Arthroscopic Posterior Labral Repair (Posterior Shoulder Instability)

Surgical Indications

Absolute Indications

• Recurrent posterior subluxation or dislocation with documented posterior labral tear on MRI or MRA
• Failed non-operative management (minimum 3-6 months of structured physiotherapy focusing on scapular stabilisation and rotator cuff strengthening)
• Positive jerk test or Kim test reproducing the patient's symptoms with corresponding labral pathology on imaging

Relative Indications

• Contact or overhead athlete with functional instability limiting sport participation
• Posterior labral tear with greater than 50 percent detachment or associated posterior capsular redundancy
• Reverse Hill-Sachs lesion less than 20 percent articular surface with no engagement

Contraindications

Absolute:

• Posterior glenoid bone loss greater than 25 percent or glenoid retroversion greater than 20 degrees (requires bone block augmentation)
• Engaging reverse Hill-Sachs lesion greater than 25 percent of humeral head articular surface
• Active infection or uncontrolled medical comorbidity precluding surgery

Relative:

• Multidirectional instability with predominant posterior component (consider global capsular shift or arthroscopic pancapsular plication)
• Poor tissue quality (Ehlers-Danlos, prior failed thermal capsulorrhaphy)
• Patient unable or unwilling to comply with postoperative rehabilitation protocol

Evidence for Non-Operative Treatment

Physiotherapy and Activity Modification

• Structured physiotherapy focusing on scapular stabilisation, rotator cuff strengthening and proprioceptive training achieves symptom resolution in approximately 50-70 percent of patients with first-time or low-demand posterior instability
• Contact athletes and those with significant labral detachment have lower success rates with non-operative care and earlier surgical referral is appropriate
• A minimum of 3-6 months of compliant physiotherapy is required before declaring failure

Evidence for Surgery

Arthroscopic vs Open Repair

Arthroscopic reverse Bankart repair with capsular plication:

• Allows direct visualisation and anatomic restoration of the labral bumper
• Permits simultaneous treatment of associated pathology (SLAP tears, rotator cuff lesions, chondral injury)
• Lower morbidity, faster return to sport and better cosmesis than open approaches
• Modern series report 85-95 percent success rates with proper patient selection and technique

Open posterior approach:

• Reserved for cases requiring bone block augmentation or when arthroscopic access is limited by body habitus or prior surgery
• Higher morbidity, longer recovery and greater risk of stiffness

Key Evidence

Posterior Shoulder Anatomy Relevant to Instability

Glenoid Labrum and Capsule

The posterior labrum is a fibrocartilaginous structure attached to the glenoid rim that deepens the glenoid socket by approximately 50 percent and serves as the attachment for the posterior capsule and inferior glenohumeral ligament (IGHL). Detachment of the posterior labrum (reverse Bankart lesion) allows posterior translation of the humeral head and is the primary pathology in traumatic posterior instability.

The posterior capsule is thinner than the anterior capsule and blends with the infraspinatus tendon. Redundancy of the posterior capsule is a common associated finding and must be addressed with plication at the time of labral repair.

Glenoid Version and Bone Loss

Normal glenoid version is 0 to 7 degrees of retroversion. Retroversion greater than 15 degrees or posterior glenoid bone loss greater than 20 percent of the glenoid width significantly increases the risk of failure after soft-tissue repair alone. Bone loss is quantified on 3D CT using the circle method or Pico method on the en-face glenoid view.

Reverse Hill-Sachs Lesion

An anterior humeral head impaction fracture (reverse Hill-Sachs) occurs when the humeral head impacts the posterior glenoid rim during a posterior dislocation. Lesions involving greater than 20 percent of the articular surface or those that engage the glenoid rim in internal rotation require additional procedures (remplissage, bone grafting) at the time of labral repair.

Portal Anatomy and Neurovascular Structures

• Standard posterior portal: 2 cm inferior and 1 cm medial to the posterolateral acromion corner; enters the joint through the infraspinatus or between infraspinatus and teres minor.
• Accessory posterior (7 o'clock) portal: 1 cm lateral and 1 cm inferior to the standard posterior portal; used for inferior anchor placement. The axillary nerve lies 1.5-2.5 cm inferior to the inferior glenoid rim; portals must stay superior to this level.
• Anterior superior portal: established under direct vision in the rotator interval; used for viewing and suture management.
• Anterior inferior portal: optional for anterior working access if needed.

The suprascapular nerve is at risk with medial dissection or aggressive superior labral work but is rarely an issue in isolated posterior repair.

Positioning and Preparation

Patient position: Lateral decubitus with the operative arm in 10-15 pounds of balanced suspension traction. The arm is positioned in 20-30 degrees of abduction and 20 degrees of forward flexion. This position opens the posterior and inferior joint spaces and allows excellent access to the posteroinferior labrum. Beach-chair position is an acceptable alternative but requires careful portal placement and may limit inferior access.

Anaesthesia: General anaesthesia with interscalene block for postoperative analgesia. Hypotensive anaesthesia (systolic blood pressure 90-100 mmHg) minimises bleeding and improves visualisation.

Consent: Counsel regarding recurrence risk (8-15 percent overall, higher in contact athletes), stiffness (5-10 percent), chondral injury, nerve injury (axillary nerve less than 1 percent with proper portal placement), and the possibility of conversion to open procedure or bone block if bone loss is underestimated.

