Idiopathic coccygodynia. Lateral roentgenograms in the sitting position and coccygeal discography.

STUDY DESIGN: The authors hypothesized that the source of coccygodynia was a lesion of the coccygeal disc.

OBJECTIVES: This study analyzed the motion of the painful coccyx in the sitting position as compared with the lateral decubitus in a patient and a control group and reported the first results of coccygeal discography (dynamic study).

SUMMARY OF BACKGROUND DATA: Coccygodynia are usually attributed to soft tissue injuries or psychologic disturbances. No previous study has assessed the coccygeal discs as a source of pain.

METHODS: Fifty-one patients with coccygodynia and 51 controls sustained a dynamic study. Coccygeal mobility was documented by superimposing graph paper with a double reading. The accuracy of the measurement was +/- 2.6 degrees intra- and interobserver variations 15.3 and 12.5%. This dynamic study was followed by coccygeal discography in the patient group.

RESULTS: An abnormal motion (luxation or hypermobility) of the coccyx that occurred in the sitting position and spontaneously was reducible when placed in the lateral decubitus position was found in 25 patients. Such lesions could be responsible for the pain because no similar findings were seen in the controls and coccygeal discography was positive in these cases. Of the 26 patients with a normal dynamic study, coccygeal discography, using a combination of provocation and anesthetization, was positive in 15 of 21.

CONCLUSIONS: Common coccygeal pain could come from the coccygeal disc in approximately 70% of cases.