The effect of head trauma on fracture healing: biomechanical testing and finite element analysis.

OBJECTIVES: We aimed to evaluate the effect of head trauma on fracture healing with biomechanical testing, to compare the results obtained from a femur model created by finite element analysis with experimental data, and to develop a finite element model that can be employed in femoral fractures. METHODS: Twenty-two Wistar albino rats were randomized into two groups. The control group was subjected to femoral fracture followed by intramedullary fixation, whereas the head trauma group was subjected to femoral fracture followed by intramedullary fixation along with closed blunt head trauma. Bone sections obtained with computed tomography from rat femurs were transferred into a computer and a 3D mathematical model of femur was created. At the end of week 4, femurs were examined by biomechanical testing and finite element analysis. RESULTS: The mean maximum fracture load was significantly higher in the head trauma group than in control group (p<0.05). Maximum strain values were also significantly high in the head trauma group (p<0.05). There was no significant difference between the groups with regard to maximum deformation (p>0.05). The head trauma group had significantly higher mean bending rigidity than the control group (p<0.05). The head trauma group showed no significant difference from the control group in terms of strain energy and elasticity module (p>0.05). There was no significant difference between experimental biomechanical test and finite element analysis (p>0.05). CONCLUSION: Noninvasive methods such as finite element analysis are useful in examination of the mechanical structure of bones. Experimental biomechanical test and finite element analysis methods suggest that head trauma contributes to fracture healing.

[Histopathologic and morphometric changes in rat nerve and blood vessels associated with femoral lengthening]. / Femoral uzatmanin sinir ve damarlara etkisi: Siçanlarda histopatolojik ve morfometrik degisiklikler.

OBJECTIVES: We investigated histopathologic and morphometric changes in rat femoral arteries, veins, and nerves associated with femoral lengthening. METHODS: The study included 42 male Wistar-albino rats. All the rats underwent left femoral osteotomy which was stabilized with an external fixator device. The rats were divided into five groups except for seven control rats which were left untreated. Femoral lengthening was performed with a distraction of 0.35 mm four times a day, which was continued for three days in group 1 (10%), and seven days in the other groups (30%). Before sacrification of each group of rats under general anesthesia after 3, 7, 14, 21, and 31 days of osteotomy, respectively, biopsy samples were obtained from distraction sites involving femoral artery, vein, and nerves for histopathologic and histomorphometric studies. RESULTS: Arterial changes observed in the first four groups were flattening and/or focal absence of the lamina elastica interna and externa, and hydropic degeneration and cytoplasmic vacuolization of the smooth muscle cells of the tunica media. Group 5 exhibited a normal arterial appearance except for fibrosis. Femoral vein changes were characterized by smooth muscle cell degeneration and cytoplasmic vacuolization in the first three groups, and by irregularities in elastic fibres and fibrosis in the remaining two. In group 5, the diameter of the femoral vein decreased by 27.9%. No histologic changes were noted in nerve morphology. In group 2, perineurium thickness and the diameter of myelinated nerve fibers notably increased by 164.6% and 58.4%, respectively. CONCLUSION: Our results show that the effect of femoral lengthening is heavily on blood vessels rather than on nerves.