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

Benefit-risks analysis of thoracoplasty in adolescent idiopathic scoliosis treated by sublaminar bands

INTRODUCTION

Cosmetic concerns are one of the main complaints of patients with adolescent idiopathic scoliosis (AIS). Several studies have shown a significant improvement in self-image scores after thoracoplasty. However, the effects of thoracoplasty on pulmonary function and clinical outcomes remain debated. The objective was to analyze the benefits and risks of thoracoplasty during AIS surgery using a hybrid construct with sublaminar bands.

MATERIAL AND METHODS

In this monocentric prospective cohort study, 68 patients with thoracic AIS were consecutively included between 2016 and 2017. All patients had low-dose 3D radiographs. Surgical correction was performed via the posterior approach, using the posteromedial translation technique with a hybrid construct (thoracic sublaminar band and lumbar pedicle screws). A thoracoplasty was proposed in cases of severe rib hump (more than 3cm). Pulmonary function was assessed by pulmonary function tests (PFT) with forced vital capacity, forced expiratory volume in 1 second and total lung capacity). Radiographic parameters and PFT were compared between patients who had or had not had a thoracoplasty preoperatively and 2 years postoperatively. The SRS-22 score was collected at follow-up.

RESULTS

The average age was 15±3 years. Nineteen patients (27%) had a thoracoplasty. The demographic, radiographic and respiratory data of the 2 groups were comparable preoperatively. The correction was similar between the groups on sagittal and coronal views. At 2 years, the PFTs were comparable to those performed preoperatively and no difference was found between the groups. None of the 12 patients who had a pleural effusion had it drained. The total SRS-22 score and the cosmetic subscore were higher in the thoracoplasty group (p<0.03).

DISCUSSION

The association of a thoracoplasty with AIS surgery improves the self-image of patients without altering the PFTs at 2 years postoperatively. Given the low morbidity of thoracoplasty, it seems reasonable to offer it to patients with severe rib hump and high cosmetic demands.

LEVEL OF EVIDENCE

III.

Bipolar Fusionless Versus Standard Fusion Surgery in Neuromuscular Scoliosis: A Two-center Comparative Study

STUDY DESIGN

Nonrandomized controlled cohort.

OBJECTIVE

To compare early results between bipolar fusionless construct (BFC) and single posterior fusion (SPF) surgery in neuromuscular scoliosis (NMS).

BACKGROUND

Surgical treatments for NMS have traditionally been characterized by high complication rates. A mini-invasive BFC was developed to reduce these risks while maintaining adequate curve reduction. There is, however, a current lack of studies comparing clinical and radiologic perioperative outcomes between both techniques.

METHODS

All patients surgically treated for NMS with to-pelvis construct between 2011 and 2021 at 2 centers were included and divided into 2 groups according to the surgical technique (BFC or SPF). Gender, age, main deformity region, etiology, preoperative and postoperative main curve magnitude and pelvic obliquity, surgery time, estimated blood loss and transfusion rates, length of hospital stay, the magnitude of main curve and pelvic obliquity correction, and early complications were compared. Quantitative data were compared through ANOVA or Mann-Whitney test. Analysis of qualitative outcomes was performed through Fisher exact test and logistic regressions. Kruskal-Wallis test was used to compare complications between groups.

RESULTS

Eighty-nine NMS patients were included: 48 in the SPF group and 41 in the BFC group. Surgery time (203 vs. 241 min), rate (32 vs. 52%) and severity of complications, unplanned returns to the operating room (15 vs. 39%), estimated blood loss (179 vs. 364 cc), and transfusion rates (27 vs. 73%) were lower in the BFC group ( P <0.05). There were no significant differences in age, maturity stage, preoperative curve magnitude, preoperative pelvic obliquity and postoperative curve, and pelvic obliquity correction between groups.

CONCLUSIONS

BFC may be a safer and less invasive option for NMS surgical treatment, resulting in similar curve corrections while significantly decreasing the number and severity of complications as well as intraoperative blood loss when compared with SPF.

LEVEL OF EVIDENCE

Level -lll.

Enhanced recovery following posterior spinal fusion for adolescent idiopathic scoliosis: A medical and economic study in a French private nonprofit pediatric hospital

INTRODUCTION

Little data exist on the efficacy of enhanced recovery after surgery (ERAS) protocols in patients undergoing posterior spinal fusion (PSF) for adolescent idiopathic scoliosis (AIS).

