Role of polyethylene particles in peri-prosthetic osteolysis:A review

There is convincing evidence that particles produced by the wear of joint prostheses are causal in the periprosthetic loss of bone,or osteolysis,which,if it progresses,leads to the phenomenon of aseptic loosening.It is important to fully understand the biology of this bone loss because it threatens prosthesis survival,and loosened implants can result in peri-prosthetic fracture,which is disastrous for the patient and presents a difficult surgical scenario.The focus of this review is the bioactivity of polyethylene(PE)particles,since there is evidence that these are major players in the development and progression of osteolysis around prostheses which use PE as the bearing surface.The review describes the biological consequences of interaction of PE particles with macrophages,osteoclasts and cells of the osteoblast lineage,including osteocytes.It explores the possible cellular mechanisms of action of PE and seeks to use the findings to date to propose potential nonsurgical treatments for osteolysis.In particular,a nonsurgical approach is likely to be applicable to implants containing newer,highly cross-linked PEs(HXLPEs),for which osteolysis seems to occur with much reduced PE wear compared with conventional PEs.The caveat here is that we know little as yet about the bioactivity of HXLPE particles and addressing this constitutes our next challenge.

Osteolysis in total hip arthroplasty in relation to metal ion release: Comparison between monolithic prostheses and different modularities

BACKGROUND Among the various complications associated with total hip arthroplasty(THA)periprosthetic osteolysis and wear phenomena due to the release of metal particles,are two of the most common and have been reported to be correlated because of inflammatory responses directed towards released particles that generally activate macrophagic osteolytic effects.Therein,new masses known as pseudotumors can appear in soft tissues around a prosthetic implant.To date,there is paucity of reliable data from studies investigating for any association between the above mentioned adverse events.AIM To investigate for the existence of any association between serum and urine concentrations of metal-ions released in THA and periprosthetic osteolysis for modular neck and monolithic implants.METHODS Overall,76 patients were divided into three groups according to the type of hip prosthesis implants:Monoblock,modular with metal head and modular with ceramic head.With an average f-up of 4 years,we conducted a radiological evaluation in order to detect any area of osteolysis around the prosthesis of both the femur and the acetabulum.Moreover,serum and urinary tests were performed to assess the values of Chromium and Cobalt released.Statistical analysis was performed to determine any association between the ion release and osteolysis.RESULTS For the 3 study groups,the monolithic,modular ceramic-headed and modular metal-headed implants had different incidences of osteolysis events,which were higher for the modular implants.Furthermore,the most serious of these(grade 3)were detected almost exclusively for the modular implants with metal heads.A mapping of the affected areas was performed revealing that the highest incidences of osteolysis were evidenced in the pertrochanteric region at the femur level,and in the supero-external region at the acetabular level.Regarding the evaluation of the release of metals-ions from wear processes,serum and urinary chromium and cobalt values were found to be higher in cases of modularity,and even more so for those with metal head.Statistical linear correlation test results suggested positive correlations between increasing metal concentrations and incidences areas of osteolysis.However,no cases of pseudo-tumor were detected.CONCLUSION Future studies are needed to identify risk factors that increase peri-prosthetic metal ion levels and whether these factors might be implicated in the triggering of local events,including osteolysis and aseptic loosening.