The femoro-sacral posterior angle: an anatomical sagittal pelvic parameter usable with dome-shaped sacrum

Evaluation of the effectiveness of the femoro-sacral posterior angle system for measuring spino-pelvic morphology in high-dysplastic developmental spondylolisthesis

OBJECTIVE

The Femoro-Sacral Posterior Angle (FSPA) system and the pelvic incidence (PI) system are utilized for measuring sagittal spino-pelvic morphology in patients with high-dysplastic developmental spondylolisthesis (HDDS). This study aimed to analyze the accuracy and stability of these two systems.

METHODS

A retrospective analysis was conducted on 45 patients diagnosed with HDDS who underwent surgical treatment at our hospital (HDDS group), along with 45 patients without spondylolisthesis (normal group). Three orthopedic surgeons utilized the FSPA and PI systems to measure various parameters, including FSPA, pelvic angle(PA), sacral incidence (SI), PI, pelvic tilt (PT), and sacral slope (SS), respectively. The intraclass correlation coefficient (ICC) was employed to assess the inter-observer consistency of measurements.

RESULTS

There was significant differences in all the parameters between the normal and HDDS groups (p < 0.05), except for SS (p = 0.508). Specifically, SI was lower in HDDS group than in the normal group (23.0 ± 13.4 vs. 38.6 ± 7.1), whereas SS was higher (35.3 ± 15.7 vs. 33.6 ± 7.4). Within HDDS group, there was no statistically significant difference in PI (p = 0.159), SS (p = 0.319), and FSPA (p = 0.173) between pre- and post-surgery measurements. The ICC results indicated superior reliability for the FSPA system (0.842-0.885) compared to the PI system (0.682-0.720) within the HDDS group.

CONCLUSION

Compared with the PI system, the FSPA system demonstrated higher accuracy in evaluating spino-pelvic morphology in HDDS patients. Moreover, it exhibited higher ICC values, indicating higher inter-observer reliability, thus serving as an effective method for assessing spino-pelvic morphology in HDDS patients.

Spine surgeon versus AI algorithm full-length radiographic measurements: a validation study of complex adult spinal deformity patients

INTRODUCTION

Spinal measurements play an integral role in surgical planning for a variety of spine procedures. Full-length imaging eliminates distortions that can occur with stitched images. However, these images take radiologists significantly longer to read than conventional radiographs. Artificial intelligence (AI) image analysis software that can make such measurements quickly and reliably would be advantageous to surgeons, radiologists, and the entire health system.

MATERIALS AND METHODS

Institutional Review Board approval was obtained for this study. Preoperative full-length standing anterior-posterior and lateral radiographs of patients that were previously measured by fellowship-trained spine surgeons at our institution were obtained. The measurements included lumbar lordosis (LL), greatest coronal Cobb angle (GCC), pelvic incidence (PI), coronal balance (CB), and T1-pelvic angle (T1PA). Inter-rater intra-class correlation (ICC) values were calculated based on an overlapping sample of 10 patients measured by surgeons. Full-length standing radiographs of an additional 100 patients were provided for AI software training. The AI algorithm then measured the radiographs and ICC values were calculated.

RESULTS

ICC values for inter-rater reliability between surgeons were excellent and calculated to 0.97 for LL (95% CI 0.88-0.99), 0.78 (0.33-0.94) for GCC, 0.86 (0.55-0.96) for PI, 0.99 for CB (0.93-0.99), and 0.95 for T1PA (0.82-0.99). The algorithm computed the five selected parameters with ICC values between 0.70 and 0.94, indicating excellent reliability. Exemplary for the comparison of AI and surgeons, the ICC for LL was 0.88 (95% CI 0.83-0.92) and 0.93 for CB (0.90-0.95). GCC, PI, and T1PA could be determined with ICC values of 0.81 (0.69-0.87), 0.70 (0.60-0.78), and 0.94 (0.91-0.96) respectively.

CONCLUSIONS

The AI algorithm presented here demonstrates excellent reliability for most of the parameters and good reliability for PI, with ICC values corresponding to measurements conducted by experienced surgeons. In future, it may facilitate the analysis of large data sets and aid physicians in diagnostics, pre-operative planning, and post-operative quality control.

The difference in the relationship of spinal sagittal alignment between individuals with flat lumbar and normal lordosis posture based on global and regional angles

BACKGROUND

According to previous studies, the relationship between lumbar lordosis and thoracic kyphosis or that between pelvic parameters and thoracic kyphosis have been inconsistent.

OBJECTIVE

The purpose of this study was to investigate spinal sagittal alignment and its relationship to global and regional lumbar and thoracic angles, pelvic and sway angles, and C7-S1 distance measurements, followed by a detailed subgroup analysis using an inertial measurement unit system.

METHODS

A total of 51 asymptomatic volunteers stood in a comfortable posture with inertial measurement units attached to the T1, T7, T12, L3, and S2 vertebrae. T1, T7, T12, L3, and S2 sagittal angles were acquired during standing posture using the Eulerian angle coordinate system. All angles are reported as the mean of three 5-s measurements. Following the measurement of lumbar lordosis angles (T12 relative S2), participants were divided into the flat lumbar and normal lordosis groups.

RESULTS

There were different correlation patterns between groups because of spinal sagittal imbalance, which was greater in the flat lumbar group than in the normal lordosis group. In addition, sacral inclination proved the ideal parameter to evaluate reciprocal balance in lumbar lordosis, showing a stronger correlation with lower than with upper lumbar lordosis. T1 was the key element in assessing thoracic kyphosis, which showed a stronger correlation with upper than with lower thoracic kyphosis.

CONCLUSION

We suggest that when assessing posture, it is necessary to identify the global and regional angles and it is useful to classify spinal sagittal alignment into subgroups according to lumbar lordosis and evaluate the groups separately.

Impact of Obesity, Osteopenia, and Scoliosis on Interobserver Reliability of Measures of the Spinopelvic Sagittal Radiographic Parameters

INTRODUCTION

We investigated the relationships between patient factors, including obesity, osteopenia, and scoliosis, and the reliability of measures of the spinopelvic sagittal parameters using conventional X-radiography (Xp) and slot-scanning Xp devices (EOS) and examined the differences in interobserver measurement reliability between them.

METHODS

We retrospectively enrolled 55 patients (52.7±25.3 years, 27 females) with conventional whole-spine Xp and EOS images taken within three months. Patients were classified according to obesity (Body mass index≥25 kg/m2), osteopenia (T score<-1), and scoliosis (Cobb angle>20°). The associations between patient factors and reliability of radiological parameter measurements were examined with interobserver intraclass correlation coefficient (ICC), defined as poor, <.40; good, 40-.79; and excellent, ≥.80.

RESULTS

All parameters measured with EOS showed excellent reliability except for L4-S (ICC:.760, 95% CI:.295-.927) in the obesity+ group. All parameters measured with conventional Xp were excellent except for those classified as good: L4-S (.608,.093-.868) and pelvic incidence (PI) (.512,.078-.832) in the obese+ group; T1 slope (.781,.237-.952), L4-S (.718,.112-.936), sacral slope (SS) (.792,.237-.955), pelvic tilt (PT) (.787,.300-.952), and center of acoustic meatus and femoral head offset (CAM-HA) (.690,.090-.928) in the osteopenia+ group; and lumbar lordosis (LL, L4-S) (.712,.349-.889), SS (.608,.178-.843), and CAM-HA (.781,.480-.917) in the scoliosis+ group.

CONCLUSIONS

Reliability of EOS measurements was preferable except for L4-S in patients with obesity. The reliability of conventional Xp measurements of pelvic parameters SS, PT, and PI was affected by patient factors, including obesity, osteopenia, and scoliosis. When evaluating lower lumbar and pelvic parameters in patients with these factors, we recommend substituting thoracic parameters, LL (L1-S), sagittal vertical axis (SVA), and T1 pelvic angle (TPA), or combining computed tomography (CT) measurements.

Differences in Involvement of Whole-Body Compensatory Alignment for Decompensated Spinopelvic Sagittal Balance

BACKGROUND

The aim of this study was to investigate the differences in the involvement of whole-body compensatory alignment in different conditions of spinopelvic sagittal balance (compensated/decompensated).

METHODS

We enrolled 330 individuals who underwent medical checkups and divided them according to sagittal vertical axis (SVA): for the compensated group, this was <4 cm, (group C) and for the decompensated group, it was ≥4 cm, (group D). The correlation between the lack of ideal lumbar lordosis (iLL), which was calculated by using the Schwab formula, and the compensatory radiographic parameters in each group was analyzed. The threshold value of knee flexion (KF) angle, which indicated spinopelvic sagittal imbalance (SVA ≥ 4), was determined by a ROC-curve analysis.

RESULTS

The correlation analysis of the lack of iLL and each compensatory parameter showed a strong correlation for pelvic tilt (PT) (r = -0.723), and a weak correlation for thoracic kyphosis (TK) (r = 275) in Group C. In Group D, the correlations were strong for PT (r = -0.796), and moderate for TK (r = 0.462) and KF (r = -0.415). The optimal cutoff value for the KF angle was determined to be 8.4 degrees (sensitivity 89%, specificity 46%).

CONCLUSIONS

The present study shows differences between compensated/decompensated spinopelvic sagittal balance in the correlation strength between lack of iLL and whole-body compensatory parameters.

Posterior Pubic Incidence: A Novel Morphologic Spinopelvic Parameter Nearly Equal to Pelvic Incidence

BACKGROUND

Pelvic incidence (PI) and Jackson's angle are 2 major spinopelvic parameters that define the position of the sacrum within the pelvis. These parameters are measured on standing lateral radiography, and the identification of the hip axis is essential for measurements. Moreover, identifying the hip axis in patients with hip diseases or femoral head deformity is challenging. In this study, we described a novel parameter named posterior pubic incidence (PPI) that could be measured using the posterior pubic edge instead of the hip axis.

