Does Intra-operative Fluoroscopy Significantly Improve Component Position in a Primary Total Hip Arthroplasty? Our...

Optimal component placement, equalization of leg lengths, and recreation of offset are important surgical objectives during total hip arthroplasty (THA). Historically, many surgeons have aimed for the Lewinnek's " safe zone," which is defined as 30°-50° of abduction and 5°-25° of anteversion. Methods for optimizing cup position include anatomic landmarks, room landmarks, acetabular cup coverage, and ischial or pubis palpation. Malposition of the acetabular component after total hip arthroplasty (THA) is related to dislocation of the prosthetic femoral head, increased polyethylene liner wear, and limited range of motion. The orientation of the acetabular component comprises inclination and anteversion. Although the inclination of the acetabular component can be easily measured on plain radiographs, the calculation of the anteversion is difficult. This study evaluates the effect of intra-operative fluoroscopy on component position, mainly anteversion and inclination of the acetabular cup, during a total hip arthroplasty.

106 hips undergoing total hip arthroplasty were assessed, and the decision to use fluoroscopy assistance was randomized based on a simple randomization technique. A total of 48 patients were operated on with fluoroscopy assistance and 58 patients without fluoroscopy assistance. All patients were evaluated postoperatively for version of component on anteroposterior radiographs of the hip using the method of Liaw et al. and for inclination of component on anteroposterior radiographs using the method of Woo and Morrey.

The mean version for the non-fluoroscopy (NF) group was 15.62° and the mean inclination was 44.22°, with 15.5% (9 out of 58) of the patients who did not fit into Lewinnek's safe zone for version and 25.9% (15 out of 58) of the patients who were outliers for inclination of the acetabular cup position. The mean version for the fluoroscopy group (F) was 11.80° and the mean inclination was 47.05°, with 0% (0 out of 48) of the patients who did not fit into Lewinnek's safe zone for version and 12.5% (6 out of 48) of the patients who were outliers for inclination of the acetabular cup position.

While the mean version and inclination of the acetabular component were comparable for both groups, outliers for version and inclination were far more common in the group of patients who underwent surgery without intra-operative fluoroscopic assistance. Therefore, intra-operative fluoroscopy imaging confirms appropriate inclination (abduction) and version of acetabular cup position according to Lewinnek's safe zone and prevents undesirable component position during a total hip arthroplasty while adding a maximum of 5 min to the operative time.