Search PubMed⌕ Search

Biomedical subjects

M Rudert

Publications and source records attributed to M Rudert.

At least 19 recordsLinked to original sources
PubMed2007

[Radiologic evaluation of cup placement variation in conventional total hip arthroplasty].

PURPOSE: Determination of the amount of variation in conventional acetabular cup positioning (radiological inclination and anteversion) in view of different factors that could influence the measured angles. MATERIALS AND METHODS: The intended acetabular cup position of 45 degrees inclination and 20 degrees anteversion was checked radiologically in 950 patients who received a cementless total hip replacement. The qualifications of the surgeon, operated side and implant model were recorded and analyzed with respect to a possible correlation with the results. Since a "safe angle" cannot be defined without consideration of other variables, a tolerable deviation of the target position was investigated. RESULTS: The mean inclination angle was 48.7 degrees (SD 7 degrees, minimum 28 degrees, maximum 75 degrees ). Anteversion was measured with a mean of 18.6 degrees (SD 9 degrees, minimum -9 degrees, maximum 50 degrees ). Assuming an acceptable deviation of +/- 5 degrees from the target position (45 degrees inclination and 20 degrees anteversion), only 22.7 % of the acetabular cups were in this range. In the case of an acceptable deviation of +/- 10 degrees, 34.5 % of the cups were still outside of the acceptable range. The qualifications of the surgeon, the implanted model, as well as the operated side did not have a significant influence on the results. CONCLUSION: The common implantation technique yielded significant variation with respect to anteversion and inclination. The application of computer-aided navigation in the placement of acetabular cups would help to improve accuracy and reproducibility considerably in total hip arthroplasty.

Acetabulum↗
PubMed2006

[Pigmented villonodular synovitis].

Pigmented villonodular synovitis (PVNS) is a rare, strongly proliferative disease of the lining of thejoint, synovial bursa and tendon (synovial) sheath. If left untreated, it leads to severe destruction of the joint resulting in an early need for endoprosthetic replacement. The clinical signs are unspecific. Using the diagnostic gold standard MRI, the complete extent of PVNS can usually be determined non-invasively. Once histological confirmation has been obtained, radical tumor resection, synovectomy, possibly curettage, and postoperative irradiation must be applied.

Arthroplasty, Replacement, Knee↗
PubMed2006

Multiple skeletal metastases from a giant cell tumour of the distal fibula with fatal outcome.

A giant cell tumour is a primary lesion of bone of intermediate severity. Its histogenesis is unclear. In a few cases pulmonary metastases have been described. Multiple skeletal metastases in the absence of sarcomatous change have been observed. We present a case report of a 25-year-old woman with a recurrent giant cell tumour of the distal fibula. After a second recurrence and six years after the initial diagnosis, she rapidly developed multiple bony metastases. The outcome was fatal.

Adult↗
PubMed2005

Cell-based treatment of osteochondral defects in the rabbit knee with natural and synthetic matrices: cellular seeding determines the outcome.

INTRODUCTION: Matrix-associated transplantation of cartilage constructs is an appealing method in cartilage repair. Three different matrices seeded with allogenic chondrocytes were compared in an osteochondral defect model in the rabbit. An investigation was conducted to identify the best matrix for cell-based treatment of osteochondral defects in the rabbit knee joint. MATERIALS AND METHODS: Osteochondral defects (diameter 3 mm) were created in the trochlea and the femoral condyles of 33 New Zealand White rabbits, which were then treated with bioartificial cartilage constructs. The cartilage constructs were created in vitro using three different resorbable carrier materials (two fleece matrices: one of PLLA, and one composite of polydioxanon/ polyglactin, as well as one consisting of lyophilized dura) cultured with isolated allogenic chondrocytes. The defects were evaluated macroscopically, by histological and immunhistological techniques, and by scanning electron microscopy after 6 weeks, 6 months, and 12 months. The chondrocyte-seeded constructs were compared to defects treated with carrier material alone as well as to untreated control defects. RESULTS: There was a significant improvement in defect repair quality in the transport materials, which were cultured with chondrocytes prior to implantation (P < 0.0005). No significant differences were observed between the three carrier matrices, and no significant differences were seen between the unseeded matrices and the untreated control defects. CONCLUSION: There is no difference in the outcome between the three tested matrices in the treatment of osteochondral defects in the rabbit knee. The results of this in vitro experiment are promising and with refinement may lead to useful clinical therapies.

