Sagittal Outlet Research Articles

PELVİS TİPLERİNİN TRANS-SAKRAL VİDA KORİDOR ÇAPINA ETKİSİNİN DEĞERLENDİRİLMESİ (BİLGİSAYARLI TOMOGRAFİ VERİLERİ KULLANILARAK YAPILAN RETROSPEKTİF ANALİZ.)

Aims: The aim of this study was to investigate the effect of pelvis type on the trans-sacral(TS) screw corridor diameter.
 Methods: Pelvis computed tomography (CT) scans between 2017 and 2020 were retrospectively reviewed. Age, gender, height, weight and body mass index (BMI) of the patients were determined during the CT examination. Pelvic CT scans were examined using the imaging system's multi-plane reconstruction (MPR) mode, and the TS screw corridor was measured for both the upper and second sacral segments. In addition, pelvic incidence (PI), sacral tilt (SS), and pelvic tilt (PT) values were measured. Pelvis typing was performed using the large transverse diameter, anteroposterior diameter, interspinous, intertuberocytosis, transverse outlet diameter, sagittal mid-pelvic diameter, and sagittal outlet values.
 Results: 81(38%) male and 132(62%) female patients were included in the study. Gynecoid pelvis type was more common in females and android pelvis in males (p < 0.001). The largest diameters in the TS screw corridor at the S1 level belonged to the anthropoid pelvis type. However, in the TS corridor at the S2 level, there was a significant difference between the pelvis-type groups in the mean values of AP and CC (p < 0.001). The effect of gender difference on the TS screw corridor width at the S1 and S2 levels was significant. An adequate corridor width for the TS screw corridor was detected in 50.8% of females and 67.9% of males at the S1 level, while in 21.2% of females and 70.4% of males at the S2 level.
 Conclusions: There is a significant difference in the dimensions of the trans-sacral screw corridor according to the pelvis type and gender, with the largest diameter observed in the anthropoid pelvis type and males. In critical situations, especially in males and individuals with android-anthropoid pelvis, the trans-sacral screw option should be considered primarily not only for the S1 trans-sacral corridor but also for the S2 trans-sacral corridor in pelvic posterior ring injuries

Three-dimensional magnetic resonance pelvimetry: A new technique for evaluating the female pelvis in pregnancy

ObjectiveTo describe three-dimensional (3D) magnetic resonance imaging (MRI) pelvimetry methods and to establish the pelvimetric reference in a large population of Chinese females at term pregnancy. MethodsThree-hundred one pregnant women at term who underwent MRI were included. Three-dimensional pelvic models were reconstructed using Mimics. 10.0 software based on MRI data sets, and measurements of these models were made. Pelvimetric results according to delivery modality were presented. Additionally, the previously described CT 3D pelvimetry method for predicting cephalopelvic disproportion (CPD) was used to validate its accuracy. ResultsTwo hundred ten women underwent vaginal delivery, and 13 underwent caesarean delivery for CPD. 3D modelling of the pelvis of pregnant women was feasible using MR data sets. Pelvimetric parameters in the vaginal delivery group were as follows: transverse diameter, 134.7 mm ± 7.5; obstetric conjugate, 126.9 mm ± 8.3; interspinous distance, 113.4 mm ± 8.2; sagittal midpelvis, 117.8 mm ± 8.1; intertuberous distance, 127.1 mm ± 10.4; sagittal outlet, 110.2 mm ± 8.9, and posterior sagittal outlet, 59.7 mm ± 8.1. According to the previously described CT 3D pelvimetry method for predicting CPD, 67.6% (142/210) of women in the vaginal delivery group were diagnosed with CPD. Conclusion3D MR pelvimetry is a novel method for determining pelvic dimensions at term pregnancy. A prospective trial is needed to establish a useful value for predicting CPD in Chinese females at high risk of CPD.

Pelvimetry in nulliparous and primiparous women using 3 Tesla magnetic resonance imaging.

