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

Automated spinopelvic measurements on radiographs with artificial intelligence: a multi-reader study

PURPOSE

To develop an artificial intelligence (AI) algorithm for automated measurements of spinopelvic parameters on lateral radiographs and compare its performance to multiple experienced radiologists and surgeons.

METHODS

On lateral full-spine radiographs of 295 consecutive patients, a two-staged region-based convolutional neural network (R-CNN) was trained to detect anatomical landmarks and calculate thoracic kyphosis (TK), lumbar lordosis (LL), sacral slope (SS), and sagittal vertical axis (SVA). Performance was evaluated on 65 radiographs not used for training, which were measured independently by 6 readers (3 radiologists, 3 surgeons), and the median per measurement was set as the reference standard. Intraclass correlation coefficient (ICC), mean absolute error (MAE), and standard deviation (SD) were used for statistical analysis; while, ANOVA was used to search for significant differences between the AI and human readers.

RESULTS

Automatic measurements (AI) showed excellent correlation with the reference standard, with all ICCs within the range of the readers (TK: 0.92 [AI] vs. 0.85-0.96 [readers]; LL: 0.95 vs. 0.87-0.98; SS: 0.93 vs. 0.89-0.98; SVA: 1.00 vs. 0.99-1.00; all p < 0.001). Analysis of the MAE (± SD) revealed comparable results to the six readers (TK: 3.71° (± 4.24) [AI] v.s 1.86-5.88° (± 3.48-6.17) [readers]; LL: 4.53° ± 4.68 vs. 2.21-5.34° (± 2.60-7.38); SS: 4.56° (± 6.10) vs. 2.20-4.76° (± 3.15-7.37); SVA: 2.44 mm (± 3.93) vs. 1.22-2.79 mm (± 2.42-7.11)); while, ANOVA confirmed no significant difference between the errors of the AI and any human reader (all p > 0.05). Human reading time was on average 139 s per case (range: 86-231 s).

CONCLUSION

Our AI algorithm provides spinopelvic measurements accurate within the variability of experienced readers, but with the potential to save time and increase reproducibility.

Sacrum1-pubic angle: a novel and alternative morphologic radiological parameter for assessing spinopelvic sagittal alignment in human adults

OBJECTIVE

Spinopelvic sagittal balance ensures efficient posture and minimizes energy expenditure by aligning the spine, pelvis, and lower extremities. Deviations can cause clinical issues like back pain and functional limitations. Key radiographic parameters, including pelvic tilt (PT), pelvic incidence (PI), sacral slope (SS), and lumbar lordosis (LL), are essential for evaluating spinal pathologies and planning surgeries. Accurate PI measurement is challenging in certain conditions, necessitating alternative parameters. This study aimed to introduce a new, easily measurable parameter and examine its reliability and correlation with established sagittal parameters.

METHODS

This study analyzed 107 asymptomatic adult volunteers (57 males and 50 females), with an average age of 36.75 years. Whole-spine radiographs in the standing position were taken using EOS technology. The established spinopelvic sagittal parameters and a novel parameter, sacrum1-pubic angle (S1PA), were measured. The correlation coefficient of each parameter, the regression equation of PI using S1PA, and the regression equation of PTα using PTβ were obtained. The intraclass correlation coefficients (ICCs) was calculated to evaluate the measurement reliability.

RESULTS

Morphologic (S1PA, PI) and positional parameters (PTα, PTβ, PTγ, SS, LL) showed no significant gender differences (p > 0.05). S1PA had strong correlations with PI (r = -0.883, p < 0.001) and other parameters. PTα demonstrated a strong correlation with PTβ (r = -0.929, p < 0.001). PI could be predicted according to the regression equation: PI = 71.672 - 4.537 × S1PA (R² = 0.779, p < 0.001). The PTα could be predicted using the following equation: PTα = 67.245 - 0.865 × PTβ (R² = 0.864, p < 0.001). Reliability analysis showed high intra- and inter-rater agreement in all the spinopelvic parameters.

CONCLUSION

The S1PA is a dependable parameter for evaluating the morphology and orientation of the pelvis. PI could be precisely predicted using the S1PA. These insights are valuable for clinicians, enhancing their ability to assess spinopelvic sagittal alignment accurately.

Automated measurement of pelvic parameters using convolutional neural network in complex spinal deformities: overcoming challenges in coronal deformity cases

BACKGROUND CONTEXT

Accurate and consistent measurement of sagittal alignment is challenging, particularly in patients with severe coronal deformities, including degenerative lumbar scoliosis (DLS).

PURPOSE

This study aimed to develop and validate an artificial intelligence (AI)-based system for automating the measurement of key sagittal parameters, including lumbar lordosis, pelvic incidence, pelvic tilt, and sacral slope, with a focus on its applicability across a wide range of deformities, including severe coronal deformities, such as DLS.

DESIGN

Retrospective observational study.

PATIENT SAMPLE

A total of 1,011 standing lumbar lateral radiographs, including DLS.

OUTCOME MEASURE

Interclass and intraclass correlation coefficients (CC), and Bland-Altman plots.

METHODS

The model utilizes a deep-learning framework, incorporating a U-Net for segmentation and a Keypoint Region-based Convolutional Neural Network for keypoint detection. The ground truth masks were annotated by an experienced orthopedic specialist. The performance of the model was evaluated against ground truth measurements and assessments from two expert raters using interclass and intraclass CC, and Bland-Altman plots.

RESULTS

In the test set of 113 patients, 39 (34.5%) had DLS, with a mean Cobb's angle of 14.8°±4.4°. The AI model achieved an intraclass CC of 1.00 across all parameters, indicating perfect consistency. Interclass CCs comparing the AI model to ground truth ranged from 0.96 to 0.99, outperforming experienced orthopedic surgeons. Bland-Altman analysis revealed no significant systemic bias, with most differences falling within clinically acceptable ranges. A 5-fold cross-validation further demonstrated robust performance, with interclass CCs ranging from 0.96 to 0.99 across diverse subsets.

