Single Long-Incision Minimally Invasive Surgery.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: The objective of this study is to determine differences in outcomes in patients with adolescent idiopathic scoliosis undergoing spinal deformity correction surgery using a posterior spinal fusion (PSF) approach versus single and triple-incision minimally invasive surgery (MIS). SUMMARY OF BACKGROUND DATA: MIS increased in popularity as surgeons' focus moved towards soft tissue preservation, but it carries technical demands and increased surgical time compared with PSF. PATIENTS AND METHODS: Surgeries performed from 2016 to 2020 were included. Cohorts were formed based on surgical approach: PSF versus single long-incision MIS (SLIM) versus traditional MIS [3-incision MIS (3MIS)]. There were a total of 7 subanalyses. Demographic, radiographic, and perioperative data were collected for the 3 groups. Kruskal-Wallis and χ 2 tests were used for continuous and categorical variables, respectively. RESULTS: Five hundred thirty-two patients met our inclusion criteria, 294 PSF, 179 3MIS, and 59 SLIM.Estimated blood loss (mL) ( P < 0.00001) and length of stay (LOS) ( P < 0.00001) was significantly higher in PSF than in SLIM and 3MIS. Surgical time was significantly higher in 3MIS than in PSF and SLIM ( P = 0.0012).Patients who underwent PSF had significantly lower postoperative T5 to T12 kyphosis ( P < 0.00001) and percentage kyphosis change ( P < 0.00001). Morphine equivalence was significantly higher in the PSF group during total hospital stay ( P = 0.0042).Patients who underwent SLIM and 3MIS were more likely to return to noncontact ( P = 0.0096) and contact sports ( P = 0.0095) within 6 months and reported lower pain scores ( P < 0.001) at 6 months postoperation. CONCLUSION: SLIM has a similar operative time to PSF and is technically similar to PSF while maintaining the surgical and postoperative outcome advantages of 3MIS.

Does a dedicated "Scoliosis Team" and surgical standardization improve outcomes in adolescent idiopathic scoliosis surgery and is it reproducible?

PURPOSE: The objective of this study was to determine if standardization improves adolescent idiopathic scoliosis (AIS) surgery outcomes and whether it is transferrable between institutions. METHODS: A retrospective review was conducted of AIS patients operated between 2009 and 2021 at two institutions (IA and IB). Each institution consisted of a non-standardized (NST) and standardized group (ST). In 2015, surgeons changed institutions (IA- > IB). Reproducibility was determined between institutions. Median and interquartile ranges (IQR), Kruskal-Wallis, and χ2 tests were used. RESULTS: 500 consecutive AIS patients were included. Age (p = 0.06), body mass index (p = 0.74), preoperative Cobb angle (p = 0.53), and levels fused (p = 0.94) were similar between institutions. IA-ST and IB-ST had lower blood loss (p < 0.001) and shorter surgical time (p < 0.001). IB-ST had significantly shorter hospital stay (p < 0.001) and transfusion rate (p = 0.007) than IB-NST. Standardized protocols in IB-ST reduced costs by 18.7%, significantly lowering hospital costs from $74,794.05 in IB-NST to $60,778.60 for IB-ST (p < 0.001). Annual analysis of surgical time revealed while implementation of standardized protocols decreased operative time within IA, when surgeons transitioned to IB, and upon standardization, IB operative time values decreased once again, and continued to decrease annually. Additions to standardized protocol in IB temporarily affected the operative time, before stabilizing. CONCLUSION: Surgeon-led standardized AIS approach and streamlined surgical steps improve outcomes and efficiency, is transferrable between institutions, and adjusts to additional protocol changes.

Effect of Pedicle Screw Size on Surgical Outcomes Following Surgery for 412 Adolescent Idiopathic Scoliosis Patients.

