The effect of enhanced milk yield of dairy cows by frequent milking or suckling on intake and digestibility of the diet

The prevalence of osteoporosis and the incidence of fractures are substantially lower in black than in white subjects, a finding generally attributed to racial differences in adult bone mass. Whether these racial differences are present in childhood is the subject of considerable interest, as the amount of bone gained during growth is a major determinant of future susceptibility to fractures. We measured the density and size of the vertebrae and femurs of 80 black and 80 white healthy children, 8-18 yr of age, matched for age, gender, height, weight, and stage of sexual development, using computed tomography. Race had a significant and differential effect on the bones in the axial and appendicular skeletons. In the axial skeleton, black children had greater cancellous bone density, but similar cross-sectional area of the vertebral bodies. In contrast, in the appendicular skeleton, black children had greater femoral cross-sectional area, but similar cortical bone area and cortical bone density. Compared to white children, vertebral bone density and femoral cross-sectional area at sexual maturity were, on the average, 10.75% and 5.7% higher, respectively, in black children. Such significant variations may contribute to the racial differences in the prevalence of osteoporosis between black and white adults.     

Quantitative histologic evaluation of LTI carbon, carbon-coated aluminum oxide and uncoated aluminum oxide dental implants

The response of mandibular bone to identical geometry LTI carbon, carbon-coated aluminum oxide, and uncoated aluminum oxide blade-type dental implants in baboons for 2 years was evaluated using histologic, microradiographic, and scanning electron microscopic methods. In addition, a quantitative histologic analysis was performed identifying the type, amount, and distribution of tissue surrounding the dental implant systems. This is the final phase of a study investigating the effect of implant elastic modulus and implant surface chemical composition on the performance of dental implants. Previous studies have utilized clinical and radiographic evaluations, postretrieval mechanical testing, and finite element stress analysis to evaluate the dental implant performance. The results of the histologic study revealed a direct implant-bone interface with no intervening soft tissue in 16 of the 21 implants (76%). A fibrous tissue interface was observed in 5 of 21 implants (24%). Quantitative histologic results for the implants with a direct implant-bone interface showed statistically larger crestal cortical plates (p less than 0.05) and greater area fraction crestal cancellous bone (p less than 0.05) in the LTI carbon implant compared to the carbon-coated and uncoated aluminum oxide implants. The carbon-coated and uncoated aluminum oxide implants demonstrated statistically greater area fraction cancellous bone at the inferior region of the implant (p less than 0.05) and thinned and reduced crestal cortical plates when compared to the LTI carbon implants. The results indicate that significant stress shielding of the crestal bone had occurred with the rigid carbon-coated and uncoated aluminum oxide implants when compared to the LTI carbon implants which had a material elastic modulus similar to cortical bone. Based upon the histologic results, it appears that the LTI carbon implants with the direct implant-bone interface exhibited a greater potential for long-term successful performance compared to the aluminum oxide substrate implants.     

Changes in the aortic endothelium and plasma von Willebrand factor levels during the onset and progression of insulin-dependent diabetes in BB rats

The superior volume maintenance of membranous over endochondral bone has been shown in several studies and provides the basis for its preferred clinical use as an onlay grafting material in the craniofacial skeleton. The scientific rationale for this seeming embryologic advantage, however, has never been proven. Our hypothesis is that the pattern of onlay bone graft resorption is primarily determined by a graft's micro-architecture (relative cortical and cancellous composition) rather than its embryologic origin (membranous versus endochondral). Twenty-five adult New Zealand, White rabbits were used for this study. Eight animals were killed at 3 weeks, eight animals at 8 weeks, and nine animals at 16 weeks. Three graft types were placed onto each rabbit cranium: cortical bone graft of membranous origin and cortical and cancellous bone graft of endochondral origin. Fluorochrome markers were injected into all living rabbits at 1, 6, and 14 weeks. Microcomputed tomography scanning was performed on all of the bone grafts to determine postsacrifice volumes and to obtain detailed information regarding the bone graft's trabecular architecture. In addition, specimens were examined histologically. Volume analysis showed a statistically greater resorption rate in the cancellous endochondral bone graft than in either the endochondral or membranous cortical bone grafts (p < 0.05) for all time points. In addition there was no significant difference in the resorption rates between the endochondral and membranous cortical bone grafts. A post-test power analysis (alpha = 5 percent) of the volume data comparing the two types of cortical bone grafts showed that a difference in resorption of 8.9 percent would be detected with a 90-percent probability. Previous studies, which have shown a seeming superiority of membranous over endochondral bone grafts, used composite grafts composed of both cortical and cancellous portions. By separating these components, we have shown that cortical bone grafts maintain their volumes significantly better than cancellous bone grafts. In addition, we found no statistical difference in the resorption rates between the two cortical onlay bone grafts of different embryologic origins, a finding that has never been previously published. From our results, we believe cortical bone to be a superior onlay grafting material, independent of its embryologic origin. We believe these results challenge the currently accepted theories of bone graft dynamics and may lead to a change in the way clinicians approach bone graft selections for craniofacial surgery.     

