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8

LATERAL APPROACH TO THE HUMERUS

USES

This approach is used primarily for fracture work.

ADVANTAGES

This approach is internervous because the anterior musculature of the biceps and brachialis is innervated by the musculocutaneous nerve and the triceps is innervated by the radial nerve. Campbell and Hoppenfeld describe this approach as the anterolateral approach to the humerus, and both describe splitting the brachialis muscle. But splitting the brachialis muscle risks denervating the lateral half of the muscle by cutting the small nerves crossing laterally.

DISADVANTAGES

For fractures of the midshaft, this is an excellent approach. However, if the fracture line extends distally, then this approach provides poor visualization to the posterior aspect of the humerus where internal fixation will frequently need to be placed.

STRUCTURES AT RISK

The major structure at risk with this approach is the radial nerve, which crosses from posterior to anterior in the region of the junction of the middle and distal thirds. This nerve must be identified in all plating of the humerus and protected. The key landmark for finding the radial nerve is the fibers of the brachioradialis. Since these fibers come in perpendicular to the shaft of the humerus, they can generally be fairly easily differentiated from the fibers of the biceps or triceps. The nerve crosses around the lateral aspect of the humerus just proximal to the muscle origin.

TECHNIQUE

A straight midline lateral approach is used through the subcutaneous tissue. The biceps is identified anteriorly, the triceps posteriorly, and the usually easy palpable interval between them is developed. The humerus is generally palpable at that point. In the region of the deltoid insertion laterally, you can cut straight down on the humerus. Once you are at the area of the midhumerus, care needs to be taken to identify the radial nerve before cutting directly down on the bone. Once the humerus is exposed, the appropriate procedure can be done. The brachialis can be reflected in its entirety medially with a Bennett retractor.

TRICKS

As just stated, the deltoid insertion on the lateral humerus is a guide to the interval between the biceps and triceps. The other major trick with this approach is to identify the fibers of the brachioradialis, because they act as a warning sign for the radial nerve. If you are working proximal to where the radial nerve crosses lateral to the humerus, a Bennett retractor posterior to the humerus protects the radial nerve.

HOW TO TELL IF YOU ARE LOST

It is possible to be too far anterior or posterior with this approach, especially in overweight patients who do not have much muscle definition. It is difficult to tell whether you are lost anteriorly or posteriorly because both the biceps and the triceps fibers are running parallel to the humerus. The main thing to do is feel the humerus. The deltoid insertion is a good landmark more proximally. It is in the interval between the biceps and the triceps. Once you find that insertion, you will also find the interval between those muscles, which will guide you directly to the humerus.

FIGURE 8–1 The skin incision.

FIGURE 8–2 The subcutaneous tissue spread showing the underlying muscle. The posterior aspect of the biceps is visible.

FIGURE 8–3 The interval between the biceps and triceps developed so that there is ready access to the humeral shaft.

FIGURE 8–4 The biceps anterior to the brachialis origin and the triceps posterior.

Biceps

Triceps

Humerus

Radial Nerve

Deltoid Insertion

FIGURE 8–5 The dissection proceeding proximally, showing the fibers of the deltoid coming in obliquely along with the white deltoid insertion.

FIGURE 8–6 The incision extended distally, showing the radial nerve as it starts to wrap around the humerus coming from posterior to anterior at the junction of the middle and distal thirds.

Biceps

Triceps

Humerus

Radial Nerve

Deltoid Insertion