STUDY DESIGN: Retrospective Review. OBJECTIVE: The objective of this study was to determine differences in surgical and post-operative outcomes in AIS patients undergoing spinal deformity correction surgery using standard or large pedicle screw size. SUMMARY OF BACKGROUND: Use of pedicle screw fixation in spinal deformity correction surgery is considered safe and effective. Still, the small size of the pedicle and the complex 3D anatomy of the thoracic spine makes screw placement challenging, with improper pedicle screw fixation leading to catastrophic complications including injuries to nerve roots, spinal cord, and major vessels. Thus, insertion of larger diameter screw sizes has raised concerns amongst surgeons, especially in the pediatric population. MATERIALS AND METHODS: AIS patients undergoing PSF between 2013 and 2019 were included. Demographic, radiographic, and operative outcomes collected. Patients in the large screw size group (GpI) received 6.5 mm diameter screw sizes at all levels while standard screw size group (GpII) received 5.0 to 5.5 mm diameter screw sizes at all levels. Kruskall-Wallis and Fisher's exact test performed for continuous and categorical variables respectively.Subanalyses included (1) screw accuracy in patients with available CT scans, (2) stratified analysis of large- and standard-screw patients with ≥60% flexibility rate, (3) stratified analysis of large- and standard-screw patients with <60% flexibility rate, and (4) matched analysis of large- and standard-screw patients by surgeon and year of surgery. RESULTS: GpI patients experienced significantly higher overall curve correction ( P <0.001), with 87.6% experiencing at least one grade reduction of apical vertebral rotation from preoperative to postoperative visit( P =0.008).Patients with larger screws displayed higher postoperative kyphosis. No patient experienced medial breaching. CONCLUSION: Large screw sizes have similar safety profiles to standard screws without negatively impacting surgical and perioperative outcomes in AIS patients undergoing PSF. Additionally, coronal, sagittal, and rotational correction is superior for larger-diameter screws in AIS patients.

The Volume-Cost Relationship: How Does Surgical Volume Affect Cost and Value in AIS Surgery.

STUDY DESIGN: Retrospective review. OBJECTIVE: The objective of this study was to evaluate and compare distribution of hospital and operating room charges and outcomes during posterior spinal fusion for adolescent idiopathic scoliosis (AIS) patients by high-volume (HV) and standard-volume (SV) surgeons at one institution and examine potential cost savings. SUMMARY OF BACKGROUND DATA: Increased surgical volume has been associated with improved perioperative outcomes after spinal deformity correction. However, there is a lack of information on how this may affect hospital costs. METHODS: Retrospective study of AIS patients undergoing posterior spinal fusion between 2013 and 2019. Demographic, x-ray, chart review and hospital costs were collected and compared between HV surgeons (≥50 AIS cases/y) and SV surgeons (<50/y). Comparative analyses were computed using Wilcoxon rank-sum, Kruskal-Wallis, and the Fisher exact tests. Average values with corresponding minimum-maximum rages were reported. RESULTS: A total of 407 patients (HV: 232, SV: 175) operated by 4 surgeons (1 HV, 3 SV). Radiographic parameters were similar between the groups. HV surgeons had significantly lower estimated blood loss (385.3 vs. 655.6 mL, P <0.001), fewer intraoperative transfusions (10.8% vs. 25.1%, P <0.001), shorter surgery time (221.6 vs. 324.9 min, P <0.001), and lower radiation from intraoperative fluoroscopy (4.4 vs. 6.4 mGy, P <0.001). HV patients had a significantly lower length of stay (4.3 vs. 5.3, P <0.001) and complication rate (0.4% vs. 4%, P =0.04).HV surgeons had significantly lower total costs ($61,716.24 vs. $72,745.93, P <0.001). This included lower transfusion costs ( P <0.001), operative time costs ( P <0.001), screw costs ( P <0.001), hospital stay costs ( P <0.001), and costs associated with 30-day emergency department returns ( P <0.001). CONCLUSION: HV surgeons had significantly lower operative times, lower estimated blood loss and transfusion rates and lower perioperative complications requiring readmission or return to emergency department resulting in lower health care costs. LEVEL OF EVIDENCE: Level III.

Ambulatory Neuromuscular Scoliosis Patients Have Superior Perioperative Results Than Nonambulatory Neuromuscular Scoliosis Patients and Can Approach Adolescent Idiopathic Scoliosis Outcomes After Posterior Spinal Fusion.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: This study aims to identify differences in perioperative outcomes between ambulatory patients with neuromuscular scoliosis (ANMS) and adolescent idiopathic scoliosis (AIS) following spinal fusion. SUMMARY OF BACKGROUND DATA: NMS patients have severe curves with more comorbidities and procedural complexity. These patients require extensive fusion levels, increased blood loss, and suffer increased periop complications. However, NMS patients have a variable severity spectrum, including ambulation status. METHODS: Chart and radiographic review of NMS and AIS patients undergoing PSF from 2005 to 2018. NNMS included NMS patients who were completely dependent (GMFCS IV-V). ANMS consisted of community ambulators without significant reliance on wheeled assistive devices (GMFCS I-III). Subanalysis matched by age, sex, levels fused and preoperative Cobb angle was conducted as well. Wilcoxon Rank-Sum, Kruskal-Wallis, χ2, and Fisher exact tests were performed. RESULTS: There were 120 patients in the NNMS group, 54 in ANMS and 158 in the AIS group. EBL was significantly lower for ANMS and AIS patients (P < 0.001). Complications within 30 days were similar between ANMS and AIS (P = 1.0), but significantly higher for NNMS (P < 0.001). Two (1.3%) AIS patients, (1.7%) nonambulatory NMS patients, and one (1.9%) ANMS patient required revision surgery (P = 1.0). However, all NMS patients had increased fusion levels, fixation points, and surgery time (P < 0.05). NNMS had significantly longer ICU (P < 0.001), hospital stay (P < 0.001), intraoperative transfusions (P < 0.001), and fewer patients extubated in the OR (P < 0.001) than ANMS and AIS patients. In the subanalysis, ANMS had similar radiographic measurements, EBL, transfusion, surgery time, extubation rate, and complication rate (P > 0.05) to AIS. CONCLUSION: Our data show radiographic outcomes, infections, revisions, and overall complications for ANMS were similar to the AIS population. This suggests that NMS patients who ambulate primarily without assistance can expect surgical outcomes comparable to AIS patients with further room for improvement in length of ICU and hospital stay.Level of Evidence: 4.

