Coronal Correction Research Articles

Correction of the spine with magnetically controlled growing rods in early onset scoliosis : Apre-to-post analysis of 21patients with 1‑year follow-up.

Several studies have emphasized that the magnetically controlled growing rod (MCGR) technique decreases complications and costs and could be considered asafe procedure for treating patients with early onset scoliosis (EOS). To the best of our knowledge, the sagittal profile of patients with an implanted MCGR has not been sufficiently studied before. The objectives of this study were twofold: firstly, to evaluate the influence of MCGR on the coronal, sagittal and axial planes. Secondly, to analyze changes of cervical alignment post-MCGR implantation. This was aretrospective study of patients with EOS who underwent MCGR from 2012 to 2018. Patients were included if they presented with athoracic or lumbar curvature greater than 40° (Cobb angle) and Risser's sign0. Global analysis of all patients was reported. Patients were stratified preoperatively by thoracic alignment into a hypokyphotic or kyphotic group. Furthermore, the study population was divided into an anteriorly aligned group and a posteriorly aligned group. Sagittal alignment parameters and parameters of coronal and axial plane were measured and the preoperative to postoperative change was compared then analyzed 1 year after surgery. No external funding was procured for this research and the authors' conflicts of interest are not pertinent to the present work. A total of 21 patients were included in the study. There was asignificant coronal correction of the structural and compensatory curves (p < 0.01). Before and after surgery, the coronal C7 plumbline was unchanged and remained within the normal range. Postoperatively, asignificant derotation of the apical vertebra in thoracic and lumbar curves was observed (p < 0.05). Global analysis of the sagittal profile revealed asignificant decrease of TK (p < 0.001) and T9SPi (p = 0.002) with asimultaneous significant increase of T1T3 angle (p = 0.015) and T1T4 angle (p = 0.015). No significant changes of the sagittal parameters of cervical, lumbar and spinopelvic parameters were noted. Among all groups, cervical parameters did not reveal any statistically significant changes. At 1‑year follow up the T1T3 angle (p = 0.01) and T1T4 angle (p = 0.03) were significantly increased. All other measured parameters of sagittal, coronal and axial profile were unchanged. The implantation of MCGR had asignificant impact on the sagittal profile. Notwithstanding, no further compensatory mechanisms of the cervical spine and pelvis had to be recruited to safeguard sagittal alignment.

Outcomes of Primary and Conversion Magnetically Controlled Growth Rods Are Different at Two-Year Follow-up: Results of North American Release

Study designMulticenter retrospective review. ObjectivesTo compare the radiographic outcomes and complication rates in patients with primary and conversion magnetically controlled growing rod (MCGR) implants at one and two years after surgery. Summary of background dataMany initial early-onset scoliosis (MCGR) implantations in the United States were conversions from other types of growth-friendly systems, and the outcome similarities and differences between primary and conversion MCGR implantation procedures are still relatively unknown. MethodsMulticenter retrospective review of EOS patients from two multicenter EOS registries identified consecutive EOS patients treated from 2014 to 2017 with a minimum of one-year follow-up. In addition, a subset of these patients who had two-year follow-up were further analyzed. ResultsIn total, 383 MCGR patients were identified, of which 272 (71%) were primary (P) and 111 (29%) were conversion (C). Group P patients had significantly greater coronal curves at the time of MCGR implantation and greater initial coronal correction. There was no statistically significant difference in Cobb correction at one year or between follow-up at one and two years. The preimplantation thoracic spine height was identical in both groups, with statistically greater improvement at initial implantation in P than in C patients. Significantly greater height gains were seen in P than in C patients in the one-year follow-up cohort. There was a higher rate of complications in the C group than in the P group; however, the difference was not statistically significant. Overall, most complications were implant-related. No loss of curve correction occurred in either group. ConclusionsPatients with primary MCGR insertion can be expected to have greater radiographic correction and spine length gain than those with conversion from growth-friendly instrumentation to MCGR, most likely because of increased spine stiffness in conversion patients. The rate of complications, primarily implant-related, remains higher in conversion than in primary insertion patients. Level of EvidenceLevel III.

Anterior and Posterior Fusion for Large, Rigid Idiopathic Scoliosis: Does Implant Density Matter?

Despite advancements in surgical techniques, controversy remains regarding the optimal implant density for the correction of idiopathic scoliosis. Recent evidence has suggested that equivalent radiographic and clinical outcomes can be achieved with lower implant densities for those with moderate curves and good flexibility. Among the experts, the consensus has continued that higher implant densities should be used for larger, stiffer curves. The purpose of the present study was to compare the radiographic results between high-implant density (HID) and low-implant density (LID) constructs in patients with large (>65°), rigid (<50% flexibility) curves who had undergone anterior release and posterior spinal fusion. We reviewed the idiopathic scoliosis cases performed at a single institution from 2006 to 2014. Only those meeting the inclusion criteria were selected. The patients were divided into HID and LID groups. The postoperative radiographs were compared for coronal correction, thoracic kyphosis, pelvic tilt, lumbar lordosis, and sagittal vertical axis. A statistically significant improvement in coronal correction was detected in the HID group at all follow-up points (final follow-up: HID, 81.1% vs. LID, 70.4%; P= 0.01). When preoperative thoracic kyphosis was considered, no differences were found between the 2 groups. No differences were found in the other sagittal parameters. In patients with large, rigid idiopathic scoliosis undergoing anterior release and posterior spinal fusion, a small, but statistically, significant improvement in the coronal Cobb angle was seen. It remains to be determined whether this small difference in radiographic correction will have any influence on the clinical outcome.