To perform pelvimetry in nulliparous and primiparous women using 3 Tesla magnetic resonance imaging (3T MRI). Twenty-five nulliparous volunteers and 25 primiparous women underwent pelvic 3T MRI within one week after vaginal childbirth in a prospective clinical single-center trial. The pelvimetric parameters interspinous distance (ISD), intertuberous distance (ITD), sagittal outlet (SO), obstetric conjugate (OC), and coccygeal curved length (CCL) were adapted from anthropometric measurements as well as from sonographic and computed tomography-based pelvimetry performed on high-resolution T2-weighted images. We compared the results of the two study groups to one another, recent literature and postpartum-diagnosed levator ani muscle (LAM) injuries. The mean values for primipara/nullipara were ISD 107 ± 8.3/105 ± 8.4 mm, ITD 119.8 ± 10.2/118.4 ± 13.1 mm, OC 129.4 ± 10/130.8 ± 6.9 mm, SO 114.3 ± 7.8/112.5 ± 8.9 mm, and CCL 37.3 ± 7.4/39 ± 8 mm. Significant differences (P < 0.05) were found between the results for OC, SO, and CCL (primipara) and ISD, ITD and OC (nullipara) and the values in the literature. No significant difference in pelvimetric values was found between the groups. A significant correlation was found between the pelvimetric parameters and five types of LAM injuries. Two-dimensional 3T MRI combines high-resolution images with objective pelvimetric measurements applicable in a postpartum setting. Our results provide a good foundation for further MRI-based studies evaluating the bony pelvis and its relation to LAM injuries during vaginal childbirth.

Analysis of normal pelvis morphometry of modern Chinese southern Han female and its correlation with age

To analyze the normal pelvis morphometry of Chinese southern Han female and its correlation with age. From August 2009 to September 2011, 289 Han nationality females who received pelvis CT scan at Nanfang Hospital of Southern Medical University were eligible for the study. Their mean age was 43.5 years, with normal body development and no pelvic abnormality. The patients were divided into 3 age groups: 25 to 40 (n = 109), 41 to 50 (n = 115), and >50 years (n = 65). After constructing a three-dimensional digital model of the pelvis, the following parameters were measured, including transverse inlet diameter, posterior sagittal diameter of pelvic inlet, sagittal inlet, diagonal conjugate, biischial diameter, posterior sagittal diameter of midpelvis, sagittal midpelvic diameter, intertuberous distance, posterior sagittal diameter of outlet, angle of pubic arch, sagittal outlet, penal height, sacrum length and sacrum curvature. The relationship between all parameters and age was analyzed. (1) The posterior sagittal diameters of pelvic inlet of the 25 to 40 age group, 41 to 50 age group, >50 years age group were (53 ± 8), (51 ± 7), (48 ± 6) mm. The sagittal inlet of the three groups were (122 ± 8), (120 ± 9), (114 ± 8) mm. And the diagonal conjugate of the three groups were (135 ± 10), (132 ± 9), (127 ± 9) mm. All had significant differences among the three groups (P < 0.01) . (2) The posterior sagittal diameter of midpelvis of the three groups were (43 ± 6), (44 ± 6), (43 ± 7) mm, and the sagittal midpelvic diameter of the three groups were (119 ± 8), (120 ± 8), (119 ± 7) mm, with no significant difference among the three groups (P > 0.05). (3) The intertuberous distance of the three groups were (122 ± 11), (121 ± 10), (117 ± 11) mm, and the posterior sagittal diameter of outlet of the three groups were (56 ± 9), (58 ± 8), (57 ± 9) mm. There was no significant difference among the three groups (P > 0.05) .(4) Penal height of three groups were (31 ± 3), (33 ± 3), (34 ± 3) mm, there was with significant differences (P < 0.01) .(5) Pearson correlation analysis showed that penal height was positively correlated with age (r = 0.331, P < 0.05), while sagittal inlet, posterior sagittal diameter of inlet, diagonal conjugate, intertuberous distance, angle of pubic arch, sacrum length and sacrum curvature were negatively correlated with age (r = -0.120 to -0.343, P < 0.05). The shape of the pelvic inlet of Chinese southern Han female changed from sagittal elliptic into transverse elliptic form, and the posterior part of pelvic inlet became larger.Sacral concavity was increased and the pelvis became deeper. Mid pelvis and the pelvic outlet was almost unchanged, and showed no correlation with age.

Three-dimensional pelvimetry by computed tomography

This study was undertaken to assess the agreement of computed tomography (CT) pelvimetry with different postprocessing techniques. CT data sets of 25 patients were retrospectively analysed. There were no CT examinations performed solely for pelvimetry, and there was no radiation exposure for study purposes. Six pelvimetric measurements were obtained by two independent observers in four data sets of each patient, i.e. on biplanar topograms, multiplanar reconstructions of 1-mm slices, volume-rendered images of the same data and volume-rendered images based on 5-mm-thick images. Interobserver agreement and variability were determined by Bland-Altman analysis. A human skeleton was also scanned and measured with the same techniques and by ruler as reference. With a correlation coefficient of 0.98, interobserver agreement was best for assessing 3D volume-rendered images reconstructed from 1-mm-thick slices. Interobserver variability was very good for sagittal outlet and midpelvic diameter, transverse inlet diameter and obstetric conjugate (correlation coefficients 0.96-0.99) but limited for intertuberous and interspinous distance. CT and ruler measurements of the skeleton showed excellent agreement. Pelvimetry can be obtained with low interobserver variability on 3D volume-rendered CT reconstructions. Thus, CT pelvimetry is suitable to gain exact knowledge of pelvic anatomy to identify relevant parameters for dystocia in retrospective studies.