Scoliosis Surgery Normalizes Cardiac Function in Adolescent Idiopathic Scoliosis Patients.

STUDY DESIGN: Single-center retrospective chart review with minimum 2-year follow up. OBJECTIVE: To determine incidence of pulmonary hypertension in adolescent idiopathic scoliosis patients and to determine the effect of scoliosis surgery on pulmonary hypertension. SUMMARY OF BACKGROUND DATA: Spinal deformity in adolescent idiopathic scoliosis can increase right atrial and ventricular pressures secondary to restrictive lung disease. Pulmonary hypertension leading to cor pulmonale is the most feared outcome, however mild pulmonary hypertension in adolescent idiopathic scoliosis (AIS) patients has been reported. No study has previously examined changes in the improvement of right heart function following scoliosis surgery. METHODS: Cobb angle, 2D-echo signs of structural heart disease, aortic root dimensions, tricuspid regurgitant jet velocity (TRV), pulmonary function tests (PFTs), arterial blood gas (ABG), and patient demographics reviewed. Right ventricular systolic pressure (RVSP) estimated using Bernoulli equation (4[TRV]2) and right atrial pressure. RVSP ≥36 mmHg is a surrogate marker for pulmonary hypertension. All echocardiograms were read by board certified Pediatric Cardiologists. Logistic regression used to assess for differences in TRV between groups. RESULTS: Mean preoperative RVSP was significantly elevated in AIS patients (26.9 ±â€Š0.49; P < 0.001) compared with controls (17.25 + 0.88). Only 47 (21%) Group 1 patients had elevated preoperative TRV (≥2.8 m/s) versus none in Group 2 (P < 0.001). Additionally, logistic regression showed AIS patients have odds ratio of 3.29 for elevated TRV (P = 0.007)-an indirect measure of pulmonary hypertension. In all Group 3 patients, the cardiac function normalized postoperatively (mean TRV = 2.09 + 0.23; P < 0.001). No association found between Cobb angle, aortic root parameters, or pulmonary function tests. CONCLUSION: This study found 13.9% of patients with adolescent idiopathic scoliosis had elevated TRV while controls had no TRV abnormalities. Additionally, RVSP measurements demonstrated mild pulmonary hypertension in AIS patients. These abnormal values normalized postoperatively, indicating the benefits of scoliosis surgery on cardiac function in adolescent idiopathic scoliosis.Level of Evidence: 3.

Effects of Fellowship Training on Pediatric Anterior Cruciate Ligament Reconstruction Techniques and Outcomes.

The purpose of this study is to examine differences in pediatric anterior cruciate ligament reconstruction (ACLR) between surgeons with either pediatric or sports medicine fellowship training. Patients were divided into two groups, those performed by either a pediatric or sports medicine fellowship-trained surgeon. One hundred and forty-one patients were identified: 91 (64.5%) by pediatric trained surgeons and 50 (35.4%) by sports medicine trained surgeons. Patients that had ACLR by a pediatric trained surgeon were younger (p = 0.02), had larger body mass index (BMI) (p = 0.027), and more likely to have government assisted insurance (p = 0.006). Pediatric trained surgeons had longer procedure time (p < 0.001), used smaller graft sizes (p = 0.016), used soft tissue grafts (p < 0.001) and used button fixation at both the femur and tibia (p < 0.001). There were no differences regarding meniscus surgery, surgical technique (transphyseal versus physeal sparing), arthrofibrosis, graft failure, and intraoperative complications (p > 0.05). This study shows favorable and comparable results after ACLRs with either pediatric or sports medicine fellowship training. (Journal of Surgical Orthopaedic Advances 30(3):161-165, 2021).

