Introduction to Multidirectional Instability and Capsular Shift

Multidirectional instability (MDI) of the glenohumeral joint presents a complex biomechanical challenge characterized by symptomatic global capsular laxity. Unlike unidirectional traumatic instability (e.g., classic Bankart lesions), MDI is typically atraumatic, bilateral, and involves an inherently redundant capsulolabral complex. When conservative management—focused on periscapular and rotator cuff strengthening—fails, surgical intervention is warranted.

The arthroscopic capsular shift has superseded open capsular shift procedures as the gold standard for MDI. By allowing circumferential access to the glenohumeral joint, the arthroscopic approach facilitates precise, titratable plication of the redundant capsule while minimizing surgical morbidity, preserving the subscapularis, and optimizing proprioceptive recovery. The primary objective is to reduce capsular volume and restore the normal tension of the glenohumeral ligaments without causing iatrogenic overconstraint, which could lead to secondary osteoarthritis or severe loss of motion.

Preoperative Evaluation and Examination Under Anesthesia (EUA)

A meticulous Examination Under Anesthesia (EUA) is the critical first step in any capsular shift procedure. The EUA dictates the exact degree and vector of plication required.

Conducting the EUA

1. Bilateral Comparison: Always examine the contralateral (asymptomatic) shoulder if accessible, establishing the patient's baseline physiologic laxity.
2. Load and Shift Test: Assess anterior and posterior translation. Grade the translation from 1 to 3 (Grade 1: to the rim; Grade 2: over the rim but spontaneously reduces; Grade 3: locks out).
3. Sulcus Sign: Apply inferior traction to the adducted arm. A sulcus sign greater than 2 cm indicates significant incompetence of the rotator interval (superior glenohumeral ligament and coracohumeral ligament) and the inferior capsular pouch.
4. Gage the Shift: The degree of hyperlaxity determined during the EUA directly informs the size of the capsular bites (typically 1 cm) and the extent of the rotator interval closure required.

Clinical Pearl: The EUA is paramount. In MDI, the capsule is globally redundant, but the symptomatic direction of instability is often asymmetric. The surgical plication must be biased toward the side of the shoulder demonstrating the most profound clinical instability.

Patient Positioning and Operating Room Setup

Proper positioning is essential for optimal visualization and access to the inferior capsular recess, which is notoriously difficult to navigate.

Lateral Decubitus Positioning

While the beach chair position is utilized by some surgeons, the lateral decubitus position is highly advantageous for a global capsular shift as it provides superior access to the inferior and posterior capsule.

• Immobilization: Place the anesthetized patient in the lateral decubitus position. Maintain strict spinal alignment using a vacuum beanbag and a kidney rest.
• Protection: Carefully pad all bony prominences (e.g., fibular head, greater trochanter) to prevent neurapraxia. Apply a heating blanket to maintain normothermia and serial compression devices (SCDs) to the lower extremities for deep vein thrombosis (DVT) prophylaxis.
• Arm Suspension: Place the operative arm in a dedicated traction sleeve. Suspend the arm in 45 degrees of abduction and 20 degrees of forward flexion.
• Traction: Apply exactly 10 lb of balanced traction. Excessive traction can cause brachial plexus neurapraxia, while insufficient traction limits joint space visualization.

Surgical Warning: During the procedure, it is highly beneficial to have a trained surgical assistant manipulate the shoulder. The assistant can apply gentle anterior or posterior translation to open the joint space dynamically, providing the most advantageous view of the capsular recesses when slight manual traction is necessary.

Portal Placement and Diagnostic Arthroscopy

Precise portal placement is the foundation of a successful arthroscopic capsular shift. Poorly placed portals will result in an unfavorable angle of approach, making capsular plication exponentially more difficult.

Establishing the Portals

Outline all bony landmarks (acromion, clavicle, coracoid process) and potential portal sites on the skin prior to insufflation.

