A novel approach to gradual correction of severe spinal deformity in a pediatric patient using the magnetically-controlled growing rod

Increased lengthening frequency does not adversely affect the EOSQ scores in magnetically controlled growing rod surgeries in 133 subjects followed to final fusion

PURPOSE

Magnetically Controlled Growing Rod (MCGR) allows frequent outpatient rod lengthening when treating Early Onset Scoliosis (EOS) patients. But there is lack of expert consensus on the optimal MCGR lengthening interval. EOS 24-Item Questionnaire (EOSQ) is validated for assessing health-related quality of life (HrQOL), family burden, and satisfaction. This is the first study assessing how MCGR lengthening intervals affects patient-perceived outcomes.

METHODS

This is a multicentred cohort study with subjects recruited from 2012 to 2018 and followed till fusion. EOS subjects who underwent MCGR surgeries were grouped into high, medium or low lengthening interval subgroups based on 16 and 20 week cut-offs. Repeated measure analysis was performed on EOSQ's specified 12 domains. EOSQ results were taken: before index surgery, after index surgery, and prior to definitive treatment. Demographic, clinical and radiographic data were included in model adjustment.

RESULTS

133 subjects with mean follow-up of 3.5 (± 1.3) years were included, with 60 males and 73 females; 45 idiopathic, 23 congenital, 38 neuromuscular, and 27 syndromic patients. Mean Cobb angle at surgery was 67° (± 22°) with mean age of 8.3 (± 2.5) years. Between groups, clinical and radiographic parameters were comparable. Higher EOSQ scores in medium lengthening interval subgroup was present in fatigue (p = 0.019), emotion (p = 0.001), and parental impact (p = 0.049) domains, and overall score (p = 0.046). Trendline contrast between subgroups were present in general health (p = 0.006) and physical function (p = 0.025) domains.

CONCLUSION

Patient-perceived outcome improvements appear similar between lengthening interval subgroups. All MCGR lengthening intervals were tolerated by patients and family, with no negative impact observed.

LEVEL OF EVIDENCE

Prognostic Level III.

Clinical and radiological results of final fusion in patients who underwent lengthening with magnetically controlled growing rods. About 66 patients with a mean follow-up of 5 years

PURPOSE

The aim of this study was to evaluate the effects of definitive arthrodesis on frontal and sagittal spine balance in EOS patients treated with MCGR, as well as the complications associated with this procedure and the outcome at last follow-up.

METHODS

This was a multicentre study in 10 French centres. All patients who underwent posterior spinal arthrodesis after completion of MCGR treatment, regardless of age, etiology of scoliosis between 2011 and 2022, were included.

RESULTS

A total of 66 patients who had a final fusion after the lengthening programme were included in the study. The mean follow-up time was 5.5 ± 1.7 years (range: 2.1-9). The mean follow-up time after arthrodesis was 24 ± 18 months (range: 3-68) and the mean age at arthrodesis was 13.5 ± 1.5 years (range: 9.5-17). The main and secondary curves were significantly (p < 0.005 and p = 0.03) improved by arthrodesis (16.4° and 9° respectively) and stabilised at the last follow-up. The T1-T12 and T1-S1 distances increased by 8.4 mm and 14 mm with spinal fusion, with no significant difference (p = 0.096 and p = 0.068). There was no significant improvement in the rest of the parameters with arthrodesis, nor was there any significant deterioration at last follow-up. After final fusion, there were a total of 24 complications in 18 patients (27.3%) that routinely led to repeat surgery.

CONCLUSION

Final fusion after MCGR provides satisfactory additional correction of the main and secondary curves and a moderate increase in the T1-T12 distance but has no impact on sagittal balance and other radiological parameters. The post-operative complication rate is particularly high in patients at risk of complications.

LEVEL OF EVIDENCE

Level 4.

Spinal screening, malignancy, medical therapy, and surgical correction of deformity in pediatric patients with neurofibromatosis type 1: a systematic review

The objective of this systematic review was to synthesize evidence regarding spinal screening recommendations, types of spinal and thoracic neurofibromatosis type 1 (NF1) tumors, medical therapy for NF1-associated neoplasms, and treatment with magnetically controlled growing rods (MCGRs) or cervical kyphosis correction in pediatric patients with NF1. We queried PubMed, Embase, Cochrane Library, Web of Science, Scopus, Clinicaltrials.gov, and medRxiv for studies reporting spinal screening recommendations, prognosis, and medical therapy for NF1-associated spinal tumors and MCGR use or cervical kyphosis correction in pediatric NF1 patients, yielding 758 publications, 33 of which were included. There is no consensus on spinal screening interval. Computed tomography is recommended for postoperative monitoring. Patients with gangliomas and spinal neurofibromas had nearly complete symptom resolution after resection. Plexiform neurofibromas were most commonly treated with resection and laminectomy; some patients reported tumor enlargement after intervention. Malignant nerve sheath tumors have high rates of metastasis even after chemoradiation and resection. MEK-inhibitors produced limited regression in tumor size. Sirolimus and thalidomide reduced tumor size but caused more severe adverse effects than MEK-inhibitors. Improvements in major curves and T1-T12 height gain were reported after MCGR intervention. Anteroposterior arthrodesis produced the greatest correction of dystrophic cervical kyphosis. There may be value in establishing standardized spinal screening protocols for pediatric NF1 patients. Surgical correction of NF1-associated spinal deformity is effective, though current medical therapies for spinal tumors have limited success. Areas for further investigation include determining appropriate screening intervals, choice of medical therapy for spinal tumors, and long-term outcomes of MCGRs. Level of Evidence: IV.

Longitudinal comparison of direct medical cost, radiological and health-related quality of life treatment outcomes between traditional growing rods and magnetically controlled growing rods from preoperative to maturity

Background

Magnetically controlled growing rods (MCGR) have replaced traditional growing rods (TGR) in the past decade, however, a comparison of their direct costs and treatment outcomes based on real longitudinal data is lacking. This study aims to compare the direct cost and treatment outcomes between TGR and MCGR, whilst incorporating complications, reoperations and changes in health-related quality of life (HRQoL) throughout the entire treatment course.

Methods

Patients with early onset scoliosis (EOS) who underwent initial growing rod surgery between 2003 and 2016 at a tertiary scoliosis clinic were studied with longitudinal data. Accumulated direct medical costs were calculated based on the unit cost of surgeries of each TGR and MCGR, costs incurred for any rod exchange or remedial surgery for post-operative complication. Treatment outcomes were evaluated via: Patient’s HRQoL using SRS-22r questionnaire, and radiological parameters (including major curve correction, spine length gains, spinal balance) throughout the treatment until maturity.

Results

A total of 27 EOS patients (16 MCGR, 11 TGR) were studied. Total direct cost of index surgery for MCGR was HKD$223,108 versus lower cost of HKD$135,184 for TGR (p < 0.001). At 2–3 years post-index surgery, accumulative total direct medical cost of MCGR and TGR became most comparable (TGR:MCGR ratio = 1.010) and had reached neutrality between the two groups since. Radiological parameters had no intergroup differences at maturity. For HRQoL, TGR group had shown the trend of less pain (domain score mean difference: 0.53, p = 0.024) post-index surgery and better self-appearance (domain score mean difference: 1.08, p = 0.017) before fusion. Higher satisfaction with treatment (domain score mean difference: 0.76, p = 0.029) was demonstrated by TGR patients at fusion/maturity. MCGR had negative (r_s = -0.693) versus TGR’s positive (r_s = 0.989) correlations (p < 0.05) of cost and SRS-22r total scores at 2–3 years post-index surgery.

Conclusions

From index surgery to maturity, TGR demonstrated better satisfaction with treatment by patients and comparable overall HRQoL with MCGR during the treatment course, as MCGR did not show apparent benefit despite less surgeries and cost neutrality between the two groups at 2–3 years post-index surgery.

"Law of Temporary Diminishing Distraction Gains": The Phenomenon of Temporary Diminished Distraction Lengths With Magnetically Controlled Growing Rods That Is Reverted With Rod Exchange

STUDY DESIGN

Prospective study.

OBJECTIVES

To study the increasing divergence between targeted and achieved distractions observed with magnetically controlled growing rod (MCGR)lengthening, and the relationship of this reduced rate of achieved lengthening with remaining rod length.

METHODS

Patients with early onset scoliosis (EOS) who underwent MCGRs with minimum 2-year follow-up were consecutively enrolled. Targeted and achieved lengths were compared. Correlation between percentage of lengthening achieved from targeted length was identified with the timing of rod exchanges.

RESULTS

A total of 20 patients fulfilled the inclusion criteria. The mean age at index surgery was 9.5 years and mean postoperative follow-up was 68 ± 28 months. Of these, 8 patients had at least one rod exchange that occurred at 23 ± 4 months. A decrease in rate of achieved lengthening was observed when compared with targeted distractions. The achieved lengthening drops from 86% of targeted length at the first distraction to only 58.8% at the 21st distraction episode for the first set of rods. After rod exchange, the average achieved lengthening went back up to 81.3% of the targeted length but subsequently had a gradual reduction to 35% at the 19th distraction episode.

CONCLUSIONS

We propose a "law of temporary diminishing distraction gains" that MCGR users should be aware of when monitoring rod lengthening. Diminishing distraction length gains is observed as the rod is lengthened and is a phenomenon independent of patient factors. It is only temporary as the rates of achieved lengthening returns to baseline after rod exchange.

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.

