Significant variability in surgeons' preferred correction maneuvers and instrumentation strategies when planning adolescent idiopathic scoliosis surgery

High-density and moderate-density implant constructs for adolescent idiopathic scoliosis have equivalent clinical and radiographic outcomes at 2 years

PURPOSE

Implant density for posterior spinal fusion in AIS remains controversial. As limited data exist to guide surgeons, we aimed to evaluate the effect of implant density on radiographic and patient reported outcomes (PROMs).

METHODS

This is a retrospective review of prospectively collected multicenter data. Radiographic, perioperative, and PROMs were compared for patients treated with high-density (> 1.8) and moderate-density (≤ 1.8-1.4) screw constructs. Patients were stratified according to the Lenke classification.

RESULTS

1865 patients met inclusion criteria: 1225 high-density and 640 moderate-density screw construct patients. The groups had similar mean age (14.7 vs 14.6, p > 0.05) and sex (81.5% vs 79.5% female, p > 0.05). There were similar radiographic outcomes between groups [final curve magnitude (19° vs 19°, p = 0.540)] with only small differences in the percent correction for Lenke 2 curves (66% vs 61%, p = 0.001) producing a 1° difference in curve correction (19° vs 20°, p = 0.001) in the high-density group at 2 years. Excluding thoracoplasty patients, 2-year rib rotation was similar between the two groups (4.5° vs 6.3°, p < 0.05). The mean time to follow-up was shorter in the high-density group (4.5 vs 5 years, p < 0.001), but no statistically significant differences in the two-year SRS-22 scores.

CONCLUSION

Patients treated with both high and moderate-density constructs had similar SRS scores and radiographic results at 2-year follow-up. High-density constructs produced marginally better axial, sagittal, and coronal correction. However, these differences are small and not clinically meaningful with no difference in PROMs in curves ≤ 70°. The use of a moderate-density construct should be considered for routine AIS surgery.

LEVEL OF EVIDENCE

III.

Severe (>100 Degrees) Thoracic Adolescent Idiopathic Scoliosis - A Comparison of Surgical Approaches

Study DesignRetrospective.ObjectiveSevere curves >100° in adolescent idiopathic scoliosis (AIS) are rare and require careful operative planning. The aim of this study was to assess baseline, perioperative, and 2-year differences between anterior release with posterior instrumentation (AP), posterior instrumentation with posterior column osteotomies (P), and posterior instrumentation with 3-column vertebral osteotomies (VCR).MethodsTwo scoliosis datasets were queried for primary cases of severe thoracic AIS (≥100°) with 2-year follow-up. Pre- and 2-year postoperative radiographic measures (2D and estimated 3D kyphosis), clinical measurements, and SRS-22 outcomes were compared between three approaches.ResultsSixty-one patients were included: 16 AP (26%), 38 P (62%), 7 VCR (11%). Average age was 14.4 ± 2.0 years; 75.4% were female. Preoperative thoracic curve magnitude (AP: 112°, P: 115°, VCR: 126°, P = 0.09) and T5-T12 kyphosis (AP: 38°, P: 59°, VCR: 70°, P = 0.057) were similar between groups. Estimated 3D kyphosis was less in AP vs P (-12° vs 4°, P = 0.016). Main thoracic curves corrected to 36° in AP vs 49° and 48° for P and VCR, respectively (P = 0.02). Change in estimated 3D kyphosis was greater in AP vs P and VCR (34° vs 13°, P = 0.009; 34° vs 7°, P = 0.046). One incomplete spinal cord injury had residual deficits (P; 1/61, 1.6%). All SRS-22 domains improved postoperatively.ConclusionAll approaches obtained satisfactory coronal and sagittal correction, but AP had smaller residual coronal deformity and greater kyphosis restoration than the other approaches. This information may help inform the decision of whether to include an anterior release for large thoracic AIS curves.

