Maximum stopping torques normalized by screw thread area engaged by the host material were 15.2N/mm (cortical screws) and 13.4N/mm (cancellous screws) in sawbone blocks and 20.9N/mm (cortical screws) and 6.1N/mm (cancellous screws) in human femurs.
There were weak (R=0.25) to strong (R=0.99) linear correlations of absolute and normalized torque vs. stopping torque, and then further tightened until failure of the screw-bone interface, i.e. Using a torque screwdriver, 3.5-mm diameter cortical screws and 6.5-mm diameter cancellous screws were inserted for adequate tightening as determined subjectively by an orthopedic surgeon, i.e. Sixteen fresh-frozen human femurs of known standardized bone mineral density (sBMD) were also used. Sawbone blocks were obtained having densities from 0.08 to 0.80g/cm(3). The present aim was to measure stopping and stripping torque of cortical and cancellous screws in artificial and human bone over a wide range of densities. Few studies have quantified stripping torque in human bone, and only one older study from 1980 reported stopping/ stripping torque ratio. stopping torque, and attempt to avoid accidental over-tightening that leads to screw-bone interface failure, i.e.
Orthopedic surgeons apply torque to metal screws manually by "subjective feel" to obtain adequate fracture fixation, i.e. Tsuji, Matthew Crookshank, Meghan Olsen, Michael Schemitsch, Emil H Zdero, Rad The biomechanical effect of artificial and human bone density on stopping and stripping torque during screw insertion. TTI should be considered in the exploration of muscle fatigue during sustained isometric contractions. These results suggest that central and peripheral alterations accounting for muscle fatigue are similar following isometric contractions with similar TTI. EMG activity of VL and RF muscles increased in the same extent during the 3 contractions (VL: 54.5±40.4% RF: 53.1±48.7%). Potentiated doublet amplitude was similarly reduced in the 3 conditions (-19.7Â☑.5%), but VL and RF M-wave amplitudes remained unchanged. VAL decreased significantly in a similar extent (-3.1Â☑.3%) after the 3 sustained contractions. MVC torque reduction was similar in the 3 conditions after the exercise (-23.4Â☒.7%). EMG activity of the vastus lateralis (VL) and -rectus femoris (RF) muscles was recorded during the sustained contractions.
MVC torque, maximal voluntary activation level (VAL), M-wave characteristics and potentiated doublet amplitude were assessed before and immediately after the sustained contractions. Sixteen participants performed 3 sustained contractions at different intensities (25%, 50%, and 75% of Maximal Voluntary Contraction (MVC) torque) with different durations (68.5Â☓3.4 s, 35.1Â☑6.8 s and 24.8Â☑2.9 s, respectively) but similar TTI value. The aim of this study was to compare neuromuscular alterations following different isometric sub-maximal contractions of the knee extensor muscles but with similar TTI. Torque time integral (TTI) is the combination of intensity and duration of a contraction. Rozand, V Cattagni, T Theurel, J Martin, A Lepers, R Neuromuscular fatigue following isometric contractions with similar torque time integral.