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Biomedical subjects

G Ritter

Publications and source records attributed to G Ritter.

At least 73 records · Page 4Linked to original sources
PubMed1994

[Bone healing after unreamed intramedullary nailing].

Good clinical results of unreamed nailing have been observed primarily in cases of open fracture. However, it is still unclear whether unreamed nailing is a suitable procedure for fractures that have previously been treated with reamed nailing. Since histological findings on bone healing after unreamed nailing were not available, an animal experiment on sheep was undertaken. The aim was to investigate whether there were differences in the nature of bone healing following reamed and unreamed nailing procedures. Fluorescence microscopy clearly showed that maximal callus formation occurred within 4 weeks after unreamed nailing and within 6 weeks after reamed nailing. Callus formation was also more prolific after unreamed than after reamed nailing. It was demonstrated by microradiography that bone regeneration progressed more rapidly, in terms of both periosteal and interfragmentary callus, after unreamed nailing. No disturbances of bone healing and no greater risk of pseudarthrosis were observed following unreamed nailing. Histological investigations showed that bone healing was faster after unreamed nailing and there was a reduced loss of vitality. This is of particular clinical relevance in the surgical treatment of fractures with severe soft tissue injury and of open and comminuted fractures. These results indicate that an extension of the indications for unreamed nailing should be considered.

Animals↗
PubMed1994

[Technique of plate osteosynthesis of the femur].

When plating is performed for fixation of complex femoral fractures the need for medial buttress to give durable weight-bearing ability of the bone is mandatory. However the means of achieving this is controversial. Many authors are in favour of mechanical reconstruction of the medial buttress, if necessary with a bone graft. Alternatively, medial buttress can be achieved by means of a technique allowing biological fracture healing, which is only possible, when the vascularity of all fragments is preserved. In 39 cases of osteosynthesis with plates for complex femoral fractures the bridging technique was used at surgery, to avoid denudation of the fragments. All osteosyntheses were performed without the application of bone clamps. After minimal exposure of the femur at the lateral side only, the plates were fixed in the main proximal fragment with one screw, in the case of blade plates the blade was fixed without bone clamps too. Afterwards the main distal fragment was drawn up to the plate and fixed directly and with a screw. In 9 cases the plates were inserted behind the vastus lateralis muscle, preserving its continuity, and fixed distally with another screw. After fine checking of the fracture alignment for rotation and length the plates were fixed with four or five screws in each main fragment, all at sites distant from the fracture. Meanwhile, all 39 fractures have consolidated. There were no cases of infection. Bone grafting was necessary in 8 cases. Only in 2 cases were the defects located in the medial area. In 37 of the 39 osteosyntheses an excellent medial buttress was achieved by bone healing.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone Plates↗
PubMed1993

[Accident risk in epilepsy].

Patients with seizures without daytime preference are highly jeopardized by accidents. The majority of seizure-related accidents occurred in the household. All household accidents lead to injuries. Therefore, household activities carry the highest risk. Traffic-related accidents were also common but severe injuries occurred less frequently. Car drivers had only property damages. Only one third of all car drivers were seizure-free for two years. Accidents while working or exercising occurred very infrequently, hence indicating no increased risk at work of sports (N = 104 patients).

Accident Prevention↗
PubMed1993

Pathogenesis and prophylaxis of circulatory reactions during total hip replacement.

Circulatory reactions such as a drop in blood pressure, bradycardia, cardiac arrest, and even intraoperative death after insertion of the stem are well known events during total hip replacement. The present paper reports bone marrow intravasation after rise of intramedullary pressure in the femoral cavity during insertion of hip prostheses, demonstrated by intraoperative transesophageal echocardiography. In an animal study, the ultrasound echoes were identified as "mixed emboli" consisting of a core of bone marrow surrounded by thrombus. These results suggested the use of an intramedullary plug to restrict the intravasation of bone marrow. A trial was undertaken in 60 total hip replacement operations. The first 30 were performed using the conventional technique without an intramedullary plug. In a second series of 30 operations, an intramedullary plug made of cancellous bone taken from the resected femoral head was placed 2 cm below the expected location of the tip of the stem. The cement was applied from distal to proximal by syringe. After implantation of the prosthesis using the conventional technique, a significant drop in blood pressure was observed. In the second series, the drop in blood pressure did not occur. In conclusion, it was demonstrated that effective venting of the bone marrow cavity by a bore hole, and avoidance of compression of the bone-marrow-filled distal femoral cavity by using a plug, results in effective prevention of circulatory reactions: no drop in blood pressure occurred. The use of an intramedullary plug is discussed and recommended.