Dynamic assessment of pelvic floor and bony pelvis morphologic condition with the use of magnetic resonance imaging in a multiethnic, nulliparous, and healthy female population

Objective The purpose of this study was to determine dynamic pelvic floor and bony pelvis morphologic condition in asymptomatic multiethnic women. Study design Pelvic floor anthropometry, at rest and after the Valsalva maneuver, and pelvimetry were compared with the use of magnetic resonance imaging in nulliparous young volunteers from 5 ethnic groups (n = 11 × 5 volunteers: Emirati, other Arab, Filipino, Indian/Pakistani, and European/white volunteers), with the white volunteers as the reference group. Results The white volunteers were significantly taller ( P < .0001) than the other women. Their levator hiatus was significantly longer than the Emirati women ( P = .03) and wider than the Filipino women ( P = .04). The bladder neck descent on straining was also significantly greater than the other groups ( P < .00001). The white women also had the longest transverse diameter of the pelvic inlet ( P = .002). Their sagittal outlet diameter was significantly longer than the Emirati and Arab women ( P = .02), and their interspinous diameter was significantly longer than the Arab women ( P = .002). Conclusion Nulliparous, healthy white women have larger levator hiatus and bony pelvis with greater bladder neck descent on straining than non-white women.

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.

Obstetric MR pelvimetry: reference values and evaluation of inter- and intraobserver error and intraindividual variability.

To establish obstetric magnetic resonance (MR) pelvimetric reference values in a large study population and stratify them according to delivery modality and to determine the intra- and interobserver error and intraindividual variability of MR pelvimetric assessment in volunteers. MR pelvimetric data were retrospectively reviewed in 781 women (mean age, 28.9 years +/- 5.2 [SD]) clinically referred, and the data were correlated to obstetric history to derive normative values. Five observers assessed results of multiple MR pelvimetric examinations in 10 female volunteers (mean age, 34.7 years +/- 6.0; eight nullipara, two primipara) to provide data for measurement error analysis. All values were higher in the spontaneous vaginal delivery subgroup (n = 100) and lower in the cesarean section or vacuum extraction subgroup (n = 130; intersubgroup difference, P <.001, Mann-Whitney U test). Pelvimetric parameters in the group undergoing spontaneous vaginal delivery were as follows: obstetric conjugate, 121.7 mm +/- 8.6; interspinous distance, 112.3 mm +/- 7.9; intertuberous distance, 120.6 mm +/- 11.3; transverse diameter, 129.5 mm +/- 8.7; and sagittal outlet, 115.8 mm +/- 9.9. In the volunteer study, intraobserver, interobserver, and intraindividual reliabilities were high for the obstetric conjugate (0.94-0.96), interspinous distance (0.92-0.95), and transverse diameter (0.95-0.98) but low for intertuberous distance (0.64-0.87) and sagittal outlet (0.66-0.85). Pelvimetric dimensions are smaller in women undergoing cesarean section or vacuum extraction than they are in those delivering vaginally. The pelvimetric parameters associated with the largest measurement errors are intertuberous distance and sagittal outlet.

MR obstetric pelvimetry: effect of birthing position on pelvic bony dimensions.

The aim of our study was to measure the impact of supine and upright birthing positions on MR pelvimetric dimensions. MR pelvimetry was performed in 35 nonpregnant female volunteers in an open 0.5-T MR imaging system with patients in the supine, hand-to-knee, and squatting positions. The obstetric conjugate; sagittal outlet; and interspinous, intertuberous, and transverse diameters were compared among positions. With patients in the hand-to-knee and squatting positions, the sagittal outlet (11.8 +/- 1.3 cm and 11.7 +/- 1.3 cm) exceeded that in the supine position (11.5 +/- 1.3 cm; p = 0.002 and p = 0.01, respectively), as did the interspinous diameter (11.6 +/- 1.1 cm and 11.7 +/- 1.0 cm vs 11.0 +/- 0.7 cm; p < 0.0001, in both cases). Intertuberous diameter was wider with patients in the squatting position than in the supine position (12.7 +/- 0.8 cm vs 12.4 +/- 1.1 cm; p = 0.01). Only the obstetric conjugate was smaller with patients in the upright squatting position than in the supine position (12.3 +/- 0.8 cm vs 12.4 +/- 0.9 cm; p = 0.01). Transverse diameter did not change significantly in any position. An upright birthing position significantly expands female pelvic bony dimensions, suggesting facilitation of labor and delivery.

