The determinants of minimal levator hiatus and their relationship to the puborectalis muscle and the levator plate.

OBJECTIVE

To determine the muscles comprising the minimal levator hiatus.

DESIGN

Cross-sectional study.

SETTING

The University of Oklahoma Health Sciences Center, USA.

POPULATION

Eight female fresh frozen pelves and 80 nulliparouswomen.

METHODS

Three-dimensional endovaginal ultrasound was performed in eight fresh frozen female pelves. The structures of the levator hiatus were tagged with needles and the cadavers were dissected to identify the tagged structures. A group of 80 nullipara underwent 3D endovaginal ultrasound, and the minimal levator hiatus area, puborectalis area, and anorectal angle were assessed, and normal values were obtained.

MAIN OUTCOME MEASURES

Anatomic borders of minimal levator hiatus and normality in pelvic floor measurements.

RESULTS

The pubococcygeus forms the inner lateral border and anterior attachment of the minimal levator hiatus to the pubic bone. The puboanalis fibres are immediately lateral to pubococcygeus attachments. There are variable contributions of the puborectalis fibres lateral to the puboanalis attachment. The posterior border of the minimal levator hiatus is formed by the levator plate. Eighty community-dwelling nulliparous women underwent 3D endovaginal ultrasound. The median age was 47 years (range 22-70 years). The mean of minimal levator hiatus and puborectalis hiatus areas were 13.4 cm(2) (±1.89 cm(2) SD) and 14.8 cm(2) (±2.16 cm(2) SD). The mean anorectal and levator plate descent angles were 156° (±10.04° SD) and 15.9° (±8.28° SD).

CONCLUSION

Anterior and lateral borders of the minimal levator hiatus are formed mostly by pubococcygeus. The puborectalis, pubococcygeus, and iliococcygeus form the bulk of the levator plate.