Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “BONES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,279 records · Page 71Linked to original sources
PubMed2006

Larger bone graft size and washing of bone grafts prior to impaction enhances the initial stability of cemented cups: experiments using a synthetic acetabular model.

BACKGROUND: Bone defects after failed total hip arthroplasty can be reconstructed with impacted morselized bone grafts and a cemented cup. On the acetabular side, the effects on initial cup stability of washing bone grafts prior to impaction and bone graft size remain unclear. Related to these variables, cement penetration and inter-particle shear resistance have been suggested to be critical factors to ensure initial cup stability. METHODS: Using a synthetic acetabular model, we studied the effects of (1) washing bone grafts prior to impaction, and (2) bone graft size on the initial stability of cemented cups. In addition, cement penetration was measured using CT scans. RESULTS: Reconstructions with large, washed bone grafts provided the highest stability during mechanical compression and in a lever-out situation. Washing of the bone grafts had a positive effect on initial cup stability, but the size of the bone grafts appeared to be more important. Cement penetration was affected by bone graft size but not by washing. INTERPRETATION: From a mechanical standpoint, large bone grafts that have been washed prior to impaction may be preferable in order to obtain optimal cup stability using the bone impaction grafting technique.

Acetabulum↗
PubMedDate not supplied

Differentiation of cartilage from calvarial bone under the influence of bone matrix gelatin in vitro.

Fetal rat calvarium in an optimum (CMRL-1066) culture medium (with respect to amino acids. Tween 80, DNA precursors and hydrogen acceptors used in oxidative metabolism) produces new lamellar bone. The explanted osteoprogenitor cells survive, proliferate on living membrane bone surfaces and remodel membrane bone into lamellar bone. In the same culture medium, calvarial connective tissue and osteoprogenitor cells grow out of the membrane bone interstices onto a substratum consisting of bone matrix gelatin (BMG) and differentiate not into bone but into hyaline cartilage. Outgrowths from either bone or muscle onto a substratum of BMG prepared from bone autodigested in neutral buffer solutions, produce only fibrous connective tissue. In BGJ, a culture medium containing suboptimal ingredients for cell proliferation, calvarial bone produces neither lamellar bone nor new cartilage but is gradually resorbed and replaced by fibroblasts. In CMRL culture medium, outgrowths of mesenchymal-like cells from muscle onto a substratum of living membrane bone produce an epiphyseal plate-like columnar deposit of new hyaline cartilage. These observations suggest that the function of BMG is to evoke mesenchymal cell differentiation into prechondroblasts during the latent or migratory morphogenetic phase while the effect of the culture medium is to provide the bionutritional requirements for synthesis of hyaline cartilage matrix by chondrocytes during the patent phase of development.

Animals↗
PubMed2003

Comparison of internal bone transport and vascularized fibular grafting for femoral bone defects.

OBJECTIVE: To compare results between vascularized fibular grafting and internal bone transport for large bone defects of the femur. DESIGN: Retrospective review of patients. SETTING: University teaching hospitals. PATIENTS: This study included 37 patients with femoral bone loss: 20 patients were treated with internal bone transport and seventeen patients were treated with vascularized fibular grafting. MAIN OUTCOME MEASUREMENTS: The outcomes investigated were external fixation time, external fixation index, bone results (union, infection, deformity, leg length discrepancy), and functional results. RESULTS: The mean amount of filled defect was 8.4 cm with internal bone transport and 8.9 cm with vascularized fibular grafting. The external fixation index was 1.4 months/cm with internal bone transport and 1 month/cm with vascularized fibular grafting. The bone results and functional results of the internal bone transport were excellent in 65% and 0%, good in 5% and 45%, fair in 5% and 40%, poor in 25% and 15%, respectively, whereas those of the vascularized fibular grafting were excellent in 35% and 0%, good in 25% and 47%, fair in 5% and 35%, and poor in 35% and 18%. CONCLUSION: With vascularized fibular grafting, careful monitoring of circulation and early intervention surgery is necessary to avoid vascular failure. With internal bone transport, repeated radical debridement until control of infection is achieved, bone grafting at the docking site for early union, and avoiding stress fracture are recommended to improve bone results.

