Abstract
Purpose: Fracture of the neck of the femur in elderly subjects is generally treated by arthroplasty, either using a total or intermediary hip prosthesis, but with a high risk of dislocation, estimated at about 10% in the literature. We investigated the contribution of a double mobile cup to lower this risk.
Material and methods: This prospective study was conducted by several operators in the same university unit between 1998 and 2001. A total of 177 mobile prostheses were implanted in patients with fracture of the anatomic neck of the femur (n=145), the neck and trochanter (n=22), or pathologic fracture (n=4). For six patients, the prosthesis was implanted after failed osteosynthesis of a trochanteric fracture. The postero-lateral approach was used for 136 women and 41 men (age range 61 – 92 years) living at home (n=124), or in an institution with a high degree of independence (n=53). The femoral stem was cemented (n=115) or impacted (n=62). A double mobile cup was used in all cases. A chromium-cobalt/ polyethylene couple was used and head diameters were 28 mm (n=150) or 22.2 mm (n=27). We studied outcome and risk of dislocation one year after implantation.
Results: There were six deaths during the postoperative period. Among the 171 patients, 134 were seen at two months, 108 at six months and 89 at one year: 39 were questioned to ascertain outcome. During the first postoperative year, there were 37 deaths; these patients were followed. Six patients were lost to follow-up. We had two cases of intraprosthetic dislocation related to a defect in the chromium-cobalt head retention of the polyethylene insert. These two cases required revision and were reported to material surveillance with corrective measures for the manufacturer.
There were three true dislocations (2%): 1) a posterior dislocation on day 24 in a female patient presenting a fracture with impaction of the femoral stem; 2) a posterior dislocation on day 22 in a female patient in very poor general condition (severe cardiorespiratory failure, death at 48 hr); 3) one recurrent posterior dislocation related to major acetabular retroversion, revised at four months.
Discussion and conclusion: The double-mobile cup appears to be a simple reproducible method for preventing dislocation of prostheses implanted for fracture of the neck of the femur.
The abstracts were prepared by Docteur Jean Barthas. Correspondence should be addressed to him at Secrétariat de la Société S.O.F.C.O.T., 56 rue Boissonade, 75014 Paris.
