A Stepwise Approach to Analyzing Musculoskeletal Imaging Data With Artificial Intelligence

The digitization of medical records and expanding electronic health records has created an era of "Big Data" with an abundance of available information ranging from clinical notes to imaging studies. In the field of rheumatology, medical imaging is used to guide both diagnosis and treatment of a wide variety of rheumatic conditions. Although there is an abundance of data to analyze, traditional methods of image analysis are human resource intensive. Fortunately, the growth of artificial intelligence (AI) may be a solution to handle large datasets. In particular, computer vision is a field within AI that analyzes images and extracts information. Computer vision has impressive capabilities and can be applied to rheumatologic conditions, necessitating a need to understand how computer vision works. In this article, we provide an overview of AI in rheumatology and conclude with a five step process to plan and conduct research in the field of computer vision. The five steps include (1) project definition, (2) data handling, (3) model development, (4) performance evaluation, and (5) deployment into clinical care.

Institutional Variability in Anesthesia Time for Mehta Casting in Early-Onset Scoliosis (EOS)

PURPOSE

Mehta casting is a potentially curative intervention for early-onset scoliosis (EOS) that typically requires multiple anesthetics. The Food and Drug Administration (FDA) reported that >3 hours of anesthesia under the age of 3 years old may alter brain development; however, no standard exists for the duration of anesthesia during casting. The purpose of this study is to quantify the variability in anesthesia during Mehta casting. We hypothesize that significant institutional variability exists and may be attributed to modifiable factors.

METHODS

An EOS registry was used to identify patients who underwent at least one Mehta casting procedure. Anesthesia exposure was quantified, and site variability was assessed by patient characteristics, cast placement, procedure type, and equipment used.

RESULTS

Our cohort consisted of 208 patients from 5 institutions (age 2.6±1.4 y). There were 1097 Mehta casting procedures, with 5.4±3.6 castings per patient. Of these patients, 106 (51%) were female, with an average age of 2.11±1.29 years old at the time casting was initiated. Patient etiologies included 154 idiopathic (74.0%), 22 syndromic (10.6%), 18 congenital (8.7%), 11 neuromuscular (5.3%), and 3 unknown (1.4%). Anesthesia time was 69±31 minutes and varied significantly between sites (59±14 to 117±46 min; P <0.001). Cumulative anesthesia time for patients under 3 years was 320±197 minutes with 120/161 (74.5%) patients exceeding 3 hours. Anesthesia time was lower after the FDA warning in 2016 compared with pre-2016 (71±30 vs. 66±32, P =0.008).

CONCLUSIONS

Patients undergoing Mehta casting are at significant risk of exceeding 3 hours of anesthesia, which the FDA has stated may be harmful for children <3 years. Significant site variability indicates that standardization protocols should be developed to encourage best practices and minimize anesthetic times.

LEVEL OF EVIDENCE

Prognostic Level II.

How Long Can You Delay? Curve Progression While Awaiting Vertebral Body Tethering Surgery

Background: The implications of delaying surgical intervention for patients with adolescent idiopathic scoliosis (AIS) wishing to undergo vertebral body tethering (VBT) have not yet been explored. It is important to understand how these delays can impact surgical planning and patient outcomes. Methods: This was a retrospective review that analyzed all AIS patients treated between 2015 and 2021 at a single tertiary center. Time to surgery from initial surgical consultation and ultimate surgical plan were assessed. Patient characteristics, potential risk factors associated with increased curve progression, and reasons for delay were also analyzed. Results: 174 patients were evaluated and 95 were scheduled for VBT. Four patients later required a change to posterior spinal fusion (PSF) due to excessive curve progression. Patients requiring PSF were shown to have significantly longer delays than those who received VBT. Additionally, longer delays, younger age, greater curve progression, and lower skeletal maturity were correlated with significant curve progression (≥5 degrees). Conclusions: Surgical delays for AIS patients awaiting VBT may lead to significant curve progression and necessitate more invasive procedures. Patients with longer delays experienced an increased risk of needing PSF instead of VBT. Of those requiring PSF, the majority were due to insurance denials. Optimizing surgical timing and shared decision-making among patients, families, and healthcare providers are essential for achieving the best outcomes.

Artificial intelligence-based three-dimensional templating for total joint arthroplasty planning: a scoping review

PURPOSE

The purpose of this review is to evaluate the current status of research on the application of artificial intelligence (AI)-based three-dimensional (3D) templating in preoperative planning of total joint arthroplasty.

METHODS

This scoping review followed the PRISMA, PRISMA-ScR guidelines, and five stage methodological framework for scoping reviews. Studies of patients undergoing primary or revision joint arthroplasty surgery that utilised AI-based 3D templating for surgical planning were included. Outcome measures included dataset and model development characteristics, AI performance metrics, and time performance. After AI-based 3D planning, the accuracy of component size and placement estimation and postoperative outcome data were collected.

RESULTS

Nine studies satisfied inclusion criteria including a focus on computed tomography (CT) or magnetic resonance imaging (MRI)-based AI templating for use in hip or knee arthroplasty. AI-based 3D templating systems reduced surgical planning time and improved implant size/position and imaging feature estimation compared to conventional radiographic templating. Several components of data processing and model development and testing were insufficiently covered in the studies included in this scoping review.

CONCLUSIONS

AI-based 3D templating systems have the potential to improve preoperative planning for joint arthroplasty surgery. This technology offers more accurate and personalized preoperative planning, which has potential to improve functional outcomes for patients. However, deficiencies in several key areas, including data handling, model development, and testing, can potentially hinder the reproducibility and reliability of the methods proposed. As such, further research is needed to definitively evaluate the efficacy and feasibility of these systems.

Coronal decompensation following thoracic vertebral body tethering in idiopathic scoliosis

PURPOSE

Post-operative coronal decompensation (CD) continues to be a challenge in the treatment of adolescent idiopathic scoliosis (AIS). CD following selective spinal fusion has been studied. However, there is currently little information regarding CD following Vertebral Body Tethering (VBT). Thus, the goal of this study is to better understand the incidence and risk factors for CD after VBT.

METHODS

Retrospective review of a prospective multicenter database was used for analysis. Inclusion criteria were patients undergoing thoracic VBT, a minimum 2-year follow-up, LIV was L1 or above, skeletally immature (Risser ≤ 1), and available preoperative and final follow-up AP and lateral upright radiographs. Radiographic parameters including major and minor Cobb angles, curve type, LIV tilt/translation, L4 tilt, and coronal balance were measured. CD was defined as the distance between C7PL and CSVL > 2 cm. Multiple logistic regression model was used to identify significant predictors of CD.

RESULTS

Out of 136 patients undergoing VBT, 94 patients (86 female and 6 male) met the inclusion criteria. The mean age at surgery was 12.1 (9-16) and mean follow-up period was 3.4 years (2-5 years). Major and minor curves, AVR, coronal balance, LIV translation, LIV tilt, L4 tilt were significantly improved after surgery. CD occurred in 11% at final follow-up. Lenke 1A-R (24%) and 1C (26%) had greater incidence of CD compared to 1A-L (4%), 2 (0%), and 3 (0%). LIV selection was not associated with CD. Multivariate logistic regression analysis yielded 1A-R and 1C curves as a predictor of CD with the odds ratio being 17.0.

CONCLUSION

CD occurred in 11% of our thoracic VBT patients. Lenke 1A-R and 1C curve types were predictors for CD in patients treated with VBT. There were no other preoperative predictors associated with CD.

Evaluating compliance with the best practice guidelines for wrong-level surgery prevention in high-risk pediatric spine surgery

PURPOSE

In 2018, Best Practice Guidelines (BPGs) were published for preventing wrong-level surgery in pediatric spinal deformity, but successful implementation has not been established. The purpose of this study was to evaluate BPG compliance 5 years after publication. We hypothesized higher compliance among BPG authors and among surgeons with more experience, higher caseload, and awareness of the BPGs.

METHODS

We queried North American and European surgeons, authors and nonauthors, and members of pediatric spinal study groups on adherence to BPGs using an anonymous survey consisting of 18 Likert scale questions. Respondents provided years in practice, yearly caseload, and guideline awareness. Mean compliance scores (MCS) were developed by correlating Likert responses with MCS scores ("None of the time" = no compliance = MCS 0, "Sometimes" = weak to moderate = MCS 1, "Most of the time" = high = MCS 2, and "All the time" = perfect = MCS 3).

RESULTS

Of the 134 respondents, 81.5% reported high or perfect compliance. Average MCS for all guidelines was 2.4 ± 0.4. North American and European surgeons showed no compliance differences (2.4 vs. 2.3, p = 0.07). Authors and nonauthors showed significantly different compliance scores (2.8 vs 2.4, p < 0.001), as did surgeons with and without knowledge of the BPGs (2.5 vs 2.2, p < 0.001). BPG awareness and compliance showed a moderate positive correlation (r = 0.48, p < 0.001), with non-significant associations between compliance and both years in practice (r = 0.41, p = 0.64) and yearly caseload (r = 0.02, p = 0.87).

CONCLUSION

Surgeons reported high or perfect compliance 81.5% of the time with BPGs for preventing wrong-level surgery. Authorship and BPG awareness showed increased compliance. Location, study group membership, years in practice, and yearly caseload did not affect compliance.

LEVEL OF EVIDENCE

Level V-expert opinion.

Radiation exposure in navigated techniques for AIS: is there a difference between pre-operative CT and intraoperative CT?

PURPOSE

Utilization of navigation improves pedicle screw accuracy in adolescent idiopathic scoliosis (AIS). Our center switched from intraoperative CT (ICT) to an optical navigation system that utilizes pre-operative CT (PCT). We aim to evaluate the radiation dose and operative time for low-dose ICT compared to standard and low-dose PCT used for optical navigation in AIS patients undergoing posterior spinal fusion.

