Magnetic Resonance Measurements of Sacrococcygeal and Intercoccygeal Angles in Normal Participants and those with Idiopathic Coccydynia.

Background: In the past, few studies have been done to objectively measure the sacrococcygeal (SC) and intercoccygeal (IC) angles in the population and in patients with coccydynia. Coccydynia is an age-old disorder, the exact incidence of which has not been determined. It is reported to be more common in females and the obese. The magnetic resonance imaging (MRI) studies done in the past have calculated the curvature indices. In this study, we used MRI to objectively measure the angles in the normal participants as well as those with idiopathic coccydynia.

Materials and Methods: Two groups of patients were identified. Group A was "control group" of 106 normal participants and Group B comprised "study group" of ten patients suffering from idiopathic coccydynia. In all these patients, midsagittal T1-weighted MRI image acquired in supine position was used to calculate SC and IC angles. Data were analyzed, and angles were compared between the study and control groups. Statistical analysis was done with Chi-square test.

Results: In the control group, the average SC and IC angles in the control group were 126.8° and 33.5°, respectively. In the study group, the average SC angle and the average IC angle turned out to be 127.1° and 43.2°, respectively. The difference between the SC angles in the control and study groups was not significant ( P = 0.7), whereas the difference between the IC angles in the two groups was significant ( P = 0.002).

Conclusions: From our study, we observed that the IC angle shows a decreasing trend with increasing age. In addition, increased IC angle was identified as a possible cause of idiopathic coccydynia.