Magnetically Controlled Growing Rods Research Articles

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.

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

Background ContextGrowing 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. PurposeThe study aims to address the prospective clinical utility of ultrasound compared with plain radiographs for assessing MCGR distractions. Study DesignThis is a prospective study. Patient SampleThe study includes patients with early-onset scoliosis undergoing distractions after MCGR implant. Outcome MeasuresThe distraction length on plain radiographs and ultrasound was measured. MethodsThis 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. ResultsNine 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). ConclusionsThis 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.

Radiological and clinical assessment of the distraction achieved with remotely expandable growing rods in early onset scoliosis

Magnetically controlled growing rods (MCGR) allow controlled distraction of the immature spine for the treatment of early onset scoliosis. This study's primary aim was to determine the disparity between 'true' (TD) and 'intended' (ID) distraction. The secondary aim was to assess truncal growth and development during sequential lengthening. Twenty-one patients with a maximum follow up of 37months were included in the study. Patients in the study underwent three monthly distractions. The amount of TD was determined by measuring the expansion gap on dedicated fluoroscopic images of the actuator. The total TD to date was compared to the ID measurement reported on the external adjustment device (EAD). Weight, sitting and standing heights were recorded at each distraction. The average number of three monthly distractions was 8. The true to intended distraction ratio was calculated as 0.33. Patients who had undergone previous surgery gained less distraction with a ratio of 0.30 compared to patients undergoing MCGR as a primary procedure with a ratio of 0.35. Weight, sitting and standing heights increased in all patients by an average of 3.1kg, 2.3 and 5.2cm per year. The Cobb angle following surgical correction was maintained in 19 of 21 patients at the latest follow-up. The TI ratio of 0.33 suggests that for every unit of distraction registered on the EAD approximately 33% of true distraction occurs in vivo. Increases in sitting and standing heights were observed in all patients in the study.

Magnetically controlled growing rod in early onset scoliosis

Background Magnetically controlled growing rods (MCGR) are increasingly used for the treatment of early onset scoliosis. Aim of the study is to retrospectively review our patients treated with MCGR focusing on complications. Materials and methods We retrospectively reviewed 7 patients, affected by early onset scoliosis and surgically treated with magnetically controlled growing rods (minimum follow up 6 months). There were 7 children, 3 females and 4 males, with an age ranging from 4 to 11 years. The aetiology was 6 idiopathic (infantile or juvenile), 1 congenital. In one case a VEPTR was first implanted before using MCGR. In all cases a dual growing rod was implanted, using as distal anchors pedicle screws, as proximal anchors hooks. Results At a minimum follow up of 6 months, after performing 5.7 lengthening procedures per patient (lengthening performed every 60-90 days), main thoracic scoliosis was corrected from 62.7° to 32.0° (mean correction 49%), lumbar curve form 58.5° to 32.0° (45%). The correction was maintained at final follow up. No neurological or infective complications occurred. In one patient a revision surgery was performed due to persistent sciatica secondary to lumbar misplaced screw. In another one, a revision was performed due to proximal hooks mobilization. At final follow up, no patient presents pain or functional limitation. Conclusions Those results showed that MCGR can be safely and effectively used in patients affected by early onset idiopathic scoliosis, with an acceptable complications incidence (33%) if compared with literature regarding

Traditional Growing Rods Versus Magnetically Controlled Growing Rods for the Surgical Treatment of Early-Onset Scoliosis: A Case-Matched 2-Year Study

IntroductionTraditional growing rod (TGR) surgery is a treatment technique commonly used for progressive early-onset scoliosis. Studies have shown that repeated TGR lengthenings can significantly increase the risk of complications. Magnetically controlled growing rods (MCGR) are currently available outside of the United States and early results have been promising. The purpose of this study was to compare the effectiveness of MCGR versus TGR for the treatment of early-onset scoliosis. MethodsMagnetically controlled growing rod patients were selected based on the following criteria: aged less than 10 years, major curve greater than 30°, thoracic height less than 22 cm, no previous spine surgery, and minimum 2-year follow-up. A total of 17 MCGR patients met the inclusion criteria, 12 of whom had complete data available for analysis. Each MCGR patient was matched with a TGR patient by etiology, gender, single versus dual rods, preoperative age, and preoperative major curve. ResultsMagnetically controlled growing rod patients had a mean age of 6.8 years and mean follow-up of 2.5 years. Mean follow-up was greater for TGR patients by 1.6 years. Major curve correction was similar between MCGR and TGR patients throughout treatment. The MCGR patients experienced an average of 8.1 mm/year increase in T1–S1 during the lengthening period, compared with 9.7 mm/year for TGR patients (p = .73). There was a mean increase in T1–T12 of 1.5 mm/year for MCGR patients and 2.3 mm/year for TGR patients (p = .83). The TGR patients had 73 open surgeries, 56 of which were lengthenings. The MCGR patients had 16 open surgeries and 137 noninvasive lengthenings. Three TGR patients underwent 5 unplanned revision surgeries whereas 3 MCGR patients underwent 4 unplanned revisions. ConclusionsMajor curve correction was similar between MCGR and TGR patients throughout treatment. Annual T1–S1 and T1–12 growth was also similar between groups. The MCGR patients had 57 fewer surgical procedures than TGR patients. Incidence of unplanned surgical revisions as a result of complications was similar between groups.

