Magnetically Controlled Growing Rods (MCGR) for the Treatment of Progressive Early-Onset Scoliosis (EOS)
An 8+2 year-old boy was diagnosed with idiopathic early onset scoliosis (EOS) at the age of 9-months. The patient had an otherwise normal birth and development with no pulmonary issues. At that time it was noted that he had a thoracic curve measuring 20° with the curve apex at T7 (Figure 1). The patient was monitored until the age of 3-years-old, after which he began orthotic treatment and continued for 4 years albeit inconsistent compliance. Family history is significant for paternal grandmother and aunt who were diagnosed with scoliosis.
Figure 1: Posteroanterior radiograph at 9-months of age showing a mild thoracic curve.
Figure 2: Posteroanterior radiograph at 3-years of age shows the major thoracic curve measuring 54°.
Pre-operative Clinical Examination
Clinical evaluation showed a well-nourished 9-year-old male of average height for his age with a right-sided thoracic prominence measuring greater than 30° using a scoliometer and a left sided lumbar prominence of approximately 7°. Pelvis was level and his C7 plumb line was 3 cm to the right. Sagittal balance appeared to be within normal limits. The patient did not report any pain and the parents denied any physical limitations to their child's daily activities. He participates in yoga, martial arts and is otherwise an active child. Neurological exam was unremarkable, and a review of systems was negative for any additional complaints.
Pre-operative Radiographic Examination
Pre-operative radiographic imaging show a double thoracic curve with a right thoracic curve from T5 to L1 measuring 105° and a left proximal thoracic compensatory curve from T1 to T5 measuring 46°. T1-S1 spinal height was 206 mm with a right coronal balance of 27 mm. Maximum thoracic kyphosis and L1-S1 lumbar lordosis were 77° and -69°, respectively.
Figure 6: Pre-operative standing posteroanterior radiograph.
Figure 7: Pre-operative standing lateral radiograph.
Figure 8: Pre-operative push prone flexibility film shows correction of the major curve to 59° (44% correction).
Progressive idiopathic early onset scoliosis.
Based on patient age and curve progression, despite non-operative treatment, it was recommended that he undergo distraction-based growing rod treatment. However, the patient's parents were adamantly against the prospect of repeat surgical lengthening procedures. Magnetically controlled growing rod (MCGR) treatment was considered as a possible option due to the parents' specific request and the manufacturer's (Ellipse Technologies, Irvine, CA) willingness to facilitate the use of the device (MAGEC™) via the U.S. FDA Compassionate Use regulatory pathway.
After obtaining FDA and IRB approval for Compassionate Use treatment, the patient underwent posterior spinal instrumentation from T2 to L4 using dual MCGR with limited posterior spinal fusion (using allograft) at the upper and lower foundations. The upper foundation included T2-T3 with proximal hook anchors and the lower foundation included L3-L4 with bilateral pedicle screws. Intra-operatively there was a proximal sublaminar hook pull-out on the right side of T3 which was replaced with a pedicle screw. There were no other intraoperative complications.
Figure 9: Immediate post-operative posteroanterior radiograph.
Figure 10: Immediate post-operative lateral radiograph.
Figure 11: Post-operative clinical photograph.
Figure 12: Post-operative clinical photograph.
Immediate Post-operative: Patient tolerated the procedure well without any post-operative complications. There was immediate post-operative improvement of the major curve from 105° to 67° (36% correction) and the T1-S1 spinal height increased from 206 mm to 283 mm (77 mm increase). Compensatory proximal thoracic curve slightly increased from 46° to 60°. Maximum thoracic kyphosis and lumbar lordosis improved to 56° and -54°, respectively.
Follow-up: A total of 2 non-invasive lengthenings have been performed thus far; one at the 1-month follow-up and another at the 3-month follow-up. The lengthenings were performed in an outpatient clinic setting, and the patient experienced no pain.
Figure 13: The external adjustment device used to distract the MCGR.
At the 3-month time point, major thoracic curve measured 65° and T1-S1 spinal height was 295 mm (12 mm increase from immediate post-operative). Maximum thoracic kyphosis was 46° and L1-S1 lumbar lordosis remained at -56°.
Figure 14: Latest follow-up, posteroanterior radiograph with the magnified image showing the actuator. The arrow indicates the part of the device used to measure how many millimeters of lengthening was achieved.
Figure 15: Latest follow-up, lateral radiograph.
Growth-friendly techniques for the treatment of early onset scoliosis have greatly evolved since the advent of Harrington rods. Traditional growing rods require periodic open surgical lengthening procedures under general anesthesia and are associated with a relatively high risk of complications.1 The goal of magnetically controlled growing rods (MCGR) is to reduce the need for frequent open surgical procedures. Pre-clinical research demonstrated its safety and efficacy and early clinical outcome studies have shown promising results. 2-5 Currently, MCGR is being used in over 20 countries and approximately 500 cases have been performed worldwide. However, the device is not currently FDA approved for sale and use in the United States.
1. Bess, S., et al. Complications of growing-rod treatment for early-onset scoliosis: analysis of one hundred and forty patients. J Bone Joint Surg Am, 2010. 92(15):2533-43.
2. Akbarnia, B.A., et al. Innovation in growing rod technique: a study of safety and efficacy of a magnetically controlled growing rod in a porcine model. Spine (Phila Pa 1976), 2012. 37(13):1109-14.
3. Akbarnia, B.A., et al. Next generation of growth-sparing techniques: preliminary clinical results of a magnetically controlled growing rod in 14 patients with early-onset scoliosis. Spine (Phila Pa 1976), 2013. 38(8):665-70.
4. Cheung, K.M., et al. Magnetically controlled growing rods for severe spinal curvature in young children: a prospective case series. Lancet, 2012. 379(9830):1967-74.
