Vertebral Location Research Articles

Automatic Vertebrae Localization and Identification by Combining Deep SSAE Contextual Features and Structured Regression Forest.

Automatic vertebrae localization and identification in medical computed tomography (CT) scans is of great value for computer-aided spine diseases diagnosis. In order to overcome the disadvantages of the approaches employing hand-crafted, low-level features and based on field-of-view priori assumption of spine structure, an automatic method is proposed to localize and identify vertebrae by combining deep stacked sparse autoencoder (SSAE) contextual features and structured regression forest (SRF). The method employs SSAE to learn image deep contextual features instead of hand-crafted ones by building larger-range input samples to improve their contextual discrimination ability. In the localization and identification stage, it incorporates the SRF model to achieve whole spine localization, then screens those vertebrae within the image, thus relieves the assumption that the part of spine in the field of image is visible. In the end, the output distribution of SRF and spine CT scans properties are assembled to develop a two-stage progressive refining strategy, where the mean-shift kernel density estimation and Otsu method instead of Markov random field (MRF) are adopted to reduce model complexity and refine vertebrae localization results. Extensive evaluation was performed on a challenging data set of 98 spine CT scans. Compared with the hidden Markov model and the method based on convolutional neural network (CNN), the proposed approach could effectively and automatically locate and identify spinal targets in CT scans, and achieve higher localization accuracy, low model complexity, and no need for any assumptions about visual field in CT scans.

Study of lumbar spine activity regularity based on Kanade-Lucas-Tomasi algorithm

Abstract The diagnosis of lumbar spine pathologies such as lower back pain (LBP) is extremely difficult, and a consensus regarding a diagnostic standard has not yet been reached. Accurate measurement of intervertebral kinematic parameters helps to understand the etiology and diagnosis of related diseases, and to evaluate the subsequent treatment. Quantitative fluoroscopy (QF) which can obtain continuous, dynamic image sequences of lumbar motion at low radiation doses were introduced. The estimation of intervertebral kinematics depends on the precise localization of lumbar vertebrae. Usually, vertebral corners are identified and tracked by automated methods or manual method. This study presents a novel method for vertebral tracking based on the KLT (Kanade-Lucas-Tomasi, KLT) algorithm for intervertebral kinematics analysis. Accuracy of the proposed method was tested using a sagittal human image which contained two vertebral bodies, and the average errors achieved for displacement and angle were within 0.25 mm and 0.3°, respectively. To test the proposed method under clinical conditions, totally 11 volunteers were recruited and a result of more smoothness and stability in the intervertebral kinematics was obtained with comparing to the manual method by an experienced and trained clinician. In conclusion, the proposed method is an effective, accurate way to assess lumbar vertebrae tracking.

Bilateral dentoalveolar asymmetries in female patients with adolescent idiopathic scoliosis

The aim of this cross-sectional research was to quantify left-right dentoalveolar fluctuating (FA) and directional asymmetries (DA) in patients with adolescent idiopathic scoliosis and to assess the relationship between these asymmetries and the side, location, and severity of scoliosis. The study group comprised of 60 females aged 12-16 years, with idiopathic scoliosis, and 54 healthy controls. Measurements were made with the use of digital caliper on full-mouth dental casts. The following variables were measured from each subject: a shift of the incisor midline, left and right incisor overjet, deviation of canine and buccal segment relation as well as maxillary and mandibular arch chords. The data were statistically analyzed with significance taken as p < 0.05. Statistically significant differences in the mean shift of the incisor midline, buccal segment relation on the left and canine deviation on the left between the control group and the study group were detected ( p = 0.0419, p = 0.0.458 and p = 0.0204, respectively). FA of the midline deviation and canine deviation were statistically significantly higher for subjects with IS, compared to healthy controls ( p = 0.0315 and p = 0.0415, respectively). Neither direction of the curve nor apical vertebra's location or apical translation significantly affected the magnitude of dentoalveolar asymmetries. Our results confirmed that bilateral asymmetries are a common feature of the young females' occlusion. Individuals with IS show higher tendency to Angle Class II malocclusion, as well as higher FA of incisor midline discrepancy and canine deviation, compared to the controls.

