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PubMed1993

[Reconstitution of femoral bone stock in loosening of total hip prosthesis].

Between 1986 and 1990, 18 femoral loosenings were treated for severe destruction with an original technique. The average age of the 16 patients was 62 years. Two hips had a second loosening. According to the score of Merle d'Aubigné the pain was evaluated at a mean of 2.1 preoperatively. The gait was scored 1 in half of the patients. The prostheses were trochanterodiaphyseal in 14 patients and self-locking in 4 patients. The aim of this technique was: 1. to bridge the diaphyseal bone loss by healthy cortical bone, for good primary stability, 2. to reconstruct the bone stock with fragmented allografts, 3. to avoid mixing grafts and cement, by using an interposed titanium net. The frequent postoperative complications (2 fractures, 4 diaphyseal bursts, 6 false channels) occurred during extraction of the cement. Weightbearing was allowed after an average of 2 months postoperatively. With a follow-up of 33.4 months, the functional result was excellent in 11 cases (score 17 and 18). No massive resorption of the endomedullary graft was observed; trabeculation of the graft was seen in 8 patients. No migration of the prosthesis was noted. In later years, there will be a problem of extracting the rod, and there exists a risk of stress shielding, due to the length of the stem.

Adult↗
PubMed2003

The computer simulation of wear behavior appearing in total hip prosthesis.

Computer algorithms are proposed for the estimation of wear appearing in artificial hip joints using finite element analysis based on the modified Archard's wear law, contact features and an analogue wear process. A pin-on-disk plate experiment is reconstructed to assess the efficiency and validity of the algorithms proposed here. Through the successful verification of wear depth and volume loss of the pin-on-disk plate as well as the artificial hip joint, the current algorithms provide significant agreement with experiments, clinical measurements and numerical calculations and are shown to be both valid and feasible. Further investigation into the effect of femoral heads with various sizes suggests that the larger femoral head may induce larger wear volume but gives a smaller wear depth and that wear depth and volume loss are apparently nonlinearly related to the femoral head diameter. It is shown that the current algorithms are useful and helpful in understanding wear behavior for alternative or new designs of artificial hip joints and even for other analogous structures.

Arthroplasty, Replacement, Hip↗
PubMed1990

K-edge digital subtraction arthrography of the painful hip prosthesis: a feasibility study.

K-edge energy subtraction radiography is a method for detecting the presence of iodinated contrast material by subtracting two digital radiographs produced by X-ray beams with energies above and below the iodine K edge. We performed a feasibility study on the application of K-edge energy digital subtraction arthrography (KEDSA) to painful hip prostheses. During arthrography, loosening of the prosthesis is implied if contrast material is seen dissecting around the prosthesis, an often difficult detection task because of adjacent prosthesis metal or cement. In conventional arthrography a preliminary mask image is thus used from which films obtained after injection of iodinated contrast material are subtracted. Movement by the patient during this process may preclude subsequent subtraction. With KEDSA, since multiple image pairs may be obtained after the injection of contrast material, the problem of patient motion is virtually eliminated. A conventional X-ray tube operating between 55 and 65 kVp was alternately filtered by iodine and cerium filters to produce the KEDSA images. The apparatus was capable of producing a subtracted image within 3 sec. The technique was applied to phantoms and to six patients immediately after hip arthrography that had been positive for prosthesis loosening. Although of lower spatial resolution, the KEDSA images were, in all cases, positive for loosening in a pattern consistent with the conventional arthrographic images. KEDSA was shown to be successful in detecting extraarticular contrast material. During a single study, subtraction in various imaging planes as well as postexercise subtraction imaging can be accomplished-techniques not heretofore possible in routine subtraction arthrography.

Aged↗
PubMed1983

[Treatment of femoral neck fractures using a total hip prosthesis].

