1. Copyright © 2015 Lippincott Williams & Wilkins. Unauthorized commercial reproduction of this slide is prohibited Supplemental PowerPoint Slides Analysis of retrieved growth guidance sliding LSZ-4D devices for early onset scoliosis and investigation of the use of Nitinol rods for this system Elena Lukina1,2, MSc, Mikhail Kollerov2, PhD, Jay Meswania3, PhD, David Wertheim1, PhD, Peter Mason1, PhD, Paul Wagstaff1, MSc, Aleksandr Laka4, PhD, Hilali Noordeen FRCS (Tr & Orth)5, Wai Weng Yoon FRCS (Tr & Orth)5, Gordon Blunn3 PhD 1 – Kingston University London, UK elenaalukina@rambler.ru and K1067803@kingston.ac.uk 104 Roehampton Vale, SW15 3RX 2 – “MATI”-RSTU, Russia 3 – University College London, UK 4 – Russian University of Peoples’ Friendship, Moscow, Russia 5 – Royal National Orthopedics Hospital, UK

2. 2 Results: The volume wear rate for the retrieved LSZ- 4D device is12.5 mm 3 per year from which 5mm 3 per year is the rods contribution and 7.5 mm 3 per year is the contribution of fixtures Volume wear loss of retrieved growth guidance sliding device LSZ- 4D for Early Onset Scoliosis treatment LSZ-4D sliding device Locked fixtures are locked on one level; other fixtures are unlocked, thus enabling sliding Material of rods and fixtures: Ti6Al4V Methods: Volume wear loss of LSZ-4D device components retrieved from 3 patients (average implantation time 4.3 years) were measured using interferometric images of wear scars processed in MATLAB software

3. 3 Results: Wear resistance of Nitinol tested against titanium alloy Ti6Al4V in the simulated body environment is 100 times higher compared to titanium alloy Ti6Al4V and comparable to that of Cobalt Chromium alloy Investigation of Nitinol wear resistance in biological environment for revealing its potential to replace Ti rods in spinal devices Methods: Wear resistance of Nitinol, Ti6Al4V and CoCr (all tested against Ti6Al4V counter- face) were compared using in-vitro pin-on-disk wear test: Reciprocating sliding movement; Frequency 1Hz; Diluted bovine serum; T= 37±1 O C

4. 4 Limitations of the study:  Only 3 retrieved implants have been investigated in our study.  Nevertheless, it was shown that the in-vitro wear tests are able to replicate wear damage mechanisms and the shape and size of wear particles isolated from tissues adjacent to LSZ-4D implants. This made it possible to compare the wear performance of Nitinol, which might be a prospective material for spinal instrumentation in the future with metal materials which are currently used.  However, further in-vivo testing of Nitinol performance would be necessary for its safe application. Conclusions:  Application of wear resistant coatings on Ti components in growth guidance sliding devices for treatment of early onset scoliosis will be useful.  High wear resistance of Nitinol combined with its superelastic and shape memory properties could make application of Nitinol rods for spinal instrumentation beneficial.