Dorsolateral Approach to the Scaphoid

The dorsolateral approach offers an excellent and safe exposure of the scaphoid bone. Its major drawback is that it endangers the superficial branch of the radial nerve, and it also may interfere with the dorsal blood supply of the scaphoid.41 Its uses include the following:

1. Bone grafting for nonunion

2. Excision of the proximal fragment of a nonunited scaphoid

3. Excision of the radial styloid in combination with either of the two above procedures

4. Open reduction and internal fixation of fractures of the scaphoid. When this approach is used for this indication, it is frequently combined with a volar approach to the scaphoid.40

5. Repair of complete ruptures of the scapholunate ligament

Position of the Patient

Place the patient supine on the operating table, with the arm extended on an arm board. Pronate the forearm to expose the dorsoradial aspect of the wrist, and apply an exsanguinating bandage and tourniquet (see Fig. 5-1).

Landmarks and Incision

Landmarks

The radial styloid process is truly lateral when the hand is in the anatomic position. Palpate it in this position and then pronate the arm, keeping a finger on the styloid process.

The anatomic snuff-box is a small depression that is located immediately distal and slightly dorsal to the radial styloid process. The scaphoid lies in the floor of the snuff-box. Ulnar deviation of the wrist causes the scaphoid to slide out from under the radial styloid process, and

it becomes palpable. The radial pulse is palpable in the floor of the snuff-box, just on top of the scaphoid.

The first metacarpal can be palpated between the snuff-box and the metacarpophalangeal joint.

Incision

Make a gently curved, S-shaped incision centered over the snuff-box. The cut should extend from the base of the first metacarpal to a point about 3 cm above the snuff-box (Fig. 5-67).

Internervous Plane

There is no true internervous plane, because the plane of dissection falls between the tendons of the extensor pollicis longus and extensor pollicis brevis muscles, both of which are supplied by the posterior interosseous nerve. Because both muscles receive their nerve supply well proximal to this dissection, using this plane does not cause denervation.

Superficial Surgical Dissection

Identify the tendons of the extensor pollicis longus muscle dorsally and the extensor pollicis brevis muscle ventrally (Fig. 5-68). To confirm their identity, pull on the tendons and observe their action on the thumb. Open the fascia between the two tendons, taking care not to cut the sensory branch of the superficial radial nerve, which lies superficial to the tendon of the extensor pollicis longus muscle. Usually the radial nerve has divided into two or more branches at this level. Both branches cross the interval between the tendons of the extensor pollicis brevis and the extensor pollicis longus, lying superficial to the tendons. Their course is variable, and they must be sought and preserved during superficial dissection (see Figs. 5-67 and 5-68).

Figure 5-67 Incision for dorsolateral approach to the scaphoid. Make a gently curved S-shaped incision centered over the snuff-box. The superficial branch of the radial nerve crosses directly beneath the incision.

Now, separate the tendons, retracting the extensor pollicis longus dorsally and toward the ulna, and the extensor pollicis brevis ventrally. Identify the radial artery as it traverses the inferior margin of the wound, lying on the bone (Fig. 5-69). Find the tendon of the extensor carpi radialis longus muscle as it lies on the dorsal aspect of the wrist joint. Mobilize it and retract it in a dorsal and ulnar direction, together with the tendon of the extensor pollicis longus muscle, to expose the dorsoradial aspect of the wrist joint.

Deep Surgical Dissection

Incise the capsule of the wrist joint longitudinally (Fig. 5-70). Reflect the capsule dorsally and in a volar direction to expose the articulation between the distal end of the radius and the proximal end of the scaphoid. The radial artery retracts radially and in a volar direction with the joint capsule.

Place the wrist in ulnar deviation and continue stripping the capsule off the scaphoid to expose the joint completely (Fig. 5-71). Try to preserve as much soft tissue attachments to the bone as possible especially in the region of the dorsal ridge. Modern aiming guides have substantially reduced the need for radial dissection in open reduction and internal fixation of scaphoid fractures.

Figure 5-68 Identify the superficial branch of the radial nerve and retract it with the dorsal skin flap. Identify the tendons of the extensor pollicis longus dorsally and the extensor pollicis brevis ventrally. Incise the fascia between the tendons.

Figure 5-69 Retract the extensor pollicis longus dorsally and the extensor pollicis brevis ventrally. Identify the radial artery and its dorsal carpal branch, taking care to preserve the arterial branch.

Figure 5-70 Incise the joint capsule. The scaphoid is exposed.

Figure 5-71 Place the wrist in ulnar deviation to expose the proximal third of the scaphoid in its entirety.

Figure 5-72 Blood supply to the scaphoid. Most branches enter the scaphoid from the dorsal aspect. These branches must be preserved to prevent necrosis of its proximal fragment.

Dang

Nerves

The superficial radial nerve is at risk during this exposure. Because it lies directly over the tendon of the extensor pollicis longus muscle, it is extremely easy to cut as the tendon is mobilized. Incising the nerve may produce a troublesome neuroma, as well as an awkward (although not handicapping) area of hypoesthesia on the dorsal aspect of the hand.

Arteries

The blood supply to the proximal pole of the scaphoid comes from the dorsal carpal branch of the radial artery (see Fig. 5-72). These branches are at risk during incision of the joint capsule and must be preserved if possible.