METHODS

A single-center matched-control cohort study of 38 patients was conducted. Nineteen patients underwent ICT navigation (O-arm) and were matched by sex, age, and weight to 19 patients who underwent PCT for use with an optical-guided navigation (7D, Seaspine). A total of 418 levels were instrumented and reviewed. PCT was either a standard dose (N = 7) or a low dose (N = 12). The mean volume CT dose index, dose-length product, overall effective dose (ED), ED per level instrumented, and operative time per level were compared.

RESULTS

ED per level instrumented was 0.061 ± 0.029 mSv in low-dose PCT and 0.14 ± 0.05 mSv in low-dose ICT (p < 0.0001). ED per level instrumented was significantly higher in standard PCT (1.46 ± 0.39 vs. 0.14 ± 0.03 mSv; p < 0.0001). Mean operative time per level was 31 ± 7 min for ICT and 33 ± 3 min for PCT (p = 0.628).

CONCLUSION

Low-dose PCT resulted in 0.70 mSv exposure per case and 31 min per level, standard-dose was 16.95 mSv, while ICT resulted in 1.34-1.62 mSv and a similar operative time. Use of a standard-dose PCT involves radiation exposure about 9 times higher than ICT and 23 times higher than low-dose PCT per level instrumented.

LEVEL OF EVIDENCE

Level III.

Does radiographic calibration affect linear radiographic measurements in a large pediatric spine registry?

PURPOSE

Large registries are increasingly at the forefront of modern pediatric spine research, with manual, centralized, trained radiographic measurement serving as the gold standard for spine research. However, there is limited data regarding the reliability of registry measurements which may be subject to differences in radiographic calibration. We undertook this study to evaluate reliability of T1-T12 height, L1-S1 height, and coronal balance measurements for a large registry of early onset scoliosis patients.

METHODS

Three trained technicians from the Pediatric Spine Study Group measured 43 radiographs for T1-T12, L1-S1, and coronal balance using 3 different calibration techniques. All radiographs were AP views of patients with magnetically controlled growing rods with known diameters. The calibration techniques used a pre-export manually drawn line, a digital automatically generated computerized marker, and the diameter of a magnetically controlled growing rod. The intraclass correlation coefficient (ICC) was calculated to determine reliability.

RESULTS

1161 measurements were performed. For each of the three raters, coronal balance, T1-T12 height and L1-S1 height had excellent agreement regardless of the calibration technique (alpha 0.93-1.0). Among the parameters, coronal balance had the worst inter-rater reliability, whereas there was excellent interrater reliability regarding T1-T12 height and L1-S1 height (alpha 0.91-0.99).

CONCLUSION

There was excellent agreement among reviewers and between the 3 different calibration techniques. While calibration using rod diameter served as the gold standard, this data shows that other standard calibration methods were adequate and achieved excellent reliability for registry radiographs.

The Effect of Implant Density on Adolescent Idiopathic Scoliosis Fusion: Results of the Minimize Implants Maximize Outcomes Randomized Clinical Trial

BACKGROUND

Severe adolescent idiopathic scoliosis (AIS) can be treated with instrumented fusion, but the number of anchors needed for optimal correction is controversial.

METHODS

We conducted a multicenter, randomized study that included patients undergoing spinal fusion for single thoracic curves between 45° and 65°, the most common form of operatively treated AIS. Of the 211 patients randomized, 108 were assigned to a high-density screw pattern and 103, to a low-density screw pattern. Surgeons were instructed to use ≥1.8 implants per spinal level fused for patients in the high-implant-density group or ≤1.4 implants per spinal level fused for patients in the low-implant-density group. The primary outcome measure was the percent correction of the coronal curve at the 2-year follow-up. The power analysis for this trial required 174 patients to show equivalence, defined as a 95% confidence interval (CI) within a ±10% correction margin with a probability of 90%.

RESULTS

In the intention-to-treat analysis, the mean percent correction of the coronal curve was equivalent between the high-density and low-density groups at the 2-year follow-up (67.6% versus 65.7%; difference, -1.9% [95% CI: -6.1%, 2.2%]). In the per-protocol cohorts, the mean percent correction of the coronal curve was also equivalent between the 2 groups at the 2-year follow-up (65.0% versus 66.1%; difference, 1.1% [95% CI: -3.0%, 5.2%]). A total of 6 patients in the low-density group and 5 patients in the high-density group required reoperation (p = 1.0).

CONCLUSIONS

In the setting of spinal fusion for primary thoracic AIS curves between 45° and 65°, the percent coronal curve correction obtained with use of a low-implant-density construct and that obtained with use of a high-implant-density construct were equivalent.

LEVEL OF EVIDENCE

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

Automated measurements of interscrew angles in vertebral body tethering patients with deep learning

BACKGROUND CONTEXT

Vertebral body tethering is the most popular nonfusion treatment for adolescent idiopathic scoliosis. The effect of the tether cord on the spine can be segmentally assessed by comparing the angle between two adjacent screws (interscrew angle) over time. Tether breakage has historically been assessed radiographically by a change in adjacent interscrew angle by greater than 5° between two sets of imaging. A threshold for growth modulation has not yet been established in the literature. These angle measurements are time consuming and prone to interobserver variability.

PURPOSE

The purpose of this study was to develop an automated deep learning algorithm for measuring the interscrew angle following VBT surgery.

STUDY DESIGN/SETTING

Single institution analysis of medical images.

PATIENT SAMPLE

We analyzed 229 standing or bending AP or PA radiographs from 100 patients who had undergone VBT at our institution.

OUTCOME MEASURES

Physiologic Measures: An image processing algorithm was used to measure interscrew angles.

METHODS

A total of 229 standing or bending AP or PA radiographs from 100 VBT patients with vertebral body tethers were identified. Vertebral body screws were segmented by hand for all images and interscrew angles measured manually for 60 of the included images. A U-Net deep learning model was developed to automatically segment the vertebral body screws. Screw label maps were used to develop and tune an image processing algorithm which measures interscrew angles. Finally, the completed model and algorithm pipeline was tested on a 30-image test set. Dice score and absolute error were used to measure performance.

RESULTS

Inter- and Intra-rater reliability for manual angle measurements were assessed with ICC and were both 0.99. The segmentation model Dice score against manually segmented ground truth across the 30-image test set was 0.96. The average interscrew angle absolute error between the algorithm and manually measured ground truth was 0.66° and ranged from 0° to 2.67° in non-overlapping screws (N=206). The primary modes of failure for the model were overlapping screws on a right thoracic/left lumbar construct with two screws in one vertebra and overexposed images. An algorithm step which determines whether an overlapping screw was present correctly identified all overlapping screws, with no false positives.

CONCLUSION

We developed and validated an algorithm which measures interscrew angles for radiographs of vertebral body tether patients with an accuracy of within 1° for the majority of interscrew angles. The algorithm can process five images per second on a standard computer, leading to substantial time savings. This algorithm may be used for rapid processing of large radiographic databases of tether patients and could enable more rigorous definitions of growth modulation and cord breakage to be established.

Potential endpoints for assessment of bone health in persons with neurofibromatosis type 1

Neurofibromatosis type 1 is a genetic syndrome characterized by a wide variety of tumor and non-tumor manifestations. Bone-related issues, such as scoliosis, tibial dysplasia, and low bone mineral density, are a significant source of morbidity for this population with limited treatment options. Some of the challenges to developing such treatments include the lack of consensus regarding the optimal methods to assess bone health in neurofibromatosis type 1 and limited data regarding the natural history of these manifestations. In this review, the Functional Committee of the Response Evaluation in Neurofibromatosis and Schwannomatosis International Collaboration: (1) presents the available techniques for measuring overall bone health and metabolism in persons with neurofibromatosis type 1, (2) reviews data for use of each of these measures in the neurofibromatosis type 1 population, and (3) describes the strengths and limitations for each method as they might be used in clinical trials targeting neurofibromatosis type 1 bone manifestations. The Response Evaluation in Neurofibromatosis and Schwannomatosis International Collaboration supports the development of a prospective, longitudinal natural history study focusing on the bone-related manifestations and relevant biomarkers of neurofibromatosis type 1. In addition, we suggest that the neurofibromatosis type 1 research community consider adding the less burdensome measurements of bone health as exploratory endpoints in ongoing or planned clinical trials for other neurofibromatosis type 1 manifestations to expand knowledge in the field.

Non-Fusion Versus Fusion Surgery in Pediatric Idiopathic Scoliosis: What Trade-Offs in Outcomes Are Acceptable for the Patient and Family?

BACKGROUND

Vertebral body tethering and other non-fusion techniques for the treatment of pediatric idiopathic scoliosis are increasing in popularity. There is limited physician consensus on this topic as the result of a paucity of published data regarding which patients most benefit from non-fusion strategies. Thus, much of the decision-making is left to patients and parents, who must select a treatment based on their goals and values and the information available from health-care providers, the internet, and social media. We sought to understand patient and family preferences regarding the attributes of fusion versus non-fusion surgery that drive these choices.

METHODS

Patients and families were recruited from 7 pediatric spine centers and were asked to complete a survey-based choice experiment that had been jointly developed with the U.S. Food and Drug Administration (FDA) to evaluate patient preferences. Choices between experimentally designed alternatives were analyzed to estimate the relative importance of outcomes and requirements associated with the choice options (attributes). The attributes included appearance, confidence in the planned correction, spinal motion, device failure, reoperation, and recovery period. The inclusion criteria were (1) an age of 10 to 21 years and (2) a diagnosis of adolescent idiopathic scoliosis in patients who were considering, or who had already undergone, treatment with fusion or non-fusion surgery. Preference weights were estimated from the expected changes in choice given changes in the attributes.

