Arthroscopic Approach to the Shoulder

Shoulder arthroscopy is indicated for the following conditions:

1. Arthroscopic subacromial decompression for chronic rotator cuff tendinopathy.
2. Treatment of partial rotator cuff tears.
3. Treatment of glenoid labrum tears.
4. Management of degenerative acromioclavicular joint disease.
5. Removal of loose bodies.
6. Treatment of osteochondritis dissecans.
7. Synovectomy.
8. Resection of the distal clavicle.
9. Release of suprascapular nerve entrapment.
10. Release of scar tissue/contractures.
11. Biceps tenotomy/tenodesis.

Patient Positioning

Patient positioning during arthroscopic shoulder access is critical. The two main positions are the beach chair and the lateral decubitus position.

Beach Chair Position

Advantages

• Easy conversion to an open deltopectoral approach if necessary.
• Reduced venous pressure and bleeding.

Disadvantages

1. Improper positioning and padding can lead to neuropraxia, affecting several nerves:
   • Supraorbital nerve: A tight or poorly padded face mask over the forehead can cause paresthesia over the forehead and anterior scalp.
   • Great auricular nerve: Face mask straps placed too far posteriorly or poorly padded over the mastoid process can cause paresthesia over the ear, posterior auricular area, and angle of the mandible.
   • Lateral femoral cutaneous nerve: A poorly positioned and padded lateral abdominal bolster can cause paresthesia over the anterolateral thigh, with a higher risk in obese patients due to pannus weight.
2. Improper neck positioning:
   • Hyperextension: Increases the risk of stroke and cranial nerve palsy (CN12 hypoglossus).
   • Hyperflexion: Increases the risk of spinal cord ischemia and resulting quadriplegia.
3. Increased risk of cerebral hypoperfusion compared to the lateral decubitus position.

Lateral Decubitus Position

• Advantage of joint distraction: Can be associated with traction neuropraxia.

Landmarks and Incisions

Primary Portals for Arthroscopic Shoulder Access

Posterior Portal

Function: Primary viewing portal for diagnostic arthroscopy.

Location and Technique:

• Located 2 cm inferior and 1 cm medial to the posterolateral corner of the acromion.
• The portal can pass between the infraspinatus (suprascapular nerve) and the teres minor (axillary nerve) or through the substance of the infraspinatus.
• This is usually the first portal placed, directed anteriorly toward the tip of the coracoid.

Anterior Portal

Function: Visualization and subacromial decompression.

Location and Technique:

• Located lateral to the coracoid process and anterior to the AC joint.
• The portal passes between the pectoralis major (medial and lateral pectoral nerves) and the deltoid (axillary nerve).

This portal is typically placed under direct visualization from the posterior portal using a spinal needle.

Lateral Portal

Function: Subacromial decompression.

Location and Technique:

• Located 1-2 cm distal to the lateral edge of the acromion.
• The portal passes through the deltoid muscle (axillary nerve).

Secondary Portals for Arthroscopic Shoulder Access

Anteroinferior (5 o'clock) Portal

Function: Placement of anchors for anterior labral repair.

Location and Technique:

• Located just inferior to the coracoid.
• Typically placed under direct visualization from the posterior portal using a spinal needle.

Posteroinferior (7 o'clock) Portal

Function: Placement of anchors for posterior labral repair.

Location and Technique: Typically placed under direct visualization from the posterior portal using a spinal needle.

Neviaser (Supraspinatus) Portal

Function: Visualization of the anterior glenoid and for SLAP repairs.

Location and Technique: Located just medial to the lateral acromion and passes through the supraspinatus muscle (suprascapular nerve).

Port of Wilmington (Anterolateral) Portal

• Function: Used for evaluation/repair of posterior SLAP and rotator cuff lesions.
• Location and Technique: Located directly anterior to the posterolateral corner of the acromion.

This portal is typically placed under direct visualization from the posterior portal using a spinal needle.

Internervous Plane

• There is no true internervous plane in arthroscopic shoulder access.

Superficial Dissection

Diagnostic Scope

Performed with a 30° scope through the posterior portal to identify:

1. Biceps tendon
2. Supraspinatus
3. Infraspinatus and teres minor
4. Rotator interval (formed by the biceps tendon, superior edge of subscapularis, and glenoid)
5. Anterior band complex (MGHL, IGHL)
6. Subscapular recess (for loose bodies)
7. Anterior labrum
8. Glenoid
9. Humeral head

Anatomic Variations

The region of the anterosuperior labrum and the MGHL shows significant anatomic variability:

• Most common: A firmly attached labrum with a broad MGHL.
• Sublabral hole with a cord-like MGHL.
• Buford complex: Absent labrum and a cord-like MGHL.

Areas of exposed cartilage are normal on:

• The central glenoid.
• The posterior humeral head.

Dangers

Structures at risk during arthroscopic shoulder access include:

Posterior Portal

1. Axillary nerve:
   • Exits the axilla through the quadrangular space and winds around the humerus on the deep surface of the deltoid, running approximately 7 cm below the acromion tip.
   • At risk if the posterior portal is placed too inferiorly.
2. Suprascapular nerve:
   • Runs through the supraspinatus and infraspinatus fossae before innervating both muscles.
   • At risk if the posterior portal is placed too medially.

Anterior Portal

• Cephalic vein: Runs in the deltopectoral groove and is at risk if the portal is too lateral.
• Musculocutaneous nerve:
  • Enters the muscles 2–8 cm distal to the tip of the coracoid.
  • At risk if the anterior portal is placed too inferiorly.

Anesthesia

• Phrenic nerve: At risk with interscalene block (anesthesia).

References

1. Campbell's Operative Orthopaedics, 12th Edition.
2. Surgical Exposures in Orthopaedics: The Anatomic Approach, 4th Edition.