Less invasive spinal deformity surgery: the impact of the learning curve at tertiary spine care centers.

The past decade has seen major advances in techniques for treating more complex spinal disorders using minimally invasive surgery (MIS). While appealing from the standpoint of patient perioperative outcomes, a major impediment to adoption has been the significant learning curve in utilizing MIS techniques. Data were retrospectively analyzed from a multicenter series of adult spinal deformity surgeries treated at eight tertiary spine care centers in the period from 2008 to 2015. All patients had undergone a less invasive or hybrid approach for a deformity correction satisfying the following inclusion criteria at baseline: coronal Cobb angle ≥ 20°, sagittal vertical axis (SVA) > 5 cm, or pelvic tilt > 20°. Analyzed data included baseline demographic details, severity of deformity, surgical metrics, clinical outcomes (numeric rating scale [NRS] score and Oswestry Disability Index [ODI]), radiographic outcomes, and complications. A minimum follow-up of 2 years was required for study inclusion. Across the 8-year study period, among 222 patients, there was a trend toward treating increasingly morbid patients, with the mean age increasing from 50.7 to 62.4 years (p = 0.013) and the BMI increasing from 25.5 to 31.4 kg/m2 (p = 0.12). There was no statistical difference in the severity of coronal and sagittal deformity treated over the study period. With regard to radiographic changes following surgery, there was an increasing emphasis on sagittal correction and, conversely, less coronal correction. There was no statistically significant difference in clinical outcomes over the 8-year period, and meaningful improvements were seen in all years (ODI range of improvement: 15.0-26.9). Neither were there statistically significant differences in major complications; however, minor complications were seen less often as the surgeons gained experience (p = 0.064). Operative time was decreased on average by 47% over the 8-year period.Trends in surgical practice were seen as well. Total fusion construct length was unchanged until the last year when there was a marked decrease in conjunction with a decrease in interbody levels treated (p = 0.004) while obtaining a higher degree of sagittal correction, suggesting more selective but powerful interbody reduction methods as reflected by an increase in the lateral and anterior column resection techniques being utilized. The use of minimally invasive methods for adult spinal deformity surgery has evolved over the past decade. Experienced surgeons are treating older and more morbid patients with similar outcomes. A reliance on selective, more powerful interbody approaches is increasing as well.

69. Coronal correction using the kickstand rod technique: a pilot adult scoliosis study and analysis of early outcomes and complications

BACKGROUND CONTEXT A major goal of adult spinal deformity (ASD) surgery is more harmonious spinal alignment. Sagittal alignment has been emphasized since it was demonstrated to have the greatest impact on postoperative pain and functional outcomes. However, growing evidence suggests the impact of coronal alignment has likely been underestimated. Kickstand rods are a new technique recently utilized for achieving coronal balance. The kickstand spans from the thoracolumbar junction to a 3rd iliac screw. Using the iliac wing as a base, kickstand distraction produces powerful coronal realignment forces. Limited literature exists for this novel technique, and its associated outcomes and complications after ASD surgery are unknown. PURPOSE The objective of this pilot study was to investigate early outcomes and complications after coronal correction with kickstand rods. STUDY DESIGN/SETTING Retrospective review of single-center database. PATIENT SAMPLE Consecutive ASD patients. OUTCOME MEASURES Radiographic alignment correction using standing long-cassette films (both coronal and sagittal spinopelvic measurements), back and leg pain assessed with numerical rating scale (NRS) scores (0-no pain; 10-unbearable pain), and associated complications. METHODS All ASD patients who had deformity correction using kickstand rods. Demographic, surgical, coronal- and sagittal-plane radiographic measurements, and back and leg pain NRS scores were analyzed. A kickstand rod correction classification was devised to illustrate our technique: Subtype (1a) Curve Pattern: C7PL towards major concavity and fractional convexity; Kickstand Distraction: corrects major curve onlySubtype (1b) Curve Pattern: C7PL towards major concavity with neutral/concave fractional curve; Kickstand Distraction: corrects major curve +/- simultaneous fractional correction; Subtype (2) Curve Pattern: C7PL towards major convexity; Kickstand Distraction: corrects fractional curve +/- simultaneous major correction; Subtype (3) Curve Pattern: global coronal balance with scoliosis; Kickstand distraction corrects major curve, but typically after fractional correction “shifts” the spine. RESULTS The cohort comprised 19 patients (mean age: 67±7 yrs; 79% women; 63% prior lumbar fusion) with mean follow-up 21 weeks (range: 2-72 weeks). All patients had posterior-only approach surgery with tri-iliac fixation (3rd iliac screw for the kickstand) for mean fusion length 12 levels. Kickstand correction was subtype 1a, 1b, 2, and 3 in 4 (21%), 6 (32%), 7 (37%), and 2 (9%) patients, respectively. 3-column osteotomy and lumbar TLIF were performed in 5 (26%) and 15 (79%) patients, respectively. Alignment was significantly improved (coronal balance: 8 to 1cm [p CONCLUSIONS Kickstand rod distraction can achieve significant coronal correction in ASD. Kickstand subtype 1a+b was most commonly utilized (since coronal curves with C7PL shifted to the major curve concavity are most common). Back and leg pain were significantly improved, and complications rates were reasonable. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