RESULTS

A total of 344 respondents (124 patients, 92 parents, and 128 parent/patient dyads) completed the survey. One hundred and seventy-three patients were enrolled prior to surgery, and 171 were enrolled after surgery. Appearance and motion were found to be the most important drivers of choice. For the entire cohort, fusion was preferred over non-fusion. For patients who were considering surgery, the most important attributes were preservation of spinal motion and appearance.

CONCLUSIONS

Patients and families seeking treatment for idiopathic scoliosis value appearance and preservation of spinal motion and, to a lesser extent, reoperation rates when considering fusion versus non-fusion surgery.

Evaluating compliance with the 2013 best practice guidelines for preventing surgical site infection in high-risk pediatric spine surgery

PURPOSE

Best Practice Guidelines (BPGs) were published one decade ago to decrease surgical site infection (SSI) in pediatric spinal deformity. Successful implementation has not been established. This study evaluated surgeon compliance with items on the BPG. We hypothesized that BPG authors and surgeons with more experience, higher caseload, and awareness of the BPG would have higher compliance.

METHODS

We queried North American and European surgeons, authors and non-authors, and members of various spine study groups on adherence to BPGs using an anonymous survey. Mean compliance scores (MCSs) were developed by correlating Likert responses with MCSs ("None of the time" = no compliance = MCS 0, "Sometimes" = weak to moderate = MCS 1, "Most of the time" = high = MCS 2, "All the time" = perfect = MCS 3).

RESULTS

Of the 142 respondents, 73.7% reported high or perfect compliance. Average compliance scores for all guidelines was 2.2 ± 0.4. There were significantly different compliance scores between North American and European surgeons (2.3 vs 1.8, p < 0.001), authors and non-authors (2.5 vs. 2.2, p = 0.023), and surgeons with and without knowledge of the BPGs (2.3 vs. 1.8, p < 0.001). There was a weak correlation between BPG awareness and compliance (r = 0.34, p < 0.001) and no correlation between years in practice (r = 0.0, p = 0.37) or yearly caseload (r = 0.2, p = 0.78) with compliance.

CONCLUSIONS

Compliance among our cohort of surgeons surveyed was high. North American surgeons, authors of the BPGs and those aware of the guidelines had increased compliance. Participation in a spine study group, years in practice, and yearly caseload were not associated with compliance.

LEVEL OF EVIDENCE

Level V-expert opinion.

Few-shot biomedical image segmentation using diffusion models: Beyond image generation

BACKGROUND

Medical image analysis pipelines often involve segmentation, which requires a large amount of annotated training data, which is time-consuming and costly. To address this issue, we proposed leveraging generative models to achieve few-shot image segmentation.

METHODS

We trained a denoising diffusion probabilistic model (DDPM) on 480,407 pelvis radiographs to generate 256 ✕ 256 px synthetic images. The DDPM was conditioned on demographic and radiologic characteristics and was rigorously validated by domain experts and objective image quality metrics (Frechet inception distance [FID] and inception score [IS]). For the next step, three landmarks (greater trochanter [GT], lesser trochanter [LT], and obturator foramen [OF]) were annotated on 45 real-patient radiographs; 25 for training and 20 for testing. To extract features, each image was passed through the pre-trained DDPM at three timesteps and for each pass, features from specific blocks were extracted. The features were concatenated with the real image to form an image with 4225 channels. The feature-set was broken into random patches, which were fed to a U-Net. Dice Similarity Coefficient (DSC) was used to compare the performance with a vanilla U-Net trained on radiographs.

RESULTS

Expert accuracy was 57.5 % in determining real versus generated images, while the model reached an FID = 7.2 and IS = 210. The segmentation UNet trained on the 20 feature-sets achieved a DSC of 0.90, 0.84, and 0.61 for OF, GT, and LT segmentation, respectively, which was at least 0.30 points higher than the naively trained model.

CONCLUSION

We demonstrated the applicability of DDPMs as feature extractors, facilitating medical image segmentation with few annotated samples.

Anonymizing Radiographs Using an Object Detection Deep Learning Algorithm

Radiographic markers contain protected health information that must be removed before public release. This work presents a deep learning algorithm that localizes radiographic markers and selectively removes them to enable de-identified data sharing. The authors annotated 2000 hip and pelvic radiographs to train an object detection computer vision model. Data were split into training, validation, and test sets at the patient level. Extracted markers were then characterized using an image processing algorithm, and potentially useful markers (eg, "L" and "R") without identifying information were retained. The model achieved an area under the precision-recall curve of 0.96 on the internal test set. The de-identification accuracy was 100% (400 of 400), with a de-identification false-positive rate of 1% (eight of 632) and a retention accuracy of 93% (359 of 386) for laterality markers. The algorithm was further validated on an external dataset of chest radiographs, achieving a de-identification accuracy of 96% (221 of 231). After fine-tuning the model on 20 images from the external dataset to investigate the potential for improvement, a 99.6% (230 of 231, P = .04) de-identification accuracy and decreased false-positive rate of 5% (26 of 512) were achieved. These results demonstrate the effectiveness of a two-pass approach in image de-identification. Keywords: Conventional Radiography, Skeletal-Axial, Thorax, Experimental Investigations, Supervised Learning, Transfer Learning, Convolutional Neural Network (CNN) Supplemental material is available for this article. © RSNA, 2023 See also the commentary by Chang and Li in this issue.

Outcome of bracing vs. surgical treatment in adolescents with idiopathic scoliosis based on device measured daily physical activity: a prospective pilot study

Adolescent idiopathic scoliosis (AIS) can be treated with bracing or surgery, which may affect patient's physical activity (PA). However, there are limited objective assessments of PA in patients with AIS. This study aims to compare the outcome of spinal bracing vs. surgery in patients with AIS based on a device that measured daily PA. In total 24 patients with AIS participated, including 12 patients treated with bracing and 12 with spinal surgery. Daily PA was measured throughout 4 consecutive days using four tri-axial accelerometers and patient-reported functional status was reported using the SRS-22 questionnaire. The participants were assessed both before the treatment and after treatment at a 12-month follow-up. Patients with AIS had no significant change in their PA levels at the 12-month follow-up after surgical correction. On the contrary, patients with AIS following a year-long bracing treatment had significantly reduced time spent active ( P  = 0.04) with an average reduction in walking steps by 2137 steps/day ( P  = 0.005). There was no significant difference in function, pain, self-image and mental health domains following both treatments, as reported by the SRS-22. There was a significant improvement in satisfaction for both treatment groups ( P  ≤ 0.02). Significantly reduced PA and increased sedentary time are reported in patients with AIS following bracing treatment. An objective PA assessment is recommended to track the effect of scoliosis treatment on PA. Patients with AIS should be actively encouraged to achieve and maintain their recommended daily PA levels irrespective of the type of treatment. Level of evidence: Level II.

Biomechanical Computational Study of Pedicle Screw Position and Density in Adolescent Idiopathic Scoliosis Instrumentation

STUDY DESIGN

Computer simulation of adolescent idiopathic scoliosis instrumentation.

OBJECTIVE

To test the hypothesis that different screw densities would result in different apical vertebral rotation (AVR) corrections and bone-screw forces in adolescent idiopathic scoliosis instrumentation.

SUMMARY OF BACKGROUND DATA

The "Minimize Implants Maximize Outcomes" Clinical Trial revealed that the use of more versus fewer screws resulted in similar coronal plane correction for Lenke 1A curves. However, the biomechanical impact of screw density on transverse plane correction is still unclear. Further investigation is needed to determine if and how transverse plane correction is correlated with screw density.

PATIENTS AND METHODS

We simulated apical vertebral derotation after segmental translation using patient-specific computer models of 30 patients from the "Minimize Implants Maximize Outcomes" Trial. For each case, 10 alternative screw patterns were tested with overall densities ranging between 1.2 and 2 screws per level fused, and local density at the 3 apical levels ranging between 0.7 and 2 (total: 600 simulations). Main thoracic (MT) Cobb angle, thoracic kyphosis (TK), AVR, and bone-screw forces were computed and compared.

RESULTS

The presenting MT (62 ± 11°; range: 45° to 86°), TK (27 ± 20°; -5° to 81°), and AVR (14±7°; -2° to 25°) were corrected through segmental translation to 22 ± 7° (10° to 41°), 26 ± 5° (18° to 45°), and 14 ± 7° (-4° to 26°). After apical vertebral derotation, they became 16 ± 8° (1° to 41°), 24 ± 4° (13° to 40°), and 4 ± 5° (-12° to 18°). There was no significant difference in MT among screw patterns; higher screw density had lower bone-screw forces ( P < 0.05). The apical vertebral derotation maneuver reduced AVR by an average of 70%, positively correlated with apical screw density ( r = 0.825, P < 0.05). There was no significant difference in TK.

CONCLUSION

Screw density had no significant effect on 3-dimensional correction through the primary segmental translation maneuver. Transverse plane correction through subsequent apical vertebral derotation was positively correlated with screw density at the apical levels ( r = 0.825, P < 0.05). Bone-screw forces were negatively correlated with overall screw density ( P < 0.05).

Creating High Fidelity Synthetic Pelvis Radiographs Using Generative Adversarial Networks: Unlocking the Potential of Deep Learning Models Without Patient Privacy Concerns

BACKGROUND

In this work, we applied and validated an artificial intelligence technique known as generative adversarial networks (GANs) to create large volumes of high-fidelity synthetic anteroposterior (AP) pelvis radiographs that can enable deep learning (DL)-based image analyses, while ensuring patient privacy.

METHODS

AP pelvis radiographs with native hips were gathered from an institutional registry between 1998 and 2018. The data was used to train a model to create 512 × 512 pixel synthetic AP pelvis images. The network was trained on 25 million images produced through augmentation. A set of 100 random images (50/50 real/synthetic) was evaluated by 3 orthopaedic surgeons and 2 radiologists to discern real versus synthetic images. Two models (joint localization and segmentation) were trained using synthetic images and tested on real images.

