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Biomedical subjects

L Claes

Publications and source records attributed to L Claes.

At least 181 records · Page 10Linked to original sources
PubMed1983

Mechanical properties of ligament replacement with carbon fibres.

1. The tensile strength and modulus of elasticity of carbon fibres are comparable to those of stainless steel. 2. The small diameter (7-8 microns) produces high fibre flexibility, permitting braiding and weaving of this material. 3. The strength of braided ligament prostheses is about 2-3 times higher than the rupture strength of natural knee ligaments. 4. The elasticity and extensibility of a ligament prosthesis made of braided carbon fibres are higher than when there is a unidirectional arrangement. 5. The growth of connective tissue between the braided carbon fibres increases the elasticity and extensibility of the ligament replacement in vivo, so that 50-110% of the values for natural ligaments can be achieved. 6. The low shearing strength of the carbon fibres can be increased by a layer of collagen. 7. Intraosseous anchorages of the carbon fibre ligaments after 12 weeks of implantation exhibit strengths corresponding to 49-107% of the rupture strength of natural ligaments.

Animals↗
PubMed1983

The biological reaction of the tissues to carbon fibre ligament prosthesis in sheep-knees.

The biological reaction of the tissues to carbon fibre ligament prosthesis was examined in sheep knees. Connective tissue and bone grew into the alloplastic ligament at the insertion points in cancellous bone. There was tissue ingrowth around the carbon fibres intra- and extra-articularly. The bony ingrowth into the ligament increases with time and there was no resorption present. The carbon fibre ligament should not be used as an internal splint in the fresh ligamentous repairs. The easiest method of ligament replacement in a chronically unstable knee is the application of alloplastic ligament material. Therefore the search for a good substitute has never been given up. Carbon fibres are found to be a very good scaffolding and a permanent prosthesis for ligament replacement [1, 2, 6, 8]. The biocompatibility of carbon fibres in animals has been proved [4, 6, 7]. The mechanical properties, tensile strength and flexibility, make the fibres suitable for use as ligament substitutes. The braiding of carbon fibre bundles has improved its biomechanical properties [3]. In this study the biological reaction of sheep-knees to carbon implants is investigated: 1. Does connective tissue grow into the ligament prosthesis under physiological conditions? 2. Is there tissue growth around the carbon ligaments intraarticularly? 3. Is a C-ligament useful as an internal splint in fresh ligamentous repairs? 4. What is the fate of the bone-ligament interface in long term use?

Animals↗
PubMed1983

Treatment by external fixation of open fractures associated with severe soft tissue damage of the leg. Biomechanical principles and clinical experience.

External fixation is the treatment of choice for fractures of the leg involving severe damage to the soft tissue. Each of the various patterns of application has advantages and disadvantages. Based on various biomechanical studies and clinical experience, the authors use a right-angle arrangement for the screws. If the type of fracture permits, internal and external fixation may significantly increase stability. During the period from 1978 to 1980, 56 patients with second- and third-degree open fractures were treated. A combination of external and internal fixation was used in 42 patients. Of the 44 patients re-evaluated at follow-up examinations, 19 had returned to unrestricted weight-bearing within 19.8 weeks. If no signs of bony union are noted ten to 12 weeks after the initial operation, cancellous bone grafting and internal fixation instead of external fixation are indicated. Twenty-three patients were fully weight-bearing an average of 14 weeks after internal fixation and cancellous bone grafting. Two patients had difficult problems and did not return to full weight-bearing until about 45 weeks after operation.

Adult↗
PubMed1981

Quantitative investigations on newly-built bone and defects. Its time-dependent changes of morphological and biomechanical properties.

Bone growth in drillholes in sheep tibiae were examined morphologically and biomechanically after 4, 6, 9, and 12 weeks. Selected bone specimens were removed from the defective areas and used to determine the strength and, with the aid of microradiographs, the volume of new bone. Strength as well as volume of new bone increased in the defects within the healing time. However, the strength of the newly-formed bone reached only 20% of the strength of normal cortical bone. This is caused by the random structure of new bone which, despite the repair of the defect and the nearly normal mineralization, is not yet adapted to the adjacent normal cortical bone.

Animals↗
PubMed1981

[Biomechanical investigations about the transfer of axial load in different forms of plate-osteosynthesis (author's transl)].

The anchorage of various internal fixation plates on bones was tested. The results showed significant differences depending on the type of plates and the number of screws. Normal round hole plates slipped at higher forces more often than dynamic-compression plates (DCP). DC-plates with a rough surface revealed a higher strength than the same plates with a smooth surface. The anchorage strength of the plate-bone connection does not increase proportionally to the number of screws.

