Orientation of the human sacrum: Anthropological perspectives and methodological approaches

Abstract

Discovering the nature of sacral orientation is of considerable anthropological importance. Therefore, this study aims at presenting a new anthropologically based definition for sacral anatomical orientation (SAO) angle, establishing standards of SAO for human population; examining the relationship between pelvic incidence (PI) and SAO; and associating SAO with demographic parameters. The study population consisted of 424 adult and 14 sub-adult (13-18 years, for SAO only) pelvises. Sacral orientation was measured using two different definitions: a) SAO is the angle created between the intersection of a line running parallel to the superior surface of the sacrum and a line running between the anterior superior iliac spine (ASIS) and the anterior-superior edge of the symphysis pubis; b) PI is the angle created between the perpendicular to the sacral plate at its midpoint and the line connecting this point to the middle of the axis of the acetabulum. SAO was measured using a specially designed mechanical measurement tool and a 3D digitizer. PI was measured via the 3D digitizer. The methods developed by us for measuring SAO and PI in skeletal material are valid and reliable. SAO and PI measures were highly correlated (r = -0.824, P < 0.001). The average SAO was 49.01 degrees (SD = 10.16), and the average PI 54.08 degrees (SD = 12.64). SAO was independent of ethnicity and sex, yet age dependent. This study establishes a methodology for estimating SAO and PI in skeletal material and furnishes the anthropological milieu with base line data regarding these parameters. Future studies in human evolution can greatly benefit from this study.

Middle Pleistocene lower back and pelvis from an aged human individual from the Sima de los Huesos site, Spain

“…These three variables are angular position-independent anatomical parameters. In modern humans, the SAO has been found to be strongly and negatively correlated with the PI (r = −0.824) (26). Modern humans also show significantly positive correlations between the pelvic anatomical parameter PI and the positional parameter sacral slope (SS) (r = 0.63-0.86) that in turn is also significantly positively correlated with the positional parameter lumbar lordosis (LL) (r = 0.68-0.89).…”

Radiographic evaluation of the lumbar lordotic angle of the spine in a population of Nigerians

“…Authors using relatively younger subjects; but significant increases in lumbar lordotic angle with age. However, 11,20,25 any significant association between lumbar lordosis and age. The higher standing of the Coefficient of variation in the younger age group and the significant association between lumbar curvature and old age, is remodeling through the mechanism of osteoclasts osteoblasts, as opposed to degenerative changes in the older age group, with greater involvement This study consisted mainly of young adults, middle age and the old adults.…”

“…17 , in his study of 105 Nigerians, using a flexi curve, found an increase in the thoraco lumbar curvature of more than 20% in Nigerians compared to Caucasians. To the contrary, 17,18 the greater curvature seen in African Americans is due to greater buttock size, whereas lumbar lordosis angle of 61 0 in whites By way of single variable calculus, and using table 3 and figure 2, a probability density function curve he cumulative sum of the frequency of a given angle, summed progressively over successive angles and then multiplying by 100/N(300) was constructed(figure3), using the om table 2 An increase in lumbar lordotic angle was observed from 18 years, to 37 years, with a plateau about age 47 to 67 years investigation also demonstrated significant age related differences in lumba lordosis angle, which were observed between different age groups particularly 58-77 years (Table3 flexibilities in the degree of lordosis in age were noted by 20 gradual increase in lumbar lordotic angle up to middle age followed by a decrease. This result is also similar to the works of statistically significant variation in lordosis angle of different age groups, with older individuals showing higher values.…”

“…This result is also similar to the works of 21, 12, and 23 , who found a statistically significant variation in the lumbar lordosis angle of different age groups, with older individuals showing higher values. Authors using subjects; 24,5 observed gradual but significant increases in lumbar lordotic angle 11,20,[25][26][27] failed to demonstrate any significant association between lumbar lordosis and age. The higher standing of the Coefficient of variation in the younger age group and the significant association between anterior curvature and old age, is remodeling mechanism of osteoclasts and osteoblasts, as opposed to degenerative changes group, with greater involvement of osteoclasts.…”

“…The probability density function curve derived from (Table 2 & Figure 2), provides a practical mathematical selection tool for estimating the magnitude of deviation from normal, given an individual's race, age, gender and estimated angle of lumbar lordosis. Authors using relatively younger subjects......However, 11,20,[25][26][27] , failed to demonstrate any significant association between lumbar lordosis and age.…”