Adolescent↗
PubMed1999

Evaluation of bone height in osseous free flap mandible reconstruction: an indirect measure of bone mass.

Osseous free flaps have become the preferred method of mandibular reconstruction after oncologic surgical ablation. To elucidate the long-term effects of free flap mandibular reconstruction on bone mass, maintenance or reduction in bone height over time was used as an indirect measure of preservation or loss in bone mass. Factors potentially influencing bone mass preservation were evaluated; these included site of reconstruction (central, body, ramus), patient age, length of follow-up, adjuvant radiotherapy, and the delayed placement of osseointegrated dental implants. A retrospective analysis of patients undergoing osseous free flap mandible reconstruction for oncologic surgical defects between 1987 and 1995 was performed. Postoperative Panorex examinations were used to evaluate bone height and bony union after osteotomy. Fixation hardware was used as a reference to eliminate magnification as a possible source of error in measurement. There were 48 patients who qualified for this study by having at least 24 months of follow-up. There were 27 male and 21 female patients, with a mean age of 45 years (range, 5 to 75 years). Mandibular defects were anterior (24) and lateral (24). Osseous donor sites included the fibula (35), radius (6), scapula (4), and ilium (3). There were between zero and four segmental osteotomies per patient (excluding the ends of the graft). Nineteen percent of all patients had delayed placement of osseointegrated dental implants. Initial Panorex examinations were taken between 1 and 9 months postoperatively (mean, 2 months). Follow-up Panorex examinations were taken 24 to 104 months postoperatively (mean, 47 months). The bony union rate after osteotomy was 97 percent. Bone height measurements were compared by site and type of reconstruction. The mean loss in fibula height by site of reconstruction was 2 percent in central segments, 7 percent in body segments, and 5 percent in ramus segments. The mean loss in bone height after radial free flap mandible reconstruction was 33 percent in central segments and 37 percent in body segments; ramus segments did not lose height. The central and body segments reconstructed with scapular free flaps did not lose height, but one ramus segment lost 20 percent of height. There was no loss in bone height in mandibular body reconstruction with the ilium free flap. Fibula free flaps did not significantly lose bone height when evaluated with respect to age, follow-up, radiation therapy, or dental implant placement. The retention in bone height demonstrated in this study suggests that bone mass is preserved after osseous free flap mandible reconstruction. The greatest amount of bone loss was seen after multiply osteotomized radial free flaps were used for central mandibular reconstruction. The ability of the fibula free flap to maintain mass over time, coupled with its known advantages, further supports its use as the "work horse" donor site for mandible reconstruction.

Adolescent↗
PubMed2005

Bone strength influences periprosthetic bone loss after hip arthroplasty.

UNLABELLED: Our primary question was whether bone strength at the time of surgery, reflected by the lumbar spine T-score and femoral cortical thickness, influences periprosthetic bone loss after a total hip arthroplasty. Using dual energy xray absorptiometry we preoperatively and postoperatively examined 38 consecutive patients having cementless total hip arthroplasties for their bone density. Bone strength was estimated using lumbar spine bone mineral density and the ipsilateral diaphyseal cortical thickness of the femur measured on radiographs. Periprosthetic femoral bone mineral density was measured with dual energy xray absorptiometry within 1 week postoperatively and at 2, 4, 6, 9, 12, and 24 months thereafter. Periprosthetic bone loss was influenced by the patient's bone strength at the time of surgery. Bone loss in the calcar femoris (as much as 54% after 2 years) was greater in patients with a low lumbar spine T-score or low femoral cortical thickness. Preoperative assessment of bone strength (ie, lumbar spine bone mineral density and femoral cortical thickness on radiographs) served as a reliable indicator in predicting the extent of periprosthetic bone loss after total hip arthroplasty. LEVEL OF EVIDENCE: Prognostic Study, Level I (high quality prospective study-all patients were enrolled at the same point in their disease with > or = 80% followup of enrolled patients). See the Guidelines for Authors for a complete description of levels of evidence.

