Lumbosacral transitional vertebrae morphology: a South African population

Lumbosacral transitional vertebrae (LSTV) are defined as congenital anatomical variations, observed unilaterally or bilaterally, in which the transverse process of the last lumbar vertebra exhibits signs of dysplasia evident as increased craniocaudal height, with varying degrees of articulation or fusion to the ‘first' sacral vertebra. Such variations give rise to vertebral morphology that may display lumbar or sacral characteristics at the terminal lumbar spine, together with subsequent enumeration variation. The purpose of this study was to establish baseline data on the prevalence rates of LSTV and to describe the morphological characteristics (Type, subtype, frequency of side and spinal enumeration) of LSTV in the South African population. This study was subdivided into two main sections, namely Part 1: medical imaging appraisal and Part 2: osteological morphology appraisal. In Part 1, both retrospective and prospective cohort randomised sampling methods of data collection of medical images were used. The appraisal of the medical images included radiographs, magnetic resonance imagers and computerised tomography scans. Prevalence rates, utilising the Castellvi et al. (1984) classification, were established via radiographs only. Additionally, lumbar spine enumeration, namely lumbarisation and sacralisation, was made through the appraisal of lumbar radiographs. Images were obtained from medical radiology practices located at Groote Schuur Hospital in Cape Town, Western Cape Province and Charlotte Maxeke Johannesburg Academic Hospital in Johannesburg, Gauteng Province. The total imaging cohort included 3096 individuals of which 308 individuals (10%) were found to contain LSTV. Prevalence rates were further evaluated by subdivision of the three largest ancestries in South Africa. Ancestries were classified as African (n=1032), Mixed (n=1032) and European (n=1032). The prevalence of LSTV in the three ancestral groups was 10.5%, 9.3% and 9.9% respectively and the sex distribution was greater in females (52.1%) then in males (47.9%). The morphological assessment found the prevalence of LSTV by Type was Type II (67.9%) followed by Types III (27.6%) and IV (4.5%). The most frequent subtype by prevalence was Type IIA (41.9%) followed by Type IIB (26%), Type IIIB (21.8%), and Type IV (5.8%). Additionally, the frequency of side was bilateral (47.7%), left (26.6%), right (21.1%), and other (4.5%). Comparison of ancestry and spinal enumeration analyses established statistical significance for individuals of African-ancestry (67.0%) and Mixed-ancestry (72.9%) both of which demonstrated a greater affinity of prevalence for sacralisation (p=0.008), with a small effect size (V=0.178) over the European-ancestry subgroup (52.4%). Furthermore, a statistical significance with a medium effect size (V=0.256) was found in males (p=0.010) when comparing ancestry and spinal enumeration between sexes. In Part 2, a systematic search of the total cadaveric skeletal collection housed at the University of Witwatersrand (the Dart Collection of skeletons) yielded 1797 human skeletal specimens of between 21 and 65 years of age at time of death. One-hundred and fourteen skeletal remains were identified as containing LSTV. Damage and loss of vertebral elements resulted in a subset of 91 LSTV for study. A sex balanced control group cohort of 30 males and 30 females was selected at random from the Dart Collection for comparative analyses. A number of osteometric measurements were evaluated comparing the LSTV and control group cohorts. Numerous osteometric comparisons were statistically significant highlighting the many changes in lumbar and sacral morphology associated with LSTV. There are several original findings to emerge. Thisis the first study to establish the prevalence of LSTV in a large sample from the South African population, subdivided into the three largest ancestral groups. Novel findings associated with LSTV include iliolumbar articulation, bipartition of the sacral foramen, intra-articular vacuum phenomenon of accessory articulations of LSTV, enlargement of the contralateral TVP associated with Types III and IV LSTV, lumbar ossified bridging syndrome and a novel complex named by the researcher as the transverso-sacro-iliac articulation. Furthermore, the researcher has proposed three modifications to the Castellvi et al. (1984) classification, namely (1) that there should be a sub-classification of the Type IV LSTV into right and left nomenclature, (2) the inclusion of a new subtype of Type II LSTV morphology, a unilateral right or left iliolumbar articulation associated with contralateral Type IIA morphology, and (3) a modified morphological classification of LSTV based on the presence of an extended sacroiliac articulation either directly or via the transverso-sacro-iliac articulation. The latter effectively increases the size of the sacroiliac joint and is thought to increase spinopelvic stability. The transverso-sacroiliac articulation was demonstrated for all clinically significant LSTV Types (II-IV), both unilateral (right or left) and bilateral. Finally, this is the first study to incorporate an in situ and an ex situ study in the same population by examining spinal morphology of LSTV using medical images and skeletal remains for descriptive analyses