RESULTS

The final model was trained on 37,640 real radiographs (16,782 patients). In a computer assessment of image fidelity, the final model achieved an "excellent" rating. In a blinded review of paired images (1 real, 1 synthetic), orthopaedic surgeon reviewers were unable to correctly identify which image was synthetic (accuracy = 55%, Kappa = 0.11), highlighting synthetic image fidelity. The synthetic and real images showed equivalent performance when they were assessed by established DL models.

CONCLUSION

This work shows the ability to use a DL technique to generate a large volume of high-fidelity synthetic pelvis images not discernible from real imaging by computers or experts. These images can be used for cross-institutional sharing and model pretraining, further advancing the performance of DL models without risk to patient data safety.

LEVEL OF EVIDENCE

Level III.

Biomechanical modeling and assessment of lumbar vertebral body tethering configurations

PURPOSE

Vertebral body tethering (VBT) is a fusionless spinal growth modulation technique, which shows promise for pediatric idiopathic scoliosis (IS) curve correction. This technique, mainly used for thoracic curves, is increasingly being used to treat lumbar curves in order to preserve spine flexibility. It remains necessary to adequately define the cord tension to be applied during the operation and the instrumented levels to biomechanically predict correction over time for the lumbar spine.

METHODS

Twelve pediatric patients with lumbar IS, treated with lumbar-only or lumbar and thoracic VBT, were selected for this study. Three independent variables were tested alternately using a patient-specific finite element model (FEM), which includes an algorithm modeling vertebra growth and spine curve changes due to growth modulation for 24 months post-operatively according to the Hueter-Volkmann principle. Parameters included cable tensioning (150N/250N), upper instrumented level (actual UIV, UIV-1) and lower instrumented level (actual LIV, LIV + 1). Each FEM was personalized using 3D radiographic reconstruction and flexibility supine radiographs.

RESULT

An increase in cord tension (from 150 to 250N) had significant effects on main thoracic and thoraco-lumbar/lumbar Cobb angles, as well as on lumbar lordosis, after surgery (supplementary average correction of 3° and 8°, and increase of 1.4°, respectively) and after 24 months (4°, 10° and 1.1°) (p < 0.05). Adding a level to the actual UIV or LIV did not improve correction.

CONCLUSION

This parametric study showed that cord tension is the most important biomechanical parameter on the simulated immediate and 2-year increase in lumbar curve correction. Our preliminary model suggests that it is not advantageous to add additional instrumented levels.

LEVEL OF EVIDENCE

This computational study uses a retrospective validation cohort (level of evidence 3).

Long-Term Outcomes at Skeletal Maturity of Combined Pelvic and Femoral Osteotomy for the Treatment of Legg-Calve-Perthes Disease

Surgical treatment for Legg-Calve-Perthes disease (LCPD) is recommended for older children with moderate to severe disease. We sought to determine whether double osteotomies lead to improved radiologic outcomes compared to reported non-operative outcomes. Patients older than 6 years of age diagnosed with LCPD lateral pillar B or C who were treated with pelvic and femoral osteotomies were included. Radiologic outcomes and leg-length discrepancies were assessed using the Stulberg classification and were compared with the current literature. Fifteen hips in fourteen patients were treated with double osteotomy for LCPD, and seven had lateral pillar C disease (47%). The mean age at surgery was 8.6 years (range, 7.2-10.4) and the mean age at follow-up was 20.2 years (range, 14.2-35.6). At a mean 11.6-year follow-up (range: 6.3-25.2), double osteotomy resulted in 40% of patients having Stulberg I/II scores, 27% having Stulberg III scores, and 33% having Stulberg IV/V scores. The mean leg-length discrepancy was 1.4 cm in lateral pillar C patients compared to 0.8 cm in lateral pillar B patients. Four patients underwent additional surgeries, including two who required total hip arthroplasty. Double osteotomy as an alternative surgical procedure for the treatment of LCPD did not show improved outcomes when compared to historic non-operative cohorts.

Consensus-Based Best Practice Guidelines for the Management of Spinal Deformity and Associated Tumors in Pediatric Neurofibromatosis Type 1: Screening and Surveillance, Surgical Intervention, and Medical Therapy

BACKGROUND

Spinal conditions, such as scoliosis and spinal tumors, are prevalent in neurofibromatosis type 1 (NF1). Despite the recognized importance of their early detection and treatment, there remain knowledge gaps in how to approach these manifestations. The purpose of this study was to utilize the experience of a multidisciplinary committee of experts to establish consensus-based best practice guidelines (BPGs) for spinal screening and surveillance, surgical intervention, and medical therapy in pediatric patients with NF1.

METHODS

Using the results of a prior systematic review, 10 key questions that required further assessment were first identified. A committee of 20 experts across medical specialties was then chosen based on their clinical experience with spinal deformity and tumors in NF1. These were 9 orthopaedic surgeons, 4 neuro-oncologists/oncologists, 3 neurosurgeons, 2 neurologists, 1 pulmonologist, and 1 clinical geneticist. An initial online survey on current practices and opinions was conducted, followed by 2 additional surveys via a formal consensus-based modified Delphi method. The final survey involved voting on agreement or disagreement with 35 recommendations. Items reaching consensus (≥70% agreement or disagreement) were included in the final BPGs.

RESULTS

Consensus was reached for 30 total recommendations on the management of spinal deformity and tumors in NF1. These were 11 recommendations on screening and surveillance, 16 on surgical intervention, and 3 on medical therapy. Five recommendations did not achieve consensus and were excluded from the BPGs.

CONCLUSION

We present a set of consensus-based BPGs comprised of 30 recommendations for spinal screening and surveillance, surgical intervention, and medical therapy in pediatric NF1.

Concave and convex growth do not differ over tethered vertebral segments, even with open tri-radiate cartilage

PURPOSE

To assess the following hypotheses related to vertebral body tethering (VBT): 1. VBT is associated with asymmetric (concave > convex) increases in height over the instrumented vertebra. 2. The instrumented Cobb angle improves following VBT surgery with growth.

METHODS

This is a retrospective case series of pediatric patients from a multicenter scoliosis registry treated with VBT between 2013 to 2021.

INCLUSION CRITERIA

patients with standing radiographs at < 4 months and ≥ 2 years after surgery. Distances between the superior endplate of the UIV and the inferior endplate of the LIV were measured at the concave corner, mid-point, and convex corner of the endplates. The UIV-LIV angle was recorded. Subgroup analyses included comparing different Risser scores and tri-radiate cartilage (TRC) closed versus open using student t-tests.

RESULTS

83 patients met inclusion criteria (92% female; age at time of surgery 12.5 ± 1.4 years) with mean follow-up time of 3.8 ± 1.4 years. Risser scores at surgery were: 0 (n = 33), 1 (n = 12), 2 (n = 10), 3 (n = 11), 4 (n = 12), and 5 (n = 5). Of the 33 Risser 0 patients, 17 had an open TRC, 16 had a closed TRC. The UIV-LIV distance at concave, middle, and convex points significantly increased from immediate post-op to final-follow-up for Risser 0 patients, but not for Risser 1-5 patients. Increases in UIV-LIV distance were not significantly different between concave, middle, and convex points for all groups. There was no significant improvement or worsening in UIV-LIV angle for any group.

CONCLUSION

At a mean of 3.8 years following VBT, 33 Risser 0 patients demonstrated significant growth in the instrumented segment, though there was no difference between concave or convex growth, even for patients with open TRC.

Does Shorter Time to Treatment of Pediatric Supracondylar Humerus Fractures Impact Clinical Outcomes?

BACKGROUND

Treatment of supracondylar humerus (SCH) fractures within 18 hours of presentation is a tracked quality metric for ranking of pediatric hospitals. This is in contrast with literature that shows time to treatment does not impact outcomes in SCH fractures. We aim to determine whether an 18-hour cutoff for pediatric supracondylar humerus fracture treatment is clinically significant by comparing the complication risks ofpatients on either side of this timepoint. Our hypothesis is that there will be no statistically significant differences based on time to treatment.

METHODS

A retrospective review of clinical outcomes was performed for 472 pediatric patients who underwent surgical management of isolated supracondylar humerus fractures between 1997 and 2022 at a single level I pediatric trauma hospital. The cohort was split based on time to surgery (within or ≥18 h from Emergency Department admission).

RESULTS

Surgical treatment occurred within 18 hours of arrival in 435 (92.2%) patients and after 18 hours in 37 (7.8%) patients. Mean age was 5.6±2.2 years and 51.5% of patients were female. Gartland fracture classification was type II [n=152 (32.3%)], type III [n=284 (60.3%)], type IV [n=13 (2.8%)], or flexion-type [n=18 (3.8%)]. There were no differences in demographic characteristics or fracture classification between cohorts. Fractures in the ≥18-hour cohort were treated more commonly with 2 pins (62.2% vs. 38.5%, P =0.04). There were no statistically significant differences in open versus closed reduction, utilization of medial pins, or postoperative immobilization between cohorts. We were unable to detect any differences in postoperative complications, including non-union, delayed union, stiffness, malunion, loss of reduction, iatrogenic nerve injury, or infection. This remained true when type II fractures were excluded.

CONCLUSIONS

Using an arbitrary time cutoff of <18 hours does not influence clinical outcomes in the surgical treatment of SCH fractures. This held true when type II fractures were excluded. For this reason, we recommend modification to the USNWR guidelines to decrease emphasis on time-to-treatment of SCH fractures.

LEVEL OF EVIDENCE

Level III.

Minimum 5-Year Results of Elongation Derotation Flexion Casting for Early Onset Scoliosis: The Story Is Not Over Until Skeletal Maturity

BACKGROUND

Early conservative treatment for patients with idiopathic infantile scoliosis (IIS) with elongation derotation flexion (EDF) casting and subsequent serial bracing has become widely utilized. However, the long-term outcomes of patients treated with EDF casting are limited.

