Bony Pelvic Dimensions Research Articles

Variations in pelvic floor thickness in relation to bony dimensions in South African women: using computed tomography scans

Pelvic floor disorders (PFDs) are a common reason for urogynaecological consultation around the world, especially in elderly women. These disorders have been associated with disruption to the structural integrity of the pelvic floor. This study explored whether there are variations in pelvic floor muscle (PFM) thickness in relation to parity, population group and age. Additionally, the study explored whether there were any correlations between PFM thickness and the bony pelvic parameters measured. This was a quantitative retrospective analysis of computerised tomography (CT) scans. A total of 125 CT scans of women belonging to black and white South African population groups were sampled from a tertiary hospital in Pretoria, South Africa. Statistical analyses were performed using Paleontological Statistics (PAST). A thicker pelvic floor was noted in black compared to white women. Pelvic floor thickness decreased with parity and age in both population groups. The intertuberous diameter, as well as the surface areas of the urogenital triangle and the perineum, were statistically significantly larger in white than in black women. Correlations between PFM thickness and bony dimensions were statistically significant for anteroposterior (AP) pelvic outlet diameter, where a greater AP outlet was associated with thinner PFMs in black women. Bony correlations with parity showed that the interspinous diameter in black women increased significantly with parity. The variations in bony pelvic dimensions and pelvic floor muscle thicknesses noted between population groups, in addition to the co-factors of parity and aging, will contribute to a better understanding of the anatomical reasons for incontinence.

In silico prediction of maximum perineal muscle strain during vaginal delivery by design of experiment

Background and objectiveThe prevalence of pelvic floor muscle injuries induced by childbirth is higher than 23 % in the general women population. Such injuries can lead to prolapses and other pathologies in future female life. Leveraging computational biomechanics, the study implements an advanced female pelvic floor model for computing the maximum pelvic muscle strain, which serves as an injury risk indicator. The design of experiment method, abbreviated as DoE, is used to compute the maximum strain for boundary values of bony pelvis dimensions, namely the anterior-posterior diameter (abbreviated as APD) and the transverse diameter (abbreviated as TD). This is done in combination with small, medium and large percentiles of fetal head circumference (abbreviated as HC). MethodsWe utilized a previously developed finite element model of a female pelvic floor, as a reference, and enhanced it with new features, including a more detailed tissue geometry and advanced constitutive material models. The APD and TD dimensions were sourced from the set of MRI of 64 nulliparous women. This data was used to estimate the boundary dimensions of the female bony pelvis, combining both small and large values of APD and TD. Together with the 10th and the 95th percentiles for HC, a three-dimensional domain was constructed to assess the maximum pelvic muscle strain. In boundary cases, the maximum pelvic muscle strain was computed across 8 full-factorial design models (each situated at one corner of the domain, thereby combining the minimum and the maximum values of APD, TD and HC). This was done to define a response surface that predicts the maximum pelvic muscle strain within the domain. The accuracy of this response surface prediction was validated using 15 additional intermediate design models. These models were placed at the center of the domain (1 point), the centres of the domain boundary surfaces (6 points), and midway along each domain boundary edge (8 points). ResultsThe maximum strain results for 8 combinations of APD, TD, and HC were employed to construct a linear response surface as a function of APD, TD, and HC. Tests at an additional 19 domain points served to evaluate the efficiency of the response surface prediction. The response surface demonstrated strong predictability, with an absolute average error of 1.52 %, an absolute median error of 1.52 %, and an absolute maximum error of 11.11 %. HC emerged as the most influencing dimension, accounting for 16 % of influence. ConclusionsThe reference finite element pelvic floor model was scaled to 8 full-factorial female-specific pelvic floor models, which represent the combination of boundary values for APD, TD, and HC. The maximum pelvic floor muscle strain from these 8 models was used to design a response surface. When implementing the DoE approach to construct the response, there was consistent predictability for the maximum perineal muscle strain, as validated by the additional 19 intermediate design models. As a result, the response surface methodology can serve as an initial predictor for potential childbirth-induced pelvic floor muscle injury.

