Application of extracorporeal shock wave lithotripter (ECSWL) in orthopaedics. II. Dose-response and pressure distribution measurements.
In order to apply the extracorporeal shock wave lithotripter (ECSWL) technique to the loosening of the bone-cement interface for the extraction of the cement during revision arthroplasty it is essential to know the dose-response characteristics.  The present study shows that the number of shocks needed to break the interface between a 2- and 6-mm-thick bovine femoral bone and bone cement is similar to the fatigue behavior of a material, that is, Log(N) = C(kV) + D, where N is the number of shock impulses, kV is the power setting of the lithotripter machine in kilovolts, and C and D are constants. Iso-pressure distribution of the traveling shock wave front through a simulated bone in a Plexiglass tube using Fuji pressure film showed quantitative pressure contours from which one can understand the effective area of shock wave and its distribution.  The most effective area of the shock wave was about 1.5 cm in diameter at 23 and 25 kV with pressure at least 7.0 MPa which is more than sufficient to break the bone-cement interface in tension.
Department of Biomedical Engineering, University of Iowa, Iowa City 52242.
J B
JB
Park
S H
SH
Park
J N
JN
Weinstein
S
S
Loening
D
D
Oster
D000818:Animals; D001843:Bone Cements; D002417:Cattle; D005269:Femur; D008096:Lithotripsy / Q000295:instrumentation / Q000379:methods; D008422:Materials Testing; D011312:Pressure; D013718:Tensile Strength; D014465:Ultrasonics