Bone Mineral Density Of Vertebral Body Research Articles

Does the Bone Mineral Density of the Lumbar Spine Correlate With Dual-Energy X-ray Absorptiometry T Score? A Cadaveric-Based Analysis of Computed Tomography Densitometry.

Pedicle screw loosening is a complication of spinal instrumentation in osteoporotic patients. Dual-energy x-ray absorptiometry scans are not able to detect variations in bone mineral density (BMD) within specific regions of vertebrae. The purpose of this study was to investigate whether spine T scores correlate with cortical and cancellous BMD of pedicles and other 6 anatomical regions of lumbar spine. Eleven cadaveric spines with a mean age of 73 years were digitally isolated by applying filters for cortical and cancellous bone on computed tomography images. Eleven L5 vertebrae were separated into 7 anatomical regions of interest using 3-dimensional software modeling. Hounsfield units (HU) were determined for each region and converted to cortical and cancellous BMD with calibration phantoms of known BMD. Correlations between T scores and HU values were calculated using Pearson correlation coefficient. Mean vertebral T score was 0.15. Cortical BMD of pedicles was strongly correlated with T score (R 2 = 0.74). There was moderate correlation between T score and cortical BMD of lamina, inferior articular process (IAP), superior articular process (SAP), spinous process, and vertebral body. There was weak correlation between T score and cortical BMD of transverse process (R 2 = 0.16). Cancellous BMD of vertebral body was strongly correlated with T score (R 2 = 0.82). There was moderate correlation between T score and cancellous BMD of pedicles, spinous process, and transverse process. There was weak correlation between T scores and cancellous BMD of lamina, IAP, and SAP. There is a strong correlation between T scores and cortical BMD of lumbar pedicle. There is strong correlation between T scores and cancellous BMD of vertebral body. Cortical and cancellous BMD of transverse process and lamina were weakly correlated with T score and less affected by osteoporosis. Patients with osteoporosis may especially benefit from the development of extrapedicular fusion strategies due to the relatively higher bone density of these fixation sites.

Effect of Zoledronic Acid on the Vertebral Body Bone Mineral Density After Instrumented Intervertebral Fusion in Postmenopausal Women With Osteoporosis.

Retrospective cohort study. To evaluate the effect of zoledronic acid, an anti-osteoporosis treatment, during the perioperative period on vertebral body bone mineral density (BMD) after spinal fusion surgery in postmenopausal women with osteoporosis. The medical records of postmenopausal patients with osteoporosis who underwent instrumented intervertebral fusion for lumbar degenerative disease between July 2016 and May 2018 were reviewed. Patients with comorbidities or condition which might affect bone metabolism were excluded. Forty-six patients did not receive anti-osteoporosis treatment before surgery and during the postoperative follow-up (untreated group). Another 46 patients who was treated with zoledronic acid perioperatively were matched for age and body mass index to patients in the untreated group. Preoperative and postoperative dual-energy X-ray absorptiometry (DEXA) records and lumbar BMD values of the involved spinal segments and of the cephalad levels, as well as of the femoral neck were recorded. A significant decrease of cephalad vertebral BMD values was observed in the untreated group (-11.47%, P < 0.001), with a slight decrease of the femoral neck (-1.28%, P > 0.05). Zoledronic acid prevented rapid bone loss after instrumented intervertebral fusion surgery, with a bone loss in the cephalad levels of -0.76 ± 4.71% compared to -11.47 ± 16.45% in the untreated group (P < 0.001). while the change in BMD of the femoral neck in the treated group was 1.52 ± 5.88% compared to -1.28 ± 6.58% in the untreated group (P = 0.036). Perioperative zoledronic acid treatment may offer protection against a significant decrease in BMD of cephalad vertebrae after spinal fusion surgery among postmenopausal women with osteoporosis.

Evaluation of vertebral bone mineral density in scoliosis by using quantitative computed tomography.

PurposeScoliosis is described as a lateral curvature of the spine. We aimed to evaluate bone mineral density (BMD) in patients with scoliosis by using quantitative computed tomography (QCT) and compare the BMD of idiopathic and congenital scoliosis patients.Material and methodsForty-three patients aged 1 to 40 years with idiopathic, congenital, or neuromuscular scoliosis and 41 matched controls of the same sex and approximate age were included in the study. Measurements of BMD were performed by QCT analysis for each vertebral body from T12 to L5, and mean BMD was calculated for each case.ResultsTwenty-two of the patients with scoliosis were idiopathic, 15 were congenital, four were neuromuscular, and two were neurofibromatosis. The mean BMD values of patients with scoliosis were significantly lower compared with the control group (106.8 ± 33.4 mg/cm3 vs. 124.9 ± 29.1 mg/cm3, p = 0.009). No significant difference in BMD values was found between idiopathic and congenital scoliosis patients (p > 0.05).ConclusionsThis study illustrated that the vertebral body BMD values of the patients with scoliosis were significantly lower than those seen in the control group.