147. Prospective randomized controlled trial of implant density in AIS: results of the Minimize Implants Maximize Outcomes study

BACKGROUND CONTEXT The role of implant density (anchors per level fused) has not been prospectively studied for a large cohort of AIS patients. In the Minimize Implants Maximize Outcomes (MIMO) Clinical Trial of equivalence, patients with Lenke 1A curve patterns were randomized to more versus fewer screws (high or low density) to determine if there was a difference in percent coronal Cobb angle correction within a 10% margin. PURPOSE This prospective randomized cotrolled trial was designed to determine if there was a difference in curve correction between high density and low density pedicle screw placement in single right thoracic Lenke 1A curves where maximal curve correction was the desired goal. STUDY DESIGN/SETTING Fourteen sites accrued patients in the MIMO Clinical Trial (NCT01792609). Patients with Lenke 1A curves between 45-65° were randomized to a high- (>1.8 screws per level fused, HD) vs low- ( PATIENT SAMPLE Power analysis showed that 174 patients were needed to detect a difference in % correction with a 10% margin at each time point. Follow-up was performed at 3 month (189 patients), 1 year (156 patients), and 2 years (124 patients). OUTCOME MEASURES Data was centrally collected and X-ray images measured by trained reviewers. Cobb angle was the primary outcome variable. METHODS RCT. Surgeons were given assignment to high or low density for each patient. Preop 3-month, 1-year and 2-year radiographs were obtained. Demographic and process measure data were also collected. RESULTS There was no difference in age, gender, preop curve magnitude, or race between the two groups. Mean % Cobb correction at three months was 74% in HD vs 70% in LD (p=0.065, 95% CI −0.2 to 6.8%), 69% in HD vs 66% in LD at 1 year (p=0.25, 95% CI, −1.7 to 6.7%), and 67% vs 64% at 2 years (p=0.18, CI, −1.5 to 7.8%). There was no difference in operative time, blood loss, or length of stay amongst the two groups. There was no difference in pre- or postop thoracic kyphosis between the HD and LD groups. There were six reoperations in each group (p=1.0). Age was lower for patients who completed 2-year follow-up (11.6 years vs. 12.8, p CONCLUSIONS For Lenke 1A curves between 45°-65° randomized to low- vs high implant density, this prospective, randomized, controlled study showed equivalent % coronal curve correction. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Difference in joint line convergence angle between the supine and standing positions is the most important predictive factor of coronal correction error after medial opening wedge high tibial osteotomy.

Coronal correction errors after medial opening wedge high tibial osteotomy (MOWHTO) occasionally occur even with the assistance of navigation. The purpose of the present study was to determine the navigation accuracy in MOWHTO and to identify factors that affect the coronal correction error after navigation-assisted MOWHTO. A total of 114 knees treated with navigation-assisted MOWHTO were reviewed retrospectively. Mechanical axis (MA) on standing radiograph and medial proximal tibial angle (MPTA) were measured preoperatively and at 6months postoperatively, and the differences (ΔMA and ΔMPTA) were calculated. Joint line convergence angle (JLCA) on supine and standing radiographs was measured preoperatively, and their difference (ΔJLCA) was calculated. To assess the navigation accuracy, ΔMA and ΔMPTA were compared with the coronal correction by navigation (ΔNMA) using intraclass correlation coefficients (ICCs). Univariable and multivariable regression analyses were used to identify factors that affect coronal correction discrepancy (ΔMA - ΔNMA). The reliability of navigation was good in terms of bony correction (ICC between ΔNMA and ΔMPTA, 0.844) and fair in terms of MA correction (ICC between ΔNMA and ΔMA, 0.706). The mean coronal correction discrepancy was 2.0° ± 2.4°. In the multivariable analysis, ΔJLCA was shown to be a predictive factor of coronal correction discrepancy (unstandardized coefficient, 1.026; R2, 0.470). Navigation in MOWHTO provided reliable information about bony correction; however, MA tended to be overcorrected. The difference in JLCA between the supine and standing radiographs was the most important preoperative factor that predicted the coronal correction discrepancy after MOWHTO. In patients with larger ΔJLCA, each degree of ΔJLCA should be subtracted from the planned amount of correction angle when preoperative planning is performed using standing radiographs. IV.

