Ultrasound assessment of the posterior sacroiliac ligaments

Posterior ligaments of the sacroiliac joints (SIJ) are comprised of the long and the short posterior sacroiliac ligaments. They are recognised as a potential source of aspecific low back pain or peripartum pelvic pain. The aim of this study was to assess the characteristics of these ligaments using high resolution ultrasonography (HRUS).

The features of the ligaments was first studied in a formalin-preserved intact cadaver. US characteristics were then recorded in 20 volunteers with a Philips HD11 XE unit using a multifrequency linear transducer (5-12 Mhz).

US was performed in 8 men and 12 women, with a mean age of 45±15 year and mean body mass index (BMI) of 25.45 (±3.57). Ligaments were identified in all the volunteers. The short posterior sacroiliac ligament (median length 2.17 cm and 2.31 cm in the right and left SIJ respectively) was described as a fibrilar structure attached to the posterior tuberosity of the ilium and the sacrum. The long posterior sacroiliac ligament (median length 3.42 cm and 3.56 cm in the right and left SIJ, respectively) was a fibrilar structure attached superiorly to the posterior superior iliac spine and inferiorly to the third sacral transverse tubercle.

Our study shows that US can be used to identify the posterior ligaments of the sacroiliac joint. US could be useful to detect any pathological change associated with pain and to guide steroid injection in these ligaments.