Postoperative Limb-Offset Discrepancy Notably Affects Soft-Tissue Tension in Total Hip Arthroplasty

Area of Science:

• Orthopedic Surgery
• Biomechanical Engineering

Background:

• Inadequate soft-tissue tension post-total hip arthroplasty (THA) is linked to dislocation and abductor weakness.
• Limb offset discrepancy, encompassing femoral and acetabular components, is a potential contributing factor.

Purpose of the Study:

• To evaluate the impact of postoperative limb offset discrepancy on soft-tissue tension during THA.
• To compare this effect with other factors influencing soft-tissue tension in unilateral hip disease.

Main Methods:

• 89 patients underwent mini-incision THA with computer navigation.
• Soft-tissue tension was assessed via traction (40% body weight) at varying flexion angles (0-45°).
• Cup-head separation, a measure of tension, was recorded using the navigation system.

Main Results:

• Cup-head separation varied significantly with flexion angles, peaking at 15° (11 ± 5 mm).
• Postoperative limb-offset discrepancy, anterolateral approach, and preoperative range of motion correlated with separation at 15° flexion.
• Limb-offset discrepancy showed a negative correlation with cup-head separation at 0°, 15°, and 30° flexion.

Conclusions:

• Postoperative limb-offset discrepancy significantly influences soft-tissue tension in THA across different flexion degrees.
• Restoring normal limb offset without overlengthening is essential for achieving adequate soft-tissue tension and improving THA outcomes.