Analysis of three-dimensional spine growth for vertebral body tethering patients at 2 and 5 years post operatively.

PURPOSE: Scoliosis can be treated with vertebral body tethering (VBT) as a motion-sparing procedure. However, the knowledge of how growth is affected by a tether spanning multiple levels is unclear in the literature. Three-dimensional true spine length (3D-TSL) is a validated assessment technique that accounts for the shape of the spine in both the coronal and sagittal planes. This study aimed to assess if 3D-TSL increases over a five-year period after VBT implantation in thoracic curves for idiopathic scoliosis. METHODS: Prospectively collected radiographic data from an international pediatric spine registry was analyzed. Complete radiographic data over three visits (post-operative, 2 years, and 5 years) was available for 53 patients who underwent VBT. RESULTS: The mean age at instrumentation of this cohort was 12.2 (9-15) years. The average number of vertebrae instrumented was 7.3 (SD 0.7). Maximum Cobb angles were 50° pre-op, which improved to 26° post-op (p < 0.001) and was maintained at 5 years (30°; p = 0.543). Instrumented Cobb angle was 22° at 5 years (p < 0.001 vs 5-year maximum Cobb angle). An accentuation was seen in global kyphosis from 29° pre-operative to 41° at 5 years (p < 0.05). The global spine length (T1-S1 3D-TSL) started at 40.6 cm; measured 42.8 cm at 2 years; and 44.0 cm at the final visit (all p < 0.05). At 5 years, patients reached an average T1-S1 length that is comparable to a normal population at maturity. Immediate mean post-operative instrumented 3D-TSL (top of UIV-top of LIV) was 13.8 cm two-year length was 14.3 cm; and five-year length was 14.6 cm (all p < 0.05). The mean growth of 0.09 cm per instrumented level at 2 years was approximately 50% of normal thoracic growth. Patients who grew more than 0.5 cm at 2 years had a significantly lower BMI (17.0 vs 19.0, p < 0.05) and smaller pre-operative scoliosis (48° vs 53°, p < 0.05). Other subgroup analyses were not significant for age, skeletal maturity, Cobb angles or number of spanned vertebras as contributing factors. CONCLUSIONS: This series demonstrates that 3D-TSL increased significantly over the thoracic instrumented levels after VBT surgery for idiopathic scoliosis. This represented approximately 50% of expected normal thoracic growth over 2 years.

Differential vertebral body growth is maintained after vertebral body tethering surgery for idiopathic scoliosis: 4-year follow-up on 888 peri-apical vertebrae and 592 intervertebral discs.

PURPOSE: To radiographically evaluate if vertebral body tethering (VBT) can maintain differential peri-apical vertebral growth at medium-term follow-up of 4 years. METHODS: A prospective, international, multicenter database was queried to identify idiopathic scoliosis patients treated with thoracic VBT. Concave vs. convex vertebral body height, vertebral wedging, and disc wedging of the 3 peri-apical vertebrae were measured by two independent observers at 5 timepoints (pre-operative to 4-year follow-up). RESULTS: 65 skeletally immature patients (60 female, mean 12.8 years old, 21 with open triradiate cartilages) met inclusion criteria. Mean pre-operative maximum scoliosis of 50 ± 8° decreased significantly post-operatively to 27 ± 9° (p < 0.001), which remained stable at 4-year follow-up 30 ± 17° (p = 0.38 vs. post-operative). Mean instrumented scoliosis was 21 ± 14° at 4-year follow-up, which was significantly different than 4-year maximum scoliosis (p < 0.001). Mean pre-operative kyphosis of 30 ± 12° did not significantly change post-operatively (p = 1.0) and remained stable at 4-year follow-up (35 ± 18°; p = 0.05). Mean individual convex vertebral height increased from 17.7 ± 1.9 mm to 19.8 ± 1.5 mm (p < 0.001), while mean individual concave height increased from 14.8 ± 1.9 mm to 17.6 ± 1.6 mm (p < 0.001). Summing the peri-apical heights, the difference in height from pre-operative to 4-year follow-up was greater on the concave (8.3 ± 4.7 mm) than on the convex side (6.2 ± 4.7 mm) (p < 0.001). Mean individual vertebral wedging decreased from 6 ± 2° at pre-operative to 4 ± 2° at 4-year follow-up (p < 0.001). Mean total vertebral and disc wedging started at 29 ± 7° pre-operatively, decreased to 16 ± 6° at post-operative (p < 0.001), then further decreased to 14 ± 8° at 4-year follow-up (p < 0.001). Patients with open triradiate cartilages at the time of surgery had a larger height change over the 4 years compared to those with closed triradiate cartilages (p < 0.001). CONCLUSION: Patients with idiopathic scoliosis treated with VBT demonstrated differential vertebral growth which was maintained at minimum 4-year follow-up. This effect was more pronounced in patients whose triradiate cartilages were open at the time of surgery. LEVEL OF EVIDENCE: III.

