Ten-year Risk of Recall of Novel Spine Devices.

STUDY DESIGN: Observational epidemiological study. OBJECTIVE: This study's primary objective was to examine the risk of recall for novel spine devices over time. Secondarily, we sought to analyze interbody fusion and vertebral body replacement (VBR) devices (corpectomy cages) as a risk factor for recall. SUMMARY OF BACKGROUND DATA: The recall risk of a novel spine device over time has not been reported. Additionally, FDA regulations were lowered for interbody fusion devices to enter the market in 2007. As well, VBR implants were recently approved by the FDA for use in the cervical spine in 2015. METHODS: Spine devices cleared between January 1, 2008 and December 31, 2018 were identified from the FDA's 510(k) database. All recall data was collected from the database in January of 2021 to provide a 2-year minimum follow-up for a recall to occur. Product labels were used to classify interbody fusion and VBR devices. Cumulative incidence function was conducted to compare the overall risk of recall for FDA cleared spine devices, and the hazard ratio determined for VBR and all other devices vs interbody implants during the study period. RESULTS: 2,384 spine devices were cleared via 510(k) in the study period. The hazard of recall at 5 years was 5.3% (95% CI: 4.4%-6.2%) and 6.5% (95% CI: 5.4-7.7%) at 10 years. No significant difference in recall risk was identified for interbody fusion and VBR devices. CONCLUSION: The risk of recall at 5 and 10 years of a novel spine device is about half the 12% rate reported for orthopedic devices in general. Despite lowered FDA regulations for interbody fusion devices and recent approval for VBR device use in the cervical spine, no increased risk of recall was detected. Further research is necessary to explain the reason for the lower risk of recall with spine devices. LEVEL OF EVIDENCE: V.

A novel antibacterial compound decreases MRSA biofilm formation without the use of antibiotics in a murine model.

Despite significant advancements in material science, surgical site infection (SSI) rates remain high and prevention is key. This study aimed to demonstrate the in vivo safety and antibacterial efficacy of titanium implants treated with a novel broad-spectrum biocidal compound (DBG21) against methicillin-resistant Staphylococcus aureus (MRSA). Titanium (Ti) discs were covalently bound with DBG21. Untreated Ti discs were used as controls. All discs were implanted either untreated for 44 control mice or DBG21-treated for 44 treated mice. After implantation, 1 × 107 colony forming units (CFU) of MRSA were injected into the operating site. Mice were killed at 7 and 14 days to determine the number of adherent bacteria (biofilm) on implants and in the peri-implant surrounding tissues. Systemic and local toxicity were assessed. At both 7 and 14 days, DBG21-treated implants yielded a significant decrease in MRSA biofilm (3.6 median log10 CFU [99.97%] reduction [p < 0.001] and 1.9 median log10 CFU [98.7%] reduction [p = 0.037], respectively) and peri-implant surrounding tissues (2.7 median log10 CFU/g [99.8%] reduction [p < 0.001] and 5.6 median log10 CFU/g [99.9997%] reduction [p < 0.001], respectively). There were no significant differences between control and treated mice in terms of systemic and local toxicity. DBG-21 demonstrated a significant decrease in the number of biofilm bacteria without associated toxicity in a small animal implant model of SSI. Preventing biofilm formation has been recognized as a key element of preventing implant-related infections.

Implant Surface Technologies to Prevent Surgical Site Infections in Spine Surgery.

Spine surgeries are occurring more frequently worldwide. Spinal implant infections are one of the most common complications of spine surgery, with a rate of 0.7% to 11.9%. These implant-related infections are a consequence of surface polymicrobial biofilm formation. New technologies to combat implant-related infections are being developed as their burden increases; however, none have reached the market stage in spine surgery. Conferring antimicrobial properties to biomaterials relies on either surface coating (physical, chemical, or combined) or surface modification (physical, chemical, or combined). Such treatment can also result in toxicity and the progression of antimicrobial resistance. This narrative review will discuss "late-stage" antimicrobial technologies (mostly validated in vivo) that use these techniques and may be incorporated onto spine implants to decrease the burden of implant-related health care-acquired infections (HAIs). Successfully reducing this burden will greatly improve the quality of life in spine surgery. Familiarity with upcoming surface technologies will help spine surgeons understand the anti-infective strategies designed to address the rapidly worsening challenge of implant-related health care-acquired infections.

Estimating pulmonary function after surgery for adolescent idiopathic scoliosis using biplanar radiographs of the chest with 3D reconstruction.

