Aim:. AIS causes a loss of trunk height. This paper documents this loss against sitting height standards and assesses formulae for adjusting height loss back to the standard. Methods:. A total of 334 patients (84% female) with AIS and no other known systemic disease had sitting height measured. This was compared to standards of sitting height with age and the ratio of height to sitting height with age (HSH). The corrected height was calculated using published formulae and replotted against these standards. Results:. Both sexes had significant numbers of patients under the 5th centile compared to those above the 95th centile for sitting height (p<0.05 in males and females) and for HSH centiles (p<0.05 in males and females). All formulae increased the sitting height back to within the standards. In males only the Ylikoski formula demonstrated any significant difference in sitting height and HSH. In females the Kono formula gave the least significant difference between those above and below the 95th and 5. th. centiles for sitting height and the Hwang formula for HSH. Discussion:. Scoliosis causes a loss of sitting height seen with the centile standards for sitting height and height to sitting height ratios. This can be corrected, the most accurate formula being Hwang, correcting the data to lie between the 5th and 95th centiles for sitting height with no significant difference between the number of outliers to these centiles. Outliers after use of this formula may suggest alternative pathology. Conflict Of Interest Statement: No conflict of interest

Background. A stem sitting proud (SP) or that above the final rasp position remains in some patients who undergo hip replacement using proximally coated tapered wedge stems. Surgeons may face challenges providing the best fit due to unpredictable stem seating. Zimmer Inc. introduced a new rasp to solve this issue but the clinical results of this rasp have not yet been published. Therefore, we aimed to address the following: 1) What is SP incidence using a proximally coated cementless tapered wedge stem? 2) Does the new rasp system improve seating height? 3) What are the risk factors of SP?. Methods. We performed a retrospective study with 338 hips, in which Tri-Lock Bone Preservation Stem (BPS) was used in 181 and M/L Taper stem was used in 157 hips (82 hips before and 75 hips after the new rasp). A positive stem SP was defined as a stem proud height of >2 mm. We analyzed and compared SP incidence in two stems and in M/L Taper stems before and after the new rasp use. Results. Statistical differences were found across mean age, sex, preoperative diagnosis, and Dorr type between the Tri-Lock BPS and M/L Taper stem groups (P < 0.05); however, no significant difference was found within the M/L Taper groups before and after the 0-mm Rasp use. The sitting proud incidence of the stem was 13% (23/181 hips) with a mean height of 3.0 mm (range: 2.1–4.3 mm) in Tri-Lock BPS and was 15% (12/82 hips) in M/L Taper stem before the 0-mm Rasp use with a mean height of 2.8 mm (range: 2.1–4.0 mm). After the 0-mm Rasp use, only 4% (3/75 hips) showed stem sitting proud with a mean height of 2.2 mm (range: 2.1–2.5 mm). There was no significant difference in the sitting proud incidence between the Tri-Lock BPS and M/L Taper stem groups; however, the sitting proud incidence with M/L Taper stem substantially decreased after the 0-mm Rasp use (P = 0.024). According to the results of the univariate analysis, stem sitting proud was significantly higher at high offset (19%) than at standard offset (8%) in the Tri-Lock BPS system (P < 0.043). In the M/L Taper stem, however, there were no significant differences across all variables, including stem offset, between the stem sitting proud and non-proud groups (Tables 3 and 4). Regarding preoperative diagnosis, the sitting proud incidence was lower in fragility fractures in patients aged ≥50 years (0/18 hips) than in other diagnoses (12/64 hips) using M/L Taper stem before the 0-mm Rasp use, but this result was not statistically significant. When multiple logistic regression analysis was performed, the significant risk factor for stem sitting proud was use of the high offset option in Tri-Lock BPS (P = 0.048; OR = 2.474; 95% CI, 1.009–6.063). There was no substantial difference in the sitting proud incidence between the case groups, each consisting of 30 cases. Regarding femoral head offset, short offset was more frequently used in the stem proud group (13% in Tri-Lock BPS and 58% in M/L Taper stem) than in the non-proud group (4% in Tri-Lock BPS and 21% in M/L Taper stem), and there was a significant difference in M/L Taper stem (P = 0.013). The mean postoperative LLD was 3.0 ± 2.9 mm in Tri-Lock BPS, 3.6 ± 3.2 mm in M/L Taper stem before the 0-mm Rasp use, and 2.7 ± 2.3 mm in M/L Taper stem after the 0-mm Rasp use. There was no significant difference in the mean postoperative LLD between the stem proud and non-proud groups regardless of stem type. At a minimum 6-month follow-up, there was no measurable stem subsidence across all cases. Conclusions. The proximally coated cementless tapered wedge stems are associated with potential problems related to stem sitting proud. The newly developed 0-mm Rasp of M/L Taper stem showed significant improvement in initial seating height compared with the conventional rasp system without postoperative stem subsidence. The use of high offset Tri-Lock BPS stem was the only risk factor for stem proud, but its clinical significance remains unknown. Therefore, large-scale multicenter studies should be conducted to determine relevant risk factors for sitting proud of these stems using a conventional rasp system. For any figures or tables, please contact the authors directly

