[Effect of ultrasonic shock waves on the bone-bone cement interface].
OBJECTIVE
Identification of the impact of ultrasound shock wave on the integration of bone cement in the bone and the examination of a potential application of this method in order to facilitate the extraction of cemented implants, mainly femoral component of total hip arthroplasty.


METHODS
We used pig proximal femurs from which we made fragments involving approximately one third to one half of the profile of the bone and Palacos bone cement.


METHODS
We made a groove in the cancellous bone, pressed bone cement with a wire loop in the cavity and let it harden. The samples were divided by random selection into two groups. Samples from A group were exposed to ultrasound shock waves and group B served as a control group. Then we measured the force needed for the extraction of the cement plug from the bone.


RESULTS
Our measuring has shown an evident decrease of the force necessary for the extraction of the bone cement after the application of ultrasound shock wave. We did not find out any macroscopically evident damage of the bone cement or of the surrounding cortical bone.


CONCLUSIONS
The results of our measuring are influenced by a different shape and size of the examined samples which also substantially differ from the situation when a stem of the endoprosthesis is implanted in the femoral canal and is surrounded by a cement mantle. As concerns risks associated with the application of the shock wave in this indication there is a risk of a fracture of the cortical bone around THR stem (the literature does not mention this complication) and a risk of the increase of pressure in the medullary cavity of the femur combined with a risk of fat embolism. In our view this increase of pressure is comparable with the effect of the implantation of femoral component. This method cannot be used for releasing cementless implants as the surrounding cortical bone gets damaged before the implant is released.


CONCLUSIONS
Ultrasound shock wave is still used rarely in orthopaedics, however, the existing results are promising in many aspects. Of great importance is the fact that it is a non-invasive method. The field dealt with by this work covers only experiments in vitro but the results provide hope for a future clinical use.
Hach
J
J
Ortopedická klinika 1. LF UK, Praha. janhach@centrum.cz
Benes
A
A
Hani
A B
AB
Sosna
A
A
Sunka
P
P
D000818:Animals; D001843:Bone Cements; D001842:Bone and Bones; D002484:Cementation; D005269:Femur; D066298:In Vitro Techniques; D019904:Polymethyl Methacrylate; D013552:Swine; D014465:Ultrasonics
D001843:Bone Cements; D019904:Polymethyl Methacrylate
Působení ultrazvukové rázové vlny na spojení kostního cementu s kostí.