CONCLUSION

This AI-based system offers a reliable and efficient automated measurement of sagittal parameters in spinal deformities, including severe coronal deformities. The superior performance of the model compared with that of expert raters highlights its potential for clinical applications.

Impact of Flatback Deformity and Stiff Spinopelvic Mobility on 3-Dimensional Pelvic and Hip Kinematics After Total Hip Arthroplasty

Background

Spinopelvic abnormalities have been reported to be a risk factor for dislocation after total hip arthroplasty (THA). This study aimed to compare the kinematics of the pelvis and hip joints in patients with and without spinopelvic abnormalities after THA and to elucidate dynamic forward-leaning movement during chair-rising, which are not detectable through static radiographs.

Methods

This case series included 108 hips that underwent dynamic anteroposterior radiographic imaging of the sit-to-stand motion after THA. The average age at surgery was 68 ± 10 years, with 95 hips (88%) in women (average body mass index, 23.5 ± 3.2 kg/m2). Kinematic analysis was performed to measure the anterior pelvic plane angle (APPa) and hip flexion/extension angles from seated to standing positions using model-image registration techniques. Pelvic incidence (PI) and lumbar lordosis (LL) were measured to calculate PI-LL.

Results

Flatback deformity was present in 45 hips (42%) and stiff spinopelvic mobility (SPM) in 35 hips (32%), with both deformities present in 21 hips (19%). The pelvis was consistently significantly posteriorly tilted in the flatback deformity group throughout the movement compared with the normal group, with the greatest difference observed in the standing position. The hip flexion angles in the flatback deformity group showed significant extension in the standing position (7° greater than that in the normal group). For stiff SPM, a significant posterior tilt in the standing position was observed. Accordingly, the range between the maximum hip flexion and extension was 13° greater. There was no significant difference between the maximal flexion and extension centers.

Conclusions

Patients with flatback deformities consistently exhibited posterior APPa, especially when standing. In stiff SPM, a large range of hip flexion and extension while chair-rising increased the risk of impingement, indicating the necessity for a wider range of motion without changing the target orientation. These findings highlight the importance of considering spinopelvic alignment when planning cup positioning in THA to minimize the risk of dislocation.

Level of Evidence

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

Paraspinal muscle fibre structural and contractile characteristics demonstrate distinct irregularities in patients with spinal degeneration and deformity

BACKGROUND

Paraspinal and spinopelvic muscular dysfunction are hypothesized to be a causative factor for spinal degeneration and deformity; however, our fundamental understanding of paraspinal muscle (dys)function remains limited.

METHODS

Twelve surgical patients with spinal degeneration were recruited and categorized into group DEG (four patients) with no sagittal imbalance and no usage of compensatory mechanisms; group DEG-COMP (four patients) with no sagittal imbalance through use of compensatory mechanisms; and group DEG-COMP-UNBAL (four patients) with sagittal imbalance despite use of compensatory mechanisms. From each patient, four biopsies were collected from right and left multifidus (MULT) and longissimus (LONG) for single fibre contractile and structural measurements.

RESULTS

Eight of 48 (17%) biopsies did not exhibit any contractile properties. Specific force was not different between groups for the MULT (p = 0.47) but was greater in group DEG compared to group DEG-COMP-UNBAL for the LONG (p = 0.02). Force sarcomere-length properties were unusually variable both within and amongst patients in all groups. Thin filament (actin) lengths were in general shorter and more variable than published norms for human muscle.

CONCLUSION

This study is the first to show a heightened intrinsic contractile muscle disorder (i.e. impaired specific force generation) in patients with spinal degeneration who are sagittally imbalanced (compared to patients without deformity). Additionally, there are clear indications that patients with spinal degeneration (all groups) have intrinsic force sarcomere-length properties that are dysregulated. This provides important insight into the pathophysiology of muscle weakness in this patient group.

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.

Landet: an efficient physics-informed deep learning approach for automatic detection of anatomical landmarks and measurement of spinopelvic alignment

PURPOSE

An efficient physics-informed deep learning approach for extracting spinopelvic measures from X-ray images is introduced and its performance is evaluated against manual annotations.

METHODS

Two datasets, comprising a total of 1470 images, were collected to evaluate the model's performance. We propose a novel method of detecting landmarks as objects, incorporating their relationships as constraints (LanDet). Using this approach, we trained our deep learning model to extract five spine and pelvis measures: Sacrum Slope (SS), Pelvic Tilt (PT), Pelvic Incidence (PI), Lumbar Lordosis (LL), and Sagittal Vertical Axis (SVA). The results were compared to manually labelled test dataset (GT) as well as measures annotated separately by three surgeons.

RESULTS

The LanDet model was evaluated on the two datasets separately and on an extended dataset combining both. The final accuracy for each measure is reported in terms of Mean Absolute Error (MAE), Standard Deviation (SD), and R Pearson correlation coefficient as follows: [ S S ∘ : 3.7 ( 2.7 ) , R = 0.89 ] ,[ P T ∘ : 1.3 ( 1.1 ) , R = 0.98 ] , [ P I ∘ : 4.2 ( 3.1 ) , R = 0.93 ] , [ L L ∘ : 5.1 ( 6.4 ) , R = 0.83 ] , [ S V A ( m m ) : 2.1 ( 1.9 ) , R = 0.96 ] . To assess model reliability and compare it against surgeons, the intraclass correlation coefficient (ICC) metric is used. The model demonstrated better consistency with surgeons with all values over 0.88 compared to what was previously reported in the literature.

CONCLUSION

The LanDet model exhibits competitive performance compared to existing literature. The effectiveness of the physics-informed constraint method, utilized in our landmark detection as object algorithm, is highlighted. Furthermore, we addressed the limitations of heatmap-based methods for anatomical landmark detection and tackled issues related to mis-identifying of similar or adjacent landmarks instead of intended landmark using this novel approach.

