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Biomedical subjects

Yasusuke Hirasawa

Publications and source records attributed to Yasusuke Hirasawa.

15 recordsLinked to original sources
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

Kneeling view: a new roentgenographic technique to assess rotational deformity and alignment of the distal femur.

Computed tomography (CT) has been used to assess the rotational alignment of the distal femur. The purpose of this study was to establish a simple radiographic technique to evaluate the posterior femoral condyles. For this study, 39 osteoarthritic knees and 19 normal knees were examined. The condylar twist angle and posterior condylar angle were measured using a new roentgenographic technique ("the kneeling view") and CT images. The kneeling view is a posteroanterior projection parallel to the articular surface with 80 degrees knee flexion. In this view, the transepicondylar axis and posterior condylar line can be seen. We noted statistically significant correlation between the angles on the kneeling view and those on CT images. Therefore, the kneeling view can be used as a substitute for CT in the measurement of rotational alignment of the distal femur.

Aged↗
PubMed2003

Dissemination of metals from a failed patellar component made of titanium-base alloy.

Complications related to the patella are the most common problems in total knee arthroplasty and major reasons for revision surgery. Among patellofemoral problems, metal-to-metal contact between patellar and femoral components is the worst. We measured levels of titanium, aluminum, and vanadium in serum and urine samples and compared these measures from cases in which metal-to-metal contact of the patellar component occurred with those in cases in which only polyethylene wear occurred. Serum levels of the metals in cases with metal-to-metal contact were over 10 times higher than those in cases without metal-to-metal contact. This suggests that different ranges of serum metal ion levels could eventually be correlated with a variety of mechanisms of patellar failure. Therefore, cases with metal-to-metal contact should be distinguished from cases without metal-to-metal contact. These should not be considered as a single group in patellar component failure.

Alloys↗
PubMed2002

Histological and electrophysiological analysis of the peripheral nerve allografts using an immunosuppressive agent.

In peripheral nerve allografts, use of an immunosuppressive agent is one of the ways of reducing nerve rejection. FK506 is a newly discovered substance, extracted from Streptomyces tsukubaensis, and has strong immunosuppressive effects. In the present study, immunosuppressive effects of FK 506 were examined using allografts of rat sciatic nerves. Good nerve regeneration was demonstrated through 12 weeks in this model. The immunosuppressed group gained weight over the course of the experiment. Another study was performed to observe the histological changes caused by ceasing the administration of FK506. Administration of FK506 was terminated 12 weeks after grafting. At 8 weeks after cessation, cellular infiltration and large unmyelinated axons were observed in the extended subperineurial space of grafts. At 12 weeks, histological characteristics of rejection were not observed. In the electrophysiological study, the temporal dispersions were recorded at 4 and 8 weeks. However, the normal electrophysiological waves were recorded at 12 weeks after cessation. It was concluded that FK506 is effective for preventing rejection of nerve allografts without any serious side effects on rats, and findings of total rejection of grafts were not recognized after ceasing the administration of FK 506. In peripheral nerve allografts, short-term administration of an immunosuppressive agent is sufficient to lead to good nerve regeneration.

Action Potentials↗
PubMed2002

In situ strain and stress of nerve conduction blocking in the brachial plexus.

The objective of the present study was to determine the in situ strain and stress of nerve conduction blocking in the brachial plexus. The measurement of the in situ tension stress inducing functional failure of the brachial plexus consisted of two steps. Step I (in vivo): The brachial plexus of the rabbit was stretched laterally until electrophysiological conduction blocking occurred. The distance between two dye marks placed on the lower trunk was simultaneously recorded using a video dimensional analyzer system. Step II (in vitro): The lower trunk that was removed was loaded again, and the nerve tension was recorded. The load at complete conduction blocking was determined by a load-elongation curve. The results showed that when the in situ nerve strain reached 8.1 +/- 0.5%, the compound muscle action potential was not evoked. The in situ load and stress were 2.5 +/- 0.4 N and 0.89 +/- 0.14 MPa, respectively, at complete conduction blocking. These findings should be helpful in understanding the mechanism of brachial plexus traction injury.