From October 1. 1977 to December 1. 1982 106 patients suffering from fractures of the femoral neck (n = 75) or necroses of the femoral head and nonunions of the neck fracture respectively (n = 33) underwent total hip replacement by TEP (type Müller-Charnley). The results obtained were much better in comparison to other methods of treatment: less complications, shortening of in-hospital stay (average 21.1 days) and satisfactory till good late results in 82.8%. The mortality rate came up to 13.9% (fractures: 20.0%, necrosis of the head and nonunion: 0.0%). Concerning complications we observed wound infections 0.9%, dislocations 1.9%, twice fractures of the thigh bone, twice loosening of the shaft of the prosthesis and once its fracture. The authors emphasize that in spite of the good results obtained for the time being total hip replacement for fractures of the femoral neck should be reserved to special wards.

Female↗
PubMedDate not supplied

[Ideal total hip prosthesis in 1993].

Although it is a hazardous adventure to define what is an ideal in any field, it would appear that there is a certain consensus about total hip prostheses. The fundamental principle of the total hip replacement was based on the articulation of a spheric segment, a mobile head contained in a hemispheric non-retaining element. To date, the first material is a titanium in a alloy containing 6% aluminum and 4% vanadium. The second material facing the titanium is polyethylene or alumine. Thus the joint couple could be "polyethylene-metal", or "polyethylene-alumine" or even "alumine-alumine". The hemispheric element can be a massive piece of polyethylene or formed by a peripheral metal (an open hemisphere) filled with the joint surface, itself made of polyethylene. This solution offers the possibility of changing the prosthesis in case of wear without interrupting the implant-bone contact. The first type is cemented to the bone with methyl polymethacrylate. With the second, the metallic part need not to be cemented and can be fitted to the bone by simple pressing. Several points are essential in the femoral piece. It should include a removable head so the length of the neck can be adjusted. It must fill the medullary canal as closely as possible and fill the methaphyseal space. It is fixed by a self-fitting system leading to stable secondary long-term fixation-a porous covering, sometimes with hydroxy apatite can also be useful. In certain cases it must be cemented, although the cement must only play the role of adaptation.(ABSTRACT TRUNCATED AT 250 WORDS)

Biocompatible Materials↗
PubMedDate not supplied

[The cement free hollow hip prosthesis to reduce intramedullary pressure].

PURPOSE: A hollow cementless femoral stem has been developed to reduce intramedullary pressure and fat embolism during implantation. METHODS: In a prospective randomized clinical study, cementless hip stems (ALPHA-FIT) were implanted in 42 patients (24 women, 18 men, mean age: 65.9 years). In Group I (n=21) a solid standard stem was used. In Group II (n=21) a modified hollow stem was implanted with vertical and longitudinal communicating drill holes opening at the implant surface. During surgery the intramedullary pressure was measured by a cannula fixed distally. RESULTS: During stem insertion the mean pressure was 82 mmHg (minimum-maximum, 12-259 mmHg) for Group I and 27 mmHg (minimum-maximum, 0-48 mmHg) for Group II. This difference was statistically significant (t-test, p < 0.00076). The pressure measured in Group II was similar to the base pressure before opening of the intramedullary canal (mean 35 mmHg; minimum-maximum, 4-72 mmHg). In both groups higher pressures were found for opening of the canal, drilling with the smallest drill size and rasping. CONCLUSION: Using the hollow prosthesis, the intramedullary pressure could be reduced significantly. The higher pressures during preparation of the femoral canal need further research.

Adult↗
PubMed2006

Failure of the uncoated titanium ProxiLock femoral hip prosthesis.

UNLABELLED: New prostheses should be evaluated for stability and clinical performance. In a prospective randomized clinical trial, we implanted 22 titanium (Ti) and 20 hydroxyapatite-coated (HA) ProxiLock femoral hip prostheses during total hip arthroplasty in 42 patients. The patients were followed for 24 months with clinical, radiographic and radiostereometric analysis. Full weightbearing was allowed immediately postoperatively. One patient with a titanium stem was lost to followup. During the first two months, 34 of the 41 stems subsided and/or rotated towards retroversion, regardless of stem type. At the 24-month followup 35 of the 41 prostheses were either fully stabilized (16 HA and 11 Ti stems) or had clinical irrelevant migration (four HA and four Ti stems). Six Ti prostheses showed continuous migrations with maximums of 4.7 mm translation and 12.2 degrees retroversion; four of these were revised, the other two had no clinical complaints. CLINICAL RELEVANCE: The migration pattern we found indicates insufficient primary fixation of the ProxiLock stem in an immediate full weightbearing protocol. The HA coating improves the secondary stability of the prosthesis compared to the uncoated stem. Early migration is associated with an increased risk of possible future loosening and revision, and therefore we discontinued the use of this prosthesis. LEVEL OF EVIDENCE: Therapeutic Level I. See Guidelines for Authors for a complete description of levels of evidence.