Comparison of Bony Pelvic Dimensions and Demographic Risk Factors in Individuals With and Without Pelvic Organ Prolapse [ID: 1377653

INTRODUCTION: Previous studies have noted a correlation between bony pelvic measurements and the diagnosis of prolapse via musculofascial insertion points on magnetic resonance imaging. We investigated the importance of bony measurements of the lumbar spine and pelvis as risk factors in the development of prolapse via routine computed tomography (CT) imaging. METHODS: We sampled 171 UBMD obstetrics and gynecology clinic patients who were at least 40 years of age and had an abdominal/pelvic CT scan. Demographic and medical history was reviewed and collected. Participants were then divided into those with and without prolapse. CT images were uploaded to 3D Slicer 5.10. Each study was analyzed by a trained annotator blinded to prolapse status. The area of the anterior pelvis, interspinous diameter, pelvic outlet, ischial spine to pubic symphysis, sacrococcygeal junction to ischial spine, and lumbar and sacrococcygeal curvature were annotated. Demographic characteristics and measured annotations were compared using χ2 test. RESULTS: Women with prolapse were more likely to be older (P<.05) and of lower weight (mean 71.6 kg, P<.05) than controls. Patients with prolapse had a significantly larger area of their anterior pelvis (P<.05) and a significantly longer interspinous diameter (P<.05). Distance from ischial spine to pubic symphysis was significantly longer (P<.05), and pelvic outlet in women with prolapse was significantly longer than in controls (P<.05). CONCLUSION: In addition to known risk factors, bony measurements of the pelvis are significantly different in those with and without pelvic organ prolapse, which may be observed on routine CT imaging.

Effect of prostate and bony pelvic dimensions measured by preoperative magnetic resonance imaging on robot-assisted radical prostatectomy.

Bone pelvic dimensions and body habitus may have effects on robot-assisted radical prostatectomy (RARP). In this study, we examined the effects of body mass index, bone pelvis measurements and prostate measurements on console time (CT), decrease in postoperative hemogram level (DHL) and surgical margin(SM) in patients who underwent RARP for clinically localized prostate cancer in our institution. The data of transperitoneal RARP cases performed by a single surgeon between November 2016 and August 2020 were analyzed retrospectively. It was included in 125 patients who met the study criteria. Bone and soft tissue measurements were made on magnetic resonance imaging T2-weighted imaging in the mid-sagittal and transvers plane. In multivariate linear regression analyzes, only soft tissue width/transverse diameter of the prostate and CT were found to be correlated (p = 0.026). For the DHL, no pelvic dimension and body habitus had a significant association on multivariate linear regression analysis. In multivariate analyzes, a statistically significant difference was found only between pathological Gleason Score and SM (p = 0.008). Although we found statistically significant associations between prostate diameters and pelvic bone measurements and operative difficulties, we believe that further studies are needed to confirm these results. Such information can help identify patients with challenging anatomy and can be used in robotic surgery training to achieve optimal patient outcomes after RARP.

Investigation of correlation between bony pelvis dimensions and pelvic organ prolapse in different compartments

ObjectiveTo investigate the association between bony pelvis dimensions and anterior, apical, and posterior compartment pelvic organ prolapse (POP) and explore the mechanism of different types of POP from an anatomical point of view. Study designA total of 253 patients with POP were selected as the experimental group (138 patients with anterior compartment defect, 86 with apical compartment defect, and 29 with posterior compartment defect); 253 patients with uterine myoma constituted the control group. Their demographics were recorded, and anteroposterior diameters of the pelvic inlet, intertuberous diameter, and interspinous diameter were measured. One-way analysis of variance, least significant difference t-test, and Student’s t-test were used to evaluate the pelvic measurements among the four groups. ResultsThe anteroposterior diameter of the pelvic inlet in the apical compartment POP group was smaller than that in the other groups (P < 0.05). Interspinous diameters in the anterior and apical groups were larger than those in the posterior POP and control groups (P < 0.05). Intertuberous diameter in the control group was smaller than that in the anterior and apical POP groups and larger than that in the posterior POP group (P < 0.05). ConclusionWomen with apical compartment POP are more likely to have a smaller anteroposterior diameter. Larger interspinous and intertuberous diameters were associated with anterior and apical POP, and smaller intertuberous diameter was associated with posterior POP.