Classical target coronal alignment in high tibial osteotomy demonstrates validity in terms of knee kinematics and kinetics in a computer model.

The purpose of this study was to determine the ideal coronal alignment under dynamic conditions after open-wedge high tibial osteotomy (OWHTO). It was hypothesised that, although the classical target alignment was based on experimental evidence, it would demonstrate biomechanical validity. Musculoskeletal computer models were analysed with various degrees of coronal correction in OWHTO during gait and squat, specifically with the mechanical axis passing through points at 40%, 50%, 60%, 62.5%, 70%, and 80% of the tibial plateau from the medial edge, defined as the weight-bearing line percentage (WBL%). The peak load on the lateral tibiofemoral (TF) joint, the medial collateral ligament (MCL), and anterior cruciate ligament (ACL) tensions, and knee kinematics with or without increased posterior tibial slope (PTS) were evaluated. The classical alignment with WBL62.5% achieved sufficient load on the lateral TF joint and maintained normal knee kinematics after OWHTO. However, over-correction with WBL80% caused an excessive lateral load and non-physiological kinematics. Increased WBL% resulted in increased MCL tension due to lateral femoral movement against the tibia. With WBL80%, abnormal contact between the medial femoral condyle and the medial intercondylar eminence of the tibia occurred at knee extension. The screw-home movement around knee extension and the TF rotational angle during flexion were reduced as WBL% increased. Increased PTS was associated with increased ACL tension and decreased TF rotation angle because of ligamentous imbalance. The classical target alignment demonstrated validity in OWHTO, and over-correction should be avoided as it negatively impacts clinical outcome. IV.

Comparison of Circular and Sagittal Reinforced Rod Options on Sagittal Balance Restoration in Adolescents Undergoing Pedicle Screw Instrumentation for Idiopathic Scoliosis

Pedicle screw instrumentation is widely used for spinal deformity correction and fusion in adolescents for idiopathic scoliosis. The goal is to achieve and sustain good alignment in all 3 planes. We compared 2 different cobalt-chromium (CoCr) rod designs with different stiffnesses with regard to the restoration of coronal and sagittal balance in adolescents operated on for idiopathic scoliosis. A prospective comparative study was made of 90 consecutive adolescents, mean age (standard deviation) 15.6 years (2.1 years), with idiopathic scoliosis who underwent posterior spinal fusion by the use of bilateral segmental pedicle screw instrumentation (PSI) with 6.0 Co-Cr rods. Fifty-four adolescents (43 girls) were operated on by the use of circular rods and 36 (27 girls) by the use of sagittal reinforced rods, with a 2-year follow-up. Preoperative major coronal curves were similar and at 2 years: 11° (5.0) and 17° (7.2) with correction percentages of 78% (10) and 69% (12) in the circular and reinforced rod groups (P < 0.01). Thoracic kyphosis at 2 years measured 16° (7) and 21° (6) in the circular and reinforced rod groups (P < 0.01). The number of patients with hypokyphosis was lower in the reinforced rod group at 2 years (P= 0.02). In the reinforced rod group, there was a negative correlation between coronal correction and thoracic kyphosis (r=-0.52, P < 0.01). Both circular and sagittal reinforced 6.0-mm CoCr rods provide adequate coronal correction for adolescents with idiopathic scoliosis. The use of sagittal reinforced rods provided better thoracic kyphosis restoration and a lower risk for postoperative hypokyphosis.

Minimal invasive posterior correction of Lenke 5C idiopathic scoliosis: comparative analysis of minimal invasive vs. open surgery

IntroductionSurgical management of adolescent idiopathic scoliosis in spite of usually favourable outcomes is still a major operation. Therefore, efforts are being undertaken to minimalize the procedure, reduce the surgical trauma and postoperative convalescence. The study was designed to compare posterior minimal invasive surgery using navigation based on intraoperative 3D imaging and standard open instrumented fusion in Lenke 5C idiopathic scoliosis treatment.Materials and methodsFrom eight patients with Lenke 5C curves planned for posterior correction and instrumented fusion, four were treated with minimally invasive and four had open procedure. Operation length, estimated blood loss, number of fusion levels, days of opioid intake, length of hospital stay and radiation doses required were noted. Radiographic assessment of spinal curvatures was performed (magnitude, flexibility, sagittal alignment). The comparison of the data was done between open and minimally invasive treated patients.ResultsIn minimally invasive surgery group, the operations were longer on average 285 min ± 47.5 than in the open surgery group, 242.5 min ± 44.5 (p = 0.371) and resulted in slightly inferior coronal curve correction by 68.25% ± 6.2 vs. 78.25% ± 8.8, respectively (p = 0.072). We observed a clear reduction of intraoperative blood loss in minimally invasive patients (mean 138.75 ± 50 vs. 450 ± 106 ml, p = 0.016), shorter hospital stay, average 3.75 vs. 7 days (p = 0.043) and lower opioid requirements postoperatively − 2 vs. 3.25 days (p = 0.015).ConclusionsThe minimally invasive approach to idiopathic scoliosis treatment is a very promising technique to limit the extent of surgery maintaining the same goals as in the open method. It allows for lower blood loss, less requirement for opioids and a shorter hospital stay.

