Measurement of piriformis muscle stiffness in athletes with lower back pain and piriformis syndrome: A shear-wave elastography study with consideration of the onset of piriformis syndrome

Abstract

Problem Statement: Piriformis syndrome is a common cause of buttock, leg, and lower back pain due to piriformis muscle stiffness. Only a few treatments for lower back pain are efficacious. Purpose: This study aimed to assess piriformis muscle stiffness by shear-wave elastography in athletes with lower back pain and piriformis syndrome to establish a standard diagnostic method and determine the onset of unexplained lower back pain in such athletes. This pre–post-test design study was conducted at Shibahara Orthopaedic Sports Joint Clinic. Twenty-eight athletes with lower back pain and piriformis syndrome and 30 healthy athletes were enrolled. After relaxing the piriformis muscle contracture using strain–counter strain techniques, therapeutic manual traction was employed to move the displaced femoral head forward via piriformis muscle contracture to the center of the hip joint acetabulum. Ultrasound examination using shear-wave elastography, straight leg-raise, flexion abduction external rotation, and Gillet test were performed. The pain scores were recorded on a numerical rating scale before and after treatment. Results: Significant differences between the scores of the lower back pain among athletes before and after treatment were noted on comparing the mean and maximum elasticity modulus values from all test results. Differences between the scores of athletes after treatment and controls were not significant. Conclusions: Piriformis syndrome may be one of the causes of nonspecific low back pain, and the treatment of sacroiliac joint dysfunction may well be useful in reducing piriformis syndrome. Moreover, shear-wave elastography provides a painless, noninvasive, and objective method for evaluating athletes with lower back pain and piriformis syndrome. The onset of most cases of unexplained low back pain in athletes with piriformis syndrome can thus be attributed to the sacroiliac joint.