Normative values of the alpha angle and triangular index measured from the hip radiographs of an African population.

INTRODUCTION: Undetected femoroacetabular impingement (FAI), caused by asphericity of the femoral head, has been implicated as a leading cause of hip osteoarthritis in later stages. Two known types of impingement of the femur head with the acetabulum include the cam-type and pincer type, and the alpha angle and triangular index are indices applied in determining the presence of FAI in a hip radiograph. OBJECTIVE: To determine the normal range and upper limit of normal of the alpha angle and triangular index of an African population using non-pathological hip radiographs. MATERIALS AND METHODS: Hip radiographs of 104 subjects reported to be normal were retrospectively studied. The images were reassessed jointly by three radiographers and afterwards by three consultant radiologists. The alpha angle and triangular index of selected radiographs were measured with appropriate electronic callipers. Values obtained were correlated with the age and gender of the patients. RESULTS: The mean ± SD of the alpha angle for the population studied was 46.70 ± 12.340 with a range of 33.300-96.820 (males: 45.09 ± 12.030, females: 47.32 ± 12.370), and the upper limit of normal obtained was 79.160. The mean triangular index was 1.71±1.38 with a range of 0.03-5.98 (males: 1.77 ± 1.39, females: 1.65 ± 1.36), 4.12 being the upper limit of normal. There was no statistically significant difference between measurements of both indices with age and gender. However, there was excellent agreement between and within raters for both measurements (alpha angle: 0.992; triangular index: 0.924). CONCLUSION: The upper limits of normal for the alpha angle and triangular index of the studied population are 79.160 and 4.12. Age and gender were independent of the values measured, and the measurements demonstrated excellent inter-rater and intra-rater agreement. A normal range is thus provided, with upper limits beyond which a possible femoroacetabular impingement may be diagnosed.

Sonographic correlation of foetal neck circumference and area with gestational age among pregnant women in Port Harcourt, Nigeria.

The purpose of this study was to create a reference range nomogram of foetal neck circumference (FNC) and foetal neck area (FNA) in a Nigerian population using polynomial regression models. This cross-sectional study involved 723 pregnant women between 14 and 40 weeks of gestation. Axial measurements of the FNC and FNA were obtained in three measurements and the mean taken as the final value and the 5th, 50th and 95th percentiles for each foetal gestational age (FGA) were calculated. FNC and FNA correlated strongly with FGA, biparietal diameter, abdominal circumference, head circumference, and femoral length. Cubic models fitted the FNC vs FGA, and FNA vs. FGA values, and the mathematical relationships are given as: [Formula: see text] [Formula: see text] [Formula: see text]. Nomograms of FNC and FNA are thus generated. Impact statement The foetal neck circumference (FNC) and foetal neck area (FNA) can serve as predictors of foetal gestational age (FGA) since they correlate strongly and positively with FGA and known biometric parameters. The measurements obtained vary with the population studied. This study provides a nomogram of the FNA and FNC for an African population. The values correlate with that of the Caucasian population up to 32 weeks FGA. Interestingly, FNA and FNC measurements demonstrate high correlation but poor agreement in measurements between sonographers. Even though FNA and FNC could be used as predictors of foetal gestational age, the measurements vary significantly between sonographers. This is attributable to the difficulty in obtaining a satisfactory axial view of foetal neck, which is dependent on foetal presentation.