Medial Collateral Ligament of the Elbow : Wheeless' Textbook of Orthopaedics

- Anatomy:
    - humeral origin of MCL lies posterior to axis of elbow flexion, creating cam effect;
- hence, anterior fibers are stressed in extension & posterior fibers are stressed in flexion;
    - anterior oblique, posterior oblique ligament, & small transverse ligament are 3 major portions of the elbow MCL;
- anterior oblique ligament:
       - primary stabilizer of elbow for functional ROM from 20-120 deg;
     - significant portion of anterior band inserts near coronoid process and that significant MCL instability may
                           result from low coronoid process frx;
   - posterior oblique ligament:
- weak fan-shaped thickening of capsule, which is absent in primates;
    - it arises at the posterior aspect of the medial epicondyle and inserts over the olecranon;
    - it forms the floor of the cubital tunnel;
    - this functions as a secondary stabilizer only at 30 deg of flexion;
    - references:
           - Experimental elbow instability after transection of the medial collateral ligament.
           - Biomechanics of elbow instability: the role of the medial collateral ligament.
           - Valgus stability of the elbow. A definition of primary and secondary constraints.
           - Biomechanical study of ligaments around the elbow joint.
           - Valgus stability of the elbow.
           - The Medial Collateral Ligament of the Elbow Is Not Isometric: an in vitro biomechanical study.
           - Effect of the Posterior Bundle of the Medial Collateral Ligament on Elbow Stability

- Function:
    - primary medial stabilizer of the flexed elbow joint;
- in full extension MCL provides about 30 % of stability versus about 54% in 90 deg flexion (some estimate that ligament provides over 70%);
- in contrast the radial head is an important secondary stabilizer in extension as well as flexion (provides 30-33% of stability);
- 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 elbow, and may produce subluxation or dislocation;
- MCL laxity most often results from repetitive valgus loading such as throwing;
    - Role of MCL in Flexion Contracture of the Elbow: (see Flexion Contracture of the Elbow)
           - Release of the medial collateral ligament to improve flexion in post-traumatic elbow stiffness.
           - The medial approach for operative release of post-traumatic contracture of the elbow.

- Radiographs:
- w/ MCL tear, look for abnormally wide joint space on the medial side;

- MRI:
- w/ MCL tear, MRI (T2) images will show focal discontinuity of the ligament and joint fluid extravasation;
    - MRI arthrography is the imaging study of choice for evaluation of medial collateral ligament injuries.
    - references:
           - Noncontrast MR imaging and MR arthrography of the ulnar collateral ligament of the elbow: prospective evaluation of two-dimensional pulse sequences for detection of complete tears.
           - Anterior bundle of ulnar collateral ligament: evaluation of anatomic relationships by using MR imaging, MR arthrography, and gross anatomic and histologic analysis.
           - Medial epicondylitis and cubital tunnel syndrome in the throwing athlete
           - Nonoperative Treatment of Ulnar Collateral Ligament Injuries in Throwing Athletes

- Chronic MCL Laxity:
    - power point slide show
    - often occurs from chronic repetive throwing which stresses the elbow in mid-flexion;
- in about 30 deg of flexion, neither the radial head nor the anterior joint capsule provide significant resistance to valgus stress, which leaves
                     the MCL vulnerable to overload;
- posteromedial olecranon impingement occurs which results in inflammation, chondral injury, and eventual osteophytes and loose body formation;
- this condition is demonstrated by posteromedial elbow tenderness as a valgus force is applied against the fully extended elbow;
- osteochondrosis of medial epicondyle
- in children the medial epicondylar physis is weaker than the MCL complex and chronic injury to this apophysis results
                      growth disturbances and overgrowth;
- diff dx: medial epicondylitis
- in the report by Rettig AC et al (2001), the authors evaluated 31 throwing athletes with ulnar collateral ligament injuries (from 1994 to 1997);
- the authors sought to determine what percentage of athletes could return to their sport without surgical intervention;
- nonop treatment included a minimum of 3 months’ rest w/ rehab exercises, allowed 42% of the athletes (N = 13) to return to
                   their previous level of competition;
- those who returned to sports did so at an average of 24.5 weeks after diagnosis;
- surgical repair:
- w/ proximal tears, consider reattachment thru drill holes in medial epicondyle;
- w/ intra-substance tears consider augmentation w/ palmaris longus;
            - references:
                   -  Traumatic Valgus Instability of the Elbow: Pathoanatomy and Results of Direct Repair