Biomedical subjects
R W Porter
Publications and source records attributed to R W Porter.
Stereotactic radiosurgery for cavernous malformations: Kjellberg's experience with proton beam therapy in 98 cases at the Harvard Cyclotron.
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Spinal arteriovenous malformations.
Spinal cord arteriovenous malformations encompass a variety of distinct lesions with aberrant connections between the arterial and venous circulation. Symptomatology and clinical presentation of such lesions are directly related to their location and particular pathophysiology. In the authors' surgical experience, 90% of patients have had the same or improved neurologic function and long-term follow-up.
Career guidance for doctors. RCSE is doing much to help surgical trainees and medical students.
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The natural history of trunk list, its associated disability and the influence of McKenzie management.
Lumbosacral list is a clinical sign that is frequently associated with low back pain and intervertebral disc lesions. This study examines the influence of McKenzie management on the natural history of trunk list. Patients with trunk list and low back pain were randomised into two groups: a control group receiving non-specific back massage and general back care advice, and a group treated according to the McKenzie protocol. Trunk list was measured over a period of 90 days and patients completed Oswestry Disability Questionnaires. There was a significantly greater resolution of list after 90 days in the group receiving McKenzie treatment compared to the control group. There was poor correlation between list magnitude and Oswestry scores. These data support previous observations that trunk list is not necessarily related to the degree of physical disability. The McKenzie method of assessment and treatment may assist in the resolution of trunk list, but it was ineffective in improving clinical condition.
Achilles tendon rupture and sciatica: a possible correlation.
The association between Achilles tendon rupture and sciatica was investigated by questionnaire in 138 patients who underwent repair of an Achilles tendon rupture, and in a group of individuals nominated by the patients, matched for age, sex, and occupation. A total of 102 patients (74%) and 128 peer nominated controls (71%) replied to the questionnaire. Of the 102 respondent patients, 18 had an officebased job, 47 were involved in skilled nonmanual work, and 16 were retired. Back pain had been experienced by 63 of the patients who replied to the questionnaire, and by 91 (75%) of the individuals in the control group (difference not significant). In about 30% of both groups, the pain confined them to bed for at least two days, and resulted in absence from work. Thirteen of the patients and 16 of the controls had undergone thoracic, lumbar, or sacral radiography. One individual in each group had received surgery for back pain. However, 35 of 102 patients had experienced sciatic pain before Achilles tendon rupture. Pain of a similar nature had been experienced by only 15 individuals in the control group (12%) (p < 0.001). Using this study design, we found a highly significant association between Achilles tendon rupture and sciatica. We propose that this association could be due to impaired afferent signals from the lower leg, or to similar collagen or vascular anomalies of the vertebral disc and the Achilles tendon.
Radiation-induced cavernous malformation.
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Vascular decompression of a vertebral artery loop producing cervical radiculopathy. Case report.
Vertebral artery tortuosity and loop formation are rare causes of cervical radiculopathy. The authors present the case of a 70-year-old man with 9 years of progressive right-sided cervical and scapular pain but no history of trauma. Computerized tomography myelography and magnetic resonance imaging revealed an ovoid mass in the right C3-4 intervertebral foramen. The patient underwent a right C-3 and C-4 hemilaminectomy and a complete C3-4 facetectomy. A pulsatile vascular structure was found compressing the right C-4 nerve root. The bone overlying the vascular structure was removed, producing decompression of the nerve root. Immediate postoperative angiography showed that this lesion was a focal vertebral artery loop. The patient's symptoms resolved after surgery, supporting the use of vascular decompression of a cervical nerve root compressed by a vertebral artery loop for the relief of radicular symptoms.
The Henderson Trust Lecture. The development of the vertebral canal and associated neuro-physiological abnormalities.
In this lecture I have attempted to demonstrate that the size of the lumbar vertebral canal has clinical importance. The canal develops very early in life, and impaired growth at this time affects other growing systems. The patient with spinal stenosis has more than a spinal disadvantage. Improved obstetric and childhood care has the potential not only to prevent some of the troublesome back problems, but also to influence the health and neurological status in adult life. I hope that the first Henderson Trustees would have been encouraged by this lecture. It supports some of the philosophy that stimulated an interest in Phrenology. In the lumbar spine at least, the container-the vertebral canal-seems to have an important relationship to the function of its neurological contents.
Significant antenatal factors in the development of lumbar spinal stenosis.