Introduction. Accurate and reproducible cup positioning is one the most important technical factors that affects outcomes of total hip arthroplasty (THA). Although Lewinnek's safe zone is the most accepted range for anteversion and abduction angles socket orientation, the effect of fixed lumbosacral spine on pelvic tilt and obliquity is not yet established. Questions:. What is the change in anteversion and abduction angle from standing to sitting in a consecutive cohort of patients undergoing THA?. What is the effect of fixed and flexible spinal deformities on acetabular cup orientation after THA?. Material and Methods. Between July 2011 and October 2011, 68 consecutive unilateral THAs were implanted in 68 patients with a mean age of 71 ± 6 years old. Radiographic evaluation included standing anteroposterior (AP) and lateral pelvic radiographs, and sitting lateral pelvic radiograph, measuring lumbosacral angle (LSA), sacral angle (SA), and sagittal pelvic tilt angle (SPTA). Computer generated 3D pelvis models were used to analyze the correlation between different pelvic tilts and acetabular cup orientation in abduction and anteversion. Results. The mean standing STPA was 3.7º of anterior tilt (range: −9º of anterior tilt to 25º of posterior tilt). The mean SPTA in sitting was −17.7º of posterior tilt (range: −38º of posterior tilt to 7º of anterior tilt). In a fixed spinal deformity (54%) the SPTA was significantly smaller compared to the flexible pelvis group (10º versus 30.9º, p=0.0001). Flexible pelvises (46%) had a posterior tilt from standing to sitting resulting in increased anteversion. Overall, mean change in LSA and SA from standing to sitting was 22.5º and 20.2º, respectively. The mean post-operative functional anteversion and abduction angles were 19.2º and 42.1º, respectively. In the virtual 3D pelvic models, when the abduction angle was between 40 and 45 degrees, anteversion changed of 0.75 degrees for 1 degree of change of pelvic tilt. Discussion. There is a significant change in pelvic tilt from standing to sitting, especially in patients with flexible spines, where the functional anteversion increases with sitting. Patients with a fixed pelvis have significantly less change in sagittal tilt and therefore less change in anteversion from standing to sitting position. Care should be taken to adjust cup positioning in fixed spinal deformity

Introduction. Spatial orientation of the pelvis in the sagittal plane is a key parameter for hip function. Pelvic extension (or retroversion) and pelvic flexion(or anteversion) are currently assessed using Sacral Slope (SS) evaluation (respectively SS decrease and SS increase). Pelvic retroversion may be a risk situation for THA patients. But the magnitude of SS is dependant on the magnitude of pelvic incidence (PI) and may fail to discriminate pelvic position due to patient's anatomy and the potential adaptation mechanisms: a high PI patient has a higher SS but this situation can hide an associated pelvic extension due to compensatory mechanisms of the pelvic area. A low PI patient has a lower SS with less adaptation possibilities in case of THA especially in aging patients. The individual relative pelvic version (RPV) is defined as the difference between « measured SS » (SSm) minus the « normal SS »(SSn) described for the standard population. The aim of the study was to evaluate RPV in standing and sitting position with a special interest for high and low PI patients. Materials and Methods. 96 patients without THA (reference group) and 96 THA patients were included. Pelvic parameters (SS and PI) were measured on standing and sitting EOS images. RPV standing (SSm-SSn) was calculated using the formula SSm – (9 + 0.59 × PI) according to previous publications. SSn in sitting position was calculated according to PI using linear regression: RPV sitting was calculated using the formula RPV = SS – (3,54+ 0,38 × PI). Three subgroups were defined according to pelvic incidence (PI): low PI <45°, 45°<normal PI<65° or high PI>65°. Results. For THA patients, pelvic parameters were:. SSm standing 41° (SD 11°; 8°.73°). SSm sitting 25° (SD 12°;−3°.54°). SSm variation 16°(SD 11°; 9°.46°). RPV standing −2°(SD 9°; −27°.21°). RPV sitting 7° (SD 10; −15°.29°). For non THA patients, pelvic parameters were:. SSm standing39° (SD 10°; 13°.63°). SSm sitting 17° (SD 11°;−5°.48°). SSm variation 27°(SD 13°; −27°.46°). RPV standing −1°(SD 7°; −29°.12°). RPV sitting 0° (SD 10,5; −29.35). Standing-sitting SS variations and RPV were not correlated with PI. Low PI incidence patients had very low RPV standing and sitting. In non THA patients RPV standing and sitting were very low. In THA patients standing-sitting SS variations and RPV were higher than for non THA patients. Sitting RPV was higher than in standing position. Discussion, Conclusion. The overall analysis of SS has limitations: higher or lower SS may be linked to 2 factors: pelvic morphology (PI) and sagittal orientation of the pelvis. RPV and PI were not correlated: a higher or lower value of RPV directly represents the sagittal orientation of the pelvis. Low PI patients have a specific postural pattern with low pelvic adaptability. THA patients specificity for RPV needs further studies for understanding the impact on postoperative rebalancing and instability problems

