Yoshihiko Kotoura

A bioabsorbable delivery system for antibiotic treatment of osteomyelitis. The use of lactic acid oligomer as a carrier

We prepared a composite of D,L-lactic acid oligomer and dideoxykanamycin B for use as a biodegradable antibiotic delivery system with sustained effect. The composite was implanted in the distal portion of the rabbit femur, and the effective concentration of the antibiotic was measured in the cortex, the cancellous bone, and the bone marrow. In all bone tissues around the implant, the concentration of antibiotic exceeded the minimum inhibitory concentration for the common causative organisms of osteomyelitis for six weeks. Most of the implant material had been absorbed and the bone marrow had been repaired to a nearly normal state within nine weeks of implantation. The implant caused no systemic side effects, and it is likely to prove clinically useful as a drug delivery system for treating chronic osteomyelitis.

Septum-like structures in lipoma and liposarcoma: MR imaging and pathologic correlation

ObjectiveTo investigate the septum-like structures in pre-dominantly lipomatous tumors, by correlating fat-suppressed MR images with histopathologic findings.Design and patientsThe MR findings of three cases of well-differentiated liposarcoma (atypical lipoma), one case of lipoma-like component of dedifferentiated liposarcoma, and nine cases of lipoma were analyzed. T1-, T2-, and fat-suppressed T1-weighted images after Gd-DTPA administration were obtained. Surgical specimens from five patients (four with liposarcoma and one with lipoma) were also scanned with a MR unit, and compared with the pathologic findings.Results and conclusionsEnhancement features of lipoma and liposarcoma were well visualized on fat-suppressed T1-weighted images after Gd-DTPA administration. The septum-like structures of liposarcoma are thick and enhanced considerably, while septa of lipoma are thin and enhanced only slightly. Pathologically, the septum-like structures of liposarcoma contained muscle fibers and the septa of lipoma represented fibrous capsule. Identification of well-enhanced septa in a predominantly lipomatous tumor helps to differentiate malignant tumors from lipomas. As the septum-like structures of lipo-sarcoma contain a skeletal muscle component the tumor might need more extensive surgical procedures including resection of adjacent muscles.

Changes in bone after high-dose irradiation. Biomechanics and histomorphology

We studied the effects of high-dose irradiation on the mechanical properties and morphology of cortical bone in rabbits for 52 weeks after a single dose of 50 Gy of electron-beam to the tibia. After four weeks, the bending strength of the irradiated bone was unchanged, but at 12 weeks, the strength had decreased significantly. At 24 weeks after irradiation mean strength was less than half of controls but by 52 weeks there was a tendency toward recovery. Similar, synchronous changes of damage and recovery were seen in cortical porosity, haematopoietic cells in the bone marrow and endosteal new bone formation.

Bioactivity of CaO·SiO2 glasses added with various ions

The purpose of this investigation was to study the fundamental compositional dependence of bioactivity for bioactive glasses by adding a third component such as Na2O, B2O3, Al2O3, Fe2O3, P2O5 or F− to binary calcium silicate glass. Rectangular specimens of these six kinds of calcium silicate glasses containing each 3 wt ratio third component were implanted into the tibias of mature rabbits for 8 or 25 weeks. Contact microradiograms and SEM-EPMA showed that all glasses, except for Fe2O3-containing glass, formed a Ca, P-rich layer in combination with a Si-rich layer on their surfaces within 8 weeks. The other four kinds of glass except that containing Al2O3 became attached to bone through these layers within 8 weeks, and even Al2O3-containing glass became attached to bone by 25 weeks. Fe2O3-containing glass did not form these layers, nor did it attach to bone even at 25 weeks. A detachment test, performed 8 weeks after implantation, showed that only glasses containing B2O3, P2O5 and F− bonded tightly with bone. Glass containing B2O3 maintained a tight bond at 25 weeks, but the other two kinds of glass showed decreased loads at 25 weeks.

Long-term changes in the haversian systems following high-dose irradiation. An ultrastructural and quantitative histomorphological study.