Total flavonoid extract of Epimedium herb increases the peak bone mass of young rats involving enhanced activation of the AC10/cAMP/PKA/CREB pathway

Ethnopharmacological relevanceEpimedium sagittatum brevicornum Maxim. is an important traditional Chinese herb that has long been used to promote bone fracture healing and treat osteoporosis. Aim of the studyAchieving peak bone mass by adolescence has now been accepted to be fundamental for preventing osteoporosis in adulthood life. This study investigated the possibility of increasing peak bone mass in young rats using the total flavonoid extract of Epimedium herb (TFE). Materials and methodsTFE was intragastrically administered to one-month-old Wistar rats at a low (100 mg/kg), middle (200 mg/kg) or high dose (400 mg/kg). Whole body bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry every two weeks. When BMD of any one of TFE groups was found to be significantly higher than that of the control, all rats were sacrificed, serum samples were collected for bone turnover biochemical assays, and femurs, tibiae and vertebrae were isolated and used in BMD, mechanical, micro-structural, histomorphometric and mechanistic studies. ResultsAdministration of TFE at middle and high doses for two months significantly increased the whole body, femoral and vertebral BMDs, and improved the bone mechanical and micro-architectural properties. The serum turnover biochemical results and the enhanced expression levels of bone-formation regulatory genes (Runx-2, OSX, and BMP-2) demonstrated that TFE administration increased bone formation but had no effect on bone resorption. The increased phosphorylation levels in femurs of PKA and CREB and expression of AC10 (the only soluble form of adenylyl cyclase) and the increased serum cAMP level after 4 h of TFE administration indicated that TFE promoted bone formation by activating the AC10/cAMP/PKA/CREB pathway in vivo. ConclusionsOral administration of TFE at 200 mg/kg for two months can increase the peak bone mass of growing rats, suggesting the possibility of using total flavonoid extract of Epimedium herb to increase the peak bone mass in adolescence which is important for preventing osteoporosis in adult life.

Effects of combined treatment with ibandronate and pulsed electromagnetic field on ovariectomy-induced osteoporosis in rats.

Ibandronate (IBN) and pulsed electromagnetic field (PEMF) have each shown positive effects for treating osteoporosis, but no study has evaluated the relative effects of these treatments combined. This study investigated the effects of IBN + PEMF on bone turnover, mineral density, microarchitecture, and biomechanical properties in an ovariectomized (OVX) rat model of osteoporosis. Fifty 3-month-old rats were randomly apportioned to receive a sham-operation (n = 10), or ovariectomy (n = 40). The latter group was equally divided as the model (OVX control) or to receive IBN, PEMF, or IBN + PEMF. Beginning the day after surgery, the IBN and IBN + PEMF groups received weekly subcutaneous IBN; the PEMF and IBN + PEMF groups were given daily PEMF during the same 12 weeks. After 12 weeks of treatments, biochemical parameters, bone mineral density (BMD), microarchitecture parameters, biomechanical properties, and some metabolic modulators that are involved in bone resorption were compared. The L5 lumbar vertebral body BMDs of the IBN, PEMF, and IBN + PEMF groups were 121.6%, 119.5%, and 139.6%; maximum loads were 111.4%, 112.7%, and 121.9%; and energy to failure was 130.8%, 129.2%, and 154.9% of the OVX model, respectively. The IBN + PEMF group had significantly lower levels of serum tartrate-resistant acid phosphatase 5b, and greater improvement in BMD, bone microarchitecture, and strength of the lumbar spine compared with monotherapy groups. Results showed that IBN + PEMF had a more favorable effect on the lumbar spine in this osteoporosis model than did either monotherapy. Bioelectromagnetics. 38:31-40, 2017. © 2016 Wiley Periodicals, Inc.

