Biomedical subjects

Isao Ohnishi

Publications and source records attributed to Isao Ohnishi.

14 recordsLinked to original sources

PubMed2007

Distraction osteogenesis promotes angiogenesis in the surrounding muscles.

Distraction osteogenesis is used to treat atrophic nonunion and focal osteomyelitis. It enhances blood vessel formation in the distracted callus and in the surrounding soft tissues. Long-term angiogenesis, however, is not well described. We hypothesized newly formed blood vessels persist in the surrounding muscles until the late consolidation period. We performed unilateral tibial lengthening in eight adult Beagles. Seven days after tibial osteotomy, we began lengthening for 30 days, following which consolidation was allowed to proceed for another 60 days. We took bilateral microangiograms of the bilateral tibialis anterior, extensor digitorum longus, and gastrocnemius muscles. We determined the blood vessel volume density and the longitudinal and transverse microangiographic scores. The number of blood vessels in specified diameter ranges was determined histologically. The blood vessel volume density of the distracted limb was higher in all three muscles. The longitudinal microangiographic score was higher for the tibialis anterior and extensor digitorum longus muscles on the distracted side, whereas the transverse microangiographic score was not higher. Histologically, the number of blood vessels less than 100 mum in diameter on the distracted side was higher in the tibialis anterior and extensor digitorum longus muscles. Our data suggest distraction osteogenesis activates angiogenesis and maintains increased vascularity until the late consolidation period.

Angiography↗

PubMed2006

Prediction of strength and strain of the proximal femur by a CT-based finite element method.

Hip fractures are the most serious complication of osteoporosis and have been recognized as a major public health problem. In elderly persons, hip fractures occur as a result of increased fragility of the proximal femur due to osteoporosis. It is essential to precisely quantify the strength of the proximal femur in order to estimate the fracture risk and plan preventive interventions. CT-based finite element analysis could possibly achieve precise assessment of the strength of the proximal femur. The purpose of this study was to create a simulation model that could accurately predict the strength and surface strains of the proximal femur using a CT-based finite element method and to verify the accuracy of our model by load testing using fresh frozen cadaver specimens. Eleven right femora were collected. The axial CT scans of the proximal femora were obtained with a calibration phantom, from which the 3D finite element models were constructed. Materially nonlinear finite element analyses were performed. The yield and fracture loads were calculated, while the sites where elements failed and the distributions of the principal strains were determined. The strain gauges were attached to the proximal femoral surfaces. A quasi-static compression test of each femur was conducted. The yield loads, fracture loads and principal strains of the prediction significantly correlated with those measured (r=0.941, 0.979, 0.963). Finite element analysis showed that the solid elements and shell elements in undergoing compressive failure were at the same subcapital region as the experimental fracture site.

Adult↗

PubMed2006

Nonlinear finite element model predicts vertebral bone strength and fracture site.

STUDY DESIGN: A study on computed tomography (CT)-based finite element (FE) method that predicts vertebral strength and fracture site using human cadaveric specimens. OBJECTIVE: To evaluate the accuracy of the nonlinear FE method by comparing the predicted data with those of mechanical testing. SUMMARY OF BACKGROUND DATA: FE methods may predict vertebral strength and fracture site but the prediction has been difficult because of a complex geometry, elastoplasticity, and thin cortical shell of the vertebra. METHODS: FE models of the 12 thoracolumbar vertebral specimens were constructed. Nonlinear FE analyses were performed, and the yield load, the fracture load, the sites where elements failed, and the distribution of minimum principal strain were evaluated. A quasi-static uniaxial compression test for the same specimens was conducted to verify these analyses. RESULTS: The yield loads, fracture loads, minimum principal strains, and fracture sites of the FE prediction significantly correlated with those measured. CONCLUSIONS: Nonlinear FE model predicted vertebral strength and fracture site accurately.

Adult↗

PubMed2006

[Prediction of bone strength using a CT based finite element method].

