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Biomedical subjects

P G Anderson

Publications and source records attributed to P G Anderson.

At least 19 recordsLinked to original sources
PubMed2004

Single or double-level anterior interbody fusion techniques for cervical degenerative disc disease.

BACKGROUND: The number of surgical techniques for decompression and solid interbody fusion as a treatment for cervical spondylosis has increased rapidly, but the rationale for the choice between different techniques is unclear. OBJECTIVES: The goal of this study was to determine which method of anterior cervical interbody fusion at a single or double-level provides the best clinical and radiological outcome in patients with degenerative disc disease. SEARCH STRATEGY: Studies were identified with a computer-assisted search of electronic databases in the Cochrane Central Register of Controlled Trials (Issue 1, 2004), MEDLINE (1966 to 2004), EMBASE (1980 to 2004), and Current Contents (1996 to 2004). We also searched references of selected articles. SELECTION CRITERIA: With the aid of a checklist, two reviewers independently screened the identified references. Consensus was reached through negotiation. A third reviewer was consulted if consensus could not be reached. Inclusion criteria included: articles were reports of randomised comparative studies; treatments compared anterior cervical decompression and interbody fusion techniques, participants were individuals scheduled for surgery for a chronic (longer than 12 weeks) diagnosis of degenerative disc disease. DATA COLLECTION AND ANALYSIS: Methodological quality was assessed independently by two reviewers, using the van Tulder list of criteria. With the aid of a data extraction form, data was extracted independently by two reviewers on group characteristics, intervention details and outcome measures. MAIN RESULTS: Fourteen studies with 939 patients evaluated three comparisons of different fusion techniques. From these comparisons it appears that discectomy alone has a shorter operation time, hospital stay, and post-operative absence from work than discectomy with fusion, while there is no statistical difference for pain relief and rate of fusion. It also appears that fusion techniques that use autograft give a better chance for fusion than interbody fusion techniques that use a cage, but other outcome variables could not be combined. REVIEWERS' CONCLUSIONS: The low quality of the trials prohibits extensive conclusions from this review. More studies with better methodology and reporting are needed. There should be a more general agreement between researchers on which outcome parameters should be used in the evaluation of anterior cervical fusion procedures.

Cervical Vertebrae↗
PubMed2004

CT density measurement of bone graft within an intervertebral lumbar cage: increase of hounsfield units as an indicator for increasing bone mineral content.

Radiographic assessment of lumbar interbody fusion is difficult, especially in the presence of cages and metal artifacts. The purpose of this study is to assess whether impacted bone chips in intervertebral lumbar cages show a tendency toward increased attenuation on postoperative computed tomography (CT) scans as a sign of ongoing revascularization and increased bone mineral content inside the cage. Twenty-one patients with single- or double-level lumbar fusion underwent CT scanning 1-44 months postoperatively. CT attenuation of bone inside the cage was measured with Hounsfield units. Intra- and interobserver variability were evaluated. Regression analysis showed an increase of 7.5 HU/month postoperatively for an initial value of 615 HU. Intra- and interobserver variability showed an interclass coefficient of 0.97. CT attenuation of bone graft inside an intervertebral cage increases in the postoperative period. Hounsfield unit measurement can be performed with a high degree of accuracy and reproducibility and may in the future provide a useful tool in studying cage contents in individual patients.

Bone Density↗
PubMed2003

Patients with lateral tracking patella have better pain relief following CT-guided tuberosity transfer than patients with unstable patella.

