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Biomedical subjects

J Witvoet

Publications and source records attributed to J Witvoet.

At least 37 records · Page 2Linked to original sources
PubMed1991

[Conflict between psoas and total hip prosthesis].

This conflict leads to a chronic irritation of the psoas by the antero-medial part of the cup, but it has been poorly described in the past. A study of six patients suffering from this trauma, and who were re-operated revealed that the muscle was worn thin in front of the prominent cup. In the case of 4 of the 6 patients pain had started to occur shortly after total hip replacement. The following symptoms were noted among all 6 patients: pain was suffered during flexion--extension movements--walking up stairs--arising from a chair. Pressure on the medial part of the groin was painful, especially during active elevation of the lower limb. Passive mobility was normal and painless. Psoas bursitis was observed in three cases. The main cause of this conflict is the protrusion of the cup beyond the antero-medial edge of the acetabulum; this protrusion may be either due to a bone graft or a bit of cement, but most often an acetabular insufficiency (congenital dysplasia) favors the formation of this anterior overhang. The spiral cup screwed into the bone can be especially aggressive when it protrudes. Treatment includes the resection of the overhang, but post-operative results will be uncertain unless the resection is really complete. In the case of 4 patients the results of such an intervention were only mild to poor. This problem can be avoided by proper care and preventive measures in the original replacement avoiding all projections beyond the anterior edge of the acetabulum--cup, bone graft, cement, especially if dysplasic.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
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

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

[Knee prosthesis in 1990. Apropos of a 15 years' experience].

Knee prostheses have been greatly refined over the past ten years. A range of prostheses with various designs are currently used. On the basis of their 15-year experience, the authors assess the role of the various prostheses. Among partial prostheses, the femoropatellar prosthesed have a restricted place and are reserved for isolate degenerative diseases of the femoropatellar joint without femorotibial involvement: 34 such prostheses have been used by the authors and the department of professor J.H. Aubriot in Caen. About 75% of the results are satisfactory, with a follow-up in time of more than 8 years in 6 of these cases. Single-compartment prostheses are used in degenerative disease on an angular deviation, condylar necrosis or post-traumatic lesions, as far as one compartment only is affected. The authors have inserted 115 "Lotus" uni-compartment prostheses at Saint-Louis hospital. 75.6% of these have very good or good results maintained in time, as 72% of the 32 prostheses still produce satisfactory results after 5 years or more. The greatest progress was made above all for total prostheses replacing all the compartments of the knee. Hinge prostheses now have only rare indications as first-intention prostheses due to the immediate vital risks and to the high percentage of suppuration and long-term loosening. Sliding prostheses have taken an increasingly dominant place. The authors used Insall's total condylar prostheses, which do not preserve the posterior cruciate ligament, until 1983. 45 prostheses were followed up for 1 to 10 years, showing 71% of very good or good results.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
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

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↗
PubMed1987

Spherocylindric (Luck) cup arthroplasty for osteonecrosis of the hip.

Osteonecrosis (ON) in young adults is a serious condition causing pain and functional disability. Thirty-eight hips with ON were treated, beginning in 1972, with a spherocylindric cup (SCC) derived from the original Luck. The mean follow-up time was six years, 11 months (minimum, one year; maximum, 12 years). The overall results, using the Merle d'Aubigne grading system, were excellent in four, very good in nine, good in nine, fair in one, and failure in seven. No acetabular protrusio was observed. The seven failures were associated with deep infection in one case and unsatisfactory technique in three. One failure was unexplained, except that the ON was Grade IV. Two failures occurred in one patient with predisposing factors, such as hyperlipidemia, hyperuricemia, and exogenous hypercortisonism. Although the results are not as satisfactory as those of total hip arthroplasty (THA) with respect to relief of persistent pain, some patients remain stable with time even after more than ten years. With correct indications and good surgical technique, SCC arthroplasty is a justifiable alternative to THA in young adults.

Adolescent↗
PubMed1985

Treatment of chronic anterior knee instabilities with combined intra- and extra-articular transfer augmented with carbon-PLA fibers.

