U. E. Pazzaglia

Thermal behaviour of hydroxyapatite intended for medical applications.

Four commercial hydroxyapatites (both natural and synthetic) were tested to assess transformations of the chemical and crystalline structure following variation of temperature from 20 to 1600 degrees C. The thermal behaviour of hydroxyapatite is relevant for biomedical applications such as plasma spraying of metallic implants. Thermogravimetric analysis showed a weight loss from each hydroxyapatite specimen, due to a release of structural H2O molecules; all the specimens up to 1300 degrees C were made of crystalline hydroxyapatite, determined by X-ray diffraction; at 1470 degrees C they were made of both hydroxyapatite and calcium phosphate, but at 1570 degrees C of calcium phosphate exclusively. The diffractograms of the hydroxyapatite coatings showed the same peaks as the original powders, so at the chosen plasma-spray procedure level no new phases were formed. The peak height was nevertheless lower in the plasma-sprayed hydroxyapatites for all interplanar spacing values, which indicated a lower degree of crystallinity, associated with a random structure derived from an alteration to the original crystalline network.

METAL DETERMINATION IN ORGANIC FLUIDS OF PATIENTS WITH STAINLESS STEEL HIP ARTHROPLASTY

In 20 stainless steel Charnley hip arthroplasties (with a follow-up of 10-13 years) nickel, chromium and manganese levels were measured in blood, plasma and urine by atomic absorption spectrophotometry. Skin patch tests for these metals, and clinical and roentgenographic results of arthroplasty were also assessed. Metal levels in organic fluids were plotted against a control population homogeneous for age, residence and anamnestic conditions with the first, but which had never undergone a prosthesis or other metallic implant surgical procedure. Nickel levels in blood, plasma and urine, manganese levels in blood and urine and chromium levels in plasma were significantly higher in the hip prostheses population. Metal ion release from stainless steel prostheses is discussed with regard to implant failure, metal sensitivity and carcinogenesis.

Pathology of disappearing bone disease: a case report with immunohistochemical study

Summary. A case of disappearing bone disease of the proximal femur is reported with histopathological and immunohistochemical studies. There was a densely packed cellular tissue, positive to endothelial antibodies, in areas of massive bone destruction. A more differentiated vascular tissue was present where trabecular cancellous or cortical bone was preserved with only focal zones of accelerated bone remodelling. The self-limited course correlates well with two phases of evolution of the histopathological lesions with neoplastic-like proliferation of endothelial cells corresponding to the rapid and massive bone destruction, and a later differentiation of the cells in mature vascular structures, but still with accelerated bone resorption which is partly compensated by appositional activity.Résumé. Nous décrivons un cas d’ostéolyse massive idiopathique localisée à l’extremitè proximale du fémur ainsi qu’une étude histopathologique et immunohistochimique. Là où il y a une plus grande destruction osseuse on observe un tissu avec des cellules en amas, ayant une réaction positive aux anticorps endotheliaux. Par contre il y a une plus grande différenciation vasculaire la où l’os spongieux et cortical ètait preservé avec seulement des petites zones ayant un remodelage osseux accéléré. L’évolution autolimitante de cette pathologie est mise en corrélation avec deux phases évolutives des lésions histopathologiques. En premier la proliferation des cellules endotheliales néoplasiques correspond à une énorme et rapide destruction de l’os, ensuite une differentiation successive des cellules en structures vasculaires matures, tandis que la resorption osseuse, est compensèe partiellement par une néoapposition.

Bone resorption in vitro: macrophages and giant cells from failed total hip replacement versus osteoclasts.

Macrophages and giant cells which ingested material particles in loosening of total hip prostheses were tested for their ability to resorb bone in vitro, using osteoclasts as the control. Macrophages and giant cells did not form pits or resorption lacunae on the bone substrates as osteoclasts did. The results support the view that around implants also bone resorption is mediated by osteoclasts. A role of macrophages in the attachment phase of bone resorption is suggested.

The role of macrophages and giant cells in loosening of joint replacement.

