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Biomedical subjects

Yuji Yasunaga

Publications and source records attributed to Yuji Yasunaga.

At least 37 records · Page 2Linked to original sources
PubMed2004

Biomechanical analysis and quantitative analysis of bone scintigraphy on thrust plate hip prosthesis.

INTRODUCTION: To study the load distribution of the thrust plate hip prosthesis (TPP, Sulzer Medica, Baar, Switzerland) on femoral bone, a TPP insertion group and intramedullary cemented stem insertion group were prepared with the use of embalmed femoral anatomic specimens, and strain on the femoral bone induced by loading was measured. MATERIALS AND METHODS: Bone scintigraphy was performed in 26 joints which underwent total hip arthroplasty with the use of TPP, to enable quantitative evaluation of postoperative remodeling of the bone. RESULTS: In the TPP insertion group, the strain was almost equivalent to that in the untreated femoral control group. On the other hand, compared with the control group and TPP insertion group, strain in the proximal portion of the femoral bone (medial side of the femoral neck) was significantly smaller in the cemented stem group (control group versus cemented stem insertion group, p=0.0062; cemented stem insertion group versus TPP 130 degrees insertion group, p=0.0005; cemented stem insertion group versus TPP 140 degrees insertion group, p=0.0031). Bone scintigrams revealed decreased uptake at 12 weeks after operation compared with 6 weeks after operation, indicating that TPP allows earlier implant stabilization than the conventional stem. CONCLUSION: Compared with the conventional stem, TPP is a prosthesis that can perform physiological load transmission.

Aged↗
PubMed2004

Evaluation of systemic chemotherapy with magnetic liposomal doxorubicin and a dipole external electromagnet.

The development of an active drug delivery system is an attractive approach to increase the targetability of anticancer agents. In the present study, we examined the efficiency of systemic chemotherapy with small magnetic liposomes containing doxorubicin (magnetic DOX liposomes) and an externally applied electromagnetic force in osteosarcoma-bearing hamsters. Syrian male hamsters inoculated with osteosarcoma, OS515, in the limb were studied 7 days after inoculation. The efficiency of this system was evaluated by measuring the tissue distribution and tumor-suppressing effects of DOX on primary tumor growth and lung metastases. A DC dipole electromagnet was used, and the hamster's tumor-bearing limb was placed between 2 poles after the i.v. administration of liposomes. The dose of DOX and the magnetic field strength were fixed at 5 mg/kg and 0.4 T, respectively. Administration of magnetic DOX liposomes followed by 60 min application of magnetic field produced a 3- to 4-fold higher maximum DOX concentration in the tumor. This newly designed systemic chemotherapy significantly suppressed primary tumor growth for at least 2 weeks, though other DOX treatments also suppressed compared to control. Histologic examination confirmed a greater antitumor effect of this systemic chemotherapy compared to standard methods. In addition, this approach significantly suppressed lung metastases measured at 3 weeks posttreatment. These results suggest that this systemic chemotherapy can effectively reduce primary tumor growth and suppress lung metastasis due to increased targeting of DOX. Such targeted drug delivery for anticancer agents would provide clinical advantages compared to current methods.

Animals↗
PubMed2004

Acceleration of surgical angiogenesis in necrotic bone with a single injection of fibroblast growth factor-2 (FGF-2).

The aim of this study was to accelerate angiogenesis in necrotic bone by combining vascular bundle implantation and fibroblast growth factor-2 (FGF-2) administration. Twenty-four Japanese white rabbits were evaluated in this study. A portion of a rabbit iliac crest bone was removed as a free bone graft and frozen in liquid nitrogen to ensure complete cellular necrosis. A narrow hole was created in the bone and the graft was placed in the proximal thigh. In group 1, FGF-2 was injected into the hole at a single dose of 100 microg, and the saphenous artery and its venae comitantes were passed through the hole of the bone. In group 2, injection of saline into the hole and the vascular bundle implantation was used as a control. Neovascularization around the vessel was evaluated at weeks 1 and 2 after surgery. Neovascularization was observed along the implanted vascular bundle in both groups. At both 1 and 2 weeks after surgery, the vessel density of group 1 was significantly higher than that of group 2. The average length of newly formed vessels of group 1 was also significantly longer than that of group 2 at both 1 and 2 weeks after surgery. Both the vessel density and length were greater in week 2 animals than week 1. A local single injection of FGF-2 improved surgical angiogenesis in necrotic bone in this study. As FGF-2 is recognized as a potent mitogen for a variety of mesenchymal cells, the combination of vascular bundle implantation and FGF-2 administration may contribute to the treatment of ischemic osteonecrosis.

