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.
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.
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DELTOID SPLITTING APPROACH
USES
This approach is used for anterior acromioplasties if they are done open. It is usually used for rotator cuff repairs and for fractures of the humerus where a rod(s) will be started proximally in the region of the greater tuberosity. Hoppenfeld calls this the lateral approach.
ADVANTAGES
This approach is easy, as it comes directly down on the pathology and can also be extended anteriorly and posteriorly by taking the deltoid off of the acromion subperiosteally.
DISADVANTAGES
This approach is limited inferiorly by the axillary nerve, which usually crosses below, 5 cm distal to the acromion. If the axillary nerve is cut, the entire anterior deltoid will be denervated and shoulder flexion will be markedly impaired. The nerve has been seen as high as within 4 cm of the acromion.
STRUCTURES AT RISK
The only significant structure at risk is the axillary nerve, but it is not a problem as long as distal splitting of the deltoid is limited to the safe zone.
TECHNIQUE
The incision usually starts 1 cm proximal, that is, superior, to the lateral edge of the acromion, crosses the edge of the acromion, and proceeds distally. A so-called saber incision can be made from anterior to posterior, 1 cm distal to the edge of the acromion. Once deep to the skin, the approach is the same. The incision should not go beyond 5 cm distal to the lateral edge of the acromion. Splitting the deltoid more distally than that puts the axillary nerve at risk. The subcutaneous tissue is split. The fascia overlying the deltoid is split and its fibers are separated. The bursa is then encountered, which can be split or resected. This brings you down on the rotator cuff tendons. For greater exposure, you can subperiosteally take the deltoid off anteriorly or posteriorly.
TRICKS
Subperiosteal stripping of the deltoid allows this approach to be extended anteriorly or posteriorly and provides greater exposure. Distal splitting of the deltoid down to the axillary nerve also provides greater exposure. Any distal splitting beyond 4 cm should be done with the use of a nerve stimulator guiding the dissection, so that the axillary nerve going to the anterior deltoid is not inadvertently transected.
Repair of the deltoid is critical. It should be done through drill holes