The influence of the insertion technique on the pullout force of pedicle screws: An experimental study

Chatzistergos, PE; Sapkas, G; Kourkoulis, SK

dc.contributor.author	Chatzistergos, PE	en
dc.contributor.author	Sapkas, G	en
dc.contributor.author	Kourkoulis, SK	en
dc.date.accessioned	2014-03-01T01:34:46Z
dc.date.available	2014-03-01T01:34:46Z
dc.date.issued	2010	en
dc.identifier.issn	0362-2436	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/20843
dc.subject	Insertion technique	en
dc.subject	Pedicle screw	en
dc.subject	Pullout force	en
dc.subject	Self tapping	en
dc.subject.classification	Clinical Neurology	en
dc.subject.classification	Orthopedics	en
dc.subject.other	polyurethan foam	en
dc.subject.other	article	en
dc.subject.other	cancellous bone	en
dc.subject.other	force	en
dc.subject.other	osteoporosis	en
dc.subject.other	pedicle screw	en
dc.subject.other	priority journal	en
dc.subject.other	pullout force	en
dc.subject.other	self tapping insertion	en
dc.subject.other	surgical technique	en
dc.subject.other	Bone Screws	en
dc.subject.other	Equipment Design	en
dc.subject.other	Equipment Failure Analysis	en
dc.subject.other	Internal Fixators	en
dc.subject.other	Materials Testing	en
dc.subject.other	Stress, Mechanical	en
dc.subject.other	Tensile Strength	en
dc.title	The influence of the insertion technique on the pullout force of pedicle screws: An experimental study	en
heal.type	journalArticle	en
heal.identifier.primary	10.1097/BRS.0b013e3181ba0b0c	en
heal.identifier.secondary	http://dx.doi.org/10.1097/BRS.0b013e3181ba0b0c	en
heal.language	English	en
heal.publicationDate	2010	en
heal.abstract	Study Design: The pullout strength of a typical pedicle screw was evaluated experimentally for different screw insertion techniques. Objective: To conclude whether the self-tapping insertion technique is indeed the optimum one for self-tapping screws, with respect to the pullout strength. Summary of Background Data: It is reported in the literature that the size of the pilot-hole significantly influences the pullout strength of a self-tapping screw. In addition it is accepted that an optimum value of the diameter of the pilot-hole exists. For non self-tapping screw insertion it is reported that undertapping of the pilot-hole can increase its pullout strength. Finally it is known that in some cases orthopedic surgeons open the threaded holes, using another screw instead of a tap. Methods: A typical commercial self-tapping pedicle screw was inserted into blocks of Solid Rigid Polyurethane Foam (simulating osteoporotic cancellous bone), following different insertion techniques. The pullout force was measured according to the ASTM-F543-02 standard. The screw was inserted into previously prepared holes of different sizes, either threaded or cylindrical, to conclude whether an optimum size of the pilot-hole exists and whether tapping can increase the pullout strength. The case where the tapping is performed using another screw was also studied. Results: For screw insertion with tapping, decreasing the outer radius of the threaded hole from 1.00 to 0.87 of the screw's outer radius increased the pullout force 9%. For insertion without tapping, decreasing the pilot-hole's diameter from 0.87 to 0.47 of the screw's outer diameter increased its pullout force 75%. Finally, tapping using another screw instead of a tap, gave results similar to those of conventional tapping. Conclusion: Undertapping of a pilot-hole either using a tap or another screw can increase the pullout strength of self-tapping pedicle screws. © 2010, Lippincott Williams & Wilkins.	en
heal.publisher	LIPPINCOTT WILLIAMS & WILKINS	en
heal.journalName	Spine	en
dc.identifier.doi	10.1097/BRS.0b013e3181ba0b0c	en
dc.identifier.isi	ISI:000277223900015	en
dc.identifier.volume	35	en
dc.identifier.issue	9	en
dc.identifier.spage	E332	en
dc.identifier.epage	E337	en