The effect of age on sagittal plane profile of the lumbar spine according to standing, supine, and various sitting positions

A method for calculating vector forces at human-mattress interface during sleeping positions utilizing image registration

The vector forces at the human-mattress interface are not only crucial for understanding the distribution of vertical and shear forces exerted on the human body during sleep but also serves as a significant input for biomechanical models of sleeping positions, whose accuracy determines the credibility of predicting musculoskeletal system loads. In this study, we introduce a novel method for calculating the interface vector forces. By recording indentations after supine and lateral positions using a vacuum mattress and 3D scanner, we utilize image registration techniques to align body pressure distribution with the mattress deformation scanning images, thereby calculating the vector force values for each unit area (36.25 mm × 36.25 mm). This method was validated through five participants attendance from two perspectives, revealing that (1) the mean summation of the vertical force components is 98.67% ± 7.21% body weight, exhibiting good consistency, and mean ratio of horizontal component force to body weight is 2.18% ± 1.77%. (2) the predicted muscle activity using the vector forces as input to the sleep position model aligns with the measured muscle activity (%MVC), with correlation coefficient over 0.7. The proposed method contributes to the vector force distribution understanding and the analysis of musculoskeletal loads during sleep, providing valuable insights for mattress design and evaluation.

Sagittal balance in sitting and standing positions: A systematic review of radiographic measures

Background

Sagittal imbalance can be caused by various etiologies and is among the most important indicators of spinal deformity. Sagittal balance can be restored through surgical intervention based on several radiographic measures. The purpose of this study is to review the normal parameters in the sitting position, which are not well understood and could have significant implications for non-ambulatory patients.

Methods

A systematic review was performed adhering to PRISMA Guidelines. Using R-software, the weighted means and 95% confidence intervals of the radiographic findings were calculated using a random effect model and significance testing using unpaired t-tests.

Results

10 articles with a total of 1066 subjects reported radiographic measures of subjects with no spinal deformity in the sitting and standing position. In the healthy individual, standing sagittal vertical axis -16.8°was significantly less than sitting 28.4° (p < 0.0001), while standing lumbar lordosis 43.3°is significantly greater than sitting 21.3° (p < 0.0001). Thoracic kyphosis was not significantly different between the two groups (p = 0.368). Standing sacral slope 34.3° was significantly greater than sitting 19.5° (p < 0.0001) and standing pelvic tilt 14.0° was significantly less than sitting 33.9° (p < 0.0001).

Conclusions

There are key differences between standing and sitting postures, which could lead to undue stress on surgical implants and poor outcomes, especially for non-ambulatory populations. There is a need for more studies reporting sitting and standing radiographic measures in different postures and spinal conditions.

Anterior Column Reconstruction of Destructive Vertebral Osteomyelitis at the Thoracolumbar Spine with an Expandable Vertebral Body Replacement Implant: A Retrospective, Monocentric Radiological Cohort Analysis of 24 Cases

BACKGROUND

Vertebral osteomyelitis (VO) often necessitates surgical intervention due to bone loss-induced spinal instability. Anterior column reconstruction, utilizing expandable vertebral body replacement (VBR) implants, is a recognized approach to restore stability and prevent neurological compromise. Despite various techniques, clinical evidence regarding the safety and efficacy of these implants in VO remains limited.

METHODS

A retrospective cohort analysis, spanning 2000 to 2020, was conducted on 24 destructive VO cases at a Level 1 orthopedic trauma center. Diagnosis relied on clinical, radiological, and microbiological criteria. Patient demographics, clinical presentation, surgical interventions, and radiological outcomes were assessed.

RESULTS

The study included 24 patients (62.5% male; mean age 65.6 ± 35.0 years), with 58% having healthcare-associated infections (HAVO). The mean radiological follow-up was 137.2 ± 161.7 weeks. Surgical intervention significantly improved the bi-segmental kyphotic endplate angle (BKA) postoperatively (mean -1.4° ± 13.6°). However, a noticeable loss of correction was observed over time. The study reported a mortality rate of 1/24.

CONCLUSIONS

Anterior column reconstruction using expandable VBR effectively improved local spinal alignment in destructive VO. However, the study underscores the necessity for prolonged follow-up and continuous research to refine surgical techniques and postoperative care. Addressing long-term complications and refining surgical approaches will be pivotal as the field progresses.

Finite element modelling and biodynamic response prediction of the seated human body exposed to whole-body vibration

Biodynamic modelling of seat-occupant systems can assist in seat comfort design. A finite element (FE) model of the seated human body, including detailed modelling of the lumbar spine, was established to reflect the human response to vibration and biodynamic response of the lumbar spine under whole-body vibration (WBV). The lumbar spine model was established and validated against the in-vitro results and calculated data. The posture of the lumbar spine was adjusted according to the radiological research results, and the adjusted model was combined to establish a FE model of the seated human body. The present seated human model with backrest inclination angles of 10, 20, and 30°, validated by comparing the measured apparent mass and seat-to-lumbar spine transmissibility, was used to calculate the biodynamic response of the lumbar spine with three inclined backrests under WBV. The results showed that the model could characterise the apparent mass, seat-to-lumbar spine transmissibility, and the biodynamic response of the lumbar spine. Practitioner summary: Biodynamic models can represent dynamic characteristics of the human body exposed to vibration and assist in seat comfort design. The three-dimensional FE model of the human body can be used to explore the human response to vibration and the biodynamic response of the lumbar spine under WBV.

Trabecular structural difference between the superior and inferior regions of the vertebral body: a cadaveric and clinical study

Background

Osteoporotic vertebral compression fractures commonly involve the superior vertebral body; however, their associated causes have not yet been clearly established. This study aimed to determine the trabecular structural differences between the superior and inferior regions of the vertebral body using cadaveric and clinical studies.

Materials and methods

First, five vertebrae were collected from three human cadavers. The trabecular structures of the superior and inferior regions of each vertebral body were analyzed using micro-computed tomography (micro-CT), finite element analysis (FEA), and biomechanical test. Based on the results of the ex vivo study, we conducted a clinical study. Second, spine CT images were retrospectively collected. Bone volume and Hounsfield unit were analyzed for 192 vertebral bodies. Finally, after sample size calculation based on the pilot study, prospectively, 200 participants underwent dual-energy X-ray absorptiometry (DXA) of the lateral spine. The bone mineral densities (BMDs) of the superior and inferior regions of each lumbar vertebral body were measured. The paired t-test and Wilcoxon signed-rank test were used for the statistical analyses, and p-value < 0.05 was considered significant.

Results

Cadaver studies revealed differences between the superior and inferior trabecular bone structures. The bone volume ratio, BMD, and various other trabecular parameters advocated for decreased strength of the superior region. Throughout the biomechanical study, the limitations of the compression force were 3.44 and 4.63 N/m2 for the superior and inferior regions, respectively. In the FEA study, the inferior region had a lower average displacement and higher von Mises stress than the superior region. In the clinical spine CT-based bone volume and BMD study, the bone volume was significantly higher in the inferior region than in the superior region. In the lateral spine DXA, the mean BMD of the superior region of vertebral bodies was significantly lower compared with that of the inferior region.

Conclusion

The superior trabecular structure of the lumbar vertebral bodies possesses more biomechanical susceptibility compared with the inferior trabecular structure, confirming its dominant role in causing osteoporotic vertebral fractures. Physicians should also focus on the BMD values of the superior region of the vertebral body using lateral spine DXA to evaluate osteoporosis.

The effect of ethnicity on the age-related changes of spinopelvic characteristics: a systematic review

Aims

Spinopelvic characteristics influence the hip’s biomechanical behaviour. However, to date there is little knowledge defining what ‘normal’ spinopelvic characteristics are. This study aims to determine how static spinopelvic characteristics change with age and ethnicity among asymptomatic, healthy individuals.

Methods

This systematic review followed the Preferred Reporting Items for Systematic Review and Meta-Analyses guidelines to identify English studies, including ≥ 18-year-old participants, without evidence of hip or spine pathology or a history of previous surgery or interventional treatment, documenting lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT), and pelvic incidence (PI). From a total of 2,543 articles retrieved after the initial database search, 61 articles were eventually selected for data extraction.

Results

When all ethnicities were combined the mean values for LL, SS, PT, and PI were: 47.4° (SD 11.0°), 35.8° (SD 7.8°), 14.0° (SD 7.2°), and 48.8° (SD 10°), respectively. LL, SS, and PT had statistically significant (p < 0.001) changes per decade at: −1.5° (SD 0.3°), −1.3° (SD 0.3°), and 1.4° (SD 0.1°). Asian populations had the largest age-dependent change in LL, SS, and PT compared to any other ethnicity per decade at: −1.3° (SD 0.3°) to −0.5° (SD 1.3°), –1.2° (SD 0.2°) to −0.3° (SD 0.3°), and 1.7° (SD 0.2°) versus 1.1° (SD 0.1°), respectively.

Conclusion

Ageing alters the orientation between the spine and pelvis, causing LL, SS, and PT to modify their orientations in a compensatory mechanism to maintain sagittal alignment for balance when standing. Asian populations have the largest degree of age-dependent change to their spinopelvic parameters compared to any other ethnicity, likely due to their lower PI.

Cite this article: Bone Joint Res 2023;12(4):231–244.