Stature estimation formulae based on bony pelvic dimensions and femoral length.

We investigated the feasibility of estimating living stature in Japanese subjects using femoral length and pelvic dimensions measured on three-dimensional (3D) pelvic models reconstructed from cross-sectional computed tomography (CT) images. For this cross-sectional study, we recruited 106 healthy Japanese subjects. Maximum and bicondylar femoral length, as well as pelvic width, depth, and height, were measured on 3D bone models reconstructed from multi-slice CT images. The correlation of stature with each parameter was evaluated, and multiple regression equations were derived as formulae for living stature estimation. Prediction accuracy was evaluated as the mean absolute difference (MAD) between the measured and estimated statures. Maximum and bicondylar femoral lengths were similar and showed strong correlations with stature (> 0.8 in both males and females). Among the pelvic dimensions, height (craniocaudal length) showed the strongest correlation with stature in both males (r = 0.649) and females (r = 0.684). Formulae using femoral length plus pelvic height provided the best estimation of living stature in both males and females (MAD, 25-26 mm). Among the studied pelvic dimensions, height provided the best estimation of living stature when used alone (MAD, 34-36 mm) in both males and females. The intraclass correlation coefficients were high (> 0.9) for both intraobserver and interobserver reliability. Femoral length and pelvic height measured on CT images are reliable predictors of living stature in the Japanese population. Such tools are particularly useful in disaster victim identification, when the long bones are often not intact but the pelvic bones are.

Re: Effect of Surgeon Experience and Bony Pelvic Dimensions on Surgical Performance and Patient Outcomes in Robot-Assisted Radical Prostatectomy.

Re: Effect of Surgeon Experience and Bony Pelvic Dimensions on Surgical Performance and Patient Outcomes in Robot-Assisted Radical Prostatectomy.

Effect of surgeon experience and bony pelvic dimensions on surgical performance and patient outcomes in robot-assisted radical prostatectomy.

To evaluate the effects of surgeon experience, body habitus, and bony pelvic dimensions on surgeon performance and patient outcomes after robot-assisted radical prostatectomy (RARP). The pelvic dimensions of 78 RARP patients were measured on preoperative magnetic resonance imaging and computed tomography by three radiologists. Surgeon automated performance metrics (APMs [instrument motion tracking and system events data, i.e., camera movement, third-arm swap, energy use]) were obtained by a systems data recorder (Intuitive Surgical, Sunnyvale, CA, USA) during RARP. Two analyses were performed: Analysis 1, examined effects of patient characteristics, pelvic dimensions and prior surgeon RARP caseload on APMs using linear regression; Analysis 2, the effects of patient body habitus, bony pelvic measurement, and surgeon experience on short- and long-term outcomes were analysed by multivariable regression. Analysis 1 showed that while surgeon experience affected the greatest number of APMs (P<0.044), the patient's body mass index, bony pelvic dimensions, and prostate size also affected APMs during each surgical step (P<0.043, P<0.046, P<0.034, respectively). Analysis 2 showed that RARP duration was significantly affected by pelvic depth (β=13.7, P=0.039) and prostate volume (β=0.5, P=0.024). A wider and shallower pelvis was less likely to result in a positive margin (odds ratio 0.25, 95% confidence interval [CI] 0.09-0.72). On multivariate analysis, urinary continence recovery was associated with surgeon's prior RARP experience (hazard ratio [HR] 2.38, 95% CI 1.18-4.81; P=0.015), but not on pelvic dimensions (HR 1.44, 95% CI 0.95-2.17). Limited surgical workspace, due to a narrower and deeper pelvis, does affect surgeon performance and patient outcomes, most notably in longer surgery time and an increased positive margin rate.

