Summary Medial Ulnar Collateral Ligament Injuries are characterized by attenuation or rupture of the ulnar collateral ligament of the elbow leading to valgus instability in overhead throwing athletes. Diagnosis is usually made by a combination of physical exam and MRI studies. Treatment for most individuals is rest and physical therapy. Surgery is reserved for high level overhead athletes such as pitchers. Epidemiology Incidence literature shows increasing occurrence of UCL injuries and reconstructions becoming more common among high school and amateur pitchers Demographics overhead athletes who place significant valgus stress on their elbows originally described among javelin throwers, now much more common in baseball pitchers relatively uncommon in skeletally immature throwing athletes little leaguers' elbow login to view 1 more bullet Risk factors exceeding youth baseball pitch count and inning restrictions higher pitch velocity deficits along kinetic chain (shoulder and core weakness, loss of shoulder motion, etc.) Etiology Pathophysiology mechanism of injury acute trauma login to view 1 more bullet overuse injury login to view 5 more bullets iatrogenic login to view 1 more bullet Associated conditions traction-related ulnar neuritis olecranon (posteromedial) impingement elbow arthritis Anatomy Osseous elbow is complex hinge composed of ulnohumeral, radiocapitellar, and radioulnar joints valgus carrying angle ranging from 6 to 11 degrees Ligaments medial ulnar collateral ligament (UCL) divided into three components anterior oblique ligament login to view 6 more bullets posterior oblique ligament (posterior bundle) login to view 2 more bullets transverse ligament login to view 1 more bullet Biomechanics elbow stability evenly split between osseous and soft tissue structures UCL primary restraint to valgus stress from 30 to 120 degrees of flexion flexor-pronator and joint capsule also contribute Presentation History acute injuries may present with a "pop" associated with pain and difficulty throwing Symptoms decreased throwing performance loss of velocity loss of control and accuracy pain medial or posterior elbow pain during late cocking and acceleration phases of throwing many throwers also have posteromedial pain due to valgus extension overload felt during the deceleration phase ulnar nerve symptoms paresthesias down ulnar arm into ring and small fingers Physical examination inspection tenderness along elbow at or near MCL origin login to view 1 more bullet evaluate the integrity of the flexor-pronator mass evaluate for presence of palmaris longus tendon range of motion seasoned throwers may lack full extension evaluate shoulder and rest of kinetic chain neurovascular evaluate for ulnar neuropathy and/or subluxation provocative tests valgus stress test login to view 2 more bullets milking maneuver login to view 3 more bullets moving valgus stress test login to view 3 more bullets Imaging Radiographs recommended views AP and lateral of the elbow login to view 2 more bullets optional views oblique views to evaluate the olecranon gravity or manual stress radiographs of both elbows login to view 1 more bullet findings assess for a posteromedial osteophyte (due to valgus extension overload) MRI indications high suspicion for UCL injury and/or intra-articular pathology MR-arthrogram - diagnostic use of dye more accurate sensitivity 92%, specificity 100% findings thickened ligament (chronic injury), calcifications, and tears midsubtance tears or proximal/distal avulsions full-thickness or partial undersurface tears capsular "T-sign" with contrast extravasation Dynamic ultrasound can evaluate laxity with valgus stress dynamically sensitivity and specificity operator dependent Differential Medial epicondylitis Flexor-pronator strain Ulnar neuropathy Valgus extension overload Treatment Nonoperative rest and physical therapy indications login to view 2 more bullets outcomes login to view 1 more bullet Operative UCL anterior band ligament reconstruction (Tommy John Surgery) indications login to view 2 more bullets outcomes login to view 5 more bullets UCL repair indications login to view 2 more bullets outcomes login to view 2 more bullets Techniques Rest and physical therapy technique 6 weeks of cessation from throwing initiate physical therapy for flexor-pronator strengthening and improving throwing mechanics (after 6 weeks and symptoms/pain have resolved) progressive return to throwing program UCL anterior band ligament reconstruction overview various modifications of original Jobe technique exist all create an anatomic reconstruction of the native ligament from medial epicondyle to ulnar sublime tubercle login to view 1 more bullet approach flexor-pronator muscle-splitting approach (decreased morbidity of historic flexor-pronator mass detachment) login to view 1 more bullet in-situ ulnar nerve decompression login to view 3 more bullets UCL and joint capsule identified, ligament repaired in side-to-side fashion soft tissue palmaris longus autograft most common graft (gracilis autograft or allograft also options) login to view 4 more bullets bony work and reconstruction modified Jobe technique login to view 6 more bullets docking technique login to view 4 more bullets hybrid interference-screw technique login to view 3 more bullets cortical suspensory fixation, ex. "Endo-button" (Smith & Nephew) reconstruction login to view 2 more bullets postoperative care early login to view 3 more bullets mid-term login to view 2 more bullets return to competitive throwing at 9-12 months post-op UCL repair approach as above soft tissue ulnar nerve in-situ release or transposition ligament dissected and avulsion identified bony work ligament sutured and secured to either humerus or ulna with suture anchor repair can be augmented with high-strength suture postoperative care similar to UCL reconstruction Complications Ulnar neurapraxia most common, 3-26% incidence treatment observation as majority resolve within a few months Medial antebrachial cutaneous (MABC) nerve injury crosses at distal aspect of the incision Fracture of ulna or medial epicondyle risk factors small bone bridge during tunnel placement treatment may require internal fixation of fracture, or switch to larger graft fixation device Elbow stiffness risk factors heterotopic ossification treatment early directed therapy focusing on obtaining motion HO excision around 6 months, if present Inability to regain preinjury level throwing ability more common following revision reconstructions Prognosis Formerly a career-ending injury UCL reconstruction provides high rates of return to throwing and sport worse outcomes following revision reconstructions Outcomes and return to sport following surgical MUCL reconstruction (Tommy John surgery) depend on precise recreation of the MUCL and diligent rehabilitation.