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Basics ⬇

Author(s): Benjamin D.Brusch, MD and Robert L.Jones, MD, CAQSM

Description

Scapholunate (SL) dissociation may be more accurately characterized as a spectrum of SL instability resulting from a tear of the SL interosseous ligament (SLIL). Concomitant or subsequent injury to secondary ligamentous restraints alter the biomechanics of the wrist, resulting in progressive carpal instability and leading to a predictable pattern of debilitating, degenerative changes of the wrist (1,2).

Epidemiology

  • Most common ligamentous instability of the wrist (2)
  • Frequently associated with a distal radius fracture
  • Precise epidemiologic data is lacking.

Etiology and Pathophysiology

  • Often a fall on an outstretched hand with hyperextension, ulnar deviation, and supination (1,2)
  • Axial compression can drive the capitate between the scaphoid and lunate (1).
  • Repetitive motion after an isolated SLIL injury may produce attritional changes in the secondary stabilizers leading to their eventual failure, thus completing the SL dissociation (1,2).
  • May also result from repetitive minor trauma

Risk-Factors

Active individuals who have ulnar-negative variance; shorter distal ulna compared with the radius on a neutral anteroposterior (AP) radiograph of the wrist (measured from the articular surface of the ulna to the lunate fossa of the radius)

Diagnosis ⬆ ⬇

  • Early diagnosis and surgery offers the best chance for successful outcome (1,3).
  • There are different levels of injury, which can be classified by increasing severity of wrist instability (1,2,3,4):
    • Occult instability: isolated tear or attenuation of a portion of the SLIL. There is no radiologic evidence of SL widening, and wrist pain is usually only with mechanical loading.
    • Dynamic instability: subtotal or complete tear of the SLIL, including the dorsal portion, with a partial secondary ligament injury; may have normal static radiographs, but instability will be apparent on stress radiographs
    • SL dissociation: involves a complete tear of the SLIL with additional tear of one or more secondary ligaments. SL widening is apparent on static radiographs (>3 mm).
    • Dorsal intercalated segment instability (DISI): term used to describe the shifted positions of the bones of the carpus, as viewed on lateral radiograph, due to lack of association between the lunate and scaphoid (1). Abnormalities include flexion of the scaphoid, extension of the lunate and triquetrum, and dorsal and proximal translation of the distal carpal row.
    • SL advanced collapse (SLAC): end stage of the spectrum of instability (1). There is predictable and progressive degeneration and arthritis of the carpus due to the irreversible postural changes of the scaphoid, capitate, and lunate.

History

  • Patient may report a fall or sudden load applied to the wrist but may not recall any specific fall or injury.
  • Pain or swelling in the dorsal wrist (1,2)
  • Pain or weakness with hyperextension and loading of the wrist
ALERT

May not seek immediate care because initial injury seems too trivial

  • Subacutely, there may be symptoms of painful popping or clicking with activities, or decreased grip strength (1).
  • Later on, limited motion may be a complaint (4).

Physical Exam

  • In the acute setting, pain may be poorly localized about the periscaphoid area. Swelling may be diffuse or localized to the SL region (2).
  • In the subacute setting, there is usually well-localized tenderness about the scaphoid and dorsal SL interval (distal to Lister tubercle).
  • The patient may have weakness of grip and pinch strength (2).
  • Watson scaphoid shift test should be performed:
    • Compare to the contralateral side as false positives occur frequently (1).
    • The shift test may become negative in chronic cases as arthritis stabilizes the scaphoid.
    ALERT

    Patient places wrist in ulnar deviation, and the physician puts dorsal pressure on the palmar scaphoid tubercle with the thumb. The physician then radially deviates the patient’s wrist. Relief of thumb pressure will allow the scaphoid to reduce, often with an audible or palpable clunk. Pain with a clunk may represent SL instability.

Differential Diagnosis

  • Scaphoid or other carpal fracture
  • Lunotriquetral instability
  • Radial styloid or distal radius fracture
  • Synovitis
  • Radioscaphoid impingement
  • Occult ganglion cyst
  • Triangular fibrocartilage complex tear
  • Osteoarthritis or rheumatoid arthritis
  • Kienböck disease

Diagnostic Tests & Interpretation

Initial Tests (lab, imaging)

  • Imaging should be obtained in individuals with appropriate history and positive scaphoid shift test.
  • Initial plain films should include AP, lateral, and stress views.
  • Radiographs of the opposite wrist should always be obtained for comparison (2)[C].
  • Normal static and stress films in the acute setting do not always rule out serious injury because it may take time for instability to develop (4)[C].
  • By the time frank dissociation is present on static films, significant damage is already present (1).
  • Key findings on the lateral film (wrist in neutral):
    • SL angle >70 degrees is considered highly suggestive of diagnosis (normal 30 to 60 degrees) (1,2,3,5).
    • Radiolunate angle exceeding 15 degrees indicates DISI (1,2).
  • Key findings on the AP film:
    • Scaphoid ring sign: Distal scaphoid tubercle is superimposed on the scaphoid waist when scaphoid is flexed >70 degrees (1).
    ALERT
    Gap >3 mm (2,3,4) between scaphoid and lunate on AP is indicative of SL dissociation with 97% specificity (4).
    ALERT
    “Pencil grip posteroanterior (PA)” is the most useful stress view (2,3)[C]. It profiles the SL joint and demonstrates pathologic SL widening (>3 mm) under axial loaded conditions (2)[C]. Additional stress view could include AP in ulnar deviation (3).
  • Radiography has a sensitivity of 57–81% and specificity of 73–98% (4).
  • Cineradiography (functional fluoroscopy) has a sensitivity of 86–96% and specificity of 80–97% (4).
  • CT arthrography has been reported as having a sensitivity of 80–100%, whereas magnetic resonance (MR) arthrography has a sensitivity of 85–100%; both have a specificity of 80–100% (4). Traction MR arthrography has been proposed to have greater sensitivity and specificity (3).
  • Traditional arthrography is limited by its static nature and the high prevalence of degenerative tears, which are often asymptomatic and bilateral (1,2).
  • Static imaging modalities are felt to often miss early cases of instability when intervention may be most effective.
  • The dorsal SL ligament can be assessed with ultrasound.
  • Wrist arthroscopy remains the gold standard for diagnosis (1,3,4,5).