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.

Vertebral body tethering for Lenke 1A curves: the lumbar modifier predicts less optimal outcomes.

INTRODUCTION: The addition of the L4 "AR" and "AL" lumbar modifier for Lenke 1A idiopathic scoliosis (IS) has been shown to direct treatment in posterior spinal fusion; however, its utility in vertebral body tethering (VBT) has yet to be evaluated. METHODS: A review of a prospective, multicenter database for VBT in IS was performed for patients with Lenke 1A deformities and a minimum of 2 years follow-up. Patients were categorized by their lumbar modifier (AR vs AL). Less optimal VBT outcome (LOVO) was defined as a final coronal curve > 35°, lumbar adding-on, or revision surgery for deformity progression or adding-on. RESULTS: Ninety-nine patients met inclusion criteria (81% female, mean 12.6 years), with 55.6% being AL curves. Overall, there were 23 instances of tether breakage (23.3%) and 20 instances of LOVO (20.2%). There was a higher rate of LOVO in AR curves (31.8% vs 10.9%, P = 0.01). Patients with LOVO had greater preoperative deformity, greater apical translation, larger coronal deformity on first erect radiographs, and less coronal deformity correction. Failure to correct the deformity < 30° on first erect was associated with LOVO, as was LIV selection short of the last touch vertebra (TV). Independent risk factors for LOVO included AR curves (OR 3.4; P = 0.04) and first erect curve magnitudes > 30 degrees (OR 6.0; P = 0.002). DISCUSSION: There is a 20.2% rate of less optimal VBT following VBT for Lenke 1A curves. AR curves are independently predictive of less optimal outcomes following VBT and require close attention to LIV selection. Surgeons should consider achieving an initial coronal correction < 30 degrees and extending the LIV to at least the TV to minimize the risk of LOVO.

Anterior Vertebral Body Tethering: A Review of the Available Evidence.

Idiopathic scoliosis is a complex three-dimensional deformity of the spine with anterior overgrowth (hypokyphosis), coronal curvature, and axial rotation. Scoliosis treatment in the skeletally immature spine is therapeutically challenging because of growth and was commonly limited to observation, bracing treatment, or fusion. Fusion accomplishes powerful deformity correction at the expense of future growth and mobility of the involved segments, increasing the risk of adjacent segment degeneration and intervertebral disk disease later in life. Anterior vertebral body tethering is a motion-preserving technique that exploits the Hueter-Volkmann principle by applying compression at the anterior and convex aspects of the curve to stimulate differential vertebral growth for gradual deformity reduction without fusion. The appropriate timing, curve magnitude, tensioning, growth prediction, indications, and limitations of tethering are being refined as this technique becomes more prevalent. Early outcome studies show that growth modulation with vertebral body tethering is safe, can achieve good results, and preserve motion in select patients.

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.

Thoracolumbar curve behavior after selective thoracic anterior vertebral body tethering in Lenke 1A vs Lenke 1C curve patterns.

STUDY DESIGN: Retrospective review of a prospective database. OBJECTIVES: The purpose of this study is to evaluate changes in the thoracic and thoracolumbar/lumbar curves and truncal balance in patients treated with selective thoracic anterior vertebral body tethering (AVBT) with Lenke 1A vs 1C curves at a minimum of 2 years follow-up. Lenke 1C curves treated with selective thoracic AVBT demonstrate equivalent thoracic curve correction and reduced thoracolumbar/lumbar curve correction compared to Lenke 1A curves. Additionally, at the most recent follow-up, both curve types demonstrate comparable coronal alignment at C7 and the lumbar curve apex, though 1C curves have better alignment at the lowest instrumented vertebra (LIV). Rates of revision surgery are equivalent between the two groups. METHODS: A matched cohort of 43 Risser 0-1, Sanders Maturity Scale (SMS) 2-5 AIS pts with Lenke 1A (1A group)and 19 pts with Lenke 1C curves (1C group) treated with selective thoracic AVBT and a minimum of 2-year follow-up were included. Digital radiographic software was used to assess Cobb angle and coronal alignment on preoperative, postoperative and subsequent follow-up radiographs. Coronal alignment was assessed by measuring the distance from the center sacral vertical line (CSVL) to the midpoint of the LIV, apical vertebra for thoracic and lumbar curves and C7. RESULTS: There was no difference in the thoracic curve measured preoperatively, at first erect, pre-rupture or at the most recent follow-up, nor was there a significant difference in C7 alignment (p = 0.057) or apical thoracic alignment (p = 0.272) between the 1A and 1C groups. Thoracolumbar/lumbar curves were smaller in the 1A group at all-time points. However, there was no significant difference between the percent correction between the two groups thoracic (p = 0.453) and thoracolumbar/lumbar (p = 0.105). The Lenke 1C curves had improved coronal translational alignment of the LIV at the most recent follow-up p = 0.0355. At the most recent follow-up the number of patients considered to have successful curve correction (Cobb angle correction of both the thoracic and thoracolumbar//lumbar curves to ≤ 35 degrees), was equivalent between Lenke 1A and Lenke 1C curves (p = 0.80). There was also no difference in the rate of revision surgery between the two groups (p = 0.546). CONCLUSION: This is the first study to compare the impact of lumbar curve modifier type on outcomes in thoracic AVBT. We found that Lenke 1C curves treated with selective thoracic AVBT demonstrate less absolute correction of the thoracolumbar/lumbar curve at all time points but have equivalent percent correction of the thoracic and thoracolumbar/lumbar curves. The two groups have equivalent alignment at C7 and the thoracic curve apex, and Lenke 1C curves have better alignment at the LIV at the most recent follow-up. Furthermore, they have an equivalent rate of revision surgery compared to Lenke 1A curves. Selective thoracic AVBT is a viable option for selective Lenke 1C curves, but despite equivalent correction of the thoracic curve, there is less correction of the thoracolumbar/lumbar curve at all-time points.

