Effect of plate working length on plate stiffness and cyclic fatigue life in a cadaveric femoral fracture gap model stabilized with a 12-hole 2.4 mm locking compression plate

Abstract

BackgroundThere are several factors that can affect the fatigue life of a bone plate, including the mechanical properties of the plate and the complexity of the fracture. The position of the screws can influence construct stiffness, plate strain and cyclic fatigue of the implants. Studies have not investigated these variables in implants utilized for long bone fracture fixation in dogs and cats. The purpose of the present study was to evaluate the effect of plate working length on construct stiffness, gap motion and resistance to cyclic fatigue of dog femora with a simulated fracture gap stabilized using a 12-hole 2.4 mm locking compression plates (LCP). Femora were plated with 12-hole 2.4 mm LCP using 2 screws per fracture segment (long working length group) or with 12-hole 2.4 mm LCP using 5 screws per fracture segment (a short working length group).ResultsConstruct stiffness did not differ significantly between stabilization techniques. Implant failure did not occur in any of the plated femora during cycling. Mean ± SD yield load at failure in the short plate working length group was significantly higher than in the long plate working length group.ConclusionIn a femoral fracture gap model stabilized with a 2.4 mm LCP applied in contact with the bone, plate working length had no effect on stiffness, gap motion and resistance to fatigue. The short plate working length constructs failed at higher loads; however, yield loads for both the short and long plate working length constructs were within physiologic range.

Biomechanical Analysis of Locking Reconstruction Plate Using Mono- or Bicortical Screws

“…Several studies of locked plates have evaluated whether bone-plate constructs are able to resist cyclic loading within physiological limits of cycles and loads of the species under evaluation 17,[30][31][32][33] . Despite the lack of significant intergroup differences in the same test, the lower number of cycles to failure occurred in torsion as compared to axial compression and four and four-point bending tests.…”

The effect of intramedullary pin size and monocortical screw configuration on locking compression plate-rod constructs in an in vitro fracture gap model

“…66 However, they only used a single locking screw in hole 2 of each fragment and bicortical compression screws in all other holes so the plate was compressed to the bone. Therefore this study was met with the same limitation since the working length of the plate was limited to that of the 10mm fracture gap.…”

“…[14][15][16][17]66 Most of this variability arises from methodological variations where nonlocking plates or LCPs are anatomically contoured and compressed to the bone with cortical compression screws thereby reducing the working length to that of the fracture gap regardless of the position of the screws. Experimental models which use LCPs with a small plate to bone clearance and locking screws only, generate consistent data that shows the effect of plate working length on construct stiffness and strength.…”

Proximal Femoral Locking Plate versus Dynamic Hip Screw for Unstable Intertrochanteric Femoral Fractures

“…The screw placement was checked in both the anteroposterior and lateral planes using an image intensifier. 4. Good reduction of the medial and posteromedial cortex, rather than only the calcar 'kickstand screw', can provide a stable fixation.…”

“…The biomechanical study cited also acknowledges this fact in a clinical scenario. 4 The 'kickstand screw' provides a secure bony hold in the calcar, especially in osteoporotic patients, which only augments the stability of good reduction of the medial and posteromedial cortex. 5.…”