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Assessment of the predictive value of X-ray pelvimetry and biparietal diameter in cephalopelvic disproportion.

The value of X-ray pelvimetry and ultrasonic measurement of the biparietal diameter for trial of labor prognosis was assessed in 172 healthy primiparas with suspected cephalopelvic disproportion. A decision diagram which is able to correctly predict 50% of the cesarean sections without increasing the number of unnecessary cesarean sections is proposed. In addition, the study confirms the superfluity of X-ray pelvimetry in cases of high station of the fetal head at the end of pregnancy.

Apgar Score↗

Is X-ray pelvimetry useful in a trial of labour after caesarean section?

In a trial of labour after caesarean section, X-ray pelvimetry has generally been regarded as an important part in the evaluation of patients before a decision is made. A review of 445 patients with trial of labour has shown that although the measurements of the pelvic inlet were greater in patients who delivered vaginally, the incidence of successful trial was not related to the measurements of the pelvis. Maternal height was also unrelated to the outcome. Only a history of previous vaginal delivery was predictive of a successful trial. The results suggest that X-ray pelvimetry is not necessary in the majority of patients if the past obstetric history and the clinical assessment are in favour of a successful trial. It is only useful when there is doubt and in this case both a lateral and an antero-posterior film are necessary as the obstetric conjugate alone was unreliable in predicting the transverse diameter of the inlet as well as the outcome.

Cesarean Section↗

Pelvimetry by digital radiography.

We studied the ability of digital radiographs generated on a computed tomography scanner to replace conventional pelvimetry. Two digital radiographs were usually sufficient to measure the maternal pelvis. The antero-posterior (AP) digital radiograph allowed measurement of the transverse diameter of the pelvic inlet, the interspinous distance and the intertuberous diameter. These three distances were corrected for magnification after reference to the lateral digital radiograph. The lateral radiograph gives the AP diameter of the pelvic inlet and the low sagittal diameter. Dosimetry studies demonstrated that maternal skin doses and fetal gonad doses were very low. Pelvimetry using digital radiography is a simple procedure which offers the advantage of low radiation exposure to both fetus and mother and a high accuracy of measurement.

Female↗

Pelvimetry by magnetic resonance imaging as a diagnostic tool to evaluate dystocia.

OBJECTIVE: To test the clinical value of magnetic resonance imaging (MRI) pelvimetry for the diagnosis of cephalopelvic disproportion. METHODS: All deliveries from January 1993 through December 1994 were reviewed to identify 42 nulliparas at term with vertex presentation and cesarean delivery due to dystocia. Complete data were available for 41 women, and subjects were divided into the following two subgroups, according to clinical data: "cephalopelvic disproportion" (n = 28) and "failure to progress" (n = 13). Ten nulliparous women with uncomplicated vaginal delivery served as controls. Pelvimetry data from postpartum MRI were correlated with fetal and neonatal dimensions to evaluate various criteria for the diagnosis of cephalopelvic disproportion. RESULTS: Comparing both the fetal head volume derived from antepartum ultrasound assessment and the neonatal head volume (postpartum measurement) with maternal pelvic capacity determined by MRI, cephalopelvic disproportion (head volume exceeding pelvic capacity) indicated that 25 and 27, respectively, of the 28 women had been clinically diagnosed correctly with cephalopelvic disproportion, corresponding to sensitivities of 89% and 96%, respectively. Fetal head volume was not larger than pelvic capacity in any of the women in the control group. In seven of the 13 women diagnosed as "failure to progress," the fetal head volume exceeded the pelvic capacity. CONCLUSION: A fetal head volume estimate exceeding MRI-measured pelvic capacity is a frequent finding in nulliparas with cesarean birth due to cephalopelvic disproportion. An appropriate prospective study to determine the benefits of an antepartum diagnosis of cephalopelvic disproportion in high-risk nulliparas is warranted.

Adult↗

[Ultrafast pelvimetry using Snapshot-FLASH-MRT--a comparison with the Spinecho and FLASH techniques].

