Radiological stability of a quadrangular uncemented femoral component compared with its shortened version in primary total hip arthroplasty : a prospective randomized controlled trial.

Aims: Cementless femoral fixation is widely used in total hip arthroplasty (THA), with increasing interest in shorter femoral component designs. These femoral components aim to preserve proximal bone, promote physiological load transfer, and facilitate minimally invasive approaches. Among these, 'shortened' femoral components, derived from conventional stems and retaining a diaphyseal extension, may offer advantages in terms of implant positioning. However, clinical evidence regarding their mechanical reliability remains limited. This study aimed to compare the two-year radiological stability of a shortened uncemented quadrangular femoral component with that of its conventional-length counterpart in patients undergoing THA for osteoarthritis.

Methods: We conducted a prospective, single-blind, randomized, noninferiority trial between January 2018 and December 2021. Patients undergoing primary THA were randomly assigned to receive either the conventional-length quadrangular femoral component or its shortened version. The primary outcome was femoral component migration at two years, assessed with Ein Bild Roentgen analyze - femoral component analysis (EBRA-FCA). Secondary outcomes included intraoperative and postoperative complication rates, as well as the 12-item Oxford Hip Score (OHS) at 12 months.

Results: A total of 143 hips were randomized, with 139 (70 conventional-length, 69 shortened) included in the clinical analysis. Per-protocol radiological analysis was carried out on 98 hips (49 hips per group). At two years, mean femoral component migration was 0.94 mm (SD 0.49) in the shortened-femoral component group and 0.86 mm (SD 0.52) in the conventional-length group. The upper bound of the 90% CI (-0.09 to 0.25) was below the prespecified noninferiority margin of 1 mm. No significant differences were observed in complication rates or functional outcomes (p > 0.05).

Conclusion: At two years, radiological outcomes of the shortened quadrangular femoral component were consistent with noninferiority compared with the conventional-length version. Although the planned sample size was not fully reached, the findings remained within the prespecified noninferiority margin.