Ebook: Research into Spinal Deformities 6

The International Research Society for Spinal Deformities (IRSSD) was founded in 1994. The first concepts of forming the Society were raised by a group of researchers who had first gathered in Vermont in 1980 to hold what subsequently became a series of biennial meetings devoted to surface topography and deformity. At a meeting held in 1992 in Montreal, focussed on 3 dimensional interpretations of spinal deformities, discussions were held into whether a formal Society should be formed, and while debate rejected this concept at the time, it was two years later at a meeting in Pescara, Italy 1994 that the IRSSD finally came into being.

The Society has its roots in mathematical modelling, biomechanics and medical research and has always encouraged researchers to report their on-going projects in all aspects of the spinal deformities associated with scoliosis and other spinal deformity conditions. The biomechanical approach led to a better understanding of how the vertebral column behaves under stresses and how the surface shape related to the underlying columnar deformity. Developments in imaging and electronics allowed researchers to develop systems such as ISIS as a non-invasive method of recording back shape in out patient clinics as well as a tool for researchers.

Biologically based studies were also reported. It was appreciated early on by the membership that children with scoliosis have a range of growth disturbances associated with a marked skeletal asymmetry. While the biological approach has enabled a considerable amount of data to be amassed which relates to etiology and pathogenesis, no actual breakthrough into fully understanding why the spinal column rotates and curves to cause scoliosis has yet occurred.

The biennial meetings of the Society chart this research progress in each of the volumes of proceedings, with some reports being final papers while others are progress reports. This is a unique resource for the researcher, holding the key to many different aspects of the problems of the spine. However, some authors choose not to submit to the volumes as they are publishing elsewhere in peer-reviewed Journals, a trend which is inevitably going to challenge the way conference proceedings are reported in the future. There is therefore a challenge to the IRSSD to find an answer to this issue.

2008 could be viewed as a time of potentially exciting breakthroughs in our understanding of the deformity of scoliosis. The rapid advances in imaging technology will allow better and more detailed images of the spine, both on its surface and deeper internally, using techniques such as Laser scanning, Magnetic Resonance Imaging and ultrasound. There is little doubt these technologies are going to advance massively, new ones will come into the hands of clinicians and researchers and a better understanding of the complex functional anatomy of the spine will be developed. This will undoubtedly aid biomechanicians to model the spine and its function, under gravity and movement, allowing new insight into progressions of curves and ways to surgically control deformities.

However, it is probably the potential of biology and medical research which offer the greatest opportunities to further our understanding. The incredible advances at the molecular level, the expanding knowledge of genetics and the recent discoveries in the field of neurophysiology offer for the first time real potential for unravelling the puzzles of etiology. The discovery of molecular biochemical pathways, signalling agents, hormones such as leptin, genetic markers and a greater appreciation of the role of the nervous systems, both central, peripheral and autonomic, all indicate that the research field could expand dramatically with new ideas and inputs from research workers in fields outside the traditional ones devoted to the spine.

It is thus clear that to find a solution, we must build on these new developments and look beyond the spine to the whole body to discover if its biological functions are disturbed. A growing child is a dynamic environment internally, with rapid growth changes reflected in adolescence and these are known to result in tall, thin and asymmetrical children. These changes point to a whole body biological involvement. Researchers must reflect on this totality since it must ultimately allow us to explain the etiology and pathology of what are probably going to prove to be secondary events manifest as spinal curvatures.

These are exciting times and I hope the participants in the Liverpool meeting in 2008 will look back on it as a watershed in our understanding of the spinal deformities. Let's hope this is true, since a therapeutic intervention must surely be better than surgery or external bracing from the purely psychological, if not cosmetic, view of a growing child.

I would like to thanks all participants and authors for submitting their work to the meeting and to my colleagues Professor Nachi Chockalingam, Mr. Ashley Cole and Mr. El-Nasri Ahmed, for their help and support and to our sponsors who supported the meeting in Liverpool, European Capital of Culture 2008.

Peter Dangerfield, Liverpool, UK, April 2008

Evaluation of the incidence of nucleus abnormalities in buccal epithelium allows detecting the presence and intensity of the effect of various ecological conditions and pathologies of the musculoskeletal system. Two coefficients were used: mean number of NA per cell and ratio of cells with karyolysis to the total number of cells with NA. Coefficient of karyolysis decreases with increasing anthropogenic load In pupils of a special school in Moscow these coefficients were similar. Analysis of coefficients showed that karyolysis coefficient was reduced in mothers of children with spinal deformities.

