Variability of trabecular microstructure is age-, gender-, race- and anatomic site-dependent and affects stiffness and stress distribution properties of human vertebral cancellous bone

Cancellous bone microstructure is an important determinant of the mechanical integrity of vertebrae. The numerous microstructural parameters that have been studied extensively are generally represented as a single value obtained as an average over a sample. The range of the intra-sample variability of cancellous microstructure and its effect on the mechanical properties of bone are less well-understood. The objectives of this study were to investigate the extent to which human cancellous bone microstructure within a vertebra i) is related to bone modulus and stress distribution properties and ii) changes along with age, gender and locations thoracic 12 (T12) vs lumbar 1 (L1).Vertebrae were collected from 15 male (66 ± 15 years) and 25 female (54 ± 16 years) cadavers. Three dimensional finite element models were constructed using microcomputed tomography images of cylindrical specimens. Linear finite element models were used to estimate apparent modulus and stress in the cylinders during uniaxial compression. The intra-specimen mean, standard deviation (SD) and coefficient of variation (CV) of microstructural variables were calculated.Mixed model statistical analysis of the results demonstrated that increases in the intra-specimen variability of the microstructure contribute to increases in the variability of trabecular stresses and decreases in bone stiffness. These effects were independent from the contribution from intra-specimen average of the microstructure. Further, the effects of microstructural variability on bone stiffness and stress variability were not accounted for by connectivity and anisotropy. Microstructural variability properties (SD, CV) generally increased with age, were greater in females than in males and in T12 than in L1. Significant interactions were found between age, gender, vertebra and race. These interactions suggest that microstructural variability properties varied with age differently between genders, races and vertebral levels.The current results collectively demonstrate that microstructural variability has a significant effect on mechanical properties and tissue stress of human vertebral cancellous bone. Considering microstructural variability could improve the understanding of bone fragility and improve assessment of vertebral fracture risk.     

Trabecular shear stress amplification and variability in human vertebral cancellous bone: relationship with age, gender, spine level and trabecular architecture

Trabecular shear stress magnitude and variability have been implicated in damage formation and reduced bone strength associated with bone loss for human vertebral bone. This study addresses the issue of whether these parameters change with age, gender or anatomical location, and if so whether this is independent of bone mass. Additionally, 3D-stereology-based architectural parameters were examined in order to establish the relationship between stress distribution parameters and trabecular architecture. Eighty cancellous bone specimens were cored from the anterior region of thoracic 12 and donor-matched lumbar 1 vertebrae from a randomly selected population of 40 cadavers. The specimens were scanned at 21-microm voxel size using microcomputed tomography (microCT) and reconstructed at 50microm. Bone volume fraction (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), bone surface-to-volume ratio (BS/BV), degree of anisotropy (MIL1/MIL3), and connectivity density (-#Euler/Vol) were calculated directly from micro-CT images. Large-scale finite element models were constructed and superoinferior compressive loading was simulated. Apparent cancellous modulus (EFEM) was calculated. The average trabecular von Mises stress generated per uniaxial apparent stress (sigma (-)VM / sigmaapp) and coefficient of variation of trabecular von Mises stresses (COV) were calculated as measures of the magnitude and variability of shear stresses in the trabeculae. Mixed-models and regression were used for analysis. sigma(-)VM / sigmaapp and COV were not different between genders and vertebrae. Both sigma(-)VM / sigmaapp and COV increased with age accompanied by a decrease in BV/TV. Strong relationship of sigma(-)VM / sigmaapp with BV/TV was found whereas COV was strongly related to EFEM/(BV/TV). The results from T12 and L1 were not different and highly correlated with each other. The relationship of sigma(-)VM / sigmaapp with COV was observed to be different between males and females. This difference could not be explained by architectural parameters considered in this study. Our results support the relevance of trabecular shear stress amplification and variability in age-related vertebral bone fragility. The relationships found are expected to help understand the micro-mechanisms by which cancellous bone mass and mechanical properties are modulated through a collection of local stress parameters.     

Does thoracic or lumbar spine bone architecture predict vertebral failure strength more accurately than density?

