Search PubMed⌕ Search

Biomedical subjects

L Sedel

Publications and source records attributed to L Sedel.

At least 91 records · Page 5Linked to original sources
PubMed1990

[Recurrent instability and luxation of the shoulder].

Instability and recurrent dislocation of the shoulder result from injuries affecting the capsule, ligaments or bones. The positive diagnosis rests on careful clinical investigation where a well-oriented questioning plays an essential role. Paraclinical examinations, such as radiography, ultrasonography, CT and MRI, provide a very accurate assessment of the state of relevant structures. Surgical treatment consists of a stabilizing operation which may be Bankart operation (i.e. suture of the detached capsule onto the anterior part of the glenoid labrum), or a Latarget operation (i.e. screwing of a bony buttress) when the anterior part of the glenoid labrum is deformed by a fracture or worn out by frequent passages of the humeral head. When thoughtfully decided and well executed, these operations regularly give excellent results with resumption of previous activities at the same performance level.

Arthrography↗
PubMed1990

[The influence of the elasticity module of the femoral shaft and neck of a total hip prosthesis on the distribution of stress in the femur ].

Experiments have shown that stress shielding resulting from implantation of a prosthesis is related to the stiffness of the implant. Stiffness depends on the Young's modulus of the material used and the design of the implant. Most published studies have not attempted to define the relative importance of these two components. We have studied the influence of the elastic modulus only in an experiment using implants of a uniform design. Strain gauges were attached to the calcar in five femurs, three of which also had gauges placed on their medial, lateral and anterior aspects. Surface strain was measured in the intact femur and after implantation of cemented prostheses of the same design but manufactured with or without a collar in stainless steel or titanium alloy. The highest level of calcar strain was recorded with the titanium alloy prosthesis, and the presence of a collar appeared to increase the stress transfer of bone. This effect on stiffness was statistically significant, but was limited to the proximal part of the upper femur. It was not significant in the sub-trochanteric area, due to individual variations in bone geometry and cortical thickness. These results indicate that stress shielding can be directly related to the Young's modulus of the material used, independent of the design of the prosthesis.

Biomechanical Phenomena↗
PubMed1990

[Excision of the lunate bone in Kienboeck's disease. Report of 17 cases].

We have performed excision of the lunate in 17 cases (partial excision of the lunate in two cases and total excision of the lunate in 15 cases) for the Decoulx stage III Kienböck's disease with an average follow-up of 11 years 7 months. Excellent and good results were obtained in 11 cases ont of 17 (65 per cent). After partial excision of the lunate, the shape of the lunate was conserved. After total excision of the lunate, the rearrangement of the remaining carpus maintained mobility and satisfactory force. Excellent and good results were obtained for pain in 14 cases out of 17. Total excision of the lunate gave poor results for the three heavy manual workers out of 12 manual workers after long-term follow-up.

Adult↗
PubMed1990

A comparative experimental study of vascularized and nonvascularized nerve grafts.

In order to compare vascularized and nonvascularized nerve grafts in a normal bed, 96 median nerve grafts were performed in rabbits. The median nerves were grafted in situ bilaterally, whether vascularized or nonvascularized. The length of the grafts was 2 cm, 4 cm, or 6 cm. A morphometric study was performed eight weeks and 24 weeks after the operation. No significant differences were found between vascularized and nonvascularized grafts at the same levels of nerve grafts. However, significant differences between vascularized and nonvascularized grafts were found for 4-cm and 6-cm grafts at eight weeks, and for 6-cm grafts at 24 weeks postoperatively, comparing the proximal normal nerve segments with the nerve segments distal to the nerve grafts.

Animals↗
PubMed1990

Alumina-on-alumina hip replacement. Results and survivorship in young patients.

Total hip replacement using an alumina head and socket and a titanium alloy stem is evaluated in a series of patients under 50 years of age. Between April 1977 and December 1986, 86 such replacements were performed in 75 patients, but mainly because patients had difficulty travelling from Africa, only 71 hips were followed up adequately; of these, 56 were primary procedures and 15 revisions. Survivorship analysis showed that 98% of the prostheses were retained for 10 years. On clinical and radiological examination 51 of the 71 hips were stable and acceptable, 15 had radiological changes on the acetabular side, and one on the femoral side; four other cases had clinical and radiological changes suggesting impending failure, possibly because fixation of the socket was inadequate. There were no differences between the results of the primary procedures and those of revisions. In these young patients, the results seem better with alumina-on-alumina hips than with other varieties, possibly because of their remarkably low wear.

