Letter to the editor on “Dislocations after use of dual-mobility cups in cementless primary total hip arthroplasty: prospective multicentre series” by Hwang et al.

Excerpt

We read with great interest the study by Hwang et al. [1] regarding the incidence of dislocation in cementless primary total hip arthroplasty (THA) using a dual-mobility (DM) construct. This prospective multicentre series aimed to assess the dislocation rate at a minimum of six months’ follow-up in 165 patients with a mean age at surgery of 72 years, 69% of whom were women. The population studied was at very high risk of dislocation, including 142 femoral-neck fractures and 21 cases of osteonecrosis. The approach used was posterior in 120 hips and anterolateral in 47 cases. An M²-a-Magnum™ cup (Biomet, Warsaw, IN, USA) was implanted in all cases. This is a monoblock acetabular component designed specifically for large-diameter metal-on-metal bearing. The mobile liner was a vitamin-E1-impregnated polyethylene (PE), which is the liner of the Avantage™ cup (Biomet) designed for DM use for this manufacturer. In this series, mean cup diameter was 51 mm, with a mean cup inclination of 42°. Four early dislocations occurred (2.3%) at a mean one month delay after surgery (all dislocations occurred for femoral-neck fractures using a posterior approach). Cup diameters in the dislocation group were 48, 56, 58 and 60 mm. …