Authors of section

Authors

Anton Fürst, Wayne McIlwraith, Dean Richardson

Executive Editor

Jörg Auer

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Plate fixation

1. Positioning and approach

Positioning

Usually, internal fixation is applied under general anesthesia with the horse in lateral recumbency with the fractured splint bone up.

In cases where fissure fractures of the third metacarpal/metatarsal bone are expected or diagnosed the plate can be applied in standing position with the horse under deep sedation and regional anesthesia.

Approach

A longitudinal skin incision of 8-10 cm length is performed directly over the lateral/medial aspect of the proximal splint bone.

Further information on approaches to the splint bones can be found here.

Proximal splint bone fracture - plate fixation

The fibers of the collateral ligament, which inserts on the proximal splint bone need to be split to allow plate and/or screw placement to the abaxial or palmar/plantar surface of the proximal splint bone. Dissection has to be extended to free up the palmaro/plantaro-lateral/medial aspect of the splint bone respectively.

Proximal splint bone fracture - approaches

AO Teaching videos

Proximal Fracture of MC IV - 6-hole 3.5 one-third Tubular Plate

2. Plate selection and preparation

Plate selection

A 3.5 mm (narrow) DCP, LC-DCP or LCP, third-tubular plate or reconstruction plate (LCP/DCP) is appropriate in most cases.
Usually a 5-hole plate can be used. The distal part of the splint bone becomes very thin, which prevents the use of a longer plate in most horses.

Plate selection

Plate position

The plate is positioned on the palmaro/plantaro-latero/medial side of the splint bone. Special care must be taken to the orientation and location of the plate, so that at least two screws can be inserted on each side of the fractured zone. In the distal part, the screws need to be very short to avoid protrusion into the third metacarpal/-tarsal bone.

Plate position

Plate preparation

Minimal contouring of the plate is necessary to match the contours of the proximal splint bone. No torsional adjustments of the plate are required. The plate can be bent with either the bending pliers or the bending press.

Plate preparation

3. Considerations about screw positioning

Screws may engage only the splint bone (left) or include the near cortex of the third metacarpal/metatarsal bone (right).
The fusion of the splint bone with the third metacarpal/metatarsal bone results in joint stability; however, this is not ideal from a physiological standpoint because it eliminates normal micro-movement within the joint and between the splint bone and the third metacarpal/metatarsal bone.
Therefore, whenever possible the screws should only engage the fractured bone.

plate fixation

4. Reduction and fixation

Manual reduction

Normally, the first reduction can be achieved by digital pressure on the fragments.

Manual reduction

Application of the plate

The plate is then applied to the proximal fragment with one screw applying routine technique.

Application of the plate

Insertion of the second screw

Before the second screw is inserted correct positioning of the plate is assured. Plate orientation cannot be changed after insertion of the second screw.
The plate is fixed to the distal fragment with the help of another screw inserted, in load position, if deemed necessary. Thereby, the fracture is reduced into its anatomical position.

Insertion of the second screw

Additional screws

The remaining plate holes are subsequently filled with screws inserted in neutral position. If a plate hole is positioned over the fracture line, the hole is left empty or the screw is inserted at an angle avoiding the fracture plane.

Additional screws

Completed fixation

plate fixation

5. Plate fixation with fusion to the third metacarpal/metatarsal bone

Occasionally, one cannot achieve sufficient stability with screws placed in the splint bones only. In such cases inclusion of the palmaro/plantaro-lateral/medial cortex of the third metacarpal/metatarsal bone in the fixation should be considered.
It must be kept in mind, that this eliminates normal micro movement within the joint and between the splint bone and the third metacarpal/metatarsal bone.

Fusion to the cannon bone

Dislocation of proximal stump

If the proximal part of the splint bone is not firmly attached to the third metacarpal/metatarsal bone and/or is very short, there is a high risk of dislocation. In such cases, fixation of the proximal stump to the third metacarpal/metatarsal bone can represent a good option to achieve a stable fixation.

Dislocation of proximal stump

6. Alternative: Screw fixation for simple oblique fractures

Screw fixation

Screws can only be used in simple oblique and minimally displaced splint bone fractures, because screw fixation alone is generally associated with a relatively high rate of technical failure. The application of a plate is the preferred treatment, however, because it serves as a tension band when fixed also to the distal fragment.

Alternative: Screw fixation for simple oblique fractures

In Warmblood-, Thoroughbred-, Arabian- and American Quarter horses 3.5 mm screws should be used. In small Islandic horses, ponies or foals 2.7 mm screws can be used.

Alternative: Screw fixation for simple oblique fractures

Usually, two screws can be used. If possible, a third screw should be introduced to improve the stability of the fixation.

Alternative: Screw fixation for simple oblique fractures

Complications

Example of a postoperative complication with fixation failure.
In this case, screws were also inserted into the third metacarpal/-tarsal bone. Screws without a plate are too fractious to achieve stable fixation of the splint bone to the third metacarpal/-tarsal bone.

Alternative: Screw fixation for simple oblique fractures

7. Aftertreatment

A bandage is applied for two weeks.
Perioperative antibiotics are administered for 3 days postoperatively.
The sutures are removed after 10 days.

The horse is kept in a stall for 4 weeks before hand-walking exercises are initiated for another 8 weeks.

Follow-up x-rays are taken 4 and 12 weeks after surgery to evaluate fracture healing. If all looks good, the horse can go back to its intended work.

plate fixation