In patients with either lateral tracking patella or unstable patella the pathological lateral position of the tuberosity can be corrected by a medial transfer. This study compared the results of subtle CT-guided correction of the tuberosity for objective unstable patella (n=27) with the results for lateral tracking patella (potential instability) as described by Dejour (n=16). Follow-up was 37 months. CT revealed a pathological lateralization of the tibial tuberosity-trochlear groove greater than 15 mm in 41 knees. These patients underwent medialization of the tibial tuberosity up to 10-12 mm lateral from the trochlear groove, and 28 patients underwent a distalization to normalize the Caton index to 1.0-1.2. Results were evaluated using Cox' method. Patients with objective patellar instability were rated as 11% excellent, 52% good, 33% fair, and 4% poor. All patients became stable except one who had a 6 degrees valgus alignment. Although 96% had improved stability, 33% of the patients still had pain. The patients with lateral tracking patella (potential instability) were rated as 37.5% excellent, 44% good, and 19% fair. The lower proportion of pain relief in patients with unstable patella is likely the result of the cartilage damage experienced by these patients following multiple dislocations. Thus the patient with lateral tracking patella without patella dislocations must be differentiated from the one with unstable patella. Their prognosis in pain relief is better.

Cohort Studies↗
PubMed2003

Teardrop-femoral head distance after shelf acetabuloplasty for Perthes' disease.

Shelf acetabuloplasty is an accepted treatment for Perthes' disease. Favourable outcomes have been reported. This study aimed at determining whether changes in femoral head subluxation after shelf acetabuloplasty occur and whether they predict outcome. We assumed that reduction of subluxation after shelf acetabuloplasty would improve the long-term outcome. During follow-up, growth presented as a source of error when comparing the amount of absolute subluxation. Correction for growth was achieved by calculating a subluxation index. This index showed a significant reduction during follow-up. There was no correlation between clinical and radiological outcome, but the fact that the subluxation index showed a decreasing trend could be promising regarding outcome. This might be one of the reasons why shelf acetabuloplasty produces its effect. Following shelf acetabuloplasty the enlarged acetabulum could possibly direct the growth of the femoral head to a better-contained joint. This could result in better joint congruity and lesser tendency to degenerative arthritis.

Acetabulum↗
PubMed2002

Posterior reduction and anterior lumbar interbody fusion in symptomatic low-grade adult isthmic spondylolisthesis: short-term radiological and functional outcome.

The aim of this study was to evaluate the short-term radiological and functional outcome of surgical treatment for symptomatic, low-grade, adult isthmic spondylolisthesis. Twelve patients underwent a monosegmental fusion for symptomatic spondylolisthesis. Posterior reduction with pedicle screw instrumentation was followed by second-stage anterior interbody fusion with a cage. All patients underwent a decompressive laminectomy. At an average of 2.1 (range 1.4-3.0) years following surgery, all patients completed the Oswestry questionnaire, VAS back pain score and a questionnaire detailing their work status. Radiographs were evaluated for maintenance of reduction and fusion. The patients (nine male, three female; mean age 42, range 22-54 years) had experienced preoperative symptoms for an average of 38 (range 6-96) months. An average preoperative slip of 21% (range 11-36%) was reduced to 7% (range 0-17%). Reduction of slip was maintained at latest follow-up, at which time the average VAS score was 2.8 (range 0-8) and the average Oswestry score was 13 (range 0-32). All patients achieved a successful fusion. There were no postoperative nerve root deficits. All patients stated that they would be prepared to undergo the same procedure again if required. Seventy-five percent returned to their pre-symptom work status. Our findings suggest that posterior reduction and anterior fusion for low-grade adult isthmic spondylolisthesis may yield good functional short-term results. A high fusion rate and maintenance of reduction with a low complication rate may be expected. Further follow-up is necessary to evaluate long-term outcome.

Adult↗
PubMed2001

Nitric oxide partitioning into mitochondrial membranes and the control of respiration at cytochrome c oxidase.