Adult↗
PubMed2006

Growth hormone stimulates bone healing in a critical-sized bone defect model.

Growth hormone plays an important role in bone metabolism. Treating bone deficits is a major topic in orthopaedic surgery. Our hypothesis was that local continuous growth hormone administration stimulates bone healing in a canine critical-sized bone defect model. Bone formation in the defects was quantified using densitometric image analysis and histomorphometry. After growth hormone treatment, expression levels of insulin-like growth factors-I and II, and growth hormone receptor were determined in the bone regenerate of the original defects. Circulating plasma concentrations of insulin-like growth factors-I and II, and insulin- like growth factor binding proteins-4, and 6 were measured during treatment. Growth hormone administration resulted in healing of bone defects but without an additional effect of local infusion. Expression of insulin-like growth factor-I in the bone regenerate was lower in the growth hormone-treated dogs, whereas insulin-like growth factor-II and growth hormone receptor expression were not increased. Growth hormone increased circulating insulin-like growth factor-I and growth factor-II plasma concentrations. Continuous infusion of growth hormone stimulated bone healing in a canine critical-sized bone defect model. Local delivery of growth hormone did not additionally enhance bone healing. Increased circulating plasma concentrations of insulin-like growth factors-I and II most likely induced bone formation.

Animals↗
PubMed2006

Comparison between polyurethanes containing castor oil (soft segment) and cancellous bone autograft in the treatment of segmental bone defect induced in rabbits.

The aim of this study is to compare polyurethanes containing castor oil (soft segment) in granular form compared to cancellous bone autograft applied to a segmental bone defect. Norfolk adult female rabbits - approximately 13 months of age with a mean body weight of 4.5 kg - are used. In both radial diaphyses, 1 cm osteoperiosteal segmental defects are created. The defect in the left radius is filled with the castor-oil-based polyurethane, and the right one, filled with cancellous bone autograft, collected from the left proximal humerus. The rabbits are euthanazed at 15, 30, 60, and 120 days postsurgery (5 animals/ period), for histological analyses. By radiographic analyses, at these time points, the bone regeneration is more evident and accelerated in the bone defects treated with the cancellous bone autograft. At 120 days postsurgery, the segmental bone defects treated with the cancellous bone autograft are totally reconstituted and remodeled, while the bone defects treated with polyurethane polymer have bone formation of 79%. Histological study shows that the polyurethane acts as a space filler, minimizing the local production of fibrous tissue. No granule degradation, resorption or any inflammatory reaction is detected. Thus, it is possible to conclude that the castor-oil-plant-based polyurethane - in the granule presentation - is biocompatible and osteointegrated, but does not show the same bone regeneration capacity as the cancellous bone autograft.

Animals↗
PubMed2006

Distribution of lovastatin to bone and its effect on bone turnover in rats.

Statins, the widely used lipid-lowering drugs, are inhibitors of 3-hydroxy-3-methyl-glutaryl coenzyme A (HMG-CoA) reductase, which catalyses a rate-limiting step in the biosynthesis of cholesterol. Many previous reports show that statins can act both as bone anabolic and as anti-resorptive agents but their beneficial effects on bone turnover are still controversial. Considering their high liver specificity and low oral bioavailability, the distribution of statins to the bone microenvironment is questionable. In this study, the distribution of lovastatin and its active metabolites to bone, with respect to plasma and liver compartments, was examined after oral and intravenous administration in female rats. As compared with oral administration, the distribution of lovastatin to the bone compartment was significantly enhanced after intravenous administration. Further, the effect of lovastatin on bone turnover was studied in-vitro and in-vivo to assess its anti-osteoporotic potential. Lovastatin acid but not lovastatin was found to inhibit parathyroid-hormone-induced bone resorption in an in-vitro chick embryo bone assay. Oral, as well as intravenous, short-term lovastatin treatment significantly reduced the serum total cholesterol, serum total alkaline phosphatase and urinary crosslinks in ovariectomized rats. In accordance with its increased distribution to the bone compartment, intravenously administered lovastatin was more effective in reducing the ovariectomy-induced increase in markers of bone metabolism, especially urinary crosslinks. The findings of this study suggest that statins inhibit bone resorption and that their anti-resorptive efficacy can be increased by administering them by routes other than oral so as to achieve their enhanced concentration in bone.

