BETTER ALIGNMENT AND CEMENT MANTLE QUALITY WITH NEW MODERN TECHNIQUE FOR INSERTION OF THE CHARNLEY STEM. A COMPARISON BETWEEN OLD AND NEW TECHNIQUE IN HEMIPROSTHESIS FOR PRIMARY FEMORAL NECK FRACTURE

Abstract

Malalignment and cement mantle quality have been implicated in loosening of the Charnley stem [2]. Several types of cemented prosthesis have adopted a modern insertion technique, which has not been available for the Charnley stem. We implemented a new technique for insertion of the Charnley stem via the Hardinge approach including a distal centralizer, broaches and specific entry into the femoral canal via the piriformisfossa, and compared it to the old technique for alignment of the stem and cement mantle quality.

Material and methods: Forty-two patients (34 women) operated with an old technique were compared with forty-nine patients (39 women) with the modern technique. All patients were operated through the Hardinge lateral approach, with primary hemiprosthesis by residents. Post-operative anteroposterior and true lateral radiographs were taken and evaluated for cementing quality [1], mantle thickness in the 14 Gruen zones, and alignment of the femoral stem in both planes.

Results: For the Barrack classification there was 9 grade A with the new technique, compared to none with the old (p< 0.0001, Table 1), and only 1 grade B with the old technique. The cement mantle thickness was more uniform (p< 0.0001), and the mean thickness was higher with the new technique for zones 1-3, 5-10 and 12 compared to the old technique. Alignment as measured in the lateral plane by the mean anteroposterior angle was 5.2° with the old technique, compared to 2.2° for the new technique (p=0.0001). In the frontal plane there was no difference.

Discussion: A modern insertion technique for the Charnley stem gave a much better cementing quality, better cement mantle uniformity and a thicker mantle in the critical zones, and more neutral alignment of the stem. As poor alignment and thin or absent cement mantle has been implicated in loosening the results should hopefully confer into longer survival.