Implant diameter and bone density: effect on initial stability and pull-out resistance.

It is well known that the standard diameter dental implant so often utilized is often inadequate in patients with poor bone quality or quantity, and larger diameter implants have been utilized to overcome this deficiency. The objective of this study was to compare the pull-out resistance of small and large diameter (3.25- and 4.5-mm) dental implants and the relationship of these implants to bone density. Two groups of implants, consisting of 18 implants of each diameter, were placed in the mandibles of five embalmed humans. The bone mineral density of the area surrounding the implant site in the coronal cross section was measured by quantitative computed tomography (QCT). Initial implant stability was tested with a periodontium diagnostic device and pull-out resistance was tested with a mechanical testing system. Results showed the same initial stability for the two implants. The maximum pull-out force required for the large diameter implants was 15% greater than that required for the small diameter implants, although given the small number of samples, this difference was not statistically significant. There were significant positive correlations between the pull-out resistance and the bone density for both the large and small diameter implants (p < 0.05, p < 0.01). We conclude that larger diameter implants appear to have advantages over smaller ones; however, more extensive testing is needed to determine quantitatively the increased load-carrying capacity.

Vertebral size in elderly women with osteoporosis. Mechanical implications and relationship to fractures.

Reductions in bone density are a major determinant of vertebral fractures in the elderly population. However, women have a greater incidence of fractures than men, although their spinal bone densities are comparable. Recent observations indicate that women have 20-25% smaller vertebrae than men after accounting for differences in body size. To assess whether elderly women with vertebral fractures have smaller vertebrae than women who do not experience fractures, we reviewed 1,061 computed tomography bone density studies and gathered 32-matched pairs of elderly women, with reduced bone density, whose main difference was absence or presence of vertebral fractures. Detailed measurements of the dimensions of unfractured vertebrae and the moment arm of spinal musculature from T12 to L4 were calculated from computed tomography images in the 32 pairs of women matched for race, age, height, weight, and bone density. The cross-sectional area of unfractured vertebrae was 4.9-11.5% (10.5 +/- 1.4 vs 9.7 +/- 1.5 cm2; P < 0.0001) smaller and the moment arm of spinal musculature was 3.2-7.4% (56.4 +/- 5.1 vs 53.1 +/- 4.4 mm; P < 0.0001) shorter in women with fractures, implying that mechanical stress within intact vertebral bodies for equivalent loads is 5-17% greater in women with fractures compared to women without fractures. Such significant variations are very likely to contribute to vertebral fractures in osteoporotic women.

Spinal fractures during fluoride therapy for osteoporosis: relationship to spinal bone density.

Recent studies report that fluoride therapy for osteoporosis increases spinal bone density without improving vertebral fracture rate, challenging the notion that restoration of bone mass improves bone fragility. To further evaluate this issue, the relationship between spinal bone density and vertebral fracture rate was examined in a large number of fluoride-treated, osteoporotic patients. A retrospective assessment was made of clinical data collected from our observations of 389 osteoporotics treated with fluoride 30 +/- 8 mg/day (mean +/- SD) (equivalent to 66 +/- 17 mg NaF/day) and calcium 1500 mg/day for 28 +/- 18 months. Fracture rate and bone density were assessed in the same region of the spine (i.e., T12 through L4) using quantitative computed tomography (QCT). Spinal bone density increased with time on fluoride, but the relationship was hyperbolic (r = 0.99, p less than 0.0001; asymptote = 167 mg/cc on double-reciprocal plot), suggesting a plateau in the response. The spinal fracture rate decreased as a function of time on therapy (r = -0.83, p less than 0.01), and was inversely related to spinal bone density during fluoride therapy (r = 0.70, p less than 0.001 on arithmetic plot; r = -0.79, p less than 0.001 on semi-log plot). The subgroup of patients who responded to treatment with a significant increase in spinal bone density had a 48% reduction in spinal fracture rate compared with non-responders (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Hip mineral density in females with a recent hip fracture.

