Management of ECU Tendon Subluxation
For acute traumatic ECU tendon subluxation, immobilize the wrist in a long-arm cast with the elbow flexed to 90°, wrist in 30° extension, radial deviation, and pronation for 4-8 weeks; if conservative treatment fails or for chronic cases, proceed to surgical reconstruction of the ECU tendon sheath. 1
Initial Assessment and Diagnosis
Confirm the diagnosis with dynamic ultrasound, which is highly effective and noninvasive for detecting ECU tendon subluxation during wrist supination and pronation movements 2. Dynamic ultrasonography can reveal volar subluxation of the ECU tendon and identify associated pathology such as longitudinal tendon splitting 3.
Key Clinical Features to Identify:
- Painful snapping at the ulnar wrist during supination and pronation 2
- Mechanism of injury typically involves forced supination, ulnar deviation, and wrist flexion 1
- The ECU tendon subluxes palmarly and ulnarly during wrist circumduction when the subsheath is disrupted 1
Critical Differential Diagnoses to Exclude:
- Distal ulnar fracture
- Ulnar collateral ligament sprain
- Triangular fibrocartilage complex lesion
- Lunotriquetral instability
- Distal radioulnar joint injury
- Pisotriquetral joint injury
- ECU tendinopathy without subluxation 1
Conservative Management for Acute Cases
Initial Immobilization Protocol:
Start with a long-arm cast positioned with:
- Elbow flexed to 90°
- Wrist in approximately 30° extension
- Radial deviation
- Pronation
- Duration: 4-8 weeks 1
Common pitfall to avoid: A short-arm cast alone is often insufficient. In one documented case, a short-arm cast for 4 weeks failed to stabilize the tendon, requiring conversion to a long-arm cast for an additional 4 weeks 1.
Post-Immobilization Protocol:
- After cast removal, transition to a rigid wrist brace for 3 additional weeks 1
- Initiate rehabilitation during the bracing period 1
- Reassess tendon stability before returning to activities 1
Surgical Management
Indications for Surgery:
Proceed to surgical reconstruction if:
- Conservative treatment fails after 4-8 weeks of appropriate immobilization 1
- Chronic or recurrent subluxation persists 2, 4
- The patient has persistent symptoms despite adequate conservative management 1
Surgical Technique (Anatomic Reconstruction):
The most effective approach involves anatomic ECU tendon sheath reconstruction 2:
- Elevate the ECU tendon dorsally and radially within its sheath 2
- Deepen the distal ulnar groove using a power burr 2
- Place 2-3 suture anchors along the ulnar margin of the reconstructed groove 2
- Pass sutures through the ulnar border of the ECU sheath and tie them, securing the tendon sheath to bone 2
Expected Surgical Outcomes:
This anatomic reconstruction technique demonstrates:
- Statistically significant improvement in wrist flexion-extension arc 2
- Improved radial-ulnar deviation 2
- Enhanced pronation-supination 2
- Increased grip strength 2
- Significant reduction in pain scores 2
- Improved DASH (Disabilities of the Arm, Shoulder, and Hand) scores 2
- Mean follow-up of 31 months (range 24-45 months) shows sustained improvement 2
Special Considerations
Associated Pathology:
Be aware that ECU subluxation can occur simultaneously with other extensor tendon subluxations, such as sagittal band subluxation at the metacarpophalangeal joints 3. When multiple tendons are involved, evaluate for underlying inflammatory conditions 5.
Type of Tendinopathy Matters:
- Constrained tendinopathies (tendon entrapment with thickened tendon): Goal is to prevent further degeneration 4
- Unconstrained tendinopathies (ruptured ECU subsheath with subluxation): Goal is to re-establish normal ulna-ECU connections 4
Activity-Related Risk:
ECU tendinopathies are particularly common in athletes using bats, sticks, or clubs 4. Consider sport-specific modifications during rehabilitation and return-to-play planning.