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Biomedical subjects

R Andresen

Publications and source records attributed to R Andresen.

At least 19 recordsLinked to original sources
PubMed2006

[Current treatment of hamate hook fractures].

PURPOSE: Hamate hook fractures can be treated conservatively or surgically, whereby fragment and fracture position, age of the fracture, associated injuries, and individual needs of the patient all influence the choice of the therapeutic procedure. Acute non-displaced fractures are frequently treated conservatively, while displaced fractures and nonunions undergo surgical treatment. We report our experience in diagnostic and therapeutic management of 14 hamate hook fractures. CLINICAL MATERIAL AND METHOD: During a three-year period, 14 patients (eleven men and three women) 21 to 73 years old (42.0 +/- 17.9 years) with fractures at the base of the hamate hook were treated at three hand surgery units. The retrospective study of all patients included a chart review, postoperative radiological imaging after one year, and clinical examinations with grip strength measurements after 18 to 34 months (27.8 +/- 4.9 months). In six patients (43 %), the acute fracture was immobilized in a lower arm cast for six weeks, while eight patients (57 %) were operated primarily. In five cases (36 %) excision of the fragment and in three cases (21 %) open reduction and internal fixation using a screw were performed. Of six patients treated conservatively, five developed nonunion after two to five months (3.0 +/- 1.2 months) with persistent pain and underwent secondary surgery. One patient was asymptomatic despite a nonunion and declined surgical treatment. In three cases the fragment was excised, while two patients underwent open reduction and internal fixation with a screw. RESULTS: All patients operated primarily were free of complaints three months after surgery. The success rate of surgical treatment (8/8) was therefore significantly higher than that after conservative treatment (1/6). CONCLUSION: Compared to conservative treatment of acute non-displaced hamate hook fractures, which is associated with a high risk of developing symptomatic nonunion, primary surgical treatment reliably yields a good clinical outcome. Here, results after fragment excision and open reduction and internal fixation are comparable.

Adult↗
PubMed2003

[Outpatient primary stent-angioplasty in symptomatic internal carotid artery stenoses].

In 81 patients, average age 69.3 (57-79) years with symptomatic ICA stenosis stent implantation was performed under outpatient conditions. An interdisciplinary consensus ascertained that the patients were suitable for outpatient therapy. In accordance with the NASCET criteria all patients belonged to the high-risk group. Within 120 days before the intervention, the following clinical events had occurred: 32 minor strokes, 43 TIA, 20 amaurosis fugax. 61/81 patients revealed a bulbar, 20/81 a postbulbar ICA stenosis, the average degree of stenosis was 88.6 % (75-97). Stent application, using 3 different stent models, and subsequent PTA were always performed under protection. The transfemoral route was always treated with an endovascular closure system. All patients were given follow-up examinations by means of colour duplex sonography (CDS) of the neck vessels on days 1, 30, 180 and 360, and contrast-medium intensified MRT on day 5 post-intervention. The technical success rate with regard to stenting and PTA was 100 %. One case of hypotonic dysregulation occurred during the intervention. Atheromatous particles and plaque fragments were found in the protection system in 3/81 (3.7%) of the patients. A plaque embolism was excluded clinically and in the contrast-medium intensified MRT 5 days after the intervention in 79/81 (97.5%) of the patients, while two patients were found to sustain an asymptomatic cortical barrier impairment. After 180 days, no restenosis or stent dislocation were found in the CDS, all ECAs were perfused. After 360 days, one asymptomatic occlusion and four restenoses > 70% were found (5/81 = 6.2% restenosis rate after 1 year), which were successfully treated by angioplasty. The method presented bears a low complication rate and shows a high success rate. If patient recruitment is adequate, this intervention can safely be performed on an outpatient basis.

Aged↗
PubMed2002

[Characteristic mechanical properties of balloon-expandable peripheral stent systems].

