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Segmentation gives rise to the anterior-posterior axis in many animals, and in vertebrates this axis comprises serially arranged vertebrae. Modifications to the vertebral column abound, and a recurring, but functionally understudied, change is the elongation of the body through the addition and/or elongation of vertebrae. Here, we compared the vertebral and axial kinematics of the robustly limbed Fire skink (Riopa fernandi) representing the ancestral form, the limbless European glass lizard (Ophisaurus apodus), and the Northern water snake (Nerodia sipedon). We induced these animals to traverse through channels and peg arrays of varied widths and densities, respectively, using high-speed X-ray and light video. We found that even though the snake had substantially more and shorter vertebrae than either lizard, intervertebral joint angles did not differ between species in most treatment levels. All three species decreased the amplitude and wavelength of their undulations as channels narrowed and the lizard species increased wave frequency in narrower channels. In peg arrays, both lizard species decreased wave amplitude, while the snake showed no differences. All three species maintained similar wavelengths and frequencies as peg density increased in most cases. Our results suggest that amplitude is decoupled from wavelength and frequency in all three focal taxa. The combination of musculoskeletal differences and the decoupling of axial kinematic traits likely facilitates the formation of different undulatory waves, thereby allowing limbless species to adopt different modes of locomotion.

Vertebral deformities can impair health, welfare, and product quality in farmed Atlantic salmon. Deformities detected early in the production cycle raise questions about their further development: which types of deformities will progress and which types of deformities will worsen over time? To study this, Atlantic salmon parr (start experimental feeding weight 13.5 g) were fed diets with low (6.8 g/kg), regular (10.0 g/kg), or high (13.0 g/kg) total dietary P for 11 weeks to provoke deformities. This was followed by long-term monitoring of deformity development up to harvest size (4.5 kg) through repeated radiology of individually tagged animals. Further insights were obtained by histological analyses, mineral analyses, and testing for mechanical properties of vertebral centra. Four categories of deformity development were defined: (1) recovery, (2) containment, (3) progression, and (4) late-onset. Deformities detected early, in freshwater, which affected the vertebral centra but not the intervertebral joints, could fully recover in seawater. These involved low-mineralised vertebrae, single vertically shifted vertebrae, hyper-dense vertebrae (HDV), and two or three adjacent vertebrae with compression-related deformities. HDV were provoked by low dietary P but disappeared in seawater. Fusions were either contained (two to three vertebrae) (stable vertebral fusions) or progressed (more than three vertebrae) (progressive vertebral fusions). Vertical shifts, fusions, and compressions could also have a late-onset in seawater but did not develop into severe deformities in harvest size animals. In conclusion, low-mineralised vertebrae and HDV are abundant in animals with LP diet history but can recover in seawater. The frequency of all other types of deformities was not significantly different among animals of different diet history groups. Under the current experimental conditions, a period of high or low dietary P in freshwater had no significant effect on the prevalence of early- or late-onset deformities at harvest.

Deficiency in dietary phosphorus (P) is considered as a nutritional risk factor for the development of vertebral column deformities in farmed Atlantic salmon Salmo salar, L. This mono-factorial study examines how 11-week deficiency and excess of dietary P influence the structure and microstructure of the vertebral bodies in juvenile, freshwater stages of Atlantic salmon. Animals were fed continuously with three diets containing different levels of total P (tP) and soluble P (sP), respectively: low P (LP) = 6.8 g/kg tP, 3.5 g/kg sP, regular P (RP) = 10.0 g/kg tP, 5.6 g/kg sP, and high P (HP) = 13.0 g/kg tP, 9.3 g/kg sP. Animals were analysed for plasma and bone mineral content, vertebral column deformities (x-ray), vertebral centra stiffness, bone mineralisation pattern and vertebral body micro anatomy (cells and connective tissue structures). A low (background) level of deformities was observed on a gross morphological level but no increase and no specific type of vertebral column deformity was associated with either of the three groups. While feed intake was comparable among all diet groups animals fed LP showed a 50% reduction in total calcium (Ca) and P content in abdominal vertebrae and opercula. Regular P and HP animals showed similar levels of total Ca and P in abdominal vertebrae and opercula. Animals in all diet groups showed well-developed vertebral bodies. Low P animals had vertebral centra, neural and haemal arches with large areas of non-mineralised bone. Vertebral centra stiffness in LP animals was reduced accordingly. Regular P and HP animals showed comparable values for vertebral centra stiffness. Non-mineralised vertebral body end plates of LP animals developed a slight inward bending increased length and thickness of intervertebral ligaments. The cellular and extracellular components of the intervertebral joints remained intact without structural alterations that would indicate the development of vertebral centra compression or fusion. Animals from all three diet groups showed active osteoblasts at the vertebral body growth zone. Despite the three-fold decline in plasma inorganic P in LP animals growth continued at the same rate as in RP and HP animals. It is discussed whether the use of a P-reduced diet under a continuous feeding regime can maintain growth without adverse effects for animal health and welfare. This study further discusses that HP diet relative to RP diet has no beneficial effect concerning bone formation, bone mineralisation, growth and prevention of vertebral centra deformities in the feed for Atlantic salmon parr.