Surgical Outcomes of Cerebral Palsy Patients With Scoliosis and Lumbar Hyperlordosis: A Comparative Analysis With 2-year Minimum Follow-up.

STUDY DESIGN: Retrospective review of a prospectively collected multicenter database. OBJECTIVE: To compare outcomes of patients with cerebral palsy (CP) who undergo surgery for scoliosis with normal lordosis (NL) versus hyperlordosis. SUMMARY OF BACKGROUND DATA: Surgical correction of scoliosis with lumbar hyperlordosis is challenging. Hyperlordosis may confer higher perioperative morbidity, but this is not well understood. MATERIALS AND METHODS: A multicenter database was queried for CP patients who underwent surgery from 2008 to 2017. The minimum follow-up was 2 years. Two groups were identified: lumbar lordosis <75° (NL) versus ≥ 75° hyperlordosis (HL). Perioperative, radiographic, and clinical outcomes were compared. RESULTS: Two hundred seventy-five patients were studied: 236 NL and 39 HL (-75 to -125°). The mean age was 14.1 years, and 52.4% were male. Patients with hyperlordosis had less cognitive impairment (76.9% vs. 94.0%, P =0.008) and higher CPCHILD scores (59.4 vs. 51.0, P =0.003). Other demographics were similar between the groups. Patients with hyperlordosis had greater lumbar lordosis (-90.5 vs. -31.5°, P <0.001) and smaller sagittal vertical axis (-4.0 vs. 2.6 cm, P <0.001). Patients with hyperlordosis had greater estimated blood loss (2222.0 vs. 1460.7 mL, P <0.001) but a similar perioperative complication rate (20.5% vs. 22.5%, P =0.787). Significant correction of all radiographic parameters was achieved in both groups. The HL group had postoperative lumbar lordosis of -68.2° and sagittal vertical axis of -1.0 cm. At a 2-year follow-up, patients with hyperlordosis continued to have higher CPCHILD scores and gained the greatest benefit in overall quality of life measures (20.0 vs. 6.1, P =0.008). The reoperation rate was 10.2%: implant failure (3.6%), pseudarthrosis (0.7%), and wound complications (7.3%). There were no differences in the reoperation rate between the groups. CONCLUSION: Surgical correction of scoliosis with hyperlordosis is associated with greater estimated blood loss but similar radiographic results, perioperative morbidity, and reoperation rate as normal lordosis. Patients with hyperlordosis gained greater overall health benefits. Correction of ≥25% of hyperlordosis seems satisfactory. LEVEL OF EVIDENCE: 3.

Posterior cervical spinal fusion in the pediatric population using modern adult instrumentation - clinical outcome and safety.

PURPOSE: Traditionally, less rigid fixation techniques have been applied to the pediatric cervical spine. There is a lack of long-term outcome data for rigid fixation techniques. The purpose of this study was to define the clinical outcome and safety of posterior instrumented fusion in the pediatric population using adult posterior instrumentation. METHODS: A multicenter, retrospective review of pediatric patients who underwent posterior cervical fusion using a 3.5 mm posterior cervical system for any indication was performed. Outcome parameters included complications, revision and fusion rates, operative time (OR), blood loss, and postoperative neurologic status. Outcomes were compared between patient groups (posterior only versus anterior/posterior approach, short versus intermediate versus long fusion, and between different etiologies) using Mann-Whitney and chi-square test. RESULTS: Seventy-nine patients with a mean age of 9.9 years and mean follow-up of 2.8 years were included. At baseline 44 (56%) had an abnormal neurologic exam. Congenital deformities and basilar invagination were the most common indications for surgery. Posterior-only surgery was performed in 71 (90%) cases; mean number of levels fused was 4 (range 1-15). Overall, 4 (5%) operative complications and 4 (5%) revisions were reported at an average postoperative time of 2.6 years. Neurologic status remained unchanged in 74%, improved in 23%, and worsened in 3%. When comparing outcome measures between the various groups, 2 significant differences were found: OR was longer in the anterior/posterior approach group and decline of neuro status was more frequent in the long fusion group. CONCLUSION: Posterior cervical fusion with an adult 3.5 mm posterior cervical system was safe in this cohort of 79 pediatric patients irrespective of surgical technique, fusion length, and etiology, resulting in a high fusion and low complication/revision rate.

