Minoru Sakurai

Comparative Study on Osteoconductivity by Synthetic Octacalcium Phosphate and Sintered Hydroxyapatite in Rabbit Bone Marrow

Octacalcium phosphate (OCP) is thought to be a precursor of the mineral crystals in biological apatite. Synthetic OCP has been shown to be converted into an apatite structure when implanted in murine calvarial bone, to enhance bone regeneration more than synthetic hydroxyapatite (HA), and to degrade faster than biodegradable β-tricalcium phosphate. This study was designed to investigate whether OCP implantation enhances the formation and resorption of new bone (remodeling) concomitant with OCP degradation when implanted intramedullary in a rabbit femur for 12 weeks, compared to sintered HA ceramic. Histological and histomorphometric analyses using undecalcified specimens showed that the area of bone apposition was significantly higher on OCP than on HA between 2 and 3 weeks, whereas it subsequently became smaller on OCP than on HA. The area attacked by multinucleated giant cells, including tartrate-resistant acid phosphatase (TRAP)-positive cells, was significantly higher for OCP than for HA at 8 weeks. Radiography revealed resorption of OCP but not of HA. The results disclose some osteoconductive characteristics of synthetic OCP in the bone marrow space: (1) enhancement of bone regeneration at the initial bone apposition stage and (2) stimulation of resorption of the newly formed bone coupled with OCP biodegradation mediated by TRAP-positive osteoclast-like cells. These results suggest that synthetic OCP would be a more useful bone substitute than HA in implant applications where rapid bone formation and concomitant implant resorption are important considerations.

Maclura pomifera agglutinin-binding glycoconjugates on converted apatite from synthetic octacalcium phosphate implanted into subperiosteal region of mouse calvaria

We have previously shown that the mineral in granules of synthetic octacalcium phosphate (OCP) implanted subperiosteally in mouse calvariae was converted to apatitic crystals and that the OCP implantation stimulated bone formation. The matrix components accumulated on the converted apatite were very similar to those of bone nodules (starting locus of calcification) in intramembranous osteogenesis. In the present study, the nature of the matrices accumulated on OCP implants in calvariae was compared with that of the matrices accumulated in abdominal subcutaneous implants. The comparison was facilitated by the use of Maclura pomifera agglutinin (MPA) lectin which is known to have a high affinity for the primary intramembranous bone matrix. Micro-beam x-ray diffraction indicated conversion of the implanted OCP to apatitic crystals in situ, both in subperiosteal and subcutaneous sites, after 10 days. Additional bone formation was detected on the converted apatite after 13 days in subperiosteal implantation, whereas bone was not formed in the subcutaneous implantation. MPA reaction was strongly manifested after 10 days in matrices accumulated on the converted apatite in both subperiosteal and subcutaneous implantations. Biochemical data showed that intensely and weakly MPA-blotted molecules (53.0 and 152.6 kDa, respectively) were in all the mouse sera, in the guanidine HCl-EDTA extracts of mouse calvarial bone and in the extracts of the implanted OCP in both subperiosteal and subcutaneous sites. These findings indicated that the glycoconjugates accumulated on the converted apatite from OCP were similar to the glycoconjugates in the serum in terms of reactivity with MPA and molecular weights. Furthermore, the results suggest that MPA-binding glycoconjugates which had accumulated on the converted apatite may be a requisite for the differentiation of mesenchymal cells into osteoblasts in periosteum but not in subcutaneous sites.

Adult-onset vitamin D-resistant osteomalacia. A case with seventeen-year follow-up.

McCance, in 1947, apparently was the first to report the case of a patient who had adult-onset vitamin D-resistant osteomalacia, and the features of the disease were well described by Dent and Stamp in l971 . In most reports, including that of McCance, the disease was associated with tumors2, and that variant of the disease is now classified as tumor-induced osteomalacia9’2. The disease may be diagnosed as adult-onset vitamin D-resistant osteomalacia or as adult-onset idiopathic osteomalacia because there may be a tumor that is too small to be detected; often there is a lag between the diagnosis of osteomalacia and the discovery of the tumor’2. Recently, Ryan and Reiss pointed out that tu-

Cartilaginous endplate in cervical disc herniation

Study Design Cervical herniated disc tissue obtained at surgery for myelopathy and intervertebral discs from autopsy cases were examined histologically. Objectives To clarify the characteristic histology of cervical disc herniation and the processes by which herniated masses are produced. Summary of Background Data Except for nucleus pulposus or anulus fibrosus, no other disc tissue has been described histologically in the cervical spine. Methods Twenty-one herniated cervical discs from 20 surgical cases (patients aged 37-68 years) and mid-sagittal slabs of 135 cervical discs from 41 autopsy cases (aged 20-85 years) were examined histologically. Results All the surgical specimens had cartilaginous endplate fragments together with nucleus pulposus or anulus fibrosus. Of the autopsy disc specimens, 61% had a horizontal cleft longer than two thirds of the anteroposterior diameter of the disc, and 49% had one or more vertical clefts extending to the cartilaginous endplate. Thirty-three percent showed separation of the cartilaginous endplate, and 15% had a herniated mass including parts of the cartilaginous endplate. These abnormal features increased with aging. The same order of decreasing frequency from horizontal cleft formation through herniation was observed in all decades. Conclusions The cartilaginous endplate-type of herniation is the predominant type of herniation in the cervical spine. It results from horizontal and vertical cleft formations of the disc.

