibrocartilage Complex (TFCC): This is a crucial structure acting as the primary stabilizer of the DRUJ. It's a complex of cartilage and ligaments that cushions the joint, binds the radius and ulna together, and transmits load across the wrist. The TFCC includes the articular disc, dorsal and volar radioulnar ligaments, and meniscal homologue.

The intricate interplay of these structures allows for a remarkable range of rotational motion, essential for daily activities, sports, and occupational tasks.

What is DRUJ Dislocation?

A DRUJ dislocation occurs when the distal ulna and radius lose their normal anatomical alignment and articulation. This is a severe injury that disrupts the crucial stability provided by the TFCC and surrounding soft tissues. When the joint dislocates, the mechanical axis of forearm rotation is compromised, leading to significant pain, deformity, and loss of function.

Dislocations are typically classified based on the direction of the ulnar head's displacement relative to the radius:

• Posterior (Dorsal) Dislocation: The more common type, where the ulnar head dislocates towards the back (dorsal aspect) of the wrist. This often occurs with a fall onto an outstretched hand (FOOSH) with the forearm in pronation.
• Anterior (Volar) Dislocation: Less common, where the ulnar head dislocates towards the front (volar aspect) of the wrist. This usually results from a FOOSH injury with the forearm in supination.

Causes and Risk Factors

DRUJ dislocations are predominantly caused by high-energy trauma, often involving a combination of axial load, rotation, and hyperextension or hyperflexion forces applied to the wrist.

Common causes and associated risk factors include:

• Falls onto an Outstretched Hand (FOOSH): This is the most frequent mechanism of injury, especially when the impact occurs with the forearm in a position of extreme pronation or supination.
• Direct Trauma: A direct blow to the wrist or forearm can force the joint out of alignment.
• Sports Injuries: Activities involving high impact, falls, or repetitive stress on the wrist (e.g., gymnastics, football, skiing, cycling accidents).
• Motor Vehicle Accidents: High-velocity impacts can lead to complex wrist and forearm injuries, including DRUJ dislocation.
• Associated Fractures: DRUJ dislocation frequently occurs in conjunction with other fractures, particularly:
  • Distal Radius Fractures: Fractures of the radius near the wrist, often leading to secondary DRUJ instability or dislocation.
  • Essex-Lopresti Injury: A severe injury involving a radial head fracture, interosseous membrane disruption, and DRUJ dislocation.
• Chronic Instability: Prior injuries, ligamentous laxity, or degenerative changes can predispose individuals to recurrent DRUJ dislocations or subluxations.

Recognizing the Symptoms

The symptoms of a DRUJ dislocation are typically acute and noticeable, requiring immediate medical attention.

Key indicators include:

• Severe Pain: Localized pain at the wrist, particularly on the ulnar (pinky finger) side, which worsens with movement.
• Visible Deformity: A prominent bump or depression on the back or front of the wrist, corresponding to the displaced ulnar head. This is often described as a "piano key sign" if the ulnar head can be depressed but springs back up.
• Limited Range of Motion: Significant difficulty and pain with forearm pronation and supination. Wrist flexion/extension may also be affected.
• Swelling and Bruising: Inflammation and discoloration around the wrist joint.
• Instability or Weakness: A feeling of the wrist "giving way," particularly with gripping or rotational movements.
• Clicking or Grinding Sensation: May be present with attempted movement, indicating abnormal joint articulation.
• Nerve Impingement (less common): Tingling, numbness, or weakness in the hand if surrounding nerves are compressed.

Diagnosis: How DRUJ Dislocation is Identified

Accurate and timely diagnosis is crucial for effective management of DRUJ dislocations.

The diagnostic process typically involves:

• Clinical Examination:
  • History Taking: The physician will inquire about the mechanism of injury, onset of symptoms, and prior wrist issues.
  • Physical Inspection: Observing for visible deformity, swelling, and bruising.
  • Palpation: Gently feeling the wrist for tenderness and the position of the ulnar head.
  • Range of Motion Assessment: Evaluating the active and passive range of pronation, supination, and wrist flexion/extension.
  • Stability Tests: Specific maneuvers to assess DRUJ stability, such as the "piano key test" or stress tests.
• Imaging Studies:
  • X-rays: Standard radiographs (AP, lateral, and oblique views) are essential to confirm the dislocation, determine its direction (anterior or posterior), and rule out associated fractures of the radius or ulna. Specific views, like true lateral views with the elbow at 90 degrees, are critical for assessing DRUJ alignment.
  • Computed Tomography (CT) Scan: Often used to provide detailed cross-sectional images of the joint, precisely defining the degree of displacement, identifying subtle fractures, and assessing the congruity of the joint surfaces. This is particularly valuable for surgical planning.
  • Magnetic Resonance Imaging (MRI) Scan: While not always necessary for acute dislocation diagnosis, an MRI is excellent for evaluating soft tissue injuries, especially the TFCC and other stabilizing ligaments, which are frequently torn in DRUJ dislocations.

