Auto-segmentation of thoraco-abdominal organs in pediatric dynamic MRI.

Purpose: Analysis of the abnormal motion of thoraco-abdominal organs in respiratory disorders such as the Thoracic Insufficiency Syndrome (TIS) and scoliosis such as adolescent idiopathic scoliosis (AIS) or early onset scoliosis (EOS) can lead to better surgical plans. We can use healthy subjects to find out the normal architecture and motion of a rib cage and associated organs and attempt to modify the patient's deformed anatomy to match to it. Dynamic magnetic resonance imaging (dMRI) is a practical and preferred imaging modality for capturing dynamic images of healthy pediatric subjects. In this paper, we propose an auto-segmentation set-up for the lungs, kidneys, liver, spleen, and thoraco-abdominal skin in these dMRI images which have their own challenges such as poor contrast, image non-standardness, and similarity in texture amongst gas, bone, and connective tissue at several inter-object interfaces. Methods: The segmentation set-up has been implemented in two steps: recognition and delineation using two deep neural network (DL) architectures (say DL-R and DL-D) for the recognition step and delineation step, respectively. The encoder-decoder framework in DL-D utilizes features at four different resolution levels to counter the challenges involved in the segmentation. We have evaluated on dMRI sagittal acquisitions of 189 (near-)normal subjects. The spatial resolution in all dMRI acquisitions is 1.46 mm in a sagittal slice and 6.00 mm between sagittal slices. We utilized images of 89 (10) subjects at end inspiration for training (validation). For testing we experimented with three scenarios: utilizing (1) the images of 90 (=189-89-10) different (remaining) subjects at end inspiration for testing, (2) the images of the aforementioned 90 subjects at end expiration for testing, and (3) the images of the aforesaid 99 (=89+10) subjects but at end expiration for testing. In some situations, we can take advantage of already available ground truth (GT) of a subject at a particular respiratory phase to automatically segment the object in the image of the same subject at a different respiratory phase and then refining the segmentation to create the final GT. We anticipate that this process of creating GT would require minimal post hoc correction. In this spirit, we conducted separate experiments where we assume to have the ground truth of the test subjects at end expiration for scenario (1), end inspiration for (2), and end inspiration for (3). Results: Amongst these three scenarios of testing, for the DL-R, we achieve a best average location error (LE) of about 1 voxel for the lungs, kidneys, and spleen and 1.5 voxels for the liver and the thoraco- abdominal skin. The standard deviation (SD) of LE is about 1 or 2 voxels. For the delineation approach, we achieve an average Dice coefficient (DC) of about 0.92 to 0.94 for the lungs, 0.82 for the kidneys, 0.90 for the liver, 0.81 for the spleen, and 0.93 for the thoraco-abdominal skin. The SD of DC is lower for the lungs, liver, and the thoraco-abdominal skin, and slightly higher for the spleen and kidneys. Conclusions: Motivated by applications in surgical planning for disorders such as TIS, AIS, and EOS, we have shown an auto-segmentation system for thoraco-abdominal organs in dMRI acquisitions. This proposed setup copes with the challenges posed by low resolution, motion blur, inadequate contrast, and image intensity non-standardness quite well. We are in the process of testing its effectiveness on TIS patient dMRI data.

Changes in research quality and surgical trends at the international congress on early-onset scoliosis.

PURPOSE: The founding of the International Congress for Early Onset Scoliosis (ICEOS) and first annual meeting in 2007 represented a significant milestone in advancing the care of patients with EOS. Due to the complexity and rarity of EOS, this annual conference is the premiere venue for physicians, researchers, and advanced practice providers to identify and understand the best treatments for children with EOS. This study examines the trend of various treatment modalities presented at ICEOS and the changes in research quality since its inception. METHODS: Podium presentations from the 2007 through 2021 ICEOS annual meetings were reviewed to determine the number of study patients, use of a study group, and key features of study design. Treatment strategies being evaluated were recorded and included non-operative treatments (casting/bracing), traditional growing rods (TGR), vertical expandable prosthetic titanium rib (VEPTR), Shilla growth guidance, magnetically controlled growing rods (MCGR), and vertebral body tethering (VBT). Linear regressions were performed to analyze changes in research topic and study group utilization. RESULTS: A total of 532 abstracts were reviewed. An average of 97.5 ± 81.3 patients were included per study with a significant increase from 42.3 ± 89.7 in 2007 to 337.6 ± 587.4 in 2021 (r2 = 0.632, p < 0.001). A total of 130 (24.4%) abstracts resulted from multicenter study groups with the proportion increasing significantly from 13.0% in 2007 to 36.4% in 2021 (p = 0.039, r2 = 0.289). The majority (96.2%) of study group-based projects were from either the Growing Spine Study Group (GSSG), Chest Wall and Spine Deformity Study Group (CWSDG), Children's Spine Study Group (CSSG), or the Pediatric Spine Study Group (PSSG). Additionally, a significant increase in studies utilizing patient-reported outcome measures (PROMs) was observed (r2 = 0.336, p = 0.023). Significant increases in the proportion of presentations discussing MCGR (r2 = 0.738, p < 0.001) and VBT (r2 = 0.294, p = 0.037) as surgical treatments were observed. CONCLUSION: The trends in EOS device implantation observed in registry studies align with the trends in research presented at ICEOS including the increased proportion of studies focusing on MCGR and VBT over the past decade. An attempt to increase the quality of research presented at ICEOS through multicenter study groups, increased patient recruitment, and utilization of PROMs has been seen since its inception. LEVEL OF EVIDENCE: V.

