ALPSA Lesions

The Labroligamentous Complex

• Labrum: Fibrocartilaginous bumper. Increases glenoid depth by 50%.
• IGHL: Inferior Glenohumeral Ligament. Main static restraint.
• Periosteum: Thick anterior scapular periosteum.

In ALPSA, the forceful anterior dislocation strips the periosteum without rupturing it.

This creates a "sleeve" that slides medially.

The Healing Trap

• Because the tissue remains vascularized (via periosteum) and in contact with bone, it heals.
• BUT: It heals on the glenoid neck, medial to the rim.
• Consequence: The glenoid concavity is lost ("Flat glenoid"). The "chock block" effect is gone.
• The active restraint (IGHL) is also effectively lengthened/lax.

This explains high recurrence rates in untreated ALPSA.

Biomechanical Consequences

• Glenoid Depth Reduction: Loss of labral height reduces effective glenoid concavity by up to 50%.
• Capsular Laxity: Medialized healing elongates the IGHL complex, reducing tension.
• Force Couples: Disrupted force distribution across the glenohumeral joint.
• Stability Ratio: The force required to cause dislocation is significantly reduced.

The Compression-Concavity Mechanism

The labrum normally creates a "chock block" that resists humeral head translation. When medialized, this effect is lost even though tissue is present. The joint becomes functionally equivalent to a glenoid with bone loss.

This is why repair WITHOUT mobilization fails - the bumper never returns.

Neviaser Classification

• Acute (Type I): Less than 3 months. Tissue is mobile. Can be reduced easily.
• Chronic (Type II): Greater than 3 months. Tissue is scarred and fixed. Requires sharp dissection/release.

This distinction is crucial for surgical planning.

Chronic lesions often require a capsular release (anterior and inferior) to gain excursion.

MRI Signs

• Medialization: The key sign.
• Synovial Stripping: Contrast tracking under the sleeve.
• Bone Loss: Assess for concomitant Bony Bankart (often remodelled in chronic cases).
• Hill-Sachs: Usually present due to recurrence.

Look for the "Cul-de-sac" deep to the capsule.

CT Arthrography

CT arthrography (CTA) is particularly useful for:

• Bone Loss Quantification: Precise measurement of glenoid bone loss.
• Chronic Cases: When MRI interpretation is difficult due to scarring.
• Preoperative Planning: 3D reconstructions for surgical approach.

CTA Findings in ALPSA

• Medialized Contrast: Contrast tracks medially with the labrum.
• Intact Periosteal Sleeve: Visible as soft tissue connection to scapula.
• Glenoid Morphology: Assess for erosive bone loss vs inverted pear glenoid.

CTA is superior to MRI for detecting subtle bone loss less than 10%.

Glenoid Bone Loss Assessment

Critical for surgical planning - significant bone loss may require Latarjet.

Measurement Methods

• Best-Fit Circle: Measure defect as percentage of inferior glenoid circle.
• Glenoid Index: Ratio of anterior to posterior glenoid width.
• En-Face View: 3D CT reconstruction for direct visualization.

Thresholds

• Less than 15%: Soft tissue repair adequate.
• 15-25%: Consider augmentation (remplissage, bone graft).
• Greater than 25%: Latarjet typically required.

These thresholds guide surgical decision-making for optimal outcomes.

Decision Making

• Non-Operative: High failure rate in young patients. (Not recommended for athletes).
• Operative: Indicated for recurrent instability.
• Approach: Arthroscopic Repair is Gold Standard. Open repair rarely needed unless massive bone loss.

The key is the technical execution of the repair.

Timing

• Early repair (Acute) is easier as tissue is not scarred.
• Chronic repair is equally successful IF adequately mobilized.

Do not delay if diagnosis is confirmed.

Arthroscopic Repair Steps

1. Diagnostic Scope: Confirm diagnosis (Probe the labrum - it may feel "healed" but lacks bumper function).
2. Mobilization (CRITICAL):
   • Use an elevator or shaver to detach the scarred labrum from the glenoid neck.
   • Release anteriorly and inferiorly (around the corner).
   • "Float the Labrum": It must rise to the rim effortlessly.
3. Preparation: Decorticate the glenoid rim (create bleeding bed).
4. Fixation: Suture anchors on the face (articular margin).
5. Shift: Tension the tissue superiorly and laterally to restore the bumper.

Failure to mobilize turns this into a non-anatomical plication.

Surgical Pearls

• The 5 O'clock Portal: Essential for inferior release.
• Viewing: Switch to Anterior Superior portal to view the "drive-through" sign reduction.
• Anchors: Use 3 or more anchors for robust fixation.

If the tissue is poor, incorporate capsule (Bankart Repair + Capsular Shift).