Vertebral body tethering for non-idiopathic scoliosis: initial results from a multicenter retrospective study.

PURPOSE: Vertebral body tethering (VBT) has been described for patients with idiopathic scoliosis. Results of the technique for non-idiopathic scoliosis have not yet been reported. METHODS: An international multicenter registry was retrospectively queried for non-idiopathic scoliosis patients who underwent VBT with minimum 2-year follow-up. Success at 2 years was defined as Cobb angle < 35 degrees and no fusion surgery. RESULTS: Of the 251 patients treated with VBT, 20 had non-idiopathic scoliosis and minimum 2-year follow-up. Mean age at surgery was 12.4 years (range 10 to 17 years). Mean major Cobb angle at enrollment was 56 degrees. Of those, 18 patients had a major thoracic curve and two had a major lumbar curve. Of the 20 patients, nine met criteria for success (45%). Eight of the 20 patients had poor outcomes (four fusions, four with curve > 50 degrees). Success was associated with smaller preoperative Cobb angle (50 vs. 62 degrees, p = 0.01) and smaller Cobb angle on initial postop imaging (28 degrees vs. 46 degrees, p = 0.0007). All patients with Cobb angle < 35 degrees on 1st postop imaging had a successful result, with the exception of one patient who overcorrected and required fusion. Syndromic vs. neuromuscular patients had a higher likelihood of success (5 of 7, 71%, 2 of 10, 20%, p = 0.03). CONCLUSION: Selected non-idiopathic scoliosis can be successfully treated with VBT, but failure rates are high and were associated with large curves, inadequate intraoperative correction and neuromuscular diagnosis. Achieving a Cobb angle less than 35 degrees on 1st standing radiograph was associated with a successful outcome which was achieved in 45% of patients. LEVEL OF EVIDENCE: Level IV (retrospective review study).

Reliability of radiographic assessment of growth modulation from anterior vertebral body tethering surgery in pediatric scoliosis.

PURPOSE: To assess the reliability of vertebral height and angular measurements for anterior vertebral body tethering (AVBT). METHODS: Eight observers measured PA radiographs of 15 idiopathic scoliosis patients treated with AVBT, pre-operative and 4-year follow-up. Vertebral wedging, disc wedging, convex vertebral body heights, and concave vertebral body heights of the 3 apical vertebrae were measured. For each observer, there were a total of 90 measurements for vertebral body height and 75 measurements for all wedging types At least 14 days elapsed between first and second round measurements. RESULTS: From the pre-operative to the 4-year follow-up time-point, the total wedging angle over the 3 peri-apical levels fell from 30 ± 7° to 16 ± 6° (p < 0.001) and the difference between the convex and concave vertebral heights decreased from 9 ± 4 to 6 ± 3 mm (p < 0.001). Interobserver agreement for pre-operative vertebral body heights was good [ICC = 0.80; 95% CI (0.74-0.85)]. At 4-year follow-up there was a moderate agreement [ICC = 0.67 (0.59-0.74)]. There was a poor interobserver agreement for pre-operative wedging angle measurements [ICC = 0.41 (0.32-0.52)] and 4-year follow-up [ICC = 0.45 (0.36-0.56)]. The Limits of Agreement with the Mean (LOAM) for pre-op heights was ± 2.4 mm, similar to the follow-up ± 2.6 mm. When raters are averaged in random groups of two the agreement limits decrease to ± 1.8 mm pre-op and ± 1.6 mm at follow-up. Similarly for wedging angles, LOAM values among the 8 observers of ± 4.6° pre-op and ± 4.2° dropped to ± 2.7° for both pre-op and follow-up when random groups of two raters were averaged together. Intraobserver agreement ranged from good to excellent per individual (ICC = 0.84-0.94) for pre-operative vertebral body heights, but this decreased at 4-year follow-up (ICC = 0.52-0.88). Intraobserver agreement was low overall for wedging (pre-operative ICC = 0.41-0.71; 4-year follow-up ICC = 0.41-0.76). CONCLUSION: Based on 8 individual observers, interobserver agreement ranged from good (pre-operative vertebral body heights) to moderate (4-year follow-up vertebral body heights) to poor (all wedging angles). To improve the reliability of the measurement of wedging angles, we recommend averaging the measurements of at least two observers.