Differential effect of gender on the sizes of the bones in the axial and appendicular skeletons

Recent observations suggest that throughout life the size of the vertebral bodies in females is smaller than that in males even after accounting for differences in body size. To confirm these reports and to determine whether similar differences exist in the appendicular skeleton, detailed measurements of the sizes of the vertebrae and the femur were obtained using computed tomography in 30 pairs of prepubertal boys and girls matched for age, height, and weight. Anthropometric parameters as well as gender influenced the cross-sectional area of the vertebrae. Heavier children had greater vertebral cross-sectional area than slender children regardless of gender, and the vertebral bodies were found to be significantly smaller in girls than in matched boys (approximately 11%), both using Student's t test (P < 0.0001) and its multivariate analog, the Hotelling's T2 test (P < 0.0001). In contrast to these findings in the axial skeleton, gender status did not influence the size of the bones in the appendicular skeleton, and neither the cross-sectional area (3.28 +/- 0.84 vs. 3.10 +/- 0.56 cm2) nor the cortical bone area (1.80 +/- 0.37 vs. 1.85 +/- 0.36 cm2) at the midshaft of the femur differed between boys and girls. These values, however, correlated strongly with all anthropometric indexes, and multiple regression analyses indicated that both measurements were primarily related to weight. The results suggest that although increases in mechanical loading associated with growth are the main determinant of the cross-sectional properties of the appendicular skeleton in children, factors other than body mass and related to gender have a significant role in the regulation of the sizes of the bones in the axial skeleton.     

Enchondroma versus chondrosarcoma in the appendicular skeleton: differentiating features

Distinction of enchondroma versus intramedullary chondrosarcoma affecting the appendicular skeleton (proximal to the metacarpals and metatarsals) is a frequent diagnostic dilemma. The authors studied a large series of patients with these lesions (92 with enchondromas, 95 with chondrosarcomas) using statistical assessment of both clinical parameters and numerous radiologic manifestations on images from multiple modalities to identify differentiating features. Multiple clinical and imaging parameters demonstrated statistically significant differences between enchondroma and chondrosarcoma, particularly pain related to the lesion, deep endosteal scalloping (greater than two-thirds of cortical thickness), cortical destruction and soft-tissue mass (at computed tomography or magnetic resonance imaging), periosteal reaction (at radiography), and marked uptake of radionuclide (greater than the anterior iliac crest) at bone scintigraphy. All of these features strongly suggested the diagnosis of chondrosarcoma. These criteria allow distinction of appendicular enchondroma and chondrosarcoma in at least 90% of cases.     

Bone mass and ageing

Bone can be divided into two kinds of tissue, cortical and trabecular bone. The skeleton comprises approximately 80% cortical bone, mainly in peripheral bones, and 20% trabecular bone, mainly in the axial skeleton. Bone density increases with skeletal growth to a peak in late adolescence or early adulthood. Bone loss subsequently occurs with ageing in both sexes, and in females accelerated loss occurs at the menopause. The risk of osteoporotic fracture in later life is the result of peak bone mass achieved at skeletal maturity and subsequent age-related and postmenopausal bone loss. Peak bone mass is largely genetically determined but is also influenced by environmental factors such as dietary calcium and physical activity. Bone loss with ageing occurs at different rates and different times in different skeletal sites. Femoral neck bone loss probably occurs in a linear fashion throughout life from early adulthood but may be accelerated at the menopause. Spinal bone loss may commence before the menopause but is rapidly increased in the immediate postmenopausal years. Bone strength is directly related to bone density, but the loading force is also relevant to risk of fracture.     