Assessment of Regional Functional Effects of Surgical Treatment in Thoracic Insufficiency Syndrome via Dynamic Magnetic Resonance Imaging.

BACKGROUND: Quantitative regional assessment of thoracic function would enable clinicians to better understand the regional effects of therapy and the degree of deviation from normality in patients with thoracic insufficiency syndrome (TIS). The purpose of this study was to determine the regional functional effects of surgical treatment in TIS via quantitative dynamic magnetic resonance imaging (MRI) in comparison with healthy children. METHODS: Volumetric parameters were derived via 129 dynamic MRI scans from 51 normal children (November 2017 to March 2019) and 39 patients with TIS (preoperatively and postoperatively, July 2009 to May 2018) for the left and right lungs, the left and right hemi-diaphragms, and the left and right hemi-chest walls during tidal breathing. Paired t testing was performed to compare the parameters from patients with TIS preoperatively and postoperatively. Mahalanobis distances between parameters of patients with TIS and age-matched normal children were assessed to evaluate the closeness of patient lung function to normality. Linear regression functions were utilized to estimate volume deviations of patients with TIS from normality, taking into account the growth of the subjects. RESULTS: The mean Mahalanobis distances for the right hemi-diaphragm tidal volume (RDtv) were -1.32 ± 1.04 preoperatively and -0.05 ± 1.11 postoperatively (p = 0.001). Similarly, the mean Mahalanobis distances for the right lung tidal volume (RLtv) were -1.12 ± 1.04 preoperatively and -0.10 ± 1.26 postoperatively (p = 0.01). The mean Mahalanobis distances for the ratio of bilateral hemi-diaphragm tidal volume to bilateral lung tidal volume (BDtv/BLtv) were -1.68 ± 1.21 preoperatively and -0.04 ± 1.10 postoperatively (p = 0.003). Mahalanobis distances decreased after treatment, suggesting reduced deviations from normality. Regression results showed that all volumes and tidal volumes significantly increased after treatment (p < 0.001), and the tidal volume increases were significantly greater than those expected from normal growth for RDtv, RLtv, BDtv, and BLtv (p < 0.05). CONCLUSIONS: Postoperative tidal volumes of bilateral lungs and bilateral hemi-diaphragms of patients with TIS came closer to those of normal children, indicating positive treatment effects from the surgical procedure. Quantitative dynamic MRI facilitates the assessment of regional effects of a surgical procedure to treat TIS. LEVEL OF EVIDENCE: Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Molecular diagnosis and novel genes and phenotypes in a pediatric thoracic insufficiency cohort.

Thoracic insufficiency syndromes are a genetically and phenotypically heterogeneous group of disorders characterized by congenital abnormalities or progressive deformation of the chest wall and/or vertebrae that result in restrictive lung disease and compromised respiratory capacity. We performed whole exome sequencing on a cohort of 42 children with thoracic insufficiency to elucidate the underlying molecular etiologies of syndromic and non-syndromic thoracic insufficiency and predict extra-skeletal manifestations and disease progression. Molecular diagnosis was established in 24/42 probands (57%), with 18/24 (75%) probands having definitive diagnoses as defined by laboratory and clinical criteria and 6/24 (25%) probands having strong candidate genes. Gene identified in cohort patients most commonly encoded components of the primary cilium, connective tissue, and extracellular matrix. A novel association between KIF7 and USP9X variants and thoracic insufficiency was identified. We report and expand the genetic and phenotypic spectrum of a cohort of children with thoracic insufficiency, reinforce the prevalence of extra-skeletal manifestations in thoracic insufficiency syndromes, and expand the phenotype of KIF7 and USP9X-related disease to include thoracic insufficiency.

QdMRI: A system for comprehensive analysis of thoracic dynamics via dynamic MRI.

Quantitative thoracic dynamic magnetic resonance imaging (QdMRI), a recently developed technique, provides a potential solution for evaluating treatment effects in thoracic insufficiency syndrome (TIS). In this paper, we integrate all related algorithms and modules during our work from the past 10 years on TIS into one system, named QdMRI, to address the following questions: (1) How to effectively acquire dynamic images? For many TIS patients, subjects are unable to cooperate with breathing instructions during image acquisition. Image acquisition can only be implemented under free-breathing conditions, and it is not feasible to use a surrogate device for tracing breathing signals. (2) How to assess the thoracic structures from the acquired image, such as lungs, left and right, separately? (3) How to depict the dynamics of thoracic structures due to respiration motion? (4) How to use the structural and functional information for the quantitative evaluation of surgical TIS treatment and for the design of the surgery plan? The QdMRI system includes 4 major modules: dynamic MRI (dMRI) acquisition, 4D image construction, image segmentation (from 4D image), and visualization of segmentation results, dynamic measurements, and comparisons of measurements from TIS patients with those from normal children. Scanning/image acquisition time for one subject is ~20 minutes, 4D image construction time is ~5 minutes, image segmentation of lungs via deep learning is 70 seconds for all time points (with the average DICE 0.96 in healthy children), and measurement computation time is 2 seconds.