Lower body mass index (BMI) and lower circulating leptin levels have been reported in girls with AIS. In this paper we evaluate skeletal sizes and asymmetries by higher and lower BMI subsets about the means for each of three groups of girls age 11–18 years: 1) normals, 2) school screening referrals, and 3) preoperative girls. Higher and lower BMI subsets, likely to have separated subjects with higher from those with lower circulating leptin levels, identify: 1) girls with relatively earlier and later menarche; 2) trunk width size greater in the higher than in the lower BMI subset, of all three groups; 3) abnormal upper arm length (UAL) asymmetries (right minus left) in the lower BMI subset of the preoperative girls; and 4) in thoracic AIS of screened and preoperative girls, Cobb angle and apical vertebral rotation each significantly and positively correlate with UAL asymmetry in the lower BMI subset but not in the higher BMI subset. In preoperative girls, the lower BMI subset shows the combination of relatively reduced pelvic width and abnormal UAL asymmetry, suggesting that both are linked to lower circulating leptin levels. An earlier puberty with hormonal changes provides a plausible explanation for the larger trunk width at the shoulders and pelvis especially at the younger ages in the higher BMI subsets. At the shoulders, this widening is driven by the ribcage which, in human evolution was acquired with decoupling of head and trunk movements required for efficient bipedal gait. The UAL asymmetry patterns within the groups and BMI subsets are not explained by hormonal mechanisms. It is hypothesized that 1) normal trunk widening of the thoracic cage by hormones in human adolescence is supplemented via the sympathetic nervous system under leptin-hypothalamic control influenced by energy stores (metabolic fuel); and 2) hypothalamic dysfunction with altered hypothalamic sensitivity to leptin through a SNS-driven asymmetric effect may create skeletal length asymmetries in upper arms, ribs, ilia and vertebrae, and initiate AIS. Additional mechanisms acting in the spine and trunk may be required for AIS to progress including 1) somatic nervous system dysfunction, 2) biomechanical spinal growth modulation, and 3) osteopenia.

Idiopathic scoliosis leads to a three-dimensional thoracic deformity. The purpose of this study is to measure thoracic dimensions and volume related to growth and to verify the influence of moderate and severe scoliosis. 176 children (36 boys, 140 girls; 4–16 years) with scoliosis <45 degrees and 17 patients (2 boys, 15 girls) with scoliosis >65 degrees were compared to 239 children without spinal deformity (97 boys, 142 girls) using an optical system. Thoracic volume, perimeter, anterior-posterior and transversal diameters, T1–T12 and sternal lengths were calculated. These measurements were related to age and sitting height. Thoracic volume (3–16 dm³) did not differ significantly over growth between reference and moderate scoliosis groups. At 4 years, it represents 33%, at 10 years it represents 55% of its volume compared with age 16. It triples from 4–16 years and doubles during puberty. In severe scoliosis, the age related thoracic volume was always lower than volumes in reference and moderate scoliosis groups. During growth, the transversal diameter corresponds to 30%, the anterior-posterior diameter represents 20% and the thoracic perimeter 100% of sitting height. In severe lordoscoliosis the anterior-posterior diameter represents less than 20%. Scoliosis <45 degrees does not influence thoracic volume significantly. Severe deformities seem to inhibit volumetric growth. Thoracic parameters should be related to growth parameters such as sitting height rather than age because of possible height variations in one age section. The established relationships offer a reliable orientation of thoracic proportions. They help to understand the global deformity and represent a baseline for surgical treatment using vertical expandable prosthetic titanium ribs.