VERTEBRAL HYDATIDOSIS: BIBLIOGRAPHICAL REVIEW AND CLINICAL CASE REPORT

ABSTRACT We will present a literature review of the vertebral location of hydatidosis. It is a rare, locally aggressive condition with a high recurrence rate that requires clinical treatment (antihelminthic drugs) and surgery, with decompression of the spinal canal. We report a case with more than 11 years of follow-up, which required surgical treatment on 4 occasions. Level of Evidence V; Therapeutic-investigational study of treatment results.

Cervical Intervertebral Disk to Vertebral Body Ratios of Different Dog Breeds Based on Sagittal Magnetic Resonance Imaging.

Objective: To establish sagittal area and length reference values and ratios between apparently normal canine cervical vertebrae and intervertebral disks using magnetic resonance imaging.Sample: Retrospective evaluation of cervical vertebral column magnetic resonance imaging studies of 44 dogs representing 5 different breeds (Labrador Retriever, n = 10; French Bulldog, n = 10; Great Dane, n = 9; Chihuahua, n = 10; Dachshund, n = 5).Procedures: Mid-sagittal measurements of vertebral body and disk areas were obtained from C3 through C7 vertebrae and C2/C3 through C6/C7 intervertebral disks. Disk to vertebra area ratios were calculated and compared among dog breeds. Additionally, sagittal vertebral body and disk length measurements were obtained and disk to vertebra length ratios calculated. Inter and intra observer variability was assessed.Results: There were significant differences for disk to vertebral body area and length ratios between evaluated dog breeds and cervical vertebral locations (p < 0.001). Mean area ratio of Chihuahuas was significantly larger than all other breeds, while results from Dachshunds were only significantly different than Chihuahuas and Labrador Retrievers. Mean area ratios were statistically different between the cranial and caudal cervical vertebral locations. Regarding length ratios, results from Chihuahuas were significantly different than all breeds except Dachshunds. Mean length ratios were statistically different between all cervical locations, except C2/C3 compared to C3/C4. Intra- and interobserver variability was very good to excellent.Conclusion and Clinical Relevance: There are significant differences in area and length ratios between dog breeds. Differences also exist in area and length ratios between the cranial and caudal cervical vertebral column. These differences may play a role in the development of vertebral column diseases including intervertebral disk disease.

Distribution of Marbling Throughout the M. Longissimus Thoracis et Lumborum of Beef Carcasses Using an Instrument-Grading System

Beef Loin, Strip Loins (IMPS #180; n = 20) with marbling scores between Modest00 and Modest30 at the 12th and 13th rib interface of the M. longissimus thoracis et lumborum (LL) were collected. Each strip loin was fabricated into 6 samples taken perpendicular to the long axis of the LL from the 13th thoracic vertebra to the fifth lumbar vertebra with the cut made on the anterior side of the respective vertebra. A Computer Vision System Cold Camera measured the LL cross-section of each sample location for USDA marbling score, marbling distribution, average marbling fleck size, LL area, LL length (distance medial to lateral), and LL width (distance dorsal to ventral). In the present study, mean LL marbling score decreased (P &lt; 0.05) from the second lumbar vertebrae location to the fifth lumbar vertebrae location. Marbling size and marbling distance were the smallest (P &lt; 0.05) in samples from the 13th thoracic vertebrae location. The LL area and width was largest (P &lt; 0.05) for the samples from the most anterior location and thus decreased (P &lt; 0.05) as the samples became more posterior. Samples from the most posterior end of the strip loin were the longest (P &lt; 0.05) in length. It was observed that marbling score, distribution, and size, as well as, LL area, length, and width vary from anterior to posterior in the strip loin which can have potential marketing implications for food service distributors and retailers.

