1、Bridge vs. Tension Band Construct for Spinal Fractures Fixation: A Biomechanical Analysis,C. Richards, J. Ouellet, M. Fouse, N. Noiseux, P. Jarzem, R. Reindl, D. Giannitsios, T. Steffan,ORTHOPAEDIC RESEARCH LABORATORY Division of Orthopaedic Surgery, McGill University,Problem,Traditional pedicle scr
2、ew instrumentation: Parallel to endplateKyphotic collapse is a known complicationRisk of posterior pullout if not supported anteriorly,Hypothesis,For spinal fracture fixation bridge-type fixation = divergent screwsvs. tension-band = parallel screwsSignificantly stiffer Better resistance to failure i
3、n kyphosis Better resistance to screw pull-out,Hypothesis,Hypothesis,Purpose,Bridge vs. Tension Band Constructs Construct stiffness Ultimate failure load,Stiffness,Ultimate Failure Load,Materials and Methods,Finite Element Analysis of ASTM Polyethylene Constructs,Methods and Materials,Finite Element
4、 Analysis of ASTM Polyethylene Constructs Mechanical testing of ASTM Polyethylene Construct,Methods and Materials,Finite Element Analysis of ASTM Polyethylene Constructs Mechanical testing of ASTM Polyethylene Construct Mechanical testing of Cadaveric Constructs,ASTM Corpectomy Model,UHMWPE blocks W
5、orst case scenario for vertebral body fracture Followed precisely for T-B Constructs Pedicle screws inserted parallel to horizontal plane,ASTM Corpectomy Model,Altered for Bridge Constructs Change in pedicle screw orientation w.r.t. horizontal plane 16.5 superiorly 26.4 inferiorly,Finite Element Ana
6、lysis,Linear FEA 3-D models of ASTM constructs Mechanical properties of polyethylene and titanium,Finite Element Analysis,Models loaded at 100N, 300N, & 600N Displacement data generated for each load,Polyethylene Construct,6 constructs built 3 TB 3 Bridge Constructs loaded using MTS Load and displac
7、ement data generated,Cadaveric Constructs,6 male cadavers dissected 3 Matched pairs based on Vertebral body size and BMD instrumented T11-L1 3 TB Construct 3 Bridge Construct,#2 Osteotome,Cadaveric Constructs,Potted in PMMA Anterosuperior endplate of superior vertebra free Anteroinferior endplate of
8、 inferior vertebra free,Cadaveric Constructs,Loaded using MTS Load and displacement data generated,Results Stiffness (N/mm),34.1,21.6,17.3,20.6,15.2,18.4,FEA,Polyethylene,Cadavers,p=0.015,p=0.012,Results Ultimate Failure Load,419,622,p=0.076,Results,All specimens were evaluated for accuracy and safe
9、ty of schanz screw insertion Maximum angles as determined by the anatomic study were achieved No breech of pedicle wall,Results,Pattern of Failure Tension Band Construct All 3 constructs failed into kyphosis Screw pullout at the pedicle-body junction,Results,Pattern of Failure Bridge Construct 2/3 c
10、onstructs failed Screw pullout at the pedicle-body junction Screw pullout through superior endplate,Discussion,Increased stiffness Better protection of anterior column Allows better potential for healing Decrease risk of kyphotic failure,Conclusions,Bridge Construct is significantly stiffer than the
11、 Tension Band Construct Ultimate failure load was 50% greater for the Bridge Construct Further Cadaveric testing is required and is ongoing,Thank You,C. Richards, J. Ouellet, M. Fouse, N. Noiseux, P. Jarzem, R. Reindl, D. Giannitsios, T. Steffan,ORTHOPAEDIC RESEARCH LABORATORY Division of Orthopaedic Surgery, McGill University,
