Morphological Variations of the Posterior Superior Iliac Spine in Chinese Population: Potential Effects on the Reliability of Palpation

OBJECTIVES: The posterior superior iliac spine (PSIS) is an important anatomical landmark often involved in spinal manipulation and surgical bone harvest. Hence, knowledge of variations in the PSIS may be predictive and valuable in clinical settings. Taking the complex morphology into account, the study is aimed at proposing a classification of PSIS in the Chinese population. METHODS: An anatomical study was undertaken on 288 human ilia. First, the morphological features of variations in the PSIS were noted following visual inspection. Then, 12 variable anatomical parameters were measured in order to determine the differences based on morphology, side, and sex. RESULTS: Overall, four types of PSIS were found among 288 bones, including type I “V-shape” (106, 36.8%), type II “U-shape” (121, 42.0%), type III “W-shape” (36, 12.5%), and type IV “ossification-shape” (25, 8.7%). There were no significant sex or bilateral differences in the morphological distribution of the PSIS (p > 0.05). Furthermore, the measurements showed that type I was the narrowest and type III the broadest (p < 0.05). Moreover, female specimens had an overall larger distance and width of surrounding landmarks (p < 0.05), and a significant difference was found in the width of the PSIS between the left and right sides (p < 0.05). CONCLUSION: The PSIS samples displayed multiple morphological variations and could be classified into four types. In addition, sex-based or bilateral differences existed in the size and relative positions. It is thus likely that differences in the morphology and asymmetry of the PSIS provide references for palpation, bone harvest, and other clinical settings.