The present cross sectional study reveals trunk asymmetry (TA) in “normal” Mediterranean juveniles for the first time. The scoliometer readings in both standing and sitting forward bending position (FBP) of 3301 children, (1645 boys, and 1656 girls) aged from 3 to 9 years old were studied. TA was quantified by measuring angle of trunk rotation (ATR) and children were divided in two groups. In group I the ATR was 1° to 6° degrees and in group II≥7°. 71.25% of boys and 73.27% of girls in standing while 81.13% of boys and 80.74% of girls in sitting FBP, were symmetric (ATR=0°). The symmetry difference at standing minus sitting FBP for boys and girls was 9.88% and 7.43% respectively. Severe asymmetry (ATR≥7°) was found in 1.74% of boys and in 1.75% of girls at the standing and in 1.21% and 1.22% at the sitting FBP respectively. Analysing ATR by age it appears that significant TA changes occur between 8–9 years of age for boys and between 6–7 and 8–9 years for girls. The amount of trunk asymmetry in children is the indicator for referral and further orthopaedic assessment. This report provides, for the first time information about the variability of back morphology in “normal” juveniles which is worth knowing when a child is examined for juvenile scoliosis.

Wedging of the scoliotic inter-vertebral disc (IVD) was previously reported as a contributory factor for progression of idiopathic scoliotic (IS) curves. The present study introduces a theoretical model of IVD's role in IS pathogenesis and examines if, by reversing IVD wedging with conservative treatment (full- and night-time braces and exercises) or fusionless IS surgery with staples, we can correct the deformity of the immature spine. The proposed model implies the role of the diurnal variation and the asymmetric water distribution in the scoliotic IVD and the subsequent alteration of the mechanical environment of the adjacent vertebral growth plates. Modulation of the IVD by applying corrective forces on the scoliotic curve restores a close-to-normal force application on the vertebral growth plates through the Hueter-Volkmann principle and consequently prevents curve progression. The forces are now transmitted evenly to the growth plate and increase the rate of proliferation of chondrocytes at the corrected pressure side, the concave. Application of appropriately directed forces, ideally opposite to the apex of the deformity, likely leads to optimal correction. The wedging of the elastic IVD in the immature scoliotic spine could be reversed by application of corrective forces on it. Reversal of IVD wedging is thus amended into a “corrective”, rather than “progressive”, factor of the deformity. Through the proposed model, treatment of progressive IS with braces, exercises and fusionless surgery by anterior stapling could be effective.

In the scoliotic spine, torsion is generally evaluated in relation to axial rotation of the apical vertebra. In the lower limbs, the changes in torsion by age of femoral anteversion (FAV) relative to tibial torsion (TT) have been studied in dried bones, normal growing subjects and adults and subjects with osteoarthritis of the hip or the knee. This paper reports the application of real-time ultrasound to FAV and TT in normal children age 11–18 years and in scoliosis screening referrals with particular reference to how FAV relates to TT as 1) ratios, and 2) tibio-femoral index (TFI) of torsion, calculated as TT minus femoral FAV. The FAV/TT ratio findings show an abnormal normal relationship of FAV to TT both proximo-distally and in left-right asymmetry. These may express torsional abnormalities in femoral and/or tibial growth plates with left-right asynchrony suggesting the possibility of similar torsional abnormalities in vertebral end-plates and/or rib growth plates initiating the deformity of AIS. TFI of the right limb in the scoliosis girls is greater than in the normals that is interpreted as resulting from earlier skeletal maturation of FAV. FAV/TT ratios and TFI are unrelated to the spinal deformity (Cobb angle and apical vertebral rotation) except for boys where TFI is associated with apical vertebral rotation. FAV/TT ratios may be a more accurate method estimating the relationship of FAV to TT. than TFIs.

The course of the ossification of the iliac apophysis is considered in adolescent patients with idiopathic scoliosis, under the name of the Risser sign, to determine the remaining spinal growth. Although the iliac crest develops in the three-dimensional space as a complex structure, the iliac apophysis ossification has been assessed only on a one plane frontal spinal radiograph. This study points out the usefulness of the lateral radiograph for the visualization of the whole iliac crest, especially the posterior region which otherwise cannot be observed. Two young female pelvis specimen were examined with anatomical measurements and radiography. Lateral spinal radiographs of 201 girls were analyzed for the iliac apophysis excursion.

The measures of the width of the iliac bone beneath the iliac crest revealed one anterior and one posterior thick regions, coupled with an intermediate thin region. The regions of the maximal thickness corresponded to the earliest appearance of the apophysis ossification (Risser 1), while the thin part of the iliac bone corresponded to late appearance of the apophysis ossification (Risser 3-4). The ossification of the posterior part of the crest was best visualized with the lateral radiograph, which was exclusive in showing the posterior superior iliac spine region. On the frontal spinal radiograph the end of the course of the apophysis (Risser 3-4) is usually searched at the level of the sacroiliac joint, while in reality this point was found to be situated more caudal, and accessible for observation on the lateral radiograph.

