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.
Soft tissue layers of the elbow joint consist of dynamic muscle action and static capsuloligamentous structures. The dynamic components are muscle groups that cross the elbow joint and in turn help to coordinate stability and movement. The biceps, triceps, and brachialis are all examples. In particular to overhand throwing, the flexor-pronator mass muscles, such as the flexor carpi ulnaris and the flexor digitorum superficialis are the primary and secondary dynamic restraints to valgus loads at the elbow respectively.
The main static stabilizers include the medial and lateral ligament complexes. The lateral collateral ligament complex consists of four ligaments: 1) radial collateral ligament, 2) lateral ulnar collateral ligament, 3) annular ligament and 4) accessory lateral collateral ligament. These four ligaments provide rotational and varus stability. The medial collateral ligament complex, localized around the medial epicondyle, provides valgus stability and is the central focus of throwing injuries to the elbow. This complex is composed of three ligaments: 1) the anterior bundle, 2) the posterior bundle and 3) the transverse ligament. The anterior bundle is the primary valgus stabilizer. It originates from the anterior and inferior medial epicondyle of the humerus and inserts onto the sublime tubercle of the ulna. The anterior bundle can further be divided into anterior and posterior bands, which act in reciprocal to each other during movements. The posterior bundle plays a less interactive role than the anterior. Originating on the inferior medial epicondyle and inserting onto the proximal ulna, it acts as the secondary restraint to valgus loads at high degrees of flexion >90o . Finally, the transverse ligament plays a minimal stability function, acting simply as a thickening of the medial joint capsule.
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.
The throwing motion is divided into multiple phases depending on the sport. Two specific phases found in the general throwing motion cause the root of maximal stress; the late cocking phase and acceleration phase. The late cocking phase is defined as shoulder abduction, maximal external rotation of the shoulder combined with elbow flexion between 90o-120o. The ending of this phase moves onwards to the acceleration phase. Defined as forward directed forces, the shoulder internally rotates, the humerus adducts and the elbow rapidly extends from 90o-120o to roughly 20o flexion. The force of this motion can approach approximately 120 Nm, with evidence showing 34 Nm placed directly on the MCL. The rest of the force is distributed equally throughout other structures of the elbow such as the osseous architecture, the flexor carpi ulnaris and the flexor digitorium superficialis.
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.
An accurate patient history is a crucial tool that can be used in these circumstances to aid in the diagnosis. Past literature has documented that decreased control and velocity during throwing is indicative of elbow instability and specifically, injury to the MCL. Palpation of the elbow for swelling, inflammation and tenderness should be performed to localise the injury.
For overhand throwing injuries, notice should be taken to 3 bony structures in particular: medial epicondyle, radial head and the proximal olecranon. In adolescents, pain directly at the medial epicondyle is strong evidence for medial epicondyle apophysitis (MEA), also known as little league elbow. In skeletally immature athletes the epicondyle growth plate is weaker then the MCL. In older athletes this injury, although much less common, is the hardest to differentiate between it and MCL injury, requiring an MRI in order to do so. The repeated stress to the immature skeleton can lead to avulsions and fragmentation.
Pain at the radial head is an indicator for fracture, dislocation or osteochondritis dissecans of the capitellum (OCD). OCD, which is localized fragmentation of the bone or cartilage, can lead to loose bodies within the joint. It is often a consequence of too much stress caused from laxity of the MCL. A strong indicator of OCD is catching and locking during flexion-extension at the elbow.
Pain and tenderness at the posteromedial tip of the olecranon will suggest valgus extension overload (VEO). VEO is a result of the excessive forces in the elbow during the throwing motion and is characterized by the breakdown of cartilage on the olecranon. This often leads to the development of osteophytes. Loss of extension in the elbow is an important indicator of VEO. Both VEO and OCD require imaging for a definitive diagnosis.
When palpating the soft tissues, the flexor-pronator muscles and the MCL are the most important structures to be examined. Pain among flexor-pronator masses indicates potential medial epicondylitis from an overload of stress and subtle instability of the elbow. Generally, medial epicondylitis caused by throwing strongly suggests MCL ligament damage.
