Читать книгу Atlas of Orthopaedic Surgical Exposures - Christopher Jordan - Страница 19
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POSTERIOR APPROACH TO THE DISTAL HUMERUS
USES
This approach is used primarily for fracture work in the distal humerus. It is occasionally used for radial nerve explorations.
ADVANTAGES
If you are distal to where the radial nerve comes behind the humerus, this is a safe approach in an area that is devoid of nerves or arteries. It provides the best visualization of the distal humerus. There is a saying that the front door to the elbow is in the back. It is the preferred approach for supracondylar and intracondylar fractures of the distal humerus. Campbell calls this the posterior lateral approach to the elbow.
DISADVANTAGES
The upper end of the approach can place the radial nerve at risk. It also provides no access to the anterior aspect of the humerus or elbow. At its most distal extent, the ulnar nerve can also be damaged as it passes behind the medial epicondyle.
STRUCTURES AT RISK
The radial nerve is the major structure at risk with this approach. It typically crosses the back of the humerus several centimeters proximal to the brachioradialis origin. Once the nerve is lateral to the humerus, it will then go underneath the brachioradialis and enter the forearm protected by that muscle. If the dissection is carried proximal to the junction of the middle and distal thirds, then the radial nerve is at risk and the dissection needs to be done very carefully as you go proximally.
In the exposure of the medial and lateral pillars of the distal humerus, the ulnar nerve can be damaged on the medial side. It will cross from anterior to posterior behind the medial epicondyle. It is usually necessary to identify the medial epicondyle and to transpose it anteriorly when doing complex fractures of the distal humerus. It is important to remember the location of this nerve and to protect it with this dissection. Because the triceps is split in line with its fibers, there is usually no functional problem with that muscle postoperatively.
TECHNIQUE
This procedure is done with the patient lying face down or at least with the opposite side down and the arm supported on a bolster, so that the posterior portion of the humerus is facing upward. At that point, the midline incision is made. It is carried through the subcutaneous tissue and through the triceps in line with its fibers down to the humerus. As you approach the elbow, either the triceps is reflected off of the olecranon or an olecranon osteotomy is done. This then allows the triceps to be retracted in its entirety exposing the back of the distal humerus. The radial nerve is usually not encountered in the approaches to the distal humerus. It will be seen underneath, that is, deep to the triceps, as you go more proximally. For the distal medial dissection, the ulnar nerve needs to be identified and separated from its underlying tissues and allowed to fall in an anterior direction.
TRICKS
There are no special tricks with this approach except to protect the nerves.
HOW TO TELL IF YOU ARE LOST
It is difficult to get lost in this approach because it is a midline approach. The major way you can get lost is by being too far proximal or distal for the pathology, and then you simply need to extend your incision.
FIGURE 9–1 The skin incision starting 10 cm from the olecranon and going distally.
FIGURE 9–2 The subcutaneous tissue spread with the fibers of the triceps running toward the olecranon.
FIGURE 9–3 The triceps split with the humerus seen in the depth of the incision.
FIGURE 9–4 The tissue retracted such that the olecranon and posterior elbow joint are visible. The olecranon fossa has also been cleaned out and is visible.
FIGURE 9–5 The ulnar nerve on the ulnar side. This is at risk if the triceps is going to be retracted completely off the distal humerus.
FIGURE 9–6 The proximal extension of the dissection with the radial nerve just barely visible.
FIGURE 9–7 The radial nerve now more thoroughly exposed as the overlying triceps is split.
Triceps
Humerus
Triceps Split
Olecranon Fossa
Olecranon
Ulnar Nerve
Radial Nerve