Factors affecting Sandwich vertebral re-fracture after vertebral augmentation surgery for osteoporotic spine Sandwich fractures

Objective To investigate the risk factors affecting Sandwich vertebral re-fracture after vertebral augmentation surgery for osteoporotic spine Sandwich fractures. Methods A retrospective case control study was conducted on the clinical data of 90 patients with osteoporotic spine Sandwich fractures treated with vertebral augmentation surgery from January 2004 to December 2015. There were 26 males and 64 females, aged (69.9±7.4)years. The patients were divided into fracture group (n=15) and non fracture group (n=75) according to the incidence of re-fracture after operation during follow-up. Gender, age, height, weight, bone mineral density, cumulative number of cemented vertebrae, location of the Sandwich vertebrae in the thoracolumbar segment, the preoperative kyphosis angle of the Sandwich fracture segment, surgical approach, cement injection approach (unilateral or bilateral), cement injection volume, cement leakage between the Sandwich intervertebral spaces, the postoperative kyphosis angle of the Sandwich fracture segment, and follow-up duration were used as independent variables. Chi-square test and multivariate logistic regression analysis were used to analyze the risk factors of vertebral Sandwich fracture. Results There were 97 Sandwich vertebrae in 90 patients, and 226 fractured vertebrae were treated with initial intensive treatment. The mean follow-up was 18.1 months. There were no significant differences in gender, age, height, weight, cumulative number of cemented vertebrae, whether the Sandwich vertebrae was located at the thoracolumbar segment, the preoperative kyphosis angle of the Sandwich fracture segment, the cement injection approach (unilateral or bilateral), the volume of cement injection, and the cement leakage between the Sandwich intervertebral spaces (P>0.05). There were significant differences in bone mineral density, surgical approach, and postoperative kyphosis angle of the Sandwich fracture segment between the two groups (P<0.05). Further logistic regression analysis showed that bone mineral density ≤ 3.5 SD and segmental kyphosis (≥10°) were risk factors for Sandwich fracture (P<0.05). Conclusions The low bone mineral density (T value ≤-3.5 SD)and postoperative kyphotic angle (≥10°) are risk factors for re-fracture of Sandwich vertebrae. Vertebroplasty itself does not increase the risk of recurrent vertebral fractures. Key words: Spinal fractures; Osteoporosis; Cement augmentation

Asymmetric osteotomy via posterior adjacent vertebrae in treating traumatic thoracolumbar kyphotic scoliotic deformity

Objective To investigate the clinical efficacy of asymmetric osteotomy via posterior adjacent vertebrae in the treatment of traumatic thoracolumbar kyphotic scoliotic deformity. Methods A retrospective case series study was conducted on the clinical data of 16 patients with traumatic thoracolumbar kyphotic scoliotic deformity admitted to our department from January 2012 to January 2017. There were 10 males and six females, aged (42.5±7.6) years (range, 20-62 years). According to the location of injured vertebrae, there were two patients with T11, five with T12, six with L1, and three with L2, all of which had scoliosis deformity and obvious low back pain. All patients underwent asymmetric osteotomy via posterior adjacent vertebrae. The operation time and intraoperative bleeding were recorded. The imaging parameters such as kyphosis Cobb angle, scoliosis Cobb angle, distance between C7 plumbline and central sacral vertebral line (C7-CSVL), and distance between C7 plumbline and sagittal vertical axis (SVA) were measured before and after operation. At the same time, the visual analogue scale (VAS), Oswestry dysfunction index (ODI), and SRS-22 scale were used to evaluate the clinical efficacy. The AISA score was used to evaluate the neurological function recovery before and after operation. Results All patients were followed up for (26.3±16.8) months (range, 15-65 months). The operation time was (6.0±1.4)hours (range, 4.5-9.0 hours), and the intraoperative bleeding was (900.5±360.8)ml (range, 800-1600 ml). The kyphosis Cobb angle was improved from (70.3±9.8)° before operation to (12.2±2.9)° after operation (P<0.01). The scoliosis Cobb angle was improved from (47.6±11.6)° before operation to (4.0±0.9)°after operation (P<0.01). The C7-CSVL decreased from preoperative (3.1±0.8)cm to postoperative (1.2±0.4)cm (P<0.01), and the SVA decreased from preoperative (5.0±0.9)cm to postoperative (2.9±0.5)cm (P<0.01). No severe complications such as spinal cord and nerve injury occurred. The VAS decreased from preoperative (6.8±1.0) to (1.9±0.9) points at the last follow up. The ODI decreased from (54.6±4.2)% before operation to (8.1±2.5)% at the last follow up. The SRS-22 score was increased from (64.6±7.5) points before operation to (87.4±3.2)points at the last follow-up. In terms of the ASIA classification, two patients were improved from grade C to grade D after operation, and six patients were improved from grade D to grade E. Conclusion Asymmetric osteotomy via posterior adjacent vertebrae is safe and effective in the treatment of traumatic thoracolumbar scoliosis, with high correction rate of scoliosis and kyphosis at the same time. Key words: Thoracic vertebrae; Lumbar vertebrae; Spinal fractures; Old fracture