Animals↗
PubMed2002

Newly devised anterior portal technique for arthroscopic bankart repair using suture anchors.

Many techniques and instrument systems have been developed for performing arthroscopic Bankart repair using a suture anchor. The suture anchor procedure relies on a secure knot, which does not become entangled in the anterior portal. A newly devised anterior portal technique can solve this problem. We have used this technique for arthroscopic Bankart repair using suture anchor. This technique may be useful for any type of suture materials such as SLAP lesion.

Arthroscopy↗
PubMed2002

Tissue-engineered repair of osteochondral defects: effects of the age of donor cells and host tissue.

Transplantation of a tissue-engineered construct containing cells of a chondrocytic phenotype into an osteochondral defect provides a biological solution to this type of injury. Among the factors that affect cell proliferation and phenotypic expression, age is one that has not been well characterized. In this study adult and aged male donor cells, derived from perichondrium, were cultured and adsorbed into a polylactic acid (PLA) scaffold and transplanted into osteochondral defects created in adult (8- to 10-month-old) and aged (4- to 5-year-old) female rabbits. Three groups were investigated: (1) adult cells transplanted into aged defects, (2) aged cells transplanted into aged defects, and (3) aged cells transplanted into adult defects. In vitro characterization of adult and aged cells and in vivo assessment of osteochondral repair tissue at 12 weeks posttransplantation were carried out. The in vitro studies demonstrated that the proliferation rate of aged cells was less than that of mature cells during the earliest stage of culture. Also, the chondrocytic phenotype was reduced in aged cells compared with mature cells. The in vivo results showed that donor (SRY-positive) cell survival differed among the three groups: survival of adult cells into aged defect > survival of aged cells into aged defect > survival of aged cells into adult defect. The biological acceptability of the repair, defined as smooth firm cartilaginous tissue filling the defect, was < 25% of the operated specimens in each of the three groups. This repair tissue contained only 20-25% of the amounts of type II collagen and glycosaminoglycans found in normal articular cartilage. These data suggest that the outcome of tissue-engineered repair of osteochondral defects is affected by both the age of donor cells and the age of the host.

Age Factors↗
PubMed2002

Biomechanical monitoring of healing bone based on acoustic emission technology.

Acoustic emission testing is a well-established method for assessment of the mechanical integrity of general construction projects. The purpose of the current study was to investigate the usefulness of acoustic emission technology in monitoring the yield strength of healing callus during external fixation. Thirty-five patients with 39 long bones treated with external fixation were evaluated for fracture healing by monitoring load for the initiation of acoustic emission signal (yield strength) under axial loading. The major criteria for functional bone union based on acoustic emission testing were (1) no acoustic emission signal on full weightbearing, and (2) a higher estimated strength than body weight. The yield strength monitored by acoustic emission testing increased with the time of healing. The external fixator could be removed safely and successfully in 97% of the patients. Thus, the acoustic emission method has good potential as a reliable method for monitoring the mechanical status of healing bone.

Adolescent↗
PubMed2002

Migration of the lag screw within the femoral head: a comparison of the intramedullary hip screw and the Gamma Asia-Pacific nail.

OBJECTIVES: To study the functional difference in the performances of sliding femoral head screws by comparing the displacement of the screw in relation to the femoral head in hips treated with the Gamma Asia-Pacific nail (GN) and hips treated with the intramedullary hip screw (IMHS). STUDY DESIGN: Retrospective review of prospectively collected data. METHODS: Displacement of the femoral head screw in relation to the femoral head was measured in fifty-six elderly patients with intertrochanteric fractures who were treated with an IMHS or GN. Displacement of the femoral head screw was determined by comparing screw position in the immediate postoperative radiograph with a film taken 3 months after surgery. RESULTS: In the GN group, significant displacement of the screw was observed with 3.8 +/- 3.8 percent translation in the horizontal axis (P < 0.005) and 4.3 +/- 5.1 percent displacement in the vertical axis (P < 0.05) in comparison with the diameter of the femoral head. In comparison, displacement of the femoral head screw was not observed with the IMHS (P = 0.48 for horizontal, P = 0.18 for vertical). Total displacement of the femoral head screw in relation to the femoral head in the GN was twice that observed in the IMHS (P < 0.001). CONCLUSION: These results indicate that the displacement of the femoral head screw of the IMHS was less than the lag screw of the GN. However, it is still unknown whether this smaller displacement of the IMHS is clinically significant for reducing the rate of screw cut-out after surgery.

