Biomechanical alteration of stress and strain distribution associated with vertebral fracture

The phenomenon of recurrent fractures at the adjacent level of a fractured vertebra is becoming a major concern amongst medical practitioners. To date, the underlying cause of this phenomenon is still elusive; therefore, a further investigation is in dire need in order to achieve satisfactory clinical outcomes in the future. In the present study, an image based finite element analysis (FEA) was used to investigate the biomechanical alterations of spine that have been diagnosed with first lumbar (L1) vertebral compression fracture as compared to a healthy spine. The FEA assessment was made based on the model’s stress and strain distributions. A complimentary examination of bone density distribution and kyphotic deformity angle of the model would give further details on the underlying cause of this phenomenon. The results showed that the vertebral fracture model tends to produce higher stresses and strains generation in comparison to the healthy vertebral model, especially at the adjacent level of the fractured vertebra. These conditions were highly correlated to the bad quality of the bone strength due to osteoporosis, and the kyphotic structural of the fractured vertebral model. The combination of these two elements has put the structural integrity of the vertebrae at the stake of bone fracturing even under the influence of daily living activity

Finite element analysis of osteoporotic vertebrae with first lumbar (L1) vertebral compression fracture

The aim of this work is to assess the biomechanical response or load transfer response between osteoporotic (with first lumbar (L1) vertebral compression fracture) and healthy vertebrae in five vertebral physiological motions namely as compression, flexion, extension, lateral bending and axial rotation. For this purpose, an image-based heterogeneous three-dimensional patient-specific of lumbar and thoracic spinal unit (T12-L2) finite element models for healthy and osteoporotic subjects were created. The finite element analysis have shown that one of the most significant effects of osteoporosis is the tendency to produce higher stress and strain in the cancellous region of the vertebral body. The maximum stress and strain was 4.53 fold (compression) and 5.43 fold (axial rotation) higher for the osteoporotic than the healthy subject, respectively, under the similar loading activity. Uneven stress distribution patterns also have been detected in the osteoporotic vertebrae rather than the healthy vertebrae. All of these characteristics are reflected by a reduced structural strength and bone mass which might lead to an increased risk of fracture. These results strengthen the paradigm of a strong relationship between osteoporosis and its high susceptibility to fracture

Biomechanical Alteration of Stress and Strain Distribution Associated with Vertebral Fracture / Muhammad Hazli Mazlan...[et al.]

The phenomenon of recurrent fractures at the adjacent level of a fractured vertebra is becoming a major concern amongst medical practitioners. To date, the underlying cause of this phenomenon is still elusive; therefore, a further investigation is in dire need in order to achieve satisfactory clinical outcomes in the future. In the present study, an image based finite element analysis (FEA) was used to investigate the biomechanical alterations of spine that have been diagnosed with first lumbar (L1) vertebral compression fracture as compared to a healthy spine. The FEA assessment was made based on the model’s stress and strain distributions. A complimentary examination of bone density distribution and kyphotic deformity angle of the model would give further details on the underlying cause of this phenomenon. The results showed that the vertebral fracture model tends to produce higher stresses and strains generation in comparison to the healthy vertebral model, especially at the adjacent level of the fractured vertebra. These conditions were highly correlated to the bad quality of the bone strength due to osteoporosis, and the kyphotic structural of the fractured vertebral model. The combination of these two elements has put the structural integrity of the vertebrae at the stake of bone fracturing even under the influence of daily living activity

Osteoconductivity of hydrothermally synthesized beta-tricalcium phosphate composed of rod-shaped particles under mechanical unloading

Spherical beta-tricalcium phosphate (β-TCP) granules synthesized using a unique dropping slurry method expressed good osteoconductivity with prominent bone apposition and bioresorbability when implanted into the rat femur (Gonda et al, Key Eng. Mater. 361-363:1013-1016, 2008). The spherical β-TCP granules were implanted into the bone defect created in the distal end of the right femur of each 8-week-old female Wistar rat. To analyze performance of the spherical β-TCP granules as bone substitute in the bone with reduction in osteogenic potential, the right sciatic neurectomy was performed after implantation and the right hind limb was kept unloaded for 2 weeks before euthanization. Four weeks after implantation, some spherical β-TCP granules with resorption in part were surrounded by newly formed bone. Eight and 12 weeks after implantation, most of the residual β-TCP granules were embedded in newly formed bone, and total volume of the implant and newly formed bone was more than the other portions of the bone or the bone of control animals. Osteoclast activity in the implanted area was also higher than the other portions of the bone or the bone of control animals. Replacement of the intraosseous residual β-TCP granules for bone progressed at 12 weeks after implantation compared to those at 8 weeks after implantation. These data suggested that the spherical β-TCP granules stimulated osteogenesis and osteoclast activity of the unloaded bone

