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Biomedical subjects

R W Porter

Publications and source records attributed to R W Porter.

At least 73 records · Page 4Linked to original sources
PubMed1994

The growth of the lumbar vertebral canal.

STUDY DESIGN: This study examines the growth and development of the lumbar spinal canal with emphasis on early life. OBJECTIVE: Changes in dimensions of the canal were investigated throughout life. SUMMARY OF BACKGROUND DATA: Seven hundred and fifteen lumbar vertebrae were examined from the Spitalfield Collection of Skeletons at the Natural History Museum, London. METHODS: Unmagnified silhouette pictures were taken of the canals with a specially designed photographic box. Computerized image analysis provided the accurate measurements. RESULTS: Regarding the midsagittal diameter and the cross-sectional area, the cranial four lumbar vertebrae were already fully matured in infants. At L5 there was significant increase up to 4 years of age when the midsagittal diameter was even larger than in the adult. The interpedicular diameter significantly increased at L1 until 10 years of age, at the other levels until adulthood, as did the perimeter at L4 and L5 until 14 years of age. The shape of the canal was assessed by measuring the circularity, the 'trefoilness' and the situation of the centroid. The first measurement significantly decreased with age, the trefoilness increased until adulthood, and the centroid of the canal approached the vertebral body. In spines with spina bifida occulta, the lumbar canal was significantly larger proximal to the lesion than in the unaffected spines. CONCLUSION: The lumbar spinal canal exhausts its growth potential by infancy as regards the midsagittal diameter and the cross-sectional area. Thus, in the case of delayed development, it is not capable of catch-up growth.

Adolescent↗
PubMed1994

Changes of the lumbar spinal canal proximal to spina bifida occulta. An archaeologic study with clinical significance.

STUDY DESIGN: This archaeologic study, based on four populations, examines the incidence of spina bifida occulta in the lumbar spine and the size of the vertebral canal proximal to the lesion. OBJECTIVES: To ascertain any significant change in the dimensions of the lumbar spinal canal of skeletons with spina bifida occulta. The incidence of the lesion also was compared in the separate genetic groups. METHODS: Central canals of 1760 lumbar vertebrae were examined. Silhouette, unmagnified pictures of the vertebral canals were measured by computerized image analysis. RESULTS: The mid-sagittal diameter at L4 and L5 and the cross-sectional area at L5 were found to be significantly larger proximal to the lesion compared with the unaffected spines. The overall incidence was 18%. CONCLUSIONS: The capacity of the lumbar canal is greater proximal to spina bifida occulta. Therefore, delayed closure of the neural arch at a single segment has morphologic significance to the more proximal spine.

Adolescent↗
PubMed1994

Spinal stenosis and health status.

STUDY DESIGN: This study examined the hypothesis that a small adult vertebral canal is a marker of early impairment of growth, and that other sensitive systems may be impaired similarly, producing an adult relationship among a small canal, poor health, and academic ability. OBJECTIVES: Comparisons of health and some aspects of academic ability were made between patients whose canals were above and those below the mean at L5. METHODS: Seventy-five patients were examined, 42 men and 33 women. They had comprehensive cardiovascular, respiratory, and digestive system health assessments. Their post-school qualifications were recorded, and they were assessed by the Mill Hill vocabulary test and the progressive matrices test. RESULTS: Twenty-two men and 21 women had canals above the mean, and 20 men and 12 women had canals below the mean. A significant difference did not exist in the age of those with wider and narrower canals. Cardiovascular symptoms and gastrointestinal symptoms were more common in men and women with narrower canals (P = 0.04 and 0.048), but there was no significant differences in respiratory symptoms. Those with wider canals had more post-school qualifications than those with smaller canals (P = 0.04), and in men, their performance in the Mill Hill vocabulary test and the progressive matrices test approached significance (P = 0.08 and 0.06). CONCLUSIONS: The association between a smaller vertebral canal and impairment of health and certain intellectual abilities may result from an adverse environment that affects several growing systems early in life. If the small canal is a marker of a generalized developmental disturbance, it is, to some degree, preventable.

Adult↗
PubMed1994

A ten-year prospective study of vertebral canal size as a predictor of back pain.

This prospective study compared ultrasound measurement of the lumbar vertebral canal with subsequent back pain; 669 mining and nursing recruits had been measured before 1980, and 450 replied to a postal questionnaire in 1990. There was no significant difference in the prevalence of back pain or the need to be off work with back pain, in those whose canals were above and below the mean. However, going to bed with back pain was more frequent in those with small canals and approached significance (P = 0.068). Those with small canals were more likely to visit doctors and have treatment for back pain. Canal measurement is not a predictor for back pain, but as a risk factor for severe back pain in early working life, it approaches significance.

Adult↗
PubMed1994

A laboratory model of lumbar disc protrusion. Fissure and fragment.

