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 more common cause of medial elbow pain with decreased throwing effectiveness and distance 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 often associated with elbow dislocations overuse injury biomechanical forces microtrauma from repetitive valgus stress leads to rupture of the anterior band of the medial UCL baseball pitchers place significant valgus stress on the elbow in the late cocking and early acceleration phase of throwing elbow valgus load increases with poor throwing mechanics and decreases with trunk-scapular kinesis, forearm pronation, dynamic flexor-pronator stabilization valgus load is highest in the late cocking/acceleration phase of throwing iatrogenic excessive olecranon osteophyte resection places the MCL at risk 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 strongest and most significant stabilizer to valgus stress courses from anteroinferior ridge on medial epicondyle to 2.8 mm distal to the ulna articular margin on the sublime tubercle mean length of 54 mm subdivides into anterior and posterior bands. anterior band is primary restraint to valgus stress, exhibiting nearly isometric strain during elbow ROM posterior band exhibits increasing strain during higher degrees of elbow flexion posterior oblique ligament (posterior bundle) demonstrates the greatest change in tension from flexion to extension tighter in flexion transverse ligament no contribution to stability 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 posteromedial tenderness may be due to valgus extension overload 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 flex elbow to 20 to 30 degrees (unlocks the olecranon), externally rotate the humerus, and apply valgus stress 50% sensitive milking maneuver creates valgus stress by pulling on the patient's thumb with the forearm supinated and elbow flexed at 90 degrees patient may be supine or seated/standing positive test is a subjective apprehension, instability, or pain at the MCL origin moving valgus stress test place elbow in same position as the "milking maneuver" and apply a valgus stress while the elbow is ranged through the full arc of flexion and extension positive test is a subjective apprehension, instability, or pain at the MCL origin between 70 and 120 degrees 100% sensitive and 75% specific Imaging Radiographs recommended views AP and lateral of the elbow static x-rays are often normal may show loose bodies or calcifications of UCL optional views oblique views to evaluate the olecranon gravity or manual stress radiographs of both elbows may show medial joint-line opening >3 mm (diagnostic) 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 first line treatment in most cases partial tears outcomes 42% return to preinjury level of sporting activity at an average of 24 weeks Operative UCL anterior band ligament reconstruction (Tommy John Surgery) indications high-level throwers that want to continue competitive sports failed nonoperative management in partial tears and willing to undergo extensive rehabilitation outcomes 90% return to preinjury levels of throwing with newer reconstruction techniques humeral docking associated with better patient outcomes and lower complication rate compared to figure-of-8 fixation humeral docking has shown higher rates of return to sport compared to Jobe and modified Jobe techniques humeral docking and cortical button techniques are biomechanically stronger than figure-of-8 and interference screw fixation humeral docking with interference screw fixation on the ulnar side showed 95% strength of the native UCL UCL repair indications not clarified in the literature mostly performed in young athletes with avulsion-type tear patterns outcomes originally performed with poor results, replaced by reconstruction multiple, recent case series show promising results with novel, augmented techniques 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 none are stronger than native ligament approach flexor-pronator muscle-splitting approach (decreased morbidity of historic flexor-pronator mass detachment) some surgeons elevate flexor-pronator mass when perfomring modified Jobe technique in-situ ulnar nerve decompression patients without pre-operative ulnar nerve symptoms should not undergo routine ulnar nerve decompression or transposition patients with pre-operative ulnar nerve symptoms may be treated with isolated ulnar nerve decompression with or without transposition patients with ulnar nerve subluxation should be treated with ulnar nerve transposition 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) single, distal transverse incision centered over palmaris tendon identified and tagged with suture, underlying median nerve protected tendon followed proximally with additional incision made centered over tendon confirming enough length obtained, tendon harvested, and wounds closed bony work and reconstruction modified Jobe technique two connected bone tunnels made in medial epicondyle of humerus in "Y" configuration single bone tunnel created by connecting two angled drill holes in ulnar sublime tubercle alternatively, commercially available drill guides may be used graft passed through ulnar tunnel, then graft ends through humeral tunnels graft sutured to itself in figure-of-8 configuration extra strands may be added if graft accommodates this docking technique single bony socket made in medial epicondyle single bone tunnel created by connecting two angled drill holes in ulnar sublime tubercle graft passed through ulnar tunnel, suture limbs passed through two bone punctures, graft shuttled into humeral socket graft suture ends tied over bony bridge on medial epicondyle hybrid interference-screw technique docking tunnel/socket made on the humerus single longitudinal bone socket made into ulna with interference-screw fixation felt to decrease risk of iatrogenic fracture cortical suspensory fixation, ex. "Endo-button" (Smith & Nephew) reconstruction used on ulna to stabilize graft more commonly used in revision setting postoperative care early early active wrist, elbow, and shoulder range of motion incorporation of shoulder girdle, core, and hip strengthening exercises strengthening exercises beginning four to six weeks post-op mid-term initiate a progressive throwing program at four months avoid valgus stress until 4 months post-op 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.