1. ICEOS: Nov. 19 th – Nov. 20 th 2015 1 École Polytechnique of Montreal (Canada) 2 Sainte-Justine Research Hospital Center (Canada) 3 Faculty of Dentistry, University of Montreal (Canada) Presenting author 1,2 M ÉNARD A-L, 2 G RIMARD G, 2 L ONDONO I, 2,3 M OLDOVAN F, 1,2 V ILLEMURE I Application and Subsequent Removal of Static versus Dynamic Compression In Vivo on Rats: Effects on Bone Growth and Mineralization

2. 2 Intro M&M Results Discussion Disclosures Authors Disclosure Informationa.Consultant b.Stock/Shareholder Presenter: Anne-Laure MénardNo Relationships Co-Authors: Guy Grimard(a,b) Emovi, Inc Irène LondonoNo Relationships Florina MoldovanNo Relationships Isabelle VillemureNo Relationships Presenter: Anne-Laure MénardNo Relationships Co-Authors: Guy Grimard(a,b) Emovi, Inc Irène LondonoNo Relationships Florina MoldovanNo Relationships Isabelle VillemureNo Relationships

3. 3 Clinical context: fusionless devices & growth  Research evidence: compression & growth Growth plate: Growth modulation : compressive loading  bone growth and  growth plate height (Aronsson et al., 1999 ; Stokes et al., 2007 ; Cancel et al., 2008 ; Valteau et al., 2011; Ménard et al., 2014) Mineralization: Bone remodeling process (Wolff’s law):  with compression (Turner, 1998 ; Villemure et al. 2009)  with low intensity static compressive loading and its removal, in young chicks (Reich et al., 2005 ; Reich et al., 2008)  Compression-based fusionless devices: (Aronsson et al. 2011 ; Skaggs et al., 2013) Different sizes and shapes Application of compressive loading to growth plates Possible removal following spinal correction (Skaggs et al., 2013) Growth resumption & bone quality in young growing individuals after removing physiological loading ? Intro M&M Results Discussion

4. 4 Clinical research question 4 (*) Is the growth plate still active after loading removal ? RESEARCH QUESTION Intro M&M Results Discussion  Principle: use patient’s growth potential to correct deformities Hueter-Volkmann Compression based fusionless approaches D Fusionless device : compressive loading Growth plate (GP) Vicious cycle (Aronsson et al., 1999)  Growth Device removal (*)

5. 5 Hypothesis & Objectives 5 OBJECTIVES To assess and compare the effects of subsequently applying and removing static/dynamic compression on: (1) Growth rate (2) Growth plate height (3) Bone mineralization Intro M&M Results Discussion HYPOTHESIS Dynamic compression removal restores bone growth, and preserves growth plate height and bone mineralization, as opposed to static compression removal

6. In vivo protocol: rat tail Growth modulation Growth resumption? 28 43 53 Rat age in Days Loading (15 days) No loading (10 days) Surgery 6 Cd7 Proximal Distal Cd7 Control (n = 6) Sham (n = 6) Static (n = 6) Dynamic (n = 6) Static Compression Dynamic Compression Intro M&M Results Discussion (inspired by Walsh et al., 2004 ; Cancel et al., 2008 ; Valteau et al., 2011) Micro-loading device Calcein Dissection of 4-week group Dissection of 2-week group

7. Dissection & growth measures 7 Intro M&M Results Discussion Analyzed vertebra for growth measurements Cd6 Cd7Cd8 D 67 D 78  Collecting tissus Fluoroscopic images (5X) ΔXΔX GR = Δ X 3 ΔXΔX  Vertebral growth rate (GR)

8. Growth plate measurements 8  Bone mineralization/calcification Intro M&M Results Discussion  Growth plate height (GPH) Alizarin red staining (10X): Evaluation at the provisional calcification zone (Tsai et al., 2013) 100 μm Growth plate Toluidine blue stained images (10X) GPH

9. Growth rate 9 Static and dynamic compressions modulate bone growth similarly Summary Intro M&M Results Discussion One-way ANOVA, Tukey post-hoc comparisons, **p < 0.01 Growth rate of Cd7 [μm/day] ** 2-week group4-week group  Control Sham Static Dynamic Compression (15 days) Surgery Removal (10 days) 4-week group  20.1%  4.6% 2-week group  19.7% Stat vs Sham Dyn vs Sham  1.8%  17.9%  15.5%

10. Growth plate & mineralization 10 Intro M&M Results Discussion Static and dynamic compressions lead to similar growth plate heights. Summary Total growth plate height (Cd7) [μm] 2-week group4-week group  Control Sham Static Dynamic One-way ANOVA, Tukey post-hoc comparisons, *p < 0.05 and **p < 0.01 Average pixels intensity (Cd7) [intensity] 2-week group4-week group * 0  ** Removing compression  mineralization.

11. Discussion 11 Intro M&M Results Discussion  Bone growth resumption Observed under physiological loadings (Ohashi et al., 2002) Catch-up growth (Boersma et al., 1997 ; Lui et al., 2011) following compression removal  Limitations Only one value tested for magnitude/frequency No follow-up on same rat cohorts (in vivo MRI or microCT)  Future work Investigate biomolecular pathways (mineralization)  Growth & mineralization: no direct correlation (Wongdee et al., 2012) No proportional relationship between mineralization and growth rates Contribution of bone remodeling (influenced by mechanical loading) to mineralization in growing bones

12. Take home message 12 Intro M&M Results Discussion Static and dynamic compressions application & removal  modulate bone growth similarly Dynamic compression  greater bone mineralization Summary  Funding sources: