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

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)

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

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

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 2.2cm 20kg 5 – 10 yrs 1.1cm 30kg 10 yrs – Puberty 1.8cm >30kg

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

Results 21 pts – 12 males : 9 females Diagnosis 21 pts – 12 males : 9 females Average follow up 23.4 mnths (range 6-38mths) Average no. of distractions 7.5 (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

Proximal junctional kyphosis > 10 degree difference 6 pts (28.6%) Average PJK angle 25.5 degrees (range 10.6 to 35.1) Proximal screw fixation in all cases

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

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

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)

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