The role of spinal surgery in the treatment of low back pain

Low back pain (LBP) is common and a leading cause of disability and lost productivity worldwide. Acute LBP is frequently self-resolving, but recurrence is common, and a significant proportion of patients will develop chronic pain. This transition is perpetuated by anatomical, biological, psychological and social factors. Chronic LBP should be managed with a holistic biopsychosocial approach of generally non-surgical measures. Spinal surgery has a role in alleviating radicular pain and disability resulting from neural compression, or where back pain relates to cancer, infection, or gross instability. Spinal surgery for all other forms of back pain is unsupported by clinical data, and the broader evidence base for spinal surgery in the management of LBP is poor and suggests it is ineffective. Emerging areas of interest include selection of a minority of patients who may benefit from surgery based on spinal sagittal alignment and/or nuclear medicine scans, but an evidence base is absent. Spinal surgery for back pain has increased substantially over recent decades, and disproportionately among privately insured patients, thus the contribution of industry and third-party payers to this increase, and their involvement in published research, requires careful consideration.

Alignment of the Sternum and Sacrum as a Marker of Sitting Body Posture in Children

An analysis of literature on the methods of assuming a sitting position and the results of our own research indicated the need to search for biomechanical parameters and existing relationships that would enable a description of sitting body posture. The purpose of this paper is to analyze the relationship between the alignment of the body of sternum and sacrum and the changes in the thoracic and lumbar spine curvatures in children. The study involved 113 subjects aged 9-13 years. A planned simultaneous measurement of the angle parameters of the alignment of the body of sternum and sacrum relative to the body's sagittal axis and the angle parameters of the thoracic and lumbar spine curvatures was performed during a single examination session. The proposed markers of alignment in the corrected sitting body posture are characterized by homogeneous results. A high measurement repeatability was observed when determining the corrected body posture in the study setting. It was noted that changes in the alignment of the body of sternum and sacrum resulted in changes in the thoracic kyphosis and lumbar lordosis angle values, which may be an important component of clinical observations of sitting body posture in children. Implementing the body of sternum alignment angle of about 64° relative to the body's sagittal axis in clinical practice as one of the objectives of postural education may be the target solution for sitting body posture correction in children.

Long spine fusions to the sacrum-pelvis are associated with greater post-operative proximal junctional kyphosis angle in sitting position

STUDY DESIGN

A single-centre retrospective study.

BACKGROUND AND PURPOSE

Although adult patients spend most of their time in sitting positions, the assessment of spinopelvic parameters in adult deformity surgery is commonly performed in standing X-rays. Our study compares the standing and sitting sagittal alignment parameters in subjects who underwent thoracolumbar fusion.

METHODS

Patients who underwent corrective surgery for adult scoliosis with at least five instrumented vertebra were stratified according to the upper instrumented vertebra (UIV) and pelvic fixation. Group A:UIV proximal to T6 with pelvis fixation. B:UIV lower than T6 and pelvic fixation. Group C: thoracolumbar fusion without pelvic fixation. Post-operative spinopelvic sagittal parameters were measured in both standing and sitting X-rays.

RESULTS

A total of 51 patients were enrolled in the study (11:Males and 40:Females). The mean age was 52.3 ± 21.7y/o. The comparison of post-operative standing and sitting X-ray within the group A and B showed that a significant change was observed in terms of JA-Junctional Angle-(Group A 6.3 ± 4.3 vs. 8.1 ± 3.3, p value = 0.03) (Group B 8.5 ± 6.4 vs. 10.9 ± 6.4, p value = 0.02). Group C showed statistically significant difference in terms of PT (15.6 ± 11.2 vs. 19.3 ± 9.2, p value = 0.04), AVA-Acetabular Version Angle-(41.1 ± 5.9 vs. 48.3 ± 6.6, p value < 0.01) and LL (- 51.3 ± 16.0 vs. - 42.6 ± 10.7, p value < 0.01).

CONCLUSION

In our series, the post-operative sagittal alignment showed peculiar behaviours and adaptations in sitting position, depending on the length and the site of the instrumented area. If the pelvis is included, the JA tends to significantly increase in sitting position. These findings can improve the knowledge of pathologies as proximal junctional kyphosis or specific cases of anterior hip impingement.

LEVEL OF EVIDENCE

IV.

Schober Test and Its Modifications Revisited-What Are We Actually Measuring? Computerized Tomography-Based Analysis

OBJECTIVE

Examine Schober test's (ST), Modified ST (MST), and Modified-Modified ST (MMST) surface markers' accuracy in spanning lumbar L1-S1 motion segments and repeatability related to actual patient anatomy as measured on sagittal CT scans.

METHODS

The study included 25 patients of varying heights, weights, and gender without prior spinal surgery or deformity. Researchers assessed patients' CT scans for ST, MST, and MMST skin levels of the measured cephalic and caudal endpoints.

RESULTS

The original ST failed to include at least one lumbar motion segment in all patients, omitting the L1-L2 motion segment in 17 patients and the L2-L3 in another eight. The additional cephalic length of the MST did not improve the inclusion of the actual L1-S1 components. The MMST measured 19 'patients' entire L1-S1 motion segments, reaching a 76% accuracy rate. WMST, measuring 16 cm (instead of MMST's 15 cm), improved the measurement significantly, measuring the L1-S1 motion segments in all cases (with 100% accuracy).

CONCLUSION

ST and its modifications fail to span the L1-S1 motion segments and are thus prone to underestimating lumbar spine motion. This study shows that the WMST is much more accurate than previous modifications and is a better tool for evaluating lumbar spine motion.

Quantitative evaluation of correlation between lumbosacral lordosis and pelvic incidence in standing position among asymptomatic Asian adults: a prospective study

The determination of lumbopelvic alignment is essential for planning adult spinal deformity surgery and for ensuring favorable surgical outcomes. This prospective study investigated the correlation between the lumbar section of lumbar spine lordosis and increasing pelvic incidence in 324 Asian adults with a mean age of 55 ± 13 years (range: 20-80 years), comprising 115 male and 209 female volunteers. Participants were divided into three groups based on pelvic incidence (G1, G2, and G3 had pelvic incidence of < 45°, 45-55°, and ≥ 55°, respectively). We determined that distal and proximal lumbar lordosis contributed differentially to the increase in pelvic incidence, whereas the lordosis ratio of the L3-L4 and L4-L5 segments mostly remained constant. The mean contribution ratio of the segmental lordosis from L1 to S1 was as follows: L1-L2, 2.3%; L2-L3, 11.7%; L3-L4, 18.1%; L4-L5, 25.2%; and L5-S1, 42.7%. Pelvic incidence had a stronger correlation with proximal lumbar lordosis than did distal lumbar lordosis. The ratios of proximal lumbar lordosis to distal lumbar lordosis were 37.8% in G1, 45.8% in G2, and 55.9% in G3. These findings serve as a reference for future lumbar spine correction or fusion surgery for Asian adults.

Lordosis loss in degenerative spinal conditions

PURPOSE

To establish whether common degenerative lumbar spine conditions have a predictable sagittal profile and associated range of lordosis. The spinopelvic balance of a normal population and normal ranges are well described in the literature. There is also evidence that certain degenerative conditions can lead to a preponderance of loss of lordosis at specific spinal levels. There is limited literature on the range and magnitude of loss of lordosis for known degenerative lumbar spine pathologies.

METHODS

A retrospective analysis of prospectively obtained radiographs from a dual surgeon database was performed and imaging analysed for spinopelvic parameters. Degenerative conditions studied were; Lumbar degenerative spondylolisthesis (L3/4 and L4/5 analysed separately), L5/S1 degenerative disc disease, L5/S1 isthmic spondylolisthesis. Pelvic incidence, sacral slope, pelvic tilt, segmental and global lumbar lordosis, vertebral lordosis and lumbar vertical axis were measured.

RESULTS

The range of change in segmental lordosis was normally distributed for all studied degenerative spinal conditions except L5/S1 isthmic spondylolisthesis. L5/S1 degenerative disc disease affected younger adults (mean age 37), whilst degenerative spondylolisthesis at L3/4 and L4/5 affected older adults (mean ages 69.5 and 68.9 respectively). Removing an outlying high-grade L5/S1 isthmic spondylolisthesis made the data distribution approach a normal distribution.

CONCLUSION

Most degenerative spinal pathologies cause a normally distributed spectrum of deformity which should be addressed and corrected with a tailored, individualised surgical plan for each patient. Universal treatment recommendations should be interpreted with caution.

The Standing and Sitting Spino-Pelvic Sagittal Alignment in Patients with Instrumented Lumbar Fusion Might Correlate with Adjacent Segment Degeneration

OBJECTIVES

Sitting is a common weight-bearing posture, like standing, but there still lacks enough understanding of sagittal alignment in sitting position for patients after lumbar fusion. This study aimed to investigate the accommodation of fixed spine from standing to sitting position and its influence on unfused segments.

METHODS

Sixty-two patients after lumbar fusion (test group) and 40 healthy volunteers (control group) were recruited in this research. All subjects underwent lateral radiographs of entire spine in the standing and sitting positions. The spinopelvic parameters including sagittal vertical axis (SVA), T1 pelvic angle (TPA), lumbar lordosis (LL), thoracic kyphosis (TK), and pelvic tilt (PT) were measured. The changes in parameters of patients between two positions were compared with control group, and patients were divided in different groups based on fusion level and their parameters were compared.

RESULTS

When changing from standing to sitting positions, a forward-moving SVA and TPA were observed in both patients and control groups, accompanied by the decrease in LL, TK and increase in PT, but the changes of patients were smaller in TPA, LL, and TK (6.5° ± 7.2° vs 9.7° ± 6.0°, 7.7° ± 8.3° vs 13.6° ± 8.5°, 2.2° ± 6.5° vs 5.4° ± 5.1°, respectively, p < 0.05). Increase of PT in the lumbosacral fixation group was lower than that in the control group (4.4° ± 9.1° vs 8.3° ± 7.1°, p < 0.05). Patients who had adjacent segments degeneration (ASD) showed more kyphosis in unfused lumbar segments than the other patients (16.4° ± 10.7° vs -1.0° ± 4.8°, p < 0.05) from standing to sitting.