HYPOTHESIS

ERAS reduces hospital costs (HC) and length of stay (LOS) without increasing pain or complications.

MATERIALS AND METHODS

This was a retrospective comparative medical and economic study of 2 cohorts of patients who underwent PSF for AIS: a prospective group who underwent surgery with an ERAS protocol without a specially assigned care coordinator from 2020 to 2021 (n=30) and a retrospective group (control) who received standard care from 2017 to 2018 (n=30). The key amendments to the ERAS protocol were reduced preoperative investigations, opioid-sparing analgesia, ambulation starting on postoperative day (POD) 1, early resumption of oral diet, and early transition to oral analgesics. Moreover, an intensive care unit (ICU) stay, surgical drainage, and the postoperative CT scan were no longer routine. The discharge criteria were the same for both groups: normal bowel function, independent walking, pain Visual Analog Scale (VAS)<3 without strong opioids, and no signs of complications. The endpoints were: decreased HC (calculated by subtracting the costs of hospital days and complementary exams that were not carried out) and LOS, complications, and postoperative pain according to the VAS on POD 1, POD 3, and discharge. All means were reported with the standard deviation.

RESULTS

The mean age of patients undergoing surgery (14.5±1.7 years), sex ratio, curve type according to the Lenke classification, mean Cobb angle (54±12°), and the number of instrumented vertebrae (9±2) were similar in both groups (p>0.5). The HC decreased on average by 3029€ per patient. The mean LOS was 5±0.9 days in the ERAS group versus 6.5±0.6 days in the control group (p<0.001). The VAS scores on POD 1 and POD 3 were lower in the ERAS group. One postoperative complication was noted in each group.

CONCLUSION

Implementing an ERAS protocol without a specifically assigned care coordinator for patients with AIS undergoing PSF significantly decreased HC, LOS, and early postoperative pain.

LEVEL OF EVIDENCE

III; retrospective comparative study.

Sagittal plane assessment of manual concave rod bending for posterior correction in adolescents with idiopathic thoracic scoliosis (Lenke 1 and 3)

OBJECTIVES

The objectives of this study were to evaluate the repeatability and reproducibility of a method for measuring freehand rod bending and to analyze the relationship between the rod's bend and the resulting sagittal correction.

MATERIALS AND METHODS

All the children who underwent correction by posterior translation using pedicle screws at all levels were included prospectively in 2018 and 2019. The rod's sagittal parameters were measured retrospectively by three independent surgeons on two separate occasions using the same protocol. After the rods were bent but before they were inserted, the surgeon traced the contours of the rods on a sheet of paper that was later scanned and analyzed semiautomatically. The spinal parameters were calculated based on biplanar radiographs taken preoperatively, postoperatively and at the final follow-up visit. Patients who had less than 10° thoracic kyphosis (T5-T12) made up the "Lenke N-" subgroup.

RESULTS

Thirty patients were included (14 of whom were Lenke N-) who had a Cobb angle of 59.2±11.3° preoperatively and 13.3±8.4° postoperatively (p<0.00001). The inter- and intrarater ICC for the rod measurements were>0.9 (excellent). The mean kyphosis of the concave rod was 48.4±5.7° (38.3-60.9°). The mean change in T5-T12 kyphosis was 9.7±10.8° (-14.3-30.8°) (p<0.0001) in the entire population, while it was 17.7±7.1° (5.5-30.8°) (p<0.0001) in the Lenke N- subgroup. The change in thoracic kyphosis was positively correlated with the kyphosis of the concave rod (rho=0.52; p=0.003).

CONCLUSION

This study found excellent reproducibility and repeatability of measuring freehand rod bending. The kyphosis applied to the concave rod is positively correlated to the change in the resulting kyphosis and made it possible to restore satisfactory thoracic kyphosis.

LEVEL OF EVIDENCE

III.

Patient and surgical predictors of 3D correction in posterior spinal fusion: a systematic review

BACKGROUND

Restoration of three-dimensional (3D) alignment is critical in correcting patients with adolescent idiopathic scoliosis using posterior spinal fusion (PSF). However, current studies mostly rely on 2D radiographs, resulting in inaccurate assessment of surgical correction and underlying predictive factors. While 3D reconstruction of biplanar radiographs is a reliable and accurate tool for quantifying spinal deformity, no study has reviewed the current literature on its use in evaluating surgical prognosis.