Reliability of semi-automated spinal measurement software

PURPOSE

In the treatment of patients with adult spinal deformity, analysis of spinopelvic balance is essential in clinical assessment and surgical planning. There is currently no gold standard for measurement, whether done by hand or with digital software. New semi-automated software exists that purports to increase efficiency, but its reliability is unknown in the literature.

METHODS

Full spine X-rays were retrospectively reviewed from 25 adult patients seen between 2014 and 2017. Patients were included if they had > 5 cm of sagittal imbalance and radiographs of sufficient quality to perform balance measurements, without prior surgical spinal fusion and/or instrumentation. Spinopelvic parameters were measured in two radiographic programs: one with basic, non-spine-specific measurement tools (eUnity, Client Outlook, Waterloo, Canada); and a second with spine-specific semi-automated measurement tools (Sectra, Sectra AB, Linköping, Sweden). Balance parameters included SVA, PI, PT, and LL. Data were compared by examining inter-rater and inter-program reliability using interclass correlation coefficient (ICC).

RESULTS

The subjects' mean age was 67.9 ± 13.8 years old, and 32% were male. The inter-program reliability was strong, with ICC values greater than 0.91 for each parameter. Similarly, there was strong inter-observer reliability with ICC values greater than 0.88. These results persisted on delayed repeat measurement (p < 0.001 for all measurements).

CONCLUSION

There is excellent inter-observer and inter-program reliability between the basic PACS and semi-automated programs. These data demonstrate that the purported efficiency of semi-automated measurement programs does not come at the cost of measurement reliability.

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.

Does Individualization of Cup Position Affect Prosthetic or Bone Impingement Following THA?

INTRODUCTION

Spinopelvic (SP) mobility patterns during postural changes affect three-dimensional acetabular component position, the incidence of prosthetic impingement, and total hip arthroplasty (THA) instability. Surgeons have commonly placed the acetabular component in a similar "safe zone" for most patients. Our purpose was to determine the incidence of bone and prosthetic impingement with various cup orientations and determine if a preoperative SP analysis with individualized cup orientation lessens impingement.

METHODS

A preoperative SP evaluation of 78 THA subjects was performed. Data was analyzed using a software program to determine the prevalence of prosthetic and bone impingement with a patient individualized cup orientation versus six commonly selected cup orientations. Impingement was correlated with known SP risk factors for dislocation.

RESULTS

Prosthetic impingement was least with the individualized choice of cup position (9%) vs. preselected cup positions (18 to 61%). The presence of bone impingement (33%) was similar in all groups and not affected by cup position. Factors associated with impingement in flexion were age, lumbar flexion, pelvic tilt (stand to flexed seated), and functional femoral stem anteversion. Risk factors in extension included standing pelvic tilt, standing SP tilt, lumbar flexion, pelvic rotation (supine to stand and stand to flexed seated), and functional femoral stem anteversion.

CONCLUSION

Prosthetic impingement is reduced with individualized cup positioning based on SP mobility patterns. Bone impingement occurred in one-third of patients and is a noteworthy consideration in preoperative THA planning. Known SP risk factors for THA instability correlated with the It dependspresence of prosthetic impingement in both flexion and extension.

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.

Reliability of the pelvis and femur anatomical landmarks and geometry with the EOS system before and after total hip arthroplasty

Bi-plane X-ray provides 3D measurements of the lower limb based on the identification of anatomical landmarks in sagittal and frontal X-rays. In clinical practice, such measurements involve multiple operators and sessions. This study aimed at evaluating the reliability of anatomical landmarks identification and geometric parameters of the pelvis and femur measured with bi-plane X-rays before and after total hip arthroplasty (THA). Twenty-eight patients undergoing primary THA were selected retrospectively. Two operators performed three reconstructions for each patient before and after THA. Intraclass correlation (ICC) and smallest detectable change (SDC) were computed for intra-operator, inter-operator, and test-retest conditions. Most anatomical landmark positions had good to excellent SDC (< 5 mm) apart from the centre of the sacral slope, greater trochanter, and anterior superior iliac spines (up to 7.1, 16.9, and 21.5 mm respectively). Geometric parameters had moderate to excellent SDC, apart from femoral and stem torsion, pelvic incidence, and APP inclination with poor SDC (9-12°). The sagittal view had significantly higher measurement errors than the frontal view. Test-retest and inter-operator conditions had no significant differences suggesting a low influence of patient posture. Osteoarthritis and the presence of implants did not seem to influence reliability and measurement error. This study could be used as a reference when assessing lower limb structure with bi-plane X-rays.

Pelvic incidence measurement with supine magnetic resonance imaging: A validity and reliability study

OBJECTIVE

Classically, pelvic incidence (PI) and other spinopelvic sagittal parameters are measured using plain x-ray obtained with the patient standing. However, it is difficult to obtain a perfect mid-sagittal appearance of the sacral endplate and superimposition of both femoral heads from a plain x-ray. Overlapping of the iliac wings also could obscure the appearance of the sacral endplate. Recent studies showed that MRI was more reliable than x-ray for evaluating some spinal sagittal parameters. To our knowledge, measurements of spinopelvic sagittal parameters using supine MRI have not been reported previously. We assessed the validity and reliability of measurements of spinopelvic sagittal parameters from standing lateral x-rays and supine magnetic resonance imaging (MRI).

METHODS

We recruited 26 asymptomatic volunteers for this study. Standing lateral lumbosacral radiographs, including femoral heads and spinopelvic MRI images with coronal images of the femoral heads were performed. The anatomic reference point required to measure PI was found on coronal MRI images and transferred to the midline sagittal MRI using the bladder wall as a second reference point. PI, sacral slope (SS), and pelvic tilt (PT) were measured on x-ray and MRI images. Validity and reliability of results also were tested.

