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Biomedical subjects

P M Stevens

Publications and source records attributed to P M Stevens.

At least 19 recordsLinked to original sources
PubMed2001

Epidermal growth factor receptor up-regulation is associated with lung growth after lobectomy.

BACKGROUND: We hypothesized that compensatory lung growth after lobectomy is characterized by a combination of cellular hyperplasia and hypertrophy and that up-regulation of epidermal growth factor receptor (EGFR) is involved in these processes. METHODS: Age-matched mature pigs were divided into four groups. The control group (group C) did not have operation. Two groups underwent left upper lobectomy and were studied 2 weeks (group L2) or 3 months (group L3) later. The last group underwent a sham left thoracotomy, and the left lower lobe was harvested 2 weeks later for EGFR analysis. Left lower lobes were studied using wet weight, cell proliferation index through immunostaining for 5-bromo-2'-deoxyuridine, morphometry, and Western blot analysis for EGFR. Content of protein and DNA (deoxyribonucleic acid) in the lung tissue was also determined. RESULTS: Left lower lobe weights were elevated in both groups L2 and L3 compared with group C. We noted a significant rise in the proliferation index, with a concomitant increase in EGFR expression, in group L2 compared with group C. In group L3, there was an increase in the protein to DNA ratio compared with group C. CONCLUSIONS: We conclude that compensatory lung growth after lobectomy comprises an early increase in the cell proliferation index (ie, cellular hyperplasia) and a late increase in the protein to DNA ratio (ie, cellular hypertrophy). The early proliferative phase is associated with EGFR up-regulation.

Animals↗
PubMed2001

Coxa vara: another option for fixation.

Coxa vara is a progressive childhood deformity that is best remedied by a valgus intertrochanteric osteotomy. By restoring the femoral neck and its physis to a more anatomic position, hip mechanics are normalized, with consequent beneficial effects upon hip motion, limb lengths and acetabular development. In the pediatric age group, there is no implant specifically designed for this purpose. Therefore, in addition to the challenge of obtaining adequate correction, inadequate fixation may contribute to recurrent varus deformity, a problem that, according to the literature, has a 30% to 70% prevalence. We are presenting a new technique using a modified veterinary plate for osteosynthesis in children in the 5-year-old to 11-year-old age group. The rationale, implant design, surgical technique and results in a group of nine patients (12 hips) are described.

Bone Plates↗
PubMed1998

A comparison of manual versus computer-assisted radiographic measurement. Intraobserver measurement variability for Cobb angles.

STUDY DESIGN: A comparison between computer-assisted measurement using digitized radiographs, which has the potential to reduce error, and manual measurement using standard radiographs. OBJECTIVE: To assess measurement variability for the Cobb method on digital radiographs and compare it with that of manual measurements on standard radiographs. BACKGROUND DATA: Studies of the Cobb method have demonstrated multiple sources of error leading to significant intraobserver measurement variability. Estimates for the 95% confidence interval for intraobserver variability range from 2.8 degrees to 10 degrees. METHODS: Twenty-four scoliosis radiographs were measured by six examiners. Two measurement sets were done manually ("manual set"), and two measurement sets were done on digitized images using a computer mouse ("computer set"). RESULTS: For the manual set, the 95% confidence interval for intraobserver variability was 3.3 degrees (range, 2.5-4.5 degrees). For the computer set, the value was 2.6 degrees (range, 2.3-3.3 degrees). This difference in 95% confidence intervals between the manual and computer sets was statistically significant (P < 0.001). CONCLUSIONS: The results of this study demonstrate that intraobserver variability for manual and computer Cobb angle measurements yield a 95% confidence interval of approximately 3 degrees, with the computer having a slightly lower variability. The computer technique removes sources of intrinsic error, e.g., the variability introduced by using different manual protractors, the inaccuracy of standard protractors, and the use of wide-diameter radiographic markers. Identical digital images can be shared electronically between centers, without having to duplicate and mail films. Multicenter studies in which different examiners will be measuring Cobb angles may consider using the computer as a measuring device to reduce intrinsic measurement errors.

Arthrography↗
PubMed1997

An unusual cause of cyanosis in a patient with a carcinoid tumor.

