Courtesy: Amr Abdelgawad, Maimonaides Medical Centre, Brooklyn, New York

Posterior Approach to the Glenoid

• Used for fixation of posterior glenoid fractures and access to the posterior capsule.
• Internervous plane: between infraspinatus (suprascapular nerve) and teres minor (axillary nerve).
• This interval provides safe access to the posterior glenoid.
• Axillary nerve runs inferior to teres minor and must be protected.
• Excessive superior retraction of infraspinatus may stretch the suprascapular nerve and artery.
• Infraspinatus splitting approach can be used for direct access to the posterior capsule with lower risk to the axillary nerve.

Deltopectoral Approach

• Commonly used approach for proximal humerus fractures and shoulder arthroplasty.
• Interval: between deltoid muscle (laterally) and pectoralis major muscle (medially).
• Subscapularis tendon must be divided or lesser tuberosity osteotomy performed to enter the joint.
• Repair of subscapularis is required at the end of surgery.
• Postoperative precautions: limit active internal rotation and excessive passive external rotation to protect repair.

Lateral Deltoid Splitting Approach

• Used for fixation of proximal humerus fractures.
• Approach splits the deltoid muscle fibers.
• Axillary nerve runs approximately 5 cm distal to the lateral edge of the acromion.
• Incision must be limited or the axillary nerve identified before extending distally.

Posterior Approach to the Humerus

• Used for open reduction and internal fixation of humeral shaft fractures.
• Traditional approach: triceps splitting technique after identification of the radial nerve.
• Modified approach: triceps-sparing technique where medial and lateral heads are mobilized.
• Traditional approach exposes approximately 60–65% of the humeral shaft.
• Modified approach exposes up to 95% of the humeral shaft.

Brachial Plexus Overview

• Brachial plexus provides motor and sensory innervation to the upper limb.
• Formed from nerve roots C5, C6, C7, C8, and T1.
• Organization follows: Roots ? Trunks ? Divisions ? Cords ? Terminal branches.

Trunks of the Brachial Plexus

• C5–C6 form the upper trunk.
• C7 continues as the middle trunk.
• C8–T1 form the lower trunk.

Divisions

• Each trunk divides into anterior and posterior divisions.
• Anterior divisions generally supply flexor compartments.
• Posterior divisions generally supply extensor compartments.

Cords of the Brachial Plexus

• Posterior cord: formed by posterior divisions of all three trunks.
• Lateral cord: formed by anterior divisions of upper and middle trunks.
• Medial cord: formed by anterior division of the lower trunk.

Major Branches

• Long thoracic nerve (C5–C7): supplies serratus anterior.
• Upper trunk branches: suprascapular nerve and nerve to subclavius.
• Lateral cord: lateral pectoral nerve, musculocutaneous nerve, and lateral contribution to median nerve.
• Posterior cord: axillary nerve, radial nerve, thoracodorsal nerve, upper and lower subscapular nerves.
• Medial cord: ulnar nerve, medial pectoral nerve, medial cutaneous nerves of arm and forearm, medial contribution to median nerve.

Important Shoulder Nerve Supply

• Axillary nerve supplies deltoid and teres minor.
• Suprascapular nerve supplies supraspinatus and infraspinatus.
• Upper and lower subscapular nerves supply subscapularis.
• Lower subscapular nerve also supplies teres major.

Spaces Around the Shoulder

• Quadrangular space: bounded by teres minor (superior), teres major (inferior), long head of triceps (medial), and humerus (lateral).
• Contents: axillary nerve and posterior circumflex humeral artery.
• Triangular space: bounded by teres minor, teres major, and long head of triceps.
• Contents: circumflex scapular artery.
• Triangular interval: bounded by teres major, long head of triceps, and lateral head of triceps.
• Contents: radial nerve and profunda brachii artery.

Rotator Interval

• Triangular space in the anterior-superior shoulder joint capsule.
• Boundaries: supraspinatus (superior), subscapularis (inferior), coracoid process (base), transverse humeral ligament (apex).
• Contents: long head of biceps tendon, coracohumeral ligament, and superior glenohumeral ligament.
• Important for stability of the glenohumeral joint.

Glenohumeral Ligament Functions

• Coracohumeral ligament: primary restraint to inferior translation of the humeral head.
• Superior glenohumeral ligament: limits inferior translation with arm adducted.
• Middle glenohumeral ligament: limits anterior translation in mid-abduction (~45°).
• Inferior glenohumeral ligament complex: primary stabilizer at 90° abduction.

Blood Supply of the Humeral Head

• Posterior circumflex humeral artery provides approximately 60% of blood supply.
• Anterior circumflex humeral artery contributes approximately 40%.
• Ascending branch of the anterior circumflex artery forms the arcuate artery.

Rotator Cuff Footprint

• Supraspinatus insertion footprint approximately 16 mm mediolateral.
• Exposure of ~7–8 mm of bone during arthroscopy suggests about 50% tendon involvement.

Biceps Tendon and Bicipital Groove

• Long head of biceps tendon runs through the bicipital groove.
• Lateral lip: insertion of pectoralis major.
• Medial lip: insertion of teres major.
• Floor of groove: insertion of latissimus dorsi.
• Biceps pulley formed by coracohumeral ligament and superior glenohumeral ligament prevents medial subluxation.