Magnetically controlled growing rods in early onset scoliosis: radiological results, outcome, and complications in a series of 22 patients

INTRODUCTION

Magnetically controlled growing rods (MCGR) for the surgical treatment of early onset scoliosis (EOS) allow non-invasive outpatient based distractions during spinal growth. The purpose of this study is to present the results of a single center case series of 22 patients, evaluate the effect of MCGR treatment on the development of spino-pelvic parameters during growth, and report initial outcomes after end of treatment.

MATERIALS AND METHODS

Prospectively collected data of 22 EOS patients with MCGR treatment has been analyzed. The following radiological parameters were measured before index surgery, after index surgery, 1 year after index surgery, and at last follow-up: Cobb angle of the major curves, thoracic kyphosis (TK), lumbar lordosis (LL), sagittal vertical axis (SVA), pelvic incidence (PI), pelvic tilt (PT), and sacral slope (SS). Mean age at index surgery was 9.5 years (range: 4-14 years). Mean length of follow-up was 47.6 months (range: 25-121 months). Etiology of diagnosis was idiopathic in 14 patients, associated with neurofibromatosis in 2 patients, and neuromuscular or syndromic in 6 patients.

RESULTS

Mean Cobb angle of the major curve was 57° preoperatively and 29° at last follow-up (p < 0.0005). Mean TK was 20.1° preoperatively and 20° at last follow-up (p > 0.05). Mean LL was 52.8° preoperatively and 53.2° at last follow-up (p > 0.05). Mean PI was 43.2° preoperatively and 46.3° at last follow-up (p > 0.05). Mean PT was 4.1° preoperatively and 5.8° at last follow-up (p > 0.05). Mean SS was 39.2° preoperatively and 41.7° at last follow-up (p > 0.05). 14 patients finished treatment: nine received final fusion and five received rod removal without fusion. Twelve complications occurred: one deep wound infection, six patients developed proximal junctional kyphosis (PJK), one rod fracture, two rods failed to distract, one deformity progressed after rod removal and required spinal fusion, and one patient developed autofusion of the spine prior to end of treatment.

CONCLUSION

MCGR treatment is able to control deformity progression. Complication rate was 54.5%. Sagittal balance was not altered and treatment does not seem to have a negative impact on the development of spino-pelvic parameters during growth. Optimal end of treatment for the individual patient still has to be defined.

An intraoperative laterally placed distractor for gradual load sharing correction of severe spastic neuromuscular spinal deformity

PURPOSE

To analyze the overall deformity correction for severe neuromuscular scoliosis using laterally placed intra-operative distraction and compare to those receiving standard surgical technique.

METHODS

This was a retrospective, IRB-approved, cohort study of patients with GMFCS 4 or 5 spastic cerebral palsy with neuromuscular scoliosis, age greater than 10 years, who underwent posterior spinal fusion from 2007 to 2019. All patients had vectored cervical traction with Gardner-Wells tongs, with hips flexed in a relative sitting position. The study cohort underwent intraoperative, laterally placed correction using a distractor placed between two upper ribs and the ipsilateral greater trochanter while the control cohort did not. The 24 study patients were compared to 22 control patients.

RESULTS

Preoperative comparisons identified significant differences in Cobb angle, preoperative flexibility, and pelvic obliquity with the study group having larger, stiffer deformities with greater obliquity. There were no differences in pre-operative sagittal plane deformity. Mean post-operative upright Cobb angle correction was 67.3° ± 14.8° in the study and 55.3° ± 9.9° in the control group, representing a 66% and 60% correction, respectively. No neurological or other complications were noted from the use of this technique.

CONCLUSION

The use of a laterally placed distraction device from upper ribs to ipsilateral greater trochanter allowed gradual lateral un-bending of large stiff neuromuscular spine deformities with greater correction than that of standard technique. In this small series, the technique allowed load-sharing during correction, with hips remaining in a functional sitting position, and without neurological complications.

LEVEL OF EVIDENCE

Level III-retrospective cohort study.

The first magnetically controlled growing rod (MCGR) in the world - lessons learned and how the identified complications helped to develop the implant in the past decade: case report

Background

The first magnetically controlled growing rod (MCGR) was implanted in 2009. Since then multiple complications have been identified that have helped drive the development of the MCGR and its surgery. The aim of this report is to illustrate how identified complications in the first MCGR helped with developments in the past decade and to report a unique failure mechanism with stud fracture close to the barrel opening.

Case presentation

A 5-year old girl with a scoliosis of 58.5 degrees at T1–9 and 72.8 degrees at T9-L4 had a single MCGR inserted and anchored at T3–4 and L3–4. At postoperative 13 months the MCGR was noted to have lost of distraction between lengthening episodes due to unrestricted turning of the internal magnet. To prevent further loss of distraction, an external magnet was placed outside the skin to prevent the magnet from turning back. The overall balance was suboptimal and after the rod was fully distracted, proximal junctional kyphosis occurred. Subsequently, the MCGR was modified with an internal keeper plate to prevent loss of distraction and a dual set of these rods were implanted when the patient was 9 years old. Extension proximally to C7-T1 was done to manage the proximal junctional kyphosis. Her spinal balance improved and distractions continued. She subsequently developed add-on below and the piston rod was not aligned with the actuator. The lumbar spine was also observed to have autofusion. She subsequently had final fusion surgery performed at the age of 15 from C7-L4 leaving a residual tilt below to avoid fusion to the pelvis. The final extracted rod on the left side indicated the “crooked rod sign” on X-ray and rod dissections revealed a new failure mechanism of stud fracture close to the barrel opening. Body fluids and tissue may infiltrate the rod despite no obvious deformation or fractures resulting in hastened wearing of the threads.

Conclusions

There are various complications associated with MCGRs that are related to rod design and surgical inexperience. Repeated rod stalling is not recommended with potential stud fracture and “crooked rod sign”. Rotor stalling and thread wearing which indicates rod failure still require solutions.

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

BACKGROUND

Several studies have emphasized that the magnetically controlled growing rod (MCGR) technique decreases complications and costs and could be considered a safe 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.

OBJECTIVE

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.

MATERIAL AND METHODS

This was a retrospective study of patients with EOS who underwent MCGR from 2012 to 2018. Patients were included if they presented with a thoracic or lumbar curvature greater than 40° (Cobb angle) and Risser's sign 0. 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.

RESULTS

A total of 21 patients were included in the study. There was a significant 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, a significant derotation of the apical vertebra in thoracic and lumbar curves was observed (p < 0.05). Global analysis of the sagittal profile revealed a significant decrease of TK (p < 0.001) and T9SPi (p = 0.002) with a simultaneous 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.

CONCLUSION

The implantation of MCGR had a significant impact on the sagittal profile. Notwithstanding, no further compensatory mechanisms of the cervical spine and pelvis had to be recruited to safeguard sagittal alignment.

Temporary treatment with magnetically controlled growing rod for surgical correction of severe adolescent idiopathic thoracic scoliosis greater than 100°

INTRODUCTION

Correction of severe idiopathic scoliosis poses surgical challenges. Treatment options entail anterior and/or posterior release, Halo-gravity traction (HGT) and three-column osteotomies (3CO). The authors report results with a novel technique of temporary short-term magnetically controlled growing rod (MCGR) as part of a posterior-only strategy to treat severe idiopathic major thoracic curves (MTC).

METHODS

Seven patients with MTC > 100° treated with temporary MCGR were included. Mean age was 15 years. Preoperative MTC was av. 118° and TC-flexibility av. 19.8%. Patients underwent posterior instrumentation, periapical release using advanced Ponte osteotomies, segmental insertion of pedicle screws and a single MCGR. After av. 14 days, the second surgery was performed with removal of MCGR and final correction and fusion. The spinal height from lowest instrumented vertebra (LIV) to T1 was measured. MTC-correction and scoliosis correction index (SCI) were calculated.

RESULTS

No patient suffered a major complication or neurologic deficit. Instrumentation was from T2 to L3 or L4. This kind of staged surgery achieved a correction of postop MTC to av. 39°, MTC-correction 67% and SCI of av. 4.3. Spinal height T1-LIV increased from preoperative av. 288 mm to postoperative av. 395 mm indicating an increase of > 10 cm.

CONCLUSION

This is the first series of AIS patients that had temporary MCGR to treat severe thoracic scoliosis. A staged protocol including internal temporary distraction with MCGR after posterior release and definitive correction resulted in large MTC-correction and restoration of trunk height. Results indicate that technique has the potential to reduce the necessity for HGT and high-risk 3CO for the correction of severe scoliosis.

Early-Onset Scoliosis Treated With Magnetically Controlled Growing Rods

The recently developed magnetically controlled growing rod (MCGR) system has gained popularity because it limits additional surgical lengthening procedures and promises reduction of the complication rate previously reported for the traditional growing rods. A retrospective single-center study was performed. Demographic and complications data were recorded. A statistical analysis was conducted to quantify the effect of MCGR placement and of subsequent lengthening on the Cobb angle, T1-T12 kyphosis, and the distances from T1-T12 and T1-S1. Twenty-four patients met the inclusion criteria. Six had idiopathic scoliosis and 18 patients had nonidiopathic scoliosis (neuromuscular and syndromic scoliosis). Nine patients underwent primary MCGR placement, and 15 had the traditional growing rods removed and replaced with MCGRs. The mean age at surgery and at last follow-up was 6.3 years and 8.8 years, respectively. The mean follow-up was 29.2 months. The MCGR placement significantly reduced the Cobb angle and kyphosis by an average of 21.33° and 10.79°, respectively. The T1-T12 and the T1-S1 distances increased an average of 1.19 and 1.89 cm/year, respectively, during the follow-up period. The average percentage of achieved-to-intended distraction was 65% on the concave side and 68% on the convex side at last follow-up. There were 9 postoperative complications in 8 (33%) patients, 6 of whom had nonidiopathic scoliosis. The MCGR system is reliable and effective in the treatment of patients affected by early-onset scoliosis. [Orthopedics. 2020;43(6):e601-e608.].

