In the right shoulder region, the skin and superficial fascial structures have been removed to present a wide view of the muscles around the shoulder joint. These muscles are seen from the front (Fig. 1.1).

The trapezius inserts on the shoulder girdle, and the parts of the deltoid which start from approximately the same region, insert on the deltoid tuberosity over the distal side on the lateral margin of the humerus. Only the clavicular head of the pectoralis major is observed on the figure (Fig. 1.1). Pectoralis major extends to the anterolateral side of the proximal part of the humerus and inserts on the crest of the greater tubercle.

The important area here is the deltopectoral or clavipectoral triangle which lies between the clavicle, deltoid and pectoralis major. The distal part of cephalic vein was removed together with the superficial fascia. This vein passes through the triangle and extends to the axillary fossa (Fig. 1.1).

The anterior and mid sections, namely the clavicular and acromial parts of the deltoid were cut from their attachments and retracted posterior to reach the shoulder joint (Fig. 1.2).

A very important structure encountered at this level is the subdeltoid bursa. By inflating with air, the shape has become evident and the relationship with the structures surrounding the bursa is observed (Fig. 1.2). This bursa, which functions as a pillow between the deltoid and the proximal end of humerus, by usually combining with the subacromial bursa, extends as far as the level of the acromioclavicular joint (ACJ) below the acromion and coracoacromial ligament (CAL). The subdeltoid bursa extends towards the surgical neck of the humerus to as far as 4 cm to the distal from the anterolateral corner of acromion.

The coracoid process (CP), which is located below the clavicular part of the deltoid muscle, can be palpated approximately 2.5 cm below at the lateral 1/5 of clavicle. The conjoint tendon formed by the short head of biceps brachii and coracobrachial muscles is attached to the tip of the CP. With retraction of deltoid, the distal section of the pectoralis major, which inserts on the crest of the greater tubercle is visualised. The terminal part of the anterior branch of the axillary nerve, which extends below the deltoid is seen here (Fig. 1.2).

The acromion, CAL and CP form a very strong osteoligamentous girdle by supporting the shoulder joint from above. This girdle may damage the underlying structures by compressing them. The most important structure in reducing this effect is the subacromial bursa, which shows continuity with the subdeltoid bursa.

Although not described classically; CAL, CP and the conjoint tendon should be evaluated as an important osteotendinoligamentous arch supporting the shoulder joint anterosuperiorly. While the supraspinatus inserting on greater tubercle can be compressed by acromion, subscapularis inserting on the lesser tubercle can be compressed by CP in abduction. The relationships of the structures compressing under these osteofibrous arches may partially change with rotation during abduction.

The topographical relationships and structures attaching to the coracoid process (CP) are seen. The short head of the biceps brachii and coracobrachialis form the conjoint tendon which inserts on the tip of the CP. The pectoralis minor which originates from the 3rd-5th ribs inserts over the medial edge of the CP. A little more posteriorly, a small tendon of the subclavius is also seen attaching over the medial edge of the CP. The coracoacromial ligament (CAL), which is a strong, wide structure attaches to the lateral edge of the CP. More posteriorly, two important ligaments connect the clavicle and CP and attach to the superior surface of the CP. These two ligaments are the trapezoid ligament (TL) and the conoid ligament (CL).

The infraclavicular part of the brachial plexus and the axillary vessels are seen medial to the CP (Fig. 1.3).

The entry point of anterior arthroscopic portal is immediately lateral the CP. After palpating the CP, insertion of the portal can be made through the pit just lateral to the tip of the CP without damaging the axillary neurovascular structures and the conjoint tendon attaching here.

The relationship of the subdeltoid bursa and the rotator cuff muscles is shown in the figure. Pectoralis major is seen at the anterior wall of the axillary fossa and immediately below this muscle is the pectoralis minor, and above is the subclavius (Fig. 1.3).

To better demonstrate the anterior relations of the shoulder joint, pectoralis major tendon was retracted medially by cutting its humeral insertion. The conjoint tendon was also retracted medially to reveal the subscapularis muscle and the related structures at the posterior wall of the axillary fossa. More laterally, the tendon of long head of biceps brachii running in the intertubercular groove is seen. Thus the anterior part of the shoulder joint was reached through the interval between the short and long heads of the biceps brachii (Fig.
1.4).

The biceps tendon is located in the intertubercular groove wrapped with an intertubercular tendon sheath, then enters the joint cavity.

The musculocutaneous nerve courses inferolaterally after branching out from the lateral cord then passes within the coracobrachialis muscle and extends to the anterior compartment of the arm (Fig. 1.4). This nerve was moved away from the joint by pulling the conjoint tendon medially.

The subscapularis muscle, which originates from the subscapular fossa on the anterior surface of the scapula, inserts on the lesser tubercle. This muscle, which forms the anterior section of the rotator cuff is one the most important supporting structures of the shoulder joint. The posterior cord and its terminal branches are the closest neural structures located at the posterior wall of the axillary fossa. The axillary and radial nerves are the most important nerves separating from this cord. The axillary nerve runs just anterior to subscapularis leaning on it and passes through the quadrangular space (also known as the lateral axillary or quadrilateral space) at the posterior wall of the axillary fossa. Posteror circumflex humeral vessels pass through the space together with the axillary nerve (Fig. 1.4).

The anterior and posterior circumflex vessels emerge from the axillary artery. They may also be separated as a common trunk as seen here. The anterior circumflex artery is smaller and runs in front of the surgical neck. The posterior circumflex artery is bigger and by passing through the quadrangular space together with the axillary nerve comes underneath the deltoid. The axillary nerve and posterior circumflex vessels separate into branches while they pass through the space. The anterior branches course posterior to anterior around the surgical neck within the fascia of the deltoid muscle (Fig. 1.4).