CONCLUSIONS

The spine straightens in lumbar and thoracic curve, combined with forward-moving axis and pelvic retroversion when changing to the sitting position. However, these changes are relatively limited in patients after lumbar fusion, so the adjacent unfused lumbar segments compensate to stress during sitting and this may be related to ASD.

Do the three-dimensional parameters of brace-wearing patients with AIS change when transitioning from standing to sitting position? A preliminary study on Lenke I

Background

Bracing is the most common conservative treatment for preventing the progression of adolescent idiopathic scoliosis (AIS) in patients with a curve of 25°–40°. X-ray examinations are traditionally performed in the standing position. However, school-age teenagers may take more time to sit. Thus far, little is known about three-dimensional (3D) correction in the sitting position. Hence, this study aimed to determine the effects of standing and sitting positions on 3D parameters during brace correction.

Methods

We evaluated a single-center cohort of patients receiving conservative treatment for thoracic curvature (32 patients with AIS with a Lenke I curve). The 3D parameters of their standing and sitting positions were analyzed using the EOS imaging system during their first visit and after bracing.

Results

At the patients’ first visit, sagittal plane parameters such as thoracic kyphosis (TK), lumbar lordosis (LL), and sacral slope decreased when transitioning from the standing position to the sitting position (standing 29° ± 6°, 42° ± 8°, and 42° ± 8° vs. sitting 22° ± 5°, 27° ± 6°, and 24° ± 4°; p < 0.001), whereas pelvic tilt (PT) increased and sagittal vertical axis shifted forward (standing 9° ± 6° and 1.6 ± 2.7 cm vs. sitting 24° ± 4° and 3.8 ± 2.3 cm; p < 0.001). After bracing, TK and LL decreased slightly (from 29° ± 6° and 42° ± 8° to 23° ± 3° and 38° ± 6°; p < 0.001), whereas the thoracolumbar junction (TLJ) value increased (from 3° ± 3° to 11° ± 3°; p < 0.001). When transitioning to the sitting position, similar characteristics were observed during the first visit, except for a subtle increase in the TLJ and PT values (standing 11° ± 3° and 9° ± 4° vs. sitting 14° ± 3° and 28° ± 4°; p < 0.001). Moreover, the coronal and axial parameters at different positions measured at the same time showed no significant change.

Conclusions

In brace-wearing patients with thoracic scoliosis, compensatory sagittal plane straightening may be observed with a slight increase in thoracolumbar kyphosis, particularly when transitioning from the standing position to the sitting position, due to posterior rotation of the pelvis. Our results highlight that sagittal alignment in AIS with brace treatment is not completely analyzed with only standing X-Ray.

Trial registration

The study protocol was registered with the Chinese Clinical Trial Registry (ChiCTR1800018310).

Mismatch Between Pelvic Incidence and Lumbar Lordosis is the Key Sagittal Plane Determinant of Patient Outcome at Minimum 40 Years After Instrumented Fusion for Adolescent Idiopathic Scoliosis

STUDY DESIGN

Retrospective review.

OBJECTIVE

Assess measures of spinal-pelvic balance in predicting functional outcome in patients who underwent posterior spinal fusion for adolescent idiopathic scoliosis (AIS) at minimum 40-year follow-up.

SUMMARY OF BACKGROUND DATA

Back pain and long-term function are considered when choosing levels for surgery in AIS patients. Three hundred and fourteen patients underwent fusion for AIS between 1961 and 1977. One hundred and thirty-four patients were located for potential long-term follow-up.

METHODS

With Institutional Review Board approval, medical records and public resources were used to locate patients. Patients completed health-related quality of life (HRQoL) instruments, and returned for assessment including full radiographs. Radiographs were analyzed for scoliosis measures, and recognized spinal-pelvic measures including the lumbar lordosis, sagittal vertical axis (SVA), pelvic incidence, and pelvic tilt (PT). Bivariate and multivariable analyses were performed to assess the association between spinal-pelvic measures and patient-reported outcomes.

RESULTS

Thirty-five of 134 patients agreed to return for complete HRQoL and radiographic follow-up. There were no differences at baseline between those agreeing and declining participation. The cohort was 94% female, had an average age of 60.5 years, and average follow-up of 46 years. In bivariate analysis, pelvic incidence and lumbar lordosis difference (PI-LL) was the only spinal-pelvic parameter which statistically discriminated between patients doing well and not, as assessed by the Oswestry Disability Index and the Patient-reported Outcomes Measurement Information System (PROMIS) Pain Interference and Fatigue instruments. In multivariable analysis, (PI-LL > 9°) was associated with worse scores in PROMIS-Pain Interference, Physical Function, Depression, Fatigue, Social Function and the total Oswestry score. An SVA > 50 mm was associated with worse scores in the Scoliosis Research Society-7.

CONCLUSION

In a cohort of 35 patients with average follow-up of 46 years after posterior spinal instrumentation with Harrington rods (PSIF) for AIS, spinal-pelvic mismatch as identified by (PI-LL > 9°) was associated with inferior HRQoL outcomes. Other spinal-pelvic measures (SVA and PT) were not reliably associated with inferior HRQoL.Level of Evidence: 4.

Effects of the difference between lumbar lordosis in the supine and standing positions on the clinical outcomes of decompression surgery for lumbar spinal stenosis

OBJECTIVE

The authors sought to evaluate the relationship between the difference in lumbar lordosis (DiLL) in the preoperative supine and standing positions and spinal sagittal alignment in patients with lumbar spinal stenosis (LSS) and to determine whether this difference affects the clinical outcome of laminectomy.

METHODS

Sixty patients who underwent single-level unilateral laminectomy for bilateral decompression of LSS were evaluated. Spinopelvic parameters in the supine and standing positions were measured preoperatively and at 3 months and 2 years postoperatively. DiLL between the supine and standing positions was determined as follows: DiLL = supine LL - standing LL. On the basis of this determination patients were then categorized into DiLL(+) and DiLL(-) groups. The relationship between DiLL and preoperative spinopelvic parameters was evaluated using Pearson's correlation coefficient. In addition, clinical outcomes such as visual analog scale (VAS) and Oswestry Disability Index (ODI) scores between the two groups were measured, and their relationship to DiLL was evaluated using two-group comparison and multivariate analysis.

RESULTS

There were 31 patients in the DiLL(+) group and 29 in the DiLL(-) group. DiLL was not associated with supine LL but was strongly correlated with standing LL and pelvic incidence (PI) - LL (PI - LL). In the preoperative spinopelvic alignment, LL and SS in the standing position were significantly smaller in the DiLL(+) group than in the DiLL(-) group, and PI - LL was significantly higher in the DiLL(+) group than in the DiLL(-) group. There was no difference in the clinical outcomes 3 months postoperatively, but low-back pain, especially in the sitting position, was significantly higher in the DiLL(+) group 2 years postoperatively. DiLL was associated with low-back pain in the sitting position, which was likely to persist in the DiLL(+) group postoperatively.

CONCLUSIONS

We evaluated the relationship between DiLL and spinal sagittal alignment and the influence of DiLL on postoperative outcomes in patients with LSS. DiLL was strongly correlated with PI - LL, and in the DiLL(+) group, postoperative low-back pain relapsed. DiLL can be useful as a new spinal alignment evaluation method that supports the conventional spinal sagittal alignment evaluation.

Thoracolumbar Spine Trauma

Thoracolumbar spine trauma can result in potentially life-threatening consequences and requires careful management to ensure good outcomes. The purpose of this chapter is to discuss the anatomy, diagnostic tools, non-operative, and operative treatments important when addressing thoracolumbar trauma.

Radiological and mid- to long-term patient-reported outcome after stabilization of traumatic thoraco-lumbar spinal fractures using an expandable vertebral body replacement implant

Background

For the treatment of unstable thoraco-lumbar burst fractures, a combined posterior and anterior stabilization instead of a posterior-only instrumentation is recommend in the current literature due to the instability of the anterior column. Data on restoring the bi-segmental kyphotic endplate angle (BKA) with expandable vertebral body replacements (VBR) and on the mid- to long-term patient-reported outcome measures (PROM) is sparse.

Methods

A retrospective cohort study of patients with traumatic thoraco-lumbar spinal fractures treated with an expandable VBR implant (Obelisc™, Ulrich Medical, Germany) between 2001 and 2015 was conducted. Patient and treatment characteristics were evaluated retrospectively. Radiological data acquisition was completed pre- and postoperatively, 6 months and at least 2 years after the VBR surgery. The BKA was measured and fusion-rates were assessed. The SF-36, EQ-5D and ODI questionnaires were evaluated prospectively.

Results

Ninety-six patients (25 female, 71 male; age: 46.1 ± 12.8 years) were included in the study. An AO Type A4 fracture was seen in 80/96 cases (83.3%). Seventy-three fractures (76.0%) were located at the lumbar spine. Intraoperative reduction of the BKA in n = 96 patients was 10.5 ± 9.4° (p < 0.01). A loss of correction of 1.0 ± 2.8° at the first follow-up (t1) and of 2.4 ± 4.0° at the second follow-up (t2) was measured (each p < 0.05). The bony fusion rate was 97.9%. The total revision rate was 4.2%. Fifty-one patients (53.1% of included patients; age: 48.9 ± 12.4 years) completed the PROM questionnaires after 106.4 ± 44.3 months and therefore were assigned to the respondent group. The mean ODI score was 28.2 ± 18.3%, the mean EQ-5D VAS reached 60.7 ± 4.1 points. Stratified SF-36 results (ISS < and ≥ 16) were lower compared to a reference population.