Summary Trabecular bone microstructure was studied in 6 mm bone biopsies taken from the 10th thoracic and 2nd lumbar vertebra of 165 human donors and shown to not differ significantly between these sites. Microstructural parameters at the locations examined provided only marginal additional information to quantitative computed tomography in predicting experimental failure strength. Introduction It is unknown whether trabecular microstructure differs between thoracic and lumbar vertebrae and whether it adds significant information in predicting the mechanical strength of vertebrae in combination with QCT-based bone density. Methods Six mm cylindrical biopsies taken at mid-vertebral level, anterior to the center of the thoracic vertebra (T) 10 and the lumbar vertebra (L) 2 were studied with micro-computed tomography (μCT) in 165 donors (age 52 to 99 years). The segment T11-L1 was examined with QCT and tested to failure using a testing machine. Results The correlation of microstructural properties was moderate between T10 and L2 (r ≤ 0.5). No significant differences were observed in the microstructural properties between the thoracic and lumbar spine, nor were sex differences at T10 or L2 observed. Cortical/subcortical density of T12 (r ² = 48%) was more strongly correlated with vertebral failure stress than trabecular density (r ² = 32%). BV/TV (of T10) improved the prediction by 52% (adjusted r ²) in a multiple regression model. Conclusion Microstructural properties of trabecular bone biopsies displayed a high degree of heterogeneity between vertebrae but did not differ significantly between the thoracic and lumbar spine. At the locations examined, bone microstructure only marginally improved the prediction of structural vertebral strength beyond QCT-based bone density.     

Ultrasound Velocity and Attenuation in Cancellous Bone Samples from Lumbar Vertebra and Calcaneus

We report a study of ultrasound velocity and broadband ultrasound attenuation (BUA) in human cancellous bone samples. The influence of density and microarchitecture on ultrasound propagation in cancellous bone was examined. A total of 20 samples from vertebra L1 and 21 from calcanei were studied. The direction of ultrasound propagation was anteroposterior in the vertebra and lateromedial in the calcaneus. The relationships between ultrasonic parameters and density of bone samples, apparent ash density, trabecular bone volume (BV/TV) and trabecular thickness (Tb.Th) were analyzed using a simple linear model and a multiple regression model. Velocity of ultrasound and BUA were positively correlated with density and morphometric parameters, in both vertebra and calcaneus. The best correlation was found between velocity and bone sample density in vertebra (r= 0.961, p < 0.0001) and the worst between velocity and trabecular thickness in calcaneus (r= 0.632, p= 0.002). The best correlation for BUA was with BV/TV in vertebra (r= 0.960, p < 0.0001). Using the stepwise regression procedure, BV/TV only was selected as significant for BUA and apparent ash density with Tb.Th for velocity, in both vertebra and in calcaneus. The possible influence of trabecular configuration on ultrasonic parameters is discussed, emphasizing the different slopes of regression lines obtained for vertebra and calcaneus, sites with different architecture of trabecular bone. Received: 9 April 1997 / Accepted: 27 April 1998     

Interaction between playing golf and HRT on vertebral bone properties in post-menopausal women measured by QCT

Summary We investigated the effect of playing regular golf and HRT on lumbar and thoracic vertebral bone parameters (measured by QCT) in 72 post-menopausal women. The main finding of this study was that there was positive interaction between golf and HRT on vertebral body CSA and BMC at the thoracic 12 and lumbar 2 vertebra but not the third and seventh thoracic vertebras. Introduction Identifying specific exercises that load the spine sufficiently to be osteogenic is an important component of primary osteoporosis prevention. The aim of this study was to determine if in postmenopausal women regular participation in golf resulted in greater paravertebral muscle mass and improved vertebral bone strength. Methods Forty-seven postmenopausal women who played golf regularly were compared to 25 controls. Bone parameters at the mid-vertebral body were determined by QCT at spinal levels T3, T7, T12 and L2 (cross-sectional area (CSA), total volumetric BMD (vBMD), trabecular vBMD of the central 50% of total CSA, BMC and cortical rim thickness). At T7 and L2, CSA of trunk muscles was determined. Results There was a positive interaction between golf and HRT for vertebral CSA and BMC at T12 and L2, but not at T3 or T7 (p ranging < 0.02 to 0.07). Current HRT use was associated with a 10–15% greater total and trabecular vBMD at all measured vertebral levels. Paravertebral muscle CSA did not differ between groups. Vertebral CSA was the bone parameter significantly related to muscle CSA. Conclusion These findings provide preliminary evidence that playing golf may improve lower spine bone strength in postmenopausal women who are using HRT.     

