title: Time-elapsed screw insertion with microCT imaging.
abstract: Time-elapsed analysis of bone is an innovative technique that uses sequential image data to analyze bone mechanics under a given loading regime. This paper presents the development of a novel device capable of performing step-wise screw insertion into excised bone specimens, within the microCT environment, whilst simultaneously recording insertion torque, compression under the screw head and rotation angle. The system is computer controlled and screw insertion is performed in incremental steps of insertion torque. A series of screw insertion tests to failure were performed (n=21) to establish a relationship between the torque at head contact and stripping torque (R(2)=0.89). The test-device was then used to perform step-wise screw insertion, stopping at intervals of 20%, 40%, 60% and 80% between screw head contact and screw stripping. Image data-sets were acquired at each of these time-points as well as at head contact and post-failure. Examination of the image data revealed the trabecular deformation as a result of increased insertion torque was restricted to within 1mm of the outer diameter of the screw thread. Minimal deformation occurred prior to the step between the 80% time-point and post-failure. The device presented has allowed, for the first time, visualization of the micro-mechanical response in the peri-implant bone with increased tightening torque. Further testing on more samples is expected to increase our understanding of the effects of increased tightening torque at the micro-structural level, and the failure mechanisms of trabeculae.
authors.affiliation: Medical Device Research Institute, School of Computer Science, Engineering and Mathematics, Flinders University, GPO Box 2100, Adelaide, South Australia 5001, Australia. Electronic address: melissa.ryan@flinders.edu.au.
authors.forename: M K
authors.initials: MK
authors.lastname: Ryan
authors.affiliation: Medical Device Research Institute, School of Computer Science, Engineering and Mathematics, Flinders University, GPO Box 2100, Adelaide, South Australia 5001, Australia.
authors.forename: A A
authors.initials: AA
authors.lastname: Mohtar
authors.affiliation: Medical Device Research Institute, School of Computer Science, Engineering and Mathematics, Flinders University, GPO Box 2100, Adelaide, South Australia 5001, Australia.
authors.forename: T M
authors.initials: TM
authors.lastname: Cleek
authors.affiliation: Medical Device Research Institute, School of Computer Science, Engineering and Mathematics, Flinders University, GPO Box 2100, Adelaide, South Australia 5001, Australia.
authors.forename: K J
authors.initials: KJ
authors.lastname: Reynolds
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001863:Bone Screws; D005260:Female; D005270:Femur Head / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012399:Rotation; D059008:Time-Lapse Imaging; D019415:Torque; D055114:X-Ray Microtomography
keywords: Cancellous bone; Insertion torque; Screw insertion; Time-elapsed