Osteogenesis at the dental implant interface: high-voltage electron microscopic and conventional transmission electron microscopic observations

The osteogenesis of mandibular bone to endosteal dental implants was examined using an in vivo dog model. One half of the implants examined were unloaded implants, with the remaining one half prosthodontically loaded for 6 months. Undecalcified mandibular implant samples were examined with both high-voltage electron microscopy (HVEM) stereology and routine transmission electron microscopy. The osseous interface to integrated implants was shown to vary in its morphology. Mineralized bone was observed directly apposing the implant, often separated from the implant by an electron-dense deposit of approximately 50 nm. Within this densely mineralized matrix, osteocytes were routinely observed. Adjacent areas were shown to contain slightly wider zones of either a less dense mineralized matrix or, alternatively, unmineralized tissue. Other zones consisted of wider unmineralized matrices containing collagen fibers and osteoblasts. These latter zones were consistent with the appearance of an appositional type of bone growth. Because bone is a dynamic, actively remodeling tissue, a varied morphology of the support tissues to dental implant is not unexpected. Areas of mature bone interfacing with successfully integrated implants were demonstrated, as well as areas adjacent to the mature bone that were undergoing remodeling or mineralization. This study has also shown that HVEM stereology is a valuable research tool to investigate the oral tissue interface with dental implants.     

Early induction of alterations in cancellous and cortical bone histology after orchiectomy in mature rats

Androgen deficiency is associated with low bone mass in humans and animals, but the remodeling alterations that lead to bone loss are unclear. Our objective was to define early responses in both cancellous and cortical bone to orchiectomy (ORX) using histomorphometry in sexually mature (4-month-old) rats. A total of 62 male rats, 4 months of age, were divided into six groups, sham operated (SH) or orchiectomized (ORX), and sacrificed 1, 2, or 4 weeks after ORX. Calcein was given 5 and 2 days before sacrifice to label mineralizing surfaces. Bone mineral density (BMD) was measured in excised femurs by dual energy X-ray absorptiometry (DEXA). Static and dynamic histomorphometry was evaluated in the cancellous bone of the proximal tibial metaphysis and lumbar vertebral bodies, and in the cortical bone of the tibial diaphysis. Osteopenia began to develop by 2 weeks after ORX, though weight gain and femur length did not change. Femoral BMD was significantly reduced and BMC decreased (NS) by 4 weeks after ORX (p < 0.05). Tibial and vertebral cancellous bone volume decreased 19% and 13%, respectively, while osteoblast and osteoclast surfaces, and numbers of osteoclasts, increased after ORX. At 2 weeks post-ORX, an increase in cancellous bone formation rate was attributable primarily to an increase in mineralizing surfaces and a smaller rise in mineral apposition rate. In contrast, cortical bone periosteal, but not endosteal, bone formation rate and mineralizing surfaces decreased. We conclude that ORX stimulates cancellous and diminishes periosteal bone turnover rapidly after ORX, with subsequent decreases in bone volume and mineral density. The clear divergence in cortical and cancellous bone responses to hypogonadism raises important questions regarding the control of bone formation and its role in defining the skeletal phenotype.     

