The Artek cup for total hip replacement of dysplastic hip joints

One specific difficulty in total hip replacement for developmental dysplasia of the hip is a shallow acetabulum with a short anteroposterior diameter. In a prospective cohort study we investigated the short-term results of the Artek cup, designed with a shallow outline and a height-reduced metal inlay for a large size 38 mm metal head, in a group of female patients with mild dysplasia of the hip.

Fourteen consecutive patients with 17 dysplastic hip joints were included in the study. Their average age was 42 years. Fourteen hips had dysplasia Crowe grade I; 3 hips had dysplasia Crowe grade II. The femoral head centre was localized according to Pagnano in zone 1 in 3 cases, in zone 3 in 6 cases, and in zone 4 in 8 cases. The Harris hip score was 49 points (range 30-68 points).

Mean follow-up was 20 months (range 14-24 months). The Harris hip score improved to a mean of 91 points (range 78-98 points). The postoperative radiographic measurements showed an inclination angle of 52.1 degrees (range 43-66 degrees ). The femoral head centre was in Pagnano zone 1 in 13 cases, in zone 2 in 1 case, in zone 3 in 1 case, and in zone 4 in 2 cases. The mean postoperative deviation from the approximative rotational centre was 0.17 mm (range -15 to 13 cm) in the superior direction and 5.3 mm (range -5 to 17 mm) in the lateral direction.

In a small series of 17 implantations, stable press-fit fixation without screws or bone grafting was achieved despite acetabular defects. The complication rates were high. Inclination angles up to 54 degrees were not correlated with complications. Inclination angles of 60 degrees and more led to subtotal or complete dislocation. Mid-term results are still to follow concerning wear, dislocation rate, loosening and revision.