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Biomedical subjects

E S Hansen

Publications and source records attributed to E S Hansen.

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

Improved method for examination of microvascular structures in bone tissue.

Scanning electron microscopy of methylmethacrylate vascular corrosion casts was used for the morphologic examination of the microvascular system in bone. The methylmethacrylate used for vascular casting was prepared by prepolymerization with ultraviolet light. To approximate the viscosity of blood in the microcirculation, where the hematocrit of blood is lower than in the rest of the circulation, a viscosity between that of plasma and full blood was chosen for the casting material. Neither the ultraviolet prepolymerization of methylmethacrylate nor the choice of a viscosity this low has been used in microcorrosion casting in bone before. Further preparation of the tissue followed 2 directions: (1) complete maceration and decalcification of the specimens, thereby exposing all the vascular structures for detailed examination. By this procedure, it was possible to show detailed and sharp impressions of the vascular bed, and to show, for the first time, the vascular loop from a cutting cone; and (2) maceration without decalcification of the specimens, which is suitable for examination of relations between the microvascular system and the bone tissue. This technique enables studies of the role of the vascular system in bone remodeling and of the involvement of vascular structures in bone disorders. This improved technique for examination of microvascular structures in bone enables detailed studies of the vascular system and its relation to active remodeling sites in bone.

Animals↗
PubMed1996

Role of different loading conditions on resorption of hydroxyapatite coating evaluated by histomorphometric and stereological methods.

The role of different loading conditions on resorption of plasma-sprayed hydroxyapatite coating was investigated in an experimental study. Resorption of hydroxyapatite was quantified by histomorphometric and stereological methods on backscattered scanning electron images. Hydroxyapatite-coated titanium implants were inserted unilaterally into the medial femoral condyle of the knee in 14 mature dogs. Initially, all implants were subjected to controlled micromotion of 150 microns. After 4 weeks, the dogs were randomly assigned either to have the implant surgically immobilized to prevent further micromovement or to have a sham operation. Sixteen weeks after the first operation, the implants were analyzed. Six noninserted implants served as controls. The surface area and volume of the hydroxyapatite coating were reduced on the immobilized implants by 53 and 67% (p < 0.05), respectively, and were further significantly reduced on the continuously loaded implants by 83 and 87%, respectively, compared with the control implants. The hydroxyapatite coating was significantly thinner on immobilized (15 microns) and continuously loaded (15 microns) implants as compared with control implants (23 microns), but no difference between the inserted implants was found. Areas not covered with hydroxyapatite had 29 and 24% bone coverage on the immobilized and continuously loaded implants (not significant). Resorption of hydroxyapatite coating did occur in vivo. Continuous loading of the implants accelerated resorption significantly compared with immobilization of the implants. It is suggested that completely resorbed hydroxyapatite was partly replaced by bone in direct contact with the metal implant surface.

Animals↗
PubMed1996

Method for assessment of vascular reactivity in bone: in vitro studies on resistance arteries isolated from porcine cancellous bone.

Knowledge about vascular regulation in bone is central to the understanding of both normal and pathological bone physiology. This article describes a new method for direct assessment of the reactivity of bone blood vessels. Resistance arteries (diameter approximately 250 microns) were isolated from epiphyseal cancellous bone (porcine femoral condyle). Arterial segments (2 mm long) were mounted as ring preparations on a myograph, and isometric force development was measured continuously. Fifty-nine vessels from 31 pigs were investigated. The active force development was maximal at 0.9 x L100 in nine of 12 investigated arteries (L100 corresponds to the circumference the vessel would have if relaxed and exposed to a luminal pressure of 100 mm Hg [13.3 kPa]). In all subsequent experiments, the vessels were stretched to 0.9 x L100. Noradrenaline (2 x 10(-8) to 10(-5) M) induced a concentration-dependent vasoconstriction; mean maximal tension development was 3.69 N/m. This force development would enable the arteries to contract against a pressure of more than 22 kPa (165 mm Hg), indicating preserved function of the media smooth muscle. Response to acetylcholine (10(-7) to 10(-5) M) was observed in only two of 12 arteries. Bradykinin (10(-11) to 10(-6) M) induced a concentration-dependent and reproducible relaxation in all vessels; the relaxation was endothelium-dependent, since no effect of bradykinin was detected after mechanical removal of the endothelium. Sodium nitroprusside (10(-4) M) induced a reproducible and endothelium-independent vasorelaxation. The results demonstrate preserved function of both smooth muscle and endothelium in this preparation. The model allows pharmacological investigations of bone arteries under well defined conditions and enables studies on focal bone lesions and human bone tissue.

