A pilot in vitro biomechanical comparison of locking compression plate fixation and kerf-cut cylinder fixation for ventral fusion of fourth and fifth equine cervical vertebrae.

The research explores the comparative biomechanical properties of two types of implants used for fixation of horse cervical vertebrae – locking compression plates (LCP) and stainless steel kerf-cut cylinders (KCC). The study finds that LCP and KCC implants have similar biomechanical characteristics, thus presenting LCP as a potential alternative for use in clinical scenarios.

Objective and Methodology

• The main purpose of this research was to devise a method for testing the biomechanical characteristics of equine C4-C5 (fourth and fifth cervical vertebrae) articulations. Further, the study aimed to compare how these properties varied when the equine spines are stabilized using KCC and LCP.
• For the investigation, 24 equine cadaver cervical spines were used. These spines were measured using radiographs and subsequently divided into four groups.
• In the first group, KCC implants were used. For the second group, the researchers utilized an 8-hole 4.5/5.0 LCP, for the third group, an 11-hole 3.5 LCP was used, and the fourth group had no implants.
• All specimens were fixed in resin and subjected to testing under four-point bending until failure. Parameters like stiffness, maximum moment to failure, and the mode of failure were meticulously noted for all samples.

Findings

• All the tested spines, irrespective of the group they belonged to, failed at the C4-C5 junction. However, the way they failed showed differences among the groups. Group 1 (KCC insertions) showed fractures as the common mode of failure. For Group 2 and 3 (with 4.5/5.0 and 3.5 LCPs respectively), screw pullouts were more common. In Group 4 (with no implants), disarticulation was the primary method of failure.
• Importantly, the stiffness and maximum moment to failure of the spines where LCP or KCC was implanted were similar.
• The study also found that as the age of the specimen increased, the moment to failure decreased. Meanwhile, an increased size led to an increase in the moment to failure and stiffness.

Conclusion

• The research successfully established a methodology for studying the biomechanical characteristics of equine cervical vertebrae.
• Equally important, it found that the mechanical properties between both the KCC and the LCP implanted spines revealed comparable biomechanical properties.
• This suggests that LCPs can potentially be used as an alternative to KCCs in medical practice due to their similar mechanical properties.