Best Practice Guidelines for Surgical Site Infection in High-risk Pediatric Spine Surgery: Definition, Prevention, Diagnosis, and Treatment.

BACKGROUND: Prior "best practice guidelines" (BPG) have identified strategies to reduce the risk of acute deep surgical site infection (SSI), but there still exists large variability in practice. Further, there is still no consensus on which patients are "high risk" for SSI and how SSI should be diagnosed or treated in pediatric spine surgery. We sought to develop an updated, consensus-based BPG informed by available literature and expert opinion on defining high-SSI risk in pediatric spine surgery and on prevention, diagnosis, and treatment of SSI in this high-risk population. MATERIALS AND METHODS: After a systematic review of the literature, an expert panel of 21 pediatric spine surgeons was selected from the Harms Study Group based on extensive experience in the field of pediatric spine surgery. Using the Delphi process and iterative survey rounds, the expert panel was surveyed for current practices, presented with the systematic review, given the opportunity to voice opinions through a live discussion session and asked to vote regarding preferences privately. Two survey rounds were conducted electronically, after which a live conference was held to present and discuss results. A final electronic survey was then conducted for final voting. Agreement ≥70% was considered consensus. Items near consensus were revised if feasible to achieve consensus in subsequent surveys. RESULTS: Consensus was reached for 17 items for defining high-SSI risk, 17 items for preventing, 6 for diagnosing, and 9 for treating SSI in this high-risk population. After final voting, all 21 experts agreed to the publication and implementation of these items in their practice. CONCLUSIONS: We present a set of updated consensus-based BPGs for defining high-risk and preventing, diagnosing, and treating SSI in high-risk pediatric spine surgery. We believe that this BPG can limit variability in practice and decrease the incidence of SSI in pediatric spine surgery. LEVEL OF EVIDENCE: Not applicable.

Spontaneous Lumbar Curve Correction Following Vertebral Body Tethering of Main Thoracic Curves.

BACKGROUND: Growth modulation through anterior vertebral body tethering (AVBT) has emerged as a fusionless option for the treatment of progressive scoliosis. When tethering the main thoracic curve, the compensatory thoracolumbar/lumbar curve must correct indirectly as a result. The present study evaluated the response of these lumbar curves following AVBT of the main thoracic curves. METHODS: Patients who underwent thoracic AVBT and who had a minimum follow-up of 2 years were included. Magnitudes of the thoracic and lumbar curves were recorded preoperatively and at the first-erect and 2-year postoperative visits. Lumbar curves were further stratified according to their lumbar modifier (A, B, or C). Analysis of variance (ANOVA) and repeated-measures ANOVA were performed to compare correction rates, and the Pearson coefficient was utilized to determine the correlation between the tethered thoracic curve and uninstrumented lumbar curve magnitudes. RESULTS: A total of 218 patients were included. Thoracic curve correction was 40% at the first-erect visit and 43% at 2 years (p = 0.012). Lumbar correction was 30%, 26%, and 18% at the first-erect visit (p < 0.001 for all compared with preoperatively) and minimally changed at 31%, 26%, and 24% at 2 years for lumbar modifiers A, B, and C, respectively. A total of 118 patients (54%) showed thoracic curve improvement between the first-erect and 2-year visits. In a subgroup analysis, these patients had a correction in lumbar curve magnitude from preoperatively to the first-erect visit of 30%, 22%, and 16% for lumbar modifiers A, B, C, respectively, that increased to 42%, 34%, and 31% at 2 years, with strong correlation to thoracic correction at 2-year follow-up (r = 0.557, p < 0.001). CONCLUSIONS: Although there was immediate lumbar correction following AVBT of a main thoracic curve, further improvement following initial correction was only observed among patients with growth modulation of the thoracic curve. Considering all patients, the uninstrumented lumbar curve corrected 30% at 2 years and the instrumented thoracic curve corrected 40%. As indications for AVBT are refined, these data will provide insight into the response of the uninstrumented lumbar curve. LEVEL OF EVIDENCE: Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Pedicle Screw Plowing in Adolescent Idiopathic Scoliosis: How Common Is It and Is It a Problem?

