Summary Thumb Collateral Ligament Injuries, most commonly ulnar collateral (UCL), are athletic injuries that lead to a decrease in effective thumb pinch and grasp. Diagnosis relies upon thumb MCP radial-ulnar stress exam and MRI studies. Treatment involves anatomic repair or reconstruction which reliably restores the essential function of the collateral ligament. Epidemiology Incidence ulnar collateral ligament (UCL) injury is 10 times more common than radial collateral ligament (RCL) injuries UCL injuries comprises of 86% of all athletic thumb injuries Demographics acute injuries are common in many contact and non-contact sports football, soccer, downhill skiing eponymously known as a Skier's thumb chronic injuries due to attenuation of the ligament under repeated stress eponymously known as a Gamekeeper's thumb Etiology Pathophysiology mechanism of injury radially-directed force causing hyper-abduction moment at the thumb MCP i.e. stationary ski pole and strap contacting the moving skier's thumb into hyper-abduction pathoanatomy Stener lesion avulsed ligament with or without bony attachment is displaced dorsal and superficial to the adductor aponeurosis usually the distal end is retracted proximally the interposed adductor will not allow healing without surgical repair Stener-like RCL lesion rare given overlying abductor aponeurosis RCL injury leads to joint subluxation rather than overt instability Anatomy Osteology thumb metacarpal and phalanx form the metacarpophalangeal joint metacarpal condyles more flattened than finger metacarpals which increases stability Ligaments both UCL and RCL composed of proper collateral ligament resists load with thumb in flexion accessory collateral ligament and volar plate resists load with thumb in extension both ligaments run in dorsal to volar direction from proximal to distal valgus laxity in both flexion and extension is indicative of a complete collateral rupture RCL is compose Biomechanics diarthrodial joint but allows for six degrees of movement flexion-extension, adduction-abduction, and rotation static stability provided by bony anatomy, collateral ligaments, volar plate and dorsal capsule dynamic stability provided by extrinsic and intrinsic muscle groups extrinsics extensor pollicis longus, extensor pollicis brevis, flexor pollicis longus intrinsics abductor pollicis brevis, flexor pollicis brevis, adductor pollicis ulnar-sided tendinous/aponeurotic insertions more robust than radial Classification UCL/RCL Instability Grading Grade 1 Sprain with no joint instability (incomplete tear) Grade 2 Asymmetric joint laxity but endpoint present (incomplete tear) Grade 3 Joint instability without endpoint and 30-35 degrees of joint space opening or 10-15 degrees more than contralateral thumb (complete tear) Presentation History fall on outstretched hand and abducted thumb ball or racquet strike Symptoms common symptoms pain at ulnar aspect of MCP joint worse with pinch or grasp most common for UCL tear radial-sided MCP pain most common complaint for RCL tear Physical exam inspection rarely visible deformity of joint palpation tenderness at site of ligament injury (distal for UCL and proximal for RCL) tender mass signifying Stener lesion motion radial-ulnar stress exam stress both at extension and 30° of MCP flexion avoid allowing phalanx to rotate radial instability in 30° of flexion indicates injury to proper UCL radial instability in extension indicates injury to accessory and proper UCL and/or volar plate local anesthetic may be added to eliminate patient guarding provocative tests anterior and posterior drawer metacarpal held stationary and phalanx translated anteriorly and posteriorly amount of translation and absence of an end point may signify volar subluxation and RCL rupture weakness with resisted pinch Imaging Radiographs recommended views PA lateral oblique optional views stress views controversial may aid in diagnosis if a bony avulsion has already been ruled out findings UCL injury avulsion or condylar fracture Sag sign supination of proximal phalanx relative to the metacarpal volar subluxation of proximal phalanx seen on lateral view indicates associated dorsal capsular tear or extensor tendon injury RCL injury pronation of proximal phalanx MRI indications can aid in diagnosis if exam equivocal sensitivity and specificity 100% sensitivity and specificity Ultrasound accuracy is operator-dependent sensitivity and specificity 76-88% sensitive, 81-83% specific 81% accuracy, 74% positive predictive value, 87% negative predictive value Diagnosis Clinical and MRI diagnosis made by history and physical exam (thumb MCP radial-ulnar stress exam) and confirmed with MRI studies. Treatment Nonoperative immobilization for 4 to 6 weeks indications Grade 1 and 2 partial UCL and RCL tears < 15° side to side variation of varus/valgus instability outcomes excellent rate of return to sport without residual laxity or disability Operative RCL/UCL repair indications acute Grade 3 injuries with >15° side to side variation of varus/valgus instability >30-35° of opening Stener lesion outcomes >90% with outcomes rated excellent for UCL repair 96% good to excellent outcomes for RCL repair reconstruction of ligament with tendon graft indications chronic injury (older than 3-8 weeks) incompetent ligament tissues outcomes 92% satisfaction rate in one series adductor advancement indications acute UCL rupture done in conjunction with UCL repair outcomes 100% return to sport reported in one series MCP fusion or adductor advancement indications chronic injuries salvage procedure for failed repairs or reconstructions Techniques Immobilization for 4 to 6 weeks technique immobilization in splint or cast to off-load injured UCL or RCL some protocols advocate for use of removable splint and immediate active and passive range of motion patient must avoid stress on ligament during exercises grip and pinch strengthening began around 4-6 weeks RCL repair approach straight longitudinal incision on radial aspect of the thumb abductor aponeurosis may need to be resected to expose joint capsule and ligament take care to spare dorsal cutaneous branches of the radial sensory nerve technique pull-out sutures or loaded suture anchors can be used to re-oppose the ligament to its origin repair MCP joint capsule and abductor tissues K-wire may be placed to immobilize the joint temporarily UCL repair approach S-shaped or chevron incision overlying MCP joint technique trans-osseous sutures, suture anchors with or without suture augmentation, and direct ligament repair to periosteum all described rehab joint immobilization leaving the IP joint free strengthening begun at 4-6 weeks complications skin necrosis if pullout suture technique used decreased pinch strength Tendon reconstruction with tendon graft approach S-shaped or chevron incision overlying MCP joint technique multiple techniques described using various tissues sources, configurations and fixation constructs palmaris longus autograft weaved through bone tunnels can be secured with interference screws, cortical button or suture anchors Adductor advancement approach S-shaped or chevron incision overlying MCP joint technique adductor aponeurosis repaired to native distal insertion of UCL MCP fusion approach dictated by prior surgeries and concomitant pathology technique various fixation methods (k-wire, compression screws, plates) MCP fused in 15 degrees of flexion Complications Stiffness incidence MCP and IP stiffness most common complication following repair Persistent instability incidence 15% with residual instability for grade 3 injuries treated with immobilization treatment ligament reconstruction for chronic injuries Superficial radial neurapraxia numbness distal to incision treatment observation Prognosis Prognosis return to play rates approach 100% following anatomic repair