Why are some women with pelvic floor dysfunction unable to contract their pelvic floor muscles?

Many women with pelvic floor dysfunction are unable to voluntarily contract their pelvic floor muscles. This study hypothesised that women who cannot contract their pelvic floor muscles, despite specialised pelvic floor physiotherapy, are likely to have avulsion defect of the levator ani muscle, visible on 3-dimensional ultrasound.

Pelvic floor muscle strength was assessed by modified Oxford scale in all women presenting to a tertiary urogynaecology clinic with a main complaint of urinary incontinence ± pelvic organ prolapse. Women who could not contract their pelvic floor muscles (PFM) after having training with a specialised pelvic floor physiotherapist, (modified Oxford score of 0 or 1), were invited to participate in 3-dimensional transperineal ultrasound.

Of 625 women presenting with urinary incontinence and/or pelvic organ prolapse, 150 (24.0%) were unable to contract their PFM at initial assessment. After specialised pelvic floor physiotherapy, 20 of 150 (15.3%) could not contract and were termed 'noncontractors'. Of these, 12 agreed to participate in transperineal ultrasound. Levator avulsion defects were detected in 8 of 12 (66.7%).

Our results show that 67% of women who cannot contract their PFM despite physiotherapy have levator avulsion defects. The mechanism affecting the remaining 33% is yet to be discovered.