How Accurate Are Fulcrum Bending Radiographs in Estimating Postoperative Outcomes in Adolescent Idiopathic Scoliosis? A Systematic Review and Meta-analysis

BACKGROUND

Fulcrum bending radiographs can be used to assess coronal flexibility in patients with adolescent idiopathic scoliosis (AIS) to estimate postoperative correction. To obtain fulcrum bending radiographs, patients are passively bent over a radiolucent fulcrum at the apex of the curve. Available studies have disagreed about the accuracy in estimating postoperative correction, although these studies differed in terms of patients' baseline characteristics as well as other methods. Moreover, factors associated with accuracy were never explored. By pooling (meta-analyzing) results from these studies, we hoped to address these gaps in knowledge.

QUESTIONS/PURPOSES

In a meta-analysis, we asked: (1) Can fulcrum bending radiographs accurately estimate postoperative curve correction in patients with AIS? (2) What factors are associated with the accuracy of fulcrum bending estimation on postoperative coronal correction? (3) Is fulcrum flexibility associated with other surgical outcomes such as shoulder and coronal balance?

METHODS

PubMed, Embase, Medline, Journals@Ovid, Web of Science, and Scopus were searched from their inception up to August 27, 2024. Studies that (1) included patients with AIS undergoing single-stage posterior spinal fusion surgery without anterior release, (2) used fulcrum bending radiographs, (3) assessed radiographic surgical outcomes, and (4) had a minimum follow-up of 2 years were included. Studies that did not evaluate the use of fulcrum bending radiographs, those that did not report a p value, and studies with poor methodological quality were excluded. Our initial search yielded 433 articles, of which 172 remained after duplicate articles were removed. A total of 161 articles were excluded as the studies included patients who did not have AIS (n = 14), did not undergo surgery (n = 14), or did not undergo posterior spinal fusion (n = 23) or the studies did not evaluate the use of fulcrum bending radiographs (n = 59); had an insufficient follow-up duration of < 2 years (n = 15); did not evaluate the relationship between fulcrum bending radiographs and postoperative outcomes (n = 1); were reviews, commentaries, articles, conference proceedings, or non-English studies (n = 33); were animal studies (n = 1); or had poor methodological quality (n = 1). This left 11 studies for analysis. The Newcastle-Ottawa Quality Assessment Scale was used to evaluate the quality of evidence in three domains, including participant selection, comparability, and outcome measurement. Eleven included studies were of good quality except one with poor-quality evidence that was subsequently excluded from analysis. A random-effects meta-analysis was used to pool the data because of substantial statistical heterogeneity (I2 > 50%) in the included studies. The estimation of absolute correction was pooled using standardized mean differences, referred to as the mean difference; a value > 0 indicated overestimation and vice versa. Estimation of percentage correction was pooled using ratio of means between correction rate and fulcrum flexibility, referred to as fulcrum bending correction index (FBCI); a value > 1 indicated underestimation and vice versa.

RESULTS

Fulcrum bending radiographs tended to underestimate postoperative curve correction, although the difference was not clinically important (immediate postoperative mean difference -0.6° [95% confidence interval (CI) -0.9° to -0.4°], p < 0.001; immediate postoperative FBCI 1.15 [95% CI 1.09 to 1.21], p < 0.001; 2-year follow-up mean difference -0.43° [95% CI -0.6° to -0.2°], p < 0.001; 2-year follow-up FBCI 1.10 [95% CI 1.04 to 1.16], p = 0.001). To address the high between-study heterogeneity, we adjusted for potential confounders, which found that more flexible curves (regression coefficient 0.07 [95% CI 0.01 to 0.13]; p = 0.02) and proximal thoracic (immediate postoperative main thoracic versus proximal thoracic curves mean difference -0.8° [95% CI -1.4° to -0.2°], p = 0.01; 2-year follow-up main thoracic versus proximal thoracic curves mean difference -0.7° [95% CI -1.3° to -0.1°], p = 0.03) curves were associated with less underestimation. Segmental and alternate level screw placement were associated with underestimation of curve correction by fulcrum bending radiographs, although the difference was clinically unimportant. The degree of underestimation was worse with segmental screw placement at immediate postoperative (mean difference -1.0° [95% CI -1.9° to -0.1°]; p < 0.001) and 2-year follow-up (mean difference -1.0° [95% CI -1.6° to -0.4°]; p < 0.001). However, evidence surrounding more serious underestimation in segmental compared with alternate level screw placement was uncertain as only one study used a segmental screw placement strategy. Regarding the relationship between fulcrum flexibility and other radiographic outcomes, more rigid main thoracic curves were at risk of coronal imbalance, while more flexible curves were associated with postoperative shoulder imbalance. However, the evidence was inconclusive as it was reported by two or fewer studies.

