Lateral position: tilt back slightly 20°-30° so that the shoulder glenoid surface is parallel to the floor. Skin traction may be applied with a weight of 4.5-5.9 kg. Upper limb abduction 45°-70°; anterior flexion 20°-30° position. The subacromial space and acromioclavicular joint are operated on with the upper arm in 20°-45° of abduction and 0° of flexion. Intra-articular pressure is maintained at 60-70 mmHg. Posterior access: 2-3 cm below the posterior lateral angle of the acromion and 2 cm medially, through the posterior “soft spot” between the infraspinatus and teres minor muscles. If two posterior entrances are needed, they should be chosen at 3-3.5cm below the level of the acromion, and the posterior superior entrance at 1.5cm below the acromion. The hand is placed above the shoulder, the index or middle finger presses the rostral process, the thumb presses the posterior soft spot, and the other hand rotates the humerus so that the thumb can palpate the position of the posterior glenohumeral joint line. The tip of the rostral process is palpated to determine the posterior entry inlet; the needle is stabbed toward the anteromedial aspect of the rostral process to sense the joint capsule and joint cavity; 50 ml of saline is injected to fill the joint cavity; local anesthetic with epinephrine (1% lidocaine, 1:300,000 epinephrine) is injected subcutaneously; the superficial skin is incised with a No. 11 blade; a trocar and blunt puncture cone are inserted. Posterior inferior entrance: approximately 2 cm above the posterior axillary crease, from the posterior axillary fossa into the joint. Structures susceptible to injury are the suprascapular nerve, axillary nerve, and posterior spinohumeral artery. Anterior entrance: slightly lateral to the midpoint of the line between the anterolateral tip of the acromion and the rostral process. There are two basic methods of establishing the anterior portal, the cis method from the outside to the inside and the retro method from the inside to the outside. Both involve penetrating the catheter into an anterior soft spot located in an intra-articular triangle with the biceps muscle above the intra-articular portion, the subscapularis tendon below above the intra-articular portion, and the anterior border of the acromion at the base. The anterior entrance site is marked; the arthroscope is advanced and the entrance site is transilluminated; the arthroscope is returned and the lumbar puncture needle is pierced; the 11-gauge blade makes the incision; the arthroscope is moved slightly superiorly and the blunt puncture cone is penetrated into the joint capsule. Superior approach: anterior to the clavicle, lateral to the acromion, posterior to the base of the acromion and scapular spine, and inferior to the posterior superior border of the articular pelvis. This entrance goes through the trapezius muscle and then through the supraspinatus muscle belly. The nearest point of the suprascapular nerve and blood vessels is located approximately 3 cm medial to the superior entrance. Lateral incision: located 3 cm lateral to the lateral edge of the scapular crest and passes through the deltoid muscle. When inserting the sleeve, it is first directed downward toward the tuberosity so that the lateral portion of the bursa can be accessed. It can be selected as an auxiliary entrance from the anterior and posterior sides, as needed. Shoulder arthroscopy exploration sequence: In the lateral recumbent position, adjust the camera orientation so that the image on the monitor is in the same horizontal position as the shoulder glenoid; in the beach chair position, make the articular surface of the shoulder glenoid vertical and keep the lens in its normal vertical position. With the posterior approach, after inserting the lens, the position of the biceps tendon is first found, and the articular cartilage portion of the upper shoulder joint or biceps tendon and the shoulder glenoid is observed. The lens is advanced to observe the cartilaginous portion of the humeral head and the glenoid of the shoulder joint; the shoulder is rotated internally and externally and fully observed. It is then advanced to observe the upper and lower surfaces of the biceps tendon, the point of attachment of the biceps tendon and the upper glenoid labrum for partial lacerations. The opening was made using a paralleling surgical technique from the outside to the inside, and an anterior probe was placed. The biceps glenoid labrum complex is probed and the extent of injury is assessed. Normally, the cord-like middle glenohumeral ligament spans the subscapularis tendon and attaches at the two o’clock position of the scapular neck. In a variant, this ligament inserts directly into the biceps tendon, leaving part of the area above the glenoid labrum uncovered by the glenoid lip and becoming bare, called the Buford complex. The arthroscope examines the anterior bundle portion of the inferior glenohumeral ligament and the middle glenohumeral ligament further down. Normally, the anterior fascicle of the inferior glenohumeral ligament attaches between the two and four o’clock points of the scapular glenoid neck. The anterior joint capsule contains three separate ligaments with different attachment points. The arthroscope is inserted into the inferior saphenous fossa and the arthroscope is rotated toward the superior scapular glenoid to visualize the glenohumeral ligament and glenoid labrum. Signs of shoulder instability include synovitis, abrasion, free body or glenoid labral separation. If the arthroscope moves easily forward within the joint when the upper extremity is gently externally rotated, a phenomenon known as the “Warren through sign” suggests extensive ligamentous laxity that must be corrected during shoulder immobilization. The attachment point of the joint capsule at the head of the humerus is examined. The arthroscope is then gently moved posteriorly to examine the posterior glenohumeral articular surface for humeral head articular surface tenderness, and wear or partial tear of the posterior glenoid labrum of the shoulder joint. The arthroscope is then moved backward to the biceps tendon to complete the examination of the entire shoulder joint. The elbow joint is flexed to reduce biceps strain. The biceps tendon is explored via the rotator cuff, both superior and inferior; a portion of the biceps tendon is retracted into the joint with a probe via the anterior entrance in order to determine the presence of synovitis and the presence of an incomplete tear in the portion of the upper arm located more distally. The arthroscopic surface is rotated, aligned with the rotator cuff, and the upper arm is gently rotated inward and outward to carefully examine the rotator cuff for wear, partial rotator cuff tears, and foci of calcification at the stop of the ramus. The arthroscope is advanced medially along the tendon to check for synovitis, abrasion or rupture. The arthroscope is gently withdrawn and the posterior rotator cuff and bare area of the humeral head are observed, where there is no articular cartilage coverage and normal small blood vessels enter the underside of the rotator cuff. The arthroscope is moved to the anterior entrance, and a probe can be placed in the posterior entrance. The posterior articular surface, posterior glenoid labrum, posterior saphenous fossa and posterior joint capsule can be visualized for hyperplasia, synovitis and wear or inflammatory changes due to shoulder instability via the anterior portal. The arthroscope is moved anteriorly to allow observation of the rotator cuff upward and the biceps glenoid labrum complex downward toward the glenoid. The arthroscope is then moved further anteriorly and directed back toward the inferior saphenous fossa to visualize the humeral attachment point of the glenohumeral ligament and the scapular glenoid attachment point below it. The arthroscope is then rotated downward to visualize the anterior inferior glenohumeral ligament attachment and the glenoid labral attachment of the joint capsule, as well as the middle glenohumeral ligament and subscapularis tendon and the subscapularis fossa. If the subacromial bursa is explored, it can be extended posteriorly from at least 2 cm from the anterior border of the acromion to approximately the middle of the acromion. All fluid from within the humeral joint must be aspirated before removing all trocars, and then, the posterior sleeve is placed into the subacromial space.