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Biomedical subjects

R W Porter

Publications and source records attributed to R W Porter.

At least 55 records · Page 3Linked to original sources
PubMed1997

Spinal surgery and alleged medical negligence.

More than 20,000 spinal operations are carried out in the UK each year. The decision when and whether to operate requires mature judgement. Spinal surgery is technically difficult, demanding a high level of surgical skill. It is learnt only by lengthy apprenticeship. The after-care is equally important. The personal supervision of the surgeon who leads a coordinated team of clinicians, nurses and physiotherapists will ensure the best results. It is inevitable and unfortunate that mistakes will occasionally be made and only careful attention to detail in the pre-operative assessment, meticulous surgical care and supervised post-operative management will ensure consistently good results. The spinal surgeon needs to remain up-to-date, be disciplined with a systematic and careful approach and lead a coordinated team to maintain the highest standards.

Blood Vessels↗
PubMed1996

Development of the lumbar and sacral vertebral canal in utero.

STUDY DESIGN: This study analyzed the development of the lumosacral vertebral canal and dural sac in human fetus. A collection of fetuses and embryos was used to assess the development of different parameters of the spinal canal. OBJECTIVES: The data were analyzed for the dynamics of the development and also compared with mean adult spinal parameters. SUMMARY OF BACKGROUND DATA: Transversely sectioned specimens and nonsectioned specimens free of abnormalities were selected from the Boyd Collection of human embryos and fetuses. METHODS: The sections were photographed alongside a micrometric scale, and the nonsectioned specimens were scanned by magnetic resonance imaging. The films were computer analyzed for spinal and dural parameters. The error of the measurements was assessed. RESULTS: The most rapid growth period of the spinal canal parameters is between 18-36 weeks' gestation. After 30 weeks of intrauterine life, the upper lumbar canal grows faster than the lower lumbar region. The distal end of the dural sac begins to rise from S5 after 14 weeks. CONCLUSIONS: At the end of intrauterine growth, the interpedicular diameter of the spinal canal from L1 to L4 is 70% of the adult size, however, at L5, the canal is only 50% mature at birth. Therefore, if there is growth impairment in early infancy, the upper lumbar region is partially protected in contrast with the L5 level.

Adult↗
PubMed1996

Spinal stenosis and neurogenic claudication.

Neurogenic claudication is diagnosed from a classical history and complementary spinal imaging. The abnormal signs may be few. It should be distinguished from intermittent claudication (peripheral vascular disease), referred pain from the back or root pain that is aggravated by walking, and psychological distress. Pathologically, a developmentally small canal is usually affected by multiple levels of segmental degenerative change, with venous pooling in the cauda equina between two levels of low pressure stenosis. There is probably then a failure of arterial vasodilatation of the congested roots in response to exercise, with symptoms in the legs when walking. Once established, symptoms tend neither to improve nor deteriorate. Conservative management is reasonable. Otherwise decompression at the most significant stenotic level is probably adequate to obtain a good surgical result.

Diagnosis, Differential↗
PubMed1996

A comparison of methods for measuring trunk list. A simple plumbline is the best.

STUDY DESIGN: Trunk list was measured using three different techniques to compare accuracy, precision, and ease of use. OBJECTIVE: To obtain a reproducible technique for further studies of the nature, cause, and clinical relevance of trunk list. SUMMARY OF BACKGROUND DATA: Gravity-induced trunk list is a clinical sign that is frequently observed in patients with low back pain and has been associated with intervertebral disc lesions. METHODS: Patients with trunk list participated in a comparison of three techniques to determine list magnitude and direction. Paired measurements of trunk list were obtained from each patient using three techniques: a plumbline, a projected shadow, and the 3SPACE Isotrak (McDonnell Douglas Electronics Company, Colchester, VT). In addition, intra- and interobserver reliability of list measurement was assessed by comparison of paired measurements by each of two observers. RESULTS: List measurements assessed by the plumbline and the projected shadow techniques were not significantly different, but the Isotrak produced data that differed significantly (P < 0.05) from both of these techniques. Comparison of intra- and interobserver repeatability of list measurement using the plumbline technique indicated no significant difference between repeated measures by each observer or between two observers. CONCLUSIONS: A plumbline is the most useful instrument for measuring static trunk list, but its limitations and the need for standardization of measurement technique must be recognized.

Adult↗
PubMed1996

An anomalous muscle in children with congenital talipes.

An anomalous calf flexor muscle has been observed in five children (involving 7 feet) in 125 surgical corrections of congenital talipes equinovarus deformity (5.6%). The sex, frequency of bilateral to unilateral deformity, position of the child in the family, maternal age, birth weight, gestation period, and type of delivery did not distinguish these children from those without the anomalous muscle, but they did have a greater frequency of first-degree relatives with talipes.