METHODS

Group A comprised 50 volunteers who underwent standing lateral lumbosacral radiography. Group B comprised 54 patients with abdominal or urologic problems who underwent supine computed tomography. The PI, pelvic tilt (PT), sacral slope, PPI, and posterior pubic tilt were measured. The differences between PI and PPI were evaluated. Linear regression analysis was used to predict the PI value from PPI.

RESULTS

The mean PI and PPI values were 47.41° ± 12.32° and 49.32° ± 11.94° in group A and 49.19° ± 9.99° and 49.99° ± 9.25° in group B, respectively. The mean absolute differences in groups A and B were 2.41° ± 1.63° and 1.9° ± 1.62°, respectively. High correlations were obtained between PI/PPI and pelvic tilt/posterior pubic tilt. PI could be calculated as PI° = PPI° - 2° on plain radiography and as PI° = PPI° - 1° on computed tomography.

CONCLUSIONS

PPI was strongly correlated with PI, which was nearly equal to PI, and may replace PI in formulas containing PI.

Cost-Utility Analysis of Sacroiliac Joint Fusion in High-Risk Patients Undergoing Multi-Level Lumbar Fusion to the Sacrum

Purpose

Multi-level lumbar fusion to the sacrum (MLF) can lead to increased stress and angular motion across the sacroiliac joint (SIJ), with an incidence of post-operative SIJ pain estimated at 26–32%. SIJ fusion (SIJF) can help obviate the need for revisions by reducing range of motion and screw stresses. We aimed to evaluate the cost-utility of MLF + SIJF compared to MLF alone among high-risk patients from a payer perspective, where high risk is defined as high body mass index and high pelvic incidence.

Methods

A Markov process decision-analysis model was developed to evaluate cumulative 5-year costs, quality-adjusted life years (QALYs), and incremental cost-effectiveness ratio (ICER) of MLF + SIJF compared to MLF alone using published data; costs from Medicare claims data analyses and health state utility values (derived from EQ-5D) informed by three prospective, multicenter, clinical trials. The base case assumed a reduction in post-operative SIJ pain from 30% to 10% (relative risk reduction [RRR] of 67%). Costs and utilities were discounted 3% annually. The ICER is reported in 2020 US dollars. One-way, multi-way, and probabilistic sensitivity analyses were performed.

Results

With an assumed 30% incidence of SIJ pain after MLF alone, stabilizing with SIJF was associated with an additional 5-year cost of $2421 and a gain of 0.14 QALYs, resulting in an ICER of $17,293 per QALY gained (similar to total knee arthroplasty and more favorable than open discectomy). ICERs were most sensitive to the RRR of post-operative SIJ pain conferred by SIJF, time horizon, and probability of successful treatment with MLF alone. At a willingness-to-pay threshold of $50,000/QALY gained, MLF + SIJF has a 97.7% probability of being cost-effective in the target patient population.

Conclusion

Fusing the SIJ in high-risk patients undergoing MLF was cost-effective when the incidence of post-operative SIJ pain after MLF alone exceeds approximately 25%, providing value-based healthcare from a payer perspective.

An artificial intelligence powered platform for auto-analyses of spine alignment irrespective of image quality with prospective validation

BACKGROUND

Assessment of spine alignment is crucial in the management of scoliosis, but current auto-analysis of spine alignment suffers from low accuracy. We aim to develop and validate a hybrid model named SpineHRNet+, which integrates artificial intelligence (AI) and rule-based methods to improve auto-alignment reliability and interpretability.

METHODS

From December 2019 to November 2020, 1,542 consecutive patients with scoliosis attending two local scoliosis clinics (The Duchess of Kent Children's Hospital at Sandy Bay in Hong Kong; Queen Mary Hospital in Pok Fu Lam on Hong Kong Island) were recruited. The biplanar radiographs of each patient were collected with our medical machine EOS™. The collected radiographs were recaptured using smartphones or screenshots, with deidentified images securely stored. Manually labelled landmarks and alignment parameters by a spine surgeon were considered as ground truth (GT). The data were split 8:2 to train and internally test SpineHRNet+, respectively. This was followed by a prospective validation on another 337 patients. Quantitative analyses of landmark predictions were conducted, and reliabilities of auto-alignment were assessed using linear regression and Bland-Altman plots. Deformity severity and sagittal abnormality classifications were evaluated by confusion matrices.

FINDINGS

SpineHRNet+ achieved accurate landmark detection with mean Euclidean distance errors of 2·78 and 5·52 pixels on posteroanterior and lateral radiographs, respectively. The mean angle errors between predictions and GT were 3·18° and 6·32° coronally and sagittally. All predicted alignments were strongly correlated with GT (p < 0·001, R2 > 0·97), with minimal overall difference visualised via Bland-Altman plots. For curve detections, 95·7% sensitivity and 88·1% specificity was achieved, and for severity classification, 88·6-90·8% sensitivity was obtained. For sagittal abnormalities, greater than 85·2-88·9% specificity and sensitivity were achieved.

INTERPRETATION

The auto-analysis provided by SpineHRNet+ was reliable and continuous and it might offer the potential to assist clinical work and facilitate large-scale clinical studies.

FUNDING

RGC Research Impact Fund (R5017-18F), Innovation and Technology Fund (ITS/404/18), and the AOSpine East Asia Fund (AOSEA(R)2019-06).

Comparison of pelvic incidence measurement using lateral x-ray, standard ct versus ct with 3d reconstruction

PURPOSE

Pelvic incidence (PI) is a position independent parameter used to quantify spinopelvic sagittal balance. PI is generally measured on lateral radiographs, but more recent studies have suggested better accuracy with standard CT scans versus three-dimensional (3D) CT scans. This study compares PI obtained from lateral XR, standard CT scan and CT scan with 3D reconstruction.

METHODS

A total of 77 subjects with lateral XRs of the pelvis or lumbosacral spine and CT scans of the pelvis were randomly selected. Pelvic incidence on lateral XRs, standard CT scans and CT scans utilizing multiplanar reconstruction were measured and compared using intraclass correlation coefficients (ICC). PI was also measured on serial images in 28 individuals using the same imaging modality within 3 years and evaluated using ICC.

RESULTS

Mean ± SD of PI measurements on XR, standard CT and CT with 3D reconstruction were 56° ± 13°, 53° ± 12° and 53° ± 12°, respectively, demonstrating a small but significant elevation of PI measurement on XR (P < 0.001). ICC values demonstrated a higher correlation between standard CT and 3D CT (ICC 0.986), compared to XR and standard CT (ICC 0.934) and XR and 3D CT (ICC 0.937). PI measurements on repeated imaging of the same individual also demonstrated that both CT methods produced more consistent measurements (ICC 0.986 for standard CT, 0.981 for 3D CT, 0.935 for XR).

CONCLUSION

Although standard XR does provide a high level of reliability, it appears to slightly overestimate PI. CT scans do provide increased reliability, with no additional benefit of 3D reconstructions over standard CT.

Prediction of pelvic mobility using whole-spinal and pelvic alignment in standing and sitting position in total hip arthroplasty patients

PURPOSE

Dislocation is a major complication after total hip arthroplasty (THA), and pelvic stiffness is reportedly a significant risk factor for dislocation. This study aimed to investigate spinopelvic alignment, and identify preoperative factors associated with postoperative pelvic mobility.

METHODS

We enrolled 78 THA patients with unilateral osteoarthritis. The sagittal spinopelvic alignment in the standing and sitting position was measured using an EOS imaging system before and 3 months after THA. We evaluated postoperative pelvic mobility, and defined cases with less than 10° of sacral slope change as pelvic stiff type. The preoperative characteristics of those with postoperative stiff type, and preoperative factors associated with risk of postoperative stiff type were evaluated.

RESULTS

Sagittal spinopelvic alignment except for lumbar alignment were significantly changed after THA.A total of 13 patients (17%) were identified as postoperative pelvic stiff type. Preoperative lower pelvic and lumbar mobility were determined as significant factors for prediction of postoperative pelvic stiff type. Among these patients, nine patients (69%) did not have pelvic stiffness before THA. Preoperative factor associated with the risk of postoperative pelvic stiff type in those without preoperative stiffness was lower lumbar lordosis in standing position by multivariate regression analysis.

CONCLUSION

Spinopelvic alignments except lumber alignment was significantly changed after THA. The lower pelvic mobility and lumbar alignment were identified as the preoperative predictive factors for postoperative pelvic mobility. Evaluation of preoperative lumbar alignment may be especially useful for the prediction in patients with hip contractures, for these patients may possibly experience the extensive perioperative change in pelvic mobility.

Is Sacral Dysmorphism Protective Against Spinopelvic Dissociation? Multicenter Case Series

OBJECTIVES

Investigate the incidence of sacral dysmorphism (SD) in patients with spinopelvic dissociation (SPD).

DESIGN

Retrospective case series.

SETTING

Two academic level 1 trauma centers.

PATIENTS/PARTICIPANTS

One thousand eight hundred fifty adult patients with sacral and pelvic fractures (OTA/AO 61-A, B, C).

INTERVENTION

Plain pelvic radiographs and CT scans.

MAIN OUTCOME MEASUREMENTS

Incidence of SD in patients with SPD. Secondary radiographic evaluation of fracture classification and deformity on sagittal imaging.

RESULTS

Eighty-two patients with SPD were identified, and 12.2% displayed features of SD, significantly less than reported in the literature. The S2 sacral body was the most common horizontal fracture location in patients with SD and nondysmorphic sacra (ND). Roy-Camille type I patterns were more common in ND (35%), versus type II in SD patients (40%). SD patients had lower body mass indexes (19.7 vs. 25.2, P = 0.001). Segmental kyphosis (22.5 degrees ND vs. 23.8 degrees SD, P = 0.838) and sacral kyphosis (26 degrees ND vs. 31 degrees SD, P = 0.605) were similar between groups. Percutaneous fixation was the most common surgical technique.

