Risk Factors for Multiple Implant-Related Complications (MIRC) with Growing-Rod for Early-Onset Scoliosis

Study design: A retrospective single center study.Objective：To identify risk factors for multiple implant-related complications with growing-rod for early-onset scoliosis.Background: High incidence of implant-related complications in the treatment of early-onset scoliosis with traditional growing rod. The risk factors for multiple implant-related complications (MIRC) have not been adequately studied.Methods: Data of 59 early-onset scoliosis patients who had been underwent growing rod surgery at Beijing Chao-yang Hospital from September 2007 to December 2017 were reviewed. All patients had complete clinical and radiographic data. Patients were divided into groups with or without MIRC. The univariate and multivariate logistic regression analysis were performed to identify the risk factors associated MIRC.Results: The average age of insertion was 8.9 years and mean follow-up was 51.91 months. 234 implantation or expansion surgeries were performed and the average operation interval was 11.4 months. A total of 60 implant-related complications occurred. Ultimately, MIRC developed in 20 (33.9%) of 59 patients. Number of surgery procedure > 3 times , follow-up time ³50 months , preoperative thoracic kyphosis > 50°, postoperative thoracic kyphosis >50°, postoperative lumbar lordosis >50°, postoperative sagittal vertical axial >40mm are potential risk factors for MIRC (P<0.1). Multivariate logistic regression analysis showed that Number of surgery procedure > 3 times, postoperative thoracic kyphosis >50°, postoperative lumbar lordosis >50°are independent risk factors for MIFRC (P<0.05), Among them, patients with postoperative thoracic kyphosis >50°had an 18.647 times higher risk of MIFRC than postoperative thoracic kyphosis angle <50°.Conclusions: Traditional growing rod in the setting of EOS has excellent clinical and radiographic outcomes but a high multiple implant-related complications. Number of surgery procedure > 3 times, postoperative thoracic kyphosis >50°, postoperative lumbar lordosis >50° are independent risk factors for MIRC.

Premature spinal fusion after insertion of magnetically controlled growing rods for treatment of early-onset scoliosis: illustrative case

BACKGROUND Magnetically controlled growing rod (MCGR) systems have gained attention for their use in the treatment of early-onset scoliosis. Although traditional growing rods require frequent operations to lengthen the construct, MCGR allows for fewer open procedures and more frequent distractions by externally controlling rod elongation. Despite its appealing advantages, MCGR is not without limitations. OBSERVATIONS The authors describe a case of premature spinal autofusion before growing rod removal and termination of rod distraction. LESSONS This case highlights the limitations of MCGR systems, including length of use, body habitus restrictions, and risk of autofusion.

A biomechanical study on the effect of lengthening magnitude on spine off-loading in magnetically controlled growing rod surgery: Implications on lengthening frequency

Purpose: To assess whether the magnitude of lengthening in magnetically controlled growing rod (MCGR) surgeries has an immediate or delayed effect on spinal off-loading. Methods: 9 whole porcine spines were instrumented using two standard MCGRs from T9 to L5. Static compression testing using a mechanical testing system (MTS) was performed at three MCGR lengthening stages (0 mm, 2 mm, and 6 mm) in each spine. At each stage, five cycles of compression at 175N with 25 min of relaxation was carried out. Off-loading was derived by comparing the load sustained by the spine with force applied by the MTS to the spine. Micro-CT imaging was subsequently performed. Results: The mean load sustained by the vertebral body before lengthening was 39.69N, and immediately after lengthening was 25.12N and 19.91N at 2 mm and 6 mm lengthening, respectively; decreasing to 10.07N, 8.31N, and 8.17N after 25 minutes of relaxation, at 0 mm, 2 mm, and 6 mm lengthening stages, respectively. There was no significant difference in off-loading between 2 mm and 6 mm lengthening stages, either instantaneously ( p = 0.395) or after viscoelastic relaxation ( p = 0.958). CT images showed fractures/separations at the level of pedicle screws in six spines and in the vertebral body’s growth zone in five spines after 6 mm MCGR lengthening. Conclusion: This study demonstrated MCGRs cause significant off-loading of the spine leading to stress shielding. 6 mm of lengthening caused tissue damage and microfractures in some spines. There was no significant difference in spine off-loading between 2 mm and 6 mm MCGR lengthening, either immediately after lengthening or after viscoelastic relaxation.

Analysis of serum levels of titanium and aluminium ions in patients with early onset scoliosis operated upon using the magnetic growing rod—a single centre study of 14 patients

Study design A cross-sectional retrospective Level 3 study. Objective To study the serum levels of Titanium and Aluminium ions in patients operated using the magnetically controlled growing rod (MCGR) system. Summary of background data 14 consecutive patients of early onset scoliosis with varying etiology managed with MCGR system with a minimum follow-up of 24 months were selected for the study. The group consisted of two boys (14.3%) and 12 girls (85.7%). The average age of the patients at the time of surgery was 10.4 years (5–15 years). The average period of follow-up was 43.7 months (28–79 months). After informed consent of the subjects and their caretakers, serum levels of titanium and aluminium were measured. These levels were then assessed with regards to the number of screws used, number of distractions and complications. Methods The concentration of titanium and aluminium ions in the serum was measured using high resolution inductively coupled plasma mass spectrometry. Results For the sake of ease of assessment, patients were divided into three etiology-based groups—idiopathic (n = 6), neuromuscular (n = 2) and syndromic (n = 6). The mean serum titanium level was 15.9 μg/L (5.1–28.2 μg/L) while that of aluminium was 0.1 μmol/L (0.1–0.2 μmol/L). Of the 14 patients, 2 (14.2%) patients had mechanical failure (actuator pin dysfunction), 3 (21.4%) had rod breakage requiring revision surgery and one patient (7.1%) had surgical site infection managed with appropriate antibiotics. Patients undergoing revision for rod breakage did not show any metallosis of the tissues during surgery. Conclusion Analysis of patients with scoliosis operated using the magnetic growing rod system concludes that it is accompanied by presence of titanium in the blood but whether clinically significant or not needs to be ascertained by comparison of preoperative and postoperative blood concentrations of the titanium ions in individual subjects. The aluminium ion concentration remains within normal limits. Though implant malfunction may raise the titanium levels in the blood, its clinical significance needs to be determined. The aluminium levels are not affected irrespective to the presence or absence of complications. The long-term effects of raised titanium levels in the blood also warrant further prospective studies designed for precise and deeper analyses.