David H. MacDonald and 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, with a painful click noted on resisted supination, ulnar deviation, and 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.10
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.
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 is 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.
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.
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.
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.
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.
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 ulnarsided 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 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 a 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).
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.
The actual subsheath tear may or may not be visualized.
Often, inflammation and partial interstitial tendon disruption are visualized.
An MRI arthrogram 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.
Ultrasound allows dynamic assessment of ECU stability and can be useful in quantifying the degree of ECU tendon subluxation.8
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.
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 ulna-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 (less than 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 sugartong 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. Rowland7 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.
Inoue and Tamura5,6 classified three distinct patterns of injury (TABLE 1).
Treatment of type 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).
Because of its simplicity and the ability to place a gliding surface between the bone and tendon, the sling is preferred.
Treatment of type C lesions
Separation of the fibro-osseous sheath from bone necessitates repositioning of the tissue at the ulnar margin of the groove (see False Pouch Reconstruction and Imbrication for Type C Lesions).
Stretching and attenuation of the sheath without separation from bone may be effectively treated by suture imbrication, depending on the quality of the tissue.
Although this chapter describes reconstruction of traumatic ECU subluxation, reconstruction also may be considered in the patient with inflammatory arthropathy and secondary volar dislocation of the ECU tendon. The opportunity to stabilize the ulnar wrist and DRUJ while forestalling progression of deformity may lead the patient and surgeon toward surgical care even in the absence of pain.
Preoperative Planning
All preoperative information obtained from the history, the physical examination, and imaging studies should be thoroughly reviewed and synthesized into the operative plan. For example, a patient with joint line tenderness and an MRI indicating a TFCC injury might benefit from wrist arthroscopy before any open procedure is done.
Dorsal synovitis or tenosynovitis requiring débridement
The existence of a shallow ulnar osseous groove and the need to deepen the groove surgically for added stability
The paucity of soft tissue for reconstruction and the need for another graft choice for subsheath reconstruction. Graft options include the palmaris and flexor carpi ulnaris tendons.
Positioning
The patient is positioned supine on the operating table with the injured extremity extended on an armboard in the usual manner.
Initially, the procedure is performed with the arm extended and pronated. If the wrist must be placed in a neutral or supinated position, the elbow is flexed.
Approach
A precise incision is chosen to allow for the predetermined method of reconstruction.
Make a Brunner zigzag incision over the sixth extensor compartment.
The incision begins 1 to 2 cm distal to the ulnocarpal joint and is carried proximally 5 cm.
Identify and protect the dorsal cutaneous branch of the ulnar nerve in the distal incision.
Incise the extensor retinaculum on its far ulnar border and carefully separate it from the underlying sixth extensor compartment fibro-osseous sheath (see Fig 2).
Conservation of and planned incision in the extensor retinaculum is critical to allow for its use as a sling to stabilize the ECU tendon (see Retinacular Sling Reconstruction for Type A and B Lesions)
Following exposure, inspect the separate fibro-osseous sheath of the ECU and note the position of the tendon through pronosupination.
Perform a tenosynovectomy as indicated.
TECHNIQUES
RETINACULAR SLING RECONSTRUCTION 2 FOR TYPE A AND B LESIONS
Retinacular sling reconstruction 2 is performed when the sheath is ruptured and not repairable.
At the level of the ulnar groove, create a rectangular flap of tissue, 2 to 3 cm wide, based on the septum separating the fifth and sixth extensor compartments (TECH FIG 1A).
Pass this radially based sling in an ulnar direction, volar to the ECU tendon, then fold it back radially over the tendon and secure it to the ulnar portion of the fifth compartment (TECH FIG 1B).
This places the superficial surface of the retinaculum in contact with the ECU tendon.
Avoid constricting the ECU tendon by ensuring that the sling is wide and loose, which still prevents subluxation of the tendon.
The portion of the extensor retinaculum not used for the sling is repaired anatomically.
TECH FIG 1 • Retinacular sling reconstruction of type A and B lesions. A. Creation of a radially based extensor retinaculum sling. B. The retinacular flap is brought deep to the ECU tendon, then looped back over the tendon and sewn to the extensor retinaculum overlying the ulnar compartment. This places the superficial surface of the retinaculum in contact with the ECU tendon when the reconstruction is completed.
