Semester of Graduation

Spring 2019


Master of Arts (MA)


Geography and Anthropology

Document Type



Previous research shows that sacroiliac (SI) joint fusion is age and sex dependent. Older individuals—specifically starting in the fifth or sixth decade of life—are more likely to develop SI fusion. Females have a lower frequency of SI joint fusion than males, perhaps due to pregnancy or parturition. This study examines the relationship between SI joint fusion with both sex and parity status in females. The issue is whether the prevalence of SI fusion in nulliparous females is more similar to that of males or parous females. The sample consists of 46 nulliparous females, 119 parous females, and 158 males from the William M. Bass Donated Skeletal Collection. Ages of the individuals ranged from 50-89 years. Sex, age, and parity status were self-reported. Results show that the frequency of SI joint fusion is significantly different among males (13.29%), nulliparous females (6.52%), and parous females (0.84%). Pairwise comparison of the three groups for SI joint fusion shows that parous females and males are significantly different, but parous females and nulliparous females and nulliparous females and males are nonsignificantly different. Nulliparous females are intermediate in frequency of SI joint fusion between males and parous females which suggests that pregnancy or parturition is involved in lower frequencies of SI joint fusion in parous females. The relationship between surgical implants and fusion of the lumbar vertebrae on SI joint fusion was tested in males and neither showed a significant relationship. The relationship between age and SI joint fusion was tested in males; the age category 60-69 had a significantly lower frequency of fusion than the other age categories which is likely an anomaly of this sample. Results of the study show that SI joint fusion is not more likely to occur on either the right or left side of the pelvis, nor is fusion more likely to be unilateral or bilateral. In conclusion, the birth of one or more children is associated with reduced likelihood of SI joint fusion. This study offers suggestions for why nulliparous females have a frequency of SI joint fusion that is intermediate between males and parous females.

Committee Chair

Tague, Robert