CONCLUSION

Fulcrum bending radiographs offer a reliable estimate of postoperative coronal correction; the amount of underestimation that we observed on some endpoints was too small to be clinically meaningful. Although there was substantial statistical heterogeneity, the direction of effect was similar across all studies. Fulcrum bending estimation was also reliable when using alternate pedicle screw constructs. More flexible curves and proximal thoracic curves were associated with less underestimation. In more rigid curves, results of fulcrum bending estimation should be interpreted with caution, and alternate flexibility assessment methods such as traction should be considered.

LEVEL OF EVIDENCE

Level III, diagnostic study.

Reoperation Rate After Posterior Spinal Fusion Varies Significantly by Lenke Type

Background

Lenke curve types can vary in their response to treatment. We explored potential differences in reoperation rates, causes, and risk factors among patients with different Lenke types who underwent posterior spinal fusion (PSF) for adolescent idiopathic scoliosis (AIS).

Methods

We studied a multicenter database of patients with AIS who underwent index PSF at ≤21 years of age and had a minimum 2-year follow-up. Baseline and surgical characteristics were collected. Reoperation rates, causes, and risk factors were analyzed by Lenke type.

Results

A total of 3,165 patients were included. The mean age was 14.6 years, and most patients were female (81%) and Caucasian (68%). The mean follow-up period was 4.4 years. A total of 138 patients (4.4%) underwent reoperation. The reoperation rate varied by Lenke type (p = 0.02): patients with type-5 curves had the highest reoperation rate (7.2%), and those with type-1 curves had the lowest (3.0%). The most common cause of reoperation was an instrumentation complication. The rate of reoperation due to an instrumentation complication varied by Lenke type (p < 0.01). Compared with patients with type-1 curves, those with type-5 curves had significantly higher rates of reoperation due to implant prominence (odds ratio [OR], 11.7; p = 0.03), loss of fixation (OR, 3.9; p = 0.01), or a broken rod (OR, 7.8; p = 0.02) and those with type-3 curves had a significantly higher rate of reoperation due to loss of fixation (OR, 4.37; p = 0.01). Independent risk factors for reoperation were a major curve magnitude of ≥60° in patients with type-5 curves (adjusted OR [aOR], 4.18; p = 0.04), a major curve correction of ≥40° in patients with type-5 curves (aOR, 3.6; p = 0.04), and a lowest instrumented vertebra (LIV) at or above L1 in patients with type-1 curves (aOR, 2.8; p = 0.02).

Conclusions

The reoperation rate for patients with AIS who underwent PSF varied by Lenke type. Patients with type-5 curves had the highest reoperation rate, whereas patients with type-1 curves had the lowest. Patients with Lenke type-5 curves had a higher rate of reoperation due to instrumentation complications.

Level of Evidence

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

Comparison of four correction techniques for posterior spinal fusion in adolescent idiopathic scoliosis

INTRODUCTION

When performing posterior spinal fusion for adolescent idiopathic scoliosis (AIS), it is of major importance to address both coronal and sagittal deformities. Although several techniques have been described, few data exist comparing them. Our objective was to compare four techniques (in situ bending (ISB), rod derotation (RD), cantilever (C) and posteromedial translation (PMT)) for the correction of spinal deformity in AIS including thoracic deformity.

MATERIAL AND METHODS

We conducted a multicenter retrospective study including 562 AIS patients with thoracic deformity with at least 24-month follow-up. Radiographic analysis was performed preoperatively, postoperatively and at last follow-up. The main outcomes were main curve correction and thoracic kyphosis restoration (TK).