Introduction: Systematic reviews have found that sitting at work is not associated with LBP, although the biomechanical evidence does offer plausible causative mechanisms. Indeed, exposure to lumbar postures has been assessed using imprecise tools that have limited epidemiological investigations. The aim of this study was to use new technology to measure the seated lumbar postures of sedentary (call centre) workers, and survey their current and future symptoms in order to determine associations with LBP. Methods: A fibre-optic goniometer (FOG) system was attached to the lumbar spine and hip of 181 sedentary call centre workers at the start of their working shift. The lumbar FOG provides a continuous measure of sagittal lumbar curvature (lumbar position and movement), whilst the hip FOG enables quantification of sitting time. Baseline and 6-month follow-up questionnaires were used to collected symptom data, and logistic regression was used to determine associations between postural and symptom (yes/no) data. Results: Workers spent a mean proportion of 83% of work-time sitting, with 17% sitting for more than 90 minutes without a break. Current LBP (symptoms lasting more than 24hrs) was associated with a kyphotic (mean lumbar angle> 180°) sitting posture (yes/no) (OR 2.1, 1.1–4.1), although movement (mean standard deviation and angular velocity °sec-1) in sitting was not. Sitting relatively static (AV< 4.26° yes/no) (OR 3.30, 1.06–10.25), using a small amount of range (SD< 10.2° yes/no) (OR 3.79, 1.2–11.7), and adopting a kyphotic posture (yes/no) (OR 2.75, 1.02–7.3) all significantly increased the risk of future LBP. Discussion: Sitting postures at work are associated with current LBP and are statistically significant risks for recurrence. These results highlight the potential for ergonomic interventions to reduce current symptoms and the risk of future episodes. The findings from this study are novel, and the FOG system should now be used in larger investigations of sedentary risk factors for LBP

Purpose: To determine differences in muscle activity of superfical multifidus (SM) and iliocostalis lumborum (IL) between healthy subjects (H) and those with a past history of low back pain (HB) during unsupported sitting. Background: Sitting has been implicated in the incidence of low back pain. However conflcting evidence is reported on the effect of sitting on the erector spinae with some studies noting an increase, others a decrease and others no difference in activity (Callaghan and McGill 2001, Jackson et al 2001, Dankaerts et al 2006). Most studies focus on subjects with current low back pain. It is known that following an episode of back pain deficits in muscle activty may persist (Hides et al 2001). Methods: 20 subjects gave informed consent, 10 in each of the H and HB groups. Surface electromyography data was recorded from M and IL bilaterally over 4 time points over 15 minutes of unsupported ‘usual’ sitting. This data was normalised using MVCs and compared for differences using repeated measures ANOVA. Results: Descriptive data for iliocostalis lumborum and superficial multifidus are presented respectively. No significant difference was detected between groups or time points for either muscle (p> 0.05). Conclusion: This preliminary study suggests that subjects with a history of low back pain and healthy subjects have no difference in muscle activity of SM and IL in unsupported sitting. This suggests that HB subjects have no residual muscular weakness and implies no further muscular rehabilitation is required. Further research with larger samples should be undertaken

