Robotic bone preparation does not increase cement penetration into the proximal femur: a matched-pair cadaver study comparing hand-broaching versus robotic bone preparation.

In a cadaver study, we prepared 20 matched pairs of human femora using chipped-tooth broaches and robotic milling with the same geometry. For robotic bone preparation the CASPAR robotic system with a rotating milling head was used. Cancellous bone was irrigated with 1 liter of pulsed lavage and the specimens were embedded in specially-designed pots. After vacuum mixing, bone cement was introduced in a retrograde manner and subjected to a standard pressure protocol with a constant force of 3,000 N. Radiographs were taken and horizontal sections were obtained at predefined levels, using a diamond saw. Microradiographs of the bone slices were taken, digitized and analyzed to assess cement penetration into cancellous bone. No femoral fractures or fissures occurred with either preparation technique. The microradiographic evaluation showed no morphometric differences between chipped-tooth broaches and robotic milling as regards cement penetration into cancellous bone. Therefore, in the presence of pulsed lavage, we conclude that robotic bone preparation does not increase cement penetration into cancellous bone of the proximal end of the femur.