In order to understand the actual weight-bearing condition of lower extremity, the three dimensional (3D) mechanical axis of lower limb was compared with the loading direction of ground reaction force (GRF) in standing posture. Three normal subjects (male, 23–39 yo) participated in the study. A bi-planar radiograph system with a rotation table was used to take frontal and oblique images of entire lower limb. Each subject’s lower limb was CT scanned to create 3D digital models of the femur and tibia. The contours of the femur and tibia in both radiographs and the projected outlines of the 3D digital femur and tibia models were matched to recover six-degree of freedom parameters of each bone. The 3D mechanical axis was a line drawn from the centre of the femoral head to the centre of the ankle. A surface proximity map was created between the distal femoral articular surface and the proximal tibial articular surface. A force plate was positioned on the rotation table to measure GRF during biplanar X-ray exposure. Each subject put one’s foot measured on the force plate and the other on the shield. Bi-planar radiographs were taken in double-limb standing, double-limb standing with toe up in the leg measured, and single-limb standing. The anterior and medical deviations of the loading direction of GRF from the 3D mechanical axis were determined at the proximal tibia and normalized by the joint width in anteroposterior direction and by the joint width in lateral direction. For all subjects the passing points of the 3D mechanical axis at the proximal tibia were almost in the middle of the joint width in lateral direction. Compared to the 3D mechanical axis, the loading direction of GRF passed through the anterior region in double-limb standing and single-limb standing, and anteromedial region in single-limb standing. The normalized medial deviation was significantly greater in singlelimb standing than in double-limb standing (p=0.023). The separation distance tended to decrease in the medial compartment in single-limb standing, and to increase in toe up in the entire region. Deviation of the loading direction of GRF from the 3D mechanical axis at the proximal tibia varied among standing postures, relating to the change in weightbearing condition as indicated in the separation distance map. These results provide the mechanical perspective related to the causes and progression of knee OA and may contribute to the improvement of surgical treatments such as arthroplasty and osteotomy

Purpose. The aim of this study is to describe the influence of sitting and standing posture on sagittal pelvic inclination in preoperative total hip replacement patients to assist with correct acetabular component positioning. Methods. Lateral radiographs of the pelvis and lumbar spine in sitting and standing of preoperative hip arthroplasty patients with primary hip osteoarthritis were extracted. Pelvic tilt was measured using the vertical inclination of a line from the ASIS to pubic tubercle. Sacral inclination was measured as the angle between the anterior surface of the sacrum and a horizontal reference. Figure one is a representation of the pelvic tilt angle and sacrel inclination angle taken during standing. The Cobb angle of the lumbar spine was recorded represented for a sitting patient in figure 2. Hip flexion was recorded (figure 2). Results. 60 patients were identified. Mean age of the cohort was 63. Sacral inclination ranged from 1 to 55 degrees in standing with a mean of 25.7 degrees. In sitting, sacral inclination ranged from 0.3–84.5 degrees with a mean of 24.1 degrees. Pelvic tilt ranged from 30 degrees posteriorly to 21.5 degrees anteriorly in standing. Pelvic tilt in sitting and ranged from 48 posterior to 42 degrees anterior tiltLumbar lordosis ranged from 11.6 to 91.7 degrees in standing. Lumbar lordosis in sitting ranged from 29.5 degrees(kyphosis) to 42 degrees (lordosis). Total hip flexion was 107.4 degrees from standing to sitting. Conclusions. There is wide variability in pelvic orientation between individuals in both postures Orientating acetabular components for total hip arthroplasty should account for postural changes in native version

Introduction

Understanding hip-spine relationships and accurate evaluation of the pelvis position are key- points for the optimization of total hip arthroplasty (THA). Hip surgeons know the importance of pelvic parameters and the adaptation mechanisms of pelvic and sub-pelvic areas. Literature about posture after THA remains controversial and adaptations are difficult to predict. One explanation can be the segmental analysis focused on pelvic parameters and local planning.

In a significant number of patients a global analysis may be important as a cascade of compensatory mechanisms is implemented, the hip being only one of the links of this chain reaction.

3 parameters can be measured on full body images:

The objective of this preliminary study is to report the post-operative evolution of posture after THA.

