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EXTENSOR CARPI ULNARIS (ECU) SUBLUXATION

Introduction

Subluxation of the extensor carpi ulnaris (ECU) tendon is regarded as a relatively uncommon injury. It typically results from forced supination, volar flexion, and ulnar deviation of the wrist, which disrupts the ECU subsheath and subluxes the ECU tendon out of its groove in the distal ulna. These injuries are most common in athletes, especially golf and tennis players, which is due to the swing and stroke mechanics involved in these sports. Owing to its fairly generic presentation of ulnar-sided wrist pain, many ECU subluxations are missed on initial evaluation, which often leads to poor long-term outcomes. When properly diagnosed, conservative treatment is usually recommended for most acute injuries, while surgery is reserved for chronic cases and those that fail to improve after a conservative regimen.1-4

Pathophysiology

  • The ECU subsheath stabilizes the ECU during forearm rotation, and subluxation is thought to result from insufficiency of the subsheath.5
  • The injury mechanism of ECU subluxation is usually forced supination, volar flexion, and ulnar deviation of the wrist, which disrupts the ECU subsheath. This can occur in sports like golf and tennis, from a fall on an outstretched hand (FOOSH) injury or potentially from repetitive forceful supination, palmar flexion and ulnar deviation of the wrist.
    • Once the subsheath is damaged, the ECU tendon can sublux and slide under the intact extensor retinaculum.
    • The ECU tendon dislocates during supination and relocates with pronation.2,3

Related Anatomy

  • ECU tendon
  • Extensor retinaculum (superficial to the ECU subsheath and not attached to the distal ulna)
  • ECU subsheath
  • Dorsal extensor compartments
  • Fibro-osseous tunnel of the distal ulna
  • Deep antebrachial fascia
  • Distal radioulnar joint
  • Ulnar styloid
  • Ulnar capitulum
  • Pisiform
  • Triquetrum

Inoue and Tamura created a classification system that grouped ECU subluxation and dislocation into the following 3 types:

  • Type A: the fibro-osseous sheath is torn at its ulnar side, and the tendon may lie beneath the fibrous sheath
  • Type B: the fibro-osseous sheath is disrupted from the radial wall and lies in the groove beneath the tendon
  • Type C: there is detachment of the groove’s periosteum from the ulnar side in continuity with the fibro-osseous sheath, thus forming an expanded and redundant false pouch into which the tendon is dislocated6

Incidence and Related Conditions

  • Traumatic ECU subluxations and dislocations are considered to be rare, but their incidence may actually be much higher, because many cases are missed or misdiagnosed.2
  • The prevalence of ECU subluxation is particularly high in athletes who forcibly flex, supinate, and ulnar deviate their wrist—especially golf and tennis players—and the number of cases is expected to continue to rise in young, active individuals.4
    • One study found the annual prevalence of ECU tendon injury in tennis players to be 1 in 18, and 42% of affected players also had ECU instability.7

Differential Diagnosis

  • ECU dislocation
  • ECU tendinopathy
  • Triangular fibrocartilage complex (TFCC) injury
  • Lunotriquetral (LT) instability
  • Distal radioulnar joint (DRUJ) injury
  • Flexor carpi ulnaris (FCU) tendinopathy
  • Pisotriquetral (PT) joint injury
  • Distal ulnar fracture
  • Ulnar collateral ligament sprain
ICD-10 Codes

  • EXTENSOR CARPI ULNARIS (ECU) SUBLUXATION

    Diagnostic Guide Name

    EXTENSOR CARPI ULNARIS (ECU) SUBLUXATION

    ICD 10 Diagnosis, Single Code, Left Code, Right Code and Bilateral Code

    DIAGNOSISSINGLE CODE ONLYLEFTRIGHTBILATERAL (If Available)
    EXTENSOR CARPI ULNARIS (ECU) STRAIN (WRIST AND HAND LEVEL) (SUBLUXATION) S66.812_S66.811_ 

    Instructions (ICD 10 CM 2020, U.S. Version)

    THE APPROPRIATE SEVENTH CHARACTER IS TO BE ADDED TO EACH CODE FROM CATEGORY S66
    A - Initial Encounter
    D - Subsequent Routine Healing
    S - Sequela

