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Biomedical subjects

T Sakou

Publications and source records attributed to T Sakou.

At least 37 records · Page 2Linked to original sources
PubMed1999

Usefulness of Posner's definition of spinal instability for selection of surgical treatment for lumbar spinal stenosis.

The aim of this study was to determine the usefulness of Posner's definition of spinal instability for selection of surgical therapy for lumbar spinal stenosis. Sixty patients with lumbar spinal stenosis were studied. Thirty-three patients were found to have instability, as defined using Posner's method. Nineteen of the 33 patients with instability underwent decompression and instrumented fusion. The 14 remaining patients with instability underwent decompression alone. Twenty-seven patients without instability were treated by decompression alone. Patients treated by decompression and fusion obtained the best results. Good results also could be obtained by decompression alone only if patients did not have instability. However, patients treated by decompression alone in the presence of instability had the worst results. The Posner's definition of instability proved useful for selecting patients with instability for fusion treatment.

Adult↗
PubMed1998

Immunohistochemical detection of activin A, follistatin, and activin receptors during fracture healing in the rat.

Activins are multifunctional proteins that belong to the transforming growth factor-beta superfamily and are thought to play an important role in modulating the formation of bone. Activins exert their cellular effects by way of activin type-I and type-II serine/threonine kinase receptors. Follistatin is an activin-binding protein that can suppress the biological effects of activins. In this study, the immunohistochemical expression of activin A, follistatin, and activin receptors was studied during fracture healing in the rat. Activin A was weakly detected in the periosteum near the fracture ends at an early stage but was absent in the chondrocytes around the fracture gap, where endochondral ossification took place. An antibody to follistatin stained osteogenic cells in the periosteum near the fracture ends; moderate and strong staining were observed in proliferating, mature, and hypertrophied chondrocytes at the sites of endochondral ossification. Levels of activin A and follistatin were high near the osteoblasts on the surface of the newly formed trabecular bone. In addition, an intense localization of activin A was noted where multinucleated osteoclast-like cells were present. This study suggests that the activin-follistatin system may contribute to cellular events related to the formation and remodeling of bone during fracture healing. Activin type-I and type-II receptors were co-expressed in intramembranous and endochondral ossification sites. The expression of activin type-I, type-II, and type-IIB receptors in the absence of activin A in the endochondral ossification suggests that other isoforms of activins may signal by way of these receptors.

Activin Receptors↗
PubMed1998

Open reduction and varus-detorsion osteotomy with femoral shortening in treatment of congenital dislocation of the hip.

In this study, we clinically and radiographically evaluated open reduction with shortening of the femur in children more than 1 year old with refractory congenital dislocation of the hip. In 19 children (aged 1-4 years), 22 joints were operated on. The patients were followed-up for an average of 8.7 years (range, 2-13 years). Functional results were satisfactory in all joints, and differences in limb length were not significant. Radiographically, good results (grades I and II) were obtained in 16 of the 22 joints, according to Severin's criteria. This surgical procedure may be indispensable for treating refractory congenital dislocation of the hip in children over 1 year old.

Adolescent↗
PubMed1998

Distinct and overlapping patterns of localization of bone morphogenetic protein (BMP) family members and a BMP type II receptor during fracture healing in rats.

Bone morphogenetic proteins (BMPs) and their receptors (BMPRs) are thought to play an important role in bone morphogenesis. The purpose of this study was to determine the locations of BMP-2/-4, osteogenic protein-1 (OP-1, also termed BMP-7), and BMP type II receptor (BMPR-II) during rat fracture healing by immunostaining, and thereby elucidate the possible roles of the BMPs and BMPR-II in intramembranous ossification and endochondral ossification. In the early stage of fracture repair, the expression of BMP-2/-4 and OP-1 was strongly induced in the thickened periosteum near the fracture ends, and coincided with an enhanced expression of BMPR-II. On day 7 after fracture, staining for BMP-2/-4 and OP-1 immunostaining was increased in various types of chondrocytes, and was strong in fibroblast-like spindle cells and proliferating chondrocytes in endochondral bone. On day 14 after fracture, staining with OP-1 antibody disappeared in proliferating and mature chondrocytes, while BMP-2/-4 staining continued in various types of chondrocytes until the late stage. In the newly formed trabecular bone, BMP-2/-4 and OP-1 were present at various levels. BMPR-II was actively expressed in both intramembranous ossification and endochondral ossification. Additionally, immunostaining for BMP-2/-4 and OP-1 was observed in multinucleated osteoclast-like cells on the newly formed trabecular bone, along with BMPR-II. In reference to our previous study of BMP type I receptors (BMPR-IA and BMPR-IB), BMPR-II was found to be co-localized with BMPR-IA and BMPR-IB. BMP-2/-4 and OP-1 antibodies exhibited distinct and overlapping immunostaining patterns during fracture repair. OP-1 may act predominantly in the initial phase of endochondral ossification, while BMP-2/-4 acts throughout this process. Thus, these findings suggested that BMPs acting through their BMP receptors may play major roles in modulating the sequential events leading to bone formation.