Animals↗
PubMed2004

Corrective valgus osteotomy after free vascularized fibula transfer for the treatment of osteomyelitis at the neck of the femur: case report.

Reconstruction using a free vascularized fibula was performed on a long bony defect after osteomyelitis of the proximal femur. For this type of bone defect, a double-barrel fibular graft is recommended. The authors used this procedure for a 58-year-old male who had osteomyelitis of the left proximal femur. As osteotomy through a transplanted fibula can be safely performed, abduction osteotomy should be considered when coxa vara remains after reconstruction with a free vascularized fibula transfer.

Femur Neck↗
PubMed2004

Rotational acetabular osteotomy for hip dysplasia: 61 hips followed for 8-15 years.

We operated on 54 patients (61 joints) with rotational acetabular osteotomy (RAO) due to dysplasia of the hip with pre- or early-stage osteoarthritis/arthrosis. The mean follow-up was 11 (8-15) years. The Merle d'Aubigné median score increased from 14 to 15. In 2 patients (2 joints), the score decreased from 15 to 13. Progression of arthrosis was seen in 6 joints on the radiographs at follow-up. Kaplan-Meier survivorship analysis predicted an 89% (95% confidence interval 80-99) prevention of worsening of arthrosis at 10 years. Postoperative joint congruency was a risk factor for progression of arthrosis.

Acetabulum↗
PubMed2004

Effects of transforming growth factor-beta 1 on the early stages of healing of the Achilles tendon in a rat model.

We studied the effects of transforming growth factor-beta 1 (TGF-beta 1) on the genetic expression of procollagen type I and III and its effects on structural properties in the early stages of healing in rat Achilles tendon. The Achilles tendons in 90 rats were transsected and repaired immediately. TGF-beta 1 dissolved in phosphate-buffered saline was injected locally at the repair site using two different doses, and outcomes in both groups were compared to that in the control group given phosphate-buffered saline only. Five animals in each group were killed at one, two, and four weeks postoperatively, and the healing tendon was evaluated. A dose-dependent increase in the expression of procollagen type I and III mRNA was found one week postoperatively. The failure load and stiffness of the healing tendon were increased by TGF-beta 1 at two and four weeks.

Achilles Tendon↗
PubMed2004

Cervical angina caused by atlantoaxial instability.

Cervical angina is defined as a paroxysmal precordialgia that resembles true cardiac angina caused by cervical spondylosis. Cervical angina most commonly results from compression of the C7 ventral root. We present here a case of cervical angina caused by atlantoaxial instability. This case had marked atlantoaxial instability but no flexibility of the middle to lower levels of the cervical spine. Although there was mild C7 root compression on the radiologic findings, the chest pain was induced by neck motion, and the precordialgia disappeared after posterior atlantoaxial fusion without C7 root decompression. Therefore, we diagnosed this case as cervical angina caused by spinal cord compression at the C1-C2 level. It was speculated that a perturbation of the sympathetic nervous system or a hypofunction of the pain suppression pathway in the posterior horn of the spinal cord caused the pectoralgia. Although cervical angina is a rare disease, physicians should be aware of it; if there are no abnormal findings on cardiac examinations for angina pectoris, they should examine the cervical spine. Cervical angina due to atlantoaxial instability is one of the differential diagnoses of precordialgia.

Afferent Pathways↗
PubMed2003

Progressive collapse of transposed necrotic area after transtrochanteric rotational osteotomy for osteonecrosis of the femoral head induces osteoarthritic change. Mid-term results of transtrochanteric rotational osteotomy for osteonecrosis of the femoral head.

