What is the appropriate treatment for a scapholunate ligament injury with a 5 mm widened scapholunate interval and dorsal wrist superficial soft‑tissue swelling on CT?

Treatment for Scapholunate Ligament Injury with 5mm Widening

This patient requires urgent hand surgery referral for operative intervention, as a scapholunate interval of 5mm indicates complete ligament disruption with static instability that will not heal with conservative management and will progress to degenerative arthritis if left untreated.

Immediate Management

Your CT finding of 5mm scapholunate widening exceeds the critical threshold of >4mm that defines dorsal intercalated segmental instability (DISI) 1. This represents a complete scapholunate ligament tear with static carpal malalignment, not a partial injury amenable to conservative treatment.

Why Surgery is Mandatory

• Scapholunate diastasis >4mm indicates complete ligament disruption with loss of the critical dorsal component 1
• Without intervention, this predictably progresses to scapholunate advanced collapse (SLAC) - a severe degenerative arthritis pattern 2, 3
• The natural history shows irreversible cartilage degeneration from abnormal carpal kinematics 2, 4
• Conservative management (immobilization, therapy) is only effective for partial injuries without static malalignment 3

Timing Considerations

Acute repair within 4-6 weeks is strongly preferred over delayed reconstruction 2. If this is an acute injury (based on your mention of soft tissue swelling):

• Direct ligament repair is possible and has better outcomes when performed acutely 2, 5
• After 6 weeks, the ligament retracts and degenerates, requiring more complex tendon graft reconstruction rather than primary repair 2
• Arthroscopic techniques allow accurate reduction and fixation with less morbidity than open approaches 5, 6

Surgical Approach Algorithm

The hand surgeon will determine the specific technique based on:

1. Injury chronicity (acute vs chronic)
2. Reducibility of the scaphoid and lunate alignment
3. Cartilage condition (assessed arthroscopically)
4. Associated injuries (other ligaments, fractures)

For Acute Injuries (<6 weeks):

• Arthroscopic or open ligament repair with K-wire fixation 5, 6
• Direct suture repair of the dorsal scapholunate ligament
• Temporary pinning to maintain reduction during healing

For Chronic Injuries (>6 weeks):

• Ligament reconstruction using tendon grafts (various techniques available) 2, 7
• Capsulodesis procedures to stabilize the scaphoid
• May require more extensive soft tissue reconstruction

If Degenerative Changes Present:

• Salvage procedures (proximal row carpectomy, partial wrist fusion) 8, 7

Pre-Referral Actions

While awaiting hand surgery consultation:

1. Immobilize in a short arm thumb spica splint to prevent further displacement
2. Obtain plain radiographs if not already done - PA, lateral, and clenched fist views to assess for additional carpal malalignment 1
3. Expedite referral - emphasize the 5mm diastasis to convey urgency
4. Avoid activities that load the wrist

Critical Pitfall to Avoid

Do not treat this conservatively or delay referral. A 5mm scapholunate interval represents complete ligament failure requiring surgical stabilization. The dorsal soft tissue swelling suggests this may be acute, making timely intervention even more critical. Every week of delay reduces the likelihood of successful primary repair and increases the complexity of required reconstruction 2.

Diagnostic Confirmation

The hand surgeon will likely perform wrist arthroscopy, which is the gold standard for assessing ligament tear severity, cartilage condition, and determining the optimal surgical approach 9, 5, 6. CT arthrography has nearly 100% sensitivity and specificity for scapholunate ligament tears if additional imaging is needed 1.