RESULTS

Of 14 males and 12 females (average age, 31.30), PI was obtained from x-ray and MRI in 52. ± 6.89 and 51.42 ± 6.43, respectively. From standing x-ray to supine MRI, PT decreased by 3.16°, while SS increased 2.5°. A paired t-test showed a significant difference between PT values from x-ray and MRI. The correlation was highest between the x-ray and MRI measurements of PI, PT, and SS, respectively. Intraobserver and interobserver reliabilities were between 0.88 and 0.96 on x-ray and MRI. All reliabilities were excellent, although MRI values were higher.

CONCLUSION

MRI was more reliable in the measurement of spinopelvic parameters than classic standing x-ray examination. Higher reliability and being radiation-free could make MRI a good alternative to standing x-ray.

Pelvic incidence significance relative to spinopelvic risk factors for total hip arthroplasty instability

AIMS

Pelvic incidence (PI) is a position-independent spinopelvic parameter traditionally used by spinal surgeons to determine spinal alignment. Its relevance to the arthroplasty surgeon in assessing patient risk for total hip arthroplasty (THA) instability preoperatively is unclear. This study was undertaken to investigate the significance of PI relative to other spinopelvic parameter risk factors for instability to help guide its clinical application.

METHODS

Retrospective analysis was performed of a multicentre THA database of 9,414 patients with preoperative imaging (dynamic spinopelvic radiographs and pelvic CT scans). Several spinopelvic parameter measurements were made by engineers using advanced software including sacral slope (SS), standing anterior pelvic plane tilt (APPT), spinopelvic tilt (SPT), lumbar lordosis (LL), and PI. Lumbar flexion (LF) was determined by change in LL between standing and flexed-seated lateral radiographs. Abnormal pelvic mobility was defined as ∆SPT ≥ 20° between standing and flexed-forward positions. Sagittal spinal deformity (SSD) was defined as PI-LL mismatch > 10°.

RESULTS

PI showed a positive correlation with parameters of SS, SPT, and LL (r-value range 0.468 to 0.661). Patients with a higher PI value showed higher degrees of standing LL, likely as a compensatory measure to maintain sagittal spine balance. There was a positive correlation between LL and LF such that patients with less standing LL had decreased LF (r = 0.49). Similarly, there was a positive correlation between increased SSD and decreased LF (r = 0.54). PI in isolation did not show any significant correlation with lumbar (r = 0.04) or pelvic mobility (r = 0.02). The majority of patients (range 89.4% to 94.2%) had normal lumbar and pelvic mobility regardless of the PI value.

CONCLUSION

The PI value alone is not indicative of either spinal or pelvic mobility, and thus in isolation may not be a risk factor for THA instability. Patients with SSD had higher rates of spinopelvic stiffness, which may be the mechanism by which PI relates to THA instability risk, but further clinical studies are required. Cite this article: Bone Joint J 2022;104-B(3):352-358.

Analysis of measurement changes in pelvic incidence according to pelvic rotation using a three-dimensional model

Background

Pelvic incidence (PI) is used as a key parameter in surgical correction of adult spinal deformity (ASD). However, reflecting the exact center or inclination of the three-dimensional anatomical structures on the two-dimensional (2D) sagittal radiographs is limited, resulting in measurement errors. Therefore, we evaluated whether there is a change in PI measurement according to the actual rotation of the pelvis, and conducted a study on a more accurate method for PI measurement using 2D sagittal radiographs.

Methods

From 2014 to 2015, the data of 30 patients who visited our outpatient clinic were analyzed retrospectively. CT scans including those of the lower lumbar spine, pelvis, and both femurs in the DICOM format were imported to Mimics Research 17.0 (Materialise NV, Belgium), SolidWorks (Dassault systems, France), and AutoCAD 2014 (AUTODESK, US). The changes in PI according to vertical and horizontal pelvic rotations were evaluated.

Results

The average PIs according to the horizontal pelvic rotations measured on AutoCAD with 0°, 5°, 10°, 15°, 20°, 25°, 30°, 35°, and 40° were 48.8°, 48.7°, 48.3°, 47.8°, 46.9°, 45.6°, 44.0°, 42.2°, and 39.9°, respectively. The PI with an acceptable error of 6° on radiographs was 35° in the horizontal pelvic rotation. The average PIs according to the vertical pelvic rotations measured on AutoCAD with 0°, 5°, 10°, 15°, 20°, 25°, 30°, 35°, and 40° were 48.8°, 49.0°, 49.5°, 50.2°, 51.3°, 52.7°, 54.4°, 56.6°, and 59.4°, respectively. The PI with an acceptable error of 6° on radiographs was 30° in the vertical pelvic rotation.

Conclusions

This study revealed that the PI value could differ from the actual anatomical value due to the horizontal and vertical rotation of the pelvis while acquiring the radiograph. Regarding whole-spine lateral radiographs, errors in PI measurement may occur due to pelvic rotation or nonvertical projection of X-rays. In the standing pelvic lateral radiographs, ensuring superposition of the femoral heads at the center and obtaining the straight sacral endplate by referring to CT or magnetic resonance imaging would be a more accurate measurement method to define PI.

Pelvic position, lying on a traction table, during THA by direct anterior approach. Comparison with the standing position and influence on the acetabular cup anteversion

INTRODUCTION

The placement of prostheses for a total hip arthroplasty (THA) is essential to limit complications and optimize functional results. In a recent study of more than 100 THA placed through a direct anterior approach using a traction table, we found that the mean anteversion of the cup was greater (30°) than recommended (20°). To explain this phenomenon, we considered that the anterior pelvic plane (APP), defined by the plane passing through the anterior-superior iliac spines and the pubic symphysis, which serves as a landmark for the placement and calculation of the anteversion of the cup, was not horizontal when the patient was lying on the traction table. This concept has not been evaluated so we conducted a prospective study to: 1) measure the position of the pelvis on a traction table; 2) compare to the standing position, 3) assess its impact on the anteversion of the cup.