INTRODUCTION: Osteonecrosis of the femoral head is usually progressive, and once collapse of the femoral head develops, joint destruction almost invariably follows. Therefore, for partial osteonecrosis of the femoral head, various types of osteotomies have been developed in an attempt to save the femoral head and maintain the natural function of the hip joint. MATERIALS AND METHODS: We reviewed 25 hips in 21 patients for a mean follow-up period of 6.4 years after Sugioka's transtrochanteric anterior rotational osteotomy for osteonecrosis of the femoral head. RESULTS: The clinical results were excellent or good in 20 hips (80%), and radiological success was observed in 15 hips (60%) with an absence of both collapse of the newly established weight-bearing area of the femoral head and narrowing of the joint space. Progressive collapse of the transposed necrotic area was noted in 10 hips (40%), and of these 10 hips, narrowing of the joint space was observed in 7 (70%) at follow-up. A significant correlation was demonstrated between progressive collapse of the transposed necrotic area and narrowing of the joint space. Growth of an osteophyte of the femoral head was observed postoperatively in 16 hips (64%), particularly at anterior and lateral sites of the femoral head. CONCLUSIONS: Though collapse of a new weight-bearing area can be prevented, progressive collapse of the transposed necrotic area induces anterior joint instability, giving rise to osteoarthritic change. It is therefore concluded that prevention of the collapse of the transposed necrotic area is important for satisfactory long-term results.

Adult↗
PubMed2003

Bone remodeling after impacted cancellous allograft in revision hip arthroplasty based on (99m)Tc-MDP bone scintigraphy.

INTRODUCTION: Impacted cancellous allograft for the femur reported by Gie et al. (1993) has resulted in a good outcome. Revascularization of the graft was proven with plain radiographs or in some cases, biopsy and autopsy. We have attempted to document the change in appearance of impacted cancellous allograft in the femur over time on scintigraphic scans. MATERIALS AND METHODS: Bone scintigraphy was conducted following total hip arthroplasty of 20 hips without complication using impacted cancellous allograft. At 6 weeks, 1, 2 and 4 years postoperatively, uptake at 5 regions of interest around the femoral component sites was measured. RESULTS: At all 5 regions of interest, uptake was significantly decreased at 1 year postoperatively compared with that at 6 weeks postoperatively. At 2 and 4 years postoperatively, uptake was about 2-fold that of the normal femur in the greater trochanter, lesser trochanter, and stem tip and had decreased to almost the normal level at the lateral stem and medial stem. CONCLUSION: In revision hip arthroplasty using impacted cancellous allograft, remodeling of the grafted bone of the femur was still incomplete, particularly at the greater trochanter, lesser trochanter, and stem tip even after 4 years postoperatively. It is felt that further time is required for remodeling.

Aged↗
PubMed2003

Intradural extramedullary mass formation in spinal cord sarcoidosis: case report and literature review.

STUDY DESIGN: A case of myelopathy caused by intradural extramedullary spinal cord sarcoidosis. OBJECTIVES: To report a rare case of mass formation in spinal cord sarcoidosis and discuss the diagnostic approach and therapeutic management of this condition. SUMMARY OF BACKGROUND DATA: Spinal cord sarcoidosis is a rare condition that is difficult to diagnose, and intradural extramedullary mass formation is even rarer. MATERIALS AND METHODS: A 42-year-old woman first noticed numbness in her fingers, and these symptoms gradually spread to her hands and feet. MRI revealed an intradural extramedullary mass, as confirmed by an isointensity T1 and low-intensity T2 signal, and also enhanced by Gd-DTPA. The authors suspected the mass to be a meningioma and performed surgery to resect it. RESULTS: The mass was observed through the dura, and it was twined with the rootlet. After surgery, the patient experienced temporary paralysis of her right upper extremity, followed rapidly by almost complete neurologic recovery. Bilateral hilar lymphadenopathy was noted and this was diagnosed histologically as lung sarcoidosis. One year after surgery, a complete AV block occurred because of heart sarcoidosis and a pacemaker was inserted. CONCLUSIONS: Spinal cord sarcoidosis is rare disease and is difficult to diagnose, but when a mass is present in the spinal canal, it is important to remain open to the possibility of spinal cord sarcoidosis. Besides if it is diagnosed as spinal cord sarcoidosis, it is also important to remain systemic sarcoidosis before, during, and after surgery to check general conditions and to guide appropriate treatment.