Animals↗
PubMed1996

Radiological and functional outcome after anterior lumbar interbody spinal fusion.

Outcome after anterior spinal fusion has mainly been studied radiologically and reported fusion rates vary greatly. The aim of this study was to investigate radiological and long-term clinical outcome. The study comprised 120 consecutive patients, operated on during the period 1979-1987, with single-or two-level anterior interbody spinal fusion due to disc degeneration or isthmic spondylolisthesis with lumbar instability. In 64 patients a supplemental facet joint fusion was performed. Clinical outcome was evaluated 5-13 years after surgery using the patient-administered Dallas Pain Questionnaire (DPQ). Radiological outcome was determined on the basis of radiographs taken at a 2-year follow-up assessed by independent observers. The radiological follow-up rate was 98%. Complete fusion was found in 52%, questionable fusion in 24%, and definitive pseudoarthrosis in 24% of patients. Radiological results were poor in patients who had undergone previous spinal surgery (P < 0.05) and in those with two-level fusion (P < 0.05). The DPQ reply rate was 80%. Sixty-six patients claimed improvement in all functional groups. Patients with complete or questionable union had significantly better results than did those with non-union (P < 0.01). Poorer functional outcome was found in patients who had undergone previous spinal surgery (P < 0.01) or fusion at the L4/L5 level (P < 0.05), in those who had responded poorly to the preoperative test brace (P < 0.05), and in those above 45 years old at the time of surgery (P < 0.05). Radiological and functional outcome did not vary according to whether patients were treated postoperatively with a plaster jacket or with facet screw fixation. The study demonstrated a functional success rate of approximately 66% following anterior lumbar spinal fusion after a mean follow-up of 8 years. There was a clear tendency for poorer prognosis for patients who had undergone previous spinal surgery, those aged above 45 years, those operated at the L4/L5 level and those who had responded poorly to the preoperative test brace. DPQ scores correlated well with radiological outcome.

Adolescent↗
PubMed1995

Two-level spinal stenosis in minipigs. Hemodynamic effects of exercise.

STUDY DESIGN: Twenty-two Göttingen minipigs were trained to run on a treadmill. Two-level lumbar spinal stenosis was created in 12 pigs, 10 were unoperated control subjects. Blood flow of the spinal cord and nerve roots was determined with microspheres at rest, during exercise, and after exercise. OBJECTIVES: To study the effect of lumbar spinal stenosis and exercise on blood flow of spinal neural tissue. SUMMARY OF BACKGROUND DATA: Neurogenic claudication, the key symptom of lumbar spinal stenosis, may be caused by vascular impairment or mechanical distress of neural tissue during exercise. Experimental compression of the cauda equina causes reversible nerve root edema, stasis, blood flow decrease, and compromised neural function. The vascular pathophysiology of spinal stenosis during exercise has not been studied previously. METHODS: Pigs were trained daily for 3 months. Two-level 25% lumbar spinal stenosis was introduced by placement of stenosing bands around the dural sac. Neurologic function was monitored before surgery by evoked potentials and after surgery by the Tarlov score. Regional blood flow in lumbosacral neural tissue was measured 3 days after chronic catheterization using microspheres at rest, during exercise at 3 km/h for 15 minutes, and at rest 30 minutes after exercise. RESULTS: Blood flow of grey and white matter increased during exercise in both groups, with no differences between groups. slight hyperemia prevailed after exercise in white matter of the stenotic area but not in grey matter. Nerve root blood flow was largely unchanged in control subjects during exercise but was reduced in spinal stenosis at rest, further depressed during exercise, and normalized after exercise. Dural blood flow was elevated throughout. CONCLUSION: The study suggests that exercise-induced impairment of spinal nerve root blood flow plays a role in the pathophysiology of neurogenic claudication.

Animals↗
PubMed1994

Regional blood flow, plasma volume, and vascular permeability in the spinal cord, the dural sac, and lumbar nerve roots.