An emerging and important site of action for nitric oxide (NO) within cells is the mitochondrial inner membrane, where NO binds to and inhibits members of the electron transport chain, complex III and cytochrome c oxidase. Although it is known that inhibition of cytochrome c oxidase by NO is competitive with O2, the mechanisms that underlie this phenomenon remain unclear, and the impact of both NO and O2 partitioning into biological membranes has not been considered. These properties are particularly interesting because physiological O2 tensions can vary widely, with NO having a greater inhibitory effect at low O2 tensions (<20 microM). In this study, we present evidence for a consumption of NO in mitochondrial membranes in the absence of substrate, in a nonsaturable process that is O2 dependent. This consumption modulates inhibition of cytochrome c oxidase by NO and is enhanced by the addition of exogenous membranes. From these data, it is evident that the partition of NO into mitochondrial membranes has a major impact on the ability of NO to control mitochondrial respiration. The implications of this conclusion are discussed in the context of mitochondrial lipid:protein ratios and the importance of NO as a regulator of respiration in pathophysiology.

Animals↗
PubMed2001

Increased sensitivity of mitochondrial respiration to inhibition by nitric oxide in cardiac hypertrophy.

Cardiac hypertrophy is a significant risk factor for the development of congestive heart failure (CHF). Mitochondrial defects are reported in CHF, but no consistent mitochondrial alterations have yet been identified in hypertrophy. In this study selective metabolic inhibitors were used to determine thresholds for respiratory inhibition and to reveal novel mitochondrial defects in hypertrophy. Cardiac hypertrophy was produced in rats by aortic banding. Mitochondria were isolated from left ventricular tissue and the effects of inhibiting respiratory complexes I and IV on mitochondrial oxygen consumption were measured. At 8 weeks post-surgery, 65+/-2% complex IV inhibition was required to inhibit respiration half maximally in control mitochondria. In contrast, only 52+/-6% complex IV inhibition was required to inhibit respiration half maximally in mitochondria from hypertrophied hearts (P=0.046). This effect persisted at 22 weeks post-surgery and was accompanied by a significant upregulation of inducible nitric oxide synthase (iNOS, 3.0+/-0.7-fold, P=0.006). We conclude that respiration is more sensitive to complex IV inhibition in hypertrophy. Nitric oxide is a well documented inhibitor of complex IV, and thus the combination of increased NO(.)from iNOS and an increased sensitivity to inhibition of one of its targets could result in a bioenergetic defect in hypertrophy that may be a harbinger of CHF.

Animals↗
PubMed2001

Elevated potassium intake inhibits neointimal proliferation in the swine coronary artery.

BACKGROUND: Previously, we reported that elevated extracellular potassium concentration in vitro inhibited proliferation and migration of vascular smooth muscle cells, formation of free radical compounds by macrophages, and reduced platelet sensitivity to agonists. More recently, we described a reduction in neointimal proliferation after balloon angioplasty injury in the carotid arteries of rats associated with an elevation of dietary potassium intake during a 4-week experiment. In the present study we conducted a similar investigation in the swine coronary artery balloon angioplasty model. PROCEDURES: Two groups of seven castrated male swine were studied; for 28 days the normal potassium group consumed a diet containing 0.25% potassium and the high potassium group ate diet containing 2.0% potassium. After 14 days on the diet, balloon angioplasty was performed. After an additional 14 days on the same diets the hearts were removed, and normal and lesioned sections of the artery were analyzed histologically. RESULTS: The neointimal area was markedly less in the high potassium group than in the normal potassium group, 0.33+/-0.04 mm2 v 0.74+/-0.10 mm2 (P < .004). Neointimal area-to-total wall area ratio in the normal potassium group averaged 0.199+/-0.018, significantly greater than the ratio computed for the elevated potassium group, 0.120+/-0.015 (P < .006). CONCLUSION: These results support the hypothesis that a high level of dietary potassium intake inhibits neointimal proliferation after balloon angioplasty in the swine coronary artery.

Aldosterone↗
PubMed2001

Is there a relation between neuropsychologic variables and quality of life after stroke?

