Authors of section

Authors

Jörg Auer, Larry Bramlage, Patricia Hogan, Alan Ruggles, Jeffrey Watkins

Executive Editor

Jörg Auer

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Screw fixation

1. Principles

Anatomic reduction

Anatomic reduction of the articular surface is of paramount importance for successful surgical management and future athletic soundness. Failure to properly reduce the fracture and create friction between the two fracture components will load the cortex screws in bending, leading eventually to implant breakage. Failure to reconstruct the proximal articular surface will lead to osteoarthritis and lameness.

A lateral incision into the fracture plane and possibly an arthrotomy of the lateral joint capsule of the fetlock joint may help to achieve perfect anatomic reduction.
The result should always be confirmed radiographically once temporary fixation is in place.

Loading the cortex screws in bending

Intraoperative imaging

Intraoperative radiographic control is essential for proper placement of internal fixation in the proximal phalanx. Either a real-time imaging system or anatomic references, such as 2 mm drill bits, can be used.
The radiographic markers are placed after reduction has been achieved and maintained with reduction forceps. The drill bits also serve as temporary fixation.

Intraoperative imaging

Pitfall: Arthroscopic evaluation

Arthroscopic evaluation prior to reduction and fixation of the fracture may complicate the procedure because of extravasation of fluid into the soft tissue and loss of the normal anatomical landmarks.

2. Approach

Positioning

The horse is positioned in lateral recumbency with the affected limb positioned uppermost.

Lateral recumbency

Displaced fractures can often be reduced closed, and cortex screws be placed in lag fashion through stab incisions on the dorsal surface of the proximal phalanx.

If necessary for visualization and reduction, a lateral incision into the fracture plane may be performed. This incision can be extended to include an arthrotomy of the lateral joint capsule of the fetlock joint to ensure perfect anatomic reduction. This approach also allows removal of debris from the fracture plane.

Approach

3. Reduction

Achieving and maintaining reduction

In acute minimally displaced fractures, reduction is typically accomplished by palpation and with temporary reduction and radiographic control. Maintenance of reduction is initially achieved through application of two reduction forceps. Insertion of 2 mm drill bits across the fracture proximally and distally further stabilizes the fracture. These drill bits also serve as reference points for screw insertion.

Reduction

Confirmation of reduction

Anatomic reduction is confirmed by radiographs after temporary fixation with 2 mm drill bits and reduction forceps.

Confirmation of reduction

4. Fixation

Insertion of the first two screws

Since the fracture originates at the proximal articular surface, the most proximal screws are always implanted immediately below the fetlock joint.

Insertion of the first two screws

Insertion of the first two screws

A cortex screw is placed in lag fashion in the proximal-medial and proximal-lateral aspect of the proximal phalanx in a dorsal to palmar/plantar direction using routine technique.

Insertion of the first two screws

Additional screws

Additional screws are placed coursing distally on the proximal phalanx in a dorsal to palmar/plantar direction as needed. All cortex screws are placed in lag fashion.
Typically 5.5 mm cortex screws are used.

Additional screws
Clinical example of internal fixation with screws

5. Aftertreatment

Postoperative management

External coaptation is necessary for all dorsal complete biarticular fractures.

Postoperative management includes box stall confinement for 8 weeks with cast changes at 2-3 week intervals as necessary, usually for 6 weeks.
Anti-inflammatory drugs are used for a minimum of 10 days postoperatively.

plate fixation transarticular lag screws

Radiographic follow up

Fracture healing is followed radiographically at 8 weeks post surgery. If the fracture is healing satisfactorily hand-walking exercise may be begun 8 weeks after surgery. Additional exercise recommendations are based on radiographic and clinical progress.

screw fixation