Adolescent↗
PubMed1990

[Total hip prosthesis in patients less than 50 years of age. Value of ceramic materials].

87 consecutive cases of sealed total hip prosthesis with an alumina/alumina friction couple, placed in 76 patients less than 50 years old, have been studied. The surveillance period ranged between 2 and 13 years for 74 of them. 51 have been followed over more than 5 years, 10 have been lost out of sight and 3 died. 5 failures are to be deplored, one by fracture of a 22 mm ceramic head, the normal size in this series being 32 mm; the 4 others occurred after 6, 6, 10 and 11 years and are the consequence of a cotyloid loosening. Compared to the other series in literature concerning young patients and therefore those considered to be "at risk", the results obtained are better, especially if the high number of cases re-operated upon in this series (18 prosthesis exchanges out of 87) is taken into account. The actuarial method of Kaplan Meier gives a probability of 94% of keeping the prosthesis for 8 years. It is undoubtedly the quality of the design of the titanium femoral stem and especially the small amount of erosion scraps produced by the alumina/alumina couple which explain this result. The hip replacement must however remain an exceptional indication in a young subject.

Adult↗
PubMed1989

Comparison of coral resorption and bone apposition with two natural corals of different porosities.

Previous studies showed that natural coral implanted into bone tissue was gradually resorbed and progressively replaced by newly formed bone. The objectives of this study were to compare the fate of two Madreporian corals, Porites and Acropora, after implantation during 1 and 2 months into sheep and pig long bones. These materials are identical in composition (CaCo3) but differ in volume (49 +/- 2%, 12 +/- 4%, respectively) and mean size (250 vs. 500 microns) of porosities. The non-decalcified histological slices were observed under light microscopy. Implant resorption and new bone formation were quantified through an automatic image analysis system. Quantitative results showed that the larger the porosity volume, the greater was the coral resorption as well as the new bone apposition. Large differences were found between the two animal species. Histological findings were identical to those previously reported: implants were resorbed and progressively replaced by newly formed bone. Coral was found to be an osteoconductive biomaterial which acted as a scaffold for a direct osteoblastic apposition and consequently could be an interesting alternative to bone auto-, allo-, or xenografts.

Animals↗
PubMed1989

The evaluation of bone remodeling about orthopaedic implants with ultrasound.

Total hip arthroplasty causes biomechanical changes in the normal femur, including a redistribution and concentration of stress. These mechanical alterations in the femur cause local remodeling and resorption that affect the geometry and mechanical properties of the bone. Two complementary ultrasonic techniques were used to study the local adaptive remodeling of bone due to prosthesis implantation. An ultrasonic wave propagation technique was used to determine elastic properties and a new scanning acoustic microscope (SAM) mapped the acoustic impedance profile of each section. The effects of the implantation of two types of hip prostheses, an uncemented bipolar prosthesis with an Austin-Moore type stem and a cemented Charnley prosthesis, were investigated. Both prostheses had a detrimental effect on local elastic properties as determined by acoustic velocity measurements. The SAM system provided information about local inhomogeneities in bone properties not obtainable by any other means. The acoustic impedance maps highlighted bone resorption and bone remodeling on a microstructural level.

Aged↗
PubMed1989

[Results of surgery of nerve trunks in the treatment of post-traumatic brachial plexus paralysis].

Between 1972 and 1985, 256 patients with a brachial plexus injury were operated on in our institution. One hundred fifty-nine post-traumatic injuries, with a minimal follow-up of 2 years for partial palsies and 3 years for complete palsies were reviewed. Clinical examination is particularly important, and CT scan combined with myelography and more recently Magnetic Resonance Imaging ensures exact assessment of the lesions. The operative procedure is described, depending on the level and the number of injured nerve roots. Eighty-six fascicular grafts, 9 trunk grafts and 35 nerve transfers were performed. In 40 cases a neurolysis only was performed. Results were analyzed: at follow-up a motor and sensory recovery was observed in 70% of cases allowing to relieve the pain and to improve the function of the limb. The operation must therefore be performed at the appropriate time according to the most appropriate procedure depending on the number of usable roots. Secondary palliative transfers also help to improve function.

Adolescent↗
PubMed1989

[Magnetic resonance imaging in paralysis of the upper limb of traumatic origin].