Animals↗
PubMed1998

Effects of exercise training and etidronate treatment on bone mineral density and trabecular bone in ovariectomized rats.

This study was designed to assess the effects of exercise training (Tr) following an etidronate treatment (E) on bone mineral density (BMD) of the femur and trabecular bone of the tibia in ovariectomized (ovx) rats. Female Wistar rats were ovariectomized (ovx) or sham-operated (sham) at 15 weeks of age and divided into five experimental groups: sham; ovx; ovx + E; ovx + Tr; ovx + E + Tr. Etidronate treatment of 5 mg/kg, 5 days/week was administered for 2 weeks and exercised on a treadmill for 30 m/min, 60 min/day, 5 days/week for 10 weeks. BMD of the femur and the trabecular bone area of the proximal tibia were significantly (p < 0.05) higher in E and/or Tr compared to ovx groups. However, the cortical region was not affected significantly by ovariectomy. The area partially filled with the trabecular bone at the constant width was observed only in the E rats. The number of osteoclasts in E group was significantly lower (p < 0.05) than in the ovx and ovx + Tr groups. The ovx + Tr rats had a higher number of osteoblasts (p < 0.05) than the ovx and ovx + E groups. There was a significant interaction between ovx + Tr and ovx + E on BMD in the proximal region of the femur (p < 0.05) and trabecular bone area of the tibia (p < 0.001). These results suggest that the etidronate treatment for 2 weeks beforehand influenced the effects of subsequent exercise training on maintaining the BMD in the proximal femur and the trabecular bone area of the tibia.

Absorptiometry, Photon↗
PubMed1998

Genetic mapping of ossification of the posterior longitudinal ligament of the spine.

Ossification of the posterior longitudinal ligament of the spine (OPLL) is recognized as a common disorder among Japanese and throughout Asia. Estimates of its prevalence are in the range of 1. 9%-4.3%. Although its etiology is thought to involve a multiplicity of factors, epidemiological and family studies strongly implicate genetic susceptibility in the pathogenesis of OPLL. In this study we report an identification of a predisposing locus for OPLL, on chromosome 6p, close to the HLA complex. The evidence for this localization is provided by a genetic-linkage study of 91 affected sib pairs from 53 Japanese families. In this sib-pair study, D6S276, a marker lying close to the HLA complex, gives evidence for strongly significant linkage (P = .000006) to the OPLL locus. A candidate gene in the region, that for collagen 11A2, was analyzed for the presence of molecular variants in affected probands. Of 19 distinct variants identified, 4 showed strong statistical associations with OPLL (highest P = .0004). These observations of linkage and association, taken together, show that a genetic locus for OPLL lies close to the HLA region, on chromosome 6p.

Chromosome Mapping↗
PubMed1998

Difference in incidence and transmission mode of methicillin-resistant Staphylococcus aureus among surgery, orthopedics, and pediatrics wards: a prospective study at a university hospital.

The incidence and circumstances of colonization by methicillin-resistant Staphylococcus aureus were prospectively investigated. Among 404 patients, 15 (3.7%) were carriers on admission, and 43 (10.6%) became colonized, mainly after surgical operation. A different mode of transmission was suggested in each ward.

Adult↗
PubMed1998

Alternate activity in the synergistic muscles during prolonged low-level contractions.

The purpose of this study was to investigate the functional interrelationship between synergistic muscle activities during low-level fatiguing contractions. Six human subjects performed static and dynamic contractions at an ankle joint angle of 110 degrees plantar flexion and within the range of 90-110 degrees (anatomic position = 90 degrees) under constant load (10% maximal voluntary contraction) for 210 min. Surface electromyogram records from lateral gastrocnemius (LG), medial gastrocnemius (MG), and soleus (Sol) muscles showed high and silent activities alternately in the three muscles and a complementary and alternate activity between muscles in the time course. In the second half of all exercise times, the number of changes in activity increased significantly (P < 0.05) in each muscle. The ratios of active to silent periods of electromyogram activity were significantly higher (P < 0.05) in MG (4.5 +/- 2.2) and Sol (4.3 +/- 2.8) than in the LG (0.4 +/- 0.1), but no significant differences were observed between MG and Sol. These results suggest that the relative activation of synergistic motor pools are not constant during a low-level fatiguing task.