Inhaled nitric oxide therapy for pulmonary disease in pediatrics

Prostaglandin E2 (PGE2) is an anabolic agent of bone in vivo but the mechanism of its action still remains unclear. The aim of this study was to determine whether the effect of PGE2 on skeleton is mediated by pituitary hormones. Forty female, Sprague-Dawley rats were divided into four groups: baseline control (basal), age-matched intact control (CON), hypophysectomy (HX), and HX + PGE2 (2 mg/kg/day) with 10 animals in each group. The basal group was sacrificed at 2 months of age, and the remaining groups after 6 weeks of treatment. Cancellous and cortical bone histomorphometry was performed on double fluorescent-labeled 40 micron-thick sections of the proximal tibia and tibial shaft. Our results show that HX resulted in a cessation of bone growth, a decrease in cancellous bone volume, and cortical bone gain compared with the age-matched, intact CON rats. Compared with the HX group, the HX + PGE2 group had a significantly greater tibial bone density (mean +/- SE, HX + PGE2:1.595 +/- 0.007 versus HX:1.545 +/- 0.013), percent cancellous bone volume (21.4 +/- 2.0 versus 8.41 +/- 1.70), percent cortical bone area (87.2 +/- 0.85 versus 81.7 +/- 0.7), and ratio of cortical area to marrow area (7.14 +/- 0.56 versus 4.52 +/- 0.21). Increased bone masses by PGE2 in the HX animals were accompanied by an increase in the trabecular and endosteal-labeled surface and bone formation rate. The trabecular number and width were increased whereas trabecular separation was decreased in the HX + PGE2 group compared with the HX group (P < 0.05). PGE2 treatment also caused a decrease in the tibial endosteal eroded surface and medullar cavity of the HX animals. In conclusion, this study clearly demonstrates that PGE2 (2 mg/kg/day) in the HX rats increases both cortical and cancellous bones and improves trabecular architecture in the tibia after 6 weeks of treatment. These skeletal alterations are due to a stimulation of bone formation and a suppression of bone resorption activity. These findings suggest that the anabolic effect of PGE2 in bone is independent of pituitary hormones.     

Epidermal growth factor receptor ectodomain in the urine of patients with squamous cell carcinoma

Female Sprague-Dawley rats were ovariectomized (OVX) or sham-operated at 3 months of age and maintained untreated for 1 year after surgery. Baseline control and OVX rats were killed at the beginning of treatment when the rats were 15 months of age and 1 year postovariectomy. The remaining rats were treated with hPTH 1-34 (80 micrograms/kg BW, 5 days/week) or vehicle for 10 weeks. Quantitative bone histomorphometry was performed on undecalcified longitudinal sections of the proximal femur from each rat. Baseline OVX rats exhibited cancellous and cortical osteopenia at the femoral neck as their mean cancellous bone volume and cortical width were significantly decreased compared to the means for baseline control rats. In addition, baseline OVX rats had increased osteoblast and osteoclast surfaces and a greater cancellous bone formation rate than baseline control rats. OVX rats remained osteopenic with no further bone loss from the femoral neck after 10 weeks of vehicle treatment. In contrast, cancellous bone volume and cortical width in OVX rats treated with PTH were increased to the level of vehicle-treated control rats. The hormone restored lost bone in the femoral neck of OVX rats by markedly stimulating both cancellous and cortical bone formation. These histomorphometric findings in concert with recent biomechanical studies of bone strength indicate that the femoral neck of aged OVX rats is a promising sample site for studies of the prevention and treatment of bone loss induced by estrogen depletion.     

Ectopic hematopoietic bone marrow in the appendicular skeleton after trauma

METHODS: Combined bone scanning and immunoscintigraphy (IS) with 99mTc-monoclonal antigranulocyte antibodies were performed in two patients with suspected reactivation of chronic osteomyelitis of the lower extremity. Because bone scanning and IS were strongly positive, both patients underwent surgical intervention. RESULTS: Macroscopic findings did not show purulent infection and microbiologic results remained negative, but histology revealed unexpected ectopic bone marrow, explaining the strong uptake on IS. One patient exhibited active hematopoietic bone marrow at the former fracture site of the tibial bone. The second patient presented with interspersed bone marrow in the cortical bone of the femoral diaphysis after several intramedullary surgical procedures. CONCLUSION: Unexpected ectopic hematopoietic marrow may occur in the appendicular skeleton after trauma and repeated surgical interventions. The bone marrow shows a physiologic uptake with IS and may be misinterpreted as granulocyte accumulation due to infection. This may lead to false-positive diagnosis in cases of suspected osteomyelitis.     