Risk of ventriculoperitoneal shunt malfunction in operatively treated early onset spinal deformity.

PURPOSE: Ventriculoperitoneal (VP) shunt placement is a common neurosurgical procedure performed in patients with early onset scoliosis (EOS). To provide insight into the risks of spine lengthening operations, we investigate the rate of VP shunt complications in patients with EOS undergoing spinal deformity correction interventions. METHODS: A retrospective review was performed of all patients with EOS at a single institution undergoing spinal deformity correction procedures from 2007 to 2018. Patients having undergone VP shunt implantation prior to deformity correction were included. A minimum of 2-year follow-up was required for inclusion. Clinical records and imaging studies were reviewed. RESULTS: Nineteen patients with VP shunts underwent Vertical Expandable Prosthetic Titanium Rib (VEPTR) implantation for treatment of early onset spinal deformity. The mean age at shunt placement and spine instrumentation surgery was 13.7 months (1 day to 13 years) and 6.1 years (0.5-15.1) respectively. The diagnoses associated with shunt implantation were: 12 spina bifida, 3 structural defects or obstructions, 2 intraventricular hemorrhage, 1 cerebral palsy, and 1 campomelic dwarfism. During the first 2 years following rib-based insertion, there was a mean of 2.5 expansion/revision procedures (0-5) with no shunt-related complications. The mean length of follow-up in this series was 7.0 years (2.6-13.2). A total of three (16%) patients required shunt revision following their rib-based device insertion, two patients with proximal shunt malfunctions and one with a mid-catheter breakage, at 2.4, 2.6, and 5.6 years, respectively, after rod implantation (Fig. 2). Each of these shunt revisions occurred more than 50 days following an expansion procedure (1.9, 2.9, and 5.7 months, respectively). CONCLUSION: Growing instrumentation procedures in EOS are associated with low risk for post-operative shunt complications in patients with ventriculoperitoneal shunts. There were no shunt revision procedures performed in the first 2 years following rib-based device insertion. Sixteen percent of patients went on to require a shunt revision at some point during their follow-up, which is comparable to the baseline rate of shunt revision in non-EOS patients. LEVEL OF EVIDENCE: IV, Case series.

Weight gain and gastrostomy tube safety during serial body casting for early onset scoliosis.

PURPOSE: Serial casting has been shown to improve curve deformity for patients with early-onset scoliosis (EOS). However, despite prior literature demonstrating the importance of weight and nutrition in EOS patients, there is limited information regarding complications and weight gain ability for children undergoing serial casting. Additionally, parents of patients undergoing serial casting often have concerns regarding weight gain and patient comfort, which tend to be amplified in patients with gastrostomy tubes (g-tubes). We aim to understand changes in weight, g-tube complications, and cast-related complications in patients being treated with serial casting. METHODS: A single center retrospective review of all EOS patients less than 6 years old treated with serial casting was performed. Patient weight out of cast throughout their treatment was converted to a percentile based on CDC growth charts. Patients with documented calls regarding cast concerns, complications requiring cast removal, or g-tube procedures were recorded. RESULTS: A total of 32 patients treated with serial casting were included with four having g tubes. Overall, the average weight percentile increased from pre-casting to post-casting (27-38%, p < 0.001) with 21 patients showing an increase. Of the 22 patients with a starting weight below the 25th percentile, 14 (64%) demonstrated an increase. Patients with g tubes increased an average of 4.2 kg during casting compared to 3.0 kg in patients without g tubes (p = 0.588). 18 parents registered a cast concern during the treatment and 5 patients required at least one early cast removal. No difference in cast concerns (p = 0.597) or cast removals (p = 0.488) was observed when comparing patients with g tubes to those without. There were no instances of g-tube dysfunction during casting. CONCLUSION: While the average weight percentile for patients initiating serial casting is below average, the majority increased their weight percentile during treatment. Patients with and patients without g tubes were able to maintain or gain weight during casting treatment. While it was common for parents to contact providers with cast concerns, patients with g tubes did not appear to have a greater risk of cast or g tube-related complications. LEVEL OF EVIDENCE: Level IV.

Surgical and Nonsurgical Factors Associated with Salvaging Exposed Vertical Expandable Prosthetic Titanium Rib Hardware.

