Elbow collateral ligament insufficiency is commonly seen in sports participants involved in overarm-throwing sports such as cricket, baseball, and tennis. Trauma and postdislocation injuries are other common causes of collateral ligament injury, which can occur on either side of the joint. An understanding of the normal anatomy is required for diagnosis and successful surgical reconstruction. [1, 2, 3, 4, 5, 6, 7, 8, 9]
The elbow is one of the most congruous joints in the body. It consists of three articulations between the humerus, ulna, and radius within a capsule. The medial elbow collateral ligament resists valgus force and supports the ulnohumeral joint. The lateral ligament prevents rotational instability between the distal humerus and the proximal radius and ulna.
History of the Procedure
Jobe et al first described double-strand reconstruction of the ulnar collateral ligament (UCL) with use of a free tendon graft that was secured to the medial epicondyle and the proximal aspect of the ulna in a figure-eight fashion. 
Several complications are associated with this procedure, such as detachment of the flexor-pronator muscle group, extensive drilling of the medial epicondyle, and transposition of the ulnar nerve. Studies have focused on techniques of UCL reconstruction that minimize the potential for complications, particularly those related to the medial epicondyle and the ulnar nerve. [4, 5, 7, 8, 10, 11, 12, 13, 14, 15, 16]
Medial elbow instability and posterolateral rotatory instability in overhead-throwing athletes are increasingly popular topics. The diagnosis and treatment have been the focus of much basic-science and clinical research. Methods for accurately diagnosing elbow instability continue to evolve. Patient history, physical examination, and magnetic resonance imaging (MRI), as well as arthroscopic techniques for diagnosis and treatment, continue to play a vital role in differentiating between nonoperative and operative candidates. [6, 17, 18, 19, 20, 21, 22, 23]
In a study of 72 professional baseball players who underwent arthroscopic or open elbow surgery, the most common causes of elbow symptoms were posteromedial olecranon osteophyte (65%), UCL injury (25%), and ulnar neuritis (15%). In the United States, the estimated incidence of all baseball-related overuse injuries is 2-8% per year (20-50% of these injuries occur in adolescents and school-age children).
The true worldwide incidence of sports-related injuries is not known, because a large number of athletes never seek medical care and because the statistical data are not available from various countries. 
The two most common causes of elbow instability are sports (commonly chronic) and trauma (acute onset, as with ligamentous injuries in elbow dislocation).
During the throwing motion, high loads of valgus stress on the elbow joint results in tension on the medial structures (ie, medial epicondyle, medial epicondylar apophysis, and medial collateral ligament [MCL] complex) and compression of the lateral structures (ie, radial head and capitellum). Repeated MCL stress due to medial tension overload may result in MCL strain or rupture. This chronic injury may lead to development of ulnar traction spurs, deposition of calcium, and medial ligament instability.
Injuries associated with specific sports include the following:
Golf - Medial epicondylitis of the trailing arm and lateral epicondylitis of the leading arm
Racquet sports - Lateral epicondylitis with backhand
Bowling - Medial epicondylitis
Baseball and volleyball - Valgus stress of medial structures and compression of lateral structures
Weight training - UCL strain and ulnar neuritis
Canoeing and kayaking - Distal bicipital tendinitis
Archery - Lateral epicondylitis of the bow arm
Rock climbing - Distal bicipital and brachialis tendinitis
Football - Valgus stress with throwing a pass
UCL injuries can manifest as acute ligament tears following a single valgus stress or as overuse sprains following repetitive valgus overloads. Repetitive medial stress can also cause attenuation and microstretching of the UCL complex, causing instability over time.
Maximal MCL stress occurs when the elbow remains flexed between 60 º and 75 º and the wrist begins to cock in preparation for the throw in the late cocking phase of throwing, as well as in the acceleration phase, when maximal humeral external rotation occurs.
The common pathway of posterolateral instability includes the following:
Extension overload - Medial ulnar collateral ligament insufficiency alters contact area and pressure between the posteromedial trochlea and olecranon and helps explain the development of posteromedial osteophytes
Triceps muscle strain
Avulsion fracture tip of olecranon
Loose bodies in the olecranon fossa
Tears of brachialis and anterior capsule
Fixed flexion contracture
Recurrent microtrauma of the skeletally immature elbow joint in children can lead to little leaguer's elbow, a syndrome that encompasses the following:
Delayed or accelerated growth of the medial epicondyle (medial epicondylar apophysitis)
Traction apophysitis (medial epicondylar fragmentation)
With posterior dislocation of the elbow joint, dislocation begins on the lateral side of the elbow and progresses to the medial side in three stages, as follows:
Stage 1 - Partial or complete disruption of the lateral collateral ligament (LCL; mainly its ulnar part); this results in posterolateral rotatory subluxation, which can reduce spontaneously
Stage 2 - Incomplete posterolateral dislocation, in which the concave medial edge of the ulna rests on the trochlea
Stage 3a - Disruption of all of the soft tissues around, and including, the posterior part of the MCL, leaving the important anterior band, which provides stability if the forearm is kept in pronation, to prevent posterolateral rotatory subluxation
Stage 3b - Disruption of the entire MCL, which makes the elbow unstable after reduction
Stage 3c - Stripping of soft tissue from the entire distal aspect of the humerus, which makes the elbow unstable, even in 90 º flexion
Patients with posterolateral rotatory instability often remember a distinct traumatic event, most often a posterior dislocation. The athlete has a sense of instability and reports a snapping sensation, which causes pain when throwing.
Patients with olecranon impingement syndrome often complain of posterior elbow pain with locking or snapping when throwing. The pain is worst when the elbow is extended. Throwers often complain of loss of velocity and control.
