Comment: Biomechanical Comparison of Three Locking Compression Plate Constructs from Three Manufacturers under Cyclical Torsional Loading in a Fracture Gap Model

10.1055/s-0044-1788920

I have read the paper by Lai et al[1] with interest. It is unclear whether the difference in torsional stiffness and cycles to failure is intrinsic to the constructs in their entirety or individual component(s) of these constructs, but it seems reasonable that the initial construct stiffness is attributed predominantly to the plates and the cycles to failure either directly to the screws or the manner in which the screws are loaded in the different constructs.

It is reported that the working span between constructs was the same. Although the distance between screw centres is the same along each limb of the plates, I understand the span between central holes in the Veterinary Instrumentation (VI) plate is around 1mm greater than the comparators; the design intent was to make it easier and safer to place screws in adjacent holes on either side of the fracture line. This results in the VI construct having a working span of approximately 1.5 to 1.6% greater than the other constructs depending on the criteria you use to measure span. This might not sound much, but it is potentially enough to influence the conclusions of the study.

If corrected for unit length, there will be greater equivalence of stiffness between constructs, perhaps enough to take the differences out of statistical significance with the study's limited power. Taking this into consideration as well as correcting the Y-axis of the Fig. 5 histogram to start at zero, the graphic representation of difference in stiffness is much less exaggerated than as published.

I would still expect the stiffness of the VI plates to be marginally less by unit length, but not to the exaggerated extent in which these appear to be presented on cursory review. The VI plates had been designed so that non-locking screws sit deeper in them to reduce shear loading of non-locking screw heads to increase screw longevity and, following finite element analysis, the undercuts on the under-surface of the plates were extended to permit more uniform contouring and more uniform loading in situ to hopefully improve cycle life of the plates themselves. Both of these adjustments remove metal, reducing overall stiffness, but it is expected these adjustments would likely increase construct longevity under different test conditions.

Since construct failure was through screw breakage, I feel it is imperative we know the specification of the screws used in the study. I presume the Synthes were stardrive, but the information isn't there for the Knight Benedict or Vi screws. Vi continues to produce 3.5-mm locking screws with either hex or stardrive, but the stardrive can be expected to exhibit better performance since it retains more metal around the areas of maximum stress. It follows that swapping what I believe to be compatible screws from the different manufacturers between constructs might offer clarity as to whether the torsional cycle life might be more of a screws factor, more of a plates factor, or related more to the constructs as a whole.

I feel it is important to address these matters to permit a truer interpretation of the observed differences in biomechanical performance and better inform clinical use and any future developments.

Publication History

Article published online:
08 January 2026

• Reference

• 1 Lai LH, James DR, Appleyard RC, Cadman J. Biomechanical comparison of three locking compression plate constructs from three manufacturers under cyclical torsional loading in a fracture gap model. Vet Comp Orthop Traumatol 2025; 38 (01) 25-33