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Biomedical subjects

D D Cody

Publications and source records attributed to D D Cody.

17 recordsLinked to original sources
PubMed1999

Premature partial closure and other deformities of the growth plate: MR imaging and three-dimensional modeling.

PURPOSE: To examine growth plates of the distal femur and tibia with magnetic resonance (MR) imaging to detect bone bridges and other deformities in children. MATERIALS AND METHODS: Thirteen children (nine boys and four girls, aged 5-13 years; mean age, 9.8 years) were referred because of suspected or known bone bridging of the growth plate. Among the 13 patients, 10 had Salter-Harris fractures of the knee or ankle, two had Blount disease, and one had neonatal sepsis. Fat-saturated spoiled gradient-recalled images enabled reconstruction of a three-dimensional model of the growth plate. Patients underwent one to four MR examinations. RESULTS: Nine patients had bone bridging of less than 1% to 39% of the area of the growth plate. On MR images obtained in the growth plate of five patients, a stripe of low signal intensity indicated fracture. On MR images obtained in three patients, intrusions of growth plate cartilage into the metaphysis were seen to increase in depth over time. MR images obtained in four patients showed no bridges. In the two patients who underwent surgery, excellent correspondence was found between MR findings and surgical observations. CONCLUSION: Marked undulation or splitting of the growth plate may occur with fixation of some cartilage in the metaphysis or epiphysis while growth continues. The configuration of the growth plate and bone bridges can be accurately mapped with MR imaging. Treatment planning is facilitated.

Adolescent↗
PubMed1997

Decrease in canine proximal femoral ultimate strength and stiffness due to fatigue damage.

Fractures of the proximal femur represent a significant health concern especially in the elderly. Fatigue damage and microfractures have been implicated in the etiology of hip fractures; however, the extent to which these factors are sufficient to bring about significant reductions in proximal femur strength and stiffness is unknown. This study examined the hypothesis that fatigue loading of the proximal femur results in highly correlated decreases in bone stiffness and strength through the accumulation of bone microdamage. One canine femur from each of 10 pairs was monotonically loaded to failure to determine the ultimate strength. The contralateral femur was then cyclically loaded at 50% of the ultimate load value for either 3600 cycles or until a 40% reduction in stiffness was achieved. This femur was then monotonically loaded to failure. For two additional femur pairs, the fatigued femur was histologically processed to reveal bone microdamage. In support of the hypothesis, the data demonstrated a linear relationship between strength loss and stiffness loss (Adj. R2 = 0.79, p < 0.0004) with significant decreases in residual whole bone strength (p < 0.004) following cyclic loading. In addition, damage (microcracks) in the cortical bone and broken trabeculae were observed in the neck and head region of the femur fatigued until its stiffness was reduced by 40% but not fractured subsequent to cyclic loading.

Animals↗
PubMed1997

Segmentation of acoustic neuromas with magnetic resonance imaging and Eigen image filtering.

OBJECTIVE: This study aimed to determine whether magnetic resonance imaging with Eigen image filtering can segment acoustic neuromas as a preliminary requirement to the development and validation of a volumetric method of measuring tumor size and growth using Eigen image filtering. STUDY DESIGN: This was an observational study. SETTING: The study was performed in an academic, comprehensive multi-specialty group practice. PATIENTS: Patients were a convenience sample of adults of both sexes who had acoustic neuromas identified by magnetic resonance imaging. Tumors ranged widely in size. INTERVENTION: Magnetic resonance imaging with digital image analysis using Eigen image filtering was the intervention. MAIN OUTCOME MEASURE: Observation and analysis of magnetic resonance images was the main outcome measure. RESULTS: The ability of magnetic resonance imaging with Eigen image filtering to segment acoustic neuromas of various sizes and shapes is illustrated. CONCLUSIONS: Magnetic resonance imaging with digital image analysis using Eigen image filtering is a promising method for volumetric measurement of acoustic neuroma size and growth. The potential for acoustic neuromas to grow may be underestimated by linear methods because of their relative lack of precision and of the geometric error that occurs in representing the volumetric growth of a three-dimensional tumor as a linear diameter.

