Patterned CoCrMo and Al2 O3 surfaces for reduced free wear debris in artificial joint arthroplasty.

Surface wear of corresponding tribological pairings is still a major problem in the application of artificial joint surgery. This study aims at developing wear reduced surfaces to utilize them in total joint arthroplasty. Using a pico-second laser, samples of medical CoCrMo metal alloy and Al2 O3 ceramic were patterned by laser material removal. The subsequent tribological investigations employed a ring-on-disc method. The results showed that those samples with modified surfaces show less mass or volume loss than those with a regular, smooth surface. Using calf serum as lubricating medium, the volume loss of the structured CoCrMo samples was eight times lower than that of regular samples. By structuring Al2 O3 surfaces, the wear volume could be reduced by 4.5 times. The results demonstrate that defined surface channels or pits enable the local sedimentation of wear debris. Thus, the amount of free debris could be reduced. Fewer abrasives in the lubricated so-called three-body-wear between the contact surfaces should result in less surface damage. Apart from direct influences on the wear behavior, less amounts of free debris of artificial joints should also be beneficial for avoiding undesired reactions with the surrounding soft tissues. The results from this study are very promising. Future investigations should involve the use of simulators meeting the natural conditions in the joint and in vivo studies with living organisms.

Results of total hip replacement using the Robodoc surgical assistant system: clinical outcome and evaluation of complications for 97 procedures.

BACKGROUND: A computerized robotic surgical system was developed from 1986 by the Thomas J. Watson Research Center. In 1992 the system unit Orthodoc and the milling robot Robodoc were first used on humans. We present the results achieved with Robodoc-assisted total hip arthroplasty in 97 hips. METHODS: Between 1997 and 2002, 143 total hip replacements (128 patients) were performed using the Robodoc system. This is a consecutive series. Complete follow-up was possible in 97 hips at a mean follow-up period of 3.8 years. RESULTS: Technical complications directly related to the robotic device occurred in nine cases (9.3%). The pre-operative Merle d'Aubigne score was determined at 8.1 points compared to a post-operative mean score of 16.2. There was no sign of femoral stem loosening on radiographs. CONCLUSIONS: Robotic-assisted total hip arthroplasty with the Orthodoc/ Robodoc system achieves equal results as compared to a manual technique. However, there was a high number of technical complications directly or indirectly related to the robot.