Study of recognition of atlanto-axial intervertebral space for the localization of fetal vertebrae with three-dimensional ultrasound

Objective To study the feasibility of visualization of atlanto-axial intervertebral space for the localization of fetal centrums with three-dimensional ultrasound and to explore the relationship of intervertebral space with gestational weeks. Methods A total of 223 cases of normal single pregnancy in the second trimester were enrolled in the study to acquire the 3D volume of fetal spines. The distances between the transverse processes of cervical vertebra were measured in vertical horizontal line. The distance between the first and second cervical vertebra was labeled C1, and then labelled C2, C3, C4, C5 and C6 as follows. Results The successful rate of 3D acquisition of 206 cases was 92.4%.The distance between ICC values of C1-C6 were 0.985, 0.984, 0.971, 0.956, 0.978, 0.923, respectively and the consistency data measuring was well. The atlanto-axial intervertebral space was significantly larger than other intervertebral space (P=0.012) and the mean ratios of C1 to C2-C6 were 1.41, 1.39, 1.37, 1.40, 1.39, respectively, which had no correlation with gestational ages (P=0.877, 0.915, 0.838, 0.859, 0.908, respectively). Conclusions Visualization of the atlanto-axial intervertebral space with three-dimensional ultrasound is a direct and simple method without any consumption, which can help to quickly locate the axial vertebra and other vertebras and conus medullaris. Key words: Ultrasonography, prenatal; Fetal vertebra; Conus medullaris; Fetus

Differentiation and classification of thoracolumbar transitional vertebrae.

The literature states that transitional vertebrae at any junction are characterized by features retained from two adjacent regions in the vertebral column. Currently, there is no published literature available that describes the prevalence or morphology of thoracolumbar transitional vertebrae (TLTV). The aim of this study was to identify the qualitative characteristics of transitional vertebrae at the thoracolumbar junction and establish a technique to differentiate the various subtypes that may be found. A selection of vertebral columns from skeletal remains (n=35) were evaluated in this study. Vertebrae were taken based on features that are atypical for vertebrae in each relative region. The transitional vertebrae were qualitatively identified based on overlapping thoracic and lumbar features of vertebrae at the thoracolumbar junction. The following general overlapping characteristics were observed: aplasia or hypoplasia of the transverse process, irregular orientation on the superior articular process and atypical mammillary bodies. The results show that the most frequent location of the transitional vertebrae was in the thoracic region (f=23). The second most frequent location was in the lumbar region (f=10). In two specimens of the selection (f=2), an additional 13th thoracic vertebra was present which functioned as a transitional vertebra. This study concluded that one can accurately identify the characteristics of transitional vertebrae at the thoracolumbar junction. In addition, the various subtypes can be differentiated according to the region in the vertebral column the vertebra is located in and the relative number of vertebral segments in the adjacent regions of the vertebral column. This provides a qualitative tool for researchers to differentiate the transitional vertebrae from distinctly different typical thoracic or lumbar vertebrae at the thoracolumbar junction.

