Thumb UCL Injury

Patients present acutely with pain, swelling, and bruising at the ulnar aspect of the thumb MCP after a forced abduction injury. Weak pinch grip and pain on activities that load the thumb in radial deviation (turning keys, opening jars, picking up small objects) are characteristic. Bruising tracks volarly and may be marked.

Examination:

• •Tenderness over the ulnar MCP, with palpable swelling, sometimes a "Stener lump" (the retracted ligament under the skin proximal to the joint)
• •Stress test of the UCL: stabilise the metacarpal, then apply radial deviation force to the proximal phalanx in BOTH MCP extension and 30 degrees of MCP flexion. Compare with the contralateral thumb. Local anaesthetic infiltration can be used to overcome guarding
• •Grade III is defined by gross laxity (over 35 degrees of radial deviation, or over 15 degrees more than the contralateral side) with NO firm endpoint
• •Grade II is laxity with a firm endpoint; Grade I has no laxity
• •Weak key-pinch strength (assessed quantitatively if a pinch dynamometer is available)

Stress testing in extension alone misses partial proper collateral tears (which require MCP flexion to engage the proper collateral). Always test in both positions. Differentiate from radial collateral ligament injury (less common, ulnar deviation force, pain at the radial MCP), volar plate injury (hyperextension mechanism, dorsal swelling), and thumb metacarpal Bennett fracture (axial load mechanism, X-ray finding).

Plain radiographs (PA, lateral, oblique thumb) are first-line in any acute thumb UCL injury, looking for an avulsion fragment from the volar-ulnar base of the proximal phalanx. A non-displaced avulsion may be managed conservatively; a displaced avulsion (over 2-3 mm) or a rotated fragment indicates operative fixation. Stress radiographs (under local anaesthetic if needed) document instability objectively but are not routine.

Ultrasound is the first-line soft-tissue investigation in many UK fracture clinics: dynamic, point-of-care, identifies the ligament, the adductor aponeurosis, and the position of the avulsed end relative to it. A skilled operator can detect Stener lesions with high sensitivity and specificity. Ultrasound-guided stress is the bedside discriminator of partial vs complete tear in equivocal cases.

MRI is reserved for:

• •Ultrasound equivocal
• •Suspected proximal-pole avulsion or complex injury
• •Pre-operative planning
• •Chronic / delayed presentations where surgical reconstruction is being considered

MRI shows the ligament course, the adductor aponeurosis position, retraction distance, and bone bruising. CT is generally not indicated unless there is a complex bony fragment to plan fixation around.

Management is stratified by Grade and presence or absence of Stener lesion (BSSH BEST 2024, UK practice).

Grade I (partial tear, no laxity): conservative.

• •Thumb spica splint (forearm-based, IP joint free) for 4 weeks
• •Simple analgesia; ice in the acute phase
• •Hand-therapy-led ROM and progressive loading from 4 weeks

Grade II (partial tear with laxity, firm endpoint): conservative with structured rehab.

• •Thumb spica splint for 4-6 weeks
• •Sport-specific custom orthosis for early return to non-contact training
• •Hand therapy supervision for progressive loading

Grade III without Stener (complete tear, intact aponeurosis): trial of conservative management or surgical repair, depending on demand and shared decision.

• •Conservative: full-time thumb spica for 4-6 weeks, then transitional bracing for 4-6 weeks. Acceptable in low-demand and elderly patients
• •Surgical repair: open repair within 2-3 weeks of injury (ligament-to-bone with suture anchor or bone tunnel; pull-out suture). Early repair gives best outcomes. Indicated in high-demand patients, those who require precision pinch, and athletes

Grade III with Stener lesion: surgical repair.

• •Open repair within 2-3 weeks, with reduction of the displaced ligament beneath the aponeurosis and reattachment to its insertion (suture anchor or transosseous suture)
• •Delayed repair (beyond 3 weeks) becomes technically harder; chronic Stener may need free tendon graft reconstruction (e.g. palmaris longus)

Displaced bony UCL avulsion (avulsion fragment over 2-3 mm or rotated): operative fixation (typically tension-band wire, screw, or suture anchor).