PURPOSE

To summarize the current evidence on patient and surgical factors affecting sagittal alignment and curve correction after PSF based on 3D parameters derived from reconstruction of biplanar radiographs.

METHODS

A comprehensive search was conducted by three independent investigators on Medline, PubMed, Web of Science, and Cochrane Library to obtain all published information on predictors of postoperative alignment and correction after PSF. Search items included "adolescent idiopathic scoliosis," "stereoradiography," "three-dimensional," "surgical," and "correction." The inclusion and exclusion criteria were carefully defined to include clinical studies. Risk of bias was assessed with the Quality in Prognostic Studies tool, and level of evidence for each predictor was rated with the Grading of Recommendations, Assessment, Development, and Evaluations approach. 989 publications were identified, with 444 unique articles subjected to full-text screening. Ultimately, 41 articles were included.

RESULTS

Strong predictors of better curve correction included preoperative normokyphosis (TK > 15°), a corresponding rod contour, intraoperative vertebral rotation and translation, and upper and lower instrumented vertebrae selected based on sagittal and axial inflection points. For example, for Lenke 1 patients with junctional vertebrae above L1, fusion to NV-1 (1 level above the neutral vertebra) achieved optimal curve correction while preserving motion segments. Pre-op coronal Cobb angle and axial rotation, distal junctional kyphosis, pelvic incidence, sacral slope, and type of instrument were identified as predictors with moderate evidence. For Lenke 1C patients, > 50% LIV rotation was found to increase spontaneous lumbar curve correction. Pre-op thoracolumbar apical translation and lumbar lordosis, Ponte osteotomies, and rod material were found to be predictors with low evidence.

CONCLUSIONS

Rod contouring and UIV/LIV selection should be based on preoperative 3D TK in order to achieve normal postoperative alignment. Specifically, Lenke 1 patients with high-lying rotations should be fused distally at NV-1, while hypokyphotic patients with large lumbar curves and truncal shift should be fused at NV to improve lumbar alignment. Lenke 1C curves should be corrected using > 50% LIV rotation counterclockwise to the lumbar rotation. Further investigation should compare surgical correction between pedicle-screw and hybrid constructs using matched cohorts. DJK and overbending rods are potential predictors of postoperative alignment.

Systematic review and meta-analysis for the impact of rod materials and sizes in the surgical treatment of adolescent idiopathic scoliosis

PURPOSE

To assess surgical and safety outcomes associated with different rod materials and diameters in adolescent idiopathic scoliosis (AIS) surgery.

METHODS

A systematic literature review and meta-analysis evaluated the surgical management of AIS patients using pedicle screw fixation systems (i.e., posterior rods and pedicle screws) with rods of different materials and sizes. Postoperative surgical outcomes (e.g., kyphosis and coronal correction) and complications (i.e., hyper/hypo-lumbar lordosis, proximal junctional kyphosis, revisions, reoperations, and infections) were assessed. Random-effects models (REMs) pooled data for outcomes reported in ≥ 2 studies.

RESULTS

Among 75 studies evaluating AIS surgery using pedicle screw fixation systems, 46 described rod materials and/or diameters. Two studies directly comparing titanium (Ti) and cobalt-chromium (CoCr) rods found that CoCr rods provided significantly better postoperative kyphosis angle correction vs. Ti rods during a shorter follow-up (0-3 months, MD = - 2.98°, 95% CI - 5.79 to - 0.17°, p = 0.04), and longer follow-up (≥ 24 months, MD = - 3.99°, 95% CI - 6.98 to - 1.00, p = 0.009). Surgical infection varied from 2% (95% CI 1.0-3.0%) for 5.5 mm rods to 4% (95% CI 2.0-7.0%) for 6 mm rods. Reoperation rates were lower with 5.5 mm rods 1% (95% CI 0.0-3.0%) vs. 6 mm rods [6% (95% CI 2.0-9.0%); p = 0.04]. Differences in coronal angle, lumbar lordosis, proximal junctional kyphosis, revisions, and infections did not differ significantly (p > 0.05) among rods of different materials or diameters.