Tuberculous Spondylitis. Burden of Diagnosis. Case Presentation

Introduction: Tuberculosis continues to pose a problem of public health worldwide. Mycobacterium tuberculosis infects 1/3 of the world's population and seems to be responsible for 1.4 million deaths annually. In our country, the incidence is 6.5 times higher than in the EU countries. In 2016 there were 12836 cases of pulmonary TB (new and recurrent cases) of which 530 cases were TB MDR/XDR. The screening rate increased to 94% for new cases and 85% for MDR tuberculosis cases. Extrapulmonary tuberculosis remains a challenge by delaying of the diagnosis and the duration of treatment.Case presentation: We present the case of a 73-year-old patient with no significant pathological history admitted to the National Institute for Infectious Diseases “Prof. Dr. Matei Bals”, Bucharest, in July 2017 (21 days) for myalgia and fever apparently after an episode of a respiratory tract infection. Due to myalgia, the occurrence of muscular atrophy and accelerate weight loss he referred to our hospital where was established the diagnosis of Tuberculous Spondylitis.Results and methods: The diagnosis was established following numerous clinical and paraclinical investigations approximately 6 weeks after the first presentation to our hospital. As risk factors, the patient was diagnosed by the time of admission with other diseases that he wasn’t aware of as diabetes and renal impairment. Evolution under anti-tuberculosis treatment was arduous due to the development of hepatic toxicity, episodes of acute exacerbation of chronic renal disease and post-antibiotic diarrhoea. The final clinical and paraclinical outcome was favourable.Discussion: Diagnosis of TB spondylitis requires both multidisciplinary collaborations and diagnosis experience. Anamnesis and understanding of symptoms are also important for proper selecting paraclinical tests panel. To understand these results in view of imposing a nephrotoxic and hepatotoxic treatment in the patient with pre-existing liver and kidney pathology, we returned to understanding the pathophysiology of Tuberculous Spondylitis.Conclusions: Diagnosing the vertebral location of extrapulmonary tuberculosis requires understanding pathophysiology of this infection. Requesting of paraclinical investigation and performing differential diagnostics can help shorten the time required for diagnosis.

237 - Clinical Translation of the LevelCheck Algorithm for Automatic Localization of Target Vertebrae in Spine Surgery

237 - Clinical Translation of the LevelCheck Algorithm for Automatic Localization of Target Vertebrae in Spine Surgery

Experimental study of adjacent vertebral refracture after vertebroplasty on embalmed specimens

Objective To study the causes of fractures in untreated adjacent vertebraes after vertebroplasty. Methods Twelve spinal segements (four T9-T10, four T12-L2, and four L3-L5) from four embalmed human cadavers were divided into groups A and B (n=6/group). In group A, experimental vertebral compression fractures were created at middle vertebraes (T10, L1, L4), and these middle vertebraes were augmented with polymethymethacryclate. Then all spinal segements were compressed until a new fracture occured at any vertebrae, and the location of fractured vertebrae, maximum veritical load, and stiffness were investigated. Results There was statistically significant difference in the maximum vertical load between groups A and B (t=-2.267, P=0.047). The maximum veritical load in group A was, on average, 15% lower than that in group B [(3 048±403), (3 586±418) N, respectively]. There was no significant difference in stiffness between the two groups (t=-0.542, P=0.600). In the group A, new fractures following percutaneous verteoplasty (PVP) occurred at T9 in 2 specimens, T12 in 2, and L3 in 2. All new fractures occurred in the superior vertebrae in the group A. In the group B, the fractures occurred at T9 in 1 specimen, T10 in 1, T12 in 1, L1 in 1, and L3 in 2. Conclusion The failure strength of spinal segments can be decreased by vertebroplasty, which will increase the risk of adjacent vertebral body fracture, especially the superior vertebrae. Key words: Vertebroplasty; Adjacent vertebral body refracture; Bone cement; Maximum veritical load; Stiffness

Vertebrae localization in CT using both local and global symmetry features

Automatic vertebrae segmentation and localization in CT images are essential in many medical treatments such as disease diagnosis and surgical planning. However, vertebra is one of the most complex organs to locate precisely due to its complex shape, deformation and occlusion by other organs. In this paper, we propose to incorporate local appearance features with global translational symmetry and local reflection symmetry features. Symmetrical structure of each vertebra provides strong cue for accurate localization. In order to efficiently investigate 3-dimensional reflection symmetry in CT images, we propose a Sphere Surface Expansion method and iterative optimization framework. Quantitative and qualitative evaluations show that the proposed method outperforms existing localization method.

