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.

CORRELATION OF SPINOPELVIC PARAMETERS WITH DISABILITY STATUS IN PATIENTS WITH DEGENERATIVE LUMBAR DISEASES.

Lumbar degenerative disease usually manifests in spine clinics. This study examines the spino-pelvic characteristics of lumbar degenerative disease patients as well as the clinical ramifications in the Indian population which help in early identification of sagittal spine anomalies. Purpose - to study the spinopelvic parameters and correlate them with disability status in patients with degenerative lumbar diseases. This cross-sectional observational study focused on patients aged 40 to 60, diagnosed with degenerative lumbar spine diseases, seen at the Orthopedics Outpatient Department. Thorough history, clinical examination, and disability assessment were conducted using the modified Oswestery Disability Questionnaire (ODI). Radiological evaluation included measuring spinopelvic parameters-Pelvic Incidence (PI), Pelvic Tilt (PT), Sacral Slope (SS), and Lumbar Lordosis (LL)-correlated with disability. Disability status was determined through the Oswestry Low Back Pain Disability (ODI) Questionnaire. Among the study population, the difference in mean of Pelvic Tilt, Sacral slope, Lumbar lordosis, Pelvic incidence across disability status was not statistically significant. BMI and sacral slope showed positive correlation to sacral slope and negative correlation to Pelvic Tilt, Lumbar Lordosis, ODI. This study concluded there was no association between spinopelvic characteristics and level of disability in degenerative lumbar disease. Early detection of spinopelvic changes can aid in early intervention, slow down disease progression, and lessen impairment brought on by degenerative disc diseases.

Assessment of fetal radiation exposure in pregnant women undergoing computed tomography and rotational angiography examinations for pelvic trauma.

This study aimed to assess fetal radiation exposure in pregnant women undergoing computed tomography (CT) and rotational angiography (RA) examinations for the diagnosis of pelvic trauma. In addition, this study aimed to compare the dose distributions between the two examinations. Surface and average fetal doses were estimated during CT and RA examinations using a pregnant phantom model and real-time dosemeters. The pregnant model phantom was constructed using an anthropomorphic phantom, and a custom-made abdominal phantom was used to simulate pregnancy. The total average fetal dose received by pregnant women from both CT scans (plain, arterial and equilibrium phases) and a single RA examination was ~60 mGy. Because unnecessary repetition of radiographic examinations, such as CT or conventional 2D angiography can increase the radiation risk, the irradiation range should be limited, if necessary, to reduce overall radiation exposure.

[Effect of Kümmell's disease with kyphosis on spinal-pelvic sagittal parameters].

OBJECTIVE: To explore the effect of Kümmell's disease with kyphosis on the sagittal morphology of the spine-pelvis. METHODS: A retrospective analysis of 34 patients of Kümmell's disease with kyphosis （Kümmell group） admitted from August 2015 to September 2022, including 10 males and 24 females with an average age of （71.1±8.5） years old. A control group of 37 asymptomatic population aged （69.3±6.7） years old was matched. Spinal-pelvic sagittal parameters were measured on the anterior-posterior and lateral X-rays of the whole spine in the standing position, including segmental kyphosis（SK） or thoracolumbar kyphosis（TLK）, thoracic kyphosis（TK）, lumbar lordosis（LL）, pelvic incidence（PI）, pelvic tilt（PT）, sacral slope（SS）, sagittal vertical axis（SVA）, T1 pelvic angle（TPA） and PI-LL. Vertebral wedge angle（WA） in Kümmell was measured and differences in parameters among groups were analyzed and the relationship between spino-pelvic parameters and WA, SK were also investigated. RESULTS: TK, SK, PT, SVA, TPA and PI-LL in Kümmell group were significantly larger than those in control group （P<0.05）, LL and SS in Kümmell group were significantly decreased than those in control group （P<0.05）, and there was no significant difference in PI between two groups （P>0.05）. In Kümmell group, WA（30.8±5.9）° showed a positive correlation with SK and TK（r=0.366, 0.597, P<0.05）, and SK was significantly correlated with LL and SS（r=0.539, -0.591, P<0.05）. Strong positive correlation between LL and PI, SS, SVA, TPA, PI-LL were also confirmed in patients with Kümmell with kyphosis（r=0.559, 0.741, -0.273, -0.356, -0.882, P<0.05）. CONCLUSION: Patients with Kümmell with kyphosis not only have segmental kyphosis, but also changes the overall spinal-pelvic sagittal parameters, including loss of lumbar lordosis, pelvic retrorotation, trunk forward tilt. The surgical treatment of Kümmell disease should not only pay attention to the recovery of the height of the collapsed vertebra, but also focus on the overall balance of the spine-pelvic sagittal plane for patients with kyphosis.