To evaluate the role of local bone mineral density (BMD) in the etiology of hip fractures, we measured the hip BMD using dual photon absorptiometry in 29 females who had recently suffered a hip fracture associated with minimal or moderate, but not major, trauma and compared their BMD to those of 14 young normal females, 58 early postmenopausal normal females, 13 age-matched normal females, and 114 spinal osteoporotic females without a hip fracture. Hip-fractured patients had a BMD significantly lower (P less than 0.001) than that of all other studied groups, suggesting that a low hip BMD is associated with hip fracture risk. A femoral neck BMD below 0.75 g/cm2 suggests an increased likelihood for developing a hip fracture. Peak BMD was measured at 1.03 g/cm2, a value comparable to published normative data. Thus, a loss in hip BMD of approximately 30% from peak mineral density appears necessary before a hip fracture may occur after moderate trauma.

Fluoride therapy for osteoporosis: a review of dose response, duration of treatment, and skeletal sites of action.

Osteoporosis is a disease characterized by a reduction in bone density which predisposes to fracture after even minimal trauma. Fluoride, because it has consistently been shown to stimulate bone formation and increase trabecular bone density, has been widely studied for the treatment of osteoporosis. The article focuses on the dose response, duration of treatment, and skeletal sites of action of fluoride; we also include comments on the effect of fluoride on vertebral and appendicular fracture rates. The skeletal response to fluoride doses, ranging from 15 to 43 mg elemental fluoride per day, included a linear increase in spinal bone density at an average rate of 1.25 +/- 0.91 mg/cm3 per month. The rate of increase in spinal bone density was related to the dose of fluoride (r = 0.34, P less than 0.03). Spinal bone density had increased above the fracture threshold in 44% of patients treated with fluoride for 32 +/- 10 months. The time required to achieve this goal was, however, influenced by the pretreatment spinal bone density and interpatient variation in response to fluoride treatment. Patients whose spinal bone density remained below the fracture threshold had lower pretreatment bone densities and/or slower rates of increase in spinal bone density (P less than 0.001). The osteogenic effect of fluoride was not limited to the spine. After 2 years of fluoride therapy, we found bone density in the femoral condyle (measured by QCT) to have increased by 13 +/- 2.6 mg/cm3 (n = 38, P less than 0.001); bone density in the hip (measured by DPA) was increased by 0.0261 +/- 0.015 g/cm2 (n = 55, P less than 0.025).(ABSTRACT TRUNCATED AT 250 WORDS)

The causes of bone scintigram hot spots in fluoride-treated osteoporotic patients.

We previously described new bone formation in fluoride-treated osteoporotic patients. Since then, several investigators have contended that fluoride-induced "hot spots," as seen on bone scintigrams, represent stress fractures. To further evaluate this issue we analyzed scintigrams, radiographs, and quantitative computer tomography (CT) scans of the spine and femoral condyles from 129 patients, obtained before and during therapy. Hot spots, new or of increased intensity, were more than twice as common in the weight-bearing peripheral skeleton than in nonweight-bearing sites (p less than 0.001). The hot spots were usually diffuse, multiple, bilateral, and mostly seen early in therapy, a pattern quite different from that expected of stress fractures. Previously, we postulated that mechanical stress and fluoride act synergistically to stimulate new bone formation. If this hypothesis were correct, we would expect to see a greater increase in femoral condyle bone density in patients with hot spots. Consistent with this hypothesis, patients who developed hot spots in the knees had a greater increase in condylar density (22 +/- 2.5 vs. 9 +/- 3.3 mg/cc) than those without hot spots and stress fractures were not seen in either group. Additionally, patients with more than 5 hot spots in the peripheral skeleton had greater increases in spinal and condylar density than those with fewer than 5 hot spots. Finally, stress fractures were found in less than 2% of our patients. While we do not exclude the possibility that some additional patients may have had stress fractures, our data support the hypothesis that the great majority of hot spots seen on the scintigrams are the sites of new bone formation.

Fluoride therapy for osteoporosis promotes a progressive increase in spinal bone density.