Biomechanical evaluation of two different types of interbody cages in posterior lumbar interbody fusion

Posterior lumbar interbody fusion (PLIF) related complications such as cage instability, cage subsidence and pedicle screws loosening are among the most prevalent cases reported postoperatively. These conditions are highly related to mechanical factors (PLIF design and material), patient health condition as well as activities conducted by the patient after undergone the surgery. Latest advancement on PLIF technology has created a new technique that allows the application of unilateral cage insertion in an oblique orientation. This solution has potentially overcome the problem related to an unintended mechanical and clinical shortcoming, provided that a bilateral posterior instrumentation (PI) is instrumented to the construct and the cage is fabricated from a material that is closely imitate the modulus elasticity of the cortical bone. In order to prove these statements, an image based finite element analysis (FEA) was conducted to assess the phenomena of cage subsidence and screw loosening by examining the stress profile on the cage construct and the vertebral bodies. Obliquely-placed unilateral PLIF with PI showed the most promising results. It showed the most minimal stress distortion at cage-endplate and pedicle screw-bone interface. In conclusion, the selection of a biocompatible cage material is the most crucial factors that has to be considered in achieving biomechanical superiority in PLIF surgery

A Functional SNP in BNC2 Is Associated with Adolescent Idiopathic Scoliosis

Adolescent idiopathic scoliosis (AIS) is the most common spinal deformity. We previously conducted a genome-wide association study (GWAS) and detected two loci associated with AIS. To identify additional loci, we extended our GWAS by increasing the number of cohorts (2,109 affected subjects and 11,140 control subjects in total) and conducting a whole-genome imputation. Through the extended GWAS and replication studies using independent Japanese and Chinese populations, we identified a susceptibility locus on chromosome 9p22.2 (p = 2.46 × 10−13; odds ratio = 1.21). The most significantly associated SNPs were in intron 3 of BNC2, which encodes a zinc finger transcription factor, basonuclin-2. Expression quantitative trait loci data suggested that the associated SNPs have the potential to regulate the BNC2 transcriptional activity and that the susceptibility alleles increase BNC2 expression. We identified a functional SNP, rs10738445 in BNC2, whose susceptibility allele showed both higher binding to a transcription factor, YY1 (yin and yang 1), and higher BNC2 enhancer activity than the non-susceptibility allele. BNC2 overexpression produced body curvature in developing zebrafish in a gene-dosage-dependent manner. Our results suggest that increased BNC2 expression is implicated in the etiology of AIS

Stimulatory effect of hydrothermally synthesized biodegradable hydroxyapatite granules on osteogenesis and direct association with osteoclasts.

Calcium-deficient hydroxyapatite (HA) granules with a unique spherical shape were prepared using an applied hydrothermal method. Spherical stoichiometric HA granules were also prepared by normal sintering and both granules were used for implantation into rat tibiae to compare the biological responses to each implant. Twelve and 24 weeks after implantation, the volume of calcium-deficient HA granules was significantly less than that of stoichiometric HA granules, and the biodegradability of calcium-deficient HA granules was confirmed. The larger number of osteoclasts, larger osteoblast surface and larger bone volume in the implanted area of calcium-deficient HA than those of stoichiometric HA suggested that osteoclastic resorption of calcium-deficient HA affected osteogenesis in that area. To analyze the direct contribution of osteoclasts to osteogenesis, C2C12 multipotent myoblastic cells, which have the potential to differentiate into osteoblasts in the presence of bone morphogenetic protein 2, were cultured with supernatants of osteoclasts cultured on calcium-deficient HA, stoichiometric HA, beta-tricalcium phosphate disks or plastic dishes, or bone marrow macrophages cultured on plastic dishes. Supernatants of osteoclasts but not bone marrow macrophages stimulated the expression of Runx2 and osteocalcin in C2C12 cells in concert with bone morphogenetic protein 2. The expression of alkaline phosphatase was stimulated with supernatants of osteoclasts cultured on ceramic disks. These results suggested that osteoclasts produced certain soluble factors which stimulated osteoblastic differentiation and they were thought to be associated with the induction of a larger osteoblast surface and bone volume in the animals implanted with calcium-deficient HA granules

Scoliosis in Shprintzen–Goldberg Syndrome

We report a case of scoliosis in a 12-year-old girl with Shprintzen–Goldberg syndrome. She was diagnosed with Shprintzen–Goldberg syndrome at birth. She was hospitalized for a surgical treatment because scoliosis gradually progressed. Preoperative X-ray confirmed 80° symptomatic scoliosis in T10–L5. Posterior correction and fusion were performed, and postoperative X-ray showed a correction to 43°in T10-L5. Limited subcutaneous tissues and fragile bones must be considered when selecting the appropriate surgical method. Accurate placement of a screw into thin pedicle is essential to obtain sufficient correction and fusion. The use of a navigation system is recommended