Due to abnormal neuromuscular development, functional capability in children with cerebral palsy is often severely compromised. Single event multi-level surgery (SEMLS) is the gold standard surgical treatment for patients with cerebral palsy. It has been demonstrated to improve gait, however, how standing posture is affected is unknown. The aim was to investigate the effect of SEMLS in patients with spastic cerebral palsy on walking and standing posture using 3D gait analysis. Participants were identified from the One Small Step Gait Laboratory database. Standardised 3D-Gait analysis was performed within 2 years pre- and post-SEMLS. Gait abnormality was measured using the Gait Profile Score (GPS) index; standing abnormality was measured using the newly-developed Standing Profile Score (SPS) index. A control group (n=20) of age/sex-matched CP patients who did not undergo surgery were also assessed. 104 patients (73 boys, 31 girls) with spastic cerebral palsy underwent SEMLS with appropriate pre- and post-gait analyses (2000–2015). 91 patients had bilateral limb involvement, 14 had unilateral limb involvement. Average age at surgery was 10.38 years (range 4.85–15.60 years). A total of 341 procedures were performed, with hamstring and gastrocnemius lengthening representing approximately 65% of this. There was a 20% mean improvement in walking (GPS reduced 2.4°, p<0.001) and standing (SPS reduced 3.4°, p<0.001) following SEMLS. No improvement was noted in the control group. Significant correlations were observed between the changes in SPS and GPS following surgery (r2, p<0.001). Patients with poorer pre-operative standing posture (SPS) reported the most significant improvement following surgery. We confirmed improvement in walking following SEMLS using the Gait Profile Score (GPS). This is the first paper to report that standing posture is also improved following surgery using a novel index, the Standing Posture Score (SPS). SPS could be adopted as a tool to assess functional capability and predict post-operative changes

Introduction. Hip osteoarthritis (OA) results in reduced hip range of motion and contracture, affecting sitting and standing posture. Spinal pathology such as fusion or deformity may alter the ability to compensate for reduced joint mobility in sitting and standing postures. The effects of postural spinal alignment change between sitting and standing is not well understood. Methods. A retrospective radiographic review was performed at a single academic institution of patients with sitting and standing full-body radiographs between 2012 and 2017. Patients were excluded if they had transitional lumbosacral anatomy, prior spinal fusion or hip prosthesis. Hip OA severity was graded by the Kellgren-Lawrence grades and divided into two groups: low-grade OA (LOA; grade 0–2) and severe OA (SOA; grade 3–4). Spinopelvic parameters (Pelvic Incidence (PI), Pelvic Tilt (PT), Lumbar Lordosis (LL), and PI-LL), Thoracic Kyphosis (TK; T4-T12), Global spinal alignment (SVA and T1-Pelvic Angle; TPA; T10-L2) as well as proximal femoral shaft angle (PFSA: as measured from the vertical), and hip flexion (difference between change in PT and change in PFSA) were also measured. Changes in sit-stand radiographic parameters were compared between the LOA and SOA groups with unpaired t-test. Results. 548 patients were identified with sit-stand radiographs, of which there were 311 patients with LOA & 237 with SOA. After propensity score matching for Age, BMI, and PI, 183 LOA & 183 SOA patients were analyzed. Standing alignment analysis demonstrated that SOA patients had greater SVA (31.1 ± 36.68 vs 21.7 ± 38.83, p=0.02), and lower TK (−36.21 ± 11.98 vs −41.09 ± 11.47, p<0.001). SOA patients had lower PT, greater PI-LL, lower LL, lower T10-L2, and lower TPA (p>0.05). PFSA (9.09 5.19 vs 7.41 4.48, p<0.001) was significantly different compared to LOA while SOA KA was not significantly different compared to LOA. Sitting alignment analysis demonstrated that SOA patients had higher PT (29.69 ± 15.65 vs 23.32 ± 12.12, p<0.001), higher PI-LL (21.64 ±17.86 vs 12.44 ±14.84 p<0.001), lower LL (31.67 ± 16.40 vs 41.58 ± 14.73, p<0.001), lower TK (−33.22 ± 15.76 vs −38.57 ± 13.01, p=0.01), greater TPA (27.91 ± 14.7 vs 22.55 ± 11.38 p=0.01). TK, SVA, and PFSA were not significantly different compared to LOA. SOA and LOA groups demonstrated differences in standing and sitting spinopelvic alignment for all global and regional parameters except PI. When examining the postural changes from standing to sitting, there was less hip ROM in SOA than LOA (71.45 ± 18.55 vs 81.64 ± 12.57, p<0.001). As a result, SOA patients had more change in PT (15.24 ± 16.32 vs 7.28 ± 10.19, p<0.001), PI-LL (20.62 ± 17.25 vs 13.74 ± 11.16, p<0.001), LL (−21.37 ± 15.55 vs −13.09 ± 12.34, p<0.001), and T10-L2 (−4.94 ± 7.45 vs −1.08 ± 5.19, p<0.001) to compensate. SOA had a greater improvement in TPA (15.06 vs 9.59, p<0.001), and less change in PFSA (86.65 vs 88.81, p<0.001) compared to LOA. Conclusions. Spinopelvic compensatory mechanisms are adapted for reduced joint mobility associated with hip OA in standing and sitting