Distribution and orientation of bone in the human lumbar vertebral centrum.

This article describes regional variations in cancellous bone morphology within the human lumbar spine of a 60-year-old woman. An automated imaging technique, based upon the method of directed secants, was used to quantify variations in bone porosity and trabecular size, distribution, and orientation within serial transverse histological sections of the L1 and L2 vertebral centrum. Several morphologically distinct levels of organization were observed along the axis of the centrum. The superior and inferior sections of the centrum were made up of an open-celled network of trabeculae, while the translational and middle sections consisted primarily of plate-like trabeculae forming a closed-cell structure. The densest and most oriented bone was found in the superior and inferior sections of the posterior-lateral centrum, whereas least dense and least oriented bone was found in the central third of the anterior centrum. Average trabecular thickness did not vary appreciably from level to level, but varied considerably within a given level, particularly in the inferior sections of the centrum. The number of trabeculae was lowest in the central sections of the centrum, where plate-like trabeculae were most prevalent. The topological architecture of different levels within the centrum exhibited a remarkable degree of organization, which suggests that the spine, like other skeletal structures, has adapted to functional stresses produced during daily activities. Detailed morphological data are tabulated and should be of use to investigators interested in modeling the three-dimensional structural and physical properties of the lumbar spine.     

The biomechanical effects of kyphoplasty on treated and adjacent nontreated vertebral bodies

It remains unclear whether adjacent vertebral body fractures are related to the natural progression of osteoporosis or if adjacent fractures are a consequence of augmentation with bone cement. Experimental or computational studies have not completely addressed the biomechanical effects of kyphoplasty on adjacent levels immediately following augmentation. This study presents a validated two-functional spinal unit (FSU) T12-L2 finite element model with a simulated kyphoplasty augmentation in L1 to predict stresses and strains within the bone cement and bone of the treated and adjacent nontreated vertebral bodies. The findings from this multiple-FSU study and a recent retrospective clinical study suggest that changes in stresses and strains in levels adjacent to a kyphoplasty-treated level are minimal. Furthermore, the stress and strain levels found in the treated levels are less than injury tolerance limits of cancellous and cortical bone. Therefore, subsequent adjacent level fractures may be related to the underlying etiology (weakening of the bone) rather than the surgical intervention.     

Relationships between bone structure in the iliac crest and bone structure and strength in the lumbar spine

The purpose of this study was to examine the relationship between histomorphometric variables of cancellous bone structure and ultimate compressive strength (UCS) in the second lumbar vertebra (L2) and to determine whether structural variables in the iliac crest are predictive of the same variables and of UCS in L2. At autopsy, 7.5 mm diameter cores were removed from the iliac crest and from L2 of 29 subjects who had died suddenly without bone disease. Cancellous bone volume (BV/TV, %) was significantly lower in L2 than in iliac crest due to lower trabecular number (Tb.N, per mm) and thickness (Tb.Th, µm). There were significant correlations between iliac crest and L2 for BV/TV, Tb.N and trabecular separation (Tb.Sp, µm), but not for Tb.Th. BV/TV was negatively correlated, and Tb.Sp was positively correlated with age at both sites. Tb.Th was not significantly correlated with age in the iliac crest, but a significant negative correlation was observed in L2. The UCS of vertebral cores was negatively correlated with age. BV/TV and Tb.Th in L2 were positively correlated with UCS in L2. Cortical width and BV/TV in iliac crest were positively correlated with UCS in L2. We conclude that: (1) cancellous bone volume in the iliac crest is higher than in the lumbar spine due to thicker, more closely spaced trabecular plates, (2) the changes in structural variables with age are generally similar in the iliac crest and lumbar vertebra, but trabecular thinning with age is more evident in the spine than in the ilium, and (3) the compressive strength of cancellous bone in the lumbar spine is correlated with histomorphometric variables of bone structure, as measured both in the lumbar spine and in the iliac crest.     