Adult↗
PubMed1996

Predictive value of proximal femoral bone densitometry in determining local orthogonal material properties.

Models which are based on non-invasive bone measurements may in the future be able to successfully identify individual subjects at an increased risk for hip fracture; thus, we designed a study to determine the usefulness of dual-energy X-ray absorptiometry (DXA) and quantitative computed tomography (QCT) in predicting the local material properties of human proximal femoral cancellous bone. There has been some disagreement in the scientific literature regarding appropriate predictive models for local material properties of cancellous bone. We sought to confirm that density-mechanical property relationships were consistent from subject to subject, and that three-dimensional QCT measurements were stronger predictors of mechanical properties than two-dimensional DXA results. Linear and power fit relationships between these densitometric measures and material properties were also examined to determine which were more appropriate. Bone cubes from specific regions of highly oriented trabeculae were analyzed separately to determine if cube orientation had an effect on mechanical properties independent of bone density. Ten pairs of ex vivo femurs (five male, five female; age 30-93, mean age 62) were prepared such that specific anatomic planes were visible radiographically. Both QCT and DXA measurements were made on all 20 femurs. Cancellous bone cubes were obtained proceeding along two distinct directions from the proximal end of each femur pair. Unexpectedly, the density-modulus relationships among these ten donors were found to be significantly different at p <0.01 (83 percent of the tests were different at p <0.0001). Density-strength regressions were also significantly different at p <0.01, but this effect was not as consistent nor as statistically significant. In general, the QCT method did not produce predictions of local cancellous bone material properties superior to the DXA method. The linear and power fit models appeared to produce consistent results, with neither being obviously more advantageous. These density measurements explained at best 30-40 percent of the variance in modulus and 50-60 percent of the variance in ultimate stress. The orientation of cancellous cubes in the principal compressive trabeculae region was a significant contributor to mechanical properties (p= 0.0001) independent of bone density. This finding was not as dramatic in the femoral neck cancellous bone region.

Absorptiometry, Photon↗
PubMed1995

Static and fatigue failure properties of thoracic and lumbar vertebral bodies and their relation to regional density.

This study investigated (1) whether a characterization of the macroscopic architecture within the vertebral centrum would improve predictions of vertebral strength, (2) if regions in the centrum where least bone loss with age occurs are more predictive of vertebral strength, and (3) whether different patterns of the macroscopic architecture are predictive of static as compared to fatigue strength. To characterize the vertebral macroscopic architecture, a regional bone mineral density (rBMD) technique was used that estimated the cancellous density distribution (in 18 specific regions of the vertebral centrum) for vertebrae T7-L4, from spines of 20 female cadavers. Static and fatigue failure properties of whole vertebrae were obtained, and predictive models of static and fatigue failure properties of whole vertebrae were examined. We found that (1) vertebral failure properties were better predicted by combinations of vertebral regional cancellous density (multiple linear regressions) rather than by any individual region of cancellous density alone (simple linear regressions); (2) models using regions of density that demonstrated minimum decline with age [from the data of Flynn and Cody (Calcif. Tissue Int. 53, S170-S175 (1993))] resulted in better correlations with ex vivo vertebral static failure properties than models using density regions that showed maximum decline with age, and (3) static and fatigue characteristics required different density regions to reach significance. (A comparison of models predictive of static and fatigue failure properties revealed that anterior density regions were most often included in predictive models of the static properties while posterior regions were more predictive of the fatigue properties).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Hearing loss in Paget's disease of bone: the relationship between pure-tone thresholds and mineral density of the cochlear capsule.

