SCAPHOID FRACTURE(Greek :skaphos means boat)

                69% of all carpal injuries,common among young men with a male to female ratio 71:29 &average age of 35 years. The average time for healing of a nondisplaced scaphoid fracture in a cast is 8 to 12 weeks

        

The scaphoid is 80% articular, especially the ulnar side. Proximally, the scaphoid articulates with the distal radius at the scaphoid fossa, and distally with the trapezoid and trapezium. Ulnarly, it articulates with the lunate proximally and the capitate distally. volar surface is partly nonarticular

Vascularity

The blood supply of the scaphoid derives from two sources: a group of vessels entering the palmar aspect of the distal pole, and a group entering the dorsal aspect of the distal pole. The first group contributes largely to the vascularity of the distal one third, and the dorsal group supplies the proximal two thirds of the bone.

Proximal pole fractures rely largely on the distal-to-proximal intraosseous blood flow and are therefore prone to delayed union and nonunion.
Nonoperative treatment requires a prolonged period of plaster immobilization (3-6 months).

80% of the surface of the scaphoid is covered with articular cartilage. This greatly limits points of entry for fixation devices. An additional constraint is the curved morphology of the scaphoid.This means that a wire or fixation device along the true central axis of the scaphoid is not possible. Occasionally, access to a distal entry point for a device can only be gained by a limited excavation of the edge of the trapezium

Choice of implant

If the proximal pole fragment is larger than 5 mm, a cannulated, headless, self-compressing screw is the implant of choice.
For smaller proximal pole fragments, the use of a mini headless bone screw is advisable.
For very small fragments (flakes), K-wires may be a better option.

In cases of comminuted proximal one third to half of the scaphoid, a combination of a screw and K-wires is recommended.

Approach

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

Inspect the fracture

Look for additional lesions, especially scapholunate (SL) ligament ruptures.
The picture shows a proximal pole fracture combined with a complete SL rupture. The head of the capitate is visible deeper in the wound.

Reduction

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

Comminuted fractures

Comminuted fractures of the proximal half of the scaphoid can not be fixed with a headless screw alone.

Additional K-wires are advisable for the fixation of small fragments bearing articular cartilage.
If a bony avulsion fracture of the SL ligament from the scaphoid is present, it is necessary to fix the fragment, either with K-wires, or a small screw (1.5 mm).

Image intensification in at least two planes is used to confirm accurate advancement of the guide wire in the scaphoid axis, and perpendicular to the fracture plane.
Do not penetrate the scaphotrapezial joint with the guide wire.

Drilling and tapping

Use only the dedicated drill bit. A power drill will exert a smaller and more controlled force on the fragments than manual drilling, and will reduce the risk of displacing the fragments. A small power drill with slow rotation is preferable.
Use Ringer lactate solution to cool the drill bit, in order to minimize thermal injury.
If the drill guide is used, attach a nut to the drill bit in order to limit penetration to the desired length only.
Check the position of the tip of the drill bit using image intensification.
Then tap the drill hole manually if not using self-tapping screws.

Screw insertion

The proximal end of the screw should be advanced until it is buried beneath the subchondral bone.

Pitfall: Overinsertion
The near thread must not lie within the fracture plane, as this would cause displacement rather than compression.