Scapholunate Advanced Collapse (SLAC) Wrist
Initial Evaluation
Begin with standard 3-view wrist radiographs (PA, lateral, and oblique), supplemented with stress views to confirm scapholunate instability 1. Standard radiographs are the foundation for staging SLAC wrist, though X-ray interpretation alone has poor interrater reliability 2.
Key Imaging Considerations:
- MRI without contrast is useful when diagnosis is uncertain, with 70-87% sensitivity and 90-97% specificity for scapholunate tears at 3.0T 1
- Wrist arthroscopy significantly improves diagnostic accuracy - adding arthroscopy changed stage classification in 55% of cases in one study, as radiographs alone are unreliable for accurate staging 2
- Avoid ultrasound for scapholunate instability evaluation - an interdisciplinary consensus specifically recommended against its inclusion 1
Clinical Presentation:
SLAC wrist patients are typically younger males (mean age 53 years), with 80% being male, 70% reporting prior trauma, and 49% involved in manual labor 3. Symptoms may persist for years (average 10.3 years) before presentation 3.
Stage-Based Management Algorithm
Stage I (Radial Styloid-Scaphoid Arthritis Only):
Conservative management should be attempted first with NSAIDs, activity modification, and splinting. When surgery is needed:
- Radial styloidectomy with or without scaphoid excision
- Wrist denervation (AIN/PIN) as standalone or adjunct procedure - 46.3% of ASSH surgeons use denervation for all SLAC stages 4
- Soft tissue procedures (capsulodesis, tenodesis) are preferred in younger patients to delay salvage operations 5
Stage II (Radioscaphoid and Scaphocapitate Arthritis):
For Stage II without capitolunate arthritis, proximal row carpectomy (PRC) is the preferred motion-sparing procedure 5, 6, 7. PRC avoids the technical demands, lengthy immobilization (typically 3+ months), and nonunion risk associated with four-corner fusion 7.
Alternative options include:
- Four-corner fusion (scaphoid excision with capitolunate-hamate-triquetral arthrodesis)
- Capitolunate arthrodesis
- Three-corner fusion
- Wrist denervation - particularly when motion preservation must be maximized (64.4% of surgeons prefer this indication) 4
Critical decision point: PRC and four-corner fusion yield comparable pain relief and grip strength at 5+ years follow-up, but PRC preserves better wrist extension 7. Both procedures show continued improvement in grip strength and range of motion for at least 1 year postoperatively 7.
Stage III (Radioscaphoid, Scaphocapitate, AND Capitolunate Arthritis):
Four-corner fusion is recommended over PRC when capitolunate arthritis is present 6, 7. The presence of capitate arthritis is a relative contraindication to PRC, as pain relief may be unsatisfactory and conversion to total wrist arthrodesis may be required 7.
Alternative considerations:
- Osteochondral grafting combined with PRC for select cases 8
- Total wrist arthrodesis for failed motion-sparing procedures or severe disease
- Wrist denervation can be used at any stage 4
Important Surgical Nuances
Proximal Row Carpectomy:
- Shorter operative time and recovery
- No risk of nonunion
- Better wrist extension preserved
- Contraindicated with capitolunate arthritis - one study reported symptomatic radiocarpal arthritis requiring conversion to arthrodesis in this setting 7
Four-Corner Fusion:
- Incomplete correction of lunate extension results in diminished wrist extension compared to PRC 7
- Requires 8-12 weeks immobilization
- 5-10% nonunion risk
- Better theoretical load distribution when capitolunate arthritis present
Wrist Denervation:
- 62.1% of surgeons perform combined AIN/PIN denervation as standalone procedure 4
- Most surgeons (84.2%) do not consider loss of proprioception a significant complication 4
- 33.5% of surgeons never perform diagnostic blocks prior to denervation 4
- Can be combined with other procedures
Common Pitfalls
- Relying solely on radiographs for staging - arthroscopy changes classification in >50% of cases 2
- Performing PRC with capitolunate arthritis - leads to poor outcomes and potential conversion to total arthrodesis 7
- Overlooking wrist denervation - nearly half of hand surgeons use this for all SLAC stages, particularly valuable when motion preservation is critical 4
- Assuming bilateral disease requires trauma - SLAC can appear bilaterally from chronic pseudogout without clear injury history 6