Since osteoporosis is a disease of diminished bone density, and since osteoporotic fractures occur most commonly in the spine, the ideal therapeutic agent for osteoporosis is one which can increase spinal bone density and thereby reduce the risk for vertebral fractures. In the current study we sought to examine the effect of fluoride therapy on spinal bone density utilizing quantitative computed tomography to measure changes in vertebral trabecular bone density during treatment with fluoride. A group of 61 postmenopausal osteoporotic females, aged 70 +/- 9 years, were treated with 34 +/- 7 mg elemental fluoride/day (equivalent to 75 +/- 15 mg NaF/day) and 1500 mg calcium/day for 19 +/- 6 months. Spinal bone density was increased within the first 6 months of fluoride therapy by 42% or 10 +/- 13 mg/cm3 (p less than 0.001) and continued to increased throughout 2 years of observation. The skeletal response to fluoride therapy was also associated with an early increase in serum alkaline phosphatase activity (p less than 0.001), which was related to the increase in spinal bone density (r = .58, p less than 0.001). Large interpatient variation was observed in the spinal bone response to fluoride therapy, which was not explained by variations in the pretreatment spinal bone density (r = .04), age of the patient (r = .15), or dose of fluoride (r = .16). Results from these studies demonstrate (1) the therapeutic value of fluoride to increase trabecular bone density linearly for 2 years in the osteoporotic spine and (2) the clinical value of measuring spinal bone density and/or serum alkaline phosphatase activity as indices of the skeletal response to fluoride.

Efficacy of long-term fluoride and calcium therapy in correcting the deficit of spinal bone density in osteoporosis.

Long-term fluoride therapy for osteoporosis has been shown to increase the thickness of vertebral trabeculae as seen on spinal radiographs. To determine if this qualitative finding represents a measurable increase in spinal bone density, quantitative computed tomography was utilized to measure trabecular vertebral body density (TVBD) in the lumbar spine of 18 female osteoporotic patients, all of whom had been treated with sodium fluoride, 77 +/- 13 mg/day (mean +/- SD), and calcium, 1000 mg/day, for 57 +/- 24 months. TVBD in these fluoride treated osteoporotic patients (132 +/- 82 mg/cm3) was found to be significantly greater than mean TVBD for an age-matched group of untreated female osteoporotic patients (51 +/- 21 mg/cm3, n = 89, p less than 0.001). The value for TVBD in the long-term fluoride treated osteoporotics was not only similar to previously published values for TVBD (104 +/- 30 mg cm3) in normal females of similar age, but was also above the calculated TVBD "fracture threshold" of 100 mg/cm3 for females. Only one of the 18 fluoride treated osteoporotics continued to have spinal fractures during therapy, accounting for 4 fractures per 87.2 patient years of observation, a value which is significantly lower than the published incidence of 76 fractures per 91 patient years for untreated osteoporotic patients (p less than 0.001). Together, these findings demonstrate that long-term fluoride and calcium therapy for osteoporosis increases TVBD in the majority of patients within a reasonable time frame and significantly reduces the risk for spinal fractures.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of sex steroids on peak bone density of growing rabbits.

To determine the effect of sex hormones on bone density (BD) during growth, longitudinal quantitative computed tomography (QCT) measurements were obtained in growing, castrated New Zealand White rabbits following administration of normal saline, testosterone, or estrogen from 6 wk of age until the time of skeletal maturity. Vertebral QCT densities increased during growth, were highest at the time of epiphyseal closure, and were significantly greater (P less than 0.001) in hormone-treated animals. In vivo QCT measurements in 12 vertebraes correlated strongly (r = 0.92) with percentage of calcium per weight assessed in vitro by neutron activation analysis.

Peak trabecular vertebral density: a comparison of adolescent and adult females.

To determine when spinal bone density reaches its peak, the trabecular vertebral density was assessed, via quantitative computed tomography, among females from two age groups: (1) adolescents (aged 14-19 years; N = 24); and (2) young adults (aged 25-35 years; n =24). The adolescent girls had a higher mean trabecular vertebral density (P less than 0.01), suggesting that spinal density reaches its peak around the time of cessation of longitudinal growth and epiphyseal closure.

Relationship between trabecular vertebral body density and fractures: a quantitative definition of spinal osteoporosis.