Introduction. Literature describes pelvic rotation on lateral X rays from standing to sitting position. EOS full body lateral images provide additional information about the global posture. The projection of the vertical line from C7 (C7 VL) is used to evaluate the spine balance. C7 VL can also measure pelvic sagittal translation (PST) by its horizontal distance to the hip center (HC). This study evaluates the impact of a THA implantation on pelvic rotation and sagittal translation. Materials and Method. Lumbo-pelvic parameters of 120 patients have been retrospectively assessed pre and post- operatively on both standing and sitting acquisitions (primary unilateral THA without complication). PST is zero when C7VL goes through the center of the femoral heads and positive when C7VL is posterior to the hips' center (negative if anterior). Three subgroups were defined according to pelvic incidence (PI): low PI <45°, 45°<normal PI<65° or high PI>65°. Results. Pre-operatively PST standing was −0.9 cm (SD 4.5; [−15.1 to 7.2]) and PST sitting was 1.3cm (SD 3.3; [−7.7 to 11.8]). The overall mean change from standing to sitting was 2.2 cm ([−7.2 to 17.4]) (p<0.05). Post-operatively PST standing was 0.2 cm (SD 4.7; [−17 to 8.1]) and PST sitting was 1.4cm (SD 3.5; [−7.3 to 10.4]). The overall mean change from standing to sitting was 1.2 cm ([−14.2 to 22.4]) (p<0.05). In low PI group pre and post-operatively, PST increased significantly from standing to sitting (p<0.05; with HC going anterior to C7VL). When comparing pre and post operative changes, standing PST significantly increased (p=0.001). Pre to postoperative PST variation (sitting-standing) decreased significantly (p=0,01). In normal PI group pre-operatively, PST increased from standing to sitting (p=0.004). When comparing pre and postoperative changes, PST increased (p=0.006). Pre to postoperative PST variation (sitting-standing) decreased significantly (p=0,04). In high PI group pre and post operatively, PST increased from standing to sitting (p=0.034) while there are no significant changes from pre to post-operative status in standing and in sitting. Discussion. Anteroposterior pelvic tilt is not the only adaptation strategy for postural changes from standing to sitting positions. Anteroposterior pelvic translation (quantified by PST) is an important adaptation mechanism for postural changes. Comparison of pre and post-operative values of PST points out the importance of pelvic translation for low and standard PI patients after THA. The anteroposterior translation appears to change significantly in different functional positions pre and post operatively. This is an important variable to consider when assessing the patients' posture change or investigating the causes of the hip dislocation after total hip arthroplasty or spinal fusion. Conclusion. Pelvic translation must be considered as a significant mechanism of adaptation after THA. Further studies are needed to study the impact on subluxation or dislocation

Introduction. Pelvic flexion and extension in different body positions can affect acetabular orientation after total hip arthroplasty, and this may predispose patients to dislocation. The purpose of this study was to evaluate functional acetabular component position in total hip replacement patients during standing and sitting. We hypothesize that patients with degenerative lumbar disease will have less pelvic extension from standing to sitting, compared to patients with a normal lumbar spine or single level spine disease. Methods. A prospective cohort of 20 patients with primary unilateral THR underwent spine-to-ankle standing and sitting lateral radiographs that included the lumbar spine and pelvis using EOS imaging. Patients were an average age of 58 ± 12 years and 6 patients were female. Patients had (1) normal lumbar spines or single level degeneration, (2) multilevel degenerative disc disease or (3) scoliosis. We measured acetabular anteversion (cup relative to the horizontal), sacral slope angle (superior endplate of S1 relative to the horizontal), and lumbar lordosis angles (superior endplates of L1 and S1). We calculated the absolute difference in acetabular anteversion and the absolute difference in lumbar lordosis during standing and sitting (Figure 1). Results. Nine patients had normal lumbar spines or scoliosis, and 11 patients had multilevel disc disease. The median change in cup anteversion for normal and scoliosis patients was 29° degrees (range 11° to 41°) compared to 21° degrees (range 1° to 34°) for multilevel disc disease patients (p=0.03). There was a positive correlation between the change in cup anteversion and the change in lumbar lordosis (p=0.01; Figure 2). From standing to sitting, cup anteversion always increased and lumbar lordosis always decreased. Conclusions. The change in cup anteversion from standing to sitting was variable in patients with normal, degenerative, and scoliosis lumbar spines. Patients with degenerative disc disease have less pelvic extension, and thus less acetabular anteversion in the sitting position compared to normal spines. This may increase their risk of posterior dislocation

Introduction: Hip dislocation remains a relevant complication of total hip arthroplasty.The implants position plays a major role, especially cup anteversion.It has been demonstrated that anteversion measured on CTscan depends on the pelvic position in a lying patient. This prospective study evaluates the influence of pelvic tilt according to standing and sitting positions. Material and Methods: The radiological records of 328 consecutive asymptomatic patients with THP were analyzed. These were routine radiological controls of non cemented THP with metal back acetabular implants. All patients had AP and lateral radiographs in standing and sitting position and a “low-dose” CT scan of the pelvis in lying position.Patients were checked for the absence lower limb length discrepancy and lumbosacral junction abnormality. All the measurements were done by two independent observers and averaged. From the standard radiographs, the sacral slope (SS), the acetabular frontal inclination (AFI), and the acetabular sagittal inclination (ASI) were measured in standing, sitting, and lying positions. From the CT scan sections, the anatomical ante-version (AA) was measured in lying position on axial images according to Murray. The results were compared to a previously described protocol replicating standing and sitting positions: CTscan sections were oriented according to sacral slope. Results: We confirmed that the anatomical anteversion (AA), the frontal inclination (FI), and the sagittal inclination (SI) were functional parameter which significantly varied between standing, sitting, and lying positions according to sacral slope variations.The acetabular parameters in lying position highly correlated to the one in standing position, while poorly correlated with sitting position. The difference between the lying and the sitting positions was about 10°, 25°, and 15° for the AA, the AFI, and the ASI respectively.Mean lying anteversion angle was 24.2° (SD6,9°).Posterior pelvic tilt in sitting position, (sacral slope decrease) was linked to anteversion increase (mean value 38,8° - SD 5,4°). Anterior pelvic tilt in standing position (sacral slope increase) was linked to lower anteversion (mean value 31,7° - SD5,6°). Discussion and Conclusions: Our study confirms the interest CTscan sections oriented according to sacral slope.The strong correlation between lying and standing measurements suggests that classical CTscan protocol is relevant for standing anteversion. According to the poor correlation between lying and sitting positions, it is less contributive for the investigation of dislocations in sitting position