Discs of 20 human lumbar motion segments from donors between 20 and 52 years of age were subjected to a procedure that effected a radial fissure of the anulus, sparing a peripheral layer of approximately 1 mm in thickness. In addition, fragmented tissue pieces that resembled those retrieved at surgery for prolapse were created in the center of the disc. The disc contour was measured under pure axial load as well as in flexion and extension. In the intact specimen, the disc contour shifts in ventral direction in flexion and in dorsal direction in extension. In the 'fissure and fragment' discs a broad-based protrusion develops dorsolaterally at the location of the fissure. The magnitude of the protrusion is independent of flexion or extension angles in the range of +/- 5 degrees. The 'fissure and fragment' discs exhibit disc prolapse at loads between 0.9 and 6.1 kN and flexion angles below 10 degrees, i.e., under loading conditions well in the physiologic range. The findings of this experiment support the hypothesis that disc prolapse--aside from the hyperflexion trauma described in the literature--has to be preceded by generation of radial fissures and tissue fragmentation within the disc. Thus, prolapse appears to be a late event during the course of a long-term degenerative process.

Adult↗
PubMed1994

Broadband ultrasound attenuation and dual energy X-ray absorptiometry in patients with hip fractures: which technique discriminates fracture risk.

There is considerable interest in predicting risk of hip fracture in order to allow targeting of preventive care. This study aimed to determine which of two methods best discriminates a hip fracture population from controls. Fifty women with fractured neck of femur, and 50 control subjects were scanned using dual energy X-ray absorptiometry (DXA) of the spine and hip and broadband ultrasound attenuation (BUA) of the os calcis. Significant differences between the two populations could be found for both DXA and BUA, with BUA showing the largest percentage difference (27%). The mean z-scores showed that BUA had the lowest, with the exception of DXA trochanter. However, no significant difference between BUA and DXA trochanter Z-scores was found. A receiver operator characteristic (ROC) analysis showed that BUA has a superior sensitivity and specificity compared with DXA measurements, with DXA of the hip being better than the spine. This retrospective study shows that BUA is a better discriminator of hip fracture than DXA lumbar spine or DXA hip, which may have important implications for predicting those at risk of future hip fracture.

Absorptiometry, Photon↗
PubMed1994

Pharmacological management of back pain syndromes.

The symptom of back pain may be the result of many different pathologies. As such, patients with back pain require careful assessment to determine whether the cause is from the spine or other systems. For acute mechanical back pain, treatment is often symptomatic. Symptomatic treatment may include analgesics, anti-inflammatories and/or muscle relaxants. Patients may also need hypnotics in the short term to help them sleep at night. However, drug therapy should be reduced and stopped as soon as possible. Furthermore, too much bedrest may be counterproductive. Paracetamol (acetaminophen) is the standard treatment for transient back pain. More severe pain may require the addition of an opioid, such as codeine or dextropropoxyphene. Morphine and pethidine (meperidine) may be necessary in patients with back pain due to neoplastic disease or osteoporotic fracture. However, the opioid analgesics are associated with dependence, tolerance and adverse effects. Nonsteroidal anti-inflammatory drugs (NSAIDs) have analgesic efficacy comparable with paracetamol. Individual patients respond differently to different NSAIDs, and several agents may have to be tried. Long term therapy with NSAIDs is necessary in diseases with an inflammatory component such as ankylosing spondylitis. Calcitonin reduces bone resorption and bone blood flow, and has been suggested to have central analgesic effects. As such, it has been used successfully in patients with Paget's disease, osteolytic bone disease and osteoporosis. Bisphosphonates also inhibit osteoclastic bone resorption and may be useful in Paget's disease, osteolytic metastases and osteoporotic fractures. Other drugs which may be useful in relieving back pain associated with specific circumstances include the tricyclic antidepressants, anxiolytics, antiepileptic agents, corticosteroids, colchicine and chymopapain.

Adrenal Cortex Hormones↗
PubMed1994

Nerve traction during correction of knee flexion deformity. A case report and calculation.

We report the case of a child with cerebral palsy and spastic diplegia treated for bilateral fixed flexion of the knee by bilateral hamstring lengthening. An attempt to straighten the legs from 90 degrees to 20 degrees flexion damaged the sciatic nerve. There are no objective means of estimating how much deformity can be reduced safely. We present a method of calculating the extra strain in the sciatic nerve produced by reducing a flexion deformity. The result, combined with clinical judgement, provides guidelines for safe corrective surgery.

Cerebral Palsy↗
PubMed1993

Double-level cauda equina compression: an experimental study with continuous monitoring of intraneural blood flow in the porcine cauda equina.

