Surgical Treatment for Extensor Carpi Ulnaris Subluxation
David H. MacDonald
Thomas R. Hunt III
DEFINITION
Extensor carpi ulnaris (ECU) subluxation occurs when the separate subsheath of the sixth dorsal compartment is torn or attenuated.
Incompetence of the ECU subsheath permits subluxation or dislocation of the ECU tendon out of the ulnar groove of the ulna, often with a painful click noted on resisted supination, ulnar deviation, and mild palmar flexion.
ANATOMY
The dorsal extensor retinaculum of the wrist is composed of two primary layers (FIG 1).
The supratendinous retinaculum originates 2 to 3 cm proximal to the radiocarpal joint and ends distinctly at the carpometacarpal joints. The most radial attachment on the distal radius forms the radial septum for the first extensor compartment. The supratendinous retinaculum courses medially, surrounding the ulna.11
The supratendinous retinaculum participates as a block to tendon subluxation for the first through fifth extensor compartments but does not function to prevent subluxation of the ECU.
The infratendinous retinaculum runs from the radiocarpal to the carpometacarpal joints. It is found deep to the fourth and fifth extensor compartments on the radius. The ECU lies in its own separate fibro-osseous subsheath, which represents a duplication of the infratendinous retinaculum.
FIG 1 • Axial representation of dorsal extensor compartments. The ECU tendon has a separate compartment along the dorsum of the ulna. The supratendinous retinaculum courses ulnarward over the sixth compartment and does not communicate with the separate ECU fibro-osseous subsheath in any significant way.
The ECU sheath is separated from the supratendinous retinaculum by loose areolar tissue.
The fibro-osseous subsheath of the sixth dorsal compartment overlies 1.5 to 2.0 cm of the distal ulna and arcs from the radial to ulnar wall of the ECU osseous groove. It ensheathes the ECU and maintains the tendon tightly in the groove (FIG 2).
The ECU subsheath contributes to the dorsal portion of the triangular fibrocartilage complex (TFCC).
PATHOGENESIS
The mechanism of a traumatic injury most commonly involves active ECU contraction combined with forced supination, palmar flexion, and ulnar deviation.
Injuries resulting from trauma can range from simple attenuation to complete rupture of the ECU fibro-osseous sheath.
Traumatic ECU subluxation is commonly reported in association with racket sports, baseball, and golf.
 FIG 2 • Dorsal anatomic view of the sixth dorsal component. This representation shows the relation between the deep ECU subsheath and the superficial supratendinous extensor retinaculum. |
NATURAL HISTORY
Chronic subluxation of the ECU tendon over the ulnar prominence of the groove in the distal ulna can lead to painful snapping of the tendon with supination and pronation. This can progress to ECU tendinopathy and partial tendon tears.
An injury to the ECU sheath resulting in volar dislocation of the ECU tendon can result in distal radioulnar joint (DRUJ) instability. This joint laxity may cause pain and dysfunction, eventually leading to degenerative changes.
Dislocation of the ECU tendon removes a dynamic stabilizer of the DRUJ.
The subsheath of the sixth extensor compartment represents a component of the dorsal peripheral TFCC. Disruption can result in static instability of the DRUJ.
Some patients may experience relatively minor ECU subluxation and related symptoms that do not progress and often improve with minimal intervention.
PATIENT HISTORY AND PHYSICAL FINDINGS
Patients may present following an acute injury or, more commonly, in the subacute phase, complaining of persistent ulnar wrist pain aggravated by activities requiring pronation and supination. They may relate the sensation of a “click.”
A complete physical examination of the patient’s ulnar-sided wrist complaints should be conducted to elucidate associated pathology and rule out confounding conditions in the differential diagnosis.
Palpation and inspection of sixth dorsal compartment and ECU tendon helps to localize the area of discomfort and focus the physical examination. Most patients with acute sheath ruptures and tendinopathies will be tender to palpation at the level of the distal ulna and groove. Tenderness at the joint line may indicate an associated TFCC tear.
In range-of-motion testing, an inflamed ECU tendon usually will be most painful with full passive radial wrist flexion, although motion most often is full except in the acute setting.
If the tendon dislocates with passive supination, palmar flexion, and ulnar deviation, the ECU is grossly unstable. If the addition of ECU contraction is required for frank dislocation, some inherent stability remains. Pain with subluxation is the critical finding when contemplating surgical treatment.
In resisted finger abduction, pain over the wrist and ECU tendon signifies an inflammatory ECU condition, possibly due to subluxation or overuse.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Routine anteroposterior (AP), lateral, and oblique radiographs in neutral rotation are important.
Pronated grip views and other specialized plain radiographs of the wrist can provide information on other pathologies that contribute to ulnar-sided wrist pain (see Differential Diagnosis).
