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Biomedical subjects

I Ohnishi

Publications and source records attributed to I Ohnishi.

12 recordsLinked to original sources
PubMed2005

A new method for measurement of bone deformation by echo tracking.

No method has been available to noninvasively detect bone deformation or strain under loading in vivo. We focused on ultrasonic measurement of the displacement at a certain point on a bone using the echo-tracking method (ET). To develop a method that can noninvasively detect bone deformation in vivo, a preliminary investigation was performed. We investigated the accuracy of measuring displacement with our echo tracking system by using a flat metal panel and found that the method could measure displacement with a precision of a few microns. A three-point bending test of a porcine tibia with both ends fully constrained was performed to measure bone surface displacement, and simultaneous measurement of the surface strain was done using two strain gauges. The correlation between the displacement measured by ET and the strain gauge readings was completely linear (r=0.999), showing that the method could precisely detect bone deformation. The loads versus displacement curves obtained with cyclic loading were typical hysteresis loops that showed viscoelastic properties of the measured bone. We also improved a multi-ET system capable of simultaneously tracking multiple points to detect deformation of the bone surface. Measurement by this echo tracking system was also compared with strain gauge readings during a three point bending test with both ends of the tibia supported. The linearity of both methods was very high (r=0.998). Our ET method might have considerable potential for noninvasive measurement of bone viscoelasticity and plasticity.

Aluminum↗
PubMed2002

Intraoperative lymphatic mapping and sentinel lymph node biopsy in patients with papillary carcinoma of the thyroid gland.

We examined the feasibility of sentinel lymph node biopsy for thyroid cancer. Thirty-eight patients with papillary thyroid carcinoma underwent intraoperative lymphatic mapping and sentinel lymph node biopsy. At surgery, we exposed the thyroid gland and used a tuberculin syringe to inject 0.2 ml of 1% patent blue dye directly into the thyroid mass. The lymphatics and the lymph node dyed with blue dyes, was excised as a sentinel lymph node. Modified radical neck dissection was performed following sentinel lymph node biopsy and the diagnostic ability of sentinel lymph node biopsy was examined. A sentinel lymph node was identified successfully in 27 (71%) of 38 patients. Sentinel lymph node biopsy removed one to three lymph nodes (median, two nodes). Eighteen patients had paratracheal sentinel lymph nodes, five patients had jugular sentinel lymph nodes, and four patients had both. Histological nodal metastasis was recognized in 16 of 27 cases. The positive rate of cancer metastases in sentinel lymph nodes was 58%, which was significantly higher than 11% in non-sentinel lymph nodes. Diagnostic ability of sentinel lymph node biopsy showed that accuracy was 89%, sensitivity was 84%, and specificity was 100%. Our preliminary study indicated that sentinel lymph node biopsy was available on detection of non-palpable nodal metastasis in the patients with thyroid cancer; however, further experience and refinement are needed.

Adult↗
PubMed2001

Insulin secretory response is positively associated with the extent of ossification of the posterior longitudinal ligament of the spine.

BACKGROUND: Glucose intolerance is frequently found in patients with ossification of the posterior longitudinal ligament of the spine. This study was undertaken to examine the relationship between glucose intolerance and the extent of ossification in patients with ossification of the posterior longitudinal ligament. METHODS: A total of 100 patients with ossification of the posterior longitudinal ligament (the overall study group), including fifty-two inpatients who were scheduled to have an operation (the inpatient group) and forty-eight outpatients who had undergone an operation, were analyzed. Indices of glucose metabolism-fasting plasma glucose and serum insulin levels, hemoglobin A1c level, and insulinogenic index (a ratio of the increment of the serum level of insulin to that of glucose)-as well as age and body-mass index were correlated with the extent of ossification, as determined by the number of vertebral levels affected with ossification of the posterior longitudinal ligament (extent of ossification), in the inpatient group. In addition, a similar analysis was performed in twenty-eight inpatients (the selected inpatient group) whose ages and body-mass indices were within one standard deviation of the mean values of those of the inpatient group. Association of a polymorphism in the gene of insulin receptor substrate-1, an essential substrate in insulin signaling, with the extent of ossification was evaluated with genomic DNA extracted from the overall study group. RESULTS: Multiple-regression analysis revealed direct correlations of age (p = 0.038), body-mass index (p = 0.006), and insulinogenic index (p = 0.0003) with the extent of ossification of the posterior longitudinal ligament in the inpatient group. The fasting plasma glucose level, the hemoglobin A1c level, and the stage of glucose tolerance were not associated with the extent of ossification. In the analysis of the selected inpatient group, only the insulinogenic index was correlated with the extent of ossification (p = 0.002). However, no significant association was seen between the insulin receptor substrate-1 polymorphism and the extent of ossification. CONCLUSIONS: The insulin secretory response was associated with the extent of ossification of the posterior longitudinal ligament. Since insulin receptor substrate-1 is expressed both in the spinal ligament and in the tissues regulating glucose metabolism, we speculate that some other molecules related to insulin signaling that are impaired only in the tissues regulating glucose metabolism may be responsible for the progression of ossification. We also speculate that the upregulation of insulin production due to the impairment of insulin action may stimulate osteoprogenitor cells in the ligament to induce ossification. CLINICAL RELEVANCE: The insulinogenic index may be useful as a serum marker for the prediction of progression of ossification of the posterior longitudinal ligament. This study may serve as a stimulus for evaluation of the use of various drugs that may improve the response to insulin in the tissues regulating glucose metabolism to prevent the progression of ossification.