Systematic investigation of metallosis associated with magnetically controlled growing rod implantation for early-onset scoliosis

AIMS

To investigate metallosis in patients with magnetically controlled growing rods (MCGRs) and characterize the metal particle profile of the tissues surrounding the rod.

METHODS

This was a prospective observational study of patients with early onset scoliosis (EOS) treated with MCGRs and undergoing rod exchange who were consecutively recruited between February 2019 and January 2020. Ten patients were recruited (mean age 12 years (SD 1.3); 2 M:8 F). The configurations of the MCGR were studied to reveal the distraction mechanisms, with crucial rod parts being the distractable piston rod and the magnetically driven rotor inside the barrel of the MCGR. Metal-on-metal contact in the form of ring-like wear marks on the piston was found on the distracted portion of the piston immediately outside the barrel opening (BO) through which the piston rod distracts. Biopsies of paraspinal muscles and control tissue samples were taken over and away from the wear marks, respectively. Spectral analyses of the rod alloy and biopsies were performed to reveal the metal constituents and concentrations. Histological analyses of the biopsies were performed with haematoxylin and eosin staining.

RESULTS

Titanium (Ti), vanadium (V), and neodymium (Nd) concentrations in the biopsies taken near the wear marks were found to be significantly higher than those in the control tissue samples. Significantly increased Nd concentrations were also found in the tissues near the barrel of the MCGR. Chronic inflammation was revealed by the histological studies with fibrosis and macrophage infiltration. Black particles were present within the macrophages in the fibrotic tissues.

CONCLUSION

Ti and V were generated mainly at the BO due to metal-on-metal contact, whereas the Nd from the rotor of the MCGR is likely released from the BO during distraction sessions. Phagocytotic immune cells with black particles inside raise concern regarding the long-term implications of metallosis. Cite this article: Bone Joint J 2020;102-B(10):1375-1383.

The potential of spring distraction to dynamically correct complex spinal deformities in the growing child

Purpose

Current treatment of progressive early onset scoliosis involves growth-friendly instrumentation if conservative treatment fails. These implants guide growth by passive sliding or repeated lengthenings. None of these techniques provide dynamic correction after implantation. We developed the spring distraction system (SDS), by using one or multiple compressed springs positioned around a standard sliding rod, to provide active continuous distraction of the spine to stimulate growth and further correction. The purpose of this study was to determine feasibility and proof of concept of the SDS.

Methods

We developed a versatile, dynamic spring distraction system for patients who would benefit from active continuous distraction. This prospective case series evaluates four patients with exceptional and progressive congenital spine deformities.

Results

Four patients had a mean age of 6.8 years at surgery with a mean follow-up of 36 months (range 25–45). The mean progressive thoracic lordosis, which was the reason for initiating surgical treatment in two patients, changed from 32° lordosis preoperatively to 1° kyphosis post-operatively. During follow-up, this further improved to 32° thoracic kyphosis. In the two other patients, with cervicothorcacic scoliosis, the main coronal curve improved from 79° pre-operatively to 56° post-operatively and further improved to 42°. The mean T1-S1 spine growth during follow-up for all patients was 1.3 cm/year. There was one reoperation because of skin problems and no device-failures.

Conclusion

These early results show the feasibility and the proof of concept of spring-based distraction as a dynamic growth-enhancing system with the potential of further correction of the deformity after implantation.

Current status of the magnetically controlled growing rod in treatment of early-onset scoliosis: What we know after a decade of experience

The magnetically controlled growing rod (MCGR) has had approximately 10 years of clinical experience worldwide. Clinical effectiveness to control early-onset scoliosis is consistent even at final surgery. MCGRs have significantly lower relative percentage of infection or wound complications as compared to traditional growing rods. Most common complications include foundation failure and failure of distraction. Contouring of the rod especially at the proximal segment while accommodating for the straight actuator remains a difficult task and its failure may lead to proximal junctional kyphosis. Unique complications of MCGR include clunking, temporary diminishing distraction gains, and metallosis. Temporary reductions in distraction gains are observed as the MCGR lengthens but return to normal baseline distraction gains after rod exchange. Lack of standardization for rod configuration, distraction strategies and decisions of whether to keep the rods in situ, remove without fusion surgery or to perform spinal fusion at skeletal maturity will require further study.

Clinical and Radiological Outcomes of Less Invasive Temporary Internal Distraction Followed by Staged Pedicle Screw Instrumentation in Adolescents with Severe Idiopathic Scoliosis at 2-Year Minimum Follow-Up

OBJECTIVES

Temporary placement of an internal distraction rod is one of the surgical options in the treatment of severe scoliosis to avoid preoperative halo traction or vertebral column resection. This technique can be applied in a single session or staged. The aim of our study was to report the outcomes of less-invasive temporary internal distraction (LI-TID) in the surgical treatment of adolescents with severe idiopathic scoliosis (IS).

METHODS

We performed a single-center, retrospective study of 22 adolescents (19 girls; mean age, 14.8 ± 2.0 years) with severe IS (major curve, ≥90°) who had undergone LI-TID, followed by staged pedicle screw instrumentation, with a minimum of 2 years of follow-up available. The demographic data, radiographic outcomes, pulmonary function test results, perioperative data, revised 22-item Scoliosis Research Society Outcomes questionnaire results, complications, and neuromonitoring data were collected.

RESULTS

The average major curve was 120° (range, 90°-160°) preoperatively and 59° (range, 29°-69°) at the final follow-up examination. Thoracic kyphosis (T5-T12) had improved from an average of 80° preoperatively to 33° postoperatively (range, 22°-69°), and the spinal height (T1-S1) had increased from 332 mm (range, 198-432 mm) preoperatively to 405 mm (range, 258-495 mm) at the final follow-up visit. Of the 22 patients, 5 (22.7%) had experienced an intraoperative neuromonitoring change without postoperative neurologic deficits, and 2 had developed superior mesenteric artery syndrome, with resolution after conservative treatment. The mean percentage of the predicted forced vital capacity had improved from 44.5% ± 11.3% to 66.5 ± 10.8 at final follow-up (P < 0.05). The total questionnaire score had improved significantly from 2.9 ± 0.61 to 4.1 ± 0.44 (P < 0.05).

CONCLUSION

The results from the present study have shown that staged LI-TID, followed by pedicle screw instrumentation, is safe and effective in adolescents with severe IS, with improvements in spinal deformity, pulmonary function, and health-related quality of life.

Severe adolescent idiopathic scoliosis: posterior staged correction using a temporary magnetically-controlled growing rod

PURPOSE

A two-staged posterior correction, using a temporary magnetically controlled growing rod (MCGR), was employed to gradually and safely correct severe adolescent idiopathic scoliosis (AIS). The aim of the study is illustrating the results of this procedure.

METHODS

A retrospective review of a consecutive series of 17 severe AIS. The first surgery was a posterior release (multiple Ponte osteotomies) with implant of pedicle screws and MCGR on the concave side of the curve. In post-operative days, a distraction was applied with MCGR, which allowed to obtain a total mean lengthening of 2 cm in about 2 weeks, with no complications arising. In the second posterior surgery, MCGR was removed and the definitive rods were applied for final fusion. The mean pedicle screws density was 93.3% (85-100). The extension of the final posterior fusion-instrumentation was of 13.8 levels (12-15).

RESULTS

At an average follow-up (FU) of 2.9 years, the main scoliosis curves from average pre-operative Cobb angle of 98.2° (91°-138°) bent down to 38.3° (35°-76°) after definitive fusion (p < 0.05); at last FU, the overall correction was 58.7% (50.4-71.2), with an average correction loss of 2.1° (1.5°-3.1°). At last FU, no complications were reported.

CONCLUSIONS

Gradual traction with MCGR in severe AIS proved to be a safe method to achieve progressive curve correction before posterior final fusion, with no neurologic complications associated to more aggressive one-stage surgeries. In a staged approach, MCGR appears as an alternative to halo traction, avoiding frequent traction-related complications.

The effect of magnetically controlled growing rods on three-dimensional changes in deformity correction

STUDY DESIGN

Prospective radiographic study.

OBJECTIVES

To determine the three-dimensional (3D) changes in deformity correction with magnetically controlled growing rod (MCGR) distractions. MCGRs can achieve similar coronal plane correction as traditional growing rods. The changes in the sagittal and axial planes are unknown and should be studied as these factors reflect potential for proximal junctional kyphosis and rotational deformity. Frequent MCGR distractions may potentially improve axial plane deformities to the same extent as coronal and sagittal plane deformities.

METHODS

Early onset scoliosis (EOS) patients who underwent dual MCGRs with minimum 2-year follow-up were included in this study. 3D reconstructions of 6-monthly biplanar images were used to study changes in coronal, sagittal and axial planes. Changes in growth parameters (body height and arm span) were scaled to changes in coronal Cobb angles, sagittal profile (T1-12, T4-12, L1-L5, L1-S1), and rotational profile at the proximal thoracic, main thoracic and lumbar curves, and pelvic parameters (sagittal pelvic tilt, lateral pelvic tilt and pelvis rotation).