AIMS: This study addressed two questions: first, does surgical correction of an idiopathic scoliosis increase the volume of the rib cage, and second, is it possible to evaluate the change in lung function after corrective surgery for adolescent idiopathic scoliosis (AIS) using biplanar radiographs of the ribcage with 3D reconstruction? METHODS: A total of 45 patients with a thoracic AIS which needed surgical correction and fusion were included in a prospective study. All patients underwent pulmonary function testing (PFT) and low-dose biplanar radiographs both preoperatively and one year after surgery. The following measurements were recorded: forced vital capacity (FVC), slow vital capacity (SVC), and total lung capacity (TLC). Rib cage volume (RCV), maximum rib hump, main thoracic curve Cobb angle (MCCA), medial-lateral and anteroposterior diameter, and T4-T12 kyphosis were calculated from 3D reconstructions of the biplanar radiographs. RESULTS: All spinal and thoracic measurements improved significantly after surgery (p < 0.001). RCV increased from 4.9 l (SD 1) preoperatively to 5.3 l (SD 0.9) (p < 0.001) while TLC increased from 4.1 l (SD 0.9) preoperatively to 4.3 l (SD 0.8) (p < 0.001). RCV was correlated with all functional indexes before and after correction of the deformity. Improvement in RCV was weakly correlated with correction of the mean thoracic Cobb angle (p = 0.006). The difference in TLC was significantly correlated with changes in RCV (p = 0.041). It was possible to predict postoperative TLC from the postoperative RCV. CONCLUSION: 3D rib cage assessment from biplanar radiographs could be a minimally invasive method of estimating pulmonary function before and after spinal fusion in patients with an AIS. The 3D RCV reflects virtual chest capacity and hence pulmonary function in this group of patients. Cite this article: Bone Joint J 2022;104-B(1):112-119.

Surgical Treatment of a Symptomatic Diaphyseal Tibiofibular Synostosis in a Professional Rugby Player: A Case Report and Literature Review.

CONTEXT: Diaphyseal tibiofibular synostosis (DTS) is a rare pathology with unknown origin especially occurring in intensive sport athletes. No therapeutic guideline has been well established in the literature. CASE PRESENTATION: A rare case of DTS in a 26-year-old professional rugby player has been described. A 5-month exhaustive conservative treatment including physiotherapy and oral medication has been achieved but failed. Management and Outcomes: Following the conservative treatment failure, the DTS has been widely removed including the adjacent interosseous membrane, and the patient could return to competition at the same level after 5 months of convalescence. No recurrence has been revealed at a 35-month follow-up at least. CONCLUSION: In accordance with the literature data and even if the pathophysiology remains obscure, resection of DTS seems to be the adapted treatment to allow and to reduce professional athletes' recovery time at the same sport level. The resection including a part of the tibiofibular interosseous membrane could avoid the occurrence of recurrence. Conservative treatment should be reserved for senior patients with a low sport activity.

[Physiological aging spine]. / Vieillissement physiologique de la colonne vertébrale.

Physiological aging spine. The process of physiological aging or senescence of the spine begins in the first decade of life and then accelerates from the third. It is essentially fundamentally linked to a phenomenon of entropy that inexorably alters the machinery of all the cells of the body, to which are added random pathologies. Senescence is thus responsible for so-called degenerative multisystem alterations so that the term «degenerative disc disease¼, is too restrictive and inappropriate. All the connective structures of the column are involved (intervertebral discs, articular joints and vertebral bone) but also muscle, vascular and neural components. In addition, there are neurological abnorma¬lities in the cerebral cortex and cerebellum that regulate the functioning of the verte¬bral column. The sum of the functional and tissue alterations modifies mechanical behavior both in the vertebrae (osteoporosis often complicated by fractures and de¬formities) than that of the intervertebral mobile segments, responsible for disc rupture, spondylolisthesis or degenerative deformities sometimes complicated by radicular or myelopathic abnormalities depending on the levels concerned. The impact of degene¬rative lesions in the spine is, however, highly variable from one subject to another depending on genetics, lifestyle, and for low back pain, the psychosocial context.

