Ultrastructural analysis of different skeletal cell types in mucopolysaccharidosis dogs at the onset of postnatal growth.

The mucopolysaccharidoses (MPS) are a family of lysosomal storage disorders characterized by deficient activity of enzymes that degrade glycosaminoglycans (GAGs). Abnormal development of the vertebrae and long bones is a hallmark of skeletal disease in several MPS subtypes; however, the underlying cellular mechanisms remain poorly understood. The objective of this study was to conduct an ultrastructural examination of how lysosomal storage differentially affects major skeletal cell types in MPS I and VII using naturally occurring canine disease models. We showed that both bone and cartilage cells from MPS I and VII dog vertebrae exhibit significantly elevated storage from early in postnatal life, with storage generally greater in MPS VII than MPS I. Storage was most striking for vertebral osteocytes, occupying more than forty percent of cell area. Secondary to storage, dilation of the rough endoplasmic reticulum (ER), a marker of ER stress, was observed most markedly in MPS I epiphyseal chondrocytes. Significantly elevated immunostaining of light chain 3B (LC3B) in MPS VII epiphyseal chondrocytes suggested impaired autophagy, while significantly elevated apoptotic cell death in both MPS I and VII chondrocytes was also evident. The results of this study provide insights into how lysosomal storage differentially effects major skeletal cell types in MPS I and VII, and suggests a potential relationship between storage, ER stress, autophagy, and cell death in the pathogenesis of MPS skeletal defects.

The effect of intravertebral heterogeneity in microstructure on vertebral strength and failure patterns.

UNLABELLED: The goal of this study was to determine the influence of intravertebral heterogeneity in microstructure on vertebral failure. Results show that noninvasive assessments of the intravertebral heterogeneity in density improve predictions of vertebral strength and that local variations in microstructure are associated with locations of failure in the vertebral body. INTRODUCTION: The overall goal of this study was to determine the influence of intravertebral heterogeneity in microstructure on vertebral failure. METHODS: Trabecular density and microarchitecture were quantified for 32 thoracic vertebrae using micro-computed tomography (µCT)-based analyses of 4.81 mm, contiguous cubes throughout the centrum. Intravertebral heterogeneity in density was defined as the interquartile range and quartile coefficient of variation of the cube densities. The vertebrae were compressed to failure to measure stiffness, strength, and toughness. Pre- and post-compression µCT images were analyzed using digital volume correlation to quantify failure patterns in the vertebrae, as defined by the distributions of residual strain. RESULTS: Failure patterns consisted of large deformations in the midtransverse plane with concomitant endplate biconcavity and were linked to the intravertebral distribution of bone tissue. Low values of connectivity density and trabecular number, and high values of trabecular separation, were associated with high strains. However, local microstructural properties were not the sole determinants of failure. For instance, the midtransverse plane experienced the highest strain (p < 0.008) yet had the highest density, lowest structure model index, and lowest anisotropy (p < 0.013). Accounting for the intravertebral heterogeneity in density improved predictions of strength and stiffness as compared to predictions based only on mean density (strength: R(2) = 0.75 vs. 0.61, p < 0.001; stiffness: R(2) = 0.44 vs. 0.26, p = 0.001). CONCLUSIONS: Local variations in microstructure are associated with failure patterns in the vertebra. Noninvasive assessments of the intravertebral heterogeneity in density--which are feasible in clinical settings--can improve predictions of vertebral strength and stiffness.

Micro-computed tomography study of the subchondral bone of the vertebral endplates in a porcine model: correlations with histomorphometric parameters.

