Anatomic changes in the macroscopic morphology and microarchitecture of denervated long bone tissue after spinal cord injury in rats

Neonatal brachial plexus injuries and their impact on growing bone. An experimental study

Neonatal brachial plexus palsy remains a problem, even in light of current advances in perinatal care. While many cases resolve spontaneously, the concern remains on the best means of surgical management for restoration of elbow flexion and shoulder reanimation. The present experimental study in an animal model examines the evidence that supports that neonatal brachial plexus injuries result in structural changes in the affected bone. The study suggests that if the microsurgical reinnervation takes place early enough, these changes may be diminished. On the other hand there is no way to identify at birth, which injuries will be permanent and will need surgical repair and which will spontaneously improve.

Electrical stimulation and denervated muscles after spinal cord injury

Spinal cord injury (SCI) population with injury below T10 or injury to the cauda equina region is characterized by denervated muscles, extensive muscle atrophy, infiltration of intramuscular fat and formation of fibrous tissue. These morphological changes may put individuals with SCI at higher risk for developing other diseases such as various cardiovascular diseases, diabetes, obesity and osteoporosis. Currently, there is no available rehabilitation intervention to rescue the muscles or restore muscle size in SCI individuals with lower motor neuron denervation. We, hereby, performed a review of the available evidence that supports the use of electrical stimulation in restoration of denervated muscle following SCI. Long pulse width stimulation (LPWS) technique is an upcoming method of stimulating denervated muscles. Our primary objective is to explore the best stimulation paradigms (stimulation parameters, stimulation technique and stimulation wave) to achieve restoration of the denervated muscle. Stimulation parameters, such as the pulse duration, need to be 100–1000 times longer than in innervated muscles to achieve desirable excitability and contraction. The use of electrical stimulation in animal and human models induces muscle hypertrophy. Findings in animal models indicate that electrical stimulation, with a combination of exercise and pharmacological interventions, have proven to be effective in improving various aspects like relative muscle weight, muscle cross sectional area, number of myelinated regenerated fibers, and restoring some level of muscle function. Human studies have shown similar outcomes, identifying the use of LPWS as an effective strategy in increasing muscle cross sectional area, the size of muscle fibers, and improving muscle function. Therefore, displaying promise is an effective future stimulation intervention. In summary, LPWS is a novel stimulation technique for denervated muscles in humans with SCI. Successful studies on LPWS of denervated muscles will help in translating this stimulation technique to the clinical level as a rehabilitation intervention after SCI.

A Primary Care Provider's Guide to Bone Health in Spinal Cord-Related Paralysis

Individuals with spinal cord injury/disorder (SCI/D) are at high risk for developing secondary osteoporosis. Bone loss after neurologic injury is multifactorial and is dependent on the time from and extent of neurologic injury. Most bone loss occurs in the first year after complete motor paralysis, and fractures occur most commonly in the distal femur and proximal tibia (paraplegic fracture). The 2019 International Society for Clinical Densitometry Position Statement in SCI establishes that dual-energy X-ray absorptiometry (DXA) can be used to both diagnose osteoporosis and predict lower extremity fracture risk in individuals with SCI/D. Pharmacologic treatments used in primary osteoporosis have mixed results when used for SCI/D-related osteoporosis. Ambulation, standing, and electrical stimulation may be helpful at increasing bone mineral density (BMD) in individuals with SCI/D but do not necessarily correlate with fracture risk reduction. Clinicians caring for individuals with spinal cord-related paralysis must maintain a high index of suspicion for fragility fractures and consider referral for surgical evaluation and management.

Gene expression changes are associated with severe bone loss and deficient fracture callus formation in rats with complete spinal cord injury

STUDY DESIGN

Animal study.

OBJECTIVES

To investigate the effects of SCI on bone quality and callus formation.

SETTING

University and hospital-based research center, Ribeirão Preto Medical School, Brazil.

METHODS

Rats sustaining a complete SCI for 10 days received a fracture at the femoral diaphysis and were followed-up for 14 days. Bone callus and contralateral nonfractured tibia were assessed by DXA, µCT, ELISA, histomorphometry, immunohistochemistry, biomechanical test, and gene expression.

RESULTS

SCI downregulated osteoblastic-related gene expression in the nonfractured tibias, associated with a twofold increase in osteoclasts and overexpression of RANK/RANKL, which resulted in lower bone mass, impaired microarchitecture, and weaker bones. On day 14 postfracture, we revealed early and increased trabecular formation in the callus of SCI rats, despite a marked 75% decrease in OPG-positive cells, and 41% decrease in density. Furthermore, these calluses showed higher porosity and thinner newly formed trabeculae, leading to lower strength and angle failure.

CONCLUSIONS

SCI-induced bone loss resulted from increased bone resorption and decreased bone formation. We also evidenced accelerated bone healing in the SCI rats, which may be attributed to the predominant intramembranous ossification. However, the newly formed bone was thinner, less dense, and more porous than those in the non-SCI rats. As a result, these calluses are weaker and tolerate lesser torsion deformation than the controls, which may result in recurrent fractures and characterizes a remarkable feature that may severely impair life quality.

The effect of peripheral nervous system in growing bone biomechanics. An experimental study

Objective

There are several factors which affect bone growth. One of them is the peripheralnervous system whose effect on the biomechanics has not been extensively studied. The purpose of this study is to assess the effect of peripheral nervous system in bone biomechanics in an experimental rat model.

Materials & methods

27 male Wistar rats were used. In all animals, the roots of the right brachial plexus were dissected and after that the animals were divided into three groups A, B and C. The animals were sacrificed six, nine, and twelve months respectively after the denervation. Both humerus were resected and biomechanical analysis was performed.

Results

According to the findings of the present study the denervated bones sustain less loading before fracture and they become also more elastic. Additionally, in greater time after denervation plastic deformity is noticed.

Conclusion

Apart from structural changes, the peripheral nerves are responsible for biomechanic changes in the bones such the greater elasticity of the bone and the reduced strength.