Review Question - QID 219504

This patient presents with a chronic lateral ulnar collateral ligament (LUCL) injury, which results in posterolateral rotatory instability. The LUCL originates on the lateral humeral epicondyle and inserts on the supinator crest (Answer 3).

The LUCL is a primary static stabilizer of the elbow joint and acts as a restraint to varus and external rotation stresses. The diagnosis of a LUCL injury can be made with a thorough history, physical examination, and imaging modalities. Patients with this diagnosis often notice exacerbation of elbow symptoms when rising from a chair, which places a varus force through the elbow joint. Also, physical examination maneuvers such as the lateral pivot shift test (Figure A) can be utilized to identify LUCL incompetence. LUCL reconstruction techniques must recreate the native anatomy to provide adequate restraint and restore stability. This is typically accomplished by establishing the isometric point about the LUCL's origin on the lateral epicondyle of the humerus and identifying the supinator crest, which allows for distal graft passage just inferior to the tubercule of insertion (Illustration A).

Camp et al. comprehensively characterized the lateral ulnar collateral (LUCL) complex using 3-D reconstructed CT in 10 cadaveric elbows. Their findings revealed that the footprint of the LUCL origin about the lateral epicondyle of the humerus averaged 26.0 mm2, while the insertional footprint at the supinator crest averaged 22.9 mm2. Importantly, the study concluded that these precise measurements and anatomical insights aid surgeons in performing accurate anatomic ligament reconstruction procedures for patients with posterolateral rotatory instability of the elbow.

Moritomo et al. aimed to elucidate the role of the LUCL and radial collateral ligament in elbow flexion and identify the isometric point for LUCL reconstruction. Using markerless bone-registration techniques and MRI, the three-dimensional kinematics of these ligaments were analyzed in seven healthy volunteers. Results indicated that the three-dimensional distance of the LUCL increased during elbow flexion secondary to the osseous protrusion of the lateral epicondyle during flexion. Ultimately, analysis of their kinematic data of the LUCL allowed for the conclusion that the most isometric point for reconstruction is approximately 2 mm proximal to the center of the capitellum.

Figure A: This depicts the lateral pivot shift test. The left side of the image demonstrates how valgus stress with axial load administered with the elbow extended in full supination leads to subluxation. The right side of the image demonstrates how elbow flexion leads to reduction secondary to increased triceps tension.

Illustration A: This is an intra-operative image demonstrating the identification of the supinator crest with corresponding drill holes for distal graft passage.

Incorrect Answers:
1: The bicipital tuberosity is on the proximal radius and is the insertion site for the biceps tendon, not the LUCL.
2: The coronoid tip is an insertion site for the elbow capsule, not the LUCL.
4: The lateral epicondyle of the humerus is the origin of the LUCL, not the insertion.
5: The sublime tubercule is the insertion site for the medial ulnar collateral ligament, not the LUCL.