CONCLUSIONS

We report a significantly lower prevalence of SD in patients with SPD than previously reported in the literature. This suggests that variations in sacral osseous anatomy alter force transmission across the sacrum during traumatic loading, which may be protective against certain high-energy fracture patterns. Preoperative evaluation of sacral anatomy is critical, not only in determining the size and orientation of sacral segment safe zones for screw placement, but also to better understand the pathomechanics involved in sacral trauma.

LEVEL OF EVIDENCE

Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Position-related Change of Pelvic Incidence Depends on the Nonfused Sacroiliac Joint in Patients with Degenerative Spinal Diseases

STUDY DESIGN

A retrospective cross-sectional study.

OBJECTIVE

This study aims to determine whether the sacroiliac (SI) joint motion correlated to pelvic incidence (PI) change from standing to supine position in patients with degenerative spinal diseases.

SUMMARY OF BACKGROUND DATA

PI was found an unstable parameter after adolescence as the fixed nature of PI was challenged by several studies. The SI joint has been shown to have some motion, age-related degenerative changes of cartilage and SI ligaments contribute to SI joint instability.

METHODS

The study contains both specimen study and radiographic study. One human specimen was acquired, on which PI was measured with different sacrum-ilium positions. In radiographic study, patients with old thoracolumbar fracture, lumbar disc herniation, stenosis, and spondylolisthesis were included. Ankylosing spondylitis (AS) patients were also included as control group. PI was measured on standing x-rays and scanogram of computed tomography images in supine position.

RESULTS

Specimen study result revealed that SI motion would lead to the change of PI with fixed pelvic thickness. In radiographic study, 101 patients with different etiology and 30 AS patients were included. After stratifying into different age groups, standing PI was significantly larger than supine PI in each age groups (P = 0.002, <0.001, and <0.001, respectively). In patients with degenerative diseases, PI was significantly larger on standing position than that on supine position. ΔPI showed no significant difference across etiologies. However, in AS patients, standing PI and supine PI revealed no significant difference (P = 0.528).

CONCLUSION

Mobile SI joint may be the cause of increased PI in the aging spine. The dynamic change of PI is etiology-independent if the SI joint was not fused. Older patients have greater position-related change of PI.Level of Evidence: 4.

Sacropelvic Parameters and L5 Spondylolysis: Computed Tomography Analysis

Study Design

Retrospective analysis of computed tomography scans.

Purpose

This study aims to determine the association of sagittal sacropelvic parameters with L5 spondylolysis.

Overview of Literature

The association of increased pelvic incidence (PI) and decreased sacral table angle (STA) with spondylolysis has been reported, but no study has simultaneously analyzed multiple sacropelvic variables to compare their association.

Methods

In this study, computed tomography scans obtained to assess major trauma in patients aged >16 years were analyzed. Scans meeting one of the following criteria were excluded: abnormal anatomy, previous spine or hip/pelvis surgery, or spinal pathology, including deformity, infection, tumor, or trauma. sacral anatomic orientation (SAO), PI, pelvic thickness (PTH), femoro-sacral posterior angle (FSPA), STA, and sacral kyphosis (SK) were measured.

Results

Overall, 202 scans were analyzed: 25 with L5 spondylolysis and 177 normal. Among the groups, a significant difference was observed in SAO (43.3° vs. 51.6°), PI (61.7° vs. 49.8°), STA (95.4° vs. 101.8°), and SK (31.0° vs. 23.7°). Based on the logistic regression analysis, only PI (odds ratio [OR], 1.074; 95% CI, 1.026–1.124) and STA (OR, 0.822; 95% CI, 0.734–0.920) remained significant predictors for the presence of spondylolysis. In the spondylolysis group, PI correlated significantly with PTH (r=−0.589), FSPA (r=0.880), and SK (r=0.576), whereas in the normal group, PI correlated significantly with FSPA (r=0.781) and SK (r=0.728).

Conclusions

By simultaneously assessing multiple sacropelvic parameters, we associated increasing PI with L5 spondylolysis. Decreasing STA, which likely represents a chronic remodeling secondary to spondylolysis, was also associated with increased risk. Back pain in an adolescent or young adult with high PI or low STA should raise suspicion of a possible occult spondylolysis.

Association between fatty infiltration of paraspinal muscle, sagittal spinopelvic alignment and stenosis grade in patients with degenerative lumbar spinal stenosis

Introduction

Sagittal balance and fatty infiltration of paraspinal muscle are important factors in patients with lumbar spinal stenosis (LSS) that may affect patients’ quality of life. Sagittal spinopelvic parameters and fatty infiltration may be associated with the severity of LSS. The purpose of this study was to test the hypothesis that severity of fatty infiltration correlates with severity of LSS and with sagittal pelvic alignment independent of age.

Methods

Age and body mass index (BMI) were extracted. Fatty infiltration was rated according to Goutallier classification and the severity of LSS was graded according to Schizas at five intervertebral disc levels. Overall fatty infiltration was computed as average fatty infiltration (aFI) and severity of LSS was defined as the highest severity of LSS of all segments. The sagittal spinopelvic parameters pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL) and PI-LL were measured. Associations among parameters were assessed using Spearman correlation coefficients adjusted for age (α = 0.05).

Results

165 LSS patients with a median age of 69 years were included. All parameters correlated with age (R>0.162, P<0.05) except BMI and LL (R<0.007, P>0.05). aFI correlated with PI, PT and PI-LL before (R>0.371, P<0.05) and after (R>0.180, P<0.05) adjusting for age. Severity of LSS correlated with PI, PT and PI-LL before (R>0.187, P<0.05) but not after (R<0.130, P>0.05) adjusting for age. aFI correlated with severity of LSS before (R=0.349, P<0.05) but not (R=0.114, P>0.05) after adjusting for age.

Conclusions

The correlation of aFI with sagittal spinopelvic parameters indicates that there might be a relationship between muscle characteristics and the sagittal alignment. Sagittal spinopelvic parameters and fatty infiltration of paraspinal muscles are not associated with radiological severity of LSS. Whether they are associated with clinical manifestation of LSS remains to be investigated.

Multidrug-resistant tuberculosis of lumbosacral spine producing extensive destruction with lumbosacral kyphosis

It is uncommon to get lumbosacral junction deformity due to tuberculosis. Lumbosacral junction alignment is of paramount importance in maintaining global sagittal balance. In this case report, we present a case of a 42-year-old woman with multidrug-resistant tuberculosis of lumbosacral spine with complete destruction of L3, L4 and L5 vertebra with partial destruction of L2 and S1 vertebra leading to significant shortening and lumbosacral kyphosis. The patient had severe axial low back pain, inability to sleep in supine position due to deformity and difficulty in walking due to loss of spinal alignment. The patient was treated with 6 weeks of antituberculous drugs followed by all posterior decompression with instrumentation from D10 to S2 with a reconstruction of anterior vertebral bodies with the help of an expandable cage. Antituberculous treatment was continued for 18 months. At present, the patient is asymptomatic with no neurological deficit and has completed 3.5 years of regular follow-up.

Spinopelvic Characteristics in Acetabular Retroversion: Does Pelvic Tilt Change After Periacetabular Osteotomy?

BACKGROUND

Acetabular retroversion may lead to impingement and pain, which can be treated with an anteverting periacetabular osteotomy (aPAO). Pelvic tilt influences acetabular orientation; as pelvic tilt angle reduces, acetabular version reduces. Thus, acetabular retroversion may be a deformity secondary to abnormal pelvic tilt (functional retroversion) or an anatomic deformity of the acetabulum and the innominate bone (pelvic ring).

PURPOSE

To (1) measure the spinopelvic morphology in patients with acetabular retroversion and (2) assess whether pelvic tilt changes after successful anteverting PAO (aPAO), thus testing whether preoperative pelvic tilt was compensatory.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A consecutive cohort of 48 hips (42 patients; 30 ± 7 years [mean ± SD]) with acetabular retroversion that underwent successful aPAO was studied. Spinopelvic morphology (pelvic tilt, pelvic incidence, anterior pelvic plane, and sacral slope) was measured from computed tomography scans including the sacral end plate in 21 patients, with adequate images. In addition, the change in pelvic tilt with aPAO was measured via the sacrofemoral-pubic angle with supine pelvic radiographs at an interval of 2.5 ± 2 years.

RESULTS

The spinopelvic characteristics included a pelvic tilt of 4° ± 4°, a sacral slope of 39° ± 9°, an anterior pelvic plane angle of 11° ± 5°, and a pelvic incidence of 42° ± 10°. Preoperative pelvic tilt was 4° ± 4° and did not change postoperatively (4° ± 4°) (P = .676).

CONCLUSION

Pelvic tilt in acetabular retroversion was within normal parameters, illustrating "normal" sagittal pelvic balance and values similar to those reported in the literature in healthy subjects. In addition, it did not change after aPAO. Thus, acetabular retroversion was not secondary to a maladaptive pelvic tilt (functional retroversion). Further work is required to assess whether retroversion is a reflection of a pelvic morphological abnormality rather than an isolated acetabular abnormality. Treatment of acetabular retroversion should focus on correcting the deformity rather than attempting to change the functional pelvic position.

Scheuermann’s disease: non-surgical improvement in whole spine sagittal alignment in the treatment of a symptomatic patient using Chiropractic BioPhysics^® technique

[Purpose] To present the dramatic improvement of sagittal posture in a young male with Scheuermann’s disease suffering from pain ailments as treated by Chiropractic BioPhysics^® technique. [Participant and Methods] An 18 year old reported low back pain and headaches for several years. Full spine radiographic assessment revealed pronounced thoracic hyperkyphosis, anterior head translation, posterior thoracolumbar sagittal balance, and a reduced sacral base orientation. The patient was treated by Chiropractic BioPhysics methods incorporating mirror image^® exercises, traction, as well as spinal manipulation. [Results] Assessment after 35 treatment sessions over 14-weeks revealed a dramatic improvement in postural parameters. The thoracic kyphosis reduced by 13°, and was accompanied by a reduction in forward head posture, reduction in posterior sagittal balance, and an increase in sacral base angle to normal. The low back pain and headaches were alleviated. [Conclusion] This case adds to the accumulating evidence demonstrating CBP methods offers an effective approach to reduce the burden of postural disorders including those with Scheuermann’s disease. Since thoracic hyperkyphosis is a serious disorder, the routine comprehensive assessment via full-spine radiography is essential for the quantification of relevant postural parameters.

