STANDARDIZED RADIOLOGIC PROTOCOL FOR THE STUDY OF COMMON COCCYGODYNIAAND CHARACTERISTICS OF THE LESIONS OBSERVED IN THE SITTING POSITION -CLINICAL-ELEMENTS DIFFERENTIATING LUXATION, HYPERMOBILITY, AND NORMALMOBILITY

Study Design. Ninety-one patients with common coccygodynia and 47 cont rol subjects prospectively underwent dynamic radiographic imagery. Obj ectives. To standardize the radiologic protocol to better define norma l and abnormal mobility of the coccyx, and to study clinical parameter s useful in classifying and differentiating the lesions. Summary of Ba ckground Data. in a previous study, comparison of films taken in the s itting and standing positions allowed to individualize two distinct co ccygeal lesions: luxation and hypermobility, Measurement technique was precise and reproducible, but the control group was not pain-free, No specific clinical features were described. Methods. Standing films we re made first. Control subjects were healthy volunteers. The following items were recorded: presence of an initial traumatic event, elapsed time before investigation, body mass index, presence of an acute pain when passing from sitting to standing, effect of intradiscal steroid i njection, and angle of the coccyx with respect to the seat. Results. H ypermobility was defined as a flexion of more than 25 degrees, luxatio n by displacement of more than 25% of the coccyx, The base angle is a good predictor of the direction in which The coccyx moves when sitting . In the ''luxation'' group, a history of initial trauma, a shorter cl inical course, pain when standing up, increased body mass index, and s atisfactory results with intradiscal injection were found more frequen tly than in the ''normal'' group, The ''hypermobility'' group had char acteristics between these two groups. Conclusion. Common coccygodynia is associated in 48.4% of patients with a luxation or hypermobility of the coccyx. A distinct clinical presentation was found in individuals with luxation of the coccyx.