Animals↗
PubMed2002

Vital marking of articular chondrocytes by retroviral infection using green fluorescence protein.

OBJECTIVE: One of the main open questions in chondrocyte transplantation is the fate of the implanted cells in vivo. We intended to establish prerequisites for such studies in animal models and to show the feasibility of this approach in rabbits. Isolated articular chondrocytes were retrovirally marked using green fluorescence protein (GFP) as a cell-specific marker in order to allow an in vivo follow-up of these cells. METHODS: Chondrocytes from rabbits, sheep, cattle and humans were isolated and infected with murine leukemia virus-derived retroviruses carrying the GFP gene. The influence of the host range of three packaging cell lines (PA317, PT67, PG13), start cell concentrations, number of cell passages and number of infection cycles on the efficiency of infection was investigated. Stability of GFP expression was followed by FACS analysis, confocal imaging and fluorescence microscopy. For in vivo follow-up of GFP expression we used marked allogeneic chondrocyte populations grown on scaffold material and implanted them into full-thickness defects in knee joints of rabbits. RESULTS: Retroviruses from all three packaging cell lines were able to infect rabbit and human chondrocytes, whereas only retroviruses released from PG13 cells were able to infect sheep and bovine chondrocytes efficiently. Optimization of the infection with these viruses resulted in efficiencies of 60-90% GFP-expressing chondrocytes. Populations of 100% marked chondrocytes were obtained by cell sorting. GFP expression stability of such marked chondrocyte populations was followed in monolayer culture and in 3-D culture on different scaffold materials. The expression of GFP was stable on all tested materials for at least 4 weeks. In monolayer culture GFP expression was stable for more than 8 months. In vivo, we observed stable GFP expression in the transplants during a four-week time course. CONCLUSION: Retroviral GFP gene transfer led to long-term expression in chondrocytes from rabbits, sheep, cattle and humans. Transgene expression and the number of implanted chondrocytes remain stable for at least 4 weeks in vivo. This method permits a rapid monitoring of chondrocytes and provides a basis for following the fate of these cells in vivo.

Animals↗
PubMed2000

Agrobacterium-mediated sorghum transformation.

Agrobacterium tumefaciens was used to genetically transform sorghum. Immature embryos of a public (P898012) and a commercial line (PHI391) of sorghum were used as the target explants. The Agrobacterium strain used was LBA4404 carrying a 'Super-binary' vector with a bar gene as a selectable marker for herbicide resistance in the plant cells. A series of parameter tests was used to establish a baseline for conditions to be used in stable transformation experiments. A number of different transformation conditions were tested and a total of 131 stably transformed events were produced from 6175 embryos in these two sorghum lines. Statistical analysis showed that the source of the embryos had a very significant impact on transformation efficiency, with field-grown embryos producing a higher transformation frequency than greenhouse-grown embryos. Southern blot analysis of DNA from leaf tissues of T0 plants confirmed the integration of the T-DNA into the sorghum genome. Mendelian segregation in the T1 generation was confirmed by herbicide resistance screening. This is the first report of successful use of Agrobacterium for production of stably transformed sorghum plants. The Agrobacterium method we used yields a higher frequency of stable transformation that other methods reported previously.

Agrobacterium tumefaciens↗
PubMed2000

Bioartificial cartilage.

