Does Fluoroscopic-Aided Enabling Technology Improve Acetabular Component Position and Reduce Radiation Exposure in Direct Anterior Total Hip Arthroplasty?

Abstract

Accurate acetabular component positioning is crucial for the success of total hip arthroplasty (THA). Malplacement of the acetabular component increases the risk of post-surgery complications, most notably dislocation.1 Furthermore, malposition can also result in wear of the polyethylene liner, limited range of motion, and osteolysis.2,3 These complications have led to controversy regarding the optimal acetabular component position. The historic Lewinnek "safe zone" defines the ideal acetabular placement as within 40° +/- 10° abduction and 15° +/- 10° anteversion.4 However, recent controversy has emerged regarding the ideal placement of the acetabular component with one systematic review showing acetabular components placed within the Lewinnek parameters having no significant difference in dislocation rate to those components placed outside the "safe zone."5 Callanan et al. found that a range of 30-45° of abduction and 5-25° of anteversion was the ideal target zone while other studies have argued that the historic safe zone, while useful, should not be considered completely protective against dislocations.6,7 In addition, the spinopelvic relationship as it relates to changes in acetabular cup orientation from a standing to seated position may alter cup placement from the "ideal" position to accommodate reduced spinopelvic junction motion and limit the risk of postoperative instability.8 Secondary to risk of acetabular cup malposition during THA, fluoroscopically aided enabling technology (FET) has gained popularity recently, secondary to proposed benefits of improved accuracy of intraoperative component positioning over standard landmark identification or the use of fluoroscopy alone (FA), as well as minimizing the risk of significant postoperative leg length discrepancies.9,10 In addition, further factors such as not needing special preoperative imaging, minimal change to workflow or surgical approach, and the possibility of reduced operative times have made the use of this technology appealing.11 In addition to the debate regarding ideal acetabular component position to reduce postoperative complications, there has been ongoing discussion regarding the potential detrimental effects of cumulative radiation dose to the surgeon, patient, and operating room personnel when using fluoroscopy for placement of the acetabular component in direct anterior approach total hip arthroplasty (DAA-THA). Prior studies have shown that during DAA- THA, average radiation time was 15.1 seconds (secs), and exposure was 2.00mGy with increasing exposure seen as patient body mass index (BMI) increased.12,13 In theory, FET may help to reduce radiation exposure through less use of intraoperative fluoroscopy for confirmation of acetabular component position. The questions proposed in this study are: 1) Does FET improve the accuracy of acetabular component position versus FA in DAA-THA? and 2) Does FET reduce fluoroscopy time and radiation exposure compared to FA in DAA-THA, and is this dependent upon the BMI of the patient?