Contribution of the xenograft bone plate-screw system in lumbar transpedicular stabilization: An in vivo study in dogs.

OBJECTIVES: Xenograft bone plate-screws (XBPSs) can be alternative tools in lumbar transpedicular stabilization (TS). The aim of this study was to show biomechanical and histopathological contribution of the XBPSs system in lumbar TS. MATERIALS AND METHODS: Fifteen (n = 15) hybrid dog and ten (n = 10) L2-4 cadaveric specimens were included in the study. The dogs were separated according to surgical techniques: L3 laminectomy and bilateral facetectomy (LBF) in Group I (experimental group [EG I] (n = 5), L3 LBF plus TS with metal plate-screws (MPSs) in Group II (EG II) (n = 5), and L3 LBF plus TS with XBPSs in Group III (EG III) (n = 5). The cadaveric specimens were separated to L2-4 intact in Group I (CG I), (n = 5), and L3 LBF in Group II (CG II), (n = 5). The dogs were sacrificed at the end of 3rd month, and their L2-4 spinal segments were en bloc removed and prepared as in control groups. Flexion, extension, left-right bending, rotation, and compression tests were applied to all segments. Stiffness values were calculated and analyzed statistically. All dog segments were evaluated histopathologically. RESULTS: XBPS system showed a higher average stiffness values for left bending, extension, flexion, and compression compared to MPS, but these differences were not statistically meaningful. XBPS system had superiority to the fusion formation, as well. CONCLUSIONS: XBPSs provide stability and help the fusion formation, but this system does not have a biomechanical advantage over MPS system in TS.

The effect of nicotine on distraction osteogenesis: an experimental study on rabbits.

BACKGROUND: Tobacco smoke contains more than 4,000 constituents, but not all of them are reported to have adverse effects on bone healing after distraction osteogenesis. No research on the systemic administration of nicotine has been done on distraction osteogenesis of the weight-bearing long bones of the lower extremity. METHODS: Fourteen New Zealand white male rabbits underwent distraction osteogenesis on the right tibia and lengthening by 1 cm. Transdermal nicotine bands were applied onto the dorsal skin of the rabbits in the study group. Mineral density of the distraction zone was measured at weekly intervals using quantitative computerized tomography. Mechanical properties were assessed by torsional loading, and the regenerated bone tissue was subjected to histopathological examination. RESULTS: Comparisons of weekly measurements in both groups showed that while the increase in bone density in the nicotine group was higher, relative to the initial values, it was still far behind the average density obtained in the control group at the end of the experiment. Statistical analysis of mechanical data showed significant differences in the gradient of the regression lines and maximum torsional angles between the two groups. The histopathological assessments showed noticeable neovascularization in the study group, which was concluded to be a compensatory mechanism for the negative delaying effect of nicotine on bone healing. CONCLUSION: Systemic administration of nicotine can cause delays in the process of healing in distraction osteogenesis by its negative effect on the mineralization of the regenerate. Patients should be made aware of this negative impact of nicotine before the limb-lengthening surgery.

Contribution of the xenograft bone plate-screw system in lumbar transpedicular stabilization of dogs: an in-vitro study.

We performed biomechanical comparison of a xenograft bone plate-screw (XBPS) system for achieving cadaveric lumbar transpedicular stabilization (TS) in dogs. Twenty dogs' cadaveric L(2-4) lumbar specimens were harvested and their muscles were removed, but the discs and ligaments were left intact. These specimens were separated to four groups: the L(2-4) intact group as control (group I, n = 5), the L(3) laminectomy and bilateral facetectomy group (LBF) (group II, n = 5), the LBF plus TS with metal plate-screw group (group III, n = 5) and the LBF plus TS with XBPS group (group IV, n = 5). Five kinds of biomechanical tests were applied to the specimens: flexion, extension, left-right bending and rotation. The averages of the 16 stiffness values were calculated and then these were statistically analyzed. The statistical results show that the XBPS system contributes spinal stability and this system can be a good choice for achieving TS.

[The effect of bone marrow ablation on regional biomechanical properties of rat tibia]. / Kemik iligi ablasyonunun siçan tibiasinin bölgesel biyomekanik özellikleri üzerine etkileri.

OBJECTIVES: Regional (metaphyseal-diaphyseal) biomechanical properties of normal rat tibia, and changes on these biomechanical properties after bone marrow ablation, a model of fracture healing, were examined. METHODS: The study included 24 Sprague-Dawley rats that underwent tibial marrow ablation, and eight control rats with no surgical procedure. Proximal metaphyseal, proximal diaphyseal, distal diaphyseal, and distal metaphyseal samples were prepared from the tibias of all rats. In the control group, stiffness (elastic modulus, E), strength (maximum strength, Smax), and toughness (total energy absorption, U) parameters of the regional tibial segments were evaluated under compression loads. In the experimental group, compression was applied following bone marrow ablation on days 1, 3, 7, 9, and 15, and ablation-induced changes in the regional biomechanical properties were studied. RESULTS: The lowest E, Smax, and U values were obtained from the proximal metaphysis. The highest E and Smax values were from the distal diaphyseal, and the highest U values were from the proximal diaphyseal regions. In ablation-induced rats, decreases were observed in all the mechanical test values during days 1 to 7, followed by slight increases on days 7 to 9, and eventual decreases on days 9 to 15. There were significant differences between the two groups with respect to biomechanical parameters (p<0.05), but no significant differences were found between the tibial regions (p>0.05). CONCLUSION: Biomechanically, the most resistant and the weakest anatomic regions of normal rat tibia are the diaphyseal region and proximal metaphysis, respectively. The metabolic changes occurring after bone marrow ablation lead to changes in the mechanical properties of the tibia. The most affected tibial segments from ablation-induced intramedullary injury are the metaphyseal segments.