'That's just the Ovary!' and other cases of mistaken identity on CT of the female pelvis.

CT is often the first imaging test in female patients with lower abdominal and pelvic pain because of the wide availability of CT and differential diagnoses that span both gynecologic and gastrointestinal disease. Pathology within the female pelvis may be difficult to diagnose on CT owing to suboptimal delineation of anatomy in comparison to MRI and ultrasound. These challenges are confounded by overlapping imaging features of a wide range of gynecologic entities and can lead to diagnostic dilemmas. High value CT interpretation will direct the clinician to the best next diagnostic step as ultrasound and MRI provide superior soft tissue delineation. Other imaging modalities, laboratory investigations, or tissue sampling may be necessary to definitively characterize indeterminate lesions. In this review, we illustrate various cases of mistaken identity on CT of the female pelvis involving the ovaries, uterus, and peritoneal cavity while highlighting clinical pearls that may aid the radiologist in arriving at the correct diagnosis and avoiding potential pitfalls.

Hip and pelvis region MRI reference image atlas for scoring inflammation in peripheral joints and entheses according to the OMERACT-MRI WIPE scoring system in patients with spondyloarthritis.

OBJECTIVE: To develop a reference image atlas for scoring the hip/pelvis region according to the OMERACT whole-body MRI scoring system for inflammation in peripheral joints and entheses (MRI-WIPE). METHODS: We collected image examples of each pathology, location and grade, discussed them at web-based, interactive meetings and, finally, selected reference images by consensus. RESULTS: Reference images for each grade and location of osteitis, synovitis and soft tissue inflammation are provided, as are definitions, reader rules and recommended MRI-sequences. CONCLUSION: A reference image atlas was created to guide scoring whole-body MRIs for arthritis and enthesitis in the hip/pelvis region in spondyloarthritis/psoriatic arthritis clinical trials and cohorts.

Auto-segmentation of pelvic organs at risk on 0.35T MRI using 2D and 3D Generative Adversarial Network models.

PURPOSE: Manual recontouring of targets and Organs At Risk (OARs) is a time-consuming and operator-dependent task. We explored the potential of Generative Adversarial Networks (GAN) to auto-segment the rectum, bladder and femoral heads on 0.35T MRIs to accelerate the online MRI-guided-Radiotherapy (MRIgRT) workflow. METHODS: 3D planning MRIs from 60 prostate cancer patients treated with 0.35T MR-Linac were collected. A 3D GAN architecture and its equivalent 2D version were trained, validated and tested on 40, 10 and 10 patients respectively. The volumetric Dice Similarity Coefficient (DSC) and 95th percentile Hausdorff Distance (HD95th) were computed against expert drawn ground-truth delineations. The networks were also validated on an independent external dataset of 16 patients. RESULTS: In the internal test set, the 3D and 2D GANs showed DSC/HD95th of 0.83/9.72 mm and 0.81/10.65 mm for the rectum, 0.92/5.91 mm and 0.85/15.72 mm for the bladder, and 0.94/3.62 mm and 0.90/9.49 mm for the femoral heads. In the external test set, the performance was 0.74/31.13 mm and 0.72/25.07 mm for the rectum, 0.92/9.46 mm and 0.88/11.28 mm for the bladder, and 0.89/7.00 mm and 0.88/10.06 mm for the femoral heads. The 3D and 2D GANs required on average 1.44 s and 6.59 s respectively to generate the OARs' volumetric segmentation for a single patient. CONCLUSIONS: The proposed 3D GAN auto-segments pelvic OARs with high accuracy on 0.35T, in both the internal and the external test sets, outperforming its 2D equivalent in both segmentation robustness and volume generation time.

Influences of lumbo-sacral transitional vertebrae for anterior lumbar interbody fusion.