The interbody fusion system is a support used to re-establish the spinal stability in the spinal disorder. It can maintain the intervertebral height and decompress the nerve root. The interbody fusion system included the anterior interbody fusion system, the lateral interbody fusion system, and the posterior interbody fusion system. The materials of interbody fusion system are varied and contained the autograft bone, titanium, PEEK, etc. The functions of various interbody fusion systems are (1) to stabilize intervertebral joint, (2) to increase or maintain intervertebral interval height, and (3) to act as carrier of bone graft material. The chapter introduces the different interbody fusion systems in detail. At the same time, the procedure of insertion of interbody cage in the spine is shown as a step-by-step example. Pearls and pitfalls of the interbody fusion system are summarized at the end of this chapter.

Objectives To study the presence of high signal intensity of the intervertebral disc, syndesmophytes, vertebral corner bridging and transdiscal ankylosis on spinal T1-weighted MR images in spondyloarthritis (SpA). Methods A retrospective case-control study of whole spine MRI examinations, obtained in 100 patients with axial SpA and in 100 control patients, was performed. All disco-vertebral units (DVUs) were analyzed on T1-weighted MR images for normal or high signal intensity of the intervertebral disc, presence of syndesmophytes, vertebral corner bridging or transdiscal ankylosis and correlated with final diagnosis. Sensitivity, specificity, and positive and negative likelihood ratios were calculated. Results In this study group, intradiscal high signal intensity, vertebral corner bridging and transdiscal ankylosis on T1-weighted MR images of the spine were all highly specific (specificity: 100%) for diagnosis of axial SpA. However, these signs all had low sensitivity (vertebral corner bridging: 15.0%; intradiscal high signal intensity on T1-weighted MR images: 12.0%; transdiscal ankylosis: 8.0%). Syndesmophytes on spinal MRI were observed in 25 patients but had a more limited diagnostic value (sensitivity: 16.0%, specificity: 91.0%). Conclusions When present in a patient with inflammatory back pain, intradiscal high signal intensity on T1-weighted MR images could be a specific and reliable sign of the presence of axial SpA. Vertebral corner bridging and transdiscal ankylosis also show potential as specific and reliable signs of axial SpA. In contrast, syndesmophytes on MRI do not show potential as a specific or reliable sign of axial SpA.

There are various correctional exercise methods for forward head posture (FHP) with insufficient scientific criteria for the best choices. The purpose of this research was to understand the biomechanical effect of the chin tuck exercise on FHP, focusing on the major neck extensor muscles splenii and the major flexor muscle with musculoskeletal dynamics analysis software SIMM. Subjects are divided into two groups: normal head posture (NHP) and FHP. Kinematic alignment of the cervical spine model of each subject in the FHP group was modified according to the medical images of each subject. A motion analysis system was used to obtain the trajectories of the cervical spine during the chin tuck exercise. Inverse dynamics analysis was performed for the chin tuck exercise to compare muscle forces, intervertebral joint forces, and torques between the two groups. For the FHP group, average muscle forces were approximately 33% of those of the NHP group. Average joint forces and torques of the FHP group were approximately 38.0% and 20.2% higher during protraction and 36.1% and 25.3% lower during retraction, respectively, than the NHP group. From the present analysis, the therapeutic effects of the chin tuck exercise on FHP might be inferred. This study suggests that inverse dynamics analysis with a subject-specific musculoskeletal model might be useful to estimate the correctional effects of various exercises.