Ambulating children with bilateral spastic cerebral palsy (BSCP) demonstrate atypical posture and gait due to abnormal muscle and skeletal growth when compared to typically–developing (TD) children. Normal postural alignment in standing facilitates many of the tasks of daily living because it allows a stable base of support without requiring significant muscular effort. Similarly, increasing gait abnormality is associated with poorer functional capacity. Our aims were to compare the standing posture of TD children and children with BSCP using the Standing Profile Score and identify if any abnormality in standing is correlated with abnormality in walking in children with BSCP using the Gait Profile Score index. We retrospectively compared 44 typically-developing children to 74 age-matched children with BSCP (GMFCS I & II). We performed 3D Gait Analysis during long-standing (10seconds) and in gait after application of 16 retro-reflective markers on anatomical landmarks of the lower limb and pelvis. Analysis of all kinematics was performed for movements in the sagittal, coronal and axial planes. The Gait Profile score (GPS) is a validated index of overall gait pathology. The Standing Profile Score (SPS) was developed using the same calculations for GPS but during static trials. A significant correlation was observed between the Standing Profile Score (SPS) and Gait Profile Score (GPS) in children with BSCP (p<0.001). Significant differences were exhibited in GPS between the two groups, across all parameters, except the pelvic obliquity (p<0.05). A significant positive correlation existed for hip rotation in both groups, however the correlations observed at hip flexion and ankle dorsiflexion were significantly greater in the BSCP group compare to the TD group (p<0.01). We have shown that posture during gait (GPS) is predictable from standing posture (SPS) in patients with BSCP. This biomechanical relationship can aid surgical decision-making

Introduction and Objective. Medial Knee Osteoarthritis (MKO) is associated with abnormal knee varism, this resulting in altered locomotion and abnormal loading at tibio-femoral condylar contacts. To prevent end-stage MKO, medial compartment decompression is selectively considered and, when required, executed via High Tibial Osteotomy (HTO). This is expected to restore normal knee alignment, load distribution and locomotion. In biomechanics, HTO efficacy may be investigated by a thorough analysis of the ground reaction forces (GRF), whose orientation with respect to patient-specific knee morphology should reflect knee misalignment. Although multi-instrumental assessments are feasible, a customized combination of medical imaging and gait analysis (GA), including GRF data, rarely is considered. The aim of this study was to report an original methodology merging Computed-Tomography (CT) with GA and GFR data in order to depict a realistic patient-specific representation of the knee loading status during motion before and after HTO. Materials and Methods. 25 MKO-affected patients were selected for HTO. All patients received pre-operative clinical scoring, and radiological/instrumental assessments; so far, these were also executed post-operatively at 6-month follow-up on 7 of these patients. State-of-the-art GA was performed during walking and more demanding motor tasks, like squatting, stair-climbing/descending, and chair-rising/sitting. An 8-camera motion capture system, combined with wireless electromyography, and force platforms for GRF tracking, was used together with an own established protocol. This marker-set was enlarged with 4 additional skin-based non-collinear markers, attached around the tibial-plateau rim. While still wearing these markers, all analyzed patients received full lower-limb X-ray in standing posture a CT scan of the knee in weight-bearing Subsequently, relevant DICOMs were segmented to reconstruct the morphological models of the proximal tibia and the additional reference markers, for a robust anatomical reference frame to be defined on the tibia. These marker trajectories during motion were then registered to the corresponding from CT-based 3D reconstruction. Relevant registration matrices then were used to report GRF data on the reconstructed tibial model. Intersection paths of GRF vectors with respect to the tibial-plateau plane were calculated, together with their centroids. Results. Pre-operative clinical and radiological scoring confirmed MKO and associated abnormal varism. The morphological characterization of GRF was successfully achieved pre- and post- HTO on patient-specific tibial plateau. Pre-operative GFR patterns and peaks, including those related to knee joint moments, were observed medially on the knee, as expected. In post-HTO, these resulted lateralized and much closer to the tibial plateau spine, as desired. In detail, when post- is compared to pre-op, the difference of the centroids were, on average, 54.6±18.1 mm (min÷max: 36.7÷72.8 mm) more lateral during walking and 52.5±28.5 mm (24.7÷87.6 mm) during stair climbing. When reported in % of the tibial plateau width, these values became 69.2±20.1 (46.1÷81.4) and 78.1±30.1 (43.4÷98.0), respectively. Post-op also clinical scores and GA revealed a considerable overall improvement, especially in functional performances. Conclusions. The reported novel approach allows a combination of motion data, including GFR, and tibial-plateau morphology. Relevant pre- and post-operative routine application offer a quantification of the effect of the original deformity and executed joint realignment, and an assistance for surgical planning in case of HTO as well as ideally in other orthopedic treatments

