Photo 1. Deltoid m.

2.) Reflect the deltoid laterally to see the neurovasculature of the deltoid m., the axillary n. and posterior circumflex humeral a., if not already completed.

Note: With the deltoid m. reflected laterally and from the posterior, one can see some of the rotator cuff mm. in association with the scapula and proximal humerus. The neurovasculature which serves the deltoid m. (axillary n. & posterior circumflex humeral a.) is transmitted through the quadrangular space (the area bounded laterally by the surgical neck of the humerus, medially by the long head of triceps brachii m., superiorly by teres minor m., and inferiorly by teres major m.). 

Photo 2. Axillary n. & posterior circumflex humeral a.

3.) Locate the latissimus dorsi m., and review its neurovasculature, attachments, and actions.

Photo 3. Latissimus dorsi m.

Photo 4. Latissimus dorsi and thoracodorsal neurovasculature

Examine the ‘rotator cuff’ muscles and teres major m.

Find these structures:

• • ‘Rotator cuff’ muscles

    • Supraspinatus m.

    • Infraspinatus m.

    • Teres minor m.

    • Subscapularis m.

  • Teres major m.

4.) Identify the ‘rotator cuff’ mm.

Note: The rotator cuff mm. are found in close association with the scapula (from which they originate) and the proximal portion of the humerus (to which their tendons insert). The muscles (and their tendons) of the rotator cuff received their name from surrounding (cuffing) the proximal portion of the humerus and (as a group) acting to produce either lateral or medial rotation of the arm.

 Photo 5. Rotator cuff mm.

Photo 6. Rotator cuff mm.

Unilaterally, dissect and locate the neurovasculature of the shoulder

Find these structures:

• Suprascapular n.

• Suprascapular a.

• Dorsal scapular a.

• Circumflex scapular a.

Note: The arterial supply of the shoulder is derived from branches of the subclavian & axillary aa. Reflecting upon the triangular shape of the scapula and its three borders (superior, medial, and lateral), each of these borders (and muscles that attach along them) is typically served by an artery, and these arteries form an extensive series of anastomoses, providing collateral blood flow to the shoulder. The borders of the scapula, and the arteries which serve them (and proximate structures) are:

• superior border - suprascapular a.: supraspinatus & infraspinatus mm.; shoulder joint

• medial border - dorsal scapular a.: levator scapulae, rhomboid major & minor mm.

• lateral border - circumflex scapular a.: teres major & minor, infraspinatus mm.

5.) Laterally reflect the supra- & infraspinatus mm. from the scapula. Start at the proximal (medial) portion of the spine of scapula, and bluntly reflect the supra- & infraspinatus mm. away from their respective fossae. Take care to preserve the neurovasculature (e.g. the suprascapular a. & n.) deep to these mm.

Note: The suprascapular n. originates from the superior trunk of the brachial plexus, travels laterally (deep to trapezius m.), and then posteriorly through the suprascapular notch, deep to the superior transverse scapular ligament. The suprascapular n. is often accompanied by the suprascapular a., which typically originates from the thyrocervical trunk. Suprascapular a. travels laterally (also deep to trapezius m.), and then superior to the superior transverse scapular ligament. Once on the posterior surface of the scapula, the suprascapular a. & n. travel inferiorly, serving the supraspinatus and infraspinatus mm.

6.) Locate the dorsal scapular a. along the medial border of the scapula.

Note: Dorsal scapular a. typically originates from the 3rd part of the subclavian a., but in about a third of cases branches from the transverse cervical a. (thyrocervical trunk). Dorsal scapular a. supplies the muscles attaching to the medial border of the scapula (levator scapulae m, rhomboid major & minor mm.), and anastomosis with the suprascapular and circumflex scapular aa.

7.) Bluntly separate the teres minor m. from the infraspinatus m., then gently move the teres minor m. inferiorly to locate the circumflex scapular a.

Note: It may be difficult to separate the infraspinatus and teres minor mm. as their fasciae (& sometimes fibers) may fuse.

