Abstract
BackgroundThe levator ani muscle (LAM) consists of different subdivisions, which play a specific role in the pelvic floor mechanics. The aim of this study is to identify and describe the appearance of these subdivisions on 3-Dimensional (3D) transperineal ultrasound (TPUS). To do so, a study designed in three phases was performed in which twenty 3D TPUS scans of vaginally nulliparous women were assessed. The first phase was aimed at getting acquainted with the anatomy of the LAM subdivisions and its appearance on TPUS: relevant literature was consulted, and the TPUS scan of one patient was analyzed to identify the puborectal, iliococcygeal, puboperineal, pubovaginal, and puboanal muscle. In the second phase, the five LAM subdivisions and the pubic bone and external sphincter, used as reference structures, were manually segmented in volume data obtained from five nulliparous women at rest. In the third phase, intra- and inter-observer reproducibility were assessed on twenty TPUS scans by measuring the Dice Similarity Index (DSI).ResultsThe mean inter-observer and median intra-observer DSI values (with interquartile range) were: puborectal 0.83 (0.13)/0.83 (0.10), puboanal 0.70 (0.16)/0.79 (0.09), iliococcygeal 0.73 (0.14)/0.79 (0.10), puboperineal 0.63 (0.25)/0.75 (0.22), pubovaginal muscle 0.62 (0.22)/0.71 (0.16), and the external sphincter 0.81 (0.12)/0.89 (0.03).ConclusionOur results show that the LAM subdivisions of nulliparous women can be reproducibly identified on 3D TPUS data.
Highlights
The levator ani muscle (LAM) consists of different subdivisions, which play a specific role in the pelvic floor mechanics
LAM subdivisions can be identified on transperineal ultrasound (TPUS) of women with intact LAM
The 20 patients included in the study presented with symptoms of overactive pelvic floor confirmed by physical examination
Summary
The levator ani muscle (LAM) consists of different subdivisions, which play a specific role in the pelvic floor mechanics. The prevalence of pelvic floor disorders is high [1, 2], and the long-term effectiveness of treatments relatively limited [3, 4] This prompted DeLancey to publish a paper in 2005 in which a goal was set to achieve 25% reduction in occurrence and 25% improvement in treatment success by 2025 [5]. Computer simulations and measurements are produced from image data. The functional consequence of LAM injury may depend on the region of muscle affected [11] To test this hypothesis in imaging studies, the different LAM regions (or subdivisions) have to be correctly identified, which prompted the current study
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