We have developed a unique method of quantitative computed tomography (QCT) that enables measurement of the density of the cochlear capsule in vivo. We performed pure-tone audiometry and QCT on 67 ears from 35 subjects with radiographically confirmed Paget's disease of the skull and on 40 ears from twenty volunteer subjects. The Pearson product-moment correlation coefficients (age- and sex-adjusted) in the group affected by Paget's disease were -0.63 for left ears and -0.73 for right ears for high-frequency air conduction pure-tone thresholds (mean of 1, 2, and 4 kHz) versus cochlear capsule density. Correlation coefficients (age- and sex-adjusted) between cochlear capsule density and air-bone gap (mean at 0.5 and 1 kHz) for the affected group were -0.67 for left ears and -0.63 for right ears. All correlations between hearing thresholds and cochlear capsule density in pagetic subjects were significant at p < 0.001. The regressions were consistent throughout the ranges of hearing level. There were no significant correlations between cochlear capsule mean density and hearing level in the volunteer subjects. These findings demonstrate the feasibility of precise and accurate density measurements in the temporal bone in vivo and support the use of the mean cochlear capsule density as a marker of disease effect. Alteration of cochlear capsule bone density may be related to the mechanisms of hearing loss in Paget's disease of bone.

Adult↗
PubMed1995

Hearing loss in Paget's disease of bone: evidence of auditory nerve integrity.

Auditory brainstem responses (ABRs) were recorded in 64 ears with radiographically confirmed Paget's disease involving the skull. Responses were absent in eight ears, all of which had elevated high pure-tone thresholds. Auditory brainstem responses were interpreted as normal in 56 ears; none were abnormal. Computed tomography and digital image analysis were used to quantify internal auditory canal (IAC) dimensions. The midlength diameter and minimum diameter of the IAC of 68 temporal bones from subjects with Paget's disease were found to have no statistically significant relation to hearing thresholds. Increased IAC length showed a limited relation to reduced hearing level in pagetic subjects, possibly consistent with bossing adjacent to the porus acusticus. Findings support the principle that hearing loss in Paget's disease of bone is generally associated with intact auditory nerve function and also support a cochlear site of lesion.

Audiometry, Pure-Tone↗
PubMed1994

Application of quantitative computed tomography to Paget's disease of bone.

Serial evaluation of pagetic lesions is handicapped by the inability of conventional methods to reproduce precisely the positioning of the area of interest. A computed tomography method that provides visual and quantitative comparisons between data sets acquired at different times has been developed. The utility of this method is illustrated with an example of serial examinations that demonstrate the effect of treatment on small lytic lesions in the lumbar spine. A further demonstration is made of the ability of this method to identify and quantify lytic changes within the cochlear capsule.

Aged↗
PubMed1993

The assessment of vertebral bone macroarchitecture with X-ray computed tomography.

On a macroscopic scale, the structural characteristics of whole bone are likely dependent on the distribution of typically applied loads to the bone surface, the full bone shape, the thickness of the cortex at the various surface positions, and the distribution of cancellous bone material. X-ray computed tomography is presently the best available method for assessing the macroarchitecture of bone in-vivo. Fine detail, three-dimensional CT methods are available to measure regional bone mineral density (rBMD) in contiguously spaced small volumes and have been applied to the assessment of macroarchitecture in vertebrae. The more detailed rBMD methods produce radiation exposures to the subject similar to lumbar radiography and substantially higher than traditional QCT. The cancellous bone within lumbar vertebral bodies has been found in cross-sectional studies to have increased density in the inferior, posterior and lateral regions. Notably, regions with higher density at age 40 have a larger decline with age. The vertebral body cortex declines with age at a slower rate than observed for cancellous bone; however, the decline with age of cortical bone appears to vary substantially amongst subjects. The amount of cortical bone in the anterior portion of the body is less than in the lateral portion, which may explain previous discrepancies in assessing the fraction of vertebral body bone in the cortex.

Adult↗
PubMed1993

Measurement of regional bone mineral density: a new technique for the evaluation of the temporal bone.