Early and long-term changes in adjacent vertebral body bone mineral density determined by quantitative computed tomography after posterolateral fusion with transpedicular screw fixation

ObjectiveThe aim of this study is to investigate vertebral body bone mineral density (BMD) changes following posterolateral fusion with transpedicular screw fixation using quantitative computerized tomography (QCT) in short and relatively long-term periods. Patients and methodsA retrospective study was performed to investigate vertebral body BMD changes in the patients who underwent posterolateral fusion with transpedicular screw fixation at thoracic and lumbar spine. A total of 160 patients were enrolled into the study. According to the follow-up period, patients were divided into two subgroups (group 1, early follow-up, mean follow-up period, 279.3±162.3 days and group 2, later follow-up, mean follow-up period, 969.1±274.2 days). The trabecular BMDs (mg/cm³) were measured from T12 to L5 as screw free levels by using QCT measurement software. Comparisons between preoperative and postoperative BMD values were assessed using paired t-test. ResultsThe mean postoperative BMD values of both group 1 and 2 weresignificantly lower, compared with the preoperative values (79.2±31.3mg/cm³ vs. 91.5±31.4mg/cm3, 76.1±25.5mg/cm3 vs. 89.3±30.4mg/cm3, p<0.001 and p<0.001, respectively). There was no significant correlation between BMD loss and number of fused segments. Vertebral BMD loss was significantly higher in the L3 vertebra when located caudally to the operation site than when located cranially (−27.7±19.8% vs. −12.8±27.1%; p<0.01). ConclusionsThe vertebral body BMD values are decreased at the adjacent of the posterolateral fusion with transpedicular screw fixation levels in both cephalad and caudad sides at an average of 9-months-follow-up postoperatively. This BMD loss persisted, but not worsened at an average of 32-months-follow-up. Vertebral BMD loss was significantly higher in the L3 vertebra when located caudally versus cranially to the surgery site.

Long-term effects of ovariectomy on the properties of bone in goats.

Large animal models of osteoporosis are essential for osteoporosis research. However, the time required to establish an accurate osteoporosis model is unknown. Therefore, the aim of the present study was to establish a large animal model of osteoporosis in goats. In total, 14 Chinese goats were divided into an ovariectomized (OVX, n=7) or sham-operated (SHAM, n=7) group. Vertebral bodies were used to measure the bone mineral density (BMD) prior to the ovariectomy and at 24 months after the ovariectomy. In addition, the BMD of the femoral neck, femoral diaphysis and tibial diaphysis were measured 24 months postoperatively. Bone samples from the vertebral body, femoral head and femoral neck were scanned by micro-computed tomography (CT) to visualize the trabecular and cortical microstructure. Furthermore, the vertebral body, femoral head, femoral neck and tibial diaphysis were analyzed for mechanical strength. The BMD of vertebral body of the OVX group decreased significantly (P<0.01) at 24 months after the ovariectomy when compared with the baseline measurements. Micro-CT scans of the vertebral body revealed that the bone volume fraction, trabecular number, trabecular thickness and the degree of anisotropy decreased by 37.1, 36.7, 10.5 and 16.5%, respectively (P<0.01) in the OVX group when compared with the SHAM group. Additionally, the specific bone surface and trabecular spacing significantly increased by 37.7 and 62%, respectively in the OVX group (P<0.001). Cortical bone porosity in the vertebral body and femoral neck was greater in the OVX group when compared with the SHAM group (P<0.05). In addition, mechanical testing revealed a statistically significant difference between the vertebral bodies of the OVX group and the SHAM group. In conclusion, the present study demonstrated that an ovariectomy was able to induce significant osteoporosis and deterioration of mechanical properties in the bones of goats.

Association between Radiographic Severity of Osteoarthritis of Finger Joints and Bone Mineral Density

Objective: To determine whether or not there is a correlation between the severity of hand osteoarthritis (OA) and low bone mineral density (BMD). Materials: In 30 patients with hand OA who attended our department with chief complaint of arthralgia in the fingers, data on BMD and the radiographic severity of hand OA were statistically analyzed. Of the 30 subjects studied, 24 were females and 6 males. All subjects aged between 49 and 85 years (mean: 70.0 years). They consisted of 18 subjects with Heberdenʼs nodes, 8 with Bouchardʼs nodes, and 9 with rhizarthrosis. Methods: Radiographic severity of hand OA was scored with the Kellgren/Lawrence scale (grade 0-4). BMD of vertebral bodies was measured by dual-energy X-ray absorptiometry. Results: A statistically significant correlation was found between the radiographic severity of Heberdenʼs nodes and low BMD, whereas neither rhizarthrosis nor Bouchardʼs nodes showed any correlation between radiographic severity and BMD. Conclusions: A statistically significant correlation between the radiographic severity of hand OA and BMD was established solely for Heberdenʼs nodes. Although low BMD may influence the progression of hand OA, there may also be other influencing factors.

Rapid increase in marrow fat content and decrease in marrow perfusion in lumbar vertebra following bilateral oophorectomy: an MR imaging-based prospective longitudinal study.