METHODS

We performed a retrospective chart review of all patients who had undergone serial elongation derotation flexion casting and subsequent bracing for scoliosis presenting at a single large tertiary center. All patients were followed for a minimum of 5 years or until surgical intervention.

RESULTS

Our study included 21 patients diagnosed with IIS and treated with EDF casting. At a mean 7-year follow-up, 13 of the 21 patients were considered successfully treated with a mean final major coronal curvature of 9 degrees compared to a pretreatment coronal curve of 36 degrees. These patients, on average, began casting at 1.3 years old and spent 1 year in a cast. Patients that did not have substantial improvement began casting at mean 4 years old and remained in a cast for 0.8 years. Three patients initially had substantial improvement with the correction to <20 degrees at a mean age of 7; however, their curves worsened in adolescence with poor brace compliance. All 3 patients will require surgical intervention. Of the patients not successfully treated with casting, 7 required surgery at a mean 8.2 years of age, 4.3 years after initiation of casting. A significant predictor of treatment failure was older age of cast initiation (P<0.001).

CONCLUSIONS

EDF casting can be an effective cure for IIS patients if initiated at a young age with 15 of 21 patients successfully treated (76%). However, 3 patients had a recurrence in adolescence resulting in an overall success rate of only 62%. Casting should be initiated early to maximize the likelihood of treatment success and periodic monitoring should be continued through skeletal maturity as recurrence during adolescence can occur.

Normative Femoral and Tibial Lengths in a Modern Population of Twenty-First-Century U.S. Children

BACKGROUND

The Green-Anderson (GA) leg-length data remain the gold standard for the age-based assessment of leg lengths in children despite their methodologic weaknesses. We aimed to summarize current growth trends among a cross-sectional cohort of modern U.S. children using quantile regression methods and to compare the median femoral and tibial lengths of the modern U.S. children with those of the GA cohort.

METHODS

A retrospective review of scanograms and upright slot-scanning radiographs obtained in otherwise healthy children between 2008 and 2020 was completed. A search of a radiology registry revealed 3,508 unique patients between the ages of 2 and 18 years for whom a standard-of-care scanogram or slot-scanning radiograph had been made. All patients with systemic illness, genetic conditions, or generalized diseases that may affect height were excluded. Measurements from a single leg at a single time point per subject were included, and the latest available time point was used for children who had multiple scanograms made. Quantile regression analysis was used to fit the lengths of the tibia and femur and overall leg length separately for male patients and female patients.

RESULTS

Seven hundred patients (328 female and 372 male) met the inclusion criteria. On average, the reported 50th percentile tibial lengths from the GA study at each time point were shorter than the lengths in this study by 2.2 cm (range, 1.4 to 3.3 cm) for boys and 2 cm (range, 1.1 to 3.1 cm) for girls. The reported 50th percentile femoral lengths from the GA study at each time point were shorter than the lengths in this study by 1.8 cm (range, 1.1 to 2.5 cm) for boys and 1.7 cm (range, 0.8 to 2.3 cm) shorter for girls.

CONCLUSIONS

This study developed new growth charts for femoral and tibial lengths in a modern U.S. population of children. The new femoral and tibial lengths at nearly all time points are 1 to 3 cm longer than traditional GA data. The use of GA data for epiphysiodesis could result in underestimation of expected childhood growth.

LEVEL OF EVIDENCE

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

Drain options after vertebral body tethering

PURPOSE

Since the introduction of vertebral body tethering (VBT) for adolescent idiopathic scoliosis (AIS), a variety of post-operative chest drainage systems have been utilized. Most surgeons use formal chest tubes with a Pleur-evac, while others use smaller bulb suction drains (e.g., Blake drain). In addition, some centers utilize pleural closure. This multicenter study evaluates whether drain type or pleural closure impact perioperative and 90 day complication rates.

METHODS

A retrospective review was conducted from three institutions with established VBT programs. All preoperative, perioperative and 90 day postoperative data were analyzed to determine differences in outcomes between three cohorts: standard chest tube (SCT), standard chest tube with pleural closure (SCTPC) and 10 French Bulb drain (BD).

RESULTS

104 patients were identified for the study. 57 SCT, 25 SCTPC and 22 BD. All data are listed in order: SCT, SCTPC, BD. Length of stay (3.7, 4.3, 3.0 days) was less in the BD group (p = 0.009); post-operative drainage (460, 761, 485 cc) was less in the SCT and BD groups (p < 0.001); intra-operative estimated blood loss (EBL) 146, 382, 64 cc was less in the BD group (p < 0.001). No significant difference in number of days (3.2, 3.2, and 2.8 days) drainage was in place, groups (p = 0.311). Complication profile was similar with 2 chest tube reinsertions in the SCT and one hemothorax that resolved spontaneously in BD group.

CONCLUSIONS

In this series of 104 patients, SCT, SCTPC and BD all had a similar safety profile. All three methods were safe and effective in managing post-operative chest drainage after thoracic VBT. In the series, BD group had significantly shorter LOS than both groups that used chest tubes.

LEVEL OF EVIDENCE

Level III, Retrospective cohort study.

Prediction of post-operative adding-on or compensatory lumbar curve correction after anterior vertebral body tethering

PURPOSE

Anterior Vertebral Body Tethering (AVBT), a fusionless surgical technique based on growth modulation, aims to correct pediatric scoliosis over time. However, medium-term curvature changes of the non-instrumented distal lumbar curve remains difficult to predict. The objective was to biomechanically analyze the level below the LIV to evaluate whether adding-on or compensatory lumbar curve after AVBT can be predicted by intervertebral disc (ID) wedging and force asymmetry.

METHODS

33 retrospective scoliotic cases instrumented with AVBT were used to computationally simulate their surgery and 2-year post-operative growth modulation using a finite element model. The cohort was divided into two subgroups according to the lumbar curvature evolution over 2 years: (1) correction > 10° (C); (2) maintaining ± 10° (M). The lumbar Cobb angle and residual ID wedging angle under LIV were measured. Simulated pressures and moments at the superior endplate of LIV + 1 were post-processed. These parameters were correlated at 2 years postoperatively.

FINDINGS

On average, the LIV + 1 simulated moment was 538 Nmm for subgroup C, 155 Nmm for subgroup M with lumbar Cobb angle > 20° and 34 Nmm for angle < 20° whereas the ID angle was 1° for C and 0° for M.

INTERPRETATION

On average, a positive moment on the LIV + 1 superior growth plate led to correction of the lumbar curvature, whereas a null moment kept it stable, and a parallel immediate postoperative ID under LIV contributed to its correction or preservation. Nevertheless, the significant interindividual variability suggested that other parameters are involved in the distal non-instrumented curvature evolution.

LEVEL OF EVIDENCE

IV.

Bedside hip aspiration results in decrease in total general anesthesia time in pediatric patients: A multicenter study

PURPOSE

The purpose of this study is to compare pediatric hip aspiration in the operating room under general anesthesia or via bedside aspiration under moderate sedation and delineate the anesthetic time required.

METHODS

A database query conducted at two academic institutions identified all patients under the age of 17 who underwent hip aspiration between 2000 and 2017. At one institution, aspiration was performed in the operating room under general anesthesia. Patients were kept anesthetized until cell count was complete. At the second institution, aspiration was performed in the emergency room at bedside under sedation. The medical record was reviewed for demographic data, hip aspiration results, diagnoses, treatment, and anesthesia time.

RESULTS

A total of 233 patients (233 hips) with a mean age of 7.2 years were identified. Seventy-five patients underwent aspiration in the operating room, and 158 patients underwent bedside aspiration. Patients with a negative aspiration averaged 87 min under anesthesia when performed in the operating room and 29 min under sedation when performed at bedside. Patients with a negative aspiration performed in the operating room after 5 pm averaged 99 min under anesthesia, and 73 min under anesthesia when performed between 7 am and 5 pm (p < 0.01). Seventy-eight (49%) patients who underwent bedside aspiration did not require operative intervention and therefore avoided general anesthesia.

CONCLUSION

Pediatric hip aspiration performed in the operating room results in prolonged anesthesia times while synovial fluid is transported and processed. Anesthesia times are significantly longer after 5 pm. Bedside aspiration resulted in significantly less anesthesia exposure, with half of patients undergoing bedside aspiration avoiding general anesthesia altogether.

LEVEL OF EVIDENCE

Level III.

Summary of the FDA virtual public workshop on spinal device clinical review held on September 17, 2021

The mission of Food and Drug Administration (FDA)'s Center for Devices and Radiological Health is to protect and promote public health. It assures that patients and providers have timely and continued access to safe, effective, and high-quality medical devices and safe radiation-emitting products by providing meaningful and timely information about the products we regulate and the decisions we make. On September 17, 2021, an FDA workshop was held to provide information to stakeholders, including members of the spine community, device manufacturers, regulatory affairs professionals, clinicians, patients, and the general public regarding FDA regulations, guidance and regulatory pathways related to spinal device clinical review. It was not intended to communicate any new policies, processes, or interpretations regarding medical device marketing authorizations. This workshop consisted of individual presentations, group discussions, question and answer sessions, and audience surveys. Information-sharing included discussions related to patient-reported outcomes, clinician-reported outcomes, observer-reported outcomes, and performance outcomes. Discussions involving external subject matter experts covered topics related to spinal device clinical studies including definition of a target population, enrollment criteria, strategies for inclusion of under-represented patient groups, reporting of adverse event and secondary surgical procedures, clinical study endpoints, and clinical outcome assessments. A meeting transcript and webcast workshop link are currently posted on the FDA website. Important related issues and challenges were discussed, and an exciting range of new ideas and concepts were shared which hold promise to advance regulatory science, patient care and future innovation related to spinal devices.