Spinal curvatures alter measured stature and may influence the evaluation of skeletal maturity and growth based on stature measurements. Methods: A dataset of calibrated measurements of vertebral positions of 407 radiographs in the frontal plane, together with clinically measured Cobb angles was used to determine the difference between spinal length and spinal height (‘height loss’) as a function of Cobb angles for radiographs indicating both single (N=182) and double (N=225) curves. Results: An apparently quadratic relationship: Height loss (mm)=1.0+0.066*Cobb+0.0084*Cobb*Cobb was found between height loss and each patient's mean Cobb angle for double curves. There was close agreement of the regression coefficients for single and double curves, and the present findings were very similar to the relationship reported by Ylikoski (Eur Spine J, 2003, 12:288–291). The relationships differed substantially from those proposed by Bjure (Clin Orthop, 1973 93:44–52) and by Brookenthal (SRS Exhibit 15, 2002). Discussion and Conclusions: The findings of the present study indicate that height loss (in mm) occurring with a 10 degrees increase in mean Cobb angle (for two curves) would be 1.1+0.16 times the mean Cobb angle (in degrees). For example, for a Cobb angle change from 30 to 40 degrees, the expected height loss would be 1.1+35*0.16 mm=6.7 mm. This assumes that height loss occurs only as a result of altered curvature, without alteration in disc height associated with an increase in scoliosis.

Unclear etiology in scoliotic and kyphotic deformities of the spine is responsible for uncertainty in treatment options. Normal all-day factors can be of importance. Newly developed or revisited clinical examination of sitting and supine children and consequent testing of neuro-muscular tightness shows to be useful in understanding the different spinal deformations and postural problems during growth and point to neuromuscular tension in growth. The goal is: -Better understanding of the role and individual characteristics of the central nervous system, especially the cord and roots in proper and improper growth of the human spine. -Clarifying that preservation of lordosis and good function at the thoracolumbar junction at the end of growth can be of value for normal configuration and function of the spine in adult life. -Present obvious important and consistent clinical observations in children in sitting and supine position with early and advanced adolescent deformities, by photographic studies and video fragments.

Use of work on growth and deformation of the spine by Milan Roth on uncoupled neuro-osseous growth and other historical literature. -Relate these clinical findings and background literature with common knowledge about adolescent spinal deformities and mechanical laws on tensile and compressive forces in structures. Overview of relevant clinical tests in the growing child presented with deformities show possible correlation with the proposed internal balancing problem (uncoupled neuro-osseous growth) researched by Roth. Concomitant radiological and MRI signs are shown. Around 1900 most orthopaedic surgeons and anatomists saw relationship between the new habitude of children to sit for prolonged periods in schools and spinal deformities. A physiological explanation as adaptations needed by the total neuromuscular system (“the growing system”) was widely postulated (Hueter-Volkmann principle) and subject in research but a concise theory was not achieved. By recognising positive effects of creating lordosis at the thoracolumbar junction of the spine and consistent clinical findings in early deformations scientific support was found by earlier experimental work of Roth. With a leading role of the central nervous system in growth of the spine of standing and sitting vertebrates by steering a tension based system, deformation can be understand as adaptations. Consequences for new preventive measures and therapeutic strategies in deformities seems possible.

The accurate quantification of internal efforts in the human body is still a challenge in biomechanics. The aim of this study is to quantify the intervertebral efforts along the spine during walking, in order to compare the dynamical behaviours between a healthy and a scoliotic subject. Practically, one healthy subject, one scoliotic patient before an instrumentation surgery (Cobb 41°) and after this instrumentation (Cobb 7.5°) walked on a treadmill at 4 km/h. The acquisition system included optokinetic sensors, recording the 3D-joint coordinates, a treadmill equipped with strain gauges, measuring the external forces independently applied to both feet, and bi-planar radiographs, enabling the 3D reconstruction of the spine from C7 to L5, using a free form interpolation technique. The intervertebral efforts were computed using an inverse dynamical model of the human body in 3D. As results, significant differences of the spine kinematics were recorded which lead to different internal effort behaviour in magnitude, shift, coordination and pattern when normalized to the subject mass. Particularly, the normalized antero-posterior intervertebral torques are less uniform for the scoliotic patient (from min −2.5 to max 1.9 Nm/kg) than the healthy subject (from −1.5 to 1.5 Nm/kg). This disequilibrium in the left-right balance of the scoliotic patient is a bit rectified after surgery (from −1.3 to 1.1 Nm/kg).