Introduction. : Measurements of overall vertebral bone mineral density (BMD. v. ) do not adequately explain the observed patterns of osteoporotic vertebral fracture. Perhaps bone loss from specific regions of the vertebra has a more important effect on vertebral strength, and risk of fracture, than overall bone loss? We hypothesise that ‘stress shielding’ of the anterior vertebral body by the neural arch in erect standing postures can reduce BMD. v. in the anterior vertebral body and thereby reduce vertebral compressive strength. Materials and Methods: A compressive force of 1.5kN was applied to lumbar ‘motion segments’. positioned to simulate erect standing posture. Compressive stresses within the intervertebral disc were measured by pulling a miniature pressure transducer through it. ‘Stress profiles’ were integrated over area to calculate the total compressive force on the disc. 1. This was subtracted from the 1.5kN to calculate the force resisted by the neural arch. Motion segments were then compressed to failure in moderate flexion (to simulate heavy lifting) and their compressive strength obtained. After disarticulation, the BMD. v. , of the whole and the anterior half of each vertebral body was measured by dual energy x-ray absorptiometry (DXA). We report preliminary results from 9 specimens, aged 72–92 yrs. Results: Vertebral strength (in flexion) was inversely related to load-bearing by the neural arch in erect posture (r. 2. =0.42, p=0.05). Strength was directly related to the BMD. v. of the whole (r. 2. =0.65, p=0.06) and the anterior (r. 2. =0.8, p=0.005) vertebral body. Conclusions: These results suggest that habitual load-bearing by the neural arch in erect postures can lead to stress shielding of the anterior vertebral body so that the latter losesBMD. v. , and the vertebra is weakened in the anterior vertebral body appears to be a BMD. v. better predictor of vertebral strength than BMD. v,. of the whole vertebra

Introduction. Hip-Spine syndrome has various clinical aspects. For example, schoolchild with severe congenital dislocation of the hip have unfavorable standing posture and disadvantageous motions in ADL. Hip-Spine syndrome is closely related closely as the adjacent lumbar vertebrae and the hip joint. Furthermore, not only the pelvis and the lumbar spine, but also the neck position might influence on the maximum hip flexion angle. In this study, we examined the maximum hip flexion angle and pelvic movement angle by observing the lumbar spine, the pelvis and the neck in three different positions. Subjects and Methods. The participants were five healthy volunteers (three males and two females) and ranged in age from 16 to 49 years. We measured the hip flexion angle (=∠X) and the pelvic tilt angle (=∠Y), using Zebris WinData and putting the six markers on skin. The positions of the marker are Femur lateral condyle (M1), Greater trochanter (M2), Lateral margin of 10th rib (M3), Anterior superior iliac spine (M4), Superior lateral margin of Iliac (M5), and Acromion (M6). We performed maximum hip flexion three times in three positions and measured ∠X (=∠M1,2,3) and ∠Y (=∠M4,5,6) and calculated the mean and SD of each position. The first position (P1) that we investigated is the regular position specified by the Japanese Orthopedics Association and Rehabilitation Medical Association. The second position (P2) is performed in the limited position of the posterior pelvic tilt and lumbar movement, by placing the tube under the subject's lower back. The third position (P3) is the altered limited position of P2 added by placing the 500ml PET bottle filled water under the back of the subject's neck. Analysis. A two way factorial analysis of variance was used for statistical analysis to examine the difference among three different positions (P1, P2 and P3) in ∠X and ∠Y. A significance level was set at P < 0.05. We also calculated Spearman rank correlation coefficients to determine the correlation between ∠X and ∠Y. Results. There was a statistically significant difference among three different positions (P1, P2 and P3) in both ∠X and ∠Y (p < 0.01). Slight strong correlations were found between ∠X and ∠Y in three different positions. (r =0.5178571). The smallest values of ∠X and ∠Y were obtained in P1. The values of ∠X and ∠Y in P3 were all smaller than those in P2. Conclusions. The limited movement of pelvic and lumbar spine, and neck different positions give the limit to a maximum hip joint flexion angle