Vieillissement physiologique de la colonne vertébrale. Le processus de vieillissement physiologique ou sénescence de la colonne vertébrale débute dès la première décennie de la vie puis s'accélère à partir de la troisième. Il est pour l'essentiel fondamentalement lié à un phénomène d'entropie qui altère inexo¬rablement la machinerie de toutes les cellules de l'organisme auquel s'ajoutent les pathologies aléatoires que chacun peut développer. La sénescence est ainsi responsable d'altérations multitissulaires dites dégénératives si bien que le terme de « degenerative disc disease ¼, trop restrictif, est inapproprié. Toutes les structures conjonctives de la colonne sont plus ou moins concernées (disques intervertébraux, jointures interfacet¬taires et os des vertèbres ) mais aussi les composants musculaires, vasculaires et nerveux. De plus, s'y ajoutent des anomalies neurologiques au niveau des centres nerveux médullaires et cérébraux qui régulent le fonctionnement de la colonne. La somme des altérations tissulaires et fonctionnelles modifie le comportement mécanique tant au niveau des vertèbres (ostéoporose souvent compliquée de fractures et de déformations) qu'au niveau des segments mobiles intervertébraux, responsable de ruptures discales, de spondylolisthésis ou de déformations dégénératives parfois com¬pliqués de radiculalgies ou de myélopathies selon les niveaux concernés. Le retentis¬sement des lésions dégénératives de la colonne est cependant très variable d'un sujet à un autre en fonction de la génétique, du mode de vie, et, pour la lombalgie, du contexte psychosocial.

Rib Cage Measurement Reproducibility Using Biplanar Stereoradiographic 3D Reconstructions in Adolescent Idiopathic Scoliosis.

BACKGROUND: A reproducibility study of preoperative rib cage three-dimensional (3D) measurements was conducted for patients with Adolescent Idiopathic Scoliosis (AIS). No prior reliability study has been performed for preoperative 3D reconstructions of the rib cage by using stereoradiography in patients with preoperative AIS. Our objective was to assess the reliability of rib cage 3D reconstructions using biplanar stereoradiography in patients with AIS before surgery. METHODS: This series includes 21 patients with Lenke 1 or 2 scoliosis (74±20 degrees). All patients underwent low-dose standing biplanar radiographs. Two operators performed reconstructions twice each. Intraoperator repeatability, interoperator reproducibility, and intraclass coefficients (ICC) were calculated and compared between groups. RESULTS: The average rib cage volume was 4.71 L (SD±0.75 L). Two SD was 0.19 L with a coefficient of variation of 4.1%; ICC was 0.968. The thoracic index was 0.6 (SD±0.1). Two SD was 0.03 with a coefficient of variation of 4.7% and a ICC of 0.820. As for the Spinal Penetration Index (6.4%; SD±2.4), 2SD was 0.9% with a coefficient of variation of 14.3% and a ICC of 0.901. The 3D rib hump 2SD (average 27±8 degrees) was 1.4 degrees. The coefficient of variation and ICC were respectively 5.1% and 0.991. CONCLUSIONS: Three-dimensional reconstruction of the rib cage using biplanar stereoradiography is a reliable method to estimate preoperative thoracic parameters in patients with AIS. LEVEL OF EVIDENCE: Level IV-diagnostic study.

Traumatic posterior Atlanto-axial dislocation: case report of an atypical C1-C2 dislocation with an anterior arch fracture of C1.

BACKGROUND: An atypical case of a traumatic posterior C1-C2 dislocation with an anterior arch fracture of C1 is reported. A novel conservative treatment for this rare lesion is described. CASE PRESENTATION: An eighty-nine-year-old male fell off a ladder at home and presented with an acute traumatic cervical spine trauma, which we believe involved a distraction mechanism. The patient was neurologically intact; he denied any weakness, numbness or paresthesia. A preoperative CT-scan demonstrated a posterior dislocation with an anterior arch of C1 fracture. Conservative management was elected. Reduction was achieved by closed manual reduction under general anesthesia. A postoperative CT demonstrated a complete reduction of the atlanto-axial dislocation. CONCLUSION: Based on this case report and relevant literature, we present an unusual lesion of the upper cervical spine treated nonoperatively with closed manual reduction under general anesthesia. To date, there is no available consensus for the management of these lesions.

Head to pelvis alignment of adolescent idiopathic scoliosis patients both in and out of brace.

