[Scientific Assessment of 350 Failed Metasul-LDH® Hip Prostheses with DUROM® Acetabulum Component with Probable Conus Insufficiency, Implanted in a Single Centre During 2003 to 2008]. / Wissenschaftliche Auswertung von 350 fehlgeschlagenen Metasul-LDH®-Hüftprothesen mit DUROM®-Azetabulumkomponente bei Verdacht auf Konusinsuffizienz, implantiert in einem einzelnen Zentrum 2003 bis 2008.

Introduction: The revision rates were high for patients with Metasul-LDH® hip prosthesis (LDH = large-diameter head) with DUROM® acetabulum components implanted in a single centre between 2003 and 2008. This suggested that there was a system-related weakness in total hip replacements with large diameter heads. It was suspected that the tapered connection between head and stem was responsible for the implantation failure. This led to a scientific reappraisal of the unsuccessful hip prostheses, in order to clarify whether there was a tribological problem or a cone failure. Method: To this end, data on serum metal concentrations, types of prosthesis and stem alloys were collected and analysed for the 315 patients with 350 DUROM®-LDH-HTP. Results: There were significant differences between blood metal concentrations in patients with different types of stem. For patients with titanium stems, there were more serious affects on bone substance surrounding the affected joint, and significantly higher serum cobalt concentrations. Conclusion: It was concluded that the problem did not lie with the tribology of the sliding surfaces, but with the cone-stem connection.

Damping Factor as a Diagnostic Parameter for Assessment of Osseointegration during the Dental Implant Healing Process: An Experimental Study in Rabbits.

The purpose of this study was to evaluate the possibility of using damping factor (DF) analysis to provide additional information on osseointegration of dental implants during the healing period. A total of 30 dental implants were installed in the bilateral femoral condyles of 15 rabbits. A DF analyzer detected with an impulse-forced vibration method and a commercialized dental implant stability analyzer based on resonance frequency (RF) analysis were used to measure the implant stability immediately after implant placement and 1, 2, 4, and 8 weeks post-surgically. Results of DF and RF analyses at different time points were compared with the corresponding osseointegration performance of dental implants via micro-computed tomography (micro-CT), histological and histomorphometrical analysis. The DF values revealed a decrease with time and reached 0.062 ± 0.007 at 8 weeks after implantation, which is almost 50% lower than the initial value. Moreover, highly significant correlations between DF values and bone volume densities (R 2 = 0.9797) and percentages of bone-to-implant contact measured at trabecular bone area (R 2 = 0.9773) were also observed. These results suggested that DF analysis combined with RF analysis results in a more sensitive assessment of changes in the dental implant/bone complex during the healing period than RF analysis alone.