RESULTS

Coronal correction rate was significantly different among the four treatment groups (ISB 64% vs C 57% vs RD 55% vs PMT 67%, p < 0.001). Multivariate regression revealed that correction technique did not influence correction rate, whereas implant density, convex side compression and use of derotation connectors did. TK increase was significantly higher in the PMT group (average + 13°) than in DR (+ 3°), while ISB (-3°) and cantilever (-13°) resulted in TK decrease (p < 0.001). Multivariate analysis revealed that TK increase was only influenced by the reduction technique (p < 0.001) and preoperative TK (p < 0.001).

DISCUSSION

The four techniques had the same ability to correct spinal deformity in the coronal plane. Three factors were identified to improve correction rate: implant density, convex compression and use of derotation connectors. On the other hand, PMT was more effective in restoring TK, particularly in hypokyphotic patients.

How low can you go? Implant density in posterior spinal fusion converted from growing constructs for early onset scoliosis

STUDY DESIGN

Retrospective, multicenter comparative.

OBJECTIVES

Our purpose was to compare early onset scoliosis (EOS) patients treated with ultra-low, low, and high implant density constructs when undergoing conversion to definitive fusion. Larson et al. demonstrated that implant density (ID) at fusion does not correlate with outcomes in the treatment of adolescent idiopathic scoliosis, but did not address growth-friendly graduates.

METHODS

EOS patients treated with growth-friendly constructs converted to fusion between 2000 and 2017 were reviewed from a multicenter database. ID was defined as number of pedicle screws, hooks, and sublaminar/bands per level fused. Patients were divided into ultra-low ID (< 1.3), low (≥ 1.3 and < 1.6), and high ID (≥ 1.6).

EXCLUSION CRITERIA

< 2 years follow-up from fusion or inadequate radiographs.

RESULTS

A total of 152 patients met inclusion criteria with 39 (26%) patients in the high ID group, 33 (22%) patients in the low ID group, and 80 (52%) in the ultra-low ID group. Groups were similar in operative time (p = 0.61), pre-fusion major curve (p = 0.71), mean number of levels fused (p = 0.58), clinical follow-up (p = 0.30), and radiographic follow-up (p = 0.90). Patients in the low ID group (11.6 ± 1.5 years) were slightly younger at the time of definitive fusion than patients in the ultra-low ID group (12.9 ± 2.2 years) and high ID group (12.5 ± 1.7 years) (p = 0.009). There was significantly more blood loss in the high ID group than the other two groups (high ID: 946.8 ± 606.0 mL vs. low ID: 733.9 ± 434.5 mL and ultra-low ID: 617.4 ± 517.2 mL; p = 0.01), but there was no significant difference with regard to percent of total blood volume lost (high ID: 59.3 ± 48.7% vs. low ID: 54.5 ± 37.5% vs. ultra-low ID: 51.7 ± 54.9%; p = 0.78). There was a difference in initial improvement in major curve between the groups (high ID: 21.6° vs. low ID: 18.0° vs. ultra-low ID: 12.6°; p = 0.01). However, during post-fusion follow-up, correction decreased 7.1° in the high ID group, 2.6 in the low ID group, and 2.8 in the ultra-low ID group (p = 0.19). At final follow-up, major curve correction from pre-fusion was similar between groups (high ID: 14.5° vs. low ID: 15.5° vs. ultra-low ID: 9.7°, p = 0.14). At final follow-up, there was no difference in T1-T12 length gain (p = 0.85), T1-S1 length gain (p = 0.68), coronal balance (p = 0.56), or sagittal balance (p = 0.71). The revision rate was significantly higher in the ultra-low ID group (13.8%; 11/80) versus the high ID group (2/39; 5.1%) and low ID group (0/33; 0%) (p = 0.04).

CONCLUSIONS

Although an ID < 1.3 in growth-friendly graduates produces similar outcomes with regard to curve correction and spinal length gain as low and high ID, this study suggests that an ID < 1.3 is associated with an increased revision rate.

LEVEL OF EVIDENCE

III.

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.