What preoperative factors predict postoperative sitting pelvic position one year following total hip arthroplasty?

Aims

The aims of this study were to measure sagittal standing and sitting lumbar-pelvic-femoral alignment in patients before and following total hip arthroplasty (THA), and to consider what preoperative factors may influence a change in postoperative pelvic position.

Patients and Methods

A total of 161 patients were considered for inclusion. Patients had a mean age of the remaining 61 years (sd 11) with a mean body mass index (BMI) of 28 kg/m2 (sd 6). Of the 161 patients, 82 were male (51%). We excluded 17 patients (11%) with spinal conditions known to affect lumbar mobility as well as the rotational axis of the spine. Standing and sitting spine-to-lower-limb radiographs were taken of the remaining 144 patients before and one year following THA. Spinopelvic alignment measurements, including sacral slope, lumbar lordosis, and pelvic incidence, were measured. These angles were used to calculate lumbar spine flexion and femoroacetabular hip flexion from a standing to sitting position. A radiographic scoring system was used to identify those patients in the series who had lumbar degenerative disc disease (DDD) and compare spinopelvic parameters between those patients with DDD (n = 38) and those who did not (n = 106).

Results

Following THA, patients sat with more anterior pelvic tilt (mean increased sacral slope 18° preoperatively versus 23° postoperatively; p = 0.001) and more lumbar lordosis (mean 28° preoperatively versus 35° postoperatively; p = 0.001). Preoperative change in sacral slope from standing to sitting (p = 0.03) and the absence of DDD (p = 0.001) correlated to an increased change in postoperative sitting pelvic alignment.

Conclusion

Sitting lumbar-pelvic-femoral alignment following THA may be driven by hip arthritis and/or spinal deformity. Patients with DDD and fixed spinopelvic alignment have a predictable pelvic position one year following THA. Patients with normal spines have less predictable postoperative pelvic position, which is likely to be driven by hip stiffness. Cite this article: Bone Joint J 2018;100-B:1289–96.

Sagittal Balance and Health-Related Quality of Life Three Decades After in Situ Arthrodesis for High-Grade Isthmic Spondylolisthesis

BACKGROUND

This case series of consecutive patients evaluated sagittal balance and health-related quality of life (HRQoL) 3 decades after in situ arthrodesis for high-grade isthmic spondylolisthesis.

METHODS

Global sagittal balance, pelvic parameters, and compensatory mechanisms were evaluated on standing lateral radiographs of the spine and pelvis for 28 of 39 consecutive patients, 28 to 41 years after in situ arthrodesis for high-grade L5 to S1 spondylolisthesis. The mean age at surgery was 14 years (range, 9 to 24 years), and the mean age at the time of follow-up was 48 years (range, 39 to 59 years). A subset of the radiographic parameters was compared with the corresponding data from an 8-year follow-up examination of the same patients. HRQoL was evaluated with the Scoliosis Research Society (SRS)-22r questionnaire.

RESULTS

We found that 3 of the 28 patients had a global sagittal imbalance (T1 spinopelvic inclination of >0°). Signs of compensatory mechanisms, such as reduced thoracic kyphosis and pelvic retroversion, were frequent. There was a significant decrease in sacral slope compared with 8-year follow-up data (p = 0.01). The median SRS-22r subscore was on the same level as Swedish normative data. We found no association between radiographic parameters and SRS-22r outcome.

CONCLUSIONS

Three decades after in situ arthrodesis for high-grade spondylolisthesis, radiographic signs of noncompensated sagittal imbalance were observed in only a few individuals. The patients had normal SRS-22r scores. There was no association between any radiographic parameter and SRS-22r outcome. The findings are relevant in the controversial discussion on whether to perform a reduction procedure to treat high-grade spondylolisthesis.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Spino-pelvic radiological parameters in normal Indian population

INTRODUCTION

There is increasing emphasis on the sagittal spino-pelvic alignment and its interpretation is of critical importance in the management of spinal disorders. A cross-sectional study of several spino-pelvic radiographic parameters was conducted to determine the physiological values of these parameters, to calculate the variations of these parameters according to epidemiological data, and to study the relationships among these parameters.

MATERIAL AND METHOD

Fifty normal healthy volunteers (29 males and 21 females) with no history of back pain were selected and were subjected to standing sagittal spino-pelvic radiographs. All the measurements of various radiographic parameters were performed with use of a software program. A statistical analysis was done to study the relationships among them.

RESULTS

The mean values of pelvic incidence (PI) and lumbar Lordosis Angle (LLA) were 48.52 ± 8.99 and 58.78 ± 9.51, respectively. There was statistical difference between male and female parameters in LLA, lumbo-sacral angle (LSA), sacral horizontal angle (SHA), sacral inclination angle (SIA), sacropelvic angle (PRS1), pelvisacral angle (PSA), and PI. A majority of parameters had higher values for female subjects when compared to male subjects. PI was positively correlated with LLA, pelvic angle (PA), pelvic overhang (PO), pelvic tilt (PT), sacrofemoral distance (SFD), SHA, and sacropelvic translation (SPT), which were highly significant, whereas LLA was positively correlated with SHA and SIA only. PI and LLA were both negatively correlated with PSA, pelvic thickness (PTH), and PRS1.

CONCLUSIONS

This study presents the various spino-pelvic radiographic parameter values of a sample of the normal asymptomatic Indian population. There was significant difference in radiographic parameters between males and females in about half of the parameters studied in the sample. The values obtained are comparable with the values presented as normal in the literature. A comparison of the study results with data published about other populations revealed no differences in any of the pelvic parameters between the Indian, Brazilian, and Korean populations.

Pelvic Incidence Can Be Changed not only by Age and Sex, but also by Posture Used during Imaging

OBJECTIVE

Computed tomography (CT), rather than conventional 2-dimensional radiography, was used to scan and measure pelvic parameters. The results were compared with measurements using X-ray.

METHODS

Pelvic parameters were measured using both CT and X-ray in 254 patients who underwent both abdomino-pelvic CT and X-ray at the pelvic site. We assessed the similarity of the pelvic parameters between the 2 exams, as well as the correlations of pelvic parameters with sex and age.

RESULTS

The mean values of the subjects' pelvic parameters measured on X-ray were: sacral slope (SS), 31.6°; pelvic tilt (PT), 18.6°; and pelvic incidence (PI), 50.2°. The mean values measured on CT were: SS, 35.1°; PT, 11.9°; and PI, 47.0°. PT was found to be 4.07° higher on X-ray and 2.98° higher on CT in women, with these differences being statistically significant (p<0.001, p<0.001). PI was 4.10° higher on X-ray and 2.78° higher on CT in women, with these differences also being statistically significant (p<0.001, p=0.009). We also observed a correlation between age and PI. For men, this correlation coefficient was 0.199 measured using X-ray and 0.184 measured using CT. For women, this correlation coefficient was 0.423 measured using X-ray and 0.372 measured using CT.

CONCLUSION

When measured using CT compared to X-ray, SS increased by 3.5°, PT decreased by 6.7°, and PI decreased by 3.2°. There were also statistically significant differences in PT and PI between male and female subjects, while PI was found to increase with age.

What is the Risk of Developing Proximal Junctional Kyphosis During Growth Friendly Treatments for Early-onset Scoliosis?

BACKGROUND

Rib-based and spine-based systems are commonly used distraction-based growth friendly treatments for early-onset scoliosis (EOS). Our primary purpose was to determine the risk of developing postoperative proximal junctional kyphosis (PJK) during distraction-based growth friendly surgery.

METHODS

A multicenter, retrospective, radiographic comparison was performed for a group of 40 children with EOS who were treated with posterior distraction-based implants. PJK was defined as proximal junction sagittal angle (PJA)≥10 degrees and PJA at least 10 degrees greater than preoperative.

RESULTS

Eight subjects (20%) at immediate postoperative follow-up and 11 subjects (27.5%) at minimum 2-year follow-up had developed PJK. The risk of developing PJK between rib-based and spine-based growing systems was not significantly different at immediate postoperative (17% vs. 25%) or at final (25% vs. 31%) follow-ups.Further analysis combining both treatment groups demonstrated that PJK subjects were significantly older at time of initial surgery (7.1 y PJK vs. 5.0 y no PJK). Radiographic comparisons between PJK versus no PJK: Preoperative scoliosis (69.9 vs. 76.0 degrees), thoracic kyphosis (45.1 vs. 28.7 degrees), lumbar lordosis (53.1 vs. 44.0 degrees), PJA (2.2 vs. 2.8 degrees), sagittal vertical axis (1.5 vs. 2.6 cm), pelvic incidence (52.8 vs. 47.4 degrees), pelvic tilt (14.3 vs. 8.7 degrees), and sacral slope (37.7 vs. 35.9 degrees). At both initial postoperative and at final follow-up visits, a significant difference was found for cervical lordosis 32.2 versus 14.0 degrees and 42.0 versus 16.6 degrees, respectively. Risk ratio for developing PJK at final follow-up was 2.8 for subjects with preoperative thoracic hyperkyphosis and was 3.1 for subjects with high pelvic incidence (P<0.05).

CONCLUSIONS

The risk of developing PJK during distraction-based growth friendly treatment for EOS was 20% immediately after implantation and 28% at minimum 2-year follow-up, with no difference observed between rib-based and spine-based treatment groups. As this study identifies a significant risk of developing PJK during the treatment of EOS, it allows clinicians to preoperatively council patients and their families about this possible complication. In addition, several potential risk factors for the development of postoperative PJK were identified, but should be investigated further in future studies.

