Related Experiment Video
Updated: May 31, 2026

Four-Dimensional CT Analysis Using Sequential 3D-3D Registration
Published on: November 23, 2019
Piriformis muscle: clinical anatomy with computed tomography in korean population
Chan Hong Park1, Sang Ho Lee, Sang Chul Lee
1Department of Anesthesiology and Pain Medicine, Daegu Wooridul Hospital, Daegu, Korea.
Background:
The objective was to evaluate the distance from the skin and the diameter of the piriformis muscle and their relationship to the body mass index (BMI).
Methods:
The study was a prospective study involving 60 patients. Patients were prepared on a radiological table in the prone position. Several images were obtained of each. In this view, the distance between the subcutaneous tissue and the piriformis muscle, and the diameter of the piriformis, were measured at three points (medially to laterally).
Results:
The distance to the piriformis from the skin was 6.6 ± 0.9 cm, 6.3 ± 0.8 cm, and 5.2 ± 0.9 cm in terms of the lateral, center, and medial measurement, respectively. The center of the piriformis had a greater diameter with 1.7 ± 0.4 (0.9-2.5) cm. The distance to the piriformis increased with BMI.
Conclusions:
This study shows that the lateral of the piriformis muscle has a relatively greater distance from the skin. The center of the piriformis showed a greater diameter than other two portions. We found that the distance of the piriformis from subcutaneous tissues was correlated with BMI, but the diameter of the piriformis was not affected by BMI. These measurements can be used as a reference for determining the piriformis injection site in patients with piriformis syndrome.
Related Concept Videos
Imaging Studies III: Computed Tomography
Bones of the Lower Limb: Femur and Patella
Computed Tomography
The technique was invented in the 1970s and is based on the principle that as X-rays pass through the body, they are absorbed or reflected at different levels. In the technique, a patient lies on a motorized platform while a computerized axial tomography (CAT) scanner rotates...
Muscles that Move the Thigh
Three other significant muscles are the gluteus maximus, gluteus medius, and gluteus minimus. The gluteus maximus originates from the posterior surface of the ilium, sacrum, and coccyx, and the thoracolumbar fascia...

