Axial rotation mechanics in a cadaveric lumbar spine model: a biomechanical analysis

Abstract Background context Postoperative patient motions are difficult to directly control. Very slow quasistatic motions are intuitively believed to be safer for patients, compared with fast dynamic motions, because the torque on the spine is reduced. Therefore, the outcomes of varying axial rotation (AR) angular loading rate during in vitro testing could expand the understanding of the dynamic behavior and spine response. Purpose To observe the effects of the loading rate in AR mechanics of lumbar cadaveric spines via in vitro biomechanical testing. Study design An in vitro biomechanical study in lumbar cadaveric spines. Methods Fifteen lumbar cadaveric segments (L1–S1) were tested with varying loading frequencies of AR. Five different frequencies were normalized with the base line frequency (0.125 Hz n=15) in this analysis: 0.05 Hz (n=6), 0.166 Hz (n=6), 0.2 Hz (n=10), 0.25 Hz (n=10), and 0.4 Hz (n=8). Results The lowest frequency (0.05 Hz) revealed significant differences (p 2 >0.75, p Conclusions Evidences suggest that measurements at very small frequencies (0.05 Hz) of torque, SAV, AV, RF, and EL are significantly reduced when compared with higher frequencies (0.166 Hz, 0.2 Hz, 0.25 Hz, and 0.4 Hz). Higher frequencies increase torque, RF, passive SAV, and AV. Higher frequencies induce a greater IDP in comparison with lower frequencies.