3rd and 4th  degree perineal tears extend into or through the anal sphincter complex and may be associated with pelvic floor dysfunction. To date there is scant knowledge on pelvic floor muscle (PFM) function after severe perineal tears. The aim of this study was to test the association between measurement with surface electromyography (sEMG) of the PFM and transperineal ultrasound of levator hiatus (LH) dimensions during maximum voluntary contraction (MVC) of the PFM in women with diagnosed 3rd and 4th  degree perineal tears.

This was a cross-sectional study of 16 primi- and multiparous women, mean age 32.9 years (±7.8) with 3rd and 4th degree perineal tears identified during, and corrected after delivery. Both evaluations for each participant were conducted on the same day at the hospital birth clinic, in average 16.7 months after delivery (range 4 -27). 
Before the assessments women answered a questionnaire with sociodemographic and obstetric data, the ICIQ-UI-SF14 and were asked about AI symptoms. Ability to perform a correct PFM contraction was assessed by a physical therapist using vaginal palpation before sEMG and 3/4D transperineal ultrasound evaluation of LH dimensions (antero-posterior and transverse diameters; LH area) at rest and during MVC. 
sEMG was performed with a portable EMG biofeedback device, Physioplux Clinical, and the Periform intravaginal probe. In order to reduce crosstalk and ensure isolated contraction of the PFM, bipolar adhesive electrodes were unilaterally placed on the right rectus abdominal muscle and the right hip adductor muscle. Any activation of the gluteal muscles was controlled by visual observation.
The 3D/4D transperineal ultrasound was performed with an empty bladder, in the dorsal lithotomy position, using the GE Voluson Expert 8 ultrasound with a 4-8 MHz curved array volume transducer, with an acquisition angle of 85 degrees. LH area, anteroposterior (AP) and transversal (TR) diameters were measured in the plane of minimal hiatal dimensions, defined as the minimal distance between the symphysis pubis and the anterior margin of the central aspect of the puborectalis muscle.

MVC of the PFM measured through sEMG resulted in a signal amplitude of 23.3 ± 13.9 µV (peak) (range 4-50). Regarding the proportional change in LH dimensions, the AP diameter (18.82 ± 11.25 %) was greater than the TR diameter (4.94 ± 11.47 %), (p=0.002) (table 1). The proportional change in LH area was 21.47 ± 15.42 % (table 1). 
sEMG of PFM MVC correlated well with ultrasonography of LH area and antero-posterior diameter (r=0,412; r=0,615) (table 2). A negative and weak association was found between MVC and LH transverse diameter (r=-0,046) (table 2).

sEMG correlated well with ultrasonography of the LH area and AP diameter for measurement of MVC of the PFM in women with 3rd and 4th degree perineal tears in the past. The proportional change in LH AP diameter was the ultrasound measurement with strongest correlation to sEMG.  
The comparison of our findings with other studies is limited because we have not been able to find other studies that have assessed the correlation between PFM strength using sEMG and LH variables measured by ultrasonography in women with severe perineal tear. 
Some authors demonstrated a stronger correlation between PFM strength measured by manometry and LH AP diameter than LH TR diameter and support the results of the present study, where the proportional change in LH area and AP diameter showed greater agreement with the MVC (peak).
The MVC measured through sEMG in the present study showed lower values than those reported by other studies conducted in women with pelvic floor dysfunctions, but without 3rd and 4th degree perineal tears, or in healthy women. As there was no comparison with a group of women with no tears or less severe tears in the present study, our results can only indicate that women with 3rd and 4th degree perineal tear may have lower PFM activation.

To our knowledge, this is the first study to investigate the correlation between sEMG and ultrasonography in women with 3rd and 4th degree perineal tears, and most of the published studies carried out with these instruments have included healthy women only.10,12,21-23 The results may be important for clinical practice as sEMG is portable, a widely used tool, requires less experience and with a low cost, therefore being more accessible and providing data to improve physical therapist’s assessment. Our findings provide new data on the assessment of women with severe perineal tears, who are at increased risk of developing pelvic floor dysfunctions, with sEMG showing good correlation with ultrasonography.