Bony pelvis dimensions in women with and without polycystic ovarian syndrome

To test the null hypothesis that bony pelvis dimensions are different in women with and without polycystic ovarian syndrome (PCOS). In this case-control study all subjects underwent hysterosalphingography examination. The interspinous, intertuberous diameters and subpubic angle were measured from the images independently by author blinded to the clinical and laboratory data of the patients. Women with PCOS had shorter interspinous diameter. There was no significant differences in the length of intertuberous diameters and subpubic angles between the two groups. Significant difference in interspinous diameter was identified when comparing reproductive-aged women with PCO and their similar aged controls.

Predicting the pathological features of the mesorectum before the laparoscopic approach to rectal cancer.

Pelvic anatomy and tumour features play a role in the difficulty of the laparoscopic approach to total mesorectal excision in rectal cancer. The aim of the study was to analyse whether these characteristics also influence the quality of the surgical specimen. We performed a prospective study in consecutive patients with rectal cancer located less than 12 cm from the anal verge who underwent laparoscopic surgery between January 2010 and July 2013. Exclusion criteria were T1 and T4 tumours, abdominoperineal resections, obstructive and perforated tumours, or any major contraindication for laparoscopic surgery. Dependent variables were the circumferential resection margin (CMR) and the quality of the mesorectum. Sixty-four patients underwent laparoscopic sphincter-preserving total mesorectal excision. Resection was complete in 79.1% of specimens and CMR was positive in 9.7%. Univariate analysis showed tumour depth (T status) (P = 0.04) and promontorium-subsacrum angle (P = 0.02) independently predicted CRM (circumferential resection margin) positivity. Tumour depth (P < 0.05) and promontorium-subsacrum axis (P < 0.05) independently predicted mesorectum quality. Multivariate analysis identified the promontorium-subsacrum angle (P = 0.012) as the only independent predictor of CRM. Bony pelvis dimensions influenced the quality of the specimen obtained by laparoscopy. These measurements may be useful to predict which patients will benefit most from laparoscopic surgery and also to select patients in accordance with the learning curve of trainee surgeons.

Assessment of Bony Pelvis and Vaginally Assisted Deliveries

Objective. To evaluate whether pelvic measurements have any association with operative vaginal deliveries and the duration of the second stage of the delivery. Study design. A retrospective study of pregnant women at an increased risk of fetal-pelvic disproportion during 2000–2008 in North-Carelian Central Hospital. The mode of the vaginal delivery was chosen to represent the reference standard. The target condition was spontaneous vaginal delivery. Patients were divided into subgroups according to the size of the fetus and also by the parity to evaluate the variability reflecting differences in patient groups. Receiver operating characteristic (ROC) curves were established. Results. A total of 226 participants with fetal cephalic presentation delivered vaginally; of these, 184 women delivered spontaneously, and 42 women required operative vaginal delivery with vacuum extraction. There were no clinically or statistically significant differences between the size of the maternal pelvic outlet and the different modes of delivery types within these subgroups. With respect to the pelvic inlet and outlet, the areas under the curve in ROC were 0.566 with the P value of 0.18 and 95% confidence interval (CI) of 0.465–0.667 and 0.573 (95% CI: 0.484–0.622; P = 0.14). Conclusions. The maternal bony pelvic dimensions exhibited virtually no correlation with the need for operative vaginal deliveries.

