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Biomedical subjects

Michael Rieger

Publications and source records attributed to Michael Rieger.

24 records · Page 2Linked to original sources
PubMed2003

A computer assisted surgical technique for retrograde autologous osteochondral grafting in talar osteochondritis dissecans (OCD): a cadaveric study.

This study describes a new method for the treatment of osteochondritis dissecans (OCD) in the medial talar dome. Ten cadaveric lower extremities were used to develop and evaluate a retrograde osteochondral grafting technique applying computer-assisted surgery. With the help of a computed tomography (CT)-based navigation system, a guide wire was placed from the lateral talar process into the posteromedial talar trochlea where OCD lesions are predominantly located. Cannulated reamers and arthroscopic shavers were used for the preparation of the recipient hole. The grafts, with diameters of 4.5 mm, 6.5 mm or 8.5 mm were harvested from the lateral femoral trochlea and inserted in a retrograde fashion. The last five cadavers were analyzed for accuracy of surface reconstruction and graft stability. For this purpose a medial malleolar osteotomy and a CT scan was performed. We found steps in the joint surface to range from 0.5 mm to 1.5 mm (mean 0.9 mm, SD 0.4) with the graft always below the surrounding cartilage. Graft subsidence occurred at an applied force of 26.4 +/- 4.6 N. This study indicates that osteochondral cylinders can be inserted in a retrograde fashion to reconstruct the posteromedial talus. Good surface congruency and sufficient graft stability can be achieved.

Bone Transplantation↗
PubMed2003

Vascular ring causing tracheal compression in an adult patient.

A 65-year-old woman was referred for evaluation because of a few years' history of inspiratory obstruction without dysphagia. A right aortic arch with mirror image bracheocephalic vessels narrowing the trachea was considered to be the reason for the dyspnea. Immediate decompression of the trachea and symptomatic relief was achieved through surgical treatment.

Aged↗
PubMed2003

Localization, dynamics, and function of survivin revealed by expression of functional survivinDsRed fusion proteins in the living cell.

Survivin, a member of the inhibitor of apoptosis protein family, has attracted growing attention due to its expression in various tumors and its potential application in tumor therapy. However, its subcellular localization and function have remained controversial: Recent studies revealed that survivin is localized at the mitotic spindle, binds caspases, and could thus protect cells from apoptosis. The cell cycle-dependent expression of survivin and its antiapoptotic function led to the hypothesis that survivin connects the cell cycle with apoptosis, thus providing a death switch for the termination of defective mitosis. In other studies, survivin was detected at kinetochores, cleavage furrow, and midbody, localizations being characteristic for chromosomal passenger proteins. These proteins are involved in cytokinesis as inferred from the observation that RNA interference and expression of mutant proteins led to cytokinesis defects without an increase in apoptosis. To remedy these discrepancies, we analyzed the localizations of a survivinDsRed fusion protein in HeLa cells by using confocal laser scanning microscopy and time-lapse video imaging. SurvivinDsRed was excluded from the interphase nucleus and was detected in centrosomes and at kinetochores. It dissociated from chromosomes at the anaphase/telophase transition and accumulated at the ends of polar microtubuli where it was immediately condensed to the midbody. Overexpression of both survivinDsRed and of a phosphorylation-defective mutant conferred resistance against apoptosis-inducing reagents, but only the overexpressed mutant protein caused an aberrant cytokinesis. These data characterize in detail the dynamics of survivin in vertebrate cells and confirm that survivin represents a chromosomal passenger protein.

Apoptosis↗
PubMed2003

Volume-rendered multidetector CT angiography: noninvasive follow-up of patients treated with renal artery stents.

OBJECTIVE: The purpose of our study was to evaluate the role of multidetector CT (MDCT) angiography with volume rendering for estimating the patency of renal artery stents. SUBJECTS AND METHODS: In 16 patients, 16 renal artery stents were evaluated with MDCT renal angiography and digital subtraction angiography (DSA). CT data were evaluated using multiplanar volume reformations and the volume-rendering algorithm with three different volume-rendered parameter settings (low-to-high, high-to-low, and high-low-high opacity transfer functions: VR(LH), VR(HL), and VR(VE), respectively). Targeted images of each stent were rendered in paraaxial and paracoronal planes and were interactively interpreted. The overall restenosis severity was measured on postprocessed paraaxial and paracoronal images and compared with that obtained on DSA using linear regression analysis. Image quality and lumen delineation on rendered images were also compared using Wilcoxon's signed rank test. RESULTS: Eight restenoses were identified on DSA. Correlations between restenosis severity measured with DSA and those measured with MDCT were significant (p < 0.001). Volume rendering with VR(HL) allowed the best correlation with DSA (reviewer 1, r(2) = 0.86; reviewer 2, r(2) = 0.94) and was significantly better than multiplanar volume reformations (p = 0.028). Overall image quality was high with all rendering techniques and with no significant differences (p > 0.59, for all comparisons). Stent lumen was well delineated with volume-rendering modalities; however, VR(HL) was significantly better than VR(LH) (p = 0.033). CONCLUSION: Volume-rendered MDCT angiography enabled high-quality three-dimensional reproducible evaluation of the patency of implanted renal artery stents. Volume rendering with VR(HL) achieved the best performance.

Aged↗
PubMed2002

Placement of endovascular stent-grafts for emergency treatment of acute disease of the descending thoracic aorta.

OBJECTIVE: The aim of this study was to evaluate the feasibility, safety, and effectiveness of endovascular stent-graft placement for the emergency treatment of acute descending thoracic aortic disease. MATERIALS AND METHODS: From January 1996 through November 2001, 18 patients underwent emergency endovascular stent-graft placement for various types of acute descending thoracic aortic disease. Five patients had Stanford type B aortic dissection, six had traumatic ruptures of the thoracic aorta, five had ruptured aortic aneurysms, and two had penetrating atherosclerotic aortic ulcers. All patients presented with life-threatening symptoms requiring treatment with stent-grafts from the emergency kit. All were at high surgical risk due to serious comorbidities. The efficacy of the procedure was assessed at follow-up studies before discharge and at 3, 6, and 12 months after intervention and yearly thereafter. RESULTS: The primary technical success rate was 78%. Four patients had primary perigraft leaks. The secondary technical success rate was 83%. One patient died 20 hr after intervention from stent-graft-related causes. Follow-up studies revealed stent-graft migration in one patient. Progression of disease was observed in one patient treated for dissection and in both patients treated for penetrating ulcers. One patient died 7 months after intervention of unknown reasons; all other patients are alive. The mean follow-up time was 17.4 months (range, 0-38 months). CONCLUSION: Emergency repair of acute descending thoracic aortic disease with stent-graft placement can be successfully accomplished and may be a promising alternative to open-chest surgery, especially in patients at high risk.

Acute Disease↗