OBJECTIVES: To describe the quality of life (QOL) of stroke patients and to distill neuropsychologic predictors for poor QOL. DESIGN: A cohort study in which patients were neuropsychologically assessed at a mean of 72.2 days after stroke, with follow-up at a mean of 9.8 months after stroke. SETTING: Research department of a rehabilitation center. PATIENTS: A consecutive sample of 164 stroke patients (mean age, 55.2yr) recruited from a university hospital, a regional hospital, and a rehabilitation center. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Orientation, memory, attention and concentration, visuospatial and visuoconstructive functions, language, and arithmetic skills were assessed with neuropsychologic tests. QOL was assessed with the Sickness Impact Profile (SIP). RESULTS: An overall mean SIP score +/- standard deviation of 20 +/- 11 showed that stroke has a high impact on everyday functioning. Further analyses indicated that QOL is related in particular to tests measuring spatiotemporal and/or sequential aspects of behavior. Forward/backward stepwise regression analysis (n = 106) showed that poor QOL was more likely if patients had a poor result on the Trailmaking Test (TMT) B and/or were women. CONCLUSION: The predictive value of the TMT is most effective and very useful because the TMT is a short and economical procedure. However, the gender-related aspects of recovery deserve more attention, as does the possible bias that can be caused by the composition of a measurement. Further research is needed to refine predictive models that are needed to facilitate the development of more adequate, individual rehabilitation programs.

Adolescent↗
PubMed2001

Results with the M. E. Müller cemented, straight-stem total hip prosthesis: a 10-year historical cohort study in 180 women.

In 1986, 242 M. E. Muller (MEM) cemented, straight-stem total hip arthroplasty prostheses were implanted in 229 patients; 15 hips (13 patients) were lost to follow-up. Of the remaining 227 implants, 180 were placed in women, and 47 were placed in men (each with mean age, 71 +/- 7.7 years). After 10 years, 66 patients had died, and 152 implants were still in situ. As a result of aseptic loosening, 9 hips were revised (5 femoral and 4 acetabular components); two of these patients had a Girdlestone as a result of postoperative infection. Because 50% of the men died during follow-up, further analysis was performed with the 180 implants in women. The incidence of revision for aseptic loosening was 5.9 per 1,000 implants. The cumulative survival rate after 10 years was 94%. Survival was not influenced significantly by age, indication for operation, or having a contralateral hip prosthesis. The 10-year follow-up results for the MEM straight-stem total hip prosthesis in our hospital are satisfactory despite the probability that the cement mantle produced with this stem is not uniform in thickness.

Aged↗
PubMed2001

Mechanisms of cell signaling by nitric oxide and peroxynitrite: from mitochondria to MAP kinases.

Many of the biological and pathological effects of nitric oxide (NO) are mediated through cell signaling pathways that are initiated by NO reacting with metalloproteins. More recently, it has been recognized that the reaction of NO with free radicals such as superoxide and the lipid peroxyl radical also has the potential to modulate redox signaling. Although it is clear that NO can exert both cytotoxic and cytoprotective actions, the focus of this overview are those reactions that could lead to protection of the cell against oxidative stress in the vasculature. This will include the induction of antioxidant defenses such as glutathione, activation of mitogen-activated protein kinases in response to blood flow, and modulation of mitochondrial function and its impact on apoptosis. Models are presented that show the increased synthesis of glutathione in response to shear stress and inhibition of cytochrome c release from mitochondria. It appears that in the vasculature NO-dependent signaling pathways are of three types: (i) those involving NO itself, leading to modulation of mitochondrial respiration and soluble guanylate cyclase; (ii) those that involve S-nitrosation, including inhibition of caspases; and (iii) autocrine signaling that involves the intracellular formation of peroxynitrite and the activation of the mitogen-activated protein kinases. Taken together, NO plays a major role in the modulation of redox cell signaling through a number of distinct pathways in a cellular setting.

Animals↗
PubMed2001

Bioenergetics in cardiac hypertrophy: mitochondrial respiration as a pathological target of NO*.

