Mechanical Evaluation of the Ideal Plate-Bone Distance in Torsion for 2.0 mm Locking Plate Constructs Using a Feline Bone Model Surrogate

Introduction: To mitigate the shortcomings of traditional nonlocking plates, locking compression plates (LCP) were devised. Due to their angular stability, LCPs can be placed away from the bone surface, reducing the need for precise anatomical contouring. While this provides biological advantages, there are associated mechanical shortcomings. Few studies exist evaluating the mechanical effect of plate-bone distance (PBD). Furthermore, these studies used small fracture gap models which do not adequately represent comminution, the most common pattern seen in small animals. Our hypothesis was that outcome measures would be significantly larger as PBD increased.

Materials and Methods: Mid-diaphyseal 30 mm gap models were created using a previously validated short-fibre epoxy bone surrogate. Constructs (n = 4/group) were stabilized with 2.0 mm LCPs at one of three PBD (0, 1, and 3 mm) and tested nondestructively for 10 cycles. Outcome measures (mean torsional compliance [TC between 0.3 and 0.7 Nm] and maximum angular deformation [AD] from the 10th cycle) were statistically compared using a one-way ANOVA (p < 0.05). A post hoc Tukey was used to identify means significantly different from one another.

Results: The 3 mm offset constructs had the highest (p < 0.0006) TC (43.10 ± 0.74 degrees/Nm) and AD (78.06 ± 0.77 degrees) overall. The TC was higher in the 1 mm offset constructs (39.58 ± 0.77 degrees/Nm; p = 0.0008) compared with 0 mm (36.37 ± 0.88 degrees/Nm), however, the maximum AD was not different between these (71.66 ± 0.52 and 68.62 ± 2.5 degrees, respectively; p = 0.05).

Discussion/Conclusion: Larger PBD increased construct compliance, resulting in larger angular deformations. Clinically, this may represent a higher risk of construct failure in nonreconstructible fractures. Accordingly, our results suggest that PBD should be minimized when using 2.0 LCPs.

Acknowledgment

Support was provided by DePuy Synthes in the form of plate donations.

Publication History

Article published online:
15 July 2025