Adult↗
PubMed2000

New instrumentation for video-assisted anterior spine release.

Endoscopic surgery in the area of orthopedics has been evolving, particularly in spine surgery. We describe the clinical outcome of thoracoscopic anterior spine release using new instruments. A harmonic scalpel (HS) with a 5-mm hook dissector was used to dissect the spine and rib and to coagulate and transect the vascular bundles. A rib dissector and resector were used for excision of the rib to be implanted in the disk spaces. We treated scoliosis in four patients (three male, one female) with a mean age of 19.5 +/- 4.5 years and thoracolumbar kyphosis in a 16-year-old male patient. A mean number of 6.5 +/- 2.5 vertebrae with scoliosis and four vertebrae with kyphosis were released. In all cases, division of the vascular bundle and exposure of the spine were completed using only the HS, and excision of a rib segment was performed via a port incision using only the rib dissector and resector. The mean duration of thoracoscopic anterior release was 92 +/- 28 min. Blood loss was minimal during and after surgery. Thoracoscopic anterior spine release can be facilitated by the new instruments described above.

Adolescent↗
PubMed1999

Autogenous onlay grafting for enhancement of extracortical tissue formation over porous-coated segmental replacement prostheses.

BACKGROUND: Prosthetic reconstruction with extracortical bone-bridging is an effective method of limb salvage after resection of a malignant or locally invasive benign bone tumor. Use of cancellous bone graft alone is less effective in achieving extracortical bone-bridging. The present study was performed to investigate the effects of a corticocancellous onlay graft on bone and soft-tissue formation over a porous-coated replacement prosthesis in the mid-diaphyseal region of canine femora. METHODS: Bilateral resection of a six-centimeter segment of the femoral diaphysis and reconstruction with a porous-coated segmental prosthesis was performed in six mongrel dogs. In one limb (the experimental side), eight strips of corticocancellous bone were evenly placed around the junctions between the femur and the prosthetic surface. Cancellous bone was placed under and between the strips of cortical bone. No graft was used in the other limb (the control side). The animals were followed for twelve weeks, with sequential assessments of load-bearing and radiographic evaluation. Biomechanical, histological, and microradiographic analyses of the specimens were performed after death. RESULTS: On the control side, load-bearing at four weeks postoperatively was significantly decreased compared with the preoperative value (p<0.05); no difference in these values could be detected on the experimental side. Both the area of the callus and the contact area between the bone and the prosthetic shoulder were greater on the experimental side (p<0.05). The mechanical stiffness and the maximum torque at failure of the extracortical bridging tissue across the junction between the bone and the prosthetic shoulder were eighteen (p<0.007) and five times greater (p<0.05), respectively, on the experimental side. CONCLUSIONS: Extracortical bone-bridging was accomplished with corticocancellous onlay bone-grafting. Without bone-grafting, bone formed only occasionally. Bone-grafting also enhanced the formation of a soft-tissue capsule around the prosthesis.

Animals↗
PubMed1998

Sliding performance of unilateral external fixators for tibia.

Some unilateral external fixators have a sliding mechanism to achieve dynamic axial fixation. However, it has been reported that binding of this mechanism occurs during routine ambulation. The Hifixator, a unilateral external fixator, has been developed which has a new type of sliding mechanism. The mechanism of the Hifixator was tested by connecting it to a fractured bone model with pins, and applying dynamic axial loading. The conditions of connection between the pins and bone model were varied to simulate loosening of the pins. Two other external fixators commonly used for tibias, Orthofix and Monotube (blue), were tested for comparison. The amount of sliding motion of the Hifixator was maintained at more than 72% of the motion at the fracture site even when pins were loose and a torque of 4 N m was applied. The sliding mechanism of the Hifixator was shown to be more durable than those of the other fixators tested for conditions found in application to tibias.

Biomechanical Phenomena↗
PubMed1995

Relationship between the anatomic and dermatomal levels of spinal cord tumors in the thoracic region.

