EFFECTS OF HIGH-ENERGY SHOCKWAVES ON NORMAL HUMAN FIBROBLASTS IN SUSPENSION

To gain insight in the effects of shockwaves on human cells the relationship between the energy density and the number of shockwaves as well as their effect on suspensions of normal cells was studied. At energy densities of 0.37, 0.6, 0.78, and 1.20 mJ/mm(2) fibroblasts were subjected to 50, 100, 250, 500, and 1000 shockwaves. Each test was performed three times and one sample was used as control. A decrease in viability related to the logarithm of both the number (P = 0.0000) and the energy density (P = 0.001) of the shockwaves was statistically demonstrable 1 hr after the shockwave application. The energy density of the shockwaves has less influence on the viability than the number of applied shockwaves, Seeding of viable cells 1 hr after the shockwave application showed that the decrease in the 48-hr growth potential was statistically dependent of the number of applied shockwaves only (P = 0.0007). After 24 hr no difference in the 48-hr growth potential could be demonstrated between viable shockwave-treated cells and control cells. The literature as well as our own investigations in vitro and in vivo indicate that shockwaves have a logarithmic dose-dependent destructive effect on cells in suspension, but they also seem to have a dose-dependent stimulating influence on the healing process in damaged tissues. Due to the logarithmic relationship between the viability and both the number and energy density of the applied shockwaves it might be expected that even excessive numbers of high-energy-density shockwaves don't soon lead to total destruction of all cells in the suspension. The cytodestructive effect of the shockwaves on cells appears to be an immediate effect that wears off within 24 hr. Although the mechanism of the tissue-repair-stimulating effect of shockwaves is still under investigation we suppose that this phenomenon is based on an increased blood flow and not on direct cytostimulation by shockwaves. Provided that infections are absent in the application area our findings support the opinion that although shockwaves can induce minor damage to the soft body tissues, they can be regarded as a safe nonsurgical treatment option in various application areas, e.g., fracture healing disturbances, wound healing disturbances, and possibly some forms of sterile tendinitis. The results indicate that for clinical use a low number of shockwaves of high energy density is preferable. (C) 1994 Academic Press, Inc.