Adult↗
PubMed1998

3- to 11-year followup of occipitocervical fusion for rheumatoid arthritis.

The relief of myelopathy usually is unsatisfactory by a conventional Gallie type atlantoaxial fusion for patients with rheumatoid arthritis who have irreducible atlantoaxial dislocation. To accomplish a decompressive laminectomy of the atlas in the treatment of myelopathy, the authors have been performing a new surgical procedure since 1985 for occipitocervical fusion using a rectangular rod. The postoperative outcomes for 25 patients with rheumatoid arthritis were evaluated clinically and radiographically with a 3- to 11-year (mean, 6.5 years) followup. A decompressive laminectomy of the atlas accompanied the fusion in 21 of the 25 patients. The incidence of occipital or nuchal pains improved notably in most cases, and myelopathy was relieved in 12 of 18 (67%) cases, showing an improvement of more than one level based on Ranawat's criteria. No serious postoperative complications were seen, except for one case of a failed bone union. The cumulative survival in patients with myelopathy was 79.4% in the first 5 years after operation and 27.5% at 10 years. Occipitocervical fusion using a rectangular rod accompanied by a decompressive laminectomy of the atlas can contribute to the relief of a neurologic deficit in an irreducible atlantoaxial dislocation in rheumatoid arthritis.

Aged↗
PubMed1997

Clinical course of conservatively managed rheumatoid arthritis patients with myelopathy.

STUDY DESIGN: The clinical course of rheumatoid arthritis patients with myelopathy who do not undergo surgery was studied. OBJECTIVES: To establish a more accurate prognosis for rheumatoid arthritis patients who do not undergo surgery. SUMMARY OF BACKGROUND DATA: Cervical myelopathy has been reported in two thirds of rheumatoid arthritis patients with atlantoaxial dislocation. Atlantoaxial fusion, or occipitocervical fusion, is widely performed on these patients. However, several researchers reported serious complications from the surgery, including nonunion, worsening myelopathy, and high mortality. The natural course of disease in rheumatoid arthritis patients with myelopathy should be known before definitive treatments can be outlined. MATERIALS AND METHODS: Twenty-one rheumatoid arthritis patients with myelopathy resulting from atlantoaxial dislocation were studied. Fourteen of the 21 cases were associated with upward migration of the odontoid process. All of these patients were recommended for surgery, but they refused. Patients were reviewed by direct examination yearly. Radiographic changes and clinical course, including the survival rate, were observed. RESULTS: Atlantodental interval and Redlund-Johnell measurements deteriorated. The patients showed no neural improvement, and deterioration was found in 16 (76%) cases during follow-up. All patients became bedridden within 3 years of the onset of myelopathy. Seven of the 21 patients died suddenly for unknown reasons, 3 died of pneumonia, and 1 died of multiple organ failure. The three sudden-death cases showed progressive upward migration of the odontoid process. The cumulative probability of survival was 0% in the first 7 years after the onset of myelopathy. CONCLUSIONS: The clinical results for rheumatoid arthritis patients with myelopathy treated without surgery are extremely poor. Surgical treatment is recommended for rheumatoid arthritis patients with myelopathy.

Activities of Daily Living↗
PubMed1997

Occipitocervical fusion with C1 laminectomy in children.

STUDY DESIGN: Eight children in whom atlantoaxial dislocation had developed underwent occipitocervical fusion using a rectangular rod. The postoperative results are presented, and the postoperative growth and deformation of the cervical spine were determined radiographically. OBJECTIVES: To investigate in a relatively long-term follow-up study whether occipitocervical fusion affects the growth of the cervical spine and induces spinal deformation. SUMMARY OF BACKGROUND DATA: It has been reported that children who have undergone C1-C2 posterior fusion are likely to develop abnormal curvature or deformation of the cervical spine as a result of a disturbance of growth of the fused vertebrae. There have been no studies, however, to confirm that these changes occur after occipitocervical fusion in children. METHODS: The subjects were one boy and seven girls who had undergone occipitocervical posterior fusion during childhood. The average age at the time of surgery was 8.3 years, and the average follow-up period was 5.9 years. The following were assessed radiographically: redislocation of the atlas, bone union, changes in the curvature of the cervical spine, the height and width of the vertebral bodies, and the anteroposterior diameter of the spinal canal. RESULTS: Solid bone union was achieved in all patients with maintenance of the reduced position at the time of surgery. None of the patients exhibited abnormal curvature of the cervical spine. The rate of increase in height of the C2 vertebral body was significantly less than that of vertebral bodies below C3. The rate of increase in width of the vertebral body and the anteroposterior diameter of the spinal canal of the C2 vertebral body and vertebral bodies below C3 did not differ significantly. CONCLUSIONS: Occipitocervical fusion with a rectangular rod is useful for treating atlantoaxial dislocation in children and yields excellent results because of the firm internal fixation it achieves. This surgery induced no apparent postoperative spinal deformations.