Robotic Simulation of Disc Arthroplasty Surgery: Influence of Surgical Placement on Motion Segment Dynamics

A variety of total disc replacement (TDR) designs exist for the treatment of disc pathologies. A key design parameter for a constrained ball and socket device is the location of the fixed center of rotation (COR). A previous study demonstrated that intact motion segment unit (MSU) mechanics and range of motion (ROM) were sensitive to the location of a prescribed sagittal plane rotational axis. Mal-alignment between the implant COR and the COR of the MSU may lead to an overloaded or over constrained condition. Two paradigms exist for the placement of a fixed COR TDR device relative to MSU anatomy: positioning the implant midline or posterior to midline. Presently, there are no data to indicate which paradigm may lead to better biomechanical/clinical outcome. This research attempts to evaluate changes in MSU mechanics and ROM as a result of variations in the size and placement of a simulated ball and socket TDR, like the ProDisc-L lumbar disc prosthesis. Six human cadaveric lumbar MSUs, L4-L5, were tested in flexion/extension using the Spine Robot to an end load limit of 8Nm. A fixed axis protocol was used to impose a pure rotation about a desired anatomical location. The Spine Robot was programmed to rotate the MSU about the COR of the implant. Subsequently, with the MSU held rigid, the implant was removed and rotation about the implant’s COR was repeated. Thereafter, simulated CORs were tested in different anatomical locations as defined by a customized grid pattern. The grid pattern consisted of 8 CORs which simulated the placement of a medium and large size constrained ball and socket device. Measurements of shear forces along the disc plane, axial force normal to the disc plane, segmental bending moment, and segmental ROM were analyzed at each grid point. Analysis of MSU mechanics and ROM for the ProDisc-L and Simulated Implant cases revealed that the two conditions were not comparable. Transfer of tissue pretension from the implant to the Spine Robot on removal of the implant, and dynamic contact forces at the implant surfaces were the contributing factors to the differences observed. Simulated COR testing demonstrated that the posterior tissue response was sensitive to varying placements of the simulated implant. For both implant sizes, posterior positioning of the COR required distraction of the disc space. During flexion, posterior positioning resulted in significantly higher shear and axial forces as well as a trend for reduced ROM. ROM in flexion may have been influenced by different starting positions within the neutral zone due to disc space distraction. During extension, the posterior placement of the COR reduced loading and increased rotation suggesting better alignment with, or separation of the facet joints. This novel study was able to delineate significant differences in spinal tissue response to varying simulated sizes and placements of an ideal fixed COR TDR device. The results of this study suggested that with both implant sizes the posterior placement of the COR will tend to distract the disc space and provide significantly increased ROM in extension at the expense of increased loads on posterior ligaments in flexion

A radiographic study of ossification in the spine and limbs of the human fetus

Until recently relatively little has been known about factors which affect growth and development in early life. and which have a fundamental influence on later adult life. Thus pre- and postnatal growth and development must be studied as a continuum for they have a profound effect on ultimate physical and mental development. However, legal and ethical problems governing the availability of human fetal material diminish the prospects for assembling large comprehensive surveys. Because of this, there is often inaccuracy and inconsistency in many reports of human fetal development and, in particular, the study of certain regions has been considerably neglected. Ossification of the human fetal spine and limbs is one such example. The initial purpose of the present study was an attempt to increase knowledge in an area where there appears to be substantial gaps. [Continues.

