Anterior Approach to the Radius
Anterior Approach to the Radius
The anterior approach offers an excellent, safe exposure of the radius, exposing the entire length of the bone. Although the approach can be used for exposure of the volar surface of the distal radius, alternative approaches are available for volar plating in the treatment of wrist fractures which are described on pages 196. Exposing the proximal third of the radius endangers the posterior interosseous nerve. By stripping the supinator muscle off the radius subperiosteally and using it to protect the nerve, however, the anterior approach avoids this danger. Still, great care must be taken in positioning retractors, because the nerve actually may touch the bone at the level of the distal portion of the neck of the radius, opposite the bicipital tuberosity, and posteriorly placed retractors can compress it against the bone. The approach first was described by Henry, and his name usually is associated with it.1
The uses of the anterior approach include the following:
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Open reduction and internal fixation of fractures2
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Bone grafting and fixation of fracture nonunions
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Radial osteotomy
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Biopsy and treatment of bone tumors
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Excision of sequestra in chronic osteomyelitis
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Anterior exposure of the bicipital tuberosity
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Treatment of compartment syndrome
This section describes an approach that exposes the entire length of the bone. Ordinarily, only a portion of the approach is required.
Position of the Patient
Place the patient supine on the operating table, with the arm on an arm board. Place a tourniquet on the arm, but do not exsanguinate it fully before inflating the tourniquet. Venous blood left in the arm makes the vascular structures easier to identify. Finally, supinate the forearm (Fig. 4-1).
Landmarks and Incision
Landmarks
Palpate the biceps tendon, which is a long, taut structure that crosses the front of the elbow joint just medial to the brachioradialis muscle.
Palpate the brachioradialis, which is a fleshy muscle that arises with the extensor carpi radialis longus muscle from the lateral supracondylar ridge of the humerus. These two muscles and extensor carpi radialis brevis which arises from the common extensor origin on the front of the lateral epicondyle form a “mobile wad” of muscle that runs down the lateral aspect of the supinated forearm.
Palpate the styloid process of the radius. Note that this bony process is truly lateral when the hand is in the anatomic (supinated) position. The styloid process is the most distal part of the lateral side of the radius.
Incision
Make a straight incision from the anterior flexor crease of the elbow just lateral to the biceps tendon down to the styloid process of the radius. The length and site of the incision depends on the amount of bone that needs to be exposed and the position of the lesion to be exposed (Fig. 4-2).
Internervous Plane
Distally, the internervous plane lies between the brachioradialis muscle, which is innervated by the radial nerve, just proximal to the elbow joint, and the flexor carpi radialis muscle, which is innervated by the median nerve (Fig. 4-3). Proximally, the internervous plane lies between the brachioradialis muscle, which is innervated by the radial nerve, and the pronator teres muscle, which is innervated by the median nerve.
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Figure 4-1 Position of the patient on the operating table, for the anterior approach to the radius.
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Figure 4-2 Make a straight incision on the anterior part of the forearm, from the flexor crease on the lateral side of the biceps down to the styloid process of the radius.
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Figure 4-3 Internervous plane. The plane lies between the brachioradialis (radial nerve) and the flexor carpi radialis (median nerve).
Superficial Surgical Dissection
Incise the deep fascia of the forearm in line with the skin incision. Identify the medial border of the brachioradialis as it runs down the forearm, and develop a plane between it and the flexor carpi radialis distally. More proximally, the plane lies between the pronator teres and brachioradialis muscles (Fig. 4-4). Note that the medial border of the brachioradialis is surprisingly far across the forearm. At the level of the elbow the brachioradialis extends almost halfway across the forearm. It is surprisingly easy to mistake the plane between brachioradialis and extensor carpi radialis for the correct intermuscular plane. The presence of the sensory branch of the radial nerve serves as a guide since this nerve runs on the underside of the brachioradialis muscle.
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Figure 4-4 Incise the fascia and develop the plane between the brachioradialis and the flexor carpi radialis.
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Figure 4-5 A leash of vessels from the radial artery supplies the brachioradialis. The vessels must be ligated to mobilize the brachioradialis laterally. Retract the superficial branch of the radial nerve with the brachioradialis muscle.
Begin dissection distally and work proximally. Identify the superficial radial nerve running on the undersurface of the brachioradialis and moving with it. The brachioradialis receives a number of arterial branches from the radial artery (called the recurrent radial artery) just below the elbow joint. Ligate this recurrent leash of vessels (Fig. 4-5). Take time and care to ligate these vessels and not avulse them, as avulsion is a potent cause of postoperative hematoma formation. Many vessels are present and all will need to be ligated and divided to allow the brachioradialis to be mobilized laterally. Each artery is usually accompanied by two veins
The radial artery lies beneath the brachioradialis in the middle part of the forearm; therefore, it is quite close to the medial edge of the wound. It runs with its two venae comitantes, which remain prominent if the limb is not exsanguinated before the tourniquet is applied. Often, the artery may have to be mobilized and retracted medially to achieve adequate exposure of the deeper muscular layer, particularly at the upper and lower ends of the approach (see Fig. 4-5).
The superficial radial nerve, which is a sensory nerve in the forearm, also runs under cover of the brachioradialis muscle. Preserve the nerve, because damage to it may create a painful neuroma at the operative site (see Fig. 4-5). It is retracted laterally with the brachioradialis muscle.
Deep Surgical Dissection
Proximal Third
The key to safe exposure of the proximal radius in fixation of very high fractures is the biceps tendon. Follow the biceps tendon to its insertion into the bicipital tuberosity of the radius. Just lateral to the tendon is a small bursa; incise the bursa to gain access to the proximal part of the shaft of the radius. Because the radial artery lies superficial and just medial to the tendon at this point, deepen the wound on the lateral side of the biceps tendon (Fig. 4-6).