BACKGROUND: Vertical expandable prosthetic titanium rib (VEPTR) devices were designed to treat childhood scoliosis and thoracic insufficiency syndrome. Although they have drastically reduced patient mortality, they present a profound subcutaneous hardware burden. The authors examined the surgical and nonsurgical factors associated with salvage of VEPTR hardware exposures. METHODS: Between 2014 and 2020, a prospective institutional database was queried for patients with VEPTR hardware complications who required soft-tissue reconstruction. Hardware salvage was considered successful if reconstruction allowed the hardware to be retained until the next VEPTR expansion. RESULTS: Fifty-eight patients required VEPTR hardware salvage. Hardware complications were successfully salvaged in 62.1 percent of patients at 60.0 percent of operative sites. Neuromuscular scoliosis (p = 0.041) and nonambulatory status (p = 0.018) were factors associated with VEPTR hardware salvage failure, whereas congenital scoliosis was associated with successful hardware salvage (p = 0.012) and preventing need for immediate hardware removal (p = 0.049). Exposed hardware, as compared to threatened exposure, was more likely to require immediate removal (p = 0.045) and result in unsuccessful hardware salvage (p = 0.015). CONCLUSIONS: Local and regional muscle flaps were able to prevent VEPTR hardware removal in the majority of patients, even in the setting of infection, immobility, incontinence, and multiple systemic comorbidities. Patients with neuromuscular scoliosis and nonambulatory status were at increased risk for failure, whereas those with incontinence and low body mass index trended toward increased risk of failure. Threatened exposure was associated with higher rates of salvage than exposed hardware, and thus earlier referral to plastic surgeons for soft-tissue salvage may be advised. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, III.

Regional diaphragm motion analysis via dynamic MRI.

Breathing-related movement analysis is important in the study of many disease processes. The analysis of diaphragmatic motion via thoracic imaging in particular is important in a variety of disorders. Compared to computed tomography (CT) and fluoroscopy, dynamic magnetic resonance imaging (dMRI) has several advantages, such as better soft tissue contrast, no ionizing radiation, and greater flexibility in selecting scanning planes. In this paper, we propose a novel method for full diaphragmatic motion analysis via free-breathing dMRI. Firstly, after 4D dMRI image construction in a cohort of 51 normal children, we manually delineated the diaphragm on sagittal plane dMRI images at end-inspiration and end-expiration. Then, 25 points were selected uniformly and homologously on each hemi-diaphragm surface. Based on the inferior-superior displacements of these 25 points between end-expiration (EE) and end-inspiration (EI) time points, we obtained their velocities. We then summarized 13 parameters from these velocities for each hemi-diaphragm to provide a quantitative regional analysis of diaphragmatic motion. We observed that the regional velocities of the right hemi-diaphragm were almost always statistically significantly greater than those of the left hemi-diaphragm in homologous locations. There was a significant difference for sagittal curvatures but not for coronal curvatures between the two hemi-diaphragms. Using this methodology, future larger scale prospective studies may be considered to confirm our findings in the normal state and to quantitatively assess regional diaphragmatic dysfunction when various disease conditions are present.

Automatic lung segmentation in dynamic thoracic MRI using two-stage deep convolutional neural networks.

Lung segmentation in dynamic thoracic magnetic resonance imaging (dMRI) is a critical step for quantitative analysis of thoracic structure and function in patients with respiratory disorders. Some semi-automatic and automatic lung segmentation methods based on traditional image processing models have been proposed mainly for CT with good performance. However, the low efficiency and robustness of these methods and inapplicability to dMRI make them unsuitable to segment the large numbers of dMRI datasets. In this paper, we present a novel automatic lung segmentation approach for dMRI based on two-stage convolutional neural networks (CNNs). In the first stage, we utilize the modified min-max normalization method to pre-process MRI for increasing the contrast between the lung and surrounding tissue and propose a corner-points and CNN based region of interest (ROI) detection strategy to extract the lung ROI from sagittal dMRI slices, which can reduce the negative influence of tissues located far away from the lung. In the second stage, we input the adjacent ROIs of target slices into the modified 2D U-Net to segment the lung tissue. The qualitative and quantitative results demonstrate that our approach achieves high accuracy and stability in terms of lung segmentation for dMRI.

OFx: A method of 4D image construction from free-breathing non-gated MRI slice acquisitions of the thorax via optical flux.