We report the second case of a right-to-left interatrial shunt due to a carcinoid tumor, which was successfully corrected by surgery. The patient had closure of a patent foramen ovale and tricuspid valve replacement. One and a half years after surgery, the patient had no symptoms related to heart disease.

Aged↗
PubMed1995

Closed reduction and percutaneous pinning of displaced supracondylar humerus fractures in children: description of a new closed reduction technique for fractures with brachialis muscle entrapment.

A retrospective review of 43 displaced extension-type supracondylar humerus fractures in children was performed. Thirty-four fractures were completely displaced (type III). Ninety-one percent (39 of 43) of the fractures were managed by immediate closed reduction and percutaneous pinning. Ten type III fractures exhibited clinical or radiographic evidence of brachialis muscle penetration. A closed reduction maneuver designed to "milk" the entrapped brachialis muscle off of the proximal fracture spike was developed and was successful in all eight cases in which it was attempted. At mean follow-up of 35 months, 97% (38 of 39 patients) achieved a good or excellent result based on the Flynn grading scale.

Child↗
PubMed1992

Dopamine agonist treatment of fluctuating parkinsonism. D-2 (controlled-release MK-458) vs combined D-1 and D-2 (pergolide)

Adjunctive treatment with the very potent and selective dopamine D-2 agonist MK-458 (controlled-release formulation) improved the control of parkinsonism in patients with fluctuating responses to levodopa therapy (with carbidopa). We subsequently switched patients to adjunctive treatment with pergolide, a less potent D-2 agonist. Pergolide therapy controlled parkinsonism more effectively than controlled-release MK-458. Unlike MK-458, pergolide mesylate also has D-1 agonist properties, apparently accounting for its greater antiparkinsonism efficacy. Adjunctive treatment with controlled-release MK-458 elicited less choreiform dyskinesias than either pergolide adjunctive therapy or therapy with carbidopa-levodopa alone; this finding suggests that D-1 receptor stimulation contributes to the elicitation of medication-induced chorea. The highest doses of controlled-release MK-458 resulted in paradoxical freezing of gait in almost one third of patients. This finding suggests that gait freezing, common in untreated parkinsonism, can also be elicited by excessive D-2 stimulation.

Adult↗
PubMed1991

L plate fixation for osteotomies.

It is generally acknowledged that stable fixation of osteotomies offers certain benefits, including maintenance of predictable alignment, while permitting rapid mobilization and rehabilitation. A variety of implants are available which require technical proficiency and familiarity by the surgeon for successful implantation. The ability to customize implants before or during surgery allows the surgeon critical control in a variety of situations. An L plate, which is a pre-bent dynamic compression plate (DCP), applied as a tension band with interfragmentary screws serves this purpose well.

Adolescent↗
PubMed1990

The value of preliminary traction in the treatment of congenital dislocation of the hip.

In forty-one children who had forty-seven congenitally dislocated hips, the results of attempted closed reduction with general anesthesia, but without preliminary traction, were studied. Twenty (43 per cent) of the hips could not be reduced closed, and an open reduction was needed. After the reduction, all of the involved hips were immobilized in the so-called human position (marked flexion and slight abduction). At a minimum follow-up of two years, osteonecrosis of the femoral head had developed in only two hips (4 per cent). Patients who were more than one year old when the hip was reduced had a higher incidence of osteonecrosis of the femoral head and were more likely to need reconstructive procedures later. Patients who were more than eighteen months old at the time of the attempted closed reduction were more likely to need an open reduction of the hip. Treatment of congenital dislocation of the hip in young children remains an extremely complex problem. It has not been clearly established that the use of preliminary traction decreases the incidence of osteonecrosis of the femoral head or improves the outcome of treatment. In our experience, uncomplicated (non-teratological, postnatal) congenital dislocation of the hip has been safely treated with either open or closed reduction without preliminary traction in patients who were younger than two years old, provided that the reduction could be obtained without excessive force.

Female↗
PubMed1989

Radiographic distortion of bones: a marker study.

