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.
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.
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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