Conclusion

The treatment of traumatic thoraco-lumbar fractures with an expandable VBR implant lead to a high rate of bony fusion. A significant correction of the BKA could be achieved and no clinically relevant loss of reduction occurred during the follow-up. Even though health related quality of life did not reach the normative population values, overall satisfactory results were reported.

Spinal and Pelvic Alignment of Sitting Posture Associated with Smartphone Use in Adolescents with Low Back Pain

This study aimed to assess the association between smartphone use in the sitting posture and changes in thoracolumbar kyphosis, lumbar lordosis, and pelvic asymmetry in adolescents with low back pain (LBP). Twenty-five adolescents with LBP and 25 healthy adolescents participated in this study. They were instructed to sit on a height-adjustable chair with their hips and knees bent at 90° for 30 min in their usual sitting postures. Thoracolumbar kyphosis, lumbar lordosis, and pelvic asymmetry were measured using a three-dimensional motion capture system. Thoracolumbar kyphosis and lumbar lordosis increased after 30 min of sitting compared to the baseline. In both groups, thoracic kyphosis and lumbar lordosis angle increased with increasing sitting time. Compared to healthy adolescents, adolescents with LBP presented greater thoracolumbar kyphosis and lumbar lordosis after prolonged sitting. Pelvic asymmetry showed no significant difference between the sitting time and groups. Using a smartphone during prolonged sitting may lead to a slumped posture; these associations were more pronounced in adolescents with LBP.

Analysis of individual differences in pelvic and spine alignment in seated posture and impact on the seatbelt kinematics using human body model

Analysis using human body models has been performed to reduce the impact of accidents; however, no analysis has shown a relationship between lumbar and pelvic/spine angle and seat belts in reducing human damage from accidents. Lumbar and pelvic/spine angles were measured in 75 individuals and the measurements were used to create three different angles for the Total Human Model for Safety model. In the present study, we focused on lumber lordosis (LL) and pelvic angle (PA). A normal distribution and histogram were used for analysis of PA (01, 10, and 50). The Total Human Model for Safety, including LL and PA, was corrected using finite element software. Simulations were conducted under the conditions of the Japan New Car Assessment Programme (JNCAP) 56 kph full lap frontal impact. Using the results of the FEM, the amount of lap-belt cranial sliding-up, anterior movement of the pelvis, posterior tilt of the pelvis, head injury criterion (HIC), second cervical vertebrae (C2) compressive load, C2 moment, chest deflectiou (upper, middle, and lower), left and right femur load, and shoulder belt force were measured. The lap-belt cranial sliding-up was 1.91 and 2.37 for PA10 and PA01, respectively, compared to PA50; the anterior movement of the pelvis was 1.08 and 1.12 for PA10 and PA01, respectively; and the posterior tilt of the pelvis was 1.1 and 1.18 for PA10 and PA01, respectively. HIC was 1.13 for PA10 and 1.58 for PA01; there was no difference in C2 compressive load by PA, but C2 moment increased to 1.59 for PA10 and 2.72 for PA01. It was found that as LL increases and the PA decreases, the seat belt becomes likely to catch the iliac bone, making it harder to cause injury. This study could help to reconsider the safe seat and seatbelt position in the future.

Computed tomography study of the relationship between pelvic incidence and bony contribution to lumbar lordosis in children

There is little data regarding the relationship in children and how it may change with aging. The aim of this radiographic study was to define the relationship between pelvic incidence (PI) and segmental vertebral body lordosis through childhood. In 150 children, CT scans of the lumbar spine and pelvis were analyzed measuring PI, sacral table angle (STA), sacral kyphosis (SK), and segmental lordosis (SL) individually L1-L5. Children were grouped by age: (1) 0-60 months; (2) 61-120 months; (3) 121-185 months. Mean PI for the entire cohort was 40.4, mean SL for L1-0.6, L2 0.0, L3 1.8, L4, 4.7, and L5 11.4. There were 40 children in Group 1, 63 in Group 2 and 37 in Group 3. SL differed between age groups at all levels except at L2. L1 and L2 became more kyphotic with increasing age; L3, L4, and L5 became more lordotic with increasing age. The correlation between PI and SL at each level became stronger with increasing age. Similarly, the correlation between PI and STA and between PI and SK also became stronger with increasing age. As children mature, the relationship between PI and segmental lordosis at each level of the lumbar spine becomes stronger-the relationship between PI and lordosis trends toward that seen in the adult. Future work should aim to define when the adult PI-LL relationship is realized.

Standard reference values of the upper body posture in healthy middle-aged female adults in Germany

In order to classify and analyze the parameters of upper body posture, a baseline in form of standard values is demanded. To this date, standard values have only been published for healthy young women. Data for female adults between 51 and 60 years are lacking. 101 symptom-free female volunteers aged 51–60 (55.16 ± 2.89) years. The mean height of the volunteers was 1.66 ± 0.62 m, with a mean body weight of 69.3 ± 11.88 kg and an average BMI of 25.02 ± 4.55 kg/m². By means of video raster stereography, a 3D-scan of the upper back surface was measured in a habitual standing position. The confidence interval, tolerance range and ICCs were calculated for all parameters. The habitual standing position is almost symmetrical in the frontal plane the most prominent deviation being a slightly more ventral position of the left shoulder blade in comparison to the right. The upper body (spine position) is inclined ventrally with a minor tilt to the left. In the sagittal plane, the kyphosis angle of the thoracic spine is greater than the lordosis angle of the lumbar spine. The pelvis is virtually evenly balanced with deviations from an ideal position falling under the measurement error margin of 1 mm/1°. There were also BMI influenced postural variations in the sagittal plane and shoulder distance. The ICCs are calculated from three repeated measurements and all parameters can be classified as "almost perfect". Deflections from an ideally symmetric spinal alignment in women aged 51–60 years are small-scaled, with a minimal frontal-left inclination and accentuated sigmoidal shape of the spine. Postural parameters presented in this survey allow for comparisons with other studies as well as the evaluation of clinical diagnostics and applications.

Effect of different Pilates workout endings on the kyphotic and lumbar lordotic angles

Abstract Introduction: There are no studies that investigate whether different workout endings of the Pilates method (PM), either prioritizing the activation of powerhouse muscles or the relaxation of muscles trained during the session, affects spinal curvature. Objective: Identify the immediate effect of a PM session that ends with soft tissue mobilization or wall exercises on the kyphotic and lumbar lordotic angles. Methods: A crossover clinical trial with 19 female Pilates practitioners that used a Flexicurve ruler to evaluate thoracic and lumbar spine curvature before and after a PM exercise protocol, and after endings that involved soft tissue mobilization using massage balls or wall exercises. The order of the different endings was chosen by random draw and the study volunteers participated in two interventions, with intervals of seven to ten days between them. Two two-way ANOVAs were performed (one for each postural variable), using the factors “assessment time” (pre-session; post-PE; post-ending) and “type of ending” (soft tissue or wall exercises). Results: There was no significant difference between the assessment times or endings for the kyphotic (p = 0.972; p = 0.747) and lumbar lordotic angles (p = 0.574; p = 0.627), respectively. Conclusion: Pilates instructors can opt for more relaxing or more active endings without affecting the kyphotic and lumbar lordotic angles.

Risk Factors Predicting C- Versus S-shaped Sagittal Spine Profiles in Natural, Relaxed Sitting: An Important Aspect in Spinal Realignment Surgery

STUDY DESIGN

A cross-sectional study on a randomly selected prospective cohort of patients presenting to a single tertiary spine center.

OBJECTIVE

The aim of this study was to describe the clinical and radiographic parameters of patients with S- and C-shaped thoracolumbar sagittal spinal profiles, and to identify predictors of these profiles in a natural, relaxed sitting posture.

SUMMARY OF BACKGROUND DATA

Sagittal realignment in adult spinal deformity surgery has to consider the sitting profile to minimize the risks of junctional failure. Persistence of an S-shaped sagittal profile in the natural, relaxed sitting posture may reflect a lesser need to accommodate for this posture during surgical realignment.

METHODS

Consecutive patients with low back pain underwent whole body anteroposterior and lateral radiographs in both standing and sitting. Baseline clinical data of patients and radiographic parameters of both standing and sitting sagittal profiles were compared using χ, unpaired t tests, and Wilcoxon rank-sum test. Subsequently, using stepwise multivariate logistic regression analysis, predictors of S-shaped curves were identified while adjusting for confounders.

RESULTS

Of the 120 patients included, 54.2% had S-shaped curves when sitting. The most common diagnoses were lumbar spondylosis (26.7%) and degenerative spondylolisthesis (26.7%). When comparing between patients with S- and C-shaped spines in the sitting posture, only diagnoses of degenerative spondylolisthesis (odds ratio [OR], 5.44; P = 0.01) and degenerative scoliosis (OR, 2.00; P = 0.039), and pelvic incidence (PI) >52.5° (OR, 5.48; P = 0.008), were predictive of an S-shaped sitting sagittal spinal alignment on multivariate analysis.

CONCLUSION

Stiffer lumbar curves (eg, patients with degenerative spondylolisthesis and degenerative scoliosis) or those who have a predilection for an S-shaped standing sagittal profile when sitting (eg, high PI) may be more amenable to fusion in accordance with previously studied sagittal realignment targets. In contrast, more flexible curves may benefit from less aggressive lordotic realignment to prevent potential junctional failures.