Compression of the spinal nerve roots may occur clinically at multiple levels at the same time; however, the basic pathophysiology of multi-level compression is largely unknown. In this study, the intraneural blood flow was analyzed continuously in the uncompressed segment between two compression balloons, with a pig used as an experimental model and a thermal diffusion method. At 10 mm Hg compression, there was a 64% reduction of total blood flow in the uncompressed segment compared with pre-compression values. Total ischemia occurred at pressures 10-20 mm Hg below the mean arterial blood pressure. After two-level compression at 200 mm Hg for 10 min, there was a gradual recovery of the intraneural blood flow towards the baseline. Recovery was less rapid and less complete after 2 h of compression. Double-level compression of the cauda equina can thus induce impairment of blood flow, not only at the compression sites, but also in the intermediate nerve segments located between two compression sites, even at very low pressures. These findings may have clinical importance in the understanding of the pathophysiology of multiple-level cauda equina compression.

Animals↗
PubMed1993

Screening for osteoporosis: comparison between dual energy X-ray absorptiometry and broadband ultrasound attenuation in 1000 perimenopausal women.

This paper compares dual-energy X-ray absorptiometry (DXA) of the spine and hip and broadband ultrasound attenuation (BUA) of the os calcis in 1000 perimenopausal women aged between 45 and 49 years who attended a randomized Osteoporosis Screening Programme. Significant correlations were found between all DXA results and BUA, with the trochanter giving the best numerical correlation with BUA (r = 0.354, p < 0.0001). BUA was not successful in predicting women with low DXA measurements, with only 44.0% of the women whose spinal DXA falls within the lowest quartile being in the lowest quartile of BUA. Although BUA is a poor predictor of spinal and hip bone mineral density it may provide additional structural information important in fracture prediction.

Absorptiometry, Photon↗
PubMed1993

Measurement of vertebral foraminal dimensions using three-dimensional computerized tomography.

The dimensions of lumbar intervertebral foramina were measured in cadaveric spines using three-dimensional computerized tomography. Six different image reconstruction protocols were used. The results were compared with measurements of the same foramina using calipers after dissection. All the three-dimensional computerized tomographic measurements underestimated the true foraminal dimensions. The best agreement, as well as the best images, were obtained using 4/3 slices and a reconstruction threshold of 300 Hounsfield Units. This method is not recommended for measurement of foraminal dimensions. However, there may be a use in assessment and planning surgical management.

Aged↗
PubMed1993

Factors that affect surgical correction in congenital talipes equinovarus.

Children with congenital talipes deformity were assessed photographically at birth, and radiologically prior to a standard staged surgical procedure, carried out by one surgeon. A total of 111 feet of 86 children were assessed clinically and radiologically at 4 years of age. Feet with more deformity at birth and poorer preoperative calf muscle required more surgery and had less satisfactory results. Unilaterally affected feet required less surgery and had significantly better postoperative clinical results than bilaterally affected feet. There was a trend toward poorer results in children with a positive family history of talipes, but gender did not affect the outcome.

Clubfoot↗
PubMed1992

Failed lumbar spinal surgery.

Failures and poor results of 160 patients after lumbar spinal surgery between 1980 and 1984 were analysed retrospectively. A self-rated questionnaire carried out 12 months after operation revealed 20 poor results; these occurred most commonly after multiple operations, decompression and fusion as compared to disc excision. The commonest cause was failure to recognise abnormal pain behaviour before operation. A more careful preoperative assessment should reduce the incidence of failure.

Adult↗
PubMed1992

Measurement of blood flow in tibial fracture patients using positron emission tomography.

The quantification of local bone blood flow in man has not previously been possible, despite its importance in the study of normal and pathological bone. We report the use of positron emission tomography, using 15O-labelled water, to measure bone blood flow in patients with closed unilateral fractures of the tibia. We compared fractured and unfractured limbs; alterations in blood flow paralleled those found in animal models. There was increased tibial blood flow at the fracture site as early as 24 hours after fracture, reaching up to 14 times that in the normal limb at two weeks. Blood flow increase was less in displaced than in undisplaced fractures. The muscle to bone ratios of blood flow were similar to those in previous animal work using other techniques. Positron emission tomography will allow study of human bone blood flow in vivo in a wide variety of pathological conditions.

Adult↗
PubMed1992

Cauda equina dysfunction. The significance of two-level pathology.

The pathophysiology of neurogenic claudication is not well understood. It is generally believed that stenosis of the central vertebral canal is significant, but some believe that it is root canal stenosis or stenosis of the foramen that is important, not pathology in the central canal. There are, however, clinical anomalies incompatible with either view. In this article, 49 patients with neurogenic claudication were examined with myelography and computed tomography, recording the frequency of multilevel central canal stenosis and the presence of coexistent root canal stenosis. Of the 49 patients, 46 had either multilevel central canal stenosis or stenosis of both central and root canals. It was concluded that neurogenic claudication is generally associated with at least two levels of stenosis. A hypothesis of two-level venous compression, with venous pooling of one or several nerve roots, explains some of the pathophysiology of neurogenic claudication. This hypothesis is compatible with clinical and experimental observations, but it has yet to be confirmed.

Cauda Equina↗