ALTERNATE RETINACULAR SLING RECONSTRUCTION FOR TYPE A AND B LESIONS
An alternate retinacular sling reconstruction9 requires the development of an ulnarly based, rectangular flap, 2 to 3 cm wide, of supratendinous retinacular tissue, beginning at Lister's tubercle or over the second extensor compartment if more length is required (TECH FIG 2A).
The flap is based on the ulnar septum of the fifth extensor compartment.
Pass the tissue ulnarly, deep to the ECU tendon, then back over the tendon to create the sling.
This places the deep surface of the retinaculum in contact with the ECU tendon.
Insert suture anchors on the radial and ulnar margins of the ulnar groove, and use this suture to stabilize the flap (TECH FIG 2B).
Avoid constricting the ECU tendon, as discussed previously.
TECH FIG 2 • Alternate retinacular sling reconstruction of type A and B lesions. A. The ulnarly based extensor retinaculum flap is harvested, then swung ulnarward, deep to the ECU tendon. B. The tissue is then brought back over the tendon and secured to itself and the ulna, using bone anchors. The remaining retinaculum is repaired in an anatomic fashion. This places the deep surface of the retinacular flap in contact with the ECU tendon when the reconstruction is complete.
RETINACULAR GRAFT AUGMENTATION FOR TYPE A AND B LESIONS
Retinacular graft augmentation4 is performed when the sheath is ruptured and not repairable.
Harvest a 2- × 2-cm square graft from the distal suprtendinous retinaculum (TECH FIG 3A).
Secure this graft to the periosteum on the ulnar and radial borders of the ulnar osseous groove to maintain the ECU tendon within the groove.
Roughen the bone surface to encourage attachment, and place suture anchors at the anatomic attachment sites along the radial and ulnar borders of the ulnar osseous groove.
Secure the harvested graft to the margins of the ulnar groove, allowing bony contact between the graft and the ulna (TECH FIG 3B).
Place the deep surface of the graft against the tendon.
This provides secure fixation and does not rely on questionable soft tissue for early fixation.
TECH FIG 3 • Free retinacular flap reconstruction of type A and B lesions. A 2- × 2-cm portion of distal extensor retinaculum is harvested and secured to the ulnar osseous groove using small bone anchors.
FALSE POUCH RECONSTRUCTION AND IMBRICATION FOR TYPE C LESIONS
False pouch reconstruction and imbrication6 is done when the fibro-osseous sheath of the ECU tendon is attenuated and stretched, but intact. The tendon subluxates out of the ulnar groove during forearm rotation (TECH FIG 4A,B).
Incise the sheath on its ulnar margin (TECH FIG 4C).
If the sheath has separated from the deep periosteum, roughen the medial surface of the ulna deep to the false pouch (TECH FIG 4D).
Insert suture anchors at the site of the true ulnar attachment of the sheath (TECH FIG 4E).
Use suture from the bone anchors to capture and repair the fibro-osseous sheath, securing it to the prepared bone bed (TECH FIG 4F).
The effect is to imbricate the attenuated sheath and obliterate the false pouch.
Place additional permanent sutures to complete the repair (TECH FIG 4G).
TECH FIG 4 • Type C lesion. A. The supratendinous retinaculum has been incised, revealing the ECU subsheath. The subsheath is inflamed, stretched, and attenuated, allowing tendon subluxation. B.Diagrammatic representation of a type C lesion in which the sheath has pulled away from the bone. C. An incision is made in the attenuated subsheath, allowing visualization of the tendon. Despite MRI findings that indicate potential intrasubstance injury (see Fig 3A), the tendon itself appears normal. D. The bone underlying the ulnar subsheath flap is roughened with a rasp. E,F. Mini–bone anchors are used to secure the tissue to the ulnar border of the groove and imbricate the subsheath. G. Additional permanent sutures complete the repair.
DEEPENING OF THE ULNAR OSSEOUS GROOVE
Deepening of the ulnar osseous groove is an optional technique that may be used to address all lesion types.
This technique is added to the reconstruction when preoperative studies or intraoperative findings suggest that a shallow ulnar osseous groove contributes significantly to subluxation of the ECU tendon (TECH FIG 5A).