Non-fusion technology in spine surgery reduces surgical morbidity and degeneration of the adjacent levels by the insertion of dynamic spinal implants. Despite these advantages, a dynamic spinal implant (DSI) generates complications which require clinical follow-up, the continuous development of constructive solutions and structured optimization of the implant architecture using current mechanical design methods. This study structures this optimization process of a DSI concept by incorporating the mechanical behavior of the device, design variables and functional requirements into a global design model. The geometric (descriptive anatomy) and mechanical (materials, components, etc.) characteristics are obtained from a literature review. By combining these parameters, variables and requirements, appropriate values can be determined. The resulting mathematical model is then used to design and implement a device that is suitably adapted in movements and stiffness. The model assumes linear or non-linear behavior. We describe the optimization of the design variables to ensure the correct functioning of the mechanism when adapted to the patient. The optimization purpose is to determine the architecture of the implant, the choice of materials and the geometric parameters of implantation. An optimized implant model corresponding to specific degrees of degeneration in the intervertebral joint can then be envisaged.

The purpose of this study was to determine which office chair feature is better at improving spine posture in sitting.Participants (n = 28) were radiographed in standing, maximum flexion and seated in four chair conditions: control, lumbar support, seat pan tilt and backrest with scapular relief. Measures of lumbar lordosis, intervertebral joint angles and sacral tilt were compared between conditions and sex.Sitting consisted of approximately 70% of maximum range of spine flexion. No differences in lumbar flexion were found between the chair features or control. Significantly more anterior pelvic rotation was found with the lumbar support (p = 0.0028) and seat pan tilt (p 0.0001). Males had significantly more anterior pelvic rotation and extended intervertebral joint angles through L1-L3 in all conditions (p 0.0001).No one feature was statistically superior with respect to minimising spine flexion, however, seat pan tilt resulted in significantly improved pelvic posture. Practitioner Summary: Seat pan tilt, and to some extent lumbar supports, appear to improve seated postures. However, sitting, regardless of chair features used, still involves near end range flexion of the spine. This will increase stresses to the spine and could be a potential injury generator during prolonged seated exposures.

Background There have been some disagreements on the comparison of disc pressures in the standing and sitting postures in literature. Most research on in vivo pressure needle measurement found higher disc pressure in sitting than in standing. The disc pressure data can help to advocate better postures for clinical advice. Objective The aim of this paper is to develop a procedure to study the compressive load on intervertebral joint in the standing and sitting postures through the approach of motion capture and musculoskeletal modeling. Methods The marker data of six subjects performing various standing and sitting postures was obtained during the motion capture experiment and used to train the musculoskeletal model with an enhanced discretized spine developed for subject in the inverse and forward simulations. Results Compressive loads on L3-L4 and L4-L5 joints are found higher in upright sitting than in upright standing. Slumped sitting, cross-legged sitting and flexion sitting can introduce higher compressive loads on intervertebral joints compared with upright sitting. Conclusions These findings indicate the effects of standing and sitting postures on the spinal joint loads. The results can provide doctors and therapists with more information on clinical advice on better postures for people with spinal problems.