MCL injury is the most thoroughly examined and sought out injury of the elbow. There are three tests to test the stability of the ligament. In all tests, the shoulder should be abducted and extended.
Valgus stress test
The patient is seated with an examiner holding the forearm with the elbow flexed at 20-30o in order to unlock the ulno-humeral articulation. Valgus stress is then placed on the MCL. This test is designed to target the anterior band of the MCL. A positive test is whereby pain and increased opening at the medial joint line occurs when compared to the asymptomatic elbow.
This test eliminates glenohumeral motion by externally rotating and extending the humerus of the patient. With the forearm supinated, the examiner then creates a valgus stress at the elbow by pulling down on the back of the thumb. A positive test again will reproduce pain and increased opening at the medial side of the elbow.
Moving Valgus Stress Test
The patient’s elbow is moved throughout a range of motion of 30o-120o flexion. A positive test will generate pain in the elbow within the shear zone, the arc of flexion between 70o and 120o. This zone is a replication of that during an overhand throwing motion.
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.
Treatment options vary based on the pathology. For individuals and athletes who aren't looking to return to high levels of throwing, non-operative treatment is the preferred option. A phase of rest for approximately six weeks, designed to reduce the inflammation and pain is the first step. This can be achieved by the avoidance of throwing, ice and anti-inflammatory drugs such as NSAIDs., This phase is then followed by passive range of motion exercises followed by the gradual work-up towards active exercises. By 12 weeks, a patient should have pain free range of motion. At this point, a gradual introduction into a strengthening program is introduced and designed to strengthen the surrounding muscles around the elbow joint to regain dynamic stability and proprioception.
If non-operative treatment fails, and the patient still experiences symptoms, surgery is the next option. To treat ulnar neuritis surgically, the options involve medial epicondylectomy, release of the flexor carpi ulnaris aponeurosis and cubital tunnel retenaculum (decompression) or anterior transposition of the nerve (subcutaneous, intramuscular, and submuscular). The literature remains divided on which method is superior in terms of overall benefit, but decompression is the recommended treatment due to its simplicity and avoidance of the risk of devascularising the mobilized segment of the nerve during transposition.
Surgical treatment for associated medial epicondylitis is only considered if a significant fracture occurs greater then 5mm that requires surgical reattachment. Along with diagnosis of valgus extension overload, if osteophytes or loose bodies are found, elbow arthroscopic debridement is recommended.
If the injury is diagnosed as osteochondritis dissecans of the capitellum with noticeable loose bodies, surgical treatment is the preferred procedure. Arthroscopic debridement is the performed, along with fragment pinning or excision. However, if no looses bodies are located and the patient is an adolescent with open growth plates, non-operative treatment is the preferred method.
Surgical treatment for MCL repair is dependent on two major factors. Does the patient wish to return to high levels of competition as prior to the injury, and are they willing to undergo up to 12 months of rehabilitation? Since the original MCL repair performed by Jobe in 1974, on pitcher Tommy John, thus dubbing this procedure as the famous Tommy John surgery, there have been various improvements in the surgical methods.
The original Jobe technique involved a longitudinal incision over the medial epicondyle, followed by complete detachment of the flexor pronator mass from the medial epicondyle. The ulnar nerve is identified, exposed and protected and transposed anteriorly. Two holes are drilled posteriorly, on the humeral epicondyle, penetrating the posterior humeral cortex. A tunnel is also drilled on the proximal ulna at the sublime tubercle. A tendon graft, either palmaris longus, gracilis, toe extensor or allograft, is then passed through the ulnar tunnel and humeral tunnel in a figure 8 fashion. The graft is then secured and tensioned by a suture.
The modified Jobe Technique involves splitting the flexor pronator mass rather than completely detaching it in association with ulnar nerve transposition.
The docking technique involves a single tunnel on the inferior humeral side with two small exit holes superiorly allowing for a Krakow suture over a bone bridge. This increases secure fixation in addition to an increase of ease of tensing the graft. The Jobe technique is still used for ulnar fixation.
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.