Patients with an anterior capsule strain present with anterior elbow pain, which often is aggravated by repetitive hyperextension and is not affected by elbow flexion.
Patients with an MCL sprain experience referred pain down the arm into the little finger and ring finger, which mimics the symptoms of cubital tunnel syndrome (a more common reason for this condition is ligament laxity in the sixth and seventh cervical vertebrae or in the UCL, not a pinched nerve).
MCL insufficiency manifests as medial elbow pain with laxity to valgus stress.
Medial epicondylar apophysitis is caused by repetitive valgus stress and generally manifests as progressive medial pain, decreased throwing effectiveness, and decreased throwing distance.
Medial epicondyle fracture manifests as point tenderness and swelling over the medial epicondyle, often with an elbow flexion contracture greater than 15°.
Neurologic injuries such as C8-T1 radiculopathy and ulnar neuritis, though uncommon in children, can manifest as medial elbow pain and should be included in the differential diagnosis.
Surgical reconstruction is indicated in the following patients:
Overhead-throwing athletes with acute complete MCL ruptures or chronic instability for more than 6 months, with medial elbow pain that prevents throwing and is refractory to conservative treatment
Patients in whom preoperative standard noncontrast magnetic resonance imaging (MRI) demonstrates medial UCL injury
Patients with clinically apparent medial UCL insufficiency
Unstable reduction after traumatic fracture dislocation of the elbow joint
Anatomic constraints on elbow instability
There are three primary static constraints on elbow instability, as follows:
MCL - This ligament comprises three bundles: the anterior bundle, which is tight in extension and loose in flexion-restraint to valgus rotation  ; the posterior bundle, which is tight in flexion and loose in extension; and the transverse bundle, which has a variable presence
LCL, especially its ulnar part - The LCL complex (which is characterized by a large amount of variation) includes the radial collateral ligament (RCL), the lateral ulnar collateral ligament (LUCL), the accessory lateral collateral ligament (ALCL), and the annular ligament (AL)
There are four secondary restraints on elbow instability, as follows:
Radial head and capsule - The anterior capsule prevents hyperextension of the elbow
Common flexor and extensor origins
Flexor-pronator and extensor-supinator groups (stabilizing against valgus and varus stress, respectively)
Dynamic stabilizers - These are the muscles that cross the joint and provide compressive forces at the articulation (anconeus-triceps, brachialis)
Both the MCL and the LCL are strong fan-shaped thickenings of the fibrous joint capsule. These ligaments prevent excessive abduction and adduction of the elbow joint. The AL wraps around the radial head and holds it tight against the ulna.
Medial collateral ligament
The humeral origin of the MCL lies posterior to the axis of elbow flexion, creating a cam effect; hence, anterior fibers are stressed in extension, and posterior fibers are stressed in flexion. The MCL has the following three major portions (see the image below):
Anterior oblique ligament
Posterior oblique ligament
Transverse ligamentSchematic diagram of medial collateral ligament of elbow shows 3 bundles. Anterior bundle is major stabilizer of elbow to valgus stress.
The anterior oblique ligament is the primary stabilizer of the elbow for functional range of motion (ROM) from 20 º to 120º. It arises from the anteroinferior surface of the medial epicondyle and inserts at the sublimis tubercle, adjacent to the joint surface. Given that a significant portion of the anterior band inserts near the coronoid process, MCL instability may result from low coronoid process fracture.
The anterior oblique bundle has two subportions, anterior and posterior. The anterior band is the primary restraint to valgus rotation at 30 º, 60 º, and 90º of flexion and is a coprimary restraint at 120º; it is more likely to be injured with the elbow in extension. The posterior band is the coprimary restraint at 120º; it is more likely to be injured in flexion (though injury to this band usually occurs along with injury to the anterior band).
The posterior oblique ligament is a weak, fan-shaped thickening of the joint capsule, which arises at the posterior aspect of the medial epicondyle and inserts over the olecranon; it forms the floor of the cubital tunnel and functions as a secondary stabilizer only at 30º of flexion.
The transverse ligament is a constant anatomic structure that is intra-articularly visible within the lower part of the medial joint capsule; it strengthens the articular joint capsule and contributes to elbow stability.
The MCL is the primary medial stabilizer of the flexed elbow joint. In full extension, it provides about 30% of stability, versus about 54-70% in 90º flexion. The radial head is an important secondary stabilizer in extension, as well as in flexion. After excision of the radial head alone, there is a 30-33% loss in valgus stability of the elbow, which does not significantly improve even after replacement with a silicone rubber radial head.
Resection of the anterior band of the MCL will result in gross instability, except in full elbow extension. Resection of both the MCL and the radial head results in gross instability of the elbow and may produce subluxation or dislocation of the elbow. The anterior bundle of the MCL is tested with the elbow in 90º of flexion.
Lateral collateral ligament and annular ligament
Anatomically, the LCL consists of a ligamentous expansion proceeding down from the lateral epicondyle to the ulna (a major expansion, which inserts into supinator crest of the ulna) and also sends expansions down to the AL and the radius.
The LCL has a greater role with increased flexion of the elbow. LUCL deficiency leads to posterolateral rotatory instability. Additional deficiency of the RCL results in dislocation of the elbow.
The ECU (extensor carpi ulnaris) tendon and the supinator tendon merge with the LCL and resist posterolateral instability.
Relative contraindications for surgical treatment include the following:
Medical contraindication to surgery
An elbow joint that is stable after closed reduction through a functional (30-130°) range of motion, with minimally displaced fractures following fracture dislocations of the elbow
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