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Effect of cortical thickness and cancellous bone density on the holding strength of internal fixator screws
Author(s) -
Seebeck J.,
Goldhahn J.,
Städele H.,
Messmer P.,
Morlock M. M.,
Schneider E.
Publication year - 2004
Publication title -
journal of orthopaedic research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.041
H-Index - 155
eISSN - 1554-527X
pISSN - 0736-0266
DOI - 10.1016/j.orthres.2004.04.001
Subject(s) - cancellous bone , cortical bone , internal fixation , materials science , fixation (population genetics) , bending , cantilever , orthodontics , biomedical engineering , biomechanics , osteoporosis , flexural strength , bone density , composite material , anatomy , medicine , population , environmental health , endocrinology
Internal fixators are a new class of implants designed to preserve the periosteal blood supply of the bone. In contrast to conventional plate fixation in which the screws have spherical heads and are loaded mainly by axial pullout forces, screws in internal fixators are “locked” within the plate and therefore subjected to axial as well as bending loads. In this study the ultimate loads of screws of a commercially available internal fixator system were tested in a pullout ( n = 72) and cantilever bending mode ( n = 72) in metaphyseal and diaphyseal regions of four pairs of human tibiae with different bone qualities. Cortical thickness and cancellous bone density were determined at the screw insertion sites. Stepwise multiple linear regression revealed that cortical thickness and cancellous density can explain 93% and 98% of the variance of the ultimate load of the screws in an axial pullout and cantilever bending mode. Screws in internal fixators are better suited to transmit shear forces and thereby make better use of the strength potential of bone than screws used in conventional plate fixation: this is especially advantageous when bone strength is reduced, e.g. due to osteoporosis. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.