HYPOTHESIS

The standing pelvic version is identical to the supine pelvic version on the traction table.

MATERIAL AND METHODS

A prospective 3-month monocentric study was conducted. All patients operated on for a THA by a direct anterior approach, on a traction table, were included. The position of the pelvis was assessed by measuring the tilt of the APP on lateral pelvic X-rays, while on the traction table and while standing. The impact of the position of the pelvis on the positioning of the cup, as well as the anteversion, were measured using the EOS imaging system. The anatomic anteversion of the cup was measured in relation to the APP.

RESULTS

Fifty-eight patients were included (32 women, 26 men) with an average age of 67 years. The tilt of the supine APP was 6°±8.3 [range of -10.5 to 31.0] (indicating a retroverted pelvis on the traction table). The difference between the tilt of the standing and lying APP (within 90°) was not significant (standing was on average 4.5° [range of -11.0 to 27.0] versus lying on the table, was on average 6° [range of -10.5 to 31.0] (p=0.75). A strong correlation was observed between the tilt of the supine APP and the anatomic anteversion of the cup (p<0.001). Thus, the more retroverted the pelvis was on the traction table, the lower the anatomic anteversion of the acetabular cup.

CONCLUSION

The supine pelvis on the traction table is not always horizontal and its position on the traction table is similar to its standing position, within 90 degrees. The analysis of the positioning of the preoperative pelvis appears to be essential in the planning of a THA through direct anterior approach using a traction table.

LEVEL OF EVIDENCE

IV; Prospective Cohort Study.

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.

Determining the validity and reliability of spinopelvic parameters through comparing standing whole spinal radiographs and upright computed tomography images

Background

Standing whole spinal radiographs are used to evaluate spinal alignment in adult spinal deformity (ASD), yet some studies have reported that pelvic incidence, pelvic tilt, and thoracic kyphosis (TK) intra- and inter-observer reliability is low. This study aimed to evaluate the accuracy of spinopelvic parameters through comparing standing whole spinal radiographs and upright CT images.

Methods

We enrolled 26 patients with ASD. All standing whole spinal posterior/anterior and lateral radiographs and upright whole spinal CT had been obtained in a natural standing position. Two examiners independently measured 13 radiographic parameters. Interclass correlation coefficients (ICCs) were used to analyze measurement intra- and inter-observer reliability. Paired t- and Pearson’s correlation tests were used to analyze validity of the standing whole spinal radiographs.

Results

ICCs of upright CT were excellent in both intra- and inter-observer reliability. However, intra-observer ICCs for TK2–12, TK1–5, TK2–5, and TK5–12 on standing lateral radiographs were relatively low, as were inter-observer ICCs for TK2–12, TK1–5, TK2–5, and TK5–12. Concerning TK values, the difference between the radiographs and CT in TK1–12 and TK2–12 were 4.4 ± 3.1 and 6.6 ± 4.6, respectively, and TK values from T2 showed greater measurement error (p < 0.05).

Conclusions

Upright CT showed excellent intra- and inter-observer reliability in the measurement of spinopelvic parameters. Measurement of TK with T2 on standing whole spinal radiographs resulted in a greater measurement error of up to 6.6°. Surgeons need to consider this when planning surgery and measuring postoperative TK changes in patients with ASD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04786-5.

Pelvic incidence change on the operating table

PURPOSE

While a change in the pelvic incidence (PI) after long spine fusion surgery has been reported, no studies have examined the change in the PI on the operating table. The present study examined the PI-change on the operating table and elucidated the patients' background characteristics associated with this phenomenon.

METHODS

This study included patients who underwent lumbar posterior spine surgery and had radiographs taken in a full-standing position preoperatively and a pelvic lateral radiograph in the prone position in the operative room. The patients with PI-change on the operating table (PICOT; PICOT group) and without PICOT (control group) were compared for their background characteristics and preoperative radiographic parameters.

RESULTS

There were 128 eligible patients (62 males, 66 females) with a mean age (± standard deviation) of 69.9 ± 11.7 (range: 25-93) years old. Sixteen patients (12.5%) showed a decrease in the PI > 10°, which indicated placement in the PICOT group. The preoperative lumbar lordosis (LL) and PI-LL in the PICOT group were significantly worse than those in the control group (LL: 20.8 ± 16.6 vs. 30.6 ± 16.2, p = 0.0251, PI-LL: 33.9 ± 19.0 vs. 17.3 ± 14.8, p < 0.0001). The PICOT group had a higher proportion of patients who underwent fusion surgery than the control group, but the difference was not significant (62.5% vs. 44.6%, p = 0.1799).

CONCLUSION

A decreased PI was observed in some patients who underwent lumbar posterior surgery on the operating table before surgery. Patients with a PI decrease on the operating table had a significantly worse preoperative global alignment than those without such a decrease.

LEVEL OF EVIDENCE I

Diagnostic: individual cross-sectional studies with the consistently applied reference standard and blinding.

Accuracy and Reliability of Standing Lateral Lumbar Radiographs for Measurements of Spinopelvic Parameters

STUDY DESIGN

Retrospective observational study.

OBJECTIVE

To assess the accuracy and reliability of standing lateral lumbar radiographs for measurements of spinopelvic parameters, compared with whole-spine EOS® images.

SUMMARY OF BACKGROUND DATA

Lateral lumbar radiographs are commonly used for measurements of spinopelvic parameters. However, variable magnifications by fan-beam x-ray projection at margins may cause measurement errors.

