Influence of Pubovisceral Avulsion on Perineal Body Descent and Prolapse Development

Pubovisceral muscle (PVM) avulsion affects over a third of women post-vaginal childbirth and is a significant risk factor for pelvic floor dysfunction (PFD). Prior studies show that even a 5 mm posterior-inferior shift of the perineal body (PB) enlarges the genital hiatus, contributing to prolapse. Building on this, we investigated the relationship between PVM avulsion and PB movement, correlated prolapse metrics, and sacrum/coccygeal movement with the injury. Moreover, we used statistical shape modeling (SSM) to see shape variation among different groups.

A total of 112 MR defecography scans were included from a mixed sample of clinical defecography's. This includes 68 radiologic cystocele patients, 20 patients who were obstruction defecation patients, and 20 nulliparous patients, taken from previous studies Routzong et al. (Ann Biomed Eng 51(7):1461-70); Martin et al. (Int Urogynecol J 36:1607-1615); Routzong et al. (Comput Methods Biomech Biomed Eng 24(2):122-30). These scans were analyzed using axial T2 images to assess PVM avulsion. Patients were categorized into four groups: asymptomatic-nulliparous, non-avulsed, partial avulsed, and avulsed. The asymptomatic group was excluded from statistical analysis because of differences in demographic variables. Measurements were performed on mid-sagittal slices using HOROS at rest and evacuation. SSM was then used to assess shape variation of the pelvic floor.

Among 89 parous patients, 25 had avulsion, 18 partial avulsions, and 46 were non-avulsed. The avulsed group was significantly older (p = 0.001), with more pregnancies (p = 0.049) and deliveries (p = 0.021). At rest, they showed increased pubic symphysis-to-PB distance (p < 0.001), and greater bladder descent during evacuation (p = 0.003). Vaginal apex was well-supported in the non-avulsed group at rest (p < 0.001), while sacrococcygeal angle (p = 0.031) significantly increased in avulsed patients. SSM identified shape variation with the avulsed group having the greatest descent of the pelvic floor musculature, perineal body shift, and overall increased levator bowl area.

In a cohort of women undergoing pelvic MR defecography, we observed PVM avulsion is associated with inferior PB shift, increased bladder descent, and shape changes to the sacrum/coccyx, underscoring its impact on level III support. Despite limitations from the retrospective design and patient selection, these findings offer valuable insight into the anatomical consequences of avulsion during rest and defecation.