Proximal junctional kyphosis after posterior hemivertebra resection and instrumented fusion in young children with congenital scoliosis

Objective: To investigate the risk factors of proximal junctional kyphosis(PJK) in young children who underwent posterior hemivertebra resection and instrumented fusion. Methods: This study reviewed the charts and radiographs of 136 consecutive young children with congenital scoliosis who underwent posterior hemivertebra resection and instrumented fusion in Department of Orthopaedics, Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School from January 2009 to June 2014, including 75 males and 61 females, with an average age of (5.0±1.7)years(3-10 years). Proximal junctional angle(PJA), spino-pelvic parameters and segmental kyphosis (SK) were recorded pre- and post-operation and at last follow-up.The changes of PJA and radiographic features of proximal junction were also observed.χ(2) test and t-test were used to analyzed enumeration data and measurement data, respectively. Results: The average follow-up period was (32.8±10.3)months (ranging from 24 to 73 months) by June 2016. Among these patients, PJK occurred in 19 cases. Fifteen patients developed PJK during the first 3 months after surgery.The most common type of PJK was ligamentous failure.Compared with the non-PJK group (22.2%, 37.6%, 13.7%), the PJK group showed higher rate of preoperative TK>40°(9/19), fusion levels >4 (13/19) and greater SK change > 30°(9/19)(χ(2)=7.259, 6.375, 12.368; all P<0.05), while there were no difference between the two groups in terms of preoperative PJA, lumbar lordosis, SVA and upper instrument vertebra location(all P>0.05). The average PJA increased from 7.5°±2.9° to 21.3°±4.3° at 3 months after surgery to 20.6°±3.7° at the final follow-up visit in the PJK group.At the time of the final follow-up visit, ten patients received brace treatment, with no significant progression of PJA. Conclusions: PJK might mainly occurs within 3 months postoperatively.Its prognostic factors include preoperative hyperkyphosis, over correction of kyphosis and ligamentous failure.

Location of Vertebral Fractures is Associated with Bone Mineral Density and History of Traumatic Injury.

The upper and lower thoracolumbar spine have been associated with different biomechanical outcomes. This concept, as it applies to osteoporotic fracture risk, has not been well documented. This was a case-control study of 120 patients seen in an osteoporosis clinic. Vertebral fractures were identified from lateral radiographs using Genant's semi-quantitative assessment method. An association between bone mineral density (BMD) T-scores and vertebral fracture location was assessed. In an additional analysis, the association between a history of any traumatic injury and possible predictor variables was also explored. The median age of patients was 75 (IQR 67-80), and 84.2% of patients were female. A history of trauma was reported by 46.7% of patients. A vertebral fracture in the lower thoracolumbar spine (T11-L4) was associated with significantly higher femoral neck (p < 0.001), lumbar (p = 0.005), trochanteric (p = 0.002), intertrochanteric (p < 0.001), and total hip (p = 0.0006) BMD T-scores. The odds of having a femoral neck (OR 0.24, 95% CI 0.07-0.75, p = 0.01) or total hip (OR 0.19, 95% CI 0.06-0.65, p = 0.008) T-score less than -2.5 was also lower among patients with vertebral fractures in the lower thoracolumbar spine. A fracture in the upper thoracolumbar spine (T4-T10) decreased the odds of having a history of traumatic injury (OR 0.32, 95% CI 0.14-0.76, p = 0.01), while a non-vertebral fracture increased the odds of such an injury (OR 2.41, 95% CI 1.10-5.32, p = 0.03). Vertebral fractures in the lower thoracolumbar spine are associated with higher BMD T-scores. This should be studied further to understand possible correlations with patients' future fracture risk.

Prevention of Proximal Junctional Kyphosis: Are Polyaxial Pedicle Screws Superior to Monoaxial Pedicle Screws at the Upper Instrumented Vertebrae?

