Instability of the elbow resulting from injury severely compromises the action of the overhand throwing motion. The medial collateral ligament (MCL, also known as the ulnar collateral ligament), supplying 54% of stability during 90o elbow flexion is the source of the majority of cases. This once career-threatening injury has now evolved with modern techniques allowing on average 80-90% of athletes to return to the same if not higher levels of play.
Structure and Function
The skeletal architecture, along with the various interactions between muscles and ligaments, contribute to the elbow joint's movement and stability. Depending upon the position of the elbow throughout the flexion-extension arc, these structures each contribute different amounts to the stability of the elbow.
The osseous framework consists of three separate articulations. The first occurs at the ulnohumeral joint. This hinge joint is an articulation between the trochlear notch of the ulna and the trochlear of the humerus. It allows for flexion and extension, supplying most stability at the elbow during this motion, particularly during extension. The radiocapitellar joint, considered a limited ball in socket joint, is an articulation between the head of the radius and the capitulum of the humerus. This joint provides longitudinal stability and rotation of the forearm and is an important secondary stabilizer to valgus stress with the primary being the anterior band of the MCL. Lastly, the proximal radioulnar joint connects the ulna to the radius between the head of the radius and the radial notch of the ulna and enables rotation of the forearm.
Stability contribution by the various structures is dependent on the degree of flexion and extension. At extreme extensions, the anterior capsule, MCL and bone share equal valgus stability. However, at elbow flexions close to 90 degrees, the MCL contributes to roughly 54% of valgus stability.
Chronic overuse injuries of the MCL are rare in the general population and are limited almost exclusively to those frequently involved with an overhand throwing motion. By far the highest prevalence is found among professional baseball players, specifically pitchers. Although not as common, this injury can also arise among athletes incorporating overhand throwing mechanics in sports such as football, lacrosse, tennis and the javelin. Fortunately, an isolated injury specifically to the MCL is only problematic in the motion of throwing and generally does not inhibit daily activities and movements.
The mechanism of a throwing injury to the elbow is the repetitive valgus stress placed on the joint. The elbow acts as a fulcrum between the hand and the trunk of the body during the explosive internal rotation of the shoulder accompanied with extension at the elbow. As a result, this joint experiences the brunt of the force during overhand throwing motion. This large amount of force can reach near failure tensile stress levels among soft tissues within the elbow. The repeated action ultimately causes valgus instability as micro tears and attenuation of the MCL occurs with the possibility of an eventual complete tear. In addition, other structures within the elbow become prone to injury risk. Individuals may experience various symptoms leading to the diagnosis of other injuries such as valgus extension overload, medial epicondylitis and stress fractures.
Patients will present with various symptoms localized to the medial epicondyle depending on the injury. Acute pain can be present in static motion, and often significantly greater during throwing motion. Patients will often report decreased throwing velocity and accuracy. Swelling and tenderness can also be apparent along the medial elbow. Numbness or pain along the medial forearm towards the hand can also be a complaint due to inflammation around the cubital tunnel causing compression of the ulnar nerve. Finally a decrease in range of motion at the elbow is often observed.
If forces exceed the tensile strength of the MCL, micro tears can arise from repetitive action. It is these micro tears that cause pain during the throwing motion. The red flag is when a "popping" sensation at the elbow is felt during the acceleration phase of throwing, often signalling a complete tear of the MCL. This is generally followed by acute pain at the elbow regardless of being static or in the throwing motion.
Diagnosis of throwing injuries to the elbow can be very difficult due to the complexity of the joint along with the various injuries associated with it. The following are such injuries: 1) MCL tear, 2) Ulnar neuritis, 3) Medial Epicondylitis (Flexor-Pronator muscle strain or tendinitis), 4) Medial Epicondyle Apophysitis, 5) Valgus extension overload, 6) Olecranon stress fractures or osteochondritis dissecans of capitellum associated with loose bodies.
Finally, it is important to diagnose any associated ulnar nerve dysfunction. This involves examining the sensory and motor aspects of the ulnar nerve territory along with palpation for irritability, performing Tinel’s test and identifying subluxation out of the ulnar groove which may be a cause of symptoms.