RESULTS

A total of 10 EOS patients were studied. The mean age at index surgery was 8.2 ± 3.0 years and mean postoperative follow-up of 34.3 ± 9.5 months. Six patients had rod exchange at mean 29.5 ± 11.8 months after initial implantation. Despite consistent gains in body height and arm span, the main changes in coronal and rotational profiles only occurred at the initial rod implantation surgery with only small changes occurring with subsequent follow-ups. Patients with higher preoperative proximal junctional angles had flattening of the sagittal plane occurring at initial surgery with early rebound. No changes in pelvic parameters were observed.

CONCLUSIONS

The 3D changes with MCGR are mainly observed with initial rod implantation and no significant changes are observed with distractions. The MCGR can prevent deformity progression in the axial plane.

LEVEL OF EVIDENCE

IV.

Clinical Outcome of Magnetically Controlled Growing Rod in Early-onset Scoliosis: A Systematic Review

STUDY DESIGN

This was a systematic literature review.

OBJECTIVE

To evaluate the efficacy and safety of magnetically controlled growing rod (MCGR) in treating early-onset scoliosis.

SUMMARY OF BACKGROUND DATA

Preliminary studies reported the promising potential of MCGR in deformity correction and spine growth preservation with noninvasive distraction. This study was conducted on the basis of data from published literatures.

MATERIALS AND METHODS

A systematic search from multimedical database was conducted for studies of MCGR. Involved studies should provide at least one of the followings: deformity correction, spine growth, and complication. During treatment period, improvement or progression of scoliosis/kyphosis, annual T1-S1/T1-T12 extension, incidence of complication, and unplanned surgery were summarized and the correlations with term of follow-up were investigated.

RESULTS

In total, 13 studies (n=249) were involved, with an average of 22.2-month follow-up. Scoliosis correction was well maintained, improving from 36.4 degrees at postinitial to 37.1 degrees at last follow-up (P=0.794). Kyphosis progressed from 28.8 degrees at postinitial to 34.4 degrees at last follow-up (P=0.024). Annual T1-S1 and T1-T12 longitudinal extensions were 8.7 and 4.7 mm/year, respectively. As follow-up went on, no significant decline was observed in annual extension of T1-S1 (P=0.4680) or T1-T12 (P=0.8053). The incidences of alignment-related, implant-related, and wound-related complication were 3.5%, 30.1%, and 6.9%, respectively. No significant correlation was observed between occurrence of complication and term of follow-up. The rate of receiving unplanned surgery was 24.3%.

CONCLUSIONS

MCGR is efficient in the maintenance of coronal correction and preservation of spine growth, with loss of sagittal correction and a 24.3% unplanned revision rate.

Mean 6-Year Follow-up of Magnetically Controlled Growing Rod Patients With Early Onset Scoliosis: A Glimpse of What Happens to Graduates

BACKGROUND

There is no agreement on frequency of distractions of magnetically controlled growing rods (MCGRs) but more frequent and smaller amounts of distractions mimic physiological spine growth. The mid- to long-term follow-up and management at skeletal maturity is unknown.

OBJECTIVE

To analyze patients with mean 6 yr of follow-up and describe the fate of MCGR graduates.

METHODS

Early onset scoliosis (EOS) patients treated with MCGRs with minimum 4 yr of follow-up and/or at graduation were studied. Parameters under study included Cobb angle, spine and instrumented lengths, and rod distraction gains. Relationship between timing of rod exchanges with changes in rate of lengthening was studied.

RESULTS

Ten EOS patients with mean 6.1 yr of follow-up were studied. The greatest Cobb angle correction occurred at the initial implantation surgery and was stable thereafter. Consistent gains in T1-12, T1-S1, and instrumented segment were observed. Rate of lengthening reduced after the first year of use but improved back to initial rates after rod exchange. Seven of the ten patients experienced complications with reoperation rate of 40% for rod distraction failure and proximal foundation problems. Only mild further improvements in all radiological parameters were observed pre- and postfinal surgery. No clinically significant curve progression was observed for rod removal only. All postfinal surgery parameters remained similar at postoperative 2 yr.

CONCLUSION

This study provides an outlook of the end of MCGR treatment. Although this is a fusionless procedure, instrumented segments do experience stiffness limiting further correction and length gain during final surgery whether fusion or rod removal is performed.

A high degree of variability exists in how "safety and efficacy" is defined and reported in growing rod surgery for early onset scoliosis: a systematic review

Established criteria for reporting safety and efficacy have not yet been defined in growing rod surgery for early onset scoliosis. A systematic literature review revealed a high degree of variability in how authors stratified complications and patient outcomes as a means to define safety and efficacy for this challenging patient population.

INTRODUCTION

Several publications have reported the safety and efficacy of traditional growing rods (TGR) and magnetically controlled growing rods (MCGR) using various parameters. Radiographic parameters are most commonly used to measure efficacy, while incidence and type of complications are used to assess safety. A systematic review of peer-reviewed articles was performed to identify whether a consensus exists in how safety and efficacy parameters are reported in EOS patients treated with TGR and MCGR.

HYPOTHESIS

There is no consensus on the parameters used for reporting safety and efficacy in growing rod treatment for early onset scoliosis.

STUDY DESIGN

Systematic literature review.

METHODS

Four databases were searched on November 10, 2016 to identify all qualified peer-reviewed articles using specific keyword searches. All peer-reviewed articles published in English language reporting any data related to safety and efficacy of the TGR and/or MCGR surgical technique were included. Articles that met the inclusion criteria were scored by modified Downs and Black scoring system (J Epidemiol Community Health 52(6):377-384, 1998) for non-randomized studies. All reported safety and efficacy data were extracted and analyzed.

RESULTS

Search of the databases resulted in 111 unique citations including: PubMed (50), Embase (68 with 21 duplicates), Web of Science (29 with 15 duplicates), and CINAHL (15; all duplicates). Fifty-six of 111 citations were excluded during the review of the titles and abstracts. In addition, 16 citations were excluded at the time of full manuscript review. The remaining 39 articles included 23 TGR (2007-2016) and 16 MCGR papers (2012-2016). The overall Downs and Black score was 63.9 for TGR papers vs. 64.0 for MCGR papers (p = 0.97). Efficacy measures were not consistently reported among the publications. The only consistently reported efficacy parameter in majority (> 90%) of papers was curve size. Complication reporting was highly variable.

CONCLUSION

Major curve size was the only consistent parameter to report efficacy in peer-reviewed TGR and MCGR publications. Since complications were not consistently reported, assessing safety of either treatment was infeasible. Establishing standardized safety and efficacy parameters in growing rod surgery for EOS would improve the quality of future studies and makes comparison of different treatment modalities possible. Indeed, other clinically relevant parameters such as health-related quality of life, pulmonary function, nutritional status, and psychiatric and developmental health should also be considered to improve the future safety and efficacy reporting.

Contactless treatment for scoliosis by electromagnetically controlled shape-memory alloy rods: a preliminary study in rabbits

PURPOSE

To evaluate the safety and efficacy of a system aiming to correct scoliosis called "electromagnetically controlled shape-memory alloy rods" (EC-SMAR) used in a rabbit model.

METHODS

We heat-treated shape-memory alloy (SMA) rods to achieve a transition temperature between 34 and 47 °C and a C-shape austenite phase. We then developed a water-cooled generator capable of generating an alternating magnetic field (100 kHz) for induction heating. We next studied the efficacy of this system in vitro and determined some parameters prior to proceeding with animal experiments. We then employed a rabbit model, in which we fixed a straight rod along the spinous processes intraoperatively, and conducted induction heating postoperatively every 4 days for 1 month, while performing periodic X-ray assessments.

RESULTS

Significant kyphotic deformations with Cobb angles of about 45° (p < 0.01) were created in five rabbits, and no complications occurred throughout the experiment. The rabbits are still very much alive and do not show any signs of discomfort.

CONCLUSIONS

This is the first system that can modulate spinal deformation in a gradual, contactless, noninvasive manner through electromagnetic induction heating applied to SMA alloy rods. Although this study dealt with healthy spines, it provides promising evidence that this device also has the capacity to correct human kyphosis and even scoliosis in the future. These slides can be retrieved under Electronic Supplementary Material.

The Crooked Rod Sign: A New Radiological Sign to Detect Deformed Threads in the Distraction Mechanism of Magnetically Controlled Growing Rods and a Mode of Distraction Failure

STUDY DESIGN

Case report.

OBJECTIVE

To report a unique mechanical failure of magnetically controlled growing rods (MCGRs) that is related to continuous rod slippage.

SUMMARY OF BACKGROUND DATA

Despite the growing popularity of MCGR in the management of patients with early onset scoliosis, postoperative complications and reoperations are not uncommon. Unique complications or unplanned reoperations are observed in patients with MCGRs that are not seen in traditional growing rods. The complications include rod slippage, mismatch between targeted and achieved distraction length, metallosis, and actuator pin fracture. We have identified an unreported failure mechanism whereby deformed threads occur in the internal distraction mechanism of the MCGR. This phenomenon may indicate increased MCGR internal screw friction and increased distraction resistance. Increased friction and resistance ultimately led to distraction failure and revision surgery.