Intervertebral Disk Health Following Vertebral Body Tethering for Adolescent Idiopathic Scoliosis: A Preliminary Study

BACKGROUND

Interest in vertebral body tethering (VBT) as an alternative to posterior spinal fusion for adolescent idiopathic scoliosis (AIS) continues to grow. The purpose of this study was to prospectively assess intervertebral disk health on magnetic resonance imaging (MRI) at 1 year following VBT in AIS patients.

METHODS

AIS patients were enrolled in a prospective surgeon-sponsored Food and Drug Administration (FDA) Investigational Device Exemption (IDE) Study and underwent MRI at 1-year following VBT. All spanned disks and the untethered disks immediately adjacent to the upper instrumented vertebra and lowest instrumented vertebra levels were evaluated according to Pfirrmann grading criteria. Associations between patient factors and preoperative and postoperative disk health and patient-reported outcomes were evaluated.

RESULTS

Twenty-two patients were enrolled with a postoperative MRI (25 curves, 188 disks), and 7 patients (7 curves) had both preoperative and postoperative MRIs (67 disks). The mean age was 12.7 years. Most were Risser 0 (65%) and either Sanders Skeletal Maturity Score 3 (35%) or 4 (53%). In the 7 patients with preoperative and postoperative MRI, the mean Pfirrmann grade of the disks spanned by the tether was 1.88 preoperatively and 2.31 postoperatively ( P =0.0075). No statistically significant differences in preoperative versus postoperative Pfirrmann grade were identified in the disks adjacent to the upper or lower instrumented vertebrae. No association was found between patient-reported outcomes and Pfirrmann grade.

CONCLUSION

At 1 year postoperatively, increased degenerative changes in disks spanned by the tether was identifiable on MRI without evidence of adjacent segment disk disease. These changes were not associated with patient-reported outcomes.

LEVEL OF EVIDENCE

Level III.

When successful, anterior vertebral body tethering (VBT) induces differential segmental growth of vertebrae: an in vivo study of 51 patients and 764 vertebrae

PURPOSE

This study aimed to determine (1) does vertebral body tethering (VBT) produce differential growth modulation in individual vertebrae in patients with idiopathic scoliosis, (2) does VBT change disc shape, and (3) does VBT affect total spine length?

METHODS

Patients with idiopathic scoliosis treated with VBT of the main thoracic curve and minimum 2-year follow-up were included. Vertebrae and discs were categorized as uninstrumented proximal thoracic, instrumented main thoracic, or uninstrumented thoracolumbar-lumbar. The left- and right-sided heights of each vertebra and disc were measured on subsequent radiographs to assess for differential growth. T1-T12 thoracic and T1-S1 thoracolumbar growth velocities were compared with standardized reference data.

RESULTS

Fifty-one patients (764 vertebrae and 807 discs) were analyzed. The average major curve magnitude improved from 46° ± 11° to 17° ± 11° at 2-year follow-up. Differential growth was observed in MT vertebrae, in which the left/concave side grew 2.0 ± 2.2 mm compared with 1.5 ± 2.3 mm on the right/convex (tethered) side (p < 0.001). Differential height changes were observed for all discs, but were most pronounced in instrumented MT discs, in which the right/convex sides decreased by an average of 1.2 mm each, compared with no significant height change on the left/concave side. Total spinal growth velocities were not significantly different from standard reference data.

CONCLUSION

Vertebral body tethering limits convex spinal growth as designed while permitting concave growth. Curve correction results from differential vertebral growth and decreased convex disc height. Overall spinal growth continues at the expected rate.

LEVEL OF EVIDENCE

Level IV case series.

Innovation With Ethics in Pediatric Orthopaedics

Surgeons should thoughtfully consider whether to introduce a new procedure into their practice. Considerations include the severity of the condition, potential risk of harm, treatment alternatives, patient population, ability to appropriately consent patient/families, and available clinical and institutional resources as well as published evidence and regulatory status. Whenever possible, new procedures should be standardized, studied, and reported upon so that the greater community can learn from experience and refine the indications to minimize risks for future patients. Small scale innovation can readily be introduced into practice. Surgeons should always strive to systemically study new procedures so as to be able to assess benefits and effects.

Are Serum Ion Levels Elevated in Pediatric Patients With Metal Implants?

BACKGROUND

Previous studies report elevated serum titanium (Ti) levels in children with spinal implants. To provide additional data on this topic, we sought to assess serum ion levels at multiple timepoints in pediatric patients with growing spine devices, spinal fusion instrumentation, and extremity implants placed for fracture treatment. We hypothesized that serum Ti, cobalt (Co), and chromium (Cr) levels would be elevated in pediatric patients with growing spine devices compared with patients with extremity implants.

METHODS

Pediatric patients undergoing any primary spine implant placement, those with spine implant revision or removal surgery and patients with other appendicular implant removal had serum Ti, Co, and Cr ion levels drawn at the time of surgery. Fifty-one patients (12 growing spine devices, 13 fusions, and 26 extremity implants) had one set of labs, 31 of whom had labs drawn both preoperatively and postoperatively. Biopsies obtained from tissue specimens at the time of implant revision were analyzed histologically for the presence of metal debris and macrophage activity.

RESULTS

Patients with growing spine implants had elevated serum Ti (3.3 vs. 1.9 ng/mL, P=0.01) and Cr levels (1.2 vs. 0.27 ng/mL, P=0.01) in comparison to patients with fusion rods or extremity implants. With respect to patients with extremity implants, patients with growing spine devices had elevated serum Ti (3.3 vs. 0.98 ng/mL, P=0.013), Co (0.63 vs. 0.26 ng/mL, P=0.017), and Cr levels (1.18 vs. 0.26 ng/mL, P=0.005). On matched pairs analysis, patients who had labs drawn before and after spine implantation had significant increase in serum Ti levels (0.57 vs. 3.3 ng/mL, P=0.02). Histology of tissue biopsies adjacent to growing spine implants showed presence of metal debris and increased macrophage activity compared with patients with extremity implants.

CONCLUSION

Serum Ti, Co, and Cr levels are elevated in children with spinal implants compared with those with extremity implants, particularly in those with growing spine devices. However, the clinical significance of these findings remains to be determined.

LEVEL OF EVIDENCE

Level II-prospective comparative study.

0.4% incidence of return to OR due to screw malposition in a large prospective adolescent idiopathic scoliosis database

PURPOSE

In contrast to infection and curve progression, return to OR for implant malposition is potentially within the surgeon's control. With increasing surgeon familiarity with freehand/fluoroscopic pedicle screw placement, rates of return to OR due to malposition may have decreased over time. We sought to document the incidence and risk factors for return to OR due to screw malposition in a large cohort of patients with idiopathic scoliosis.

METHODS

AIS patients enrolled in a multicenter prospective registry with minimum 2-year follow-up undergoing PSF between 2003 and 2017 were included. Surgeries with the use of intraoperative CT-guided navigation were excluded. Return to OR due to screw malposition over time was tabulated. Lenke class, age at surgery, year of surgery, height, weight, surgeon and site were evaluated.

RESULTS

2435 patients underwent PSF with non-navigated open pedicle screw instrumentation. Mean age was 14.6 years, mean thoracic curve magnitude was 53°, and mean lumbar was 40°. Patients did not routinely undergo intraoperative or postoperative CT evaluation. There were 10 returns to OR for screw malposition at a mean of 0.83 years postoperatively (range 0.1-3.4 years), for an overall incidence of 0.4%. Of the 14 screws, 10 were thoracic, 7 were left-sided. No association was found between screw malposition and curve size, enrolling site, surgeon, BMI, Lenke class, or age. Five patients had radiculopathy which improved after screw revision. Return to OR for screw malposition changed from 2003 to 2017 (1-0.2%) but this did not reach statistical significance.

CONCLUSION

Although the incidence of asymptomatic malpositioned screws is unknown, the rate of return to the OR for implant malposition overall in this registry was 1 in 250 patients. Recent data suggest the rate has decreased to 1 in 500 patients. Further work may determine whether enabling technologies can reduce the rate, ideally to a "never event".

Connective Tissue Disease Patients Maintain Greater Distraction During Growth Friendly Surgery

STUDY DESIGN

Multicenter retrospective study.

BACKGROUND

Recent studies have demonstrated diminishing returns in patients with early onset scoliosis (EOS) undergoing repeated lengthening of growing rods. Little is known about whether this same phenomenon occurs in patients with lax connective tissue disease (CTD). The primary purpose of this study is to investigate whether EOS patients with connective tissue laxity disorders have diminishing returns during growth friendly surgery.

METHODS

CTD EOS patients below 10 years old, underwent growth friendly spine surgery with distal anchors and at least 1 proximal spine anchor, and had minimum follow-up of 5 years were included in this study. Coronal T1-S1 height at preindex surgery, postindex, and every available lengthening was assessed. Mean coronal height change during early set distractions and late set distractions were calculated for the cohort. To account for varying distraction intervals, we normalized the distractions by the time interval. The outcome parameter was T1-S1 height gain, mm/year.

RESULTS

Twenty-one CTD patients were included in this study. Total coronal height (T1-S1) was 26.7MHCcm before index, 32.2 cm at D1-D3, 34.7 cm at D4-D6, and 36.7 cm at D7-L10. There were no significant differences in coronal height gains between early and late distractions (P=0.70). Moreover, when normalized for time, there was no significant difference in net gain per year at different lengthening time points for the CTD group, P=0.59.

CONCLUSION

There is no evidence of diminishing returns in coronal T1-S1 height gain in patients with EOS in the setting of CTD.

LEVEL OF EVIDENCE

Level III.

Navigation Options for Spinal Surgeons: State of the Art 2021

The use of navigation in spinal surgery has been increasing over the past decade. There are three primary types of navigation in spinal surgery: three-dimensional image-based computer-assisted navigation, robot-assisted navigation, and three-dimensional printed patient-specific drill guides for navigation. All three have demonstrated increased accuracy in placement of spinal instrumentation versus freehand or fluoroscopic-assisted techniques. Each has unique preoperative and intraoperative technical considerations. All three typically rely on three-dimensional imaging and will have varied radiation exposure to the patient and surgical staff based on specific imaging settings used. Navigation options are continually improving and are expected to broaden efficiency, accuracy, and indications in the future.