A rat aortic banding model of cardiac hypertrophy was used to test the hypothesis that reversible inhibition of mitochondrial respiration by nitric oxide (NO*) elicits a bioenergetic defect in the hypertrophied heart. In support of this hypothesis, the respiration of myocytes isolated from hypertrophied hearts was more sensitive to exogenous NO* (IC(50) 200 +/- 10 nM vs. 290 +/- 30 nM in controls, P = 0.0064). Hypertrophied myocytes also exhibited significantly elevated inducible NO* synthase (iNOS). Consistent with this endogenous source for NO*, the respiration of hypertrophied myocytes was significantly inhibited at physiological O(2) tensions versus controls. Both the nonspecific NOS inhibitor nitro-L-arginine and the iNOS-specific inhibitor N-[3-(aminomethyl)- benzyl]acetamidine. 2HCl reversed this inhibition, with no effect on respiration of control myocytes. Consistent with an NO*-mediated mitochondrial dysfunction, the ability of intact perfused hearts to respond to a pacing workload was impaired in hypertrophy, and this effect was reversed by NOS inhibition. We conclude that endogenously generated NO* can modulate mitochondrial function in the hypertrophied heart and suggest that this bioenergetic defect may underlie certain pathological features of hypertrophy.

Amidines↗
PubMed2001

Shelf acetabuloplasty for Perthes' disease: 12-year follow-up.

The goal of all therapies for Perthes' disease is to achieve an optimal shape of the acetabulum and an optimal coverage of the femoral head. Thirty patients who were included in this follow-up study (mean follow-up 12 years) underwent a shelf acetabuloplasty for Catterall group III or IV. The mean IOWA hip score at follow-up was 96 (max. 100 points, range 74-100). The mean acetabular-head quotient increased from 82.9% pre-operatively to 107.9% postoperatively, and remained 102.4% at follow-up. There was a decrease in mean lateral subluxation ratio from 1.44 pre-operatively to 1.27 postoperatively, which remained 1.23 at follow-up. According to the Stulberg classification in the 18 adult hips, 6 hips had a good result (Stulberg 1 or 2), 10 hips had a fair result (Stulberg 3), and 2 hips had a poor result (Stulberg 4 or 5). These results appear to be better than the natural history as described by Stulberg. Shelf acetabuloplasty can be considered as an appropriate surgical treatment for severe cases of Perthes' disease.

Acetabulum↗
PubMed2000

Concentration-dependent effects of nitric oxide on mitochondrial permeability transition and cytochrome c release.

The mitochondrial permeability transition pore (PTP) and associated release of cytochrome c are thought to be important in the apoptotic process. Nitric oxide (NO( small middle dot)) has been reported to inhibit apoptosis by acting on a variety of extra-mitochondrial targets. The relationship between cytochrome c release and PTP opening, and the effects of NO( small middle dot) are not clearly established. Nitric oxide, S-nitrosothiols and peroxynitrite are reported to variously inhibit or promote PTP opening. In this study the effects of NO( small middle dot) on the PTP were characterized by exposing isolated rat liver mitochondria to physiological and pathological rates of NO( small middle dot) released from NONOate NO( small middle dot) donors. Nitric oxide reversibly inhibited PTP opening with an IC(50) of 11 nm NO( small middle dot)/s, which can be readily achieved in vivo by NO( small middle dot) synthases. The mechanism involved mitochondrial membrane depolarization and inhibition of Ca(2+) accumulation. At supraphysiological release rates (>2 micrometer/s) NO( small middle dot) accelerated PTP opening. Substantial cytochrome c release occurred with only a 20% change in mitochondrial swelling, was an early event in the PTP, and was also inhibited by NO( small middle dot). Furthermore, NO( small middle dot) exposure resulted in significantly lower cytochrome c release for the same degree of PTP opening. It is proposed that this pathway represents an additional mechanism underlying the antiapoptotic effects of NO( small middle dot).

Animals↗
PubMed2000

A systematic literature review to identify the best method for a single level anterior cervical interbody fusion.

