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Watch Professor Kenneth MC Cheung performing a remote distraction of the magnetically-controlled growing rod …


Magnetically controlled rods

A new procedure to treat scoliosis in children

Magnetically controlled growing rods are showing promise in correcting curvature in children’s spines caused by scoliosis. What makes this idea revolutionary? After initial surgery to install the device, all future adjustments are made externally. The technology shows big potential to lessen treatment risks and account for growth—both attractive benefits when working with children.


Traditional treatment for scoliosis can require implantation of a rod to straighten the spine, which is then surgically lengthened every six months or so. While this traditional scoliosis treatment is usually effective, it can demand as many as 20 surgeries to lengthen the implanted rods.

Growth friendly option

However, a novel technology has been developed with the input of a number of centers around the world and it utilizes magnetically controlled growing rods (MCGR) to correct spine curves that don’t respond to other forms of treatment.

Recent clinical trial results reveal MCGR technology shows promise in treating scoliosis in a much less invasive, growth-friendly manner, as distractions (adjustments/lengthening of the rods) are performed externally and do not require additional surgeries beyond implantation and removal.

In fact, rods are lengthened or retracted in a medical office using a handheld magnetic device in about 15 to 30 seconds at outpatient appointments. Radiographs or ultrasound images are taken before and after the distraction to measure the degree of the spinal curvature, rod distraction length and spinal length.


Developing the technology

A few companies manufacture magnetic rods, but only the product of Ellipse Technologies in California, US has been used in a multi-center study with results from their Hong Kong partner published in The Lancet in 2012.

In 2007, the Ellipse-engineers figured out how to spin a magnet inside a titanium tube from a distance using an external magnet source. This patented concept allows a surgeon to distract and/or retract a telescoping rod without the need for surgery.

Positive results

In 2008, Ellipse started working with a team of pediatric scoliosis surgeons led by Behrooz Akbarnia (US) and Hilali Noordeen (UK). The group published their results in The Bone and Joint Journal.

In 2009 Professor Kenneth Cheung (Department of Orthopaedics and Traumatology, University of Hong Kong) implanted the first device in a child with scoliosis. In late 2012, the two year outcome results of the first two early-onset scoliosis patients treated with this technology were reported in The Lancet.

The research

From November 2009 to March 2011, Professor Kenneth Cheung and the Hong Kong University spine team implanted magnetic rods into five patients and followed up with monthly outpatient appointments.

At the two year follow-up examination for the first two implantations, the expected amount of distraction measured similar to the actual amount of distraction in both patients. Neither of the patients reported any pain or discomfort, and they both reported positive function and satisfaction with the results.

A multi-centre report of 14 patients treated with the magnetic device by Dr Akbarnia and his colleagues noted that partial distraction loss was observed following 14 of the 68 distractions but was regained in subsequent distractions. There was no neurologic deficit or implant failure. They concluded the preliminary results indicate the magnetic rods are safe and provide adequate distraction.

The UK group had similar results with the MCGR technology in their 34 early onset scoliosis cases and when speaking with AOSpine Spotlight Dr Noordeen shared some unpublished facts that he feels highlights the benefits of MCGR in patients with neuromuscular disorders. “Quite a few of our neuromuscular patients were not suited for the conventional process. After discussions with a multidisciplinary team we decided that these 5-6 year olds with spinal muscular atrophy could only be subjected to one surgery. With MCGR rods we were able to improve their respiratory function in a statistically significant way, by about 35%.”

Is it worth the cost?

While the overall results were positive, Dr Dino Samartzis, co-author of the Hong Kong study, notes that the magnetic rods may not fully distract as desired after the initial lengthening. “We are currently addressing this observation and its determinants. However, we are not convinced that this is a deleterious event, but could perhaps be a fail-safe mechanism of the body to prevent excessive distraction and remain within normal, comfortable limits.”

There is also the concern about cost; the magnetic rods are more expensive than traditional rods (USD$6200 vs $3200). Yet Dr Noordeen suggests that when compared to the traditional method the device pays itself back if you avoid even one additional surgery. “You save the cost of additional distraction surgeries and the cost of complications is huge. In the end you are saving a lot of money.”