PURPOSE: To determine the short-term effect of bracing of adolescent idiopathic scoliotic (AIS) patients on the relationships between spinopelvic parameters related to balance, by comparing their in and out-of-brace geometry and versus healthy subjects. METHODS: Forty-two AIS patients (Cobb angle 29° ± 12°, ranging from 16° to 61°) with a prescription of orthotic treatment were included retrospectively and prospectively. They all underwent biplanar radiography and 3D reconstruction of the spine and pelvis before bracing as well as less than 9 months after bracing. Eighty-three age-matched healthy adolescents were also included as control group and underwent biplanar radiography and 3D reconstruction. RESULTS: Sacral slope was higher in AIS than healthy patients (p = 0.005). Bracing induced large changes of pelvic tilt (between - 9° and 9°), although patients' sagittal spinopelvic alignment tended to remain within the normality corridors defined by the healthy patients. Patients had flatter backs compared to healthy subjects and bracing further reduced their spinal curves. The head tended to remain above the pelvis in-brace. CONCLUSION: Analysis of sagittal alignment from head to pelvis showed that bracing further flattened the patients' backs and induced large compensating reorientations of the pelvis. Sagittal balance should be included in the planning and evaluation of brace treatment, since it could play a role in its outcome. These slides can be retrieved under Electronic Supplementary Material.

Influence of posture on relationships between pelvic parameters and lumbar lordosis: Comparison of the standing, seated, and supine positions. A preliminary study.

BACKGROUND: Pelvic incidence (PI) is an anatomical parameter that is considered invariable in a given individual. Although changes in posture influence the mobile lumbar spine, lumbar lordosis (LL) and the pelvis are typically evaluated only in the standing position. Thus, whether other positions commonly used during daily activities influence the relationship between LL and PI is unknown. The objective of this study was to determine whether LL and sacral slope (SS) correlated with PI, using two standardised positions, seated and supine, different from the standing position that is generally used. HYPOTHESIS: We are supposing that lumbar lordosis and sacral sloop are correlated to pelvic incidence whatever the posture. The goal of this study was to confirm or deny this hypothesis, using two standardize positions (sitting and lying) different that the usual standing position. LL and SS correlate with PI in the standing, seated, and supine positions. METHOD: Lumbar and pelvic parameters were measured on radiographs obtained in the standing, seated, and supine positions in 15 asymptomatic adult volunteers younger than 50years of age. Mean values with their standard deviations were computed and compared across the three positions using ANOVA. Spearman's test was applied to assess correlations. RESULTS: PI had the same value in all three positions. The L1-S1 LL angle was 54.8±9.8° in the standing position, 15.9±14.6° in the seated position, and 50.2±9.6° in the supine position. Pelvic tilt (PT) in the same three positions was 12.1±6.3°, 37.7±10.4°, and 9.5±5.1°, respectively; and SS was 37.1±6.3°, 11.3±10.8°, and 41±7.2°, respectively. Correlations were strongest in the supine position between PI and LL (r=0.72), LL and SS (r=0.9), and PI and SS (r=0.84). CONCLUSION: Whereas PI remains unchanged in a given individual, lumbar lordosis and sacral orientation show significant changes across positions used in daily life, with the greatest changes seen in the seated position. During spinal fusion surgery, adjusting LL based on IP is crucial even in patients who have limited physical activity. LEVEL OF EVIDENCE: IV.

Radiographic Classification for Degenerative Spondylolisthesis of the Lumbar Spine Based on Sagittal Balance: A Reliability Study.

STUDY DESIGN: Inter- and intraobserver reliability study. OBJECT: To assess the reliability of a new radiographic classification of degenerative spondylolisthesis of the lumbar spine (DSLS). SUMMARY OF BACKGROUND DATA: DSLS is a common cause of chronic low back and leg pain in adults. To this date, there is no consensus for a comprehensive analysis of DSLS. The reliability of a new DSLS classification system based on sagittal alignment was assessed. METHODS: Ninety-nine patients admitted to our spinal surgery department for surgical treatment of DSLS between January 2012 and December 2015 were included. Three observers measured sagittal alignment parameters with validated software: segmental lordosis (SL), lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), and sagittal vertical axis (SVA). Full body low-dose lateral view radiographs were analyzed and classified according to three main types: Type 1A: preserved LL and SL; Type 1B: preserved LL and reduced SL (≤5°); Type 2A: PI-LL ≥10° without pelvic compensation (PT <25°); Type 2B: PI-LL ≥10° with pelvic compensation (PT ≥25°); Type 3: global sagittal malalignment (SVA ≥40 mm). The three observers classified radiographs twice with a 3-week interval for intraobserver reproducibility. Interobserver reproducibility was calculated using Fleiss κ and intra-class coefficient. Intraobserver reproducibility was calculated using Cohen κ. RESULTS: Mean age was 68.8 ± 9.8 years. Mean sagittal alignment parameters values were the following: PI: 60.1° ± 12.7°; PI-LL was 12.2° ± 13.9°, PT: 24.7° ± 8.5°; SVA: 44.9 mm ± 44.6 mm; SL: 16.6° ± 8.4°. Intraobserver repeatability showed an almost perfect agreement (ICC > 0.92 and Cohen κ > 0.89 for each observer). Fleiss κ value for interobserver reproducibility was 0.82, with percentage agreement among observers between 88% and 89%. CONCLUSION: This new classification showed an excellent inter- and intraobserver reliability. This simple method could be an additional sagittal balance tool helping surgeons improve their preoperative DSLS analysis.

