Comparison of 2 devices to measure spinal fluid glucose concentration in hyperbaric spinal anesthesia

OBJECTIVES: To compare spinal fluid glucose measurements recorded by the laboratory analyzer Synchron LX20 Pro and the glucometer Ascensia Elite XL during continuous spinal anesthesia after injection of 10 mg of hyperbaric bupivacaine, in order to assess the reliability and speed of the 2 devices for monitoring changes in glucose concentration. PATIENTS AND METHODS: Prospective study of 34 patients under continuous spinal anesthesia administered through a 22-gauge catheter; 9 samples of spinal fluid were extracted from each patient for glucose level measurement. The first extraction was before administration of the anesthetic and the remaining ones were during spinal anesthesia until the end of complete motor block. Correlation was assessed with the Pearson test and agreement with the Bland-Altman method. RESULTS: A total of 241 pairs of measurements were obtained. The correlation was r = 0.96 (P < .01). The mean (SD) difference in measurements from the 2 devices was -1.06 (34.82 mg x dL(-1)). The percentage of variation (systematic error) was -1.9% (11.8%), placing the 95% confidence interval between -25% and 21.2%. CONCLUSIONS: Measurements from the 2 devices are highly correlated. The absolute and percentage systematic error (bias) is negligible. Finding that 95% of measurements are within 23% of the mean seems a fair percentage of error to us. We therefore believe the percentage variation, or systematic error, is clinically acceptable and that either device can be used.     

Reliability and measurement error of digital planimetry for the measurement of chronic venous leg ulcers

Area measurements of a chronic wound are the gold standard outcome measure to determine if a wound is on a healing or nonhealing trajectory. The use of digital planimetry can provide increased accuracy in measuring wound area however it is important to know the reliability and measurement error of these devices when used by multiple assessors. The aim of this study is to determine the within rater, between rater, and standard error of measurement of a digital planimetry device. Wound area in 42 patients was measured weekly for 12 weeks by two different raters, with each rater measuring the wound 10 times per visit. Intraclass correlation coefficients (ICC 1,k) and standard error of measurement were calculated for both within and between raters using 10 and the first three repeated measures to determine if using less measurements was as reliable. The true change in wound area was calculated by dividing stander error of measurements by mean wound areas. Within rater reliability for raters 1 and 2 were 0.995 and 0.992 for 10 measurements, and 0.996 and 0.992 for 3 measurements per time point. Between rater reliability was 0.979 for 10 measurements and 0.996 for 3 measurements per time point. The within rater standard error of measurement for raters 1 and 2 was 0.98 cm² and 1.28 cm² for 10 measurements and 0.895 cm² and 1.29 cm² for 3 measurements at each time point. The standard error of measurement for between raters was 2.07 cm² for 10 measurements and 2.25 cm² for 3 measurements per time point. The true change in wound size varied from 6.4% for within one rater to 15.7% for across different raters. This study found that both within and between rater reliability of the digital planimetry device was very high for three measurements per time point.     

Ultrasound measurements of torsions in the tibia and femur

BACKGROUND: The purpose of the present study was to determine the validity and reliability of using ultrasound to measure tibial and femoral torsion. METHODS: In vitro ultrasound measurements of torsion in 118 matched dried tibiae and femora were compared with direct anatomical measurements with use of simple regression. The second part of the study involved repeated in vivo ultrasound measurements made on twenty adult limbs to determine the clinical reliability of our methods. RESULTS: The in vitro ultrasound measurements of femoral and tibial torsion were significantly related to the anatomical measurements (p < 0.001 for both). The inter-rater correlation coefficients between three examiners were 0.84 for both the tibial and femoral measurements, and the intra-rater correlation coefficients ranged from 0.86 to 0.98. The in vivo measurements were similar to the in vitro measurements, and the intra-rater correlation coefficients for repeated measures were 0.91 and 0.93 for femoral and tibial torsion, respectively. CONCLUSIONS: Ultrasound is a viable tool for measuring torsion of the tibia and femur. In order to minimize measurement errors, the ultrasound measurement should be used to calculate the predicted value of torsion with use of the regression equation.     

