A substantial body of evidence supports the use of extracorporeal shock wave therapy (ESWT) for fracture non-unions in human medicine. However, the success rate (i.e., radiographic union at six months after ESWT) is only approximately 75%. Detailed knowledge regarding the underlying mechanisms that induce bio-calcification after ESWT is limited. The aim of the present study was to analyse the biological response within mineralized tissue of a new invertebrate model organism, the zebra mussel Dreissena polymorpha, after exposure with extracorporeal shock waves (ESWs). Mussels were exposed to ESWs with positive energy density of 0.4 mJ/mm² or were sham exposed. Detection of newly calcified tissue was performed by concomitantly exposing the mussels to fluorescent markers. Two weeks later, the fluorescence signal intensity of the valves was measured. Mussels exposed to ESWs showed a statistically significantly higher mean fluorescence signal intensity within the shell zone than mussels that were sham exposed. Additional acoustic measurements revealed that the increased mean fluorescence signal intensity within the shell of those mussels that were exposed to ESWs was independent of the size and position of the focal point of the ESWs. These data demonstrate that induction of bio-calcification after ESWT may not be restricted to the region of direct energy transfer of ESWs into calcified tissue. The results of the present study are of relevance for better understanding of the molecular and cellular mechanisms that induce formation of new mineralized tissue after ESWT. Specifically, bio-calcification following ESWT may extend beyond the direct area of treatment.

Introduction

Several options exist for the treatment of periprosthetic osteolysis in revision knee surgery. We describe our preliminary short-term experiences using trabecular metal (TM) technology in order to fill bony defects either on the femoral or on the tibial side.

Aims: Little is known about effects of extracorporeal shock wave application (ESWA) on normal bone physiology. Therefore, we investigated ESWA effects on intact distal rabbit femura as an in vivo animal model. Methods: Animals received 1,500 SW pulses each of different energy ßux densities (EFD) on either left or right femur or remained untreated. ESWA effects were investigated by bone scintigraphy, MRI and histopathological examination. Results: Ten days after ESWA, local blood ßow and bone metabolism were decreased (0.5 mJ/mm2 and 0.9 mJ/mm2 EFD), but were increased 28 days after ESWA (0.9 mJ/mm2). ESWA with 0.9 mJ/mm2 EFD (but not with 0.5 mJ/mm2 ) resulted in MRI signs of soft-tissue-edema, epiperiosteal ßuid and bone marrow edema one day after ESWA, as well as in hemosiderin deposits found epiperiosteally and within the marrow cavity ten days after ESWA. Conclusions: ESWA with both 0.5 mJ/mm2 and 0.9 mJ/mm2 EFD had effects on normal bone physiology in the distal rabbit femur, with considerable damaging side effects of ESWA with 0.9 mJ/mm2 EFD on periosteal soft tissue and tissue within the bone marrow