Does Compensatory Anterior Pelvic Tilt Decrease After Bilateral Periacetabular Osteotomy?

Area of Science:

• Orthopedic surgery
• Hip biomechanics
• Pelvic anatomy

Background:

• The relationship between lumbar spine, pelvic tilt, and hip is hypothesized but understudied in acetabular dysplasia.
• Patients with acetabular dysplasia may exhibit compensatory anterior pelvic tilt, potentially influenced by acetabular reorientation.

Purpose of the Study:

• To determine if compensatory pelvic tilt decreases after bilateral periacetabular osteotomy (PAO).
• To validate the pubic symphysis to sacroiliac (PS-SI) index as a surrogate measure for pelvic tilt using a synthetic bone model.
• To assess the interrater reliability of the PS-SI index.

Main Methods:

• Retrospective analysis of 40 patients undergoing staged bilateral PAO.
• Measurement of pelvic tilt using the PS-SI index on preoperative and postoperative radiographs.
• Validation of the PS-SI index with a synthetic bone model and direct pelvic tilt measurement.
• Assessment of interrater reliability using the intraclass correlation coefficient (ICC).

Main Results:

• 93% of patients showed a decrease in pelvic tilt post-PAO, with a mean reduction of 8 mm in the PS-SI index (p < 0.001).
• A strong linear correlation (R=0.99) was found between the PS-SI index and measured pelvic tilt in the synthetic bone model.
• The PS-SI index demonstrated excellent interrater reliability both preoperatively (ICC=0.986) and postoperatively (ICC=0.988).

Conclusions:

• Bilateral PAO leads to a modest reduction in anterior pelvic tilt, indicating acetabular reorientation influences pelvic position.
• The PS-SI index is a reproducible radiographic tool for assessing pelvic tilt in patients with acetabular dysplasia.
• Further research should explore the clinical implications of pelvic tilt changes, including potential effects on back pain.