Noninvasive measurement of lumbar sagittal mobility. An assessment of the flexicurve technique

The use of flexicurves to measure lumbar sagittal mobility was subjected to a series of reliability and validation experiments. Appropriate statistical methods were described and used to quantify intraobserver and intrasubject variability and to determine limits of agreement with measurements from radiographs. It was shown that the traditional use of correlation coefficients can produce misleading or inadequate information. The flexicurve technique had an intraobserver variability of 3-4 degrees of movement, was not significantly influenced by intrasubject variability, and provided measurements typically within 6 degrees of radiographic measurements. The data suggest that the flexicurve technique is less biased than the inclinometric method. These results demonstrate the use of suitable statistical methods to assess the clinical usefulness, or level of interchangeability, of spinal measurement instruments.     

Reliability and validity of lateral curvature assessments using clinical ultrasound for the patients with scoliosis: a systematic review

Clinical ultrasound is radiation-free, low cost and user friendly, which makes it probable in assessment of scoliosis. Numerous studies have been conducted about the feasibility of using clinical ultrasound to assess scoliosis; thus, an inclusive review of the literature would be beneficial for researchers, clinicians and patients. This study aimed to systematically review the reliability and validity of coronal curvature assessments obtained from different clinical ultrasound imaging methods. A comprehensive search of 6 databases and Google Scholar search engine was performed for retrieving articles assessing reliability and/or validity of spinal curvature measurements obtained from clinical ultrasound. Two reviewers assessed the methodological quality of selected articles independently using criteria appraisal instrument. The results were analysed and synthesized qualitatively using level of evidence method. Fourteen articles were included. Thirteen articles investigated both the reliability and validity, of which nine were of high quality; and one article evaluated only the reliability and was of high quality. Totally five ultrasound methods were evaluated. Very high reliability (intra-class correlation coefficient = 0.80–1.00) but limited levels of evidence were found for the majority of the studied ultrasound methods. Almost all the methods showed good to excellent validity (correlation coefficient = 0.76–1.00) but limited to moderate levels of evidence. A high level of evidence was found in support of the reliability and validity of the COL (centre of lamina) ultrasound method. Further reliability and validity studies should be conducted to strengthen the level of evidence for those ultrasound methods with moderate, limited or conflicting level of evidence. These slides can be retrieved under Electronic Supplementary Material.     

Verification of measurements of lumbar spinal dimensions in T1- and T2-weighted magnetic resonance imaging sequences

Background contextMagnetic resonance imaging (MRI) is commonly used to assess patients with lumbar spinal stenosis. No single MRI sequence has been shown to be superior in spinal canal measurements. There are also cost concerns for the increased clinical and research use of MRI. Using only a single sequence may lower the financial burden; however, this requires spinal canal measurements in both T1 and T2 MRI to be reliable. Evidence for this is currently lacking.PurposeThe aim of this study was to determine the intra- and inter-reader reliability of MRI measurements of the lumbar spine and the reliability of measurements using T1- and T2-weighted MRI films.Study design/settingRetrospective study.Patient sampleForty-two randomly selected patients who underwent spinal stenosis surgery.Outcome measuresLumbar spinal canal measurements and reliability analysis between T1- and T2-weighted MRI.MethodsQualitative ratings of MRI features were performed according to previously published criteria by 2 independent readers (JP-YC, HS). Measurements in axial scan included midline anteroposterior (AP) vertebral body diameter, midvertebral body width, midline AP spinal canal diameter, midline AP dural sac diameter, spinal canal width/interpedicular distance, pedicle width (right and left), and lamina angle. Measurements in the sagittal scan included midline AP body diameter, midvertebral body height, and AP spinal canal diameter. Cronbach alpha was used to characterize intra- and inter-reader reliability for qualitative rating data. Similarly, T1 and T2 comparison also was performed in the same manner.ResultsGood to excellent intra- and interobserver reliability was obtained for all measurements. Reliability analysis of all T1 and T2 measurements was excellent.ConclusionsEither T1 or T2 images can be used for measurements of spinal canal dimensions. These findings are of importance, as not every patient undergoing preoperative MRI assessment will necessarily have both sequences performed and only a single sequence is required for research studies. Our findings are also of relevance in measurement of lumbar canal diameters.     

