Travmatologiâ i Ortopediâ Rossii (Sep 2023)
Structural Reorganization of the Third Metatarsal Bone Shaft After Autogenous Plasty of the Tibial Portion of the Sciatic Nerve
Abstract
Background. Previous research has shown that neurectomy of the sciatic nerve leads to a reduction in bone density in the femur and tibia of laboratory mice and rats. However, the impact of surgeries aimed at restoring nerve innervation on the bones of distal limb parts has not been studied. Aim of the study — to identify structural changes in the shaft of the third metatarsal bone after primary autogenous plasty of the resection defect of the tibial portion of the sciatic nerve in rats. Methods. Autologous neuroplasty of the tibial portion of the sciatic nerve was performed on 16 Wistar rats (aged 8-10 months). The animals were euthanized at 4 and 6 months after the surgery, and a control group of 7 intact rats of similar age was included. Histomorphometric analysis was conducted on a dissected fragment of the forefoot at the level of the metatarsal bones. The ratio of fuchsinophilic and anilinophilic structures of the cortical plate was determined using point-count volumetry on Masson-stained images of transverse sections of the third metatarsal bone shaft. The thickness of the cortical plate, numerical density, area, and diameter of osteons and Haversian canals were measured. Results. After 4 months, compared to the control group, a 15% decrease (p = 0.0001) in the proportion of mineralized structures of the cortical plate and a 12.7% reduction (p = 0.0184) in its thickness were observed. Osteolysis signs were present in the osteonal layer, along with decreased numerical density and dimensional characteristics of osteons, and the presence of osteons with dilated Haversian canals. At 6 months, the thickness of the cortical plate did not significantly differ from the norm (p = 0.2067), but there was a progressive 33.6% decrease (p = 0.0001) in the proportion of mineralized structures. Reduced values of numerical density, area, and diameter of osteons persisted in the osteonal layer, while the diameters of Haversian canals in osteons increased over time. Conclusion. From 4 to 6 months, the thickness of the cortical layer in the compact bone of the third metatarsal bone shaft was restored. However, changes in the numerical and dimensional composition of osteons, along with decreased mineralization of the extracellular matrix and erosion of the subperiosteal bone layer, continued to progress. The developed experimental 2D model can be used to assess denervation osteopenia in distal limb parts and further explore rehabilitation interventions that enhance and improve reinnervation.
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