Pelvimetry by means of snapshot-FLASH-MRI was carried out during the last trimester in 20 pregnant women. In 10 cases the results were compared with conventional spin-echo and FLASH-MRI. Snapshot-FLASH-MRI resulted in identical measurements but in addition provided images free from motion artifacts with good contrast of bone and soft tissue structures. The reduction in acquisition time resulted in pelvimetry in a few seconds. The total examination time and comfort for the patient were thereby improved.

Female↗

[Status of radiologic pelvimetry].

The diagnostic value of radiological pelvimetry is subject to controversial interpretation. This examination is being conducted at the Department of Gynaecology in Aarau (Frauenklinik Aarau) mainly in pregnant women in pelvic presentation or during the puerperium after Caesarean section. Based on 164 radiological pelvimetric measurements in breech presentation and 112 X-ray films after Caesarean section an attempt was made to assess the prospective value of this examination. Abnormal shapes of the pelvis and narrow pelvic dimensions were found about equally often. Analysis of the indications of the section yielded both in breech presentation and in the entire group of the patients examined post partum an almost equally high percentage of about 20% of indications for a disproportionate head-pelvis relationship. Radiologically, considerably narrowed pelvic dimensions were seen in 10% of the examined women. The most frequent finding was a funnel-shaped pelvis, whereas an assimilation pelvis was never seen. Every pathologically narrowed funnel-shaped pelvis and generally narrow pelvis was detected also by digital palpation. All cases of conjugata vera masses below 10 cm concerned generally narrow cases of pelvic dimensions and were thus detectable by digital palpation. We recommended to abstain from routine performance of radiometric pelvimetry. Lateral pelvic X-ray can be an additional help in difficulties in pregnant women with regard to determining the mode of birth in breech presentation and after Caesarean section in case there is an urgent suspicion of malproportionate head-pelvis ratios.

Cesarean Section↗

Radiation doses and image information in digital pelvimetry with a phosphorous screen.

PURPOSE: The aim of the investigation was to determine the patient dose in digital pelvimetry by means of a phosphorous screen as compared to a screen-film combination of very high sensitivity. MATERIAL AND METHODS: Entrance dose measurements and absorbed dose determinations in a series of patient exposures were made. In the first series the exposure reduction was achieved by reducing the mAs (tube current x exposure time) for the lateral and the a.p. views as compared with those used for the screen-film system. In the second series the tube potential, kV, was increased for both projections in order to increase the penetration capacity of the radiation. RESULTS AND CONCLUSION: The imaging plate technique can be used in pelvimetry with a dose reduction (and a corresponding reduction of the radiation risk to the foetus) to less than 50% of that achieved with a screen-film system of the very highest sensitivity.

Female↗

Intrinsic measurement bias on computed tomography scout view is unpredictable: Computed tomography pelvimetry using a phantom.

Our aim was to determine the degree of bias in CT scanogram measurements. We obtained standard lateral and anteroposterior (AP) pelvimetry scanograms of a phantom pelvis after placing ball bearings or aluminium rods to mark bony landmarks. Computed tomography pelvimetry was carried out at the manufacturer-recommended table height on two commercial CT scanners and at 10-mm increments up to 50 mm above and below this height. The AP inlet, AP outlet, interspinous distance and transverse diameters were each measured three times for each scanogram. The true measurements were obtained directly from the disassembled phantom. Bias was defined as the difference between the CT measurement and the true measurement. Observer error was negligible. The transverse diameter was overestimated at high table positions and underestimated at low table positions on both scanners (+6 to -10 mm). After correcting for geometric distortion, up to 6 mm bias was still present. The point at which no bias occurred was different for each scanner and did not correspond to the manufacturers' recommended table height. The outlet was overestimated on both scanners by up to 5 mm. The true inlet measurement was overestimated by 1.2 mm. The interspinous distance was minimally underestimated on both scanners. The measurements on CT scanogram were underestimated or overestimated in an inconsistent and unpredictable fashion, varying from one type of measurement to another and from CT scanner to CT scanner. This has implications for the accuracy and clinical utility of measurements obtained from a CT scanogram.

