Diaphyseal radial fractures have a tendency to displace medially, where there is limited soft tissue coverage, and become an open fracture. Because the major muscles are positioned along the lateral and caudal aspect of the forelimb, contraction of the muscles following in injury displaces the distal limb laterally, forcing the sharp fracture fragments medially. Due to the limited soft tissue coverage medially, there is a high risk that these fragments will penetrate the soft tissue envelope opening the fracture to external contamination (A). A simple bandage does not counteract these forces (B). But a lateral split extending to the shoulder joint does (C).
The splints should therefore be applied on the caudal and lateral aspect of the limb with the caudal splint extending from the ground to the point of the elbow and the lateral splint extending from the ground beyond the proximal extent of the bandage to prevent abduction of the distal limb and displacement of the fracture into the medial soft tissues.
These fractures as well as other simple fractures of the diaphysis are readily repaired and have a good prognosis in foals. In adult horses, diaphyseal radial fractures that have a simple configuration and are closed represent the best opportunity for a favorable outcome. However they are not routinely repaired because of the high rate of complications and substantial expense associated with internal fixation in these injuries.
Because of the strong cranial curvature of the radius the cranial surface is considered the tension band surface and one plate should always be applied to this aspect of the bone.
Intraoperative imaging is in this procedure to assist in implant positioning and aid in screw placement.
Because these fractures usually have an oblique component, the fracture can be reduced by using pointed reduction forceps and traction to gradually slip down the obliquity. It may be helpful to use the serrated jaw reduction forceps (see insert) to aid in this process if the pointed reduction forceps are inadequate.
Once anatomic reduction has been achieved, one or two cortex screws are placed across the fracture in lag fashion to hold the reduction and obtain additional interfragmentary compression. It is important to position the screws so they will not interfere with plate placement. If this is not possible, it may be feasible to remove these screws once the cranial plate is placed and then use these same screw holes for lag screws placed through the lateral plate. If this is to be attempted, it is important to plan their position carefully prior to placement.
Plate selection and preparation
In foals, a 4.5 mm broad plate of appropriate length (spanning the entire length of the radius from the proximal to the distal physis) for application on the cranial cortex and a 4.5 mm narrow plate, which may be a little shorter distally, for application on the lateral side are usually sufficient. LCP, DCP and LC-DCPs have been used successfully. In adult horses, a 5.5 mm broad plate or a DCS plate may be used in place of the 4.5 mm broad plate on the cranial aspect of the radius.
Note: the cranial aspect of the radius has a strong curvature and the cranial plate needs to be bent to match this curvature. In addition, it will be necessary to twist the proximal aspect of lateral plate.
Application of the first plate
First, the plate to the cranial aspect of the radius is applied. Interfragmentary axial compression is achieved by a combination of using the dynamic compression principles of the plate and placing as many cortex screws in lag fashion through the plate overlaying the fracture plate as possible. When an LCP is used, cortex screws are applied before placing any locking head screws.
Locking head screws should be inserted adjacent to the fracture line and near the ends of the plate.
Application of the second plate
An additional plate is applied to the medial or lateral aspect of the radius as dictated by fracture configuration and soft-tissue limitations. The author prefers to place the plate on the lateral aspect of the radius when possible, 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 if a medial approach is used to place the plate on the medial aspect of the limb.
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(s) applied for temporary fixation interfere(s) with plate placement, it/they 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 is likely. 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. An aseptic compression bandage is applied to the wound.
7. Overview of rehabilitation
The patient 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. Adult horses are usually kept in stall rest for a minimum of 90 days and re-evaluated radiographically prior to increasing their exercise level. 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 horses 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.