Posterior Approach to the Shoulder

What it exposes. The posterior approach gives direct access to the posterior glenoid, the posterior humeral head, and the posterior soft-tissue stabilisers. It is less commonly used than the anterior or deltopectoral approaches but remains essential for a defined set of indications. Primary indications (open posterior approach): - Posterior instability requiring open stabilisation - revision cases after failed arthroscopy, or significant posterior glenoid bone loss

• Posterior glenoid fractures and glenoid bone-grafting procedures
• Locked posterior shoulder dislocation with an associated reverse Hill-Sachs impaction lesion
• Posterior capsular procedures including capsular shift
• Selected posterior humeral head fractures with posterior comminution Why it is used less often now. Historically the posterior approach was the standard route for posterior labral repair and posterior stabilisation. With advances in arthroscopic techniques, most posterior labral pathology is now treated arthroscopically, and the open posterior approach is reserved for revision cases, bone loss requiring grafting, and specific fracture patterns.

Advantages and disadvantages. The strengths of the posterior approach are a true internervous plane (infraspinatus versus teres minor), direct visualisation of the posterior glenoid, few vascular structures at risk, and good access to the posterior humeral head. Its weaknesses are limited exposure of the rotator cuff, the axillary nerve at risk during the deltoid split, the need for lateral-decubitus or prone positioning, and the fact that infraspinatus detachment may be required for extensive exposure. Indications for an open posterior approach are absolute when there is a posterior glenoid fracture requiring ORIF, significant posterior bone loss (greater than 20%) requiring graft, or failed arthroscopic posterior stabilisation with bone loss. They are relative for locked posterior dislocation, revision posterior instability even without bone loss, and a large reverse Hill-Sachs lesion requiring bone graft. Bone-loss thresholds that drive the decision. Posterior glenoid bone loss is measured on axial CT at the mid-glenoid level against the normal glenoid circle: less than 15% is managed with arthroscopic soft-tissue repair, 15-25% prompts consideration of a posterior bone block, and greater than 25% generally requires a bone block. On the humeral side, a reverse Hill-Sachs lesion of less than 20% is observed or grafted small, 20-40% is managed with a McLaughlin (subscapularis transfer) procedure, 40-50% with allograft reconstruction, and greater than 50% may warrant arthroplasty. Position and landmarks. The position sets up the whole exposure.

Work down through the layers from the posterior acromion, splitting the deltoid within its safe zone, then develop the infraspinatus/teres minor internervous plane to reach the posterior capsule and glenoid. This dissection is the heart of the approach.

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Structures at risk, by layer

The axillary nerve exits the quadrangular space with the posterior circumflex humeral vessels, courses along the inferior border of teres minor, and then runs around the surgical neck deep to the deltoid. It is injured by a deltoid split extended too far inferiorly, by stretch from excessive retraction, or by thermal injury from cautery. Injury presents as inability to abduct (deltoid paralysis) with sensory loss over the lateral shoulder (the badge area), confirmed on EMG/NCS. If recognised intraoperatively, explore and assess it: a nerve in continuity is usually a neuropraxia with good prognosis (observe 3-6 months), while a transected nerve needs tension-free microsurgical repair or tagging for delayed repair. With no recovery by 6 months, consider nerve exploration or tendon transfer. The suprascapular nerve passes through the suprascapular notch, around the base of the scapular spine in the spinoglenoid notch, and supplies infraspinatus as a motor branch only - so excessive medial dissection denervates the muscle without any sensory warning. Its closest infraspinatus branch lies on average about 20mm medial to the posterior glenoid rim, with no branch entering at the level of the infraspinatus raphe (Bailie 1999). Keep medial retraction within roughly 1.5cm of the rim. Quadrangular space boundaries - superior: teres minor; inferior: teres major; medial: long head of triceps; lateral: surgical neck of the humerus. The axillary nerve and posterior circumflex humeral vessels traverse this space, so deep dissection along the inferior aspect of the approach places them at risk. Extensile options. Extend superiorly along the scapular spine to reach the supraspinatus fossa and scapular body (useful for scapular fractures). Extend inferiorly toward the posterior axillary fold to reach the inferior glenoid and humeral shaft - but this requires deliberate identification and protection of the axillary nerve. Some pathology needs a combined anterior and posterior approach (complex glenoid fractures with anterior and posterior columns, revision arthroplasty with component removal, locked dislocations needing subscapularis transfer plus posterior access); these may be staged (anterior first, then posterior) or done simultaneously. Complications

• Posterior bone block for posterior glenoid bone loss - the principal bony procedure through this exposure.
• Posterior labral repair and posterior capsular shift (open, for revision or bone-loss cases; primary labral repair is now arthroscopic).
• ORIF of posterior glenoid fractures via direct access to the posterior column.
• Locked posterior dislocation - reduction with management of the reverse Hill-Sachs lesion (McLaughlin or modified McLaughlin subscapularis transfer, allograft, or arthroplasty depending on defect size).
• Posterior shoulder arthroplasty access when a posterior route is required. Outcomes by procedure

Global epidemiology and context. Posterior glenohumeral instability accounts for roughly 2-10% of all shoulder instability; locked posterior dislocation is rare and is missed at first presentation in up to half of cases, most often after seizures, electrocution, or high-energy trauma. The shift from open to arthroscopic posterior labral repair is reflected across high-volume centres worldwide, with open posterior approaches now reserved for bone loss, revision, and fracture.

Registry and outcome evidence. Dedicated registries for posterior instability are limited; most outcome data come from single-centre and multicentre cohort series rather than national joint registries, which capture arthroplasty rather than soft-tissue stabilisation. Where a locked posterior dislocation progresses to arthroplasty, national arthroplasty registries (for example NJR, AOANJRR, and the Scandinavian registries) inform implant selection and survivorship but do not specifically track the posterior approach. Practice variation by resource setting. 3D CT for glenoid bone-loss quantification and MR arthrography for labral assessment are standard in well-resourced centres but may be unavailable in lower-resource settings, where plain radiographs - critically the axillary view - and CT carry more diagnostic weight. Structural allograft availability varies internationally, influencing the choice between autograft and allograft for a posterior bone block.