LEVEL OF EVIDENCE

Level III-therapeutic study (retrospective, comparative).

Grayscale inversion radiographic view provided improved intra- and inter-observer reliabilities in measuring spinopelvic parameters in asymptomatic adult population

Background

Recently, a grayscale inversion view was reported to improve intra- and inter-observer reliabilities in measuring coronal curvature with Cobb and pedicle methods in scoliosis patients. However, the grayscale transformation has never been applied to the measurements of spinopelvic parameters. The purpose of this study was to compare the measurement reliabilities of the spinoplevic sagittal parameters between the ‘Standard View’ and the ‘Grayscale Inversion View’ in normal adult populations.

Methods

A total of 30 asymptomatic subjects aged between 30 and 40 years were included in this study. Whole-spine posteroanterior radiographs were used to measure the spinoplevic sagittal parameters including thoracic kyphosis (TK), lumbar lordosis (LL), sagittal vertical axis (SVA), pelvic incidence (PI), sacral slope (SS) and pelvic tilt (PT) in both standard view and grayscale inversion view. Two independent observers measured the parameters twice at a 2-week interval. Intra- and inter-observer reliabilities were compared between the two radiographic views. The absolute differences between the two sets of measurements on each view were calculated and compared.

Results

The intra-class correlation coefficients (ICCs) of PI, PT and SVA were greater in the grayscale inversion view than in the standard view (0.972 vs 0.817, 0.937 vs 0.833 and 0.964 vs 0.901 for observer 1, respectively; 0.990 vs 0.826, 0.995 vs 0.842 and 0.969 vs 0.919 for observer 2, respectively). Overall, the improvement of ICC was greater in parameters of sagittal pelvic alignment than in those of sagittal spinal alignment. As for the mean absolute differences between two measurements, significant differences existed between the two views in terms of PI, PT and SVA (p = 0.014, 0.016 and 0.011 for observer 1, respectively; p = 0.014, 0.025 and 0.046 for observer 2, respectively).

Conclusions

A grayscale inversion view provided improved intra- and inter-observer reliabilities in measuring spinoplevic alignment when compared with a standard view. This view was more useful in subjects whose pelvic anatomical structures can’t be identified clearly on the standard X-ray view.

Does Degenerative Lumbar Spine Disease Influence Femoroacetabular Flexion in Patients Undergoing Total Hip Arthroplasty?

BACKGROUND

Sitting pelvic tilt dictates the proximity of the rim of the acetabulum to the proximal femur and, therefore, the risk of impingement in patients undergoing total hip arthroplasty (THA). Sitting position is achieved through a combination of lumbar spine segmental motions and/or femoroacetabular articular motion in the lumbar-pelvic-femoral complex. Multilevel degenerative disc disease (DDD) may limit spine flexion and therefore increase femoroacetabular flexion in patients having THAs, but this has not been well characterized. Therefore, we measured standing and sitting lumbar-pelvic-femoral alignment in patients with radiographic signs of DDD and in patients with no radiographic signs of spine arthrosis.

QUESTIONS/PURPOSES

We asked: (1) Is there a difference in standing and sitting lumbar-pelvic-femoral alignment before surgery among patients undergoing THA who have no radiographic signs of spine arthrosis compared with those with preexisting lumbar DDD? (2) Do patients with lumbar DDD experience less spine flexion moving from a standing to a sitting position and therefore compensate with more femoroacetabular flexion compared with patients who have no radiographic signs of arthrosis?

METHODS

Three hundred twenty-five patients undergoing primary THA had preoperative low-dose EOS spine-to-ankle lateral radiographs in standing and sitting positions. Eighty-three patients were excluded from this study for scoliosis (39 patients), spondylolysis (15 patients), not having five lumbar vertebrae (7 patients), surgical or disease fusion (11 patients), or poor image quality attributable to high BMI (11 patients). In the remaining 242 of 325 patients (75%), two observers categorized the lumbar spine as either without radiographic arthrosis or having DDD based on defined radiographic criteria. Sacral slope, lumbar lordosis, and proximal femur angles were measured, and these angles were used to calculate lumbar spine flexion and femoroacetabular flexion in standing and sitting positions. Patients were aligned in a standardized sitting position so that their femurs were parallel to the floor to achieve approximately 90° of apparent hip flexion.

RESULTS

After controlling for age, sex, and BMI, we found patients with DDD spines had a mean of 5° more posterior pelvic tilt (95% CI, -2° to -8° lower sacral slope angles; p < 0.01) and 7° less lumbar lordosis (95% CI, -10° to -3°; p < 0.01) in the standing position compared with patients without radiographic arthrosis. However, in the sitting position, patients with DDD spines had 4° less posterior pelvic tilt (95% CI, 1°-7° higher sacral slope angles; p = 0.02). From standing to sitting position, patients with DDD spines experienced 10° less spine flexion (95% CI, -14° to -7°; p < 0.01) and 10° more femoroacetabular flexion (95% CI, 6° to 14°; p < 0.01).

CONCLUSIONS

Most patients undergoing THA sit in a similar range of pelvic tilt, with a small mean difference in pelvic tilt between patients with DDD spines and those without radiographic arthrosis. However, in general, the mechanism by which patients with DDD of the lumbar spine achieve sitting differs from those without spine arthrosis with less spine flexion and more femoroacetabular flexion.

CLINICAL RELEVANCE

When planning THA, it may be important to consider which patients sit with less posterior pelvic tilt and those who rotate their pelvises forward to achieve a sitting position, as both mechanisms will limit or reduce the functional anteversion of the acetabular component in a patient with a THA. Our study provides some additional perspective on normal relationships between pelvic tilt and femoroacetabular flexion, but further research might better characterize this relationship in outliers and the possible implications for posterior instability after THA.

Spinopelvic dissociation: multidetector computed tomographic evaluation of fracture patterns and associated injuries at a single level 1 trauma center

The objective of the present study is to evaluate multidetector computed tomographic (MDCT) fracture patterns and associated injuries in patients with spinopelvic dissociation (SPD). Our institutional trauma registry database was reviewed from Jan. 1, 2006, to Sept. 30, 2012, specifically evaluating patients with sacral fractures. MDCT scans of patients with sacral fractures were reviewed to determine the presence of SPD. SPD cases were characterized into the following fracture patterns: U-shaped, Y-shaped, T-shaped, H-shaped, and burst. The following MDCT features were recorded: level of the horizontal fracture, location of vertical fracture, kyphosis between major fracture fragments, displacement of fracture fragment, narrowing of central spinal canal, narrowing of neural foramina, and extension into sacroiliac joints. Quantitative evaluation of the sacral fractures was performed in accordance with the consensus statement by the Spine Trauma Study Group. Medical records were reviewed to determine associated pelvic and non-pelvic fractures, bladder and bowel injuries, nerve injuries, and type of surgical intervention. Twenty-one patients had SPD, of whom 13 were men and eight were women. Mean age was 41.8 years (range 18.8 to 87.7). Five fractures (24 %) were U-shaped, six (29 %) H-shaped, four (19 %) Y-shaped, and six (29 %) burst. Nine patients (43 %) had central canal narrowing, and 19 (90 %) had neural foramina narrowing. Eleven patients (52 %) had kyphotic angulation between major fracture fragments, and seven patients (33 %) had either anterior (24 %) or posterior (10 %) displacement of the proximal fracture fragment. Fourteen patients (67 %) had associated pelvic fractures, and 20 (95 %) had associated non-pelvic fractures. Two patients (10 %) had associated urethral injuries, and one (5 %) had an associated colon injury. Seven patients (33 %) had associated nerve injuries. Six patients (29 %) had surgical fixation while 15 (71 %) were managed non-operatively. On trauma MDCT examinations, patients with SPD have characteristic fracture patterns. It is important to differentiate SPD from other pelvic ring injuries due to high rate of associated injuries. Although all SPD injuries are unstable and need fixation, the decision for operative management in an individual patient depends on the systemic injury pattern, specific fracture pattern, and the ability to attain stable screw fixation.

Relationship between pelvic incidence and osteoarthritis of the hip

Objectives

Sagittal alignment of the lumbosacral spine, and specifically pelvic incidence (PI), has been implicated in the development of spine pathology, but generally ignored with regards to diseases of the hip. We aimed to determine if increased PI is correlated with higher rates of hip osteoarthritis (HOA). The effect of PI on the development of knee osteoarthritis (KOA) was used as a negative control.

Methods

We studied 400 well-preserved cadaveric skeletons ranging from 50 to 79 years of age at death. Each specimen’s OA of the hip and knee were graded using a previously described method. PI was measured from standardised lateral photographs of reconstructed pelvises. Multiple regression analysis was performed to determine the relationship between age and PI with HOA and KOA.

Results

The mean age was 60.2 years (standard deviation (sd) 8.1), and the mean PI was 46.7° (sd 10.7°). Multiple regression analysis demonstrated a significant correlation between increased PI and HOA (standardised beta = 0.103, p = 0.017). There was no correlation between PI and KOA (standardised beta = 0.003, p = 0.912).

Conclusion

Higher PI in the younger individual may contribute to the development of HOA in later life.

Cite this article: Dr J. J. Gebhart. Relationship between pelvic incidence and osteoarthritis of the hip. Bone Joint Res 2016;5:66–72. DOI: 10.1302/2046-3758.52.2000552.

Accuracies in Measuring Spinopelvic Parameters in Full-Spine Lateral Standing Radiograph

STUDY DESIGN

Prospective comparative study of measuring pelvic incidence (PI) among standing radiographs of whole spine and pelvis and computed tomographic (CT) scans in a cohort of patients.

OBJECTIVE

To analyze accuracies in measuring PI and other spinopelvic parameters.