STUDY DESIGN: Adverse factors during pregnancy may permanently stunt the growth of the spinal canal. Subsequently, even in an optimal environment the canal cannot catch up in growth with the trunk and long bones because of its early maturation. The degree of retardation in canal size depends on the severity and timing of the adverse effect. The catch-up growth of the long bones mask the narrow canal, because the latter does not have growth potential, resulting in an adult of sufficient height and good proportions, but with a canal at risk for stenosis. OBJECTIVES: To investigate the influence of the antenatal environment on the growth of the lumber spinal canal. SUMMARY OF BACKGROUND DATA: To date, little is known about the effects of an adverse environment on the growth of the spinal canal, and no data have been reported on antenatal influencing factors. METHODS: Lumbar magnetic resonance imaging scans from 58 patients were examined. Dimensions of the central spinal canals were measured by computerized image analysis and compared with the subjects' obstetric data from their mothers' pregnancies. RESULTS: The L3 canal was found to be the most sensitive to the influence of the examined factors. Gestational age was the most significant factor; if short, it resulted in small adult canal. Small placental weight, greater maternal age, primiparity, low socioeconomic class, and low birth weight were also found to be significant in affecting the growth of the canal. CONCLUSIONS: An adverse antenatal environment does have a permanent, retarding effect on the growth of the lumbar spinal canal.
Surgical training. Structured training is now being used.
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An in vitro study of the biomechanical effects of flexible stabilization on the lumbar spine.
STUDY DESIGN: Lumbar motion segments were tested in vitro to examine biomechanical changes after posterior fixation by a flexible device. OBJECTIVES: To assess changes in load distribution and conformation of vertebral structures after a flexible stabilization. This should provide the foundations for a scientific understanding of the immediate effects of this surgical procedure. METHODS: Hooks were placed over the proximal spinous process and the distal laminas of a motion segment and connected by a polyester braid. Tension applied to the braid then generated a compression of the posterior elements. The force between the articular facets, the displacement of the posterior anulus fibrosus of the intervertebral disc, and the change in the relative position of the adjacent vertebrae were measured as the applied tension was increased. RESULTS: Facet joint force, disc bulge, and vertebral angulation increased with applied tension until a position of "locking" was achieved, apparently when the bony margin of the superior half of the facet joint contacted the inferior pars interarticularis. A tension of between 50 to 100 N in the braid was required for this. Facet joint force was less than 40% of this, and disc bulge was only 0.15 mm. The extension of the motion segment was between 2 degrees and 8 degrees. CONCLUSIONS: The results suggest that if such a system is applied surgically, stabilization is produced by compaction of the bony margins of the facet joints. Only a relatively small proportion of the posteriorly applied load is carried by the facet joints themselves, and little angulatory change is expected with minimal disc bulge.
Assessment of late results of surgery in talipes equino-varus: a reliability study.
UNLABELLED: The variability of a method for clinical and functional assessment of the long-term results of surgical correction of idiopathic congenital talipes equino varus was studied in ten boys and four girls (average age: 19.1 (SD 2.3 years); 22 affected feet) with radiographical evidence of fusion of the foot and ankle ossification centres. Patients were measured twice, 1 week-1 month apart, by the same investigator and were assessed twice on each visit. Assessment included anthropometry, functional assessment and subjective functional evaluation. Calf circumference, skinfold thickness, foot length and width were highly reproducible. Foot length was not significantly influenced by the operation whereas calf circumference, skinfold thickness and foot width were. Although highly reproducible, hopping was not significantly affected by operation. Active and passive range of motion were significantly different. Each was highly reproducible and both were significantly affected by the operation. Patients reported a high and highly reproducible (within two points) functional level. CONCLUSION: An assistant-administered functional questionnaire together with measurement of active and passive range of motion allows easy, valid and reproducible assessment of long-term results of surgery for idiopathic congenital talipes equino-varus correction. A significant effect of the number and type of operation was evidenced.
Concurrent aneurysm rupture and thrombosis of high grade internal carotid artery stenosis: report of two cases.
BACKGROUND: The simultaneous presentation of aneurysmal subarachnoid hemorrhage and thrombosis of a high-grade internal carotid artery stenosis is rare, and their management raises several treatment dilemmas. METHODS: Two such patients with ruptured aneurysms are presented: one with high-grade internal carotid artery stenosis that progressed to occlusion and one with acute internal carotid artery occlusion. RESULTS: Both patients were treated with craniotomy for clipping of the ruptured aneurysm followed by carotid thromboendarterectomy. CONCLUSIONS: We advocate urgent surgical treatment of both lesions, dealing with the most symptomatic lesion first. These two cases demonstrate the importance of reestablishing blood flow in patients with an acutely thrombosed carotid artery.
De novo formation of a central nervous system cavernous malformation: implications for predicting risk of hemorrhage. Case report and review of the literature.
The authors present a documented sporadic de novo cavernous malformation of the central nervous system (CNS) in a patient undergoing follow-up magnetic resonance imaging after resection of an acoustic neuroma. The authors believe that this is the first report of a de novo cavernous malformation in a patient without a familial history of this disease or a history of treatment with cranial radiation. The occurrence of de novo lesions invalidates the common assumption that cavernous malformations are congenital lesions. The use of this assumption to calculate bleeding risks retrospectively in patients with cavernous malformations is likely to underestimate the risk of symptomatic hemorrhage significantly. Consequently, the de novo formation of cavernous malformations may be more common than appreciated and may explain the higher bleeding rates reported in prospective compared with retrospective studies of these lesions.
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.
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.
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.