An indication of the cost effectiveness of the technology, despite higher upfront costs, is that most of the UK Trust has started using it. According to Dr Noordeen, just about every UK center uses it.

Overall, the potential health care cost savings provided by magnetic rod technology are enormous. "An estimation of this is difficult to determine because health-care costs vary between cities and countries,” says Dr Samartzis. “However, monthly distraction of the magnetic rods takes only a few seconds during a clinical visit, whereas distraction of the traditional growing rods entails frequent surgery and hospitalization for several days, necessitating general anesthesia, spinal cord monitoring, pain medication, manpower, consumables and time off of work for the parents.”

Distraction philosophies

There are different distraction philosophies in the UK and Hong Kong: Dr Noordeen distracts to the maximum possible every 3 to 6 months and the Hong Kong group makes patient specific calculations that guide monthly distractions. Regardless of the approach, both groups have seen positive results.

The switch from distraction surgery to seconds of in-office magnetic manipulation has impacted at least one doctor’s clinical practice. Dr Noordeen explains: “I used to have full days of patients requiring distraction surgery. Now they come to my office and in 15-20 seconds are finished. It is fast and well tolerated. As a result I have more time to do some of my more complex cases.”

From X-ray to ultrasound

The major disadvantage to the magnetic rods is the monthly X-ray exposure to document the degree of magnetic rod distractions. However, the Hong Kong researchers have developed a novel technique of ultrasonography, which has no ionizing radiation exposure, to assess the degree of rod lengthening.
Initial studies assessing the technology and its reliability have been very promising and as such may eliminate the use of frequent X-ray exposure in these patients. The results on the use of ultrasonography were presented at the 2013 Global Spine Congress in Hong Kong.

Hope for the future

There has been significant surgeon interest in MCGR. Currently, the US Food and Drug Administration (FDA) clearance is being sought to allow the use of this technology in the United States (Last month they granted Compassionate use to use magnetic rods on two patients).

Although the initial results are promising, larger and long-term studies are needed to assess its efficacy and potential complications. However, the use of magnetic rods represents a tremendous leap forward in the management of young children with severe scoliosis, providing new hope and improved outcomes compared to traditional methods.



Hong Kong results (Lancet)


Patient 1
(female, Ehlers-Danlos syndrome)

Patient 2
(female, early-onset idiopathic scoliosis)

Follow-up period

24 months

24 months

Age at implantation

(single rod)

(dual rod)

Baseline height

111.6 cm (3'6")

130 cm (4'3")

Height 24 months post-op

125 cm (4'1")

142.7 cm (4'8")

Baseline arm span

100.4 cm (3'4")

130 cm (4'3")

Arm span 24 months post-op

109.5 cm (3'7")

143 cm (4'8")

Baseline Cobb angle



Cobb angle 24 months post-op



Increase in rod length at each distraction

1.4 mm

1.9 mm for right rod
1.7 mm for left rod

Timing of distractions

Every 30 days

Every 30 days


minor postoperative wound infection treated with antibiotics






Source: Cheung KM, Cheung JP, Samartzis D et al (2012) Magnetically controlled growing rods for severe spinal curvature in young children: a prospective case series. Lancet; 379(9830):1967-1974.




UK results (Bone & Joint Journal)


34 children, early onset scoliosis

Follow-up period

12 – 18 months (mean 15)

Age at implantation

5 – 12 (mean 8)

Rod configuration

22 – dual rod; 12 single rod

Baseline Cobb angle

46° to 108°(mean 69°)

Cobb angle post-op

28° to 91° (mean 47°)

Cobb angle at final review

27° to 86° (mean 41°)

Number of distractions

3 – 6 (mean 4.8)

Timing of distractions

Every 3-6 months


Superficial wound infection (2)
Loss of distraction (2)
Rod breakage (2) 1 dual, 1 single rod
Hook pullout (1) dual rod
Developed prominent metalwork (1) dual rod


Source: Dannawi Z, Altaf F, Harshavardhana NS, et al (2013) Early results of a remotely-operated magnetic growth rod in early-onset scoliosis. Bone Joint J; 95-B(1):75-80.