Knowledge of joint kinematics in the lower limb is important for understanding joint injuries and diseases and evaluating treatment outcomes. However, limited information is available about the joint kinematics required for high flexion activities necessary for floor sitting life style. In this study, the hip and knee joint kinematics of ten healthy male and ten healthy female subjects were investigated using an electromagnetic motion tracking system. We measured the hip and knee joints' functions moving into 1) kneeling on knees with legs parallel without using arms, 2) kneeling on knees with legs parallel with using arms, 3) kneeling on knees with one foot forward without using arms, 4) cross-legged sitting, 5) kneeling with legs to the side, 6) sitting with legs stretched out, and 7) deep squatting, and moving out of the above seven conditions. Conditions 1) through 3) were Japanese seiza style. On conditions 4) through 7), arms were not used. We further measured the functions of putting on and taking off a sock under such conditions as 8) with standing position and 9) sitting position (Fig 1). Here special attention was paid for flexion and extension motion. The data were used to produce the pattern of joint angulation against the percentage of the cycle for each individual conducting each activity. The kinematic curves were split into 3 phases: moving into the rest position, the rest position and out of the rest position. It should be noted that the moving into and the rest phases were split at the moment when the peak value was determined during the moving into phase. Thus the initiation of the rest phase on the curve was not coinciding with the moment the subject reached at the rest position. This was necessary in order not for the mean kinematic curve to become too dull in shape. Same was true when the end of rest phase was determined. The maximum hip and knee joint angles during the cycle were determined. Further a relationship between the hip and knee joint excursions were investigated. The results indicated condition 8) requires the maximum flexion angles to the hip among all conditions, 157.5 ± 20.4° and condition 3) to the knee joint, 157.1 ± 10.0° respectively (Fig 2). The results also indicated in many activities, the maximum joint angles were recorded not during the rest phase but during the moving into or out of phase. In any conditions even including donning on and off a sock, a strong relationship was found between the hip and knee joints motion (Fig 3), indicating the bi-articular muscles' co-contraction during the sit to stand activities. The data presented in this study will increase the knowledge of high-flexion needs especially in non-Western cultures and provide an initial characterization of the prosthesis kinematics in high flexion

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

Background. Recent literature points out the potential interest of standing and sitting X-rays for the evaluation of THA patients. The accuracy of the anterior pelvic plane measures is questionable due to the variations in the quality of lateral standing and sitting X-rays. The EOS® (EOS imaging, Paris, France) is an innovative slot-scanning radiograph system allowing the acquisition of radiograph images while the patient is in weightbearing position with less irradiation than standard imagers. This study reports the “functionnal” positions of a 150 THA cohort, including the lateral orientation of the cups. Methods. The following parameters were measured: sacral slope (SS), pelvic tilt (PT), pelvic incidence (PI) and anterior pelvic plane (APP) sagittal inclination (ASI), frontal inclination (AFI) and planar anteversion (ANT). Irradiation doses were calculated in standing and sitting acquisitions. Variations of sagittal orientation of the cup were measured on lateral standing and sitting images. Descriptive and multivariate analysis were performed for the different parameters studied. Results. The mean doses for full body were 0,80 mGy ± 0,13 for standing position and 0,94 mGy ± 0,25 for sitting position. The mean value for PI was 55,8° ± 11,4. The mean values standing position were 39,01° ± 9,9 for SS, 17,23° ± 10,2 for PT, and 0,74° ± 8,4 for APP. The mean values were 46,36° ± 9,8 for AFI, 39,49° ± 15,1 for ASI and 22,09° ± 11,1 for ANT. In sitting position, the mean values were 20,87° ± 10,2 for SS, 35,37° ± 13,1 for PT and 21,13° ± 11,2 for APP. The mean values were 56,41° ± 12,3 for AFI, 51,71° ± 14,7 for ASI and 33,45° ± 12,9 for ANT. Conclusions and Clinical Relevance. Unexpected variations of the anterior pelvic plane can be observed as well as the influence of pelvic incidence on pelvic orientation. The EOS® imaging system provides new informations regarding the pelvis functionnal anatomy in THA patients with potential applications for the study of unstable cases and wear phenomenons

