Masters Technique: MdGRs
[Magnet driven Growing Rods]
Mr. MH Hilali Noordeen
MA, FRCS(Tr & Orth)
Consultant Spinal Surgeon
Royal National Orthopaedic Hospital and
University College of London
United Kingdom
Magnet driven Growing Rods (MdGR)
for Early-onset Scoliosis (EOS)
Presenter:
MHH Noordeen
Co-author:
NS Harshavardhana
ICEOS annual meeting, Warsaw
20th -21st, Nov 2014
Authors Disclosure Information
K2M, Ellipse Tech & Stryker
(a, b & c)
No relationships
a. 
b. 
c. 
d. 
e. 
Grants/Research Support
Consultant
Stock/Shareholder
Speakers’ Bureau
Other Financial Support
Background: What is MdGR?
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Novel growing rod with incorporated magnet
• 
A new ‘Game changer’ in surgical management
of Early-onset scoliosis (EOS)
• 
Aim: One-off surgery eliminating the need for
repetitive anaesthesia every 4-6 months
• 
I share my experience with at least 100 MdGR
insertions over past 4½ years
Principle behind MdGR
The
Coil
Extension
in the
shaft
Rotating
Magnetic
Flux
The
Implant
inside
patient’s
limb
An external rotating magnetic field captures a powerful magnet
mounted inside the growing rod causing it to rotate in synchronisation
generating a small torque. This torque is then amplified through a
gearbox driving a power screw that telescopes and lengthens the rod.
---------------26cm ----------------
47cm
PROXIMAL
ROD
, -- 9c=m ---s , ---- 1 2 c m ---4
J
MdGR: Standard and Off-set rod
• 
• 
• 
• 
Available in 4.5 mm and 5.5 mm diameter rods
The proximal and distal rods can be bent / contoured to match the
desired (natural) curvature of the spine.
The MdGR rod is attached to the spine using standard anchors
(hooks / screws) which could be either rib or spine based
A permanent magnet in the actuator area can be non-invasively
lengthened by the External Remote Controller (ERC)
S L rod
S L R rod
The magnet is off-set in the SLR rod: Differential distraction
MdGR: Biomechanical Tests
Stronger than a standard 5.5mm Ti rod over 5m cyclical loading Withstands
up to 270N distraction force ( Eq. to 3mm gap per lengthening)
My Practice for EOS (Past)
• 
Up to yrs. ago: Used conventional growing rods for EOS
  Single & Dual sub-muscular
•  Repetitive 4-6monthly distractions: ↓ GA
• 
Law of diminishing returns: Force needed
doubled by 5th lengthening
Growth Rods: In-vivo distractive forces
700
600
500
400
VAR00
004
wt
on
N
e
16
300
200
100
0
1
2
3
4
5
6
7
8
10
number
Noordeen MHH et al, Spine 2011
Number of lengthenings
The Future of EOS Surgery: MdGR
Magic & The Magician
=
•  Embrace new technology
•  Exclusively using MdGR over past 4.5yrs
Why I use MdGR?
•  Risk of developing learning disabilities Hazard
ratio: 2.12 (95% CI: 1.26 - 3.54)
•  Highest risk: Children aged < 2 yrs.
•  Repetitive anaesthesia: Independent risk factor
after adjusting for health status
•  Time to ask: Is this preventable or inevitable ?
Health Economics: MdGR
•  Cost-utility analysis with 10 year costs projection
•  14 MdGR insertion over 4 years (2009-12)
•  Initial insertion: MdGR costs £11,000 more than CGRs
•  10 year forecast projects saving of £48,000 for MdGRs
MdGR: How do I insert them?
•  Two 2” - 3” incisions to expose
  T2-T5 (all EOS)
  L4 – S1 (EOS-NMD)
•  Prepare the sub-muscular bed
•  Insertion of anchors
 Upper (Hybrid: Spine based Hooks
& screws)
 Lower (All screws construct)
•  Testing the MdGR & appropriate sagittal contouring
Tips & Tricks I: Proximal anchors
Minarets have 7-120 outward tilt: Intentional
In event of earthquake: The central dome is protected
(minarets falling outwards)
Optical illusion: From distance - appear erect
TP Hooks: Apply laterally directed forces
In event of screw loosening, they do not migrate
medially and compress spinal cord
Proximal anchors: Two pair of pedicle screws and one pair
of TP Hooks
The Taj Mahal construct
I - MdGR distal end: Not long enough
• 
Proximal end: 26 cms & Distal end: 12 cms
•  Magnetic coil / actuator area: 9 cms
(should not be bent / contoured)
• 
In severe lumbar hyperlordosis: The
actuator should lie in thoracic spine
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Distal end: 12 cms may be too short for
anchorage (esp. if fusion to pelvis)
•  My Solution: Deliberate upside-down
insertion (make use of 26 cms)
•  Distraction: By holding in reverse fashion
MdGR: Stanmore Experience (2013)
•  World’s largest published series to this day (English)
•  My 1st MdGR insertion at GOSH in Mar 2010
•  My preferred option for Rx EOS: All cases
Case 1: Juvenile IS (single rod)
Pre-op
Post-op
After 3 distractions: 19mm
After 9 distractions: 28mm
T1-S1: 360mm
Cobb ^le – 620
T1-S1: 375mm