Cartilage is a highly differentiated tissue. Its three-dimensional composition of cells and matrix is able to resist intensive mechanical loads. The capacity of cartilage tissue for regeneration is limited. Chondrocytes are responsible for matrix production of cartilage tissue. Enzymatic isolation and expansion of chondrocytes with cell culture techniques has been improved in the last years. These cells can be cultured on different three-dimensional culture systems suitable for transplantation to repair localized cartilage defects. Two types of bioresorbable polymer fleece matrices (PLLA and a composite fleece of polydioxanone and polyglactin) and lyophilized dura as a biological carrier are tested. Phenotypic and morphological appearance of the cultured articular rabbit chondrocytes is preserved on all three types of transport media. Production of glycosaminoglycans has been shown by Alcian blue staining, production of collagen by azan staining. Chondroitin 4- and 6-sulfate are detected immunohistochemically in the created constructs. The different carriers have specific characteristics regarding their suitability for the creation of bioartificial cartilage. This tissue is transplantable into articular cartilage defects and could, therefore, improve the minor intrinsic healing capacity of cartilage tissue.

Animals↗
PubMed2000

[Tissue engineering for therapy of osteochondral cartilage lesions].

Cartilage defects still represent an unsolved problem in joint surgery. The intrinsic healing capacity of cartilage is insufficient and at best leads to reparative tissue like fibrous cartilage or cartilage like tissue regardless of the therapy applied. Cell culture techniques and generation of tissue specific matrix tread new paths to treat traumatic cartilage lesions. This technology referred to as tissue engineering allows for formation of constructs consisting of chondrocytes capable of production of cartilage specific matrix in combination with three-dimensional cell carriers. Polymers such as polylactid, co-polymers like polydioxanon with polyglactin and lyophilized dura have been used successfully to create such constructs with chondrocytes of different animal species. Cartilage specific compounds can be detected by histological and immunohistochemical techniques. To apply these constructs in humans, the distinguishing characteristics and problems of cell culture with human chondrocytes have to be considered. A further improvement of the artificially created tissue is conceivable using growth factors even including genetic manipulation of the applied cells.

Animals↗
PubMed1999

[Growth behavior of chondrocytes on various biomaterials].

Chondrocytes can be cultured on different three-dimensional culture systems suitable for transplantation to enhance the repair of localized cartilage defects. Articular cartilage chondrocytes from adult rabbit knees and from bovine calf metacarpophalangeal joints were isolated by enzymatic digestion and cultured in a monolayer system to amplify cell count. After amplification the cells were seeded on different biocompatible materials. We investigated two types of bioresorbable polymer fleece matrices (a composite fleece of polydioxanon and polyglactin and a resorbable poly-L-lactic acid fleece) and lyophilized dura as a biological carrier. On all three types of transport media the phenotypic and morphological appearance of cultured chondrocytes could be observed. The production of glycosaminoglycans was revealed by Alcian blue staining and immunohistochemical detection of Chondroitin-4 and 6-sulfate in the created constructs. The material properties of the carriers allow for transplantation of the artificial cartilage-like products into full thickness articular cartilage defects and could therefore improve the minor intrinsic healing capacity of cartilage tissue. Bioartificial cartilage may become a future perspective in the treatment options of orthopaedic and plastic surgery.

Animals↗
PubMed1999

[Lateral ankle ligament rupture. When is surgical management indicated and when conservative therapy preferred?].

In lateral ankle ligament tears, the anterior talofibular ligament ruptures most commonly, often in conjunction with the calcaneofibular ligament. The posterior talofibular ligament is rarely affected. Associated injuries at the adjacent ligamentous structures or at the articular cartilage of the ankle commonly occur. The diagnosis is established clinically with the anterolateral drawer sign and an increased lateral talar tilt. Stress radiographs in two planes demonstrate talar tilt and anterior displacement of the talus, in comparison to the unaffected side. Magnetic resonance imaging provides an early diagnosis of concomitant injuries. Simple, acute lateral ankle ligament tears are treated non-operatively. Surgery is indicated in dislocated bone avulsions and in chondral or osteochondral fractures. A recurrent tear in an athletic patient should also be treated operatively. Athletic endeavours, the number of torn ligaments and patient age are no useful indicators for surgical treatment. Conservative treatment consist of oedema therapy, immobilization of the fibular ligaments with as little compromise of ankle joint function as possible, and rehabilitation with muscle strengthening and proprioception training. During surgery, the ligament stumps are reapproximated in anatomic position, reinforced with local tissue if necessary, and the articular surface is examined for concomitant injuries.