The functional pelvic tilt when standing and sitting forward of 7402 cases on the OPS, Optimized Ortho, Australia Data Base were reviewed. All patients had undergone lateral radiographs when standing simulating extension of the hip, and sitting forward when the hip is near full flexion. Pelvic tilt was measured as the angle of the Anterior Pelvic Plane to the vertical Sagittal Plane, rotation anteriorly being given a positive value. Pelvises that had rotated more than 13 degrees anteriorly (+ve) when sitting forward or posteriorly (-ve) when standing were considered to place the hip at increased risk of dislocation or edge loading when flexed or extending respectively. This degree of rotation has the effect of changing the acetabular version by approximately10. 0. Most safe zones that have been described have given a range of anteversion of 20. 0. as safe. A change of 10. 0. would potentially place the acetabular orientation outside this range. Further, clinical studies have supported this concept. All lateral radiographs were reviewed to confirm that 281 had undergone instrumented spinal fusion at some level between T12 and S1. There was a large variability in the number and the levels arthrodesed. The range of pelvic mobility in the non-arthrodesed group in extension was −37. 0. to 31. 0. (mean −0.9. 0. , Standard deviation 7.49) and in flexed position was −70. 0. to 49. 0. (mean −1.9. 0. , Standard deviation 14.01). For the group with any fusion the range of pelvic tilt in extension was −31. 0. to 22. 0. (mean −4. 0. , Standard deviation 8.21) and flexed −32. 0. to 46. 0. (mean 4.4. 0. , Standard deviation 13.79). Of the 7121 cases without instrumented fusion, 15.5% were considered to be at risk when in flexion and 6.1% when extended. The risk for those with any fusion was approximately doubled in both flexion and extension. Further, those with extensive arthrodesis from T12 to S1 had a range of pelvic tilts similar to the non-fused group, although they had a significantly higher percentage of cases in the ‘at risk’ zones. The proportion of the cases in the ‘at risk’ zones decreased progressively as the arthrodesed levels moved from L5/S1 to the upper lumbar spine, and with decreasing number of levels fused. Conclusion. Spinal fusion is not just one group as there are many combinations of different levels fused. Patients with instrumented spinal fusions do have a proportionately high risk of failure of their THR than the majority of cases with no instrumentation, though the risk varies significantly with the number of levels and actual levels arthrodesed. Further approximately 21% of cases with no spinal fusion have functional pelvic movements that would potentially place them ‘at risk’ of edge loading or dislocation. For any figures or tables, please contact authors directly

Introduction. The combination of spinal fusion and THP is not exceptional. Disorders of the pelvic tilt and stiffness of the lumbosacral junction modify the adaptation options while standing or sitting. Adjusting the cup can be difficult and THP instability is a potential risk. This study reports an experience with EOS® simultaneous measurements on AP and lateral views of spine and hips in THP patients. Material and methods. 29 men and 45 women were included in this prospective study. 21cases had bilateral THP. Patients were separated into two groups: long fusions including the thoraco-lumbar junction (group 1) and shorter fusions below L1 (group 2). We analyzed the impact of the arthrodesis on the position of the pelvis by measuring variations of the sacral slope (SS) and APP angle. Cup position was defined by coronal inclination and functional anteversion in the horizontal plane standing and sitting. We compared the data to a previous series of 150 THP patients with asymptomatic and non fused spine. Results. Table1 reports the results of the fusion series. The overall analysis of all patients demonstrates that the values for the cup functional anteversion and coronal inclination are statistically different when comparing standing to sitting (respectively p <0.01and p <0.001). The same results are obtained for SS and APP. This difference is not significant for group 1 patients. The mean range of variation for cup anteversion and inclination is 5° and 7° in the fused cases. Table 2 reports the results of the non fusion series. SS, APP and cup orientation values are statistically significant between standing and sitting. All of the values are statistically different when compared to the fused patients. The mean range of variation for cup anteversion and inclination is 11,6° and 10°. Discussion. The population of THP patients is characterized by pelvic retroversion and a significant reduction of sagittal pelvic mobility when compared to young asymptomatic individuals. Patients combining THP and spine fusion showed significant reduction of adaptation possibilities due to low variations for SS and cup orientation angles. Conclusion. This preliminary study shows the importance of planning THP taking into account not only the orientation of the spine but also its mobility for adaptation in standing and sitting positions. This is a key issue because of the growing number of elderly THP patients whose spine is degenerative or fused. A particular attention must be drawn to the cases with long fusions. The interest of a global vision of the hip-spine relationship is evident in the prevention or in management of dislocations and subluxations, and especially for the indications of dual-mobility prostheses. To view tables/figures, please contact authors directly