Tiered Guidelines in a Pediatric Orthopaedic Practice Reduce Opioids Prescribed at Discharge

BACKGROUND

Data regarding opioid prescribing patterns following pediatric orthopaedic procedures is limited. The aim of this work was to evaluate the effects of tiered guidelines for discharge opioid prescriptions following common pediatric orthopaedic procedures.

METHODS

Quality improvement project conducted at a single academic institution. Guidelines for discharge opioid prescriptions were implemented January 2018 and established 4 tiers of increasing invasiveness for 28 common pediatric orthopaedic procedures. Patients who underwent these procedures in 2017 comprised the preguideline cohort (N=258), while patients treated in 2019 comprised the postguideline cohort (N=212). Opioid prescriptions were reported as oral morphine equivalents (OMEs). Univariate tests were performed to assess statistically significant differences before and after implementation of the guidelines.

RESULTS

There was a significant decrease in OME prescribed between preguideline and postguideline cohorts (median OME 97.5 vs. 37.5). When analyzed according to procedure tiers, tiers 1, 2, and 4 showed significant decreases in OME prescribed between 2017 and 2019. The rate of no opioids prescribed at discharge increased from 13% to 23% between preguideline and postguideline cohorts. The 30-day refill rate did not significantly change. After implementation of guidelines, 91% of all prescriptions were within the guideline parameters, and there was a significant reduction in prescription variability. In tier 4 procedures, median OME prescribed decreased from 375 preguideline to 188 postguideline, but was associated with greater opioid refills within 30 days of discharge (10.2% preguideline vs. 28.8% postguideline).

CONCLUSIONS

Tiered guidelines for discharge opioid prescriptions following pediatric orthopaedic procedures can significantly decrease the quantity of opioids prescribed. Furthermore, we noted excellent adherence and no overall increase in the rates of narcotic refills. Such guidelines may improve pediatric orthopaedists' ability to responsibly treat postoperative pain while limiting the distribution of unneeded opioids.

LEVEL OF EVIDENCE

Level IV-quality improvement project.

Brd4 is required for chondrocyte differentiation and endochondral ossification

Differentiation of multi-potent mesenchymal stromal cells (MSCs) is directed by the activities of lineage-specific transcription factors and co-factors. A subset of these proteins controls the accessibility of chromatin by recruiting histone acetyl transferases or deacetylases that regulate acetylation of the N-termini of H3 and H4 histone proteins. Bromodomain (BRD) proteins recognize these acetylation marks and recruit the RNA pol II containing transcriptional machinery. Our previous studies have shown that Brd4 is required for osteoblast differentiation in vitro. Here, we investigated the role of Brd4 on endochondral ossification in C57BL/6 mice and chondrogenic differentiation in cell culture models. Conditional loss of Brd4 in the mesenchyme (Brd4 cKO, Brd4^fl/fl: Prrx1-Cre) yields smaller mice that exhibit alteration in endochondral ossification. Importantly, abnormal growth plate morphology and delayed long bone formation is observed in juvenile Brd4 cKO mice. One week old Brd4 cKO mice have reduced proliferative and hypertrophic zones within the physis and exhibit a delay in the formation of the secondary ossification center. At the cellular level, Brd4 function is required for chondrogenic differentiation and maturation of both ATDC5 cells and immature mouse articular chondrocytes. Mechanistically, Brd4 loss suppresses Sox9 levels and reduces expression of Sox9 and Runx2 responsive endochondral genes (e.g., Col2a1, Acan, Mmp13 and Sp7/Osx). Collectively, our results indicate that Brd4 is a key epigenetic regulator required for normal chondrogenesis and endochondral ossification.

Measurable Thoracic Motion Remains at 1 Year Following Anterior Vertebral Body Tethering, with Sagittal Motion Greater Than Coronal Motion

BACKGROUND

Anterior vertebral body tethering is an alternative to fusion surgery for the treatment of adolescent idiopathic scoliosis (AIS) that is purported to preserve spinal motion. There is limited information regarding the measurable motion that is maintained over the instrumented levels following thoracic anterior vertebral body tethering surgery in humans. The purpose of the present study was to assess radiographic spinal motion 1 year after anterior vertebral body tethering.

METHODS

As part of a prospective U.S. Food and Drug Administration investigational device exemption study, 32 patients were treated with thoracic anterior vertebral body tethering. At 1 year postoperatively, patients were evaluated with standing flexion-extension and side-bending radiographs in a microdose biplanar slot scanning imaging system. The angle subtended by the screws at the upper instrumented vertebra (UIV) and lower instrumented vertebra (LIV) was measured on left and right-bending radiographs to evaluate the coronal arc of motion and was compared with preoperative values over the same levels. At 1 year postoperatively, the sagittal Cobb angle was measured over the instrumented levels on flexion and extension radiographs.

RESULTS

Side-bending radiographs revealed that the mean angle subtended by the screws changed from 15° ± 8° on left-bending radiographs to 8° ± 6° on right-bending radiographs. The mean coronal arc of motion on bending was 7° ± 6°, with 20 (62.5%) of 32 patients having a coronal arc of motion of >5°. The mean preoperative coronal arc of motion over the instrumented segments was 30° ± 9°. On flexion-extension lateral radiographs made at 1 year postoperatively, the mean kyphotic angle over the instrumented segments was 33° ± 13° in flexion and 11° ± 14° in extension, for a mean postoperative arc of motion of 21° ± 12° between flexion and extension radiographs.

CONCLUSIONS

At 1 year following thoracic anterior vertebral body tethering for the treatment of AIS, the thoracic spine showed a measurable range of coronal and sagittal plane motion over the instrumented levels without evidence of complete autofusion. Motion in the coronal plane decreased by 77% following anterior vertebral body tethering. These findings provide proof of concept that sagittal spinal motion is preserved after thoracic anterior vertebral body tethering, although the functional importance remains to be determined.

LEVEL OF EVIDENCE

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

Fresh Osteochondral Allograft Transplantation in the Knee: A Viability and Histologic Analysis for Optimizing Graft Viability and Expanding Existing Standard Processed Graft Resources Using a Living Donor Cartilage Program

OBJECTIVE

This study aims to (1) determine and validate living cartilage allograft transplantation as a novel source for viable osteochondral allograft (OCA) tissues and (2) perform histologic and viability comparisons of living donor cartilage tissues to currently available clinical-grade standard processed grafts.

DESIGN

Using healthy cartilage from well-preserved contralateral compartments in 27 patients undergoing total knee arthroplasty (TKA) and 10 clinical-grade OCA specimens obtained immediately following operative implantation, standard and living donor OCA quality was evaluated at the time of harvest and following up to 3 weeks of storage on the basis of macroscopic International Cartilage Repair Society grade, histology, and viability.

RESULTS

Osteochondral samples demonstrated a consistent decrease in viability and histologic quality over the first 3 weeks of storage at 37°C, supporting the utility of an OCA paradigm shift toward early implantation, as was the clinical standard up until recent adoption of transplantation at 14 to 35 days following donor procurement. Samples from the 10 clinical-grade OCAs, implanted at an average of 23 days following graft harvest demonstrated a mean viable cell density of 45.6% at implantation, significantly lower (P < 0.01) than the 93.6% viability observed in living donor allograft tissues.

CONCLUSIONS

Osteochondral tissue viability and histologic quality progressively decreases with ex vivo storage, even when kept at physiologic temperatures. Currently available clinical OCAs are stored for 2 to 5 weeks prior to implantation and demonstrate inferior viability to that of fresh osteochondral tissues that can be made available through the use of a living donor cartilage program.

Modernizing Storage Conditions for Fresh Osteochondral Allografts by Optimizing Viability at Physiologic Temperatures and Conditions

Objective. Osteochondral allograft (OCA) transplantation has demonstrated good long-term outcomes in treatment of cartilage defects. Viability, a key factor in clinical success, decreases with peri-implantation storage at 4°C during pathogen testing, matching logistics, and transportation. Modern, physiologic storage conditions may improve viability and enhance outcomes. Design. Osteochondral specimens from total knee arthroplasty patients (6 males, 5 females, age 56.4 ± 2.2 years) were stored in media and incubated at normoxia (21% O₂) at 22°C or 37°C, and hypoxia (2% O₂) at 37°C. Histology, live-dead staining, and quantitative polymerase chain reaction (qPCR) was performed 24 hours after harvest and following 7 days of incubation. Tissue architecture, cell viability, and gene expression were analyzed. Results. No significant viability or gene expression deterioration of cartilage was observed 1-week postincubation at 37°C, with or without hypoxia. Baseline viable cell density (VCD) was 94.0% ± 2.7% at day 1. At day 7, VCD was 95.1% (37°C) with normoxic storage and 92.2% (37°C) with hypoxic storage (P ≥ 0.27). Day 7 VCD (22°C) incubation was significantly lower than both the baseline and 37°C storage values (65.6%; P < 0.01). COL1A1, COL1A2, and ACAN qPCR expression was unchanged from baseline (P < 0.05) for all storage conditions at day 7, while CD163 expression, indicative of inflammatory macrophages and monocytes, was significantly lower in the 37°C groups (P < 0.01). Conclusion. Physiologic storage at 37°C demonstrates improved chondrocyte viability and metabolism, and maintained collagen expression compared with storage at 22°C. These novel findings guide development of a method to optimize short-term fresh OCA storage, which may lead to improved clinical results.