Diagnostic Procedures/Other

Arthroscentesis indicating hemarthrosis may be helpful in the acute setting when initial imaging is negative, but clinical suspicion remains high (2)[C].

Treatment ⬆ ⬇

  • Treatment must be predicated by the patient’s symptoms and clinical exam, not imaging.
  • Management of injuries may depend on age, sport, position, level of competition, and schedule (3)[C].
    ALERT

    The treatment is most often surgical, so do not delay referral.

  • The goal of surgery is to restore carpal kinematics to arrest the degenerative process (3).
  • Emergency department (ED) treatment:
    • Stabilize with a thumb spica splint.
    • Refer for appropriate follow-up.

Medication

Nonsteroidal anti-inflammatory drugs (NSAIDs) or acetaminophen for pain

Additional Therapies

  • Occult instability may be successfully treated with immobilization for 4 to 6 wk followed by therapy (3)[C].
  • There has been some success with casting, splinting, NSAIDs, and therapy without surgical intervention for dynamic instability (2)[C]. This would include a short arm cast for 4 to 6 wk, followed by removable splint for active range of motion (ROM) exercises and gentle strengthening across the wrist.
  • All treatment courses should be followed by rehabilitation consisting of strengthening and proprioceptive training (3)[C].

Surgery/Other Procedures

  • In general, unstable wrists should undergo surgical repair as soon as possible if the athlete desires to return to play. The procedures performed are dictated based on the timing and severity of the wrist instability.
  • Occult instability:
    • There has been some success with arthroscopic débridement with or without pinning, but usually this is treated with conservative measures (3)[C]. There is also some evidence for K-wire fixation and/or electrocautery for electrothermal collagen shrinkage following arthroscopic débridement (1,3)[C]. However, the mechanism for pain reduction is felt to be a result of denervation rather than mechanical stabilization.
  • Acute, dynamic instability:
    • Usually require early surgical intervention
    • Some will use closed reduction and K-wire fixation, attempting to allow the torn ligaments to heal (1,5)[C]. Otherwise, attempt is made to repair the damaged ligaments before they degenerate (3,5)[C].
  • Subacute or chronic injuries:
    • Typically require ligament reconstruction (3)[C]
  • Chronically injured wrists with fixed deformity such as DISI or SLAC:
    • Salvage procedures are sometimes needed to alleviate pain (1)[C].
  • A salvage procedure is performed to restore alignment, improve load distribution, and attempt to slow degenerative changes. Unfortunately, salvage procedures are likely to indicate the end of an athletic career (3)[C].
  • Salvage procedures may include scaphoid excision, carpal fusion, or proximal row carpectomy (1)[C].

Ongoing Care ⬆ ⬇

Follow-up Recommendations

  • Following repair, immobilize the wrist for 8 wk and then slowly rehab.
  • Decisions about return to play must be individualized based on sport-specific demands and competition level.
  • In general, an athlete may return after demonstrating progression in strength and ROM in a supervised rehabilitation program.
  • Physical therapy should be performed within pain tolerance.
  • Avoid power gripping and weight-bearing exercises of the upper extremity.
  • Gentle putty or sponge gripping can help improve grasp strength.

Complications

  • Injury has the potential to be career ending (3).
  • Arthritis of the wrist, which can be severe and debilitating

References ⬆ ⬇

  1. Manuel J, Moran SL. The diagnosis and treatment of scapholunate instability. Orthop Clin North Am. 2007;38(2):261–277.
  2. Kitay A, Wolfe SW. Scapholunate instability: current concepts in diagnosis and management. J Hand Surg Am. 2012;37(10):2175–2196.
  3. Morrell NT, Moyer A, Quinlan N, et al. Scapholunate and perilunate injuries in the athlete. Curr Rev Musculoskelet Med. 2017;10(1):45–52.
  4. Cheriex KCAL, Sulkers GSI, Terra MP, et al. Scapholunate dissociation; diagnostics made easy. Eur J Radiol. 2017;92:45–50.
  5. Geissler WB, Burkett JL. Ligamentous sports injuries of the hand and wrist. Sports Med Arthrosc Rev. 2014;22(1):39–44.

Clinical Pearls ⬆

  • Most common ligamentous injury of the wrist
  • Normal static and stress films in the acute setting do not always rule out serious injury.
  • Radiographs of the contralateral side should always be obtained.
  • Early diagnosis and treatment can avoid potentially career-ending, lifelong morbidity.