Veterinary surgery : VS1999; 28(5); 333-340; doi: 10.1111/j.1532-950x.1999.00333.x

An in vitro biomechanical comparison of an interlocking nail system and dynamic compression plate fixation of ostectomized equine third metacarpal bones.

Lopez, MJ
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Wilson, DG
·
Vanderby, R
·
Markel, MD

Abstract: To compare the mechanical properties of two stabilization methods for ostectomized equine third metacarpi (MC3): (1) an interlocking nail system and (2) two dynamic compression plates. Animal or Sample Population-Ten pairs of adult equine forelimbs intact from the midradius distally. Methods: Ten pairs of equine MC3 were divided into two test groups (five pairs each): caudocranial four-point bending and torsion. Interlocking nails (6 hole, 13-mm diameter, 230-mm length) were placed in one randomly selected bone from each pair. Two dynamic compression plates one dorsally (12 hole, 4.5-mm broad) and one laterally (10 hole, 4.5-mm broad) were attached to the contralateral bone from each pair. All bones had 1 cm mid-diaphyseal ostectomies. Five construct pairs were tested in caudocranial four-point bending to determine stiffness and failure properties. The remaining five construct pairs were tested in torsion to determine torsional stiffness and yield load. Mean values for each fixation method were compared using a paired t-test within each group. Significance was set at P<.05. Results: Mean (+/-SEM) values for the MC3-interlocking nail composite and the MC3-double plate composite, respectively, in four-point bending were: composite rigidity, 3,454+/-407.6 Nm/rad and 3,831+/-436.5 Nm/rad; yield bending moment, 276.4+/-40.17 Nm and 433.75+/-83.99 Nm; failure bending moment, 526.3+/-105.9 Nm and 636.2+/-27.77 Nm. There was no significant difference in the biomechanical values for bending between the two fixation methods. In torsion, mean (+/-SEM) values for the MC3-interlocking nail composite and the MC3-double plate composite were: composite rigidity, 124.1+/-16.61 Nm/rad and 262.4+/-30.51 Nm/rad; gap stiffness, 222.3+/-47.32 Nm/rad and 1,557+/-320.9 Nm/rad; yield load, 94.77+/-7.822 Nm and 130.66+/-20.27 Nm, respectively. Composite rigidity, gap stiffness, and yield load for double plate fixation were significantly higher compared with interlocking nail fixation in torsion. Conclusions: No significant differences in biomechanical properties were identified between an interlocking nail and double plating techniques for stabilization of ostectomized equine MC3 in caudocranial four-point bending. Double plating fixation was superior to interlocking nail fixation in torsion.

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Publication Date: 1999-09-24 PubMed ID: 10493637DOI: 10.1111/j.1532-950x.1999.00333.xGoogle Scholar: Lookup

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Summary

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This study compared two methods of stabilizing a surgically cut (ostectomized) horse’s third metacarpal bone: (1) the interlocking nail system, and (2) the double dynamic compression plate technique. The results showed that while both techniques had similar performance in bending tests, the double plating method was superior in resistance to twisting or torsion.

Research Methodology

The research involved ten pairs of adult horse forelimbs. The third metacarpal bones (MC3) from these limbs were divided into two groups for testing: one examined the bones’ response to bending (caudocranial four-point bending), while the other measured twisting or torsion resistance.
In each group, one bone was fixed with interlocking nails, while the contralateral bone was fitted with two dynamic compression plates, one dorsally and one laterally. All bones underwent mid-diaphyseal ostectomies, a surgical procedure where a segment of the bone is removed.
Each construct was subjected to specific tests to measure rigidity, the bending moment at which deformation starts (yield bending moment), and the bending moment at which the construct fails (failure bending moment).
These results were then compared within each pair using a statistical technique known as paired T-test to find if any significant difference existed between the performances of the two fixation methods. The threshold for statistical significance was set at P<.05.

Results

In the context of bending, both the interlocking nail and double plating techniques displayed similar performances. There was no significant difference in composite rigidity, yield bending moment, and failure bending moment between the two.
However, in torsion tests, the double plating technique was significantly superior. It outperformed the interlocking nail system in terms of composite rigidity, gap stiffness (a measure of how a bone can resist deformation when subjected to torsional forces), and yield load (the torque at which deformation commences).

Conclusions

The study concluded that both fixation methods — the interlocking nail system and the double dynamic compression plate technique — are equally effective in terms of their biomechanical properties when subjected to bending forces.
However, when it comes to torsion, the double plating technique is markedly more effective than the interlocking nail system in stabilizing ostectomized equine MC3. It offered higher composite rigidity, gap stiffness, and yield load, making it the preferred option for situations where resistance to twisting is crucial.

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APA

Lopez MJ, Wilson DG, Vanderby R, Markel MD. (1999). An in vitro biomechanical comparison of an interlocking nail system and dynamic compression plate fixation of ostectomized equine third metacarpal bones. Vet Surg, 28(5), 333-340. https://doi.org/10.1111/j.1532-950x.1999.00333.x