PURPOSE: Since real-time 4D dynamic magnetic resonance imaging (dMRI) methods with adequate spatial and temporal resolution for imaging the pediatric thorax are currently not available, free-breathing slice acquisitions followed by appropriate 4D construction methods are currently employed. Self-gating methods, which extract breathing signals only from image information without any external gating technology, have much potential for this purpose, such as for use in studying pediatric thoracic insufficiency syndrome (TIS). Patients with TIS frequently suffer from extreme malformations of the chest wall, diaphragm, and spine, leading to breathing that is very complex, including deep or shallow respiratory cycles. Existing 4D construction methods cannot perform satisfactorily in this scenario, and most are not fully automatic, requiring manual interactive operations. In this paper, we propose a novel fully automatic 4D image construction method based on an image-derived concept called flux to address these challenges. METHODS: We utilized 25 dMRI data sets from 25 pediatric subjects with no known thoracic anomalies and 58 dMRI data sets from 29 patients with TIS where each patient had a dMRI scan before and after surgery. A time sequence of 80 slices are acquired at each sagittal location continuously at a rate of ~480 ms per slice under free-breathing conditions, with 30-40 sagittal locations across the chest for each subject depending on the thoracic size. In our approach, we first extract the breathing signal for each sagittal location based on the flux of the optical flow vector field of the body region from the image time series. Here, for each time point of respiratory phase, the net flux of the body region can be regarded as the flux going into or out of the body region, which we term Optical Flux (OFx). OFx provides a very robust representation of the real breathing motion of the thorax. OFx allows us to perform a full analysis of all respiratory cycles, extract only normal cycles in a robust manner, and map all extracted normal cycles on to one cosine respiration model for each sagittal location. Subsequently, we re-sample one normal cycle from the respiration model for each location independently. The normal cycle models associated with the different sagittal locations are finally composited to form the final constructed 4D image. RESULTS: We employ several metrics to evaluate the quality of the 4D construction results: Eie - error in locating time instants corresponding to end inspiration and end expiration; Eto - deviation from correct temporal order in each detected normal cycle; Ess - deviation in spatial smoothness; and Esc - deviation from spatial continuity as scored by a reader. The means and standard deviations of these metrics for normal subjects and TIS patients are found to be, respectively: Eie: 0.25 ± 0.05 and 0.38 ± 0.16 in units of time instance (ideal value = 0); Eto: 2.7% ± 2.3% and 1.8% ± 2% (ideal value = 0%); Ess: 0.5 ± 0.17 and 0.54 ± 0.25 in pixel units (ideal value = 0); Esc: 4.6 ± 0.48 and 4.56 ± 0.98 (score range: best = 5, worst = 1). The results show that the OFx method achieves excellent spatial and temporal continuity and its yield was 100% meaning that it successfully performed 4D construction on every data set tested. Compared to a recently published method, OFx is fully automatic requiring about 5 min of computational time per study starting from acquired dMRI scans. The method achieves high temporal and spatial continuity even on complex TIS data sets that include many abnormal respiratory cycles. CONCLUSIONS: A new 4D dMRI construction method based on the concept of optical flux is presented which is fully automatic and very robust in deriving respiratory signals purely from dynamic image sequences even when presented with complex breathing patterns due to severe disease conditions like TIS. Evaluations show that its accuracy is comparable to the variations found in manual annotations. An important characteristic of the method is that it is independent of the number of sagittal locations used in the construction process, which suggests that it is applicable to imaging techniques where data are acquired at only a few sagittal locations instead of the full width of the thorax. The method is not tied to any specific imaging modality, as demonstrated in this paper on not just dMRI but dynamic computed tomography (CT) as well.

Rib-based Distraction Device Implantation Before Age 3 Associated With Higher Unplanned Rate of Return to the Operating Room.

BACKGROUND: Surgical treatment of early-onset scoliosis (EOS) with rib-based implants such as the vertical expandable prosthetic titanium rib (VEPTR) is associated with a high rate of complications including surgical site infection, skin breakdown, and implant migration. Many of these complications warrant the need for unplanned reoperations, increasing the burden on an already vulnerable patient population, and introducing the further risk of infection. To provide insight into the risks of early intervention, we investigate the relationship between initial device implantation before the age of 3 and the rate of unplanned reoperation. METHODS: A retrospective review was performed of all patients at a single institution who had undergone VEPTR insertion for EOS with at least a 2-year follow-up from 2007 to 2016. Patients were stratified into the case-cohort (0 to 2 y of age) or the comparison cohort (3 to 10 y of age) based on age at the time of device implantation. Multivariate regression accounting for age and scoliosis etiology was performed to identify factors predictive of unplanned reoperation. RESULTS: A total of 137 of 185 patients treated with VEPTR were identified with 76 (56%) undergoing at least 1 unplanned reoperation during the study time period. There were 68 and 69 patients in the age 0- to 2-year and 3- to 10-year cohorts, respectively. Patients aged 0 to 2 years underwent a higher number of total procedures compared with those aged 3 to 10 (13.1±6.5 vs. 10.6±4.8, P=0.032). A significant difference was found in the rate of unplanned reoperation between the 2 cohorts with 44 (65%) patients aged 0 to 2 and 32 (46%) patients aged 3 to 10 undergoing at least 1 unplanned reoperation (P=0.031). Binary logistic multivariate regression accounting for age and scoliosis etiology demonstrated that patients aged 0 to 2 had a significantly greater odds of undergoing an unplanned reoperation (odds ratio=3.050; 95% confidence interval: 1.285-7.241; P=0.011) compared with patients aged 3 to 10 years. CONCLUSION: Overall, EOS patients aged 0 to 2 at initial VEPTR implantation are up to 3 times higher risk of undergoing an unplanned reoperation compared with those aged 3 to 10. LEVEL OF EVIDENCE: Level III.

