Determination of the hip rotation centre from landmarks in pelvic radiograph

OBJECTIVE: The hip rotation centre (HRC) is an important reference point in cases of total hip arthroplasty (THA). The aim of this study is to investigate the reference points in the Turkish population that enable the identification of the HRC in standard pelvic radiographs. METHODS: The pelvic radiographs of 50 women and 50 men were examined. The mean age was 46.2 (range; 18–91). Patients with deformity of the hip joint and non-standard pelvic radiograph due to hip flexion contracture were excluded from the study. The pelvic height (PH), the distance between the HRC and teardrop (HRC-Td), and the HRC and the line tangent tuber ischiadicums (HRC-TI) were measured. The ratio of HRC-Td and HRC-TI to PH were calculated. The first is called “the horizontal-HRC ratio” and the second, “the vertical-HRC ratio”. RESULTS: Mean PH was 239 (±13.58) mm in males and 225 (±12.52) in females (p < 0.0001). The distances of HRC-TI were 71 (±6.35) and 65 (±6.72) mm (p < 0.0001) and the distance of HRC-Td were 34 (±3.73) and 30 (±4.05) mm (p = 0.0007), respectively. The vertical-HRC ratios were 30.01% (±2.05) for males, 29.10% (±2.35) for females, the horizontal-HRC ratio, 14.25% (±1.42) and 13.69% (±1.38), respectively (p > 0.05). CONCLUSION: Although the quantitative values obtained in the present study differ between the genders, the ratios (“vertical-HRC” and “horizontal-HRC”) are comparable in both sexes. The results show that these proposed ratios can be used in THA planning, regardless of gender in the Turkish population LEVEL OF EVIDENCE: Level IV, diagnostic study.