PURPOSE: To measure in vitro geometric-mechanical characteristics of balloon-expandable peripheral stent systems for determining suitability for specific vascular regions. MATERIALS AND METHODS: Balloon-expandable stents including their delivery systems manufactured by Guidant (OTW Megalink trade mark ), Inflow Dynamics (Antares), Medtronic (AVE Bridge trade mark ), Biotronik (Peiron trade mark ) and Cordis (Corinthian IQ trade mark ) were selected for this study. When expanded, all stents had a nominal diameter of 8 mm. The length was 38 - 40 mm. Stent profile, trackability, length change on expansion, stiffness, elastic recoil, and radio-opacity in the crimped and expanded state of these stent systems were determined with specially developed test methods. RESULTS: The Corinthian IQ trade mark, Megalink trade mark and Peiron trade mark required the smallest force to pass through the vascular model. While the Bridge trade mark system had the largest profile with a diameter of 2.430 mm, all other stent systems had a significantly smaller diameter ranging from 1.970 mm for the Peiron trade mark to 2.078 mm for the Corinthian IQ trade mark. In the distal region of the stent delivery system, the Megalink trade mark was the most flexible and the Bridge trade mark system the stiffest. Elastic recoil for all stents was in the range of 2.5 % to 3.5 %, with the exception of the Bridge trade mark stent, which had an elastic recoil of 4.79 %. The Corinthian IQ trade mark stent had noticeably the highest radial stiffness. In the expanded condition, the Peiron trade mark was the most flexible while the Corinthian IQ trade mark and the Antares trade mark were found to be the stiffest. Length change (shrinkage on expansion) ranged from 0.54 to 6.57%, with the exception of the Corinthian IQ, which shrunk > 7mm (18.5%) on expansion. All stent systems in the crimped and expanded state were readily visible radiographically. CONCLUSION: Specific data of significant parameters are available to aid in the selection of balloon expandable stents systems to be deployed in complex vascular regions. All examined stent systems showed adequate mechanical properties, but clinically relevant differences were found in stent trackability, bending stiffness and shrinkage on expansion.

Angioplasty, Balloon↗
PubMed2001

[Segmental variants of the inferior vena cava--manifestations with embryological correlation in differentiation from secondary vena cava occlusion].

The vast variability of the overall rare congenital anomalies of the inferior vena cava (IVC) are mostly detected by accident through different imaging modalities. These cannot be classed as pathological findings, and should not be confused with lymphomas and has to differ from secondary collateral venous pathways. Based on 656 CT examinations 10.5% known forms of IVC anomalies were found. According to the embryological development three main groups of IVC variants could be nosologically classified: agenesis of the suprarenal IVC, anomalies of the pars renalis and anomalies of the infrarenal IVC. Additionally three unusual anomaly complexes were found. For the understanding details of the embryology based on a simplified depiction are presented.

Adolescent↗
PubMed2001

[Imaging and therapy of hamulus-ossis-hamati fracture].

The relatively rare fractures of the hamate bone are the most common osseous injuries of the distal carpal row, whereby fractures of both the body and the hook of the hamate occur. We present a hamulus ossis hamate fracture that was caused by direct trauma in a high-level game of underwater rugby. Although this was diagnosed by conventional x-ray, the precise position of the fracture was clearly imaged using thin-layer CT, while additional multiplanar MRT revealed further sequelae of the trauma. A CT follow-up after 10 weeks of conservative therapy did not show any osseous consolidation, which indicated the need for surgical revision with extirpation of the hamulus.

Adult↗
PubMed2000

Interrater reliability of the Camberwell Assessment of Need Short Appraisal Schedule.

OBJECTIVE: Australian mental health policy aims to introduce evidence-based practice within a community care approach. This aim requires reliable measures that can be used by a wide variety of professionals. The interrater reliability of the Camberwell Assessment of Need Short Appraisal Schedule (CANSAS) was assessed under routine conditions. METHOD: Three interviewer-observer dyads assessed the needs of 14 inpatients and 18 day patients of a psychiatric rehabilitation unit in New South Wales, Australia. RESULTS: Agreement on the identification of an area of need was high. However, agreement was higher on patient ratings than on staff ratings. Correlations on staff ratings of met needs were also moderate (r = 0.53), suggesting discrepancies in rating the level of need. CONCLUSION: Differences in staff ratings may be attributed to ambiguity in the definition of need and levels of need and/or the sources of information used by the rater making the assessment. An approach to establishing an operational definition of need is suggested, and an increase in the number of levels of need is recommended. Implications for Australian mental health policy are noted.