Tumoral calcinosis in the upper cervical spine: a case report.

Study Design An elderly women with tumoral calcinosis between the C1 posterior arch and the C2 lamina is reported. Objectives To describe a rare occurrence of tumoral calcinosis in the spine and discuss its pathomechanism. Summary of Background Data Tumoral calcinosis is a rare condition occurring predominantly in the juxtaarticular regions of the extremities. Involvement of the spine has been reported in only one case in the lumbar spine. The calcium phosphate crystals that have been identified are those of hydroxyapatite. Methods The calcified material was removed, and its crystalline phase was analyzed. Results Neck pain was relieved by removal of the calcified material. Scanning electron microscopy and energy-dispersive x-ray microanalysis revealed that the material consisted of crystals of calcium pyrophosphate dihydrate. Conclusions Tumoral calcinosis should be included among the clinical presentations of calcium pyrophosphate dihydrate crystal deposition disease.

Bone marrow scintigraphy in the early diagnosis of experimental metastatic bone carcinoma

Paralleled experimental studies of radioisotopic bone marrow imaging, bone scanning, and skeletal radiologic survey were undertaken upon the intramedullary‐implanted and hematogenously metastatic VX‐2 rabbit bone carcinoma in order to see their temporal relationship in delineating such lesions. Both bone and bone marrow scans turned positive far earlier than the x‐rays. Moreover, lesion‐depicting marrow scans were obtainable before the bone scans became positive. Radiocolloidal marrow scanning appears to be one of the techniques of choice in the early diagnosis of metastatic skeletal malignancies.

Long-term observations of vertebral fractures in spinal osteoporotics

SummaryThe changes in the number and distributions of vertebral fractures were studied from the long-term observations (average 7 years) of 21 spinal osteoporotic patients. Distribution of wedge fractures was biphasic with peak frequencies at the midthoracic and thoracolumbar spine. Biconcave fractures occurred predominantly in the lumbar spine. These patterns of distribution did not change during the period of observation. The rate of biconcave fracture increased, the rate of wedge fracture decreased, and that of collapse remained the constant in follow-up. The changes in the number of fractures were divided into three types; increasing, plateau, and unchanged type. With the advance of osteoporosis, the increasing type was considered to change into the plateau type, which is probably the terminal stage of spinal osteoporosis. The unchanged type, in contrast, was distinct from the other two types because of increased spinal bone mineral density and decreased urinary calcium, which suggests that spinal osteoporosis is heterogeneous with regard to calcium metabolism.

Ossification of the Achilles Tendon: A Case Report

Ossification of the Achilles tendon is a rare condition. We recently treated a patient with ossification of bilateral Achilles tendons. The patient was a 50 year old male whose chief complaint was discomfort around the Achilles tendon. He had a previous history of treatment of bilateral club feet On the roentgenograms, the length of the bony mass in the Achilles tendon was 5.5 cm on the right side and 1.5 cm on the left side. The left side was treated by surgical removal of a bony mass and suture of the tendon. Microscopic examination of the extirpated specimen revealed bone formation through enchondral and intramembranous ossification in the Achilles tendon.

The mechanical behavior and morphological structure of callus in experimental callotasis.

Experimental callotasis was made in rabbit femurs. In order to compare mechanical behaviors and morphological structure of callus in callotasis, mechanical tests and histological examination were performed. Twenty Japanese white male rabbits were used. The right femurs were osteotomized at the level of the midshaft with a rotary cutter and fixed with a mini-model external fixator. After a 5-day waiting period, bone lengthening was started at the rate of 0.25 mm two times a day. Animals were divided into four groups. Group 1 and Group 2 were continual distraction group, Group 3 and Group 4 discontinued distraction group. The viscoelastic property was demonstrated in continual distraction group irrespective of distraction period, we thought the central undifferentiated connective tissue in callus was mainly responsible for the mechanical behavior. On the other hand, in discontinued distraction group, viscoelastic property shifted to elastic property corresponding to the rest period, we thought this change of mechanical behavior was histologically owing to the replacement of undifferentiated connective tissue by cartilage and the partial union of bone in callus.

One-stage anterior and posterior correction of severe kyphosis of the cervical spine in neurofibromatosis. A case report.

A case is presented of a 29-year-old woman with neurofibromatosis, who had a 100 degrees dystrophic kyphosis of the cervical spine and was successfully treated by a one-stage anterior and posterior correction. Anterior distractive and posterior compressive corrections were simultaneously applied keeping the posterior longitudinal ligament intact. The kyphosis was corrected to 42 degrees. Safety and better results of the one-stage correction of kyphosis is based on a concept of shortening the spinal canal.