Assessment of the Femoral Neck-shaft Angles of Adults in Nigeria: Establishing an Age and Gender Stratified Reference Values

Background: The femoral neck-shaft angle (FNSA) has essential roles in the diagnosis of hip pathologies such as femoral neck fractures, developmental dysplasia of the hip and coxa vara and in the templating of implants and prosthesis for surgical fixation of femoral neck fractures and arthroplasties for hip pathologies. Most studies on the FNSA were done in western countries, and current hip implants in use are based on these studies. Since anthropometric measurements differ among races, it is possible that the FNSA might be different in Africans compared to the Caucasians.

Aim: This study aims to establish normal FNSA for adults in Nigeria stratified by age and gender.

Methods: This work was a cross-sectional study. We examined the pelvic x-rays of 75 patients, 30 males and 45 females, with no hip pathology. We also collected relevant biodata such as age, gender, weight and height. The ages of the subjects were categorized in a 10-year grouping from 20 to 99 years. The body mass index (BMI) was calculated for each participant and each subject was classified as normal weight, overweight or obese based on the BMI value. The FNSA was measured with a Goniometer both for the right and left side. The values of the FNSA was compared for both genders and the age categories. We also compared the mean FNSA for the right and left sides and assessed for significant differences in the FNSA among the groups of the body mass index.

Results: The mean age of the participants was 64 years ± 16.93 years. The mean FNSA was 131.04°± 3.86, with a range of 20° (120 – 140°). Males had a mean FNSA of 131.43° compared to females who had a mean FNSA of 130.78°, although the difference was not statistically significant. Also, no significant differences in the mean FNSA were seen concerning age categories, sides and BMI groups.

Conclusion: The mean FNSA of adults in this study is different from the western textbook value of 125°. This should be borne in mind when manufacturing hip implants and prostheses for domestic use.