Acute management triage:

• •Splint at presentation (thumb spica)
• •Plain radiograph
• •Urgent referral to hand surgery / fracture clinic within 7-10 days for ultrasound and management decision
• •Avoid delay - acute repair (under 3 weeks) outperforms delayed repair on long-term pinch strength and stability

Chronic UCL deficiency with established instability or post-traumatic arthritis: ligament reconstruction (free tendon graft, e.g. palmaris longus, Brand or Glickel reconstruction) or MCP arthrodesis as salvage. Discuss the demand-dependent trade-off.

Conservative pathway (Grade I-II, Grade III without Stener):

• •Weeks 0-4: full-time thumb spica with IP joint free; ice, elevation, finger ROM
• •Weeks 4-6: transition to removable splint for activity; passive then active MCP ROM under hand therapy supervision; pinch loading begins at 6 weeks
• •Weeks 6-10: progressive pinch and grip strengthening, sport-specific loading
• •Return to non-contact sport: 6-10 weeks. Contact sport (with custom orthosis) often by 8-10 weeks; without orthosis at 10-12 weeks if pain-free with full pinch strength

Post-operative (UCL repair):

• •Weeks 0-2: thumb spica plaster cast, then thumb spica orthosis. IP joint mobilised from day 1
• •Weeks 2-6: removable orthosis; hand therapy-led gentle MCP ROM and isometric pinch
• •Weeks 6-12: progressive pinch and grip strengthening; sport-specific orthosis use as required
• •Return to non-contact training: 8-10 weeks. Contact sport with orthosis: 10-12 weeks; without orthosis: 12-16 weeks per surgeon-specific protocol

Post-reconstruction (chronic / Stener-delayed): longer recovery, protected ROM for 6-8 weeks, with full return at 4-6 months.

Persistent instability, weakness, or pain beyond 3 months after conservative trial should prompt reassessment for missed full-thickness tear or Stener lesion. Late surgical repair or reconstruction remains possible but with reduced outcomes versus acute repair.

• •BSSH BEST guideline (2024) - Primary UK framework: ultrasound is first-line soft-tissue imaging; MRI is reserved for equivocal cases; acute repair (under 3 weeks) outperforms delayed repair for complete tears and Stener lesions.
• •Stener (1962) - Original anatomical and clinical study describing aponeurosis interposition; established the surgical rationale that persists today.
• •Heyman et al. (1993, 2008) - Long-term outcome data on conservative vs surgical management of Grade III tears: surgical repair gives superior pinch strength and stability, with the gap widening over time and in high-demand patients.
• •Cooper et al. (Cochrane 2008) - Comparative review of conservative vs surgical for complete UCL tears: surgical repair preferred when Stener present; conservative reasonable for Grade III without Stener in low-demand patients.
• •Chuter et al. (2009) - Demonstrated high sensitivity and specificity of ultrasound for detecting Stener lesions in expert hands; underpins current BSSH first-line imaging guidance.

• •Stener lesion = avulsed distal UCL displaced PROXIMAL to the adductor aponeurosis. The aponeurosis prevents healing; this is an operative indication.
• •Stress test the UCL in both MCP extension AND 30 degrees of flexion. Testing in extension alone misses partial proper collateral tears (proper collateral is taut in flexion).
• •BSSH BEST 2024: ultrasound is first-line soft-tissue imaging; MRI is reserved for equivocal ultrasound or pre-operative planning. Plain X-ray always to look for avulsion fragment.
• •"Skier's thumb" is the modern acute presentation; "gamekeeper's thumb" is the historical chronic-attrition descriptor (animal-handling injuries). The eponyms are interchangeable but skier's thumb is the more accurate term for acute UCL injury.
• •Acute repair (under 3 weeks) outperforms delayed repair on long-term pinch strength and stability. Delay risks chronic instability and post-traumatic MCP arthritis. Refer suspected complete tears to hand surgery within 7-10 days.
• •A displaced (over 2-3 mm) or rotated UCL avulsion fragment on X-ray is an operative indication regardless of Stener status. Non-displaced bony avulsion may be managed conservatively.