METHODS

A girl with early onset scoliosis (EOS) was treated by dual MCGRs. She developed proximal junctional kyphosis (PJK) and continuous rod slippage. Distractions in the out-patient clinic and under sedation did not achieve successful rod lengthening. A tell-tale "crooked rod" radiological sign was identified by angulation between the actuator and the extendable portion of the rod.

RESULTS

Rod exchange was performed and she is now 2 years after revision surgery with successful lengthening episodes. Upon review of the extracted MCGR, distraction was not possible even after rod removal and was only resumed after the screw was manually reinserted along its correct threads.

CONCLUSION

Deformed threads is a complication that cannot be reverted without rod removal and exchange. Users should be aware of this potential failure mechanism and proceed to early rod exchange rather than attempting any further distractions.

LEVEL OF EVIDENCE

4.

Development of a novel murine femur fracture and fixation model

BACKGROUND

Animal models have been used for decades to simulate human fractures in the laboratory setting. Fracture models in mice are attractive because they offer a high volume, relatively low-cost method of investigating fracture healing characteristics. We report on the development of a novel murine femur fracture model that is rapid, reproducible and inexpensive.

METHODS

As part of a pilot study to investigate the effects of smoking on fracture healing, fifteen 35-43 g twelve-week old female CD-1 mice underwent a novel surgical protocol using direct visualization of femur fracture creation and fixation. Following surgery, mice were sacrificed at 14 days, 28 days and 42 days. After sacrifice, the femora were analyzed using MicroCT and histology to evaluate progression of healing.

RESULTS

Of the 14 mice that survived the surgical procedure (one succumbed to a complication of anesthesia), two lost reduction and did not heal. Histology demonstrated at 14 days 44.1% (SD±2.9%) of callus composed of cartilage. At 28 days there was 19.0% (SD±3.4%) of callus composed of cartilage. At 42 days there was 8.4% (SD±2.6%) callus composed of cartilage (p < 0.005). MicroCT demonstrated that from 14 to 42 days the average callus volume decreased from 101.6 mm3 to 68.2 mm3 while the relative bone volume of callus increased from 14 to 42 days (15%-31%) (p = 0.068).

CONCLUSIONS

Our novel fracture and fixation model is an effective, rapid, reproducible and inexpensive method to simulate a fracture in a laboratory setting. Additionally, our model reliably creates a reproducible progression of radiographic and histological bone healing.

Congenital Etiology Is an Independent Risk Factor for Complications in Adolescents Undergoing Corrective Scoliosis Surgery: Comparison of In-hospital Comorbidities Using Nationwide KID's Inpatient Database

BACKGROUND

Congenital scoliosis (CS) is associated with more rigid, complex deformities relative to adolescent idiopathic scoliosis (AIS) which theoretically increases surgical complications. Despite extensive literature studying AIS patients, few studies have been performed on CS patients. The purpose of this study was to evaluate complications associated with spinal fusions for CS and AIS.

METHODS

A retrospective review of the Kid's Inpatient Database (KID) years 2000 to 2009 was performed. Inclusion: patients under 20 years with ICD-9 diagnosis codes for idiopathic scoliosis (IS-without concomitant congenital anomalies) and CS, undergoing spinal fusion from the KID years 2000 to 2009. Two analyses were performed according to age below 10 years and 10 years and above. Univariate analysis described differences in demographics, comorbidities, intraoperative complications, and clinical values between groups. Binary logistic regression controlling for age, sex, race, and invasiveness predicted complications risk in CS (odds ratios; 95% confidence interval).

RESULTS

In total, 25,131 patients included (IS, n=22443; CS, n=2688). For patients under age 10, CS patients underwent 1 level shorter fusions (P<0.001), had fewer comorbidities (P<0.001), and sustained similar complication incidence. In the 10 and over age analysis, CS patients similarly had shorter fusions, but greater comorbidities, and significantly more complications (odds ratio, 1.6; confidence interval, 1.4-1.8).

CONCLUSIONS

CS patients have higher in-hospital complication rates. With more comorbidities, these patients have increased risk of sustaining procedure-related complications such as shock, infection, and Adult Respiratory Distress Syndrome. These data help to counsel patients and their families before spinal fusion.

LEVEL OF EVIDENCE

Level III-retrospective review of a prospectively collected database.

Minimum 2-Year Experience with Magnetically Controlled Growing Rods for the Treatment of Early-Onset Scoliosis: A Systematic Review

Magnetically controlled growing rods have been used to treat early-onset scoliosis for the last 9 years; however, few studies have been published, with only short-term follow-up. The aim of the present study is to systematically review the outcomes of magnetically controlled growing rods in the treatment of early-onset scoliosis with a minimum of 2-year follow-up. Studies were included if patients with early-onset scoliosis (scoliosis diagnosed before 10 years of age) underwent implantation of magnetically controlled growing rods with a minimum of 2-year follow-up. The literature review and data extraction followed the established preferred reporting items for systematic review and meta-analysis guidelines. Data of distraction frequency, number of distractions, distracted length, Cobb angle, kyphosis, T1-T12 length, and T1-S1 length preoperatively, postoperatively, and at final follow-up were collected. Data regarding complications and unplanned reoperations were also extracted. The mean values of these parameters were calculated, or pooled meta-analysis was performed if available. Ten articles were included in this systematic review, with a total of 116 patients and a follow-up period between 23 and 61 months. The mean preoperative Cobb angle and kyphosis angle were 60.1° and 38.0°, respectively, and improved to 35.4° and 26.1° postoperatively. At final follow-up, the Cobb and kyphosis angles were maintained at 36.9° and 36.0°, respectively. The average preoperative T1-T12 and T1-S1 lengths were 180.6 mm and 293.6 mm, respectively, and increased to 198.3 mm and 320.3 mm postoperatively. T1-T12 and T1-S1 lengths were 212.3 mm and 339.3 mm at final follow-up, respectively. The overall rate of patients with complications was 48% (95% confidence interval [CI], 0.38-0.58) and unplanned reoperation 44% (95% CI, 0.33-0.55) after sensitivity analysis. The current evidence from different countries with a minimum of a 2-year follow-up suggests that magnetically controlled growing rods are an effective technique to treat pediatric scoliosis and promote spine growth. However, nearly half of patients still developed complications or required unplanned reoperations.

Is Magnetically Controlled Growing Rod the Game Changer in Early-onset Scoliosis? A Preliminary Report

BACKGROUND

Magnetically controlled growing rod (MCGR) concept was introduced with the premise of minimizing the repetitive lengthening surgeries, which is default in traditional growing rod (TGR) treatment for early-onset scoliosis (EOS). Despite good radiographic outcomes, previous studies did not compare identical patient groups in terms of etiology and deformity characteristics; therefore, a true comparison of the MCGR and TGR is essential. This study was designed to compare 2 techniques in terms of clinical, radiologic, and health-related quality of life (HRQoL) outcomes.

METHODS

Patients with long sweeping congenital curves who underwent convex growth arrest and concave distraction (with TGR or MCGR) were retrospectively reviewed. Instrumented all-posterior convex growth arrest and concave distraction with growing rod technique were performed. Demographic parameters, follow-up time, number of lengthening procedures, radiographic parameters, number of unplanned surgeries, and complications were recorded. The Early-Onset Scoliosis Questionnaire (EOSQ-24) was used to evaluate HRQoL outcomes.

RESULTS

A total of 20 patients were included (10 MCGR, 10 TGR). No significant differences were found with regard to average age, follow-up time, radiographic parameters, or complications. Overall surgery per patient including index surgery, and planned and unplanned procedures were significantly lower in the MCGR group (8.8 vs. 1.3) (P=0.01). No patient in either group had graduated from growing rod treatment. HRQoL analysis revealed no significant difference between the 2 groups in any specific domain or in the overall score of the EOSQ-24.

CONCLUSIONS

Although equally effective in controlling the deformity and superior in reducing the number of surgeries with comparable complication rates, MCGR does not offer any significant improvement in HRQoL outcomes or the overall complication rate. Despite the obvious advantages, according to this preliminary report, the current technology and technique of MCGR may not be sufficient to be the long-awaited "game changer" in the treatment of EOS.

Maximal Force Generated by Magnetically Controlled Growing Rods Decreases With Rod Lengthening

OBJECTIVES

To evaluate the maximal force generated by magnetically controlled growing rods (MCGRs) at three different lengthened positions.

SUMMARY OF BACKGROUND DATA

The introduction of MCGRs has been met with great enthusiasm by surgeons managing early-onset scoliosis. These devices offer the potential to decrease the cost and morbidity associated with repeated surgeries, compared to traditional growing rods. One potential negative consequences of growing rod treatments is the law of diminishing returns, where the spine length gained decrease with each subsequent lengthening. The cause of this phenomenon is unknown and probably multifactorial, yet it may be affected by the strength of the lengthening mechanism in the MCGRs.

METHODS

Twelve MCGRs (90-mm actuator length) were obtained and tested to evaluate the maximal force generated at different lengths. The maximal lengthening force measured in pounds-of-force generated by each rod was recorded at expansion lengths of 0, 25, and 40 mm. Longitudinal analysis was performed using mixed effects linear regression to account for repeated measures and variability between individual implants.

RESULTS

At 0 mm of actuator lengthening, the mean maximum force was 46.8 lb (standard deviation [SD] 2.06, range 43-50). At 25 mm of expansion, the mean maximum force was 44.9 lb (SD 2.48, range 39.4-49.5). At 40 mm of lengthening, the mean maximum force was 43.2 lb (SD 5.56, range 27.3-49.1). In the mixed effects linear model, there was a statistically significant decrease in the maximal force generated with progressive MCGR lengthening, at an average decrease of 0.089 lb of force (95% CI, 0.030-0.148; p = .003) per millimeter of lengthening.