ObjectiveBilateral oophorectomy leads to reduced bone mineral density (BMD), and reduced BMD is associated with increased marrow fat and reduced marrow perfusion. Purpose of this study was to investigate how soon these changes occur following surgical oophorectomy.Materials and MethodsSix patients who underwent hysterectomy and bilateral salpingo-oophorectomy were studied. At baseline, mean patient age was 49.5 years (range: 45-54 years). Third lumbar vertebral body BMD measurement using quantitative CT, marrow fat fraction (FF) using MR spectroscopy and marrow perfusion using dynamic contrast enhanced MRI were conducted immediately prior to surgery and at 3, 9, and 21 months after surgery.ResultsReduced BMD, increased marrow FF, and reduced marrow perfusion occurred synchronously post-oophorectomy. There was a sharp decrease of 12.5 ± 7.2% in BMD (n = 6), a sharp increase of 92.2 ± 46.3% (n = 6) in FF, a sharp decrease of 23.6 ± 3.9% in maximum contrast enhancement (n = 5), and of 45.4 ± 7.7% for enhancement slope (n = 5) during the initial 3 months post surgery. BMD and marrow perfusion continued to decrease, and marrow FF continued to increase at a slower rate during the following 18 months. Friedman test showed a significant trend for these changes (p < 0.05).ConclusionBilateral oophorectomy leads to a rapid decrease in lumbar BMD, an increase in marrow fat content, and a decrease in marrow blood perfusion.

Characteristics of Rat Lumbar Vertebral Body Bone Mineral Density and Differential Segmental Responses to Sex Hormone Deficiency: a Clinical Multidetector Computed Tomography Study

ObjectiveTo investigate sex hormone deficiency related osteoporosis and efficacy of different therapies. MethodsOrchiectomized and ovariectomized rat models are used to investigate sex hormone deficiency related osteoporosis and efficacy of different therapies. A rat vertebral body can be longitudinally divided into central portion, which contain more trabecular bone, and para-endplate portions which contain more compact bone. In matured male and female Wistar and Sprague-Dawley rat lumbar spines, we investigated baseline bone mineral density (BMD) characteristics and the differential segmental responses in bone loss within the lumbar vertebral body post gonadal surgery with clinical multidetector computed tomography. ResultsPara-endplate sections had a higher BMD than central sections. The cephalad para-endplate sections had a higher BMD than the caudad para-endplate sections. Eight weeks after gonadal removal, there was more bone loss in central sections than para-endplate sections. The relative difference of bone loss between para-endplate and central sections was more apparent in male rats than in female rats. There was more bone loss in caudad sections than cephalad sections; this lead to a further increase of BMD difference between caudad para-endplate sections and cephalad para-endplate sections post gonadal surgery. ConclusionThe approach described in this study provided a consistent way to study BMD change within predominantly compact bone portion and trabecular bone portion of the vertebral body.

Longitudinal changes in lumbar bone mineral density distribution may increase the risk of wedge fractures

BackgroundTrabecular bone strength diminishes as a result of osteoporosis and altered biomechanical loading at the vertebral and spinal levels. The spine consists of the anterior, middle and posterior columns and the load supported by the anterior and middle columns will differ across different regions of the spine. Stress shielding of the anterior column can contribute to bone loss and increase the risk of wedge fracture. There is a lack of quantitative data related to regional spinal bone mineral density distribution over time. We hypothesize that there is an increase in the posterior-to-anterior vertebral body bone mineral density ratio and a decrease in whole-body bone mineral density over time. MethodsBone mineral density was measured in 33 subjects using quantitative computed tomography scans for L1–L3 vertebrae, region (anterior and posterior vertebral body), and time (baseline and 6years after). FindingsLumbar bone mineral density decreased significantly (Δ: ~15%) from baseline to the 6th year visit. Individual vertebra differences over time (L1: ~14%, L2: ~14%, L3: ~17%) showed statistical significance. Anterior bone mineral density change was significantly greater than in the posterior vertebral body region (Δ anterior: ~18%; Δ posterior: ~13%). Posterior-to-anterior bone mineral density ratio was significantly greater in the 6th year compared to baseline values (mean (SD), 1.33 (0.2) vs. 1.23 (0.1)). InterpretationThis study provides longitudinal quantitative measurement of bone mineral density in vertebrae as well as regional changes in the anterior and posterior regions. Understanding bone mineral density distribution over time may help to decrease the risk of wedge fractures if interventions can be developed to bring spine loading to its normal state.

