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SUPERIOR APPROACH TO THE SUPRASCAPULAR NERVE

USES

This approach is used primarily to release the suprascapular notch in cases of suprascapular nerve entrapment. It also allows exposure of the lateral portion of the trapezius and the supraspinatus muscle belly.

ADVANTAGES

By approaching the nerve from the posterior side, we avoid all the vascular structures anteriorly and the brachial plexus. Also, this approach allows the branch of the nerve to the infraspinatus to be freed simply by taking the posterior deltoid off of the spine of the scapula and coming down onto the region of the nerve.

DISADVANTAGES

For the purposes for which it is intended, this approach does not have disadvantages.

STRUCTURES AT RISK

Posteriorly, there are no significant structures at risk. The trapezius is lifted off of the spine of the scapula subperiosteally to promote the ease of the repair. If the repair of the trapezius is not done carefully, the potential for its avulsion exists.

The suprascapular artery will not uncommonly pass superior to the suprascapular ligament while the nerve goes underneath it. You cannot indiscriminately release the ligaments until you are sure that there is no artery at risk. If there is, be sure to gently retract it out of the way before releasing the ligament.

TECHNIQUE

The incision is made just superior to the scapular spine and typically is 6 or 7 cm in length. You go through the subcutaneous tissue until you encounter the fascia overlying the trapezius muscle. Palpate the spine of the scapula and strip the trapezius muscle along with its periosteum off of the scapula. As you are moving anteriorly through the trapezius, be aware of the orientation of the fibers. When you come to the fibers running medially and laterally, you are looking at the supraspinatus muscle and you want to stay on top of that muscle. Strip as much trapezius as necessary to obtain adequate visualization.

Once the supraspinatus is clearly in view, palpate the base of the coracoid and move slightly medially until you can feel the ligament overlying the suprascapular notch. This ligament is frequently covered with fat. If there is a large amount off at between the two muscles, then remove it or retract it so you can see the supraspinatus and the suprascapular ligament. Remember that the artery will sometimes pass on top of the ligament, whereas the nerve will be below it.

Once the ligament is identified, it can be transected with a scalpel or, for better control, a Kerrison rongeur can be used.

TRICKS

The major trick to this approach is to identify the interval between the trapezius and the supraspinatus. There is usually fat between these two muscles, and the fiber orientation is different.

The second trick is to feel the base of the coracoid and then go medial to that to feel the suprascapular notch. Finally, be aware of the fact that the artery may cross over the top of the ligament, and take care not to injure it.

HOW TO TELL IF YOU ARE LOST

It is hard to get lost inferiorly with this approach because the incision starts above the spine of the scapula, and the spine is easily palpable.

It is possible to be too far medial or lateral. If your goal is to free up the suprascapular notch, it is important to realize it is approximately 1 cm medial to the coracoid base, so that the approach can be adjusted once you are deep to the trapeziusand the coracoid base is then palpable.

It is also possible to be too deep and separate the supraspinatus muscle off of the spine of the scapula and its fossa along with the trapezius. Coming in underneath the supraspinatus muscle does put the suprascapular nerve at risk. It is important, therefore, to clearly identify the plane between the trapezius and the supraspinatus. The fiber orientation is different for the two muscles, and so if you see fibers running straight medial to lateral, you are looking at the supraspinatus, not the trapezius.

FIGURE 5–1 The skin incision superior to the spine of the scapula.

FIGURE 5–2 The trapezius muscle approaching the spine of the scapula.

FIGURE 5–3 The spine of the scapula and the trapezius muscle being separated from it. Note that there is a large amount of fat beneath the trapezius, which is usually a good clue to the interval between the trapezius and the supraspinatus.

FIGURE 5–4 The fat cleared out of the way. The trapezius is retracted anteriorly. The muscle belly of the supraspinatus is clearly visible.

Spine of Scapula

Trapezius

Fat Above Supraspinatus

Supraspinatus

Vessel Over Top of Ligament

Suprascapular Ligament

Suprascapular Nerve in Notch

Cut End of Ligament

FIGURE 5–5 The supraspinatus being held in a posterior direction. The trapezius is retracted anteriorly. The suprascapular ligament is clearly visualized. Note the artery coming over the top of the ligament.

FIGURE 5–6 The view after the ligament has been cut. The suprascapular nerve is clearly visible now that the ligament has been transected.