Low-field MRI pelvimetry.

The purpose of this study was to evaluate the usefulness of low-field MRI pelvimetry and to correlate the results with X-ray pelvimetry. A total of 19 women underwent low-field MRI pelvimetry. Mediosagittal and transverse planes were used to measure the diameters of the minor pelvic cavity. Correlations between MRI and X-ray pelvimetry were 0.96 for the sagittal inlet, 0.94 for the sagittal outlet, 0.93 for the transverse diameter (diameter transversa, DT) and 0.94 for the bispinous distance (interspinous distance, IS). The repeatability of the measurements was good. For fetuses with cephalic presentation it was also possible to determine the biparietal diameter (BPD). Low-field MRI pelvimetry was well accepted by the patients. The scanning time was less than 6 min, which is comparable with the time of X-ray examination with two planes. Magnetic resonance imaging provides a reliable method to image pelvic structures and soft tissue without ionizing radiation.

Reliability of radiographic pelvimetry. A methodological study.

The purpose of this study was to assess the reliability of radiographic pelvimetry. 48 radiologists were asked to estimate the pelvic inlet and outlet diameters from copies of 20 pelvimetry radiographs. We found that every third patient will have the sum of her pelvic outlet over- or underestimated by at least 4 mm, and 3% by more than 10 mm. The random measurement error of the sum of the pelvic outlet is about four times greater than the systematic error. The random error of the sagittal outlet diameter contributes to almost half of the total measurement error of the pelvic outlet sum. The measurement values of radiographic pelvimetry are often expressed in mm, which may give an impression of exactness that is obviously not well founded. Only in a few cases where the measurements suggest a severe feto-pelvic disproportion is it justified to do an elective cesarean section on the basis of radiographic pelvimetry only.

Pelvimetry revisited

To describe three-dimensional (3D) magnetic resonance imaging (MRI) pelvimetry methods and to establish the pelvimetric reference in a large population of Chinese females at term pregnancy.Three-hundred one pregnant women at term who underwent MRI were included. Three-dimensional pelvic models were reconstructed using Mimics. 10.0 software based on MRI data sets, and measurements of these models were made. Pelvimetric results according to delivery modality were presented. Additionally, the previously described CT 3D pelvimetry method for predicting cephalopelvic disproportion (CPD) was used to validate its accuracy.Two hundred ten women underwent vaginal delivery, and 13 underwent caesarean delivery for CPD. 3D modelling of the pelvis of pregnant women was feasible using MR data sets. Pelvimetric parameters in the vaginal delivery group were as follows: transverse diameter, 134.7 mm ± 7.5; obstetric conjugate, 126.9 mm ± 8.3; interspinous distance, 113.4 mm ± 8.2; sagittal midpelvis, 117.8 mm ± 8.1; intertuberous distance, 127.1 mm ± 10.4; sagittal outlet, 110.2 mm ± 8.9, and posterior sagittal outlet, 59.7 mm ± 8.1. According to the previously described CT 3D pelvimetry method for predicting CPD, 67.6% (142/210) of women in the vaginal delivery group were diagnosed with CPD.3D MR pelvimetry is a novel method for determining pelvic dimensions at term pregnancy. A prospective trial is needed to establish a useful value for predicting CPD in Chinese females at high risk of CPD.

THE USE OF THE VACUUM-EXTRACTOR IN NARROW OUTLETS.

The problem of cephalo-pelvic disproportioii is always a question of great interest in obstetrics. As has been pointed out many times, the narrow inlets have grown more rare during the last decades. Outlet disproportion, however, is is still not uncommon, the frequency in Sweden being given by Borell and Fernstrom (1960) to between 0.2-2.5 per cent. There seems to have been no change in this number during the last years. According to Borell and Fernstrom (1960), the capacity of the outlet is best defined by stating the sum of 3 diameters determined by X-ray pelvimetry, the posterior intertuberous (i. t. d.), the interspinous (i s. d.) and the sagittal outlet diameter (s. 0. d.). - Using the values obtained by the modified technique of B ore 11 and R B d b er g (I 964), in which a so-called ortho-diagraphic projection is used, the sums of outlet diameters can be divided into 3 groups, one group of normal outlets with a sum exceeding 31.5 em, one group of contracted outlets with a sum below 29.5 cm, where complications are met with to a great extent, and finally a so-called “border-line” group, 29.5-31.5 cm, in which is found a varying rate of complicated deliveries. In the last group obviously many factors play a part, e.g. the size of the fetus, the nature of labour and so on. Each case must be evaluated individually. However, there is in this group a possibility of surmounting a slight degree of disproportion by the use