Direct costs associated with the management of progressive early onset scoliosis: Estimations based on gold standard technique or with magnetically controlled growing rods

BackgroundThe main disadvantage of the surgical management of early onset scoliosis (EOS) using conventional growing rods is the need for iterative surgical procedures during childhood. The emergence of an innovative device using distraction-based magnetically controlled growing rods (MCGR) provides the opportunity to avoid such surgeries and therefore to improve the patient's quality of life. HypothesisDespite the high cost of MCGR and considering its potential impact in reducing hospital stays, the use of MCGR could reduce medical resource consumption in a long-term view in comparison to traditional growing rod (TGR). Materials and methodsA cost-simulation model was constructed to assess the incremental cost between the two strategies. The cost for each strategy was estimated based on probability of medical resource consumption determined from literature search as well as data from EOS patients treated in our centre. Some medical expenses were also estimated from expert interviews. The time horizon chosen was 4years as from first surgical implantation. Costs were calculated in the perspective of the French sickness fund (using rates from year 2013) and were discounted by an annual rate of 4%. Sensitivity analyses were conducted to test model strength to various parameters. ResultsWith a time horizon of 4years, the estimated direct costs of TGR and MCGR strategies were 49,067 € and 42,752 €, respectively leading to an incremental costs of 6135 € in favour of MCGR strategy. In the first case, costs were mainly represented by hospital stays expenses (83.9%) whereas in the other the cost of MCGR contributed to 59.5% of the total amount. In the univariate sensitivity analysis, the tariffs of hospital stays, the tariffs of the MCG, and the frequency of distraction surgeries were the parameters with the most important impact on incremental cost. DiscussionMCGR is a recent and promising innovation in the management of severe EOS. Besides improving the quality of life, its use in the treatment of severe EOS is likely to be offset by lower costs of hospital stays. Level of evidence (with study design)Level IV, economic and decision analyses, retrospective study.

Next Generation of Growth-Sparing Techniques

Prospective nonrandomized study. To report the preliminary results of magnetically controlled growing rod (MCGR) technique in children with progressive early-onset scoliosis. The growing rod (GR) technique is a viable alternative for treatment of early-onset scoliosis. High complication rate is attributed to frequent surgical lengthening. The safety and efficacy of MCGR were recently reported in a porcine model. Multicenter study of clinical and radiographical data of patients who underwent MCGR surgery and at least 3 distractions. Distractions were performed in clinic without anesthesia/analgesics. T1-T12 and T1-S1 heights and the distraction distance inside the actuator were measured after lengthening. Fourteen patients (7 girls, 7 boys) with a mean age of 8 years, 10 months (3 yr, 6 mo to 12 yr, 7 mo) had 14 index surgical procedures. Of the 14, 5 had single-rod (SR) surgery and 9 had dual-rod (DR) surgery, with overall 68 distractions. Diagnoses were idiopathic (N = 5), neuromuscular (N = 4), congenital (N = 2), syndromic (N = 2), and neurofibromatosis (N = 1). Mean follow-up was 10 months (5.8-18.2). The Cobb angle changed from 60° to 34° after initial surgery and 31° at latest follow-up. During distraction period, T1-T12 height increased by 7.6 mm for SR (1.09 mm/mo) and 12.12 mm for DR (1.97 mm/mo). T1-S1 height gain was 9.1 mm for SR (1.27 mm/mo) and 20.3 mm for DR (3.09 mm/mo). Complications included superficial infection in 1 SR, prominent implant in 1 DR, and minimal loss of initial distraction in 3 SR after index. Partial distraction loss observed after 14 of the 68 distractions (1 DR and 13 SR) but regained in subsequent distractions. There was no neurological deficit or implant failure. Preliminary results indicated MCGR was safe and provided adequate distraction similar to standard GR. DR achieved better initial curve correction and greater spinal height during distraction compared with SR. No major complications were observed during the follow-up.

