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.
In comminuted fractures, the large fragments are reduced and fixed to the parent bone until converted to a two-part fracture, which can then be repaired as a simple fracture.
Because of the strong cranial curvature of the radius the cranial surface is the tension band surface and one plate should always be applied to this aspect of the bone. The second plate is applied laterally or medially. The fracture configuration and/or local skin trauma are major parameters to help decide where to apply the second plate.
Intraoperative imaging is important in this procedure to assist in implant positioning and aid in screw placement.
The fracture fragments – in this case a single butterfly fragment – are reduced to the parent bone and temporarily fixed with a cortex screw applied in lag fashion.
The two remaining fragments are brought into alignment. With a transverse fracture line as in this example, this can be achieved by tenting the fracture ends out of the incision, abut the far cortices and gradually bring the ends back into the incision, thereby reducing the fracture. The reduction is held in position by another cortex screw applied in lag fashion.
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 physis to the distal physis) for application on the cranial side 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 lateral aspect of the radius.
Note: The cranial aspect of the radius has a strong curvature and the plate needs to be contoured to match this curvature.
Application of the first plate
First, the plate to the cranial aspect of the radius is applied. Interfragmentary 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 as possible. When an LCP is used, cortex screws are applied before placing any locking screws.
Locking 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 put 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 proximal end of the lateral plate will need 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 protect the wound(s).
Recovery from anesthesia should be controlled and assisted to minimize risk of catastrophic injury during recovery from anesthesia. If available, a pool recovery system (left) may be advantageous in larger individuals to reduce risk to personnel and the patient injury.
Note: while preoperative casts are indicated, they should not be applied for the recovery period because the cast changes the tension surfaces within the bone to the caudal cortex. As the plates were applied cranially and laterally they are prone to catastrophic failure during recovery.
7. Case example
In some cases it is difficult to decide whether on or two plates should be applied. This 8-year old pony suffered a comminuted radius fracture with the main fragment being located in the caudal cortex.
It was repaired with an interfragmentary 3.5 mm cortex screw placed in lag fashion to fix the butterfly fragment to the proximal fragment in combination with a narrow 4.5 mm LCP applied as neutralization plate.
With the one plate the animal stayed lame. Therefore a second plate was applied to the medial side. The animal recovered well and the lameness subsided 2 days postoperatively.
8. 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. Critical cases and adult horses may be kept in a sling during the immediate postoperative period.
Follow up radiographs are taken at 60 days. If healing appears to be progressing without complications the patient is gradually transitioned to free paddock exercise. Adult horses are usually kept in stall rest for a minimum of 90 days and are 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.
At 6 months post application of the second plate the fracture was healed. The plates were left in place.
Pre- and postoperative craniocaudal radiographs of an adult horse with a slightly comminuted oblique mid-radius fracture. A full-limb cast was applied for the recovery and immediate postoperative period.
The lateral radiographic projections reveal an ulnar fracture with minimal displacement (left) and progressive displacement in the immediate postoperative period (right). It can be seen that the cast ends at the level where both plates end. The weight of the cast and the fulcrum caused by the cast represented excessive stress risers for the repaired bone to withstand these forces. Additionally the tension side of the bone changed to the caudal aspect.