Degenerative lumbar listhesis and bone mineral density in elderly women. The study of osteoporotic fractures

STUDY DESIGN: A cross-sectional and prospective study. OBJECTIVES: To investigate the association between lumbar listhesis in elderly white women and bone mineral density at the spine, hip, radius, and calcaneus. SUMMARY OF BACKGROUND DATA: Several types of degenerative spinal changes have been found to be associated with high bone mineral density at the spine and other body sites. METHODS: Lateral radiographs of the lumbar spine for 1400 elderly women enrolled in the Study of Osteoporotic Fractures were digitized. Listhesis (antero and retro) was assessed at L3-L4, L4-L5, and L5-S1. Bone mineral density was measured at the spine, hip, calcaneus, and the distal and proximal radius. RESULTS: After adjusting the data for age and body mass index, retrolisthesis at L3-L4, L4-L5, and L5-S1 was associated with mean spinal bone mineral density levels that were 9% to 13% higher compared with those levels in women with no listhesis (P < 0.0001). In addition, bone mineral density at the hip and appendicular sites increased from 4% to 9%. The mean lumbar spinal bone mineral density of women with anterolisthesis at L3-L4 was 12% higher (P < 0.05) than that of women with no listhesis; it was the same for both groups at L4-L5 and was 7% lower (P < 0.005) at L5-S1. At L5-S1 the bone mineral density level at the hip and appendicular sites was also lower among the women with anterolisthesis at that level. CONCLUSIONS: This study suggests that retrolisthesis, like other spinal degenerative diseases, is associated with increased spinal bone mineral density. Anterolisthesis, however, may involve a different etiology, because its association with bone mineral density varies by spinal level.     

Plain radiographic, discographic, and direct observations of Schmorl's nodes in the thoracolumbar junctional region of the cadaveric spine

The perceivability of Schmorl's nodes in plain radiographs and discograms in the thoracolumbar junctional region (T10-L1) of the cadaveric spine was assessed by comparing the radiologic measurements with bone measurements. Schmorl's nodes in bone specimens were encountered in 19 of 24 spines studied. They were more than two times as common between vertebrae T10-11 and T11-12 as between T12 and L1 (P less than 0.01). When the areas of actual Schmorl's nodes exceeded 0.5 cm2 (corresponding to an aperture with a diameter of 0.8 cm), 47% of the nodes were seen in plain lateral radiographs and 68% in discograms. When the area measured 0.5 cm2 or less, only 24% could be perceived in plain lateral radiographs and 23% in discograms. The clinical significance of Schmorl's nodes remains uncertain as long as they are difficult to detect in vivo.     

Thoracolumbar spinal fractures: segmental range of motion after dorsal spondylodesis in 82 patients: a prospective study

In order to study the effect of dorsal spondylodesis on intervertebral movement in patients treated for thoracolumbar fractures, we measured the sagittal range of motion (ROM) in the segments above and below the fractured vertebral body 2 years after operation. Between 1991 and 1996, 82 consecutive patients with a fracture of the thoracolumbar spine (T12, L1, L2 and L3) were treated operatively with open reduction and stabilisation using an internal fixator, combined with transpedicular cancellous bone graft and dorsal spondylodesis. Eighteen T12, 42 L1, 17 L2 and 5 L3 fractures were included. The range of motion of two segments above and two segments below fracture level was measured. This was done on plain flexion and extension radiographs. The data were compared to normal values and to the zero distribution with the Kolmogorov-Smimov test. At all fracture levels the ROM of the segment adjacent to the disturbed endplate of the fractured body was zero (K-S test). All other evaluated segments showed significant loss of ROM (P<0.05) compared to normal values, except segment L1-L2 in L3 fractures (P=0.058). Dorsal spondylodesis at the level of the disturbed endplate in thoracolumbar spinal fractures leads to immobility in this segment, measured on flexion-extension radiographs 2 years after primary operative treatment. More than 50% loss of motion in the two adjacent levels is equivalent to complete loss of ROM in a second segment.     