Note: Circumflex scapular a. typically originates from the subscapular a., a branch of the 3rd part of the axillary a. The circumflex scapular a. typically anastomose with the suprascapular & dorsal scapular aa.

Photo 7. Scapular anastomoses

Examine the three parts of the axillary a., and identify their major branches

Find these structures:

• • Axillary v.

  • Axillary a.

    • 1st part

    • 2nd part

      • Thoraco-acromial a.

    • 3rd part

      • Subscapular a.

        • Thoracodorsal a.

        • Circumflex scapular a.

      • Anterior circumflex humeral a.

      • Posterior circumflex humeral a.

8.) Locate the three parts of the axillary a. and their branches.

Note: The axillary a. is a continuation of the subclavian a. at the lateral margin of the 1st rib. At the inferior margin of teres major m., the axillary a. transitions into the brachial a. The axillary a. is conceptually divided in three parts. The 1st part of the axillary a. is medial to pectoralis minor m., the 2nd part is posterior to pectoralis minor m., and the 3rd part is lateral to pectoralis minor m.

Note: The branches (and their targets) of the axillary a. are as follows:

• • Axillary a.

    • 1st part

      • Superior thoracic a. - intercostal spaces 1 & 2

    • 2nd part

      • Thoraco-acromial a. - pectoralis major & minor mm, subclavius m., deltoid m., shoulder joint

      • Lateral thoracic a. - serratus anterior m.

    • 3rd part

      • Subscapular a.

        • Thoracodorsal a. - latissimus dorsi m.

        • Circumflex scapular a. - teres major & minor mm., infraspinatus m.

      • Anterior circumflex humeral a. - deltoid m., arm mm. adjacent to the surgical neck of the humerus

      • Posterior circumflex humeral a. - deltoid m., arm mm. adjacent to the surgical neck of the humerus

Photo 8. Axillary a. parts

 Photo 9. Axillary a. branches

Note: The anterior & posterior circumflex humeral aa. branch from the 3rd part of the axillary a., and wrap around the surgical neck of the humerus, where they anastomose. Typically, the posterior circumflex humeral a. is larger than its counterpart, and it is most often the last branch of the axillary a. The anterior & posterior circumflex humeral aa. supply the deltoid m. and portions of arm muscles adjacent to the surgical neck of the humerus. The anterior & posterior circumflex humeral aa. also frequently anastomose with the acromial branch of the thoraco-acromial a.

Review and locate the cords and terminal branches of the brachial plexus, noting relationships to muscles and vasculature of the upper limb

Find these structures:

• • Medial cord

    • Ulnar n.

    • Contribution to median n.

  • Lateral cord

    • Musculocutaneous n.

    • Contribution to median n.

  • Median n.

  • Posterior cord  

    • Axillary n.

    • Radial n.

9.) Locate the cords of the brachial plexus and the terminal branches of the cords.

Note: Recall that the elements of the brachial plexus are often named for their relationship to the axillary a., and the cords are no exception. The cords are the beginning of the infraclavicular portions of the brachial plexus, so they are typically found inferior to the clavicle. The posterior cord is formed from contributions from the three posterior divisions of the brachial plexus. The terminal branches of the posterior cord (and their targets) are as follows:

• • posterior cord

    • axillary n. - deltoid m., teres major m., & skin of the proximal, lateral arm

    • radial n. - muscles and skin of the posterior (extensor) compartments of the arm & forearm.

Photo 10. Posterior cord

Note: The lateral cord is formed from anterior divisions from the superior and middle trunks, and lays lateral to the axillary a. The lateral cord supplies a contribution to the median n. The musculocutaneous n. is the terminal branch of the lateral cord. The musculocutaneous n. pierces the coracobrachialis m. and innervates it and the remainder of the anterior (flexor) compartment of the arm.  

Photo 11. Lateral cord

Note: The medial cord is formed from the anterior division from the inferior trunk, and lies medial to the axillary a. The medial cord supplies a contribution to the median n. The ulnar n. is the terminal branch of the medial cord. The ulnar n. innervates most of the mm. of the hand, 1.5 mm. in the anterior (flexor) compartment of the forearm, and the skin of some (ulnar side) of the wrist, palm and associated digits.