METHODS

Fifty consecutive patients with standing lateral lumbar radiographs and whole-spine EOS® images were retrospectively reviewed from March to July in 2019. Two orthopedic surgeons (observers) independently measured the spinopelvic parameters including pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), and lumbar lordosis (LL) on the computers. These spinopelvic parameters of each patient were measured twice on both lateral lumbar radiograph and EOS® image by two observers with the usage of Surgimap software. The measurement difference and agreement of each parameter value between lateral lumbar radiographs and EOS® images were analyzed by paired t test and the interclass correlation coefficient (ICC) respectively. Intra- and inter-observer's reliabilities of both imaging methods were assessed by ICC.

RESULTS

The measurement difference of each spinopelvic parameter on EOS® images and lateral lumbar radiographs was less than 1° on average. Only the measurement difference of PI value revealed statistically significant (P = 0.020) with 0.9° discrepancy (95% confidential interval: 0.2-1.6), which indicated no clinical significance. The ICC values of lateral lumbar radiographs and EOS® images were more than 0.870 (range, 0.872-0.976), thus showed good to excellent measurement agreement between both imaging methods. All the ICC values for evaluating intra- and inter-observer reliability were greater than 0.960 (range, 0.963-0.993), indicating excellent reliability for observer's measurements.

CONCLUSION

Measurements of spinopelvic parameters (PI, PT, SS, and LL) on standing lateral lumbar radiographs are accurate and reliable, which are comparable to whole-spine EOS® images.Level of Evidence: 3.

Impact of appendicular and trunk skeletal muscle mass and back extensor strength on sagittal spinal alignment in Japanese women without vertebral fracture

Objectives

Progressive and generalized loss of skeletal muscle mass (SMM) and strength are characteristics of sarcopenia. However, the impact of appendicular and trunk SMM and back extensor strength (BES) on spinal sagittal alignment remains unclear. Herein, we investigate the relationship between these factors and spinal sagittal alignment.

Methods

In total, 202 women without vertebral fractures (median age, 66.9 years; interquartile range, 61.4–71.9 years) were analyzed at an orthopedic outpatient clinic. Pelvic incidence (PI), lumbar lordosis (LL), sagittal vertical axis (SVA), and pelvic tilt (PT) were measured on whole spine radiographs. Body mass index (BMI), appendicular and trunk relative SMM index, and BES were also evaluated. These measurements were compared between spinal sagittal alignment groups using the Mann–Whitney U test. Finally, the factors contributing to abnormal alignment were analyzed using multiple logistic regression analysis.

Results

BES was significantly lower in all abnormal sagittal alignment groups, as defined by PI-LL (≥ 10°), SVA (≥4 cm), and PT (≥20°) (all P < 0.001). On multivariate analysis, BES was a contributing factor for abnormal PI-LL (P < 0.001), SVA (P = 0.001), and PT (P < 0.001). Conversely, a decrease in appendicular and trunk relative SMM index did not statistically affect abnormal spinal sagittal alignment.

Conclusions

BES was associated with changes in spinal sagittal alignment; however, SMM, which is often used for diagnosing sarcopenia, did not affect spinal sagittal alignment.

Automatic analysis of global spinal alignment from simple annotation of vertebral bodies

Purpose: Measurement of global spinal alignment (GSA) is an important aspect of diagnosis and treatment evaluation for spinal deformity but is subject to a high level of inter-reader variability. Approach: Two methods for automatic GSA measurement are proposed to mitigate such variability and reduce the burden of manual measurements. Both approaches use vertebral labels in spine computed tomography (CT) as input: the first (EndSeg) segments vertebral endplates using input labels as seed points; and the second (SpNorm) computes a two-dimensional curvilinear fit to the input labels. Studies were performed to characterize the performance of EndSeg and SpNorm in comparison to manual GSA measurement by five clinicians, including measurements of proximal thoracic kyphosis, main thoracic kyphosis, and lumbar lordosis. Results: For the automatic methods, 93.8% of endplate angle estimates were within the inter-reader 95% confidence interval ( CI 95 ). All GSA measurements for the automatic methods were within the inter-reader CI 95 , and there was no statistically significant difference between automatic and manual methods. The SpNorm method appears particularly robust as it operates without segmentation. Conclusions: Such methods could improve the reproducibility and reliability of GSA measurements and are potentially suitable to applications in large datasets-e.g., for outcome assessment in surgical data science.

Effects of Sagittal Spinal Alignment on Postural Pelvic Mobility in Total Hip Arthroplasty Candidates

BACKGROUND

Recent research has demonstrated that patients with reduced pelvic mobility from standing to sitting have higher rates of dislocation after total hip arthroplasty (THA). This study evaluates the effect of sagittal spinal deformity, defined by pelvic incidence-lumbar lordosis mismatch (PI-LL), on postural changes in pelvic tilt (PT).

METHODS

A multicenter database of 1100 preoperative THA patients was queried. Anterior-pelvic-plane tilt (APPt), spinopelvic tilt (SPT), and LL were measured from radiographs of patients in supine, standing, flexed-seated, and stepping-up postures; PI was measured from computed tomography. Patients were separated into 3 groups based on PI-LL (<-10°, -10° to 10°, >10°) and propensity-score matched by PI. Lumbar flatback-deformity was defined as PI-LL > 10°, hyperlordosis: PI-LL < -10°. SPT/APPt, including changes between each posture were compared across PI-LL groups using analysis of variance, with post-hoc Tukey tests. Pearson correlations were reported when testing associations between SPT/APPt change and PI-LL.

RESULTS

After propensity-score matching, 288 patients were analyzed (mean 65 y; 49% F). SPT and APPt change differed across all PI-LL categories from standing to seated, supine, and stepping-up with less SPT/APPt recruitment among hyperlordotic vs flatback patients (all P < .001). Greater PI-LL correlated with greater SPT recruitment from standing to seated (R = 0.294), supine (R = 0.292), and stepping-up (R = 0.207) (all P < .001). Smaller LL changes from standing to seated were associated with greater SPT recruitment (R = 0.372, P < .001).