The three-dimensional shape of the back of 60 patients attending a spinal deformity clinic was measured using ISIS2, a non-commercial surface topography system using digital photography and structured light. Wire-frame and contour plots were displayed, presenting quantitative information and providing a useful pictorial representation of the whole back. A numerical parameter representing the height of the rib hump was also recorded. Repeat measurements, with the patient walking around the room between photographs were carried out. The mean difference between the pairs of measurements was −0.08 mm (sd 4.18 mm) and the 95% tolerance limits were −9.82 mm to 9.66 mm. Changes of greater than ±10 mm are therefore necessary as indicative of clinical change.

Thoracic kyphosis angle measurements using surface topography with ISIS2 were carried out to estimate the inherent variability in the parameter caused by natural change in the patient's stance, breathing and muscle tension. A mean kyphosis angle of 33.8° (sd 13.4°, range 6°–66°) was measured from repeat tests on 61 patients. The mean difference between the pairs of measurements was −0.02° (sd 3.18°) and the 95% tolerance limits were −7.41° to 7.38°. This variability is lower than the clinically significant change in kyphosis angle reported in the literature. Thus kyphosis angle in ISIS2 is suitable for monitoring progress in kyphotic deformities.

A long thoracolumbar sagittal rectitude is sometimes present in adolescent idiopathic scoliosis. The purpose of this study was to identify typical patterns, by comparing frontal plane deformities and vertebral rotation leading to this rectitude. Surgical thoracolumbar alignment correction by three-dimensional in situ bending of rods was then analyzed. Pre- and postoperative radiographs of 24 patients with scoliosis (36–104 degrees) were reviewed using Spineview software. Frontal curves and levels of sagittal rectitude were determined. Thoracic kyphosis, lumbar lordosis, sacral slope, pelvic incidence, pelvic tilt, T9 and T1 tilt were measured. Vertebral rotation was measured by computed tomography, Perdriolle's, Nash and Moe's methods. The intervertebral mobility of the rectitude was analyzed on side bending radiographs. Three patterns leading to sagittal rectitude were identified: 11 main thoracic curves (Lenke 1, King 3) with cranial prolongation of the physiological thoracolumbar junction (T7T12) and maximal vertebral rotation above this zone, 13 double major or thoracolumbar curves (Lenke 3 or 5, King 1 or 2) with cranial and caudal prolongation (T9L3) and maximal rotation above and below, 1 lumbar curve (Lenke 5) with caudal rectitude (T12L4) and maximal rotation at L1. There was no relationship between intervertebral mobility and rectitude. Postoperatively, this zone of rectitude disappeared in 17 out of 24 patients after anterior release followed by posterior instrumentation using the in situ bending technique. In situ bending realizes a stepwise correction of the three-dimensional deformity at different levels. An accurate preoperative analysis is mandatory to achieve an adequate sagittal balance, frontal curve correction and vertebral derotation simultaneously. The determined patterns of thoracolumbar rectitude are helpful to plan surgical correction accurately.

Since several years our group is working on a project to merge into a full 3D reliable and detailed human skeleton representation various segmental biomechanical models presented in literature. The obtained 3D skeleton model is fully parametric and can be fitted to each subject anthropometric characteristics. A non-ionising approach based on 3D opto-electronic measurements of body landmarks labelled by passive markers has been chosen to build the 3D parametric biomechanical skeleton model. A special focus has been devoted to identify and model the spine with a correct degree of accuracy and reliability. In spine pain related pathologies is of major importance the evaluation of functional limitations associated. This requires to integrate morphological characteristics with information deriving from other measurements devices as force platform data, surface EMG, foot pressure maps. The aim of this study is to present a multi-factorial approach which integrates rachis morphological characteristics with full skeleton kinematic, dynamic and SEMG measurements to quantify spine function and mobility in particular for neck and low back pain. A set of clinical-biomechanical tests have been implemented. Static posture characteristics are first evaluated. After that, patient is asked to perform specific motion test batteries in order to fully measure the whole ROMs (spine angles ranges and spine shape modifications) for Axial rotations, forward-backward flexion-extension, lateral bendings per each spine functional units (Skull and neck, thoracic and lumbar districts). During forward bending also a digital Schober test is performed. Such data are correlated to simultaneous SEMG muscle activities recording to investigate motor co-ordination/dysfunction as well as the presence absence of flexion-relaxation phenomena associated to pain.