1. Posterior Viewing Portal:
2. Created approximately 3 cm distal and slightly medial to the posterolateral edge of the acromion.
3. This portal serves as the primary viewing portal for anterior and inferior work.
4. Anterosuperior Lateral Portal:
5. Placed high in the rotator interval, just anterior to the supraspinatus tendon.
6. Used primarily for visualization when working in the posterior compartment.
7. Anterior Central (Mid-Anterior) Portal:
8. Established approximately 1 cm lateral to the coracoid process, entering the joint just superior to the subscapularis tendon.
9. Serves as the primary working portal for anterior and inferior plication.

Once the portals are established, perform a comprehensive diagnostic arthroscopy. Evaluate the labrum, articular cartilage, and rotator cuff. In true MDI, the labrum is typically intact but hypoplastic, and the capsular recesses are voluminously enlarged. Place working 8.25-mm threaded cannulas in the posterior and anterior central portals to facilitate the smooth passage of suture shuttles and knot pushers later in the procedure.

Tissue Preparation: Optimizing the Biologic Milieu

A capsular shift relies on the biological healing of the plicated capsule to the labrum and glenoid rim. Without adequate tissue preparation, the plication will fail, leading to recurrent instability.

Capsulolabral Abrasion

• Introduce a small arthroscopic rasp or a motorized shaver (without suction to avoid damaging the intact labrum) through the working cannula.
• Systematically abrade the capsule and the labrum around the entire area targeted for plication.
• This preparation generally extends along the length of the glenohumeral ligament attachments, starting posteriorly at the 9-o’clock position (in a right shoulder), extending inferiorly through the 6-o'clock position, and continuing anteriorly through the 3-o’clock position.
• The goal is to freshen the soft tissue, creating a bleeding bed that stimulates a robust fibroblastic healing response.

Capsular Plication: Surgical Technique and Biomechanics

The core of the procedure is the volumetric reduction of the capsule. This is achieved by taking discrete bites of the redundant capsule and shifting them superiorly and laterally toward the labrum.

The Pinch-Tuck Method and Suture Shuttling

Starting on the side of the shoulder where the EUA demonstrated the most profound instability, begin the plication.

1. Bite Size: Plicate the capsule using 1-cm bites. The exact size depends on the patient's physical size and the severity of the capsular laxity.
2. Directionality: Plications must always start inferiorly (at the 6-o'clock position). With each subsequent plication, the capsular "tuck" is advanced superiorly. This superior shift eliminates the dependent axillary pouch.
3. Instrumentation: A 45-degree spectrum suture hook or a commercial 45-degree suture shuttle device is ideal.

Suture Selection and Passage

Surgeons may choose between absorbable (e.g., No. 1 PDS) or nonabsorbable sutures based on preference and patient pathology.

• Using Absorbable Sutures (No. 1 PDS): Pass the suture through the capsule and labrum. Tie using a secure sliding knot (e.g., Weston or SMC knot) backed up by alternating half-hitches. Ensure all knots are tied off the edge of the articular surface to prevent iatrogenic chondral abrasion.
• Using Nonabsorbable Sutures: Employ the pinch-tuck method.
  • Grasp approximately 1 cm of the redundant capsule.
  • Bring the needle up through the capsule, exiting lateral to the labrum.
  • Pass the needle up and under the labrum while placing upward-directed tension on the capsule, effectively advancing the capsule superiorly.
  • Retrieve the suture shuttle out of the posterior cannula, and carry the nonabsorbable suture out anteriorly through the working cannula for knot tying.

Advanced Suture Configurations

For enhanced biomechanical fixation, particularly in patients with profound hyperlaxity or poor tissue quality, complex suture configurations are recommended:

• Mattress Suture: Use the suture shuttle to pinch the capsule up through the labrum and carry the suture out. Retrieve the second limb of the suture from the posterior cannula and carry it out to the anterior cannula. Tie the mattress configuration to create a broad footprint of capsular compression against the labrum.
• Figure-of-Eight Suture: Pass the same limb of the suture from anterior to posterior through the capsule and labrum twice. Retrieve it back out anteriorly. This configuration provides excellent resistance to tissue pull-through.

Surgical Warning: The Axillary Nerve
When carrying the capsular plication around the inferior pole (the 6-o'clock position), extreme caution must be exercised. Do not pass the suture passing device too deep or too far laterally from the labrum. The axillary nerve lies in close proximity to the inferior capsule (often within 10 to 15 mm of the glenoid rim). Deep bites in the axillary pouch carry a high risk of iatrogenic axillary nerve entrapment or transection.

