Influence of screw insertion order on compression generated by bone plates in a fracture model.

Abstract

Present recommendations regarding order of screw insertion for compression plate osteosynthesis in veterinary training are variable. We hypothesized that placement of a neutrally positioned screw would reduce the magnitude of compression that could be generated by a subsequently placed compression screw. Canine tibial diaphyseal segments were fixed to a plate attached to a bone surrogate and load cell, and the compression generated by screw tightening was measured. Three different screw insertion order patterns were evaluated using both dynamic compression plate (DCP) and limited contact dynamic compression plate (LC-DCP) implants. In group CN, the first screw was placed in compression mode and the second in neutral mode; in group NC, the first screw was placed in neutral mode and the second in compression mode; in group LNC, the first screw was placed partially tightened in neutral mode and the second in compression mode followed by complete tightening of the neutral screw. Screw insertion order significantly influenced the amount of compression generated with both groups CN and LNC demonstrating significantly greater compression generation when compared with group NC (p <0.0001). Compression generated by group CN constructs was also significantly greater than group LNC (p = 0.0013). Evaluation of group CN data to assess the influence of plate and drill guide combinations on compressive force generated did not demonstrate a statistically significant difference. To maximize compression using a load screw in a bone plate, following securement of the opposite bone fragment to the plate, it should be placed before a neutral screw is placed.