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.

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.