Midterm Results of Hemivertebrae Resection and Transpedicular Short Fusion in Patients Younger Than 5 Years: How Do Thoracolumbar and Lumbosacral Curves Compare?

Study DesignRetrospective case series with comparative analysis. ObjectiveTo analyze a consecutive cohort of very young patients operated for congenital scoliosis secondary to a single hemivertebra (HV) and compare thoracolumbar (TL) versus lumbosacral (LS) curve results. Summary of Background DataDespite the published successful results regarding early hemivertebra resection and short fusion for congenital hemivertebrae, literature lacks midterm results, especially in very young children. MethodsPatients under 5 years of age, operated by HV resection and transpedicular short fusion, with follow-up longer than 5 years, were included. Preoperative, postoperative (1-year), final radiographic parameters, and complications were recorded. Midterm results were analyzed and TL versus LS curves were compared. ResultsTwenty-three patients were included (14 TL and 9 LS HV). The mean age was 3.5 ± 1.7 years and the mean follow-up was 7.6 years (4.7–13.7). The mean preoperative Cobb angle (40.3° ± 6.7°), corrected 65% postoperatively and 50% at final follow-up. The compensatory cranial curve improved spontaneously from 25.3° ± 14.8° to 13.5° ± 12° and finally to 19.9° ± 10.7°. Preoperative coronal balance corrected postoperatively but worsened at the final follow-up. TL curves corrected more initially than LS curves (TL: −29°, 68%, vs. LS: −22°, 59%; p = .043); however, both groups lost correction at the final follow-up (TL: 4°, 56%, vs. LS: 7°, 39%; p = .186). The LS group had a larger preoperative compensatory curve, which corrected with surgery but lost more correction at the final follow-up (p = .046). Segmental kyphosis was especially corrected in the TL group (TL: −14° vs. LS: −2°, p = .018) and was maintained over time. ConclusionEarly hemivertebra resection and transpedicular short fusion allowed good coronal correction initially, which was difficult to maintain at midterm, especially at the LS junction. Sagittal plane correction was excellent in TL deformities and was maintained over time. Results were more challenging in the LS group compared with TL deformities. Guidance to avoid unwanted results is proposed. Level of EvidenceLevel III.

Experience with definitive instrumented final fusion after posterior-based distraction lengthening in patients with early-onset spinal deformity: single center results.

Limited reports exist with regard to clinical and radiographic details of patients with early-onset spinal deformity (EOSD) undergoing definitive instrumented final fusion (FF) following implantation of a growing construct. Charts and radiographs were queried for all patients who underwent FF after management of EOSD with a distraction-based posterior construct at a single institution from 2006 to 2017. Patients managed during the growth modulation period with either proximal rib or spinal fixation were included. Thirteen patients qualified for inclusion. Spinal deformity etiologies were varied (neuromuscular: 5, idiopathic: 4, congenital: 4). Average age at implantation was 6.5 years, and patients underwent an average of 8.15 lengthening procedures over an average of 69 months. After the growing program, modest correction in main coronal Cobb was obtained at FF (average 52.4° before FF, 37.6° following FF, P<0.001; average percent improvement of 27%). Five patients required posterior column osteotomies. Using criteria proposed by Flynn and colleagues, 'minimal' coronal correction was achieved in 23% of patients and 'moderate' in 77%. No patient achieved 'substantial' (>50%) correction. Subjective poor bone quality was appreciated in 67% of patients, and 85% were noted to have areas of autofusion over previously spanned levels. Two (15%) patients sustained a total of four complications. After growth modulation procedures, EOSD deformities are generally stiff, bone quality is often subjectively poor, and autofusion is common, even after use of proximally rib-based systems. Modestly improved coronal Cobb correction can be obtained at FF but may require single or multiple posterior osteotomies. Intraoperative difficulties can be expected, and clinicians should be alert for intraoperative and postoperative complications.