The goal of this systematic literature review was to determine, for patients with degenerative disc disease, which method of single-level anterior cervical interbody fusion using the anterior approach gives the best clinical and radiological outcome. The number of new techniques for obtaining a solid fusion has increased rapidly, but the rationale for choosing between different techniques is unclear. Randomised comparative studies on anterior cervical interbody fusions were identified in a sensitive Medline, Cochrane and Current Contents database search. Two independent reviewers evaluated the articles that met the selection criteria, using a checklist. The search yielded eight randomised, controlled trials for the systematic literature review. Three of these studies were judged to be of sufficient quality with regard to methodology and the information provided. In the three articles, five different treatment methods were investigated, four of which were interbody fusions. Fusion rates varied between 28% for an allograft method and 63% for a discectomy-alone method. In one study, kyphosis varied from 40% to 62% between treatments. Good clinical outcome (disability, pain and symptoms) ratings varied from 66% to 82%. A meta-analysis to determine the best method for an anterior interbody fusion could not be performed due to the heterogeneity of the methods reported and because no standard outcome parameter was used. From this systematic literature review, a gold standard for the treatment of degenerative disc disease could not be identified.

Cervical Vertebrae↗
PubMed2000

Anterior lumbar interbody fusion with threaded fusion cages and autologous bone grafts.

The goal of this study was to evaluate the ability of Ray threaded fusion cages, when used in an anterior approach, to restore intervertebral height and to improve the functional and occupational performance of the patients. The present study was initiated because insertion of fusion cages through a posterior approach causes destruction of facet joints and violation of the spinal canal. The anterior approach for insertion of threaded fusion cages to accomplish lumbar interbody fusion was evaluated in a series of 13 patients suffering monosegmental disc disease. The patients' functional and occupational performance was evaluated using the Prolo score. Radiological measurements were used to evaluate disc height and degree of penetration into the endplates, and to confirm fusion. Seven of the 13 patients were short-term failures and had to be revised within 2 years. The study found that revised patients had poorer Prolo scores than non-revised patients. Although for the non-revised patients, the mean Prolo scores remained relatively stable during the 1st year, they dropped after 3 years. We were not able to identify any further clinical or radiological differences between the groups. These results indicate that although the anterior approach seems technically suitable for insertion of threaded fusion cages, destruction of the anterior longitudinal ligament and the anterior part of the annulus fibrosis appears to result in destabilisation of the motion segment.

Adult↗
PubMed2000

High potassium intake inhibits neointima formation in the rat carotid artery balloon injury model.

Recently, we reported that elevated extracellular potassium concentration in vitro inhibited proliferation and migration of vascular smooth muscle cells, formation of free radical compounds by macrophages, and reduced platelet sensitivity to agonists. In the present study we analyzed the effects of long-term, in vivo elevation of extracellular potassium concentration resulting from changes in dietary potassium intake on the vascular response to injury. The rat carotid artery balloon injury model was employed in 70 adult Sprague Dawley rats assigned to three groups. Beginning 14 days before surgical placement of the carotid lesion and continuing until death, the animals were fed diets containing either low (0.1% potassium, n = 25), normal (1.5% potassium, n = 19), or high potassium (4.0% potassium, n = 26). Fourteen days postsurgery the animals were killed and the arteries were analyzed to determine quantitatively the ratio of neointimal to medial area. Dietary potassium had a significant effect on arterial plasma potassium concentration (one-way analysis of variance, P < .01). Group mean and standard errors were 4.26+/-0.12 mmol/L for the low-potassium group, 5.22+/-0.19 mmol/L for normal, and 5.80+/-0.23 mmol/L for the high-intake group. Increases in dietary potassium attenuated neointima formation significantly (P < .05, one-way analysis of variance), with the mean ratio of neointimal area to medial area being 0.447+/-0.106 for the low-intake animals, 0.384+/-.116 for normal, and 0.240+/-.046 for the high-intake group. These results are consistent with a hypothesis that a high level of potassium intake is effective in inhibiting neointima formation in vivo.

Animals↗