Photo 12. Medial cord

Note: The median n. is formed from contributions from the lateral & medial cords. The median n. innervates most of the anterior (flexor) compartment of the forearm, some of the mm. of the hand, and the skin of some (radial side) of the palm and associated digits.  

Dissect the joints in the shoulder region

Find these structures:

• • Joints

    • Acromioclavicular joint

    • Glenohumeral joint

  • Ligaments:

    • Acromioclavicular ligament

    • Coraco-acromial ligament

    • Coracoclavicular ligament

    • Transverse humeral ligament

    • Capsule

  • Rotator cuff tendons

10.) Clean the muscular soft tissue from the superior portion of the acromioclavicular (AC) joint, and locate the acromioclavicular ligament.

Note: The acromioclavicular (AC) joint, a plane joint, connects the acromion of the scapula to the lateral (acromial end) clavicle.

Note: The acromioclavicular ligament covers the superior portion of the acromioclavicular joints, and its fibers often interweave with the aponeuroses of deltoid and trapezius mm. and the intra-articular disc (if present).

Photo 13. Acromioclavicular ligament

11.) With blunt dissection, clean the space between the clavicle and coracoid process, as well as the acromion and coracoid process of the scapula. Locate the coracoclavicular and coraco-acromial ligaments. During the cleaning process, conceptualize where the subacromial bursa would be located. Bursae are very difficult to observe in embalmed cadavers.

Note: The coracoclavicular ligament is the strongest ligament of the acromioclavicular joint, although it is actually an accessory ligament for this joint. There are two parts of this ligament: trapezoid (anterolateral and broad) and conoid (posteromedial and thicker). Severe shoulder separations include a complete tear of this ligament.

Note: The coraco-acromial ligament is an important component (along with the acromion and coracoid process of the scapula) of the coraco-acromial arch, which is located superior to the humeral head.

Note: The subacromial (subdeltoid) bursa is located between the coraco-acromial arch and the glenohumeral joint, specifically the supraspinatus tendon. This bursa facilitates movement of the supraspinatus tendon, particularly in circumduction. It does not directly communicate with the joint cavity.

Photo 14. Coracoclavicular & coraco-acromial ligaments

12.) Unilaterally, open (with scissors, not a scalpel) the acromioclavicular joint capsule by incising just medial to the acromion. Slightly separate the acromion from the acromial end of the clavicle, and locate the articular disc, if present.

Note: With age the articular disc changes from a complete disc (in juveniles and young adults) to incomplete, particularly inferiorly or in the center of the disc.

Photo 15. Opened AC joint, articular disc

13.) Locate all rotator cuff muscles and follow their tendons to the glenohumeral joint. Conceptualize where the subtendinous bursa of the subscapularis muscle would be located.

Note: The rotator cuff tendons intertwine with the lateral portion of the external part of the capsule of the glenohumeral joint: supraspinatus m. (superior), infraspinatus & teres minor mm. (posterior), and subscapularis (anterior). These muscles and tendons are the main source of stability for the glenohumeral joint.

Note: The subtendinous bursa of the subscapularis muscle is located between the tendon of the subscapularis muscle and the scapula. It protects the tendon of subscapularis as is passes across the neck of the scapula. It typically communicates with the cavity of the glenohumeral joint through an opening in the joint capsule.

Photo 16. Rotator cuff tendons & capsule

14.) Clean and locate the transverse humeral ligament.

Note: The transverse humeral ligament connects the greater and lesser tubercles of the humerus and forms a tunnel for the tendon of the long head of the biceps brachii m.

Photo 17. Transverse humeral ligament

15.) With the donor in a prone position, unilaterally make a longitudinal incision (with scissors, not a scalpel) through the glenohumeral joint capsule. Reflect the capsule in medial and lateral directions in order to expose the humeral head. Forcefully laterally rotate the humerus in order to view structures within the joint cavity.

Photo 18. Joint cavity