The importance of curve severity, type and instrumentation strategy in the surgical correction of adolescent idiopathic scoliosis: an in silico clinical trial on 64 cases

Adolescent idiopathic scoliosis is a three-dimensional deformity of the spine which is frequently corrected with the implantation of instrumentation with generally good or excellent clinical results; mechanical post-operative complications such as implant loosening and breakage are however relatively frequent. The rate of complications is associated with a lack of consensus about the surgical decision-making process; choices about the instrumentation length, the anchoring implants and the degree of correction are indeed mostly based on personal views and previous experience of the surgeon. In this work, we performed an in silico clinical trial on a large number of subjects in order to clarify which factors have the highest importance in determining the risk of complications by quantitatively analysing the mechanical stresses and loads in the instrumentation after the correction maneuvers. The results of the simulations highlighted the fundamental role of the curve severity, also in its three-dimensional aspect, and of the instrumentation strategy, whereas the length of the fixation had a lower importance.

In silico patient-specific optimization of correction strategies for thoracic adolescent idiopathic scoliosis

BACKGROUND

With modelling and simulation (or in silico) techniques, patient-specific optimization algorithms represent promising tools to support the surgical decision-making process, particularly in 3D correction of adolescent idiopathic scoliosis, where the best intraoperative instrumentation strategy and the correction goals are debated.

METHODS

1080 biomechanical intraoperative simulations of a representative pediatric thoracic curve were run according to a full-factorial design approach. Widely accepted instrumentation configurations (5 screw patterns, 4 upper and 3 lower instrumented vertebrae, 6 rod curvatures and 3 rod stiffnesses) were analyzed, assuming concave rod rotation and en bloc derotation as main correction maneuvers. Results in terms of 3D correction and mobility were rated using an objective function for thoracic scoliosis also including surgeon-dependent correction objectives. An extensive sensitivity analysis on correction objectives was performed.

FINDINGS

Multiple optimal strategies were identified, depending on the selected correction objective. They provided significantly better coronal (67% vs. 55%) correction, using comparable instrumented levels (9.9 ± 1.6 vs. 10.7 ± 2.1), screw patterns and significantly higher implant density (1.6 ± 0.3 vs. 1.4 ± 0.2 screws/vertebra) compared to worst ones. Optimal strategies typically included the neutral and the last touching vertebrae in the construct and high stiffness (CoCr, 6 mm) differentially/highly contoured rods.

INTERPRETATION

The computerized algorithm determined the best instrumentation parameters to achieve optimal correction for the considered thoracic case. Multiple clinically equivalent strategies may be used, as supported by the variety of considered correction objectives. The current approach could be translated to any scoliotic curves, including surgeon preferences in terms of instrumentation parameters, intraoperative correction maneuvers and correction objectives.

Correction objectives have higher impact than screw pattern and density on the optimal 3D correction of thoracic AIS: a biomechanical study

STUDY DESIGN

Assessment of screw pattern, implant density (ID), and optimization of 3D correction through computer-based biomechanical models.

OBJECTIVE

To investigate how screw pattern and ID affect intraoperative 3D correction of thoracic curves in adolescent idiopathic scoliosis, and how different correction objectives impact the optimal screw pattern. Screw pattern, ID, correction objectives and surgical strategies for posterior fusion of AIS are highly variable among experienced surgeons. The "optimal" instrumentation remains not well defined.

METHODS

10 patient-specific multibody models of representative adolescent idiopathic scoliosis Lenke 1A cases were built and used to compare alternative virtual correction surgeries. Five screw patterns and IDs (average: 1.6 screws/instrumented level, range: 1.2-2) were simulated, considering concave rod rotation, en bloc derotation, and compression/distraction as primary correction maneuvers. 3D correction descriptors were quantified in the coronal, sagittal and transverse planes. An objective function weighting the contribution of intraoperative 3D correction and mobility allowed rating of the outcomes of the virtual surgeries. Based on surgeon-dependent correction objectives, the optimal result among the simulated constructs was identified.

