Evaluating changes in the strength of the levator ani muscle after vaginal delivery using T2-parameter mapping

Objective: To evaluate pelvic floor muscle injury in patients with levator ani muscle (LAM) weakness after vaginal delivery using T2-parameter mapping.Materials and methods: 40 parturients (patient group) and 25 nonparturients (healthy control group) were enrolled in the study. The LAM weakness group had a Modified Oxford Grading System (MOGS) grade of less than 3 after vaginal delivery. All participants underwent pelvic magnetic resonance imaging (MRI) scans, including T2 and T2* mapping, on which the main branches of the LAM, the puborectalis and iliococcygeus, were evaluated. The differences in T2 and T2* values in the puborectalis and iliococcygeus between patients with LAM weakness and controls were analyzed using an independent samples t test or a Mann-Whitney U test.Results: For both the right and left iliococcygeus, the T2* values of the patient group were lower than those of the control group (P = 0.002 and 0.008, respectively), while no significant difference was observed in the T2 values between the groups (P = 0.45 and 0.69, respectively). For both the right and left puborectalis, no significant differences in the T2* (P = 0.25 and P = 0.25, respectively) or T2 values (P = 0.38 and 0.43, respectively) were observed between the patient and control groups.Conclusion: T2* mapping as a quantitative measurement is an effective imaging tool to assess LAM injury in women after vaginal delivery. The iliococcygeus was more susceptible to vaginal delivery damage than the puborectalis, and pelvic floor dysfunction may be mainly driven by iliococcygeus injury.