Lunotriquetral Instability Pain Syndrome
Lunotriquetral instability pain syndrome is caused by trauma or, rarely, degenerative changes to the wrist. The lunotriquetral ligament stabilizes the wrist and helps maintain the proper spacing of the lunotriquetral gap.
Degeneration of the lunotriquetral ligament complex begins to occur as part of the natural aging process in the third decade. This degenerative process predisposes the lunotriquetral ligament complex to traumatic injury. Common injuries that lead to lunotriquetral instability pain syndrome include backward falls onto a hyperextended wrist.
If the tear is partial, the patient reports dorsoulnar wrist pain. If the tear is complete, instability of the wrist accompanies the pain. Some patients report an audible click with any ulnar deviation of the wrist.
What are the Symptoms of Lunotriquetral Instability Pain Syndrome
Physical examination of patients with lunotriquetral instability pain syndrome reveals pain on ulnar or radial 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 felt on palpation of the lunate and triquetrum, and a widening of the lunotriquetral gap may be appreciated.
A clicking sensation may be appreciated by the examiner on range of motion. A positive lunotriquetral shear test is often present. This test is performed by displacing the triquetrum dorsally while displacing the lunate palmarly. The test is considered positive if the examiner demonstrates increased excursion of the lunotriquetral joint over the normal side. With complete lunotriquetral disruption, static collapse can occur causing a classic dinner fork deformity.
How is Lunotriquetral Instability Pain Syndrome diagnosed?
Plain radiographs are indicated in all patients who present with lunotriquetral instability pain syndrome to rule out underlying occult bony pathological processes and identify widening of the lunotriquetral gap. 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 suspected to have lunotriquetral instability pain syndrome or if other causes of joint instability, infection, or tumor are suspected. Electromyography is indicated if coexistent ulnar or carpal tunnel is suspected. A gentle injection of the lunotriquetral 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, carpometacarpal, and interphalangeal joints; dorsal wrist ganglion; and tendinitis may coexist with lunotriquetral instability pain syndrome and exacerbate the patient’s pain and disability.
Kienböck disease and lunate fractures also may mimic the pain of lunotriquetral instability pain syndrome, as can tear of the triangular fibrocartilage complex and ulnar impaction syndrome.
Initial treatment of the pain and functional disability associated with lunotriquetral instability pain 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 lunotriquetral 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 lunotriquetral instability pain syndrome surgically usually results in continued pain and disability and in some patients leads to ongoing damage to the wrist.
Injection of the 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.
Lunotriquetral instability pain syndrome and other disorders of the lunate and triquetrum 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 included it in the differential diagnosis with all patients with ulnar-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.