Biomechanical Phenomena↗
PubMed1981

[Comparative investigations on the stability of fracture fixations with different fixateurs externes (author's transl)].

Short oblique fractures of the tibiae were stabilized with two-dimensional (frame spanner), three-dimensional and various V-shaped fixateurs externes, applied at the ventral-medial side. The stability of all these different types of fracture fixations was tested with and without an additional lag screw. Under a torsional load the stability of the area of osteotomy was measured. The three-dimensional fixateur externe and the V-shaped fixateur externe yielded the best results. The use of an additional lag screw produced a greater and significant (p less than 0,01) improvement.

Biomechanical Phenomena↗
PubMed1981

[Biomechanical examination of stress distribution in the femoral neck for varus-implanted and valgus-implanted cups (author's transl)].

Femoral neck fractures occur after cup-prosthesis implantation and inadequate trauma. By reaming the head the tension stress in the lateral tension banding system of the femoral neck is reduced. Therefore high unphysiological bending moments occur in the medial trabecular system, which resists only high pressure forces. Our investigations showed that the unfavourable change in the stress distribution in the femoral neck is worse for the varus- than for the valgus-implanted cup. This could be the cause for the femoral neck fractures after cup implantation and inadequate trauma.

Biomechanical Phenomena↗
PubMed1980

[Possibilities of geometric X-ray examination of the pelvis for partial pelvis replacement].

Patients with tumors of the pelvis, which cannot be treated by chemotherapy or radiation, must undergo hemipelvectomy. The postoperative prosthetic treatment was difficult und not always sufficient. So, a complete internal hemipelvectomy was done by replacement of an artificial part of half pelvis. Before the operation it was necessary to know the measurements of the pelvis exactly. This was done by taking X-ray pictures in anterior--posterior, lateral and axial direction which brought out the relevant diameters for the construction of the artificial pelvis. By using the Computer-Tomography we could get exact slices of the pelvis in the transversal plane. The slices were centrally positioned, then the model was covered with modelling-mass. The result was an exact positive feature of the pelvis which must be replaced.

Bone Neoplasms↗
PubMed1980

[Closure of abdominal wall defects without tension using a carbon cloth implant (author's transl)].

On 20 rabbits a defect in the abdominal wall was closed by a carbon cloth (SIGRATEX KDS). A tensile force test and a histological examination was performed. Eleven days and 3 months after implantation, 10 animals with an operative-produced abdominal wall hernia and 10 normal animals were controls. A tensile force test on the specimen 3 months after implantation revealed a strength twice as high as on the normal abdominal wall. Eleven days after surgery the strength was equal to the scar tissue of the hernias. Histologically, a connective tissue ingrowth into the implant was observed, which enveloped the single carbon fibers. Collagen fibers in the direction of the carbon filaments were present. Foreign body giant cells were always seen. These results indicate that a carbon cloth seems to be suitable for the repair of abdominal wall hernias.

Abdominal Muscles↗
PubMed1980

[Long-term observation after implantation of a carbon fiber-reinforced carbon hip joint endoprosthesis in foxhounds (author's transl)].

A hip-joint endoprosthesis, comprising a carbon fiber-reinforced stem, aluminum oxide head, and polyethylene acetabular cup, was studied in vivo trials in ten foxhounds after implantation with bone cement. Observations over 6 months and 1 year demonstrated that carbon fiber-reinforced carbon exhibits adequate strength for use as a stem material under the observed conditions.

Animals↗
PubMed1980

[Biomechanical and histologic evaluation of refixation of ruptured collateral ligaments (author's transl)].

This paper describes the use of a new one-hole plate for the refixation of ligaments. The anchorage of ligaments was of sufficient strength as judged by biomechanical experiments on medial collateral ligaments of sheep in vivo and knees of human cadavers. Microangiographic and histologic investigations showed good vascularization and normal structure of the ligament under the one-hole plate.

Animals↗
PubMed1980

[The use of carbon fiber strands for replacement of collateral ligaments at the knee joint (author's transl)].

Two different anchorage systems of carbon fiber strands were tested on 16 human cadaver knees. To pull the C-strands out of the scale and channel anchorage almost the same force was necessary as to break the natural collateral ligaments. The ingrowth of connective tissues and newly formed bone around the C-fibers was studied in 11 sheep. A biomechanical strength test revealed, 3 months after implantation, a 60% strength compared to the natural ligaments. Histologically a C-fiber connective tissue composite with collagen fibers was found. Newly formed bone closely surrounded the carbon. These results indicate that carbon fiber strands are suitable for ligament replacement, which allows early joint motion. Good long-term results could be assumed as a result of the high biocompatibility.

Biomechanical Phenomena↗