Experience with portable ultrasound equipment and measurement of urine volumes: inter-user reliability and factors of patient position

A portable ultrasound unit has been developed that provides a noninvasive technique to measure urine volume. We assessed the effect of patient position on the accuracy of measurements as well as inter-user reliability and user training. There were 63 ultrasound measurements of urine volume made by a trained and an inexperienced examiner, and the values were compared to true volumes obtained by catheterization in 16 adults with a neurogenic bladder. Subjects were tested in the seated and supine positions. Correlation for ultrasound volumes between the trained and inexperienced examiners was highly significant. Accuracy and precision of the ultrasound measurements were not affected by patient position. Thus, little training is necessary to use this instrument, inter-user reliability is good, and accuracy and precision are clinically acceptable whether patients are in the seated or supine positions.     

Between-day repeatability and symmetry of multifidus cross-sectional area measured using ultrasound imaging

STUDY DESIGN: Prospective test-retest, intrarater reliability study. OBJECTIVES: To estimate the intrarater reliability, asymmetry, and associated error with measurement of the cross-sectional area (CSA) of the bilateral S1 multifidi when measured by a physical therapist following a short course of self-directed training in ultrasound imaging. BACKGROUND: There is increasing interest in the assessment of the lumbar multifidus during the recovery from low back injury. It is important to know the error associated with the CSA measurements obtained by a physical therapist with limited experience in ultrasound imaging when using a portable unit. METHODS AND MEASURES: Thirty healthy females (mean +/- SD age, 23 +/- 2 years; mean +/- SD mass, 63.1 +/- 9.2 kg; mean +/- SD height, 1.63 +/- 0.06 m) participated. Fourteen subjects returned within 1 to 4 days for repeated measurements. RESULTS: For all 30 subjects, the average (+/- SD) CSA of the left S1 multifidus (4.18 +/- 0.55 cm2) was larger (P<.05) than the right (4.11 +/- 0.57 cm2), with a standard error of the measurement (SEM) of 0.13 cm2 and average +/- SD asymmetry of 3.5% +/- 3.4%. For a subset of 14 subjects, the between-day intrarater reliability for the right S1 multifidus muscle was ICC3,1 = 0.80 (95% CI, 0.49-0.93), while the ICC for the left side was 0.72 (95% CI, 0.34-0.90). The day-to-day average differences for the left and right side were 0.02 cm2 and 0.04 cm2, respectively. For the most conservative estimate, the between-day SEM was 0.37cm2. CONCLUSIONS: A physical therapist, newly trained in ultrasound imaging, obtained reasonable between-day intrarater reliability when imaging the S1 multifidus. A high degree of symmetry was found between the bilateral S1 multifidi in a sample of healthy subjects, which is consistent with previous reports from measurements by skilled ultrasonographers.     

An investigation into the use of MR imaging to determine the functional cross sectional area of lumbar paraspinal muscles

The purpose of this study was to investigate the use of magnetic resonance (MR) imaging and image processing software to determine the functional cross-sectional area (FCSA) (the area of muscle isolated from fat) of the lumbar paraspinal muscles. The measurement of the morphology of the lumbar paraspinal muscles has become the focus of several recent investigations into the aetiology of low back pain. However, the reliability and validity of determining the FCSA of the lumbar paraspinal muscles using MR imaging are yet to be reported. T2 axial MR scans at the L1-S1 spinal levels of six subjects were obtained using identical MR systems and scanning parameters. Lean paraspinal muscle, vertebral body bone and intermuscular fat were manually segmented using image analysis software to assign a grey scale range to the MR signal intensity emitted by each tissue type. The resultant grey scale range for muscle was used to determine FCSA measurements for each of the paraspinal muscles, psoas, quadratus lumborum, erector spinae and lumbar multifidus on each scan slice. As various biological, instrument and measurement factors can affect MR signal intensity, a sensitivity analysis was conducted to determine the error associated in calculating FCSA for paraspinal muscle using a discrete grey scale range. Cross-sectional area and FCSA measurements were repeated three times and reliability indices for the FCSA measurements were obtained, showing excellent reliability, intra class correlation coefficient (mean=0.97, range 0.90–0.99) and %SEM (mean=2.6%, range 0.7–4.8%). In addition, the error associated with miscalculation of the grey scale range for the MR signal intensity of muscle was calculated and found to be low with an error of 20 grey scale units at the upper end of the muscles grey scale range resulting in a very small error in the measured muscle FCSA. The method presented in this paper has a variety of practical applications in areas such as evidence-based rehabilitation, biomechanical modelling and the determination of segmental inertial parameters.Research carried out at Edith Cowan University, Western Australia and the University of Nottingham, UK. The experiments comply with the current laws of the country in which they were performed in and ethical approval for the study was granted by the Local and Regional ethics committees of Edith Cowan University, Western Australia and the University of Nottingham, UK.     