STUDY DESIGN: Multicenter retrospective review. OBJECTIVE: To calculate overall incidence of pedicle screw "plowing" in adolescent idiopathic scoliosis (AIS) patients who underwent posterior spinal fusion (PSF). To identify risk factors for pedicle screw plowing and associated postoperative outcomes, including loss of correction and revision rate. SUMMARY OF BACKGROUND DATA: Curve correction of AIS generates perpendicular stresses that can cause pedicle screws to lose alignment and "plow" through pedicles craniocaudally. METHODS: We reviewed records of 1057 patients who underwent PSF for AIS from 2002 to 2015. Preoperative and first postoperative erect radiographs were evaluated by two observers to determine (1) presence of plowing and (2) subsequent loss of correction (LOC). Plowing was defined as more than 25° sagittal angulation compared with pedicle axis or entry of the most dorsal part of the screw outside the pedicle projection. LOC was defined as postoperative change in focal angulation of an instrumented spinal level, when in consensus of both reviewers. Bivariate analyses were performed (alpha = 0.05). RESULTS: Nineteen thousand five hundred sixty nine screws were assessed across our cohort of 1057 patients. Both observers agreed that 48 patients (4.5%) demonstrated plowing of more than or equal to one pedicle screw. For 72 screws (0.4%), both observers noted plowing, most commonly through the cranial cortex of the pedicle (65/72 screws) and at the lowest instrument vertebra (LIV) (17/72 screws). Factors associated with plowing included larger curves (P = 0.02); lower mean pedicle screw density (P = 0.0003); skeletal immaturity as measured by open triradiate cartilage (P = 0.04); and younger chronological age at time of surgery (P = 0.04). LOC occurred in 13 patients, most commonly at LIV (P < 0.0001). Revision rate for loss of screw fixation was higher in the plowing group (P = 0.003). CONCLUSION: Pedicle screw plowing occurred in 4.5% of AIS patients, especially in those skeletally immature and with decreased implant density. Plowing commonly occurred in the cranial direction and was associated with LOC, particularly at the LIV.Level of Evidence: 3.

Complications following surgical treatment of adolescent idiopathic scoliosis: a 10-year prospective follow-up study.

BACKGROUND: Accurate reporting of long-term complications of surgical treatment of adolescent idiopathic scoliosis (AIS) is critical, but incomplete. This study aimed to report on the rate of complications following surgical treatment of AIS among patients with at least 10 years of follow-up. METHODS: This was a retrospective review of prospectively collected data from a multicenter registry of patients who underwent surgical treatment for AIS with minimum 10-year follow-up. Previously published complications were defined as major if they resulted in reoperation, prolonged hospital stay/readmission, neurological deficits, or were considered life-threatening. Rates and causes of reoperations were also reviewed. RESULTS: Two hundred and eighty-two patients were identified with mean age at surgery of 14.6 ± 2.1 years. Mean follow-up was 10.6 (range 9.5-14) years. Eighty-seven patients had anterior spinal fusion (ASF); 195 had posterior spinal fusion (PSF). The overall major complication rate was 9.9% (n = 28) in 27 patients. Among PSF patients, the complication rate was 9.7% (n = 19) in 18 patients. The complications were surgical site infection (37%), adding-on (26%), pulmonary (16%), neurologic (11%), instrumentation (5%), and gastrointestinal (5%). In ASF patients, the complication rate was 10.3% (n = 9) among nine patients. The complications were pulmonary (44%), pseudoarthrosis (22%), neurologic (11%), adding-on (11%), and gastrointestinal (11%). The reoperation rate was 6.0% (n = 17) among 17 patients. Although most of the complications presented within the first 2 years (60.7%), surgical site infection and adding-on were also seen late into the 10-year period. CONCLUSION: This is the largest prospective study with at least a 10-year follow-up of complications following spinal fusion for AIS, the overall major complication rate was 9.9% with a reoperation rate of 6.0%. Complications presented throughout the 10-year period, making long-term follow-up very important for surveillance. LEVEL OF EVIDENCE: Therapeutic II.

Use of Vancomycin Powder in Spinal Deformity Surgery in Cerebral Palsy Patients is Associated With Proteus Surgical Site Infections.

PURPOSE: Surgical site infection (SSI) rates in pediatric spinal deformity surgery for cerebral palsy (CP) patients are higher than that in idiopathic scoliosis. The use of vancomycin powder is associated with decreased risk of SSI in neuromuscular patients. Prior studies in adult and pediatric early-onset scoliosis patients have shown that vancomycin powder alters microbacterial profile in patients that develop SSI. However, the effects of topical vancomycin powder on microbiology in spinal deformity surgery for CP patients has not been studied. METHODS: An international multicenter database of CP neuromuscular scoliosis patients was used in this retrospective cohort study. All patients that underwent posterior spinal instrumented fusion for CP neuromuscular scoliosis from 2008 to 2019 were queried, and 50 cases complicated by postoperative SSI were identified. Intraoperative antibiotic details were documented in 49 cases (98.0%). Microbiology details were documented in 45 cases (91.8%). Microbiology for patients that received topical vancomycin powder were compared with patients that did not. A multivariate regression model was used to control for potential confounders. RESULTS: There were 45 patients included in this study. There were 27 males (60.0%) and 18 females (40.0%). Mean age at surgery was 14.8±2.4 years. There were 24 patients that received topical vancomycin powder (53.3%). The mean time from index surgery to SSI was 4.3±11.3 months.On univariate analysis of microbiology cultures by vancomycin powder cohort, there were no significant differences in culture types. Proteus spp. trended on significance with association with vancomycin powder use (P=0.078). When controlling for potential confounders on multivariate analysis, intraoperative topical vancomycin powder was associated with increased risk for proteus infection (adjusted odds ratio: 262.900, 95% confidence interval: 1.806-38,267.121, P=0.028). DISCUSSION: In CP patients undergoing pediatric spinal deformity surgery, the use of vancomycin powder was independently associated with increased risk for proteus infections. Further study into antibiotic regimens for spinal deformity surgery in the CP population should be performed. LEVEL OF EVIDENCE: Level III-retrospective cohort study.

