Clinical Anatomy of the Shoulder Part 3: Surgical Approaches
My name is Gavin Jennings. I am an orthopaedic surgeon specialising in the treatment of shoulder problems.
This is the third part of a presentation on the clinically relevant anatomy of the shoulder and will cover surgical approaches.
I will briefly discuss arthroscopic then anterior and posterior open approaches.
The standard posterior viewing portal is always used to first gain entry to the shoulder arthroscopically. This is located in the soft spot about 2 cm inferior and 1 cm medial to the posterolateral corner of the acromion.
Anterior portals are located in the safe zone lateral to the conjoined tendon to avoid the risk of damage to important neves and blood vessels.
The standard anterior working portal for access to both the glenohumeral and AC joints is located just in front and about 1 cm inferior to the front of the AC joint. If the joint easily cannot be palpated, it can be found directly in front of the soft spot formed at the apex of the arrow shape formed by the clavicle and scapular spine.
The deltopectoral approach provides good exposure of the front of the shoulder and glenohumeral joint. It is suitable for many procedures including arthroplasty. It is performed in the beach chair position. After infiltrating the skin vertical incision is made. If more of the humerus needs to be exposed, an incision angled on to the humerus can be performed instead.
The cephalic vein is identified in the fat stripe between the deltoid and pec major and can be taken medially (where there is less risk of subsequent traction damage) or laterally with the deltoid (which removes the need to cauterise the branches to the muscle. The interval between the pec major and deltoid is then entered to expose the conjoined tendon.
The clavipectoral fascia is then divided just lateral to the short head of biceps, and the conjoined tendon carefully retracted medially to expose the underlying subscapularis, which can be incised along with the capsule to enter the joint.
The main structure at risk at this point is the axillary nerve which passes back just below the lower border of the subscapularis and over the upper border of the lat. dorsi tendons. It then passes through the quadrangular space along with the posterior circumflex artery. It then curls back around the posterior and lateral parts of the surgical neck of the humerus on the undersurface of the deltoid.
It may be helpful to incise the upper portion of the pec major tendon to help locate the nerve as it crosses the upper border of the lat dorsi.
The posterior approach is used for access to the posterior glenoid, labrum and scapular neck for example when treating posterior instability or fractures. A vertical incision is made from the posterolateral corner of the acromion inferiorly. The exposure is continued between the posterior and middle bellies of the deltoid.
The interval between the infraspinatus and teres minor is divided to expose the posterior joint capsule. Care must be take to enter the correct interval as the axillary nerve will be at risk if the interval between the two teres muscles is inadvertently entered.
Other noteworthy anatomical features at the posterior aspect of the shoulder include the course of the suprascapular nerve. This passes back through the supra scapular notch, supplies the supraspinatus, then curves around the spinoglenoid notch to supply the infraspinatus. Thus if the nerve is compressed at the suprascapular notch both the supra and infraspinatus muscles will be affected. If compression occurs at the spinoglenoid notch, weakness and wasting of the infraspsinatus muscle alone will result. Note also the passage of the radial nerve through the triangular space along with the profound brachii artery.
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