SUMMARY OF BACKGROUND DATA

Previous reports indicated relatively low agreement in measuring PI even among experienced spinal surgeons; intra- and inter-rater reliability in manually measuring PI were 0.69 (0.62-0.74) and 0.41 (0.36-0.45), respectively; the mean interclass correlation coefficient value of manually measuring PI was 0.881. No study compared PI on standing radiographs with that measured on CT scans.

METHODS

A total of 120 consecutive patients with spinal disease (38 patients had history of hip arthroplasty) who admitted to our hospital from April 2012 for 6 months were enrolled. Subjects had obtained full-spine lateral standing radiograph, standing radiograph of pelvis, and CT scans. Pelvic incidence on full-spine lateral standing radiograph and that on pelvis lateral standing radiograph were measured manually by 2 experienced spinal surgeons. Intra- and interobserver reliability of the measurements were analyzed by using interclass correlation coefficient. On CT scans, PI was measured using 3-dimensional CT scan software (CT-PI). PI among 3 different imaging modalities was evaluated using correlation coefficients.

RESULTS

In whole-spine radiographs, the intra- and interobserver agreement rates with measurements in PI (0.84 and 0.79, respectively) and sacral slope (0.87 and 0.83, respectively) were lower than those in pelvic tilt (0.98 and 0.96, respectively) and PI-lumbar lordosis (0.97 and 0.97, respectively). The correlation coefficient between P-PI and CT-PI was higher (0.95) than that between FS-PI and CT-PI (0.81) and between FS-PI and P-PI (0.85).

CONCLUSION

The reliability of measuring PI is comparatively lower than that of other spinopelvic parameters, and the variability of PI measurement is mainly due to difficulty of precisely identifying sacral endplate.

LEVEL OF EVIDENCE

2.

Analysis of hip dysplasia and spinopelvic alignment in cerebral palsy

BACKGROUND CONTEXT

Knowledge of sagittal spinopelvic parameters and hip dysplasia is important in cerebral palsy (CP) patients because these parameters differ from those found in the general population and can be related to symptoms.

PURPOSE

The purpose of this study was to analyze sagittal spinopelvic alignment and determine its relation to hip dysplasia in CP patients.

STUDY DESIGN

Radiological analysis was conducted on patients with CP.

PATIENT SAMPLE

Fifty-four patients with CP and 24 normal controls were included in this study.

OUTCOME MEASURES

Participants underwent radiographs of the whole spine.

METHODS

The patient and control groups comprised 54 CP patients and 24 volunteers, respectively. All underwent lateral radiography of the whole spine and hip joint anteroposterior radiography. The radiographic parameters examined were sacral slope, pelvic tilt, pelvic incidence, S1 overhang, thoracic kyphosis, thoracolumbar kyphosis, lumbar lordosis, sagittal balance, center edge angle, acetabular angle, and migration index. Statistical analysis was performed to identify significant differences and correlations between the two groups.

RESULTS

Sacral slope, thoracolumbar kyphosis, lumbar lordosis, sagittal balance, acetabular angle, and migration index were significantly higher in CP patients, whereas pelvic tilt, S1 overhang, and center edge angle were significantly lower (p<.05). Correlation analysis revealed that pelvic incidence, sacral slope, pelvic tilt, and S1 overhang were related to each other and that thoracolumbar kyphosis was related to the thoracic kyphosis and lumbar lordosis (p<.05). For spinal and pelvic parameters, lumbar lordosis was related to sacral slope, pelvic incidence, pelvic tilt, and S1 overhang; for hip dysplasia parameters, center edge angle and acetabular angle were found to be interrelated (p<.05). Regarding symptoms, pelvic tilt, S1 overhang, and thoracolumbar kyphosis were found to be correlated with symptom severity in patients. However, no hip dysplasia parameters were found to be related to hip or spinal symptoms.

CONCLUSIONS

This study found significant differences between CP patients and normal controls in terms of spinopelvic alignment and hip dysplasia. Furthermore, relationships were found between the sagittal spinopelvic parameters and hip dysplasia, and correlations were found between sagittal spinopelvic parameters and pain.

Idiopathic scoliosis in children and adolescents: assessment with a biplanar X-ray device

Idiopathic scoliosis is one of the most common conditions encountered in paediatric practice. It is a three-dimensional (3D) spinal deformity. Conventional radiography is still the modality of choice for evaluation of children and adolescents with idiopathic scoliosis, but it requires repeat radiographs until skeletal maturity is reached and does not provide information about spinal deformity in all three planes. A biplanar X-ray device is a new technique that enables standing frontal and lateral radiographs of the spine to be obtained at lowered radiation doses. With its specific software, this novel vertical biplanar X-ray unit provides 3D images of the spine and offers the opportunity of visualising the spinal deformity in all three planes. This pictorial review presents our experience with this new imaging system in children and adolescents with idiopathic scoliosis.

KEY POINTS

• The biplanar X-ray device produces two orthogonal spine X-ray images in a standing position. • The biplanar X-ray device can assess idiopathic scoliosis with a lower radiation dose. • The biplanar X-ray device provides 3D images of the spine.

Sacrum pubic incidence and sacrum pubic posterior angle: two morphologic radiological parameters in assessing pelvic sagittal alignment in human adults

PURPOSE

The morphology and position of pelvis are critical in regulating the biomechanical organization of spine-pelvis-leg in the sagittal plane. Several radiological parameters have been developed to present the sagittal morphology of the pelvis such as pelvic incidence (PI) and Jackson's angle (PRS1). In addition, the femoral sacral posterior angle (FSPA) was developed for patients with a dome-shaped deformity in the upper plate of the sacrum. The identification of hip axis, which was represented by the line connecting the centers of femoral heads in normal subjects, was important for these parameters measurement. However, in subjects with fused hip joint or deformed femoral heads, the accurate localization of hip axis become imprecise. Herein, the upper edge of the pubic symphysis, which is easy to identify on the lateral X-ray film, was selected as an alternative landmark of the hip axis, and two morphologic parameters, the sacrum pubic incidence (SPI) and sacrum pubic posterior angle (SPPA), were proposed accordingly. The present study aimed to understand the reliability of these two parameters and their value in predicting PI, PRS1 and FSPA.

METHODS

Upright standing spine and pelvis radiographs of 60 normal adults (30 male and 30 female) with an average age of 38.5 years were obtained. Two independent observers then measured the following radiological parameters on the films: PI, PRS1, FSPA, SPI, SPPA, sacral slope, pelvic tilt and lumbar lordosis. The SPI is the angle between the line perpendicular to the superior plate of the first sacral vertebra at its midpoint and the line connecting this point to the upper edge of the pubic symphysis, while the SPPA is the angle between the line extending from the posterior upper edge of the sacrum to the upper edge of the pubic symphysis and the posterior side of the first sacral vertebral body. The intra-observer and inter-observer reliabilities of the parameters were analyzed using intraclass correlations. The correlations between parameters were analyzed by Pearson's correlation coefficients. Regression analysis was carried out to establish formulas to predict the values of PI, PRS1 and FSPA using the SPI and SPPA. A p < 0.05 was considered statistically significant.

RESULTS

The SPI was 64.4° ± 9.5° and 68.3° ± 9.4°, and the SPPA was 77.7° ± 7.5° and 78.7° ± 9.4° in males and females, respectively. These radiological parameters showed excellent intra- and inter-observer reliabilities, with an intraclass correlation >0.8. No gender differences were identified in these morphologic and positional radiological parameters. The SPI demonstrated strong correlation with PI and PRS1 (R (2) > 0.9, p < 0.001). In addition, strong correlation was also found between SPPA and FSPA (R (2) > 0.9, p < 0.001). Furthermore, both SPPA and FSPA showed close correlations with the other morphologic and positional parameters. Linear regression analysis established equations to predict PI and PRS1 using SPI and to predict FSPA by SPPA with significantly high reliability.

CONCLUSIONS

Both SPI and SPPA are reliable parameters for determining the morphology of the pelvis. The SPI is precise in predicting PI and PRS1, while SPPA is reliable in predicting FSPA. The SPI and SPPA will allow further study on lateral spinal-pelvic alignment in patients with hip joint abnormalities.

Evaluation of pelvic morphology in the sagittal plane

BACKGROUND CONTEXT

It is generally accepted that for normal subjects the angle of pelvic incidence (PI) increases during childhood and then remains unchanged throughout adolescence and adulthood. However, recent findings show that PI increases linearly throughout the lifespan due to morphological changes of the pelvis.

PURPOSE

A retrospective study aiming to determine the extent of morphological changes of the pelvis related to the age of the subjects.

STUDY DESIGN

Pelvic morphology was evaluated in a normal adult population by measuring the anatomical parameters of sagittal pelvic alignment.

PATIENT SAMPLE

The final study cohort consisted of 330 subjects (mean age, 45.3 years; standard deviation, 18.1 years; range, 18-87 years; 164 male and 166 female subjects).

OUTCOME MEASURES

Physiologic measures, obtained as measurements of PI, sacral end plate width (S1W), and pelvic thickness (PTH).

METHODS

Parameters of PI, S1W, and PTH were evaluated from computed tomography images of the subjects. The measured PTH was normalized according to S1W and age of the subjects, allowing the comparison among anatomies of different sizes. The normalized components of PTH in anteroposterior and cephalocaudal directions were computed to determine the configuration and extent of changes in pelvic morphology related to subject age.

RESULTS

Statistically significant correlation with both age and PI was obtained for all normalized parameters (except for the anteroposterior component of PTH for male subjects), and no statistically significant differences were observed between the sexes. With increasing PI that occurs due to the aging process, a decrease of PTH can be observed that is manifested not only as an increase of the distance between the sacrum and the hip axis in the anterior direction but considerably more as a decrease of the distance between the sacrum and the hip axis in the cephalic direction. By considering these morphological changes in the pelvis simultaneously, the hip axis can move only within a narrow area.

