Proper fist aid management should be applied to the patient including a well-padded splint bandage. A well conformed bandage extending from the hoof to the elbow should be applied. A caudal splint, which extends the length of the bandage, and a lateral splint, which extends from the hoof to the region of the shoulder should be affixed to the underlying bandage to provide rigid coaptation for transport. The lateral splint is applied as described to counter the tendency for the distal limb to abduct and displace the fracture fragments into the medial soft tissues where they are prone to penetrate the skin. Small foals can be restrained in a recumbent position in direct view of the mare for transport. If managed properly transverse fractures displace only minimally allowing the patient to bear some weight on the limb.
Strength of fixation
Because mid-diaphyseal transverse fractures are typically encountered in small foals they can in some instances be repaired with a single broad plate applied to the cranial surface of the radius. This should be considered only in instances where cortical contact can be ensured through the entire circumference of the radius when the fracture is reduced. In larger foals or if absolute cortical abutment is not assured, double-plate fixation is advocated.
Tension surface and plate position
Because of the strong cranial curvature of the radius the cranial surface is the tension band surface and a plate should always be applied to this aspect of the bone. If a second plate is indicated it may be applied to either the medial or lateral aspect of the bone, dependent on the condition of the overlying soft tissue envelope as well as the configuration of the fracture. If a lateral plate is used, it can be applied using the same incision as for the cranial plate. If the lateral plate extends to the distal radius, it will be necessary to place the distal screws through separate stab incisions. Application of a medial plate may require a separate incision. It may be possible in some cases, to modify the approach and use a medially based curvilinear incision and apply both the cranial and medial plates via a single incision along with stab incisions to place selected screws.
Intraoperative imaging is in this procedure to assist in implant positioning and aid in screw placement.
Transverse fractures are usually only minimally displaced, provided state of the art first aid was administered. The fracture can usually be brought into anatomical reduction by tenting the fracture ends into the incision, abutting the far cortices and gradually realigning the bone segments, by pressing the ends back into the incision.
If feasible, a cortex screw can be placed in lag fashion obliquely across the fracture to hold the fracture in reduction. Care must be taken to avoid complete tightening of the screw. Because the screw has to be inserted obliquely to the fracture line, complete tightening of the screw may lead to displacement of the fragments. Alternatively, a position screw may be applied to maintain reduction.
Plate selection and preparation
A 4.5 mm broad plate of appropriate length (spanning the entire length of the bone from the proximal physis to the distal physis) is contoured to fit the cranial surface. LCP, DCP and LC-DCPs have been used successfully. Note that the cranial aspect of the radius has a strong curvature and the plate needs to be bent to match this curvature. If it is too straight a gap will form at the caudal aspect of the fracture, leading to cycling of the plate, predisposing to plate failure postoperatively.
The plate is applied using the dynamic compression principles to achieve axial interfragmentary compression. When an LCP is used, 1 or 2 cortex screws are applied first on both sides of the fracture to compress the plate to the bone and provide interfragmentary compression using the DCU component of the combi holes in the plate.
Locking screws should be inserted adjacent to the fracture line and near the ends of the plate. Particularly with a single plate fixation in a foal, the construct with the most strength and stability is indicated and consists of a 4.5 mm broad locking plate in conjunction with 5.5 mm cortex screws and 5.0 mm locking screws in the configuration shown in this diagram. In very young foals reinforced 3.5 mm LCPs may be used. This plate has the same cross-section as the narrow 4.5 mm LCP but contains more combi holes and the combi holes are smaller, therefore leaving more plate stock between the plate resulting in a stronger plate.
Application of an additional plate
In larger foals or in foals where there may be some cortical incongruity or other reasons for concerns that dictate a stronger and more stable fixation, an additional plate can be applied to the medial or lateral aspect of the radius. The author prefers to put the plate on the lateral aspect of the radius, unless the configuration of the fracture dictates otherwise, because there is more soft-tissue coverage and the plate can be applied through the craniolateral approach. (The distal screws may have to be inserted through stab incisions distant from the original incision). In addition, the soft tissues on the medial aspect of the limb are often damaged by the fracture fragments during the preoperative period and predispose to incisional complications.
Because of the strong curvature of the radius the ends of the lateral plate have to be torqued to allow the screws that are in the mid-portion of the plate to lie on the lateral aspect of the bone.
Note: if the screw applied for temporary fixation interferes with plate placement, it may have to be removed or alternatively may be reinserted in lag fashion through the plate.
Antibiotic impregnated polymethylmethacrylate beads are placed around the implants prior to closure. In the depth of the surgical wound the muscle bellies are apposed to obliterate dead space where seroma formation could develop. The deep antebrachial fascia, subcutaneous tissues and skin are closed in separate layers. Some surgeons prefer to use suction drains, but the author does not routinely use them. The wound is bandaged aseptically and protected with a compression bandage extending distally to the foot.
6. Overview of rehabilitation
The foal is kept in stall rest for a minimum of 60 days. The first 30 days hand-grazing only is advised, followed by 30 days of hand-walking.
Follow up radiographs are taken at 60 days. If healing appears to be progressing without complications the foal is gradually transitioned to free paddock exercise.
60-day postoperative radiograph of a foal that acquired a mid- radius fracture at one week of age. It was treated with a reinforced 3.5 mm LCP using only one cortex screw through the proximal hole. All the other combi holes were filled with locking head screws.
In general implant removal is not recommended. However, indications for implant removal include complications secondary to infection where chronic drainage persists after the fracture has healed. In these instances the infected implant(s) is/are removed. Another indication may be in foals intended for performance activities. In these cases the cranial plate and its associated screws are removed. If two plates have been used, it is advisable to stagger plate removal with at least 30 days of pasture exercise prior to removal of each plate.
More information about plate removal can be found here.
4 month follow up radiographs of the same foal showing complete fracture healing. The animal presented with 2/5 lameness in the previously fractured limb. At this point it was decided to remove the plate.
Note: the plate is proximally covered by a thin bone layer.