The osseous shadows observed on radiographs are distorted by parallax and magnification error. Parallax may be minimized by proper centering of the subject; magnification error is governed by the subject-to-cassette and exposure distances. The usual assumption that radiographic magnification is 15% is, therefore, erroneous and misleading. A triangular marker was used to assess radiographic distortion of bones on films exposed at "standard" distances of 40 and 72 inches, varying the subject-to-cassette distance to simulate the effect of positioning problems posed by body habitus or joint contracture. Osseous magnification ranged from 6% to 36% on the 40-in exposures and from 3% to 17.5% at 72 in. Using a mid-sagittal marker, true bone size can be more closely determined; once the magnification is known, linear measurements can be normalized for accuracy, permitting valid comparison of quantitative data. Preoperative planning of reconstructive procedures, including implant sizing with templates, is greatly facilitated.

Anthropometry↗
PubMed1987

Computer corner #17. Computer-assisted preoperative planning (CAPP) on an office personal computer.

Determination of a preoperative plan is one of the more challenging aspects of performing corrective osteotomies for traumatic or other skeletal deformities. With the advent of sophisticated graphics hardware in personal computers, a method of preoperative planning has been developed which is less time-consuming and more versatile than conventional methods. Using OrthoPlan, radiographs are traced on a backlit, digitizing tablet attached to a microcomputer. A variety of osteotomies may be rapidly simulated on the computer screen and the surgical outcome visualized. Computer-assisted preoperative planning (CAPP) can be effectively used to decrease planning time, allow visualization of multiple surgical options, and predict results.

Bone and Bones↗
PubMed1984

Radiographic comparison of adductor procedures in cerebral palsied hips.

Hip muscle imbalance in cerebral palsy may cause subluxation or dislocation. Pelvic radiographs were used to assess hip stability in 40 affected hips before and after open adductor surgery. Preoperative rates of hip migration were determined from radiographs using the center-edge angle and migration percentage. Either an open adductor tenotomy with partial obturator neurectomy or a posterior adductor transfer was performed. Follow-up averaged 5 years, with a reversal of preoperative lateral hip migration in 36 of 40 hips. There was no statistically significant difference in the radiographic outcome of the two procedures. Lateral hip migration can be arrested or reversed with properly timed hip adductor surgery.

Adolescent↗
PubMed1983

Inhibition of airway reactivity by nifedipine in patients with coronary artery disease.

Nine patients with coronary artery disease were challenged with aerosolized methacholine before and 3 days after the daily oral administration of 30 mg of nifedipine. Resting airway tone appeared to be generally unaffected by nifedipine, as there were no significant changes in the baseline ventilatory functions. Serial measurements of spirometry and airway resistance were made after cumulative methacholine doses of 1.25, 3.75, and 8.75 mg. Identical doses of methacholine induced smaller changes in specific airway conductance (p less than 0.02), airway resistance (p less than 0.001), FEV1 (p less than 0.02), and FEF25-75% (p less than 0.01) after nifedipine therapy than before. These differences were significant at all methacholine dosage levels by paired t test except for FEV1 at the 3.75 mg dose. This study demonstrated that the bronchospastic response to methacholine in patients with coronary artery disease is reduced after the administration of nifedipine. This salutary effect on ventilatory function may be of importance to cardiac patients with concomitant chronic airway obstruction who are intolerant of beta-adrenergic blocking agents.

Airway Resistance↗
PubMed1981

Innominate osteotomy for Perthes' disease.

Seventy children who underwent innominate osteotomy for Perthes' disease were reviewed. They had been subjected to this surgery because they were considered to have a poor prognosis as indicated by age, Catterall grading, and by the presence of uncovering of the femoral head. The period of follow-up ranged from 2 to 11 years and averaged 4.3 years. The clinical results were satisfactory. The radiological results were graded (using the Sundt criteria) as good in 54%, fair in 19%, and poor in 27%. Seven children developed postoperative stiffness sufficient to require hospitalization; usually these and the children with a poor result had been subjected to late surgery and had significant hip irritability or femoral head deformity preoperatively. Based on this analysis, our indication for innominate osteotomy is for a child, over the age of 6 years, with the greater part of the femoral head affected by the disease and uncovering of the femoral head. The surgery should be performed within 8 months of presentation.

Child↗