MAGEC Rods are not the Solution to the Paediatric Scoliotic Spine

Question 1

Teoh, 2016 literature describes how metalosis was found in how many patients with MAGEC rods?

Answer 1

4/5 patients were found to have metalosis following the implantation of MAGEC rods.

Question 2

What was discussed on the ‘Great Implant Scandal’ on BBC about the MAGEC rods?

Answer 2

It was discussed that the MAGEC rods had only been tested on pigs and dead bodies before being approved for general use in the EU. Experts also said the rods seem to snap too easily, however they are recommended by the NHS.

Question 3

What does the literature Jones 2016 ‘The Spine’ say about the MAGEC rods?

Answer 3

This piece of literature describes how there was actuator (drive) pin fracture in two cases of patients with implanted MAGEC rods.

Question 4

Newcastle Uni gets sent explanted MAGEC rods, they found grooves on the surface of the extended bar, what were these grooves like?

Answer 4

The grooves does not extend all the way around the circumference of the extending bar. They were at 180 degrees from each other

Question 5

What did they find about the seal in the explanted MAGEC rods?

Answer 5

Pieces of rubber could be seen protruding from the rod, this was part of the seal. This meant that the seal was damaged and was no longer working as intended.

Question 6

What is the function of the seal in the MAGEC rod?

Answer 6

The seal is suppose to stop the movement of fluid in or out of the MAGEC rod.

Question 7

What process takes place at Newcastle in order to analyse the MAGEC rods?

Answer 7

The rods are cut open, disassembled, and photographed. Dimensional measurements are taken and internal debris is collected and analysed by EDX.

Question 8

What is EDX?

Answer 8

Energy - Dispersive - X-ray spectroscopy

Question 9

What problems were found with the radial bearings of the MAGEC rods?

Answer 9

They were misplaced, some had no outer race, missing rolling elements.

Question 10

What problems were found in the o-ring seals of the MAGEC rods?

Answer 10

The o-ring seals were found snapped.

Question 11

What was found with the drive/actuator pin in the explanted MAGEC rods?

Answer 11

The drive/actuator pin was found snapped.

Question 12

How do Newcastle Uni define ‘broken’ rods?

Answer 12

They define a broken rod as having either:
A) Non-functioning internal bearing (so the magnet would struggle to rotate)
B) Obvious seal damage (so bodily fluids could get into the rods and any internal wear debris could escape)
C) Broken drive pin (so MAGEC rod might not grow)
D) Internal wear debris

Question 13

They assessed the damage of 34 explanted MAGEC rods, and what were the results?

Answer 13

• 25 were found to have non-functioning internal bearing
• 18 were found to have badly damaged seals
• 15 had fractured drive pins
• 34 had internal wear debris

Question 14

What were the results from the EDX analysis of the debris?

Answer 14

The EDX showed that the majority of the debris was made up of titanium.

Question 15

What is the most common medical grade of titanium?

Answer 15

Ti6AI4V, made up of 6% aluminium and 4% vanadium.

Question 16

What did analysis into why the MAGEC rods fail yield?

Answer 16

It found that there is off axis loading in vivo, this makes sense as the spine is not completely straight. This off axis loading causes the rigid extending bar to contact the internal surface of the outer casing on one side only. This was creating a mark on the surface. As the rods grow, this mark is then repeated. The other end of the extending bar impinges on the internal surface and wears on one side only at 180 degrees to the first.

Question 17

How else was it confirmed that the off axis loading was taking place?

Answer 17

It could be shown on x-rays of patients, 4 years after implantation. A gap could also be seen on one side of the rods in another x-ray, indicating off axis loading.

Question 18

What may have caused the seal to break?

Answer 18

It could be affected by the off axis loading.

Question 19

What could be caused if the seal is broken and debris leaks out?

Answer 19

This could cause metalosis

Question 20

What is metalosis?

Answer 20

This is the black staining of soft tissue of the body due to the deposition/build up of metal debris.

Question 21

Newcastle Uni published an article called ‘Analysis of Explanted Magnetically Controlled Growing Rods from Seven UK Spinal Centres’, what was special about this literature?

Answer 21

This had the largest number of MAGEC rod explants collection reported in scientific literature to date.

Question 22

49 explanted rods were analysed at Newcastle uni, seeing what percentage of MAGEC rods produce less force than when new. What were the results?

Answer 22

• 32 had zero force output
• 7 had reduced force output
• 10 had expected force output

Question 23

How long had the explants at Newcastle been implanted for on average?

Answer 23

3 years (36months)

Question 24

What were some of the limitations to the analysis done on MAGEC rods at Newcastle?

Answer 24

• They do not know how man rods had been implanted in total so cannot calculate overall success rates.
• Newcastle do not have access to full clinical data as the manufacturers do not give this information for commercial in confidence.

Question 25

What are the estimates for how many pairs of MAGEC rods have been implanted ?

Answer 25

The British Spine Registry is nascent, but estimates are of 140 MAGEC rod pairs implanted per year, estimates by NICE.

Question 26

What is the manufacturer of the MAGEC rods called?

Answer 26

Nuvasive