Body mass index affects outcomes after vertebral body tethering surgery.

PURPOSE: To compare the outcomes of anterior Vertebral Body Tethering (AVBT) surgery between overweight and non-overweight patients. METHODS: AIS/JIS patients with AVBT with 2-year follow-up from a multi-center pediatric spine database were evaluated pre-operatively, 1st post-operative erect, and 2 years post-operatively. ANOVA was used to compare 3 categories of BMI with significance as per Tukey-Kramer HSD post hoc test. Risk of scoliosis progression was analysed with Mid-P exact test. RESULTS: 121 patients (51 underweight, 58 normal, 12 overweight; mean age 12.5 ± 1.6 yr; BMI 18.8 ± 4.6 kg/m2) were identified. Comparing underweight, normal, and overweight groups: mean pre-operative age (13 yr, 13 yr, 12 yr), scoliosis (52°, 50°, 52°), pre-operative kyphosis (29°, 28°, 33°), peri-operative scoliosis correction (44%, 42%, 46%), and complications by 2-year follow-up (23%, 24%, 17%) were similar between groups. There was one broken tether in each of the underweight and normal weight groups. Change in percent scoliosis correction from 1st erect to 2-year post-operative (i.e., growth modulation phase) was not significantly different between groups; however, the risk ratio for scoliosis progression during this period was 4.74 (1.02-22.02; p = 0.04) for overweight patients. CONCLUSION: Our findings demonstrate that, as compared to normal weight and underweight patients, overweight patients did not have a statistically significant difference in intra-operative scoliosis correction or in risk of experiencing complication; however, overweight patients had a risk ratio of 4.74 for progression of scoliosis during the growth modulation phase of treatment from first erect radiographs to minimum 2-year follow-up. LEVEL OF EVIDENCE: III.

Anterior Vertebral Body Tethering Compared with Posterior Spinal Fusion for Major Thoracic Curves: A Retrospective Comparison by the Harms Study Group.

BACKGROUND: Anterior vertebral body tethering (AVBT) is an alternative to posterior spinal fusion (PSF) for the surgical treatment of scoliosis. The present study utilized a large, multicenter database and propensity matching to compare outcomes of AVBT to PSF in patients with idiopathic scoliosis. METHODS: Patients with thoracic idiopathic scoliosis who underwent AVBT with a minimum 2-year follow-up retrospectively underwent 2 methods of propensity-guided matching to PSF patients from an idiopathic scoliosis registry. Radiographic, clinical, and Scoliosis Research Society 22-Item Questionnaire (SRS-22) data were compared preoperatively and at the ≥2-year follow-up. RESULTS: A total of 237 AVBT patients were matched with 237 PSF patients. In the AVBT group, the mean age was 12.1 ± 1.6 years, the mean follow-up was 2.2 ± 0.5 years, 84% of patients were female, and 79% of patients had a Risser sign of 0 or 1, compared with 13.4 ± 1.4 years, 2.3 ± 0.5 years, 84% female, and 43% Risser 0 or 1 in the PSF group. The AVBT group was younger (p < 0.001), had a smaller mean thoracic curve preoperatively (48 ± 9°; range, 30° to 74°; compared with 53 ± 8°; range, 40° to 78° in the PSF group; p < 0.001), and had less initial correction (41% ± 16% correction to 28° ± 9° compared with 70% ± 11% correction to 16° ± 6° in the PSF group; p < 0.001). Thoracic deformity at the time of the latest follow-up was 27° ± 12° (range, 1° to 61°) for AVBT compared with 20° ± 7° (range, 3° to 42°) for PSF (p < 0.001). A total of 76% of AVBT patients had a thoracic curve of <35° at the latest follow-up compared with 97.4% of PSF patients (p < 0.001). A residual curve of >50° was present in 7 AVBT patients (3%), 3 of whom underwent subsequent PSF, and in 0 PSF patients (0%). Forty-six subsequent procedures were performed in 38 AVBT patients (16%), including 17 conversions to PSF and 16 revisions for excessive correction, compared with 4 revision procedures in 3 PSF patients (1.3%; p < 0.01). AVBT patients had lower median preoperative SRS-22 mental-health component scores (p < 0.01) and less improvement in the pain and self-image scores between preoperatively and the ≥2-year follow-up (p < 0.05). In the more strictly matched analysis (n = 108 each), 10% of patients in the AVBT group and 2% of patients in the PSF group required a subsequent surgical procedure. CONCLUSIONS: At a mean follow-up of 2.2 years, 76% of thoracic idiopathic scoliosis patients who underwent AVBT had a residual curve of <35° compared with 97.4% of patients who underwent PSF. A total of 16% of cases in the AVBT group required a subsequent surgical procedure compared with 1.3% in the PSF group. An additional 4 cases (1.3%) in the AVBT group had a residual curve of >50° that may require revision or conversion to PSF. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Anterior Vertebral Body Tethering for Treatment of Idiopathic Scoliosis in the Skeletally Immature: Results of 112 Cases.