Minimally Invasive Versus Standard Surgery in Idiopathic Scoliosis Patients: A Comparative Study.

STUDY DESIGN: Retrospective review of prospective case-control study. OBJECTIVE: To compare minimally invasive scoliosis surgery (MIS) and posterior spinal fusion (PSF) in a large group of patients. SUMMARY OF BACKGROUND DATA: MIS, has been shown to have benefits over standard PSF in adolescent idiopathic scoliosis (AIS). METHODS: Radiographic, clinical, and operative review of a multi-institutional prospective database from 2013 to 2018. MIS patients with minimum 2-year XR follow up were compared with open PSF technique patients. RESULTS: Four hundred eighty five patients were included; 192 MIS and 293 PSF. Preoperative Cobb (P = 0.231) and kyphosis were similar (P = 0.501). Cobb correction was comparable (P = 0.46), however percent improvement in thoracic kyphosis was significantly higher in MIS (P < 0.001). MIS had significantly lower blood loss (P < 0.001), transfusions (P < 0.001), fixation points (P < 0.001), opioid consumption (P = 0.001), and hospital stay (P < 0.001). Operative time was shorter (P = 0.001) and 30-day complications rate was similar (P = 0.81). CONCLUSION: This is the largest study comparing the surgical outcomes of MIS and PSF. MIS patients benefit from increased kyphosis, fewer transfusion, lower opioid consumption, and shorter hospital stay with similar Cobb correction. Increased postoperative kyphosis is likely from muscle sparing dissection in MIS.Level of Evidence: 3.

Screw Malposition: Are There Long-term Repercussions to Malposition of Pedicle Screws?

BACKGROUND/INTRODUCTION: Pedicle screws have long been part of the continued advancements in spine surgery. Despite the many techniques that have been devised for their safe placement, malposition of screws continues to occur. Studies have evaluated the possible safe limits of screw malposition, and have given some insight on anatomic variation in spinal deformity. Review of the literature reveals several cases of deleterious long-term sequelae of malpositioned screws. DISCUSSION: With the current experience, proposed recommendations are provided to detect and avoid the potential long-term sequelae. Though the literature has helped to define possible concerning screws, there are no good studies predicting long-term risk. CONCLUSION: Improvements in technology and techniques, advancements in intraoperative confirmation and postoperative surveillance, studies that assist risk stratification, and expert consensus evaluations will help guide surgeons in their decision for addressing misplaced screws.

Are All Hardware Removals Equal?

The objective of this study is to report operative time and associated complications of six types of implants and to determine if surgeons are adequately compensated. Hardware removals were analyzed from 2014-2019. Implants were flexible nails, intramedullary rigid nails, long plates, screw(s), single guided-growth plates, and multiple guided-growth plates. Patient demographics, operative time, blood loss, complications, and relative value units (RVU)/min were collected. RVU/min was used to maximize rate. In total, 392 patients were analyzed. Long plate removals took significantly longer than screw removal, therefore RVU/min was significantly lower (p < 0.001). Long plate removals also took significantly longer, and RVU/min was significantly lower compared to guided-growth plate removal (p < 0.001). Intramedullary nails took significantly longer compared to flexible nails, nearly double the RVU/min (p = 0.02). The results from this study indicate that the RVU/ minute for these six different types of implant removals are not equal. Surgeons can use this data to set up their schedule to ensure maximum utilization. (Journal of Surgical Orthopaedic Advances 30(1):020-023, 2021).

Surgeon volume affects short- and long-term surgical outcomes in idiopathic scoliosis.