CONCLUSION

For AIS, CoCr rods provided better correction of thoracic kyphosis compared to Ti rods. Patients with 5.5 mm rods had fewer reoperations vs. 6.0 and 6.35 mm diameter rods.

LEVEL OF EVIDENCE

III.

Comparison of four correction techniques for posterior spinal fusion in adolescent idiopathic scoliosis

INTRODUCTION

When performing posterior spinal fusion for adolescent idiopathic scoliosis (AIS), it is of major importance to address both coronal and sagittal deformities. Although several techniques have been described, few data exist comparing them. Our objective was to compare four techniques (in situ bending (ISB), rod derotation (RD), cantilever (C) and posteromedial translation (PMT)) for the correction of spinal deformity in AIS including thoracic deformity.

MATERIAL AND METHODS

We conducted a multicenter retrospective study including 562 AIS patients with thoracic deformity with at least 24-month follow-up. Radiographic analysis was performed preoperatively, postoperatively and at last follow-up. The main outcomes were main curve correction and thoracic kyphosis restoration (TK).

RESULTS

Coronal correction rate was significantly different among the four treatment groups (ISB 64% vs C 57% vs RD 55% vs PMT 67%, p < 0.001). Multivariate regression revealed that correction technique did not influence correction rate, whereas implant density, convex side compression and use of derotation connectors did. TK increase was significantly higher in the PMT group (average + 13°) than in DR (+ 3°), while ISB (-3°) and cantilever (-13°) resulted in TK decrease (p < 0.001). Multivariate analysis revealed that TK increase was only influenced by the reduction technique (p < 0.001) and preoperative TK (p < 0.001).

DISCUSSION

The four techniques had the same ability to correct spinal deformity in the coronal plane. Three factors were identified to improve correction rate: implant density, convex compression and use of derotation connectors. On the other hand, PMT was more effective in restoring TK, particularly in hypokyphotic patients.

Prevention of surgical site infections in pediatric spines: a single-center experience

PURPOSE

To describe the potential issues in the methodology of surgical site infection (SSI) prevention and how it was investigated and corrected in a single institution.

METHODS

A pediatric orthopedic unit experienced an increase of SSI, concerning up to 10% of scoliosis surgery cases from 2011 to 2013. An institutional procedure of multimodal and interdisciplinary risk evaluation was initiated, including a review of the literature, a morbi-mortality meeting, internal and external audits concerning the hygiene conditions in the operating room, the antibiotic prophylaxis, patients, and sterile material pathways. Several preventive actions were implemented, including the improvement of air treatment in the operating room, wound irrigation with 2L of saline before closure, application of topic vancomycine in the wound, verification of doses and timing of antibiotics injection, and use of waterproof bandages. We compared the rates of spine SSI before (retrospective group, 2011-2013) and after the implementation of various preventive measures (prospective group, 2014-2018).

RESULTS

SSI occurred in 12 patients (6 idiopathic and 6 neuromuscular) out of 120 operated on (93 idiopathic, 18 neuromuscular, 9 others) in the retrospective group and 2 (both neuromuscular) out of 196 (150 idiopathic, 33 neuromuscular,13 others) in the prospective group (10% vs 1%, odds ratio=9.7, p=0.001). The groups were comparable for age, etiology, duration of surgery, body mass index, American Society of Anesthesiologists score, number of levels fused, and blood loss (p>0.2).

CONCLUSION

The systematic analysis of SSI allowed for the understanding of the failures and correcting them. The current process is effectively preventing SSI.

LEVEL OF EVIDENCE

3: prospective series with case-control analysis.

Proximal junctional kyphosis is a rebalancing spinal phenomenon due to insufficient postoperative thoracic kyphosis after adolescent idiopathic scoliosis surgery

PURPOSE

Many authors tried to explain proximal junctional kyphosis (PJK) after adolescent idiopathic scoliosis (AIS) surgery by looking for risk factors. Latest publications focus on sagittal alignment. Each healthy adolescent has a specific thoracic kyphosis (TK) depending on their pelvic parameters and lumbar lordosis (LL). The objective of this work is to determine if the difference between TK at follow-up (TKFU) and the patient-specific TK (PSTK) plays a role in PJK occurrence after AIS surgery. The secondary objective was to find other risk factors.