STUDY DESIGN: Prospective case series. OBJECTIVE: Determine the efficacy of anterior vertebral body tethering (AVBT) in skeletally immature patients. SUMMARY OF BACKGROUND DATA: The value of AVBT is currently unclear given the paucity of available data. METHODS: Consecutive skeletally immature patients with idiopathic scoliosis were treated with AVBT between 2012 and 2018 by one of two surgeons working at two independent centers and followed up for >2 years. Data were collected prospectively and supplemented retrospectively where necessary. Outcomes were measured preoperatively, at first erect radiograph (FE), 1-year postoperatively and at most recent follow up (FU). RESULTS: One hundred twelve patients underwent 116 primary tethering procedures (108 thoracic and eight lumbar tethers). Four patients had primary tethering of both lumbar and thoracic curves. At surgery mean age was 12.7 ±â€Š1.4 years (8.2-16.7) and Risser 0.5 ±â€Š0.9 (0-3). Follow up was mean 37 ±â€Š9 months (15-64). Preoperative mean coronal Cobb angle of the 130 tethered curves was 50.8°â€Š±â€Š10.2 (31-81) and corrected significantly to 26.6°â€Š±â€Š10.1 (-3-61) at FE radiograph (P < 0.001). Further significant improvement was seen from FE to 1-year, to mean 23.1°â€Š±â€Š12.4 (-37-57) (P < 0.001). There was a small but significant increase between 1-year and FU to 25.7°â€Š±â€Š16.3 (-32-58) (P < 0.001), which appeared to reflect tether breakage. Untethered minor curves were corrected from 31.0°â€Š±â€Š9.5 (3-57) to 20.3°â€Š±â€Š10.3 (0-52) at FU (P < 0.001). Rib hump was corrected from 14.1 ±â€Š4.8 (0-26) to 8.8°â€Š±â€Š5.4 (0-22) at FU (P < 0.01). Twenty-five patients (22%) had 28 complications. Fifteen patients (13%) requiring 18 revision operations including six completed and one awaited fusions. CONCLUSION: AVBT of immature cases is associated with satisfactory deformity correction in the majority of cases. However, complication and revision rates suggest the need for improved implants and patient selection. Long-term follow-up remains crucial to establish the true efficacy of this procedure.Level of Evidence: 3.

What is the effect of intraoperative traction on correction of adolescent idiopathic scoliosis (AIS)?

PURPOSE: Determine the efficacy of intraoperative traction (IOT) on curve correction in AIS. METHODS: A prospective, multicenter, longitudinal database identified patients with major thoracic AIS (Lenke 1-4) treated with surgery using IOT and follow-up of 2 years. These cases were matched to comparable cases treated without traction (non-IOT). All patients were treated with single-stage posterior only surgery with pedicle screw constructs. Perioperative, radiographic and clinical outcome data at 2 years post-op were compared between the groups. RESULTS: 104 cases treated with IOT were matched to 104 treated without IOT. Operating room time was significantly greater in the IOT group (339 vs. 306 min, p = < 0.001). Neuromonitoring alerts were more frequent in the IOT group (23% vs. 5%, p < 0.001). There were no postoperative neurological deficits in either group. The IOT group showed significantly greater MT curve correction (IOT 71% vs. non-IOT 66.7%, p < 0.003), with the effect most pronounced in curves > 70° (IOT 72% vs. non-IOT 64%, p = 0.04). IOT was associated with a significant reduction in 2D T5-T12 kyphosis measurements (IOT - 6.5° vs non-IOT + 0.48°, p < 0.001), yet significant improvements in estimated 3D thoracic kyphosis were made in both groups, with the non-IOT group making greater improvement when compared to the IOT group (IOT + 18.1° vs. non-IOT + 22.3° vs., p = 0.008). CONCLUSIONS: IOT is associated with modestly enhanced coronal deformity correction. Surgeons should be aware of the increased rates of neuromonitoring alerts when using this technique and its affect on the sagittal profile. Given this IOT may be best suited to larger curves. LEVEL OF EVIDENCE: 3.