To evaluate the relationship between vertebral fractures and trabecular vertebral body density (TVBD), as measured by computed tomography (CT), we evaluated 110 female and 38 male patients referred consecutively to our clinic for an osteoporosis evaluation. Number of fractures per patient and TVBD was negatively correlated in both males and females (r = -.64, P less than .001 and r = -.69, P less than .001, respectively). Based on this relationship and that between percent of patients with fracture and TVBD, we devised four different approaches to calculate the fracture threshold. (1) Because the x-axis intercept of this regression line represents the TVBD value at zero fractures, this intercept can be considered the fracture threshold, which was 103 mg/cm3 for females and 132 mg/cm3 for males. (2) Breakpoint analysis of the relationship between the number of vertebral fractures per patient v TVBD gave a fracture threshold value of 98 mg/cm3 for females, but for males we were unable to compute a threshold value because of the small sample size. The percentage of patients with fractures was also negatively correlated with TVBD for males and females (r = -.98, P less than .001, and r = -.94, P less than .001, respectively). (3) the x-axis intercept of this relationship, which represents the fracture threshold, was 123 mg/cm3 for males and 101 mg/cm3 for females. (4) The fracture threshold, calculated as the mean TVBD + 2 SD for patients with fracture(s), was 120 and 92 mg/cm3 for males and females, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Vertebral bone density in children: effect of puberty.

To determine changes in bone density during growth, trabecular vertebral density and an index of spinal cortical bone were measured with quantitative computed tomography in 101 children. The children were divided by age into three groups: prepubertal, indeterminate, and pubertal. Compared with prepubertal children, pubertal adolescents had significantly higher trabecular bone density and more compact bone in the spine (P less than .001). After controlling for puberty, vertebral bone density failed to correlate significantly with age, sex, weight, height, surface area, and body mass index. The results indicate that bone density increases markedly during puberty.

Usefulness of SPECT in evaluating osteosarcoma metastases to the lung.

The differentiation of osteosarcoma metastases to the lung vs the ribs with bone scanning agents is not always clear. Single photon emission computed tomography is useful in such differentiation.

Osteoporosis: radiographic detection of fluoride-induced extra-axial bone formation.

New bone formation in the peripheral skeleton was detected radiographically in 67% (22/33) of patients studied for new periarticular pain among 72 patients with osteoporosis being treated with fluoride, 66-88 mg/d, for 6 or more months. Changes included periosteal and endosteal new bone formation as well as trabecular thickening and were localized in areas of high mechanical stress. Sufficient mineral deposition for radiographic detection required 6 or more months of fluoride treatment. Radiologists must differentiate fluoride-induced new bone formation from other-processes, such as fractures and tumor, and elicit information on fluoride intake in suspicious cases.

Post-laryngectomy localization of I-131 at tracheostomy site on a total body scan.

A post-thyroidectomy, post-I-131-therapy patient had a laryngectomy and neck dissection for recurrent papillary thyroid carcinoma. A subsequent I-131 total body scan revealed persistent anterior neck activity, which disappeared upon removal of the tracheostomy tube and dressings.

Skeletal scintigraphic changes in osteoporosis treated with sodium fluoride: concise communication.

An appendicular skeletal response to sodium fluoride (NaF) was detected by total skeletal scintigrams. Twelve postmenopausal osteoporotic women were treated with NaF (88 mg/day) and calcium (1500 mg/day). Total skeletal scintigrams were obtained before and during treatment. Within 4 to 21 mo (mean: 8.3), all 12 patients showed new areas of increased uptake corresponding to metaphyseal regions and short bones of the appendicular skeleton. The number of peripheral bones involved in each subject ranged from four to 12. The most frequently involved sites (11 of 12 patients) were the right distal femur and proximal tibia. Nine patients showed an increase in serum alkaline phosphatase activity, which was attributed to an increase in the skeletal isoenzyme. Seven of 12 patients developed bone pain in one or more of the regions of increased uptake. This study establishes that the skeletal scintigram is a sensitive index of the peripheral skeletal response to NaF.

Nuclear medicine-important advances in clinical medicine: the role of nuclear and ultrasonic thyroid imaging.

The Scientific Board of the California Medical Association presents the following inventory of items of progress in nuclear medicine. Each item, in the judgment of a panel of knowledgeable physicians, has recently become reasonably firmly established, both as to scientific fact and important clinical significance. The items are presented in simple epitome and an authoritative reference, both to the item itself and to the subject as a whole, is generally given for those who may be unfamiliar with a particular item. The purpose is to assist busy practitioners, students, research workers or scholars to stay abreast of these items of progress in nuclear medicine that have recently achieved a substantial degree of authoritative acceptance, whether in their own field of special interest or another.The items of progress listed below were selected by the Advisory Panel to the Section on Nuclear Medicine of the California Medical Association and the summaries were prepared under its direction.