OBJECTIVES: This study quantified the regional blood flow (RBF), plasma volume (PV), and the vascular permeability (VP) in the spinal cord, spinal nerve roots, and the dural sac. SUMMARY OF BACKGROUND DATA: Spinal cord hemodynamics have been investigated. However, the full segmental distribution of blood flow to the spinal cord and nerve roots has not been worked out. Vascular permeability of the spinal cord and nerve roots has been investigated but results regarding the spinal nerve roots have not been consistent. METHODS: Eight Labrador dogs were used. Regional blood flow was measured with microspheres. Plasma volume and vascular permeability were assessed by the distribution spaces of radioactively labeled plasma proteins. RESULTS: Regional blood flow was highest in the cervical and lumbar cord. Average (SEM) RBF values of the cord and spinal nerve roots were 10.4 +/- 1.0 and 4.4 +/- 0.5 mL/min 100 g, respectively. Plasma volume of the spinal cord was 0.85 +/- 0.06 mL/100 g and 1.29 +/- 0.17 mL/100 g in the spinal nerve roots. Vessels in the spinal nerve roots had significantly greater permeability to albumin than those of the spinal cord (P < 0.001). CONCLUSIONS: The quantitative flow measurements showed the existence of three main anatomic territories in the cord. The vascular permeability of vessel in the spinal nerve roots appears greater than that of the spinal cord, indicating that spinal nerve roots are located outside the blood brain barrier. Diffusion might be one of the nutritional pathways to spinal nerve roots.

Animals↗
PubMed1994

[Anterior lumbar intercorporal spondylodesis. Radiological and functional therapeutic results].

The purpose of this investigation was to identify risk factors in relation to non-union following lumbar intercorporal spondylodesis and to correlate this result with the functional outcome as assessed by the Dallas Pain Questionnaire (DPQ). This comprises questions concerning daily activities, work-leisure activities, anxiety-depression and social interest, measured on visual analog scales. During the period 1979-87 a total of 132 patients were operated with spondylodesis, diagnosed as suffering from spondylolisthesis or disc degeneration. Minimal follow-up was one year. Radiological graft incorporation was complete in 52% of the cases, partial in 24% and lacking in 24%. The rate of functional outcome follow-up was 72%. Seventy percent claimed an improvement in three out of four categories. Thirty percent claimed no improvement or worsened condition. The DPQ showed signs of poor prognosis for age groups above 45 (p < 0.04) and those with former spine surgery (p < 0.02). The questionnaire showed significantly better results for the group with perfect or doubtful union compared to the group with non-union (p < 0.006). In conclusion this investigation demonstrates a success rate of 70% for anterior lumbar interbody fusion. There is a tendency to poorer prognosis for patients with previous spine surgery and age above 45 years. The Dallas Pain Questionnaire correlates significantly to X-ray analysis and seems to be a useful tool for the description of individual biopsychosocial changes following spine surgery.

Activities of Daily Living↗
PubMed1994

[Obsessive-compulsive disorders].

Obsessive-compulsive disorder (OCD) is a psychiatric illness, until recently considered a rare, mainly neurotic condition with poor prognosis. However, epidemiologic studies have shown that the condition has a 25-50 times higher frequency than previously assumed. A review of occurrence, phenomenology and comorbidity is given. Newer theories of etiology are discussed, underpinning neurobiological aspects of the illness. In its most severe forms OCD is a condition with a socially crippling course, but with the introduction of anti-depressants acting on serotonin reuptake the therapeutic possibilities have increased, especially when these drugs are given in combination with behaviour therapy.

Adult↗
PubMed1994

Differential release of endothelin in myocutaneous island flaps in response to gradually insetting venous stasis or arterial ischemia.

