Ulnar collateral ligament injury of the elbow
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| Ulnar collateral ligament injury of the elbow | |
|---|---|
 | |
| Location of UCL injury | |
| Specialty | Orthopedics |
Ulnar collateral ligament injuries can occur during certain activities such as overhead baseball pitching. Acute or chronic disruption of the ulnar collateral ligament result in medial elbow pain, valgus instability, and impaired throwing performance. There are both non-surgical and surgical treatment options.[1]
Pain along the inside of the elbow is the main symptom of this condition. Throwing athletes report it occurs most often during the acceleration phase of throwing. The injury is often associated with an experience of a sharp "pop" in the elbow, followed by pain during a single throw.[2] In addition, swelling and bruising of the elbow, loss of elbow range of motion, and a sudden decrease in throwing velocity are all common symptoms of a UCL injury. If the injury is less severe, pain can alleviate with complete rest.[3]
Causes
The UCL stabilizes the elbow from being abducted during a throwing motion. If intense or repeated bouts of valgus stress occur on the UCL, injury may occur. Damage to the UCL is common among baseball pitchers and javelin throwers because the throwing motion is similar. Physicians believe repetitive movements, especially pitching in baseball, cause UCL injuries. Furthermore, physicians have stated that if an adolescent throws over 85 throws for 8 months or more in a year, or throws when exhausted, the adolescent has a significantly higher risk of UCL injury.[4]
Gridiron football, racquet sports, ice hockey and water polo players have also been treated for damage to the UCL.[5][6] Specific overhead movements like those that occur during baseball pitching, tennis serving or volleyball spiking increase the risk of UCL injury.[7] During the cocking phase of pitching, the shoulder is horizontally abducted, externally rotated and the elbow is flexed. There is slight stress on the UCL in this position but it increases when the shoulder is further externally rotated in a throw. The greater the stress the more the UCL is stretched causing strain. During the overhead throwing motion, valgus stress on the medial elbow occurs during arm cocking and acceleration. The initiation of valgus stress occurs at the conclusion of the arm-cocking phase. In the transitional moment from arm cocking to arm acceleration, the shoulder vigorously rotates internally, the forearm is in near full supination, and the elbow flexes from 90° to approximately 125°. From late cocking to ball release, the elbow rapidly extends from approximately 125° to 25° at ball release.[8] This causes extreme valgus stress and tensile strain on the UCL.
Injuries to the UCL may result from poor throwing mechanics, overuse, high throwing velocities, and throwing certain types of pitches, such as curveballs.[citation needed] Poor mechanics along with high repetition of these overhead movements can cause irritation, microtears or ruptures of the UCL. Kinetic chain dysfunction due to poor lower extremity strength, core strength and stability can be associated with UCL injuries, as well as capsular stiffness in glenohumeral internal rotation deficit (GIRD), and scapular dyskinesis.[9][10] Injuries to the UCL in baseball players are rarely due to one-time, traumatic events. Rather, they more often occur due to small chronic strains and tears accumulating over time.[citation needed]
Anatomy
The ulnar collateral ligament (UCL, also known as medial collateral ligament) is located on the medial side of the elbow. The UCL complex comprises three ligaments: the anterior oblique, posterior oblique and transverse ligaments.[11] The anterior oblique ligament (AOL) attaches from the undersurface of the medial epicondyle to the medial ulnar surface slightly below the coronoid process.[12] It is the sturdiest of the three sections within the UCL. The AOL acts as the primary restraint against valgus stress at the elbow during flexion and extension. The posterior oblique originates at the medial epicondyle and inserts along the mid-portion of the medial semilunar notch.[11] It applies more stability against valgus stress when the elbow is flexed rather than extended. The transverse ligament connects to the inferior medial coronoid process of the ulna to the medial tip of the olecranon.[11] Since it is connected to the same bone and not across the elbow joint, the transverse ligament has no contribution to the joint's stability.
Diagnosis
In most cases, a physician will diagnose an ulnar collateral ligament injury using a patient's medical history and a physical examination that includes a valgus stress test. The valgus stress test is performed on both arms and a positive test is indicated by pain on the affected arm that is not present on the uninvolved side.[13][14] Physicians often use imaging techniques such as ultrasound, x-rays and magnetic resonance imaging or arthroscopic surgery to aid with making a proper diagnosis.[citation needed]
Classification
A slow and chronic deterioration of the ulnar collateral ligament can be due to repetitive stress acting on the ulna. At first, pain can be bearable and can worsen to an extent where it can terminate an athlete's career. The repetitive stress placed on the ulna causes microtears in the ligament resulting in the loss of structural integrity over time.[15] The ulnar collateral ligament has three bands: anterior, posterior, and transverse. The anterior band is the primary stabilizer against valgus stress, particularly during the late cocking and early acceleration phases of throwing.[16]
The acute rupture is less common compared to the slow deterioration injury. The acute rupture occurs in collisions when the elbow is in flexion such as that in a wrestling match or a tackle in football. The ulnar collateral ligament distributes over fifty percent of the medial support of the elbow.[17][18] This can result in an UCL injury or a dislocated elbow causing severe damage to the elbow and the radioulnar joints.
