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Biomedical subjects

R Schenk

Publications and source records attributed to R Schenk.

At least 37 records · Page 2Linked to original sources
PubMed1994

Bicondylar tibial plateau fractures treated with a hybrid ring external fixator: a preliminary study.

Twenty-three knees in 22 patients with Schatzker type VI tibial plateau fractures were treated with a hybrid ring external fixator using tensioned wires proximally and half-pins distally. All but two injuries were secondary to high-energy trauma. Six were open injuries, and eight patients had other major musculoskeletal trauma. Eight patients were treated with limited open reduction and internal fixation before application of the frame. The remainder received percutaneous cannulated screw fixation to stabilize the articular surface without opening the fracture site. Twenty-three fractures were followed to complete healing. Average time to healing was 4.4 months. Arc of motion averaged 107 degrees, and there were four flexion contractures of 5-15 degrees. Complications consisted of three deep wound infections, one deep venous thrombosis (DVT), one malunion, and one pin tract infection. The average knee score and patient function score were 84.7 and 80.5, respectively (Knee Society Clinical Rating System). There were 13 excellent, three good, one fair, and six poor results. The poor results were in patients who either developed deep wound infections or in those who sustained multiple musculoskeletal trauma compromising the patients' function score and ultimately the average score. This method provides good stabilization and allows early range of motion for complex tibial plateau fractures where extensive dissection and internal fixation are contraindicated due to traumatized soft tissue, osteopenia, and fracture comminution.

Adult↗
PubMed1994

[External fixator: surgical technique, pinless fixator, change in procedure].

External Fixation-Technique: The advantages of external over internal fixation are as follows: a) endosteal and periosteal blood supply is undisturbed, b) "low-tech" equipment may be used, c) secondary adjustments are possible and d) easy implant removal. These benefits however are outweighed by the main disadvantages of long term external fixation i.e. pin complications and delayed union of fractures. Better understanding of postoperative management and careful application of screws of improved design will lead to better results. Today's standard applications of external fixation for tibial fractures is a unilateral fixator, using Schanz screws. The pin-bone interface is the most critical site of all external fixation. By avoiding heat necrosis (low temperature drilling) and preventing micro motion at the pin-bone interface (by applying bending- or more recently radial-preload), pin complications such as infection and loosening can be reduced. Two Schanz screws are inserted into each main fragment and are connected with one short tube per fragment. The fracture is then reduced by using these tubes as handles. After reduction a third tube connects the first two by means of two tube-to-tube clamps. This type of fixation will easily allow for three dimensional secondary corrections of alignment. Approximately three weeks following the injury some motion at the fracture site will stimulate callus formation. This can be achieved by destabilisation, dynamisation or "active stimulation" of the fracture site [2]. Pinless fixator: The pinless external fixator holds the fragments firmly with pointed clamps that penetrate about one millimeter into cortical bone without entering and contaminating the medullary canal.(ABSTRACT TRUNCATED AT 250 WORDS)

Equipment Design↗
PubMed1993

Long-term results with the uncemented thrust plate prosthesis (TPP).

The long-term clinical results of a novel concept for total joint replacement called the Thrust Plate Prosthesis (TPP) are presented. Only a restricted number of patients were provided with this new prosthesis (115 at the Orthopedic Department, Canton Hospital, Chur, and 47 at the Department of Orthopedic Surgery, University of Zurich). All patients have undergone clinical and radiological follow-up covering a period from 1980 to 1991. The basic feature of the Thrust Plate Prosthesis is the direct load transfer to the medial cortical bone of the femoral neck, and this has been unchanged since 1978. Titanium alloy has been used since 1986. The good clinical and radiological results are confirmed by a histological examination of an 8-year-old implant: In the crucial area of load transfer newly formed bone can be seen in direct contact with the thrust plate without fibrous tissue in between. The clinical results and histological findings have confirmed the validity of the biomechanical principle of the TPP. The TPP is therefore to be considered a true alternative to the conventional hip prosthesis. In contrast to the conventional intramedullary anchored stem prosthesis the TPP requires the removal of a minimum amount of bone stock, which is certainly important in young patients.