Biomechanical Comparison of the Load-Sharing Capacity of High and Low Implant Density Constructs With Three Types of Pedicle Screws for the Instrumentation of Adolescent Idiopathic Scoliosis

Study DesignBiomechanical numerical simulation analysis of implant design and density in adolescent idiopathic scoliosis posterior instrumentation. ObjectivesTo evaluate the combined effect of pedicle screw design and density on deformity correction and construct load-sharing capacity. Summary of Background DataScrew density is an area of popular study because of the impact of cost and potential patient morbidity of higher-density constructs. Using fewer screws raises concern about reduced correction and greater forces on each screw. MethodsPersonalized spinal numerical models were created for five patients. The correction techniques from five spine surgeons using both a high- and a low-density implant pattern (2 vs. 1.4 ± 0.22 screws/level) with uniaxial, multiaxial, and favored angle screws were simulated. The predicted correction and forces sustained by the implants were compared. The postoperative load-sharing capacity of a high- and a low-density construct, with or without crosslinks, was compared by simulating daily activities motions. ResultsThe major coronal curve correction was similar with high- and low-density constructs (73% ± 10% vs. 72% ± 10%; p > .05) but was higher when using uniaxial (77% ± 8%) compared to multiaxial (69% ± 11%) and favored angle screws (71% ± 10%; p = .009). High- and low-density constructs sustained similar intraoperative peak forces (305 ± 61 N vs. 301 ± 73 N; p = .23) regardless of screw design (all p > .05). Multiaxial and favored angle screws reduced the peak axial force by 23% and 38% compared to uniaxial screws (p = .007). The high-density construct reduced the postoperative loads sustained by each implant by 31% (p = .006). Crosslinks had no effect on load sharing (p = .23). ConclusionHigh- and low-density implant patterns achieved similar coronal correction with equivalent capacity to share corrective forces regardless of the screw design. Increased degrees of freedom of the screw head reduces the capacity to correct coronal deformity but generates lower bone-screw forces. The reduced number of screws increased the postoperative forces sustained by each screw, but its effect on potential complications requires further investigations. Level of EvidenceLevel 4.

Fifteen Years and 2530 Patients: The Evolution of Instrumentation, Surgical Strategies, and Outcomes in Adolescent Idiopathic Scoliosis in a Single Institution

Over the past decade, the surgical treatment of adolescent idiopathic scoliosis (AIS) has established new techniques to reduce curve severity and shifted to include the regular use of pedicle screws. Few studies have focused on this evolving trend in AIS correction surgery. In this study, we investigated how the operative approach, instrumentation, and surgical techniques have changed over the past 15 years and to quantify the related improvements in AIS surgical treatment. This is a retrospective review of a prospective AIS registry in a single center. Patient data were reviewed from January 2001 to December 2015. The age and surgical case distribution were recorded for each year. Trends in classification use, instrumentation types, levels of fusion, and surgical approaches were analyzed by year. The major Cobb angles and correction rates were compared between different instrumentations and surgical approaches. A total of 2530 patients with AIS (83.0% female) were included, with a mean age of 15.14 years. Most patients underwent surgery at 14 years of age (473 patients, 18.7%), followed by 15 years of age (468 patients, 18.5%). In our center, the classification of patients with AIS shifted from the King classification to the Lenke classification in 2005. The major baseline Cobb angle of the entire cohort averaged 50.99° and this mean Cobb angle decreased to 14.41° after surgery. The correction rates for the first 3 years (2001-2003) were less than 70%, whereas the correction rates for the rest of the years were all greater than 70%. In addition, significantly higher correction rates were observed in patients with Cobb angles <90° (72.93% vs. 55.61%, P < 0.001). A total of 218 anterior-only surgeries and 109 combined anteroposterior surgeries were performed; the remaining 2205 surgeries were performed with a posterior-only approach. The use of anterior-only and anteroposterior approaches trended to decrease after 2005. The correction rate of anterior-only approaches was significantly greater than posterior-only and anteroposterior approaches (77.86%, 72.51%, and 59.37%, respectively). In patients corrected with a posterior-only approach, the screw-hook hybrid construct was used in 342 patients, whereas the all-pedicle-screw construct was used in 1835 patients. The shift from hybrid to all-screw construct occurred in 2006. In patients with thoracic AIS, the correction rate was significantly higher in the all-screw group (73.26% vs. 67.76%; P < 0.001). Consistent improvement of major curve correction has been achieved by the spine community over 15 years. After stabilized coronal correction and fewer fusion levels, the next steps in this evolution are the restoration of sagittal profiles, especially the hypokyphosis seen in patients with Lenke 1, the posterior minimally invasive approach, and a fast-track return to activity.