SummaryMacrophages and foreign-body giant cells from the bone-cement interface of loosened joint replacement were assayed for direct bone resorption in an in vitro experimental model. Human osteoclasts from giant cell tumors and experimental animal osteoclasts were used as controls. Macrophages and giant cells were not capable of resorbing the bone under experimental conditions, but osteoclasts are. It is suggested that macrophages and giant cells in loosened implants may initiate bone resorption, removing the extra-cellular barrier that normally protects mineral crystals from osteoclastic recognition.ZusammenfassungMakrophagen und Fremdkörperriesenzellen von der Knochen/Zementgrenze gelokkerter Gelenkendoprothesen wurden hinsichtlich der direkten Knochenresorption in einem experimentellen in vitro-Modell untersucht. Als Kontrollen dienten Osteoklasten aus menschlichen Riesenzelltumoren und von embryonalen Hühnerknochen. Während Osteoklasten unter den experimentellen Bedingungen Knochen resorbierten waren Makrophagen und Riesenzellen dazu nicht in der Lage. Es wird angenommen, daß Makrophagen and Riesenzellen bei gelockerten Implantaten die Knochenresorption anbahnen, indem sie die extrazelluläre Barriere entfernen, welche normalerweise die Mineralkristalle dagegen schützen von den Osteoklasten als solche erkannt zu werden.

Histology of the metal-bone interface : interpretation of plastic embedded slides

The interference of processing and preparation of histological slides for the study of morphology and morphometry of bone-implant interfaces was investigated in an experimental model, in which a titanium plate was inserted through the cortical bone into the medullary cavity of rat tibiae. The thickness of the sections, burr and notching of the cut border, and staining properties of the embedding resin were found to significantly influence the appearance of the bone-implant interface and, when morphometry was applied, the extent of direct bone-metal contact. The model of the interface resulting from this study is that of some bony processes abutting on the metal surface, while most of the contact is between metal and connective tissue or vascular spaces.

Inhibitory effect of salmon calcitonin on bone resorption: Morphological study of the tibial growth plate in rats

SummarySalmon calcitonin (sCT) at doses of 100 and 50 UI given subcutaneously to growing rats produced in vivo evidence of osteoclastic activity inhibition. Histological assessment was carried out by measuring the perichondrial ring of Lacroix height, and a dose-correlated effect was found. These aspects were coupled with an increase in the osteoclast number and suggested that in studies with bone resorption inhibitors, morphological evaluation based on osteoclasts count is not reliable. The changes of the metaphysis suggested also that sCT affects the activity of hypertrophic chondrocytes of the growth plate. Plasma calcium levels did not differ significantly between treated rats and controls; an increased phosphatemia was observed in sCT-treated animals.

Study of the bone pathology in early mucolipidosis II (I-cell disease)

Histological examination of the bones obtained on autopsy of a 5-month-old child with mucolipidosis II (I-cell disease) revealed inhibition of the growth plate calcification with defective vascular invasion and signs of hyperparathyroidism. These findings are the chondro-osseous basis of the early radiological ricket-like appearance of bones in the neonatal period or soon thereafter. Whether the early skeletal abnormalities of mucolipidosis II result from a primary enzymatic defect of cartilage and bone cells or from factors controlling bone metabolism deserves further study.

Case report 381

This 35-year-old woman was admitted to the hospital several times because of disseminated and symmetrical skeletal lesions of a cystqike appearance. These lesions were first observed 9 years previously, following a fracture of the left fibula. One year after this incident, the left talus and navicular bones were curetted. A yellow, fatty material, filling the cyst-like lesions, was observed in the operative procedure. When examined microscopically, fat tissue was noted, but a diagnosis was not made. The family history was not significant. It was considered possible that the skeletal lesions were congenital, but this thought was negated, inasmuch as roentgenograms of the right ankle, obtained at the age of 16 years (after trauma), showed

Chronic idiopathic hyperphosphatasia and fibrous dysplasia in the same child

A generalized skeletal dysplasia with features of chronic idiopathic hyperhosphatasia and fibrous dysplasia of the mandidible were observed in a 6-year-old child. The abnormal development of the bones resulted from enhanced remodeling and the failure of mature bone to from. The occurence of the two lessions in the same child and a review of the litterature support the hypothesis that pathogensis of fibrous dyolasia and idiopathic byperphosphatasia reflect an underlying common defect in the control of bone cell activity.