Administration, Oral↗
PubMed2004

The chloride channel inhibitor NS3736 [corrected] prevents bone resorption in ovariectomized rats without changing bone formation.

UNLABELLED: Chloride channel activity is essential for osteoclast function. Consequently, inhibition of the osteoclastic chloride channel should prevent bone resorption. Accordingly, we tested a chloride channel inhibitor on bone turnover and found that it inhibits bone resorption without affecting bone formation. This study indicates that chloride channel inhibitors are highly promising for treatment of osteoporosis. INTRODUCTION: The chloride channel inhibitor, NS3736, blocked osteoclastic acidification and resorption in vitro with an IC50 value of 30 microM. When tested in the rat ovariectomy model for osteoporosis, daily treatment with 30 mg/kg orally protected bone strength and BMD by approximately 50% 6 weeks after surgery. Most interestingly, bone formation assessed by osteocalcin, mineral apposition rate, and mineralized surface index was not inhibited. MATERIALS AND METHODS: Analysis of chloride channels in human osteoclasts revealed that ClC-7 and CLIC1 were highly expressed. Furthermore, by electrophysiology, we detected a volume-activated anion channel on human osteoclasts. Screening 50 different human tissues showed a broad expression for CLIC1 and a restricted immunoreactivity for ClC-7, appearing mainly in osteoclasts, ovaries, appendix, and Purkinje cells. This highly selective distribution predicts that inhibition of ClC-7 should specifically target osteoclasts in vivo. We suggest that NS3736 is inhibiting ClC-7, leading to a bone-specific effect in vivo. RESULTS AND CONCLUSION: In conclusion, we show for the first time that chloride channel inhibitors can be used for prevention of ovariectomy-induced bone loss without impeding bone formation. We speculate that the coupling of bone resorption to bone formation is linked to the acidification of the resorption lacunae, thereby enabling compounds that directly interfere with this process to be able to positive uncouple this process resulting in a net bone gain.

Animals↗
PubMed2006

Histologic and ultrastructural analysis of regenerated bone in maxillary sinus augmentation using a porcine bone-derived biomaterial.

BACKGROUND: The purpose of the present study was the histologic and ultrastructural evaluation of a biomaterial composed of cortical pig bone in the form of granules. METHODS: After maxillary sinus augmentation using this biomaterial, 10 specimens were retrieved after 5 months in 10 patients using this biomaterial. The specimens were processed to be observed under light microscopy (LM) and transmission electron microscopy (TEM). Histomorphometric measurements were presented by means +/- standard deviations. RESULTS: LM showed that most of the particles were surrounded by newly formed bone. In some areas, the osteoid matrix was present; however, mainly compact bone was present at the interface. There was no evidence of an acute inflammatory infiltrate. The newly formed bone was 36% +/- 2.8% and marrow spaces were 38% +/- 1.6%, whereas residual grafted material was 31% +/- 1.6%. Under TEM, all phases of bone formation (osteoid matrix, woven, and lamellar bone) were observed in proximity with the biomaterial particles. The bone-biomaterial interface showed a close contact between the porcine bone particles and the surrounding bone that had mainly features of mature bone with numerous osteocytes. A lamina limitans was sometimes present at this interface. CONCLUSIONS: According to our knowledge, this is the first study presenting data on TEM of a porcine bone-derived biomaterial used in sinus augmentation procedures in humans. Our findings show that this is a biocompatible biomaterial that can be used for maxillary sinus augmentation procedures without interfering with the normal reparative bone processes.

