Assessing Posterior Femoral Neck Cortical Line for Stem Anteversion in Direct Anterior Hip Replacement: A Retrospective Analysis

Background and Objective: Unlike the native femoral cortical line, consensus is lacking on osteotomy landmarks for stem placement. Templating alone often fails to achieve a proper femoral version, highlighting critical intraoperative neck height-cutting parameters. This study evaluated the reliability of using the posterior femoral neck cortical line on osteotomy surfaces as a reference landmark for correcting version angle during total hip arthroplasty via the direct anterior approach. Materials and Methods: Data from patients who underwent unilateral total hip arthroplasty (THA) via the direct anterior approach (DAA) by the same surgeon between March, 2015 and June, 2016 were analyzed. The 63 patients (29 females, 34 males; mean age 64.9±9.5 years) met the inclusion criteria. The CT scans and 3D reconstructions were used to measure anteversion at various lines. The study was approved by the RenMin Hospital Review Board, with informed consent obtained from all patients. Results: The indications for surgery were osteoarthritis (OA) and osteonecrosis (ON), which accounted for 43 and 20 cases, respectively. There were significant relationships between native femoral anteversion and posterior femoral cortical line anteversion (r = 0.8831, p<0.001; r = 0.866, p<0.001 and r = 0.8436, p<0.001 at 5, 10 and 15 mm cutting heights, respectively). Conclusion: There is a crucial need for the posterior cortical line to be universally adopted as a reference cutting surface to optimize stem positioning and achieve a satisfactory femoral version during DAA THA.