Cobb ^le – 470
T1-S1: 400mm
Cobb ^le – 360
T1-S1: 435mm
Cobb ^le - 320
Case 1: JIS (My 1 s t MdGR graduate)
Pre-op
9 distractions: total 28mm
3 years post MdGR insern
T1-S1: 360mm
Cobb ^le - 620
T1-S1: 435mm
Cobb ^le – 320
T1-S1: 446mm
Cobb ^le maintained at 320
Case 2: Juvenile IS (dual rod)
Pre-op
Post-op
After 5 distractions: total 19mm
T1-S1: 375mm
Cobb ^le - 620
T1-S1: 388 mm
Cobb ^le – 520
T1-S1: 415 mm
Cobb ^le - 420
Case 3 - MdGR for EOS-NMD (SMA II)
•  8/FCh with age of onset at 2yrs. Rapid progression to 880
•  Index MGR insertion at age 6yrs
•  Spectacular improvement in Cobb angle from 880 to 500
Case 3 - MdGR for EOS-NMD (SMA II)
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17mm lengthening at 18months post-op
Reduced incidence of chest infections, emergency hospital
admissions with improvement in lung function
MdGR & Pulmonary Function
Noordeen H et al 2014
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Level of Evidence (LoE): Prognostic II
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Dramatically reduced the rate of decline in pulmonary
function (statistically significant)
•  Facilitated normal developmental milestones with
improvement in quality of life
•  Fewer complications and high care giver satisfaction
MdGR & Pulmonary Function
6 patients with EOS-NMD
SMA Type II – 2
Neurofibromatosis - 2
William’s syndrome - 1
Cong muscular dystrophy – 1
MdGR & Pulmonary Function
P<0.028
• 
P<0.027
P<0.028
Box plots (SPSS v17) showing statistically significant:
Decrease in Cobb angle
Increase in both FEV1 and FVC
•  Spectacular improvement in PFT in patients with SMA-II
• 
MdGR probably arrest rapid deterioration / decline of PFT
and do NOT alter its natural history (γ error!)
MdGR: Stanmore Experience (2014)
17 patients (9♂ &
8♀ ) Mean f/u 3.35 yrs.
Follow-up range: 2.08-4.25 yrs
Single centre / single surgeon
One MdGR graduate
Etiologies
Idiopathic: 3
Neuromuscular: 7
Congenital: 2
Syndromic: 5
AAOS 2015 podium presentation
MdGR: Stanmore Experience (2014)
Patient demographics (n=17 pts)
Complications I - Rod fracture
10 yr & 3 mo old with juvenile idiopathic scoliosis: Broken single rod @ 3yrs post-op
Metal fatigue failure – Weak at actuator-rod junction
  Design modification
  Dual rods probably protective: Load sharing
Complications II - Rod fracture
Dual rod fracture at 8th post-op mo with ↓↓ in length
Break is no more at the actuator–rod junction
Complications III – Loss of distraction
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Two of my single rod MdGR pts had to wear external magnets
Index surgery in 2010 for non-dystrophic NF-1
Faulty actuator / ratchet: This has been addressed / corrected now
NICE Evidence (FDA Eq in the UK)
ISBN: 978-1-4731-0608-6
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Based on meta-analysis: From fixed and random effects model
Reduced infection rate in-comparison to CGR (p=0.03-0.04)
Similar improvement in Cobb angle and T1-S1 height gain to CGR
MdGR: NOT cost-saving if <3 yrs of remaining growth potential
NICE Position Statement (FDA Eq)
•  Evidence exists to support its use in EOS (≥2 years)
•  MdGR is cheaper than CGR (LoE Economic II)
•  MdGR breaks even at 3.25 yrs post-index insertion
•  At least ₤12,077 cost-savings at 6 yrs post-insertion
•  Particular advantage in high-risk pts (EOS-NMD)
•  Unsuitable for pts with severe kyphotic deformities
SUMMARY - I
•  EOS: Growth guided surgery is standard of care (what
growth guidance needs re-defining: MdGR vs. CGR vs.
VEPTR vs. Shilla vs. Staples)
•  I do NOT perform definitive spinal fusion for EOS
•  Understand natural history, pulmonary maturation
and life expectancy of different EOS etiologies
•  MdGR: Promising early results with favourable
cost-utility on long-term forecast analysis (10y)
SUMMARY - II
•  A new ‘game-changer’ amongst distraction based devices
in surgical treatment of EOS
•  Eliminates the need for repetitive anaesthesia
•  Has been around now for at least four years
•  Approved by NICE-UK (National institute of
clinical excellence): FDA equivalent of USA
•  Associated with improvement in PFT for EOS-NMD
My Vision for MdGRs: Research
  Multi-national collaboration with prospective cases input
  Creation of MdGR study group
  LoE II Therapeutic studies evaluating MdGRs & CGRs
  LoE I Economic studies comparing MdGRs & CGRs
  LoE I Prognostic studies for MdGRs
  Serial pre and post-op PFT in EOS-NMD
  Serial pre and post-op IQ / Cognitive tests
Limitation of MdGR
Does not address the ‘parasol’ deformity of chest
  Need for 2nd generation MdGRs that correct chest cage
in-addition to correction of spinal deformity
Thank You