Acetabular Anteversion Changes Due to Spinal Deformity Correction: Bridging the Gap Between Hip and Spine Surgeons

Area of Science:

• Orthopedic Surgery
• Spine Surgery
• Hip Surgery

Background:

• Hip osteoarthritis frequently coexists with adult spinal deformity, characterized by sagittal spinopelvic malalignment.
• A clinical debate exists regarding the optimal sequence of surgical interventions: spinal realignment or total hip arthroplasty.
• Hip extension and pelvic tilt are crucial compensatory mechanisms in sagittal spinopelvic malalignment, and their behavior changes post-spinal realignment.

Purpose of the Study:

• To evaluate the impact of surgical spinal realignment on acetabular anteversion in patients with prior total hip arthroplasty.
• To investigate the relationship between changes in spinopelvic parameters and acetabular anteversion following spinal correction.

Main Methods:

• Retrospective review of a multicenter, prospective database of adult spinal deformity patients undergoing surgical spinal realignment.
• Inclusion criteria: patients with prior total hip arthroplasty and available imaging; exclusion criteria: insufficient imaging, large-head metal-on-metal bearings, or revision total hip arthroplasty.
• Acetabular anteversion was measured using the ellipse method on standing AP radiographs preoperatively and at 6 weeks/3 months post-spinal realignment.

Main Results:

• Acetabular anteversion significantly reduced by -4.96° (p < 0.001) after spinal correction.
• The change in acetabular anteversion correlated strongly with changes in pelvic tilt (0.828), sacral slope (-0.757), lumbar lordosis (-0.691), sagittal vertical axis (0.579), and T1 pelvic angle (0.585).
• Regression analysis indicated a 1° decrease in anteversion for every 1.105° change in spinopelvic tilt, 1.032° change in sacral slope, and 3.163° change in lumbar lordosis (p < 0.001).

Conclusions:

• A high prevalence of excessively anteverted acetabular components was observed in patients with spinopelvic malalignment.
• Sagittal spinal correction following total hip arthroplasty leads to a reduction in acetabular anteversion, potentially influencing implant stability.
• Changes in acetabular anteversion are predominantly associated with alterations in pelvic tilt, occurring in an almost one-to-one ratio.