Normative values of non-radiological surface measurement of the lumbar lordosis curvature in the standing position and its association with age, sex, and body mass index: a cross-sectional study of 2,500 healthy individuals from Iran.

Study design: A cross-sectional study.

Purpose: This study aimed to define the normal values of the lumbar lordosis curve (LLC) and investigate its association with sex, age, and body mass index (BMI).

Overview of literature: The importance of the human spine's sagittal alignment, particularly in the lumbar region, has been argued from the physiological and pathophysiological points of view. The LLC size is an important predictor of lumbar pathologies. Lumbar curvature misalignment, particularly increased lumbar lordosis or hypolordosis, can, in the long term, lead to spinal instability and development of disorders such as low back pain and spondylolisthesis Therefore, knowledge about the normal LLC value and its association with age, sex, and BMI, appears crucial.

Methods: The study recruited 2,497 asymptomatic volunteers (1,264 women and 1,233 men) aged 5-85 years. Participants were assigned to different groups based on their sex, age, and BMI. The LLC was measured using a Flexicurve.

Results: Normal LLC values were established for different sexes, age, and BMI groups. Overall, normal LLC ranges from 10.2° to 74.9° with a mean of 42.34°±13° (male, 38.57°±11.44°; female, 46°±13.38°). LLC was generally higher by 7.5° in women than in men. A significant three-way interaction of sex, age, and BMI with LLC was found. The association of age and BMI with LLC was also significant.

Conclusions: Our results can be used as a reference by physicians, healthcare, etc., when the LLC values in different ages and sexes are measured noninvasively. In other words, this information can be used as reference when determining whether the obtained LLC is within the normal range.