Comparison of slot-scanning standing, supine, and fulcrum radiographs for assessment of curve flexibility in adolescent idiopathic scoliosis: a pilot study

PURPOSE

With the goal of reducing radiation dosing for patients, we sought to compare the results of slot-scanning (EOS) standing flexibility radiographs to supine bending and fulcrum radiographs for surgical planning in adolescent idiopathic scoliosis (AIS). We hypothesized that slot-scanning standing bending radiographs provide similar mean curve flexibility as supine bending and fulcrum radiographs.

METHODS

This is a retrospective review of 224 AIS patients with concomitant upright standing and flexibility images. Curve flexibility, defined the percent change in Cobb angle from standing upright to flexibility images, was used to compare the results of slot-scanning standing, supine and fulcrum radiographs. Statistical analysis utilized ANOVA one-way tests and two-sample t tests to detail differences as indicated.

RESULTS

A total of 256 imaging studies were included, 75 slot-scanning standing, 112 supine, and 69 fulcrum radiographs. Fulcrum images only investigated thoracic curves and were, therefore, excluded from proximal thoracic and lumbar flexibility comparisons. Relevant mean standing curve magnitudes were similar between the groups with some variance in thoracic curves between fulcrum and supine image series (p = 0.003). There was no statistical difference in curve flexibility for proximal thoracic curves (p = 0.389) and lumbar curves (p = 0.798). However, for thoracic curves, slot-scanning standing images result in less measured curve flexibility compared to supine (p = 1.00E-7) and fulcrum images (p = 2.84E-18). Furthermore, supine bending images resulted in less measured curve flexibility in comparison to fulcrum images (p = 2.85E-7).

CONCLUSION

Slot-scanning standing bending films show comparable results in curve flexibility as supine bending films for proximal thoracic and lumbar curves but may show reduced flexibility for thoracic curves when compared to supine or fulcrum bending films. Given lower radiation dosing, slot-scanning films could be substituted for traditional supine films for assessment of proximal thoracic and lumbar curve flexibility.

Trends in Incidence of Adolescent Idiopathic Scoliosis: A Modern US Population-based Study

BACKGROUND

A successful disease screening strategy requires a high incidence of the condition, efficacy of early treatment, and efficient detection. There is limited population-based data describing trends in incidence of adolescent idiopathic scoliosis (AIS) in the United States and potential role of school screening programs on the incidence of AIS. Thus, we sought to evaluate the incidence of AIS over a 20-year period between 1994 and 2013 using a population-based cohort.

METHODS

The study population comprised 1782 adolescents (aged 10 to 18 y) with AIS first diagnosed between January 1, 1994 and December 31, 2013. The complete medical records and radiographs were reviewed to confirm diagnosis and coronal Cobb angles at first diagnosis. Age-specific and sex-specific incidence rates were calculated and adjusted to the 2010 United States population. Poisson regression analyses were performed to examine incidence trends by age, sex, and calendar period.

RESULTS

The overall age-adjusted and sex-adjusted annual incidence of AIS was 522.5 [95% confidence interval (CI): 498.2, 546.8] per 100,000 person-years. Incidence was about 2-fold higher in females than in males (732.3 vs. 338.8/100,000, P<0.05). The incidence of newly diagnosed AIS cases with radiographs showing a Cobb angle >10 degrees was 181.7 (95% CI: 167.5, 196.0) per 100,000 person-years. The overall incidence of AIS decreased significantly after discontinuation of school screening in 2004 (P<0.001). The incidence of bracing and surgery at initial diagnosis was 16.6 (95% CI: 12.3, 20.9) and 2.0 (95% CI: 0.5, 3.4) per 100,000 person-years, respectively.

CONCLUSIONS

Overall population-based incidence of AIS decreased after school screening was discontinued. However, incidence of patients with a Cobb angle >10 degrees, initiation of bracing and surgery did not change significantly over time. This provides further data to help determine the role of scoliosis screening.

LEVEL OF EVIDENCE

Level III.

Does preoperative and intraoperative imaging for anterior vertebral body tethering predict postoperative correction?

PURPOSE

Anterior vertebral body tethering (AVBT) is an emerging approach for idiopathic scoliosis. However, overcorrection and under-correction are common causes of revision surgery, and intraoperative tensioning of the cord is one key component to achieve appropriate curve correction. We sought to determine whether preoperative flexibility radiographs or intraoperative radiographs would predict correction at first erect imaging for scoliosis patients undergoing anterior vertebral body tethering (AVBT).

METHODS

Single-center retrospective review. Fifty-one patients with a diagnosis of idiopathic scoliosis underwent anterior body tethering. Preoperative flexibility films and intraoperative radiographs were compared to first erect standing radiographs to determine if there was a correlation in Cobb angle.

RESULTS

Preoperative major Cobb angle measured 52° ± 9°. Major Cobb angle on bending films was 24° ± 8°. Intraoperative imaging showed correction to a mean of 17° ± 8°. Postoperative first erect standing radiographs showed correction to a mean of 26° ± 10°. The mean difference in major Cobb angle between intraoperative radiograph and a first erect radiograph was 10° ± 4°, whereas the mean difference from preoperative bending radiograph at first erect was 2° ± 7°. Thus, correction on preoperative flexibility films correlated with the first erect radiograph.

CONCLUSION

Preoperative bending radiographs provide a reasonable estimate of postoperative correction for patients undergoing AVBT with tensioning of the cord. Surgeons should expect the major Cobb angle to increase on first erect radiographs compared to intraoperative radiographs. These findings may guide patient selection and assist surgeons in achieving appropriate correction intraoperatively.

How do spine instrumentation parameters influence the 3D correction of thoracic adolescent idiopathic scoliosis? A patient-specific biomechanical study

BACKGROUND

Patient-specific models promises to support the surgical decision-making process, particularly in adolescent idiopathic scoliosis. The present computational biomechanical study investigates how specific instrumentation parameters impact 3D deformity correction in thoracic scoliosis.

METHODS

1080 instrumentation simulations of a representative patient were run. The independent instrumentation parameters were: screw pattern, upper and lower instrumented vertebrae, rod curvature and rod stiffness. ANOVA and correlation analyses analyzed how the instrumentation parameters influenced the 3D correction.

FINDINGS

Coronal plane correction was affected by the lower instrumented vertebra and rod stiffness (explaining 84% and 11%, respectively, of its overall variance). The sagittal profile was controlled by rod curvature and the upper vertebra (56% and 36%). The transverse plane vertebral rotation was influenced by lower, upper instrumented vertebra and screw pattern (35%, 32% and 19%). The Cobb angle correction was strongly correlated with the number of fused vertebrae, particularly when grouped by the upper instrumented vertebra (r = -0.91) and rod stiffness (r = -0.73). Thoracic kyphosis was strongly correlated with the number of fused vertebrae grouped by rod curvature (r = 0.84). Apical vertebral rotation was moderately correlated with the number of fused vertebrae grouped by upper/lower instrumented vertebra (r = 0.55/0.58), although variations were minimal.

INTERPRETATION

Instrumenting the last vertebra touching the central sacral vertical line improves 3D correction. A trade-off between a more cranial vs. caudal upper instrumented vertebra, respectively beneficial for coronal/sagittal vs. transverse plane correction, is required. High rod stiffness, differential rod contouring, and screw pattern were effective for coronal correction, thoracic kyphosis, and axial vertebral derotation, respectively.

Anterior Vertebral Body Tethering for Adolescent Idiopathic Scoliosis: Early Results and Future Directions

Anterior vertebral body tether (AVBT) is a nonfusion surgical procedure for correction of scoliosis in skeletally immature individuals. With US Food and Drug Administration approval in 2019, AVBT technology is spreading and early to midterm reports are being published. Early clinical reports are promising while precise indications, outcomes, complication profiles, and best practices are being established. Patients who are skeletally immature and wish to avoid a fusion surgery may benefit from this procedure. This article highlights the translational science foundation, early to midterm clinical reports, and future directions for this growing technique in pediatric spinal deformity surgery.

Cost-Utility Analysis of Anterior Vertebral Body Tethering versus Spinal Fusion in Idiopathic Scoliosis from a US Integrated Healthcare Delivery System Perspective

Purpose

Anterior vertebral body tethering (VBT) is a non-fusion, minimally invasive, growth-modulating procedure with some early positive clinical outcomes reported in pediatric patients with idiopathic scoliosis (IS). VBT offers potential health-related quality of life (HRQoL) benefits over spinal fusion in allowing patients to retain a greater range of motion after surgery. We conducted an early cost-utility analysis (CUA) to compare VBT with fusion as a first-choice surgical treatment for skeletally immature patients (age >10 years) with moderate to severe IS, who have failed nonoperative management, from a US integrated healthcare delivery system perspective.

Patients and Methods

The CUA uses a Markov state transition model, capturing a 15-year period following index surgery. Transition probabilities, including revision risk and subsequent fusion, were based on published surgical outcomes and an ongoing VBT observational study (NCT02897453). Patients were assigned utilities derived from published patient-reported outcomes (PROs; SRS-22r mapped to EQ-5D) following fusion and the above VBT study. Index and revision procedure costs were included. Probabilistic (PSA) and deterministic sensitivity analyses (DSA) were performed.

Results

VBT was associated with higher costs but also higher quality-adjusted life years (QALYs) than fusion (incremental costs: $45,546; QALYs gained: 0.54). The subsequent incremental cost-effectiveness ratio for VBT vs fusion was $84,391/QALY gained. Mean PSA results were similar to the base case, indicating that results were generally robust to uncertainty. The DSA indicated that results were most sensitive to variations in utility values.

Conclusion

This is the first CUA comparing VBT with fusion in pediatric patients with IS and suggests that VBT may be a cost-effective alternative to fusion in the US, given recommended willingness-to-pay thresholds ($100,000–$150,000). The results rely on HRQoL benefits for VBT compared with fusion. For improved model accuracy, further analyses with longer-term PROs for VBT, and comparative effectiveness studies, would be needed.