Scapholunate Ligament Injury

Acute presentation: dorsal radial wrist pain after FOOSH (commonly mislabelled "sprained wrist"), swelling over the SL interval, grip weakness, and crepitus or clunk on radioulnar deviation. Chronic presentation: insidious dorsal wrist pain over months to years after a forgotten FOOSH, with progressive grip weakness and loss of wrist extension.

Examination:

• •Tenderness over the SL interval: dorsal wrist, 1 cm distal to Lister's tubercle
• •Watson scaphoid shift test: palpate the scaphoid tubercle and apply dorsally directed pressure while passively moving the wrist from ulnar to radial deviation. A painful clunk as the proximal scaphoid pole subluxes dorsally over the dorsal rim of the radius is positive. Compare with the contralateral side
• •Resisted finger extension may reproduce pain (test of dorsal capsular impingement)
• •Grip strength is reduced on dynamometer compared with contralateral
• •Document range of motion, neurovascular status, and any clicking with provocation

Differentiate from scaphoid fracture (anatomical snuffbox tenderness; FOOSH), distal radius fracture (X-ray), dorsal wrist ganglion (smooth fluctuant swelling), and ECU tendinopathy (ulnar-side wrist; not dorsal-radial).

Plain radiographs are first-line: PA, lateral, oblique, ulnar-deviated PA, and clenched-fist PA (loads the SL joint and accentuates dynamic gap).

Key radiographic signs of SL dissociation:

• •Terry Thomas sign (named for the actor's gap-toothed smile): SL gap over 3 mm on PA, or asymmetry over 2 mm compared with the contralateral wrist. The clenched-fist view increases sensitivity for dynamic instability
• •Signet ring sign: the cortical ring of the rotated palmar-flexed scaphoid on PA. Reflects the scaphoid's abnormal flexion through the dissociated joint
• •Scapholunate angle over 60-70 degrees on lateral (normal 30-60 degrees) - DISI deformity
• •Radiolunate angle over 15 degrees on lateral - DISI confirmation

Further imaging:

• •MR arthrography is the imaging investigation of choice for occult and dynamic SL injuries. Direct intra-articular contrast crosses through ligament tears and demonstrates partial vs complete injury; 3-T magnet with dedicated wrist coil improves sensitivity
• •CT is used for surgical planning and bony assessment (associated fractures, established SLAC arthritis)
• •Dynamic fluoroscopy can demonstrate carpal instability under load when imaging is otherwise normal
• •Diagnostic wrist arthroscopy remains the reference standard. It directly visualises the SL ligament, allows Geissler arthroscopic grading, and permits same-setting treatment of partial tears (debridement and thermal shrinkage)

Routine bloods are not indicated. Image the contralateral wrist for comparison in equivocal cases - the normal SL gap varies from 1-2 mm.

Management is driven by chronicity, Geissler / Mayo stage, and presence of fixed carpal collapse or arthritis (BSSH, BOAST).

Acute partial tear (Geissler I-II, no static instability): conservative.

• •Below-elbow plaster cast or removable splint for 6-8 weeks
• •Simple analgesia; activity modification
• •Hand therapy referral for progressive ROM and grip strengthening from week 6-8
• •Reassess at 8-12 weeks; refer for arthroscopic assessment if symptoms persist or examination remains positive

Acute complete dorsal band tear with dynamic instability (Geissler III-IV without static gap on plain films): early operative repair.

• •Direct dorsal SL ligament repair with suture anchor, often combined with dorsal capsulodesis (Blatt or Berger procedure)
• •Timing: within 4-6 weeks of injury offers the best healing potential. Acute repair outperforms chronic repair
• •K-wire stabilisation of the SL joint for 8-10 weeks post-repair

Static dissociation, established DISI, no arthritis: ligament reconstruction.