Objectives. Normal sagittal spine-pelvis-lower extremity alignment is crucial in humans for maintaining an ergonomic upright standing posture, and pathogenesis in any segment leads to poor balance. The present study aimed to investigate how this sagittal alignment can be affected by severe knee osteoarthritis (KOA), and whether associated changes corresponded with symptoms of lower back pain (LBP) in this patient population. Methods. Lateral radiograph films in an upright standing position were obtained from 59 patients with severe KOA and 58 asymptomatic controls free from KOA. Sagittal alignment of the spine, pelvis, hip and proximal femur was quantified by measuring several radiographic parameters. Global balance was accessed according to the relative position of the C7 plumb line to the sacrum and femoral heads. The presence of chronic LBP was documented. Comparisons between the two groups were carried by independent samples t-tests or chi-squared test. Results. Patients with severe KOA showed significant backward femoral inclination (FI), hip flexion, forward spinal inclination, and higher prevalence of global imbalance (27.1% versus 3.4%, p < 0.001) compared with controls. In addition, patients with FI of 10° (n = 23) showed reduced lumbar lordosis and significant forward spinal inclination compared with controls, whereas those with FI > 10° (n = 36) presented with significant pelvic anteversion and hip flexion. A total of 39 patients with KOA (66.1%) suffered from LBP. There was no significant difference in sagittal alignment between KOA patients with and without LBP. Conclusions. The sagittal alignment of spine-pelvis-lower extremity axis was significantly influenced by severe KOA. The lumbar spine served as the primary source of compensation, while hip flexion and pelvic anteversion increased for further compensation. Changes in sagittal alignment may not be involved in the pathogenesis of LBP in this patient population. Cite this article: W. J. Wang, F. Liu, Y.W. Zhu, M.H. Sun, Y. Qiu, W. J. Weng. Sagittal alignment of the spine-pelvis-lower extremity axis in patients with severe knee osteoarthritis: A radiographic study. Bone Joint Res 2016;5:198–205. DOI:10.1302/2046-3758.55.2000538

Background and Aim. Spinal stability is associated with low back pain and affects the spines ability to support loads. Stability can be achieved if the applied force follows the curvature of the spine, passing close to the vertebral centroids. Previously we showed that calculated muscle forces required for stability in an idealised model increased with increasing and more evenly distributed lumbar curvatures. The purpose of this study was to calculate the muscle forces required for stability in standing in a group of healthy adults. Methods. Positional MRI was used to acquire sagittal images of the lumbar spine in a standing posture in 30 healthy adults. Sacral inclination was measured and active shape modelling used to characterise lumbar spine shape. A two-dimensional model of the lumbar spine was constructed using vertebral centroid positions and a simplified representation of the lumbar extensor muscles. The muscle forces required at each level to produce a follower load were calculated using a force polygon. Results. Sacral angle was positively correlated with the amount of overall curvature in the lumbar spine (P<0.001) but not the distribution of curvature. Muscle forces increased with increasing curvature at all lumbar levels (P<0.02). The distribution of curvature affected the muscle forces only at L3 (P<0.03). Conclusion. In a sample of healthy adults, muscle forces required to maintain stability are determined by the overall curviness of the lumbar spine and, to a lesser extent, the distribution of curvature. Variations in spinal shape should be considered when modelling lumbar spine loading. This abstract has not been previously published in whole or substantial part nor has it been presented previously at a national meeting. Conflicts of interest: No conflicts of interest. Sources of funding: This work was supported by a studentship granted to the University and awarded to AVP. An NHS Endowment grant provided further funding