Evidence regarding whether the polyaxial pedicle screws at the upper instrumented vertebrae (UIV) are superior to monoaxial pedicle screws in prevention of proximal junctional kyphosis (PJK) is not clear. The aim of this study was therefore to explore the influence of different types of pedicle screws at UIV on the incidence of PJK. We reviewed retrospectively 242 patients surgically treated with instrumented segmental posterior spinal fusion at a minimum of 4 motion segments. Polyaxial pedicle screws were used at UIV in 125 patients (polyaxial group), and monoaxial pedicle screws were used at UIV in 117 patients (monoaxial group). According to the occurrence of PJK at final follow-up, patients in both the polyaxial and monoaxial groups were then divided into 2 subgroups: PJK and no proximal junctional kyphosis (NPJK). To investigate the risk factors of PJK, 2 categorized variables were analyzed statistically: 1) patient characteristics: age, sex, body mass index (BMI), bone mineral density (BMD), sagittal vertical axis (SVA), thoracic kyphosis, thoracolumbar junctional angle, lumbar lordosis (LL), pelvic incidence, pelvic tilt, and sacral slope. 2) Surgical variables: Changes of radiographic parameters include the SVA, thoracic kyphosis, thoracolumbar junctional, LL, pelvic incidence, pelvic tilt, sacral slope, pedicle-upper end plate angle, the number of instrumented levels, and the most proximal and distal levels of the instrumentation. PJK was developed in 26 of 117 patients (22.2%) in the monoaxial group and 30 of 125 patients (24.0%) in the polyaxial group. Until the final follow-up, there was no significant difference in the incidence of PJK (χ2= 0.107, P= 0.734) between the monoaxial and polyaxial groups. There was no significant difference in patient characteristics and surgical variables between the 2 groups, except the proximal junctional angle change (P= 0.031). In the monoaxial group, there were no significant differences in patient characteristics between the PJK and NPJK subgroups, except BMI (P= 0.042) and BMD (P= 0.037). There were no significant differences in change of radiographic parameters, except SVA change (P= 0.036), proximal junctional angle change (P= 0.029), LL change (P= 0.025), and lower instrumented vertebrae location (P= 0.036). Multivariate logistic regression analysis revealed that obesity, osteoporosis, lower instrumented vertebra at sacrum, and LL change >10 degrees were independently associated with PJK. In the polyaxial group, there were no significant differences in patient characteristics between the PJK and NPJK subgroups, except BMI (P= 0.032) and BMD (P= 0.040). There were no significant differences in change of radiographic parameters between the PJK and NPJK subgroups, except P-UP angle (P= 0.037) and lower instrumented vertebrae location (P= 0.017). Multivariate logistic regression analysis revealed that obesity, osteoporosis, and lower instrumented vertebra at sacrum were independently associated with PJK. Polyaxial pedicle screws at UIV is not superior to monoaxial pedicle screws in prevention of PJK. Obesity, osteoporosis, and lower instrumented vertebra at sacrum are risk factors for PJK in all the patients. Excessive LL reconstruction is the unique risk factor of PJK when monoaxial pedicle screws were used at UIV.

Correlation analysis of osteoporotic vertebral compression fractures and spinal sagittal imbalance.

To evaluate the correlation between osteoporotic vertebral compression fractures and spinal sagittal imbalance, in order to provide a reference for clinical treatment. From September 2013 to March 2015, 60elderly patients with old osteoporotic vertebral compression factures (observation group) and 60healthy elderly people (control group) were studied. Whole-spine anteroposterior and lateral view X‑ray photographs were taken from all participants, the number and location of fractured vertebrae were recorded, and sagittal parameters in both groups were compared. The observation group was divided into three subgroups according to the number of fractured vertebrae. The C7/sacrofemoral distance (SFD) ratio in the three subgroups was compared, and the correlation between the number of fractured vertebrae and the C7/SFD ratio was analyzed. The thoracic kyphotic angle in patients in the observation group was higher than in the control group (P< 0.05), the lumbar lordotic angle in patients in the observation group was lower than in the control group (P< 0.05), the absolute value of the T1 spinopelvic inclination angle in patients in the observation group was lower than in the control group (P< 0.05), and the C7/SFD ratio of patients in the observation group was higher than in the control group (P< 0.05). C7/SFD ratios of the subgroups differed from each other, and the number of fractured vertebrae and C7/SFD ratio were positively correlated. Osteoporotic vertebral compression fractures can change local spinal sagittal alignment, multiple vertebral compression fractures can cause spinal sagittal imbalance, and the number of fractured vertebrae and the degree of forward movement of the spine were positively correlated.