Absorbable Implants↗
PubMed1999

Quantitative assessment of angiogenesis and osteogenesis after transplantation of bone: comparison of isograft and allograft bone in mice.

We performed a vital microscopic study in mice bearing dorsal skinfold chambers to characterize microvascular perfusion and leukocyte/endothelium interaction and their effects on elongation and mineralization of neonatal isograft and allograft bone. Isograft (C57/BL to C57/BL) and allograft bone (C57/ BL to BALB/C) revascularized simultaneously. However, vascular perfusion and density were lower in allograft bone than in isograft bone. Leukocyte/endothelium interaction was the same in isograft and allograft bones. Revascularization was not detected in allograft bone transplanted to presensitized recipients. Moreover, in preexisting vessels at the transplantation site, leukocyte/endothelium interaction was altered in allograft bone of presensitized recipients, despite a normal systemic leukocyte count. Femoral growth resulting from thickening of both epiphyses did not differ between experimental groups, however, mineralization occurred in isograft bone only. Isograft bone was histologically intact, allograft bone hypovital and allograft bone in presensitized recipients necrotic 12 days after implantation. Our findings suggest that graft incorporation or rejection is mediated by the microvasculature and that presensitizing of recipients accelerates rejection of allograft bone.

Animals↗
PubMed2003

The development of bone mass and bone strength in the mandible of the female rat.

The present study provides baseline data for a number of mandibular growth dimensions, specially on bone mass and bone strength, that were collected between the 21st and the 180th days of postnatal life, which are intended as a reference for researchers designing experimental studies, specially on mandibular catch-up growth, and as an aid for clinicians who must evaluate results from published animal studies for validity and potential extrapolation to the human clinical situation. Fifty weanling female Wistar (Hsd:Wi) rats were fed ad libitum a diet previously shown to allow normal, undeformed mandibular growth. Five of them were randomly selected at different times between 21 and 180 d of life. Mandibular growth was estimated directly on the right hemimandible by taking measurements between anatomical points; mandibular bone mass (calcium mass) was estimated from the mg of calcium, determined by atomic absorption spectrophotometry, present in the ashes of the left hemimandible; and mechanical properties of the right hemimandible were determined using three-point bending mechanical test. Dimensions, bone calcium mass and bone strength of the female rat mandible increased linearly from day 21 to approximately day 90. Bone growth, as expected, was more than twice when assessed from bone weight than when derived from mandibular area, length or height when the parameters were expressed as the relative increase from the mean infant condition. The growth rate of the posterior part of the mandible (behind the third molar) was almost five times greater than that of the anterior part. The rates of growth of the studied parameters showed a marked decline after day 90. ANOVA indicated that no statistical differences were found between day 90 and day 120 values. It could be concluded that the female rat mandible attains its adult size, peak bone calcium mass and bone structural mechanical properties at some point between 90 and 120 d of postnatal life. Because of the extremely high positive correlation between mandibular bone calcium mass and both mandibular area and mandibular weight, it was possible to calculate the mandibular peak bone mass from the relations 7.69 mgCa/cm2 and 0.19 mgCa/mg bone.

Aging↗
PubMed1992

Subchondral bone infractions in acute ligamentous knee injuries demonstrated on bone scintigraphy and magnetic resonance imaging.

Bone scintigraphy is used to detect radiographically silent fractures. Magnetic resonance imaging (MRI) is currently used to screen knee injuries for cartilage and ligament damage. MRI also delineates bone marrow and fractures. We investigated the bone scintigraphic findings in patients who had subchondral bone injuries demonstrated on MRI. Thirteen patients underwent MRI, three-phase bone scintigraphy with SPECT, and arthroscopic surgery after sustaining acute traumatic hemarthrosis of a knee. They all had clinically unsuspected subchondral bone injuries demonstrated on MRI with normal radiographs and normal overlying articular cartilage at arthroscopy, consistent with occult fractures. All showed focal bone repair on scintigraphy. Two of the 13 patients showed additional bone injuries only on bone scan. Two other patients scintigraphically showed focal bone repair at the medial femoral condyle due to avulsion of the medial collateral ligament. SPECT was easier to interpret than multi-view planar imaging. Bone scintigraphy confirms subchondral fractures demonstrated on MRI but also demonstrates ligament avulsion injuries and additional more subtle bone injuries.