Paraspinal hibernoma: Grand Round presentation of a rare benign adipocytic tumor.

INTRODUCTION: We report an uncommon case of paraspinal hibernoma with a T12-L1 foraminal extension and discuss the potential differential diagnoses of paraspinal adipocytic tumors. MATERIALS AND METHODS: A 32-year-old woman consulted our department with a right subscapular and paraspinal mass. There was no associated neurological deficit. The MRI revealed a paraspinal adipocytic tumor with a T12-L1 right foraminal extension. Percutaneous biopsy suggested a diagnosis of hibernoma. RESULTS: Hibernoma is a rare and benign adipocytic tumor arising from embryologic remnants of brown fat. Specific MRI findings are discussed to differentiate hibernoma from other soft-tissue tumors. A planned marginal resection was undertaken with the final histopathology confirming the diagnosis of hibernoma. CONCLUSION: Based on the Grand Round case and relevant literature, we discuss a rare case of paraspinal hibernoma with a foraminal component and no recurrence at 3-year follow-up.

A computed tomographic anatomical study of the upper sacrum. Application for a user guide of pelvic fixation with iliosacral screws in adult spinal deformity.

PURPOSE: Widely used in traumatic pelvic ring fractures, the iliosacral (IS) screw technique for spino-pelvic fixation remains anecdotal in adult spinal deformity. The objective of this study was to assess anatomical variability of the adult upper sacrum and to provide a user guide of spino-pelvic fixation with IS screws in adult spinal deformity. METHODS: Anatomical variability of the upper sacrum according to age, gender, height and weight was sought on 30 consecutive pelvic CT-scans. Thus, a user guide of spino-pelvic fixation with IS screws was modeled and assessed on ten CT-scans as described below. Two invariable landmarks usable during the surgical procedure were defined: point A (corresponding to the connector binding the IS screw to the spinal rod), equidistant from the first posterior sacral hole and the base of the S1 articular facet and 10 mm-embedded into the sacrum; point B (corresponding to the tip of the IS screw) located at the junction of the anterior third and middle third of the sacral endplate in the sagittal plane and at the middle of the endplate in the coronal plane. Point C corresponded to the intersection between the A-B direction and the external facet of the iliac wing. Three-dimensional reconstructions modeling the IS screw optimal direction according to the A-B-C straight line were assessed. RESULTS: Age had no effect on the anatomy of the upper sacrum. The distance between the base of the S1 superior articular facet and the top of the first posterior sacral hole was correlated with weight (r = 0.6; 95% CI [0.6-0.9]); p < 0.001). Sacral end-plate thickness increased for male patients (p < 0.001) and was strongly correlated with height (r = 0.6; 95% CI [0.29-0.75]); p < 0.001) and weight (r = 0.8; 95% CI [0.6-0.9]); p < 0.001). The thickness of the inferior part of the S1 vertebral body increased in male patients (p < 0.001). Other measured parameters slightly varied according to gender, height and weight. Simulating the described technique of pelvic fixation, no misplaced IS screw was found whatever the age, gender and morphologic parameters. CONCLUSION: This user guide of spinopelvic fixation with IS screws seems to be reliable and reproducible independently of age, gender and morphologic characteristics but needs clinical assessment. LEVEL OF EVIDENCE: Level IV.

A new classification system for degenerative spondylolisthesis of the lumbar spine.