Analysis of Variance↗

Preoperative evaluation of the "hostile pelvis" in radical prostatectomy with computed tomographic pelvimetry.

OBJECTIVE: To determine whether preoperative pelvimetry based on computed tomography (CT) can be used to predict technical difficulties during open radical prostatectomy (RP). PATIENTS AND METHODS: An open RP database accrued prospectively between January 1997 and June 2005 was used to identify 450 patients with preoperative pelvic imaging. Of these, 165 had adequate imaging of the pelvis with CT to allow pelvimetry using software provided with the medical imaging records. Several pelvic measurements were recorded in conjunction with body mass index and transrectal ultrasonographic estimates of prostatic volume. Outcome measures used to reflect technical surgical difficulties included operative duration, blood transfusion requirements within 30 days of RP, the pathological positive surgical margin and prostatic capsular breech rate. Logistic and linear regression analyses were used to determine the relationship between variables before and after RP. RESULTS: The selected pelvimetric measurements failed to predict either operative duration or the peri-operative blood transfusion requirement. Prostatic volume was predictive of operative duration; for every increase of 20 mL in prostate volume the duration increased by 8.4 min. Although pelvimetric measures failed to predict positive surgical margins at pathology, the transverse diameter predicted the likelihood of a positive margin due to capsular breech. With every 8.6 mm (1 sd) decrease in transverse diameter, the odds of a capsular breech resulting in positive surgical margins increased 5.3 times (95% confidence interval 2.1-20.0, P = 0.002). CONCLUSIONS: Although the "hostile pelvis" influences the likelihood of prostatic capsular breech resulting in positive surgical margins, CT pelvimetric screening of patients before RP is unlikely to be cost-effective. Routine pelvic CT in the evaluation of patients before RP is not supported.

Aged↗

Maternal height and external pelvimetry to predict cephalopelvic disproportion in nulliparous African women: a cohort study.

OBJECTIVE: To assess external pelvimetry and maternal height, as predictors of cephalopelvic disproportion. DESIGN: Prospective cohort study. SETTING: Four hospitals in Zaire. POPULATION: Six hundred and five nulliparous women. METHODS: Maternal height and external pelvimetry were assessed during the third trimester antenatal visit. Cut off values for considering women at risk for cephalopelvic disproportion were height < 150 cm and external pelvic distances < 10th centile for the population. Logistic regression analysis, combining height and pelvic measurements, was performed to predict women at risk for cephalopelvic disproportion. MAIN OUTCOME MEASURE: Cephalopelvic disproportion was considered when there was caesarean section for failure to progress, vacuum or forceps delivery or intrapartum stillbirth. RESULTS: Cephalopelvic disproportion was present in 42 women. In univariate analysis, height, intertrochanteric diameter and the transverse diagonal of Michaelis sacral rhomboid area were found to be associated with cephalopelvic disproportion. Logistic regression analysis showed that maternal height < 150 cm and/or transverse diagonal < 9.5 cm were the variables most associated with cephalopelvic disproportion. The adjusted odds ratios were 2 x 2 (95% CI 0.9 to 5.4) and 6.5 (95% CI 3.2 to 13.2), respectively. The positive predictive value and likelihood ratio were 24% and 4.0 (95% CI 2.8 to 5.8), respectively. The addition of transverse diagonal to maternal height increased the sensitivity in predicting cephalopelvic disproportion from 21% to 52%. CONCLUSION: In addition to height, transverse diagonal measurement is able to predict one out of two cases of cephalopelvic disproportion in nulliparous women. After validation in a separate cohort, this simple predictive method may be used in peripheral centres for timely referral of pregnant women at risk for cephalopelvic disproportion.

Adult↗

Radiographic pelvimetry for assessment of dystocia in bitches: a clinical study in two terrier breeds.