We have used magnetic resonance imaging in addition to the other imaging techniques for the examination of 31 patients with traumatic upper limb paralysis. The therapeutic indications of traumatic brachial plexus paralysis depend on the early and precise assessment of the lesions. Computed tomography with a contrast injection at a lumbar level opacifying the subarachnoid spaces provides a morphological study of the canal, spine and nerve roots and of container-contents relationships. In our experience, the diagnostic reliability for the detection of intraspinal radicular lesions is 86%. A study in all 3 spatial planes is possible with MRI with T1- and T2-weighted or gradient echo sequences. The reliability of the technique for the diagnosis of meningoceles in the detection of nerve root avulsion is similar to that of CT (85%). The excellent spatial resolution and natural high contrast allow following the nerve roots in their extraspinal course and determining the site of nerve trunk rupture (50%). The use of oblique and double-obliquity sections should yet improve these results. These first results lead us to proposing magnetic resonance imaging for the exploration of traumatic lesions of the brachial plexus. This nonagressive, more precise and more complete assessment of the lesions certainly has a significant influence on therapeutic choice.

Adolescent↗
PubMed1988

The use of dense alumina-alumina ceramic combination in total hip replacement.

The purpose of this article was to review the laboratory and clinical performances since 1970 of a total hip prosthesis using alumina-alumina combination. The chemical and physical properties of dense alumina ceramic were studied in relation to biocompatibility, mechanical strength, and surface properties. Through the examination of 35 retrieved implants, it was found that the long-term success of alumina-alumina total hip replacement depends on both the ceramic microstructure (small grain size with uniform distribution, minimum porosity, absence of inclusions) and implant geometry (sphericity deviation +/- 1 micron, radius tolerance between components 7-10 microns). Alumina component wear and fractures have disappeared with the use of high-performance materials and severe manufacturing quality control. Examination of human biopsies from well-fixed prostheses showed that alumina particles deposits increase with time with only a low-grade macrophagic reaction. When loosening occurred, an inflammatory reaction appeared; this reaction was less striking than with loose metal-polyethylene prostheses, however. The long-term behavior of cementless alumina cup fixation depends upon initial positioning and stability; survivorship analysis of the cemented ceramic cups showed an 88% survival probability after 8 years with a 1.6% average annual probability of revision. The percentage of surviving was 100% after 8 years in patients who were less than 50 years old. Aseptic loosenings occurring at the cup-cement interface were assumed to be related to stress protection secondary to the high rigidity of the ceramic leading to a weakening of the spongious bone supporting the cement mantle. Good bone stock quality as well as high-quality ceramic appear to be the prerequisites for durable fixation of alumina sockets.

Aluminum↗
PubMed1988

A reflection scanning acoustic microscope for bone and bone-biomaterials interface studies.

A relatively simple scanning acoustic microscope (SAM) that operates in the reflection mode has been constructed. The system uses a 20 MHz spherically focused transducer, acting both as transmitter and as detector, to obtain acoustic impedance information on a thin surface layer at a maximum resolution of approximately 100 micron. The specimen is mounted on an X-Y driving system (precision, 5 micron) under computer control in order to scan a grid of 256 x 256 points across areas ranging from 6.5 to 1300 mm2. An algorithm is used to reference the data against standards; specially developed software provides for pseudo-color mapping, three-dimensional images, zooming to 16 x magnification, contouring, and single line profiles of the data. The system has been used to determine inhomogeneities in surface acoustic properties of mineralized tissues and implant materials, in many cases as a complement to using ultrasonic wave propagation techniques to measure the bulk anisotropic properties.

Adult↗
PubMed1988

Role of stem design and material on stress distributions in cemented total hip replacement.

The risk of fatigue fractures of the femoral stem in a cemented total hip arthroplasty can be minimized by either increasing the stem cross-section and/or using a very high strength alloy. The object of this study was to compare important mechanical characteristics of five selected stem designs, differing in configuration and material (stainless steel, cast chrome cobalt alloy, nickel based alloy and titanium alloy). The stain pattern on the stem was analysed in a 3-point-bending jig and also after cementing it into cadaver femurs. Regardless of stem type or test method, the typical tensile stress distribution on the lateral stem was a bell shaped curve. For the cobalt-chrome and stainless steel stems, the larger the stem the lower were the stem stresses and the stress gradient, and the higher was the factor of safety. However, the factor of safety was increased even further by the use of super alloys such as MP35N and Ti6Al4V. In addition, Ti6Al4V alloy allowed the use of larger and stronger stems without the extra penalty of rigidity, which was enforced by either the steel or cobalt based alloy.

Biomechanical Phenomena↗