    ICD-10 Reference

    Reproduced from the International statistical classification of diseases and related health problems, 10th revision, Fifth edition, 2016. Geneva, World Health Organization, 2016 https://apps.who.int/iris/handle/10665/246208

Clinical Presentation Photos and Related Diagrams
Clinical Evaluation of ECU Tendon
  • ECU tendon (arrow) subluxation is demonstrated supinating the forearm while flexing and ulnar deviating the wrist.
    ECU tendon (arrow) subluxation is demonstrated supinating the forearm while flexing and ulnar deviating the wrist.
  • ECU tendon (arrow) is being palpated for tenderness and laxity
    ECU tendon (arrow) is being palpated for tenderness and laxity
Symptoms
Ulnar-sided wrist pain that worsens with forearm rotation
"Snapping" or "popping" sound with forceful forearm rotation
Decreased strength, ulnar wrist pain, and/or swelling
Impaired wrist range of motion (ROM)
Typical History

A typical patient is a 20-year-old, left-handed, collegiate female tennis player. During a regional NCAA tournament, she forcefully hit a 2-handed backhand shot with exaggerated topspin on the ball. As she struck the ball, her wrist went from an exaggerated supination position into pronation during the follow-through phase of the stroke. This transition placed excessive strain on the ECU tendon of her left wrist and led to ECU subluxation and subsequent ulnar-sided pain and clicking in her wrist when she rotated her forearm.

Positive Tests, Exams or Signs
Work-up Options
Treatment Options
Treatment Goals
  • Accurately diagnose ECU subluxation
  • Apply appropriate treatment to return function to the the injured wrist
Conservative
  • There is still some controversy regarding the optimal timing and treatment for ECU subluxation, but it generally appears that conservative treatment is appropriate for most patients with acute and uncomplicated injuries, especially if the subluxation is diagnosed accurately at the time of the initial injury.1-3
  • Conservative treatment typically consists of 4-6 weeks immobilization with the wrist in slight radial deviation and extension, and the forearm in pronation.2,5
    • Immobilization can be accomplished using a splint, short-arm cast, long-arm cast, or Muenster cast.
    • After immobilization, the patient should begin physical therapist-supervised exercises that will address any resulting stiffness and assist with the reacquisition of wrist strength and ROM.
    • In some cases a ridged brace may be worn for an additional 3 weeks as the patient regains their abilities.2,5,8
  • Other conservative interventions that may be recommended include rest, cryotherapy, non-steroidal anti-inflammatory drugs (NSAIDs) and steroid injections.8
Operative
  • Surgery is typically considered in cases of chronic ECU subluxation, when apparent traumatic insufficiency persists after casting, or when patients are unsatisfied with conservative treatment (eg, being unable to return to previous activities because of continued pain and disability).2,3,5
  • Surgical options include direct repair or reconstruction of the ECU subsheath with extensor retinaculum flap or fascial patch and surgical reconstruction of the sixth dorsal compartment.1-3
    • Surgery should be followed by a period of immobilization for ~6 weeks and restricted athletic participation and vigorous rehabilitation for another 3 months before a gradual return to activity.1,2
    • Variations in surgical techniques include reattachment of the ulnar edge of the ECU subsheath or stabilization of the tendon with a sling created from part of the extensor retinaculum and deepening of the ECU's groove in the distal ulna.5
Complications
  • Infection
  • Persistent or recurrent ECU instability
  • Residual pain
  • Over tightening of the ECU subsheath which creates a stenosing tensynovitis.
Outcomes
  • In one study, 5 elite-level tennis players with complete ECU subluxation after an acute injury were treated with short-arm cast immobilization with the wrist extended 15° for 2-3 months.
    • Pain and instability resolved in all 5 patients, and they were able to return to their previous level of play at an average of 5-6 months after diagnosis.7
  • In another study, 28 patients were treated surgically with ECU stabilization using a radially based sling of the extensor retinaculum wrapped around the ECU tendon.
    • 82% (23/28) of patients had good or excellent results a mean of 23 months after surgery.9
  • In another study, 21 consecutive patients were surgically treated with 2-3 mm deepening of the ECU groove and reattachment of the ulnar side of the subsheath using suture anchors.
    • A mean of 31 months later, motion was maintained, mean grip strength was comparable, no patients noted snapping, and pain scores improved from a mean of 0.5 to 6 on an 11-point scale.10
Key Educational Points
  • The clinical diagnosis of ECU subluxation can be easily missed, and when this occurs, it tends to result in insufficient treatments and poor outcomes.2
  • With the rising incidence of these injuries in young athletes, more active treatments may be needed to better target these patients.1
  • Mobility of the ECU tendon as a normal variation or owing to prior injury is common, and it is unclear why some patients experience enough disability to require treatment. This consequently makes recommendations for surgical intervention difficult.5
  • It is also unclear if cast immobilization actually allows for healing of the ECU subsheath or if it is simply palliative.5
  • Ultrasound is helpful for examining variations in structural morphology, alterations in mechanics, and discrepancies in structural integrity in real time.4
References

