Scapholunate Ligament Tear Syndrome
Scapholunate ligament tear syndrome is caused by trauma or, rarely, degenerative changes to the wrist. The scapholunate ligament serves as a stabilizer of the scaphoid’s palmarward rotational force against the opposite dorsalward rotational force of the lunate.
The ligament also maintains the spacing of the scapulolunate gap, keeping the proximal pole of the scaphoid in proper position relative to the lunate.
Degeneration of the scapholunate ligament complex begins to occur as part of the natural aging process in the third decade. This degenerative process predisposes the scapholunate ligament complex to traumatic injury.
Common injuries that lead to scapholunate ligament tear include falls onto a hyperextended wrist. If the tear is partial, the patient reports dorsoradial wrist pain. If the tear is complete, instability of the wrist accompanies the pain. Some patients report an audible click with any ulnar to radial deviation of the wrist.
What are the Symptoms of Scapholunate Ligament Tear Syndrome
Physical examination of patients with scapholunate ligament tear reveals pain on ulnar deviation of the wrist with the pain worsened by having the patient tightly clench the fist, which places stress on the carpal bones. Pain is present on palpation of the anatomical snuffbox, and a widening of the scapholunate gap may be appreciated.
A clicking sensation may be appreciated by the examiner on range of motion. A positive Watson’s test also is present when the wrist is moved from the ulnar to radial position while the patient tightly clutches the fist. If left untreated, degeneration of the radioscaphoid, midcarpal, and radiolunate joints results in a deformity termed scapholunate advanced collapse, which is also referred to as a scaphoid lunate advanced collapse (SLAC) wrist.
How is Scapholunate Ligament Tear Syndrome diagnosed?
Plain radiographs are indicated in all patients who present with scapholunate ligament tear syndrome to rule out underlying occult bony pathological conditions and identify widening of the scapholunate gap (also known as a positive Terry Thomas or David Letterman sign after the space between the teeth of these celebrities), palmar flexion of the scaphoid, and dorsiflexion of the lunate, which is termed scapholunate dissociation with dorsal intercalary segment instability.
Based on the patient’s clinical presentation, additional tests, including complete blood cell count, uric acid level, erythrocyte sedimentation rate, and antinuclear antibody testing, may be indicated. Magnetic resonance imaging (MRI) and ultrasound imaging of the wrist is indicated in all patients thought to have scapholunate ligament tear or if other causes of joint instability, infection, or tumor are suspected.
Scaphoid dorsal subluxation identified on these imaging modalities will strengthen the diagnosis of scapholunate ligament tear. Electromyography is indicated if coexistent ulnar or carpal tunnel syndrome is suspected.
A very gentle injection of the radioulnar joint with small volumes of local anesthetic and steroid provides immediate improvement of the pain, but ultimately surgical repair is required.
Coexistent arthritis and gout of the radioulnar, carpal, metacarpal, and interphalangeal joints; dorsal wrist ganglion; de Quervain stenosing tenosynovitis; and tendinitis may coexist with scapholunate ligament tear syndrome and exacerbate the patient’s pain and disability.
Kienböck disease, avascular necrosis of the scaphoid, and scaphoid fractures also may mimic the pain of scapholunate ligament tear.
Initial treatment of the pain and functional disability associated with scapholunate ligament tear syndrome should include a combination of nonsteroidal antiinflammatory drugs (NSAIDs) or cyclooxygenase-2 (COX-2) inhibitors and short-term immobilization of the wrist.
Local application of heat and cold also may be beneficial. For patients who do not respond to these treatment modalities, an injection of a local anesthetic and steroid into the scapholunate joint may be a reasonable next step. Ultrasound guidance may improve the accuracy of needle placement and decrease the incidence of needle-related complications.
Vigorous exercises should be avoided because they would exacerbate the patient’s symptoms. Ultimately, surgical repair is the treatment of choice.
Failure to treat significant scapholunate ligament tear surgically usually results in continued pain and disability and, in some patients, leads to ongoing damage to the wrist. Injection of the scapholunate joint with local anesthetic and steroid is a safe technique if the clinician is attentive to detail, specifically using small amounts of local anesthetic and steroid and avoiding high injection pressures, which may disrupt the ligament further.
Another complication of this injection technique is infection. This complication should be exceedingly rare if strict aseptic technique is followed.
Approximately 25% of patients report a transient increase in pain after this injection technique, and patients should be warned of this possibility.
Scapholunate ligament tear and other disorders of the scaphoid are a straightforward diagnosis in the presence of obvious antecedent trauma.
The diagnosis is less obvious in the absence of trauma, however, unless the clinician includes it in the differential diagnosis with all patients reporting radial-sided wrist pain. Coexistent arthritis, tendinitis, and gout also may contribute to the pain and may require additional treatment with more localized injection of a local anesthetic and depot steroid.
The use of physical modalities, including local heat and cold and immobilization of the wrist, may provide symptomatic relief. Vigorous exercises should be avoided because they would exacerbate the patient’s symptoms and may cause further damage to the wrist. Simple analgesics and NSAIDs may be used concurrently with this injection technique.