CONCLUSION

There is a small but statistically significant decrease in the maximal force generated by MCGR as the rods are lengthened. The decrease in force generated may result in diminished spine length gained with each subsequent MCGR lengthening.

LEVEL OF EVIDENCE

Level IV.

Reliability of Rod Lengthening, Thoracic, and Spino-Pelvic Measurements on Biplanar Stereoradiography in Patients Treated With Magnetically Controlled Growing Rods

STUDY DESIGN

Cross-sectional study.

OBJECTIVE

To assess the inter- and intraobserver reliability of thoracic, spino-pelvic, and rod lengthening measurements made on biplanar spinal stereoradiography (EOS imaging) in children treated with magnetically controlled growing rod (MCGR).

SUMMARY OF BACKGROUND DATA

MCGR treatment aims to gain spine length while gradually correcting the spinal deformity. Monitoring thoracic and spino-pelvic parameters is crucial for successful management. EOS imaging is widely used for diagnosis and monitoring of children with Early Onset Scoliosis. However, there is a paucity of literature on the reliability of thoracic and spino-pelvic parameters on EOS imaging in children treated with MCGR.

METHODS

Three independent reviewers independently read a random assortment of 20 whole spine posteroanterior and lateral radiographs from patients treated with MCGR. The measurements were repeated 4 weeks after the initial read. The following radiological parameters were measured: Cobb angle of the main and compensatory curves, coronal balance, coronal T1-S1 and T1-T12 length, chest width and depth at T6, pelvic inlet width, MCGR distracted lengths, global kyphosis, proximal and distal junctional angle, lordosis, sagittal balance, pelvic incidence, pelvic tilt and sacral slope. Statistical analysis was performed with paired t test and Cronbach alpha for inter- and intraobserver reliability.

RESULTS

All measurements had good or excellent intra- and interobserver reliability (α>0.8; P < 0.05), except measurements of the proximal junctional angle which showed only poor intra- and interobserver reliability for patients with an upper instrumented vertebra cranial to T4.

CONCLUSION

EOS imaging is reliable for diagnosis and monitoring of children with Early Onset Scoliosis treated with MCGR. EOS imaging is particularly excellent for assessment of MCGR lengthening. Diagnosis and interpretation of early proximal junctional kyphosis within the cervicothoracic junction should be made with caution.

LEVEL OF EVIDENCE

3.

Targeted Distraction: Spinal Growth in Children With Early-Onset Scoliosis Treated With a Tail-gating Technique for Magnetically Controlled Growing Rods

STUDY DESIGN

Prospective cohort study OBJECTIVE.: To understand the efficacy of a tail-gating technique (TGT) to mirror the normal spinal growth of children with early-onset scoliosis (EOS) treated with magnetically controlled growing rods (MCGR).

SUMMARY OF BACKGROUND DATA

MCGR allow outpatient distraction and guided spinal growth without the need for repeat surgery. Two techniques (maximal and targeted) are currently employed to determine the distraction amount, however the efficacy of each is unknown. This study specifically assesses the ability of targeted distraction to achieve physiological growth.

METHODS

We performed a retrospective review of European children treated with MCGR using a TGT and analyzed the post-operative clinical and radiographic outcomes, including the sitting height, standing height, coronal Cobb angle, T1-T12 and T1-S1 height. Furthermore, we compared the post-operative sitting/standing height ratio every 6 months to those reported for normal age- and sex-matched European children.

RESULTS

Thirty-five children were included with a mean follow-up of 3.4 years (1.8-5.8 years). All clinical and radiographic parameters significantly (P < 0.05) improved immediately post-operatively and were maintained until final follow-up. The TGT mirrored the normative sitting/standing height ratios for expected spinal growth (Pearson correlation 0.95 for males and 0.90 for females). The mean difference between the reference values for the sitting/standing height ratio and our results was 0.0124 (P < 0.001) for males and 0.0068 (P = 0.010) for females.

CONCLUSION

MCGR can reliably improve the coronal deformity in children with EOS while maintaining spinal growth. A TGT to determine the distraction amount at follow-up accurately mirrors the normal growth pattern of age-, sex-, and ethnicity-matched children. However, patients treated with this technique have a statistically significant, but clinically insignificant, shorter than physiologically normal spinal height.

LEVEL OF EVIDENCE

3.

Rod Lengthening With the Magnetically Controlled Growing Rod: Factors Influencing Rod Slippage and Reduced Gains During Distractions

STUDY DESIGN

Prospective study.

OBJECTIVE

To identify the factors that are associated with rod slippage and to study the pattern of achieved length gain with a standard distraction methodology.

SUMMARY OF BACKGROUND DATA

Ability to achieve successful magnetically controlled growing rod (MCGR) distraction is crucial for gradual spine lengthening. Rod slippage has been described as a failure of internal magnet rotation leading to a slippage and an inability to distract the rod. However, its onset, significance, and risk factors are currently unknown. In addition, how this phenomenon pertains to actual distracted lengths is also unknown.

METHODS

A total of 22 patients with MCGR and at least six distraction episodes were prospectively studied. Patients with rod slippage occurring less than six distraction episodes were considered early rod slippage whereas those with more than six episodes or have yet to slip were grouped as late rod slippage. The association of parameters including body habitus, maturity status, age of implantation, total number of distractions, months of distraction from initial implantation, initial and postoperative Cobb angle, T1-T12, T1-S1, T5-T12 kyphosis, curve flexibility, instrumented length, and distance between magnets in dual rods and between the magnets and apex of the curve with early or late onset of rod slippage were studied. Differences between expected and achieved distraction lengths were assessed with reference to rod slippage episodes and rod exchanges to determine any patterns of diminishing returns.

RESULTS

Patients had mean age of 7.1 years at diagnosis with mean follow-up of 49.8 months. A mean 32.4 distractions were performed per patient. Early rod slippage occurred in 14 patients and late rod slippage occurred in eight patients. Increased height, weight, body mass index, older age, increased T1-12 and T1-S1 lengths, and less distance between magnets were significantly associated with early rod slippage. Expected distraction lengths did not translate to achieve distraction lengths and reduced gains were only observed after achieving one-third of the allowable distracted length in the MCGR. Length gains return to baseline after rod exchange.

CONCLUSION

This is the first study to specifically analyze the impact of rod slippage on distraction lengths and the risk factors associated with its onset and frequency. Increased body habitus and reduced distance between internal magnets significantly influenced rod slippage events. Diminishing returns in distracted length gains were only observed after a period of usage.

LEVEL OF EVIDENCE

3.

Magnetic growth modulation in orthopaedic and spine surgery

Purpose

To examine distraction-based methods for treatment of early onset scoliosis (EOS), focusing on the magnetically controlled growing rod system (MCGR) relative to traditional growing rod system (TGR). To briefly discuss internal magnetically controlled nails for bone lengthening as another application of magnetic growth modulation.

Results

Relative to TGR, MCGR involves fewer complications related to infection and general anesthesia because of fewer successive surgeries required. Further, MCGR accounts for better psychosocial patient outcome and potentially a lower long-term cost, mainly because of shortened periods of hospitalization. Intramedullary lengthening nails involve fewer complications compared to internal limb lengthening devices related to infections, nerve damage, shortening, improper healing, stiffness, and scarring. Intramedullary lengthening nails appear to alleviate psychosocial burden of patients especially when compared to external fixators.

Conclusions

Although the current gold standard for treating some types of early onset scoliosis (EOS) is the traditional growing rod system, the magnetically controlled growing rod (MCGR) system is an alternative method for treating EOS. MCGR is promising in that it involves less surgical procedures, shorter hospital stays, and lower long-term cost relative to TGR. Similarly, the use of magnetically controlled intramedullary lengthening nails is a promising alternative to the Ilizarov method for limb lengthening.

Traditional growing rod versus magnetically controlled growing rod for treatment of early onset scoliosis: Cost analysis from implantation till skeletal maturity

PURPOSE

To compare the yearly cost involved per patient in the use of magnetically controlled growing rod (MCGR) and traditional growing rods (TGRs) in the treatment of early onset scoliosis (EOS) and to assess the overall cost burden of MCGR with reference to patient and health-care infrastructure.

METHODS

For a hypothetical case of a 5-year-old girl with a diagnosis of EOS, a decision-tree model using TreeAge Software was developed to simulate annual health state transitions and compare the 8-year accumulative direct, indirect, and total cost among the four groups: (1) dual MCGRs with exchange every 2 years, (2) dual MCGRs with exchange every 3 years, (3) TGR with surgical distraction every year, and (4) TGR with surgical distraction every 6 months. Base-case values and ranges of clinical parameters reflecting complication rate after each type of surgical distraction were determined from a review of literature and expert opinion. Government gazette and expert opinion provided cost estimation of growing rods, surgeries, surgical complications, and routine follow-up. Microsimulation of 1000 individuals was conducted to test the variation in total direct costs (in 2016 Hong Kong dollars (HKD)) between individuals, and estimated the standard deviations of total direct costs for each group.