Radiographic pelvimetry was used to assess the role of pelvic anatomy in obstructive dystocia in bitches. Based on the history of previous whelpings, 20 Boston terrier and 14 Scottish terrier bitches were divided into two equal groups: normally whelping bitches and bitches with obstructive dystocia. Additional whelpings during the period of study were closely observed and the pups were immediately weighed and measured. The bitches were clinically examined and the pelvis was radiographed in ventrodorsal and lateral projections. Measurements from the radiographs showed a significantly smaller pelvic size in the bitches with obstructive dystocia compared to the normally whelping bitches. Fetal-pelvic disproportion in the Scottish terrier was mainly due to a dorsoventrally flattened pelvic canal, whereas in the Boston terrier it arose from the combination of a dorsoventrally flattened pelvic canal and big fetuses with large heads. These results suggest that radiographic pelvimetry could be used to predict a disposition for dystocia in individual bitches, and as a basis for selection of breeding animals.

Animals↗

Pelvimetry by digital radiography: a low-dose examination.

Digital radiographs obtained with a CT scanner were evaluated as an alternative to conventional pelvimetry. Dosimetry studies demonstrated an absorbed radiation dose of 22 mrad for each digital radiograph, approximately 3% of the dose for comparable standard radiographs. Distance measurements were accurately made on digital radiographs and axial CT sections by cursor placement and a computer program with no needs to correct for magnification. Clinical studies of 10 patients confirmed that pelvimetry using digital radiographs is an accurate, simple, and extremely low-dose procedure which could replace the conventional method.

Breech Presentation↗

Magnetic resonance imaging pelvimetry before and after a periacetabular osteotomy.

BACKGROUND: The majority of patients who undergo a reconstructive pelvic osteotomy because of symptomatic hip dysplasia are young women of childbearing potential. The purpose of this paper was to evaluate the effect of periacetabular osteotomy on the dimensions of the pelvic inlet and outlet in these patients. METHODS: The dimensions of the osseous pelvis of seven women with symptomatic hip dysplasia were measured with use of magnetic resonance imaging pelvimetry before and after periacetabular osteotomy. Four measurements were made: the bispinous diameter, the anterior-posterior inlet measurement, the anterior-posterior midpelvis measurement, and the transverse inlet measurement. Radiographic correction obtained with the osteotomy was documented with preoperative and postoperative anteroposterior pelvic and false-profile radiographs. RESULTS: Periacetabular osteotomy improved the T nnis angle and the Lequesne angle of the hip joint to an average of 8 degrees and 30 degrees, respectively. The hip center of rotation was medialized an average of 8 mm. None of the four measurements made with the magnetic resonance imaging pelvimetry decreased substantially after the periacetabular osteotomy. CONCLUSION: Periacetabular osteotomy does not markedly alter the pertinent pelvic dimensions in young female patients.

Acetabulum↗

MR imaging pelvimetry: a useful adjunct in the treatment of women at risk for dystocia?

OBJECTIVE: The objective of this study was to test the clinical value of MR imaging for diagnosing cephalopelvic disproportion and for predicting labor outcome in women at risk for dystocia. SUBJECTS AND METHODS: Antepartum fetal sonography and maternal MR imaging pelvimetry measurements were performed at term in 38 pregnant women at risk for dystocia with a single fetus in cephalic presentation. Various methods used to diagnose cephalopelvic disproportion were evaluated in a blinded manner for their accuracy to predict both the presence of cephalopelvic disproportion and the mode of delivery (vaginal vs cesarean). RESULTS: None of the methods tested yielded both high sensitivity (15-100%) and high specificity (24-92%) for determining the presence of cephalopelvic disproportion and high levels of accuracy for predicting labor outcome (overall predictability, 50-74%). CONCLUSION: To achieve increased reliability of MR imaging pelvimetry in the diagnosis and treatment of dystocia and in predicting labor outcome, new methods assessing fetal-pelvic compatibility, including measurements of the pelvic outlet and the shape and configuration of the pelvis, need to be established and prospectively tested before firm recommendations for clinical use can be made.

Adult↗

X-ray pelvimetry and trial of labor after previous cesarean section. A prospective study.

