Posterior Approach to the Humerus
Posterior Approach to the Humerus
The midline posterior approach to the humerus is classically extensile, providing excellent access to the lower three-fourths of the posterior aspect of the humerus.1,10 As is true for all other approaches to the humerus, the posterior approach is complicated by the vulnerability of the radial nerve, which spirals around the back of the bone. The uses of this surgical approach include the following:
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Open reduction and internal fixation of fractures of the humerus. In fractures in which the radial nerve is transected (classically displaced transverse fractures of the mid shaft of the humerus), this incision exposes the nerve as it traverses the back of the humerus.
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Treatment of osteomyelitis
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Biopsy and excision of tumors
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Treatment of nonunion of fractures
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Exploration of the radial nerve in the spiral groove
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Insertion of retrograde humeral nails
Position of the Patient
Two positions of the patient are possible during surgery: a lateral position on the operating table with the affected side uppermost (Fig. 2-14A) or a prone position on the operating table with the arm abducted 90 degrees (Fig. 2-14B). A sandbag should be placed under the shoulder of the side to be operated on, and the elbow should be allowed to bend and the forearm to hang over the side of the table. A tourniquet should not be used because it will get in the way.
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Figure 2-14 Position of the patient for the approach to the upper arm in either the
(A) lateral or (B) prone position.
Landmarks and Incision
Landmarks
The acromion is a rectangular bony prominence that forms the summit of the shoulder.
The olecranon fossa should be palpated at the distal end of the posterior aspect of the arm. Precise palpation is difficult, because the fossa is filled with fat and covered by a portion of the triceps muscle and aponeurosis. The fossa is filled by the olecranon when the elbow is extended.
Incision
Internervous Plane
There is no true internervous plane; dissection involves separating the heads of the triceps brachii muscle, all of which are supplied by the radial nerve. Because the nerve branches enter the muscle heads relatively near their origin and run down the arm in the muscle’s substance, splitting the
Superficial Surgical Dissection
Incise the deep fascia of the arm in line with the skin incision (Fig. 2-16).
The key to superficial dissection lies in understanding the anatomy of the triceps muscle. This muscle has two layers. The outer layer consists of two heads: the lateral head arises from the lateral lip of the spiral groove, and the long head arises from the infraglenoid tubercle of the scapula. The inner layer consists of the third head, the medial (or deep) head, which arises from the whole width of the posterior aspect of the humerus below the spiral groove all the way down to the distal fourth of the bone. The spiral groove contains the radial nerve; thus, the radial nerve actually separates the origins of the lateral and medial heads (see Fig. 2-47).
To identify the gap between the lateral and long heads, begin proximally, above the point at which the two heads fuse to form a common tendon (Fig. 2-17). Proximally, develop this interval between the heads by blunt dissection, retracting the lateral head laterally and the long head medially. Distally, the muscle will need to be divided by sharp dissection along the line of the skin incision (Figs. 2-18; see Fig. 2-46). Many small blood vessels cross the muscle at this level; these need to be coagulated individually.
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Figure 2-15 Make a longitudinal incision in the midline of the posterior aspect of the arm, from 8 cm below the acromion to the olecranon fossa.
Deep Surgical Dissection
The medial head of the triceps muscle lies below the other two heads; the radial nerve runs just proximal to it in the spiral groove (see Fig. 2-18). Incise the medial head in the midline, continuing the dissection down to
the periosteum of the humerus. Then, strip the muscle off the bone by epiperiosteal dissection (Fig. 2-19). The plane of operation must remain in an epiperiosteal location to avoid damaging the ulnar nerve, which pierces the medial intermuscular septum as it passes in an anterior to posterior direction in the lower third of the arm (see Figs. 2-19 and 2-48). Detach as little soft tissue as possible to preserve blood supply to the zone of injury.
Dang
Nerves
The radial nerve is vulnerable in the spiral groove. However, after it is identified, the nerve is safe. To avoid problems, never continue the dissection down to bone in the proximal two-thirds of the arm until the nerve has been identified positively (see Fig. 2-18).
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Figure 2-16 Incise the deep fascia of the arm in line with the skin incision.
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Figure 2-17 Identify the gap between the lateral and long heads of the triceps muscle.
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Figure 2-18 Proximally develop the interval between the two heads by blunt dissection, retracting the lateral head laterally and the long head medially. Distally split their common tendon along the line of the skin incision by sharp dissection. Identify the radial nerve and the accompanying profunda brachii artery.
Vessels
The profunda brachii artery lies with the radial nerve in the spiral groove and is similarly vulnerable (see Fig. 2-18).
How to Enlarge the Approach
Extensile Measures
Proximal Extension. The bone cannot be exposed effectively above the spiral groove using the posterior approach. At this point, the deltoid muscle (which is the outer layer of the musculature) also crosses the operative field. More proximal exposures should be accomplished by the anterior route.
Distal Extension. The skin incision can be extended distally over the olecranon; deepening the approach provides access to the elbow joint via an olecranon osteotomy (see Posterior Approach to the Elbow in Chapter 3; Figs. 2-20 and 2-21). Alternatively, identify and dissect out the ulna nerve. Develop a plane between the medial aspect of the triceps muscle and the bone to expose the medial supracondylar ridge of the humerus (Fig. 2-21D). Then develop a plane on the lateral aspect of the triceps between the tendon and the bone. Retract the muscle medially to expose the lateral supracondylar ridge of the humerus (Fig. 2-21C). Pass a sling underneath the triceps and retract the muscle medially and laterally to gain access to the whole of the posterior aspect of the distal humerus (Fig. 2-21E).
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Figure 2-19 Incise the medial head of the triceps in the midline. Strip the muscle off the bone subperiosteally. The radial nerve, which runs just proximal to the origin of the muscle in the spiral groove, must be identified and preserved. The muscle must be stripped from the bone below the level of the periosteum to avoid damaging the ulnar nerve, which pierces the medial intermuscular septum. Preserve as much soft-tissue attachment to the bone as possible.
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Figure 2-20 The incision can be extended distally over the olecranon to give access to the elbow joint via an olecranon osteotomy. Proximal extension cannot be used effectively above the spiral groove because of the position of the radial nerve.
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Figure 2-21 (A) To extend the approach distally, extend the skin incision over the olecranon and subcutaneous border of the ulna. (B) Deepen the incision to expose
the triceps tendon. Identify and dissect out the ulnar nerve. (C) Develop a plane on the lateral aspect of the triceps muscle belly and tendon. Retract the muscle medially to expose the lateral supracondylar ridge of the humerus. (D) Develop a plane on the medial aspect of the triceps muscle belly and tendon. Retract the muscle laterally to expose the medial supracondylar ridge of the humerus. (E) Pass a sling underneath the triceps and retract the muscle medially and laterally to gain access to the whole of the posterior aspect of the distal humerus.