Facet sparing laminectomy biomechanical comparison between Facet Sparing Laminectomy and laminectomy with facetectomy IN lumbar spine: a finite element analysis 1Elmasry, S; 1Asfour, S; 2Gjolaj, J; 3Latta, L; 2Eismont, F; +1Travascio, F 1Biomech. Research Lab, Dept. Industrial Engr., Univ. Miami, Coral Gables, FL 2Dept. of Orthop., Univ. Miami, Miami, FL 3Max Biedermann Instit. Biomech., Mount Sinai Med. Center, Miami Beach, FL Fig. 2: Intradiscal pressure of levels (L3-L4 &L4-L5) in NP and AF after flexion and axial rotation. Normalized with respect to ‘intact spine’ case. BACKGOUND Lumbar spinal stenosis (LSS): a disease of epidemic proportions in the Nation [1] is often treated by surgeries to decompress the spinal nerve. However, often after surgery, stenosis can propagate to adjacent spinal segments [2] HYPOTHESIS surgeries for LSS may change the biomechanical environment of the adjacent segments, eventually leading to adjacent segment disease (ASD) OBJECTIVE to investigate the biomechanical alterations of operated and adjacent spine levels (L3-L4 and L4-L5) occurring after performing these procedures METHODS Finite elements modeling of the lumbar spine was constructed from CT scan of a healthy male subject (Fig.1) and validated [3, 4] by using FEBio 1.8.0 (M-S Research Lab., Univ. Utah) Hybrid loading protocol was applied [5] Facet sparing laminectomy DISCUSSION: No major post-operative increase of ROM were found after lateral bending or extension. In contrast, during flexion and axial rotation, ROM significantly increased at L3-L4 (23%) and L4-L5 (28%). This is in agreement with in vitro studies [6, 7]. Both procedures entail excision of interspinous and supraspinous ligaments which withstand the highest tensile forces during spine flexion [8]. This probably increased spine range of motion at these levels, and is an indicative of spine instability. Intradiscal pressure increased in both levels after both procedures (Fig. 2) which have a negative impact on intervertebral disc metabolism, potentially leading to disc degeneration [9]. Both procedures have similar potential in undermining spine health. This is despite the fact that facetectomy, involving more reductions, is often regarded as a riskier procedure in terms of spine stability Laminectomy with facetectomy REFERENCES [1] Arbit & Pannullo Clin Orthop Relat R 384:818-825, 2001, [2] Rahm & Hall J Spinal Disord 9:392-400, 2008,[3] Lee et al., Spine 35:1789-1793, 2010, [4] Travascio et al., J Spine, 4:220, 2015,[5] Panjabi et al., Spine, 32:959-966, 2006, [6] Bresnahan et al., Spine, 34:17-23, 2009, [7] Abumi et al., Spine, 15:1142-1147, 1990, [8] Goel et al., Spine, 10:516-523, 1985, [9] Stokes & Iatridis Spine 29:2724-32, 2004. ACKNOWLEDGEMENTS: Study supported by funds donated to the Biomechanics Research Group of the University of Miami Fig. 1: Lumbar spine FE model with the performed procedures