Adolescent↗
PubMed1989

[Study of bone remodeling mechanism induced by mechanical stress. Differentiation of osteoclasts induced by compressive force in newborn rat cultured long bone].

The purpose of this investigation was to reveal the mechanism of differentiation of osteoclast (OC) induced by mechanical stress in long bone cultivation of new born rats. A long bone was loaded with 30 gf of continuous compressive force and cultured for 5 days in CO2 incubator. Numbers of OC increased in the long bone were counted after H-E staining and compared with the control. The study was dealt with the effects of recombinant tumor necrosis factor alpha (rTNF alpha), recombinant interleukin-1 beta (rIL-1 beta), prostaglandin E2 (PGE2) and the co-cultivation of osteoblast (OB) originated from new born rat calvariae, as to differentiation of OC. Since the bone remodeling was interacted with OB and bone marrow (BM) cells, the activity of alkaline phosphatase (ALPase) was also investigated for OB in co-cultivation with BM cells originated from new born rat long bones. In the region of diaphysis of a long bone loaded with compressive force, the bend of trabecular bones was noticed after 3 days incubation. Also, the enrichment of monocyte-macrophage (Mo-M phi) lineage cells was noticed along the trabecular bones. After 5 days incubation, the increase of the number of OC was specifically recognized. The increase of the number of OC was shown in medullary cavity of the long bone by addition of rTNF alpha to the culture medium, but any synergistic effect was not shown with the treatment of rTNF alpha and compressive force to the increase of the number of OC. Furthermore, the increase of the number of OC induced by compressive force did not suppressed by addition of anti-TNF serum. Under the treatment of rIL-1 beta or PGE2, OC slightly increased in the long bone when loaded by compressive force, but the treatment of indomethacin did not suppress it completely. However, the increase of OC in the long bone loaded by compressive force was clearly inhibited in co-cultivation with OB. On the other hand, the activity of ALPase of OB was markedly abated in co-cultivation with BM cells. These results indicated that the mechanism of differentiation of OC induced by mechanical stress was different from that induced by the general inflammation. Results also indicated that it was controlled mainly by the factor(s) or interaction between BM cells and OB and was associated with Mo-M phi lineage cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1975

Bone induction effect of fine bone shavings in polyester fibre. An experimental study.

Autogenous marrow-free bone shavings of dense lamellar bone spread over polyester mesh were transplanted into muscle, the palate and the tibia. A thin sheet of silastic was used to eliminate the induction effect of the adjacent bone, and the results were evaluated histologically. It was found that finely divided autogenous bone shavings actively induce new bone formation, and that the rate of bone production depends on the proximity of bone-competent tissue, such as a muscle tendon or a muscle attachment. Osteogenesis is also stimulated by a direct blood supply from the adjacent bone. Polyester mesh (Mersilene) is a relatively inert material, which could be used to great advantage in the transplantation of bone. Preliminary results of this research indicate that it may be of great value in bone reconstruction. These experiments support the idea of a non-cellular and diffusible bone stimulatory substance which influences the inducible osteogenic precursor cells to produce bone.

Animals↗
PubMed1996

Prevention of lpr-graft-versus-host disease and transfer of autoimmune diseases in normal C57BL/6 mice by transplantation of bone marrow cells plus bones (stromal cells) from MRL/lpr mice.