Imaging can be used as a valuable tool in diagnosis. Plain radiographs (anterior-posterior and lateral views) provide an excellent general overview of the osseous structure of the elbow. It can be used to detect spurs, loose fragments, calcification within the ligament, osteophytes and osteochondral damage. Sometimes stress views of the joint can be performed to identify joint instability. This procedure has demonstrated a significant difference in images between normal and abnormal elbows. Openings between 1 and 3 mm greater then the contralateral extremity suggest MCL injury. Oblique projections are also recommended but not always necessary.
Soft tissues can be examined by use of a CT and MRI scan. Visualization vastly improves with use of an arthrogram. MRI is the modality of choice for soft tissue as it is less invasive. Sagittal, coronal and axial are the recommended planes. Finally, in order to confirm the diagnosis, an arthroscopic assessment may be performed. This can be especially useful in patients with equivocal clinical examination and imaging findings with ongoing symptoms.
Risk factors and prevention
The prevalence of throwing injuries to the elbow has increased dramatically in recent years. Youth athletes have been documented with increased frequency and thus overuse of overhand throwing motion. This leads to micro tears and attenuation of soft tissue, which can accumulate over time leading to further damage to the elbow as an adult. The study by Fleisig, et al reported a rise from 4% in 1997 to 31% in 2008 of the proportion of youth or high school pitchers requiring MCL reconstruction. A study by Lyman, et al concluded that the main risk factor in throwing injuries to the elbow is the rise in frequency of pitching. In addition, Lyman's study also concluded that pitch type, specifically sliders, have a high correlation for risk of elbow injury among youth development. Contrary to common belief, curve-balls do not place greater stress at the elbow despite what was previously thought. Furthermore, throwing mechanics and conditioning also play a role in increasing risk factors, although less significant as frequency.
Prevention of injury is directed towards limiting the frequency and duration of throwing. Specifically directed towards youths, maintaining a constant and low pitch count or use, along with adequate rest is key. Proper mechanics in combination with conditioning and flexibility are more important tools for the older athlete in higher levels of competition. Increased strength of the flexor pronator muscles such as the flexor carpi radialis and ulnaris can better accommodate and relieve stress within the MCL during throwing.
The newest technique, the hybrid, enables improved ulnar fixation. This method involves a two-stranded graft with an interference or end-button fixation on the proximal ulna. The docking technique is used at the humeral end. This method replicates the original anatomy and allows for the ability to tense an anterior and posterior band of the graft separately.
Outcomes after treatment to the elbow are very promising. Non-surgical treatment allows for the return of full range of motion to the elbow without impeding daily activities. However, (lynch article) only 42% of athletes rehabilitated non-surgically tend to return to same level of competition as prior to injury. Surgical treatment produces significantly higher return rates to the same if not higher levels of play. Jobe, et al, in 1986 demonstrated a return rate of 62% using the original Jobe technique. Thompson, et al demonstrated an 82% return rate with the modified Jobe technique and Rohrbough, et al study displayed a 92% return rate using the docking technique.
Complications arising from surgery involve infection, hematoma, bone tunnel fractures, and implant failure, the most important significant being ulnar nerve injury. However, with modern techniques, not only has the rate of reoperation decreased significantly, but the rate of ulnar nerve complications has decreased from 30% at the time of the Jobe study to the 3% during Thompson study.
Post-operative rehabilitation is generally the same regardless of the technique used. The elbow is immobilized with a splint for the first 7-10 days. Following this, the elbow is then placed in a functional brace, protecting it from valgus stress while allow limited motion of extension and flexion. As time continues, the brace is slowly adjusted to allow for passive followed by active range of motion exercises as the graft becomes more stable. This occurs over a span of 4 to 6 weeks. At 6 weeks formal therapy can begin, with the use of light weights at 12 weeks. Valgus stress is to be avoided for the first 4 months, after which a throwing rehabilitation program can be induced to the throwing athlete. Roughly 9-12 months post-operative treatment is the average time for a throwing athlete to return to same level of competition.
- About 50 active MLB pitchers have undergone MCL reconstruction, roughly 1 out of ever 7 pitchers.
- 14 232- The number of regular season days MLB pitchers have spent recovering on the disabled list due to MCL reconstruction in the past 5 years (as of march 2012)
- $193,503,317- The amount of money spent on pitcher salaries during that span on the disabled list by MLB teams
Elbow, Throwing injuries, Medial Collateral Ligament
- Recognize on physical examination valgus instability
- Correctly identify and diagnosis various forms of imaging
- Perform proper surgical treatment.