Comprehensive guide to the posterior surgical approach to the shoulder - indications, technique, internervous plane, complications, and clinical applications for orthopaedic exam
Reviewed by OrthoVellum Editorial Team
Orthopaedic clinicians and medical editors • Published by OrthoVellum Medical Education Team
Internervous Plane: Infraspinatus (Suprascapular) and Teres Minor (Axillary) | Key Access: Posterior Glenoid, Humeral Head | Primary Risk: Axillary Nerve
This is a true internervous plane between infraspinatus (suprascapular nerve) and teres minor (axillary nerve). This anatomic separation provides safe access without denervating muscles, but both nerves remain at risk with deep dissection.
The axillary nerve is the primary structure at risk. It runs along the inferior border of teres minor and subscapularis, approximately 5-7cm below the posterolateral acromion. Deltoid split must not exceed this distance.
The posterior approach is less commonly used than anterior approaches. Primary indications are posterior instability requiring open repair, posterior glenoid fractures, and locked posterior dislocations. Most posterior labral work is now arthroscopic.
Lateral decubitus is most common position, with arm supported in slight flexion and internal rotation. Prone position is alternative. Both allow gravity to assist with exposure and maintain arm position during surgery.
| Pathology | Posterior Approach? | Alternative |
|---|---|---|
| Posterior labral tear | Usually arthroscopic | Open posterior if revision or bone loss |
| Posterior glenoid fracture | Yes - direct access | Consider extensile Judet if scapular body involved |
| Locked posterior dislocation | Yes - for reduction and transfer | Deltopectoral if subscapularis transfer planned |
| Rotator cuff tear | No - poor access to cuff | Anterosuperior or arthroscopic |
| Anterior instability | No - wrong approach | Deltopectoral approach |
Memory Hook:POSTERIOR guides you through each step of the approach sequentially
Memory Hook:Stay in the SAFE ZONE - keep deltoid split within 5cm of posterolateral acromion
Memory Hook:The INTERVAL is your safe zone between two separately innervated muscles
The posterior approach to the shoulder provides direct access to the posterior glenoid, posterior humeral head, and posterior soft tissue structures. It is less commonly used than anterior approaches but remains essential for specific indications.
Primary indications:
Why Less Common?
The posterior approach was more commonly used historically for posterior labral repairs and instability. With advances in arthroscopic techniques, most posterior labral pathology is now treated arthroscopically. Open posterior approach is now reserved for revision cases, bone loss requiring grafting, and specific fracture patterns.
Advantages of posterior approach:
Disadvantages:
Surface anatomy and landmarks:
The key surface landmarks guide incision placement and approach development:
Muscular layers:
| Muscle | Innervation | Relationship to Approach |
|---|---|---|
| Deltoid (posterior) | Axillary nerve | Split in line with fibers, limited to 5cm below acromion |
| Infraspinatus | Suprascapular nerve | Superior muscle of internervous plane |
| Teres minor | Axillary nerve (branch) | Inferior muscle of internervous plane |
| Teres major | Lower subscapular nerve | Inferior to surgical field, not typically encountered |
Neurovascular structures at risk:
The axillary nerve and posterior circumflex humeral vessels exit the quadrangular space and course along the inferior border of subscapularis anteriorly and teres minor posteriorly. The nerve is located approximately 5-7cm inferior to the posterolateral corner of the acromion. This defines the safe limit for deltoid splitting.
Quadrangular space boundaries:
The axillary nerve and posterior circumflex humeral vessels traverse this space. Deep dissection along the inferior aspect of the approach risks injury to these structures.
Posterior capsule:
The posterior capsule is the deepest layer encountered. It is relatively thin compared to the anterior capsule. Opening the capsule longitudinally provides access to:
The posterior approach to the shoulder utilizes a true internervous plane, which is the key anatomic basis for this approach.
Definition of the plane:
The internervous plane exists between:
True Internervous Plane
This is a true internervous plane because the two muscles forming the interval are supplied by different nerves. Working between these muscles does not denervate either muscle, making this a safe anatomic approach. However, both nerves remain at risk from deep dissection or excessive retraction.
Characteristics of the plane:
Avascular nature:
Development technique:
Nerve anatomy related to plane:
| Nerve | Course | Protection Strategy |
|---|---|---|
| Suprascapular nerve | Through suprascapular notch to infraspinatus | Stay in internervous plane; avoid excessive medial dissection |
| Axillary nerve | Through quadrangular space to teres minor and deltoid | Limit deltoid split; avoid inferior retraction |
Suprascapular nerve:
Axillary nerve:
Functional significance:
Working in the internervous plane provides several advantages:
The internervous plane is the fundamental anatomic principle that makes the posterior approach safe and effective.
