The Mechanism Of Aseptic Loosening Of Cemented Stem Following Hip Replacements And Interventional Research Of Icariin On Osteoylysis Induced By Wear Particles

Objective:In this retrieval study, we present a detailed analysis of cement mantles retrieved at revision surgery, which demonstrate the relative contribution of mechanical events to the etiology of femoral loosening. In this cadaveric retrieval study, we examine thehypotheses that debonding and stem migration are associated with mechanical failure of the cement mantle, and that cracking of the mantle is indicative of aseptic loosening of cemented femoral stems. Vivo wear particles (Ti and PMMA) induced mouse calvarial osteolysis model was used to investigate the inhibility effect of Icariin over wear particles induced osteolysis. To observe different doses of icariin in wear particles (Ti, PMMA)on bone resorption, so asto explore the effects of Icariin to this osteoclastic osteolysis induced by wear particles and to evaluate the function of Icariin on prevention and treatment of aseptic loosening of prosthesesMethods:Retrieval study:Thirty six cemented femoral stems with complete cement mantles were retrieved at revision surgery after an average of 56 months in situ. The outer and inner surfaces of the cement mantle and the surface of the femoral component were carefully examined with stereo microscopy.The area location and severity of surface abrasion and cement cracking were recorded by Gruen zone.Cadaveric study:Eighteen cadaveric femurs with cemented femoral stems were cut from suitable area and immersed in a bath of Alcairn Blue pigment for 24 hours to staining.Each femur was bilateral along the sagittal mid-plane and examined with stereomicroscopy to identify cracks within the cement mantle and recorded by Gruen zone. The widths of cracks present on the inner surface of the mantle were measured at three equidistant locations with an instrumented microscope system. The widths of gaps along the stem/cement interface were measured by reassembling its corresponding cement mantle. Any regions of burnishing of the inner surface of the cement mantle and the stem surface were recorded too.Interventional Research of Icariin:The vivo study was divided into 9 groups. There were 6 mice in each group.The wear debris (Ti and PMMA) were put into mouse calvarial to create mouse calvarial osteolysis module. No any disposal is one group. PMMA Particles without fed Icarin was one group. Ti particles without fedding Icariin was one group. Model mice were fed with different doses of Icariin (30mg/kg,60mg/kg,120mg/kg)one times every day. These mice are sacrificed on fourteen days later and calvaria are harvested and stained for observed resorption areas and the number of osteoclasts.Results: Retrieval study:Areas of burnishing of the stem and the matching surface of the cement mantle were present on all but two cases, independent of the duration of implantation. Regions of polishing of the outer surface of the cement mantle were observed in implants, but only one of the components revised for other causes. The volume of cement removed by external abrasion of mantle exceeded that removed through stem contact by at least an order of magnitude. Cracks were visible within almost half of the mantles revised secondary to loosening, but none of the infected or dislocated cases.Cadaveric study:Almost all components were debonded from the surrounding cement mantle. Slight burnishing of the inner surface of the cement mantle was evident in sixteen specimens. Cracks were present in 83% of mantles, frequently corresponding to areas where the corners of the stem had come into contact with bone during implantation, (87%, p=0.002). None of the stems had subsided by more than 0.5mm. The average width of gaps between the stem and the cement mantle was 0.33±0.06mm. There was a strong correlation between the minimum width of longitudinal cracks and the average stem/cement gap for each specimen (r2=0.691, p=0.001).Interventional Research of Icariin:The number of absorption pits of bone slices that are stimulated by wear debris is more than no disposing group(P<0.05),and absorption pits area is also bigger than no disposing group(P<0.05). ICA group have formed smaller absorption pits and area than model group (P<0.05).Of them, ICA120mg/kg group is most evidence, ICA30mg/kg group being lest. Model group and ICA30mg/kg is no evidence difference respectively.Model Ti group and Model PMMA group is no evidence difference respectively in absorption pits areas.Conclusions:Early debonding and stem/cement motion appear to be a universal characteristic of cemented femoral stems. Abrasive wear of the outer surface of the cement mantle may be a more common cause of osteolysis and accelerated wear than abrasion of cement within the mantle. Cement cracks are frequently observed in clinically successful cemented hip replacements. Stem migration occurs once cement fractures open. Cement cracks do not necessarily result in clinical failure of cemented stems. But, with the development of micromotion, it might affect implant stability and lead to harmful effects on the bone bed and subsequent loosing of the implant.Ti Particles and PMMA Particles can induce bone absorption and accelerate osteoclasts to generate.ICA are able to hinder the osteoclastic generation and inhibit function,so to restrain periprosthetic osteolysis.Therefore,it play an important role in prevention and treatment of artificial joint aseptic loosening.