Background: Symptom modifying factors (SMFs) are everyday activities or postures that are reported to aggravate or alleviate existing LBP symptoms. In relation to sedentary jobs, workers are known to experience LBP whilst sat at work, and may report that aspects of sitting either aggravate or alleviate their symptoms. These factors appear to have received little attention in the literature, and may help to discriminate workers with different types of LBP, or identify workers likely to take sickness absence due to LBP. Methods: A new sitting and symptom modifying factors questionnaire (SSMQ) was designed and consisted of 11 items. This questionnaire was distributed to 135 sedentary workers on two occasions with a 2 week time lapse. Principal components analysis (PCA) and Cronbach’s alpha were used to explore the structure and internal consistency of the questionnaire. Paired t-tests were used to determine test-retest stability. Results: Three factors with eigenvalues > 1 were extracted that explained 62% of the total variance, and each factors items loaded > 0.06. These sub-scales related to aggravating and relieving (movement and posture) factors, and had consistency levels of 0.80, 0.72 and 0.78 respectively. The retest response rate was 46% and there were no statistically significant differences (p > 0.05) between test-retest measures. Conclusions: Validating the SSMQ has produced an instrument that can be used in sedentary jobs to investigate the influence of symptom modifying factors on LBP symptoms, care seeking and sickness absence due to LBP. This questionnaire will now be used in a prospective study of sedentary call centre workers

Introduction. The changes in sagittal spino-pelvic balance from standing to sitting in patients with end-stage osteoarthritis (OA) of the hip remain poorly characterized. Our aim was to 1) investigate the contribution of sagittal spino-pelvic movement and hip flexion when moving from a standing to sitting posture in patients with hip OA; 2) determine the proportion of OA-patients with stiff, normal or hypermobile spino-pelvic mobility and 3) identify radiographic parameters correlating with spino-pelvic mobility. Methods. This prospective diagnostic cohort study followed 116 consecutive patients with end-stage osteoarthritis awaiting THR. All patients underwent preoperative standardized radiographs (lateral view) of the lumbar spine, pelvis and proximal femur using EOS© in standing position and with femurs parallel to the floor in order to achieve a 90°-seated position. Radiographic measurements performed included lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT), pelvic incidence (PI) and pelvic-femoral-angle (PFA). The difference in PT between standing and seated allowed for patient classification based on spino-pelvic mobility into stiff (<±10°), normal (±10–30°), or hypermobile (>±30°). Results. From the standing to the sitting position, the pelvis tilted backwards by a mean of 19.1° (SD 12.8) and the hip was flexed by a mean of 56.6° (SD 17.2). Change in pelvic tilt correlated inversely with change in hip flexion (r=−0.68; P<0.01; r. 2. =0.47). Thirty-two patients (28%) had stiff, 68 (58%) normal and 16 (14%) hypermobile spino-pelvic mobility. Multivariate regression analysis adjusted for patient age, BMI, static LL, SS, PI, PT and PFA showed a correlation for static standing SS and the change in PT (p=0.03; β=2.31; r. 2. =0.34). Conclusion. Hip flexion contributes on average 75% (25–100%) of the motion required to sit upright. Pre-operative assessment would identify patients with spino-pelvic hypermobility (associated greater change in cup orientation) or stiffness (associated increased hip range-of-movement), which would be at greater risk of dislocation

Introduction: Computer assisted total hip replacement (THA) usually uses the anterior pelvic plane (plane of Lewinneck, APP) for reference because the anatomical landmarks are easy to access during the surgical procedure. However, a recent study shows the lack of correlation in between the Lewinnek angle in standing position (L) and the spinal radiological parameters for sagittal balance, specifically the incidence angle and the sacral slope. The anatomical variations of the anterior superior iliac spines account for the discrepancy. The authors propose here the assessment of the Lewin-nek – sacrum angle (LS) (anterior pelvic plane to the sacral endplate) Methods: 120 asymptomatic patients with THA had low dose lateral X-rays of the lumbo-pelvic area (Definium 8000, GE Healthcare ;dose 0,6 mSivert). The measurements of the sacral slope, incidence angle, and APP were done by two independent observers. Results: The sacral slope and incidence angles were similar to other series. The APP was no clearly identified in 78 cases. The average L angle was −3° (SD 8°) in standing position, −23° (SD 11°) in sitting postion, and −2° (SD 8°) in lying position. The average LS angle was 47° (SD 13°). The geometrical relationship between the LS a ngle, the L angle and the sacral slope is reported. Conclusion: THA stability supposes that the orientation of the acetabular component shall remain within extreme values in standing, sitting, and lying postures. The adjustment of the acetabulum takes into account the functionnal anatomy of the lumbopelvic area. The sacral slope is a reliable radiological reference and is related to the sagittal balance of the spine. The APP presents some interindividual variability and is poorly visible on the radiographs, but it is easily accessible during surgery. The author suggest using the Lewinnek sacrum (LS) angle for radiological planification and for surgical navigation procedures