Histomorphometric Evaluation of the Effects of Ovariectomy on Bone Turnover in Rat Caudal Vertebrae

The purpose of this study was to learn whether caudal vertebrae can be used to evaluate the effects of ovariectomy (OVX) in rats. Seven-month-old female Wistar rats were divided into two groups: the OVX group and the untreated control group. All rats were killed at 8 weeks and their 4th lumbar (L4), 1st caudal (C1), 3rd caudal (C3), and 5th caudal (C5) vertebrae were processed undecalcified and sectioned with Villanueva bone stain for quantitative bone histomorphometry. Both length of vertebral bodies and the cancellous tissue area in C1 were similar in size to L4 but significantly bigger than C3 and C5. Within the groups, cancellous bone volume (BV/TV) and trabecular thickness in both groups gradually increased in caudal vertebrae in relation to the distal direction. Between the groups, OVX rats exhibited a significantly lower BV/TV relative to control rats at L4 and C1, however, no significant difference were seen at C3 and C5. Bone formation-related parameters such as osteoid and mineralizing surface, and eroded surface were higher in the OVX group than in the control group in caudal as well as in lumbar vertebrae. By quantitative analysis of bone marrow composition, yellow marrow volume in C3 and C5 was significantly higher than that in L4 and C1, in both groups. Our results suggest that C1 is similar to L4 in size, bone turnover, and bone marrow composition. However, further experiments are needed to evaluate the possibility that C1 vertebra could be used as an alternative site for histomorphometric evaluation of bone changes in OVX rats. Received: 12 August 1997 / Accepted: 11 May 1998     

Antero-postero differences in cortical thickness and cortical porosity of T12 to L5 vertebral bodies

OBJECTIVE: This study will investigate interrelationships between the cortical shell and cancellous bone trabecular thickness, in vertebral bodies. METHODS: One hundred and sixty vertebral bodies from T12 to L5 were obtained at autopsy. The average age of the cohort was 59.3+/-22.1 years (range = 20-94 years). Cortical thickness, cortical porosity and trabecular thickness from the adjacent cancellous bone were measured. RESULTS: At the mid-vertebral body anterior cortical thickness was significantly greater than posterior cortical thickness (524 +/- 352 vs. 370 +/- 283 microm, respectively, P < 0.0001) and mid-anterior cortical porosity was significantly less than mid-posterior cortical porosity (24 +/- 14% vs. 32 +/- 16%, respectively, P < 0.0001). There were no anterior/posterior differences in trabecular thickness of the cancellous bone adjacent to the cortical walls. CONCLUSION: This study provides a novel perspective of T12 to L5 vertebral body bone, where measurement of cortical thickness and cortical porosity in a cohort of skeletally normal individuals revealed structural differences between load bearing anterior and posterior cortical walls. The data suggest that modulators of change to vertebral body bone may affect the cortical and trabecular bone differently. The relationships between cortical and cancellous bone suggest that the middle sectors of the vertebral body play a critical role in load bearing.     

The stability of reconstruction methods after thoracolumbar total spondylectomy. An in vitro investigation.

STUDY DESIGN: After total spondylectomy, five types of spinal reconstruction techniques were compared biomechanically. OBJECTIVES: To evaluate the stability provided by five reconstruction methods after total spondylectomy. SUMMARY OF BACKGROUND DATA: Total spondylectomy presents a worst-case scenario for spinal reconstruction. However, few investigators have biomechanically investigated spinal reconstruction stability after total spondylectomy. METHODS: Eight human cadaveric spines (T11-L5) were used. After intact analysis, a total spondylectomy was performed at L2 and reconstructed using Harms titanium mesh (Depuy-Motech, Warsaw, IN) as an anterior strut. Anterior, posterior, or circumferential instrumentation techniques were then performed using the Kaneda SR and ISOLA pedicle screw systems (AcroMed Corp., Cleveland, OH) as follows: 1) anterior instrumentation at L1-L3 with multisegmental posterior instrumentation at T12-L4 (AMP), 2) anterior instrumentation at L1-L3 with short posterior instrumentation at L1-L3 (ASP), 3) anterior instrumentation at L1-L3 (A), 4) multilevel posterior instrumentation at T12-L4 (MP), and 5) short posterior instrumentation at L1-L3 (SP). Nondestructive biomechanical testing was performed under axial compression, flexion-extension, and lateral bending loading modes. RESULTS: Only circumferential instrumentation techniques (AMP, ASP) exhibited higher stiffness than the intact spine in all loading modes (P < 0.05). Short circumferential fixation provided more stability than did multilevel posterior instrumentation (P < 0.05). Multilevel posterior fixation provided more stiffness than did short posterior and anterior instrumentation alone (P < 0.05). CONCLUSIONS: Only circumferential fixation techniques provide more stability than the intact spine in all testing modes. Short circumferential instrumentation provides more stability than multilevel posterior instrumentation alone and requires fewer levels of spinal fusion.     