Adult↗
PubMed2000

Clinical results of TRAM flap delay by selective embolization of the deep inferior epigastric arteries.

Preoperative selective embolization of the deep inferior epigastric arteries constitutes a new technique in TRAM flap delay. Whereas surgical ligation of these vessels has proved to be an effective delay procedure in experimental and clinical settings, it requires an additional operative step under general anesthesia. Despite the introduction of the free TRAM leading to improved flap perfusion, this microsurgical technique is not always available because of the requirements of specialized equipment and staff, longer operating hours, and subsequently higher expenses. The search for a minimally invasive, easy, and inexpensive technique to improve perfusion of the pedicled TRAM flap led us to selective embolization of the deep inferior epigastric arteries by an angiographic procedure. After 4 years of experience with this technique, we now present the first clinical results. Breast reconstruction by a delayed pedicled TRAM flap was performed in 40 patients with a mean age of 48.4 years (range, 31 to 66 years). The mean interval between embolization and surgery was 3.6 months. Postoperative data concerning flap survival and complications were available for all patients. Embolization of the deep inferior epigastric arteries was performed bilaterally in 35 patients (87.5 percent) and unilaterally in 5 patients (12.5 percent). Radiotherapy had been applied in 21 patients (52.5 percent) before surgery. Postoperative flap complications consisted of partial necrosis in three (7.5 percent), fat necrosis in one (2.5 percent), impaired wound healing in five (12.5 percent), and postoperative bleeding in two patients (5 percent). Abdominal wound healing complications occurred in six patients (15 percent), abdominal wall weakness in eight (20 percent), and hernia formation in four (10 percent). Surgical corrections were performed at the breast (TRAM flap) in 22 patients (55 percent) and at the abdomen (donor site) in 9 (22.5 percent). Preoperative selective embolization of the deep inferior epigastric arteries constitutes an alternative delay procedure for the pedicled TRAM flap. It is superior to the conventional procedure without delay, offers several advantages compared with surgical ligation of these vessels, and represents an alternative to the free TRAM flap in selected cases.

Adult↗
PubMed2000

Issues of threshold selection when determining the fractal dimension in HRCT slices of lumbar vertebrae.

The box counting dimension is a frequently applied tool for the classification of trabecular bone structure. The algorithm requires a binarization of the gray value data, for example that acquired by high resolution CT (HRCT). We recently proposed a method to eliminate bone mineral density (BMD) by applying a linear normalization scheme. Further consideration has shown that full BMD independence has not been achieved, and the structural parameter proposed was therefore difficult to interpret. In this study we present an alternative approach to obtain a structural parameter that is independent of BMD. HRCT volume data was acquired on 21 lumbar vertebrae from five cadavers. In the segmented spongiosa, thresholding was based on different quantiles of the gray value histogram, yielding invariance over linear and non-linear transformations. Thresholding at high gray value levels (80% quantile) shows the highest level of significance when discriminating between osteoporotic and non-osteoporotic cases. As an addition to the measurement of BMD alone, the determination of structural properties allows an improvement of the assessment of the individual fracture risk.

Algorithms↗
PubMed2000

[Catheter ablation of the inferior epigastric artery. An conservative method for conditioning the pedicled TRAM flap].

The pedicled transverse rectus abdominis musculocutaneous (TRAM) flap is a recognized, reliable method of autogenous tissue breast reconstruction after mastectomy. However, the blood supply to the distal part of the flap is often precarious after ligation of the the main feeder, the inferior epigastric artery (AEI), at time of the operation. We describe our clinical experience with a new technique to augment the superior blood stream (superior epigastric artery, AES) by selective embolization of the inferior epigastric artery some weeks prior to plastic surgery. One hundred and eleven embolization procedures were performed until now. Technique of crossover and ipsilateral epigastric spiral embolization is described, requiring minimal time and material as an in- or outpatient procedure. The anatomical situation of the m. rectus abdominis blood supply is discussed as well as possible complications of the procedure.