Treatment Approaches

Treatment for DRUJ dislocation aims to restore anatomical alignment, stabilize the joint, and regain full functional range of motion and strength. The approach depends on whether the dislocation is acute (recent) or chronic, and if it's isolated or associated with fractures.

Acute Dislocations (within hours to days of injury)

• Closed Reduction: The primary treatment for most acute DRUJ dislocations. This non-surgical procedure involves a trained medical professional manually manipulating the bones back into their correct position. It is typically performed under local anesthesia or sedation.
  • Procedure: For posterior dislocations, the forearm is usually supinated while direct pressure is applied to the ulnar head. For anterior dislocations, the forearm is pronated.
• Immobilization: Following successful reduction, the wrist and forearm are immobilized in a cast or splint for 4-6 weeks to allow the torn ligaments (especially the TFCC) to heal. The position of immobilization (pronation or supination) depends on the direction of the initial dislocation to maintain stability.
• Open Reduction: If closed reduction is unsuccessful, or if there are associated fractures preventing proper alignment, surgical intervention (open reduction) is required to directly visualize and realign the joint.

Chronic Instability (persistent instability or recurrent dislocations)

If DRUJ instability persists after initial treatment or if the dislocation is chronic and irreducible, more complex interventions may be necessary:

• Conservative Management: For mild chronic instability, physical therapy focusing on strengthening the forearm muscles and improving proprioception, along with bracing, may be attempted.
• Surgical Intervention: Various surgical procedures exist, depending on the underlying cause and extent of damage:
  • TFCC Repair/Reconstruction: If the TFCC is significantly torn or avulsed, it may be surgically repaired or reconstructed using grafts.
  • Ligament Reconstruction: Other stabilizing ligaments may need reconstruction.
  • Osteotomy: In cases of bony deformities (e.g., malunion of a distal radius fracture) contributing to instability, bone reshaping (osteotomy) may be performed.
  • Salvage Procedures: For severe, irreparable damage or chronic pain, procedures like Darrach procedure (ulnar head resection), Sauvé-Kapandji procedure (fusion of the DRUJ with creation of a pseudoarthrosis), or ulnar head replacement may be considered, though these alter the biomechanics of the joint.

Rehabilitation and Recovery

Rehabilitation is a critical phase following DRUJ dislocation treatment, regardless of whether it was managed conservatively or surgically. The goal is to restore full range of motion, strength, and stability to the wrist and forearm.

• Immobilization Phase:
  • Focus on managing pain and swelling.
  • Maintain range of motion in unaffected joints (fingers, elbow, shoulder).
  • Gentle isometric exercises for forearm muscles (if permitted).
• Early Mobilization Phase (after cast/splint removal):
  • Gradual, controlled exercises to regain pronation and supination, and wrist flexion/extension.
  • Passive and active assisted range of motion.
  • Gentle strengthening with light resistance.
• Strengthening and Functional Phase:
  • Progressive resistance exercises for all forearm and wrist muscles.
  • Focus on grip strength, rotational strength, and wrist stability.
  • Proprioceptive training to improve joint awareness and control.
  • Gradual return to functional activities, including sport-specific or work-specific movements.

Adherence to the prescribed rehabilitation program is paramount for optimal recovery and to prevent complications such as stiffness, chronic pain, or recurrent instability. The recovery period can range from several weeks to several months, depending on the severity of the injury and the chosen treatment.

Prevention Strategies

While not all traumatic injuries can be prevented, certain measures can reduce the risk of DRUJ dislocation:

• Fall Prevention:
  • Improve balance and coordination through exercise.
  • Ensure well-lit environments and clear pathways at home.
  • Use appropriate footwear.
• Protective Gear:
  • Wear wrist guards during high-risk activities or sports like snowboarding, rollerblading, or cycling.
• Strength and Flexibility:
  • Maintain overall fitness, including forearm and wrist strength and flexibility, to enhance joint resilience and proprioception.
• Proper Technique:
  • Learn and practice proper falling techniques in sports or activities where falls are common.

When to Seek Medical Attention

If you suspect a DRUJ dislocation or experience any of the symptoms described, it is crucial to seek immediate medical attention. Early diagnosis and appropriate treatment are vital to prevent long-term complications such such as chronic pain, stiffness, instability, and degenerative changes in the joint. Do not attempt to reduce the dislocation yourself, as this can cause further damage.