Background. There is limited research investigating the effects of the Saddle Chair on spinal angles and it has not been determined if there is a difference between a self –selected comfortable posture (SSCP) and a standardised ergonomic posture (SEP). Purpose of Study. Investigate if there is a difference in head tilt (HT); neck angle (NA); cervico-thoracic angle (CTA); thoracic angle (TA); lumbar angle (LA) and pelvic tilt (PT) when sitting on a saddle chair and adopting a SSCP compared with a SEP. Methods. Experimental same subject design (n = 13) using healthy subjects conducting a typing task sitting on a Saddle Chair. A standardised introduction was given to the adjustment possibilities of the saddle chair, the hydraulic table, the computer screen and the screen riser. Subjects were asked to adopt a SSCP and to carry out a split-screen typing task. Further standardised instructions were then given and adjustments made to achieve a SEP and the task repeated. Analysis was via digital photographs analysed within MatLab. Wilcoxon Signed Rank Tests were conducted for each spinal variable. Results. There was only a statistically significant difference in NA and CTA (p ≤ 0.05) when comparing the two postures. The mean neck angle was 3.61° less in the SEP and the mean CTA 1.09° less in the SEP. Conclusion. These preliminary finding suggest that in order to adopt a more upright posture in relation to NA and CTA users need to be provided with standardised ergonomic instructions, rather than adopt a SSCP. No Conflict of interest. No funding obtained. This abstract has not been previously published in whole or substantial part nor has it been presented previously at a national meeting

Purpose: Pressure ulcers at the ischial tuberosities are a significant cause of morbidity and mortality in persons with spinal cord injuries. Current prevention strategies are not fully adequate and surgical treatment is not always effective. In order to develop a novel method of ulcer prevention using magnetic repulsion, we needed to establish the relationship between pressure developed at the level of the ischial tuberosities while seated and the associated changes in blood flow in the sub-ischial tissues. Our hypothesis was that a threshold pressure or “pressure-prescription” would emerge as a target we could subsequently aim for with magnetic offloading. Method: We performed a physiologic study comparing incremental pressure applied at the ischial tuberosities with alterations in the local cutaneous perfusion. Persons with spinal cord injuries were compared to uninjured controls in order to detect any significant differences in the pressure-perfusion relationship between these two groups. Subjects were progressively lowered onto a seat where perfusion was measured with laser Doppler perfusion imaging and pressure was recorded with a pressure mapping system. The mean perfusion vs. pressure curve was determined from a zero loaded position to a maximally loaded position. Results: Healthy controls exhibited stable cutaneous ischial tissue perfusion up to sitting pressures of 150mm Hg followed by a 10% increase in blood flow at higher peak pressures. In contrast, subjects with spinal cord injuries underwent an early decrease in perfusion of 20% up to pressures of 150mm Hg, with a subsequent leveling off of their flow at higher pressures. The spinal cord injured also demonstrated lower reperfusion values indicative of a weaker reactive hyperemia in response to pressure. Conclusion: Compared to uninjured people, individuals with spinal cord injuries appear to have inherent blood flow regulation differences in response to pressure at the sub-ischial tissues, possibly due to dysfunction of an autonomic phenomenon termed pressure-induced vasodilation. Furthermore, a threshold pressure for maintaining optimal perfusion remains elusive for both healthy subjects and persons with spinal injuries. CLINICAL RELEVANCE: Targeting the altered blood flow response to pressure in patients with spinal cord injuries, pharmacologically or mechanically, may lead to a reduction in the incidence of decubital ulcers

Aims. Pelvic tilt (PT) can significantly change the functional orientation of the acetabular component and may differ markedly between patients undergoing total hip arthroplasty (THA). Patients with stiff spines who have little change in PT are considered at high risk for instability following THA. Femoral component position also contributes to the limits of impingement-free range of motion (ROM), but has been less studied. Little is known about the impact of combined anteversion on risk of impingement with changing pelvic position. Methods. We used a virtual hip ROM (vROM) tool to investigate whether there is an ideal functional combined anteversion for reduced risk of hip impingement. We collected PT information from functional lateral radiographs (standing and sitting) and a supine CT scan, which was then input into the vROM tool. We developed a novel vROM scoring system, considering both seated flexion and standing extension manoeuvres, to quantify whether hips had limited ROM and then correlated the vROM score to component position. Results. The vast majority of THA planned with standing combined anteversion between 30° to 50° and sitting combined anteversion between 45° to 65° had a vROM score > 99%, while the majority of vROM scores less than 99% were outside of this zone. The range of PT in supine, standing, and sitting positions varied widely between patients. Patients who had little change in PT from standing to sitting positions had decreased hip vROM. Conclusion. It has been shown previously that an individual’s unique spinopelvic alignment influences functional cup anteversion. But functional combined anteversion, which also considers stem position, should be used to identify an ideal THA position for impingement-free ROM. We found a functional combined anteversion zone for THA that may be used moving forward to place total hip components. Cite this article: Bone Jt Open 2021;2(10):834–841