Background: Anterior vertebral body tethering (aVBT) has emerged as a novel treatment option for patients with idiopathic scoliosis. We present the results from the first U.S. Food and Drug Administration (FDA) Investigational Device Exemption (IDE) study on aVBT. Methods: In this prospective review of a retrospective data set, eligible patients underwent aVBT at a single center from August 2011 to July 2015. Inclusion criteria included skeletally immature patients with Lenke type-1A or 1B curves between 30° and 65°. Clinical and radiographic parameters were collected, with the latter measured by an independent reviewer. Results: Fifty-seven patients (49 girls and 8 boys), with a mean age (and standard deviation) of 12.4 ± 1.3 years (range, 10.1 to 15.0 years), were enrolled in the study. The patients had a mean of 7.5 ± 0.6 levels tethered, the mean operative time was 223 ± 79 minutes, and the mean estimated blood loss was 106 ± 86 mL. The patients were followed for an average of 55.2 ± 12.5 months and had a mean Risser grade of 4.2 ± 0.9 at the time of the latest follow-up. The main thoracic Cobb angle was a mean of 40.4° ± 6.8° preoperatively and was corrected to 18.7° ± 13.4° at the most recent follow-up. In the sagittal plane, T5-T12 kyphosis measured 15.5° ± 10.0° preoperatively, 17.0° ± 10.1° postoperatively, and 19.6° ± 12.7° at the most recent follow-up. Eighty percent of patients had curves of <30° at the most recent follow-up. The most recent Scoliosis Research Society (SRS) scores averaged 4.5 ± 0.4, and scores on the self-image questionnaire averaged 4.4 ± 0.7. No major neurologic or pulmonary complications occurred. Seven (12.3%) of 57 patients had a revision: 5 were done for overcorrection and 2, for adding-on. Conclusions: Anterior VBT is a promising technique that has emerged as a treatment option for patients with immature idiopathic scoliosis. We present the results from the first FDA-approved IDE study on aVBT, which formed the basis for the eventual Humanitarian Device Exemption approval. The findings affirm the safety and efficacy of this technique and suggest opportunities for improvement, particularly with respect to reoperation rates. Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Background: Anterior vertebral body tethering (AVBT) for adolescent idiopathic scoliosis (AIS) is postulated to preserve motion compared with traditional posterior spinal fusion (PSF), but few studies exist to date. We used a validated computerized 3D model to compare trunk motion between patients treated with PSF and AVBT, and analyzed trunk motion in relation to the lowest instrumented vertebra (LIV). Methods: This was a single-center retrospective review of a consecutive series of skeletally immature patients with AIS who underwent motion analysis prior to PSF (n = 47) or AVBT (n = 65) and 2 years postoperatively. Patients were divided into 4 groups on the basis of the LIV (≤L1, L2, L3, L4). Computerized 3D kinematic evaluations included thoracic and lumbar flexion, extension, side-bending, and rotation. Patient outcomes were assessed using the Scoliosis Research Society (SRS)-22 questionnaire. Results: The LIV was ≤L1 in 48 patients treated with AVBT and 23 treated with PSF, L2 in 4 AVBT and 8 PSF patients, L3 in 10 AVBT and 8 PSF patients, and L4 in 3 AVBT and 8 PSF patients. PSF patients had a significant loss of motion in all 4 directions at 2 years postoperatively (e.g., flexion loss was 11° for ≤L1 to 30° for L4; p < 0.001). This equated to a 7° loss of trunk flexion per additional LIV level included in the fusion. AVBT patients only demonstrated loss of flexion and side-bending at 2 years postoperatively (e.g., flexion loss of 11° for L1 to 17° for L4; p < 0.001). Preoperative curve size and flexibility did not have any significant impact on differences in trunk motion between AVBT and PSF. SRS-22 scores were predominantly similar for AVBT versus PSF preoperatively and at 2 years postoperatively. Conclusions: Patients treated with AVBT experienced predominantly less motion loss compared with PSF patients at 2 years postoperatively. Patients treated with PSF demonstrated loss of motion in all planes that increased with each additional LIV from ≤L1 to L4, with 7° loss of flexion per additional LIV. However, the differences in total trunk motions were relatively modest for PSF and AVBT with an LIV of ≤L1. Preoperative curve magnitude and flexibility had no significant impact on trunk motion in either group. SRS-22 scores were similar for both groups at 2 years postoperatively. Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Background: Treatment outcomes and risk factors for neurological deficits in pediatric patients with an os odontoideum are unclear. Methods: We reviewed the data for 102 children with os odontoideum who were managed at 11 centers between 2000 and 2016 and had a minimum duration of follow-up of 2 years. Thirty-one children had nonoperative treatment, and 71 underwent instrumented posterior cervical spinal arthrodesis for the treatment of C1-C2 instability. Nonoperative treatment consisted of observation (n = 29) or immobilization with a cervical collar (n = 1) or halo body jacket (n = 1). Surgical treatment consisted of atlantoaxial (n = 50) or occipitocervical (n = 21) arthrodesis. One patient also underwent transoral odontoidectomy. Results: Thirty children (29%) presented with neurological deficits, 28 of whom had radiographic atlantoaxial instability (atlantoaxial distance >5 mm) or limited space (≤13 mm) available for the spinal cord (risk ratio, 7.8 [95% confidence interval, 2.0 to 31] compared with children with no radiographic risk factors). The 27 children without neurological deficits or atlantoaxial instability at presentation underwent nonoperative treatment and remained asymptomatic. Of the initial nonoperative cohort, one child developed atlantoaxial instability, and another had a persistent neurological deficit; both children underwent spinal arthrodesis during the study period. One child with cervical instability declined surgery and remained asymptomatic. Spinal fusion occurred in 68 patients in the surgical group by the end of the study period (mean, 3.7 years; range, 2.0 to 11.8 years). Surgical complications occurred in 21 children, including nonunion in 12, new neurological deficits in 4, cerebrospinal fluid leak in 2, symptomatic instrumentation requiring removal 2, and vertebral artery injury in 1. Nine children underwent revision surgery. In the surgical group, Japanese Orthopaedic Association neurological function scores improved significantly from preoperatively to the latest follow-up for the upper extremities (p = 0.026) and lower extremities (p = 0.007). Conclusions: The risk of developing a neurological deficit was strongly associated with atlantoaxial instability and limited space available for the spinal cord in children with os odontoideum. Nonoperative treatment was safe for asymptomatic patients without atlantoaxial instability. Spinal arthrodesis resolved the neurological deficits of children with symptomatic os odontoideum. Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Background: For large scoliosis, 2 strategies to maximize correction include intraoperative traction and/or anterior release. It is unclear which patients will benefit the most form either approach. The purpose of our study is to compare the radiographic, perioperative clinical outcomes, and health-related quality of life (HRQoL) outcomes of 2 approaches when used in severe neuromuscular scoliosis in the setting of cerebral palsy (CP). Methods: In total, 23 patients with minimum 2-year follow-up, major curves ≥100 degrees, and in whom treatment included posterior spinal fusion were evaluated. Eighteen were treated with posterior spinal fusion with intraoperative traction and 5 with anterior/posterior spinal fusion (APSF). The baseline characteristics, perioperative outcomes, and preoperative and 2-year follow-up data for HRQoL and radiographic measures were compared. Results: The groups had similar age, sex, nutritional and seizure status, GMFCS level, and change in CPCHILD scores. The groups had similar curve magnitude (120 vs. 105 degrees, P=0.330) and flexibility (28% vs. 40%, P=0.090), but the APSF group had less pelvic obliquity (POB) (24 vs. 42 degrees, P=0.009). There were similar postoperative major curves (37 vs. 40 degrees, P=0.350), but greater correction in POB (33.5 vs. 14 degrees of correction, P=0.007) in the traction group. The APSF group had longer anesthesia times (669 vs. 415 min, P=0.005), but similar hospital stays, intensive care unit and days intubated, estimated blood loss, cell saver, and red blood cells used. Although the APSF group had twice the rate of complications (22% vs. 40%) during the first 90 days postoperatively, this did not reach statistical significance. Conclusions: Both intraoperative traction and anterior surgery were used to aid correction in severe CP scoliosis. Anterior surgery did not offer superior correction or better HRQoL, and was associated with increased operative times, whereas intraoperative traction was associated with greater correction of POB. Intraoperative traction may be a viable alternative to an anterior release in severe CP scoliosis. Level of Evidence: Level II.

Chemotherapeutic bone cements can both stabilize the bone fractures as well as deliver chemotherapy agents directly to the bone metastatic site and adjacent soft tissue tumors. This study evaluated the in vitro elution and flexural properties of Vertebroplastic™ and Confidence Ultra™ bone cements (Depuy Spine Inc., Raynham, Mass., USA) containing methotrexate. In vitro elution was measured by placing bone cement specimens containing 4 different methotrexate amounts in 20 ml saline, and the methotrexate elution was measured at regular intervals for 672 h. The flexural properties of bone cement containing 2 different initial methotrexate amounts after storage in physiological saline were measured using a 3-point bending test. The drug elution rate depended on the initial methotrexate amount added and the type of bone cement used. The relationship between the initial drug amount added and the drug elution rate was not linear. Methotrexate elution decreased the flexural modulus and strength of specimens; this decrease was not proportional to the initial amount of methotrexate added. The results show that bone cements are well suited for use with chemotherapy agents. However, the elution and mechanical properties of each bone cement-drug amount combination should be thoroughly quantified in vitro before using such a combination in a clinical setting.