There have been a large number of studies reporting the knee joint force during level walking, however, the data of during deep knee flexion are scarce, and especially the data about patellofemoral joint force are lacking. Deep knee flexion is a important motion in Japan and some regions of Asia and Arab, because there are the lifestyle of sitting down and lying on the floor directly. Such data is necessary for designing and evaluating the new type of knee prosthesis which can flex deeply. Therefore we estimated the patellofemoral and tibiofemoral forces in deep knee flexion by using the masculoskeltal model of the lower limb. The model for the calculation was constructed by open chain of three bar link mechanism, and each link stood for thigh, lower leg and foot. And six muscles, gluteus maximus, hamstrings, rectus, vastus, gastrocnemius and soleus were modeled as the lines connecting the both end of insertion, which apply tensile force at the insertion on the links. And the model also included the gravity forces, thigh-calf contact forces on the Inputting the data of floor reacting forces and joint angles, the model calculated the muscle forces by the moment equilibrium conditions around each joint, and some assumptions about the ratio of the biarticular muscles. And then, the joint forces were estimated from the muscle forces, using the force equilibrium conditions on patella and tibia. The position/orientation of each segments, femur, patella and tibia, were decided by referring the literature. The motion to be analyzed was standing up from kneeling posture. The joint angles during the motion are shown in Fig.1. This motion included the motion from kneeling to squatting, rising the knee from the floor by flexing hip joint, and the motion from squatting to standing. The test subject was a healthy male, age 23[years], height 1.7[m], weight 65[kgw]. Results were shown in Fig.2. The patellofemoral force was little at standing posture, the end of the motion, however, was as large as tibiofemoral force during the knee joint angle was over 130 degrees. The reason of this was that the patellofemoral joint force was heavily dependent on the quadriceps forces, and the quadriceps tensile force was large at deep knee flexion, at kneeling or squatting posture. The maximum tibiofemoral force was 3.5[BW] at the beginning of standing up from squatting posture. And the maximum patellofemoral force was 3.8[BW] at the motion from kneeling to squatting posture. The conclusion was that the patellofemoral joint force might not be ignored in deep knee flexion and the design of the knee prosthesis should be include the strength design of patellofemoral joint

Background and Aim. Low back pain is highly prevalent, particularly in manual occupations. We previously showed that the lumbar spine has an intrinsic shape, identifiable in lying, sitting and standing postures, that affects the spine's response to load. Its effects on motion are unknown. Here we investigate whether intrinsic spinal shape is detectable throughout a greater range of postures and its effect on how healthy adults lift a weighted box. Methods. The lumbar spine was imaged using a positional MRI with participants (n=30) in 6 postures ranging from extension to full flexion. Active shape modelling was used to identify and quantify ‘modes’ of variation in lumbar spine shape. 3D motion capture analysed participants' motion while lifting a box (6–15 kg, self-selected). Results. Two modes accounted for 89.5% of variation in spinal shape, describing the overall curvature (mode 1) and distribution of curvature (mode 2). Within the first 9 modes, scores were significantly correlated between all six postures (r = 0.4−0.97, P<0.05), showing that intrinsic shape was partially maintained throughout. Individuals with straighter spines lifted with greater knee flexion (r = 0.4, P = 0.03) typical of squatting. Knee flexion negatively correlated with lumbar (r = −0.5 to −0.86, P<0.01) and pelvic flexion (r = −0.81, P<0.001). Those with curvier spines flexed significantly more at the back (r = −0.79, P=0.02) typical of stooping. Conclusion. In summary, individuals with straight spines squatted to lift while those with curvy spines stooped, indicating that the way we move to pick up a load is associated with the shape of our spine

Background and Purpose of Study:. Differences in regional lumbar angles in sitting have been observed between subgroups of NSCLBP patients exhibiting motor control impairments (MCI) (O'Sullivan, 2005; Dankaerts et al, 2006). However, differences in standing posture and other spinal regions are unknown. This study aimed to compare regional spinal angles in healthy and MCI subgroups in sitting and standing. Methods:. An observational, cross-sectional study investigated spinal kinematics of 28 Flexion Pattern (FP), 23 Active Extension Pattern (AEP) (O'Sullivan, 2005) and 28 healthy controls using 3D motion analysis (Vicon) during usual sitting and standing. Mean sagittal angle for Total Lumbar (TotLx), Total Thoracic (TotTx), Upper Thoracic (UTx), Lower Thoracic (LTx), Upper Lumbar (ULx) and Lower Lumbar (LLx) regions between groups were compared using one-way ANOVA. Results:. No differences in total thoracic and lumbar regions were observed, except TotLx in sitting between FP and AEP (Mean Difference (MD)=15.81°, p=0.003). Significant differences were observed in ULx and LTx for standing and sitting between FP and AEP (ULx Standing MD=9.89°, p=0.003; ULx Sitting MD=12.32°, p=0.000; LTx Standing MD=7.57°, p=0.05; LTx Sitting MD=11.72°, p=0.001) with AEP demonstrating greater extension in these regions. FP exhibited greater flexion compared to controls in ULx and LTx, except LTx in standing (ULx Standing MD=7.69°, p=0.018; ULx Sitting MD=6.96°, p=0.014; LTx Sitting MD=11.28°, p=0.001). No differences between AEP and controls were observed in sitting or standing. Conclusion:. Observing subdivided regional spinal angles is key to identifying MCI sub-group differences, with ULx and LTx able to discriminate between FP and AEP, and FP and healthy controls. This abstract has not been previously published in whole or substantial part nor has it been presented previously at a national meeting. Conflicts of interest: No conflicts of interest. Sources of funding: Arthritis Research UK / Presidents Research Scholarship, Cardiff University