Cited

  1. Kim BS, Yoon HG, Kim HT, et al. Subluxation of the extensor carpi ulnaris tendon associated with the extensor digitorum tendon subluxation of the long finger. Clin Orthop Surg2013;5(1):82-6. PMID: 23467477
  2. Patterson SM, Picconatto WJ, Alexander JA, Johnson RL. Conservative treatment of an acute traumatic extensor carpi ulnaris tendon subluxation in a collegiate basketball player: a case report. J Athl Train2011;46(5):574-6. PMID: 22488145
  3. Cift H, Ozkan K, Söylemez S, et al. Ulnar-sided pain due to extensor carpi ulnaris tendon subluxation: a case report. J Med Case Rep2012;6:394. PMID: 23173564
  4. Spicer PJ, Romesberg A, Kamineni S, Beaman FD. Ultrasound of Extensor Carpi Ulnaris Tendon Subluxation in a Tennis Player.Ultrasound Q2016;32(2):191-3. PMID: 27233073
  5. Iorio ML, Huang JI. Extensor carpi ulnaris subluxation. J Hand Surg Am2014;39(7):1400-2. PMID: 24799139
  6. Inoue G, Tamura Y. Surgical treatment for recurrent dislocation of the extensor carpi ulnaris tendon. J Hand Surg Br2001;26(6):556-9. PMID: 11884112
  7. Montalvan B, Parier J, Brasseur JL, et al. Extensor carpi ulnaris injuries in tennis players: a study of 28 cases. Br J Sports Med2006;40(5):424-9.PMID: 16632573
  8. Stathopoulos IP, Raptis K, Ballas EG, Spyridonos SP. Recurrent Dislocation of The Extensor Carpi Ulnaris Tendon in a Water-Polo Athlete. Trauma Mon2016;21(1):e19551. PMID: 27218041
  9. Allende C, Le Viet D. Extensor carpi ulnaris problems at the wrist--classification, surgical treatment and results. J Hand Surg Br2005;30(3):265-72. PMID: 15862366
  10. MacLennan AJ, Nemechek NM, Waitayawinyu T, Trumble TE. Diagnosis and anatomic reconstruction of extensor carpi ulnaris subluxation. J Hand Surg Am;33(1):59-64.PMID: 18261666

New Articles

  1. Kaiser P, Kellermann F, Arora R, et al. Diagnosing extensor carpi ulnaris tendon dislocation with dynamic rotation MRI of the wrist. Clin Imaging2018;51:323-326. PMID: 29958158
  2. Spicer PJ, Romesberg A, Kamineni S, Beaman FD. Ultrasound of Extensor Carpi Ulnaris Tendon Subluxation in a Tennis Player.Ultrasound Q2016;32(2):191-3. PMID: 27233073

Review

  1. Iorio ML, Huang JI. Extensor carpi ulnaris subluxation. J Hand Surg Am2014;39(7):1400-2. PMID: 24799139

Classics

  1. Burkhart SS, Wood MB, Linscheid RL. Posttraumatic recurrent subluxation of the extensor carpi ulnaris tendon. J Hand Surg Am1982;7(1):1-3. PMID: 7082460
  2. Vulpius J. Habitual dislocation of the extensor carpi ulnaris tendon. Acta Orthop Scand1964;34:105-8. PMID: 14124641
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