Clubfoot↗
PubMed1996

Seasonal differences in biochemical parameters of bone remodelling.

AIMS: To compare bone remodelling parameters in late autumn and early spring in 20 post-menopausal women. METHODS: The parameters measured were serum osteocalcin and its apparent degree of carboxylation (measured by hydroxyapatite binding), total and bone specific alkaline phosphatase and urinary bone resorption markers, (pyridinoline and deoxypyridinoline). RESULTS: Serum osteocalcin concentrations were lower in autumn than in spring but the degree of carboxylation was similar. Total and bone specific alkaline phosphatase activities in serum were higher in autumn than in spring. These results support previous observations. However, notable and previously unreported changes in urinary bone resorption markers were observed. Pyridinoline concentrations were lower and deoxypyridinoline higher in autumn compared with spring. The ratio of pyridinoline:deoxypyridinoline was therefore very different between the seasons. CONCLUSIONS: The results clearly demonstrate that seasonal changes in these variables of bone remodelling must be taken into consideration when designing, reporting or analysing studies of bone metabolism in vivo.

Aged↗
PubMed1996

Comparison of initial injury features in cervical spine trauma of C3-C7: predictive outcome with halo-vest management.

The purpose of this retrospective study was to examine specific patient variables and fracture morphologies to further elucidate the predictors of successful halo-vest treatment for cervical spine fractures (C3-C7). Eighty-seven cases of acute cervical spine injuries treated with halo-vest management were reviewed to assess initial injury features and radiographic outcomes by measuring (a) subluxation and direction, (b) angulation, (c) facet abnormalities, and (d) vertebral body fracture patterns on plain radiographs and computed tomography scans. The cases were divided into three groups: facet subluxations with fractures, facet subluxation without fractures, and fractures with no subluxation. Patients with facet subluxation and advance-staged compression-flexion fractures (stages 4 or 5) were a distinct group when treated conservatively with a halo. Despite anatomic reduction, facet subluxations associated with advance-staged compression-flexion fractures (stages 4-5), might be best treated surgically. Risk factors for late halo failure should include subluxations with advance-staged compression-flexion fractures when treated conservatively.

Adolescent↗
PubMed1995

Laser Doppler study of porcine cauda equina blood flow. The effect of electrical stimulation of the rootlets during single and double site, low pressure compression of the cauda equina.

STUDY DESIGN: This study involved a model of spinal claudication to assess the effect of single and double site compressions on blood flow in porcine cauda equina. Real-time monitoring of blood flow was achieved by using laser Doppler probes. OBJECTIVES: To ascertain the difference between single and double site compressions on blood flow and nerve conduction in the cauda equina. Also, to provide possible explanations for the mechanisms underlying the pathophysiology of neurogenic claudication. SUMMARY OF BACKGROUND DATA: The model used was based on that of K. Olmarker. Double as compared with single site compression of cauda equina showed impaired nerve impulse propagation and decreased blood flow. METHOD: Pigs weighing 22-27 kg were anesthesized and the cauda equina was exposed by dorsal laminectomy of the sacral and first three coccygeal vertebrae. Polyethylene balloons were placed over the rootlets at the first and third coccygeal segments, and stimulating electrodes were positioned on the rootlets proximally to evoke motor activity. Electromyographic activity was monitored from tail musculature. Laser Doppler probes monitored blood flow in the cauda equina both between and distal to the two compression sites. RESULTS: Single site, low level compression did not affect blood flow whereas double site compression decreased it profoundly. Proximal stimulation caused a marked increase in blood flow, which was not sustained during prolonged compression. Electromyographic activity diminished concomitantly during this compression. CONCLUSIONS: Low pressure, double site compression significantly reduces cauda equina blood flow and prevents the sustained increase in blood flow required to maintain normal neurologic rootlet function. Local blood flow failure may therefore be responsible for claudication symptoms.

Animals↗
PubMed1995

Measurement of lower limb blood flow in patients with neurogenic claudication using positron emission tomography.