In vitro and in vivo evaluation of intraluminal ultrasound in normal and atherosclerotic arteries

This study evaluated the dimensional and morphologic precision of arterial images obtained using intraluminal rotating A-scan ultrasound catheters [5.0F (30 mHz) and 8.0F (20 mHz)]. Dimensions of in vitro ultrasound images from human arteries (eight normal and nine arteriosclerotic) were compared with those from histologic sections of the vessels. In addition, in vivo ultrasound studies (23 normal and 22 arteriosclerotic) of canine femoral arteries were compared with luminal dimensions obtained from angiograms of the vessels. The correlation of in vitro ultrasound images to luminal diameters (n = 22, r = 0.96), adventitial diameters (n = 19, r = 0.83), and wall thickness (n = 19, r = 0.68) in normal human vessels was significant (p less than 0.05). In vitro measurements of images and histologic specimens from human atherosclerotic arteries also correlated significantly (p less than 0.05) with luminal diameters (n = 27, r = 0.91), adventitial diameters (n = 24, r = 0.60), and wall thickness (n = 24, r = 0.62). Morphologically, in vitro images of the wall of normal human arteries had a concentric laminated appearance and atherosclerotic vessels had patchy echodense and echolucent areas. In vivo studies showed significant correlation of diameters for both normal (n = 16, r = 0.91, p less than 0.05) and arteriosclerotic (n = 16, r = 0.57, p less than 0.05) canine arteries compared with luminal dimensions measured from uniplanar angiograms. We conclude that rotating A-scan intraluminal ultrasound accurately defines both normal and atherosclerotic arterial wall morphology and dimensions. This technology may be valuable for intravascular guidance of angioplasty devices by identifying the location and consistency of lesions.     

Error estimates in novice and expert raters for the KT-1000 arthrometer

STUDY DESIGN: Single group repeated measures with multiple raters. OBJECTIVES: To determine the inter-rater reliability of KT-1000 measurements of novice and experienced raters and to provide error estimates for these raters. BACKGROUND: The KT-1000 arthrometer is often used clinically to quantify anterior tibial displacement. Few data have been documented, however, about the relative reliability of KT-1000 measurements obtained by novice compared with experienced users. METHODS AND MEASURES: Two novice and two experienced KT-1000 users performed measurements on 29 knees of 25 patients after anterior cruciate ligament (ACL) reconstruction or with a diagnosis of ACL deficiency. Measurements were performed at 131 N. Interrater and intertrial reliability coefficients (interclass correlation coefficient; ICC) and the standard error of measurement were calculated for expert and novice raters. RESULTS: The interrater ICC for novices was 0.65 and the interrate error was +/- 3.52 mm (90% confidence interval [CI]). The interrater ICC for experts was 0.79 and the interrater error was +/- 2.94 mm (90% CI). CONCLUSIONS: These results suggest that experience in using the KT-1000 is related to the interrater error of measurements and that training is an important consideration when using the KT-1000 arthrometer.     

Determination of intraocular lens power: a comparison with and without ultrasound.

Two consecutive and sequential series of 100 pseudophakic patients were compared. In the first series intraocular lens power was determined by clinical means. In the second series axial length, using an easily operated commercially available A-scan unit, keratometry, and estimation of anterior chamber depth data were entered into an electronic calculator programmed to determine intraocular lens power. In the first series 47% of patients had a residual refractive error of 1 diopter or less, whereas 72% were within this range in the second series. With clinical lens power determination, there were three cases of residual deviation from emmetropia of more than 4 diopters; there was none greater than 3 diopters in the group using the A-scan. Lens power determination is more accurate using ultrasonography and the presently available instrumentation can be incorporated easily into a busy private practice.     