The measurement of regional bone mineral density (rBMD) is a new method of evaluation of the human temporal bone in vitro or in vivo. Modified computed tomography (CT) enables us to collect a three-dimensional array of precise, reproducible bone density values, as well as high-quality CT images. Measurements are calibrated using phantoms of known composition and density. Conventional CT provides density information that is relative, qualitative, and lacks precise reproducibility over time. The rBMD technique provides precise numeric density measurements. Additional image processing capabilities are described. In vivo data from six normal temporal bones and from two patients with Paget's disease involving the temporal bone are presented to demonstrate the technique.

Aged↗
PubMed1993

Load-bearing capacity of corticocancellous bone grafts in the spine.

We investigated the relationship between the densities and areas of commonly used autogenous tricortical bone grafts from the iliac crest and the fibula and their mechanical load-bearing abilities. Intact corticocancellous grafts, seven millimeters thick, were obtained during elective spinal arthrodeses from fifty-six patients: from the anterior part of the pelvis in twenty-four patients, the posterior part of the pelvis in twenty-nine patients, and the fibula in three patients. The apparent densities and cross-sectional areas of the cortical and cancellous bone were measured with use of a specific computed-tomographic technique before the specimens were mechanically tested to failure in uniaxial compression. Specimens from the anterior superior iliac spine were able to bear significantly higher axial loads (average, 3230 newtons; range, 430 to 8112 newtons) than were those from the posterior superior iliac spine (average, 1458 newtons; range, 350 to 4639 newtons) (p < 0.001). The cancellous density was the most significant single factor in the prediction of the load to failure of the grafts from the iliac crest (adjusted r2 = 0.58; p < 0.0001). When all of the physical variables (the cancellous and cortical densities and areas) were entered into a multiple-regression model, the combination of the cortical and cancellous densities and the cortical area was a good predictor (adjusted r2 = 0.68; p < 0.001) of the load to failure. The fibular grafts were stronger than those from the other two sites, but they had the least over-all cross-sectional area and cancellous bone.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Proximal femoral bone density and its correlation to fracture load and hip-screw penetration load.

The bone mineral density of 22 random, fresh proximal human femora was estimated by roentgenography using the Singh index (SI) and measured using a regional bone mineral density computed tomographic protocol. Uniaxial compression was used to produce an impacted subcapital fracture. The femoral heads then were isolated and mounted on a sliding screw plate compression device and loaded to failure in a push-out or hip-screw penetration mode. Wide intraobserver variation, poor reproducibility, and poor prediction of the experimental fracture properties of the proximal femur were noted for SI values. Regional bone mineral density provided a reliable estimate of both the gross fracture loads and hip-screw penetration loads. In addition, there was a high correlation between trabecular density and the experimental fracture properties of the proximal femur. Therefore, The validity of the SI as an indicator of the mechanical properties of the proximal femur should be reconsidered.

Biomechanical Phenomena↗
PubMed1991

Evaluation of orthogonal mechanical properties and density of human trabecular bone from the major metaphyseal regions with materials testing and computed tomography.

We evaluated the orthogonal mechanical properties of human trabecular bone from the major metaphyseal regions with materials testing and quantitative computed tomography (CT). The proximal tibia, distal femur, proximal femur, distal radius, and proximal humerus from fresh cadaver specimens between the ages of 55 and 70 years were excised and prepared for experimentation. The bones were embedded and scanned at 1 or 1.5 mm intervals on a Technicare HPS 1440 and GE 9800 CT scanner. After scanning, the bones were sectioned, producing 8-mm cubes of trabecular bone which were mechanically tested in uniaxial compression at a strain rate of 1%. The testing sequence consisted of preyield tests in two of the three orthogonal directions and failure in the third. After testing, the cubes were evaluated for apparent density and ash weight. The results of the study show that the strength and stiffness of trabecular bone varies significantly within metaphyseal regions and from metaphysis to metaphysis. The power and significance of relationships between density and modulus varied as a function of metaphyseal location. Both linear and nonlinear models were significant, suggesting that trabecular deformation occurs in response to both axial and bending loads. Finally, the need for architectural measures of trabecular bone to predict mechanical properties is emphasized.