Magnetic resonance imaging (MRI) is the most sensitive and specific imaging modality to detect ECU subluxation (FIG 3A).
The sensitivity increases in studies with both wrists positioned in pronation, neutral, and supination. This allows side-by-side comparison with the asymptomatic wrist and adequately shows the position of the ECU relative to the ulnar osseous groove in all three positions.
FIG 3 • A. This MRI scan shows a “perched” ECU tendon, out of the dorsal ulnar groove. Notice the increased signal in the tendon substance. B. The coronal MRI arthrogram projection illustrates leakage of the opaque dye into the ECU fibro-osseous subsheath.
The actual subsheath tear may or may not be visualized.
Often, inflammation and partial interstitial tendon disruption are visualized.
An MRI arthrogram of the wrist may depict a subsheath tear and, therefore, an injury to the peripheral TFCC.
Contrast may extravasate into the sixth extensor compartment (FIG 3B).
The study will also provide additional information concerning the remainder of the TFCC and the integrity of the intercarpal ligaments.
DIFFERENTIAL DIAGNOSIS
ECU tenosynovitis
Fullness and pain with palpation of the sixth dorsal compartment
The patient often can reproduce a painful snap or click with supination and ulnar deviation, even in the absence of ECU subluxation.
TFCC injury
Tenderness with direct palpation of the TFCC
Pain with axial loading and rotation of the ulnar-deviated wrist (TFCC compression test)
Instability of the DRUJ with manual manipulation when compared to the contralateral wrist
Lunotriquetral ligament injury
Tenderness to palpation over the dorsal lunotriquetral articulation
The patient may also describe pain and crepitance with ulnar deviation of the wrist.
Provocative maneuvers for lunotriquetral ligament injuries (ie, ballottement test, ulnar snuff box test) have sufficient sensitivity but poor specificity.
Ulnocarpal impaction syndrome
More common in patients with ulnar positive variance
Usually a dynamic phenomenon occurring during forceful activity or pronated gripping
The physical examination findings will be similar to those of TFCC injury, with pain on forced ulnar deviation of the wrist (TFCC stress test) that increases with rotation through the loaded ulnocarpal articulation.
Tenderness will be elicited along the ulnar border of the triquetrum and the distal ulna.
Ulnar styloid nonunion
Uncommon; occurs more commonly with widely displaced styloid fractures at the time of injury
The intimate relationship with the ulnar TFCC attachment means that symptomatic nonunion can be associated with TFCC dysfunction and DRUJ instability.
DRUJ arthrosis
Patients present with complaints of pain, swelling, and stiffness. The pain is exacerbated by forearm rotation, particularly when performed with manual compression of the DRUJ.
NONOPERATIVE MANAGEMENT
In the acute setting (<3 weeks since injury), immobilize the patient in an above-elbow cast. The wrist should be in neutral to slight pronation, neutral to slight radial deviation, and neutral to slight extension.
The cast is removed about 4 to 5 weeks later, and therapy is initiated. A sugar-tong splint is fabricated with the forearm in slight pronation, and a progressive active and active-assisted ROM protocol is initiated.
Three weeks later, a forearm-based splint is provided and the patient slowly progresses back to activities.
Unprotected, full activity is allowed 3 to 4 months after the initiation of treatment.
The literature does not agree on the efficacy of nonoperative treatment. Rowland8 produced a compelling case report of surgical treatment in acute, traumatic ECU subluxation.
In this case, the intraoperative findings showed the edges of the ruptured subsheath to be separated by a minimum of 7 mm, regardless of the position of the wrist.
These findings suggest that nonoperative treatment could routinely lead to clinical ECU subluxation and persistent symptoms.
SURGICAL MANAGEMENT
Surgical reconstruction of the ECU subsheath should be considered in patients with clinically significant symptoms related to painful subluxation of the ECU tendon, especially if the injury is more than 3 weeks old. Treatment must be individualized based on the needs and expectations of the patient.
The guiding principles for surgical repair depend on the essential osteofibrous sheath lesion present at the time of surgery.
Treatment of types A and B lesions
In the acute setting, suture repair is sometimes possible and may be augmented using suture anchors.
When the fibro-osseous sheath is ruptured and deemed irreparable, reconstruction is accomplished using a retinacular sling or free retinacular graft (see Techniques box).Related posts:
Anatomy and Surgical Approaches of the Forearm, Wrist, and Hand
Arthroscopic Treatment of Chondral Injuries and Osteochondritis Dissecans
Fragment-Specific Fixation of Distal Radius Fractures
Arthroscopic and Open Triangular Fibrocartilage Complex Repair
Synovectomy of the Elbow
Surgical Treatment of Septic Arthritis in the Hand and Wrist
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