Adult↗
PubMed1992

[Experiences with 216 manual esophageal anastomoses and with mechanical single and double row suture technique (SPTU, EEA, ILS) in stomach cancers].

From 1973 to 1990 we have performed 216 anastomoses of the oesophagus after resection of gastric malignancy. Both resection due to a carcinoma of the oesophagus and subtotal gastric resection due to distal carcinoma of the stomach have not been considered. In a retrospective study we present the results of our oesophageal anastomoses performed by hand-suture and stapling. The perioperative complications are shown with special regard to the insufficiency rate of the oesophageal anastomosis and the resulting mortality. In 70 by hand suturing performed anastomoses (1973-80) we have seen 3 (4.4%) leaks of the oesophagojejuno-/oesophagogastrostomy, in 146 stapled anastomoses (1980-90) 6 (4.2%) insufficiencies were seen. Two of 3 dehiscences in the hand-sewn group and one of the 6 leaks in the stapler group had a lethal outcome. The overall hospital mortality could be reduced from 18.5% to 6.9%.

Anastomosis, Surgical↗
PubMed1991

Establishment and characterization of two immortalized cell lines of the osteoblastic lineage.

Osteoblastic cells were cloned by culturing rat calvariae cells in agarose in the presence of TGF-beta and EGF. Two bone cell lines were established by immortalizing such an osteoblastic clonal cell population by the introduction of the avian v-mycOK10 gene in the form of a mouse ecotropic retrovirus. Although originating from the same clonal cell population, the two lines exhibited somewhat differing properties. IRC10/30-myc1 expressed alkaline phosphatase (AP), showed PTH- and PGE2-induced cAMP production, synthesized mainly collagen type I and a minor fraction of type III, and produced mRNA for the bone-specific protein osteocalcin. IRC10/30-myc3 did not express AP, showed no PTH responsiveness, and synthesized only about one-third as much collagen as IRC10/30-myc1 (4 versus 12% of total protein synthesis). However, the cell line IRC10/30-myc3 was induced to synthesize cAMP by PGE2 and produced osteocalcin mRNA. When cultured in vivo in diffusion chambers, both lines proved to be osteogenic. Besides bone, both lines also formed cartilage and fibrous tissue. Thus, by immortalizing a clonal cell population of the osteoblastic phenotype, cell lines expressing varying properties can emerge. Furthermore, the expression of alkaline phosphatase and PTH-inducible adenylate cyclase are not prerequisites for a cell to form bone in vivo. Finally, cells expressing the phenotype of differentiated osteoblasts, including osteocalcin synthesis, still have a multipotential differentiation capacity and form bone and cartilage in vivo.

Adenylyl Cyclases↗
PubMed1991

BM 21.0955, a potent new bisphosphonate to inhibit bone resorption.

A total of 300 new bisphosphonates were screened for their effect on bone resorption in the rat. Among these, 1-hydroxy-3-(methylpentylamino)propylidenebisphosphonate (BM 21.0955) was selected for detailed investigation. It inhibited arotinoid-stimulated bone resorption as assessed by calcemia in thyroparathyroidectomized rats at a SC dose as low as 0.001 mg P (0.016 mumol) per kg body weight per day. The compound was thus about 2, 10, 50, and 500 times more potent than risedronate, alendronate, pamidronate, and clodronate, respectively. Intravenous administration was as effective as subcutaneous, and oral administration was 100 times less effective. The effect after one administration decreased with time but was still measurable after 2 weeks. Nonstimulated bone resorption assayed by the urinary excretion of radiolabeled tetracycline from lifelong prelabeled animals was also inhibited. This effect started 3 days after a single dose and was still maximal after 7 days. Histomorphometric analysis of the tibial metaphysis in growing intact rats also showed an inhibition of bone resorption along with an increase in bone mass. The number of osteoclasts increased in animals treated with 0.01 and 0.1 mg P per kg (0.16 and 1.6 mumol/kg) body weight SC but decreased in animals given 1 mg P per kg (16.1 mumol/kg), showing that the inhibition of bone resorption was not due to an inhibition of osteoclast recruitment. No inhibition of mineralization occurred. This new bisphosphonate appears to have great potential for use in human bone disease.

