The Sacro-Femoral-Pubic Angle May Estimate Pelvic Tilt in Patients with Severe Developmental Dysplasia of the Hip and Leg Length Discrepancy Undergoing Total Hip Arthroplasty.

Abstract

Background: Spinopelvic movement disorders are associated with instability after total hip arthroplasty (THA). In patients with Crowe type 3-4 developmental dysplasia of the hip (DDH) and leg length discrepancy (LLD), sagittal radiographs may not allow accurate assessment of spinopelvic motion. This study aimed to evaluate the sacro-femoral-pubic (SFP) angle, a coronal plane parameter, as a predictor of calculated pelvic tilt (PT).

Methods: Thirty-two patients with neglected unilateral Crowe type 3-4 DDH who underwent THA were retrospectively analyzed. Preoperative SFP angle and sacral slope (SS) were measured, and preoperative PT was calculated using postoperative pelvic incidence and preoperative SS values.

Results: The SFP angle showed a strong negative correlation with calculated PT (r = -0.77, p < 0.001). Linear regression analysis demonstrated that the SFP angle was a significant predictor of PT (β = -1.02, 95% CI, -1.32 to -0.72; adjusted R ² = 0.58). The regression model demonstrated a root mean square error of 5.46°.

Conclusions: The SFP angle may serve as an indirect surrogate for calculated PT in patients with Crowe type 3-4 DDH and LLD when preoperative sagittal spinopelvic assessment is not feasible prior to THA or spinal deformity surgery.