METHODS

We analyzed retrospectively 570 thoracic AIS who underwent a posterior thoracic fusion from nine centers. The series was separated in two groups: with and without PJK. PSTK was calculated with the formula PSTK = 2(PT + LL-PI). TK Gap was the difference between TKFU and PSTK. Logistic regression was utilized to test the impact of TK Gap and other known risk factors on PJK occurrence.

RESULTS

Univariate analysis showed 15 factors significantly different between the groups. In a multivariate analysis, three factors had a strong significant influence on PJK: TKFU, TK Gain and TK Gap. Four additional factors affected the rate of PJK: Posterior translation on two rods, preoperative TK, preoperative LL and number of instrumented vertebrae.

CONCLUSION

PJK is related to the insufficient TK at follow-up, compared to the specific TK that every patient should have according to their pelvic parameters. PJK incidence is significantly reduced by a strong gain in TK and a thoracic selective fusion which leaves the proximal lumbar vertebrae free.

LEVEL OF EVIDENCE I

Diagnostic: individual cross-sectional studies with consistently applied reference standard and blinding.

How do spine instrumentation parameters influence the 3D correction of thoracic adolescent idiopathic scoliosis? A patient-specific biomechanical study

BACKGROUND

Patient-specific models promises to support the surgical decision-making process, particularly in adolescent idiopathic scoliosis. The present computational biomechanical study investigates how specific instrumentation parameters impact 3D deformity correction in thoracic scoliosis.

METHODS

1080 instrumentation simulations of a representative patient were run. The independent instrumentation parameters were: screw pattern, upper and lower instrumented vertebrae, rod curvature and rod stiffness. ANOVA and correlation analyses analyzed how the instrumentation parameters influenced the 3D correction.

FINDINGS

Coronal plane correction was affected by the lower instrumented vertebra and rod stiffness (explaining 84% and 11%, respectively, of its overall variance). The sagittal profile was controlled by rod curvature and the upper vertebra (56% and 36%). The transverse plane vertebral rotation was influenced by lower, upper instrumented vertebra and screw pattern (35%, 32% and 19%). The Cobb angle correction was strongly correlated with the number of fused vertebrae, particularly when grouped by the upper instrumented vertebra (r = -0.91) and rod stiffness (r = -0.73). Thoracic kyphosis was strongly correlated with the number of fused vertebrae grouped by rod curvature (r = 0.84). Apical vertebral rotation was moderately correlated with the number of fused vertebrae grouped by upper/lower instrumented vertebra (r = 0.55/0.58), although variations were minimal.

INTERPRETATION

Instrumenting the last vertebra touching the central sacral vertical line improves 3D correction. A trade-off between a more cranial vs. caudal upper instrumented vertebra, respectively beneficial for coronal/sagittal vs. transverse plane correction, is required. High rod stiffness, differential rod contouring, and screw pattern were effective for coronal correction, thoracic kyphosis, and axial vertebral derotation, respectively.

In silico patient-specific optimization of correction strategies for thoracic adolescent idiopathic scoliosis

BACKGROUND

With modelling and simulation (or in silico) techniques, patient-specific optimization algorithms represent promising tools to support the surgical decision-making process, particularly in 3D correction of adolescent idiopathic scoliosis, where the best intraoperative instrumentation strategy and the correction goals are debated.

METHODS

1080 biomechanical intraoperative simulations of a representative pediatric thoracic curve were run according to a full-factorial design approach. Widely accepted instrumentation configurations (5 screw patterns, 4 upper and 3 lower instrumented vertebrae, 6 rod curvatures and 3 rod stiffnesses) were analyzed, assuming concave rod rotation and en bloc derotation as main correction maneuvers. Results in terms of 3D correction and mobility were rated using an objective function for thoracic scoliosis also including surgeon-dependent correction objectives. An extensive sensitivity analysis on correction objectives was performed.

FINDINGS

Multiple optimal strategies were identified, depending on the selected correction objective. They provided significantly better coronal (67% vs. 55%) correction, using comparable instrumented levels (9.9 ± 1.6 vs. 10.7 ± 2.1), screw patterns and significantly higher implant density (1.6 ± 0.3 vs. 1.4 ± 0.2 screws/vertebra) compared to worst ones. Optimal strategies typically included the neutral and the last touching vertebrae in the construct and high stiffness (CoCr, 6 mm) differentially/highly contoured rods.