O 041 - Long-term outcome after hamstring lengthening in children with CP depends on preoperative hamstring length and velocity

Retrospective case series with comparative analysis.To analyze a consecutive cohort of very young patients operated for congenital scoliosis secondary to a single hemivertebra (HV) and compare thoracolumbar (TL) versus lumbosacral (LS) curve results.Despite the published successful results regarding early hemivertebra resection and short fusion for congenital hemivertebrae, literature lacks midterm results, especially in very young children.Patients under 5 years of age, operated by HV resection and transpedicular short fusion, with follow-up longer than 5 years, were included. Preoperative, postoperative (1-year), final radiographic parameters, and complications were recorded. Midterm results were analyzed and TL versus LS curves were compared.Twenty-three patients were included (14 TL and 9 LS HV). The mean age was 3.5 ± 1.7 years and the mean follow-up was 7.6 years (4.7–13.7). The mean preoperative Cobb angle (40.3° ± 6.7°), corrected 65% postoperatively and 50% at final follow-up. The compensatory cranial curve improved spontaneously from 25.3° ± 14.8° to 13.5° ± 12° and finally to 19.9° ± 10.7°. Preoperative coronal balance corrected postoperatively but worsened at the final follow-up. TL curves corrected more initially than LS curves (TL: −29°, 68%, vs. LS: −22°, 59%; p = .043); however, both groups lost correction at the final follow-up (TL: 4°, 56%, vs. LS: 7°, 39%; p = .186). The LS group had a larger preoperative compensatory curve, which corrected with surgery but lost more correction at the final follow-up (p = .046). Segmental kyphosis was especially corrected in the TL group (TL: −14° vs. LS: −2°, p = .018) and was maintained over time.Early hemivertebra resection and transpedicular short fusion allowed good coronal correction initially, which was difficult to maintain at midterm, especially at the LS junction. Sagittal plane correction was excellent in TL deformities and was maintained over time. Results were more challenging in the LS group compared with TL deformities. Guidance to avoid unwanted results is proposed.Level III.

Systematic review of the complications associated with magnetically controlled growing rods for the treatment of early onset scoliosis.

To analyse the complication profile of magnetically controlled growing rods (MCGRs) in early onset scoliosis (EOS). This is a systematic review using PUBMED, Medline, Embase, Google Scholar and the Cochrane Library (keywords: MAGEC, Magnetically controlled growing rods and EOS) of all studies written in English with a minimum of five patients and a 1-year follow-up. We evaluated coronal correction, growth progression (T1-S1, T1-T12) and complications. Fifteen studies (336 patients) were included (42.5% male, mean age 7.9years, average follow-up 29.7months). Coronal improvement was achieved in all studies (pre-operative 64.8°, latest follow-up 34.9° p = 0.000), as was growth progression (p = 0.001). Mean complication rate was 44.5%, excluding the 50.8% medical complication rate. The unplanned revision rate was 33%. The most common complications were anchor pull-out (11.8%), implant failure (11.7%) and rod breakage (10.6%). There was no significant difference between primary (39.8%) and conversion (33.3%) procedures (p = 0.462). There was a non-statistically significant increased complication rate with single rods (40 vs. 27% p = 0.588). MCGRs improve coronal deformity and maintain spinal growth, but carry a 44.5% complication and 33% unplanned revision rate. Conversion procedures do not increase this risk. Single rods should be avoided. These slides can be retrieved under Electronic Supplementary material.

Reciprocal Changes in Sagittal Alignment in Adolescent Idiopathic Scoliosis Patients Following Strategic Pedicle Screw Fixation.

Study DesignRetrospective observational study.PurposeTo analyze the effect of low-density (LD) strategic pedicle screw fixation on the correction of coronal and sagittal parameters in adolescent idiopathic scoliosis (AIS) patients.Overview of LiteratureLD screw fixation achieves favorable coronal correction, but its effect on sagittal parameters is not well established. AIS is often associated with decreased thoracic kyphosis (TK), and the use of multi-level pedicle screws may result in further flattening of the sagittal profile.MethodsA retrospective analysis was performed on 92 patients with AIS to compare coronal and sagittal parameters preoperatively and at 2-year follow-up. All patients underwent posterior correction via LD strategic pedicle screw fixation. Radiographs were analyzed for primary Cobb angle (PCA), coronal imbalance, cervical sagittal angle (CSA), TK, lumbar lordosis (LL), pelvic incidence, pelvic tilt (PT), sacral slope (SS), C7 plumb line, spino-sacral angle, curve flexibility, and screw density.ResultsPCA changed significantly from 57.6°±13.9° to 19°±8.4° (p <0.0001) with 67% correction, where the mean curve flexibility was 41% and screw density was 68%. Regional sagittal parameters did not change significantly, including CSA (from 10.76° to 10.56°, p =0.893), TK (from 24.4° to 22.8°, p =0.145), and LL (from 50.3° to 51.1°, p =0.415). However, subgroup analysis of the hypokyphosis group (<10°) and the hyperkyphosis group (>40°) showed significant correction of TK (p <0.0001 in both). Sacro-pelvic parameters showed a significant decrease of PT and increase of SS, suggesting a reduction in pelvic retroversion SS (from 37° to 40°, p =0.0001) and PT (from 15° to 14°, p =0.025).ConclusionsLD strategic pedicle screw fixation provides favorable coronal correction and improves overall sagittal sacro-pelvic parameters. This technique does not cause significant flattening of TK and results in a favorable restoration of TK in patients with hypokyphosis or hyperkyphosis.

Influence of Derotation Connectors on 3D Surgical Correction of Adolescent Idiopathic Scoliosis.

