title: The effect of load obliquity on the strength of locking and nonlocking constructs in synthetic osteoporotic bone.
abstract: The biomechanical performance of internal fracture fixation depends on several factors. One measure of performance is the strength of the construct. The objective of this biomechanical study was to identify the effect of load obliquity on the strength of locking and nonlocking plate and screw constructs. For this study, plates and screws were fixed to synthetic osteoporotic bone that had a 1 mm thick synthetic cortical shell. An 8-hole, 3.5 mm thick hybrid plate was fixed with either two 3.5 mm major diameter locking screws or two 4.0 mm major diameter cancellous screws. Forces were applied at 0, 45, and 90 degrees to the plate normal. Eight specimens were loaded to failure for each group. When loads were applied normal to the plate, the nonlocking construct failed initially at higher loads (123.2 ± 13.2 N) than the locking construct (108.7 ± 7.6 N, P = 0.020). For oblique loads, the locking construct failed at higher mean loads but the difference of means was not statistically significant (167.7 ± 14.9 N compared to 154.2 ± 9.4 N, P = 0.052). For loads parallel to the plate, the locking construct was much stronger than the nonlocking construct (1591 ± 227 N compared to 913 ± 237 N, P < 0.001). Stiffness and Energy outcomes are also compared.
authors.affiliation: Department of Orthopaedic Surgery, Western Michigan University Homer Stryker M.D. School of Medicine, 1000 Oakland Drive, Kalamazoo, MI 49008, USA. Electronic address: Daniel.Tensmeyer@gmail.com.
authors.forename: Daniel F
authors.initials: DF
authors.lastname: Tensmeyer
authors.affiliation: Department of Orthopaedic Surgery, Western Michigan University Homer Stryker M.D. School of Medicine, 1000 Oakland Drive, Kalamazoo, MI 49008, USA; Western Michigan University College of Engineering and Applied Sciences, 1903 West Michigan Avenue, Kalamazoo, MI 49008-5343, USA. Electronic address: Peter.Gustafson@wmich.edu.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Gustafson
authors.affiliation: Western Michigan University College of Engineering and Applied Sciences, 1903 West Michigan Avenue, Kalamazoo, MI 49008-5343, USA; Saint Alphonsus Coughlin Foot & Ankle Clinic, 1055 N. Curtis Road, Boise, ID 83706, USA. Electronic address: JRJast@gmail.com.
authors.forename: James R
authors.initials: JR
authors.lastname: Jastifer
authors.affiliation: Western Michigan University College of Engineering and Applied Sciences, 1903 West Michigan Avenue, Kalamazoo, MI 49008-5343, USA. Electronic address: Bipin.Patel@wmich.edu.
authors.forename: Bipin
authors.initials: B
authors.lastname: Patel
authors.affiliation: Department of Orthopaedic Surgery, Western Michigan University Homer Stryker M.D. School of Medicine, 1000 Oakland Drive, Kalamazoo, MI 49008, USA. Electronic address: Joseph.Chess@med.wmich.edu.
authors.forename: Joseph L
authors.initials: JL
authors.lastname: Chess
mesh_terms: D001696:Biomechanical Phenomena; D001860:Bone Plates; D001863:Bone Screws; D018786:Bone Substitutes; D004548:Elasticity; D004867:Equipment Design; D019544:Equipment Failure Analysis / Q000295:instrumentation / Q000379:methods; D006801:Humans; D010024:Osteoporosis / Q000601:surgery*; D011475:Prosthesis Failure
chemical_list: D018786:Bone Substitutes
keywords: Biomechanics; Locking compression plate; Locking screws; Non-locking screws; Osteoporotic bone