Response to “Vertebral fracture and intervertebral discs”

We thank Drs. Adams and Dolan for their interest in our work and the opportunity to further discuss the association between vertebral bone mineral density (BMD) and disc degeneration (DD) in the lumbar spine. Their comments arise from our discussion of study limitations, in which we acknowledged that ‘‘the age of our subjects was relatively young and a mean age of 50 years is probably too young to determine the full extent of the association studied.’’ We went on to speculate that there may be a stronger association between greater vertebral BMD and more severe DD in older spines, which they question. This was, of course, only speculation, as the association in the elderly could not be addressed with our data and was based on a number of previous studies of elderly women that revealed an association between greater vertebral BMD and more severe lumbar DD. In one such study of 630 women older than 60 years (73.3 6.9 years), higher dual-energy X-ray absorptiometry (DXA) lumbar spine BMD was associated with greater disc space narrowing and Kellgren-Lawrence DD scores. In another study of older women (>60 years, 72.8 6.6 years), greater radiographic disc space narrowing was found to associate with both anterior-posterior and lateral DXA vertebral BMD measurements. An association between greater disc bulging and higher DXA lumbar vertebral BMDwas also observed in women aged up to 86 years. Such associations, however, have been less studied in men, although a similar association between greater disc space narrowing and lumbar BMD acquired with DXA was observed in a cohort of 250 men (65.4 9.0 years). We were not suggesting that the relation between the structure and function of the vertebrae and discs is a simple one. Although our study was not designed to investigate underlying mechanisms of the BMD-DD association we identified, particularly in older spines, it is an important and interesting topic that Adams and Dolan highlight. Adams and Dolan discuss a possible mechanism that could lead to focal bone loss–related specifically to severe disc narrowing, seen in late-stage DD, which may be particularly relevant in the elderly. In pursuing such knowledge, distinguishing different definitions of lumbar vertebral BMD is of great importance. Whereas BMD measured using DXA is areaadjusted, BMD measured with QCT or micro–computed tomography (mCT) is volume-adjusted. The measurements acquired in the study by Adams and colleagues, are substantially different from those used in our study. They used measures of regional bone architecture parameters, such as bone volume/total volume (BV/TV) and trabecular thickness (Tb.Th), to examine focal bone variations, whereas we measured global BMD of the whole vertebra and its vertebral body. Thus, the two studies are not directly comparable. Causal inferences are uncertain and the chicken and egg dilemma remains in cross-sectional studies, including those of the BMD-DD relation. Adams’ and Dolan’s view that ‘‘in middle age, dense vertebral bone may promote disc degeneration’’ is one possible explanation for the association observed between vertebral body BMD and DD, but there are others. We did not suggest and do not agree with the view that vertebral BMD is likely to interfere withmetabolite transport through the vertebral endplate, because we did not observe an association between endplate BMD and DD in a previous study. On the other hand, we agree with Adams and colleagues that severe disc narrowing may shift more mechanical loading posteriorly to the facet joints and thus, stress-shield the anterior vertebral body. As for the measurement of disc degeneration, disc space narrowing was not selected because it is a nonspecific DD indicator and cannot reflect early DD. Furthermore, disc height measurements are prone to bias by osteophytes and endplate sclerosis, which likely are confounders of the BMD-DD association. Therefore, we used discography, which can display ‘‘successive stages in disc degeneration,’’ as a superior measure to disc space narrowing. As we have discussed in detail, although it is possible that DD is influenced by altered mechanical loading due to BMD changes, it is also possible that elevated BMD is an adaption of the vertebral bone to the changing mechanical environment related to DD. Therefore, we agree with Adams’ and Dolan’s view that ‘‘interactions between vertebrae and their adjacent discs cannot be summarized simply.’’ REPLY JBMR

Cervical spine bone mineral density as a function of vertebral level and anatomic location

