Vergleichende Analyse der Effektivität von horizontaler und vertikaler Ganzkörpervibration auf die osteoporotische Tibiafrakturheilung im Rattentiermodell

Abstract

Osteoporosis is a disease that affects millions of people worldwide and will continue to gain in relevance in view of aging populations. Previous studies (Rubin et al. 2001b; Flieger et al. 1998; Oxlund et al. 2003; Sehmisch et al. 2009; Stuermer et al. 2010a; Stuermer et al. 2010b) have already shown that whole body vibration can have an advantageous effect on osteoporosis. However, they were not able to provide any clarity regarding the optimal application (duration, frequency, position, amplitude). Previous attempts differed only in the frequencies and duration of the therapy. In this study, an animal experiment was conducted with 90 female rats to examine the different influences of vertical and horizontal vibration on osteoporotic fracture healing. 15 underwent sham surgery and 75 were ovariectomized. Within a latency period of 8 weeks, the ovariectomized animals developed osteoporosis. Thereafter, all animals were osteotomized at a standardized point on the tibial metaphysis and then treated by plate osteosynthesis. Six experimental groups were established: four groups were exposed to either horizontal or vertical whole body vibration at 35 Hz or 70 Hz (35Hz vert, 70Hz vert, 35Hz horiz and 70Hz horiz). The other two groups, one non-ovariectomized (SHAM) group and one ovariectomized (OVX) group, received no whole body vibration. The whole body vibration was carried out twice daily over a four-week period at an amplitude of 0.5 mm. After completion of this period, the animals were killed by decapitation and the tibiae were removed. Subsequently, a biomechanical test, a μCT examination, a micro-radiographic examination and a polychrome sequence marking were performed. The first two studies were carried out on the prepared bone. The latter two were carried out after embedding the bone in methyl methacrylate and producing histological sections approximately 120 µm thick. The biomechanical test showed no significant difference in elasticity or yield strength between any of the groups. The biomechanical properties of the callus could only be slightly improved at the high frequencies of 70 Hz vertical and 70 Hz horizontal. In the μCT examination, neither the horizontal nor vertical whole body vibration showed any significant positive influence on the healing of fractures compared to the osteoporotic control group. However, there were positive trends when using horizontal vibration at 70 Hz. The micro-radiographic examination showed a positive influence when using vertical and horizontal WBV at 70 Hz. In comparison to the osteoporotic control group, horizontal vibration at 70 Hz improved distal ventral cortical thickness, proximal bone diameter, ventral callus thickness, and bone density of the ventral and endosteal callus. In the polychrome sequence marking study, WBV caused deterioration of early osteoporotic fracture healing and improvement of middle and late osteoporotic fracture healing. In the early phase, all frequencies had a detrimental effect ventrally and endosteally. In the middle phase, horizontal vibration at 70 Hz was significantly more beneficial compared to the osteoporotic control group with respect to the dorsal callus surface. In the late phase, the group with horizontal 35Hz therapy showed significant improvement with respect to the ventral callus compared to the osteoporotic group and the group with vertical 35 Hz therapy. Dorsally, both horizontal frequencies showed significantly larger callus surfaces than the group with vertical 35Hz therapy. Summarizing all the tests carried out for the present study, horizontal whole body vibration at 70 Hz emerged as the most beneficial rate for positively influencing osteoporotic fracture healing at the tibial metaphysis.