The mechanisms of idiopathic scoliosis progression are still not fully understood. The aim of this study is to explore, using finite element simulation, effect of the combination of gravity and anterior spinal overgrowth on scoliosis progression. 14 adolescents (10 girls, 4 boys) with an average age of 10.8 years [range 9; 13] were divided in three groups: thoraco-lumbar scoliosis (TL), lumbar scoliosis (L), asymptomatic patients (A). Accurate 3D reconstructions of the spine have been built using bi-planar X-rays. A patient specific validated finite element model has been used. Simulations have been launched with simulation of the combined effect of gravity and growth. The progression during the simulation was defined by a maximal axial rotation movement greater or equal than 4°and a maximal lateral displacement greater or equal than 5 mm (“first order progression” for one criterion, “second order” for the both criteria). In the group TL, we notice an aggravation for 4 patients (Cobb angle increase at least by 4°, mean at 5.9°). Only three patients of the group L show a progression with a smaller Cobb angle increase (mean 3.9°). For the group A, no progression is found for 3 and a progression is found for 1. An anterior spinal overgrowth combined with gravity and a pre-existent curve in the spine could lead to a progression of scoliosis. It seems necessary to consider differently lumbar curves from other curves. Numerical simulation with a patient specific model appears as a useful tool to investigate mechanisms of scoliosis aggravation.

The objective of this study was to develop a finite element model (FEM) in order to study the relationship between hip flexion/extension and the sagittal curves of the spine. A previously developed FEM of the spine, rib cage and pelvis personalized to the 3D reconstructed geometry of a patient using biplanar radiographs was adapted to include the lower limbs including muscles. Simulations were performed to determine: the relationship between hip flexion / extension and lumbar lordosis / thoracic kyphosis, the mechanism of transfer between hip flexion / extension and pelvic rotation, and the influence that knee bending, muscle stiffness, and muscle mass have on the degree to which sagittal spinal curves are modified due to lower limb positioning. Preliminary results showed that the model was able to accurately reproduce published results for the modulation of lumbar lordosis due to hip flexion; which proved to linearly decrease 68% at 90°of flexion. Additional simulations showed that the hamstrings and gluteal muscles were responsible for the transmission of hip flexion to pelvic rotation with the legs straight and flexed respectively, and the important influence of knee bending on lordosis modulation during lower limb positioning. The knowledge gained through this study is intended to be used to improve operative patient positioning.

In this work, an accurate method to register multi-view images of the human torso is developed. In particular, a new framework that incorporates prior statistical knowledge about the registration is developed and tested. This framework leads to a computationally efficient procedure to accurately align images of the human torso. An intensity based image registration procedure is used to obtain the deformation fields by modelling them as both locally affine and globally smooth. Next, the estimated geometric deformation fields are analyzed in order to construct a prior deformation model. Two subspace analysis projection techniques are used to construct the subspaces of plausible deformations, namely principal component analysis (PCA) and independent component analysis (ICA). Accurate deformations are now guaranteed by projecting the locally computed geometric transformations onto the subspaces of plausible deformations. The proposed registration method was validated using high resolution images of the human torso. In order to handle the high resolution images, a multi-resolution framework was employed in the registration process. Experiments demonstrate promising performance in terms of mean square error and in the computational complexity. The main contribution of this work is the development of image registration method that uses subspace constraints to align images of the human torso. This method did not use the intra and inter image constraints used in most intensity based image registration algorithms in the literature.