Growth and development of the human intervertebral disc

The object of this study is to compare the growth and development of a lumbar intervertebral disc with those in the thoracic and cervical regions from embryonic life to childhood. Particular attention is paid to changes during and following the establishment of the secondary curvatures of the vertebral column. Current knowledge of development of the intervertebral disc is reviewed.Postmortem material from 67 cases and a large series of radiographs are used in histological and mensural studies. The vertical dimensions of the 'total disc' (which includes the cartilage plates), its parts, and the vertebral body above the disc are measured in each region at every age. Notochordal remnants in vertebrae and discs are used as 'natural markers' from which horizontal dimensions are measured in the median plane to give an indication of growth anteriorly and posteriorly from the position of the notochord.Notochordal cells appear to multiply during foetal life and infancy, playing an important role in growth and extension of the notochordal nucleus pulposus up to about three years, but they degenerate and disappear from about three to seven years.As the notochordal nucleus pulposus grows rapidly in V volume, principally by increase in its macoid matrix (notably in lumbar discs), the anulus fibrosus and cartilage plates bounding it become thinner. Associated with thinning of the cartilage plates, vertical growth of the central part of the 'total disc' slows down during the first two postnatal years.As secondary cervical and lumbar curvatures are established, the cervical and lumbar notochordal nuclei pulposi respectively move to more anterior and central positions, but the thoracic notochordal nucleus pulposus remains posteriorly situated. From two years onwards, the central parts of lumbar discs grow rapidly in height though the heights of the central parts of thoracic discs remain almost unchanged. The central situation of the lumbar nucleus pulposus in childhood, and the rapid increase in height of the central part of the lumbar 'total disc' from two to seven years are associated with corresponding changes in the shape of the cephalic and caudal end surfaces of lumbar vertebral bodies from convexity to concavity.During the same period (about two to seven years) there is an increase in the rate of antero- posterior growth of the lumbar vertebral column without any increase in its lateral growth rate.The present investigation throws further light on the work of Houston and Zaleski (1967) who demonstrate a relationship between 'activity' and vertebral body shape, and suggests that the rate of anteroposterior growth of the lumbar vertebral column, the vi the rate of vertical growth of lumbar vertebrae and 'total discs', and their changes in shape during childhood, all depend to some extent on the assumption of the normal erect posture

Towards Understanding the Injury Mechanics and Clinical Outcomes of Traumatic Subaxial Cervical Facet Dislocation and Fracture-Dislocation

