Concept, design and fabrication of smart orthopedic implants.

Extensive clinical experience has been built up using orthopaedic implants instrumented with strain gauges connected to a Wheatstone bridge by means of percutaneous leads. This research showed the medical relevance of the monitoring of the deformation of implants as a powerful tool to evaluate nursing and rehabilitation exercises, for tracing dangerous overloads and anticipating implant failure and also to observe the healing process. The IMPACT 3500 project focuses on the instrumentation of femoral implants with on board sensors: regular Benoist-Girard implants have been modified, to contain a 'sensing cell', and thoroughly tested in vitro and in vivo.

Comparative left-right mechanical testing of cancellous bone from normal femoral heads.

In order to assess the potential influence of various physical or chemical treatments on bone grafts, and in particular, on femoral heads to be used as bone grafts, the mechanical symmetry of the femoral head was investigated. Pairs of proximal human femora were harvested and transversally sliced using a coordinate system to orient correctly the head. After being embedded and polished, bone slices were loaded to failure between two steel columns (6 mm of diameter) in a sequential and symmetrical manner for both heads.

[Contribution to the study of pelvic stress during weight-bearing. Role of the pubic branch and trabecular bone].

Introduction: Several authors have reported evidence of loosening of the acetabular component in 14 per cent of cases at 10 years follow-up. To understand this phenomena, parametric studies of the acetabulum have involved finite element analysis, photo elastic models or strain gauges. The differing and sometimes contradictory results were due to the way the model was solicited.

Osteosynthesis of the proximal femur anchorage of a cervical nail.

One of the factors determining the stability of osteosynthesis is the mechanical strength of the bone fragments required for the anchorage of the implant. The aim is to study the driving of a Thornton nail in the proximal epiphysis of a human femur as a way to measure the strength of the trabecular bone and to predict the stability of the implanted system.

BOP: biocompatible osteoconductive polymer: an experimental approach.

BOP (biocompatible osteoconductive polymer) is a material proposed for osteosyntheses and for filling of bone defects in orthopaedics, neurosurgery and stomatology. It is a composite made of a copolymer of N-vinylpyrrolidone and methylmethacrylate, of polyamide-6 fibers and of calcium gluconate. The histological investigation includes the study of 30 intact rabbit femurs instrumented with a BOP rod, as well as the study of organs of the reticuloendothelial system.

Morphometric and physical investigations of segmental cortical bone autografts and allografts in canine ulnar defects.

Cortical bone grafts were implanted for six months in mature dogs using an osteoperiosteal 3-cm defect in the ulna to evaluate their respective morphometric and physical values compared with autografts. The bone-grafting material included fresh auto- and allografts, frozen and thimerosal preserved allografts, and partially demineralized bone allografts. The grafts were evaluated by roentgenograms, microradiograms, photon absorptiometry, porosity, fluorescence labeling measurements, and torsional loading at failure.

Cancellous bone and mechanical strength of the femoral neck.

Twenty pairs of dried macerated femora were submitted to progressive, physiologically oriented loading. The aim of this work was to determine the role of trabecular bone, the importance of the bone mineral density of the femoral shaft, and the importance of the Singh index in the mechanical strength of the femoral neck. By means of an original technique, the influence of both the principal tensile and secondary compressive trabecular groups on the mechanical strength to bending stress has been demonstrated.

Pharmacodynamic profile of the selective beta 1-adrenoceptor antagonist bisoprolol.

The pharmacodynamic activity of (+/-)-1-[4-(2-isopropoxyethoxymethyl)-phenoxy]-3-isopropylamino-2- propranol- hemifumarate (bisoprolol, EMD 33 512) has been investigated under in vitro and in vivo conditions. Bisoprolol was found to be an effective beta-adrenoceptor antagonist, the pA2 values determined against isoprenaline in guinea pig atria and tracheal muscle being 7.45 and 6.

Canine cortical bone autograft remodeling in two simultaneous skeletal sites.

The morphological and physical aspects of cortical bone autografts implanted in dogs for 1-9 months in two differently located skeletal defects are reported with a twofold aim: to provide a reference system for further comparison with various allografts and to delineate a general pattern of cortical bone graft healing. A 3-cm osteoperiosteal gap was created in the diaphyseal segment of the ulna and fibula of mature dogs. The grafts, freed from periosteum and bone marrow, were then inverted and replaced for the autografts in the left limb bone without internal fixation or external splints.

Twenty years experience in fracture healing measurement with strain gauges.

The external fixator provides a mechanical connection between the bone fragments and recording devices or power systems. We have used this characteristic of external fixation since 1965 to record deformations occurring at the fracture site and to measure the mechanical characteristics of fracture healing in more than 500 patients. As in all osteosyntheses, the fixation material (here the external rod) resists the mechanical forces applied to the bone fragments.

Feasibility of bone healing measurement with external fixation: experimental study.

The measurement of fracture healing is a problem before us now; many techniques are now being developed. One of them is strain gauge measurement, allowing control of the development of the callus stiffness. The mathematical models and the experimental controls always had to deal with "preliminary assumptions.

In vivo bone strain measurements: clinical results, animal experiments, and a proposal for a study of bone demineralization in weightlessness.

An extensive review of the literature of the aetiology of bone demineralization in weightlessness underline the prevalent effect of mechanical stimulations on bone structure and metabolism. The accurate determination of the mechanical environment of bone can be realized using strain gauges. The results of more than 10 years of clinical application of bone strain measurements demonstrate the interest of this technic.