STUDY DESIGN: Retrospective review of New York Statewide Planning and Research Cooperative System (SPARCS) Inpatient Database. OBJECTIVE: To identify the differences in short- and long-term complications, following long-segment pediatric spinal fusion in idiopathic scoliosis surgery, between surgeons with low versus high annual surgical volume. Spinal deformity surgery is complex and requires significant training and repetition to master. Surgeon and hospital volume have been shown to correlate with outcomes following cervical and lumbar spine surgery. However, there is limited literature regarding the impact of surgeon volume on long-term outcomes following pediatric idiopathic spinal deformity correction. METHODS: This is a retrospective review of the SPARCS inpatient database from 2004 to 2013 of pediatric patients who underwent idiopathic scoliosis surgery. Surgeons were stratified into high (> 15 cases/year)- and low (≤ 15 cases/year)-volume cohorts by aggregating all cases completed over the study period until 50% of the total cases were captured above and below an average case per-year threshold. This threshold occurred at 15 cases/year. Short-term and long-term readmission and medical/surgical complications were collected. Multivariate logistic regression models assessed the risk of short- and long-term complications between cohorts. RESULTS: 3910 pediatric patients underwent a primary arthrodesis from a total of 223 surgeons. More high-volume surgeons operated at academic teaching hospitals (p < 0.001), used a combined AP surgical approach (p < 0.001), and fewer utilized rhBMP (p < 0.001). High-volume surgeons had shorter lengths of stay (p < 0.001). Low-volume surgeons had increased odds of inpatient surgical complications (OR 1.55, 95% CI 1.00-2.45). Low-volume surgeons had increased odds of revision at 5 and 10 years (5 years. OR 1.56, 95% CI 1.05-2.31; 10 years. OR 1.59, 95% CI 1.09-2.31). Low-volume surgeons had increased odds of implant malfunction at 10 years (OR 1.81, 95% CI 1.15-2.86). CONCLUSIONS: High-volume surgeons had decreased odds of short- and long-term complications compared to low volume when performing primary spinal arthrodesis in idiopathic scoliosis. Low-volume surgeons experienced significantly greater odds of inpatient surgical complications, as well as increased risk of revision during long-term follow-up with a significantly increased risk of implant malfunction at 10 years post-operatively. LEVEL OF EVIDENCE: Level III.

A dual-team approach benefits standard-volume surgeons, but has minimal impact on outcomes for a high-volume surgeon in AIS patients.

STUDY DESIGN: Retrospective chart review of prospectively collected data. OBJECTIVE: This study seeks to evaluate the effect of number of surgeons, surgeon experience, and surgeon volume on AIS surgery. Recent literature suggests that utilizing two surgeons for spine deformity correction surgery can improve perioperative outcomes. However, the surgeon's experience and surgical volume are likely as important. METHODS: AIS patients undergoing PSF from 2009 to 2019 were included. Patient demographics, X-ray and perioperative outcomes were collected and collated based on primary surgeon. Analysis was performed for single versus dual surgeons, surgeon experience (≤ 10 years in practice), and surgical volume (less/greater than 50 cases/year). Median (IQR) values, Wilcoxon Rank Sums test, Kruskal-Wallis test, and Fisher's exact test were utilized. RESULTS: 519 AIS cases, performed by 4 surgeons were included. Two surgeons were highly experienced, 1 of whom was also high volume. Five cohorts were studied: a single senior high volume (S1) (n = 302), dual-junior surgeons (DJ) (n = 73), dual senior-junior (SJ) (n = 36), dual-senior (DS) (n = 21) and a single senior, standard-volume surgeon alone (S2) (n = 87). Radiographic parameters were similar between the groups (p > 0.05). Preoperative Cobb was significantly higher for DS compared to S1 (p = 0.034) Pre- and post-op kyphosis were similar (p > 0.05). Cobb correction was similar (p > 0.05). Levels fused, fixation points, anesthesia and surgical times were similar (p > 0.05). When the standard-volume surgeon operated with a second surgeon, radiographic parameters were similar (p > 0.05), but anesthesia time, surgical time, and hospital length of stay were significantly shorter (p < 0.05). Additionally, DJ had significantly shorter anesthesia and operative times (p < 0.001) and length of stay (p < 0.001) compared to S2. CONCLUSION: Standard-volume surgeons have better outcomes with a dual surgeon approach. Junior surgeons benefit operating with an experienced surgeon. A high-volume surgeon, however, does not benefit from a dual surgeon approach. LEVEL OF EVIDENCE: Level II.

Back-to-Back Surgeries in AIS Patients Can be Performed Safely Without Compromising Radiographic or Perioperative Outcomes: A 10-year Review.

STUDY DESIGN: A retrospective chart review of prospectively collected data. OBJECTIVE: The aim of this study was to determine whether back-to-back scoliosis surgeries can be performed safely without compromising outcomes and the reproducibility of the practice between institutions. SUMMARY OF BACKGROUND DATA: During the summer, spinal surgeons will often book multiple cases in one day. The complexity and demands of spinal fusion surgery call into question the safety. Change of operating room staff including anesthesiologists, nurses, and neurologists may introduce new risks. METHODS: From 2009 to 2018, index AIS surgeries were included. In Groups 1, 2, and 3, surgeries were performed by a single surgeon. In Group 4, they were performed by other institutional surgeons. Group 1: first surgery of the day, Group 2: second surgery of the day, Group 3: only surgery of the day, Group 4: only surgery of the day by different institutional surgeon. Additional analysis was done to determine reproducibility after a surgeon was moved from Institution 1 to Institution 2. RESULTS: Five hundred sixty-seven AIS patients were analyzed. Group 1 patients had similar radiographic outcomes compared with Group 2 (P > 0.05). Surgical time was similar (P = 0.51), but significantly more levels fused (P = 0.01). Compared with Group 3, Group 2 had a smaller preoperative Cobb (P = 0.02), shorter surgeries (P < 0.001), and length of stay (P = 0.04) but similar complication rate (P = 1). Compared with Group 4, Group 2 had smaller preoperative Cobb (P < 0.001), shorter surgery, and lower complication rate (P = 0.03). When determining reproducibility, institution 2 patients had significantly less blood loss, shorter surgeries, and shorter lengths of stay (P < 0.05). CONCLUSION: Although long and involved, back-to-back AIS surgeries do not compromise radiographic or perioperative outcomes. Changes in operating team do not appear to impact safety, efficiency, or outcomes. This study also found that the practice is reproducible between institutions. LEVEL OF EVIDENCE: 3.

