How do global sagittal alignment and posture change after total hip arthroplasty?

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Radiology

Background:

• Postural changes following total hip arthroplasty (THA) remain a subject of debate.
• Prior research primarily focused on pelvic motion, neglecting global sagittal posture.
• This study investigates post-operative changes in global sagittal posture, including pelvic, spinal, and lower extremity parameters.

Purpose of the Study:

• To analyze the impact of primary THA on global sagittal posture.
• To identify the correlation between pelvic incidence (PI) and post-operative postural adaptations.
• To evaluate changes in pelvic tilt, sagittal vertical angle (SVA), global sagittal angle (GSA), and T1 pelvic angle (TPA).

Main Methods:

• 139 patients undergoing primary THA without prior spinal or lower extremity surgery were included.
• Pelvic parameters (sacral slope, PI, pelvic tilt, anterior pelvic plane angle) and global posture parameters (SVA, GSA, TPA) were measured.
• Patients were stratified into low (<45°), medium (45°-65°), and high (>65°) PI groups.

Main Results:

• Mean GSA and SVA decreased post-operatively (p<0.01).
• Low PI group showed significant decreases in GSA and SVA with increased posterior pelvic tilt; TPA increased significantly (p=0.048).
• Medium PI group exhibited decreased SVA with posterior pelvic tilt; high PI group showed no significant postural changes.

Conclusions:

• Pelvic incidence (PI) is a critical determinant of pelvic tilt modification after THA.
• Patients with low PI demonstrate substantial spinal, pelvic, and lower extremity postural adjustments.
• Pelvic tilt serves as the primary adaptation mechanism for medium PI patients, while high PI patients show minimal change.