Aged↗
PubMed1993

Pathogenesis and clinical relevance of bone marrow embolism in medullary nailing--demonstrated by intraoperative echocardiography.

For the clarification of pulmonary impairment after medullary nailing of femoral fractures, the intramedullary pressure in the femoral cavity during the operative procedure was investigated. In addition, an intraoperative transoesophageal echocardiography was performed which revealed two phenomena occurring once the intramedullary pressure had increased: snow-flurry and configured emboli. An experimental study in sheep was performed in order to define the substrata of the sonographic echoes. The level of intrafemoral pressure which would result in bone marrow intravasation and the substrata of the echocardiographic echoes were studied in sheep by applying pressure to the femoral cavity. Sonography of the distal vena cava by laparotomy and macroscopic and histological investigation of the venous blood received throughout a proximal subdiaphragmal venotomy were undertaken. The intrafemoral pressure peaks correlated with the appearance of sonographic echoes in both patients and sheep. Snow-flurry is an indication of small amounts of bone marrow and already appears at an intramedullary pressure of 50 mmHg, which can easily occur during movement of non-stabilised fractures (values up to 90 mmHg were observed)--configured emboli consist of a core of bone marrow surrounded by thrombotic aggregate and only appeared at pressure increases of over 200 mmHg in the animal experiments. During medullary nailing in patients the intrafemoral pressure increases up to 200-600 mmHg in all reaming procedures. Configured emboli were seen in 8 of 20 patients being treated with reamed nailing. In five nailing procedures performed using the unreamed technique, no pressure increases greater than 70 mmHg and no configured emboli were observed. I.v. injected bone marrow results in pulmonary impairment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Effects of ganglioside administration on experimental autoimmune neuritis induced by peripheral nerve myelin or P2-specific T cell lines.

We studied the effects of ganglioside administration in two animal models of inflammatory demyelinating polyneuropathy. We administered a mixture of bovine brain gangliosides intraperitoneally to Lewis rats with myelin-induced or T cell line-mediated experimental autoimmune neuritis (EAN). Under the experimental conditions we had chosen, we only detected marginal but not statistically significant effects on disease course and severity, as evidenced by motor function, electrophysiological findings, and morphological signs of inflammation and demyelination. There was no significant induction of antibody production against gangliosides, and we did not detect signs of increased cellular reactivity towards gangliosides. We conclude that the administration of gangliosides modulates EAN at best marginally, and does not induce a cellular or humoral immune reaction.

Animals↗
PubMed1993

[Therapy of burst ceramic head of a hip prosthesis].

The therapeutical possibilities in case of fracture of a ceramic head ball of a hip prosthesis system are discussed. A seventy year old patient suffered a fracture of a ceramic ball of a cemented hip prosthesis with polyethylene cup, ceramic ball and metal stem without trauma after one year after implantation. During operative revision a marked destruction of the gliding plane of the polyethylene cup by craters and an extreme metallose because of wear of the metal conus far into the bone bed of the acetabulum was found. The reason for the very seldom occurring fracture of the ceramic ball are minimal differences in the ascent grade of the metal conus of the stem and the corresponding connection of the ceramic ball. The broken ceramic ball should be substituted by a metal ball.

Aged↗
PubMed1993

Characterization of a hamster melanoma-associated ganglioside antigen as 7-O-acetylated disialoganglioside GD3.

We previously reported a hamster animal model of melanoma in which the tumor tissue expresses gangliosides GM3, GD3, and O-acetyl GD3. This ganglioside pattern is similar to that in human melanomas (Ren, S., A. Slominski, and R. K. Yu. 1989 Cancer Res. 49: 7051). In this study, we isolated and purified these gangliosides using chloroform-methanol extraction, Folch partition, chromatographies on DEAE-Sephadex A-25, and Iatrobeads columns. The yields of gangliosides GM3, GD3, and O-acetyl GD3 were 44.1 mg, 19.6 mg, and 9 mg per 100 g of Ma melanotic melanoma tissues, respectively. The structures of these gangliosides were characterized by periodate oxidation, gas chromatographic (GC) analysis, fast-atom bombardment-mass spectrometry (FAB-MS), and nuclear magnetic resonance (NMR) studies. The structure of hamster melanoma O-acetyl GD3 is different from the 9-O-acetyl GD3 previously reported in human melanoma. The major fatty acids of this ganglioside are C16:0, C18:0, C20:0, C22:0, and C24:0 and the long-chain base is C18-sphingosine.

