Understanding Respiratory Restrictions as a Function of the Scoliotic Spinal Curve in Thoracic Insufficiency Syndrome: A 4D Dynamic MR Imaging Study.

BACKGROUND: Over the past 100 years, many procedures have been developed for correcting restrictive thoracic deformities which cause thoracic insufficiency syndrome. However, none of them have been assessed by a robust metric incorporating thoracic dynamics. In this paper, we investigate the relationship between radiographic spinal curve and lung volumes derived from thoracic dynamic magnetic resonance imaging (dMRI). Our central hypothesis is that different anteroposterior major spinal curve types induce different restrictions on the left and right lungs and their dynamics. METHODS: Retrospectively, we included 25 consecutive patients with thoracic insufficiency syndrome (14 neuromuscular, 7 congenital, 4 other) who underwent vertical expandable prosthetic titanium rib surgery and received preimplantation and postimplantation thoracic dMRI for clinical care. We measured thoracic and lumbar major curves by the Cobb measurement method from anteroposterior radiographs and classified the curves as per Scoliosis Research Society (SRS)-defined curve types. From 4D dMRI images, we derived static volumes and tidal volumes of left and right lung, along with left and right chest wall and left and right diaphragm tidal volumes (excursions), and analyzed their association with curve type and major curve angles. RESULTS: Thoracic and lumbar major curve angles ranged from 0 to 136 and 0 to 116 degrees, respectively. A dramatic postoperative increase in chest wall and diaphragmatic excursion was seen qualitatively. All components of volume increased postoperatively by up to 533%, with a mean of 70%. As the major curve, main thoracic curve (MTC) was associated with higher tidal volumes (effect size range: 0.7 to 1.0) than thoracolumbar curve (TLC) in preoperative and postoperative situation. Neither MTC nor TLC showed any meaningful correlation between volumes and major curve angles preoperatively or postoperatively. Moderate correlations (0.65) were observed for specific conditions like volumes at end-inspiration or end-expiration. CONCLUSIONS: The relationships between component tidal volumes and the spinal curve type are complex and are beyond intuitive reasoning and guessing. TLC has a much greater influence on restricting chest wall and diaphragm tidal volumes than MTC. Major curve angles are not indicative of passive resting volumes or tidal volumes. LEVEL OF EVIDENCE: Level II-diagnostic.

Quantitative Dynamic Thoracic MRI: Application to Thoracic Insufficiency Syndrome in Pediatric Patients.

Background Available methods to quantify regional dynamic thoracic function in thoracic insufficiency syndrome (TIS) are limited. Purpose To evaluate the use of quantitative dynamic MRI to depict changes in regional dynamic thoracic function before and after surgical correction of TIS. Materials and Methods Images from free-breathing dynamic MRI in pediatric patients with TIS (July 2009-August 2015) were retrospectively evaluated before and after surgical correction by using vertical expandable prosthetic titanium rib (VEPTR). Eleven volumetric parameters were derived from lung, chest wall, and diaphragm segmentations, and parameter changes before versus after operation were correlated with changes in clinical parameters. Paired analysis from Student t test on MRI parameters and clinical parameters was performed to detect if changes (from preoperative to postoperative condition) were statistically significant. Results Left and right lung volumes at end inspiration and end expiration increased substantially after operation in pediatric patients with thoracic insufficiency syndrome, especially right lung volume with 22.9% and 26.3% volume increase at end expiration (P = .001) and end inspiration (P = .002), respectively. The average lung tidal volumes increased after operation for TIS; there was a 43.8% and 55.3% increase for left lung tidal volume and right lung tidal volume (P < .001 for both), respectively. However, clinical parameters did not show significant changes from pre- to posttreatment states. Thoracic and lumbar Cobb angle were poor predictors of MRI tidal volumes (chest wall, diaphragm, and left and right separately), but assisted ventilation rating and forced vital capacity showed moderate correlations with tidal volumes (chest wall, diaphragm, and left and right separately). Conclusion Vertical expandable prosthetic titanium rib operation was associated with postoperative increases in all components of tidal volume (left and right chest wall and diaphragm, and left and right lung tidal volumes) measured at MRI. Clinical parameters did not demonstrate improvements in postoperative tidal volumes. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Paltiel in this issue.

Unicortical Fixation is Sufficient for Surgical Treatment of Tibial Tubercle Avulsion Fractures in Children.