Retract the ECU tendon out of its groove.
Carefully elevate the periosteum and a thin layer of bone along the ulnar 2 to 3 cm of the ulnar osseous groove using a sharp, curved osteotome (TECH FIG 5B).
The radial border is used as a hinge to expose the underlying cancellous bone.
Precise elevation of the osteoperiosteal flap ensures adequate coverage of the raw bony surfaces.
Remove cancellous bone using a small curette (TECHFIG 5C), no deeper than 2 to 3 mm.
The cortical bone flap is then returned to its position and tamped down using a small bone tamp (TECH FIG 5D). The periosteum is repaired (TECH FIG 5E).
Treat any remaining exposed bony surface with bone wax.
TECH FIG 5 • Deepening of the ulnar osseous groove. A. ECU tendon in a shallow ulnar groove. B. A sharp curved osteotome is used to create an osteoperiosteal “trapdoor” with a hinge of periosteum radially. C. A curette is used to remove cancellous bone. D. A bone tamp is used to close the trapdoor gently and deepen the osseous groove. E. The periosteum is then secured using 4-0 suture if feasible.
CLOSURE AND SPLINTING
Perform passive motion testing to ensure that the ECU tendon is stable in its groove following reconstruction or repair.
Close the extensor retinaculum in a side-to-side fashion using absorbable suture.
Deflate the tourniquet and obtain hemostasis.
Following routine skin closure and dressing placement, place a sugartong splint with the forearm mildly pronated and the wrist in mild extension and radial deviation.
POSTOPERATIVE CARE
The sutures are removed 2 weeks after surgery, and an above elbow cast is applied with the forearm and wrist positioned in the manner described.
This cast is removed 2 weeks later, and therapy is initiated with use of a fabricated sugartong splint and progressive range of motion as described in Nonoperative Management.
OUTCOMES
No large conclusive studies on which to base outcomes have yet been published.
A few case reports and smaller series have reported good results following surgical treatment for ECU subluxation.1–4,6,7,9 Our experience mirrors these reports.
COMPLICATIONS
The uncommon nature of ECU subluxation, the uniformly acceptable surgical outcomes, and the lack of large surgical case series result in a sparse list of postoperative complications. Trends with which to define “routine” postsurgical complications are simply not present.
Complications that have been reported in the literature include the following:
Complex regional pain syndrome1
Decreased wrist motion
Decreased grip strength
REFERENCES
1. Allende C, Le Viet D. Extensor carpi ulnaris problems at the wrist: Classification, surgical treatment and results. J Hand Surg Br 2005;30:3:265–272.
2. Burkhart S, Wood M, Linscheid RL. Posttraumatic recurrent subluxation of the extensor carpi ulnaris tendon. J Hand Surg Am 1982;7:1:1–3.
3. Chun S, Palmer A. Chronic ulnar wrist pain secondary to partial rupture of the extensor carpi ulnaris tendon. J Hand Surg Am 1987;12:1032–1035.
4. Eckhardt W, Palmer A. Recurrent dislocation of extensor carpi ulnaris tendon. J Hand Surg Am 1981;6:629–631.
5. Inoue G, Tamura Y. Recurrent dislocation of the extensor carpi ulnaris tendon. Br J Sports Med 1998;32:172–177.
6. Inoue G, Tamura Y. Surgical treatment for recurrent dislocation of the extensor carpi ulnaris tendon. J Hand Surg Br 2001;26:556–559.
7. Rowland S. Acute traumatic subluxation of the extensor carpi ulnaris tendon at the wrist. J Hand Surg Am 1986;11:809–811.
8. Pratt R, Hoy GA. Extensor carpi ulnaris subluxation or dislocation? Ultrasound measurement of tendon excursion and normal values. Hand Surg 2004;9:137–143.
9. Spinner M, Kaplan E. Extensor carpi ulnaris: Its relationship to the stability of the distal radio-ulnar joint. Clin Orthop Relat Res 1970;68:124–129.
10. Taleisnik J, Gelberman R, Miller BW, et al. The extensor retinaculum of the wrist. J Hand Surg Am 1984:9:495–501.