PURPOSE: Subchondral bone (SCB) of the vertebral endplates (VEP) is the principal site of changes in vertebral trabecular microarchitecture secondary to intervertebral disc degeneration. However, the microstructure of this region has not yet been clearly characterized. METHODS: One thoracic and one lumbar vertebral unit (vertebra-disc-vertebra) was removed in nine pigs aged 4 months. Three samples (one central and two laterals) were taken from each VEP. Micro-CT examination and histomorphometric measurements of the subchondral trabecular bone of the VEP were carried out. Correlations between micro-CT and histological parameters were sought. RESULTS: Trabecular network was significantly denser [increased bone volume fraction (BV/TV) and trabecular number (Tb.N), decreased intertrabecular separation (Tb.Sp)] in the cranial endplates of the vertebral units. It was also significantly denser and less well organized [increased degree of anisotropy (DA)] in the centre of the VEP. The thickness of the cartilage endplate (CEP), SCB and growth cartilage were significantly lower in the centre of the VEP. There was a significant negative correlation between BV/TV, Tb.N and DA with the thicknesses of the CEP and SCB whereas Tb.Sp was positively correlated with these two parameters. CONCLUSION: We observed densification of the trabecular network in the centre of the VEP overlying the nucleus pulposus, partly related to thinner hyaline cartilage. Densification is associated with more anisotropic architecture that could cause lower mechanical strength in this area. This study provides new information on the microarchitecture of the SCB of the VEP which will make it possible to validate future models.

Manganese enhanced magnetic resonance imaging in a contusion model of spinal cord injury in rats: correlation with motor function.

OBJECTIVES: Various models of spinal cord injury in rodents have been established, and also techniques for lesion quantification. Measurement of the extent of the underlying injury is essential for monitoring the reproducibility of the experimental injury and assessment of therapeutic effects. In this study, we tested manganese-enhanced magnetic resonance imaging (MEMRI) for postmortem quantification of experimental spinal cord injury in rats. MATERIALS AND METHODS: Twelve rats were subjected to contusion injuries at the 11th thoracic vertebra, followed by MnCl2 injections into the cisterna magna. After 3 days of observation, postmortem MEMRI-features were correlated with values of locomotion testing and histology. RESULTS: MnCl2 yielded a strong contrast enhancement of the uninjured spinal cord, whereas no enhancement was observed at the injury site or caudally. Magnetic resonance imaging findings correlate closely with locomotor ratings. CONCLUSIONS: MEMRI represents a reliable method for visualization and functional assessment of spinal cord integrity in rats.

Regional trabecular morphology assessed by micro-CT is correlated with failure of aged thoracic vertebrae under a posteroanterior load and may determine the site of fracture.

INTRODUCTION: Spinal mobilization is commonly used in the treatment of patients with back pain, including individuals with osteoporosis. Previous data indicated that traditional predictors of skeletal failure-lateral or anteroposterior bone mineral density (BMD) by dual energy X-ray absorptiometry (DXA) or geometry of the spinous process or vertebral body-do not predict failure load during posteroanterior spinal mobilization. Morphological differences and inhomogeneities in BMD may have important effects on vertebral strength but integral BMD values by DXA cannot reflect these potentially important differences. We investigated the determinants of spinal fracture using muCT. MATERIALS AND METHODS: We measured failure load and failure site in 11 T5-8 cadaveric specimens (mean age 78 years) when a posteroanterior load was applied at the spinous process of T6 using a servohydraulic material testing machine. Radiography and CT scan were used to verify failure site. We observed no damage to the adjacent T7 vertebrae following the T6 posteroanterior failure test. The T7 vertebrae were sectioned to produce regional samples of the spinous process, the lamina and a vertebral body core. Each sample was scanned with muCT to measure bone microarchitectural parameters. We segmented and analysed four trabecular regions (spinous process base and middle, central lamina and central vertebral body). We used one-way repeated measures ANOVA to compare regions and computed Pearson correlations to assess the relation between PA failure load of T6 and the morphological parameters of T7. RESULTS: The BV/TV at the base or middle of the T7 spinous process (fracture sites), Tb.N and Tb.Th at the base were significantly correlated with posteroanterior failure load of T6 (BV/TV base: r=0.74, p=0.01; BV/TV middle: r=0.73, p=0.01; Tb.N base: r=0.64, p=0.03; Tb.Th base: r=0.65, p=0.03). The Tb.Th of the lamina was significantly greater than Tb.Th of the spinous process base (p=0.002). CONCLUSIONS: Whereas previous data indicated that BMD by DXA was not a good predictor of posteroanterior failure load, regional BV/TV of the spinous process base and middle regions, the sites of fracture, are correlated with posteroanterior failure load. Trabecular thickness differed significantly between the base of the spinous process and the lamina, and may have influenced the site of fracture.

Scanning and transmission electron microscopy for evaluation of order/disorder in bone structure.

