ORIF through dorsal approach - Antegrade screw fixation for Scaphoid waist fracture

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Introduction

For the fixation of waist fractures of the scaphoid, headless compression screws (2.4 or 3.0 mm) may be used in an antegrade fashion through a dorsal approach.

$Scaphoid waist fracture – headless compression screw used in an antegrade fashion through a dorsal approach$

Antegrade vs retrograde screw insertion

The anatomy of the carpus limits the positioning of fixation devices along the true central axis of the scaphoid. In proximal pole fractures and most waist fractures, an antegrade screw insertion using a dorsal approach allows for a more accurate and reliable center-axis screw placement.

$Scaphoid waist fracture - in proximal pole fractures and most waist fractures, antegrade screw insertion using a dorsal approach allows for a more accurate and reliable center-axis screw placement$

This illustration shows the screw placement with a palmar approach.

Note the eccentric position of the screw within the scaphoid in the lateral view.

$Scaphoid waist fracture - screw placement with a palmar approach$

Arthroscopically assisted screw fixation

Alternatively, to an open dorsal approach, fracture management can be performed using arthroscopy, which helps control the reduction and can identify concomitant occult ligament injuries. This is technically demanding.

The thumb is usually in a finger trap for reduction with traction. If further reduction is needed, use percutaneous K-wires as joysticks and temporarily fix the fracture with a K-wire from proximal to distal.

Thumb suspended in a finger trap to apply traction to assist reduction of fragments and/or dislocations in the wrist

Comminuted scaphoid fractures

In case of a wedge fracture or comminution, a temporary K-wire may help to maintain the anatomy during screw insertion.

It is recommended to remove this K-wire after fracture compression.

$Comminuted scaphoid fracture$

Anatomical considerations

80% of the surface of the scaphoid is covered with articular cartilage. This greatly limits potential points of entry for fixation devices.

An additional constraint is the curved shape of the scaphoid.

This means that a wire or fixation device along the true central axis of the scaphoid is not possible from a palmar approach. Occasionally, access to a distal entry point for a device can only be gained by a limited excavation of the edge of the trapezium.

Fracture displacement forces

In displaced fractures of the waist of the scaphoid, the distal pole tends to rotate into flexion in relation to the proximal pole, the lunate, and the triquetrum, which lie in extension. This can create a rotational and angular deformity at the fracture site – the so-called “humpback deformity.”

$Scaphoid waist fracture - fracture displacement forces$

Preoperative planning

Conventional radiographs do not adequately demonstrate the complete fracture configuration. A CT scan is recommended to reveal the degree of displacement.

$Scaphoid fracture – CT scan$

The patient is usually supine with the arm on a radiolucent side table.

Patient in supine position with the arm on radiolucent side table

Dorsal approach

Perform a straight dorsal skin incision, starting over Lister’s tubercle, and extending distally for about 3–4 cm.

Dorsal approach to the scaphoid

Inspection of the fracture

Look for additional lesions, especially scapholunate ligament ruptures.

The picture shows a proximal pole fracture combined with a complete scapholunate rupture. The head of the capitate is visible deeper in the wound. The proximal pole fragment has been delivered into the wound and has no soft-tissue attachments to the remaining carpus. Its vitality is therefore in question.

$Scaphoid fracture – inspection of the fracture$

Reduction

If the fracture is displaced, reduce it with small pointed reduction forceps.

$Scaphoid fracture – reduction$

The entry point is at the proximal pole, directly adjacent to the scapholunate ligament insertion.

Insert the guide wire in the axis of the shaft of the first metacarpal, in radial abduction.

$Scaphoid waist fracture – guide-wire insertion$

Confirm accurate advancement of the guide wire in the scaphoid axis with an image intensifier in at least two planes and perpendicular to the fracture plane.

Do not penetrate the scaphotrapezial joint with the guide wire.

$Scaphoid fracture – guide-wire insertion: confirmation of position with image intensifier$

Insert the headless compression screw in a standard manner.

Basic technique – Headless compression screw

Select a screw 2–4 mm shorter than the measured length with the appropriate thread length. In most cases, a 16–20 mm cannulated screw is the appropriate length.

Pitfall: A long screw can impinge upon the scaphotrapezial joint and lead to articular damage of both bones, resulting in osteoarthritis.

$Scaphoid fracture – headless compression screw insertion$