Concomitant procedures with early-onset scoliosis rib-based surgeries.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: To determine if additional procedures can be safely performed under the same anesthesia as early-onset scoliosis (EOS) rib-based surgeries. EOS patients with rib-based implants often require repeated invasive surgery to treat their spinal deformity, with associated risks of cognitive development impairment from multiple anesthetic exposures. Many of these patients have comorbidities that require additional procedures, possibly increasing the risk of adverse outcomes. METHODS: We performed a retrospective review of EOS patients treated with rib-based implants with at least 2 year follow up at a single institution. Patients were divided into two cohorts: Group A included patients who never had another procedure in conjunction with a rib-based implant insertion, expansion, and/or revision surgery throughout their treatment and Group B included patients who had at least one other procedure operate in conjunction with rib-based implant surgery. Univariate analysis was performed to compare demographics, surgical parameters, and incidence of complication between the two groups. A subanalysis of patients who experienced an infection requiring surgery in Group A and Group B was also performed to further analyze the impact of concomitant procedures. RESULTS: 147 EOS patients underwent rib-based growing instrumentation at our institution. 98 patients (Group A) did not have another procedure occur under the same anesthetic as a rib-based implant surgery and 49 patients (Group B) had another procedure performed in conjunction with a rib-based implant surgery. Gender, etiology, BMI, length of follow up and number of rib-based implant procedures were similar between both cohorts (p = 0.91, 0.24, 0.28, 0.91, 0.77, respectively). The total surgical and anesthesia time was significantly longer in the patients undergoing concomitant procedures (Group B) (p < 0.0001, p < 0.0001, respectively). Among the patients in Group B, Otolaryngology was the most common department adding surgical care, followed by non-spine orthopaedics and general surgery. Mircrolaryngoscopy and bronchoscopy were performed most often (24 procedures), followed by cerumen removal under anesthesia (22 procedures), ear tube insertion (19 procedures) and bronchoscopy (19 procedures). Infection requiring irrigation and debridement was the most common complication found in both cohorts. Although Group B had a significantly lower number of patients who experienced complications (p = 0.002), the complication rate per procedure was 14% in Group A and 16% in Group B. When performing a subanalysis on patients who experienced an infection requiring irrigation and debridement surgery among Group A (47 patients) and Group B (8 patients), gender, etiology, BMI, length of follow up, and number of rib-based implant procedures were similar (p = 0.71, 0.26, 0.06, 0.69, 0.84 and, respectively). The total surgical and anesthesia time were similar (p = 0.11 and 0.13, respectively). In addition, the number of irrigation and debridement surgeries needed to treat each infection even was similar between the two groups (p = 0.59). CONCLUSION: There was no difference in complication rate per procedure when other services operate in conjunction with rib-based implant surgery. LEVEL OF EVIDENCE: III.

Estimation of the dynamic volume of each lung via rapid limited-slice dynamic MRI.

Dynamic lung volumetric parameters are useful for clinical assessment of many thoracic disorders, given that respiration is a dynamic process. Estimation of such parameters based on imaging and analysis is an important goal to achieve if implementation in routine clinical practice is to become a reality. Compared to CT, dynamic thoracic MRI has several advantages including better soft tissue contrast, lack of ionizing radiation, and flexibility in selecting scanning planes. 4D dynamic MRI seems to be the best choice for some clinical applications, notwithstanding the major limitation of a long image acquisition time (~45 minutes). Therefore, approaches to acquire images and estimate volumetric parameters rapidly is highly desirable in dynamic MRI-based clinical applications. In this paper, we present a technique for estimating lung volumetric parameters from limited-slices dynamic thoracic MRI, greatly reducing the number of slices to be scanned and therefore also the time required for image acquisition. We demonstrate a relative RMS error of predicted lung volumes of less than 5% by utilizing only 5 sagittal MRI slices through each lung compared to the current full scan involving about 20 slices per lung. As such, this approach can lead to time-saving during scan acquisition and therefore increased patient comfort and convenience for practical real-world clinical applications. This may potentially also improve image quality and usability due to the reduction of patient motion, abnormal breathing patterns, etc. ensuing from improved patient comfort and scan duration.

Lung parenchymal characterization via thoracic dynamic MRI in normal children and pediatric patients with TIS.

