Software-Aided Versus Unassisted Fluoroscopy in Optimising Limb Length and Component Placement in Direct Anterior Total Hip Arthroplasty

Background Intraoperative fluoroscopy has been the gold standard in direct anterior approach (DAA) total hip arthroplasty (THA) to assess the position of the components. Fluoroscopy could be aided by software to help surgeons plan and execute the THA optimally; however its clinical effectiveness has not been proven. This study assessed the use of fluoroscopy with intraoperative software to evaluate the ability of the software to accurately measure the component position and leg length discrepancy (LLD) in DAA. Methods Thirty-eight patients (39 procedures) were prospectively selected from consecutive patients treated using software-aided fluoroscopy (Group 1). Thirty-eight patients (38 procedures) were retrospectively enrolled into the control group (Group 2) from patients using intraoperative fluoroscopy without software analysis. Patients in both groups underwent THA using DAA. A mobile C-arm image intensifier unit was used to obtain images of the affected hip intraoperatively. In Group 1, the LLD and cup inclination were calculated intraoperatively by the software. The LLD, cup inclination and anteversion were measured for both groups using antero-posterior (AP) X-rays at six weeks postoperatively and were compared to the preoperatively planned targets. Results The mean postoperative LLD was significantly less in Group 1 when compared to Group 2 (2.2mm vs 4.6mm, p<0.01). In Group 1, 100% of hips (39/39) had a radiographic LLD within 10mm compared with 97% (37/38) in Group 2. The cup inclination and cup anteversion achieved within Group 1 were closer to the planned inclination and anteversion when compared to the control. Conclusions Intraoperative software analysis of fluoroscopy in THA aids accurate implantation of THA using the DAA approach with regard to leg length equality and acetabular component positioning.