Endothelin (ET) provokes strong and sustained contraction in preparations of isolated vascular smooth muscle, and the production of ET is thought to increase secondary to increased wall shear stress and hypoxia. The release of ET and blood flow distribution between arteriovenous shunts and capillaries were studied in autoperfused myocutaneous pig island flaps during graded arterial or venous blood flow reduction (N = 12). A group comprising four flaps was not exposed to blood flow reduction and served as controls. Total flap blood flow (venous outflow [VO]) was reduced in 1-hour periods to 50%, 25%, and 0%. Downregulation of VO caused a lower capillary blood flow (CBF) at 25% (P < .05) and at 50% (P < .05) in flaps exposed to venous stasis as compared with flaps with arterial ischemia. The reduction in blood flow was paralleled by decreasing oxygen consumption, although flaps with venous stasis had lower oxygen consumption than flaps exposed to arterial ischemia (P < .05). ET was found to be released from these island flaps before blood flow was reduced. Gradual arterial clamping caused a statistically significant (P < .05) decrease in the release of ET from 8.7 +/- 1.3 fmol/min before ischemia to 4.1 +/- 1.7 at 50% blood flow and 4.1 +/- 1.0 at 25% blood flow. In contrast, the release of ET with venous stasis remained unchanged at a level of 7.5 +/- 1.6 fmol/min before blood flow reduction, 7.3 +/- 0.7 at 50% blood flow, and 8.5 +/- 1.6 at 25% blood flow. These data suggest a relationship between CBF, intravascular pressure, and ET production.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Vasoconstrictive action of neuropeptide Y in bone. The porcine tibia perfused in vivo.

The hemodynamic effects of neuropeptide Y (NPY) and norepinephrine (NE) in bone were studied by infusion into the nutrient artery of an in vivo and in situ perfused tibia in 19 pigs. NPY and NE caused elevation of the perfusion pressure and decline in intraosseous pressure, which was evidence of intraosseous vasoconstriction. The study suggests that NPY, along with NE, acts as a sympathetic neurotransmitter in the control of vascular tone in bone.

Animals↗
PubMed1993

[Localized nodular myositis--a variation of polymyositis].

A case of focal nodular myositis is reported. The patient was a 37-year old male with no prior medical history. He had three episodes of focal nodular myositis over a three month period, recovering completely after each attack. During the last attack there were three lesions in the left quadriceps and one in the biceps muscle of the left arm. Histologically there was severe myositis. After the last attack he has been well for 12 months without sequelae.

Adult↗
PubMed1993

A follow-up study on the mortality of truck drivers.

The aim of this study was to investigate a possible relationship between occupational exposure to vehicle exhaust and cancer risk. For this purpose, a cohort of 14,225 truck drivers was followed throughout a ten-year period with regard to cause-specific mortality. Comparisons were made with another cohort of unskilled male laborers. Both of the occupational groups compared were identified at a census and no supplementary data on individual exposure history were available. The study showed an increased mortality for lung cancer (standardized mortality ratio (SMR) 160, 95% confidence interval (CI) 126-200) and multiple myeloma (SMR 439, 95% CI 142-1,024). It seems likely that exposure to diesel exhaust has contributed to the increased lung cancer risk observed. The possible relationship between multiple myeloma and certain constituents of vehicle exhaust may be worth attention in future investigations.

Adolescent↗
PubMed1993

Hydroxyapatite coating converts fibrous tissue to bone around loaded implants.

In previous studies, we have demonstrated a fibrocartilaginous membrane around hydroxyapatite-coated implants subjected to micromovement in contrast to the fibrous connective tissue which predominates around similarly loaded titanium alloy implants. In the present study, in mature dogs, we investigated the effect of immobilising titanium (Ti)- or hydroxyapatite (HA)-coated implants already surrounded by a movement-induced fibrous membrane and compared the results with those of similar implants in which continuous micromovement was allowed to continue. The implants were inserted in the medial femoral condyles of 14 dogs and subjected to 150 microns movements during each gait cycle. After four weeks (when a fibrous membrane had developed), half the implants were immobilised to prevent further micromovement. The dogs were killed at 16 weeks and the results were evaluated by push-out tests and histological analysis. The continuously loaded Ti-coated implants were surrounded by a fibrous membrane, whereas bridges of new bone anchored the HA-coated implants. The immobilised implants were surrounded by bone irrespective of the type of coating. Push-out tests of the continuously loaded implants showed better fixation of those with HA coating (p < 0.001). The immobilised Ti-coated implants had four times stronger fixation than did continuously loaded Ti-coated implants (p < 0.01) but there was no equivalent difference between the two groups of HA-coated implants. The amount of bone ingrowth was greater into immobilised HA-coated implants than into immobilised Ti-coated implants (p < 0.01). Two-thirds of the HA coating had been resorbed after 16 weeks of implantation, but 25% of this resorbed HA had been replaced by bone.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Migration of hydroxyapatite coated femoral prostheses. A Roentgen Stereophotogrammetric study.