A comparative characterization of the structure of normal and abnormal (osteoporotic) human lumbar and thoracic vertebrae samples was carried out to reveal the type of possible disorder. Samples from the bone fragments extracted during the surgery due to vertebra fractures were examined by scanning electron microscopy (SEM), conventional and high resolution transmission electron microscopy (TEM and HRTEM), and X-ray energy dispersive spectroscopy (EDS). Contrary to what might be expected in accordance with possible processes of dissolution, formation and remineralization of hard tissues, no changes in phase composition of mineral part, crystal sizes (length, width, and thickness), and arrangement of crystals on collagen fibers were detected in abnormal bones compared to the normal ones. The following sizes were determined by HRTEM for all bone samples:

Cortical and trabecular load sharing in the human vertebral body.

UNLABELLED: The biomechanical role of the vertebral cortical shell remains poorly understood. Using high-resolution finite element modeling of a cohort of elderly vertebrae, we found that the biomechanical role of the shell can be substantial and that the load sharing between the cortical and trabecular bone is complex. As a result, a more integrative measure of the trabecular and cortical bone should improve noninvasive assessment of fracture risk and treatments. INTRODUCTION: A fundamental but poorly understood issue in the assessment of both osteoporotic vertebral fracture risk and effects of treatment is the role of the trabecular bone and cortical shell in the load-carrying capacity of the vertebral body. MATERIALS AND METHODS: High-resolution microCT-based finite element models were developed for 13 elderly human vertebrae (age range: 54-87 years; 74.6 +/- 9.4 years), and parameter studies-with and without endplates-were performed to determine the role of the shell versus trabecular bone and the effect of model assumptions. RESULTS: Across vertebrae, whereas the average thickness of the cortical shell was only 0.38 +/- 0.06 mm, the shell mass fraction (shell mass/total bone mass)-not including the endplates-ranged from 0.21 to 0.39. The maximum load fraction taken by the shell varied from 0.38 to 0.54 across vertebrae and occurred at the narrowest section. The maximum load fraction taken by the trabecular bone varied from 0.76 to 0.89 across vertebrae and occurred near the endplates. Neither the maximum shell load fraction nor the maximum trabecular load fraction depended on any of the densitometric or morphologic properties of the vertebra, indicating the complex nature of the load sharing mechanism. The variation of the shell load-carrying capacity across vertebrae was significantly altered by the removal of endplates, although these models captured the overall trend within a vertebra. CONCLUSIONS: The biomechanical role of the thin cortical shell in the vertebral body can be substantial, being about 45% at the midtransverse section but as low as 15% close to the endplates. As a result of the complexity of load sharing, sampling of only midsection trabecular bone as a strength surrogate misses important biomechanical information. A more integrative approach that combines the structural role of both cortical and trabecular bone should improve noninvasive assessment of vertebral bone strength in vivo.

Vertebral cancellous bone turn-over: microcallus and bridges in backscatter electron microscopy.

Backscatter electron microscopy (BSE) is a powerful technique for investigating cancellous bone structure. Its main function is to offer information regarding the degree of mineralization of the tissue within individual trabeculae. To illustrate the qualitative information that can be drawn from BSE imaging technique, we present a study on human vertebral cancellous bone. This tissue is continuously remodeled through osteoclastic resorption and osteoblastic new bone apposition. It is thought that osteoclastic resorption pits are especially deleterious for vertebral bone architecture since they often perforate the thin trabeculae; the osteoblasts being unable to repair the gap. In addition, excessive stress may also disrupt the architecture in case of trabecular fracture or damage accumulation. Waves of new bone formation were easy to identify in BSE. Often these waves were connecting both edges of a perforation and called bridges. Additionally, we present a few images of microcallus formations. A microcallus is described as a small mass of woven bone that generally repairs a trabecula. The microstructural aspects of different microcalluses are presented and discussed. Both bridges and microcallus should be considered as examples of the repair porcess since they obviously preserve the connectivity of the trabeculae. However, bridges were much more frequent than microcallus (396 vs 15). Both mechanisms probably illustrate the normal response to different local stimuli.

Insight into bone-derived biological apatite: ultrastructure and effect of thermal treatment.