Hip fractures are the most serious complication of osteoporosis and have been recognized as a major public health problem. In elderly persons, hip fractures occur as a result of increased fragility of the proximal femur due to osteoporosis. It is essential to precisely quantify the strength of the proximal femur in order to estimate the fracture risk and plan preventive interventions. Computed tomography (CT)-based finite element analysis could possibly achieve precise assessment of the strength of the proximal femur. We have developed a three dimensional simulation model that could accurately predict the strength and surface strains of the proximal femur using a CT-based finite element method. The axial CT scans of the proximal femora were obtained with a calibration phantom, from which the 3D finite element models were constructed. Materially nonlinear finite element analyses were performed. The yield and fracture loads were calculated, while the sites where elements failed and the distributions of the principal strains and stresses were determined. The simulation is patient specific and could provide us of a useful tool to evaluate fracture risk in patients with osteoporosis. The technology utilized in this method would make a rapid progress in accordance with the progress of both imaging and computer technologies and much more precise prediction of the fracture risk will be realized in the near future.

Aged↗

PubMed2005

Measurement of the tensile forces during bone lengthening.

BACKGROUND: The purpose of this study was to investigate the effects of lengthening frequency on mechanical environment in limb lengthening. METHODS: Tensile forces were continuously monitored using a load sensor attached to a unilateral external fixator. Twenty patients were monitored. Ten patients were with acquired femoral shortening, and five of them underwent quasi-continuous lengthening of 1440 steps per day, and the other five received step lengthening twice a day. The other 10 patients were with achondropalsia. Five of them underwent the same quasi-continuous lengthening, and the other five received the same step lengthening. The circadian change and the daily course of the tensile forces were assessed and compared between quasi-continuous lengthening and step lengthening. FINDINGS: As for circadian change, an acute increase in the force took place simultaneously with each step of lengthening in the step-lengthening group, but very little change of the baseline force level was seen during quasi-continuous lengthening. As for daily course of the tensile force, it increased almost linearly in both lengthening frequency groups in the initial stage of lengthening. No significant difference of the average force increment rate in this phase was recognized between the quasi-continuous and step lengthening groups irrespective of the etiologies. INTERPRETATION: The lengthening frequency greatly affected the circadian change of the tensile force, but did not affect the increment rate of the force in the linear phase.

Adolescent↗

PubMed2005

Osteogenesis and angiogenesis in regenerating bone during transverse distraction: quantitative evaluation using a canine model.

For some patients with a bone defect, curved deformity, or small diameter bone, transverse distraction might be better indicated than bone transport or lengthening. However, detailed quantitative evaluation of osteogenesis or angiogenesis during transverse distraction by creating a well-controlled animal model has not been done. We established a transverse distraction model of the canine tibia. A rectangular cortex was separated for a distraction fragment. Seven days after the operation, 0.5-mm distraction was applied twice daily for 14 days. After a 28-day consolidation period, the animals were sacrificed. Quantitative evaluations of the rates of mineralization and the increases of bone mineral density indicated faster mineralization and earlier corticalization of the regenerating bone in the initial stage of the consolidation period. The average blood vessel volume ratio in the distraction area was more than three times greater than in the intact contralateral tibiae. We hypothesized that adequate preservation of the marrow arteries and stability of the distraction site throughout an experimental period could induce this faster osteogenesis. Our results indicated that the transverse distraction technique was feasible. The transverse distraction technique could be indicated for patients with small-diameter bones or with massive bone defects.

Animals↗

PubMed2005

Effect of vascularity on canine distracted tibial callus consolidation.

In the consolidation period of distraction osteogenesis, mineralization occurs before corticalization. We hypothesized that the increased rate of bone mineral density correlates to the density of vascularity in the callus. We unilaterally lengthened the tibia in eight adult beagles. After a waiting period of 7 days, tibiae were lengthened for 30 days. After a consolidation period of an additional 60 days, all animals were euthanized. Just before euthanasia, blood vessels were perfused with 50% w/v barium sulfate solution, and soft radiographs of the distracted callus and the control tibiae were taken. Bone mineral density of the regenerated bones was measured preoperatively by quantitative computed tomography on Days 37, 68, and 98. Increases of the percent bone mineral density (from Day 37 to Day 98 and from Day 68 to Day 98) correlated with the blood vessel volume density ratios on Day 98. Our results suggest that preservation of the higher density of blood vessels in the consolidation period could lead to the better mineralization of the distracted callus.

Angiography↗

PubMed2004

Prediction of the strength and fracture location of the femoral neck by CT-based finite-element method: a preliminary study on patients with hip fracture.