Arthroscopic Posterior Labral Repair - Step-by-Step

Step 1: Portal Establishment and Diagnostic Arthroscopy

Establish the standard posterior portal and perform a complete diagnostic arthroscopy. Assess the posterior labrum from 6 o'clock to 11 o'clock (right shoulder), the posterior capsule for redundancy, the presence and size of a reverse Hill-Sachs lesion, glenoid version, and any associated pathology (SLAP tear, rotator cuff tear, chondral injury).

Establish the anterior superior portal in the rotator interval under direct vision using an 18-gauge needle for localisation. This portal is used for viewing during posterior work and for suture management.

Step 2: Accessory Posterior Portal Placement

Localise the 7 o'clock (right shoulder) accessory posterior portal with an 18-gauge needle placed 1 cm lateral and 1 cm inferior to the standard posterior portal. The trajectory should allow perpendicular access to the posteroinferior glenoid rim. Confirm the needle enters the joint at the desired location before making the portal incision.

The axillary nerve lies 1.5-2.5 cm inferior to the inferior glenoid rim. Stay at least 1.5 cm superior to the inferior glenoid rim when placing this portal.

Step 3: Labral Preparation and Anchor Placement

Debride the posterior labrum to a stable edge using a shaver or radiofrequency device. Elevate the labrum from the glenoid rim using an elevator, creating a bleeding bony bed for healing. The labrum must be mobilised sufficiently to allow it to be reduced to the glenoid rim without tension.

Place suture anchors at the 7, 8 and 9 o'clock positions (right shoulder) or 3, 4 and 5 o'clock positions (left shoulder). Use 2.4-3.0 mm bioabsorbable or all-suture anchors loaded with high-strength suture. The most inferior anchor is placed first.

Drill or punch the anchor hole at a 45-degree angle to the glenoid surface, 2-3 mm onto the articular face of the glenoid rim. This ensures the labrum is repaired in an anatomic position that recreates the bumper effect.

Step 4: Labral Repair and Knot Tying

Pass one limb of the anchor suture through the posterior capsule and labrum using a suture passer or shuttle relay. The suture should capture a 1 cm bite of capsule and the labrum at the level of the anchor. Tie arthroscopic knots (surgeon's knot or sliding knot with three reversing half-hitches) to secure the labrum to the glenoid rim.

Repeat for each anchor, progressing superiorly. After each knot, assess the labral bumper height and the degree of capsular plication achieved.

Step 5: Posterior Capsular Plication

After labral repair, assess the posterior capsule for redundancy. Perform capsular plication using the same anchors or additional mattress sutures placed between anchors. Plicate the capsule in 5-7 mm increments, aiming for a total posterior shift of 1-1.5 cm.

Limit plication to avoid over-constraint. Intraoperative assessment of external rotation in adduction should remain at least 30-40 degrees after plication.

Step 6: Final Assessment and Closure

Perform a final dynamic assessment of stability with the arthroscope in the joint. Apply posterior force to the humerus and confirm the humeral head remains centred on the glenoid. Check external rotation and elevation to ensure no over-constraint.

Close portals with absorbable sutures. Apply a sterile dressing and place the arm in a sling with abduction pillow.

Post-operative Protocol

Phase 1: Protection (Weeks 0-6)

• Sling with abduction pillow for 6 weeks
• Pendulum exercises and elbow/wrist/hand ROM from day 1
• Passive and active-assisted forward elevation to 90 degrees only
• No active internal rotation or cross-body adduction for 6 weeks
• Isometric rotator cuff exercises (external rotation only) from week 4

Phase 2: Motion (Weeks 6-12)

• Wean sling at 6 weeks
• Progressive active ROM in all planes; goal full ROM by 12 weeks
• Begin gentle posterior capsular stretching
• Scapular stabilisation exercises
• No resistance strengthening until full pain-free ROM achieved

Phase 3: Strengthening (Weeks 12-18)

• Progressive rotator cuff and scapular strengthening
• Closed-chain exercises and proprioceptive training
• Sport-specific drills from week 16
• Return to non-contact sport at 4-5 months if strength is 80 percent of contralateral side

Phase 4: Return to Sport (Months 5-9)

• Contact sport clearance at 6-9 months
• Requires full pain-free ROM, symmetric strength, and negative apprehension testing
• Functional brace may be considered for contact athletes in first season post-return

Special Case: Posterior Glenoid Bone Loss Greater Than 20 Percent

When preoperative 3D CT demonstrates posterior glenoid bone loss greater than 20 percent or retroversion greater than 15 degrees, arthroscopic soft-tissue repair alone has recurrence rates exceeding 40 percent. In these cases, posterior bone block augmentation (using iliac crest autograft or allograft) is indicated in addition to or instead of labral repair.

The bone block is fixed to the posterior glenoid rim with two cannulated screws or a buttress plate, restoring glenoid width and version. This can be performed arthroscopically or through an open posterior approach depending on surgeon experience and patient factors.

Special Case: Engaging Reverse Hill-Sachs Lesion

A reverse Hill-Sachs lesion involving greater than 20 percent of the humeral head articular surface or one that engages the posterior glenoid rim in internal rotation requires additional treatment at the time of labral repair.

Options include:

• Remplissage (tenodesis of infraspinatus tendon into the defect)
• Humeral head bone grafting or allograft reconstruction
• Rotational osteotomy (rarely indicated)

The choice depends on lesion size, location, and patient age/activity level.