INTERPRETATION

The computerized algorithm determined the best instrumentation parameters to achieve optimal correction for the considered thoracic case. Multiple clinically equivalent strategies may be used, as supported by the variety of considered correction objectives. The current approach could be translated to any scoliotic curves, including surgeon preferences in terms of instrumentation parameters, intraoperative correction maneuvers and correction objectives.

Patient-specific rods for thoracic kyphosis correction in adolescent idiopathic scoliosis surgery: Preliminary results

INTRODUCTION

Restoring a degree of kyphosis consistent with good sagittal alignment of the spine is a key concern when performing surgery to correct adolescent idiopathic scoliosis (AIS). The objective of this study was to assess the preliminary outcomes of posterior fusion for AIS using patient-specific rods that were pre-contoured based on pelvic incidence. The primary evaluation criterion was thoracic kyphosis at last follow-up.

HYPOTHESIS

The use of pre-bent patient-specific rods has a favourable effect on thoracic kyphosis at last follow-up.

MATERIAL AND METHODS

A total of 37 patients with AIS, including 17 with hypokyphosis, managed with patient-specific rods were included in a prospective study. The rod contouring angles were based on predefined pelvic incidence criteria (25° to 40° for the rod on the convex side and the same value plus 10° for the rod on the concave side). Thoracic kyphosis was assessed before surgery and at last follow-up, after 12-36 months (mean, 19 months). Student's t test was applied to compare means. Multivariate linear regression analysis was performed.

RESULTS

At last follow-up, the mean increase in kyphosis was 14° and was comparable to the planned increase (mean difference=0, p=0.85). Factors associated with kyphosis at last follow-up were the concave rod contouring angle and the pre-operative kyphotic angle of the thoracic segment to be instrumented (p<0.05). Mean differences between kyphosis of the instrumented thoracic segment at last follow-up and target kyphosis were -5° in the subgroup with hypokyphosis (<20°) before surgery and +4° in the subgroup with normal kyphosis before surgery.

CONCLUSION

With patient-specific rods, kyphosis at last follow-up was close to the target value. Predictors of kyphosis at last follow-up were the concave rod contouring angle and pre-operative kyphotic angle of the thoracic segment to be instrumented. Over-contouring of the concave rod seems necessary in patients with preoperative hypokyphosis but not in patients with normal kyphosis.

LEVEL OF EVIDENCE

III, prospective non-comparative study.

Cobalt-chrome and titanium alloy rods provide similar coronal and sagittal correction in adolescent idiopathic scoliosis

BACKGROUND

Cobalt-chrome (CoCr) and the titanium alloy TA6V (Ti) are the materials most widely used for spinal instrumentations in patients with adolescent idiopathic scoliosis (AIS). The objective of this work was to compare the effectiveness of CoCr and Ti rods in terms of coronal and sagittal correction by pedicle screw constructs in patients with AIS.

HYPOTHESIS

Correction is similar with CoCr and Ti rods in patients with AIS.

MATERIAL AND METHOD

A retrospective single surgeon study was conducted in patients with AIS managed using pedicle screw posterior spinal fusion with high implant density and reduction by postero-medial translation. Follow-up was more than 2 years in all patients. Patients were divided into two groups based on whether the rods used were made of CoCr (n=30) or Ti (n=33). The groups were identical for age, Risser classification, follow-up duration, type of curve, and implant density. Coronal and sagittal parameters on standing full-spine radiographs were analysed using graphics software before surgery then 1 month after surgery and at last follow-up. Quantitative data were compared by applying Student's t test.

RESULTS

The percentage of main curve correction at last follow-up was the same in the two groups (76%/75%) (p=0.7). Gains in thoracic kyphosis (12°/13°) and lumbar lordosis (8°/10°) were not significantly different between groups. At last follow-up, 3 patients had proximal junctional kyphosis, 1 in the CoCr group and 2 in the Ti group (p=0.6).

CONCLUSION

For posterior spinal fusion to treat AIS, with a high density of pedicle screws, correction by translation, and 6 mm rods, CoCr rods and Ti rods produce the same amount of coronal and sagittal correction.

LEVEL OF EVIDENCE

IV, comparative retrospective study with no control group.