5. Dannawi, Z , et al. Early results of a remotely-operated magnetic growth rod in early-onset scoliosis. Bone Joint J, 2013. 95-B (1):75-80.
This case offers a glimpse into the near-future of "growth-friendly" spine constructs to treat early-onset scoliosis. The severity of the deformity presenting at age 8 (105° main thoracic curve, foreshortened spine and thoracic length, significant coronal and sagittal abnormality) argues for treatment necessarily focusing on the immediate and potential pulmonary function compromise that would be expected from such distortion of the thorax. The choice of a definitive, one-time correction and fusion is certainly an option, especially where poor follow-up and irresponsible post-operative compliance may be anticipated. Considering that this child's deformity was initially diagnosed at age 9-months, and was clearly indicated for corrective treatment (eg, casting, surgery) again at age 3, with apparent further neglect until the age 8 presentation, the definitive surgical management option could be justified, in spite of being a growth-ending procedure, to ensure prevention of further progression and avoidable morbidity.
The argument for growth-friendly treatment is based upon the determination that one-time correction and fusion may leave this patient's thoracic spine shorter in length than current guidelines for adequate thoracic volume, and pulmonary function would recommend. No pre-treatment T1-T12 length is provided. However, using Dimeglio's normal spine length data as a resource, the T1-S1 spine length in normal 8-year-old males would be in the range of 33 cm, with the thoracic spine component in the 20-21 cm range. One can easily justify a growing strategy for this patient whose T1-S1 length of 20.6 cm is well short of normal, and the projected T1-T12 length associated with his whole spine length—around 14 cm—is equally short of the absolute minimum of 18 cm suggested by Karol's data reporting pulmonary function compromise compared to spine length at maturity in early fusion patients.
Having thus decided that growth-friendly treatment is strongly indicated, the chance to use the recently developed magnetic-controlled lengthening device introduces a "game-changing" perspective on distraction-based constructs compared to traditional growing rod instrumentation. Heretofore, the repeated open surgical procedures, often performed twice a year to lengthen traditional constructs, has succeeded in attaining satisfactory thoracic and total spine length, but at a cost of a significant rate of complications, well-documented in the literature, not the least of which are the increased rates of infection, diminishing effectiveness of lengthening over time due to spontaneous ankylosis and auto-fusion, presumably from scarring, and a myriad of device-related problems (eg, anchor failure, rod fracture, junctional kyphosis)—some requiring unplanned returns to surgery. The stress on patients and families undergoing such lengthening protocols has only recently been appreciated as the children mature.
The use of the magnetic-controlled rods in this case may eliminate many of the negative aspects of traditional growth-friendly distraction. This patient has already achieved modest correction of the main thoracic deformity (to 65°) while achieving some 9 cm of overall length with a single surgical implantation and two outpatient lengthenings.
Several potential issues remain, including exacerbation of the upper thoracic curve due to the pure distractive correction vector, and the continued potential for proximal kyphosis due to the pre-operative junctional kyphosis, which has been controlled short-term by the current anchors but may resurface as continued distraction is applied from a vector placed at the thoracolumbar junction. Nevertheless, the goal of deformity control, while permitting continued growth, has been achieved in short follow-up without requiring serial operative procedures—a "game-changer" in any outcome evaluation—with the possibility of long-term single-event surgical control being accomplished, and hopefully providing enough impetus to attain timely FDA approval.
We appreciate and thank Dr. Johnston for his detailed discussion.
First, for clarification, we'd like to point out that this child's family was not negligent in seeking care for their son's spine problem. In fact, they have done due diligence to seek out all possible options for treatment with the hope of avoiding the repeated surgeries required by traditional growing rods. For this child, the parents agonized over the decision of what the best solution was for their son and considered various operative treatment options after 4 years of bracing failed. This is a dilemma many families are facing as they try to grasp the reality of the long-term commitment to provide the care needed for their child with EOS.
We agree that change (improvement) in thoracic height is a good indicator for improvement in thoracic volume and possibly pulmonary function. Although not mentioned in our original report, the pre-operative thoracic height (T1-T12) for this patient measured 122 mm. Despite having a thoracic height below the mean value for his age as suggested by Dimeglio et al,1 the patient did not have any clinical history of respiratory compromise or any other pulmonary issues. It is worth noting that the patient in this case is relatively older than the average EOS child at the time of growing rod surgery, and is much older than the patient cohort used in Karol et al's study.2 However, he still has spinal growth potential, therefore our goal is for the patient's thoracic height to reach at least 22 cm prior to "final" spinal fusion in order to minimize the chance of pulmonary compromise in the future, as described by Karol's work.
Post-operatively his thoracic height increased to 164 mm and 177 mm at the immediate post-op and latest follow up visits, respectively, with an overall improvement of 55 mm in a 3-month span. While thoracic height is expected to improve with curve correction, thoracic height improvement over time will likely depend on growth potential, maintenance of curve correction, as well as the frequency and magnitude of the non-invasive MCGR lengthenings.
We share Dr. Johnston's concern regarding the behavior of the upper thoracic curve: the curve has slightly increased from the pre-operative visit (46°) to the latest follow-up (55°). We will continue to closely monitor this in case of further curve progression.
We also agree this case presents just a small glimpse into the future of growing rod surgery. Large cohorts with long-term follow-up will certainly be needed to determine the true potential of MCGR in the surgical treatment of EOS.
1. Dimeglio A, Bonnel F, Le rachis en croissance. Springer-Verlag, Paris, 1990.
2. Karol LA, Johnston C, Mladenov K, Schochet P, Walters P, Browne RH. Pulmonary function following early thoracic fusion in non-neuromuscular scoliosis. J Bone Joint Surg Am. 2008;90(6):1272-1281.