Anastomosis, Surgical↗
PubMed2000

[Clinical results and color-coded duplex ultrasound findings 4 years after conditioned TRAM flap-plasty].

Presented is a new technique in preoperative conditioning of the pedicled TRAM-flap employing an interventional-radiologic procedure, selective embolization of the deep inferior epigastric artery (DIEA). During a four year period in 40 patients with a mean age of 48.4 (31-66) years breast reconstruction was performed by a superiorly pedicled TRAM-flap following preoperative conditioning. 30 of 40 patients were eligible for follow-up one to five years postoperatively. The mean interval between embolization and surgery amounted to 3.6 months. In 25 of 30 cases embolization of the DIEA was performed bilaterally, in 5 of 30 cases unilaterally. 14 of 30 patients underwent preoperative radiotherapy for breast cancer. Applying CCDS the peak flow values were determined in the superior epigastric arteries (TRAM/contralateral side). Pre-embolization values (54.9 cm/s/55.8 cm/s), post-embolization values (57.2 cm/s/57.9 cm/s) and late postoperative values (61.0 cm/s/61.6 cm/s) proved a statistically significant effect of selective embolization on peak flow without relevant difference between TRAM and contralateral side (p < 0.05). Postoperative flap complications consisted of partial necrosis in 2 of 30, fat necrosis in 1 of 30, impaired would healing in 5 of 30 and postoperative bleeding in 2 of 30 cases. Abdominal would healing complications occurred in 5 of 30 cases, abdominal wall weakness was found in 8 of 30 and hernia formation in 4 of 30 cases. Corrective surgery was performed at the breast (TRAM-flap) in 22 of 30 and at the abdomen (donor site) in 9 of 30 cases. Patient acceptance concerning selective embolization and TRAM-flap surgery was very high. 29 of 30 patients confirmed that they would again choose this type of breast reconstruction. The pedicled TRAM-flap following preoperative conditioning by selective embolization of the DIEA constitutes a safe and reliable method of breast reconstruction with autogenous tissue. It is superior to the pedicled TRAM-flap without delay and offers definite advantages compared to alternative techniques of enhanced flap vascularization.

Adult↗
PubMed1999

Relationship between structural parameters, bone mineral density and fracture load in lumbar vertebrae, based on high-resolution computed tomography, quantitative computed tomography and compression tests.

Different noninvasive techniques for the assessment of the individual fracture risk in osteoporosis are introduced, and the relation between structural properties of high-resolution computed tomography (HR-CT) images of vertebral bodies, their bone mineral density (BMD) and the fracture load is analyzed. In 24 unfractured lumbar vertebrae with different degrees of demineralization from six specimens, the trabecular and cortical BMD was determined using quantitative CT. A lateral X-ray image revealed the number of fractures in the entire spine. A structural analysis of spongy and cortical bone was performed based on the HR-CT images. In the spongiosa, the fractal dimension was calculated as a function of the threshold value. In the cortical shell, the maximum number of clusters of low BMD was determined at varying threshold values. After the CT measurements the vertebrae were excised and compressed until fractured. On the basis of the spongiosa BMD and the number of fractures, 3 cases were found to be severely osteoporotic; the other 3 cases showed osteopenia. The average fracture loads were determined as 3533 N for the non-osteoporotic cases (range 2602-5802 N) and 1725 N for the osteoporotic cases (range 1311-2490 N). The parameters were determined as follows: average spongiosa BMD 115.2 mg/ml (101.8-135.3 mg/ml) for the non-osteoporotic cases, 46.2 mg/ml (34.8-57.6 mg/ml) for the osteoporotic cases; average cortical BMD 285.1 mg/ml (216.4-361.9 mg/ml) for the non-osteoporotic cases, 136. 1 mg/ml (142.5-215.2 mg/ml) for the osteoporotic cases; spongiosa structure: average 0.5 (range 0.32-0.75) for the non-osteoporotic cases, average 1.05 (range 0.87-1.24) for the osteoporotic cases; cortical structure: average 81 (range 55-104) for the non-osteoporotic cases), average 136 (range 102-159) for the osteoporotic cases. Single parameters (BMD and structure) and weighted sums of these parameters were correlated with the fracture load, resulting in correlation coefficients of r(sBMD) = 0.82 (spongiosa BMD), r(cBMD) = 0.82 (cortical BMD), r(sStr) = -0.75 (spongiosa structure) and r(cStr) = -0.86 (cortical structure). The weighted sum of cortical and spongiosa BMD resulted in r(BMD) = 0.86, of cortical and spongiosa structure in r(Str) = -0.86. A weighted combination of all four parameters correlates with the fracture load at r(4) = 0.89, all correlations being statistically significant (p<0.0001). The four individual parameters show only a slight overlap between non-osteoporotic and osteoporotic subjects. The high correlation of the cortical BMD and the structural parameter in cortical bone indicates the important contribution of the cortical shell to vertebral stability. A weighted sum of multiple parameters results in a higher correlation with the fracture load and does not show an overlap between the two groups. It is best suited to estimate the individual fracture risk. The presented methods are generally applicable in vivo; and allow an improvement of the diagnosis of osteoporosis compared with the measurement of the BMD alone.

