Sonographic anatomy of the pubic symphysis in healthy nulliparous women.

Pregnancy-related symphyseal pain is a condition commonly encountered by clinicians but its pathogenesis is poorly understood. The pubic symphysis is readily visualized with ultrasound, yet the normal sonographic anatomy of the joint has not been accurately documented. This study aimed to describe the anatomy of the pubic symphysis in healthy, nulliparous women using ultrasound. An experienced and inexperienced sonographer scanned the joint in 30 female volunteers (mean age 26 years). Interobserver and intraobserver reliability of ultrasound measurements were examined and the accuracy of these measurements was validated by ultrasound and dissection of six female cadaver pelves (mean age 75 years). In healthy young women, pubic symphysis morphology varied, and six categories of anterosuperior joint shape were defined. Mean values of several anatomic parameters were obtained in supine and standing positions: joint width (widest 10.1 mm, narrowest 2.6 mm); superior pubic ligament (SPL) length and depth (41.4 and 3.4 mm, respectively); and pubic crest length (left 24.4 mm, right 24.4 mm). Statistically significant relationships between SPL width and depth and anthropometric variables (body mass index, pelvic width, and body fat percentage) were established. Larger ultrasonographic measurements, such as wide joint width and SPL length, could be measured more reliably than smaller measurements, such as narrow joint width and SPL depth, in both healthy volunteers and cadavers. Findings from this study provide normative reference data for examination of the pubic symphysis in pregnant women and may therefore be relevant to understand pregnancy-related symphyseal pain.