In the treatment of old chronic anterior knee instabilities by anterior cruciate ligament (ACL) insufficiency, isolated reconstruction of the ACL is insufficient because of an associated stretching of the lateral capsule and lateral collateral ligament. A combined intra- and extra-articular transfer (consisting of the central one-third of the patellar tendon, the prepatellar tissue, and the central one-third of the quadriceps tendon) is necessary to repair ACL instability. Augmentation of the autogenous transfer with polylactic acid-coated carbon fibers has several advantages. It improves the transfer's strength by reinforcing its weak zones; gives initial strength during graft remodeling and vascularization, thus avoiding cast immobilization; and allows early active rehabilitation and possibly return to sports activity. The surgical technique is based on biomechanical and biologic principles. The transfer remains attached to the tibial tubercle, passing through a tibial tunnel, through the intercondylar notch, behind the lateral femoral condyle in a bony groove, then on the lateral aspect of the condyle, beneath the lateral collateral ligament, and ending close to Gerdy's tubercle. The preliminary results in 30 patients are encouraging. The subjective and objective results are similar to those previously obtained with nonreinforced methods of repair, except that there is an early return to normal activities.

Carbon↗
PubMed1985

[Results of the surgical treatment of chronic external laxity of the ankle by resetting capsular ligamentous tension].

The authors review 12 patients operated for tibio-tarsal instability and summarize the effects of ligamentous sections of the capsular-ligamentous plane of the lateral part of the ankle and the importance of the anterior peroneotalar fascia. In cases of tibio-tarsal instability, the authors propose a lateral ligamentous re-tension plasty with trans-osseous reinsertion and they analyse the results of this operation in a series of 13 operated ankles which were followed clinically and radiologically. The essential criterion of evaluation was a return to the same level of sports activity (7 very good results, 3 good results, 2 moderate results and one failure). The overall favourable results suggest that this technique can be indicated in a number of rare cases: sportsmen with significant disability after failure of treatment by proprioceptive re-education. In conclusion, the authors stress the value of preventative treatment of sprained ankles, which should prevent the development of instability.

Adolescent↗
PubMed1984

[Benign osteoblastoma of the hand. A case report. Review of the literature].

One case of benign osteoblastoma, localized on the proximal phalanx of right thumb is reported. Three points are emphasized: the low frequency in the hand, only six observations are reported in the English literature, one by Jaffe (1932) and four by Lichtenstein (1964) and one from Mosher and coll. (1978). The non-specificity of the signs and X-ray are must consider chondroma, giant cell tumor, chondrosarcoma or aneurysmal cyst. The lesion is benign and so the treatment must be conservative.

Adult↗
PubMed1984

[Phosphorus metabolism in a case of tumoral calcinosis].

Hyperphosphataemia with levels of 65 mg/l was found in a black African aged 20 with a 10-year history of tumour calcinosis. Levels of blood calcium, plasma ionised calcium, serum alkaline phosphatase, 24-hour urinary calcium and phosphate were all normal, as was renal function. Tubular phosphate reabsorption (TmP) was greater than 90 mg per litre of glomerular filtrate (N = 22-42). Levels of circulating parathyroid hormone, nephrogenic cAMP and serum vitamin D metabolites [25 OH D3, 24,25 (OH)2 D3 and 1,25 (OH)2 D3] were normal. The TmP fell by 36% on exogenous PTH stimulation (N = 30.25 +/- 6.7), and by 7.9% 120 min. after injection of acetazolamide. Our results confirm the conclusions of recent studies: patients with tumour calcinosis have disordered renal phosphate excretion with normal PTH secretion, normal PTH action on the renal tubule and normal vitamin D metabolism. In fact in these hyperphosphataemic patients, circulating 1,25 (OH)2 D3 levels would be expected to be low, whereas they were normal in our patient. An attempt at treatment with acetazolamide and phosphate chelating agents gave no significant results.

Acetazolamide↗
PubMed1983

[Analysis of the mechanical function of the cruciate ligaments in antero-posterior knee laxity. An in vitro study].

In order to evaluate the contribution of both anterior (ACL) and posterior cruciate ligaments (PCL) in antero-posterior knee laxity, mechanical tests were performed on 31 fresh-cadaver-knees ranging from 20 to 68 years old. The joints flexed at 90 degrees in a mounting apparatus were placed in a testing machine with the tibia fixed in neutral rotation. The load-displacement curves were then analyzed. The results showed that the tensile strength of the ACL decreased greatly with age whereas its stiffness measured during anterior drawer test remained independent of age and sex. Successive resection of the antero-medial (AM) and postero-lateral (PL) bundles of the ACL demonstrated the AM bundle to be the major structure involved in the limitation of tibial displacement in the anterior drawer test. The amount of tibial shift during the anterior drawer test did not reflect the condition of the ACL, while its resection always induced a strong and significant drop in anterior knee stiffness. Dissection of the PCL was always followed by significant posterior tibial displacement during the posterior drawer test of over 10 mm, which did not permit the experimental apparatus to quantify the posterior load displacement relationship.

Adult↗