Aged↗
PubMed1991

Comparison of dual photon and dual energy X-ray bone densitometers in a clinic setting.

In clinical practice, decisions must be made about whether and how to convert to newer technologies. To address this issue, two separate studies were conducted. We evaluated the relationships between results of lumbar spine measurements using two dual photon absorptiometry (DPA1 and DPA2) instruments and one dual energy X-ray (DXA) instrument with the same subjects (49 volunteers), and also in 65 patients who were measured on the DPA1 and DXA machines. Second, we measured the lumbar spine and the proximal femur in three groups of 12 female volunteers three times on one instrument within 1 week. We purposely simulated a busy clinic setting with different technologists, older radioactive sources, and a heterogeneous patient group. The comparison study indicated a significant difference between the mean bone density values reported by the machines, but the results were highly correlated (R2 = 0.89-0.96). The short-term precision errors (coefficients of variation) differed among the instruments, ranging from 1.3% (DXA of the spine) to 5.1% (DPA1 of the spine), and in the femoral neck, 2.3% and 2.4% (DXA and DPA1, respectively) versus 3.5% by DPA2. This study emphasizes the differences between instruments, the potential for greater error in busy clinic environments, and the apparent superiority of dual energy X-ray absorptiometry under these less than ideal conditions.

Absorptiometry, Photon↗
PubMed1991

Correlations between vertebral regional bone mineral density (rBMD) and whole bone fracture load.

To assess the significance of regional quantitative computed tomography measurements of bone density with respect to mechanical strength in the human lumbar spine, 58 vertebrae (from 12 males, 10 females) were scanned in vitro with multiple-thin-slice quantitative computed tomography and then compressed to fracture. With computer graphics, 18 specific regions of physical density and 10 combination averages of density were identified within each vertebral body. To ensure the statistical independence of data, the individual vertebral specimens were assigned to one of three groups (T11-L1, L2-L3, or L4-L5). Use of best-subsets procedures resulted in regression models to predict fracture strength. These models used specific regional density values and often the age and sex of the donors. The correlation coefficients that resulted from the multiple regression models ranged from r = 0.88 to r = 0.95. When the density values were multiplied by the minimum cross-sectional area of the vertebral body, similar regional density averages were selected, and the predictive values were slightly improved (r = 0.94-0.97). The heterogeneity of the density samples (measured as standard deviation) in multiple regression fashion also produced strong correlation coefficients (r = 0.88-0.94). The bone density in an anterior cylinder of the midplane region, the location measured most often in quantitative computed tomography densitometry, was strongly correlated (r = 0.85) to fracture load for the T12-L1 group (N = 20), but was not significant for the other two groups of vertebrae. The cancellous bone density from the female data was not found to be significantly different from the male data set.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

A technique for measuring regional bone mineral density in human lumbar vertebral bodies.

A method for measuring the regional bone mineral density (rBMD) in human lumbar vertebral bodies using a series of contiguous computed tomography images, each 1 mm thick, is fully described. The technique has a sample volume of 0.004 cm3, a sample spacing of 0.8 X 0.8 X 1.0 mm, and results in a bone marrow radiation dose of 1.59 to 2.75 rads (0.016-0.028 Gy). The use of physical density (mg/cm3) is introduced and the measurement noise (0.7-1.3%), accuracy (2.7%), and serial precision (0.2%) have been evaluated in vitro using appropriate phantoms. The corresponding percentage errors for accuracy and precision relative to K2HPO4 concentration were 6.9% and 2.0%, respectively. A multiple region density measurement is described and evaluated.

Adult↗