OBJECTIVES: This study aims at examining the ultrastructure of bone-derived biological apatite (BAp) from a series of small vertebrates and the effect of thermal treatment on its physiochemical properties. MATERIALS AND METHODS: Femurs/fin rays and vertebral bodies of 5 kinds of small vertebrates were firstly analyzed with X-ray microtomography. Subsequently, BAp was obtained with thermal treatment and low power plasma ashing, respectively. The properties of BAp, including morphology, functional groups, and crystal characteristics were then analyzed. RESULTS: The bones of grouper and hairtail were mainly composed of condensed bone. Spongy bone showed different distribution in the bones from frog, rat, and pigeon. No significant difference was found in bone mineral density of condensed bone and trabecular thickness of spongy bone. Only platelet-like crystals were observed for BAp obtained by plasma ashing, while rod-like and irregular crystals were both harvested from the bones treated by sintering. A much higher degree of crystallinity and larger crystal size but a lower content of carbonate were detected in the latter. CONCLUSION: Platelet-like BAp is the common inorganic component of vertebrate bones. BAp distributing in condensed and spongy bone may exhibit differing thermal reactivity. Thermal treatment may alter BAp's in vivo structure and composition.

Irreversible perforations in vertebral trabeculae?

UNLABELLED: In human cancellous bone, osteoclastic perforations resulting from normal remodeling were generally considered irreversible. In human vertebral samples, examined by backscatter electron microscopy, there was clear evidence of bridging of perforation defects by new bone formation. Hence trabecular perforations may not be irreversible. INTRODUCTION: Preservation of the trabecular bone microarchitecture is essential to maintain its load-bearing capacity and prevent fractures. However, during bone remodeling, the osteoclasts may perforate the platelike trabeculae and disconnect the structure. Large perforations (>100 microm) are generally considered irreversible because there is no surface on which new bone can be laid down. In this work, we investigated the outcome of these perforations on human vertebral cancellous bone. MATERIALS AND METHODS: Using backscatter electron microscopy, we analyzed 264 vertebral bone samples from the thoracic and lumbar spine of nine subjects (44-88 years old). Nine fields (2 x 1.5 mm) were observed on each block. Several bone structural units (BSUs) were visible on a single trabecula, illustrating a dynamic, historical aspect of bone remodeling. A bridge was defined as a single and recent BSU connecting two segments of trabeculae previously separated by osteoclastic resorption. They were counted and measured (length and breadth, microm). RESULTS AND CONCLUSION: We observed 396 bridges over 2376 images. By comparison, we found only 15 microcalluses on the same material. The median length of the bridge was 165 microm (range, 29-869 microm); 86% being longer than 100 microm and 35% longer than 200 microm. Their breadth was 56 microm (range, 6-255 microm), but the thinnest were still in construction. Bridges were found in all nine subjects included in the study, suggesting that it is a common feature of normal vertebral bone remodeling. These observations support the hypothesis that perforation could be repaired by new bone formation, and hence, might not be systematically irreversible.

Intervertebral variation in trabecular microarchitecture throughout the normal spine in relation to age.

The vertebral bodies of the complete spine (C-3-L-5) were removed in 26 autopsy cases without evidence for primary or secondary bone disease (13 males aged 19-79 years and 13 females aged 17-90 years). A sagittal segment through the center of all vertebral bodies was embedded undecalcified in hydroxyethylmethacrylate and processed to so-called surface stained block grindings. Histomorphometric analysis of the complete segment was performed using a computer-assisted image analysis system (IBAS 2000). The structural parameters investigated were bone volume (BV/TV) and trabecular interconnection quantificated by trabecular bone pattern factor (TBPf). A close correlation of BV/TV and TBPf was found in all vertebral bodies irrespective of vertebral region (r = 0.8, p < 0.001). This indicates that the age-related decrease of trabecular bone mass is primarily the consequence of the transformation from plates to rods and the loss of whole trabecular structures. This basic principle is valid throughout the complete spine. However, the systematic analysis of vertebral trabecular bone from C-3 to L-5 revealed a significant intervertebral variation of trabecular microarchitecture. The density of trabecular structure of cervical vertebrae is much higher than that of thoracic and lumbar vertebrae (p < 0.001). The extent of age-related loss of trabecular bone mass and structure showed a decrease within the spine from the caudal to the cranial region (p < 0.05). The loss of bone volume in individuals between the ages of 30 and 80 years in the lumbar spine was 53%, whereas in the thoracic spine the decrease was 41%, and in the cervical spine only 24%.(ABSTRACT TRUNCATED AT 250 WORDS)

Fibroxanthosarcoma of bone.