A partial skeleton of a sauropod dinosaur, Museum of Western Colorado 8028, was recovered from the Upper Jurassic Morrison Formation near Snowmass, Colorado, USA, and in 2014 it was referred to Haplocanthosaurus sp. The material includes four proximal caudal vertebrae, which are unique in having strongly amphicoelous vertebral bodies, in which the centrum is reduced to a thin vertical plate of bone between the concave articular surfaces, and neural canals that are laterally and ventrally expanded and strongly sloped relative to the centrum. To reconstruct the soft tissues that left these traces on the skeleton, we rebuilt these vertebrae using both physical and digital techniques. We CT scanned the specimens, generated digital models, 3D-printed the vertebrae, physically sculpted missing material onto the printed models, optically scanned the sculpted vertebrae to create second-generation digital models, and finally, retro-deformed and articulated those digital versions of the vertebrae. The spaces between the deeply amphicoelous caudal centra were likely filled by large, ellipsoidal intervertebral discs, as in the amphicoelous vertebrae of Sphenodon and gekkotan lizards. The expanded neural canals remain enigmatic. In ostriches, the lumbosacral spinal cord is expanded laterally and ventrally in each vertebra, lending the spinal cord a shape that roughly resembles beads on a string. Similar spinal cord morphology might explain the expanded neural canals in the Snowmass Haplocanthosaurus, but it is not clear why a relatively small-bodied, small-tailed sauropod would need such a spinal expansion, given that similar expansions have not been reported in larger-bodied and larger-tailed taxa.

STUDY DESIGN In vivo examination of intradiscal pressure by quantitative discomanometry (QD). OBJECTIVE To determine whether an injectable, exogenous crosslinking could acutely restore intradiscal pressure of stab-injured discs in vivo by short-term treatment. SUMMARY OF BACKGROUND DATA Disc biomechanical performance depends on its integrity associated with the intradiscal pressure and mechanical properties. Genipin crosslink augmentation has demonstrated the in vitro biomechanical capability to improve intervertebral joint stability and increase mechanical properties of the annulus fibrosus. METHODS 4 lumbar discs on each of 8 swine were randomly assigned to 4 groups: intact, injured, untreated, and crosslinked. A 16G needle was stabbed into the annulus fibrosus to create the disc injury model. An injection of 0.33% genipin solution was delivered into the annulus to treat the injury. QD technique was performed to examine the intradiscal pressure for the intact and injured discs at the time of surgery, while untreated and crosslinked discs were measured 1-week postsurgery. 4 QD parameters were analyzed and compared across the 4 groups: leakage pressure and volume, and saturation pressure and volume. RESULTS The leakage and saturation pressures of the injured group were significantly lower than those of the intact group (P = 0.004 and P = 0.01, respectively). The leakage and saturation pressures of untreated discs were statistically equivalent to the injured levels, but with a 2-times higher saturation volume. Relative to the untreated group, the leakage pressure and saturation pressure of genipin-crosslinked discs had a 617% (P = 0.008) and a 473% increase (P = 0.007), respectively. CONCLUSION A large disc injury produced by annular puncture immediately lowered intradiscal pressure when left untreated. Genipin crosslinking can restore intradiscal pressure acutely in vivo without any obvious morbidity associated with the injection.

Translational vertebral motion during functional tasks manifests itself in dynamic loci for center of rotation (COR). A shift of COR affects moment arms of muscles and ligaments; consequently, muscle and joint forces are altered. Based on posture- and level-specific trends of COR migration revealed by in vivo dynamic radiography during functional activities, it was postulated that the instantaneous COR location for a particular joint is optimized in order to minimize the joint reaction forces. A musculoskeletal multi-body model was employed to investigate the hypotheses that (1) a posterior COR in upright standing and (2) an anterior COR in forward flexed posture leads to optimized lumbar joint loads. Moreover, it was hypothesized that (3) lower lumbar levels benefit from a more superiorly located COR. The COR in the model was varied from its initial position in posterior-anterior and inferior-superior direction up to ±6 mm in steps of 2 mm. Movement from upright standing to 45° forward bending and backwards was simulated for all configurations. Joint reaction forces were computed at levels L2L3 to L5S1. Results clearly confirmed hypotheses (1) and (2) and provided evidence for the validity of hypothesis (3), hence offering a biomechanical rationale behind the migration paths of CORs observed during functional flexion/extension movement. Average sensitivity of joint force magnitudes to an anterior shift of COR was +6 N/mm in upright and -21 N/mm in 30° forward flexed posture, while sensitivity to a superior shift in upright standing was +7 N/mm and -8N/mm in 30° flexion. The relation between COR loci and joint loading in upright and flexed postures could be mainly attributed to altered muscle moment arms and consequences on muscle exertion. These findings are considered relevant for the interpretation of COR migration data, the development of numerical models, and could have an implication on clinical diagnosis and treatment or the development of spinal implants.