Background context Bone mineral density (BMD) measurements acquired from quantitative computed tomography scans have been shown to correlate with bone mechanical properties such as strength, stiffness, and yield load. There are currently no reports of BMD as a function of anatomic location within each vertebra. Purpose The overall objective of this study was to characterize BMD in the cervical spine as a function of level and anatomic location. Study design Cervical spine BMD was evaluated in vivo using a clinically relevant age group. Patient sample Twenty-two subjects (13 women and 9 men) were included with an average age of 48±7 years (range, 35–61 years). Ten subjects were recently diagnosed with cervical radiculopathy (age 49±8 years; six women and four men; and two smokers and eight nonsmokers), and 12 subjects were asymptomatic controls (age 46±6 years; seven women and five men; and three smokers, three quit smoking, and six nonsmokers). Outcome measures Physiologic measures included overall BMD for C3–C7, average BMD within 11 anatomically defined regions of interest for each vertebra, and density distribution (by volume) within each anatomic region and vertebral level. Methods Subject-specific three-dimensional bone models were created from high-resolution computed tomography scans of the subaxial cervical spine (C3–C7). Custom software calculated the average BMD within 11 anatomically defined regions of interest for each three-dimensional bone model. Bone mineral density values for each voxel of bone tissue were binned into 50 mg/cc ranges to determine the density distribution by volume. Repeated-measures analysis of variance was used to test for differences within subjects by level (C3–C7) and anatomic location. The correlation between BMD in the central vertebral body and the pedicle and lateral mass regions was tested using Pearson correlation. Results Average BMDs by level were 476, 503, 507, 473, and 414 mg/cm 3 for C3–C7, respectively. C3 and C6 BMDs were significantly less than those of C4 and C5 (p<.007). C7 BMD was significantly less than those of all other levels (all p<.001). Control and female subjects showed a trend toward higher BMD than radiculopathy and male subjects across all levels (p value: .06–.17). Wide variation in BMD was observed over anatomical regions, with the pedicles having significantly higher BMD than all other anatomic locations and the anterior portion of the central vertebral body having significantly lower BMD than all other anatomic locations. There was a significant positive correlation between central vertebral body BMD and lateral mass BMD at each level. Bone mineral density distribution by volume plots revealed women had a higher volume of very high-density bone than men but only in the posterior elements. Conclusions This study has characterized BMD in the cervical spine according to vertebral level and anatomic location within each vertebral level using live subjects from a clinically relevant age group. The results indicate significant differences in BMD according to vertebral level and among anatomical regions within each vertebra. The results suggest to the surgeon and device manufacturer that surgical procedures involving instrumentation attached to C7 may require a modification in instrumentation or in surgical technique to attain results equivalent to more superior levels. The results suggest to the basic scientist that computational models may be improved by taking into account the wide variation in BMD over different anatomical regions.

The Use of Flat Panel Volumetric Computed Tomography (fpVCT) in Osteoporosis Research

Improvements in imaging technology have led to the increased use of computed tomography (CT). For example, micro-CT and quantitative CT (QCT) are now often used in osteoporosis research, in which micro-CT is able to analyze small bones or bone samples with high spatial resolution. In contrast, QCT is able to investigate large samples with low spatial resolution. The aim of this study was to test the usefulness of flat-panel volumetric CT (fpVCT) in a rat model of osteopenia. Twenty-two 3-month-old rats underwent ovariectomy and were either left untreated or supplemented with estradiol for 15 weeks. After sacrificing, the rats' second lumbar vertebral body bone mineral density (BMD) was analyzed using fpVCT and ashing. The results were compared to those of a microstructural analysis of the first lumbar vertebrae and a biomechanical evaluation of the fourth lumbar vertebrae. BMD measurements using both fpVCT (0.39 vs 0.35 mg/cm(3)) and ashing (0.52 vs 0.48 mg/cm(3)) demonstrated a significant improvement after estradiol supplementation. The correlation coefficient of the two methods was 0.858. After estradiol supplementation, the bone microstructural and bone biomechanical parameters were improved, compared to no treatment. The correlations of both the microstructural and the biomechanical evaluations were closer for BMD measured using fpVCT (r = 0.482-0.769) than on the basis of ashing (r = 0.345-0.573). FpVCT was not able to display the trabecular microstructure of the rat lumbar vertebrae. The use of fpVCT demonstrated a close relationship between morphologic and biomechanical evaluations in a rat model of osteopenia. Because of its different proportions, fpVCT might be able to bridge the gap between micro-CT and QCT in analyzing larger animals.

The role of spinal concave–convex biases in the progression of idiopathic scoliosis

Inadequate understanding of risk factors involved in the progression of idiopathic scoliosis restrains initial treatment to observation until the deformity shows signs of significant aggravation. The purpose of this analysis is to explore whether the concave-convex biases associated with scoliosis (local degeneration of the intervertebral discs, nucleus migration, and local increase in trabecular bone-mineral density of vertebral bodies) may be identified as progressive risk factors. Finite element models of a 26 degrees right thoracic scoliotic spine were constructed based on experimental and clinical observations that included growth dynamics governed by mechanical stimulus. Stress distribution over the vertebral growth plates, progression of Cobb angles, and vertebral wedging were explored in models with and without the biases of concave-convex properties. The inclusion of the bias of concave-convex properties within the model both augmented the asymmetrical loading of the vertebral growth plates by up to 37% and further amplified the progression of Cobb angles and vertebral wedging by as much as 5.9 degrees and 0.8 degrees, respectively. Concave-convex biases are factors that influence the progression of scoliotic curves. Quantifying these parameters in a patient with scoliosis may further provide a better clinical assessment of the risk of progression.