RESULTS

Low-density (ID ≤ 1.4) constructs provided equivalent 3D correction compared to higher (ID ≥ 1.8) densities (average differences ranging between 2° and 3°). The optimal screw pattern varied from case to case, falling within the low-density screw category in 14% of considered scenarios, 73% in the mid-density (1.4 < ID < 1.8) and 13% in the high-density. The optimal screw pattern was unique in five cases; multiple optima were found in other cases depending on the considered correction objectives.

CONCLUSIONS

Low-density screw patterns provided equivalent intraoperative 3D correction to higher-density patterns. Simulated surgeon's choice of correction objectives had the greatest impact on the selection of the optimal construct for 3D correction, while screw density and ID had a limited impact.

LEVEL OF EVIDENCE

N/A.

Surgical Outcomes of a New Technique Using a Convex Rod Rotation Maneuver for Adolescent Idiopathic Scoliosis

Introduction

Because of adolescent idiopathic scoliosis (AIS), most surgeons use rod rotation on the concave side for Lenke types 1 and 2 curves. Nevertheless, the accurate placement of pedicle screws within dysplastic pedicles, especially on the concave side, is sometimes challenging. Conversely, there is a concern that apical rotation might be exacerbated after convex rod rotation maneuver (RRM) because the rod is rotated in the same direction as vertebral rotation. This study aims to demonstrate the surgical technique and outcomes of a convex RRM with direct vertebral rotation (DVR) for the correction of AIS.

Technical Note

Multilevel pedicle screws were inserted into the vertebrae. The pre-bent pure titanium rod was set on the convex side and then derotated to nearly 90°. DVR was conducted for the desired vertebrae. Another pre-bent titanium alloy rod, for placement on the concave side, was contoured the same as the rod on the convex side. Using a reduction tube that allowed easier capture of the rod, the rod was connected to the concave side screws. DVR was again conducted for the desired vertebrae. Among the 59 patients, the correction rate of the main thoracic curve in Lenke types 1 and 2 AIS was 75.1% and 65.0%, respectively. The absolute value of the change in apical vertebral rotation between pre- and post-operative computed tomography (CT) scans in Lenke types 1 and 2 curves was 4.8° and 4.2°, respectively.

Conclusions

The convex RRM improved vertebral rotation in Lenke types 1 and 2 AIS. This procedure should be regarded as one of the surgical options for AIS, especially in patients with a narrow pedicle width on the concave side.

Willingness to enroll in a surgical randomized controlled trial: patient and parent preferences regarding implant density for adolescent idiopathic scoliosis fusion

STUDY DESIGN

Prospective survey of adolescent idiopathic scoliosis (AIS) patients/parents with surgical magnitude curves.

OBJECTIVE

We hypothesized that patients and families considering fusion surgery would be willing to enroll in a randomized controlled trial (RCT) evaluating the effect of number of implants on curve correction. Surgical RCTs are infrequently performed, particularly in a pediatric population. Parental willingness to enroll affects both study design and trial feasibility. The Minimize Implants Maximize Outcomes (MIMO) Clinical Trial proposes to randomize patients to more versus fewer screws (high or low density) for Lenke 1A curve patterns, but it is unclear whether families and patients are willing to enroll in such a trial.

METHODS

This study was undertaken at 4 of the 14 sites participating in the MIMO Clinical Trial. AIS patients with Cobb > 45° were included. Implant density is defined as screws per level fused. Patients and families reviewed the MIMO education module describing proposed advantages and disadvantages of high (> 1.8) vs. low (< 1.4) density screw constructs and completed a custom survey regarding their preferences about the trial.

RESULTS

159 individuals were surveyed (78 families), including 82 parents/guardians, and 77 patients. Of those surveyed, 95% mostly or completely understood the trial (range 47-78%), and 63% agreed to enroll. Parents and patients who completely understood the trial were significantly more likely to enroll.

CONCLUSION

Randomization in the MIMO Trial was acceptable to the majority (63%) of patients and parents. Clear patient and parent education materials and access to the surgeon may facilitate enrollment in the trial. Parents afforded the child much autonomy when considering enrollment, although most families agree both child and parent should be in agreement before entering the trial.

LEVEL OF EVIDENCE

II.