The aim of this study was to determine if extracorporeal shock wave therapy (ESWT) in vivo affects the structural integrity of articular cartilage. A single bout of ESWT (1500 shock waves of 0.5 mJ/mm 2 ) was applied to femoral heads of 18 adult Sprague-Dawley rats. Two sham-treated animals served as controls. Cartilage of each femoral head was harvested at 1, 4, or 10 weeks after ESWT (n ¼ 6 per treatment group) and scored on safranin-O-stained sections. Expression of tenascin-C and chitinase 3-like protein 1 (Chi3L1) was analyzed by immunohistochemistry. Quantitative real-time polymerase chain reaction (PCR) was used to examine collagen (II)a 1 (COL2A1) expression and chondrocyte morphology was investigated by transmission electron microscopy and no changes in Mankin scores were observed after ESWT. Positive immunostaining for tenascin-C and Chi3L1 was found up to 10 weeks after ESWT in experimental but not in control cartilage. COL2A1 mRNA was increased in samples 1 and 4 weeks after ESWT. Alterations found on the ultrastructural level showed expansion of the rough-surfaced endoplasmatic reticulum, detachment of the cell membrane and necrotic chondrocytes. Extracorporeal shock waves caused alterations of hyaline cartilage on a molecular and ultrastructural level that were distinctly different from control. Similar changes were described before in the very early phase of osteoarthritis (OA). High-energy ESWT might therefore cause degenerative changes in hyaline cartilage as they are found in initial OA. Keywords: shock wave; ESWT; cartilage; degeneration; in vivo Shock waves are transient pressure disturbances that propagate rapidly in three-dimensional space. In clinical applications they are characterized by their energy flux density, frequency, number of impulses and focus. The energy flux density (EFD) of extracorporeal shock wave therapy (ESWT) is an important value that is defined as the energy measured during the time of one impulse within one square millimeter. Although there is no consistent definition on high-and low-energy EFD found in the literature, an EFD of 0.5 mJ/mm 2 is described as high-energy ESWT in most cases. ESWT has been established as common mode of treatment in orthopedic surgery for periarticular affections such as calcifying tendinitis of the shoulder 1 and lateral epicondylitis 2,3 where low-energy treatment is used. Its effectiveness has been shown in a range of diseases by an increasing number of studies. [4][5][6] Osteonecrosis of the femoral head 7 and heterotopic ossifications 8 were treated in contrast by ESWT with high-energy flux density (EFD) in humans. ESWT, of which the exact biological mechanism is not known in detail, has dosedependent effects. 9 Shock waves have been used since 1977 in humans, with the principal clinical application to treat kidney stones. The renal stone fragmentation by extracorporeal shock waves (lithotripsy) has become an established procedure in urology. It was discovered that patients after lithotripsy showed modifications of their bon...

No abstract