CONCLUSIONS

The changes in pelvic morphology due to the aging process occur in the anterior direction, which may be due to the remodeling process affecting the coxal bone that results in an anterior drift of the acetabulum relative to the sacrum. More importantly, the changes are considerably more evident in the cephalic direction, which may be the result of the weight-bearing loads and consequent wear of acetabular cartilage.

Lumbar Spondylolysis and Spondylolisthesis in Down Syndrome: A Cross-sectional Study at One Institution

STUDY DESIGN

Retrospective cross-sectional study.

OBJECTIVES

To describe lumbar spondylolysis and spondylolisthesis and establish their prevalence in individuals with Down syndrome.

SUMMARY OF BACKGROUND DATA

Orthopedic problems in Down syndrome are variable and numerous. Lumbar spondylolysis and spondylolisthesis may be common conditions in Down syndrome. However, there has been a paucity of data on the association of these conditions in the published literature.

METHODS

A retrospective review of 110 patients with Down syndrome seen at a single institution from 2000 through 2012 was performed. Medical records, X-rays, and physician dictations were carefully reviewed to establish a detailed database of the study population.

RESULTS

Of the 110 patients in the study, 20 exhibited spondylolysis (unilateral, n = 11; bilateral, n = 9), whereas 38 had lumbar spondylolisthesis (isthmic, n = 9; dysplastic, n = 2; degenerative, n = 27). No gender difference was noted (p ≥ .7732). Fifteen patients reported low back pain (LBP) and/or leg pain. There was no significant association between LBP, leg pain, and spondylolysis (p = .9232). Both of these symptoms were highly predictive of lumbar spondylolisthesis, however (p = .0006). No significant findings were noted in pelvic parameters (pelvic incidence, sacral slope, pelvic tilt, or lumbar lordosis) in this study.

CONCLUSIONS

The prevalence of spondylolysis and spondylolisthesis in individuals with Down syndrome may be as high as 18.7% and 32.7%, respectively, significantly higher than in the non-Downs population. Etiopathogenesis of these conditions in Down syndrome does not appear to be related to pelvic parameters. Low back pain and leg pain may be more predictive of spondylolisthesis in Down syndrome than in the general population. Therefore, it is recommended that individuals with Down syndrome and LBP and/or leg pain be evaluated for lumbar spondylolisthesis.

Analysis of sagittal spinopelvic parameters in cerebral palsy

BACKGROUND CONTEXT

Knowledge of sagittal spinopelvic parameters is important for the treatment of cerebral palsy (CP) because they differ in the normal population and can induce symptoms.

PURPOSE

To analyze the sagittal spinal alignment and the pelvic orientation in CP.

STUDY DESIGN

Radiological analysis of patients with CP.

METHODS

The study and control groups comprised 57 CP patients and 24 healthy volunteers, respectively. All the patients underwent lateral radiography of the whole spine including hip joints. The radiographic parameters examined were sacral slope (SS), pelvic tilt (PT), pelvic incidence (PI), S1 overhang (OH), thoracic kyphosis (TK), thoracolumbar kyphosis (TLK), lumbar lordosis (LL1 and 2), and sagittal balance (SB). Statistical analysis was performed to identify the significant differences between the two study groups. In addition, correlations were sought between the parameters and symptoms.

RESULTS

The PT and OH were significantly smaller in the CP patients, whereas SS, TLK, LL1, LL2, and SB were significantly greater (p<.05). Correlation analysis revealed significant relationships between the sagittal parameters. Specifically, PI was found to be associated with SS, PT, and OH, whereas the spinal parameters LL1 and LL2 were found to be related to TK and SB. Between spine and pelvic parameters, LL1 and LL2 were found to be related to SS, PT, PI, and OH and in addition, SB was found to be related to TLK, LL1, and LL2. An analysis of relations between the symptoms and parameters revealed a positive correlation between the severities of symptoms and PT, OH, and TLK (r=0.300, p=.023; r=0.306, p=.020; r=0.289, p=.029, respectively).

CONCLUSIONS

A significant difference was observed in the sagittal spinopelvic parameters in the CP and normal control groups and was possibly related to the symptoms. The study shows that the evaluations of sagittal spinopelvic parameters could be useful during the treatment of disorders associated with CP.

Pelvic flexion measurement from lateral projection radiographs is clinically reliable

BACKGROUND

Pelvic flexion affects orientation of the acetabular cup; however, pelvic position is not static in daily activities. During THA it is difficult to know the degree of pelvic flexion with the patient in the lateral position and that position is static. However, surgeons need to appropriately determine pelvic tilt to properly insert the acetabular component.

QUESTIONS/PURPOSES

We investigated the reliability of pelvic flexion angle that was measured by manually identifying the location of the pubic symphysis and bilateral anterior superior iliac spines using synthesized lateral radiographs.

METHODS

We synthesized 49 lateral radiographs based on CT data. Each of the 49 radiographs had a unique position: 7° of varying lateral tilt and rotation in each of seven selected pelvic flexion angles. The pelvic flexion angle was measured three times by three independent observers in each position and determined the accuracy (based on the true value from the reconstructions) and reliability of the measures.

RESULTS

The measurement error was 0.1° (range, -4.8° to 4.0°). There was a tendency for errors when the pelvic flexion angle was 0° or ±5°; the errors were less when the pelvic flexion angle was ±10° or ±20°. Lateral tilt was associated with greater error than rotation. The intraclass correlation coefficient (ICC) of the average value was 0.967. For one observer, more than two measurements are necessary for the ICC to be greater than 0.8, and only one measurement was needed for two of the three observers.

CONCLUSIONS

Our data suggest measurement of pelvic flexion angle using lateral radiographs is reliable. We recommend the measurement be performed once by two observers for better reliability.

Espondilolistesis ístmica lumbosacra del adulto: laminoartrectomía y fusión in situ

OBJETIVO: La espondilolistesis ístmica del adulto se puede tratar con reparación del defecto, descompresión (sola o con fusión), fusión circunferencial, y reducción con fijación posterior. El objetivo de este trabajo es valorar los resultados a medio plazo de la descompresión y fusión in situ en pacientes operados por un solo cirujano. MÉTODO: Criterios de Inclusión: 1) Espondilolistesis Ístmica L5-S1. 2) Operados en madurez esquelética. 3) Laminoartrectomía de L5 con Artrodesis posterolateral instrumentada sin reducción. 4) Más de 3 años de seguimiento. 5) Ausencia de pseudoartrosis al seguimiento. 6) Valoración funcional y radiológica por observador independiente. Comparación de datos con bibliografía. Análisis estadístico con t - test, Chi cuadrado y ANOVA. RESULTADOS: 16 pacientes (12 ♀/4 ♂) evaluados. Edad promedio: 40,6 años (17 - 66); seguimiento promedio: 10.3 años (3.3 - 18). Deslizamiento promedio: 42,9%. Nueve presentaban dolor radicular, 3 dolor lumbar y 4 dolor lumborradicular. Score del dolor (SRS) preoperatorio promedio: 1.38, sin diferencias entre bajo y alto grado (p=0.887). 15/16 mejoraron (score final promedio: 4.44). 13/16 retornaron a su actividad previa (81%). Hubo 2 infecciones; no hubo complicaciones neurológicas. Los parámetros espinopélvicos finales, comparados con la literatura no mostraron diferencias estadísticas. La comparación entre listesis de bajo y alto grado en la serie no mostró diferencia significativa en dichos parámetros, ni en tiempo de seguimiento, niveles artrodesados, síntomas ni retorno al trabajo. CONCLUSIÓN: La descompresión y fusión posterolateral instrumentada in situ permite un 80% de buenos resultados en la espondilolistesis ístmica lumbosacra del adulto sin importar el grado.

A review of methods for evaluating the quantitative parameters of sagittal pelvic alignment

BACKGROUND CONTEXT

The sagittal alignment of the pelvis represents the basic mechanism for maintaining postural equilibrium, and a number of methods were developed to assess normal and pathologic pelvic alignments from two-dimensional sagittal radiographs in terms of positional and anatomic parameters.

PURPOSE

To provide a complete overview of the existing methods for quantitative evaluation of sagittal pelvic alignment and summarize the relevant publications.

STUDY DESIGN

Review article.

METHODS

An Internet search for terms related to sagittal pelvic alignment was performed to obtain relevant publications, which were further supplemented by selected publications found in their lists of references. By summarizing the obtained publications, the positional and anatomic parameters of sagittal pelvic alignment were described, and their values and relationships to other parameters and features were reported.

RESULTS

Positional pelvic parameters relate to the position and orientation of the observed subject and are represented by the sacral slope, pelvic tilt, pelvic overhang, sacral inclination, sacrofemoral angle, sacrofemoral distance, pelvic femoral angle, pelvic angle, and sacropelvic translation. Anatomic pelvic parameters relate to the anatomy of the observed subject and are represented by the pelvisacral angle (PSA), pelvic incidence (PI), pelvic thickness (PTH), sacropelvic angle (PRS1), pelvic radius (PR), femorosacral posterior angle (FSPA), sacral table angle (STA), and sacral anatomic orientation (SAO). The review was mainly focused on the evaluation of anatomic pelvic parameters, as they can be compared among subjects and therefore among different studies. However, ambiguous results were yielded for normal and pathologic subjects, as the reported values show a relatively high variability in terms of standard deviation for every anatomic parameter, which amounts to around 10 mm for PTH and PR; 10° for PSA, PI, and SAO; 9° for PRS1 and FSPA; and 5° for STA in the case of normal subjects and is usually even higher in the case of pathologic subjects. Among anatomic pelvic parameters, PI was the most studied and therefore represents a key parameter in the complex framework of sagittal spinal alignment and related deformities. From the reviewed studies, the regression lines for PI and the corresponding age of the subjects indicate that PI tends to increase with age for normal (PI = +0.17 × age+46.40) and scoliotic (PI = +0.20 × age+50.52) subjects and decrease with age for subjects with spondylolisis or spondylolisthesis (PI = -0.26 × age+75.69).