In vivo BMP-7 (OP-1) enhancement of osteoporotic vertebral bodies in an ovine model

Background context Prevention of osteoporotic vertebral fractures could help at-risk individuals avoid the pain and morbidity associated with these fractures. Currently, patients with osteoporosis are treated with systemic medications to reduce fracture risk. Although effective, these therapies do not eliminate fractures and also tend to have a gradual time-dependent effect on fracture risk. The mechanism of action of the bone morphogenetic protein (BMP) family theoretically makes these molecules candidates for rapidly enhancing local bone structure. Study design An in vivo study analyzing the effects of BMP-7 (osteogenic protein 1 [OP-1]) treatment on osteopenic ovine vertebral architecture and biomechanics. Purpose We tested the hypothesis that local injection of OP-1 into osteopenic ovine vertebrae will improve bone mass and trabecular distribution, thereby reducing bone fragility and fracture risk. We specifically evaluated compressive biomechanics and morphology of osteopenic ovine vertebral bodies 6 months after local OP-1 treatment. Study design In vivo animal study. Methods Skeletally mature sheep (n=24) underwent ovariectomy and were placed on low cation relative to anion diet. These interventions reduce bone density and induce skeletal fragility. After 6 months, sheep were randomly assigned to six treatment groups based on OP-1 dose (370 mg or 0 mg) and carrier with 4 animals/treatment group. Carriers A and B were poly- l-glycolic acid (PLGA) biospheres with different release kinetics (B allowing sustained BMP release); Carrier C was carboxymethylcellulose. After creating an 8-mm-diameter defect in the midvertebral body, sheep underwent intravertebral body implantation at two nonadjacent levels. Animals were euthanized 6 months after implantation and bone mineral density (BMD), biomechanics, and histomorphometry were assessed. Two-way analysis of variance was used to determine effects of OP-1 (α=0.05). Results An 81.9%, 333.2%, and 39.9% increase in stiffness was seen for OP-1 treated vertebra with Carriers A, B, and C respectively. Although these effects did not reach statistical significance, trends toward improvement were evident. Histology showed varied degrees of bony healing in the injection sites. Histomorphometrically, OP-1 treated vertebrae showed improvements in percent bone of up to 38% and star volume of up to 55% (with Carrier B). Improvements in whole vertebral body BMD were not detected for any treatment. Conclusion In this study, local OP-1 treatment showed a positive trend in improving mechanical strength and histomorphometric parameters of osteopenic vertebra, despite the absence of consistent change in BMD. Controlled slow release of OP-1 using PLGA microspheres appeared to be the most effective method of protein delivery. In conclusion, we feel that the pilot data suggest that the use of OP-1 in the treatment of vertebral osteoporosis in an attempt to enhance bone strength merits further study.

A Prospective Cohort Analysis of Adjacent Vertebral Body Bone Mineral Density in Lumbar Surgery Patients With or Without Instrumented Posterolateral Fusion

A prospective, cohort study of 11 patients who underwent either a posterior lumbar spinal fusion with instrumentation (n = 7) or a lumbar laminotomy and discectomy alone (n = 4) and who were evaluated by dual energy radiograph absorptiometry (DEXA) to determine bone mineral density (BMD) at the adjacent three cephalad vertebral levels. To determine long-term BMD changes that occur at the adjacent three levels above an instrumented posterolateral lumbar fusion or an isolated laminotomy and lumbar discectomy. No long-term prospective study has evaluated the affects of instrumented lumbar fusions on bone remodeling at adjacent vertebral levels. Several studies in animals and humans have reported a decrease in BMD at the adjacent level during the first 6 months after spinal fusion with a return to baseline at 1-year follow-up in up to 60% of patients. DEXA was performed initially at a mean postoperative follow-up of 4 years (range, 2.3-5.5 years) and again at a mean of 10.8 years (range, 9.1-2.4 years). Eleven patients were divided into two groups: laminotomy and discectomy (n = 4) and instrumented posterior spinal fusion (n = 7). All patients underwent surgical procedures at the L4-L5 or L5-S1 levels with DEXA analysis being performed on the adjacent three cephalad levels. The discectomy group (mean age, 57.8 years) underwent lumbar hemilaminotomy without fusion whereas the other group (mean age, 60 years) underwent pedicle-screw instrumentation and posterolateral lumbar fusion. Peripheral sites, including the femoral neck, were included in the DEXA analysis to normalize for individual differences in bone mineral metabolism. At the mean 10.8-year follow-up, the fusion group was noted to have at the adjacent level, two levels cephalad, and three levels cephalad normalized BMDs of 1.47, 1.39, and 1.27, respectively. A 14.8%, 10.8%, and 9.5% increase respectively in normalized BMD was observed when compared with the mean 4-year fusion values (P < 0.05). This increase was also noted on comparative T-score, Z-score, and absolute BMD values (P < 0.05). The discectomy group when evaluated revealed no statistically significant change from the mean 4 to 10.8-year follow-up (BMD, normalized BMD, T-score, Z-score). No statistically significant difference was noted in hip BMD at the mean 4-year and 10.8-year follow-up (1.05 versus 1.03), suggesting that the effects were local. The local BMD adjacent to an instrumented lumbar fusion is increased at a mean of 10.8-years after surgery. There is a gradual decrease in BMD changes with increasing distance from the fusion level. Alterations in fusion site biomechanics and modulus mismatch between the host bone and the spinal instrumentation most likely result in chronic, localized bone remodeling with an increased BMD that decreases the greater the distance from the fusion mass.