Proper patient positioning is critical for successful posterior shoulder surgery. Two main positions are used: lateral decubitus and prone.
Lateral decubitus position (most common):
This is the preferred position for most posterior shoulder procedures.
Setup steps:
Arm support options:
Arm position:
Advantages of lateral decubitus:
Disadvantages:
Lateral Decubitus Stability
In lateral decubitus position, the patient must be securely stabilized to prevent rolling. Use a bean bag or vacuum positioning device, and ensure the table is locked. An unstable patient position is dangerous and compromises surgical exposure.
Prone position (alternative):
Less commonly used but valid for specific indications.
Setup steps:
Arm position options:
Advantages:
Disadvantages:
Beach chair position (not recommended):
Beach chair is commonly used for anterior and superior shoulder procedures but is not ideal for posterior approaches:
Positioning checklist before incision:
Before making incision, confirm:
Proper positioning sets the foundation for safe and efficient surgery.
| Variant | Technique | Exposure | Primary Use |
|---|---|---|---|
| Standard Posterior | Deltoid split + infraspinatus-teres minor interval | Posterior glenoid, posterior humeral head | Most posterior pathology |
| Extensile Posterior | Extended along scapular spine | Scapular body, supraspinatus fossa | Scapular fractures |
| Mini-Open Posterior | Limited incision, smaller deltoid split | Posterior labrum, capsule | Bone block, revision |
| Posterior Deltopectoral | Lateral extension from posterior | Proximal humerus posteriorly | Humeral shaft fractures |
| Indication Category | Examples | Approach Preference |
|---|---|---|
| Posterior Instability | Labral tear, bone loss | Standard posterior |
| Glenoid Fractures | Posterior column, rim | Standard or extensile |
| Locked Dislocations | Posterior with reverse Hill-Sachs | Standard posterior |
| Scapular Fractures | Body, spine, glenoid | Extensile posterior |
History:
Physical Examination:
| Finding | Significance | Approach Decision |
|---|---|---|
| Positive jerk test | Posterior labral tear | Arthroscopic vs open (bone loss dependent) |
| Fixed posterior dislocation | Locked posterior dislocation | Posterior approach likely |
| Posterior glenoid tenderness | Posterior glenoid pathology | Posterior approach for bone work |
| Previous failed arthroscopy | Revision required | Open posterior approach |
Plain Radiographs:
CT Scan:
MRI:
| Finding | Imaging | Implication |
|---|---|---|
| Posterior glenoid bone loss greater than 20% | CT 3D reconstruction | Bone block required |
| Reverse Hill-Sachs greater than 25% | CT axial | Subscapularis transfer or graft |
| Posterior labral tear | MRA or MRI | Repair (arthroscopic or open) |
| Posterior glenoid fracture | CT | ORIF via posterior approach |
| Pathology | First Choice | Alternative | Rationale |
|---|---|---|---|
| Primary posterior labral tear | Arthroscopic | Open if bone loss | Less morbidity, good outcomes |
| Revision posterior instability | Open posterior | Combined if extensive | Soft tissue scarring, need bone graft |
| Posterior glenoid bone loss greater than 20% | Open posterior + bone block | None ideal | Cannot address bone arthroscopically |
| Locked posterior dislocation | Open posterior | Combined anterior-posterior | Direct access to reverse Hill-Sachs |
| Posterior glenoid fracture | Open posterior | Extensile if scapula involved | Direct visualization for ORIF |
Absolute:
Relative:
Identification of surface landmarks
Before incision, palpate and mark:
Mark the safe zone for deltoid split:
Plan the incision:
Incision Placement
The incision should be placed just medial to the posterior edge of the acromion and extend obliquely toward the posterior axillary fold. This provides access to the interval between infraspinatus and teres minor while avoiding injury to cutaneous nerves.
This concludes landmark identification.
| Complication | Incidence | Prevention/Management |
|---|---|---|
| Axillary nerve injury | 1-5% | Limit deltoid split to 5cm; avoid inferior retraction |
| Suprascapular nerve injury | Less than 1% | Stay in internervous plane; avoid excessive medial dissection |
| Posterior circumflex vessels | 1-2% | Identify and protect during inferior dissection |
| Deltoid weakness | 5-10% | Secure deltoid repair at closure |
| Infraspinatus weakness | 5-15% if detached | Anatomic repair with strong fixation |
| Stiffness | 10-20% | Early motion protocol; avoid excessive capsular tightening |
| Recurrent instability | 5-15% for instability cases | Adequate labral repair and capsular shift |
| Infection | Less than 2% | Sterile technique; antibiotic prophylaxis |
Axillary nerve injury:
The axillary nerve is the most important structure at risk.