Early results of a remotely-operated magnetic growth rod in early-onset scoliosis

Conventional growing rods are the most commonly used distraction-based devices in the treatment of progressive early-onset scoliosis. This technique requires repeated lengthenings with the patient anaesthetised in the operating theatre. We describe the outcomes and complications of using a non-invasive magnetically controlled growing rod (MCGR) in children with early-onset scoliosis. Lengthening is performed on an outpatient basis using an external remote control with the patient awake.Between November 2009 and March 2011, 34 children with a mean age of eight years (5 to 12) underwent treatment. The mean length of follow-up was 15 months (12 to 18). In total, 22 children were treated with dual rod constructs and 12 with a single rod. The mean number of distractions per patient was 4.8 (3 to 6). The mean pre-operative Cobb angle was 69° (46° to 108°); this was corrected to a mean 47° (28° to 91°) post-operatively. The mean Cobb angle at final review was 41° (27° to 86°). The mean pre-operative distance from T1 to S1 was 304 mm (243 to 380) and increased to 335 mm (253 to 400) in the immediate post-operative period. At final review the mean distance from T1 to S1 had increased to 348 mm (260 to 420).Two patients developed a superficial wound infection and a further two patients in the single rod group developed a loss of distraction. In the dual rod group, one patient had pull-out of a hook and one developed prominent metalwork. Two patients had a rod breakage; one patient in the single rod group and one patient in the dual rod group. Our early results show that the MCGR is safe and effective in the treatment of progressive early-onset scoliosis with the avoidance of repeated surgical lengthenings.

A New Type of Growing Rod for the Treatment of Scoliosis

Dr Hennrikus has disclosed no financial relationship relevant to this commentary. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device. Source: Cheung KM, Cheung JP, Samartzis D, et al. Magnetically controlled growing rods for severe spinal curvature in young children: a prospective case series. Lancet. 2012; 379( 9830): 1967- 1974; doi: 10.1016/S0140-6736(12)60112-3[OpenUrl][1][CrossRef][2][PubMed][3][Web of Science][4] Investigators from the University of Hong Kong and the San Diego Center for Spinal Disorders designed this prospective study in Hong Kong to determine the effectiveness and safety of a new magnetically controlled growing rod (MCGR) used to gradually distract or lengthen the spinal curvature in clinic in young growing children with scoliosis. The investigators inserted a single-use sterile titanium spinal distractible rod with an enlarged … [1]: {openurl}?query=rft.jtitle%253DLancet%26rft.stitle%253DLancet%26rft.aulast%253DCheung%26rft.auinit1%253DK.%2BM.%26rft.volume%253D379%26rft.issue%253D9830%26rft.spage%253D1967%26rft.epage%253D1974%26rft.atitle%253DMagnetically%2Bcontrolled%2Bgrowing%2Brods%2Bfor%2Bsevere%2Bspinal%2Bcurvature%2Bin%2Byoung%2Bchildren%253A%2Ba%2Bprospective%2Bcase%2Bseries.%26rft_id%253Dinfo%253Adoi%252F10.1016%252FS0140-6736%252812%252960112-3%26rft_id%253Dinfo%253Apmid%252F22520264%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [2]: /lookup/external-ref?access_num=10.1016/S0140-6736(12)60112-3&link_type=DOI [3]: /lookup/external-ref?access_num=22520264&link_type=MED&atom=%2Faapgrand%2F28%2F4%2F48.atom [4]: /lookup/external-ref?access_num=000304757700031&link_type=ISI