Segmental analysis of the sagittal plane alignment of the normal thoracic and lumbar spines and thoracolumbar junction

Recent advances in spinal instrumentation have brought about a new emphasis on the three-dimensional spinal deformity of scoliosis and especially on the restoration of normal sagittal plane contours. Normal alignment in the coronal and transverse planes is easily defined; however, normal sagittal plane alignment is not so simple. This retrospective study was undertaken to increase the understanding of the normal alignment of the spine in the sagittal plane, with a special emphasis on the thoracolumbar junction. Measurements were made from the lateral radiographs of 102 subjects with clinically and radiographically normal spines. Cobb measurements of the thoracic kyphosis (T3-T12), the thoracolumbar junction (T10-T12 and T12-L2), and the lumbar lordosis (L1-L5) were determined. The spices of the thoracic kyphosis and lumbar lordosis also were determined. Using a computerized digitalizing table, the segmental angulation was determined at each level from T1-2 to L5-S1. In conclusion, there is a wide range of normal sagittal alignment of the thoracic and lumbar spines. When using composite measurements of the combined frontal and sagittal plane deformity of scoliosis, this wide range of sagittal variance should be taken into consideration. Using norms established here for segmental alignment, areas of hypokyphosis and hypolordosis commonly seen in scoliosis can be more objectively evaluated. The thoracolumbar junction is for all practical purposes straight; lumbar lordosis usually starts at L1-2 and gradually increases at each level caudally to the sacrum.     

Trabecular bone density of male human cervical and lumbar vertebrae

The objective of this study was to determine the bone mineral density (BMD) of cervical vertebrae and correlate with the lumbar spine. Fifty-seven young adult healthy male volunteers, ranging from 18 to 41 years of age, underwent quantitative computed tomography (QCT) scanning of C2-T1 and L2-L4 vertebrae. To account for correlations, repeated measures techniques were used to compare data as a function of spinal level and region. Linear regression methods were used (+/-95% CI) to compare data as a function of spinal level and region. The mean age and body height were 25.0 +/- 5.8 years and 181.0 +/- 7.6 cm. BMD decreased from the rostral to caudal direction along the spinal column. Grouped data indicated that the neck is the densest followed by the first thoracic vertebra and low back with mean BMD of 256.0 +/- 48.1, 194.3 +/- 44.2, and 172.2 +/- 28.4 mg/cm(3), respectively; differences were statistically significant. While BMD did not vary significantly between the three lumbar bodies, neck vertebrae demonstrated significant trends. The matrix of correlation coefficients between BMD and spinal level indicated that the relationship is strong in the lumbar (r = 0.92-0.96) and cervical (r = 0.73-0.92) spines. Data from the present study show that the trabecular bony architecture of the neck is significantly different from the low back. These quantitative BMD data from a controlled young adult healthy human male volunteer population may be valuable in establishing normative data specifically for the neck. From a trabecular bone density perspective, these results indicate that lumbar vertebrae cannot act as the best surrogates for neck vertebrae. Significant variations in densities among neck vertebrae, unlike the low back counterpart, may underscore the need to treat these bones as different structures.     

A paradigm of delayed union and nonunion in the lumbosacral joint. A study of motion and bone grafting of the lumbosacral spine in sheep