Quantitative thoracic dynamic magnetic resonance imaging (QdMRI), a recently developed technique, provides a potential solution for evaluating treatment effects in thoracic insufficiency syndrome (TIS). In this paper, we demonstrate how lung parenchymal characteristics can be assessed via intensity properties in lung dynamic MRI, a modality suitable for use in pediatric patients. The QdMRI-based approach includes dynamic MR image acquisition, 4D image construction, image pre-processing with non-uniformity correction and intensity standardization, and lung segmentation from the 4D constructed image via a deep learning approach, as well as extraction of image parenchymal intensity properties from the segmented lungs and statistical comparisons among different clinical scenarios. We include 22 dMRI scans from 11 TIS patients (each with both pre-operative and post-operative scans) and 23 dMRI scans from healthy children. Two-sided paired t-testing is performed to compare lung intensity properties between end of expiration (EE) and end of inspiration (EI) within TIS patients (pre-operative and post-operative, separately) and normal children. We also compare the lung intensity properties at EE and EI among pre-operative TIS patients, post-operative TIS patients, and normal children. Experimental results show that lung (T2) intensity at EI is significantly lower than that at EE and lung intensity of post-operative TIS patients is significantly lower than that in pre-operative TIS patients and closer to that of normal children than to that of pre-operative TIS patients, indicating improvement in lung aeration. To our knowledge, this is the first study to provide a quantitative dynamic functional method to analyze lung parenchyma during tidal breathing on dynamic MRI in both healthy children and pediatric patients with TIS.

Patient-Reported Outcomes Are Equivalent in Patients Who Receive Vertebral Body Tethering Versus Posterior Spinal Fusion in Adolescent Idiopathic Scoliosis.

Anterior vertebral body tethering (AVBT), or spinal growth tethering, is an emerging technology that recently received Food and Drug Administration (FDA) approval through a humanitarian device exemption designation to treat idiopathic scoliosis patients with remaining growth. This study compared patients who underwent AVBT with those treated with standard-of-care posterior spinal fusion (PSF) to determine inherent differences in patients and families who seek cutting-edge treatments. The authors reviewed 62 PSF patients from a multicenter registry and 20 AVBT patients from an FDA-approved investigational clinical trial. The authors examined demographics, preoperative clinical and radiographic variables, and health-related quality of life (HRQOL). All included patients preoperatively were classified as Lenke type 1 or 2 with a thoracic curve of 35° to 60°, a lumbar curve less than 35°, and a skeletal maturity score of Risser sign 0 or Sanders bone age of 4 or less. Idiopathic scoliosis patients treated with surgical intervention were primarily White females who were 12 years old. No differences in demographics, clinical variables, and radiographic measures were detected between the PSF and AVBT cohorts. The AVBT group showed more thoracic flexibility on bending radiographs, correcting on average 59% compared with 43% for PSF patients (P=.005). Patients had similar HRQOL total scores and scores across each of the 5 domains of the Scoliosis Research Society Questionnaire Version 22. The percentage of patients scoring below 4.0 within each domain was comparable between cohorts. Scoliosis patients who underwent vertebral tethering at a level of deformity magnitude and maturity similar to those who underwent posterior fusion did not differ at baseline regarding demographics, clinical variables, and HRQOL. [Orthopedics. 2021;44(1):24-28.].

Thoracic Quantitative Dynamic MRI to Understand Developmental Changes in Normal Ventilatory Dynamics.

BACKGROUND: A database of normative quantitative measures of regional thoracic ventilatory dynamics, which is essential to understanding better thoracic growth and function in children, does not exist. RESEARCH QUESTION: How to quantify changes in the components of ventilatory pump dynamics during childhood via thoracic quantitative dynamic MRI (QdMRI)? STUDY DESIGN AND METHODS: Volumetric parameters were derived via 51 dynamic MRI scans for left and right lungs, hemidiaphragms, and hemichest walls during tidal breathing. Volume-based symmetry and functional coefficients were defined to compare left and right sides and to compare contributions of the hemidiaphragms and hemichest walls with tidal volumes (TVs). Statistical analyses were performed to compare volume components among four age-based groups. RESULTS: Right thoracic components were significantly larger than left thoracic components, with average ratios of 1.56 (95% CI, 1.41-1.70) for lung TV, 1.81 (95% CI, 1.60-2.03) for hemidiaphragm excursion TV, and 1.34 (95% CI, 1.21-1.47) for hemichest wall excursion TV. Right and left lung volumes at end-expiration showed, respectively, a 44% and 48% increase from group 2 (8 ≤ age < 10) to group 3 (10 ≤ age < 12). These numbers from group 3 to group 4 (12 ≤ age ≤ 14) were 24% and 28%, respectively. Right and left hemichest wall TVs exhibited, respectively, 48% and 45% increases from group 3 to group 4. INTERPRETATION: Normal right and left ventilatory volume components have considerable asymmetry in morphologic features and dynamics and change with age. Chest wall and diaphragm contributions vary in a likewise manner. Thoracic QdMRI can provide quantitative data to characterize the regional function and growth of the thorax as it relates to ventilation.

Automatic labeling of respiratory phases and detection of abnormal respiratory signals in free-breathing thoracic dynamic MR image acquisitions based on deep learning.