LEVEL OF EVIDENCE

3.

Clinical and radiological results of kyphectomy and sliding growing rod surgery technique performed in children with myelomeningocele

BACKGROUND

The aim of this study was to present clinical and radiological results of myelomeningocele (MMC) patients treated with the sliding growing rod (SGR) technique after kyphectomy.

METHODS

Between 2016 and 2019, 30 patients (21 males and nine females) who underwent the SGR technique with kyphectomy and posterior instrumentation due to MMC were retrospectively reviewed. Patients' pre- and postoperative kyphosis, scoliosis, correction rates, bleeding during surgery, blood supply during and after surgery, operation time, instrumentation levels, number of vertebrae removed, MMC onset levels, hospital stay, annual lengthening amounts, and complications were evaluated.

RESULTS

The mean patient age was 6.9 (4-10) years. Mean preoperative kyphosis was 115° (87-166°), mean early postoperative kyphosis was 3.9° (20-10°), and final follow-up postoperative kyphosis was 5.1° (22-8°). In nine patients presenting with scoliosis, scoliosis was evaluated as 60.2° (115-35°) preoperative, as 12.9° (32-0°) early postoperative, and 15.7° (34-0°) in the final measurement. The kyphotic deformity correction rate was 96.5%, and the scoliotic deformity correction rate was 74.9%. A statistically significant difference was seen between pre- and early postoperative values in kyphosis and scoliosis measurements (p < 0.05). The annual prolongation of the patients was calculated as averages of 0.72 and 0.77 cm/year between T1-T12 and T1-S1, respectively.

CONCLUSION

Kyphectomy performed during the early MMC period patients appears to be an excellent method for facilitating rehabilitation and daily care of these patients. It appears that the SGR technique, which provides lung volume protection and lengthening with kyphectomy, is a safe and reliable method in patients.

LEVEL OF EVIDENCE

Level 4.

A Novel Approach towards Early Detection of Obliteration in Lumbar Lordosis

The millennial age group (18 to 30 years) spend at least 6 hours sitting, either in college or at their workspace. High screen time as a routine, is the major cause for numerous spinal problems. Despite the wide research carried out on postural abnormalities, there exists numerous unrequited queries with regards to lumbar lordosis estimations, due to indeterminate parameters such as age, gender, lifestyle and diet. This work emphasizes the proficient method by observing the posture of a person for early detection of obliteration in Lumbar Lordosis. This further contributes to efficient diagnosis and treatment of spine ailments. With a novel approach to hardware using the myRIO hardware coupled with LabVIEW for interactive interface, the calibration is enhanced using machine learning (ML) - kNN Classifier. The use of machine learning accounts for the variations in the ideal angles of segmented sagittal measures with respect to different subjects. The device is developed to be a non-invasive, user friendly instrument to analyse the casual seated posture trends of the subject. The male subjects are expected to show the tilt angles in the range of -16.3 to -17.2 degrees and similar threshold for females are -15.8 to -16.8 degrees. Out of 120 subjects taken into consideration, the device could accurately classify subjects with obliterated or normal lumbar lordosis). An accuracy and f1- score of 94% and 90% respectively was achieved by the ML model.

Lumbar Spine Degeneration and Flatback Deformity Alter Sitting-Standing Spinopelvic Mechanics-Implications for Total Hip Arthroplasty

BACKGROUND

Spinal degeneration and lumbar flatback deformity can decrease recruitment of protective posterior pelvic tilt when sitting, leading to anterior impingement and increased instability. We aim at analyzing regional and global spinal alignment between sitting and standing to better understand the implications of spinal degeneration and flatback deformity for hip arthroplasty.

METHODS

Spinopelvic parameters of patients with full-body sitting-standing stereoradiographs were assessed: lumbar lordosis (LL), spinopelvic tilt (SPT), pelvic incidence minus LL (PI-LL), sagittal vertical axis (SVA), and T1 pelvic angle (TPA). Lumbar spines were classified as normal, degenerative (disc height loss >50%, facet arthropathy, or spondylolisthesis), or flatback (degenerative criteria and PI-LL >10°). Independent t-tests and analysis of variance were used to analyze alignment differences between groups.

RESULTS

After propensity matching for age, sex, and hip osteoarthritis grade, 57 patients per group were included (62 ± 11 years, 58% female). Mean standing and sitting SPT, PI-LL, SVA, and TPA increased along the spectrum of disease severity. Increasing severity of disease was associated with decreasing standing and sitting LL. The flatback group demonstrated the greatest sitting SPT, PI-LL, SVA, and TPA. The amount of sitting-to-standing change in SPT, LL, PI-LL, SVA, and TPA decreased along the spectrum of disease severity.

CONCLUSION

Spinal degeneration and lumbar flatback deformity both significantly decrease lower lumbar spine mobility and posterior SPT from standing to sitting in a stepwise fashion. The demonstrated hypomobility in flatback patients likely serves as a pathomechanism for the previously observed increased risk of dislocation in total hip arthroplasty.

Changes in the global spine alignment in the sitting position in an automobile

BACKGROUND CONTEXT

Studies of the changes in spine alignment in the sitting position have been limited to specific spine segments. Because there have been few studies of global spinopelvic alignment in the sitting position, it is important to assess the changes associated with this position for such settings as developing future design of seats and achieving appropriate restoration of spine alignment.

PURPOSE

This study aimed to measure changes in global spine alignment when people are sitting in car seats and to analyze the characteristics of those changes.

STUDY DESIGN

This was a prospective, collaborative study of the radiological evaluation of changes in global spine alignment.

PATIENT SAMPLE

The study included 113 asymptomatic adult participants (56 men and 57 women) without a history of spine disease or lower limb surgery, and with no current lower back or leg pain.

OUTCOME MEASURES

Radiographic findings were assessed by measurement of various angles: cervical lordosis (CL), thoracic kyphosis (TK), thoracolumbar kyphosis (TLK), lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT), pelvic incidence (PI), C7 sagittal vertical axis (C7-SVA), T1 spinopelvic inclination (T1SPI), and T1 pelvic angle (TPA).

METHODS

Radiographs were obtained in the standing and sitting positions. The objective variables analyzed statistically were spine alignments (CL, TK, TLK, LL, C7-SVA, T1SPI, TPA, SS, PT, and PI) measured in the standing position, body alignments (CL, TK, TLK, LL, C7-SVA, T1SPI, TPA, SS, and PT) measured in the sitting position, and stand-to-sit changes (∆CL, ∆TK, ∆TLK, ∆LL, ∆C7-SVA, ∆T1SPI, ∆TPA, ∆SS, and ∆PT). Explanatory variables were sex, age, body height, and body mass index.

RESULTS

Changing posture from standing to sitting decreased CL by an average of 5.3°, slightly decreased TK by an average of 1.3°, increased TLK by an average of 6.8°, decreased LL by an average of 35°, decreased SS by an average of 49.2°, increased PT by an average of 49.2°, shifted C7-SVA backward by an average of 106.7 mm, decreased T1SPI by an average of 18.8°, and increased TPA by an average of 21.1°. Statistical analysis revealed that ΔLL was significantly decreased in elderly participants. After the stand-to-sit change, ΔTLK and ∆TPA were significantly increased in taller participants and ΔT1SPI was significantly decreased in taller participants.

CONCLUSIONS

Among other changes, most notably LL is decreased and the pelvic tilt is increased when a person is sitting in a car seat. However, these changes in spine alignment differ with age and height. These findings may be useful for the development of future design of seats and for achieving appropriate surgical restoration of spine alignment.

Spinal sagittal alignment, spinal shrinkage and back pain changes in office workers during a workday

Purpose. Prolonged sitting is a risk factor for the appearance of lower back pain during work. The aim of this study was to observe changes in spinal sagittal alignment, height and the perception of back pain in office workers during a workday. Materials and methods. Forty-one office workers (20 women) were enrolled into a cross-sectional study. Height, sitting height and degrees of thoracic kyphosis and lumbar lordosis as well as perceived neck pain, lower back pain and upper back pain were determined, before and after an 8-h workday. Results. At the end of the day, workers had a significant decrease (p = 0.000) in height and sitting height, and upper back pain increased significantly (p = 0.023). In men, spinal shrinkage correlated with neck pain (r = 0.410, p = 0.027), and lumbar lordosis degrees in women correlated negatively with upper back pain at the end of the day (r = -0.440, p = 0.012). Conclusions. Spinal shrinkage equally affects men and women who perform the same work. There are no changes in spinal sagittal alignment throughout the workday in office workers. Office workers show significantly increased pain in the upper back at the end of the day.

Sagittal Spinal and Pelvic Alignment in Middle-Aged and Older Men and Women in the Natural and Erect Sitting Positions: A Prospective Study in a Chinese Population

Background

This prospective study aimed to compare the sagittal spinopelvic parameters in the erect and natural sitting positions in healthy middle-aged and older men and women in a Chinese population.

Material/Methods

Ninety healthy middle-aged and older men and women underwent lateral whole spinal radiography in the natural and erect sitting positions. The radiographic sagittal spinopelvic parameters were measured. They included the sagittal vertical axis (SVA), the T1 pelvic angle (TPA), the pelvic incidence (PI), the pelvic tilt (PT), the sacral slope (SS), thoracic kyphosis (TK), thoracolumbar kyphosis (TLK), the T1 slope (T1S), cervical lordosis (CL), and lumbar lordosis (LL).

