
Technical errors using screws and plates technique occur to all surgeons and under all circumstances. Obviously with experience the failure rate is reduced (we hope!!). Technical failures occur in the following categories: poor preoperative planning, improper intra-operative radiographic control, improper use of the equipment, improper application of the implant and any combination of the above. This lecture will demonstrate many technical errors that can happen in plate fixation of fracture repairs in the horse.
Careful preoperative radiographic evaluation and technique will reduce the rate of technical errors. Imaging control during surgery whether by radiographs, fluoroscopy or CT will prevent errors, ensure proper placement and use of implants improve results and allow the surgeon to gain confidence in the surgical techniques.
In my personal encounters with technical failures, failure to understand the biomechanical forces of the fracture, improper use of the equipment and failure to have adequate radiographic control has led to the most frequent cause of failure.
Some examples of mistakes used in plate fixation include:
Poor preoperative planning
Inadequate radiographic control
Improper use of equipment
Improper application of implants
Lag screws reduce shear forces and provide interfragmentary compression of fracture fragments. They should be used whenever possible even through plates or in concert with other repair techniques. When high torsional, bending or compressive forces are present lag screws are relatively weak when compared to plate fixation. It is common and recommended to use lag screw function, when possible, in plate fixation. Cortex screws used in plate function provide stability by compressing (lagging) the plate to the bone. Fixes angle screws lock their heads in the plate for stability but do not compress the plate to the bone and cannot be angled. They also may create a problem during placement in areas with large muscle masses. Additional it important to anticipate the location of the entire screw length when applying fixed angle screw to make sure the medullary cavity is entered in long bone repair. A common technical error with fixed angle screws is the failure to recognize bone is not fully engaged or placing them entirely in 1 cortical surface
Plates can function as neutralization, compression or buttress fashion. Double plating is the rule in unstable fractures except in areas of significant biomechanical advantage like the tension surface of the caudal ulna. In general, the following principles apply when plates in long bone repairs