4D thoracic images constructed from free-breathing 2D slice acquisitions based on dynamic magnetic resonance imaging (dMRI) provide clinicians the capability of examining the dynamic function of the left and right lungs, left and right hemi-diaphragms, and left and right chest wall separately for thoracic insufficiency syndrome (TIS) treatment [1]. There are two shortcomings of the existing 4D construction methods [2]: a) the respiratory phase corresponding to end expiration (EE) and end inspiration (EI) need to be manually identified in the dMRI sequence; b) abnormal breathing signals due to non-tidal breathing cannot be detected automatically which affects the construction process. Since the typical 2D dynamic MRI acquisition contains ~3000 slices per patient, handling these tasks manually is very labor intensive. In this study, we propose a deep-learning-based framework for addressing both problems via convolutional neural networks (CNNs) [3] and Long Short-Term Memory (LSTM) [4] models. A CNN is used to extract the motion characteristics from the respiratory dMRI sequences to automatically identify contiguous sequences of slices representing exhalation and inhalation processes. EE and EI annotations are subsequently completed by comparing the changes in the direction of motion of the diaphragm. A LSTM network is used for detecting abnormal respiratory signals by exploiting the non-uniform motion feature sequence of abnormal breathing motions. Experimental results show the mean error of labeling EE and EI is ~0.3 dMRI time point unit (much less than one time point). The accuracy of abnormal cycle detection reaches 80.0%. The proposed approach achieves results highly comparable to manual labeling in accuracy but with close to full automation of the whole process. The framework proposed here can be readily adapted to other modalities and dynamic imaging applications.

Lengthening Less Than 7 Months Leads to Greater Spinal Height Gain With Rib-based Distraction.

BACKGROUND: Severe early-onset scoliosis (EOS) has been associated with a multitude of comorbidities, chief among them being deficient thoracic spine growth and pulmonary complications. EOS management with rib-based instrumentation involves repeated lengthening. Despite expansion practice patterns, there is limited literature and no evidence-based guidelines for optimal expansion intervals. Our study evaluates clinical outcomes in relation to lengthening intervals with the aim of optimizing the timing of surgical expansion in EOS patients. METHODS: A single-institution retrospective review of 60 EOS patients treated with rib-based growth instrumentation with a minimum of 3-year follow-up and 3 expansion/revision surgeries. Patients were separated into 2 expansion cohorts: (1) more frequent lengthening [MFL group (≤7 mo)] and (2) less frequent lengthening [LFL group (>7 mo)]. Demographic information and clinical factors were recorded. Univariate and bivariate analyses were performed. RESULTS: Both the MFL group (35 patients) and LFL group (25 patients) were similar in sex distribution, diagnosis, preoperative parameters of interest, and treatment duration. The mean follow-up was 6.0 years. There was an increase in postoperative T1-S1 spine height gained in the MFL group (P=0.006) as well as a higher percent expected spine growth based on normative values (P=0.03) when compared with the LFL group. The MFL group had more expansion/revision surgeries (P=0.003) but no increase in the number of complications (P=0.86). CONCLUSIONS: More frequent lengthenings were associated with statistically significant overall spinal height gain and percent expected growth without a significant increase in complication rates. It was shown that change in major curve and space available for the lungs was not associated with the lengthening intervals. LEVEL OF EVIDENCE: Level III-a comparative retrospective study.

Prophylactic Decompression for Cervical Stenosis in Jeune Syndrome: Report From a Single Institution.

STUDY DESIGN: This is a level IV retrospective descriptive study at a single institution. OBJECTIVE: The objective of the study was to determine the preoperative signs or symptoms prompting cervicomedullary imaging in Jeune syndrome. SUMMARY OF BACKGROUND DATA: Jeune syndrome is a rare autosomal recessive disorder that results in pulmonary compromise from abnormal development of the thorax. Multiple medical comorbidities complicate timely diagnosis of cervicomedullary stenosis, which neurologically jeopardizes this patient population with regards to improper cervical manipulation. Currently, explicit screening of the cervicomedullary junction is not advocated in national guidelines. METHODS: The User Reporting Workbench and Center for Thoracic Insufficiency Syndrome (CTIS) Safety Registry was queried for patients with Jeune syndrome under the age of 18 with cervicomedullary stenosis with or without suboccipital craniectomy/craniotomy evaluated at the authors' institution from January 1, 2007 to August 21, 2018. The primary outcome was the clinical reason for cervicomedullary screening. Secondary outcomes were: age at time of surgery, preoperative myelopathy (spasticity, urinary retention), hydrocephalus, postoperative deficits (respiratory, motor, swallowing difficulty), and need for cervical fusion. RESULTS: Of 32 patients with Jeune syndrome, four (12.5%) had cervicomedullary stenosis requiring decompression. The average age at surgery was 5.25 months (2-9 mo). Two patients underwent imaging due to desaturation events while the other two patients were diagnosed with cervical stenosis as an incidental finding. No patients exhibited clinical myelopathy. Two patients had baseline preoperative swallowing difficulties. None of the patients postoperatively required cervical fusions, nor did they exhibit respiratory deficits, motor deficits, or worsening swallowing difficulties. CONCLUSION: Jeune patients should be routinely screened for cervicomedullary stenosis and undergo subsequent prophylactic decompression to minimize or eliminate the development of irreversible neurologic compromise. LEVEL OF EVIDENCE: 4.