C57BL/6 (B6) (H-2b) mice were lethally irradiated and then reconstituted with T cell-depleted MRL/Mp-lpr/lpr (MRL/lpr) (H-2k) bone marrow cells. The mice showed a short survival with splenic atrophy and fibrosis, as previously described as lpr-graft-vs-host disease (GVHD). However, when these mice received bone marrow transplantation (BMT) plus bone grafts (to recruit donor-derived stromal cells) from MRL/lpr mice, they survived for almost 1 yr without showing GVH symptoms, but showing autoimmune symptoms such as elevated serum IgG2a concentrations, autoantibody production and glomerulonephritis. When MRL/lpr bone marrow cells plus MRL/+ bones (instead of MRL/lpr bones) were transplanted into B6 mice, such improved survival was also obtained, although the MRL/+ bone grafts were less effective in prolonging survival than MRL/lpr bone grafts. H-2 typing of stromal cells in the bone marrow of the B6 mice revealed that the stromal cells had been replaced by donor(H-2k) derived stromal cells. Analyses of TCR repertoires showed that the percentage of CD4+V beta 8.1,2+ cells significantly decreased in the B6 mice that received bone marrow transplantation plus bone grafts from MRL/lpr mice. These findings suggest that stromal cells present in the bone marrow play a crucial role in the development of lpr-GVHD and autoimmune diseases.

Animals↗
PubMedDate not supplied

Bone effects of space flight: analysis by quantum concept of bone remodelling.

During the manned Skylab flights mineral losses from the calcaneum and changes in external calcium balance were in the ranges found for healthy subjects at bedrest. Calcium balance reached a nadir of -200 mg/day by two months with no change thereafter; the negative balance was due to increased urinary excretion with no change in net absorption. The total calcium loss averaged 18 g in the longest flight of 84 days; the densitiometric data suggested that about two-thirds of this came from trabecular bone and about one-third from cortical bone. These data could represent reversible bone loss due to increased birth rate of normal osteoclasts and osteoblasts and consequent increase in bone turnover and in reversible mineral deficit, or irreversible bone loss due to overactive osteoclasts and/or underactive osteoblasts. If the former explanation is correct, significant bone loss is unlikely whatever the duration of future flights, except in older persons already losing bone; if the latter explanation is correct, space flights longer than six months may lead to a significant increase in fracture risk in later life. Neither terrestrial immobilization nor unwilling animals in orbit are ideal models for the effects of space flight on human bone. To choose between reversible and irreversible mechanisms of bone loss, and to determine the effects of space flight on lifelong fracture risk, future astronauts and cosmonauts must undergo adequate histologic study of bone after in vivo tetracycline labeling.

Absorptiometry, Photon↗
PubMedDate not supplied

[Assessment of bovine biomaterials containing bone morphogenetic proteins bound to absorbable hydroxyapatite in rabbit segmental bone defects].

PURPOSE: To evaluate the osteo-regenerative capacity of two proprietary bone grafting materials, using a segmental defect model in both radial diaphyses of rabbits. METHODS: The right defect was filled with pooled bone morphogenetic proteins (pBMPs) bound to absorbable ultrathin powdered hydroxyapatite (HA) mixed with inorganic and demineralized bone matrix and bone-derived collagen, derived from bovine bone (Group A). The left defect was filled with bovine demineralized bone matrix and pBMPs bound to absorbable ultrathin powdered HA (Group B). In both groups, an absorbable membrane of demineralized bovine cortical was used to retain the biomaterials in the bone defects, and to guide the tissue regeneration. The rabbits were euthanized 30, 90 and 150 days after surgery. Radiographic, tomographic and histologic evaluations were carried out on all specimens. RESULTS: At 30 days, the demineralized cortical bone cover was totally resorbed in both groups. HA was totally resorbed from Group A defects, whereas HA persisted in Group B defects. A prominent foreign body reaction was evident with both products, more pronounced in sections from Group B. At 90 days, the defects in Group B exhibited more new bone than Group A. However, at 150 days after surgery, neither treatment had stimulated complete repair of the defect. CONCLUSION: The partial bone healing of the segmental defect occurred with low or none performance of the biomaterials tested.

Animals↗