Monocentric study comparing results of simultaneous translation on 2 rods (ST2R) with derotation connectors (prospective series) or without derotation connectors (retrospective series) in Adolescent Idiopathic Scoliosis (AIS) surgery. The objective of this study was to assess if derotation connectors influence axial, coronal, and sagittal results in AIS surgery. Conventional reduction techniques remain limited in their ability to reduce axial torsion. Direct vertebral derotation technique accomplishes partial axial derotation but decreases thoracic kyphosis. Monocentric study including AIS surgeries performed using ST2R technique with derotation connectors (group D+, n=44) or without derotation connectors (group D-, n=24). The axial intervertebral rotation was measured between apical and neutral vertebra on pre and postoperative computed tomography scan. T test was used to compare mean values. ANCOVA analyzed the influence of connectors and covariates on the primary outcome, which was the difference between preoperative and postoperative intervertebral rotation. The mean axial torsion gain in the D+ group was 23% (+3.84 degrees, 95% confidence interval, +1.95/+5.73). In the D- group, mean axial torsion increase of 4% (-0.42 degrees, 95% confidence interval, -1.19/+2.03). The result was significantly different between the 2 groups (P=0.005). The coronal correction of the main curve angle was 80% in the D+ group and 64% in the D- group (P=0.004). Kyphosis correction was similar between the 2 groups (P=0.3) with significant increase of thoracic kyphosis in the whole series (P=0.02) and no patients with postoperative hypokyphosis <10 degrees. Multivariate analysis confirmed the influence of derotation connectors on both axial and coronal correction (P<0.05). The use of derotation connectors in the surgical treatment of AIS significantly improved axial and coronal correction compared to nonuse of connectors without compromising the sagittal plane.

Corrective osteotomies using patient-specific 3D-printed guides: a critical appraisal.

Over the last decade, the technique of 3D planning has found its way into trauma surgery. The use of this technique in corrective osteotomies for treatment of malunions provides the trauma surgeon with a powerful tool. However, this technique is not entirely straightforward. We aimed to define potential pitfalls of this technique and possible solutions to overcome these shortcomings. Ten patients with either a uni-, bi- or triplanar malunion of the long bones were included in this study. These patients were divided into three groups: a weight-bearing group and a non-weight-bearing group, the latter was divided into the humerus group and the forearm group, subsequently. 2D correction parameters were defined and compared within every group, as well as the interpretations of 3D visualization. The weight-bearing group revealed an undercorrection for almost all clinical measurements of the femur and tibia, while there was adequate matching of the osteotomies and of screw entry points in all cases. In the humerus group, coronal correction angles were nearly perfect in all cases, while axial and sagittal correction rates, however, differed substantially. Screw entry points and osteotomies were all at the level as planned. The forearm group showed undercorrection in multiple planes while there were good matching entry points for the screw trajectories. Four major pitfalls were encountered using the 3D printing technique: (1) careful examination of the planned guide positioning is mandatory, since suboptimal intra-operative guide positioning is most likely the main cause of the incomplete correction; (2) the use of pre-drilled screw holes do not guarantee adequate screw positioning; (3) translation of bone fragments over the osteotomy planes in case of an oblique osteotomy is a potential hazard; (4) the depth of the osteotomy is hard to estimate, potentially leading to extensive cartilage damage.

Analysis of correlation between regional implant density and the correction rate in treatment of Lenke 1A and 1B adolescent idiopathic scoliosis with pedicle screws.

A retrospective study.The optimal implant density in patients with Lenke type 1 adolescent idiopathic scoliosis (AIS) is undefined, and there is no study reporting the correlation between the partitional implant density and the correction outcome.To determine whether the implant density in structural and nonstructural regions would affect the coronal correction outcome of Lenke 1A and 1B AIS.Preoperative general data and postoperative follow-up data of Lenke 1A and 1B AIS patients who received posterior fusion with the pedicle screw system were analyzed. Correlations between the implant density in structural and nonstructural regions and the correction rate of coronal Cobb angle, as well as between the correction rate and loss of the coronal correction angle during a 2-year follow-up period were analyzed. According to the implant density, the patients were classified into 2 groups: structural region group (including A1 and A2), and nonstructural region group (including B1 and B2). Differences in related parameters between the 2 groups were compared statistically.Except for the mean implant density, there was no statistical difference in the other parameters between group A1 and A2. In group B1 and B2, the correction rate of the main thoracic (MT) curve was 63.0% and 71.6% (P = .022), and the loss of the correction angle was 2.1° and 4.2°, respectively (P < .01), showing a statistical difference in the correction rate and postoperative angle loss of the MT curve between group B1 and B2.The correction rate of the MT curve at the coronal plane and postoperative loss of the correction angle were not related to the implant density in structural regions but may be related to the implant density in nonstructural regions in the treatment of Lenke type 1A and 1B AIS with pedicle screw instrumentation.