BACKGROUND: Although open reduction and internal fixation are recommended for displaced tibial tubercle avulsion fractures in young athletes, whether to use unicortical or bicortical fixation is debatable. The purpose of this study is to compare the outcomes of unicortical versus bicortical fixation in a series of pediatric tibial tubercle avulsion fractures. METHODS: We reviewed a consecutive series of patients with tibial tubercle fractures treated surgically at 2 level-1 pediatric tertiary care centers over a 12.5-year period. Patients aged below 18 years of age who received surgical treatment for displaced tibial tubercle fractures with postoperative follow-up were included. Fractures were classified using a modified Ogden classification system. The relative proportion of fracture types treated and incidence of complications were compared. RESULTS: The cohort included 90 fractures in 86 patients. There were 82 male and 4 female individuals; average age was 14.7 years (range, 9.0 to 18 y). In total, 87 of 90 were treated with open reduction and internal screw fixation [51 unicortical (59%), 13 mixed (15%), 23 bicortical (26%)] and 3 with percutaneous pinning. All patients were followed-up until healing and postoperative follow-up average was 8 months (range, 3 to 34 mo). There were no significant differences between the 2 groups with regard to patient age (P=0.22), patient weight (P=0.22), and activity clearance times [unicortical: 19.9 wk (range, 10.4 to 42.3 wk); bicortical: 17.7 wk (range, 12.1 to 32 wk); P=0.19]. The mixed cortical group was cleared at an average of 19.9 weeks (range, 10.6 to 29.1 wk). The relative proportion of fracture patterns treated differed negligibly between the unicortical and bicortical groups. Complications were noted in 9 of 90 procedures (10% rate); all subjects showed evidence of full radiographic healing at last follow-up. CONCLUSIONS: There was no difference in outcome whether unicortical or bicortical fixation was used. All patients exhibited full healing and return to activities with very low-complication rates. The results of this study suggest the adequacy of unicortical fixation for treating tibial tubercle fractures in young athletes. LEVEL OF EVIDENCE: Level III-retrospective comparative study.

Bi-planar spinal stereoradiography of adolescent idiopathic scoliosis: considerations in 3D alignment and functional balance.

PURPOSE: A prospective, cross-sectional study to determine the impact of arm position on the 3D spine and pelvic parameters and postural balance in adolescent idiopathic scoliosis. METHODS: A total number of 37 adolescent idiopathic scoliosis patients were enrolled prospectively. Three arm positions, (1) 45° shoulder flexion with knuckles on clavicles, (2) 90° shoulder and elbow flexion with forearms and palms on the front wall, and (3) arms hanging on either side, were instructed to the cohort. Bi-planar low dose X-ray images of the spine and pelvis were registered in a stereoradiography system in the first and second arm positions. A pressure mat recorded the position of the center of pressure in each arm position. Spinal and pelvic parameters were measured for the cohort. Statistical analysis was performed to determine the agreement between the spinal and pelvic parameters and standing balance in different arm positions. RESULTS: Thoracic kyphosis, sacral slope, sagittal vertical axis, T1 tilt, and spinal height were significantly different between the knuckles on clavicle and forearms on the wall positions p < 0.05. Significant differences were observed in the pressure distribution under the feet between the wall and freestanding positions. Bland-Altman plots determined disagreements between the first and second arm positions in clinical measurements and postural assessment of adolescent idiopathic scoliosis. CONCLUSION: The knuckles on clavicles position replicates the functional standing balance in AIS. Significant differences between the spinal and pelvic parameters suggest that the wall and clavicle arm positions should not be used interchangeably in AIS postural assessment. LEVEL OF EVIDENCE: Diagnostic level II.

Thoracic Curve Correction Ratio: An Objective Measure to Guide against Overcorrection of a Main Thoracic Curve in the Setting of a Structural Proximal Thoracic Curve.

Purpose: The correction of double thoracic (Lenke 2) curves has been associated with higher rates of postoperative shoulder imbalance that may compromise long-term outcomes following spinal deformity correction. A number of methods have been proposed to mitigate this risk, though no accepted standard measurement exists. The purpose of this study is to validate a novel quantitative method of determining the relative curve correction magnitude in double thoracic curves. Methods: Retrospective data from a multi-center database of patients undergoing surgical correction of left-proximal thoracic, right-main thoracic Lenke 2 curves were analyzed. A novel measurement tool, the Thoracic Curve Correction Ratio (TCCR), was applied for the purposes of validation against historical data. Results: A total of 305 patients with complete two-year follow-up data were included. The TCCR, or the ratio of postoperative percent correction of the thoracic curves divided by the ratio of the preoperative curve magnitudes, displayed a significant negative correlation (Pearson R = −0.66; p < 0.001) with T1 tilt at two years postoperatively. Conclusions: The TCCR could be added as an important factor in the preoperative planning process and intraoperative assessment in order to reduce postoperative T1 tilt. While T1 tilt remains an imperfect surrogate measure for clinical shoulder balance, it serves as one of many potential measures that the surgeon may evaluate quantitatively and radiographically.

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.].

Architectural Analysis on Dynamic MRI to Study Thoracic Insufficiency Syndrome.

