An in vitro biomechanical study of the effects of surgical modification upon the canine lumbosacral spine

Summary

The purpose of this study was to determine the impact of surgical decompressive procedures upon stiffness of cadaveric canine lumbosacral motion units in the dorsoventral plane. Thirty-four grossly normal lumbosacral specimens were potted, in aluminum channeling with polymethylmethacrylate, and subjected to four-point bending in dorsiflexion and ventroflexion, using a universal testing machine (Instron MA). In order to determine its yield point, each specimen was non-destructively tested before and after surgical modification and then tested to failure in ventroflexion. Dorsal laminectomy (L) did not have a significant effect upon stiffness of the lumbosacral motion unit in dorsiflexion or ventroflexion, when compared with the control group. Since this also involved excision of the interspinous and supraspinous ligaments, removal of these structures alone also did not have any significant effect upon dorsoventral stiffness in vitro. Compared with the control group, the stiffness in the other groups changed as follows: addition of discectomy (LD) did not have a statistically significant effect in dorsiflexion, but decreased mean stiffness 33.1% (95% CI 29.0 to 37.2) in ventroflexion. Dorsal laminectomy combined with bilateral facetectomy (LF) decreased stiffness 43.5% (95% CI 39.4 to 47.6) in dorsiflexion, and 30.9% (95% CI 26.8 to 35.0) in ventroflexion. The combination of dorsal laminectomy, facetectomy and discectomy (LFD) decreased the stiffness 47.9% (95% CI 43.8 to 52.0) in dorsiflexion and 56.4% (95% CI 52.3 to 60.5) in ventroflexion. This decrease in stiffness in ventroflexion was significantly greater than with laminectomy and facetectomy alone (25% less stiff; 95% CI 20.9 to 29.1).

Keywords

Canine - lumbosacral - biomechanical - vertebra

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