Lumbo-sacral transitional vertebrae (LSTV) are frequent congenital variances of the spine and are associated with increased spinal degeneration. Nevertheless, there is a lack of data whether bony alterations associated with LSTV result in reduced segmental restoration of lordosis when performing ALIF. 58 patients with monosegmental stand-alone ALIF in the spinal segment between the 24th and 25th vertebra (L5/S1)/(L5/L6) where included. Of these, 17 patients had LSTV and were matched to a control population by age and sex. Pelvic incidence, pelvic tilt, sagittal vertical axis, lumbar lordosis, segmental lordosis, disc height and depth were compared. LSTV-patients had a significantly reduced segmental lordosis L4/5 (p = 0.028) and L5/S1/(L5/L6) (p = 0.041) preoperatively. ALIF resulted in a significant increase in segmental lordosis L5/S1 (p < 0.001). Postoperatively, the preoperatively reduced segmental lordosis was no longer significantly different in segments L4/5 (p = 0.349) and L5/S1/(L5/6) (p = 0.576). ALIF is associated with a significant increase in segmental lordosis in the treated segment even in patients with LSTV. Therefore, ALIF is a sufficient intervention for restoring the segmental lordosis in these patients as well.

Segmentation of pelvic structures in T2 MRI via MR-to-CT synthesis.

Segmentation of multiple pelvic structures in MRI volumes is a prerequisite for many clinical applications, such as sarcopenia assessment, bone density measurement, and muscle-to-fat volume ratio estimation. While many CT-specific datasets and automated CT-based multi-structure pelvis segmentation methods exist, there are few MRI-specific multi-structure segmentation methods in literature. In this pilot work, we propose a lightweight and annotation-free pipeline to synthetically translate T2 MRI volumes of the pelvis to CT, and subsequently leverage an existing CT-only tool called TotalSegmentator to segment 8 pelvic structures in the generated CT volumes. The predicted masks were then mapped back to the original MR volumes as segmentation masks. We compared the predicted masks against the expert annotations of the public TCGA-UCEC dataset and an internal dataset. Experiments demonstrated that the proposed pipeline achieved Dice measures ≥65% for 8 pelvic structures in T2 MRI. The proposed pipeline is an alternative method to obtain multi-organ and structure segmentations without being encumbered by time-consuming manual annotations. By exploiting the significant research progress in CTs, it is possible to extend the proposed pipeline to other MRI sequences in principle. Our research bridges the chasm between the current CT-based multi-structure segmentation and MRI-based segmentation. The manually segmented structures in the TCGA-UCEC dataset are publicly available.

A retrospective observational study assessing mortality after pelvic trauma embolisation.

INTRODUCTION: Trauma to the pelvic ring and associated haemorrhage represent a management challenge for the multidisciplinary trauma team. In up to 10% of patients, bleeding can be the result of an arterial injury and mortality is reported as high as 89% in this cohort. We aimed to assess the mortality rate after pelvic trauma embolisation and whether earlier embolisation improved mortality. METHODS: Retrospective study at single tertiary trauma and referral centre, between 1 January 2009 and 30 June 2022. All adult patients who received embolisation following pelvic trauma were included. Patients were excluded if angiography was performed but no embolisation performed. RESULTS: During the 13.5-year time period, 175 patients underwent angiography and 28 were excluded, leaving 147 patients in the study. The all-cause mortality rate at 30-days was 11.6% (17 patients). The median time from injury to embolisation was 6.3 h (range 2.8-418.4). On regression analysis, time from injury to embolisation was not associated with mortality (OR 1.01, 95% CI 0.952-1.061). Increasing age (OR 1.20, 95% CI 1.084-1.333) and increasing injury severity score (OR 1.14, 95% CI 1.049-1.247) were positively associated with all-cause 30-day mortality, while non-selective embolisation (OR 0.11, 95% CI 0.013-0.893) was negatively associated. CONCLUSION: The all-cause mortality rate at 30-days in or cohort was very low. In addition, earlier time from injury to embolisation was not positively associated with all-cause 30-day mortality. Nevertheless, minimising this remains a fundamental principle of the management of bleeding in pelvic trauma.

Development of a biofidelic computational model of human pelvis for predicting biomechanical responses and pelvic fractures.

