An Experimental Study On Fracture Healing Complicated By Central Nervous System Injury

ObjectiveIt has been observed clinically that an overgrowth of callus and even ectopic ossification in the muscle may occur in a patient with bone fracture combined with central nervous system(cerebral and spinal cord) injury, and the speed of bone healing is accelerated. There were some clinical reports and a few experimental studies about this phenomenon.Lots of hypotheses were made but the mechanism isn't clear so far. If trauma of brain and spinal cord injury makes some brain and spinal cord components to release into the blood and there are some factors that can accelerate the fracture healing in it? It is generally believed that the process of healing after bone fracture is a recapitulation of normal development of embryo bone, including a series of changes in the bone cells and BCM (extracellular matrix), from the beginning of injury of the cells, blood vessels and bone matrix to the complete reconstruction of the bone.It is a complex process influenced in many ways and multiple aspects by the systemic and local environment and many growth factors. Whatever the ways of promoting the repair of bone injury are, it is based on the promotion of the changes in the growth factors. IGF- I is one of growth factors in bone matrix, and it is synthetized by sclerotomal cell, promoting proliferation and differentiation of sclerotomal cell .IGF- I is an important regulatory factor in process of fracture healing ,and has important regulation effect on fracture healing. The object of this study is to establish femur fracture combined with central nerves system injury model in rats to study the effect of central nerves system injury on expression of IGF- I in blood serum,bony callus and fracture healing in rats, and to expect to further explore the mechanism of accelerated fracture healing of patients with fracture combined with central nerve injury and to widen the way of repair in trauma of bone tissue .Methods80 Wistar rats were randomly divided into 4 groups:8 in normal control group;24 in simple femur fractures group,24 in femoral fracture combined with brain injury group;24 in femoral fracture combined with spinal cord injury group.Blood specimens were collected from 6 rats selected in each group randomly from the heart on day 7,14,21 after injury.Then the blood specimens were centrifuged and the level of IGF- I in serum were measured by ELISA.Six rats were sacrificed in each group on day 7,14,28 after injury (The femur X ray examination was made to observe fracture healing),and the entire femur was harvested to measured bony callus and local expression of IGF- I in fracture site were determined by immunohistochemical stain.Bone healing was examined by HE staining.All data was analyzed by a software SPSS11.5.Results1.In the group of fracture-brain injury and fracture-spinal cord injury,bone callus were larger than those in the group of femur fractures (P<0. 05). HE staining indicated that the speed of union of fracture in the group of fracture-brain injury and fracture-spinal cord injury are faster than those in the group of femur fractures .2.The concentrations of IGF- I in femur fracture group had not changed significantly, however IGF- I in fracture-brain injury group and fracture-spinal cord injury group changed more significantly (p<0.01). It increased in the third day and the maximum value was detected after seven days, and decreased gradually in two weeks,however still much higher than those in groups of normal control and simple femur fracture (p<0.01). After three weeks,the levels in fracture-brain injury group and fracture-spinal cord injury group declined to that in normal control group and there was no statistical difference among those four groups. 3. Immunohistochemical analysis: In the groups of fracture-brain injury and fracture-spinal cord injury there was significant statistical difference (p<0.01) in the count of positive cells comp with the group of simple femur fractures on week 1,and no significant statistical difference (P>0.05) on week 3.There was no significant statistical difference (P>0.05) between group of fracture-brain injury and fracture-spinal cord injury.Conclusions1.The fracture healing rate in the central nervous injuries is faster than the group only femoral fracture.2. Spinal cord and brain injury can increase the concentration of IGF- I in blood-serum and expression of bony callus ,and accelerate fracture healing in rats.