The Screw-Aorta Dilemma: Changing Patient Position in Computed Tomography Scan Is Critical in Documenting Aortic Mobility.

STUDY DESIGN: Retrospective chart review. OBJECTIVE: To determine if obtaining a prone computed tomography (CT)-scan can better delineate a questionable screw-aorta relationship. SUMMARY OF BACKGROUND DATA: Pedicle screw misplacement rate is reported between 6% and 15%. Studies looking at misplacements on a per patient basis show up to 14% of patients have screws at risk (impinging vital structures). A screw abutting the aorta is a management challenge and often requires vascular surgery intervention. However, CT scans routinely done in supine position may overestimate screw-aorta relationship. Change in patient position may allow the aorta to roll away and, in most cases, reveal an uncompromised aorta. This will allow safe removal of pedicle screws without any vascular intervention. METHODS: One hundred eleven spinal deformity patients who underwent Posterior spinal fusion from 2004 to 2009 were evaluated. Patients with concerning screw-aorta relationship underwent additional prone CT scan. Mobility of the aorta was determined and distance was compared using prone and supine CT scans. RESULTS: Two thousand two hundred ninety five screws were reviewed, 36 screws in 18 patients were in proximity to the aorta. Fourteen screws (nine patients) appeared to be impinging the aorta. On prone CT, 13 out of the 14 instances the aorta moved away from the screw. The average distance at the screw level was 13.6 ±â€Š4.8 mm in supine position and 8.9 ±â€Š5.4 mm in prone position (P = 0.001). In one instance the relationship was unchanged on prone CT. No screw was noted to violate the lumen or distort the aorta. CONCLUSION: Supine CT scan alone is not entirely accurate in determining screw-aorta relationship. Prone-CT scan provides additional information for better delineation. This additional diagnostic step can change the treatment option by limiting the need for vascular intervention. When in doubt, the additional use of an arteriogram can allow for improved visualization. LEVEL OF EVIDENCE: 3.

A Study of Critical Events That Lead to Spinal Cord Injury and the Importance of Rapid Reversal of Surgical Steps in Improving Neurological Outcomes: A Porcine Model.

STUDY DESIGN: Porcine model. OBJECTIVE: To quantify critical vascular and mechanical events that occur before and during an evolving spinal cord injury. SUMMARY OF BACKGROUND DATA: Spinal cord injuries are one of the most devastating complications in spine surgery. Intraoperative neuromonitoring changes can occur as a secondary event of spinal cord compression and decrease in spinal cord blood flow (SCBF). Laser Doppler flowmetry has been well validated for measuring blood flow. METHODS: Seventeen pigs were studied, 14 of which completed the experiment. Multilevel, midthoracic laminectomies were performed. Laser Doppler flowmetry electrodes were placed on the dura to measure SCBF. Spinal cord injury was induced by incremental balloon inflation in the epidural space. The animals were separated into two groups. After motor-evoked potential (MEP) loss, group A underwent medical interventions and then balloon decompression approximately 20 minutes later. Group B underwent immediate balloon decompression followed by medical interventions. After interventions, wake-up test was performed and computed tomography scan measured thoracic spinal canal volume. RESULTS: Median SCBF changes were seen 15.8 (5.4-25.1) minutes before MEP loss. However, the 20% threshold interval was often reached before. At the 20% threshold, median pressure was 7 psi, balloon volume was 0.5 cm, and 50% of the spinal canal was compromised. In group A, no pigs moved and all had pathology indicating ischemia. In group B, 9 of 10 were found to be moving their hind legs with 7 indicating ischemia. CONCLUSION: Compression spinal cord injury is the end of a cascade involving increasing intracanal pressure, decreasing canal volume, and hypoperfusion. Rapid relief of compression leads to MEP return. SCBF monitoring can detect ischemia preinjury, giving surgeons an opportunity for early intervention. LEVEL OF EVIDENCE: 4.

