Effect of Plate Length on Construct Stiffness and Strain in a Synthetic Short-Fragment Fracture Gap Model Stabilized with a 3.5-mm Locking Compression Plate.

Objective:  To evaluate the effect of 3.5-mm locking compression plate (LCP) length on construct stiffness and plate and bone model strain in a synthetic, short-fragment, fracture-gap model.

Study design:  Six replicates of 6-hole, 8-hole, 10-hole, and 12-hole LCP constructs on a short-fragment, tubular Delrin fracture gap model underwent four-point compression and tension bending. Construct stiffness and surface strain, calculated using three-dimensional digital image correlation, were compared across plate length and region of interest (ROI) on the construct.

Results:  The 12-hole plates (80% plate-bone ratio) had significantly higher construct stiffness than 6-hole, 8-hole, and 10-hole plates and significantly lower plate strain than 6-hole plates at all ROIs. Strain on the bone model was significantly lower in constructs with 10-hole and 12-hole plates than 6-hole plates under both compression and tension bending.

Conclusion:  Incremental increases in construct stiffness and incremental decreases in plate strain were only identified when comparing 6-hole, 8-hole, and 10-hole plates to 12-hole plates, and 6-hole to 12-hole plates, respectively. Strain on the bone model showed an incremental decrease when comparing 6-hole to 10-hole and 12-hole plates. A long plate offered biomechanical advantages of increased construct stiffness and reduced plate and bone model strain, over a short plate in this in vitro model.