Registration of MRI to intraoperative radiographs for target localization in spinal interventions

Decision support to assist in target vertebra localization could provide a useful aid to safe and effective spine surgery. Previous solutions have shown 3D–2D registration of preoperative CT to intraoperative radiographs to reliably annotate vertebral labels for assistance during level localization. We present an algorithm (referred to as MR-LevelCheck) to perform 3D–2D registration based on a preoperative MRI to accommodate the increasingly common clinical scenario in which MRI is used instead of CT for preoperative planning.Straightforward adaptation of gradient/intensity-based methods appropriate to CT-to-radiograph registration is confounded by large mismatch and noncorrespondence in image intensity between MRI and radiographs. The proposed method overcomes such challenges with a simple vertebrae segmentation step using vertebra centroids as seed points (automatically defined within existing workflow). Forwards projections are computed using segmented MRI and registered to radiographs via gradient orientation (GO) similarity and the CMA-ES (covariance-matrix-adaptation evolutionary-strategy) optimizer. The method was tested in an IRB-approved study involving 10 patients undergoing cervical, thoracic, or lumbar spine surgery following preoperative MRI.The method successfully registered each preoperative MRI to intraoperative radiographs and maintained desirable properties of robustness against image content mismatch and large capture range. Robust registration performance was achieved with projection distance error (PDE) (median ± IQR) = 4.3 ± 2.6 mm (median ± IQR) and 0% failure rate. Segmentation accuracy for the continuous max-flow method yielded dice coefficient = 88.1 ± 5.2, accuracy = 90.6 ± 5.7, RMSE = 1.8 ± 0.6 mm, and contour affinity ratio (CAR) = 0.82 ± 0.08. Registration performance was found to be robust for segmentation methods exhibiting RMSE <3 mm and CAR >0.50.The MR-LevelCheck method provides a potentially valuable extension to a previously developed decision support tool for spine surgery target localization by extending its utility to preoperative MRI while maintaining characteristics of accuracy and robustness.

A patient-specific multibody kinematic model for representation of the scoliotic spine movement in frontal plane of the human body

Multibody models of scoliotic spine have shown great promise in planning scoliosis surgery by providing predictive information concerning the surgery outcome. To provide good predictive information, it is important that the kinematic models underlying the movement of the spine models would be personalized to give good estimates of the spine in different positions, which is lacking in the existing literature. This paper aims to develop a patient-specific multibody kinematic model of the scoliotic spine to represent its movement in frontal plane of the human body. The model is an open-chain mechanism comprising rigid links interconnected with rotary joints. To represent the movement, the mechanism lays on the spine curve and estimates the curve and the location and orientation of vertebrae. To personalize the mechanism for a patient, a minimization problem is defined to give the number of the links and their length by using X-rays of different spine positions. The feasibility and capabilities of our patient-specific model are tested by using the data from preoperative X-rays of five positions of 10 AIS (adolescent idiopathic scoliosis) patients; three of the X-rays are routine in scoliosis standard care. The mechanism is personalized to each patient by using the three routine X-rays, and it is used to estimate all the five positions. Root-mean-square-errors (RMSE) of the curve, location, and orientation are 2e–5 mm, 0.27 mm, and 0.25°, respectively. The small RMSEs imply that our kinematic model is capable of estimating the scoliotic spine positions in the frontal plane and thus of describing the scoliotic spine movement in this plane. Our personalization using X-rays of three spine positions helps to set better values for the kinematic parameters (such as the length of the links) for more accurate estimates of the spine in the frontal plane.