• •Anatomical reconstruction options: SL ligament tenodesis with FCR or palmaris longus graft; Brunelli procedure; modified Mayo (3-ligament tenodesis). Choice depends on chronicity and quality of remaining tissue
• •Salvage if reducible carpus and quality bone but irreparable ligament: partial scaphoid-trapezium-trapezoid (STT) arthrodesis

Established SLAC wrist:

• •SLAC I (radial styloid): radial styloidectomy with debridement
• •SLAC II (radioscaphoid): proximal row carpectomy (PRC) or four-corner arthrodesis with scaphoid excision. Both preserve some wrist motion; PRC has slightly shorter recovery, four-corner fusion has longer durability in younger high-demand patients
• •SLAC III (capitolunate): four-corner arthrodesis with scaphoid excision is preferred. PRC contraindicated as the capitolunate articulation is the new bearing surface
• •End-stage / failed salvage: total wrist arthrodesis (fusion) or wrist arthroplasty

Referral pathway: refer all suspected scapholunate ligament injuries to hand surgery / fracture clinic within 7-10 days. Acute repair within 4-6 weeks offers far better outcomes than chronic reconstruction. Don't commit to a "watch and wait" trial in suspected complete tears.

Conservative pathway (Geissler I-II partial tears):

• •Weeks 0-6-8: cast or removable splint; finger ROM encouraged from day 1
• •Weeks 6-12: progressive wrist ROM, isometric and then isotonic grip and forearm strengthening under hand therapy supervision
• •Weeks 12-16: dart-thrower's motion training (radial-extension to ulnar-flexion arc - the kinetically safer arc for SL load distribution), sport-specific loading
• •Return to non-contact sport: 12-16 weeks. Contact sport: 16-24 weeks

Post-operative (SL repair / capsulodesis):

• •Weeks 0-8-10: short-arm thumb spica cast with K-wires in situ; finger and shoulder ROM
• •Weeks 8-10: K-wire removal; commence active wrist ROM in protected arcs (dart-thrower's motion first); gentle isometric grip strengthening
• •Weeks 10-16: progressive ROM and strengthening; resistive grip work and gentle dart-thrower's motion training
• •Weeks 16-24: sport-specific loading; full ROM and strength targets
• •Return to non-contact sport: 5-6 months. Contact sport: 9-12 months with surgeon clearance

Post-reconstruction or salvage (PRC, four-corner fusion): expect 50-70% of contralateral wrist motion and 70-85% of grip strength as the long-term outcome. Hand therapy is essential and ongoing for 3-6 months.

Dart-thrower's motion (radial-extension to ulnar-flexion arc) is the key rehabilitation concept: this arc moves through the distal carpal row with minimal SL joint loading and is the safe arc for early protected ROM.

Persistent grip weakness, painful click, or progressive radiographic widening beyond 6 months requires surgical reassessment for failed repair or progression to dissociation.

• •BSSH Scapholunate Injury Guidance - UK hand-surgery framework: early diagnosis and operative repair within 4-6 weeks for complete tears; staged salvage for SLAC wrist arthritis.
• •Geissler classification (1996) - Arthroscopic four-grade system (I haemorrhage, II step-off, III diastasis admitting probe, IV diastasis admitting arthroscope). The reference standard for surgical decision-making.
• •Watson and Ballet (1984) - Original description of SLAC wrist progression: radial styloid -> radioscaphoid -> capitolunate, with sparing of the radiolunate joint. The basis for salvage procedures preserving lunate-radius motion.
• •Pappou et al. systematic review (2013) - Direct ligament repair plus capsulodesis within 6 weeks outperforms delayed reconstruction on long-term function and progression to SLAC.
• •Garcia-Elias modified 3-ligament tenodesis (1995, 2006) - Established UK reconstruction technique for chronic reducible dissociation; reproducible outcomes when bony anatomy and partial ligament tissue are preserved.

• •The DORSAL band of the SL ligament is the primary stabiliser. The proximal membranous band shown in textbook cross-sections is the weakest. Surgical repair targets the dorsal band.
• •Terry Thomas sign = SL gap over 3 mm on PA, or over 2 mm asymmetry vs contralateral. Signet ring sign = cortical ring of rotated palmar-flexed scaphoid. Clenched-fist PA improves sensitivity for dynamic instability.
• •DISI deformity = scapholunate angle over 60-70 degrees on lateral. Reflects established dissociation with secondary stabiliser failure.
• •SLAC wrist progression: I radial styloid -> II radioscaphoid -> III capitolunate. The radiolunate joint is spared, which is why four-corner fusion with scaphoid excision works as a salvage option.
• •Acute repair within 4-6 weeks markedly outperforms chronic reconstruction. The "wrist sprain" after FOOSH with dorsal SL tenderness is the missed-diagnosis archetype - refer urgently.
• •Dart-thrower's motion (radial-extension to ulnar-flexion arc) is the safe rehabilitation arc; it moves through the distal carpal row with minimal SL joint loading.