Animals↗
PubMed1993

[Development of thromboses in hip joint endoprostheses. A study with color-coded duplex ultrasound].

After 102 hip replacements in a surgical technique that avoids bone-marrow intravasation as much as possible, color-coded duplex sonography revealed thigh thrombi in only 4 cases without any signs of thrombosis. This rate is lower than that found in all other comparable studies. The investigations stress the role of bone-marrow intravasation in the induction of deep vein thrombosis in hip replacement. With an optimal surgical technique, thigh thrombi can be greatly reduced in hip replacements, which have a higher rate than all other operations.

Aged↗
PubMed1993

[Reposition of fragments of the posterior surface of the vertebral edge with intraoperative ultrasound guidance].

The question of whether fragments of the posterior vertebral surface have to be removed in every case remains to be answered. Nevertheless, in many cases it is important to establish the situation inside the spinal canal intraoperatively. To this end we have used intraoperative ultrasound in 21 cases. The results have always corresponded closely with the findings of preoperative and postoperative computed tomography. Under the influence of this method we have modified our operative procedure. The technique of intraoperative ultrasound and our current operative practice are described in the present paper. We use typical cases to show that intraoperative ultrasound of the spinal canal is a very useful technique for several reasons: Accurate depiction of the spinal canal is always possible without destabilizing the dorsal vertebral structures. The risks and disadvantages of intraoperative myelography are avoided. The method is easy and can be repeated as often as desired, an important advantage in checking the success of the removal of fragments and in reviewing the situation after transpedicular cancellous bone grafting.

Adult↗
PubMed1992

Treatment of fish parasites. 9. Effects of a medicated food containing malachite green on Ichthyophthirius multifiliis Fouquet, 1876 (Hymenostomatida, Ciliophora) in ornamental fish.

For systemic therapy against trophozoites of the skin-inhabiting stage of Ichthyophthirius multifiliis in ornamental fish, the latter were fed medicated food flakes containing malachite green once daily for 1-11 days ad libitum. Naturally or artificially infected cardinal tetras (Paracheirodon axelrodi), blue gouramis (Trichogaster trichopterus), or clown loach (Botia macracantha) were used in the trials. The fish were maintained in aerated 12.5- or 60-1 aquaria at 23 degrees C. Ultrastructural investigations (scanning and transmission electron microscopy) revealed clear deleterious effects of malachite green on the parasitic stages. Following the initial application, the inner membrane of the mitochondria was destroyed. In fish fed for 2 days, aggregation of the mucocysts and polymerization the microtubules within the macronucleus occurred. Finally, the trophozoite's membrane was completely destroyed. In fish fed for 4 days, the medicated food killed all trophozoites of I. multifiliis. Sensitive ornamental fish (e.g., P. axelrodi) showed no adverse effects after they had been fed with only the medicated food flakes for 2 months. Therefore, the oral administration of malachite green using this newly developed medicated food considerably reduces the risk of toxic effects on the fish hosts, which are sometimes caused by malachite green following its application by immersion therapy. The feeding of flakes medicated with malachite green provides and easy-to-handle and highly effective treatment of I. multifiliis in ornamental fish.

Animal Feed↗
PubMed1992

G-estimation of the effect of prophylaxis therapy for Pneumocystis carinii pneumonia on the survival of AIDS patients.

AIDS Clinical Trial Group Randomized Trial 002 compared the effect of high-dose with low-dose 3-azido-3-deoxythymidine (AZT) on the survival of AIDS patients. Embedded within the trial was an essentially uncontrolled observational study of the effect of prophylaxis therapy for pneumocystis carinii pneumonia on survival. In this paper, we estimate the causal effect of prophylaxis therapy on survival by using the method of G-estimation to estimate the parameters of a structural nested failure time model (SNFTM). Our SNFTM relates a subject's observed time of death and observed prophylaxis history to the time the subject would have died if, possibly contrary to fact, prophylaxis therapy had been withheld. We find that, under our assumptions, the data are consistent with prophylaxis therapy increasing survival by 16% or decreasing survival by 18% at the alpha = 0.05 level. The analytic approach proposed in this paper will be necessary to control bias in any epidemiologic study in which there exists a time-dependent risk factor for death, such as pneumocystis carinii pneumonia history, that (A1) influences subsequent exposure to the agent under study, for example, prophylaxis therapy, and (A2) is itself influenced by past exposure to the study agent. Conditions A1 and A2 will be true whenever there exists a time-dependent risk factor that is simultaneously a confounder and an intermediate variable.

Acquired Immunodeficiency Syndrome↗
PubMed1992

[Experimental trial of intraoperative spinal ultrasound].

