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Arthroscopy of the Shoulder: Posterior Portal

- Technique:
    - best visualization of the shoulder joint is through the posterior portal;
    - portal usually is located 1.5-3 cm distal & 1-2 cm medial to postero-lateral tip of acromion;
    - further refine the proper location of the portal by finding the soft spot, using deep palpation of the thumb along w/ internal and external rotation of the joint;
           - the soft spot is formed by the interval between infraspinatus and teres minor;
           - always avoid placing the this portal too far laterally, since this will make joint visualization more difficult;
    - 18 or 20 gauge spinal needle is then passed into the should joint by aiming just lateral to or at the coracoid process, which is usually well palpated anteriorly;
           - note that the scapula is oriented 30 deg anterior to the coronal plane, which is the proper direction of entry;
           - inject 5-10 cc of NS w/ epinephrine to distend the joint, and then disengage the syringe and look for fluid exiting from the needle (which confirms proper placement);
           - then inject another 20 cc of fluid to fully distend the joint;
           - the distended joint will push the humeral head away from the glenoid, which lessens the chance of iatrogenic chondral injury during trochar insertion;
    - 30 deg scope with camera attached is locked in place, and the joint distended by the inflow entrance on the scope itself;
           - one should then be able to visualize the joint;
    - superior to the subscapularis edge is the interval between the subscapularis and supraspinatus;
           - this soft spot is where one can and will establish the anterior portal if an operative procedure is warranted;
    - arthroscopic acromioplasty:
           - when an arthroscopic acromioplasty is planned (along w/ the shoulder arthroscopy) this portal should be placed slightly higher than normal so that the arthroscope lies more parallel to inferior surface of acromion (allowing better visualization for acromioplasty);
           - this higher portal also gives a better perspective of the rotator cuff;
    - hazards:
           - suprascapular nerve:
                  - injury may occur from passing instruments along the lateral border of the scapular spine;
           - axillary nerve:
                  - this portal is located approx 3-4 cm superior to quadrangular space, which contains axillary nerve & PHCA