The Effect of Vibration and Posture on the Progression of Intervertebral Disc Herniation

Abstract

Study Design. Basic scientific investigation exposing partially herniated discs to vibration and shock loads in both flexed and neutral postures. Objective. To determine the effect of vibration and posture on the exacerbation of the intervertebral disc (IVD) herniation process. Summary of Background Data. There is a large body of scientific evidence to suggest that spine flexion is required in conjunction with repetitive loading to produce IVD herniation. There is also a strong epidemiological link between occupational vibration exposure and the development of IVD herniation; however, there is little basic experimental evidence to support this link. The purpose of this investigation was to examine what effect vibration, shock, and flexed posture has on the exacerbation of pre-existing partial IVD herniations. Methods. A total of 64 porcine motion segments were exposed to an established herniation loading protocol to produce partial herniation. These motion segments were randomly assigned to 1 of 4 loads (vibration to simulate whole-body vibration [WBV], static, vibration, and shock) and either in neutral or flexed postures making 8 experimental conditions with 8 motion segments per group. Computed tomography imaging was used to quantify herniation progression, whereas specimen height and average stiffness changes were quantified via excepted methods. Results. The herniation protocol was very successful in producing partial herniations (58 of 64 motion segments). Combined vibration and shock loading was the most potent load type for further exacerbation of the herniation. The flexed posture did not have an influence on the distance of nucleus tracking, probably because of the height lost in the disc, although a flexed posture made the disc marginally stiffer suggesting more damage. Conclusion. Vibration and shock loading provided sufficient mechanical injury to exacerbate pre-existing IVD herniations.