Components anteversion in primary cementless THA using straight stem and hemispherical cup: a prospective study in 91 hips using CT-scan measurements.

BACKGROUND

The recommended range of anteversion of the components in total hip arthroplasty (THA) is between 10 and 30°, but the intraoperative estimation of these versions may be inadequate.

HYPOTHESIS

The components anteversion in primary cementless THA using straight stem and hemispherical cup is not significantly different from the native anteversion of the hip joint.

OBJECTIVES

To evaluate in a prospective manner the range of anteversion currently achieved in cementless THA.

PATIENTS AND METHODS

Five senior surgeons operated 91 patients with primary cementless THA. We used a straight press fit stem and a hemispherical press fit cup. We aimed to obtain femoral anteversion of 10 to 30°, acetabular anteversion of 10 to 30° and a global combined anteversion of 25 to 55°. Cup position was checked with an impactor-positioner, and stem position was determined with the knee flexed 90°. In all cases we used elevated liners and 28 mm diameter ceramic heads. At 3 months postoperatively the component versions were measured using a General Electric LightSpeed Pro 16 (Milwaukee, Wi, USA) with the patient in supine position.

RESULTS

Femoral component measurements ranged from 17° of retroversion to 60° of anteversion with a mean of 23.0±11.8°. Similarly, acetabular component version ranged from 28° of retroversion to 46° of anteversion with a mean of 18.5±13.7°. There were no correlations to the native femoral and acetabular versions. Only 55 hips (60.4%) were within the accepted range of 25 to 55° of combined anteversion, but none of the cases dislocated during a follow-up of 2 years.

CONCLUSION

In cementless THA with our operative technique, the intraoperative estimation of femoral and acetabular anteversion, in many cases, resulted to be inadequate in relation to the intended range of 10 to 30° of anteversion.