Continue the plication systematically, extending the capsular shift up to the 9-o’clock position posteriorly and the 3-o'clock position anteriorly, effectively obliterating the redundant inferior recess.

Rotator Interval Closure

In patients with significant multidirectional instability, particularly those demonstrating a prominent sulcus sign, isolated inferior capsular plication is insufficient. The rotator interval—comprising the superior glenohumeral ligament (SGHL), the coracohumeral ligament (CHL), and the anterior capsule—must be addressed to prevent inferior translation of the adducted arm.

Technique for Interval Closure

1. Cannula Management: Withdraw the anterior cannula until it sits just anterior to the capsule, outside the joint space.
2. Suture Passage: Introduce a spectrum suture device. Pass a No. 1 PDS suture through the superior portion of the middle glenohumeral ligament (MGHL).
3. Retrieval: Use a penetrator-type grasper to retrieve the suture just superior to the superior glenohumeral ligament (SGHL).
4. Closure: Tie the suture blindly or under direct visualization to imbricate the interval. Typically, the interval is closed with two distinct sutures anteriorly.

Posterior Capsular Closure

Upon completion of the anterior interval, the posterior capsule must be managed similarly to ensure balanced global tension.
* Pass a suture on each side of the posterior capsular rent (created by the posterior portal).
* Close the defect with the cannula positioned just outside the capsule.

Clinical Pearl: Spatial orientation during interval closure can be challenging. These techniques are executed most easily by visualizing the anterior interval closure from the posterior portal. Once complete, move the arthroscope to the anterosuperior portal to obtain a clear, unobstructed view for the posterior capsular closure.

Postoperative Care and Rehabilitation Protocol

The success of an arthroscopic capsular shift is heavily dependent on strict adherence to a phased postoperative rehabilitation protocol. The goal is to protect the plicated tissue while it heals, followed by a gradual restoration of motion and dynamic stability.

Immediate Postoperative Phase (Weeks 0-6)

• Wound Closure: Close the arthroscopic portals with subcuticular Monocryl sutures and apply sterile, non-adherent dressings.
• Immobilization: An Ultrasling (or similar abduction sling) is applied in the operating room with the arm in neutral rotation.
• Duration: The arm is strictly maintained in the sling postoperatively for 6 weeks.
• Permitted Activity: Active hand, wrist, and elbow range of motion (ROM) are encouraged immediately to prevent distal stiffness. Pendulum exercises may be initiated at week 3 or 4, depending on the surgeon's assessment of tissue quality.

Intermediate Phase (Weeks 6-12)

• Sling Weaning: Discontinue the sling at 6 weeks.
• Passive to Active-Assisted ROM: Begin formal physical therapy focusing on passive range of motion (PROM), progressing to active-assisted range of motion (AAROM).
• Restrictions: Avoid aggressive stretching, particularly in external rotation and abduction, to prevent stretching out the newly plicated anterior and inferior capsule.

Advanced Strengthening Phase (Weeks 12+)

• Dynamic Stabilization: Initiate isotonic strengthening of the rotator cuff and periscapular stabilizers.
• Proprioception: Incorporate closed-kinetic-chain exercises to enhance joint proprioception, which is often deficient in MDI patients.
• Return to Play: Return to heavy labor or overhead sports is typically restricted until 6 to 9 months postoperatively, contingent upon the restoration of symmetric strength and dynamic joint stability.

Conclusion

The arthroscopic capsular shift is a highly effective, minimally invasive solution for multidirectional shoulder instability. By adhering to strict biomechanical principles—meticulous tissue preparation, precise volumetric reduction via the pinch-tuck method, careful avoidance of the axillary nerve, and comprehensive rotator interval closure—the orthopedic surgeon can restore glenohumeral stability. Coupled with a disciplined postoperative rehabilitation regimen, this technique yields excellent long-term functional outcomes, allowing patients to return to their daily activities and athletic pursuits without the debilitating apprehension of recurrent instability.