title: Does cancellous screw insertion torque depend on bone mineral density and/or microarchitecture?
abstract: During insertion of a cancellous bone screw, the torque level reaches a plateau, at the engagement of all the screw threads prior to the screw head contact. This plateau torque (T(Plateau)) was found to be a good predictor of the insertion failure torque (stripping) and also exhibited strong positive correlations with areal bone mineral density (aBMD) in ovine bone. However, correlations between T(Plateau) and aBMD, as well as correlations between T(Plateau) and bone microarchitecture, have never been explored in human bone. The aim of this study was to determine whether T(Plateau), a predictor of insertion failure torque, depends on aBMD and/or bone microarchitecture in human femoral heads. Fifty-two excised human femoral heads were obtained. The aBMD and microarchitecture of each specimen were evaluated using dual X-ray Absorptiometry and micro-computed tomography. A cancellous screw was inserted into specimens using an automated micro-mechanical test device, and T(Plateau) was calculated from the insertion profile. T(Plateau) exhibited the strongest correlation with the structure model index (SMI, R=-0.82, p<0.001), followed by bone volume fraction (BV/TV, R=0.80, p<0.01) and aBMD (R=0.76, p<0.01). Stepwise forward regression analysis showed an increase for the prediction of T(Plateau) when aBMD was combined with microarchitectural parameters, i.e., aBMD combined with SMI (R(2) increased from 0.58 to 0.72) and aBMD combined with BV/TV and BS/TV (R(2) increased from 0.58 to 0.74). In conclusion, T(Plateau), a strong predictor for insertion failure torque, is significantly dependent on bone microarchitecture (particularly SMI and BV/TV) and aBMD.
authors.affiliation: Medical Device Research Institute, School of Computer Science, Engineering and Mathematics, Flinders University, GP.O. Box 2100, Adelaide, South Australia 5001, Australia. Electronic address: abla0002@flinders.edu.au.
authors.forename: Rosidah
authors.initials: R
authors.lastname: Ab-Lazid
authors.affiliation: Medical Device Research Institute, School of Computer Science, Engineering and Mathematics, Flinders University, GP.O. Box 2100, Adelaide, South Australia 5001, Australia.
authors.forename: Egon
authors.initials: E
authors.lastname: Perilli
authors.affiliation: Medical Device Research Institute, School of Computer Science, Engineering and Mathematics, Flinders University, GP.O. Box 2100, Adelaide, South Australia 5001, Australia.
authors.forename: Melissa K
authors.initials: MK
authors.lastname: Ryan
authors.affiliation: Medical Device Research Institute, School of Computer Science, Engineering and Mathematics, Flinders University, GP.O. Box 2100, Adelaide, South Australia 5001, Australia.
authors.forename: John J
authors.initials: JJ
authors.lastname: Costi
authors.affiliation: Medical Device Research Institute, School of Computer Science, Engineering and Mathematics, Flinders University, GP.O. Box 2100, Adelaide, South Australia 5001, Australia.
authors.forename: Karen J
authors.initials: KJ
authors.lastname: Reynolds
mesh_terms: D015502:Absorptiometry, Photon; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D015519:Bone Density; D001863:Bone Screws; D001842:Bone and Bones / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology*; D005260:Female; D005270:Femur Head / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology*; D006620:Hip Fractures / Q000473:pathology / Q000503:physiopathology / Q000601:surgery; D006801:Humans; D008297:Male; D012044:Regression Analysis; D012756:Sheep; D019415:Torque; D055114:X-Ray Microtomography / Q000295:instrumentation / Q000379:methods
keywords: Bone mineral density; Maximum torque; Microarchitecture; Plateau torque; Screw insertion