Cason Shannon N, Moalli Pamela A, Lockhart Mark E, Richter Holly E, Abramowitch Steven D, Bowen Shaniel T
University of Pittsburgh School of Medicine, Pittsburgh, PA.
Division of Urogynecology and Reconstructive Pelvic Surgery, Department of Obstetrics, Gynecology, & Reproductive Sciences, Magee Womens Research Institute, University of Pittsburgh, Pittsburgh, PA.
Am J Obstet Gynecol. 2025 Jul;233(1):49.e1-49.e20. doi: 10.1016/j.ajog.2024.12.024. Epub 2024 Dec 23.
Most studies on pelvic floor muscle morphology (dimensions, shape) and its relationship with patient characteristic risk factors of pelvic floor dysfunction (demographics, medical history) have largely pertained to White individuals with vaginas. There is a need to establish normative data on pelvic floor muscle anatomy and identify morphological differences in racially diverse cohorts that may play a role in racial differences in the prevalence and pathophysiology of pelvic floor dysfunction.
This study aimed to compare levator ani muscle thickness and levator hiatal morphology and their association with patient characteristics, between asymptomatic Black and White women-identifying individuals with a vagina of reproductive age.
In this dual-site retrospective study, pelvic magnetic resonance images of asymptomatic individuals with a vagina aged 18 to 50 years with normal pelvic anatomy-defined as normal gastrointestinal, genitourinary, or reproductive systems-were collected and categorized by self-reported race (Black, White). All individuals were imaged in the axial plane at rest in the supine position for medical indications. From these images, the levator ani muscle thickness and levator hiatal dimensions were measured. The levator hiatal area was traced to create 2-dimensional models of levator hiatal shape. Statistical shape modeling with principal component analysis was performed to quantify levator hiatal shape given by principal component scores. One-way multivariate and univariate analysis of covariance tests evaluated racial differences in levator ani muscle and levator hiatal measures with adjustments for age, body mass index, and parity. Spearman rank correlation with Fisher's z transformation tests quantified and compared correlations between patient characteristics and levator ani muscle and levator hiatal measures by racial group.
A total of 112 participants were analyzed, with 59 Black and 53 White individuals. The Black cohort, compared to the White cohort, had a larger levator hiatal area (difference, 1.31 cm; 95% confidence interval, 0.15-2.47), perimeter (difference, 0.95 cm; 95% confidence interval, 0.32-1.59), and anteroposterior diameter (difference, 0.53 cm; 95% confidence interval, 0.23-0.83). Of the patient characteristics, only parity-related correlations differed by race and were stronger in the White cohort than the Black cohort. Among White individuals, higher parity was associated with a larger levator hiatal area (r=0.60, P<.001), perimeter (r=0.49, P<.001), anteroposterior diameter (r=0.41, P=.002), and transverse diameter (r=0.49, P<.001), whereas among Black individuals, parity had no correlation with levator hiatal dimensions (r range, -0.07 to 0.00; all P>.60). Statistical shape modeling demonstrated that a more ovular, narrower levator hiatus shape predominated in Black individuals (P=.004) and correlated with higher body mass index in the Black (r=-0.45, P<.001) and White (r=0.54, P<.001) cohorts. Posterior distension of the levator hiatus (a more U-shaped levator hiatus) was associated with aging in only the Black cohort (r=-0.40, P=.002).
After controlling for age, body mass index, and parity, larger levator hiatal dimensions and a more ovular, narrower, U-shaped levator hiatus were observed in Black individuals compared to White individuals. Future longitudinal studies are necessary to gain further insight into causative mechanisms for racial morphological variability in pelvic floor muscles that may contribute to racial disparities in pelvic floor dysfunction risk.
大多数关于盆底肌肉形态（尺寸、形状）及其与盆底功能障碍患者特征性风险因素（人口统计学、病史）关系的研究主要针对有阴道的白人个体。有必要建立盆底肌肉解剖结构的规范数据，并确定不同种族人群中的形态差异，这些差异可能在盆底功能障碍的患病率和病理生理学的种族差异中起作用。
本研究旨在比较无症状的自我认定为黑人及白人的育龄期有阴道女性的肛提肌厚度和提肌裂孔形态，并探讨它们与患者特征之间的关联。
在这项双中心回顾性研究中，收集了年龄在18至50岁、盆底解剖结构正常（定义为胃肠道、泌尿生殖系统或生殖系统正常）的无症状有阴道个体的盆腔磁共振图像，并根据自我报告的种族（黑人、白人）进行分类。所有个体均在仰卧位休息时进行轴向平面成像，用于医学指征。从这些图像中测量肛提肌厚度和提肌裂孔尺寸。追踪提肌裂孔面积以创建提肌裂孔形状的二维模型。采用主成分分析进行统计形状建模，以通过主成分得分量化提肌裂孔形状。单因素多变量和单变量协方差分析评估了肛提肌和提肌裂孔测量值在种族上的差异，并对年龄、体重指数和产次进行了调整。采用Spearman等级相关与Fisher's z变换检验，按种族组量化并比较患者特征与肛提肌和提肌裂孔测量值之间的相关性。
共分析了112名参与者，其中59名黑人个体和53名白人个体。与白人队列相比，黑人队列的提肌裂孔面积更大（差值为1.31 cm；95%置信区间为0.15 - 2.47）、周长更大（差值为0.95 cm；95%置信区间为0.32 - 1.59）、前后径更大（差值为0.53 cm；95%置信区间为0.23 - 0.83）。在患者特征中，只有与产次相关的相关性存在种族差异，且在白人队列中比黑人队列更强。在白人个体中，较高的产次与更大的提肌裂孔面积（r = 0.60，P <.