Reliability of computer-assisted lumbar intervertebral measurements using a novel vertebral motion analysis system

Background contextTraditional methods for the evaluation of in vivo spine kinematics introduce significant measurement variability. Digital videofluoroscopic techniques coupled with computer-assisted measurements have been shown to reduce such error, as well as provide detailed information about spinal motion otherwise unobtainable by standard roentgenograms. Studies have evaluated the precision of computer-assisted fluoroscopic measurements; however, a formal clinical evaluation and comparison with manual methods is unavailable. Further, it is essential to establish reliability of novel measurements systems compared with standard techniques.PurposeTo determine the repeatability and reproducibility of sagittal lumbar intervertebral measurements using a new system for the evaluation of lumbar spine motion.Study designReliability evaluation of digitized manual versus computer-assisted measurements of the lumbar spine using motion sequences from a videofluoroscopic technique.Patient sampleA total of 205 intervertebral levels from 61 patients were retrospectively evaluated in this study.Outcome measuresCoefficient of repeatability (CR), limits of agreement (LOA), intraclass correlation coefficient (ICC; type 3,1), and standard error of measurement.MethodsIntervertebral rotations and translations (IVR and IVT) were each measured twice by three physicians using the KineGraph vertebral motion analysis (VMA) system and twice by three different physicians using a digitized manual technique. Each observer evaluated all images independently. Intra- and interobserver statistics were compiled based on the methods of Bland-Altman (CR, LOA) and Shrout-Fleiss (ICC, standard error of measurement).ResultsThe VMA measurements demonstrated substantially more precision compared with the manual technique. Intraobserver measurements were the most reliable, with a CR of 1.53 (manual, 8.28) for IVR, and 2.20 (manual, 11.75) for IVT. The least reliable measurements were interobserver IVR and IVT, with a CR of 2.15 (manual, 9.88) and 3.90 (manual, 12.43), respectively. The ICCs and standard error results followed the same pattern.ConclusionsThe VMA system markedly reduced variability of lumbar intervertebral measurements compared with a digitized manual analysis. Further, computer-assisted fluoroscopic imaging techniques demonstrate precision within the range of computer-assisted X-ray analysis techniques.     

Criterion-related validity of a clinical measure of dorsal first ray mobility

STUDY DESIGN: Test-retest methodological design using a sample of convenience. OBJECTIVE: To determine the criterion-related validity and the reliability of measuring first ray mobility with a ruler. BACKGROUND: Studies have questioned the accuracy of assessing first ray mobility by manual examination. Use of a ruler and adherence to strict guidelines in positioning of the patient may improve the measure. This study investigates the validity, and the intrarater and interrater reliability of measuring dorsal first ray mobility with a ruler while following recent recommendations to standardize the position of measurement. A valid and reliable mechanical device designed to measure first ray mobility was used as the validation criterion of measurement. METHODS: Three clinicians performed ruler measurement of dorsal mobility on 14 subjects. A separate examiner measured dorsal mobility with the mechanical device. Intraclass correlation coefficients (ICCs) and standard error of measurements (SEMs) were computed to quantify the intrarater reliability of both testing procedures and the interrater reliability of the ruler measurement. ICCs of agreement were also computed to determine the concurrent validity of the ruler measurement for each clinician. RESULTS: Mechanical device intrarater reliability ICC was 0.98 (SEM = 0.15 mm). Ruler intrarater ICCs were equal or less than -0.06 (SEMs = 1.1 mm); ruler interrater ICC was 0.05 (SEM = 1.2 mm). The ICCs of agreement between the mechanical device and ruler method ranged from -0.44 to 0.06. CONCLUSION: The ruler method of testing demonstrates poor reliability and validity as a clinical measure.     

Validation of three-dimensional models of in situ scapulae

A principal challenge in creating accurate models of in situ scapulae is delineating bone from surrounding soft tissues. Computed tomography scans were obtained of both shoulders of 20 embalmed cadavers. Each shoulder was rescanned after repositioning of the cadavers to test for rescan reliability. After scans were complete, all scapulae were excised and stripped of all soft tissue. Thresholding, region growing, and manual processing were used to create computer-generated 3-dimensional (3D) models. Seven anatomic measurements were performed on each scapula and 3D model. Mean differences between corresponding measurements of specimen and model were small (<3 mm). Intraobserver and interobserver reliability for cadaveric measurements and rescan and interobserver reliability for model measurements were all excellent (R(2) = 0.99). Patient positioning was not a significant source of error in obtaining measurements from 3D models. Results from this work verify that accurate and reproducible 3D models can be created from in situ scapulae by use of effective segmentation.     