Mechanism:
Prevention:
Diagnosis:
Management:
Axillary Nerve Anatomy
The axillary nerve exits the quadrangular space and travels along the deep surface of the deltoid muscle. It courses approximately 5-7cm inferior to the posterolateral corner of the acromion. Deltoid splits extending beyond this distance place the nerve at direct risk of injury.
Infraspinatus dysfunction:
If infraspinatus is detached and not properly repaired:
Prevention requires secure anatomic repair with bone tunnels or anchors.
Stiffness:
Posterior capsular scarring can lead to loss of internal rotation and forward flexion.
Prevention:
Immediate postoperative (Week 0-2):
Rehabilitation phases:
Weeks 0-6: Protection phase
Goals:
Restrictions:
Allowed activities:
Specific considerations:
Protection phase emphasizes healing while preventing stiffness.
Rehabilitation timelines must be modified based on:
Individualize the protocol to each patient and procedure.
Extensile approaches:
The posterior approach can be extended for greater exposure:
Superior extension:
Inferior extension:
Combined approaches:
Some pathology requires combined anterior and posterior approaches:
May stage approaches (anterior first, then posterior) or perform simultaneously.
Arthroscopic-assisted techniques:
Modern trend combines arthroscopy with mini-open posterior approach:
Evolution of Posterior Approach
The posterior approach has evolved with arthroscopic advances. Most posterior labral work that was historically done open is now performed arthroscopically. Open posterior approach is increasingly reserved for bone loss, revision cases, and fracture management where arthroscopy is inadequate.
Posterior Instability Surgery:
Locked Posterior Dislocation:
| Procedure | Success Rate | Recurrence | Complications |
|---|---|---|---|
| Open posterior labral repair | 85-90% | 5-10% | Stiffness 10-15% |
| Posterior bone block | 90-95% | less than 5% | Nerve injury 1-2% |
| McLaughlin procedure | 75-85% | 10-15% | Stiffness, subscap weakness |
| Posterior glenoid ORIF | 85-95% | N/A | Arthritis 10-20% |
Practice these scenarios to excel in your viva examination
"A 35-year-old male presents after a motorcycle accident with a posterior glenoid fracture involving 30% of the glenoid articular surface. The fracture is displaced 5mm. You plan open reduction and internal fixation via a posterior approach. Walk me through the surgical approach."
"A 28-year-old rugby player presents with recurrent posterior shoulder instability after a failed arthroscopic posterior labral repair 12 months ago. CT scan shows posterior glenoid bone loss of approximately 25%. What is your surgical plan and approach?"
"You are performing a posterior approach for a locked posterior dislocation. During deltoid splitting, you extend the split approximately 8cm below the acromion and the patient suddenly develops loss of deltoid tone. What has happened and what do you do?"
Internervous Plane Question
Q: What is the internervous plane for the posterior approach to the shoulder? A: Between infraspinatus (supplied by suprascapular nerve) and teres minor (supplied by axillary nerve). This is a true internervous plane providing safe access to the posterior shoulder.
Nerve at Risk Question
Q: What nerve is at highest risk during the posterior approach to the shoulder, and how is it protected? A: The axillary nerve is at highest risk. It courses approximately 5-7cm below the posterolateral corner of the acromion. Protection requires limiting deltoid split to no more than 5cm below this landmark.
Indications Question
Q: What is the primary indication for open posterior approach to the shoulder in modern practice? A: Revision posterior instability with bone loss requiring bone grafting. Most primary posterior labral repairs are now performed arthroscopically. Open posterior approach is reserved for bone loss, revision cases, and posterior glenoid fractures.
Position Question
Q: What patient position is most commonly used for the posterior approach to the shoulder? A: Lateral decubitus position on the opposite side, with the arm supported in slight flexion and internal rotation. This provides excellent posterior access and allows gravity to assist with exposure.
Complications Question
Q: A patient develops inability to abduct the shoulder after posterior approach surgery. What nerve is injured and how did it occur? A: Axillary nerve injury causing deltoid paralysis. Most common mechanism is excessive deltoid split extending beyond the safe zone (more than 5cm below posterolateral acromion), leading to direct nerve injury or excessive retraction.
Clinical practice in Australia:
Subspecialty care:
Training considerations:
Imaging access:
Operative considerations:
Exam Context
For FRACS exams, be prepared to describe the internervous plane (infraspinatus and teres minor), safe deltoid split limits (5cm below posterolateral acromion), and primary indications for the approach (posterior instability with bone loss, posterior glenoid fractures). Understanding the axillary nerve anatomy and protection is essential.
High-Yield Exam Summary