The benefits of X-ray pelvimetry and electronic monitoring of fetal heart rate and intra-uterine pressure were studied prospectively in order to predict the likelihood of a successful vaginal birth after previous cesarean section (CS). In 1982, a total of 369 parturients (7% of all deliveries) who had previously undergone CS were studied. Trial of labor (TL) was allowed in 160 cases (43.4%) and planned repeat CS was performed in 209 patients (56.6%). Patients in the TL group were compared with a matched control group. One hundred and fifty patients (94%) in the TL group gave birth by the vaginal route. There were no differences in the duration of the first and second stage of labor, duration of ruptured membranes (ROM), maternal blood loss or the incidence of CS and vacuum extraction between the TL group and the control group. Rates of low Apgar score (less than 7) at 1 and 5 min were the same in both groups. Intensive fetal monitoring during the course of labor, together with X-ray pelvimetry in selected cases, markedly reduced the incidence of acute repeat CS with no change in the overall rate of successful vaginal delivery compared with our previous results.

Cesarean Section↗

Influence of pelvic outlet capacity on labor. A prospective pelvimetry study of 1,429 unselected primiparas.

The influence of pelvic outlet capacity on labor and the efficiency of routine low-dose radiological pelvimetry to anticipate dystocia during labor were studied prospectively among 1,429 unselected term primiparas, all having fetal head presentation and normal pregnancy. Outlet contraction was found in 0.9% and borderline outlet measurement in 5.3%. In 1,402 cases labor started spontaneously and 83 emergency cesarean sections were done. The incidence of cesarean section because of dystocia increased in inverse proportion to decreasing pelvic outlet capacity. The incidence of other emergency cesarean sections was not influenced by pelvic outlet size. In 79% of cesarean section interventions due to dystocia, pelvic outlet capacity was normal. Apgar score less than 7 at one minute was more commonly associated with a small pelvic outlet. Apgar score at 5 minutes and neonatal morbidity were not influenced by pelvic outlet size. Pelvic outlet capacity had a marked influence on the mode of delivery, but the practical value of radiological pelvimetry by fetal head presentation is rarely considered, except in very selected cases.

Cesarean Section↗

[Audit on pelvimetry at a polyvalent radiology department].

PURPOSE: Study of the dose absorbed by the fetus during CT pelvimetry. MATERIAL AND METHODS: Twenty consecutive pelvimetries on pregnant women showed the mean fetal location in regard of the maternal pelvic skeleton (retrospective study). Then, thermoluminescent radiation detectors were put in the antropomorph phantom slices, in housing correspondent to the fetal's volume. The location of this volume has been determined by the first study. Two different CT units were tested. RESULTS: In case of cephalic presentation, the maximum fetal dose was 3 mGy. In case of pelvic presentation, because of an additional frontal topogram, the dose reached 3,3 to 3,6 mGy. CONCLUSION: We recommend: 1) reduction of parameters (120kV and 100mAs) for "normal" women; using other parameters for larger women; interval follow-up to evaluate results using these parameters; 2) tilting the bisciatic plane of section so to avoid direct exposure to the fetus; 3) limitation to 25 cm for the lateral scout; suppression of the routine frontal scout in case of pelvic presentation.

Female↗

Computed tomographic pelvimetry in German shepherd dogs.

Pelvimetry was performed on a computed tomographic scanner using dorsal and lateral scout-view images of 10 adult German shepherd dogs. The vertical and transverse diameters of the pelvis were measured and the pelvic inlet and pelvic outlet areas were also calculated. No significant correlations between the pelvic measurements and body weight, age and sex were found. Although the conjugata vera, diameter verticalis, diameter sacralis, sagittal diameter and the distance between the two medial tubera ischiadica were longer in females, no significant statistical difference was found between male and female animals for all measurements. It is proposed that the computed tomographic pelvimetry should be preferred for the sensitive measurements when the normal standards are determined for different animal species and the cost is reduced to an acceptable level.

Age Factors↗