Slight pelvic obliquity is normal in a healthy population: a cross-sectional study.

PURPOSE: Pelvic obliquity (PO) has not been extensively investigated, and there is no gold standard for measurement. The PO is essential for surgeons in planning hip arthroplasty, which includes the restoration of leg length discrepancy (LLD). We aimed to establish a normative range of PO angles by measuring healthy individuals without musculoskeletal disorders.

METHODS: Our study included 134 consecutive cases (70 females) referred to our institution between April 2020 and September 2021 for non-orthopedic problems. Patients were screened for normal gait and posture using the visual observation method (VOM) and the Modified Gait Abnormality Rating Scale (GARS-M). In standing standard radiographs, the PO angle was measured as the angle between the horizontal plane and the inter-teardrop line.

RESULTS: Patients' mean age and Body Mass Index (BMI) were 39.7 ± 16.8 and 22.3 ± 3.1, respectively. PO angles did not follow a normal distribution, with a median (IQR) of 2.0° (0.9°-3.1°). According to the Wilcoxon one-sample test, the median PO angle differed significantly from zero (P < 0.001). The PO angle did not differ significantly between males and females (2° vs. 2°, P = 0.46), nor did it correlate significantly with age (P = 0.24). Considering the 95% percentile of PO angles was 5.6°, this range (0°-5.6°) was regarded as a normative value.

CONCLUSION: Normative values for PO in the normal healthy population range from 0° to 5.6°, with a median value of 2.0°. The PO angle was independent of age and sex and differed significantly from 0°. Slight pelvic obliquity may be normal, and physicians should not always assume that it is caused by pain, scoliosis, or weakness of the abductors.

LEVEL OF EVIDENCE: III.