Alendronate↗
PubMed1987

[Histology of the implant-bone interface in cemented and uncemented endoprostheses].

The introduction of bone cement into endoprosthetic surgery was a significant step forward from the 'pre-cement' era. Nonetheless, its disadvantages soon stimulated the search for better means of anchoring implants without cement. Interest focuses on the so-called interface zone, which is the area between bone and foreign body. On the basis of light-microscopical findings our understanding of the biological and biomechanical interactions has influenced the principles of prosthetic design and the implant materials selected for use. The present article gives a synopsis of the histomorphology of the interface, with special reference to stability, tissue reactions, wear products, and implant fixation at bone surfaces (concerning bony ingrowth, osseointegration, and bonding). In all, 127 histological specimens of total hip and knee revisions were reviewed, in addition to a total of 24 non-cemented polyethylene cups retrieved at autopsy.

Bone Cements↗
PubMed1986

Effect of halogenmethylenebisphosphonates on bone cells in culture and on bone resorption in vivo.

Dihalogenmethylenebisphosphonates increase alkaline phosphatase activity and fatty acid oxidation in calvaria cells in culture (Cl2MBP greater than Br2MBP approximately equal to F2MBP). The monohalogen ClMBP and the non-halogenated analogues are less active on phosphatase and inactive on or inhibitory towards fatty acid oxidation. The three dihalogenbisphosphonates and ClMBP inhibit bone resorption in vivo, Cl2MBP most strongly.

Alkaline Phosphatase↗
PubMed1986

Quantitative morphometric evaluation of the inhibitory activity of new aminobisphosphonates on bone resorption in the rat.

Three new bisphosphonates of various chain length, namely, 4-amino-1-hydroxybutylidene-1,1-bisphosphonate (AHBuBP), 5-amino-1-hydroxypentylidene-1,1-bisphosphonate (AHPeBP), and 6-amino-1-hydroxyhexylidene-1,1-bisphosphonate (AHHexBP) were compared with 3-amino-1-hydroxypropylidene-1,1-bisphosphonate (AHPrBP), and dichloromethylene bisphosphonate as to their effect on metaphyseal bone remodeling in the rat. The parameters assessed were growth in length, mineralization, metaphyseal density, mean trabecular diameter, and number of trabeculae. Both metaphyseal density, an index of metaphyseal Ca balance, and number of trabeculae, an index of bone resorption, showed the following sequence of potency: AHBuBP greater than AHPrBP = AHPeBP = AHHexBP greater than Cl2MBP. All compounds decreased trabecular diameter somewhat, an index of bone formation, with AHBuBP decreasing the least. AHBuBP and possibly AHHexBP appear to be interesting new bisphosphonates for future clinical use.

Animals↗
PubMed1985

[Immunohistochemistry: theoretical potentials and practical application].

Immunhistochemical methods are increasingly used and their application in surgical pathology is obvious. Nine different immunohistochemical techniques are compared in this review article. The peroxidase anti-peroxidase method of Sternberger et al. (1970), the avidin biotin complex method of Hsu et al. (1981) and the labeled avidin biotin technique of Guesdon et al. (1979) are to be preferred. Two step methods using labeled antibodies such as alkaline phosphatase or peroxidase-labeled second antibodies are less sensitive. However, two-step methods using alkaline phosphatase-labeled antibodies offer the advantage of double staining procedures since alkaline phosphatase reacts with different azo dyes and results in a wide spectrum of colours in the final reaction product. At present, the major problems of immunohistochemistry in daily work are the selection of the fixative and of appropriate controls. Though both problems remain unresolved, immunohistochemical methods should be used for special problems in surgical pathology.

Alkaline Phosphatase↗
PubMed1984

Alkaline phosphatase isoenzymes in human kidney and urine, immunohistochemical, immunological and biochemical characterization.

