The idea of adjusting implants by remote control has been knocking around orthopedics for many years. Point the remote controller at the patient, press a button, gears whirl and a metal contraption begins to grow in the body. Hopefully the FCC has a special frequency bandwidth available. How awful would it be if a garage door opener triggered the device, or a cell phone? Bummer!
Today’s Growing Rod Approach
Most surgeons who are contemplating deformity correction surgery on a child are thinking about techniques that would allow the spine to grow even as the deformity is being corrected. This growing rod approach is accomplished in several steps and, therefore, several surgeries. The initial surgery puts an internal bracing system in the spine and that can usually correct the deformity by about 50%. Then the child must return every six months to have the rods “lengthened” approximately one centimeter to keep up with the child’s growth. While this is an outpatient procedure it still requires a small incision and most children wear a brace to protect the instrumentation. This approach, while helping to preserve the ability of the spine to grow, also has a high complication rate.
Anterior-posterior X-ray of a case of adolescent
idiopathic scoliosis post-fusion/
commons.wikimedia.orgAmong the strategies to avoid difficult and prolonged surgery is better diagnosis. One such technology which is showing substantial success in identifying accurately which children will require corrective surgery and which will not is the ScoliScore from Axial Biotech and JNJ’s DePuy division. ScoliScore is a predictive screening system for children which can reduce the chance of mistakenly diagnosing the kind of spinal deformity that requires surgery.
But for those children who do require surgical intervention and metal instrumentation, the idea of implants that grow as the bones grow and without additional surgery is extremely attractive.
Chiba University Remote Control System
In 1998, researchers from Chiba University’s Department of Orthopaedic Surgery (Takaso, Moriya, Kitahara, Minami, Takahashi, Isobe, Yamagata, Otsuka, Nakata, and Inoue) in Japan described an innovative system that would stretch and apply corrective pressure to structural deformities of the spine repeatedly and non-surgically. The researchers built the device and then tested it on five beagle dogs with induced scoliotic deformities.
The device, incidentally, was an expandable rod system with a built-in motor and wireless signal receiver. It had four parts to it—an outer cylinder with a rod, a small motor with a gear head, an inner gear and, finally, an expandable rod. The hooks were attached to the rod with conical sleeve.
Cobb angle measurement in scoliosis/
commons.wikimedia.orgThe rods and hooks were made of stainless steel. The implanted receiver box was made of die cast alloy and was connected to the implant with a lead wire covered with silicon. The motor with the gear head (also implanted) used a 13 mm diameter coreless direct current (DC) motor (manufactured by Maxon DC motor; Interelectric AG, Brünigstrasse, Sachseln, Switzerland).
Here is what the Chiba University researchers noticed when they turned on their tiny, implanted motor.
The signal from the controller started the implanted motor and began to change the shape of the metal rods which in turn induced a maximum distraction force of 194 N. That level of force was sufficient to correct up to 1 cm of deformity. The animals were awake and the correction was non-surgical.
The same 1 cm correction was then repeated at 6, 9, and 12 weeks after the operation. The average initial Cobb’s angle of induced scoliotic deformity was 25. After using the remote controller, the researchers were able to change Cobb’s angle to 20, then 18, 15 and finally 3. It took roughly 12 weeks to work down to a Cobb angle of 3.
Generally, a Cobb angle of 10 is regarded as the minimum angulation to define scoliosis. The “Cobb angle” is one of the most commonly used methods for quantifying spinal deformity.
Every correction that the researchers induced using their remote controller was performed without a single incision apart from the original surgery and there were no apparent complications from using the controller.
MAGEC
We were reminded of this intriguing 10-year-old Japanese study when we saw the news that Ellipse Technologies (Irvine, California) had presented data regarding their remote control system for spine patients at last week’s 3rd International Congress on Early Onset Scoliosis and Growing Spine Meeting in Istanbul.
Dr. Gregory Mundis of the San Diego Center for Spinal Disorders, La Jolla, California, presented Ellipse’s data. His paper was titled “Innovation in Growing Rod Technique; Study of Safety and Efficacy of Remotely Expandable Rod in Animal Model”. Co-authors were Behrooz Akbarnia, M.D., Pooria Salari, M.D., and Burt Yaszay, M.D.
Ellipse’s system is called the Magnetic Expansion Control system or MAGEC. The system also uses a remote controller to distract the spine.
During a series of routine outpatient visits, Dr. Mundis and his fellow physicians dynamically adjusted the implanted instrumentation with, according to Dr. Mundis, accurate and controlled distraction. The researchers used a remote controller to activate an expandable rod in the patient.
In a press release from Ellipse, the study’s principal investigator Dr. Akbarnia said, “Ellipse has developed a truly remarkable technology that will dramatically advance the treatment of spinal deformity, and significantly improve the otherwise traumatic experience these young children currently endure with multiple surgeries. The MAGEC device has exceeded my expectations for what I had hoped to someday witness during my clinical research career.”
MAGEC for Europeans
In November, Ellipse received the CE Mark (Conformité Européenne) for its MAGEC technology which means that it is now available to several thousand of OUS spine surgeons for the treatment of spinal deformity. Ellipse has filed numerous patent applications for the use of the MAGEC Technology for a broad range of clinical applications.
But clearly, its first indications are for spinal and orthopedic trauma applications.
MAGEC’s technology is based on using a nitinol wire spring as a form of a motor. Nitinol is an interesting composite metal that can change shape when energy is applied to it. The expandable wire is wrapped around the spine rods and when magnetic force is delivered using the remote controller, the rods move. Specifically, they slide using a pair of sleeves at the opposing ends so they can, in effect, “grow.”
The key is that this new technology is capable of non-invasively adjusting implants within the human body from outside the body via remote control. With this, a physician can dynamically adjust the implanted spine rods as an outpatient activity.
Ellipse Technologies, Inc. is based in Irvine, California, and among its financial backers is the $1.3 billion Japan Asia Investment Co. (JAIC) which is one of the premier venture capital and private equity firms in the world and is listed on the Tokyo Stock Exchange. One, among the many, objectives of JAIC is to promote U.S.-Japan cross-border business models and which could bring U.S. technologies to Japan.
Unfortunately, Ellipse is a difficult company to reach and the paper was unavailable to read. We trust it will find its way into PubMed or PearlDiver’s database soon. Still, based on a reading of Ellipse’s patents and the history of attempts to create this kind of expandable implant, the news is encouraging. Since it is now available outside the U.S. and since the paper was presented at the International meeting, we expect to be hearing much more about this remote control adjustment device in the future.