Weight-bearing is a known stimulus for bone remodelling and a reduction in weight-bearing is associated with reduced bone mineral density (BMD) in affected limbs post lower limb fracture. This study investigated short and long-term precision of a method for measuring relative left/right weight-bearing using two sets of identical calibrated scales. The effect of imbalance on BMD at the hip and on lower limb lean tissue mass (LLTM) was also assessed. 46 postmenopausal women, with no history of leg or ankle fracture, were measured three times whilst standing astride two scales (Seca, Germany). 34 of the participants were re-measured after 6 months by the same method. Bilateral hip and total body dual x-ray absorptiometry measurements were performed using a GE Lunar Prodigy (Bedford, MA). Precision errors in weight-bearing measures were calculated using the root mean square coefficient of variation (RMSCV%). The correlations at the first visit between left/right differences in weight-bearing and differences in BMD and LLTM were calculated. The short-term RMSCV% for left and right weights were 4.20% and 4.25% respectively and the long-term RMSCV% were 6.91% and 6.90%. Differences in left/right weight-bearing ranged from 0 to 24% (SD 8.63%) at visit 1 and 0 to 30% (SD 10.71%) at visit 2. Using data from visit 1, the relationship between hip BMD differences and left/right weight-bearing differences were investigated, with no significant correlations found. However, a weak, but statistically significant correlation of r=0.35 (p=0.02) was found for differences in LLTM and left/right weight-bearing differences. In conclusion, left/right weight-bearing measured using two scales is a precise method for evaluating differences in weight-bearing in the short and long-term. Differences in left/right weight-bearing in this population varied by up to 30%. Participants showed a high degree of consistency in their long-term balance in a natural standing posture. Inequalities in left/right weight-bearing did not correlate significantly with BMD at the hip, but demonstrated a weak but statistically significant correlation with lean tissue mass

Purpose: To measure the effect of the X-Stop interspinous distraction device on spinal canal, exit foramina, and disc height dimensions at the operated level; and adjacent segment endplate angle, and lumbar spine movement in patients with symptomatic lumbar spinal stenosis using upright MRI. Methods /Results: 14 patients (9 M;5 F) were scanned before and six months after operation. Age ranged from 57 to 88 years. All had symptomatic lumbar spinal stenosis- single level- 9 (L2/3-1; L3/4-1; L4/5-7); double level 5 (L3/4, L4/5). Images were taken in sitting flexed, extended, neutral, and standing. The total range of motion of the lumbar spine and of the individual segments were measured, along with changes in disc height, areas of the exit foramina, and dural sac. The mean area of the dural sac at the operated levels increased from 62.46mm2 to 77.69mm2 (p=0.004) in the standing posture and from 70.85mm2 to 94.62mm2 (p=0.019) in extension postoperatively. The area of the exit foramina in extension increased from 83.57mm2 to 107.88mm2 (p=0.002) on the left side and from 83.77mm2 to 108.69mm2 (p=0.012) on the right. The overall changes in the range of movement of the individual segments or of the lumbar spine were statistically insignificant. Conclusions: This is the first study carried out using an upright MRI scanner in patients with lumbar spinal stenosis. The X-Stop device increases the cross-sectional area of the spinal canal and exit foramina by distracting the spinous processes of the operated level without significantly affecting overall posture of the lumbar spine

Osteoporotic vertebral fractures are normally attributed to weakening of the vertebral body. However, the compressive strength of the spine also depends on the manner in which the intervertebral disc presses on the vertebral body, and on load-bearing by the neural arch. We present preliminary results from a large-scale investigation into the relative importance of these three influences on vertebral compressive strength. Lumbar motion segments from elderly cadavers were subjected to 1.5 kN of compressive loading while the distribution of compressive stress was measured along the antero-posterior diameter of the intervertebral disc, using a miniature pressure-transducer. The overall compressive force on the disc, obtained by integrating the stress profile ( . 1. ), was subtracted from the 1.5 kN applied load to give the force resisted by the neural arch. Stress profilometry was performed with each motion segment positioned to simulate the erect standing posture, and a forward stooping posture. Vertebral strength was measured by compressing the motion segments to failure in the forward stooping posture. In life, the spine is usually compressed most severely in this posture. A univariate analysis of results from the first 9 motion segments (aged 72–92 yrs) showed that vertebral strength increased from 2.0 kN to 4.6 kN as the compressive force resisted by the neural arch in erect postures decreased from 1.1 kN to 0.4 kN (r. 2. = 0.42, p = 0.05). Updated results from this on-going study will be presented at the meeting. Preliminary results suggest that habitual load-bearing by the neural arch in erect postures can lead to progressive weakening of the vertebral body, which is effectively “stress-shielded” by the neural arch. This weakening is exposed when the spine is loaded severely in a forward stooped posture, when it has a reduced compressive strength. This mechanism could explain some features of osteoporotic vertebral fractures in old people