Despite potentially devastating outcomes, the injury mechanisms of traumatic subaxial cervical facet dislocation (CFD) and fracture-dislocation (CFD+Fx) are not well understood and have not been reliably produced in biomechanical testing. In particular, bilateral CFD (BFD) with concomitant facet fracture (BFD+Fx) has not been produced experimentally, possibly due to a lack of neck muscle replication. Muscle activation may impose intervertebral compression and anterior shear during injury, increasing loading of the facets and preventing isolated dislocation via intervertebral separation – such separation has been observed during inertially-produced CFD. The mechanical behaviour of the facets during these scenarios, and the effect of axial distraction on the risk of facet fracture or dislocation, have not been investigated. The aim of this thesis was to improve understanding of the epidemiology, clinical outcomes, and injury mechanisms of CFD and CFD+Fx, and to investigate the biomechanics underlying the injury. In Study 1, a large-cohort medical record and radiographic review of subaxial cervical subluxations, dislocations, and fracture-dislocations presenting at an Australian tertiary hospital over the decade to 2014 was performed. Two primary injury causations were identified: motor vehicle accidents in younger adults, and falls in the elderly. BFD frequently caused spinal cord injury (SCI) and concomitant facet fracture was common. The C6/C7 vertebral level was most commonly involved, and injury to this level most often caused SCI. In Study 2, the bilateral inferior facets of 31 isolated human cadaver subaxial cervical vertebrae (6×C3, C4, C5, and C7, 7×C6) were loaded quasi-statically in simulated supraphysiologic anterior shear and compressive-flexion directions using a materials testing machine – these motions are thought to be associated with BFD. Facet stiffness and failure load were significantly greater in the simulated compressive-flexion loading direction, and sub-failure deflection and surface strains were higher in anterior shear. Facet tip fractures occurred during anterior shear loading, while failure through the pedicles was most common in compressive-flexion. In Study 3, the effect of intervertebral axial separation on human cadaver C6 inferior facet biomechanics during non-destructive anterior shear, axial rotation, flexion, and lateral bending motions of twelve C6/C7 functional spinal units (FSUs) was investigated. Axial compression generally increased facet deflection and strains, when compared to intervertebral distraction. In Study 4, a method was developed to reliably apply 20 mm of constrained anterior shear motion with superimposed intervertebral axial compression or distraction to twelve human cadaver cervical FSUs in a materials testing machine. The effect of superimposed axial compression vs distraction on the type of fractures observed was assessed for the subset of specimens that successfully achieved 20 mm of anterior shear. BFD+Fx was produced in five of 12 specimens, of which three had axial compression superimposed. The mechanical behaviour of the C6 inferior facets at the point of initial anatomical failure did not appear to be affected by intervertebral axial separation. This thesis presents the first large-cohort clinical investigation of CFD and provides quantitative information about the biomechanical response of the subaxial cervical facets to simulated traumatic loading. Axial compression generally increased facet surface strains and deflections when superimposed on intervertebral motions, and constrained intervertebral anterior shear can produce BFD+Fx. It is anticipated that this thesis will inform the development of improved preventative measures and provide data for the validation of models of cervical trauma.Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 201

Automated shape analysis and visualization of the human back.

Spinal and back deformities can lead to pain and discomfort, disrupting productivity, and may require prolonged treatment. The conventional method of assessing and monitoring tile de-formity using radiographs has known radiation hazards. An alternative approach for monitoring the deformity is to base the assessment on the shape of back surface. Though three-dimensional data acquisition methods exist, techniques to extract relevant information for clinical use have not been widely developed. Thi's thesis presentsthe content and progression of research into automated analysis and visu-alization of three-dimensional laser scans of the human back. Using mathematical shape analysis, methods have been developed to compute stable curvature of the back surface and to detect the anatomic landmarks from the curvature maps. Compared with manual palpation, the landmarks have been detected to within accuracy of 1.15mm and precision of 0.8111m.Based on the detected spinous process landmarks, the back midline which is the closest surface approximation of the spine, has been derived using constrained polynomial fitting and statistical techniques. Three-dimensional geometric measurementsbasedon the midline were then corn-puted to quantify the deformity. Visualization plays a crucial role in back shape analysis since it enables the exploration of back deformities without the need for physical manipulation of the subject. In the third phase,various visualization techniques have been developed, namely, continuous and discrete colour maps, contour maps and three-dimensional views. In the last phase of the research,a software system has been developed for automating the tasks involved in analysing, visualizing and quantifying of the back shape. The novel aspectsof this research lie in the development of effective noise smoothing methods for stable curvature computation; improved shape analysis and landmark detection algorithm; effective techniques for visualizing the shape of the back; derivation of the back midline using constrained polynomials and computation of three dimensional surface measurements.

CT Scanning

Since its introduction in 1972, X-ray computed tomography (CT) has evolved into an essential diagnostic imaging tool for a continually increasing variety of clinical applications. The goal of this book was not simply to summarize currently available CT imaging techniques but also to provide clinical perspectives, advances in hybrid technologies, new applications other than medicine and an outlook on future developments. Major experts in this growing field contributed to this book, which is geared to radiologists, orthopedic surgeons, engineers, and clinical and basic researchers. We believe that CT scanning is an effective and essential tools in treatment planning, basic understanding of physiology, and and tackling the ever-increasing challenge of diagnosis in our society