Influence of a Follower Load on Intradiscal Pressure and Intersegmental Rotation of the Lumbar Spine

Intradiscal pressure and intersegmental rotation of human lumbar spines were measured in vitro.To determine the effect of a follower load on mechanical behavior at all levels of the lumbar spine.Different loads have been proposed for studying the mechanical behavior of the lumbar spine. The influence of a follower load on intradiscal pressure at the different levels is unknown.Ten human cadaveric lumbar spines were loaded in the three main anatomic planes with pure moments of 3.75, 7.5, and 7.5 Nm plus a follower load of 280 N. Intradiscal pressure and intersegmental rotation were measured at all levels.An additional follower load increased the intradiscal pressure, slightly reduced the intersegmental rotation for axial rotation, and hardly affected intersegmental rotation for lateral bending and flexion-extension.A superimposed follower load renders spinal loading with pure moments more physiologic.