STUDY DESIGN: Ten subjects (seven with neurogenic claudication and three control subjects) underwent examination of lower limb muscle blood flow before and after exercise using positron emission tomography. OBJECTIVES: To investigate the hypothesis that lower limb muscle ischemia was the origin of symptoms in neurogenic claudication. BACKGROUND: Patients with neurogenic claudication secondary to spinal stenosis experience lower limb discomfort after exercise similar to that of ischemic claudication. However, they do not have clinical evidence of peripheral vascular disease. The authors postulated that the lower limb discomfort in patients with neurogenic claudication may arise from muscle ischemia due to inadequate dilatation of arterioles in response to exercise, this itself arising secondary to sympathetic dysfunction due to spinal stenosis. METHOD: Using O15-labeled water and positron emission tomography measured thigh and leg muscle blood flow response to exercise bilaterally in seven patients with unilateral neurogenic claudication and three control subjects were measured. RESULTS: The average values obtained for mid-thigh and mid-calf muscle perfusion at rest were 2.57 ml/min/100 g tissue (2.23-3.90) and 2.39 ml/min/100 g tissue (2.03-3.46), respectively. The average values obtained from mid-thigh and mid-calf perfusion after exercise were 4.41 ml/min/100 g tissue (2.8-6.0) and 4.87 ml/min/100 g (2.2-11.7). We found no difference in muscle perfusion between symptomatic and asymptomatic limbs in this group of patients. CONCLUSION: These studies suggest that muscle ischemia is not the origin of symptoms in most patients with neurogenic claudication.

Adult↗
PubMed1995

Relations between upper limb soft tissue disorders and repetitive movements at work.

To make a preliminary assessment of whether upper limb soft tissue disorders might be associated with activities at work, we have conducted a case-control study of subjects attending orthopedic clinics in three cities. All subjects between the ages of 16 and 65 years, in whom defined soft tissue conditions of the upper limb were diagnosed by the participating orthopedic surgeons, were invited to take part. Controls were subjects attending the same clinics within the same age range whose clinical diagnosis did not include disease of the upper limb, cervical or thoracic spine. Information concerning repetitive movements of the upper limbs at work was elicited by questionnaire. Five hundred eighty cases and 996 controls were studied, representing 96% and 93%, respectively, of those invited to participate. The diagnoses of the cases included soft tissue conditions affecting the shoulder, elbow, forearm, wrist, thumb, hand, and fingers. The diagnoses of the controls included traumatic, degenerative, and inflammatory conditions, mostly of the legs and lower back. Women predominated among the cases (70%) and men among the controls (56%). Of 221 female cases with injury to the wrist and forearm, 32 were cleaner/domestics (14.5%) compared to 35 to 439 controls (8%), a difference statistically significant at the 2 1/2% level. Other jobs significantly overrepresented (5% level) among female cases with injuries at various anatomical sites included hairdressers, secretary/temps, assembly line workers, and machine operators (type unspecified). Among male cases, electricians were significantly overrepresented (5% level). Jobs for which there was a suggestion (p < 0.1) of overrepresentation among cases included butchers and teacher/lecturers (both males only) and the combined job groups (chosen a priori for analysis) of keyboard operators, machine operators, and music teachers (all three jobs, females only).

Adolescent↗
PubMed1995

Sudden onset of back pain.

Patients attending a back pain clinic completed a structured interview, with particular reference to whether onset of the first episode of back pain was sudden or insidious. They were classified into four diagnostic groups. A significantly higher proportion of patients who had experienced a sudden onset of pain suffered from sciatic pain with positive root tension signs than was the case with patients whose pain had started more insidiously (50.8% vs. 20.6%; P < 0.001). These patients were also more likely to be male, to have been lifting or twisting with a weight, and to have been confined to bed or hospitalised, and have undergone manipulations, than patients with insidious onset of their pain.

Acute Disease↗
PubMed1995

Carboxylation of osteocalcin in post-menopausal osteoporotic women following vitamin K and D supplementation.

The effect of vitamin supplements on bone metabolism indices in patients with osteoporosis has received scant attention in the literature. Over a 2-week period, vitamin supplements of K and K+D were given to 20 post-menopausal osteoporotic women with previous Colles fractures. Osteoporosis was confirmed by bone mass measurements that demonstrated that broadband ultrasound attenuation (os calcis) was almost as discriminatory as dual energy X-ray absorptiometry (spine and hip) in Colles fracture patients compared with matched controls. Vitamin K corrected the carboxylation defect in osteocalcin and while less marked 4 weeks later, the improvement was still detectable. The result after K+D was similar. The level of carboxylation became the same as in premenopausal women. Total osteocalcin level (bound) osteocalcin. While there was vitamin K correctable undercarboxylation of osteocalcin, simultaneously there was no evidence of undercarboxylation of prothrombin.

Absorptiometry, Photon↗
PubMed1995

Cost analysis of fracture of the neck of femur.