BACKGROUND AND OBJECTIVE: The pelvis, a crucial structure for human locomotion, is susceptible to injuries resulting in significant morbidity and disability. This study aims to introduce and validate a biofidelic computational pelvis model, enhancing our understanding of pelvis injury mechanisms under lateral loading conditions. METHODS: The Finite Element (FE) pelvic model, representing a mid-sized male, was developed with variable cortical thickness in pelvis bones. Material properties were determined through a synthesis of existing constitutive models, parametric studies, and multiple validations. Comprehensive validation included various tests, such as load-displacement assessments of sacroiliac joints, quasi-static and dynamic lateral compression on the acetabulum, dynamic side impacts on the acetabulum and iliac wing using defleshed pelvis, and lateral impacts by a rigid plate on the full body's pelvis region. RESULTS: Simulation results demonstrated a reasonable correlation between the pelvis model's overall response and cadaveric testing data. Predicted fracture patterns of the isolated pelvis exhibited fair agreement with experimental results. CONCLUSIONS: This study introduces a credible computational model, providing valuable biomechanical insights into the pelvis' response under diverse lateral loading conditions and fracture patterns. The work establishes a robust framework for developing and enhancing the biofidelity of pelvis FE models through a multi-level validation approach, stimulating further research in modeling, validation, and experimental studies related to pelvic injuries. The findings are expected to offer critical perspectives for predicting, preventing, and mitigating pelvic injuries from vehicular accidents, contributing to advancements in clinical research on medical treatments for pelvic fractures.

Acute Hematogenous Osteomyelitis of the Pelvis in Children.

BACKGROUND: Pelvic involvement has been reported in 3%-14% of acute hematogenous osteomyelitis (AHO) cases in children. One guideline suggests need for a longer antibiotic course in pelvic AHO, however, recent data are lacking. We describe the clinical course of children with pelvic AHO and compare it to nonpelvic AHO. METHODS: A retrospective review of patients with a diagnosis of AHO admitted to Texas Children's Hospital from January 2012 to December 2020 was conducted. Patients 6 months-<19 years old and with ≤14 days of symptoms at admission were eligible. Patients with sickle cell disease or immunocompromised were excluded. Wilcoxon rank-sum test assessed for differences between continuous variables and Fisher exact for categorical variables using STATA 17. RESULTS: We compared 104 cases of pelvic AHO to 314 cases of nonpelvic AHO. Patients had similar microbiology, length of stay and length of antibiotic therapy. Patients with pelvic AHO had pyomyositis identified by magnetic resonance imaging more often (28.8 vs. 9.4%, P < 0.001) and bone abscess less often (22.1 vs. 46.5%, P < 0.001). Rates of chronic complications were comparable between patients with pelvic AHO and nonpelvic AHO (8.4% vs. 15.1%, P = 0.1). Nineteen patients (18.3%) with pelvic AHO received ≤30 antibiotic days without complications, but they had less need for intensive care or bone abscesses than patients treated longer. CONCLUSIONS: Pelvic AHO in children may be more frequent than previously reported but is not associated with more complications. Four weeks of therapy may be sufficient in selected patients. Prospective studies to compare outcomes with different lengths of therapy are needed.

MRI Features of Pelvic Nerve Involvement in Endometriosis.

Endometriosis is a common condition that mostly affects people assigned as female at birth. The most common clinical symptom of endometriosis is pain. Although the mechanism for this pain is poorly understood, in some cases, the nerves are directly involved in endometriosis. Endometriosis is a multifocal disease, and the pelvis is the most common location involved. Nerves in the pelvis can become entrapped and involved in endometriosis. Pelvic nerves are visible at pelvic MRI, especially when imaging planes and sequences are tailored for neural evaluation. In particular, high-spatial-resolution anatomic imaging including three-dimensional isotropic imaging and contrast-enhanced three-dimensional short inversion time inversion-recovery (STIR) fast spin-echo sequences are useful for nerve imaging. The most commonly involved nerves are the sciatic, obturator, femoral, pudendal, and inferior hypogastric nerves and the inferior hypogastric and lumbosacral plexuses. Although it is thought to be rare, the true incidence of nerve involvement in endometriosis is not known. Symptoms of neural involvement include pain, weakness, numbness, incontinence, and paraplegia and may be constant or cyclic (catamenial). Early diagnosis of neural involvement in endometriosis is important to prevent irreversible nerve damage and chronic sensorimotor neuropathy. Evidence of irreversible damage can also be seen at MRI, and radiologists should evaluate pelvic nerves that are commonly involved in endometriosis in their search pattern and report template to ensure that this information is incorporated into treatment planning.

