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

摘要

Background. - The recommended range of anteversion of the components in total hip arthro-plasty (THA) is between 10 and 30deg, 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. Materials 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 10deg to 30deg, acetabular anteversion of 10deg to 30deg and a global combined anteversion of 25deg to 55deg. Cup position was checked with an impactor-positioner, and stem position was determined with the knee flexed 90deg. 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 17deg of retroversion to 60deg of ante-version with a mean of 23.0deg +-11.8deg. Similarly, acetabular component version ranged from 28deg of retroversion to 46deg of anteversion with a mean of 18.5deg +-13.7deg. There were no correlations to the native femoral and acetabular versions. Only 55 hips (60.4%) were within the accepted range of 25deg to 55deg of combined anteversion, but none of the cases dislocated during a follow-up of two 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 10deg to 30deg of anteversion. Level of evidence. - Level III prospective diagnostic.