Scapholunate Advanced Collapse (SLAC) wrist is a type of wrist arthritis. The acronym SLAC describes the progressive degeneration that occurs within the wrist joint, causing discomfort and stiffness. It develops from long-term wrist instability, which leads to the wearing away of cartilage, the smooth tissue cushioning bone ends. This process ultimately results in osteoarthritis.
Understanding How SLAC Wrist Develops
The wrist is a complex structure comprising multiple small bones, including the scaphoid, lunate, and radius. A crucial component maintaining stability between the scaphoid and lunate bones is the scapholunate ligament, a strong band of tissue.
Damage or rupture of the scapholunate ligament is often the initial event leading to SLAC wrist. This injury frequently results from trauma, such as a fall onto an outstretched hand, or can stem from repetitive stress. An untreated scaphoid fracture can also contribute to this instability. When compromised, the ligament disrupts the normal alignment between the scaphoid and lunate bones.
This disruption causes the scaphoid and lunate bones to move abnormally, leading to scapholunate dissociation. The scaphoid may flex forward, and the lunate may extend backward, creating uneven pressure distribution within the wrist joint. This altered biomechanics places excessive stress on the cartilage surfaces. Over time, this abnormal pressure and movement gradually wear away the protective cartilage, initiating osteoarthritis. As cartilage degenerates, bones begin to rub directly against each other, leading to further joint damage and SLAC wrist progression.
Recognizing the Signs and Diagnosis
Chronic wrist pain is a common symptom, often worsening with activity or when bearing weight on the wrist. Stiffness and a reduced range of motion are also frequently observed. Some individuals may notice swelling in the wrist area. Weakness, particularly with gripping or lifting objects, is another common complaint. A clicking, grinding, or popping sensation during wrist movement may also be experienced.
Medical professionals diagnose SLAC wrist through a combination of physical examination and imaging tests. During a physical examination, a doctor assesses the patient’s pain, range of motion, and tenderness in the wrist. The Watson scaphoid shift test may be performed. Imaging plays a central role in confirming the diagnosis and assessing the condition’s stage.
X-rays are commonly used, as they can reveal the characteristic collapse pattern and signs of arthritis. While a torn ligament may not directly appear on X-rays, the shift in bone alignment and the presence of arthritis will be visible. MRI scans are valuable for assessing ligament damage and cartilage health. CT scans can provide more detailed images of the bone structures.
Treatment Options for SLAC Wrist
Treatment approaches for SLAC wrist vary, ranging from conservative methods to surgical interventions, depending on severity and individual needs. Initial non-surgical treatments aim to manage pain and reduce inflammation. Rest and activity modification are often recommended to alleviate stress on the wrist. Nonsteroidal anti-inflammatory medications (NSAIDs) can help reduce pain and swelling.
Splinting or bracing the wrist provides support and immobilization, which can help stabilize the joint and relieve discomfort. Hand therapy focuses on reducing pain, improving range of motion, and strengthening the wrist. Corticosteroid injections directly into the joint can offer temporary relief from pain and inflammation. These conservative measures are often suitable for early stages or for managing symptoms when surgery is not indicated.
When conservative treatments do not provide sufficient relief or for more advanced stages, surgical options may be considered. One common surgical procedure is partial wrist fusion, also known as four-corner fusion with scaphoidectomy. This involves removing the scaphoid bone and fusing the remaining carpal bones to stabilize the wrist and reduce pain. About half of the wrist’s motion can be preserved after this procedure.
Another surgical approach is Proximal Row Carpectomy (PRC), where the entire proximal row of carpal bones is removed. This procedure creates a new joint, aiming to alleviate pain while preserving some wrist motion. For very severe cases, total wrist fusion may be performed. This procedure involves fusing all the major wrist bones into one solid unit, which eliminates motion but provides pain relief. The primary goals of surgical interventions are to reduce pain and improve or preserve wrist function.