Healing of the anterior attachment of the rabbit meniscus to bone

In a rabbit model the healing process of the anterior attachment of the medical meniscus was observed during the first 12 weeks after sharp transection and refixation in a tibial bone channel. Evaluations of the healing tissue were histologic analysis, application of immunohistochemical methods to show collagen types and nerve regeneration, and mechanical load to failure tests. Secondary changes to knee joint cartilage, as signs of eventual dysfunction of the refixed meniscus, were evaluated by analysis of proteoglycan fragment concentration in joint fluid and histologic analysis of knee joint articular cartilage and synovium. The healing tissue between the refixed attachment and bone matured from highly cellular, nonspecific granulation tissue at 1 week, to bone, fibrocartilaginous, and fibrous tissues, which at some sites developed an insertion specific tissue arrangement within a 12-week period. However, the irregular interface between the fibrocartilaginous tissue and the underlying bone, which is typical for a normal insertion, was not reestablished. Labeling for collagen Types I and II in the newly formed insertion did not return to normal. In addition a few collagen fibers connected the refixed attachment tissue to bone. New bone formation turned the initially cancellous bone tunnel walls into more solid cortical bone. However, new bone formation did not fill the distal part of the channel. The refixed meniscal attachment underwent necrosis and was revitalized by cell ingrowth from the periphery. Nerve fibers were found in the newly formed insertion by 12 weeks. The failure load at tensile testing never reached more than 20% that of a normal attachment. Degeneration of articular cartilage and increased proteoglycan fragment in the joint fluid were common after this procedure. These data suggest that, despite the focal appearance of insertion specific tissues and healing of collagen fibers to bone, the tissue architecture of a normal meniscal insertion and a normal meniscal joint protective function were not reestablished.     

Histologic analysis of clinically retrieved titanium microimplants placed in conjunction with maxillary sinus floor augmentation

In this study, a new approach involving placement and subsequent retrieval of titanium microimplants was employed for the histologic investigation of the implant-tissue interface in conjunction with maxillary sinus floor augmentation. Nine patients scheduled for sinus floor augmentation and simultaneous placement of Br?nemark implants were included in the study. After a sinus graft procedure and placement of implants, an additional microimplant was placed into the graft through the lateral wall of the sinus. At abutment connection, the microimplants were retrieved using a 3- or 5-mm-wide trephine drill. Six specimens were retrieved after 6 to 14 months from sites augmented with particulate radiated mineralized cancellous allograft. Another six implants were retrieved after 6 to 12 months from maxillary sinuses augmented with particulate autogenous bone grafts. The histologic analysis showed distinct differences between the two types of grafts. The sites with autogenous bones grafts displayed a normal morphology of bone and bone marrow, including formation of bone on the surfaces of the grafted particles and remodeling of newly formed as well as grafted bone. The bone was more mature after 11 to 14 months than at 6 months. The allografted sites had a mixed morphologic appearance of newly formed bone and nonviable allograft particles (about 75% of the total bone area) in loose connective tissue. Significantly more bone was found at the autografted than at the allografted implants. The use of autogenous bone for augmentation of the maxillary sinus floor resulted in a greater amount of viable bone surrounding the implant; however, simultaneous placement of implants apparently resulted in a low proportion of bone-implant contact after 6 to 14 months irrespective of graft type.     

Impaction of cancellous bone grafts impairs osteoconduction in titanium chambers

The method of using morselized compacted cancellous allografts for hip arthroplasty revision shows results that seem to differ dramatically from other kinds of allografting. In structural cancellous allografts, bone ingrowth usually is limited to 2 to 3 mm, whereas morselized compacted grafts seem to be remodeled totally in several cases, as judged by radiography. In the current study, impacted cancellous allografts were compared with unimpacted allografts. Seventeen rats had a bone conduction chamber implanted in the tibias bilaterally. On one side the chambers contained an impacted graft (bone volume fraction 65%) and on the contralateral side an unimpacted graft (bone volume fraction 35%). Impaction of the grafts was done preoperatively with a pressure of either 25 or 2500 MPa. Ingrowing bone could enter the cylindrical interior of the chamber only at one end. After 6 weeks the mean distance the ingrown bone had reached into the graft was measured on histologic slides. With both impaction pressures, the bone ingrowth distance was decreased to 30% of the unimpacted controls. It appears that impaction alone does not have a favorable effect on the osteoconductive properties of a bone graft. On the contrary, impaction seems to disfavor osteoconduction. However, in the clinical situation this is not necessarily a disadvantage.     