Are bony pelvis dimensions associated with levator ani defects? A case–control study

Bony pelvis dimensions have been shown to differ in women with and without pelvic floor dysfunction. The goal of this study was to determine whether bony pelvis dimensions are different when comparing women with severe bilateral levator ani defects (LAD) with those with normal muscles. This is a secondary analysis of a case-control study comparing women with and those without pelvic organ prolapse. Subjects underwent pelvic organ prolapse quantification (POP-Q) examination and were classified as either having prolapse or being normal. All underwent pelvic magnetic resonance imaging (MRI). Levator defects were assessed based on the muscles' appearance on imaging and subjects were stratified into two groups--women with normal muscles (n = 99) and women with severe bilateral LAD (n = 50). Bony pelvis dimensions were measured via MRI pelvimetry. The subpubic angle, interspinous and intertuberous diameters, and the sacrococcygeal joint-to-infrapubic point (SCIPP) lengths were compared. Both groups had similar demographics. The SCIPP length was 2.5 % (3 mm) shorter in women with severe LAD than in those without defects (P = 0.02). The SCIPP measured 4 % (5 mm) less in women with prolapse and severe LAD than in subjects with prolapse but normal muscles (P = 0.01). Logistic regression identified SCIPP length and history of forceps delivery as being independent predictors of severe bilateral LAD. Severe bilateral LAD are associated with shorter SCIPP length and forceps-assisted vaginal delivery.

Bony pelvis dimensions in women with and without stress urinary incontinence

To test the null hypothesis that bony pelvis dimensions are similar in women with and without stress urinary incontinence (SUI), both in the postpartum and midlife periods. Secondary analyses were performed of two case-control studies comparing women with SUI to asymptomatic controls. One study examined primiparas in the first 9-12 months postpartum; the other study involved middle-aged women. SUI was confirmed by full-bladder stress test. All subjects underwent pelvic magnetic resonance imaging. The interspinous and intertuberous diameters, subpubic angle, and sacrococcygeal joint-to-the inferior pubic point distance were measured from the images independently by two authors. In the young cohorts, we compared primiparas with de novo postpartum SUI to both continent primiparas and nulliparas. Postpartum SUI is associated with a wider subpubic angle. There is also a trend towards wider interspinous and intertuberous diameters in the stress-incontinent primiparas as compared to the continent cohorts, although this did not reach statistical significance with our sample sizes. By contrast, no significant differences in bony pelvis dimensions were identified when comparing middle-aged women with SUI and their continent controls. Bony pelvis dimensions are different in women with SUI than in matched continent controls. However, these differences are only identified in young primiparas in the postpartum period, not in middle-aged women.

UP-2.142: Impact of Bony Pelvic Dimensions on Performing Robot-Assisted Laparoscopic Prostatectomy

UP-2.142: Impact of Bony Pelvic Dimensions on Performing Robot-Assisted Laparoscopic Prostatectomy

Effect of bony pelvic dimensions measured by preoperative magnetic resonance imaging on performing robot‐assisted laparoscopic prostatectomy

To evaluate the effect of bony pelvic dimensions measured by preoperative magnetic resonance imaging (MRI) on performing robot-assisted laparoscopic prostatectomy (RALP). In this exploratory study, we analysed the data of 141 patients who underwent RALP for clinically localized prostate cancer after undergoing MRI at our institution. Associations of various clinicopathological factors were analysed, including pelvic dimensions measured by preoperative MRI, with operative duration, estimated blood loss (EBL), surgical margin status, and postoperative urinary continence and erectile function. For operative duration, no pelvic dimension had a significant association on univariate analysis, with only the newly developed variable of pelvic cavity index approaching significance (P=0.071). Only prostate volume had a significant association with operative duration on multivariate analysis (P=0.015). For EBL, no bony pelvic dimension had a significant association on univariate analysis, with only intertuberous distance and interspinous distance approaching significance (P=0.087 and P=0.072, respectively). Again, only prostate volume was significantly associated with EBL on univariate analysis (P=0.045). No pelvic dimension had any significant effect on surgical margin status, recovery of urinary continence or erectile function at 6 months after RALP. Bony pelvic dimensions may not be a significant factor contributing to the technical difficulty of RALP among Korean patients compared with other patient-related factors such as prostate volume.