Cadaveric Study of the Safety and Device Functionality of Magnetically Controlled Growing Rods After Exposure to Magnetic Resonance Imaging.

STUDY DESIGN: Cadaveric study. OBJECTIVE: To establish the safety and efficacy of magnetically controlled growing rods (MCGRs) after magnetic resonance imaging (MRI) exposure. SUMMARY OF BACKGROUND DATA: MCGRs are new and promising devices for the treatment of early-onset scoliosis (EOS). A significant percentage of EOS patients have concurrent spinal abnormalities that need to be monitored with MRI. There are major concerns of the MRI compatibility of MCGRs because of the reliance of the lengthening mechanism on strongly ferromagnetic actuators. METHODS: Six fresh-frozen adult cadaveric torsos were used. After thawing, MRI was performed four times each: baseline, after implantation of T2-T3 thoracic rib hooks and L5-S1 pedicle screws, and twice after MCGR implantation. Dual MCGRs were implanted in varying configurations and connected at each end with cross connectors, creating a closed circuit to maximize MRI-induced heating. Temperature measurements and tissue biopsies were obtained to evaluate thermal injury. MCGRs were tested for changes to structural integrity and functionality. MRI images obtained before and after MCGR implantation were evaluated. RESULTS: Average temperatures increased incrementally by 1.1°C, 1.3°C, and 0.5°C after each subsequent scan, consistent with control site temperature increases of 1.1°C, 0.8°C, and 0.4°C. Greatest cumulative temperature change of +3.6°C was observed adjacent to the right-sided actuator, which is below the 6°C threshold cited in literature for clinically detectable thermal injury. Histologic analysis revealed no signs of heat-induced injury. All MCGR actuators continued to function properly according to the manufacturer's specifications and maintained structural integrity. Significant imaging artifacts were observed, with the greatest amount when dual MCGRs were implanted in standard/offset configuration. CONCLUSIONS: We demonstrate minimal MRI-induced temperature change, no observable thermal tissue injury, preservation of MCGR-lengthening functionality, and no structural damage to MCGRs after multiple MRI scans. Expectedly, the ferromagnetic actuators produced substantial MR imaging artifacts. LEVEL OF EVIDENCE: Level V.

When Do Patients Return to Physical Activities and Athletics After Scoliosis Surgery?: A Validated Patient Questionnaire Based Study.

STUDY DESIGN: A retrospective chart review with a survey. OBJECTIVES: This study seeks to determine time of return to normal, physical and athletic activities, and delaying factors after all pedicle screw fixation. SUMMARY OF BACKGROUND DATA: Return to athletic activity after posterior spine fusion (PSF) in adolescent idiopathic scoliosis (AIS) is largely dependent on a surgeon's philosophy. Some allow contact and collision sports by 6 and 12 months, while others avoid contact sports for 1 year and never allow collision sports. We have utilized a patient driven self-directed approach. METHODS: The sports activity questionnaire (SAQ) was developed and activities were categorized into normal (school, gym, and backpack), physical (running, bending, and bicycling) and athletics (AAP criteria: noncontact, contact and collision sports). SAQ was validated through the "test-retest" method on 25 patients and retesting after 3 weeks to minimize recall bias. Questions with kappa >0.7 were included. Patient demographics, x-ray measurements, and perioperative details were recorded. RESULTS: Ninety five patients completed the SAQ. By 3 months; 77% (72/93) returned to school, 60% (54/90) to bending, 52% (48/93) to carrying backpacks, 43% (37/87) to running, and 37% (30/81) to gym. By 6 months, 54% (27/50) returned to noncontact sports, and 63% (21/33) to contact sports. 79% and 53% returned to preoperative level of contact and noncontact sports, respectively. Higher body mass index (BMI) was a risk for delayed return (>3 mo) to school and gym (P < 0.05), while fusion below L2 and younger age for running, bending, and carrying backpacks (P < 0.05). In contrast, there was no patient/curve characteristics associated with a delay to sports. Lowest instrumented vertebra (LIV), Lenke types were not risk factors. There was no correction loss, implant failure, or complications. CONCLUSION: Patients return to athletics much earlier than expected; a quarter returned by 3 months, and over half by 6 months. Age and LIV are determinants for return to "physical activity." LEVEL OF EVIDENCE: 3.

Low-Dose Radiation 3D Intraoperative Imaging: How Low Can We Go? An O-Arm, CT Scan, Cadaveric Study.