A tumour arising from the body of the eighth thoracic vertebra is believed to be the first recordedexample of a primary fibroxanthosarcoma of bone. Apart from the absence of a demonstrable storiform pattern, the histology conformed to that of fibroxanthosarcoma of the soft tissues. Ultrastructural studies showed that asteroid-like bodies seen in the cytoplasm of some tumour cells consisted of aggregated centrioles surrounded by cytoplasmic vacuoles. The finding of Langerhans cell granules in some tumour cells supported their identification as histiocytes. These granules have not previously been recorded in the fibrous histiocytoma group of tumours.

Projection of the thoracic pedicle and its morphometric analysis.

STUDY DESIGN: This study defined the projection point of the thoracic pedicles on their posterior aspect and its relation to a reliable landmark. It also reported pedicle dimensions based on 43 thoracic spines. OBJECTIVES: To determine the projection point of the pedicle axis on the posterior aspect of the thoracic spine, quantitatively describe relations of the projection point to some reliable landmarks, and evaluate linear and angular dimensions of the thoracic pedicle. SUMMARY OF BACKGROUND DATA: Posterior segmental screw fixation is the current standard of internal fixation at the level of the second lumbar vertebrae or below. However, pedicular screw fixation in the thoracic spine, especially in the middle and upper thoracic region, is not common because the small dimensions of the pedicle in this region make screw insertion difficult. More information about pedicle axis projection (not pedicle zone) and its quantitative relationship to some reliable landmarks is essential. METHODS: Forty-three dry thoracic specimens (516 vertebrae) were obtained for study of the thoracic pedicle. Anatomic evaluation focused on the determination of the projection point of the thoracic pedicle axis on its posterior aspect and the anatomic relationship of this point to the lateral edge of superior facet and the midline of the transverse process. Also, pedicle dimensions, including linear and angular, were measured. The mean, range, and standard deviation were calculated for all of the specimens and for male and female specimens separately. RESULTS: Sexual difference was found to be significant statistically in more than half of parameters. For T1-T2, the projection point of the pedicle axis was approximately 7-8 mm medial to the lateral edge of the superior facet and 3-4 mm superior to the midline of the transverse process. For T3-T12, this point was 4-5 mm medial to the lateral margin of the facet and 5-8 mm superior to the midline of the transverse process. The transverse angle of the pedicle axis was found to be 30-40 degrees at T1-T2, 20-25 degrees at T3-T11, and 10 degrees at T12. CONCLUSIONS: This information, in conjunction with preoperative computed tomography evaluation, may enhance our knowledge of transpedicular screw fixation in the thoracic pedicle.

Anatomic relationships of the cervicothoracic junction.

STUDY DESIGN: This study analyzed the anatomic relationships between bony structures and soft tissues of the cervicothoracic junction. OBJECTIVES: To provide composite reference data for intrasegmental and intersegmental gradients of anatomic variation within the cervical-thoracic junction. SUMMARY OF BACKGROUND DATA: Because the risk of soft tissue damage during posterior spinal stabilization, an understanding of bony and soft tissue changes in the cervicothoracic junction is necessary. METHODS: Three-hundred-twenty-four cross-sectional spinal segments from nine spines were analyzed to characterize cervicothoracic junctional anatomy. RESULTS: There were predictable cranial-to-caudal alterations in both bone and soft tissue anatomy of the cervicothoracic junction. Neural and vascular structures directly anterior to the lateral mass or transverse process and lateral to the pedicle tend to decrease in frequency, whereas measured parameters of the vertebrae increase in size from C5-T3, except for pedicle dimensions that tend to increase at the C7-T1 junction. CONCLUSION: The anatomic changes that occur within the cervicothoracic junction are consistent and predictable, and their recognition should lead to a better appreciation of their clinical implications.

A synthetic porous ceramic as a bone graft substitute in the surgical management of scoliosis: a prospective, randomized study.