Do we fix front and back of every APC pelvic injury?

HISTORY-A 47-year-old male was on a cliff when he jumped into the water below. He jumped about 50 feet. Upon landing in the water, he felt his legs separate and abduct violently. He was taken to the Emergency unit of the nearest trauma center and was found to have no injuries except to his pelvis. He could not weight bear because of pelvic pain but had normal distal sensory and motor exam and rectal exam. His-pelvis was painful to examination anteriorly with minor left-sided posterior SI pain, and he had no blood at his meatus. X-rays and CT were done, (Figures 1-5).

Analysis of Spinopelvic Parameters and Lumbar Lordosis in Patients with Transitional Lumbosacral Vertebrae, with Special Reference to Sacralization and Lumbarization.

BACKGROUND: Transitional lumbosacral vertebra presents in 2 forms based on its origin: sacralization and lumbarization. These patients have 2 options for sacral endplates (upper and lower) and consequently, 2 sets of values for spinopelvic parameters and lumbar lordosis (LL). This study aimed to evaluate these parameters in asymptomatic patients with sacralization and lumbarization and compare them with each other and normative values. METHODS: Spinopelvic parameters and LL according to upper and lower endplate were measured using abdominal computed tomography in 1420 asymptomatic patients, of which 108 had Transitional lumbosacral vertebra. These parameters were compared among patients with lumbarization and sacralization and with normal controls. In addition, correlations between the upper and lower endplate parameters were determined. RESULTS: As compared to the control group, upper endplate measurements yielded lower spinopelvic parameters and LL values while lower endplate values yielded higher values. While these values were significantly different from normative values, these parameters were similar in both lumbarization and sacralization groups. Furthermore, most spinopelvic parameters of both upper and lower endplates were strongly correlated, and the differences between the upper and lower PI and LL values are relatively constant (27° and 14°, respectively. CONCLUSIONS: Upper and lower endplate parameters are comparable in patients with sacralization and lumbarization; therefore, the average spatial position of a sacralized L5 and a lumbarized S1 within the pelvis is similar and either parameter can be used for radiological measurements. Further studies with symptomatic patients are warranted to confirm these results.

Two-stage multi-task deep learning framework for simultaneous pelvic bone segmentation and landmark detection from CT images.

PURPOSE: Pelvic bone segmentation and landmark definition from computed tomography (CT) images are prerequisite steps for the preoperative planning of total hip arthroplasty. In clinical applications, the diseased pelvic anatomy usually degrades the accuracies of bone segmentation and landmark detection, leading to improper surgery planning and potential operative complications. METHODS: This work proposes a two-stage multi-task algorithm to improve the accuracy of pelvic bone segmentation and landmark detection, especially for the diseased cases. The two-stage framework uses a coarse-to-fine strategy which first conducts global-scale bone segmentation and landmark detection and then focuses on the important local region to further refine the accuracy. For the global stage, a dual-task network is designed to share the common features between the segmentation and detection tasks, so that the two tasks mutually reinforce each other's performance. For the local-scale segmentation, an edge-enhanced dual-task network is designed for simultaneous bone segmentation and edge detection, leading to the more accurate delineation of the acetabulum boundary. RESULTS: This method was evaluated via threefold cross-validation based on 81 CT images (including 31 diseased and 50 healthy cases). The first stage achieved DSC scores of 0.94, 0.97, and 0.97 for the sacrum, left and right hips, respectively, and an average distance error of 3.24 mm for the bone landmarks. The second stage further improved the DSC of the acetabulum by 5.42%, and this accuracy outperforms the state-of-the-arts (SOTA) methods by 0.63%. Our method also accurately segmented the diseased acetabulum boundaries. The entire workflow took ~ 10 s, which was only half of the U-Net run time. CONCLUSION: Using the multi-task networks and the coarse-to-fine strategy, this method achieved more accurate bone segmentation and landmark detection than the SOTA method, especially for diseased hip images. Our work contributes to accurate and rapid design of acetabular cup prostheses.

Evaluation of sex differences in pelvis and femur x-ray images in British shorthair cats by geometric morphometric method.