PURPOSE: There is no consensus for a comprehensive analysis of degenerative spondylolisthesis of the lumbar spine (DSLS). A new classification system for DSLS based on sagittal alignment was proposed. Its clinical relevance was explored. METHODS: Health-related quality-of-life scales (HRQOLs) and clinical parameters were collected: SF-12, ODI, and low back and leg pain visual analog scales (BP-VAS, LP-VAS). Radiographic analysis included Meyerding grading and sagittal parameters: segmental lordosis (SL), L1-S1 lumbar lordosis (LL), T1-T12 thoracic kyphosis (TK), pelvic incidence (PI), pelvic tilt (PT), and sagittal vertical axis (SVA). Patients were classified according to three main types-1A: preserved LL and SL; 1B: preserved LL and reduced SL (≤5°); 2A: PI-LL ≥10° without pelvic compensation (PT < 25°); 2B: PI-LL ≥10° with pelvic compensation (PT ≥ 25°); type 3: global sagittal malalignment (SVA ≥40 mm). RESULTS: 166 patients (119 F: 47 M) suffering from DSLS were included. Mean age was 67.1 ± 11 years. DSLS demographics were, respectively: type 1A: 73 patients, type 1B: 3, type 2A: 8, type 2B: 22, and type 3: 60. Meyerding grading was: grade 1 (n = 124); grade 2 (n = 24). Affected levels were: L4-L5 (n = 121), L3-L4 (n = 34), L2-L3 (n = 6), and L5-S1 (n = 5). Mean sagittal parameter values were: PI: 59.3° ± 11.9°; PT: 24.3° ± 7.6°; SVA: 29.1 ± 42.2 mm; SL: 18.2° ± 8.1°. DSLS types were correlated with age, ODI and SF-12 PCS (ρ = 0.34, p < 0.05; ρ = 0.33, p < 0.05; ρ = -0.20, and p = 0.01, respectively). CONCLUSION: This classification was consistent with age and HRQOLs and could be a preoperative assessment tool. Its therapeutic impact has yet to be validated. LEVEL OF EVIDENCE: 4.

Is it safe to perform lumbar spine surgery on patients over eighty five?

PURPOSE: The purpose of this study was to evaluate the safety and tolerance of lumbar spine surgery in patients over 85. MATERIALS AND METHODS: Patients over 85 years of age with LSS who underwent decompression surgery with or without fusion between February 2011 and July 2014 were included. Comorbidities, autonomy (Activities of Daily Life and Braden scales), surgical parameters and complications (Clavien-Dindo classification) were collected. A telephone survey was performed to assess survival and patients' satisfaction at last follow-up. RESULTS: Mean follow-up was 27.4 ± 7.6 months (range, 18-65). Mean age was 87.5 ± 2.7 years (range, 85-97). Mean ADLs and Braden scores were, respectively, 4.3 ± 1.2 and 20.2 ± 1.4. Fifteen patients had associated spondylolisthesis. Nineteen minor complications (grade I and II, 38.7%), five moderate complications (grade III, 10.2%) and six major complications (grade IV and V, 12.2%) occurred. The perioperative mortality rate was 0.02%. At last follow-up, 41 patients were very satisfied (83.7%), five patients were satisfied (10.2%) and three patients were not satisfied (6.1%). Fusion did not affect the incidence of complications (p = 0.3) nor the average number of complications per patient (p = 0.2). CONCLUSION: Advanced age should not be a contraindication to lumbar spine surgery provided careful preoperative selection is performed. This study reported a high satisfaction rate and a low mortality rate at the price of a high number of complications, most of which being minor.

Experimental validation of a patient-specific model of orthotic action in adolescent idiopathic scoliosis.

PURPOSE: Personalized modeling of brace action has potential in improving brace efficacy in adolescent idiopathic scoliosis (AIS). Model validation and simulation uncertainty are rarely addressed, limiting the clinical implementation of personalized models. We hypothesized that a thorough validation of a personalized finite element model (FEM) of brace action would highlight potential means of improving the model. METHODS: Forty-two AIS patients were included retrospectively and prospectively. Personalized FEMs of pelvis, spine and ribcage were built from stereoradiographies. Brace action was simulated through soft cylindrical pads acting on the ribcage and through displacements applied to key vertebrae. Simulation root mean squared errors (RMSEs) were calculated by comparison with the actual brace action (quantified through clinical indices, vertebral positions and orientations) observed in in-brace stereoradiographies. RESULTS: Simulation RMSEs of Cobb angle and vertebral apical axial rotation was lower than measurement uncertainty in 79 % of the patients. Pooling all patients and clinical indices, 87 % of the indices had lower RMSEs than the measurement uncertainty. CONCLUSIONS: In-depth analysis suggests that personalization of spinal functional units mechanical properties could improve the simulation's accuracy, but the model gave good results, thus justifying further research on its clinical application.