STUDY DESIGN: A prospective randomized study. OBJECTIVES: To assess the clinical and radiologic performances of a synthetic ceramic as a bone graft substitute in scoliosis surgery. SUMMARY OF BACKGROUND DATA: Surgery on the skeleton frequently requires harvesting of autogenous bone grafts from the pelvis, but this procedure often is complicated by problems. METHODS: Fifty-eight patients with idiopathic scoliosis, ages 13 to 25 years, were treated by posterior correction and arthrodesis using Cotrel-Dubousset instrumentation. Posterior spinal fusion was performed using local bone grafts combined with autogenous iliac bone grafts in 30 patients, and combined with porous biphasic calcium phosphate ceramic blocks comprising hydroxyapatite and tricalcium phosphate in another 28 patients. The patients were observed for a minimum of 24 months after surgery, with a mean postoperative observation time of 48 months. The results were assessed clinically and radiographically. RESULTS: Patients in the ceramic group had a lower average blood loss than those in the iliac graft group. They also were free from postoperative local complications in the iliac region, which were experienced by a significantly high proportion of patients belonging to the iliac graft group. Radiography demonstrated successful incorporation of the ceramic blocks within 12 months. The correction of the deformity was maintained similarly and satisfactorily in both groups. CONCLUSIONS: These results justify and favor the use of calcium phosphate ceramics as bone graft substitutes for instrumented posterior spinal fusion in teenagers and young adults. Potentially hazardous harvesting of pelvic bone is no longer necessary for such operations.

Development of the spinous process of the second thoracic vertebra of the mouse in the late fetal and early postnatal period.

The bony spinous process of T2 in certain inbred strains of the mouse is variable in size or in some cases absent. The development of this process has been investigated in histological sections of CBA, C57BL and tk/tk mice between birth and 14 days. The spinous process is shown to be modified in shape and size late in development.

Morphological differences in adolescent idiopathic scoliosis: a histological and ultrastructural investigation.

STUDY DESIGN: Histological and ultrastructural evaluation of cell morphologies at the concave and convex side of apical intervertebral discs (IVD) of adolescent idiopathic scoliosis (AIS). OBJECTIVE: To determine changes in cell morphology, viability, and cell death after asymmetric disc loading in AIS and to compare the findings with the tilt angles. SUMMARY OF BACKGROUND DATA: The reaction of cells to loading stimuli in the IVD seems to be specific. Although dynamic loads are more beneficial to the disc cells and maintain the matrix biosynthesis, static compressive loads suppress gene expression. METHODS: Apical IVDs (Th8-Th9 to L1-L2) from 10 patients with AIS were studied histologically (including TUNEL [TdT-mediated dUTP-biotin nick end labeling] staining to identify disc cell death by apoptosis) and ultrastructurally for matrix evaluations and to quantify healthy, balloon, chondroptotic, apoptotic, and necrotic cells on the concave and convex sides. Patients' spines were classified according to the Lenke classification. Degeneration was assessed according to the Pfirrmann grading system. Two groups were established; group 1 (G1) with a tilt of 5° to 9° and group 2 (G2) with a tilt of 10° to 19°. RESULTS: Balloon cells were found in significantly higher numbers at the concave side (G1-annulus fibrosus [AF]: mean 16%), with almost none found at the convex side. Mean numbers of healthy cells did not show differences comparing both sides. Significantly higher numbers of healthy cells were found with increasing tilt angle at the concave side. Necrosis (mean, 47%) increased toward the center of the disc but did not differ between the sides of the IVDs. The fibrils found in the outer AF on the convex side were 30% thinner. CONCLUSION: This study was able to show significant differences in cell morphologies in the AF on both sides and in correlation to the different tilt angles. The type and magnitude of load seem to influence disc cells. Further studies are required to provide more information on disc and cell changes in scoliosis.

Spirocerca lupi-associated vertebral changes: a radiologic-pathologic study.