Aged↗
PubMed1999

Wrist arthroplasty with a new generation of prostheses in patients with rheumatoid arthritis.

The function of the wrist is frequently considerably impaired by early destruction in patients with rheumatoid arthritis. The aim of endoprosthetic arthroplasty is to restore functional use and provide freedom from pain. In our study a newly developed, uncemented wrist prosthesis was implanted in 30 patients (24 women and 6 men) with advanced destruction of the wrist. This wrist prosthesis is a hydroxyapatite-coated cobalt-chrome prosthesis with a titanium coating of the articular surfaces. The radial component has an articular surface inclination of 10 degrees toward the ulna, and the carpal component, which is anchored with its tip in the distal carpal bones and third metacarpal bone, has a double articular surface with a radial inclination of 10 degrees. At the 18-month follow-up visit, the following parameters were examined: x-ray, grip strength, range of motion, and the patient's subjective satisfaction. Good improvement of function was found in 92% of the patients; 87% were free of pain. Eighty-eight percent of the patients rated the outcome of surgery as good. If the indication is accurately diagnosed, this wrist prosthesis can markedly improve function, which in turn leads to high patient acceptance. Various salvage procedures remain open because of the minimal loss of bone stock and the uncemented implantation of the prosthesis.

Adult↗
PubMed1999

Imaging of hamate bone fractures in conventional X-rays and high-resolution computed tomography. An in vitro study.

RATIONALE AND OBJECTIVES: To examine the ability to image fractures of the body and hook of the hamate bone in conventional X-rays and high-resolution computed tomography (HR-CT). MATERIALS AND METHODS: In an in vitro experiment using 18 cadaver hands, the hamate bone was fractured at different places. Before and after fracture, conventional X-rays were taken in different planes (anteroposterior, lateral, oblique, and carpal tunnel), and HR-CT was performed with 2-mm layer thickness in the axial, sagittal, and coronal plane. RESULTS: Taking into account all the conventional X-ray projections applied, the in vivo experiment revealed a sensitivity of 72.2%, a specificity of 88.8%, and an accuracy of 80.5%. For the HR-CT, the sensitivity was 100%, the specificity was 94.4%, and the accuracy was 97.2%. CONCLUSIONS: Fractures of the body and hook of the hamate cannot always be detected with certainty in the conventional X-ray image, even if different projectional planes are used. The HR-CT is the imaging procedure of choice for further clarification, and an axial or sagittal plane should be selected.

Adult↗
PubMed1999

Computerized analysis of gray-value profiles in spongy and cortical bone. Clinical experience.