Dorsal operative stabilization of spinal fractures by internal fixation is an established means of treatment directed at releasing the extrinsic compression of the intraspinal contents caused by the fractured posterior surface of the vertebral body. There are few ways of assessing how successful the repositioning is intraoperatively. Intraoperative ultrasound with a special small transducer is possible, but it is difficult to reach the intraspinal area by this means, because it is surrounded by bones. A laminectomy would destabilize the injured vertebral column even further. By experiments performed on six human vertebral columns we show that it is possible to view the entire length of the fractured posterior surface by ultrasound. The beam has to be projected between the laminae vertebrae following a small laminotomy. Preliminary intraoperative experiences with eight patients confirm our experimental results. The intraoperative ultrasound results have been confirmed by preoperative and postoperative CT. We expect the necessity for laminectomy for examination of the posterior surface of the vertebral body to decline in frequency in the near future.

Child↗
PubMed1992

[Computerized tomography follow-up of the ante-torsion angle after femoral shaft fractures in the adult].

Rotational deformities are common complications following fractures of the femoral shaft. Computed tomography for determination of the anteversion angle of the femoral neck has proved to be the most suitable way of quantifying rotational faults. Out of our inpatient collective, 45 patients who had undergone interlocking intramedullary nailing of the femur and 10 in whom dynamic compression plating had been performed were examined by clinical investigation and computed tomography. Patients impression and clinical findings proved to be less reliable. Computerized determination of the anteversion angle showed rotational deviations of more than 10 degrees in 18 patients with interlocking nails and in 3 with dynamic compression plates. According to our investigations, rotational deviations less than 20 degrees will not usually handicap the patient. Therefore, we suggest that use of the term "rotational fault" be restricted to deviations exceeding 20 degrees compared with the uninjured side.

Adult↗
PubMed1991

Antibody response to immunization with ganglioside GD3 and GD3 congeners (lactones, amide and gangliosidol) in patients with malignant melanoma.

GD3 is the ganglioside most abundantly expressed on the cell surface of human melanoma, and treatment with a murine MAb recognizing GD3 has induced major responses in a small proportion of patients with melanoma. We have therefore attempted to induce production of GD3 antibodies in melanoma patients by active immunization. We found, however, that vaccination with GD3-expressing melanoma cells or purified GD3 does not result in antibody production. We describe here attempts to overcome the poor immunogenicity of GD3 in patients with melanoma by chemical modification. GD3 lactones, GD3 amide and GD3 gangliosidol were synthesized, and the humoral immune response to these derivatives was analyzed. Immunization of melanoma patients with these GD3 derivatives resulted in production of IgM antibodies and, in the case of GD3 amide, also of IgG antibodies. The antibodies to the GD3 derivatives did not cross-react with GD3. This is in contrast to observations in the mouse, where GD3 lactone I induced antibodies that showed cross-reactivity with GD3. Thus, the human immune response was specifically directed toward the modified epitope, rather than to the native structure.

Amides↗
PubMed1991

[Incidence of acetabular fractures before and after introduction of compulsory seatbelt fastening].

The most common causes of acetabular fractures of the hip joint are high speed car accidents, most often as a result of a direct trauma against the knee. With these causal relations in mind this study wanted to show the preventive character of the law for obligatory safety-belt-wearing in Germany introduced in August 1984. Therefore we analyzed the incidence and the severity of acetabular fractures of the hip joint five years before and five years after 1984 within the group of patients treated by the traumatology department of the university hospital of Mainz. We found 54 patients with acetabular fractures of the hip joint, within a period of five years after 1984 in contrast to 84 injuries within an equal five year period before 1984. Car accidents where the cause of injury in 63 cases within the period of five years before 1984, and in 23 cases in the same period after 1984. Also the severity and complexity of these injuries decreased significantly. Therefore we consider the introduction of obligatory safety-belt-wearing in Western Germany as a good preventive measurement to reduce the incidence of acetabular fractures of the hip joint as a result of car accidents.

Accidents, Traffic↗
PubMed1991

[Basic considerations in fractures of the trochanter major in and after angle plate osteosynthesis].

During the operative treatment of pertrochanteric fractures intra- and postoperative fractures of the trochanter major are wellknown. In this paper the most important reasons for this complication are explained and advices to avoid it are given. One main cause for this complication is the cutting off of the M. vastus lateralis during the operation as it is described in the most technical handbooks of surgery. The most important point of weakness is the big hole in the lateral femoral corticalis, where the blade of the angle-plate is inserted into the femoral neck and head.

Bone Plates↗