Predicting cancellous bone failure during screw insertion

Time-elapsed screw insertion with microCT imaging

“…Based on 291 these, a strong linear relationship between T HC and the T max was observed (R 2 = 0.90, p < 292 0.001). The differences in the observed regression slopes between this study and the 293 study by Reynolds et al (2013) are likely due to the difference in bone quality; the latter 294 study considered a combination of osteoporotic and osteoarthritic bone specimens, 295 whereas this study looked specifically at only specimens retrieved from patients that had 296 experienced a non-traumatic hip fracture. Consequently, the bone from this study was of 297 a poorer quality, which likely contributed to the smaller regression slope.…”

“…This may have clinically implications, in light of recent literature that has demonstrated 369 the strong relationship between T HC and T max (Reynolds et al, 2013). Further testing on 370 additional specimens and alternate screw designs will provide information regarding the 371 failure mechanisms of the peri-implant bone during tightening.…”

“…The final phase, 'stripping', shows a decrease in torque as the screw 35 threads shear through the bone material (Figure 1). Previous work within our laboratory 36 has established a strong relationship between the plateau insertion torque, measured at 37 head contact (T HC ) and the maximum tightening torque (T max ) in bone surrogates, as well 38 as excised ovine vertebral and human femoral head specimens (Reynolds et al, 2013), 39 which presents the ability to predict T max based solely on the torque required to achieve 40 head contact. 41 "Time-elapsed analysis" of bone is an emerging technique using sequential image 42 acquisition to analyse bone mechanics under a given loading regime.…”

“Turn-of-the-Nut” Method Is Not Appropriate for Use in Cancellous Bone

“…(18), which comprised a torque transducer to monitor 76 insertion torque, a load cell to monitor compression under the screw head and a rotary encoder 77 for monitoring screw rotation. All signals were digitally recorded at a sample rate of 500Hz.…”

“…Page 11 of 15 demonstrates T max can be predicted from the plateau torque prior to head contact (18). Further 211 investigations should look to identify factors that may influence the ratio of T yield / T max , and any 212 differences between healthy and diseased bone.…”