Human kidney contains two antigenetically distinct isoenzymes of alkaline phosphatase (AP): a liver type and an intestinal type. The intestinal type AP is a minor component (1%-4%) of the total AP activity: it is found only in the cytoplasm. Both isoenzymes are located, found by an immunohistochemical technique, in the proximal convoluted tubules. This histochemical result eliminates the possibility that the low intestinal AP content in the kidney might only originate from blood vessels, where the intestinal isoenzyme was also found. The renal isoenzymes contribute to urinary AP. Intestinal type AP in urine of healthy persons, 10%-40% of the total AP activity, was found after high speed centrifugation predominantly in the supernatant (100,000 g), the liver type mainly in the sediment. Biochemical characterization revealed that intestinal type AP in kidney and urine are identical and differ from the isoenzyme of intestinal mucosa only slightly in their electrophoretic mobility.

Alkaline Phosphatase↗
PubMed1983

Structure-activity relationships of various bisphosphonates.

A variety of bisphosphonates with aliphatic side chains of increasing length, as well as 3-amino-1-hydroxypropylidene-1,1-bisphosphonate (AHPrBP, formerly APD), dichloromethylene-bisphosphonate (Cl2MBP, formerly Cl2MDP), and dibromomethylene bisphosphonate (Br2MBP, formerly Br2MDP), were compared in vitro and in vivo to find (a) a possible relationship between structure and activity in order to give some indication about their mechanism(s) of action on bone and (b) the most efficient and safe compound having an effect on bone resorption. Some relationship was found between inhibition of calcium phosphate precipitation in vitro and of mineralization in vivo. No correlation existed, however, between any parameter measured and bone resorption. The number of calvaria cells in culture was decreased by compounds with a chain length greater than 5-C, by AHPrBP, Cl2MBP, and Br2MBP. Lactate production by these cells in vitro was increased by the long chain bisphosphonates and AHPrBP, and was decreased by Cl2MBP. No good correlation existed between the inhibition of bone resorption measured in vitro on calvaria and that seen in vivo on rat tibiae metaphyses. The latter was inhibited the most efficiently by the bisphosphonates longer than 5-C and by AHPrBP; these were 10 times more effective than Cl2MBP. Taking into account all factors, 1-hydroxypentylidene-1,1-bisphosphonate and AHPrBP seem to be the most active compounds to inhibit bone resorption.

Alkaline Phosphatase↗
PubMed1982

Increase of whole-body calcium and skeletal mass in normal and osteoporotic adult rats treated with parathyroid hormone.

1. The effect of long-term administration of parathyroid hormone (PTH) on whole-body calcium and ash weight of individual bones has been studied in normal and osteoporotic adult female rats in order to examine whether such a treatment could induce a positive calcium balance. 2. Osteoporosis was induced by calcium restriction during pregnancy and lactation. Sequential measurements of whole-body calcium were made by neutron activation. 3. In non-osteoporotic intact and thyroparathyroidectomized rats a daily dose of 75 units of human PTH 1-34 given subcutaneously for 3 weeks increased whole-body calcium. 4. In osteoporotic animals 25-50 units of either bovine PTH 1-84 or human PTH 1-34 given subcutaneously twice daily for 6 weeks increased both whole-body calcium and ash weight of individual bones. Microradiographic examination of the tibiae indicates, however, that PTH administration does not result in the restoration of individual trabeculae lost during the development of osteoporosis. 5. The results show that PTH can enhance skeletal mass in both normal and osteoporotic rats. In osteoporotic animals the restoration of whole-body calcium and ash weight of individual bones is not accompanied by a return of the morphological structure of the tibia to normal.

Animals↗
PubMed1981

The treatment of femoral neck fractures with an isoelastic endoprosthesis implanted without bone cement.

We report about our first experiences inserting an "isoelastic" femoral endoprosthesis in cases of a fractured femoral neck. 28 patients have been observed for a period of more than 1 year after surgery. We did not find loosening or incompatibility of the polyacetal-resin material. We believe the implantation of this prosthesis type without cement fixation is especially advantageous. The histologic result of a patient who died 6 weeks after surgery did not reveal any tissue incompatibility. We observed an excellent fixation of the prosthesis by bone growth into the surface indentations of the stem.

Aged↗