The major hurdles currently preventing advance and innovation in thoracic insufficiency syndrome (TIS) assessment and treatment are the lack of standardizable objective diagnostic measurement techniques that describe the 3D thoraco-abdominal structures and the dynamics of respiration. Our goal is to develop, test, and evaluate a quantitative dynamic magnetic resonance imaging (QdMRI) methodology and a biomechanical understanding for deriving key quantitative parameters from free-tidal-breathing dMRI image data for describing the 3D structure and dynamics of the thoraco-abdominal organs of TIS patients. In this paper, we propose an idea of a shape sketch to codify and then quantify the overall thoracic architecture, which involves the selection of 3D landmark points and computation of 3D dynamic distances over a respiratory cycle. We perform two statistical analyses of distance sketches on 25 different TIS patients to try to understand the pathophysiological mechanisms in relation to spine deformity and to quantitatively evaluate improvements from pre-operative to post-operative states. This QdMRI methodology involves developing: (1) a 4D image construction method; (2) an algorithm for the 4D segmentation of thoraco-abdominal structures; and (3) a set of key quantitative parameters. We illustrate that the TIS dynamic distance analysis method produces results previously unknown and precisely describes the morphologic and dynamic alterations of the thorax in TIS. A set of 3D thoraco-abdominal distances and/or distance differences enables the precise estimation of key measures such as left & right differences, differences over tidal breathing, and differences from pre- to post-operative condition.

Quantitative dynamic MRI (QdMRI) Volumetric Analysis of Pediatric Patients with Thoracic Insufficiency Syndrome.

The lack of standardizable objective diagnostic measurement techniques is a major hurdle in the assessment and treatment of pediatric patients with thoracic insufficiency syndrome (TIS). The aim of this paper is to explore quantitative dynamic MRI (QdMRI) volumetric parameters derived from thoracic dMRI in pediatric patients with TIS and the relationships between dMRI parameters and clinical measurements. 25 TIS patients treated with vertical expandable prosthetic titanium rib (VEPTR) surgery are included in this retrospective study. Left and right lungs at end-inspiration and end-expiration are segmented from constructed 4D dMRI images. Lung volumes and excursion (or tidal) volumes of the left/right chest wall and hemi-diaphragms are computed. Commonly used clinical parameters include thoracic and lumbar Cobb angles and respiratory measurements from pulmonary function testing (PFT). 200 3D lungs in total (left & right, pre-operative & post-operative, end-inspiration & end-expiration) are segmented for analysis. Our analysis indicates that change of resting breathing rate (RR) following surgery is negatively correlated with that of QdMRI parameters. Chest wall tidal volumes and hemi-diaphragm tidal volumes increase significantly following surgery. Clinical parameter RR reduced after surgical treatment with P values around 0.06 but no significant differences were found on other clinical parameters. The significant increase in post-operative tidal volumes suggests a treatment-related improvement in lung capacity. The reduction of RR following surgery shows that breathing function is improved. The QdMRI parameters may offer an objective marker set for studying TIS, which is currently lacking.

Interactive iterative relative fuzzy connectedness lung segmentation on thoracic 4D dynamic MR images.

Lung delineation via dynamic 4D thoracic magnetic resonance imaging (MRI) is necessary for quantitative image analysis for studying pediatric respiratory diseases such as thoracic insufficiency syndrome (TIS). This task is very challenging because of the often-extreme malformations of the thorax in TIS, lack of signal from bone and connective tissues resulting in inadequate image quality, abnormal thoracic dynamics, and the inability of the patients to cooperate with the protocol needed to get good quality images. We propose an interactive fuzzy connectedness approach as a potential practical solution to this difficult problem. Manual segmentation is too labor intensive especially due to the 4D nature of the data and can lead to low repeatability of the segmentation results. Registration-based approaches are somewhat inefficient and may produce inaccurate results due to accumulated registration errors and inadequate boundary information. The proposed approach works in a manner resembling the Iterative Livewire tool but uses iterative relative fuzzy connectedness (IRFC) as the delineation engine. Seeds needed by IRFC are set manually and are propagated from slice-to-slice, decreasing the needed human labor, and then a fuzzy connectedness map is automatically calculated almost instantaneously. If the segmentation is acceptable, the user selects "next" slice. Otherwise, the seeds are refined and the process continues. Although human interaction is needed, an advantage of the method is the high level of efficient user-control on the process and non-necessity to refine the results. Dynamic MRI sequences from 5 pediatric TIS patients involving 39 3D spatial volumes are used to evaluate the proposed approach. The method is compared to two other IRFC strategies with a higher level of automation. The proposed method yields an overall true positive and false positive volume fraction of 0.91 and 0.03, respectively, and Hausdorff boundary distance of 2 mm.

Keeping the medical practice financially viable: a marketer's approach.

This paper explores a way that medical practices might develop a higher margin revenue source by offering a differentiated service that caters to patients who value more personalized service. Using SERVQUAL, German patients were surveyed to determine if there is a relationship between a desire for personalized service and a willingness to pay a premium for medical care. The results indicate that a greater desire for personalized care distinguishes those who pay a premium for medical care from those who do not. This suggests that medical practices can differentiate their service based on more personalized care and charge a higher fee for this service.