Atlanto-Axial Joint↗
PubMed1997

Biomechanical analysis of buckling alignment of the cervical spine. Predictive value for subaxial subluxation after occipitocervical fusion.

STUDY DESIGN: A biomechanical analysis of the buckling type of alignment on nonfused cervical segments was carried out in patients with occipitocervical fusion for atlantoaxial dislocation. OBJECTIVES: To examine whether biomechanical analysis is useful for preoperative prediction of subaxial subluxation after occipitocervical fusion. SUMMARY OF BACKGROUND DATA: Rheumatoid arthritis sometimes causes subaxial subluxation after occipitocervical fusion. At present, there are no widely accepted criteria for determining the appropriate extent of fusion to prevent subluxation. METHODS: The subjects were 25 patients with rheumatoid atlantoaxial dislocation and 15 patients with nonrheumatoid atlantoaxial dislocation who underwent occipitocervical fusion. Preoperative and postoperative alignment of the cervical spine were analyzed biomechanically, using a specially developed computer program. RESULTS: Five segments of nonfused cervical spine had subluxation after surgery in the rheumatoid group. For these segments, the preoperative value of buckling averaged 13.5 x 10(-4) and exceeded 10 x 10(-4) in all cases. For the segments that showed no subluxation after surgery, the preoperative value of buckling averaged 4.5 x 10(-4). Subluxation of the nonfused segments did not develop in the nonrheumatoid group. CONCLUSIONS: In patients with rheumatoid arthritis, segments that show abnormal buckling before surgery are likely to develop subluxation after occipitocervical fusion. Preoperative values of buckling over 10 x 10(-4) constitute a risk factor for subaxial subluxation after occipitocervical fusion.

Adult↗
PubMed1997

Orthotopic ossification of the spinal ligaments of Zucker fatty rats: a possible animal model for ossification of the human posterior longitudinal ligament.

Ossification of the posterior longitudinal ligament is a human genetic disease in which pathological ectopic ossification of the spinal ligaments develops. This leads to myelopathy or radiculopathy due to compression of the spinal cord. In this study, we investigated the histological features of orthotopic ossification of the spinal ligaments of senile Zucker fatty rats. A remarkably high incidence of orthotopic ossification was observed mainly in the thoracic spinal ligaments as compared with controls. The histopathological findings were similar to those for ossification of the human posterior longitudinal ligament. Bone morphogenetic proteins and activins, which exert their effects by way of specific type-I and type-II serine/threonine kinase receptors, play important roles in the formation of bone and cartilage. In the spinal ligaments of Zucker fatty rats, bone morphogenetic protein receptors and activin receptors were immunohistochemically detected around the ossified foci in a manner similar to that previously shown for the ossified tissue from patients who had ossification of the posterior longitudinal ligament. Thus, bone morphogenetic proteins and activin receptors might play important roles in orthotopic ossification of the spinal ligaments of Zucker fatty rats as well as in ossification of the posterior longitudinal ligament of humans. In addition, bone morphogenetic protein-receptor-IA was expressed in the nonossified ligament, suggesting that the spinal ligaments, of the rats may have a predisposition to orthotopic ossification. In the controls, no expression of bone morphogenetic protein receptors or of activin receptors was observed. In conclusion, there is a great degree of similarity between orthotopic ossification of the spinal ligaments of Zucker fatty rats and ossification of the posterior longitudinal ligament of humans. Thus, the rats provide a useful animal model for the study of ossification of the human posterior longitudinal ligament.

Activin Receptors↗
PubMed1997

Electromyogram patterns during plantarflexions at various angular velocities and knee angles in human triceps surae muscles.

