<![CDATA[Introduction. Biomechanical construction test of posterior instrumentation for scoliosis correction is needed to evaluate reliability and instrumentation performance. Latest biomechanical testing have validated bone model as a suitable substitute. Low pedicle screw density can correct without significant complication. This study compared biomechanics of three posterior instrumentations: Bilateral Pedicle Screw (BPS), pedicle screw on proximal end, apex, distal end concave side (PAD), and PAD with sublaminar wire the concave side (PAD+SW).Method. Three groups of vertebral model of Scoliosis Lenke I Synbone® is equipped with configurations of 15 samples posterior instrumentations divided into three groups of BPS, PAD, PAD+SW. Each of the static test is given axial force gradually from 50N, 100N, 150N, and 200N using Tensilon® AMD RTF-1310 from Japan, with dial indicator Mitutoyo, Japan. Total displacement were measured for each groups. Stiffness were also analyzed using load-displacement ratio.Results. BPS as the current gold standard showed minimal displacement, followed by BPS, PAD and PAD+SAW for 50N (p<0.001), 100N (p<0.001), and 200N (p<0.001) force, and was not significant for 150N (p=0.086). There was also significant difference between the stiffness of BPS, PAD and PAD+SW for 50N (p=0.002), 100N (p<0.001), 150N (p<0.001) and 200N (p<0.001)Conclusion. For biomechanical testing with static test, type of posterior instrumentations showed significance relationship with displacement and stiffness. BPS groups were more rigid compared to PAD+SW and PAD. Low density of pedicle screw resulted in the decrease of stiffness and posterior instrumentation sublaminar wire addition significantly added the strength.Keywords: Posterior instrumentation, adolescent idiopathic scoliosis, Lenke I, In Vitro]]>
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