Results

In the natural sitting position, LL decreased by 14.5°, TK and TLK increased by 3.2° and 2.5°, respectively, PT increased by 10.3°, T1S increased by 6.9°, and CL increased by 3.4° compared with the erect position. In the natural sitting position, the mean forward-moving SVA was 33.4 mm, and the C2–C7 SVA was 6.1 mm. Men had a larger LL and smaller PT than the women when sitting in the erect position, and a greater TK, T1S, and C2–C7 SVA than women when sitting in the natural position.

Conclusions

In the natural sitting position, a reduction in LL was associated with TK, SVA and PT increased, and there were differences between men and women. The characteristics of spinopelvic alignment in healthy older adults should be considered when planning corrective spinal surgery.

Comparison of whole body sagittal alignment during directed vs natural, relaxed standing postures in young, healthy adults

BACKGROUND CONTEXT

Imaging for adult spinal deformity is conventionally performed in a directed manner to assess the most upright standing posture one can assume. However, this method does not reflect an individual's natural, relaxed posture, which is the posture a patient likely reverts to postoperatively, and also the posture likely to explain spinal pathologies.

PURPOSE

To identify radiographic differences between directed and natural, relaxed standing postures in young healthy subjects.

STUDY DESIGN

A randomized, prospective, radiographic study.

PATIENT SAMPLE

Sixty healthy 21-year-old subjects (48 male, 12 female).

OUTCOME MEASURES

Radiographic parameters including sagittal vertical axis (SVA), C2 SVA, C2-7 SVA global cervical angle, T1-slope, global thoracic angle (GTA), thoracolumbar angle (TLA), global lumbar angle (GLA), sacral slope, pelvic tilt (PT), pelvic incidence, femoral alignment angle (FAA), and knee alignment angle (KAA).

METHODS

The EOS whole body radiographs of patients in directed and natural, relaxed standing postures were obtained, with subsequent comparison of radiographic parameters. Differences in Roussouly curve types, sagittal curve apices, and end vertebrae were also evaluated. Univariate analyses using Wilcoxon sign-rank, paired t tests, and paired chi-square tests were performed.

RESULTS

Compared with directed standing, natural, relaxed standing results in a more kyphotic spinal profile marked by a significantly less lordotic GLA, larger GTA, TLA, and T1-slope. The PT+FAA demonstrated true hip movement during sagittal balancing. Lower thoracic and lumbar apices, lower thoracolumbar end vertebrae, and lower Roussouly curve types were observed during natural, relaxed standing.

CONCLUSIONS

Our study found significant differences in sagittal radiographic parameters between directed standing and the natural, relaxed standing posture, with the latter demonstrating a more kyphotic spinal profile in terms of magnitude and span, as well as complementary changes in cervical and spinopelvic alignment. The natural, relaxed standing posture, a marker for energy conservation principles in standing, may infer value in less aggressive lordotic restoration, as well as concentration of lordosis in the lower lumbar spine.

Development of Pelvic Incidence and Lumbar Lordosis in Children and Adolescents

Pelvic incidence (PI) is a measure of the sagittal orientation of the sacrum relative to the acetabula and is not dependent on posture. In asymptomatic adults, PI correlates with lumbar lordosis. Lumbar lordosis is shown to increase with age following the onset of unassisted bipedal locomotion in children, but to what extent PI changes in relation to lumbar lordosis during skeletal maturation is unclear. The purpose of this study is to understand how PI, lumbar lordosis, and age are related in children and adolescents. PI, supine lumbar lordosis (SLL), and individual wedging angles of the lumbar vertebral bodies were measured on mid-sagittal reformatted images from 144 abdominal computed tomographic scans of individuals aged 2-20 years old, divided into three separate age categories representing pre-growth spurt (ages 2-9), growth spurt (10-15), and post-growth spurt (16-20). Our results showed that, while SLL significantly increased with age during development, PI did not. Despite the fact that PI hardly changed with age, the difference between PI and SLL decreased nonlinearly with age. SLL did not correlate with PI in the youngest age category, but positively correlated with PI in the middle and oldest age categories. The relationship between lumbar lordosis and PI, which is correlated in adults, was significant in our older age categories and not in our youngest age category. Our results indicate that PI in children and adolescents may have some predictive value for adult lumbar lordosis. Anat Rec, 302:2132-2139, 2019. © 2019 American Association for Anatomy.

Perinatal factors associate with vertebral size and shape but not lumbar lordosis in 10-year-old children

The intrauterine environment is known to influence foetal development and future health. Low birthweight has been linked to smaller vertebral canals in children and decreased adulthood spine bone mineral content. Perinatal factors affecting lumbar spine curvature have not yet been considered but could be important for adult spinal health, as lumbar movement during lifting, a risk factor for backpain, is associated with lordosis. To investigate this, lumbar spine magnetic resonance images at age 10 years and perinatal and maternal data (birthweight, placental weight, gestation length, crown-heel length, maternal age, height, weight and smoking status) from 161 children born in Aberdeen in 1988-1989 were acquired. Statistical shape modelling, using principal component analysis, quantified variations in lumbar spine shape and resulting modes of variation were assessed in combination with perinatal data using correlations and analyses of covariance, adjusted for potential confounders. Spine modes 1-3 (SM1-SM3) captured 75% of the variation in lumbar spine shape. The first and third modes described the total amount (SM1) and evenness of curvature distribution (SM3). SM2 accounted for variations in antero-posterior vertebral diameter relative to vertebral height, increasing positive scores representing a larger relative diameter. Adjusting for gestation length and sex, SM2 positively correlated with birthweight (r = 0.25, P < 0.01), placental weight (r = 0.20, P = 0.04), crown-heel length (r = 0.36, P < 0.001) and maternal weight (r = 0.19, P = 0.04), and negatively with maternal age (r = -0.22, P = 0.02). SM2 scores were lower in girls (P < 0.001) and in the low birthweight group (P = 0.02). There were no significant differences in SM1 and SM3 scores between birthweight groups, boys and girls or children of smokers (31%) and non-smokers (69%). In conclusion, some perinatal factors were associated with vertebral body morphology but had little effect on lumbar curvature.

Intervertebral disc kinematics in active duty Marines with and without lumbar spine pathology

Military members are required to carry heavy loads frequently during training and active duty combat. We investigated if operationally relevant axial loads affect lumbar disc kinematics in forty-one male active duty Marines with no previous clinically diagnosed pathology. Marines were imaged standing upright with and without load. From T2-weighted magnetic resonance images, intervertebral disc (IVD) health and kinematic changes between loading conditions and across lumbar levels were evaluated using two-way repeated measures analysis of variance tests. IVD kinematics with loading were compared between individuals with and without signs of degeneration on imaging. Linear regression analyses were performed to determine associations between IVD position and kinematic changes with loading. Fifty-eight percent (118/205) of IVDs showed evidence of degeneration and 3% (7/205) demonstrated a disc bulge. IVD degeneration was not related to posterior annular position (P > .205). Changes in sagittal intervertebral angle were not associated with changes in posterior annular position between baseline and loaded conditions at any lumbar level (r < 0.267; P = .091-.746). Intervertebral angles were significantly larger in the lower regions of the spine (P < .001), indicating increased local lordosis when moving in the caudal direction Disc height at the L5/S1 level was significantly smaller (6.3 mm, mean difference = 1.20) than all other levels (P < .001) and baseline posterior disc heights tended to be larger at baseline (7.43 mm ± 1.46) than after loading (7.18 ± 1.57, P = .071). Individuals with a larger baseline posterior annular position demonstrated greater reduction with load at all levels (P < .002), with the largest reductions at L5/S1 level. Overall, while this population demonstrated some signs of disc degeneration, operationally relevant loading did not significantly affect disc kinematics.

Effects of standing on lumbar spine alignment and intervertebral disc geometry in young, healthy individuals determined by positional magnetic resonance imaging

BACKGROUND

Most diagnostic imaging of the spine is performed in supine, a relatively unloaded position. Although the spine is subjected to functional loading that changes the spinal alignment and intervertebral disc geometry, little data exists on how healthy spines adapt to standing. This study seeks to quantify the changes of the lumbar spine from supine to standing in young, back-healthy individuals using a positional magnetic resonance imaging system.

METHODS

This is an observational study that examined the changes in the lumbar spine alignment and intervertebral disc geometry between supine and standing of forty participants (19 males/21 females) without a history of low back pain. The regional lumbar spinal alignment was measured by the sagittal Cobb angle. Segmental intervertebral disc measurements included the segmental Cobb angle, anterior-to-posterior height ratio, and intervertebral disc width measured at L1/L2 - L5/S1 levels. Intra-class correlation was performed for intra- and inter-observer measurements.

FINDINGS

The intra-observer intra-class correlation consistency model ranged from 0.76 to 0.98 with the inter-observer correlation ranging from 0.68 to 0.99. The Cobb angle decreased in standing. The L5/S1 segmental Cobb angle decreased in standing. The L2/L3 and L3/L4 anterior-to-posterior height ratios increased and the L5/S1 anterior-to-posterior height ratio decreased in standing. No difference in intervertebral disc widths was observed from supine to standing.

INTERPRETATIONS

We established normative data for a back-healthy population, using a positional magnetic resonance imaging system, that could inform future investigations that examine the standing-induced adaptations of the lumbar spine in individuals with spinal or intervertebral disc pathologies.

Changes of upright body posture in the sagittal plane of men and women occurring with aging - a cross sectional study

Background

Body posture is a fundamental indicator for assessing health and quality of life, especially for elderly people. Deciphering the changes in body posture occurring with age is a current topic in the field of geriatrics. The aims of this study were to assess the parameters of standing body posture in the global sagittal plane and to determine the dynamics of changes in standing body posture occurring with age and differences between men and women.

Methods

The measurements were performed on 226 individuals between the ages of 20 to 89 with a new photogrammetry, via which we assessed five postural angles - neck, thorax, waist, hip and knee. The data were analyzed with t-test, one-way ANOVA, linear regression model and generalized additive model.

Results

Among these segments studied here, neck changed most, while the middle segments of the body, waist and hip, were relative stable. Significant differences between men and women were found with respect to the angles of neck, thorax and hip. Three of the five postural angles were significantly influenced with aging, including increasing cervical lordosis, thoracic kyphosis and knee flexion, starting from no older than around 50 yrs. showed by fitting curve derived with generalized additive model. These changes were more marked among women. Besides, this study highlights the effects of age and gender on the complex interrelation between adjacent body segments in standing.

Conclusions

The presented results showed changes in the parameters describing body posture throughout consecutive ages and emphasized that for an individualized functional analysis, it is essential to consider age-and gender-specific changes in the neck, thorax and knee. This paper presents useful externally generalizable information not only for clinical purposes but also to inform further research on larger numbers of subjects.

Electronic supplementary material

The online version of this article (10.1186/s12877-019-1096-0) contains supplementary material, which is available to authorized users.

Effect of age and sex on lumbar lordosis and the range of motion. A systematic review and meta-analysis

Lumbar lordosis (LL) and the range of motion (RoM) are important physiological measurements when initiating any diagnosis and treatment plan for patients with low back pain. Numerous studies reported differences in LL and the RoM due to age and sex. However, these findings remain contradictory. A systematic review and meta-analysis were performed to synthesize mean values and the differences in LL and the RoM because of age and sex. The quality assessment tool for quantitative studies was applied to assess the methodological quality of the studies included. We identified 2372 papers through electronic (2309) and physical (63) searches. We assessed 218 full-text studies reporting measurements of LL or the RoM. In total, 65 studies were included, and a normative database for LL and the RoM is provided as supplementary material. Among these, 11 were included in the meta-analysis. LL and the RoM displayed non-monotonic variations with significant age and sex differences. Young females showed a significantly greater LL and the range of extension (RoE), whereas young males exhibited a greater range of flexion (RoF). Sex differences in the range of lateral bending (RoLB) were small but were significant for the axial rotation (RoAR). For the RoF, RoE and RoLB, differences because of age were significant among most of the age groups in both sexes, whereas for the RoAR, differences were significant only between the 20s vs the 30s-40s (males) and 40s vs 50s (females). Significant differences because of age/sex were identified. However, the age-dependent reduction in LL and the RoM was non-monotonic and differed in both sexes. These findings will help to better distinguish between functional deficits caused by spinal disorders and natural factors/conditions related to age and sex.

Influence of posture on relationships between pelvic parameters and lumbar lordosis: Comparison of the standing, seated, and supine positions. A preliminary study

BACKGROUND

Pelvic incidence (PI) is an anatomical parameter that is considered invariable in a given individual. Although changes in posture influence the mobile lumbar spine, lumbar lordosis (LL) and the pelvis are typically evaluated only in the standing position. Thus, whether other positions commonly used during daily activities influence the relationship between LL and PI is unknown. The objective of this study was to determine whether LL and sacral slope (SS) correlated with PI, using two standardised positions, seated and supine, different from the standing position that is generally used.

HYPOTHESIS

We are supposing that lumbar lordosis and sacral sloop are correlated to pelvic incidence whatever the posture. The goal of this study was to confirm or deny this hypothesis, using two standardize positions (sitting and lying) different that the usual standing position. LL and SS correlate with PI in the standing, seated, and supine positions.

METHOD

Lumbar and pelvic parameters were measured on radiographs obtained in the standing, seated, and supine positions in 15 asymptomatic adult volunteers younger than 50years of age. Mean values with their standard deviations were computed and compared across the three positions using ANOVA. Spearman's test was applied to assess correlations.

RESULTS

PI had the same value in all three positions. The L1-S1 LL angle was 54.8±9.8° in the standing position, 15.9±14.6° in the seated position, and 50.2±9.6° in the supine position. Pelvic tilt (PT) in the same three positions was 12.1±6.3°, 37.7±10.4°, and 9.5±5.1°, respectively; and SS was 37.1±6.3°, 11.3±10.8°, and 41±7.2°, respectively. Correlations were strongest in the supine position between PI and LL (r=0.72), LL and SS (r=0.9), and PI and SS (r=0.84).

CONCLUSION

Whereas PI remains unchanged in a given individual, lumbar lordosis and sacral orientation show significant changes across positions used in daily life, with the greatest changes seen in the seated position. During spinal fusion surgery, adjusting LL based on IP is crucial even in patients who have limited physical activity.

LEVEL OF EVIDENCE

IV.

Radiologically defining horizontal gaze using EOS imaging-a prospective study of healthy subjects and a retrospective audit

BACKGROUND CONTEXT

As sagittal alignment of the cervical spine is important for maintaining horizontal gaze, it is important to determine the former for surgical correction. However, horizontal gaze remains poorly-defined from a radiological point of view.

PURPOSE

The objective of this study was to establish radiological criteria to define horizontal gaze.

STUDY DESIGN/SETTING

This study was conducted at a tertiary health-care institution over a 1-month period.

PATIENT SAMPLE

A prospective cohort of healthy patients was used to determine the best radiological criteria for defining horizontal gaze. A retrospective cohort of patients without rigid spinal deformities was used to audit the incidence of horizontal gaze.

OUTCOME MEASURES

Two categories of radiological parameters for determining horizontal gaze were tested: (1) the vertical offset distances of key identifiable structures from the horizontal gaze axis and (2) imaginary lines convergent with the horizontal gaze axis.

MATERIALS AND METHODS

Sixty-seven healthy subjects underwent whole-body EOS radiographs taken in a directed standing posture. Horizontal gaze was radiologically defined using each parameter, as represented by their means, 95% confidence intervals (CIs), and associated 2 standard deviations (SDs). Subsequently, applying the radiological criteria, we conducted a retrospective audit of such radiographs (before the implementation of a strict radioimaging standardization).

RESULTS

The mean age of our prospective cohort was 46.8 years, whereas that of our retrospective cohort was 37.2 years. Gender was evenly distributed across both cohorts. The four parameters with the lowest 95% CI and 2 SD were the distance offsets of the midpoint of the hard palate (A) and the base of the sella turcica (B), the horizontal convergents formed by the tangential line to the hard palate (C), and the line joining the center of the orbital orifice with the internal occipital protuberance (D). In the prospective cohort, good sensitivity (>98%) was attained when two or more parameters were used. Audit using Criterion B+D yielded compliance rates of 76.7%, a figure much closer to that of A+B+C+D (74.8%). From a practical viewpoint, Criterion B+D were most suitable for clinical use and could be simplified to the "3-6-12 rule" as a form of cursory assessment. Verbal instructions in the absence of stringent postural checks only ensured that ~75% of subjects achieved horizontal gaze.

CONCLUSIONS

Fulfillment of Criterion B+D is sufficient to evaluate for horizontal gaze. Further criteria can be added to increase sensitivity. Verbal instructions alone yield high rates of inaccuracy when attempting to image patients in horizontal gaze. Apart from improving methods for obtaining radiographs, a radiological definition of horizontal gaze should be routinely applied for better evaluation of sagittal spinal alignment.

Using spinopelvic parameters to estimate residual lumbar lordosis assuming previous lumbosacral fusion-a study of normative values

BACKGROUND CONTEXT

Pelvic incidence (PI)=pelvic tilt (PT)+sacral slope (SS) is an established trigonometric equation which can be expanded from studying the fixed pelvis with the spine to a fixed spinopelvic complex with the remnant spine, in scenarios of spinopelvic fusion or ankylosis. For a fixed spinopelvic complex, we propose the equation termed: lumbar incidence (LI)=lumbar tilt (LT)+lumbar slope (LS).

PURPOSE

This study aimed to establish reference values for LI, LT, and LS at each lumbar vertebral level, and to show how LI can be used to determine residual lumbar lordosis (rLL).

STUDY DESIGN

This is a cross-sectional study of prospectively collected data, conducted at a single academic tertiary health-care center.

PATIENT SAMPLE

The study included 53 healthy patients aged 19-35 with first episode mechanical low back pain for a period of <3 months. Patients with previous spinal intervention, those with known or suspected spinal pathologies, and those who were pregnant, were excluded.

OUTCOME MEASURES

Radiological measurements of LI, LT, LS, and rLL.

METHODS

All patients had full-body lateral standing radiographs obtained via a slot scanner. Basic global and regional radiographic parameters, spinopelvic parameters, and the aforementioned new parameters were measured. LI was correlated with rLL at each level by plotting LI against rLL on scatter plots and drawing lines-of-best-fit through the datapoints.

RESULTS

The mean value of L5I was 22.82°, L4I was 6.52°, L3I was -0.92°, L2I was -5.56°, and L1I was -5.95°. LI turns negative at L3, LS turns negative at the L3/L4 apex, and LT remains positive throughout the lumbar spine. We found that the relationship of LI with its corresponding rLL follows a parabolic trend. Thus, rLL can be determined from the linear equations of the tangents to the parabolic lumbar spine. We propose the LI-rLL method for determining rLL as the LI recalibrates via spinopelvic compensation post instrumentation, and thus the predicted rLL will be based on this new equilibrium, promoting restoration of harmonized lordosis. The rLL-to-LI ratio is a simplified, but less accurate, method of deriving rLL from LI.