To investigate the influence of the various knee angles and ankle angular velocities on synergistic muscle activities, the surface electromyograms (EMG) were recorded from the triceps surae muscles, i.e. lateral gastrocnemius (LG), medial gastrocnemius (MG) and soleus (SOL) muscles. Six healthy young men performed ankle plantarflexions at three ankle angular velocities of 6, 30 and 60 degrees.s-1 and three knee angles of 0, 30 and 60 degrees (0 degree equalling full extension) under constant load (5% and 10% maximal voluntary contraction). At the fully-extended knee angle (0 degree), peak values of integrated EMG (peak iEMG) during ankle plantarflexions were significantly increased (P < 0.05) in MG and in LG, but significantly decreased (P < 0.05) in SOL with increasing angular velocity. On the other hand, although the patterns of variation of the peak iEMG in each muscle at flexed knee angles (30 and 60 degrees) were very similar to the patterns seen at the fully-extended knee angle, there were no significant differences among angular velocities. During ankle plantarflexions at any of the angular velocities (6, 30 and 60 degrees.s-1) the peak iEMG were significantly increased (P < 0.05) in SOL, but were significantly decreased (P < 0.05) in MG following increases in the knee angles. These results would suggest the possibility of selective recruitment of motor units in humans depending on the angular velocity; however, this behaviour would appear to be weakened by fixing at flexed knee angles which cause an inhibitory influence on gastrocnemius muscles and a facilitative influence on SOL.

Adult↗
PubMed1997

Expression and localization of bone morphogenetic proteins (BMPs) and BMP receptors in ossification of the ligamentum flavum.

To clarify the pathogenesis of ossification of the ligamentum flavum (OLF), we examined the expression and localization of bone morphogenetic proteins (BMPs) and their receptors (BMPRs) in the ligamentum flavum of the patients with OLF by immunohistochemical staining and compared them with staining patterns in control patients. The BMPRs appeared extensively in mature and immature chondrocytes around the calcified zone and in spindle-shaped cells and round cells in the remote part from ossified foci in examined tissue of OLF. The ligands for BMPRs, BMP-2/-4 and osteogenic protein-1 (OP-1)/BMP-7, colocalized in OLF patients. In the control cases, expression of BMPs and BMPRs was observed around the calcified zone at the insertion of the ligamentum flavum to the bone, and limited expression was found in the smaller range. Thus, the expression profile of BMPs and BMPRs in OLF patients was entirely different from the control patients, suggesting that BMPs may be involved in promoting endochondral ossification at ectopic ossification sites in OLF, and that ossification activity is continuous in these patients.

Activin Receptors↗
PubMed1997

Fibroblasts of spinal ligaments pathologically differentiate into chondrocytes induced by recombinant human bone morphogenetic protein-2: morphological examinations for ossification of spinal ligaments.

To elucidate the process of ossification in spinal ligaments, an aqueous solution containing recombinant human bone morphogenetic protein (BMP)-2 (40 micrograms/100 microL) was injected into murine ligamenta flava, and the ossification process was analyzed morphologically. In the control group, the solution administered lacked the protein; these flattened ligamentous fibroblasts possessing BMP receptors type IA and type II existed among type I collagen bundles. In the week immediately following the injection of BMP-2, ligamentous fibroblasts began to proliferate, differentiating into alkaline phosphatase-positive chondrocytes surrounded by an extracellular matrix composed of type I and II collagen. By the second week, differentiated chondrocytes of various stages were observed in type II collagen-rich matrix. These chondrocytes showed an abundance of BMP receptors type IA and II. The pathologically induced cartilage was resorbed by chondroclasts, permitting migration of blood vessels and osteogenic cells, as well as providing a site for endochondral ossification. By the third week, BMP-induced ossification had compressed the spinal cord, and by the sixth week, the ligamentous tissue had been almost completely replaced by bone. Ligamentous fibroblasts appeared to possess BMP receptors, as well as the potentiality to differentiate into chondrocytes. BMP receptors were upregulated during chondrification of ligamentous fibroblasts induced by exogenous BMP-2, suggesting that BMPs may play an important role in ossification of spinal ligaments.

Acid Phosphatase↗
PubMed1997

3-dimensional computed tomography of ossification of the spinal ligament.

Ossification of the posterior longitudinal ligament in the cervical spine was studied 3-dimensionally using computed tomography scans of 32 patients. The images produced were classified into 3 types based on the posterior configuration of the ossification: (1) plank shaped, (2) spindle shaped, or (3) rod shaped. Lesions with radiographically continuous and mixed type ossification on 3-dimensional computed tomography were plank shaped or spindle shaped. Rod shaped type lesions usually were radiographically segmented or showed some other type of ossification. The 3-dimensional computed tomography images change with the growth of ossification. Plank shaped type lesions appear to be the final result of ossification. Three-dimensional computed tomography scans of ossification of the longitudinal ligament are useful for decompressive surgery, providing valuable information regarding the site of concentration of compression of the spinal cord or nerve roots and the choice of surgical procedures.

Aged↗