A detailed cost analysis of fractures of the neck of femur in elderly patients has been conducted at Aberdeen Royal Infirmary. The aims of this study were as follows: (1) to show that the use of average orthopaedic bed day costs can lead to an overestimation of costs; (2) to identify the key explanatory variables of hip fracture costs; and (3) to identify differences in resource consumption between patient groups. The care of 50 first and ten second (contralateral) hip fracture patients admitted to Aberdeen Royal Infirmary in 1993 was costed in considerable detail. Acute care, convalescence, rehabilitation and operations accounted for more than 90% of total costs in both groups. It was found that patients who were admitted from their own homes cost significantly more than patients who were admitted from long-term care (4018 pounds vs. 2069 pounds; p < 0.001). In order to validate the costed samples, additional data were collected on all hip fracture patients admitted to Aberdeen Royal Infirmary in 1993. The main factors in explaining cost variation were the number of days spent in acute care and convalescence or rehabilitation [r2 = 0.62; logcost = (0.009 x acute days) + (0.01 x rehabilitation days) + 3.213]. Age and place of residence prior to admission explained a further 2.8% of total costs but neither variable was statistically significant. When costing fractures of the neck of femur, we recommend the collection of a minimum data set of these four variables which account for 65% of the variation in total costs.

Aged↗
PubMed1995

Surgical management of spinal epidural hematoma: relationship between surgical timing and neurological outcome.

Thirty patients were treated surgically for spinal epidural hematoma (SEH). Twelve of these cases resulted from spinal surgery, seven from epidural catheters, four from vascular lesions, three from anticoagulation medications, two from trauma, and two from spontaneous causes. Pain was the predominant initial symptom, and all patients developed neurological deficits. Eight patients had complete motor and sensory loss (Frankel Grade A); six had complete motor loss but some sensation preserved (Frankel Grade B); and 16 had incomplete loss of motor function (10 patients Frankel Grade C and six patients Frankel Grade D). The average interval from onset of initial symptom to maximum neurological deficit was 13 hours, and the average interval from onset of symptom to surgery was 23 hours. Surgical evacuation of the hematoma was performed in all patients; 26 of these improved; four remained unchanged, and no patients worsened (mean follow up 11 months). Complete recovery (Frankel Grade E) was observed in 43% of the patients and functional recovery (Frankel Grades D or E) was observed in 87%. One postoperative death occurred from a pulmonary embolus (surgical mortality 3%). Preoperative neurological status correlated with outcome; 83% of Frankel Grade D patients recovered completely compared to 25% of Frankel Grade A patients. The rapidity of surgical intervention also correlated with outcome; greater neurological recovery occurred as the interval from symptom onset to surgery decreased. Patients taken to surgery within 12 hours had better neurological outcomes than patients with identical preoperative Frankel grades whose surgery was delayed beyond 12 hours. This large series of SEH demonstrates that rapid diagnosis and emergency surgical treatment maximize neurological recovery. However, patients with complete neurological lesions or long-standing compression can improve substantially with surgery.

Adolescent↗
PubMed1995

Pathology of symptomatic lumbar disc protrusion.

There has been considerable advance in our understanding of lumbar disc protrusion. Contrary to popular belief, the healthy lumbar disc is remarkably resilient to trauma. Its nutrition is the key to failure. A fissure alone will not predispose a disc to protrusion, unless a free fragment also develops. The first symptoms of protrusion are often dramatic (the free fragment is displaced posteriorly), but this has been preceded by a long period of symptomless pathology. Protrusion is often inevitable: an incident and not an accident. Space in the vertebral canal is a major factor determining whether there is nerve root compromise. Mediators from the nucleus cause root inflammation and root tension signs. These inflammatory changes and the symptoms can resolve even though the protrusion remains. Imaging to identify the level, and surgery, are required only when conservative measures fail.

Humans↗
PubMed1995

Clubfoot: congenital talipes equinovarus.

Congenital talipes equinovarus (ctev) occurs in approximately 1.2 per thousand live births in the UK. The prevalence is less in Orientals (0.6 per thousand), and higher in Hawaiians (6.8 per thousand) and in East Africans. The aetiology is still obscure, but Ruth Wynne-Davies' view has yet to be challenged, that there is a genetic component with an environmental trigger. There is no recognisable pattern of inheritance, but if one child in a family is affected, the risk that a second will have ctev is 1 in 35.

Child↗
PubMed1995

Trefoil configuration and developmental stenosis of the lumbar vertebral canal.

The midsagittal and interpedicular diameters and the trefoil shape of lumbar vertebrae of known age at death were measured in skeletons from a population aged between 1 and 70 years. All the trefoil configurations were at L5 with the exception of one at L4. The overall prevalence was 25%, but this shape was not generally apparent until adulthood. The midsagittal diameter in the trefoil canals was found to be significantly smaller than that in the unaffected canals. This did not change significantly after six years of age indicating that the cause of the trefoil configuration is probably present early in life. The trefoil shape was no more common in the spines of the elderly subjects. Our findings indicate that the trefoil configuration of the lumbar vertebral canal has a developmental origin and is not a consequence of degenerative processes.

Adult↗