Conservative hip arthroplasty with resurfacing of the acetabulum and the femoral head is an attractive concept particularly in young and active patients. The principal advantages are less femoral bone destruction and resection, avoidance of stress shielding in the proximal femoral shaft; however this technique don’t permit a same preservation of acetabular bone stock and a mini invasive surgical approach. From January 2003 the Authors have performed 5 metal-on-metal Birmingham hip resurfacings in patient under the age of 58 with avascular necrosis of the femoral head (without a wide necrosis) or primary osteoarthritis. In all cases was performed a posterior approach slightly more extended to permit the release of the gluteus maximus tendon; the rehabilitation program involve immediate full weight bearing one day postoperatively. Data were collected intraoperatively and postoperatively in a prospective way. The early clinical and radiological results are very satisfactory: resurfacing hip arthroplasty appears to be a good alternative for the treatment of young patients, permitting a preservation of femoral bone stock and early functional recovery. In our opinion the key factors for a good result is a meticulous technique and a good bone quality.
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.
