[Ultrasound determination of sacral position in the frontal plane]

The position of the sacrum in the frontal plane is important for the statics of the spine. The most common method of investigating the sacrum is its visualisation on an antero-posterior X-ray film. The aim of this study was to find a method of determining the position of the sacrum in the frontal plane by sonography.

Criteria for the correct image of the upper rim of the sacrum are presented and the procedure for measuring sacral tilt is introduced. The results of the sonographic measurements of 107 patients are compared with the results of X-ray measurements. The intraindividual differences are described and statistically evaluated.

Almost 90% of the patients revealed a difference between the sonography and the radiology measurement of less than three millimeters. The overall sensibility was 80%. The specificity was 82%. The results were calculated for different age groups. They turned out to be better in children and adolescents than in adult patients. Obese adults had significantly worse results than patients with normal body weight.

This study suggests that the method presented can help to provide reliable information on the position of the sacrum, especially in children and adolescents. By using sonography we can partly reduce the necessary X-ray exposure, especially in the diagnosis and treatment of leg length discrepancies.