Cheung KM, Cheung JP, Samartzis D et al. (2012) Magnetically controlled growing rods for severe spinal curvature in young children: a prospective case series. Lancet; 379(9830):1967-1974.
Akbarnia BA, Mundis GM Jr, Salari P, et al (2012) 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); 37(13):1109-1114.
Dannawi Z, Altaf F, Harshavardhana NS, et al (2013) Early results of a remotely-operated magnetic growth rod in early-onset scoliosis. Bone Joint J; 95-B(1):75-80.
Akbarnia BA, Cheung K, Noordeen H, et al (2011) Next Generation of Growth-Sparing Technique: Preliminary Clinical Results of a Magnetically Controlled Growing Rod (MCGR) in 14 Patients With Early Onset Scoliosis. The 18th International Meeting on Advanced Spine Techniques (IMAST). In Final Program of 18th IMAST; p. 93-94, Paper no. 75.

Professor Kenneth Cheung

Interview: Professor Kenneth Cheung
AOSpine Spotlight spoke with Professor Kenneth Cheung of the Queen Mary University Hospital in Hong Kong and lead author of the Lancet magnetic growth rod study.

What has been your experience so far with this magnetic rod technology?
So far we have done 12 cases and being able to remotely lengthen the rod without doing open surgery has been a very positive experience for patients. In the past we were getting the patient back every six months and there always seemed to be a good reason to delay; it was never a good time to operate. The relative ease of use of this rod means we can apply it to more and more patients.


So far what have been the biggest risk factors?
In a few cases the rod has not responded as we have anticipated. We are working with the manufacturer on this and hopefully in time will have some better answers about this problem.


Who is the ideal patient for this technology and how do they react when learning about it?
I think the ideal patient is under 10 years old with early onset progressive scoliosis that can not be controlled by bracing or any other means. Patients so far have responded favorably and parents like that this option allows the spine of their child to continue to grow. We do not have many problems getting patients to accept the idea.


Could this be used on other conditions aside from scoliosis?
It could also be a way to overcome very severe deformities. We have done one case of severe deformity where the child had a 110 degree curve. Traditionally he would have undergone a XXinsert procedure nameXX, which is a dangerous procedure where the spine is chopped up and realigned. Instead, we were able to slowly distract the spine over two months and correct the curve a lot more safely.


There were concerns about the use of X-rays with this technology…
Yes, concerns had been expressed that when we distract the rods we would do X-rays to see if it was working properly. With monthly appointments for years, that adds up to a lot of X-rays for a child. In the past six months we have been experimenting with using ultrasound and we have completely perfected this technique and no longer use X-rays.


Kenneth MC Cheung MBBS(UK), MD (HK), FRCS, FHKCOS, FHKAM(Orth)
Jessie Ho Professor in Spine Surgery
Head of Department
Department of Orthopaedics & Traumatology
The University of Hong Kong



"Magnetic rods: Accepted in Europe, US approval still pending..."

InSpine spoke with Behrooz A Akbarnia, MD, co-researcher and professor of orthopedic surgery at the University of California, San Diego, USA


You are the Principle Investigator for the multi-centre, international clinical trial assessing the safety and efficacy of these magnetic growing rods. What is the status of this project ?
The study has been completed and the results show that magnetically controlled growing rods (MCGR) - in this case the MAGEC product - are as effective as traditional growing rods (TGR) in correcting scoliosis deformity, but with fewer repeated surgical procedures.


This instrumentation is not currently approved by the U.S. Food and Drug Administration. What will it take to obtain approval? How long is that process?
The approval process for any pediatric device in US is complex because right now there exists no standards for approval. There are efforts by the Pediatric Orthopaedic Society and Scoliosis Research Society, who formed a task force to work with the FDA, and other governing bodies, to develop these standards. The only device approved in the US is VEPTR. It took 17 years for approval. However, the device is CE marked (compliant with European legislation), so it is available in most European countries. It is also available in Hong Kong, New Zealand, Israel and some other countries.


Growing Spine Foundation
Behrooz A Akbarnia is also the president and founder of Growing Spine Foundation, which supports the Growing Spine Study Group, an international research group working to study and improve the care of young children with Early Onset Scoliosis, which also organizes a yearly congress covering this topic.







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