METAL-ON-METAL CEMENTLESS ARTHROPLASTY FOR THE TREATMENT OF ARTHRITIS FOLLOWING CONGENITAL HIP DISEASE

Abstract

Little is published about the use of cementless conical stems in primary hip arthroplasty for congenital hip disease. A conical stem was designed in the 80’s by Prof. Wagner. The stem is made of a rough blasted titanium alloy with a cone angle of 5° and 8 sharp longitudinal “ribs” that cut into the inner cortex, designed to achieve rotational stability: The ribs depth of penetration ranges between 0.1 and 0.5 mm and is also very important to achieve osteo-integration. The CCD angle is 135°. The stem is straight and can be implanted in any degree of version thus being very useful for dysplastic arthritis with significant femoral neck anteversion.

Between 1993 and 1998 the senior author (RB) implanted 92 conical stems in 88 consecutive patients with dysplastic arthritis. The acetabular component was cementless and titanium with tridimensional porosity. The articulating surface was a second generation Metal-on-Metal.with a femoral head of 28 mm. According to the Hartofilakidis classification 63 patients had type A, 18 type B and 11 type C.

The average follow-up was 11.2 years (range 10.1–14.8)

Using the Harris Hip Scoring system we had 82 (89%) satisfactory results, with excellent correction of pre-op pain (42/44 Harris) and no case of anterior thigh pain; 88% of patients had no or slight limp at follow-up. No patient required revision of the stem, but one cup required revision for loosening (Type C class). We had one dislocation (1%) that was treated conservatively

Radiographically, all stems were osteo-integrated, 17% showed some resorption in femoral zone 1 and 7. In the same zones we observed 4 cases of real osteolysis without loosening. No radiolucent line was observed in other femoral zones. In the acetabular side we had 13 cases (14%) of radiolucency, but in only 1 case (1%) was it progressive.

A straight conical titanium femoral stem gave very satisfactory clinico-radiographical results in dysplastic arthritis at a mean of 11.2 years of follow-up.