In a group of nine sheep (Group A), it was noted that when small, interlocking cancellous and cortical cancellous bone grafts are placed posteriorly on the lumbosacral spine, union always occurred in the interlumbar motion segments and almost never occurred at the lumbosacral joint. One of the main differences in these two areas is the amount of motion that occurs at each level with flexion and extension. Because nonunion following bone grafting for arthrodesis of the spine is a serious clinical problem, we have studied the amount of motion seen at the interlumbar and lumbosacral joints in sheep to ascertain how much motion is compatible with union and how much is associated with nonunion. In vivo studies were carried out in eight sheep (Group B), and five normal spine segments were studied in vitro to determine normal motion in this species. To simplify the complex in vivo motion that occurs at the lumbar motion segments, the simple linear displacement and strain of the fusion mass (consisting of fibrous tissue and bone grafts placed on and between the laminas posteriorly) was measured with the spine in flexion and extension. When the displacement and strain at the interlaminar level of the L6-S1 joint was measured, the linear displacement was found to be 5.2 mm and the associated linear strain 36%. The displacement at the L5-L6 interspace was 1.2 mm, and the strain 10%. The stiffness of the L5-L6 joint (which always fused) and the L6-S1 joint (which did not fuse, with one exception) were also studied. In a third group of four animals (Group C), internal fixation of the lumbosacral joint was attempted in addition to bone grafting.(ABSTRACT TRUNCATED AT 250 WORDS)     

Emerging Aspects of the Body Composition,Bone Marrow Adipose Tissue and Skeletal Phenotypes in Type 1 Diabetes Mellitus

Anthropomorphic measures among type 1 diabetic patients are changing as the obesity epidemic continues. Excess fat mass may impact bone density and ultimately fracture risk. We studied the interaction between bone and adipose tissue in type 1 diabetes subjects submitted to two different clinical managements: (I) conventional insulin therapy or (II) autologous nonmyeloablative hematopoietic stem-cell transplantation (AHST). The study comprised 3 groups matched by age, gender, height and weight: control (C = 24), type 1 diabetes (T1D = 23) and type 1 diabetes treated with AHST (T1D-AHST = 9). Bone mineral density (BMD) and trabecular bone score (TBS) were assessed by dual X-ray absorptiometry (DXA). ¹H Magnetic resonance spectroscopy was used to assess bone marrow adipose tissue (BMAT) in the L3 vertebra, and abdominal magnetic resonance imaging was used to assess intrahepatic lipids (IHL), visceral (VAT) and subcutaneous adipose tissue (SAT). Individuals conventionally treated for T1D were more likely to be overweight (C = 23.8 ± 3.7; T1D = 25.3 ± 3.4; T1D-AHST = 22.5 ± 2.2 Kg/m²; p > 0.05), but there was no excessive lipid accumulation in VAT or liver. Areal BMD of the three groups were similar at all sites; lumbar spine TBS (L3) was lower in type 1 diabetes (p < 0.05). Neither SAT nor VAT had any association with bone parameters. Bone marrow adipose tissue (BMAT) lipid profiles were similar among groups. BMAT saturated lipids were associated with cholesterol, whereas unsaturated lipids had an association with IGF1. Overweight and normal weight subjects with type 1 diabetes have normal areal bone density, but lower trabecular bone scores. Adipose distribution is normal and BMAT volume is similar to controls, irrespective of clinical treatment.     

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)     

The proportion of trabecular bone in human vertebrae

The proportion of trabecular bone in human cadaver vertebrae was assessed by anatomic dissection. Thirty-two whole thoracic and lumbar vertebrae were obtained from 10 normal human postmenopausal female cadavers, 14 from 4 normal adult human male cadavers of similar age, and 8 from one female osteoporotic cadaver. Each vertebra was opened by saw cuts and separated into four tissue types: (1) body trabecular bone and marrow; (2) body cortical bone; (3) vertebral arch trabecular bone and marrow; and (4) vertebral arch cortical bone. Calcium was determined in each tissue type for each vertebra by ashing and atomic absorption spectrophotometry. Trabeculae accounted for 24.4 +/- 4.5% of the total calcium in whole female vertebrae, and 18.8 +/- 4.4% in whole male vertebrae (p less than 0.001). The body averaged 41.8% trabecular bone in females and 33.5% in males. The arch averaged 9.7% trabecular bone in females and 4.9% in males. The proportion of trabecular bone in the whole vertebrae in the single osteoporotic spine was 28.5 +/- 3.2%, a value not significantly different from the trabecular fraction in normal females. These data indicate that whole human thoraco-lumbar vertebrae are composed of a substantially lower proportion of trabecular bone than is usually assumed, and they suggest that cortical and trabecular bone are eventually lost in equal proportion from the vertebrae during the development of spinal osteoporosis. These results are important for the interpretation of data from noninvasive bone measurement techniques that evaluate the spine, and they suggest that studies of this type are important for any site where noninvasive bone mass measurement is done.