The study covers British Shorthair cats, which is a popular domestic cat breed in our country and defined as 'brachycephalic' in terms of skull structure. Article focuses on the pelvis and femur region of cats which gynaecological and orthopaedic diseases of this cat breed, which are frequently encountered in clinical practice, is found to be important. It is aimed to reveal the shape differences between male and female individuals using geometric morphometric method. X-ray images were used to examine the pelvis and femurs of cats via geometric method. Radiological images were obtained from a total of 40 British Shorthair cats (20 females and 20 males) in two positions, ventro-dorsal (VD) and latero-lateral (LL), and shape differences between the sexes were examined. As result, it is seen that the measurement points taken from the males are more outward and have sharper angles than the females. Study also shows pelvis is a better choice than femur when it comes to sex discrimination. Although traditional morphometric methods are more useful in clinical practice, it is thought that is important to support or re-evaluate the data with the geometric morphometric method in academic field for a further approach.

Radiographic outcomes following surgical correction for lumbar degenerative kyphosis: the impact of supine pelvic tilt.

OBJECTIVE: Lumbar degenerative kyphosis (LDK), a flexible deformity, is a common form of sagittal imbalance in Asian countries. Assessing a patient's spine prior to surgery by using positional radiographs is becoming more crucial in determining surgical planning to achieve favorable clinical and radiographic outcomes, especially in patients with flexible deformities. This study aims to identify radiographic characteristics of supine pelvic tilt (sPT) and its relation to mechanical failure (MF) following LDK correction. METHODS: A single-center, single-surgeon retrospective analysis was performed in patients who underwent LDK correction with sacropelvic fixation between January 2014 and May 2019. Patients were grouped into pelvic match and mismatch groups according to the difference between postoperative pelvic tilt (PT) and sPT. Demographic, surgical, and radiographic parameters were compared. Chronological change of PT was assessed by comparing preoperative, supine, immediate postoperative, and final PT. RESULTS: Baseline demographics and sagittal alignments were similar between PT match (n = 25) and mismatch (n = 42) groups (p > 0.05). There was a significant difference in the rate of MF between PT match and mismatch groups (4% vs 31%, p = 0.021). Multivariable analysis demonstrated that after including control variables, PT mismatch was independently associated with the likelihood of MF development (OR 33.42, p = 0.04). CONCLUSIONS: sPT reflects postoperative PT changes; therefore, supine imaging may represent a tool that could be used for preoperative decision-making in patients with LDK or possibly those with flexible adult spinal deformity. PT mismatch > 10° or < 0° is a significant risk factor for MF following correction of LDK. Measurement of sPT would aid surgeons in optimal preoperative planning and in minimizing catastrophic MF following deformity correction surgery.

Predictive modeling of submarining risk in car occupants based on pelvis angle and lap belt positioning.

OBJECTIVE: The engagement of the lap belt with the pelvis is critical for occupant safety during vehicle frontal crashes to prevent occupant submarining. This study aims to develop a predictive model for submarining risk based on anthropometric parameters and lap belt positioning using finite element (FE) analyses. METHODS: FE analyses were conducted using human body models representing various body shapes (a 50th percentile male, low and high BMI males, and a 5th percentile female) in three seated postures (standard, reclined, and slouched). The lap belt-ASIS overlap and the belt-pelvis angle were used as key parameters for predicting submarining risk. A logistic regression analysis was utilized to correlate submarining occurrence with the initial values of these two parameters at the beginning of impact. Subsequently, this submarining prediction model was applied to computer tomography (CT) measurements of human subjects in different seated postures (upright, reclined, and slouched), and submarining risks were calculated based on the developed model. RESULTS: FE simulations indicated that submarining was more likely to occur as the initial belt-pelvis angle approached zero and there was a smaller initial belt-ASIS overlap. The logistic regression analysis demonstrated that the initial belt-pelvis angle and belt-ASIS overlap were statistically significant for predicting submarining risk. The derived model effectively distinguished submarining occurrence based on the initial values of these two parameters. The application of the submarining model to CT measurements of human subjects showed that submarining risk was lower in the order of upright, slouched, and reclined postures. In the reclined posture, the high submarining risk was attributed to a small belt-ASIS overlap and a rearward-tilted pelvis angle; whereas in the slouched posture, the risk was mostly associated with a rearward-tilted pelvis angle. CONCLUSIONS: The submarining prediction model was developed based on the belt-pelvis angle and the belt-ASIS overlap. This predictive model may help to design restraint systems for various body types and seated postures of occupants.