Aged↗
PubMed2002

Acridine orange excited by low-dose radiation has a strong cytocidal effect on mouse osteosarcoma.

The study was conducted to clarify the cytocidal effect of combination therapy consisting of administration of acridine orange (AO), which is a photosensitizer, and radiation therapy using in vitro and in vivo mouse osteosarcoma models. The results revealed that AO combined with low-dose X-ray irradiation of about 1-5 Gy had a strong cytocidal effect on the cultured mouse osteosarcoma cells regardless of their chemosensitivity, and that this combination therapy inhibited growth of the in vivo mouse osteosarcoma by induction of tumor necrosis. This effect was inhibited by L-histidine, but not by mannitol. These findings suggested that AO might be excited by X-rays and kill osteosarcoma cells through the release of singlet oxygen, which is toxic to living cells. This mechanism is similar to that of photodynamic therapy with AO.

Acridine Orange↗
PubMed2000

Predictive value of magnetic resonance imaging in avascular necrosis following talar fractures.

Ischemic bone necrosis following talar fractures is a problematic complication and its early diagnosis is important. Patients with Hawkins Type II and III talar fractures received internal fixation using titanium alloy screws, and chronological bone changes were observed with Magnetic Resonance Imaging (MRI). With the Type II patient, Hawkins' sign was radiographically confirmed 2 months after the surgery. Furthermore, there were no changes of MR images for 2 years and a good clinical outcome was obtained. However, in the Type III patient, Hawkins' sign was negative and MRI revealed a low signal-intensity band on the talus 2 months after the surgery and then necrosis was radiographically confirmed; pain appeared 10 months later. These 2 cases suggest that MRI is a useful means for detecting bone necrosis with talar fractures in the early post-operative period.

Journal Article↗
PubMed2000

Anterior cruciate ligament reconstruction using the double bundle method.

Clinical results of our reconstruction technique for anterior cruciate ligament using the double bundle, i.e., the combination of bone-tendon-bone (BTB) from the patellar tendon and semitendinosus tendon (ST), were evaluated. BTB was fixed in the tunnels produced on the isometric points on the tibia and femur, and ST, on the tibial tunnel through the same route as BTB. Throughout the observation period, no patients developed pain, limited range of motion, and/or instability of the operated knee. All patients were able to return to previous sports activities within 12 months. No apparent changes occurred on the reconstructed ligament. In 4 of 14 patients, knee stability was quantitatively examined, and a good result was obtained. The double bundle was found to be a useful method for patients who require physiologically more durable reconstruction.

Journal Article↗
PubMedDate not supplied

Development of the acetabulum and the acetabular labrum in the normal child: analysis with radial-sequence magnetic resonance imaging.

The degree of acetabular and labral coverage was clarified in children at different positions using radial-sequence magnetic resonance imaging. Scans were performed on 40 hips in 20 normal children (group A, 6-8 years old; group B, 9-11 years old; group C, 12-13 years old) and on 19 hips of 10 healthy adults as controls. The degrees of coverage of the femoral head by acetabulum, acetabular labrum, and both were measured at seven positions at every 15 degrees from anterosuperior 45 degrees via midsuperior to posterosuperior 45 degrees. Coverage of the femoral head by the acetabulum in young children was less than in adults at all positions, but the total coverage including the labrum was greater than in adults. Development of the acetabulum and the acetabular labrum showed differences by position.

Acetabulum↗