Adolescent↗
PubMed1998

[Not Available].

Explore the source record for details and available documents.

Journal Article↗
PubMed1998

Synthesis of articular cartilage-like tissue in vitro.

Defects in mature articular cartilage do not heal without residues, and therefore they remain a challenging problem in orthopaedic surgery. Modern tissue culture techniques facilitate the synthesis of cartilage-like tissue. A requirement of retaining the phenotypic characteristics of chondrocytes in vitro is the use of three-dimensional culture techniques. Articular chondrocytes of adult rabbits were isolated and cultured on different transplantable media for several weeks. A resorbable fleece, a non-absorbable net and lyophilized dura were used. Viability was tested by immunohistochemical techniques. Deposition of extracellular matrix could be observed by electron microscopy. The phenotypical and morphological appearance of cultured chondrocytes was preserved on the resorbable polymer fleece and the lyophilized dura. Cells cultured on the non-absorbable net had a more fibroblastic appearance. The resorbable fleece is apparently most suitable in terms of viability of the cultured chondrocytes and biocompatibility. The cultured three-dimensional artificial cartilage constructs reveal a future possibility for autologous cartilage transplantation into mature cartilage defects.

Animals↗
PubMed1997

Medial meniscus replacement by a fat pad autograft. An experimental study in sheep.

The medial meniscus in 15 sheep was replaced by a pediculated infrapatellar fat pad graft and resulted in the development of a macroscopically meniscus-like structure within 6 months. Five additional sheep with a meniscectomy were controls. Degenerative changes in the fat pad autograft were visible after one year. Osteoarthritis of the weightbearing medial compartment was detected after 6 months. A temporary protective effect on the cartilage could be attributed to the autograft, but the long term results indicated that this was not permanent. Fat is not suitable as a meniscal substitute.

Adipose Tissue↗
PubMed1997

Reconstruction of the lateral ligaments of the ankle using a regional periosteal flap.

We have treated 94 patients with chronic instability of the lateral side of the ankle by reconstruction of the ligaments with local periosteal tissue. We reviewed 90 cases after a mean follow-up of 2.8 years (2 to 9) using a questionnaire, clinical examination and radiography. The results on a 100-point ankle score indicated that 81% had a good or excellent result. The periosteal flap-replacement technique allows anatomical reconstruction and does not sacrifice other ligaments or tendons in the foot.

Adolescent↗
PubMed1997

[Cartilage cell transplantation. Experimental principles and clinical applications].

Transplantation of autologous chondrocytes proliferated in vitro to treat cartilage defects is discussed controversially. Cartilage has only a very limited capacity to regenerate. The repair tissue is of minor biomechanical stability and therefore induces degenerative arthritis of joints in the long term. Facial cartilage defects may lead to aesthetic or functional problems. Different biological and synthetic substitutes were used to treat cartilage defects in orthopaedic and facial plastic surgery. Biological tissue for transplantation is not abundant and synthetic materials may induce foreign body reactions. Amplification of autologous cells in vitro to produce a tissue similar to the impaired tissue seems tempting. It is transplantable into the defect and is tough to restore the defective surface completely. This is the intention of numerous scientific investigations concerning chondrocyte application to cartilage defects. Transplantation of isolated chondrocytes is currently used in clinical trials also. The possibilities and limitations of this technique are discussed including the fundamental principles and our own experimental investigations. A proof for the reproduction of a tissue similar to native cartilage with its typical long term mechanical properties is still missing. Further laboratory and clinical studies should be conducted before the technique is propagated in patient care.

Animals↗