Dorsal approach to the scaphoid

Introduction

Indications

• ORIF of fractures of the scaphoid;  frequently combined with a volar approach to the scaphoid.
• Bone grafting for nonunion.
• Excision of the proximal fragment of a nonunited scaphoid.
• Excision of the radial styloid as a bone graft for scaphoid nonunion.

Advantage

• Excellent and safe exposure of the scaphoid bone.

Disadvantage

• Endangers the superficial branch of the radial nerve.
• Interferes with the dorsal blood supply of the scaphoid.

Position of patient

• Place the patient supine, with the arm extended and pronated.
• Apply a tourniquet after exsanguinating the arm with a bandage.

Landmarks and incision

Landmarks

• The radial styloid process is palpated on the lateral aspect of the wrist joint.
• 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.
• The first metacarpal can be palpated between the snuff-box and the metacarpophalangeal joint.

Incision

• S-shaped incision centered over the snuff-box, extending from the base of the first metacarpal to a point about 3 cm above the snuff-box.

Internervous plane

• No true internervous plane; the plane falls between the tendons of the EPL and EPB muscles, both supplied by the posterior interosseous nerve.
• Both muscles receive their nerve supply well proximal to this dissection; using this plane does not cause denervation.

Superficial dissection

• The EPL is identified dorsally and the EPB ventrally, confirmed by pulling on the tendons and observing their action on the thumb.
• Incise the fascia between the two tendons, taking care not to cut the sensory branch of the superficial radial nerve.
• Separate the tendons, retracting the EPL dorsally and toward the ulna and the EPB ventrally.
• Identify the radial artery as it traverses the inferior margin of the wound, lying on the bone.
• Find the tendon of the ECRL 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 EPL exposing the dorsoradial aspect of the wrist joint.

Deep dissection

• Incise the capsule of the wrist joint longitudinally and reflect it 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.

Dangers

Superficial radial nerve

• At risk during this exposure, as it lies directly over the tendon of the EPL; incising it produce a neuroma.
• The radial nerve has usually divided into two or more branches at this level; both branches cross the interval between the tendons of the EPB and the EPL, lying superficial to the tendons. Their course is variable, and they must be sought during superficial dissection.

How to enlarge the approach

The approach can't be extended proximally or distally.

Figures