POLYETHYLENE WEAR LIKE CAUSE OF OSTEOLYSIS AND PERIPROSTHETIC FRACTURES

Abstract

Periprosthetic fractures certainly are one of the most dreadful complication in THA operated patients. Risk factors are both pre-operatory (age, bone quality, morphology offemoral canal) and post-operatory (periprosthetic osteolysis, trauma). There are many classifications about periprosthetic fractures, but, in ouropinion, the most complete is the Vancouver’s classification of 1994. Osteolysis main cause for sure is the presence of wear debris, fragments created by friction of the different surfaces of prosthetic components. These particles, delivered inside joint space, spread into the bone-prosthesis joint and then activate the immunity system, promoting the relief of many mediators, both infiammatory and osteolytic. The most important mediators for sure are cytochines (IL-1, IL-6 and TNF), prostaglandins (PG-E2) and some digestive enzymes. These can get to the development of osteolytic areas with direct enzymaticdigestion and osteoclastic activation. Inexorable conseguence is periprosthetic bone fragility and high risk of fracture. Between 1997 and 2003 we observed 18 perprosthetic fractures in our department, all overhauled.

We studied 22 THA patients (25 hips, 7 male, 15 female, average age 70 yy) for 11 years of follow-up. Wear rate has been calculated by the computerized Liver-more technique, using the AutoCad program. By this program we can work out a bidimensional reconstitution of the prosthesis, using a simple A-P Rx of the hip.

We calculated that average wear is 0,153 mm/y (range 0,054 −0,329 mm/y) and average total wear is 1,624 mm. 6_D_Discussion_e_Conclusions: Computerized analysis of wear rate andosteolysis rate of polyethylene, in our opinion, is an efficent way to prevent periprosthetic fractures, programing a prosthesis revision, before the periprosthetic bone-stock is too poor. More and more importance have studies about alternative coupling (reticular polyethylene, new generation ceramics, metal-to-metal). If the clinical results will confirm the literature’s encouraging datas, this materials coupling will guarantee a bone-loss reduction, increasing prosthesis longevity.

Computerized analysis of wear rate andosteolysis rate of polyethylene, in our opinion, is an efficent way to prevent periprosthetic fractures, programing a pros-thesis revision, before the periprosthetic bone-stock is too poor. More and more importance have studies about alternative coupling (reticular polyethylene, new generation ceramics, metal-to-metal). If the clinical results will confirm the literature’s encouraging datas, this materials coupling will guarantee a bone-loss reduction, increasing prosthesis longevity.