Introduction Symptoms of neurogenic intermittent claudication in spinal stenosis are explained by the narrowing of the spinal canal in the extended (upright) position and widening in the sitting (flexed) position. The X-Stop® inter-spinous process distraction device (St. francis Medical Technologies) is a new product designed to hold the affected segments in a flexed posture. This prospective study looks at the changes in the lumbar spine in a variety of postures from pre- to post-insertion. Method Using positional MRI (pMRI), patients were scanned before and six months after operation. Images were taken in sitting flexed, extended, neutral, and standing positions. The total range of motion of the lumbar spine and of the individual operated segments were measured, along with changes in disc height, areas of the exit foramina, and dural sac. 21 patients (11 males; 10 females) were included in the study. Age ranged from 57 – 88 years. All had symptomatic lumbar spinal stenosis- single level- 13 (L2/3-1; L3/4-3; L4/5-9); double level 8(L3/4, L4/5 – 7; L4/5, L5/ S1 – 1). Results The mean area of the dural sac at the operated levels increased from 89.25mm2 to 108.96mm2 (p< 0.001) in the standing posture and from 103.96mm2 to 124.94mm2 (p< 0.001) in extension postoperatively. The area of the exit foramina in extension increased from 79.15mm2 to 100.41mm2 (p< 0.001) on the left side and from 80.86mm2 to 98.74mm2 (p< 0.001) on the right side. The overall changes in the range of movement of the individual segments or of the lumbar spine were statistically insignificant. Discussion Previous, radiologic (Willen J, et al; Spine 1997) and cadaveric studies have demonstrated reduction in area of the dural sac and exit foramina as the lumbar spine moves from flexion into extension. Our study is the first to quantify these changes in symptomatic patients with lumbar spinal stenosis using postional MRI. This study supports previous studies using positional MRI scanner in patients with lumbar spinal stenosis and also demonstrates that the X-Stop device increases the cross-sectional area of the spinal canal and exit foramina by distracting the spinous processes of the operated level without significantly affecting overall posture of the lumbar spine

Osteoporotic fractures are associated with bone loss following hormonal changes and reduced physical activity in middle age. But these systemic changes do not explain why the anterior vertebral body should be such a common site of fracture. We hypothesise that age-related degenerative changes in the intervertebral discs can lead to abnormal load-bearing by the anterior vertebral body. Cadaveric lumbar motion segments (mean age 50 ± 19 yrs, n = 33) were subjected to 2 kN of compressive loading while the distribution of compressive stress was measured along the antero-posterior diameter of the intervertebral disc, using a miniature pressure-transducer. “Stress profiles” were obtained with each motion segment positioned to simulate a) the erect standing posture, and b) a forward stooping posture. Stress measurements were effectively integrated over area in order to calculate the force acting on the anterior and posterior halves of the disc ( . 1. ). These two forces were subtracted from the applied 2 kN to determine the compressive force resisted by the neural arch. Discs were sectioned and their degree of disc degeneration assessed visually on a scale of 1–4. In motion segments with non-degenerated (grade 1) discs, less than 5% of the compressive force was resisted by the neural arch, and forces on the disc were distributed evenly in both postures. However, in the presence of severe disc degeneration, neural arch load-bearing increased to 40% in the erect posture, and the compressive force exerted by the disc on the vertebral body was concentrated anteriorly in flexion, and posteriorly in erect posture. In severely degenerated discs, the proportion of the 2 kN resisted by the anterior disc increased from 18% in the erect posture to 58% in the forward stooped posture. Disc degeneration causes the disc to lose height, so that in erect postures, substantial compressive force is transferred to the neural arch. In addition, the disc loses its ability to distribute stress evenly on the vertebral body, so that the anterior vertebral body is heavily loaded in flexion. These two effects combine to ensure that the anterior vertebral body is stress-shielded in erect postures, and yet severely loaded in flexed postures. This could explain why anterior vertebral body fractures are so common in elderly people with degenerated discs, and why forward bending movements often precipitate the injury

Aims

The aim of this study was to evaluate the reliability and validity of a patient-specific algorithm which we developed for predicting changes in sagittal pelvic tilt after total hip arthroplasty (THA).