Medial Collateral Ligament Reconstruction: MCL Insufficiency

Introduction

The medial ulnar collateral ligament (MCL) of the elbow is the primary stabilizer to valgus stress and is most commonly injured in the overhead-throwing athlete. Ulnar collateral ligament insufficiency is surgically managed with MCL reconstruction, or “Tommy John surgery,” named for the first professional pitcher treated by Dr. Frank W. Jobe in 1974. First described in a javelin thrower in 1946, MCL injury is now well recognized in sports medicine and has become the preeminent injury in professional pitchers. Biomechanical investigations have improved our understanding of the relationship between the MCL complex, forearm flexors, and the bony articulations of the elbow, and clinical studies have provided outcomes on which to base treatment decisions. This chapter outlines MCL pathophysiology, patient evaluation, and surgical indications and describes recent surgical advancements and current techniques.

Pathophysiology

The anterior bundle of the MCL complex is the primary restraint and stabilizer to valgus stress of the elbow. The anterior bundle is functionally composed of anterior and posterior bands that provide a reciprocal function in resisting valgus stress through the range of flexion–extension motion. Valgus stress is generated at the elbow during throwing maneuvers in baseball, softball, football, tennis serving, and volleyball spiking. The calculated valgus torque during the acceleration phase of throwing is 64 N m, and more than 60 N m with the tennis serve. These estimated forces exceed the known ultimate tensile strength of cadaveric MCL specimens (33 N m). Thus the MCL is at risk for injury from these repetitive forces.

A cadaver model demonstrated the flexor carpi ulnaris (FCU) as the primary dynamic contributor to valgus stability in the elbow and the flexor digitorum superficialis as a secondary stabilizer. The fibers of the FCU are intimately attached to the origin of the medial epicondyle and optimally positioned to provide support directly in line with the MCL. Clinical electromyographic analysis has demonstrated decreased forearm flexor muscle activity in pitchers with MCL insufficiency, further suggesting the role of dynamic muscle contribution to elbow instability. The importance of the forearm flexor muscles is appreciated by several investigators advocating limiting dissection of the flexor-pronator mass during reconstruction of the MCL, with evidence suggesting improved clinical outcomes. Hence, the muscular dynamic stability to the medial elbow is essential and must be included in rehabilitation programs, and morbidity from surgical techniques must be minimized.

The bony articulations of the posterior compartment of the elbow share an intricate relationship with the soft tissue MCL, and this dynamic is vital in the pathophysiology of valgus instability. Andrews and Timmerman reported a series of professional baseball players who underwent olecranon debridement, where 25% developed valgus instability and eventually required MCL reconstruction. This observation suggests that both the olecranon and the MCL contribute to valgus stability. Similarly, a biomechanical study of sequential partial resection of the posteromedial aspect of the olecranon demonstrated a stepwise increase in elbow valgus angulation. Kamineni et al. also confirmed in a cadaver model that strain in the MCL is increased with increasing posteromedial olecranon resection beyond 3 mm. These studies suggest that aggressive olecranon resection may place the MCL at risk for future injury. A complementary concept suggests that subtle valgus instability may lead to posteromedial osteophyte formation. MCL injury simulated in a cadaver model results in contact alterations in the posterior compartment of the elbow that leads to osteophyte formation. This suggests that patients with posteromedial impingement pain, or valgus extension overloaded (VEO) syndrome, should be critically evaluated for underlying MCL pathology.

Epidemiology

Overuse injuries to the elbow are common in the overhead-throwing athlete, particularly in elite baseball. The frequency of MCL reconstruction in professional baseball has drawn increasing attention. As many as 10% of all players and 16% of pitchers have undergone MCL reconstruction, and there has been an estimated 10-fold increase in the procedure in the first decade of the 21st century.

Higher pitch velocity is the most predictive factor in major league baseball pitchers, with increased player weight and younger age being secondary predictors of MCL reconstruction. More alarming, evidence suggests this trend has translated to adolescent athletes, with a 50% increase in MCL reconstruction in high-school players aged 15 to 19 years reported by a single surgeon. Similarly, a database of a large, privately insured population demonstrated significant increases in MCL reconstruction in patients aged 15 to 19 years and an overall increase in MCL procedures over time. A subsequent investigation using the New York State database demonstrated a threefold increase in the incidence of MCL reconstruction in the past 10 years, particularly in those patients aged 17 to 19 years.

Diagnosis

History

Symptoms specifically related to the elbow should be ascertained, including duration of symptoms, prior episodes, exact location of discomfort, ulnar nerve symptoms, and posterior impingement signs. Patients may report a sudden event with sharp pain and an accompanying “pop” (acute injury), while others may have a gradual progression of pain with associated changes in pitching accuracy and velocity (chronic injury). Patients with MCL injuries most often complain of medial elbow pain during the acceleration phase of throwing ( Fig. 68.1 ).

Injury factors should be assessed, such as a history of overuse (particularly in skeletally immature athletes), prior surgery (arthroscopic posteromedial decompression), or change in pitching mechanics. Symptoms of MCL insufficiency can be overshowed in patients with VEO, especially in cases of chronic ligament attenuation. In these cases, the symptoms of sharp posteromedial elbow pain in both the acceleration (flexion) and more so in the deceleration (extension) phases of throwing are also associated with limited extension and mechanical catching resulting from impinging osteophytes, chondromalacia, or loose bodies.

Physical Examination

The medial aspect of the elbow should be inspected for swelling and palpated for point tenderness along the course of the MCL from its origin to insertion. The absence of pain with resisted wrist flexion and pronation and presence of tenderness posterior to the flexor-pronator origin can help differentiate MCL from flexor-pronator injury. Range of motion should be measured and compared to the contralateral side. The presence of a flexion contracture is not uncommon in elite baseball players. Provocative maneuvers for the ulnar nerve should be performed, including the Tinel test for direct nerve irritation and dynamic instability during elbow range of motion. The presence of a palmaris longus should be determined if MCL reconstruction is anticipated.

Valgus instability is assessed with the elbow flexed between 20 and 30 degrees to unlock the olecranon from its fossa. The examiner applies a valgus force attempting to elicit painful opening of the medial ulnohumeral joint ( Fig. 68.2 ). The milking maneuver is performed by either the patient or the examiner pulling on the patient's thumb to create valgus stress with the patient's forearm supinated and elbow flexed beyond 90 degrees. The moving valgus stress test, considered the most sensitive and specific maneuver, is performed by applying valgus torque while the elbow is repeatedly flexed and extended ( Fig. 68.3 ). The test is considered positive if pain is reproduced at the MCL, with pain usually maximal between 70 and 120 degrees.

Physical examination should include a global musculoskeletal assessment as problems within the kinetic chain are intimately related to the shoulder, elbow, and core in performance athletes. Careful attention should be given to the ipsilateral shoulder with respect to strength and range of motion. The presence of a glenohumeral rotation deficit (GIRD) and a lack of external rotation have been identified as independent risk factors for MCL injury.