RATIONALE AND OBJECTIVES: Osteoporosis is characterized by a loss of bone mineral density and deterioration of structure. The authors present a structural parameter for the quantitative assessment of osteoporotic changes in vertebral bone. METHODS: In 40 patients without or with known osteoporotic fractures, spongiosa and cortical bone mineral density was measured in lumbar vertebrae 1 to 3 by quantitative CT. Additional axial high-resolution CT slices were obtained for the structural analysis. In the spongiosa, the gray-value profile along a horizontal line in the CT slice was used, whereas in the cortical shell a profile was obtained from the cortical ridge. Both profiles were intersected with a horizontal line of variable position, and the maximum number of intersections was determined. RESULTS: The maximum number of intersections is significantly higher in cases with fractures (spongiosa 48.6, cortical shell 77.3) than in cases without fractures (spongiosa 42.1, cortical shell 62.4). It also correlates with bone mineral density and age. CONCLUSIONS: The presented method shows significantly different numeric results for patients with and without osteoporotic fractures. The analysis is easy to perform and provides additional information on the bone structure that may be used in combination with bone mineral density measurements.

Adult↗
PubMed1999

CT determination of bone mineral density and structural investigations on the axial skeleton for estimating the osteoporosis-related fracture risk by means of a risk score.

In addition to the pure measurement of bone mineral density (BMD) in osteodensitometry, the investigation of bone structure is becoming increasingly important for estimating fracture risk. In a clinical study, a risk score was proposed which separately assesses BMD and structural parameters for spongious and cortical bone and aggregates them into a single diagnostic parameter. In 120 lumbar vertebrae from 40 patients, BMD was determined separately for spongious and cortical bone by means of quantitative CT using a single energy procedure (SE-QCT/85 kV). In addition, structural parameters based on high resolution CT were calculated for the spongiosa and cortical bone. For all patients the number of osteoporosis-related fractures was determined on the entire skeletal system. According to WHO criteria, the patients were subdivided into four groups: 1, normal; 2, osteopenic; 3, osteoporotic without fractures; 4, severely osteoporotic. Weighting factors were determined by means of multivariate least-squares analysis and used to calculate a risk score of all parameters. The ability of the individual parameters and of the sum of discriminate between the individual groups was tested. If one considers the individual parameters (BMD and the fractal structural values for spongious and cortical bone), they allow a statistically significant separation of the four groups, although there is overlapping in the value ranges. In patients with fractures, there was a significant reduction in the cortical mineral density, accompanied by a deterioration in structural properties. The following individual values were obtained (minimum-mean-maximum): spongiosa BMD (mg ml-1), unfractured: 62-112-163, fractured: 9-48-77; cortical BMD (mg ml-1), unfractured: 190-287-405, fractured: 133-191-269; spongiosa structural parameter, unfractured: 0.35-0.73-1.01, fractured: 0.95-1.24-1.58; cortical structural parameter, unfractured: 18-31-65, fractured: 21-44-66. Above 77 mg ml-1 CaHA in the spongiosa and 270 mg ml-1 CaHA in cortical bone, no fractures were observed. By appropriately selecting the weighting factors, the score is free of overlapping between the groups with and without fractures (values: unfractured 1-9-15, fractured 16-21-29). With higher score values, the fracture risk is increasing.

Adult↗
PubMed1998

Projecting the sulcal pattern of human brains onto a 2D plane--a new approach using potential theory and MRI.

A new method is introduced to project the sulcal pattern of the brain surface onto a 2D plane. Twin brains are compared against each other using the planar representation. We obtained T1-weighted Flash-3D MRI volumes from 14 male twins (seven monozygotic, seven dizygotic) with 3 mm-thick coronal slices. The projection is based on potential theory: A virtual electrostatic field is calculated between the area of the segmented brain and a surrounding spherical electrode. Field lines starting from each border point of the segmented brain follow the gradient towards the sphere, leading to field line concentrations due to the underlying sulci. The unwrapped sphere surface with the number of field lines per area unit is used as the 2D representation of the sulcal pattern. The resulting brain projections show a distinctive pattern, and a visual assignment of the twin pairs from the unsorted set is possible because of a high similarity of the patterns between twin pairs. Global correlation coefficients for each pair of maps yield significantly higher values for matching monozygotic twin pairs (mean = 20.2, range 12.3-25.6) than for unmatched pairs (mean = 13.0, range 1.1-28.5). As a conclusion, our method allows us to map the location and depth of the sulci on a 2D plane. The resulting maps allow quantitative inter-individual comparisons on the entire brain or parts of the brain surface.

Adult↗