CONCLUSIONS

This study demonstrates the extended use of PI=PT+SS proposed as LI=LT+LS. These new spinopelvic reference values help us better understand the position of each vertebra relative to the hip. In situations when lumbar vertebrae are fused or ankylosed to the sacrum to form a single spinopelvic complex, LI can be used to determine rLL, to preserve spinal harmony within the limits of compensated body balance.

Paraplegic patients: how to measure balance and what is normal or functional?

PURPOSE

To review the current understanding and data of sagittal balance and alignment considerations in paraplegic patients.

METHODS

A PubMed literature search was conducted to identify all relevant articles relating to sagittal alignment and sagittal balance considerations in paraplegic and spinal cord injury patients.

RESULTS

While there are numerous studies and publications on sagittal balance in the ambulatory patient with spinal deformity or complex spine disorders, there is paucity of the literature on "normal" sagittal balance in the paraplegic patients. Studies have reported significantly alterations of the sagittal alignment parameters in the non-ambulatory paraplegic patients compared to ambulatory patients. The variability of the alignment changes is related to the differences in the level of the spinal cord injury and their differences in the activations of truncal muscles to allow functional movements in those patients, particularly in optimizing sitting and transferring. Surgical goal in treating paraplegic patients with complex pathologies should not be solely directed to achieve the "normal" radiographic parameters of sagittal alignment in the ambulatory patients. The goal should be to maintain good coronal balance to allow ideal sitting position and to preserve motion segment to optimize functions of paraplegia patients.

CONCLUSION

Current available literature data have not defined normal sagittal parameters for paraplegic patients. There are significant differences in postural sagittal parameters and muscle activations in paraplegic and non-spinal cord injury patients that can lead to differences in sagittal alignment and balance. Treatment goal in spine surgery for paraplegic patients should address their global function, sitting balance, and ability to perform self-care rather than the accepted radiographic parameters for adult spinal deformity in ambulatory patients.

The impact of office chair features on lumbar lordosis, intervertebral joint and sacral tilt angles: a radiographic assessment

BACKGROUND

The purpose of this study was to determine which office chair feature is better at improving spine posture in sitting.

METHOD

Participants (n = 28) were radiographed in standing, maximum flexion and seated in four chair conditions: control, lumbar support, seat pan tilt and backrest with scapular relief. Measures of lumbar lordosis, intervertebral joint angles and sacral tilt were compared between conditions and sex.

RESULTS

Sitting consisted of approximately 70% of maximum range of spine flexion. No differences in lumbar flexion were found between the chair features or control. Significantly more anterior pelvic rotation was found with the lumbar support (p = 0.0028) and seat pan tilt (p < 0.0001). Males had significantly more anterior pelvic rotation and extended intervertebral joint angles through L1-L3 in all conditions (p < 0.0001).

CONCLUSION

No one feature was statistically superior with respect to minimising spine flexion, however, seat pan tilt resulted in significantly improved pelvic posture. Practitioner Summary: Seat pan tilt, and to some extent lumbar supports, appear to improve seated postures. However, sitting, regardless of chair features used, still involves near end range flexion of the spine. This will increase stresses to the spine and could be a potential injury generator during prolonged seated exposures.

Lumbar spine postures in Marines during simulated operational positions

Low back pain has a 70% higher prevalence in members of the armed forces than in the general population, possibly due to the loads and positions soldiers experience during training and combat. Although the influence of heavy load carriage on standing lumbar spine posture in this population is known, postures in other operationally relevant positions are unknown. Therefore, the purpose of this study was to characterize the effect of simulated military operational positions under relevant loading conditions on global and local lumbar spine postures in active duty male US Marines. Secondary objectives were to evaluate if intervertebral disc degeneration and low back pain affect lumbar spine postures. Magnetic resonance images were acquired on an upright scanner in the following operational positions: Natural standing with no external load, standing with body armor (11.3 kg), sitting with body armor, and prone on elbows with body armor. Custom software was used to measure global lumbar spine posture: Lumbosacral flexion, sacral slope, lordosis, local measures of intervertebral angles, and intervertebral distances. Sitting resulted in decreased lumbar lordosis at all levels of the spine except L1-L2. When subjects were prone on elbows, a significant increase in local lordosis was observed only at L5-S1 compared with all other positions. Marines with disc degeneration (77%) or history of low back pain (72%) had decreased lumbar range of motion and less lumbar extension than healthy Marines. These results indicate that a male Marine's pathology undergoes a stereotypic set of postural changes during functional tasks, which may impair performance. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2145-2153, 2017.

Effect of patient position on the lordosis and scoliosis of patients with degenerative lumbar scoliosis

This study aimed to analyze the effect of patient positions on the lordosis and scoliosis of patients with degenerative lumbar scoliosis (DLS).Seventy-seven patients with DLS were retrospectively analyzed. We measured lordosis and Cobb's angle on preoperative upright x-rays and magnetic resonance imagings in supine position. The lordosis and scoliosis of surgical segments in intraoperative prone position were measured on intraoperative radiographs of 20 patients to compare with that in standing position. Paired t tests were performed to investigate the parameters of the sample.From standing to supine position the whole lordosis increased (29.2 ± 15.7 degree vs. 34.9 ± 11.2 degree), and the whole scoliosis decreased (24.3 ± 11.8 degree vs. 19.0 ± 10.5 degree); 53 of 77 (68.8%) cases had increased lordosis, and 67 of 77 (87%) cases had decreased scoliosis. The lordosis of surgical segments in standing position had no difference with that in intraoprerative prone position. But in changing from supine/standing position to intraoprerative prone position, the scoliosis of surgical segments decreased (14.7 ± 9.4 degree vs. 11.4 ± 7.0 degree; 19.0 ± 11.8 degree vs. 11.4 ± 7.0 degree, respectively), and 18 of 20 (90%) cases had decreased scoliosis in intraoperative prone position than that in standing position.Compared with standing position in DLS patients, supine position increased lordosis and reduced scoliosis, and intraoperative prone position reduced scoliosis significantly. When evaluating the severity of DLS and making preoperative surgical plans, lumbar lordosis in supine position should also be evaluated in addition to upright x-ray, and the effects of different positions should be taken into consideration to reduce deviation.

The effect of training on lumbar spine posture and intervertebral disc degeneration in active-duty Marines

Military training aims to improve load carriage performance and reduce risk of injuries. Data describing the lumbar spine (LS) postural response to load carriage throughout training are limited. We hypothesised that training would reduce the LS postural response to load. The LS posture of 27 Marines was measured from upright MR images: with and without load (22.6 kg) at the beginning, middle, and end of School of Infantry (SOI) training. Disc degeneration was graded at L5-S1. No changes in posture and disc degeneration were found throughout training. During load carriage the LS became less lordotic and the sacrum more horizontal. Marines with disc degeneration had larger sacral postural perturbations in response to load. Our findings suggest that the postural response to load is defined more by the task needs than by the physical condition of the Marine. Practitioner Summary: The effect of military training on lumbar spine posture is unknown. The lumbar posture of 27 Marines was measured from upright MR images, with and without load throughout infantry training. No changes in posture or IVD degeneration were found across training. Marines with degeneration at the L5-S1 level had larger sacral postural perturbations in response to load.

How the spine differs in standing and in sitting-important considerations for correction of spinal deformity

BACKGROUND CONTEXT

The current prevailing school of thought in spinal deformity surgery is to restore sagittal balance with reference to the alignment of the spine when the patient is standing. This strategy, however, likely accounts for increased rates of proximal junctional failure.

PURPOSE

The purpose of this study was to investigate the differences between the spine in standing and sitting positions as these may elucidate reasons for deformity correction failure.

STUDY DESIGN/SETTING

A prospective, comparative study of 58 healthy patients presenting to a tertiary hospital over a 6-month period was carried out.

PATIENT SAMPLE

All patients presenting with a less than 3-month history of first episode lower back pain were included. Patients who had radicular symptoms, red flag symptoms, previous spine surgery, or visible spinal deformity during forward bending test were excluded. Pregnant patients were also excluded.

OUTCOME MEASURES

Radiographic measurements including sagittal vertical axis (SVA), lumbar lordosis (LL), thoracolumbar angle (TL), thoracic kyphosis (TK), cervical lordosis (CL), pelvic incidence (PI), and pelvic tilt (PT) were collected. The sagittal apex and end vertebrae of all radiographs were also recorded.

METHODS

Basic demographic data (age, gender, and ethnicity) was recorded. Lateral standing and sitting radiographs were obtained using EOS technology. Statistical analysis was performed to compare standing and sitting parameters using chi-square tests for categorical variables and paired t tests for continuous variables.

RESULTS

Taking the standing position as the reference point, forward displacement of the SVA occurred during sitting by a mean of 6.39±3.87 cm (p<.001). This was accompanied by a reduction of LL and TK by a mean of 24.63±12.70° (p<.001) and 8.56±7.21°(p<.001), respectively. The TL became more lordotic by a mean of 3.25±7.30° (p<.001). The CL only reached borderline significance (p=.047) for increased lordosis by a mean of 3.45±12.92°. The PT also increased by 50% (p<.001). Despite relatively constant end vertebrae, the apex vertebra moved inferiorly for the thoracic curve (p<.006) and superiorly for the lumbar curve (p<.001) by approximately one vertebral level each.

CONCLUSIONS

Sagittal spinal alignment changes significantly between standing and sitting positions. Understanding these differences is crucial to avoid overcorrection of LL, which may occur if deformity correction is based solely on the spine's standing sagittal profile.