Latarjet Procedure: Bone Block, Sling, and Internal Splinting Effects

What is the triple effect of Latarjet procedure?

The Latarjet procedure achieves robust shoulder stability through a synergistic "triple effect" involving bone augmentation, a dynamic muscular sling, and static capsular tensioning, directly addressing the biomechanical deficiencies associated with recurrent anterior glenohumeral instability.

Introduction to the Latarjet Procedure

The Latarjet procedure, also known as the coracoid transfer or Bristow-Latarjet procedure, is a well-established surgical technique used primarily to treat recurrent anterior glenohumeral (shoulder) instability, especially in cases involving significant glenoid bone loss, engaging Hill-Sachs lesions, or failed arthroscopic soft tissue repairs. Unlike purely soft tissue repairs, the Latarjet procedure involves the transfer of a bone block – the coracoid process – along with its attached conjoint tendon (comprising the short head of the biceps brachii and coracobrachialis muscles) to the anterior-inferior aspect of the glenoid (shoulder socket). This bone block is secured with screws, effectively extending the glenoid articular surface and providing a multi-faceted approach to preventing future dislocations.

Understanding Shoulder Instability

Recurrent anterior shoulder instability often arises from trauma that damages the static and dynamic stabilizers of the glenohumeral joint. Common pathologies include Bankart lesions (detachment of the anterior-inferior labrum and capsule from the glenoid rim), glenoid bone loss (erosion or fracture of the glenoid bone), and Hill-Sachs lesions (a compression fracture on the posterior-superior humeral head). While soft tissue repairs (e.g., arthroscopic Bankart repair) are effective for isolated labral tears, they may be insufficient when there is substantial bone loss, which compromises the glenoid's ability to contain the humeral head. In such scenarios, the Latarjet procedure offers a superior biomechanical solution by directly addressing the bony defect and augmenting the joint's stability.

The "Triple Effect" of the Latarjet Procedure

The remarkable success and durability of the Latarjet procedure are attributed to its unique "triple effect," which combines static and dynamic stabilization mechanisms to prevent future dislocations. These three synergistic effects work in concert to restore the shoulder's integrity:

1. The Bone Block Effect (Glenoid Augmentation)

The most direct and foundational effect of the Latarjet procedure is the bone block effect. By transferring the coracoid process and securely fixing it to the anterior-inferior glenoid rim, the procedure effectively reconstructs and extends the bony articular surface of the glenoid. This increases the anterior-inferior glenoid bone stock, which is critical in cases of significant glenoid bone loss. The augmented glenoid acts as a mechanical barrier or "bumper," preventing the humeral head from dislocating anteriorly. This bony buttress directly counteracts the tendency for the humeral head to slip over the deficient glenoid rim, particularly when the arm is in vulnerable positions like abduction and external rotation. It effectively restores the glenoid's concavity and depth, enhancing the static stability of the joint.

2. The Sling Effect (Dynamic Muscular Stabilization)

The second crucial component is the sling effect, which provides dynamic stabilization to the shoulder joint. The coracoid process is transferred along with its attached conjoint tendon (the combined tendon of the short head of the biceps brachii and the coracobrachialis muscles). When the arm is abducted and externally rotated – the position most commonly associated with anterior shoulder dislocation – these muscles contract. As they contract, their pull across the anterior aspect of the joint creates a dynamic sling or hammock-like effect. This muscular tension compresses the humeral head into the glenoid, thereby reinforcing the anterior capsule and preventing anterior translation of the humeral head. This dynamic stabilization is particularly effective during movements that typically predispose the shoulder to instability, adding an active layer of protection beyond the static bone block.

3. The Internal Splinting Effect (Capsular and Ligamentous Repair/Reattachment)

The third effect, often referred to as the internal splinting effect, involves the reattachment and tensioning of the anterior joint capsule and the inferior glenohumeral ligament (IGHL) to the transferred coracoid and the remaining glenoid rim. During the procedure, the anterior capsule and labrum, which may be detached (Bankart lesion), are often repaired and reattached directly to the transferred coracoid or the adjacent glenoid. This effectively tightens the anterior capsule and reinforces the anterior ligamentous structures, particularly the IGHL, which is a primary static stabilizer against anterior and inferior translation. This re-tensioning and direct repair of the soft tissues to the newly positioned bone block provide an additional layer of static stability, effectively splinting the joint and preventing excessive anterior laxity. Some interpretations also include the effect of the subscapularis muscle being split or partially released, allowing the conjoint tendon to pass through, which might also contribute to a mild tenodesis or stabilizing effect on the subscapularis itself.

Clinical Implications and Efficacy

The triple effect explains why the Latarjet procedure demonstrates high success rates and low recurrence rates for anterior shoulder instability, particularly in high-risk patients such as contact athletes or those with significant glenoid bone loss. By addressing both the bony defect and providing dynamic and static soft tissue reinforcement, it offers a comprehensive and robust solution where less invasive soft tissue repairs might fail. While the procedure is more invasive than arthroscopic soft tissue repair, its long-term efficacy and ability to prevent re-dislocation make it the gold standard for specific indications.

Conclusion

The Latarjet procedure stands as a cornerstone in the surgical management of complex anterior shoulder instability. Its "triple effect" – the bone block effect providing a mechanical barrier, the sling effect offering dynamic muscular compression, and the internal splinting effect through capsular re-tensioning – synergistically restores the biomechanical integrity of the glenohumeral joint. Understanding these distinct yet interconnected mechanisms is crucial for appreciating the profound stability and successful outcomes achieved by this highly effective surgical intervention.