The purpose of this study was to predict fracture load and fracture location of the femora by means of the originally developed CT-based finite-element method (FEM). The femora of ten patients with contralateral hip fracture were analyzed to estimate fracture strength and to investigate whether the predicted fracture locations were similar to those of contralateral hip fractures. FEM has been utilized to determine the stress or strain distribution in bones under a certain load. FEM analyses of the strength of the femora in cadavers and patients have been reported, but those of hip fracture patients have not been analyzed. The femora of ten patients with contralateral hip fracture and those of three volunteers were analyzed based on the axial CT images of the whole femora. Prediction of hip fracture load and failure locations was made using CT-based finite-element analysis software. The predicted strength of the patients was less than half that of volunteers, and the predicted fracture lines existed at the proximal femur in all patients. It can be concluded that the FEM analyses adopted in this study are able to predict the fracture locations and load of the femora in patients with hip fracture.

Aged↗

PubMed2003

Cervical myelopathy in an adult due to atlantoaxial subluxation associated with Down syndrome: a case study.

Atlantoaxial subluxation resulting in cervical myelopathy in patients with Down syndrome has been well documented. The risk of cervical myelopathy is reported to decrease with age, and reports of adult-onset cases are limited. We report an adult patient with Down syndrome who developed cervical myelopathy and was successfully treated by surgery. Because there is little information on this condition with adult onset, we report the features of the radiographic findings. Particular care over the long term should be taken in those who have atlantoaxial subluxation combined with odontoid hypoplasia or accessory ossicles, as they are at particular risk of cervical myelopathy even during adulthood.

Adult↗

PubMed2003

Correction of tibial deformity in adults.

This report from five hospitals in Japan describes the results of correcting adult tibial deformities using external fixation. There were 49 patients with 59 lower limb deformities, with trauma being the most common cause of the deformity. Varus angulation was the most common deformity, and the most common magnitude was 11 degrees -30 degrees. Twenty-two patients had a leg-length discrepancy. The aim of the correction was to normalize both the mechanical axis and the inclination of the knee and ankle joints. In 63% of the patients corrections were performed gradually during bone lengthening or acutely after bone lengthening. Altogether, 71% of the patients were completely corrected, and no leg-length discrepancies remained after correction in 47%. Complications were encountered in 22 patients, about half of which were pin tract infections, 28% refractures, and the remainder delayed consolidation or fixator failure. There were no neurological or circulatory complications. The average fixation duration was 9 months. The average hospital charges were 3,740,000 yen in bilateral correction patients and 1,940,000 yen in unilateral correction patients. External fixation can correct not only the mechanical axis and joint inclination but also leg-length discrepancy simultaneously.

Adolescent↗

PubMed2003

A femoral neck fracture model in rabbits.

A technique was developed to create a reproducible femoral neck fracture in vitro using 5-month-old JW/CSK series male rabbits. Force attenuation of a newly developed damping material was also evaluated using this model. Ten pairs of the femora with smaller deviations in length and weight were harvested and cleaned of soft tissue. Either a right or left of each pair of the specimens was randomly selected and put into either the control or the experimental group, both of which contained equal numbers of the right and left femora. The specimens were attached to an L-shaped plate and embedded in a resin from the proximal diaphysis to the distal end so as to maintain a consistent position of the femora. They were mounted and fixed on a pedestal slanted in the coronal plane at 20 degrees. The impact load testing was conducted using an impact mallet dropped from a height of 3 cm. The impact load was applied onto the femoral head. To the specimens in the experimental group, attenuated impact forces were loaded through the damping material, but those in the control group were subjected to forces directly transmitted without the material. All the impact testing was performed in a temperature and humidity controlled chamber. All of the femoral specimens exposed to the direct impact forces (controlled group) sustained fracture at the neck. The fracture line passed from the base of the femoral head laterally and to the calcar area just proximal to the minor trochanter medially. The location of each fracture line was almost identical among the specimens. None of the specimens that were exposed to the impact force through the damping material (experimental group) sustained fracture macroscopically and roentgenographically.

Animals↗

PubMed2002

Long-term results of operative treatment for cervical spondylotic myelopathy in patients with athetoid cerebral palsy: an over 10-year follow-up study.