Comparison of bony dimensions at the level of the pelvic floor in women with and without pelvic organ prolapse

We sought to compare bony pelvis dimensions at the level of pelvic support in women with and without pelvic organ prolapse (POP). Pelvic floor dimensions of 42 white women with POP > 1 cm beyond the hymen were compared with 42 age- and parity-matched women with normal support. Bony landmarks relevant to connective tissue and levator attachments were identified on magnetic resonance imaging. Dimensions were independently measured by 2 examiners and averaged for each subject. Measurements (in centimeters) for patients and control subjects were as follows: interspinous diameter, 11.2 +/- 0.8 versus 11.1 +/- 0.7, P = .19; anterior-posterior outlet diameter, 11.7 +/- 0.7 versus 11.7 +/- 0.8, P = .71; pubic symphysis to ischial spine left, 9.5 +/- 0.5 versus 9.5 +/- 0.4, P = .91; pubic symphysis to ischial spine right, 9.5 +/- 0.4 versus 9.5 +/- 0.5, P = .81; sacrococcygeal junction to ischial spine left, 7.0 +/- 0.6 versus 7.0 +/- 0.5, P = .54; and sacrococcygeal junction to ischial spine right, 7.0 +/- 0.6 versus 6.9 +/- 0.4, P = .32. Bony pelvis dimensions are similar at the level of the muscular pelvic floor in white women with and without POP.

Impact of Variations in Bony Pelvic Dimensions on Performing Radical Retropubic Prostatectomy

To investigate the impact of variations in bony pelvic dimensions observed from preoperative magnetic resonance imaging on operative time, intraoperative blood loss, and surgical margin status on performing open radical retropubic prostatectomy. A prospective study was undertaken in which preoperative magnetic resonance imaging was performed in 190 patients who were diagnosed with clinically localized prostate cancer before radical retropubic prostatectomy. Using the magnetic resonance image findings, various bony pelvic dimensions were measured. The associations of the measured pelvic dimensions and various clinicopathologic factors with the operative time, estimated blood loss, and surgical margin status were analyzed on multivariate analyses. For operative time, none of the individual pelvic dimensions measured demonstrated significant associations on univariate analysis. In contrast, only the newly developed parameter, the pelvic dimension index, approached significance (P = 0.095). Only body mass index (BMI) proved to be independently associated with the operative time on multivariate analysis (P = 0.030). Also, only the prostate volume (P = 0.015) was independently associated with the estimated blood loss. For the surgical margin status, the preoperative PSA level (P = 0.041), pathologic Gleason score (P = 0.015), and BMI (P = 0.020), along with the pelvic dimension index (P = 0.048), demonstrated significant associations on univariate analyses. However, only the PSA level (P = 0.071) and BMI (P = 0.059) approached significance on multivariate analysis. Our results have demonstrated that variations in the bony pelvic dimensions might have some impact, but not significantly so, on open radical retropubic prostatectomy compared with other patient-related baseline factors such as the BMI or prostate volume.

MRI assessment of the bony pelvis may help predict resectability of rectal cancer

The outcome after surgical treatment of rectal cancer may be influenced by the technical difficulty of the operation, which is thought to be affected by pelvic size. The aim of this study was to examine the association between bony pelvic dimensions and CRM involvement. All patients with primary rectal cancer between December 1999 and January 2002 were studied. Staging was performed by pelvic MRI. Nine pelvic dimensions were measured from the MR images on a workstation. Pathology reports were obtained for all patients and the mesorectal specimen was examined. Technical difficulty was assessed by circumferential resection margin (CRM) involvement. Of 126 patients with primary rectal cancer, 88 had staging MRI and rectal excision; there were significant differences between the sexes in all 9 pelvic dimensions (P < 0.05). In females, the interspinous diameter was significantly shorter in patients with CRM involvement compared with patients with a negative CRM. In female patients predicted to have a negative CRM, the anteroposterior diameter of the inlet, the anteroposterior diameter of the midplane and the transverse diameter of the midplane (interspinous distance) were significantly shorter in patients who actually had a positive CRM compared with those in whom the CRM was negative. In male patients, there was no correlation between pelvic dimensions and CRM status. In certain patients with rectal cancer, CRM positivity may be predicted from pre-operative MRI pelvic measurements. This may influence the choice of adjuvant therapy.