General agreement among researchers suggests that poor seating posture may predispose individuals to developing low back pain. A variety of methods such as ergonomically designed chairs have been developed to assist people to maintain good posture and preserve the ‘natural’ lumbar curve. The aim of this study was to compare lumbar curvature on an ergonomically designed kneeling chair (EKC) with that on a standard computer chair (SCC), with reference to the standing lumbar curvature. The study used a repeated measures, within-subjects design. A convenience sample of twenty participants was recruited aged 18–35 (9 male and 11 female). Lumbar curvature was measured using the ‘Middlesbrough Integrated Assessment System’ (MIDAS) postural assessment tool in three different postures; sitting on a SCC, sitting on an EKC set at +20° inclination and standing as the reference measurement. Results were analysed by a repeated measures oneway ANOVA (1 factor) with 3 levels followed by the Bonferroni post hoc test. The results showed a statistically significant difference between standing lumbar curvature and lumbar curvature produced by both of the chairs (p<0.05). There was also a statistically significant difference between the two seated positions (p<0.05). This study suggests that ergonomically designed kneeling chairs set at +20° inclination do maintain standing lumbar curvature to a greater extent than sitting on a standard computer chair with an overall mean difference of 7.633°. Further research with a greater number of subjects and on different chair designs is warranted.

Study was aimed to determine the incidence of postural faults, level of physical activity and their possible relationship in young adults. Material included 100 subjects recruited randomly among students of Medical University of Silesia (54F aged 20–28, mean=22.9, SD=2.11 and 46M aged 20–29, mean=25.1, SD=1.86). Posture was examined according to modified Klapp protocol. For thoracic kyphosis and lumbar lordosis, values of 30°±2 were considered as normal. ATR exceeding 5° was considered as scoliosis. Physical activity was evaluated with a questionnaire, admitting 1 point for each hour of physical labour and 2 points for each hour of sport activity per week. Statistical analysis was based on the one-way ANOVA test. Postural faults were widespread in assessed group. Most common was lumbar hypolordosis (71.0%, 48.1%F and 97.8%M) and thoracic hyperkyphosis (58.0%, 53.7%F and 63.0%M). Scoliosis was observed in 54.0% (50%F and 58.7%M). Physical activity in assessed group was high, with 71% of cases (76%F and 62.5%M) within range of mean value ± 1SD. Level of activity in men was significantly higher than women (mean 20.25 vs. 6.28 points, p<0.05). Significant dependence of postural faults and physical activity was not observed. Conclusions: Young adults prefer active way of life. Postural faults are widespread among young adults. Correlation between level of physical activity and postural faults was not observed.

Endoscopic vertebral body stapling is an innovative technique intended to treat adolescent idiopathic scoliosis, but the optimal instrumentation design is not yet established. The objective was to simulate the immediate correction obtained from two stapling configurations. A parametric finite element model of a typical right thoracic scoliotic spine (Cobb 21°) was developed using geometrical and mechanical data from the literature. Staple insertion and closing were modeled. The intra-operative lateral decubitus and standing positions were taken into account. Two implant configurations, varying the number of staples per vertebra, were simulated. The major correction (9°) came by simulating the intra-operative posture. The immediate Cobb angle correction due to the staples alone was less then 1° for both configurations. However, the staples helped maintain the correction obtained by the intra-operative posture when the post-operative standing position was simulated. Next steps are to validate the model using surgical cases, implement growth modulation modeling, improve lateral decubitus modeling, and analyze different vertebral stapling strategies for different scoliotic curves.

In three recent studies we have shown how different correction objectives from a group of experienced spine surgeons add to the variability in AIS instrumentation strategies. This study examined the effect of correction objectives of three surgeons on the optimal instrumentation strategy. An optimization method using six instrumentation design parameters (e.g. limits of the instrumented segment, number, type and location of implants and rod shape) that were manipulated in a uniform experimental design framework was linked to a patient-specific biomechanical model to analyze the effects of a specific instrumentation configuration. The optimization cost function was formulated to maximize correction in the three anatomic planes and with minimal number of instrumented levels. Three surgeons from the Spinal Deformity Study Group provided their respective correction objectives for a single patient (56° thoracic and 38° lumbar Cobb angle). For each surgeon, 702 surgical configurations were iteratively simulated using a biomechanical model. The influence of the three different correction objectives on the optimal surgical strategy was evaluated. The resulting optimal fusion levels were T2-L4, T4-L2, and T4-L1. A Wilcoxon non parametric test analysis showed that fusion levels and the location of implants significantly were influenced by the correction objectives strategies (p<0.05). The optimal number of implants although different (12 vs.11 vs.10) was not statistically significant (p>0.1). Thus different surgeon-specified correction objectives produced different optimal instrumentation strategies for the same patient.