Innovation in Growing Rod Technique

STUDY DESIGN.: Prospective in vivo randomized study. OBJECTIVE.: To evaluate the safety and efficacy of a distraction-based magnetically controlled growing rod (MCGR) in a porcine model. SUMMARY OF BACKGROUND DATA.: A high number of complications related to frequent surgical rod lengthenings has been a generally accepted outcome in growing rod surgery for early-onset scoliosis. A potentially safer technique is a system that does not require repetitive surgery. METHODS.: Seven-month-old pigs were randomly assigned to an experiment group (EG; n = 6) and a sham group (SG; n = 3). One animal in the EG became paralyzed because of a misplaced pedicle screw and was killed per the study protocol. Therefore, a total of 8 animals completed the study. The EG underwent weekly spine distraction using the MCGR. Spinal height was assessed by vertebral unit height measurements on weekly lateral radiographs. RESULTS.: A total of 49 mm of distraction across the unfused vertebral levels was planned during a 7-week period (7 mm per wk). Radiographical analysis of the MCGR device revealed an average distraction of 39 mm (range, 32-46 mm), resulting in achievement of 80% of predicted spinal height. Prior to removal of implants, spinal height for the EG was similar to the SG. However, accelerated increase in vertebral unit height was noted in the EG during the 3-week period after implant removal, which resulted in significantly greater overall spinal height in the EG (32.2% vs. 11.7%, P ≤ 0.05). No MCGR-related complications occurred. CONCLUSION.: The MCGR provided 80% of predicted spinal height by noninvasive remote distraction in this animal model. The accelerated increase in spinal height of the experimental animals after implant removal was an unexpected finding which requires additional research to better understand the effect of distraction on spinal growth. This study establishes a foundation for future research in an attempt to use a less invasive technique in distraction-based correction of early-onset scoliosis.

Update on spine based surgical treatment of early onset scoliosis: what do we know in 2012?

BackgroundProgressive Early-Onset Scoliosis (EOS) is one of the most challenging problems in pediatric orthopaedics. Extensive research efforts are underway to understand different aspects of natural history, diagnostic measures and treatment options.ObjectiveUpdate on spine-based surgical techniques for treatment of progressive EOS.MethodsReview of the literature and experts’ opinions.ResultsOur first report of dual growing rod technique in 2005 showed good scoliosis correction at final follow-up and annual T1-S1 growth of 12.1 mm after the initial correction. Since then, dual growing rod technique has been used in EOS in many different etiologies and has shown the efficacy to correct scoliosis and allow for spinal growth. Complication rate has always been a concern, as the patient has to undergo repeated surgeries for lengthening. Using submuscular, dual GR rods vs subcutaneous single GR rod technique will decrease the complication rate. Younger age at initial surgery and abnormal sagittal alignment (especially thoracic hyper- or hypokyphosis) have also shown to be associated with higher complication rate. A new technology, Magnetically Controlled Growing Rod (MGCR), has been shown safe and effective in both pilot animal and human studies. Growth-guided techniques also aim to alleviate the need for surgical lengthening while it directs the spinal growth.ConclusionsTreatment of Early-Onset Scoliosis (EOS) is a long commitment for the patient and the treating surgeon. Different techniques are available, each with unique capabilities and potential drawbacks but all with the goal of correcting the deformity and allowing for growth of spine and lungs and eventually improve the quality of life of these children.

Magnetically controlled growing rods for severe spinal curvature in young children: a prospective case series

Scoliosis in skeletally immature children is often treated by implantation of a rod to straighten the spine. Rods can be distracted (lengthened) as the spine grows, but patients need many invasive operations under general anaesthesia. Such operations are costly and associated with negative psychosocial outcomes. We assessed the effectiveness and safety of a new magnetically controlled growing rod (MCGR) for non-invasive outpatient distractions. We implanted the MCGR in five patients, two of whom have now reached 24 months' follow-up. Each patient underwent monthly outpatient distractions. We used radiography to measure the magnitude of the spinal curvature, rod distraction length, and spinal length. We assessed clinical outcome by measuring the degree of pain, function, mental health, satisfaction with treatment, and procedure-related complications. In the two patients with 24 months' follow-up, the mean degree of scoliosis, measured by Cobb angle, was 67° (SD 10°) before implantation and 29° (4°) at 24 months. Length of the instrumented segment of the spine increased by a mean of 1·9 mm (0·4 mm) with each distraction. Mean predicted versus actual rod distraction lengths were 2·3 mm (1·2 mm) versus 1·4 mm (0·7 mm) for patient 1, and 2·0 mm (0·2 mm) and 2·1 mm (0·7 mm) versus 1·9 mm (0·6 mm) and 1·7 mm (0·8 mm) for patient 2's right and left rods, respectively. Throughout follow-up, both patients had no pain, had good functional outcome, and were satisfied with the procedure. No MCGR-related complications were noted. The MCGR procedure can be safely and effectively used in outpatient settings, and minimises surgical scarring and psychological distress, improves quality of life, and is more cost-effective than is the traditional growing rod procedure. The technique could be used for non-invasive correction of abnormalities in other disorders. Ellipse Technologies.