RESULTS

Over the projected treatment period, indirect costs incurred by patients and family were higher for the MCGR as compared to the TGR. However, the total costs incurred by MCGR groups (group 1: HKD164k; group 2: HKD138k) were lower than those incurred by TGR groups (group 3: HKD191k; group 4: HKD290k). Although the accumulative costs of three groups (TGR with distraction every year and MCGR replacing every 2 and 3 years) were approaching each other in the first 2 years after initial implantation, at year 3 the accumulative cost of MCGR exchange every 2 years was HKD36k more than the yearly TGR surgery due to the cost of implant exchange. The cost incurred by both the MCGR groups was less than that incurred by the TGR groups from year 4 to skeletal maturity.

CONCLUSIONS

The use of dual MCGRs, regardless of its 2- or 3-year exchange, was only cost saving and less expensive than the dual TGRs for EOS treatment from the fourth year of continuous treatment. Despite higher patient-related costs during MCGR treatment, it is important to consider the reduced risks and mental burden suffered by these children during repeat surgeries. With improved knowledge of the costs associated with long-term MCGR use, better constructed cost-effectiveness studies can be performed in the future.

Staged Growing Rods With Preimplantation of Spinal Anchors for Complex Early Onset Scoliosis

BACKGROUND

Treatment of early onset scoliosis (EOS) with growing rods (GR) can be challenging in patients with significant deformity, hyperkyphosis, or poor bone quality, due to risks of neurological deficit and hardware pull-out. The objective of this study is to report a series of EOS patients managed with a 2-stage GR technique used to minimize these complications.

METHODS

Two-stage GR technique was performed in 8 patients at mean age of 5.4 (range, 3.4 to 7.9) years. At stage 1, proximal and distal anchors were implanted with local fusion. At stage 2, the distraction rods were inserted. There were at least 3 months between stages 1 and 2, and halo-gravity traction was used before stage 2 unless contraindicated. Demographic, clinical, and surgical data were retrospectively reviewed with mean 4.9 (range, 2.0 to 9.4) years of follow-up. Radiographic measurements including Cobb and kyphosis angles were evaluated before stage 1, after halo-gravity traction, after stage 2, and at last follow-up. Indications for staging, anchor healing time, and complications were collected and analyzed.

RESULTS

Indications for 2-stage surgery were poor bone quality in 5 patients and neurological changes during initial attempt at GR placement in 3 patients. The mean time between stage 1 and 2 was 23 (15 to 45) weeks. Patients have undergone mean 7 (3 to 16) lengthenings. Three patients have been converted to magnetically controlled GR. The major coronal Cobb angle improved from mean 81 degrees (range, 61 to 97) preoperatively to 40 degrees (24 to 50) after stage 2 and remained at 40 degrees (27 to 53) at last follow-up. Kyphosis remained controlled from 45 degrees (10 to 76) preoperatively to 38 degrees (9 to 61) after stage 2 to 41 degrees (17 to 65) at last follow-up. Complications included superficial wound problems (4 patients), broken rods (2 patients), proximal migration (2 patients), and implant prominence (1 patient). At minimum 2-year follow-up, no patients had lingering neurological complications or instrumentation-bone failure of the GR construct.

CONCLUSIONS

Two-stage GR technique can effectively be utilized in EOS patients with poor bone quality or in the event of intraoperative neurological changes. Satisfactory deformity correction can be obtained and routine serial lengthenings can take place with minimal complications.

LEVEL OF EVIDENCE

Level IV- case series.

A Comparison of SHILLA GROWTH GUIDANCE SYSTEM and Growing Rods in the Treatment of Spinal Deformity in Children Less Than 10 Years of Age

BACKGROUND

The purpose of this study was to compare the outcomes of the SHILLA GROWTH GUIDANCE SYSTEM and "intermittent distraction growing rod" (IDGR) in the treatment of children (less than 10 y of age) with progressive spinal deformity. This was a multicenter retrospective study of the SHILLA used as an alternative treatment to IDGR to support an HDE submission for Food and Drug Administration approval.

METHODS

Inclusion criteria were progressive scoliosis in a patient less than 10 years of age at index procedure. The study population consisted of 19 SHILLA and 6 IDGR patients whose mean age was 6.1 and 5.8 years, respectively. Group demographics were similar between the 2 groups.

RESULTS

The initial major curve magnitude was 70.3 degrees for SHILLA and 68.3 degrees for IDGR, which decreased postoperatively to 22.4 degrees (68.1% improvement) and 32.2 degrees (52.9% improvement). During the first 4 years the correction for SHILLA varied from 40.5% to 53.4% and for IDGR from 40.9% to 56.9%. At last follow-up, T1-S1 length was 32.9 cm for SHILLA (4.2 increase from preoperation) and 34.0 cm (5.0 cm increase from preoperation) for IDGR. Average growth per month from T1-S1: SHILLA 0.14 cm, IDGR 0.11 cm. Sagittal T2-T12 preoperatively was 36.3 degrees for SHILLA and 30.0 degrees for IDGR. There were 29 reoperations in 12 of the 19 SHILLA patients (63.2%) and 40 reoperations in all 6 of the IDGR patients (100%) related to the index procedure.

CONCLUSIONS

The SHILLA GROWTH GUIDANCE SYSTEM compares favorably with traditional IDGR constructs in terms of correction of the major curve, spinal length and growth, and maintenance of sagittal alignment. The >4-fold decrease in additional surgeries makes the SHILLA an attractive alternative to minimize comorbidities associated with additional surgeries.

LEVELS OF EVIDENCE

Level III.

Managing the Pediatric Spine: Growth Assessment

Management of pediatric spinal deformities requires an accurate prediction of growth spurts to allow for timely initiation of treatment and prevention of curve progression. Determining remaining growth potential is also important for avoiding prolonged unnecessary treatment, e.g. bracing for patients nearing skeletal maturity. Many clinical and radiological growth parameters have been developed to aid clinicians in growth prediction. Of these, several commonly used measures such as height and arm span growth trends, timing of menarche, and the Risser sign are mostly retrospective and lack strong predictive utility. Bone age assessments, such as digital skeletal age and the distal radius and ulna classification, are more accurate parameters, but further research is required to determine interethnic variations and develop their role in management decisions.

Learning Curve in Monitoring Magnetically Controlled Growing Rod Distractions With Ultrasound

STUDY DESIGN

Prospective study.

OBJECTIVE

To determine whether a learning curve exists for ultrasound measurement of magnetically controlled growing rod (MCGR) distractions.

SUMMARY OF BACKGROUND DATA

For patients managed by MCGRs, close monitoring of interval distraction length gains is important to determine whether the distractions are translating into actual spine growth. Radiographs are the criterion standard for measuring length gains, but ultrasound has been shown to be effective in monitoring distraction lengths without radiation exposure. It is, however, an operator-dependent tool and thus the accuracy of ultrasound measurement of distracted length may improve with experience.

METHODS

This is a prospective correlation analysis of patients who underwent MCGR treatment for scoliosis. The study period was inclusive of 19th February 2013 to 31st March 2015. All subjects were consecutively recruited in a prospective manner. Data regarding date of the distraction visit, and the interval radiograph and ultrasound measurements of the distracted lengths were collected. Only those episodes with both radiograph and ultrasound performed were used for analysis. The mean differences in change of radiograph and ultrasound measurements were plotted to determine correlation differences and to observe for a learning curve.

RESULTS

A total of 379 distraction episodes were analyzed. The mean differences between ultrasound and radiograph measurements per distraction episode were -0.3 mm for the right rod and -0.1 mm for the left rod. For learning curve analysis, there were three distinct timepoints in which the difference of correlation became significantly better and were described as clusters. The correlation in the first cluster (19th February 2013 to 15th October 2013) was 0.612 (right rod) and 0.795 (left rod), the second cluster (16th October 2013 to 20th May 2014) was 0.879 (right rod) and 0.918 (left rod), and the third cluster (21st May 2014 to 31st March 2015) was 0.956 (right rod) and 0.932 (left rod). Thus, a plateau was observed at the second cluster, which translated to 97 to 146 rod measurements.

CONCLUSION

Correlation between radiograph and ultrasound measurements is reasonable to begin with but improves with time. During initial use, successful distractions should correlate between the clinical feel and ultrasound confirmation. Although the absolute value may not be accurate and may require radiographs to confirm, with time and experience, ultrasound measurements can then be more reliable.

LEVEL OF EVIDENCE

3.

A randomized double-blinded clinical trial to evaluate the safety and efficacy of a novel superelastic nickel-titanium spinal rod in adolescent idiopathic scoliosis: 5-year follow-up

PURPOSE

To evaluate the safety and efficacy of a superelastic shape-memory alloy (SNT) rod used in the treatment of adolescent idiopathic scoliosis (AIS).

METHODS

AIS Patients with Lenke 1 curves undergoing fusion surgery were randomized (1:1) at the time of surgery to receive either the SNT or a conventional titanium alloy (CTA) rod. Radiographs were obtained preoperatively and postoperatively up to 5 years of follow-up. Parameters assessed included coronal and sagittal Cobb angles, and overall truncal and shoulder balance. Sagittal profiles were subcategorized into Types A (<20°), B (20-40°), and C (>40°).

RESULTS

Twenty-four patients with mean age of 15 years were recruited. A total of 87.0% of subjects were followed up till postoperative 5 years, but all patients had minimum 2 years of follow-up. The fulcrum-bending correction index for the SNT group was 113% at postoperative day 4 and 127% at half-year, while the CTA group was 112% at postoperative day 4 and only 106% at half-year. In terms of sagittal profile, the SNT group moved toward type B profile at half-year follow-up with a mean correction of 7.6°, while no significant change was observed in the CTA group (-0.7°). Nickel levels remained normal, and there were no complications.

