SLAC wrist — scapholunate advanced collapse — is the most common pattern of wrist arthritis. It describes a predictable progression of arthritic changes that develop following chronic instability of the scapholunate joint. When the scapholunate ligament is disrupted, the scaphoid rotates into flexion while the lunate extends, creating abnormal contact and cartilage wear in a characteristic sequence that advances through four defined stages.
SLAC wrist is the end-stage consequence of an untreated or inadequately treated scapholunate ligament tear. Many patients with SLAC wrist have no clear memory of a specific injury — the initial ligament disruption may have been dismissed as a sprain years earlier. A closely related condition, SNAC wrist (scaphoid non-union advanced collapse), follows the same arthritic pattern when a scaphoid fracture fails to heal. Early diagnosis with MRI — before significant arthritis has developed — is the best opportunity to intervene and prevent progression to SLAC wrist.
Causes
- Chronic scapholunate ligament tear: The most common underlying cause — untreated or inadequately treated scapholunate instability leads to progressive carpal malalignment and arthritis over months to years.
- Scaphoid nonunion (SNAC wrist): A closely related condition — when a scaphoid fracture fails to heal, it follows the same arthritic collapse pattern as SLAC wrist.
- Previous wrist trauma: Significant wrist injuries, particularly FOOSH injuries, may initiate the cascade even if the original ligament tear was not identified at the time.
- Calcium pyrophosphate deposition disease (CPPD): Crystal deposition can weaken the scapholunate ligament and lead to SLAC wrist without a clear history of injury.
- Inflammatory arthritis: Rheumatoid arthritis and other inflammatory conditions can damage the scapholunate ligament and contribute to arthritic collapse.
- Occupational and repetitive stress: Chronic repetitive wrist loading may accelerate progression in predisposed individuals.
- Missed initial injury: A common scenario — the original ligament tear was subtle or dismissed as a sprain, and SLAC wrist is the first diagnosis made years later.
Symptoms
Symptoms develop gradually over months to years:
- Chronic wrist pain: Initially with activity, eventually at rest — typically located on the radial (thumb) side of the wrist.
- Swelling: Chronic swelling over the back of the wrist, particularly over the radioscaphoid joint.
- Stiffness: Progressive loss of wrist motion, particularly extension and radial deviation.
- Weakness: Decreased grip strength, making it difficult to open jars, use tools, or lift objects.
- Clicking or grinding: Crepitus and mechanical symptoms with wrist motion.
- Functional limitations: Difficulty with typing, writing, carrying, and sports.
- Progressive deformity: In advanced cases, visible carpal collapse deformity may develop.
- Activity-related worsening: Symptoms worsen with wrist use; rest pain becomes more prominent in advanced stages.
Diagnosis
Physical examination assesses swelling, tenderness over the radioscaphoid and midcarpal joints, range of motion, and grip strength. X-rays are the primary diagnostic tool for established SLAC wrist, showing the characteristic pattern of joint space narrowing, sclerosis, and osteophytes — along with a widened scapholunate interval, scaphoid flexion (signet ring sign), and carpal malalignment. The distribution of arthritic changes on X-ray directly determines the Watson stage and surgical options.
In earlier stages — when X-ray findings may be subtle or absent — a dedicated wrist MRI is the most sensitive tool for detecting cartilage loss, bone marrow edema, scapholunate ligament integrity, and synovitis. MRI is particularly valuable for distinguishing Stage I from Stage II disease and for identifying patients who may still benefit from ligament reconstruction rather than salvage surgery. CT may be added for detailed bone anatomy when surgical planning requires it.
Classification (Watson Stages)
SLAC wrist is staged based on the location and extent of arthritic changes — the radiolunate joint is typically spared until Stage IV, which is a critical surgical planning consideration:
- Stage I: Arthritis limited to the radial styloid and the tip of the scaphoid. Scapholunate relationship may be mildly abnormal.
- Stage II: Arthritis extends to involve the entire radioscaphoid joint. Scapholunate interval is widened with established instability.
- Stage III: Arthritis progresses to the capitolunate (midcarpal) joint. The radiolunate joint remains preserved — this is key for motion-preserving surgical options.
- Stage IV: Advanced arthritis involving the radiolunate joint. Most severe stage — limits reconstructive options to salvage procedures.
Treatments
Treatment depends on Watson stage, patient age, activity level, and functional demands. Early identification and treatment of the underlying scapholunate ligament tear is the best prevention for SLAC wrist — once arthritis develops, the goal shifts from restoration of normal anatomy to pain relief and preservation of function.
Conservative treatment: Activity modification to reduce wrist stress, wrist splinting for support during activities, NSAIDs, corticosteroid injection for temporary pain relief (does not halt progression), hand therapy to maintain motion and strength, and ergonomic modifications. Conservative management is appropriate for patients who are not surgical candidates or who wish to defer surgery.
Stage I — early intervention
In carefully selected younger patients with minimal arthritis limited to the radial styloid, radial styloidectomy combined with scapholunate ligament reconstruction may be considered to relieve pain and address underlying instability before further progression occurs.
Stages II–III — motion-preserving procedures
- Proximal row carpectomy (PRC): Removal of the scaphoid, lunate, and triquetrum — the capitate articulates with the radius, preserving significant wrist motion. Most successful when the capitate head and lunate fossa cartilage are preserved. Generally preferred for Stage II and lower-demand patients.
- Four-corner fusion with scaphoid excision: The scaphoid is removed and the lunate, capitate, hamate, and triquetrum are fused together. The preserved radiolunate joint maintains approximately 50% of normal wrist motion. Commonly used for Stage II and III, particularly in more active patients.
Stage IV — salvage procedures
- Total wrist fusion (arthrodesis): The carpus is fused to the radius — eliminates wrist motion but provides reliable pain relief and a strong, stable wrist. Often preferred for heavy laborers and patients with advanced multi-joint arthritis.
- Total wrist arthroplasty: Joint replacement preserves motion but has higher complication and revision rates than fusion. Generally reserved for lower-demand patients with low functional requirements.
Rehabilitation and prognosis
Cast or splint immobilization for 6–12 weeks is required after fusion procedures, followed by hand therapy to restore motion and strength. Full recovery takes 6–12 months. Most patients achieve significant pain relief and can return to activities of daily living and many recreational activities, though heavy labor and high-impact sports may be permanently limited depending on the procedure performed.
Get an MRI to Confirm Your Diagnosis
Before surgical planning or starting treatment, a clear MRI diagnosis ensures the right path forward. First Look MRI offers self-pay Wrist MRI scans — no doctor's order or insurance required — at our locations in Georgia, Texas, and Colorado.