Adult↗
PubMed2003

Injectable magnetic liposomes as a novel carrier of recombinant human BMP-2 for bone formation in a rat bone-defect model.

Small-sized magnetic liposomes with incorporated recombinant human bone morphogenetic protein-2 (rhBMP-2) were prepared, and the efficiency for bone formation after topical injection was evaluated in a rat bone-defect model. A critical-sized segmental bone defect was created in the mid-part of the femoral shaft, and a permanent magnet was attached. Topical injection onto the defects was performed with different liposomal preparations (nonmagnetic and magnetic liposomes) using different treatment modalities (different doses and different treatment timing of rhBMP-2). Weekly evaluations were made radiographically and microcomputed tomographically, histologically, and/or by mechanical testing at 9 weeks after surgery. A single topical application of magnetic liposomes with an appropriate amount of rhBMP-2 (approximately 3 microg) incorporated under magnetic induction immediately after surgery was effective for new bone formation. The combined treatment of topical magnetic rhBMP-2 liposomes and magnetic implantation at the injury site was effective for the treatment of bone defects. This injectable carrier for BMP is expected to have many advantages over solid carriers because it can be prepared easily and can be less invasively applied to the injured site at any time after surgery.

Animals↗
PubMed2003

Transplanted neuronal progenitor cells in a peripheral nerve gap promote nerve repair.

A basic experiment of peripheral nerve regeneration using neuronal progenitor cells embedded in collagen gel was performed in a rat sciatic nerve defect. First, when neuronal progenitor cells derived from the fetal rat hippocampus were cultured in atelocollagen-containing medium, neurospheres positive for anti-nestin antibody were confirmed after 8 days. These cells differentiated into astrocytes positive for anti-glial fibrillary acidic protein (GFAP) antibody, oligodendrocytes positive for anti-galactocerebroside (GalC) antibody and neurons positive for anti-neurofilament 200 (NF200) antibody, and they were capable of extending axons. They also differentiated into Schwann-like supportive cells positive for anti-s100 and anti-p75 antibody. Next, a 15-mm defect was prepared in the sciatic nerve of mature rats, and the nerve was bridged with a silicone tube filled with neuronal progenitor cells (1 x 10(5)) embedded in collagen gel. The transplanted neuronal progenitor cells were labeled in advance with 5-bromo-2-deoxyuridine (BrdU). When the regenerated tissue was examined 6 weeks and 10 weeks after grafting, the number and diameter of myelinated fibers were significantly increased compared with a control tube without neuronal progenitor cells. Action potentials were detected in the regenerated nerve. Also, cells positive for both anti-BrdU antibody and anti-S100 or anti-p75 antibody were observed in the regenerated tissue, and part of the grafted neural stem cells were considered to have differentiated into Schwann cell-like supportive cells. From these results neuronal progenitor cells derived from the fetal rat hippocampus are considered to retain their proliferative and differentiating abilities in collagen gel, and when transplanted to a site of peripheral nerve defect, part of them differentiate into supportive cells and they contributed to promotion of axonal regeneration.

Animals↗
PubMed2003

Bone-preserving prosthesis with a single axis for treating osteonecrosis of the femoral head: midterm results for the thrust plate hip prosthesis.

We studied 27 patients (31 joints) who underwent total hip arthroplasty (THA) using the thrust plate hip prosthesis (TPP) for osteonecrosis of the femoral head. The mean follow-up period was 56 months (range 38-72 months). Clinical evaluation by the Merle d'Aubigne and Postel system showed a significant improvement from a preoperative mean score of 8.1 to a final mean follow-up score of 16.6. Mechanical loosening developed about 1 year postoperatively in one joint with a bone defect. Grade 1 stress shielding was observed in four joints. Although indications for the TPP are restricted to certain cases, unlike the conventional intramedullary stem, much can be expected of TPP. It is an outstanding prosthesis for osteonecrosis of the femoral head of young patients in terms of bone preservation and physiological load transfer.