Intrahepatic vein fetal blood sampling: current role in prenatal diagnosis

We present our experience with the use of ultrasonography in the assessment of suspected primary or recurrent bone tumours of the appendicular skeleton and pelvis in 73 patients. Ultrasound can effectively assess the extraosseous component of malignant and aggressive benign lesions and those tumours arising from the surface of the bone. Periosteal reaction, cortical destruction, pathological fracture, matrix mineralization, fluid-fluid levels and involvement of the neurovascular bundle are all identified. Despite this, we could not identify any advantage of ultrasound compared to plain radiography or magnetic resonance imaging in diagnosis and local staging. However, ultrasound was found to be of great value in guiding percutaneous needle biopsy.     

Concentration of insulin-like growth factor (IGF)-I and -II in iliac crest bone matrix from pre- and postmenopausal women: relationship to age, menopause, bone turnover, bone volume, and circulating IGFs

Insulin-like growth factor-I (IGF-I) and -II are important local regulators of bone metabolism, but their role as determinants of human bone mass is still unclear. In the present study, we analyzed the concentration of IGF-I and -II in the bone matrix of 533 human biopsies from the iliac crest that were obtained during surgery for early breast cancer. There was an inverse association of bone matrix IGF-I concentration with age that was unaffected by menopause. Bone matrix IGF-I was positively associated with histomorphometric and biochemical parameters of bone formation and bone resorption and with cancellous bone volume. Based on the estimates of the linear regression analysis, women with a bone matrix IGF-I concentration 2 SD above the mean had a 20% higher bone volume than women with a bone matrix IGF-I concentration 2 SD below the mean. In contrast, serum IGF-I was neither correlated with bone turnover nor with bone volume and was only weakly associated with bone matrix IGF-I when adjusted for the serum concentration of IGF binding protein-3. Bone matrix IGF-II was positively associated with the osteoblast surface, but in contrast to IGF-I, tended to be positively associated with age and was unrelated to cancellous bone volume. In summary, our study suggests the following. 1) The concentration of IGF-I in cancellous bone undergoes age-related decreases that are similar to those of circulating IGF-I. 2) Menopause has no effect on this age-related decline. 3) Physiological differences in bone matrix IGF-I are associated with differences in iliac crest cancellous bone volume. 4) Bone matrix IGF-I is a better predictor of cancellous bone volume than circulating IGF-I. 5) The role of IGF-II in human bone tissue is clearly distinct from that of IGF-I.     

Prediction of mechanical properties of the cancellous bone of the mandibular condyle

The mechanical properties of cancellous bone depend on the bone structure. The present study examined the extent to which the apparent stiffness of the cancellous bone of the human mandibular condyle can be predicted from its structure. Two models were compared. The first, a structure model, used structural parameters such as bone volume fraction and anisotropy to estimate the apparent stiffness. The second was a finite element model (FEM) of the cancellous bone. The bone structure was characterized by micro-computed tomography. The calculated stiffnesses of 24 bone samples were compared with measured stiffnesses. Both models could predict 89% of the variation in the measured stiffnesses. From the stiffness approximated by FEM in combination with the measured stiffness, the stiffness of the bone tissue was estimated to be 11.1 +/- 3.2 GPa. It was concluded that both models could predict the stiffness of cancellous bone with adequate accuracy.     