MR Obstetric Pelvimetry: Effect of Birthing Position on Pelvic Bony Dimensions

Debate continues over the respective merits of the supine and upright birthing positions, but there has been no accurate comparison of the effects of posture on the bony pelvic dimensions. The present study, enrolling 35 nonpregnant women 22 to 43 years of age, was an attempt to determine whether birthing position influences the dimensions of the pelvic outlet as viewed using a vertically open, low-field 0.5-T magnetic resonance imaging system and body flex surface coil. Twenty-five participants were nulliparous, and 10 were parous (9 with 1 child and 1 with 2 children). All the latter women had delivered at lest 9 months before the study. Images were recorded with women in the supine, hand-to-knee, and squatting positions. T1-weighted, fast spoiled gradient-echo sequences were recorded with the patient in the midsagittal, axial, and oblique (sacral promontory to the top of the symphysis) planes. Diagnostic-quality images were consistently obtained in this study. The sagittal outlet was wider in both the hand-to-knee and squatting positions than with the women supine. The same was the case for the interspinous diameter. The intertuberous diameter was greater with squatting than with the supine position. The only parameter that was significantly smaller in the upright squatting position than the supine position was the obstetric conjugate. Transverse diameters were essentially the same in all positions. Parous women were significantly older than the nulliparas and had slightly larger pelvic dimensions, but only the difference in sagittal outlet in the squatting position was significant. Whereas no parameters seemed to influence absolute pelvic measurements in supine women, the change in the obstetric conjugate on changing to a squat was greater in younger women. Taller women had a more marked increase in interspinous diameter in changing from the supine to the hand-to-knee position. The same women also had a greater change in obstetric conjugate when changing from the supine to the hand-to-knee position. Postural differences may significantly increase pelvic dimensions in women of reproductive age. These findings provide a rationale for long-standing practices of changing birthing position to make vaginal birth easier.

Computed tomography comparison of bony pelvis dimensions between women with and without genital prolapse

Objective: To compare bony pelvis dimensions between white women with and without genital prolapse using computed tomography (CT) pelvimetry. Methods: Thirty-four multiparous white women with vaginal prolapse beyond the hymen and 34 matched white controls with no signs or symptoms of pelvic support defects underwent CT pelvimetry. The anteroposterior and transverse diameters of the pelvic inlet, the interspinous diameter of the midpelvis, and the intertuberous diameter of the pelvic outlet were measured. Post hoc power analysis showed that 22 women were needed in each group to detect a 10% difference in the pelvic dimensions between groups, with an α error of 1% and a β error of 10%, resulting in a 90% power. Results: Mean (± standard deviation [SD]) age of the subjects was 63.4 ± 8.3 years, compared with 62.9 ± 7.8 years for controls. Mean parity of the subjects was 3.3 ± 1.7, compared with 3.6 ± 1.7 for controls. Mean (± SD) anteroposterior (12.5 ± 1.3 versus 12.8 ± 1.0 cm), interspinous (11.5 ± 0.8 versus 11.2 ± 0.9 cm), and intertuberous (10.0 ± 1.0 versus 9.8 ± 0.8 cm) diameters were not significantly different between study groups. Mean transverse diameter of the pelvic inlet was significantly greater in women with prolapse than those without prolapse (12.9 ± 0.7 versus 12.4 ± 0.6 cm, P = .006). Conclusion: Women with advanced vaginal prolapse have larger transverse inlet diameters than do women with normal pelvic support.