We allocated randomly 27 patients undergoing 28 primary uncemented total hip replacements (THR) to receive prosthetic components of similar design with either plasma-sprayed titanium alloy (Ti) coating (n = 13) or hydroxyapatite (HA) coating (n = 15). After some exclusions, 15 of the patients (15 THR; 7 with HA- and 8 with Ti-coating) were followed by roentgen stereophotogrammetric analysis at 3, 6 and 12 months to measure migration of the femoral component. Twenty-six of the patients (26 THR) were followed clinically and by conventional radiography. All the femoral components had migrated at 3 months. From 3 to 12 months, the migration of Ti-coated components continued whereas the HA-coated components had stabilised. At 12 months there was significantly less migration of the HA-coated components (p < 0.05). The maximum subsidence was 0.2 mm in both groups. The Harris hip score was equal in the two groups preoperatively but at follow-up it was better in the HA-coated group (p < 0.05) and visual analogue scale scores showed that they had less pain (p < 0.05).

Aged↗
PubMed1992

A cohort study on cancer incidence among Danish gardeners.

This study was performed to examine the cancer risk of Danish gardeners having been highly exposed to pesticides. We have followed a cohort of 4,015 employed gardeners (859 females and 3,156 males) from May 1975 until the end of 1984 with regard to cancer incidence. The observed incidence was compared with expected numbers calculated from national incidence rates. For all cancer sites combined, the standardized morbidity ratio (SMbR) was 104. Among male gardeners a significantly increased incidence was seen for soft tissue sarcoma (SMbR = 526, 95% confidence interval (CI): 109-1,538), an chronic lymphatic leukemia (SMbR = 275, 95% CI: 101-599). The incidence of non-Hodgkin's lymphoma was twice that which was expected (SMbR = 200, 95% CI: 86-393). We suggest that some of the pesticides to which the gardeners have been exposed are capable of initiating or promoting the development of malignant neoplasms in tissues of mesenchymal origin.

Adolescent↗
PubMed1992

Tissue ingrowth into titanium and hydroxyapatite-coated implants during stable and unstable mechanical conditions.

Lack of initial mechanical stability of cementless prostheses may be responsible for fibrous tissue fixation of prosthetic components to bone. To study the influence of micromovements on bony ingrowth into titanium alloy (Ti) and hydroxyapatite (HA)-coated implants, a loaded unstable device producing movements of 500 microns during each gait cycle was developed. Mechanically stable implants served as controls. The implants were inserted into the weight-bearing regions of all four femoral condyles in each of seven mature dogs. Histological analysis after 4 weeks of implantation showed a fibrous tissue membrane surrounding both Ti and HA-coated implants subjected to micromovements, whereas variable amounts of bony ingrowth were obtained in mechanically stable implants. The pushout test showed that the shear strength of unstable Ti and HA implants was significantly reduced as compared with the corresponding mechanically stable implants (p less than 0.01). However, shear strength values of unstable HA-coated implants were significantly greater than those of unstable Ti implants (p less than 0.01) and comparable to those of stable Ti implants. The greatest shear strength was obtained with stable HA-coated implants, which was threefold stronger as compared with the stable Ti implants (p less than 0.001). Quantitative determination of bony ingrowth agreed with the mechanical test except for the stronger anchorage of unstable HA implants as compared with unstable Ti implants, where no difference in bony ingrowth was found. Unstable HA-coated implants were surrounded by a fibrous membrane containing islands of fibrocartilage with higher collagen concentration, whereas fibrous connective tissue with lower collagen concentration was predominant around unstable Ti implants. In conclusion, micromovements between bone and implant inhibited bony ingrowth and led to the development of a fibrous membrane. The presence of fibrocartilage and a higher collagen concentration in the fibrous membrane may be responsible for the increased shear strength of unstable HA implants. Mechanically stable implants with HA coating had the strongest anchorage and the greatest amount of bony ingrowth.

Analysis of Variance↗