CONCLUSIONS

Normative values for anatomic parameters of sagittal pelvic alignment do not exist because the variability of the measured values is relatively high even for normal subjects but can be predictive for spinal alignment and specific spinopelvic pathologies.

Correlation of sacropelvic geometry with disc degeneration in spondylolytic cadaver specimens

STUDY DESIGN

An anatomic study of sacral inclination, pelvic incidence, pelvic lordosis, and disc degeneration in cadaveric lumbar spines.

OBJECTIVE

To evaluate the relationship between sacropelvic parameters and disc degeneration in subjects with bilateral spondylolysis at L5.

SUMMARY OF BACKGROUND DATA

L5-S1 disc degeneration is greater in patients with spondylolytic defects (L5-S1) than with an intact pars interarticularis secondary to the instability caused by spondylolysis. Sacral inclination, pelvic incidence, and pelvic lordosis affect sagittal balance and axial forces on the L5-S1 disc.

METHODS

An observational study was performed on 120 cadaveric specimens with spondylolysis (L5-S1) identified of 3100 total cadaveric specimens. Nine specimens were excluded because of incomplete or degraded skeletal elements; 10 were excluded for having unilateral defects only. The specimens were evaluated for sacral inclination, pelvic incidence, and pelvic lordosis. Disc degeneration and facet arthrosis at L4-L5 and L5-S1 were measured by the classification of Eubanks et al. Linear regression analyses were then used to determine the relationship between sacropelvic parameters and degeneration at the L5-S1 segment, correcting for confounding factors such as age, sex, and race.

RESULTS

Linear regression demonstrated a significant association between sacral inclination and disc degeneration at L5-S1 (P = 0.018). Specimens were then divided into two groups, those in the highest quarter of pelvic incidence, and the remainder. Spearman rank correlation demonstrated a significant association between disc degeneration at L5-S1 and the highest quarter of pelvic incidence (P = 0.017). Increasing pelvic lordosis was also associated with an increase in facet arthrosis at L4-L5 (P = 0.006).

CONCLUSION

The findings of this study show a relationship between the sacropelvic geometry and the degree of L5-S1 disc degeneration as well as L4-L5 facet degeneration in spondylolytic specimens. This relationship may prove useful in predicting the course of disc degeneration in patients with spondylolysis.

Analysis of sagittal spinopelvic parameters in achondroplasia

STUDY DESIGN

Prospective radiological analysis of patients with achondroplasia.

OBJECTIVE

To analyze sagittal spinal alignment and pelvic orientation in achondroplasia patients.

SUMMARY OF BACKGROUND DATA

Knowledge of sagittal spinopelvic parameters is important for the treatment of achondroplasia, because they differ from those of the normal population and can induce pain.

METHODS

The study and control groups were composed of 32 achondroplasia patients and 24 healthy volunteers, respectively. All underwent lateral radiography of the whole spine including hip joints. The radiographic parameters examined were sacral slope (SS), pelvic tilt, pelvic incidence (PI), S1 overhang, thoracic kyphosis, T10-L2 kyphosis, lumbar lordosis (LL1, LL2), and sagittal balance. Statistical analysis was performed to identify significant differences between the two groups. In addition, correlations between parameters and symptoms were sought.

RESULTS

Sagittal spinopelvic parameters, namely, pelvic tilt, pelvic incidence, S1 overhang, thoracic kyphosis, T10-L2 kyphosis, lumbar lordosis 1 and sagittal balance were found to be significantly different in the patient and control groups (P < 0.05). In addition, sagittal parameters were found to be related to each other in the patient group (P < 0.05), that is, PI was related to SS and pelvic tilt, and LL was related to thoracic kyphosis. Furthermore, in terms of relations between spinal and pelvic parameters, LL was related to SS and PI, and sagittal balance was related to SS and PI. Furthermore, LL and T10-L2 kyphosis were found to be related to pain (P < 0.05), whereas no other parameter was found to be related to VAS scores.

CONCLUSION

Sagittal parameters and possible relationships between sagittal parameters and symptoms were found to be significantly different in achondroplasia patients and normal healthy controls. The present study shows that sagittal spinal and pelvic parameters can assist the treatment of spinal disorders in achondroplasia patients.

Middle Pleistocene lower back and pelvis from an aged human individual from the Sima de los Huesos site, Spain

We report a nearly complete lumbar spine from the Middle Pleistocene site of the Sima de los Huesos (SH) that is assigned to the previously published SH male Pelvis 1 [Arsuaga JL, et al. (1999). Nature 399: 255-258]. The "SH Pelvis 1 individual" is a unique nearly complete lumbo-pelvic complex from the human Middle Pleistocene fossil record, and offers a rare glimpse into the anatomy and past lifeways of Homo heidelbergensis. A revised reconstruction of Pelvis 1, together with the current fossil evidence, confirms our previous hypothesis that the morphology of this pelvis represents the primitive pattern within the genus Homo. Here we argue that this primitive pattern is also characterized by sexual dimorphism in the pelvic canal shape, implying complicated deliveries. In addition, this individual shows signs of lumbar kyphotic deformity, spondylolisthesis, and Baastrup disease. This suite of lesions would have postural consequences and was most likely painful. As a result, the individual's daily physical activities would have been restricted to some extent. Reexamination of the age-at-death agrees with this individual being over 45 y old, relying on the modern human pattern of changes of the articular surfaces of the os coxae. The presence of degenerative pathological lesions and the advanced age-at-death of this individual make it the most ancient postcranial evidence of an aged individual in the human fossil record. Additional nonpathological SH lumbo-pelvic remains are consistent with previous hypotheses, suggesting a less-pronounced sagittal spinal curvature in Neandertals compared with Homo sapiens.

The intrinsic shape of the human lumbar spine in the supine, standing and sitting postures: characterization using an active shape model

The shape of the lumbar spine in the sagittal plane varies between individuals and as a result of postural changes but it is not known how the shape in different postures is related. Sagittal images of the lumbar spines of 24 male volunteers were acquired using a positional magnetic resonance scanner. The subjects were imaged lying supine, standing and sitting. An active shape model was used to characterize shape in terms of independent modes of variation. Two modes were identified that described the total (mode 1) and distribution (mode 2) of the curvature. The spinal shape was found to be intercorrelated between the three postures for both modes, suggesting that the lumbar spine has an element of shape that is partially maintained despite postural alterations. Mode 1 values indicated that the spine was straightest when standing and curviest when sitting. Mode 2 values indicated that the distribution in the curvature was most even when sitting and least even when lying supine. Systematic differences in the behaviour of the spine, when changing posture, were found that suggest that the shape of the spine may affect its biomechanics.

New prognostic factors for adjacent-segment degeneration after one-stage 360° fixation for spondylolytic spondylolisthesis: special reference to the usefulness of pelvic incidence angle

Object.

The purpose of this study was to evaluate the correlation between adjacent-segment degeneration (ASD) and pelvic parameters in the patients with spondylolytic spondylolisthesis. Sagittal balance is the most important risk and prognostic factor in the development of ASD. The pelvic incidence angle (PIA) is an important anatomical parameter in determining the sagittal curvature of the spine and in the individual variability of the sacral slope and the lordotic curve. Thus, the authors evaluated the relationship between the pelvic parameters and the ASD.

Methods.

Among 132 patients with spondylolytic spondylolisthesis who underwent surgery at their institution, the authors selected patients in whom a one-stage, single-level, 360° fixation procedure was performed for Grade I spondylolisthesis and who underwent follow-up for more than 1 year. Parameters in 34 patients satisfied these conditions. Of the 34 patients, seven had ASD (Group 1) and 27 patients did not have ASD (Group 2). The investigators measured degree of spondylolisthesis, lordotic angle, sacral slope angle (SSA), pelvic tilt angle (PTA), PIA, and additional parameters pre-and postoperatively. The radiographic data were reviewed retrospectively.

Results.

The population consisted of nine men and 25 women whose mean age was 48.9 ± 9 years (± standard deviation) (range 28–65 years). Seven patients developed ASD after undergoing fusion. Of all the parameters, pre-and postoperative degree of spondylolisthesis, segmental lordosis, lordotic angle, SSA, preoperative PTA, and pre-operative PIA did not differ significantly between the two groups; only postoperative PTA and PIA were significantly different.

Conclusions.

The development of ASD is closely related to postoperative PIA and PTA, not preoperative PIA and PTA. The measurement of postoperative PIA can be used as a new indirect method to predict the ASD.

Orientation of the human sacrum: Anthropological perspectives and methodological approaches

Discovering the nature of sacral orientation is of considerable anthropological importance. Therefore, this study aims at presenting a new anthropologically based definition for sacral anatomical orientation (SAO) angle, establishing standards of SAO for human population; examining the relationship between pelvic incidence (PI) and SAO; and associating SAO with demographic parameters. The study population consisted of 424 adult and 14 sub-adult (13-18 years, for SAO only) pelvises. Sacral orientation was measured using two different definitions: a) SAO is the angle created between the intersection of a line running parallel to the superior surface of the sacrum and a line running between the anterior superior iliac spine (ASIS) and the anterior-superior edge of the symphysis pubis; b) PI is the angle created between the perpendicular to the sacral plate at its midpoint and the line connecting this point to the middle of the axis of the acetabulum. SAO was measured using a specially designed mechanical measurement tool and a 3D digitizer. PI was measured via the 3D digitizer. The methods developed by us for measuring SAO and PI in skeletal material are valid and reliable. SAO and PI measures were highly correlated (r = -0.824, P < 0.001). The average SAO was 49.01 degrees (SD = 10.16), and the average PI 54.08 degrees (SD = 12.64). SAO was independent of ethnicity and sex, yet age dependent. This study establishes a methodology for estimating SAO and PI in skeletal material and furnishes the anthropological milieu with base line data regarding these parameters. Future studies in human evolution can greatly benefit from this study.