The proximal third of the radius is covered by the supinator muscle, through which the posterior interosseous nerve passes on its way to the posterior compartment of the forearm.
The posterior interosseous nerve is the single most important structure left vulnerable by this approach. To displace the nerve laterally and posteriorly (away from the surgical area), fully supinate the forearm, exposing, at the same time, the insertion of the supinator muscle into the anterior aspect of the radius (Fig. 4-7).
Next, incise the supinator muscle along the line of its broad insertion. Ensure that the muscle is detached by dividing its insertion and not by splitting the muscle. Continue subperiosteal dissection laterally, stripping the muscle off the bone (see Fig. 4-7). This is one of the rare examples where the safety obtained by staying in a subperiosteal plane outweighs the vascular damage to the bone caused by stripping off periosteum. Lateral retraction of the muscle lifts the posterior interosseous nerve clear of the operative field, but be careful! Excessive retraction may cause a neurapraxia of the nerve, and it recovers very slowly, taking up to 6 to 9 months. Finally, do not place retractors on the posterior surface of the radial neck, because they may compress the posterior interosseous nerve against the bone in patients whose nerve comes into direct contact with the posterior aspect of the radial neck (about 25% of all patients).3
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Figure 4-6 Deep to the brachioradialis and the flexor carpi radialis are the supinator muscle, the pronator teres, the flexor digitorum superficialis, and, most distally, the pronator quadratus.
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Figure 4-7 With the patient’s arm in the supinated position, resect the insertion of the supinator. Reflect the muscle laterally. Leave the posterior interosseous nerve in the muscle’s substance. The radial nerve enters the supinator through the arcade of Frohse (inset). Turning the forearm upward moves the nerve laterally, away from the operative field. The insertion of the supinator muscle is easier to identify
if the surgeon stays lateral to the biceps tendon and locates the bursa between it and the supinator.
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Figure 4-8 Turn the arm downward to identify the pronator teres muscle. Resect it along its insertion on the lateral aspect of the radius.
Middle Third
The anterior aspect of the middle third of the radius is covered by the pronator teres and flexor digitorum superficialis muscles. To reach the anterior surface of the bone, pronate the arm so that the insertion of the pronator teres onto the lateral aspect of the radius is exposed (Fig. 4-8; see Fig. 4-6). Detach this insertion from the bone and strip the muscle off medially. Preserve as much soft tissue as you can compatible with accurate reduction and fixation of the fracture. This maneuver partially detaches the origin of the flexor digitorum superficialis from the anterior aspect of the radius as well (Fig. 4-9).
Distal Third
Two muscles, the flexor pollicis longus and the pronator quadratus, arise from the anterior aspect of the distal third of the radius. To reach bone, partially supinate the forearm and incise the periosteum of the lateral aspect of the radius lateral to the pronator quadratus and the flexor pollicis longus. Then, continue the dissection distally, retracting the two muscles medially and lifting them off the radius (Fig. 4-10). Controversy exists as whether detaching the origin of pronator quadratus gives superior clinical
results to just dividing the muscle in the line of the skin incision. Detaching the muscle would appear to give a better prospect of repair during closure and to provide a soft tissue pad between the superficial tendons and a volar plate. This is however as yet unproven.4
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Figure 4-9 Continue dissection distally to uncover the distal part of the radius. Leave the periosteum intact.
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Figure 4-10 With the arm in partial supination, remove the flexor pollicis longus and the pronator quadratus from the bone to expose the entire radius from its proximal to distal end.
Dang
Nerves
The posterior interosseous nerve is vulnerable as it winds around the neck of the radius within the substance of the supinator muscle. The key to ensuring its safety is to detach correctly the insertion of the supinator muscle from the radius. The insertion of the muscle is exposed completely only when the arm is supinated fully. In cases where there are extensive contusions in the area begin by identifying the tendon of biceps which is nearly always easy to do. Follow the tendon distally until the bursa is entered. This in turn will lead directly onto the surface of the bone. The origin of the supinator can then be found usually by gently wiping the surface of the muscle with a damp swab. Once the subperiosteal dissection is begun, the nerve is comparatively safe, but overzealous retraction still can lead to a neurapraxia (see Figs. 4-7, inset, and 4-13).
The superficial radial nerve runs down the forearm under the brachioradialis muscle. It becomes vulnerable when the “mobile wad” of three muscles is mobilized and retracted laterally (see Fig. 4-5). The superficial radial nerve is vulnerable to neurapraxia if it is retracted vigorously. Take great care, therefore, when retracting the nerve and warn your patients preoperatively that temporary paresthesia in the distribution of the superficial branch of the radial nerve may occur in the early postoperative phase.
Vessels
The radial artery runs down the middle of the forearm under the brachioradialis muscle. It is vulnerable twice during the anterior approach to the radius:
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During mobilization of the brachioradialis. Protection depends on recognizing the artery. Its two accompanying venae comitantes are the best surgical guide, because the artery is surprisingly small after a tourniquet has been used (see Fig. 4-5).
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In the proximal end of the wound, as the artery passes to the medial side of the biceps tendon. Damage to the artery at that level can be avoided by remaining lateral to the tendon (see Fig. 4-13).
The recurrent radial arteries are a leash of vessels that arise from the radial artery just below the elbow joint. They consist of two groups, anterior and posterior, which pass in front of and behind the superficial
radial nerve, respectively, before entering the brachioradialis muscle. They must be ligated to allow mobilization of both the artery and the nerve (see Figs. 4-9 and 4-12).
How to Enlarge the Approach
The anterior approach provides complete access to the entire length of the radius. The approach can be extended distally to expose the wrist joint.5 Although it can be extended into an anterolateral approach to the elbow and humerus, such extension rarely is required.