MINI: The objective of this study was to evaluate the accuracy and reliability of pedicle screw placement using O-Arm at dosages below the manufactured recommended dose. O-Arm at reduced dose showed a 90% accuracy when compared with computed tomography; however, about 30% medial breaches were misclassified. STUDY DESIGN: Cadaveric study. OBJECTIVE: The objective was to evaluate O-Arm's ability at low-dose (LD) settings to assess intraoperative screw placement. SUMMARY OF BACKGROUND DATA: Accurate placement of pedicle screws is crucial because of proximity to vital structures. Malposition of screws may result in significant morbidity and potential mortality. O-arm provides real-time, intraoperative imaging of patient's anatomy and provides higher accuracy in scoliosis surgeries, avoiding risk to vital structures. We hypothesize using LD or ultra-low doses (ULDs) to obtain intraoperative images allow for accurate assessment of screw placement, both minimizing radiation exposure and preventing screw misplacement. METHODS: Eight cadavers were instrumented with pedicle screws bilaterally from T1 to S1. Screws were randomly placed using O-arm navigation into three positions: contained within the bone, OUT-anterior/lateral, and OUT-medial. O-arm images were obtained at three dosage settings: LD (kVp120/mAs125-lowest manufacturer recommended), very-low dose (VLD) (kVp120/mAs63), and ULD (kVp120/mAs39). Computed tomography (CT) scan was performed using institution's LD protocol (kVp100/mAs50) and gross dissection to identify screw positions. RESULTS: LD, VLD, ULD, and CT for identifying "IN" screws relative to gross dissection had, a mean (standard deviation) sensitivity of 84.2% (±5.7), specificity of 76.1% (±9.3), and accuracy of 79.9% (±3.1) from all three observers. Across the three observers, the interobserver agreement was 0.67 (0.61-0.72) for LD, 0.74 (0.69-0.79) for VLD, 0.61 (0.56-0.66) for ULD, and 0.79 (0.74-0.84) for CT. Effective doses of radiation (mSV) for LD O-arm scan was 2.16, VLD 1.08, ULD 0.68, and our LD CT protocol was 1.05. CONCLUSION: Accuracy of pedicle screw placement is similar for O-arm at all doses and CT compared to gross dissection. Interobserver reliability was substantial for VLD and CT. Approximately 30% of medial screw breaches are, however, misclassified. ULD and VLDs can be used for intraoperative navigation and evaluation purposes within these limitations. LEVEL OF EVIDENCE: N/A.

Minimally Invasive Surgery in Patients With Adolescent Idiopathic Scoliosis: Is it Better than the Standard Approach? A 2-Year Follow-up Study.

STUDY DESIGN: This is a retrospective controlled study. OBJECTIVE: To compare the safety and efficacy of minimally invasive surgery (MIS) for the surgical management of adolescent idiopathic scoliosis (AIS) to the standard open posterior approach (PSF). SUMMARY OF BACKGROUND DATA: MIS approaches offer the potential to reduce soft-tissue trauma, intraoperative blood loss, and surgical-site infection. Thus far, MIS has been successfully utilized for the surgical correction of multilevel spine pathology in adults. It is not yet known if these results can be replicated in the surgical management of AIS. MATERIALS AND METHODS: Seven MIS patients were compared with 15 PSF patients using minimum 2-year follow-up data. Parameters studied included preoperative patient and deformity characteristics, perioperative details, extent of deformity correction, and complications. Data were compared using Mann-Whitney tests for continuous variables and Fisher exact tests for categorical variables. RESULTS: The MIS and PSF groups were similar for all preoperative characteristics collected (P>0.05). MIS patients had fewer fixation points (P=0.015), but a longer median operative time (P=0.011). There was no significant difference in estimated blood loss (EBL) (P=0.051), EBL/fixation point (P=0.204), or amount of fluids administered (P=0.888). Postoperative recovery did not differ between the 2 groups in number of intensive care unit days (P=0.362), length of hospital stay (P=0.472), time to mobilization (P=1.00), Visual Analogue Scale pain scores (P=0.698), or patient-controlled analgesia (P=1.00). The MIS technique had similar deformity correction, screw placement accuracy, and fusion status when compared with the PSF group. MIS patients had lower blood transfusion rate (P=0.02), shorter fusion (P=0.046) and fewer pedicle screws (P=0.015). CONCLUSIONS: The short-term advantages seen in MIS for adult scoliosis were not as obvious in our series. We found similar deformity correction and adequate fusion, however shortcomings related to learning curve, and instrumentation persist. MIS surgery is an innovative treatment for AIS that is technically feasible with significantly lower transfusion rate, shorter fusion lenghts and lesser pedicle screw fixation. Despite these advanatges, its role in AIS is currently difficut to define.