Characterization of a novel Streptococcus thermophilus rolling-circle plasmid used for vector construction

STUDY DESIGN: Bone mineral density and bone cross-sectional area of human cadaveric vertebral bodies were investigated radiologically and histologically, respectively. After ventral instrumentation with ventral derotation spondylodesis screws, axial pullout force was measured and compared with radiologic and histologic data. OBJECTIVES: To elucidate how well ventral derotation spondylodesis screw fixation strength can be estimated before surgery by specified applications of dual-energy x-ray absorptiometry, quantitative computed tomography, T2*-relaxation time in magnetic resonance imaging, and histomorphometry. SUMMARY OF BACKGROUND DATA: It is postulated that bone quality plays a crucial role in initial strength of the instrumented spine. Bone quality is even more important in anterior fixation because of the prevalence of spongy bone in the vertebral body. METHODS: Bone mineral density of human cadaveric lumbar-vertebral bodies was assessed by dual-energy x-ray absorptiometry and quantitative computed tomography (cancellous and cortical bone separately). Cancellous bone was also characterized by T2*-relaxation time, measured by magnetic resonance imaging and histomorphometric study. Vertebral bodies were instrumented ventrally with VDS screws, and screw axial pullout force was measured and correlated with each of the nonmechanical measures. Patients with manifest osteoporosis, osteomalacia and tumors were excluded. For statistical analysis, the Mann-Whitney rank sum test was used with a significance value of P < 0.05. RESULTS: The highest correlation with pullout force was for density of cancellous bone determined by quantitative computed tomography (r = 0.72; P < 0.001), immediately followed that determined by dual-energy x-ray absorptiometry (r = 0.70; P < 0.001). Results of measurement of T2*-relaxation time and those of histomorphometric study correlated moderately (r = 0.55; r = 0.50), whereas cortical bone density determined by quantitative computed tomography showed negligible correlation (r = 0.2). CONCLUSIONS: The absorptiometric techniques, quantitative computed tomographic scan of cancellous bone and dual-energy x-ray absorptiometric study, provide more accurate readings for preoperative estimation of initial VDS screw fixation strength than do the other methods studied.     

Comparison of bone formation rates measured by radiocalcium kinetics and double-tetracycline labeling in maintenance dialysis patients

We report 23 prospective studies on 18 maintenance dialysis patients in whom we measured skeletal mineralization rate (m) using 47Ca, analyzed by the expanding pool model, and compared it with the histologic bone formation rate (bfr), volume referent, estimated on tetracycline-labeled iliac crest bone. The patients showed a spectrum of bone disease types including adynamic bone, aluminum-related osteomalacia, and various degrees of secondary hyperparathyroidism. The mean width between double labels, on which mineral apposition rate depended, was estimated using a simple formula relating area to perimeter for each feature enclosed by the labels. Values for m ranged from 0 to 155 mmol calcium per day and for bfr from 0 to 124% per year. There was close correlation between m and bfr (r = 0.976), serum alkaline phosphatase (r = 0.968), and serum immunological parathyroid hormone (iPTH) (r = 0.868). When the volumetric bfr was converted to mass units and applied to the whole skeleton, using literature values for mineral density and cortical and trabecular mass, there was close agreement between the histologic and isotopic estimates of m (r = 0.959). The results validate the two methods and suggest they are interchangeable. However, use of a rigorous method to determine bfr appears to be essential.     

Concentration of transforming growth factor beta in human bone tissue: relationship to age, menopause, bone turnover, and bone volume

Transforming growth factor beta (TGF-beta) is thought to play an important role in bone metabolism, but its relationship to human bone turnover and bone mass has not been examined yet. In this study, we measured the concentration of TGF-beta in 811 samples of male and female bone from four representative sites of the human skeleton and in the supernatants of 72 short-term human bone marrow cultures from the iliac crest. The concentrations of TGF-beta1 and TGF-beta2 in the bone matrix were positively correlated with histomorphometric indices of bone resorption and bone formation and with serum levels of osteocalcin and bone-specific alkaline phosphatase. We also observed a positive association between the release of TGF-beta in the bone marrow cultures and serum osteocalcin. Changes in the rate of cancellous or cortical bone remodeling with age or menopause were accompanied by corresponding changes in skeletal TGF-beta. In contrast, there was no significant relationship between the concentration of TGF-beta and bone volume at any skeletal site. In conclusion, our study supports the hypothesis that TGF-beta plays an important role in human bone remodeling, but fails to demonstrate an association between the skeletal concentration of TGF-beta and human bone mass.