Reduction is always difficult because the very large muscles of the thigh cause overriding of the fracture. The bone must be brought back to a normal length prior to plate application. Fortunately the long oblique nature of most mid-shaft fractures aids in the reduction and restoration of length. After exposure, a large bone clamp is used to adapt the fracture and to gradually slide the distal fragment along the fracture plane until the fracture is anatomically reduced.
Once reduction is achieved a cortex screw is placed in lag fashion from craniolateral to caudomedial if possible. This lag screw may be removed after the first plate is in place if it interferes with the position of the second plate.
4. Plate application
Selection and preparation of the first plate
The increased strength of a broad locking plate (LCP) is advantageous in this location, however DCP and LC-DCP’s can be used. A 10 (or rarely 12) hole plate is the most commonly used implant for these fractures. The first plate is always placed on the lateral aspect of the femur from the greater trochanter to the distal physis unless additional purchase is needed in the distal fragment, in which case bridging of the physis is sometimes necessary. If the physis must be bridged, shortening of the limb will result if the plate is not removed in a timely fashion. The plate must be contoured and twisted to match the surface of the femur. At the distal aspect of the bone the plate must be placed along the cranial aspect of the lateral cortex because of the large gastrocnemius fossa that lies at the caudolateral aspect of the lateral cortex.
Application of the first plate
At least one screw is inserted in the proximal and distal fragment and axial compression created if needed. Axial compression should be created with caution because of the long oblique nature of the fracture, as the fracture will displace if excessive compression is applied. Locking screws are placed after inter-fragmentary and axial compression are created.
Cortex screws can be inserted in lag fashion to achieve interfragmentary compression in the mid-portion of the plate, if the fracture configuration allows. If the fracture passes directly under one of the screw holes of the plate, that hole is left open until all of the remaining implants are inserted. Then a glide hole is prepared across the near cortex and the screw is placed in lag screw technique to engage solid bone in the trans-cortex.
Preparation and application of the second plate
After the fracture has been stabilized with the first plate, the second plate is contoured using bending templates to fit the cranial surface of the bone. This plate can be extended from the level of the femoral neck to the level of the distal femoral physis. Proximal and distal screws are inserted first. It is almost always possible to obtain 3-4 cortex screws using lag technique to achieve additional interfragmentary compression through the cranial plate. For the second plate, an LCP can be used as well, but the difficulty in retraction of the quadriceps muscle makes a DCP or LC-DCP easier to apply because it is not imperative to insert the screws absolutely perpendicular to the plate.
In this instance a 12-hole DCP was used for the lateral plate and the distal hole was left open because of the desire not to enter the distal femoral physis. A 9-hole DCP was used on the cranial cortex as the second plate. A suction drain can be seen in position next to the cranial plate and caudal to the lateral plate.
5. Surgical technique for fractures with additional butterfly fragment
Another version of the oblique mid-shaft fracture is seen with mild comminution of the proximal aspect of the distal fragment creating a butterfly fragment cranially. It is possible to neutralize cranial comminution using the implants available. It is almost impossible to manage caudal comminution. If cranial comminution exists, stronger implants such as the Dynamic condylar screw plate (DCS) increase the strength and stability by increasing the purchase in the distal fragment. Plate application is similar to the use of two DCP’s or LCP’s, however a DCS plate is used as the lateral plate. The butterfly fragment must be reconstructed using cortex screws in lag fashion in addition to the cranial and lateral plates. Reconstruction and fixation of the butterfly fragment is accomplished prior to application of the lateral plate.
The distal end of the lateral plate is always attached first because the dynamic condylar screw is always inserted first. The barrel can be located above the femoral physis, if enough bone exists to maintain the fixation, however it can also be located in the epiphysis in more distal fractures.
The second plate is applied using identical technique as discussed before.
The large soft tissue cover in the femur supports the rapid production of callus to aid the healing of the fracture.
6. Overview of rehabilitation
Stall rest is maintained for 6-8 weeks depending on the stability of the fracture.
Radiographs are then taken to determine the next step in exercise. Complete radiographs of the femur can only be taken under general anesthesia. In proximal fractures this may be necessary. The distal one-half of the femur can be radiographed in the standing horse. For most mid-shaft and distal fractures, standing radiographs are sufficient to assess fracture healing and stability. Implants are not removed from the femur, even in foals intended for high-level athletic use.