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POSTERIOR APPROACH

USES

This approach is used primarily for posterior capsular shift procedures. It would also be useful for scapular neck osteotomies and posterior dislocations, as well as for open reductions and internal fixations of the glenoid.

ADVANTAGES

For posterior dislocators, this is the only suitable approach.

DISADVANTAGES

This approach is made more difficult by the size of the muscles overlying the bone and shoulder capsule. Also, the neurovascular structures at the inferior aspect of the incision must be protected.

STRUCTURES AT RISK

The major structure at risk is the neurovascular bundle coming through the quadrilateral space. This should be well inferior to the intended approach. If you are too far superomedial, the suprascapular nerve to the infraspinatus, which wraps around the base of the spine of the scapula, could be damaged.

TECHNIQUE

The incision usually starts 1 cm superior and 1.0 to 1.5 cm medial to the posterolateral corner of the acromion. This bony prominence is palpable even in heavy or well-muscled patients. It is useful to place a needle into the shoulder joint to help guide the medial or lateral placement of the incision. The incision goes through the subcutaneous tissue down to the deltoid muscle. In some patients the deltoid can be retracted in its entirety anteriorly. In most patients, the incision ends up splitting the fibers of the deltoid in line with the fibers. It is important when doing so to be aware that there may be branches of the axillary nerve coming back toward this posterior corner of the deltoid, which should be avoided. Once you are deep to the deltoid, you will see the fibers of the infraspinatus. It is easy to tell them apart because the orientation of the fibers is at 90 degrees to those of the deltoid.

At that point, the shoulder joint is usually palpable. The infraspinatus can either be taken off of the area of its insertions, similar to what is done to the subscapularis when approaching the shoulder from the anterior, or it can be split in line with its fibers, which is less destructive. It is very important to stay superior to the teres minor. It is often difficult to find the interval between the infraspinatus and the teres minor. The lower border of the teres, however, is usually visible. Stay 1.5 cm to 2.0 cm proximal to that. Deep to the infraspinatus, you will encounter the shoulder capsule. The posterior capsule is much thinner than the anterior capsule in most patients and can be almost paper-thin and translucent. The capsule is then opened to enter the shoulder joint itself.

Both Campbell and Hoppenfeld describe an approach with an incision along the scapular spine. That approach requires taking the deltoid off the scapula. The approach described here is also described by Tibone (The Shoulder, Lippincott-Raven, 1997) and is less destructive.

TRICKS

The major trick for proper placement of the incision, if the goal is to do a posterior capsular shift, is to place a needle into the shoulder joint like you would do for shoulder arthroscopy. This will then identify where the incision needs to be from the medial or lateral standpoint. The other trick is to identify the infraspinatus by its fiber orientation. Finally, beware of fat at the inferior portion of the teres minor because that will usually indicate the area of the neurovascular bundle.

HOW TO TELL IF YOU ARE LOST

Because of the thickness of the overlying musculature and the depth of the bones, it is relatively easy to drift too far in one direction or another with this approach, which would require extending the approach to give you access back to where you want to be.

The main way to tell if you are lost is to palpate deep to the deltoid. The shoulder is usually palpable through the infraspinatus. The infraspinatus is then split in line with its fibers. If you are too superior or inferior, again you can adjust the area through which the fibers are split. There is no significant interval between the infraspinatus and the teres minor.

If you are lost superiorly, you will simply run into the acromion, which will be easily palpable and will be in your way, making it obvious that you are too superior. If you are lost inferiorly, you will see the fat in the quadrilateral space. Be very careful if you see this fat.

FIGURE 2–1 The skin incision.

FIGURE 2–2 The deltoid muscle and the fascia underlying the subcutaneous fat.

FIGURE 2–3 The deltoid muscle split.

Fascia Over Deltoid

Infraspinatus

Posterior Lateral Acromion Border

Deltoid

Capsule

Humeral Head

FIGURE 2–4 A close-up of the infraspinatus fibers.

FIGURE 2–5 The capsule opened and the humeral head in the depth of the incision.