Assessment of pelvic floor muscle contraction in stress urinary incontinent women: comparison between transabdominal ultrasound and perineometry

Introduction and hypothesis  

Transabdominal (TA) ultrasound and perineometry have been currently used to assess lifting aspect and squeezing action of pelvic floor muscles (PFM) function, respectively, in women with stress urinary incontinence (SUI). However, no study has directly compared these measurements. The purpose of this study was to investigate the reliability and correlation between perineometry and TA ultrasound as measurements of different aspect of PFM function.     

The first intermetatarsal angle in hallux valgus: an analysis of measurement reliability and the error involved

In view of the importance placed on the first intermetatarsal angle in the assessment of surgical intervention in hallux valgus, we assessed the reliability with which one measures this angle. The study involved 10 observers of varying experience measuring the angle using a standard technique on 10 weightbearing AP X-rays of the foot on three separate occasions. The margin of error in measuring the angle was +/-3.60 degrees with a 95% confidence interval. Increasing and averaging the number of readings per observer or the readings of a number of observers, reduces the error. Experience doesn't improve reliability. In conclusion, improvement in the reliability of the measurements can be achieved by careful technique, performing the measurements at least twice, and averaging them.     

Lumbopelvic lordosis and pelvic balance on repeated standing lateral radiographs of adult volunteers and untreated patients with constant low back pain

STUDY DESIGN: Twenty volunteers and 20 patients with no prior spine surgery had two standing lateral radiographs taken, on the average, 66 months apart and 2 weeks apart, respectively. OBJECTIVES: To first determine the reliability of the measurement techniques used, and then the longitudinal variation between radiographs for the sagittal spinopelvic alignments measured in two stable populations, the one manifesting no back symptoms (volunteers) and the other showing no changes in symptoms (patients). Pelvic morphology also was assessed quantitatively, and significant correlations for the measurements were studied. SUMMARY OF BACKGROUND DATA: There are no published studies on longitudinal variation for measurements of sagittal spinal alignments in asymptomatic control subjects or untreated patients with stable back problems. It may be helpful to know not only how much variation in alignments can be expected between radiographs of the same individual, but also which measurements and measurement techniques offer the greatest clinical reliability and application. METHODS: Each patient in this study reported mechanical type low back pain that was constant in location and character as well as clinically consistent with symptomatic degenerative lumbar disc disease. Each patient and volunteer had 36-inch-long lateral radiographs taken of the entire thoracic and lumbar spine, which included the pelvis. After intervening periods of 1 to 4 weeks (patients) and 5 to 6 years (volunteers), a second radiograph was taken for comparison. Two observers made 24 different measurements on the radiographs including determinations for lumbopelvic lordosis, pelvic balance, and pelvic morphology using the pelvic radius technique. Reliabilities, longitudinal variations, and correlations for the measurements were compared. RESULTS: The most reliable measurements were for pelvic morphology, pelvic balance, and regional lumbopelvic lordosis by the pelvic radius technique. Pelvic morphology was the most constant measurement between individual radiographs. Pelvic morphology and total lumbosacral lordosis were dependent measurements that were complementary in determining total lumbopelvic lordosis. Lumbopelvic lordosis and pelvic balance also had strong correlation, whereas lumbosacral lordosis and pelvic balance were independent measurements. CONCLUSIONS: The pelvic radius technique is recommended for evaluating lordosis to the pelvis because this approach provided not only good measurement reliability on standing radiographs for lumbopelvic lordosis, but also determination of pelvic balance over the hips and the option to assess pelvic morphology quantitatively. Lumbopelvic lordosis and pelvic balance were strongly correlative. This finding, along with higher reliability and lower longitudinal variation on repeated radiographs, indicated greater clinical application for these specific measurements.     

A comparison of sonography and myelography in clinically suspected spinal stenosis

Anterio-posterior measurements of the subarachnoidal space of the lumbar spinal canal were obtained by myelography and by ultrasound. The correlation between the measurements is low and the distribution of the regression coefficient is considerable. The usefulness of diagnostic ultrasound as a screening procedure for patients with clinically suspected spinal stenosis, therefore, is limited. The noninvasive ultrasound method, nevertheless, has a certain value for selecting patients for myelography. An ultrasound measurement of 14 mm or more will exclude that the corresponding anterio-posterior measurement obtained at myelography is 8 mm or below.