Why doesn't suturing the Coracoacromial (CAL) ligament to the capsule contribute to the stability achieved by the open Latarjet procedure?

Why Suturing the Coracoacromial Ligament to the Capsule Does Not Significantly Help in Open Latarjet

Suturing the coracoacromial ligament (CAL) to the capsule in the open Latarjet procedure contributes minimally to overall shoulder stability because the primary stabilizing mechanisms are the sling effect of the conjoint tendon and subscapularis complex (76-77%) and the bone block effect (23-24%).

Biomechanical Basis of the Latarjet Procedure

The Latarjet procedure is a well-established technique for treating recurrent anterior glenohumeral instability, particularly in cases with significant glenoid bone loss. Understanding why the CAL-to-capsule suturing is not the primary stabilizing factor requires examining the key biomechanical components:

Primary Stabilizing Mechanisms

1. Sling Effect (51-77% of stability)

   • Created by the conjoint tendon and subscapularis muscle complex
   • Acts as a dynamic restraint during shoulder abduction and external rotation
   • Biomechanical studies show this provides 76-77% of stability at end-range positions 1
   • Detachment of the subscapularis tendon eliminates the stabilizing effect of the entire procedure 2

2. Bone Block Effect (23-49% of stability)

   • The coracoid bone graft restores the glenoid articular surface
   • Provides a mechanical barrier to anterior translation
   • Contributes 23-24% of stability at end-range and up to 49% at mid-range positions 1

The Limited Role of CAL-to-Capsule Suturing

Biomechanical research demonstrates that while the CAL-to-capsule repair does contribute to stability, its effect is relatively minor compared to the sling effect and bone block:

• Dissection of the CAL leads to increased anterior translation (+5.0 mm) and inferior translation (+7.3 mm) in neutral rotation 2
• However, this effect is overshadowed by the loss of stability when the subscapularis is compromised 2

Surgical Technique Considerations

During the open Latarjet procedure:

1. The CAL is typically transected 15 mm lateral to the coracoid to allow later repair to the anterior capsule 3
2. The coracoid is positioned flush or 1 mm recessed relative to the glenoid 3
3. The subscapularis is split at the junction of the upper two-thirds and lower one-third 3
4. The CAL is repaired to the capsule as one of the final steps 3

While this repair is performed routinely, its contribution to overall stability is secondary to the other mechanisms.

Clinical Implications

Understanding the relative contributions of each component has important clinical implications:

• Surgical Focus: Surgeons should prioritize proper positioning of the coracoid graft and preservation of subscapularis integrity
• Rehabilitation Concerns: Early rehabilitation protocols should protect the subscapularis repair, as this is crucial for maintaining the sling effect
• Failure Analysis: When evaluating failed Latarjet procedures, attention should be directed primarily to bone graft position and subscapularis integrity rather than CAL repair

Common Pitfalls to Avoid

1. Overemphasis on CAL repair: Focusing too much on the CAL-to-capsule repair while neglecting proper coracoid positioning or subscapularis repair
2. Subscapularis compromise: Inadequate repair of the subscapularis split can eliminate the stabilizing effect of the entire procedure 2
3. Improper coracoid positioning: The coracoid should be transferred as a bone block rather than just the tip for optimal stability 2

In conclusion, while the CAL-to-capsule repair is part of the standard Latarjet technique, its contribution to overall shoulder stability is relatively minor compared to the sling effect created by the conjoint tendon-subscapularis complex and the bone block effect of the coracoid graft.