CONCLUSIONS

Postural changes in SPT/APPt are associated with spinopelvic measures in THA candidates. Hyperlordotic patients tend to utilize their spines more compared with flatback patients who were more likely to recruit PT. Increased focus on patients with lumbar flatback and hyperlordosis may help in reducing prosthetic dislocation prevalence following THA.

Pelvic incidence measurement using a computed tomography data-based three-dimensional pelvic model

Objectives

To introduce a new method of pelvic incidence (PI) measurement based on three-dimensional (3D) pelvic models reconstructed from CT images and to report the normal distribution of PI in normal pelvic anatomy.

Methods

CT images of 320 subjects with normal pelvic anatomy who visited the Radiology Department between 2006 and 2017 were retrospectively selected and saved in Digital Imaging and Communications in Medicine (DICOM) format. A computerized method was employed to determine the bony landmarks required for the measurement of PI. To quantify the method’s accuracy and reliability, the intraclass correlation coefficient (ICC) was calculated. A subgroup of 30 DICOM files was randomly selected to perform a validation study. Three independent testers performed all procedures. All measurements were performed twice independently by the three testers on all 10 subjects with an interval of 2 weeks. Independent samples t tests were used to identify statistically significant differences in the PI value between sexes. Pearson correlation coefficient was employed to determine the relationship between PI and age.

Results

PI measurement using the new method resulted in an excellent intraobserver reliability (0.9612, range 0.8917–0.9893; p < 0.001) and interobserver reliability (0.9867, range 0.9611–0.9964; p < 0.001). PI was significantly different between sexes, with larger PI in women (p = 0.019). PI was significantly larger in the 40–80-year age group (45.94 ± 9.08°) than the < 40-year age group (43.50 ± 7.39°). We did not find any linear correlation between PI and age in the male (r = 0.140, p = 0.105) or female subgroup (r = 0.119, p = 0.107). A weak correlation between PI and age overall was observed (r = 0.142, p = 0.011).

Conclusion

Accurate PI measurement could be achieved by a CT data-based 3D pelvic model.

Intra- and Interrater Reliability of Sagittal Spinopelvic Parameters on Full-Spine Radiographs in Adults With Symptomatic Spinal Disorders

Background/Aims

To evaluate the intra- and interrater reliability (I-IR) of sagittal spinopelvic parameters from digital full-spine plain radiographs with basic software tools in an unselected adult population with degenerative spinal complaints who were evaluated for surgery.

Methods

Forty-nine adult full-spine digital radiographs were measured twice by 3 independent observers, including an experienced spine surgeon, an experienced radiologist, and a resident orthopedic surgeon. Clinical picture archiving and communication system workstations and software tools were used and landmarks were set manually. The I-IR of the sagittal vertical axis (SVA), pelvic tilt (PT), pelvic incidence (PI), sacral slope (SS), and thoracic kyphosis in T4–T12 (TK) were assessed.

Results

The intrarater intraclass correlation coefficient (ICC) scores varied from 0.82 to 0.99. The interrater ICC scores ranged from 0.78 to 0.99. The intrarater standard error of measurement (SEM) values for SS, PT, PI, and TK varied from 0.8° to 5.0°, and the interrater SEM values ranged from 2.5° to 6.2°, depending on the parameter and the reading round. The I-IR SEM values for SVA varied from 2.2 to 5.7 mm and from 4.6 to 5.0 mm, respectively. Kappa values were >0.88 for all readers. The intrarater variability was the smallest for the most experienced rater.

Conclusion

The I-IR of measuring sagittal spinopelvic parameters on digital full-spine images with basic software tools was high. Parameters consisting of several anatomic landmarks were more liable to error. Rater experience had a positive influence on reliability and repeatability. Reader experience should be assessed before accepting measurements for surgical planning and the interpretation of surgical correction during postoperative follow-up.

Combination of whole-spine lateral radiograph and lateral scanogram in the assessment of global sagittal balance

BACKGROUND CONTEXT

Global balance of human standing is analyzed as the geometric sum of the individual alignments extending from the spinal column to the pelvis, and to the lower limbs. The innovative EOS system has opened new perspectives for the global analysis of whole-body alignment, but its use is very limited because of its high cost. An alternative may be to combine the whole-spine lateral radiograph and the lateral scanogram in the global sagittal analysis of whole-body alignment.

PURPOSE

We examined to determine the validity and reliability of a lateral scanogram in the measurement of sacropelvic parameters.

STUDY DESIGN/SETTING

A retrospective radiological study was carried out.

PATIENT SAMPLE

We randomly selected 100 sets of digital radiographs, both whole-spine radiographs and lower-limb scanograms, from our database.

OUTCOME MEASURES

Sacropelvic parameters, including pelvic incidence, sacral slope, and pelvic tilt, were measured on both whole-spine radiographs and lower-limb scanograms by three independent examiners on three separate occasions.

METHODS

Agreement regarding the measurements on both image types was calculated to assess the validity of the lateral scanogram for use in whole-body alignment determinations. Intraobserver and interobserver reliabilities among the types of measurements were calculated.

RESULTS

The sacropelvic area on the lateral scanogram was not visible in 19 patients (19%). In the remaining 81 patients, the sacropelvic parameters on the lateral scanogram were similar to those on the whole-spine lateral radiograph (Pearson correlation coefficient, 0.764-0.805). Intraobserver and interobserver reproducibilities for both modalities were good to excellent (intraclass correlation coefficient, 0.657-0.984).

CONCLUSIONS

Sacropelvic parameter measurements on lateral scanogram were reliable and were similar to those measured on whole-spine lateral radiograph. Thus, global alignment can be evaluated using the lateral scanogram in combination with the whole-spine lateral radiograph.

Osteotomies in ankylosing spondylitis: where, how many, and how much?

