The direct anterior approach provokes varus stem alignment when using a collarless straight tapered stem

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering

Background:

• Inaccurate stem implantation in total hip arthroplasty (THA) can compromise outcomes.
• Direct anterior approach (DAA) learning curve presents challenges in achieving optimal stem alignment.

Purpose of the Study:

• To retrospectively analyze stem alignment during the DAA learning phase for primary THA.
• To evaluate the impact of stem alignment on femoral offset reconstruction and patient parameters.

Main Methods:

• Retrospective analysis of 93 cementless THA cases using DAA.
• Assessment of varus/valgus stem alignment on postoperative radiographs.
• Evaluation of correlations with patient demographics and radiological parameters.

Main Results:

• 59% of stems were implanted in varus alignment (mean +2.2°).
• Varus alignment correlated with male gender and preoperative coxa vara (low CCD, high femoral offset, long thigh neck).
• No correlation found between alignment and femoral offset restoration, BMI, or leg length discrepancy.

Conclusions:

• DAA learning curve is associated with a high incidence of varus stem alignment with straight tapered stems.
• Male patients with coxa vara are particularly susceptible to varus alignment.
• Intraoperative X-rays are advised during DAA learning to confirm implant positioning.