In neurologic examination of patients with a suspected compressive lesion at the thoracic region, the dermatomic level of sensory disturbance is the only index indicating the anatomic level of a lesion. Because spinal cord tumors usually are solitary compressive lesions, the relationship between the anatomic and dermatomic levels is conveniently examined. We examined the relationship between the highest dermatomic level of sensory disturbance and the anatomic level, axial location, and type of spinal cord tumors in the thoracic region in 19 patients (8 men and 11 women aged 27-78 years; 11 neurinomas, 7 meningiomas, 1 neurofibroma). The distribution of sensory disturbance was evaluated with 3-g Frey hair and 1-g pin-prick examinations. The dermatomic distribution of sensory disturbance was diagnosed according to the dermatome chart of Keegan and Garrett. The anatomic level and axial location of the tumor were highly related to the sensory disturbance. Eight of 12 tumors in which the dermatomic level of sensory disturbance was within one vertebral segment of the anatomic level were situated in the middle or lower thoracic region (T6-T10). All five tumors in which the dermatomic level was two or more vertebral segments away from the anatomic level were situated at the conus medullaris (T12) or upper thoracic region (T1-T5); the highest level of sensory disturbance was from 4 to 11 segments below the anatomic level of the tumor. In two patients with no sensory disturbance, the tumor was in the upper thoracic region (T5) and compressed the spinal cord from the dorsal side. When a spinal cord tumor at the thoracic region is suspected, imaging examinations should be performed sufficiently cranially.

Adult↗
PubMed1993

Increase of serum growth hormone-binding protein in patients with ossification of the posterior longitudinal ligament of the spine.

Serum growth hormone-binding protein (GHBP) was measured in 26 patients with ossification of the posterior longitudinal ligament of the spine (OPLL) and 19 age-matched controls. Serum GHBP level was significantly higher in the OPLL group than in the controls, whereas there was no statistical difference between the two groups in serum level of growth hormone, insulin-like growth factor (IGF)-1, and IGF-2. These results, taken together with the hypothesis that serum GHBP reflects the number of GH receptors in tissue, suggest that GH receptors are increased in patients with OPLL.

Carrier Proteins↗
PubMed1992

The role of calcium metabolism abnormalities in the development of ossification of the posterior longitudinal ligament of the cervical spine.

To study the role of calcium metabolism in the development of ossification of the posterior longitudinal ligament of the cervical spine, 39 patients with affected cervical spines were investigated using an oral calcium tolerance test and followed by cervical spinal radiography to evaluate disease progression. The average follow-up was 6 years. The patients were divided into two groups according to their responsiveness to an oral calcium load: a group of 14 patients with decreased calciuric responses and another group of 25 with normal responses. The incidence of the development of cervical ossification of the posterior longitudinal ligament in the decreased-response group was significantly higher than that in the normal group. Because these patients were managed operatively by laminoplasty, however, the incidence was low irrespective of their calciuric responses. These results suggest that the development of cervical ossification of the posterior longitudinal ligament is associated with decreased intestinal calcium absorption but that treatment with laminoplasty alters the mechanical environment of the cervical spine (eg, range of motion of the cervical spine is limited). The development of cervical ossification of the posterior longitudinal ligament may be controlled by this procedure.

Aged↗
PubMed1991

[Roentgenological manifestation of ossification of the posterior longitudinal ligament in the cervical spine causing severe spinal canal stenosis--a group comparison with and without marked spinal cord dysfunction].

Relationship between the degree of clinical symptoms and the lateral roentgenograms of the cervical OPLL causing severe spinal canal stenosis was studied among patients whose roentgenological minimum antero-posterior diameters of the available spinal canals were under 9mm. Lateral roentgenograms of 28 clinically mild patients were compared with those of 20 clinically severe patients. The type of ossification, the extent of OPLL, the narrowest level of the available spinal canal, and the minimum a-p diameter were not statistically significant parameters. The degree of canal stenosis at the 1cm cranial and 1cm caudal levels from the narrowest level, and the axial extent of canal stenosis around the narrowest level were less significantly in the group with mild symptoms than in the group with severe symptoms.

Adult↗
PubMedDate not supplied

Evaluation of the fracture site mechanical properties in vivo by monitoring the motion of a dynamic pin clamp during simulated walking.

OBJECTIVE: To monitor pin clamp motion using a displacement sensor over time during weight bearing and to investigate whether this method could contribute to quantitative assessment of the mechanical properties of fracture healing. METHODS: Patients with a shaft fracture of the tibia were monitored, all of whom were in the stage of dynamization. The hifixator equipped with a ball bearing mechanism was used as a dynamic external fixator. The displacement was recorded versus time during stamping with weight bearing of the patients. The displacement curve had an oscillatory component synchronized with touch down and lift up of the foot, a time-dependent component expressed by shifting of the baseline, and an irreversible component during a non-weight bearing period after stamping. The three components were analyzed with a simple Voigt model. RESULTS: In all patients, both the amplitude of the oscillatory component and the time-dependent component expressed as retardation time decreased as fracture healing proceeded, and by the time of fixator removal the irreversible component had disappeared. CONCLUSIONS: The monitoring method could quantitatively evaluate viscoelastoplasticity of the healing fracture site. RELEVANCE: Until now, there has been few method for assessing the viscoelastic property of the healing fracture site in vivo. Although the method described here involves some assumptions and approximations, it was able to quantitatively assess the viscoelasticity of the healing fracture site.

Adult↗