INTRODUCTION

This article presents the current concepts of correction of spinal deformity in ankylosing spondylitis (AS) patients. Untreated AS can be a debilitating disease. In a few patients, disease progression results in severe spinal deformity affecting not only the thoracolumbar, but also the cervical spine. Surgery for correction in AS patients has a long history. With the advent of modern instrumentation, standardization of surgical and anesthesiologic techniques, surgical safety and corrective results could be improved and experiences from lumbar osteotomies could be transferred to the cervical spine.

METHODS

This article presents the current concepts of correction of spinal deformity in AS patients. In particular, questions regarding the localization and number of osteotomies, the optimal surgical target angle as well as planning and prediction of postoperative alignment are discussed.

RESULTS

Insight into recent technical developments, current challenges with correction and geometric analysis of center of rotation (COR) in cervical 3-column osteotomies (3CO) will be presented.

CONCLUSION

The article should encourage readers to improve surgical correction efficacy and provide a better understanding of correction geometry in 3CO for thoracolumbar and cervical spinal deformities.

Influence of patient rotational malpositioning on pelvic parameters assessed on lateral radiographs

AIM

To estimate the effect of patients' axial rotation (AR) during pelvic radiograph acquisition, on the reliability and validity of sagittal pelvic parameters.

MATERIALS AND METHODS

Lateral digitally reconstructed radiographs (LDRRs) were obtained from the pelvic computed tomography (CT) scans of eight children and nine adults. Then, the AR of the pelvis was simulated and the corresponding LDRRs were reconstructed at 5°, 10°, 15°, and 20° of the AR. Pelvic parameters were measured digitally on each radiograph. Intra- and interobserver variability were evaluated at each AR position (three operators repeated the measurements three times each). The bias on each clinical parameter, in each AR position, was calculated relatively to the 0° position.

RESULTS

Interobserver variability increased similarly in children and adults with AR. It reached 4.4° for pelvic incidence and 4.7° for the sacral slope at 20° of AR. Biases on radiological parameters increased with AR and exceeded the acceptable threshold of errors when AR reached 10°. A linear regression was established (R²=0.834, p<0.0001) in order to estimate the AR of a patient on a lateral pelvic radiograph based on the measurement of the bifemoral distance normalized to the sagittal pelvic thickness.

CONCLUSIONS

AR of patients during radiograph acquisition can be estimated in clinical practice, which would allow physicians to discard any radiographs where the calculated AR exceeded 10°.

Measurement of Spinopelvic Parameters on Standing Lateral Lumbar Radiographs: Validity and Reliability

STUDY DESIGN

This was a radiographic validity and reliability study.

OBJECTIVE

We assessed the validity and reliability of measurements made on standing lateral lumbar radiographs, compared with lateral whole-spine radiographs, for evaluating spinopelvic parameters and lumbar lordosis (LL).

SUMMARY OF BACKGROUND DATA

A lateral whole-spine radiograph is the gold standard image for measurement of spinopelvic parameters. However, little evidence is available on the reliability of measurements made on such radiograph. A standing lateral lumbar radiograph is routinely obtained from patients with back pain and/or a disability. This image can include upper end plate of L1 vertebra, sacral dome and both femoral heads. Thus, this radiograph can be used for evaluation of spinopelvic parameters.

MATERIALS AND METHODS

We randomly selected 50 sets of digital radiographs (standing lateral lumbar and lateral whole-spine radiographs) from our database. Three experienced spinal surgeons independently measured LL, pelvic incidence, pelvic tilt, and sacral slope on all images. A paired t test and Pearson correlation was used to analyze the validity of the lateral lumbar radiograph. Interobserver and intraobserver reliabilities were assessed by intraclass correlation coefficient.

RESULTS

Thee spinopelvic parameters and LL measured on lateral lumbar radiographs were similar to those measured on lateral whole-spine radiographs (All P-values >0.05, Pearson correlation coefficients, 0.807-0.969). The intraobserver and interobserver reproducibilities of both measurement types were good-to-excellent.

CONCLUSIONS

Spinopelvic parameters and LL values measured on lateral lumbar radiographs were reproducibly similar to those measured on lateral whole-spine radiographs. Use of a standing lateral lumbar radiograph is reasonable when spinopelvic parameters and LL are to be measured.

Analysis of spinal alignment and pelvic parameters on upright radiographs: implications for acetabular development

The purpose of this study was to correlate measures of sagittal spinopelvic alignment [lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT) and pelvic incidence (PI)] and measures of acetabular coverage [lateral center edge angle (LCEA) and Tonnis angle] in asymptomatic adolescents on standing biplanar radiographs. We hypothesized that subjects with increased pelvic incidence and LL would have increased anterior PT and increased measures of acetabular coverage. Upright anteroposterior and lateral spinopelvic radiographs were obtained using EOS imaging technique. LCEA and Tonnis angle were calculated on the anteroposterior images and the lateral images were analyzed for LL, PI, PT and SS. LL was found to have a strong correlation with SS (r_s = 0.786, P  <  0.001), moderate correlation with PI (r_s  =  0.529, P  <  0.001), and a poor inverse correlation with PT (r_s  = −0.167, P  =  0.018). However, LCEA was not found to be significantly correlated with PT (r_s  =  0.084, P  =  0.238) and Tonnis angle was not found to be correlated with any of the sagittal spinopelvic measures. Healthy, asymptomatic adolescents with increased pelvic incidence and lumbar lordosis did not have increased anterior PT or increased measures of acetabular coverage. The correlations identified in previous cadaveric studies or clinical studies evaluating changes between supine and standing radiographs are not supported in this healthy adolescent population. Our findings may suggest that an individual’s acetabulum develops as a dynamic adaptation to one's particular sagittal spinopelvic alignment to optimize femoral head coverage. Level III. Diagnostic – Investigating a diagnostic test.