Читать книгу Atlas of Orthopaedic Surgical Exposures - Christopher Jordan - Страница 22

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POSTEROLATERAL APPROACH

USES

This approach is the lateral equivalent of the approach to the ulnar nerve. The incision stays behind the lateral epicondyle and thus is useful for fractures of the capitellum and for open reductions and internal fixation of the distal humerus and the radial head. The exposure is useful for lateral ligament repairs around the elbow and for contracture releases around the elbow. This approach is a combination of Hoppenfeld's lateral approach to the distal humerus and the posterolateral approach to the radial head. Campbell calls it the lateral and lateral J approach.

ADVANTAGES

This approach gives a good view of the lateral elbow and capitellum area. Also, by staying somewhat posterior, the radial nerve is less at risk.

DISADVANTAGES

It is difficult to visualize the posterior aspect of the humerus for comminuted fractures through this approach. The approach, therefore, is limited to either fractures of the capitellum or two-part supracondylar fractures. The approach is difficult to extend proximally or distally because of the radial nerve.

STRUCTURES AT RISK

The major structure at risk is the radial nerve. The radial nerve wraps around the humerus, and at the junction of the middle and distal thirds of the humerus the nerve is usually posterior. From there, it comes along the lateral border to enter the forearm anteriorly. The radial nerve can be transected if the brachioradialis is stripped off of its humeral origin because the nerve will have to come around the humerus right along the proximal edge of this muscle.

The blood supply to the capitellar fragment can be destroyed if all the soft tissue attaching to that lateral piece is removed. The blood supply to the capitellum is quite precarious and, especially in children, the soft tissue attachments need to be handled gently.

TECHNIQUE

The incision is centered on the lateral epicondyle and 1 cm posterior to it. It is carried as far proximal or distal as necessary. The incision goes through the subcutaneous tissue. The tissue plane between the brachioradialis anteriorly and the triceps posteriorly is developed. The fascia is split starting at the lateral epicondyle and proceeding in that interval along the humerus proximally. It is critical not to carry sharp dissection into or underneath the brachioradialis muscle. The dissection should be done bluntly. When the elbow capsule is identified, it can be opened as in the anconeus approach (see Case 12). Once the posterior aspect of the humerus is identified, the bone can be exposed safely.

TRICKS

The major trick is to identify the humerus by palpating the lateral epicondyle and following the bone proximally, exposing the anterior and posterior sides of the humerus as needed. The radial nerve wraps around the lateral edge of the humerus approximately 6 cm proximal to the lateral epicondyle. It is protected by the brachioradialis muscle so that as soon as the more posterior fibers of the brachioradialis are identified, there should be no further stripping along the humerus. If, for some reason, you need to expose the humerus more proximally along its lateral border, then the radial nerve should be identified underneath the brachioradialis muscle prior to exposing the humerus.

HOW TO TELL IF YOU ARE LOST

There is no difficulty in identifying that you are lost too far posteriorly. You will simply run into the triceps with its fibers parallel to the humerus if you are lost in the proximal part of the incision. If you see the longitudinal fibers of the triceps, but are not seeing its anterior edge, you are too far posterior. You will run into the subcutaneous portion of the ulna in the distal part of the incision if you are too posterior.

The landmark anteriorly is the brachioradialis muscle. This is an important landmark because the radial nerve enters the forearm just underneath this muscle. With the elbow flexed, which is usually the way the procedure is done, the brachioradialis runs from a position 4 cm proximal to the lateral epicondyle down toward the distal radius in a straight line. If you see fibers running in that direction, you are too far anterior.

FIGURE 11–1 The skin incision.

FIGURE 11–2 The triceps running along the humerus posteriorly. The fibers of the brachioradialis are perpendicular to the triceps.

FIGURE 11–3 The brachioradialis coming into the humerus. This is a large muscle with a broad insertion into the humerus spanning 4 cm or more.

FIGURE 11–4 The brachioradialis lifted anteriorly exposing the radial nerve just underneath it. The nerve has not yet divided at this point.

Triceps

Brachioradialis

Humerus

Radial Nerve

Brachioradialis Lifted Anteriorly

Capitellum

Radial Head

FIGURE 11–5 The nerve and brachioradialis retracted anteriorly. The triceps is posterior. The capitellum is easily visualized, as is the radial head.