NO PERI-PROSTHETIC RADIOLUCENCY AT 10 YEARS AROUND A PURE TITANIUM PRESS-FIT CUP: IMPORTANCE OF EQUATORIAL FINS FOR INITIAL MECHANICAL STABILITY

Abstract

Press-fit cups have given excellent clinico-radiographical results. This is a retrospective clinico-radiographical study about the long term performance of pure Titanium cementless modular press-fit cups (FitekTM) having, on the outer surface, an oriented multilayer titanium mesh (SulmeshTM) with 65% porosity (average pore size=400–640 micron). The cup was implanted after underreaming the acetabulum by 2 mm. In the cup’s equatorial area there are two “fins” originary designed to improve rotational stability but actually representing two excellent primary mechanical stabilizers.

We have evaluated the first 100 consecutive cups implanted in 92 patients with an average FU of 9,7 years (range 9–11 years). All operations have ben performed by the two Senior Authors (PGM and RB). Regarding etiology, we had 43 Primary Arthritis, 37 Dysplastic Arthritis, 12 Osteonecrosis and 8 Post-traumatic Arthritis. results were evaluated with the Harris score. Radiographic evaluation was performed using AP and lateral x-rays pre-op. post-op and at the last follow-up.

We had 86 Excellent, 10 Good, 2 Fair and 2 Poor. The 2 Poor results were 2 aseptic loosenings of the stem

The Mann-Whitney nonparametric U test and the Kruskal-Wallis test showed that the survival rate of the 100 analyzed cups, after a mean follow-up of 9.7 years, was 100% (end point: revision for any cause)

Etiology was not statistically correlated with post-op score.

Nevertheless, dysplastic patients showed inferior results compared to arthritic patients in different parameters, as pain, limp, Range Of Motion (p < 0.05), putting socks and shoes (p < 0.05).

Our cups were intentionally implanted and radiographically appear in a fairly horizontal position (36.5° on average).

In 6 cases we could calculate an eccentricity of the metal heads proving bidimensional linear wear of the liner (average 0.265 mm / year). At the last follow-up we had 3 femoral osteolysis, while in the acetabular side radiolucent lines were present in 14 % of the cases, never progressive.

In no case we found a change of position of the cup.

FitekTM cementless cups gave excellent results at 10 years with complete stability and osteo-integration. Excellent primary mechanical stability was given by the rough surface (SulmeshTM) and by the two “fins” in the equatorial area.