The Effect of the Extracorporeal Shock Wave Lithotriptor on the Bone-Cement Interface in Dogs

Abstract

The extracorporeal shock wave lithotriptor (ECSWL) is a machine that generates shock waves that transfer energy through biologic materials. This study focused the wave at a composite bone-cement (polymethylmethacrylate) interface and evaluated the effects both quantitatively and qualitatively. Six matched sets of dog femora were selected. The intramedullary canals were packed uniformly with cement. One of the set was randomly selected for treatment with impulses while the other served as the control. The bone was then sectioned transversely into discs, and scanning electron microscopy and mechanical push-out studies were performed. The results indicated that the ECSWL does have a loosening effect on the bone-cement interface. Using a paired Student's t-test, the shear strength was significantly less in the treated group than in the control (p < 0.003).Microscopically, the treated specimens revealed relative sparing of the surrounding bone. At the bone-cement interface, however, microfractures, loose bodies, and widening were seen. Revision total arthroplasty has a significant morbidity, which can be partially attributed to cement extraction. The results of this study indicate that the ECSWL may be a useful adjunct in revision surgery by facilitating the extraction of polymethylmethacrylate and thereby reducing the morbidity.Cemented total arthroplasty is a procedure that has been performed for over two de-

Medical applications and bioeffects of extracorporeal shock waves

“…This constitutes a major problem when an artificial hip with a cemented shaft has to be replaced. Studies were performed with freshly obtained bones, and initially, a loosening effect at the bone-cement interface was indeed reported (Weinstein et al 1988); in a more recent experiment, however, no effect could be documented . It seems improbable that shock waves will ever be applied for bone cement removal since they have nearly no effect on the cement itself, and complete destruction of the large contact area between cement and bone -this is the site where shock waves act -would be a major trauma leading to the release of marrow into the circulation, a potentially fatal event.…”

Effect of Extracorporeal Shock Waves on Bone: A Review of Shock Wave Experiments and the Mechanism of Shock Wave Action

“…In one of the first experiments on this topic Weinstein et al (1988) examined the physical effect of shock waves on the involved materials and their con-nection, i.e., the cement-bone interface. Twelve canine femora were freed of all adherent tissue and cut proximally; a canal was then drilled and filled with bone cement.…”

The effect of shockwaves on mature and healing cortical bone

“…The soft tissues about the tibiae studied were accoustically similar to the water in the "beach ball" and conductive gel. Thus this energy was coverted into tension waves and mechanical energy only at the site of the osteotomy [1,2,4,5,6,11,14,16,19].…”

“…Firstly, to fragment polymethylmethacrylate cement and separate it from bone [2,8,9,[17][18][19], and secondly to cause microfractures of cortical bone. Such fractures could be used to perform closed "osteotomies" or to stimulate local haematoma formation and bone healing at the site of nonunion [15].…”