1. Incidence of Proximal junctional kyphosis with Magnetic Expansion Control Rods in early onset scoliosis
P Inaparthy, JC Queruz, C Thakar, D Rolton, C Nnadi
Oxford University Hospitals

2. Introduction
High rates of complications reported with traditional growing rod techniques for Early Onset Scoliosis (EOS)
Bess et al (JBJS Am 2010)
Akbarnia et al (spine 2008)
Proximal junctional kyphosis (PJK) – a well recognised complication in deformity correction
But very little literature available on PJK with growing rods for EOS
Shah et al (2014), Watanabe et al (2014)
No literature on PJK with magnetic growing rods (MCGR)

3. Aim
To report on the incidence of PJK following treatment with magnetic growing rods in EOS
Evaluate whether Tail Gating results in reduced incidence of PJK compared to previous reports

4. Material and Methods Prospective cohort observational study
Over 3 years – 2011 to 2014
Inclusion criteria
Pts whom the surgeon felt would benefit from the use of the magnetic rods
Had a minimum of 2 lengthening procedures

5. METHODS TAIL GATING TECHNIQUE USING ANNUAL GROWTH VELOCITY T1 - L5 (Dimeglio)
Curves of growth velocity
‘Maximum’ distraction with conventional GR
‘Law of diminishing returns’
Skaggs et al Spine 2011
‘Tail-gating’ concept to shadow growth
Spine in EOS does have growth potential
Magec rods allow for controlled distraction
Apply knowledge of expected growth
Less force on construct = less risk of failure
‘Scientific approach’ 10 5 15 2 1
Annual growth velocity T1-L5.
Distraction of the spine must take into consideration this figures.
Birth – 5 yrs cm 20kg
5 – 10 yrs 1.1cm 30kg
10 yrs – Puberty 1.8cm >30kg

6. 3 lateral-view standing radiographs
METHODS
3 lateral-view standing radiographs
Pre-op
After index MCGR rod surgery (prior to the first formal lengthening)
The latest follow-up
Evaluation by 2 authors

7. Results 21 pts – 12 males : 9 females
Diagnosis
21 pts – 12 males : 9 females
Average follow up mnths (range 6-38mths)
Average no. of distractions (range 2-12)
Proximal fixation (Screws (20 pts) and hooks (1 pt))
No returns to theatre for PJK
Idiopathic scoliosis 3
Visceral associations 3
Central core myopathy 2
Neuromuscular(1), Hemivertebra(1), Arthrogryposis(1)
Syndromic 10

8. Proximal junctional kyphosis
> 10 degree difference 6 pts (28.6%)
Average PJK angle degrees (range 10.6 to 35.1)
Proximal screw fixation in all cases

9. Levels of instrumentation
PJK Cases
Levels of instrumentation
Pre-op kyphosis
Immediate post-op
Last follow-up
PJK 1
T3,4 and L4,5
19.1
14.8
43.3
24.2 2
17.4
23.6 44
26.6 3
8.6
21.3
43.7
35.1 4
T3,4,5 and L4,5
20.2
17.1
48.6
28.4 5
T3,4 and L4,5S1
3.4
24.5
31.8 6
T3,4 and T11,12,S1
7.8
18.5
18.4
10.6

10. Pre-op thoracic kyphosis
PJK Demographics
Non-PJK pts
PJK Pts
No. of pts 15 6
Avg. age
8.4 yrs
5.3 yrs
Avg. follow up
21.1 mths
32.5 mths
Male: female
4:3
2:1
Syndromic
10 out of 21
All 6
Pre-op thoracic kyphosis
47.3 deg
52.5 deg
No. of distractions
6.3
10.5

11. Conclusion Associations identified: Syndromes
Higher incidence in males (4/6)
Younger age group (5.3 years)
Higher number of distractions in the PJK group
Pre-operative hyper kyphosis (average 52.5 degrees)

12. Conclusion
Lesser incidence of PJK in our group compared to other studies using traditional growing rods
Shah et al (spine 2014) = 45% (all screw construct)
Watanabe et al (spine 2014) = 26% (but baseline of 20 deg compared to 10 deg in our group)
Incremental distraction using the Tail gating technique appears to reduce incidence of PJK