"Turn-of-the-nut" method is not appropriate for use in cancellous bone

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dc.contributor.authorRyan, M.
dc.contributor.authorMohtar, A.
dc.contributor.authorCosti, J.
dc.contributor.authorReynolds, K.
dc.date.issued2015
dc.description.abstractObjective: The level to which bone screws are tightened is determined subjectively by the operating surgeon. It is likely that the tactile feedback that surgeons rely on is based on localized tissue yielding, which may predispose the screw–bone interface to failure. A limited number of studies have investigated the ratio between clinical tightening torque and stripping torque. The purpose of this study was to measure, for the first time, the ratio between yield torque (Tyield) and stripping torque (Tmax) during screw insertion into the cancellous bone and to compare these torques with clinical levels of tightening reported in the literature. Additionally, a rotational limit was investigated as a potential end point for screw insertion in cancellous bone. Methods: A 6.5-mm outer diameter commercial cancellous bone screw was inserted into human femoral head specimens (n = 89). Screws were inserted to failure, while recording insertion torque, compression under the screw head, and rotation angle. Results: The median, interquartile ranges, and coefficient of variation were calculated for each of the following parameters: Tyield, Tmax, Tyield/Tmax, slope, Tplateau, and rotation angle. The median ratio of Tyield/Tmax and rotation angle was 85.45% and 96.5 degrees, respectively. The coefficient of variation was greatest for the rotation angle compared with the ratio of Tyield/Tmax (0.37 vs. 0.12). Conclusions: The detection of yield may be a more precise method than the rotation angle in cancellous bone; however, bone–screw constructs that exhibit a Tyield close to Tmax may be more susceptible to stripping during insertion. Future work can identify factors that influence the ratio of Tyield/Tmax may help to reduce the incidence of screw stripping.
dc.description.statementofresponsibilityMelissa K. Ryan, Aaron A. Mohtar, John J. Costi and Karen J. Reynolds
dc.identifier.citationJournal of Orthopaedic Trauma, 2015; 29(11):e437-e441
dc.identifier.doi10.1097/BOT.0000000000000385
dc.identifier.issn1531-2291
dc.identifier.issn1531-2291
dc.identifier.urihttp://hdl.handle.net/2440/99828
dc.language.isoen
dc.publisherLippincott, Williams & Wilkins
dc.relation.granthttp://purl.org/au-research/grants/nhmrc/595933
dc.rightsCopyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
dc.source.urihttps://doi.org/10.1097/bot.0000000000000385
dc.subjectInsertion torque; yield torque; stripping torque; screw stripping; cancellous bone
dc.title"Turn-of-the-nut" method is not appropriate for use in cancellous bone
dc.typeJournal article
pubs.publication-statusPublished

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