El‐Hawary, Ron

Background: Anterior vertebral body tethering (AVBT) is a promising fusionless alternative for treating idiopathic scoliosis; however, limited data exist on the learning curve for this procedure. Previous studies are limited by single-center and short-term complication data. This multicenter study assesses the learning curve by evaluating improvements in operative characteristics over time and radiographic measurements up to 2 years postoperatively. Methods: As recorded from a multicenter registry, surgeons with ≥10 index AVBT procedures for patients with idiopathic scoliosis aged 16 years and below were included. Relationships between case number and multiple surgical variables were determined using Pearson correlation and linear regression testing. For identification of an inflection point, consecutive cases were plotted against operative time per level and fitted with a locally weighted scatterplot smoothing curve. Independent samples t test and χ 2 test were used to compare outcomes between cases before and after the inflection point. Outcomes of interest included demographic, surgical, and radiographic information at the baseline, immediate postoperative, and 2-year timepointswhere available. Results: Eight surgeons and 325 index AVBT patients met the inclusion criteria. Inverse relationships were identified between case number and estimated blood loss, operative time, anesthesia time, and fluoroscopic time per level ( P < 0.005). The inflection point was identified at 15 cases. Operative time, anesthesia time, and fluoroscopy time per level were greater in the first 15 cases compared with those after ( P < 0.05). There were no significant differences in demographic variables, intraoperative complications, or length of stay between the early and late cases. Greater correction in the major coronal curve, minor coronal curve, and coronal balance occurred in the cases performed after the inflection point ( P < 0.05). Conclusions: AVBT is a safe alternative to posterior spinal fusion and demonstrates a predictable improvement in surgical performance over time. Large improvements can be expected during the first 15 AVBT cases performed with minimal differences in complications. Level of Evidence: Level III.

Background: Motion-sparing scoliosis surgeries such as the posterior dynamic distraction device (PDDD) are slowly increasing in use. However, there is limited clinical data documenting postoperative motion across the PDDD construct. With this cohort study, we aim to measure sagittal and coronal motion following PDDD. We hypothesize coronal and sagittal spinal motion will be partially preserved across the construct. Methods: Retrospective review of prospectively collected data. Preoperative and minimum 1-year postoperative coronal range of motion across the instrumented levels was compared. Available flexion/extension radiographs were evaluated postoperatively to assess sagittal arc of motion. Radiographs from latest follow-up were used. Results: At a mean of 1.9 years (1 to 5 y), flexibility radiographs were available on 29 patients treated with PDDD (17 thoracic, 12 lumbar). Mean age at surgery was 16 years (12 to 25). Postoperative coronal arc of motion in PDDD patients was 11 degrees (3 to 19 degrees) in the thoracic spine and 10 degrees (0 to 28 degrees) in the lumbar spine. Compared with preoperative motion, the thoracic arc of motion was maintained by 33% (35 to 11 degrees) and lumbar motion was maintained by 30% (34 to 10 degrees). Flexion-extension radiographs were available on 7 patients. Sagittal arc for the upper instrumented vertebral end plate to the lower instrumented vertebral endplate of the cohort was 10 degrees in the thoracic spine (6 to 18) and 14 degrees in the lumbar spine (5 to 21). Sagittal measurements for the changes in the arc of the upper and lower screws on the construct were 4 degrees in the thoracic group (2 to 8) and 9 degrees in the lumbar group (2 to 17). By latest follow-up 11 patients (38%) underwent reoperation, with most cases due to implant breakage (N=4, 14%), extender misalignment (N=2, 7%), and screw misplacement (N=2, 7%). Conclusion: At mean 1.9 years postoperatively, PDDD preserves measurable spinal motion over the construct both in the coronal and the sagittal plane without evidence for autofusion. Coronal arc of motion averages 10 to 12 degrees and sagittal arc of motion ranged from 4 to 14 degrees, although this varies by patient. This study confirms that PDDD for pediatric scoliosis preserves a measurable degree of postoperative flexibility both in the sagittal and coronal planes. Level of Evidence: Level II—therapeutic study.