12:06 25. A prospective cohort analysis of adjacent vertebral body bone mineral density in lumbar surgery patients with or without instrumented posterolateral fusion: a 9 to 12 year follow-up

12:06 25. A prospective cohort analysis of adjacent vertebral body bone mineral density in lumbar surgery patients with or without instrumented posterolateral fusion: a 9 to 12 year follow-up

Maintenance of vertebral body bone mass and strength created by human parathyroid hormone treatment in ovariectomized rats

The purpose of this cross-sectional study was to evaluate the effects of human parathyroid hormone (1–84) (hPTH) followed by maintenance administration of 17β-estradiol (E 2), risedronate (Ris), or a reduced dose of hPTH (LowPTH) on vertebral body bone mineral density (BMD) and bone strength in ovariectomized (ovx) rats. Eight groups of ovx (219 rats) and one group of intact female rats (48 rats) were left untreated for 11 weeks (age 3.5 months at the beginning). For the following 12 weeks, four ovx groups received subcutaneous injections of hPTH (75 μg/kg per day, 3 days/week) and four groups received vehicle. Treatments were then changed to: E 2 (10 μg/kg per day, 2 days/week); Ris (3 μg/kg per day, 3 days/week); LowPTH (25 μg/kg per day, 3 days/week); or vehicle for 36 weeks. Bone tissue was collected at weeks −11 (baseline), 0 (ovx effect), 12 (hPTH effect), 24, 36, and 48 (maintenance effect). The endpoints were vertebral body BMD, ultimate stress (Ultstr), and moduli of elasticity from compression tests (ModM), and from ultrasound tests (ModUS). Ovariectomy resulted in lower BMD ( p < 0.001). The hPTH treatment for 12 weeks restored BMD to the level of intact rats. Ultstr and ModUS followed a similar pattern, but the ovx-induced Ultstr was not significant ( p = 0.073, ModUS: p = 0.003), nor was the hPTH-induced increase in ModUS ( p = 0.131, Ultstr: p = 0.02). After hPTH withdrawal, BMD, Ultstr, and ModUS levels were not different from levels in ovx animals. In Ris-treated rats pretreated with hPTH, BMD (weeks 24 and 48, p < 0.002) and ModUS (week 24, p = 0.018) values were greater than in ovx animals. In LowPTH-treated rats pretreated with hPTH, BMD (weeks 24 and 48, p < 0.001) and Ultstr (week 48, p = 0.005) were greater than in ovx animals. In E 2-treated rats pretreated with hPTH, BMD was greater than in ovx rats at week 24 ( p = 0.009), but did not differ at weeks 36–48. Neither Ultstr nor ModUS in E 2-treated rats differed significantly from ovx rats at any timepoint. Of the agents and dosing regimens used, we conclude that the hPTH-related vertebral bone mass gain in ovx rats can be maintained for up to 36 weeks with risedronate and low-dose hPTH treatment. Bone strength is maintained by treatment with low-dose hPTH, but only partially maintained with risedronate.

Determination of bone mineral density in the third lumbar vertebral body using photon absorptiometry techniques

Dual-photon absorptiometry and triple-energy X-ray absorptiometry were used to investigate the total bone mineral content and density as well as the trabecular bone mineral density in the third lumbar vertebral body. Both anteroposterior (AP) and lateral (LAT) measurements were performed. By combining the two projections it was found that the mean trabecular bone mineral density for all 202 subjects included in the study was 52% (SD±20%) of the total bone mineral density in the third lumbar vertebral body. The mean trabecular bone mineral density as a fraction of the total vertebral body bone mineral density decreased as a function of age. The relative annual change in this fraction differed between males and females. It was also found that neither trabecular nor total bone mineral density differed significantly between male and female subjects aged 25–35 years, and bone mineral density (BMD), expressed in g/cm 3, showed no correlation to subject height, body weight or body mass index (BMI). Male and female individuals showed different rates of change of trabecular bone mineral density with age.