The effects of high-dose irradiation on the morphology of haversian bone were studied, over a fifty-two-week period, in seventy-seven adult rabbits, after the administration of a single dose of radiation (therapeutic x-ray; twenty-five, fifty, or 100 gray) to one knee joint. The specimens of bone were examined with microangiography, light and transmission electron microscopy, and histomorphometry. Analysis was performed on the haversian bone in the subchondral bone plate of weight-bearing portions of the femoral condyles. Microangiography demonstrated dilatation of the microvasculature four weeks after irradiation. Beginning at twelve weeks, there was a marked decrease in vascularity; no obvious recovery of the subchondral bone had occurred by fifty-two weeks. At four weeks, morphological analysis revealed two changes in the haversian canals: simple occlusion of the haversian vessels with loss of cells in the canal, and dilatation of the capillaries with abnormal resorption of the perivascular bone matrix by osteoclasts. The abnormal bone resorption was not coupled with subsequent new-bone formation, resulting in increased porosity. Beginning at four weeks, a progressive decrease in the number of haversian vessels and in cellularity became prominent. The decrease in cellularity involved all types of cells, including endothelial cells, pericytes, perivascular mesenchymal cells, osteoblasts, osteocytes, and osteoclasts. The loss of perivascular cells was often but not always associated with occlusion of the haversian vessels. Histomorphometry revealed both time-dependent and dose-dependent decreases in capillary density (the number of intraosseous capillaries per unit area) and in the number of osteocytes in the subchondral bone plate. The porosity of the same areas showed a significant increase by four weeks (p < 0.001 after administration of twenty-five gray and p < 0.01 after administration of both fifty and 100 gray), but between twelve and fifty-two weeks, there was only a slight additional increase. Statistical analysis revealed significant correlations between capillary density and osteocyte survival (p < 0.001) and between capillary density and porosity (p < 0.001). The portion of the subchondral bone plate that was located farthest from the non-irradiated normal bone showed progressive damage and no sign of recovery at fifty-two weeks.

In vivo measurement of anodic polarization of orthopaedic implant alloys: comparative study of in vivo and in vitro experiments.

A new system of single piece electrodes was applied to in vivo and in vitro measurements of anodic polarization of several alloys used in orthopaedic implants. The tested surface was scrutinized with a stereomicroscope after each experiment. This confirmed pit formation and excluded the possibility of other sudden increase of anodic current such as crevice corrosion and oxidation or reduction of organic substances. The results were reproducible. Although there were certain differences between the results obtained in the two conditions, the order of corrosion resistances of alloys was consistent.

Imaging of Soft Tissue Tumors with Tc(v)-99m Dimercaptosuccinic Acid: A New Tumor-seeking Agent

Tumor scintigraphy, using Tc(V)-99m dimercaptosuccinic acid (Tc(V)-DMS) was performed in 58 patients with soft tissue tumors, and the results were compared with that of Ga-67 citrate. Tc(V)-DMS was found to have a sensitivity of 90% for malignant tumors including aggressive fibromatosis compared to that of Ga-67 citrate, which was 56%. However, the specificity of Tc(V)-DMS for these tumors was 71% but with Ga-67 citrate the specificity was 80%. The imaging accuracy in soft tissue tumors with Tc(V)-DMS and Ga-67 citrate was 78% and 71%, respectively. Although the accumulation of Tc(V)-DMS has been detected in some benign soft tissue tumors, the reduced accumulation in inflammatory lesions compared to Ga-67 citrate was recognized, and Tc(V)-DMS could be of great use in the detection of extension or location of malignant soft tissue tumors.

Surgical Treatment of Giant-cell Tumors of the Spine

Three cases of relatively uncommon giant-cell tumors in the third cervical and first thoracic vertebra and the sacrum were treated surgically by radical resection and reconstruction. The tumor in the third cervical vertebra was treated by incomplete excision and anterior arthrodesis at a local hospital without pre- or postoperative radiotherapy. A recurrence was noted after four months, however, and an emergency operation was performed for severe quadriplegia. After posterior decompression, the tumor was resected by the lateral approach, and an autograft was performed. The tumor in the first thoracic vertebra was removed simultaneously by the anterior, posterior, and lateral approaches, and reconstruction was performed. The sacral tumor, which was radioresistant, was totally excised, and reconstruction was performed. Using these treatments, excellent results have been recorded after follow-up intervals of 1.5, three, and six years. Because of advancements in preoperative imaging techniques and better surgical techniques, radical resection is the recommended treatment for giant-cell tumors located in the spine.

Diagnostic value of Tc-99m (V) DMSA for chondrogenic tumors with positive Tc-99m HMDP uptake on bone scintigraphy

Technetium-99m (V) DMSA scintigraphy was performed In 17 patients with 37 chondrogenic tumors (13 osteochondromas, 14 enchondromas, and 10 chondrosarcomas) that had previously shown uptake of Tc-99m HMDP. Technetium-99m (V) DMSA showed high uptake by all chondrosarcomas, but low or no uptake always indicated benign chondrogenic tumors. Technetium-99m (V) DMSA scintigraphy may be superior to Tc-99m HMDP scintigraphy for distinguishing benign and malignant chondrogenic tumors, and could also be useful for diagnosing the malignant transformation of chondrogenic tumors.

Enchondroma of the Distal Phalanx of the Hand

We saw five patients who had enchondroma of the distal phalanx, a relatively uncommon site for that lesion. Three patients had pain secondary to a pathological fracture and were managed with curettage and bone-grafting through a palmar longitudinal incision. The other two patients had severe deformities of the fingertip and nail. One was managed with disarticulation of the distal interphalangeal joint and the other, with curettage and grafting through a dorsal approach followed by reconstruction of the nail matrix. We believe that the palmar incision in the pulp of the finger has few, if any, complications.