Spirocerca lupi causes a caudal esophageal mass in dogs which may be accompanied by aortic changes and caudal thoracic spondylitis. Previous literature hypothesized that the spondylitis was caused by either aberrant larval migration or was secondary to the inflammation caused by the aortic migration. The current study aimed to evaluate these hypotheses. Ten dogs of various breeds and ages with radiographic evidence of spondylitis, which were necropsied, had the affected vertebrae removed and prepared for light and transmission electron microscopy examination. Transverse and sagittal sections of the ventral vertebrae were taken from 27 spondylitis and 8 spondylosis deformans lesions as well as from 8 normal vertebrae. Early spondylitis changes were characterized by periosteal woven new bone covered by hyperplastic periosteum with some involvement of the ventral longitudinal ligament. More mature lesions were characterized by nodules of denser trabecular bone and cartilage, also covered by hyperplastic periosteum and involved the ventral longitudinal ligament. It was difficult to distinguish the spondylitis and spondylosis deformans new bone. Inflammation was seen in five spondylitis cases (edema, lymphocytes, plasma cells, eosinophils and fibrin fibers). Spirocerca eggs were seen in one histologic section. This study shows that inflammation is mild and inconsistent in spirocercosis-induced spondylitis and that aberrant migration of the larvae or adults did not appear to be a predominant cause. Inflammatory mediators or osteoproliferative growth factors, which may be related to the primary esophageal lesion or to the worm itself, could be involved. This requires further investigation.

Electron-microscopic imaging of endothoracic fascia in the thoracic paravertebral space in rats.

BACKGROUND AND OBJECTIVES: Anesthesia and analgesia with paravertebral block are reportedly variable. Existence of an endothoracic fascia has been proposed as one of the possible mechanisms leading to variability. We undertook an electron-microscopy imaging study to investigate the endothoracic fascia in the thoracic paravertebral space (TPS) in rats. METHODS: Male Wistar rats were studied in accordance with the principles of laboratory animal care. After the rats were euthanized in a CO2 chamber, the thoracic paravertebral tissues were removed en bloc and cut into consecutive transverse sections of approximately 3 mm. Stereomicroscopy and electron-microscopy assessments were performed by 2 independent observers. RESULTS: The endothoracic fascia was consistently identified in all specimens. The fascia was located between the parietal pleura and the innermost intercostal muscles or ribs. Its thickness ranged from 15 to 27 µm (mean, 20 ± 3 µm). The endothoracic fascia divided the TPS in 2 compartments: one, extrapleural and anterolateral (EPC); another, subendothoracic and posteromedial (SETC). The spinal nerves with their ganglia were found within SETC, whereas the sympathetic ganglia were consistently located within the EPC. CONCLUSIONS: The endothoracic fascia in rats appears to divide the TPS into EPC and SETC. These anatomic characteristics may have implications in thoracic paravertebral blockade.

What is the best way to optimize thoracic kyphosis correction? A micro-CT and biomechanical analysis of pedicle morphology and screw failure.

STUDY DESIGN: A human cadaveric biomechanical analysis. OBJECTIVE: The purpose of this study was to evaluate the bone density/trabecular width of the thoracic pedicle and correlate that with its resistance against compressive loading used during correction maneuvers in the thoracic spine (i.e., cantilever bending). SUMMARY OF BACKGROUND DATA: As surgeons perform cantilever correction maneuvers in the spine, it is common to have pedicle screws pullout or displace while placing corrective forces on the construct. Currently, surgeons either compress against the cephalad aspect of the pedicle or vice versa. We set out to establish which aspect of the pedicle was the most dense and to determine the optimal direction for screw compression during kyphosis/deformity correction. METHODS: Fifteen fresh-frozen cadaveric vertebrae (n = 15) were examined by micro-computed tomography to determine percent bone volume/total volume (%BV/TV) within the cephalad and caudad aspects of the pedicle. Specimens were sectioned in the sagittal plane. Pedicles were instrumented according to the straightforward trajectory on both sides. Specimens were then mounted and loading to failure was performed perpendicular to the screw axis (either the cephalad or the caudad aspect of the pedicle). RESULTS: Mean failure when loading against the caudad aspect of the pedicle was statistically, significantly greater (454.5 ± 241.3 N vs. 334.79 1 ± 158.435 N) than for the cephalad pedicle (P < 0.001). In concordance with failure data, more trabecular and cortical bones were observed within the caudad half of the pedicle compared with the cephalad half (P < 0.001). CONCLUSION: Our results suggest that the caudad half of the pedicle is denser and withstands higher forces compared with the cephalad aspect. In turn, the incidence of intraoperative screw loosening and/or pedicle fracture may be reduced if the compressive forces (cantilever bending during deformity correction) placed upon the construct are applied against the caudad portion of the pedicle.