STUDY DESIGN: A retrospective radiographic and medical record analysis of patients followed for more than 10 years after operative treatment for cervical spondylotic myelopathy complicating athetoid cerebral palsy. OBJECTIVE: To describe the incidence of late neurologic deterioration and spinal deformity after operative treatment for cervical spondylotic myelopathy in athetoid cerebral palsy. SUMMARY OF BACKGROUND DATA: The possibility of recurrence of symptoms after operative treatment for cervical spondylotic myelopathy seems greater in patients with athetoid cerebral palsy because of their involuntary neck movements. Although there are several reports of surgical results, long-term follow-up studies are very rare. METHODS: Ten patients with athetoid cerebral palsy were evaluated over an average of 15 years after anterior decompression (corpectomy) and fusion (three patients), laminectomy (one patient), and laminoplasty (six patients, four with accompanying posterior fusion). They averaged 45 years of age at surgery. Surgical results were assessed using Kurokawa's method. Late neurologic deterioration was based on decrement in the JOA score, and the evolution of kyphosis or instability of the cervical spine was observed radiographically. RESULTS: Surgical results at the most improved period were good or excellent in all 10 patients. Eight showed late neurologic deterioration, however, and six of them deteriorated from 8 to 13 years after surgery, largely because of progressive deformity. CONCLUSIONS: Long-term follow-up evaluation is essential in any type of operation, particularly with patients with athetoid cerebral palsy who often undergo this operation in their 30s or 40s.

Adult↗

PubMed2002

Effect of pulsed electromagnetic fields (PEMF) on late-phase osteotomy gap healing in a canine tibial model.

The effects of a pulsed electromagnetic field (PEMF) on late bone healing phases using an osteotomy gap model in the canine mid-tibia were investigated. A transverse mid-diaphyseal tibial osteotomy with a 2-mm gap was performed unilaterally in 12 adult mixed-breed dogs and stabilized with external fixation. Animals in the variable group (n = 6) were treated with PEMF for 1 h daily starting 4 weeks after surgery for a total of 8 weeks, whereas no stimulation signal was generated in the control group (n = 6). Functional load-bearing and radiographic assessments were conducted time-sequentially until euthanasia 12 weeks after surgery. Torsional tests and an analysis of undecalcified histology were performed on the retrieved mid-tibial diaphysis containing the osteotomy site. In the PEMF group, load-bearing of the operated limb recovered earlier when compared to the control group (p < 0.05). Load-bearing in the PEMF group at 8 weeks was greater than in the control group (p < 0.02). The periosteal callus area increased following surgery at 6 weeks (p < 0.05) and thereafter (p < 0.01) in the PEMF group, while a significant increase was observed at 8 and 10 weeks after surgery (p < 0.05) in the control group. Both the normalized maximum torque and torsional stiffness of the PEMF group were significantly greater than those of the control group (p < 0.04 and p < 0.007, respectively). Histomorphometric analyses revealed greater new-bone formation (p < 0.05) in the osteotomy gap tissue and increased mineral apposition rate (p < 0.04) and decreased porosity in the cortex adjacent to the osteotomy line (p < 0.02) in the PEMF group. PEMF stimulation of 1 h per day for 8 weeks provided faster recovery of load-bearing, a significant increase in new bone formation, and a higher mechanical strength of the healing mid-tibial osteotomy. This study revealed enhancing effects of PEMF on callus formation and maturation in the late-phase of bone healing.

Animals↗

PubMedDate not supplied

Treatment of congenital pseudarthrosis of the tibia: a multicenter study in Japan.

Treatment of congenital pseudarthrosis of the tibia (CPT) remains a challenge. To clarify the current situation in treatment, a multicenter study was carried out to obtain information on the results of CPT treatment. The objective of this study was to propose appropriate treatment guidelines for CPT. Records of 73 patients with CPT who underwent surgical treatment were collected from 32 hospitals. The modality of the treatment was 26 with Ilizarov technique, 25 with free vascularized fibular graft, 7 with a combination of the two techniques, 6 with intramedullary nailing with free bone grafting, 5 plating with free bone grafting, and 4 with other treatments. Fifty-four procedures resulted in union, 7 resulted in delayed union, 7 were left un-united, 1 underwent amputation, and the results were unknown in 4. According to the results of this study, the most acceptable methods of treatment of CPT are the Ilizarov method and the vascularized fibular graft.

Adolescent↗