Adult↗
PubMed2003

Second- and third-generation Omniflex modular femoral stem: results 3 to 8 years after surgery.

Primary cementless total hip arthroplasty (THA) using the Omniflex modular femoral stem was conducted on 73 hips in 70 patients. The arc deposition (AD)-type stem was used in 26 hips, and the hydroxyapatite (HA)-type stem was used in 47 hips. The mean follow-up period of patients in the AD group was 78 (range, 61-96) months and that of patients in the HA group was 52 (range, 36-61) months. Clinically, improvement in the Harris hip score occurred in all cases. Thigh pain was reported in 3 (11.5%) AD hips and in 1 (2.1%) HA hip. Radiologically, bone ingrowth fixation was seen in 88.5% of the AD group and in 97.9% of the HA group. No subtrochanteric stress shielding, stem migration of > 2 mm, or revision THA occurred. The second- and third- generation Omniflex stems are useful cementless devices resulting in favorable initial biologic fixation and little bone atrophy at mid-term follow-up.

Aged↗
PubMed2003

Targeted gene delivery to human osteosarcoma cells with magnetic cationic liposomes under a magnetic field.

Gene delivery using cationic liposomes results in relatively low transfection, especially under in vivo conditions. This system, however, can overcome some of the problems associated with viral delivery systems. The present study was carried out in order to improve the transfection efficiency of cationic liposomes by preparing magnetic cationic liposomes (MCL). Small MCL approximately 40 nm in diameter and incorporating one or two magnetite particles were prepared with phosphatidylethanolamine and 3beta-[N-(N', N'-dimethylaminoethane)-carbamoyl] cholesterol. The efficiency of MCL in gene delivery was evaluated by using plasmid DNA containing a luciferase reporter gene and human osteosarcoma Saos-2 cells. Without a magnetic field, maximum luciferase activity was observed when DNA was mixed with MCL at a 1:5 ratio and incubated with cells for 6 h. Under a magnetic field, maximum luciferase activity was achieved by 30-min magnetic induction. This improvement in transfection efficiency by magnetic induction was approximately 3.5-fold. The feasibility of this active transgenic system was further shown by measuring apoptosis rates after transfection of the p53 gene to Saos-2 cells. Apoptosis rates increased to 18.9% from 2.4% by magnetic induction. In conclusion, a gene delivery system including MCL and magnetic induction was found to achieve rapid and enhanced gene delivery in vitro. Such a gene delivery system may be applicable under in vivo conditions, and is expected to offer numerous clinical advantages.

Bone Neoplasms↗
PubMed2002

Effects on articular cartilage of subchondral replacement with polymethylmethacrylate and calcium phosphate cement.

Bone defects were created in rabbit medial femoral condyle in a model where subchondral bone was completely removed or about 2 mm of subchondral bone was maintained. Groups without augmentation and augmented with autogenous bone, polymethylmethacrylate, or calcium phosphate cement were sacrificed at 3, 12, and 24 weeks for evaluation of articular cartilage and observation of bone formation. In the model in which subchondral bone was completely removed, collapse of the subchondral bone together with exfoliation and prolapse of cartilage developed early in all cases. In the model in which 2 mm of subchondral bone was maintained, degeneration of articular cartilage developed at 12 weeks in the group augmented with polymethylmethacrylate, showing a significant difference when compared to the contralateral untreated control group. The group augmented with calcium phosphate cement did not demonstrate any evident difference from the control group. Mechanical properties after subchondral replacement did not differ between the groups augmented with polymethylmethacrylate and calcium phosphate cement, although calcium phosphate cement was considered histologically superior. Calcium phosphate cement was a reliable subchondral replacement material when the bone defect is adjacent to the articular cartilage.

Animals↗