CONCLUSIONS

This is the first randomized clinical trial of a novel SNT rod for treating patients with AIS, noting it to be safe and has potential to gradually correct scoliosis over time. This study serves as a pilot and platform to properly power future large-scale studies to demonstrate efficacy and superiority.

The use of the distal radius and ulna classification for the prediction of growth: peak growth spurt and growth cessation

AIMS

We report the use of the distal radius and ulna (DRU) classification for the prediction of peak growth (PG) and growth cessation (GC) in 777 patients with idiopathic scoliosis. We compare this classification with other commonly used parameters of maturity.

PATIENTS AND METHODS

The following data were extracted from the patients' records and radiographs: chronological age, body height (BH), arm span (AS), date of menarche, Risser sign, DRU grade and status of the phalangeal and metacarpal physes. The mean rates of growth were recorded according to each parameter of maturity. PG was defined as the summit of the curve and GC as the plateau in deceleration of growth. The rates of growth at PG and GC were used for analysis using receiver operating characteristic (ROC) curves to determine the strength and cutoff values of the parameters of growth.

RESULTS

The most specific grades for PG using the DRU classification were radial grade 6 and ulnar grade 5, and for GC were radial grade 9 and ulnar grade 7. The DRU classification spanned both PG and GC, enabling better prediction of these clinically relevant stages than other methods. The rate of PG (≥ 0.7 cm/month) and GC (≤ 0.15 cm/month) was the same for girls and boys, in BH and AS measurements.

CONCLUSION

This is the first study to note that the DRU classification can predict both PG and GC, providing evidence that it may aid the management of patients with idiopathic scoliosis. Cite this article: Bone Joint J 2016;98-B:1689-96.

Frequent small distractions with a magnetically controlled growing rod for early-onset scoliosis and avoidance of the law of diminishing returns

PURPOSE

To assess the effect of frequent small distractions with a magnetically controlled growing rod (MCGR) on spinal length gain and achieved distraction length in children with early-onset scoliosis (EOS), and to determine whether the law of diminishing returns applies to this group of patients with MCGR.

METHODS

A consecutive series of 3 males and 4 females with EOS who underwent MCGR implantation at a mean age of 10.2 years and were followed up for a mean of 3.8 years were reviewed. Distraction was aimed at 2 mm monthly. The coronal Cobb angle, T1-S1 length gain, and achieved distraction length were measured at 6-monthly intervals.

RESULTS

The mean total number of distractions was 31. Four of the patients had problems that may have affected distractions. The mean coronal Cobb angle improved post-operatively and was maintained throughout the follow-up period. The mean T1-S1 length gain and achieved distraction length varied over the follow-up period and did not diminish with repeated lengthening.

CONCLUSIONS

Frequent small distractions with the MCGR for EOS enable T1-S1 and achieved distraction length gain without significant reduction in gain after repeated lengthening.

Reliability Analysis of the Distal Radius and Ulna Classification for Assessing Skeletal Maturity for Patients with Adolescent Idiopathic Scoliosis

Study Design Prospective radiographic study. Objective To test the reliability of the Distal Radius and Ulna Classification (DRU). Methods This single-center study included prospectively recruited subjects with adolescent idiopathic scoliosis managed with bracing. The left-hand radiographs were measured using the DRU classification by two examiners. Intra- and interobserver reliability analysis were performed using intraclass correlation (ICC) analysis. Results From these clinics, 161 patients (124 females and 37 males) with left-hand radiographs were included in the study. The mean age was 13.3 years (standard deviation: 1.5). There was excellent intra- (ICC: 0.93 to 0.95) and interobserver (ICC: 0.97) reliability. Conclusions The DRU classification scheme has been shown to be accurate in determining the peak growth phase and growth cessation. It has now been confirmed to be a reliable tool. Future prospective studies should be performed to investigate its application in deciding when to apply bracing or operative treatment.

Clinical utility of ultrasound to prospectively monitor distraction of magnetically controlled growing rods

BACKGROUND CONTEXT

Growing rods are commonly used for surgical treatment of skeletally immature patients with scoliosis, but require repeated surgeries for distractions and are fraught with complications. As an alternative, the use of magnetically controlled growing rods (MCGR) allows for more frequent non-invasive distractions to mimic normal growth. However, more plain radiographs are needed to monitor increased distraction frequency, thereby increasing ionizing radiation exposure to the developing child. The use of ultrasound, which emits no radiation, has been found in a cross-sectional study to be reliable in measuring MCGR distractions.

PURPOSE

The study aims to address the prospective clinical utility of ultrasound compared with plain radiographs for assessing MCGR distractions.

STUDY DESIGN

This is a prospective study.

PATIENT SAMPLE

The study includes patients with early-onset scoliosis undergoing distractions after MCGR implant.

OUTCOME MEASURES

The distraction length on plain radiographs and ultrasound was measured.

METHODS

This is a prospective study of patients treated with MCGR. Patients with both single- and dual-rod systems were included. Outpatient distractions were performed at monthly intervals, targeting 2 mm of distraction on each occasion. Assessment of distraction length was monitored by ultrasound at each visit; plain radiographs were taken every 6 months and were compared with ultrasound measurements.

RESULTS

Nine patients (5 female, 4 male), with a mean of 29 distractions (standard deviation [SD] ±14.3), were recruited. The mean distracted length per 6 months was 5.7 mm (SD ±3.6 mm) on plain radiographs and 5.2 mm (SD ±3.9 mm) on ultrasound for the concave rod, and 6.1 mm (SD ±3.6 mm) on plain radiographs and 5.9 mm (SD ±3.8 mm) on ultrasound for the convex rod. Excellent inter- and intra-rater reliabilities were observed for radiographic and ultrasound measurements. An excellent correlation was noted between the two imaging modalities (r=0.93; p<.0001).

CONCLUSIONS

This is the first prospective study to validate that ultrasound assessment of MCGR distraction lengths was highly comparable with that of plain radiographs. The present study has verified that ultrasound can be used to document length changes by distraction over time and that it had high clinical utility. Ultrasound can be a reliable alternative to plain radiographs, thereby avoiding radiation exposure and its potential detrimental sequelae in the developing child.

Special article: Update on the magnetically controlled growing rod: tips and pitfalls

Magnetically controlled growing rods (MCGR) have become an important treatment option in young patients with spinal deformities. This device allows for gradual lengthening on an outpatient setting with continuous neurological monitoring in an awake patient. With its growing popularity and interest, this study reports the tips, pitfalls, and complications of the MCGR for management of scoliosis. On 3 June 2015 at the University of Hong Kong, 32 participants from 16 regions shared their experience with MCGR. Current indications for surgery include early-onset scoliosis patients. Adolescent idiopathic scoliosis and congenital scoliosis patients have less favourable outcomes. The number of instrumented levels should be minimised, as all instrumented levels must be included in the definitive fusion surgery. Rod contouring is important and owing to the straight portion of the rod housing the magnet, there is limited proximal rod portion for proper contouring, which may predispose to proximal junctional kyphosis. There is currently no consensus on the rod configuration, timing, frequency, technique, and amount of distraction. Risk factors for distraction failure include larger patients, internal magnets too close to each other, and magnets too close to the apex of the major curve. Future studies should resolve the issues regarding the technique of distraction, optimal frequency and amount of distraction per session. More comprehensive cost analyses should be performed.

Surgical treatment of adolescent idiopathic scoliosis in the United States from 1997 to 2012: an analysis of 20,346 patients

OBJECT

Adolescent idiopathic scoliosis (AIS) can cause substantial morbidity and may require surgical intervention. In this study, the authors aimed to evaluate US trends in operative AIS as well as patient comorbidities, operative approach, in-hospital complications, hospital length of stay (LOS), and hospital charges in the US for the period from 1997 to 2012.

METHODS

Patients with AIS (ICD-9-CM diagnosis codes 737.30) who had undergone spinal fusion (ICD-9-CM procedure codes 81.xx) from 1997 to 2012 were identified from the Kids' Inpatient Database. Parameters of interest included patient comorbidities, operative approach (posterior, anterior, or combined anteroposterior), in-hospital complications, hospital LOS, and hospital charges.

RESULTS

The authors identified 20, 346 patients in the age range of 0-21 years who had been admitted for AIS surgery in the defined study period. Posterior fusions composed 63.4% of procedures in 1997 and 94.1% in 2012 (r = 0.95, p < 0.01). The mean number of comorbidities among all fusion groups increased from 3.0 in 1997 to 4.2 in 2012 (r = 0.92, p = 0.01). The percentage of patients with complications increased from 15.6% in 1997 to 22.3% in 2012 (r = 0.78, p = 0.07). The average hospital LOS decreased from 6.5 days in 1997 to 5.6 days in 2012 (r = -0.86, p = 0.03). From 1997 to 2012, the mean hospital charges (adjusted to 2012 US dollars) for surgical treatment of AIS more than tripled from $55,495 in 1997 to $177,176 in 2012 (r = 0.99, p < 0.01).

CONCLUSIONS

Over the 15-year period considered in this study, there was an increasing trend toward using posterior-based techniques for AIS corrective surgery. The number of comorbid conditions per patient and thus the medical complexity of patients treated for AIS have increased. The mean charges for the treatment of AIS have increased, with a national bill over $1.1 billion per year in 2012.