Adult↗
PubMed1998

[Acetabular reconstruction using bone allograft in the revision of total hip prosthesis].

PURPOSE OF THE STUDY: Aseptic loosening of the acetabular component is the most worrying problem after hip arthroplasty. During revision surgery we prefer to rebuild a solid bony acetabulum close to the anatomy in which the implant will be cemented. On the basis of the first 48 acetabular reconstructions using deep-frozen bony allografts, we carried out a review of our results in a pathology which will surely increase in the future. MATERIAL: 48 hips were operated according to this technique. It has been possible to review 38 of them, with an average follow-up of 7.3 years (extremes 5 years, and 9.6 years). The average age of the population at the time of surgery was 63 years. Two etiologies predominated: congenital hip dislocation sequelae and primitive hip arthritis. In 10 cases of massive deterioration, a Muller's ring was used to stabilize the allograft. METHODS: The results were analyzed at 6 months, 2 years, 4 years, and at maximum follow-up, clinically, according to Merle d'Aubigné grading system. Radiologically, Ranawat's criteria were used to assess the re-centering of the reconstructed hips. The development of radiolucent lines and implants migration were also assessed. RESULTS: Clinically, the patients' comfort was always improved by pain relief. Radiologically, average acetabular upward migration of 5 mm and medialisation of 3.5 mm were observed. 24 hips presented radiolucent lines. 19 radiolucent lines were below 2 mm. 5 were greater than 2 mm and leaded to loosening. In 4 of these 5 cases of radiolucent lines, there were acetabular migrations with failure. The radiological image remained stable afterwards. In these cases there was a real loosening, necessitating further surgery. In all cases, partial resorption of the graft was observed. DISCUSSION: Study of our first 38 cases shows that bony allograft and cemented acetabulum, sometimes including an armature, is one possible solution to the problem of difficult acetabular reconstructions. However, with an average follow-up of 7.3 years, we already have 5 (13 per cent) aseptic acetabular loosening, of which one has been operated on. Radiological analysis of these does not question the allograft, but rather imperfect re-centering. Analysis of the good results, 33 (87 per cent) stable acetabulum indicates re-fixing in quasi-anatomical position, in conditions close to those of a first time arthroplasty, with the aid of perfectly stabilized bony transplants, and where contact with the receiver acetabulum is maximal. CONCLUSION: Our follow-up is one of the longest in literature. But with a migration rate already of 13 per cent, it is not yet sufficient for us to be permanently assured about the future of our patients, even if their age is greater and their activity less than those of patients having a first hip arthroplasty.

Acetabulum↗
PubMed1976

The chemical composition of circulating fat emboli released during total hip prosthesis.

Lipids of fat emboli released in the circulating blood of seven patients undergoing hip prostheses were compared with those of plasma, adipose tissue and bone marrow taken simultaneously. Similar in composition to bone marrow, fat emboli, as compared with plasma lipids, contain negligible amounts of free esterified cholesterol, a relative decrease of oleic acid and an increase of palmitic acid in triglycerides and a lower percentage of linoleic acid in phospholipids. The results of this study validate the theory that fat emboli originate from bone marrow in fractures of the long bone.

Adipose Tissue↗
PubMed2006

Morphological experimental study of bone stress at the interface acetabular bone/prosthetic cup in the bipolar hip prosthesis.

By calculating the tension and distortion of the elements composing the bipolar prosthesis under extreme conditions encountered in real life using a special post-processing program, we established the variation curves of the contact pressure at the hip bone-cup, armor-cup and cup-femoral head interface. By comparing the data obtained from all the examined cases, important conclusions were drawn regarding the influence of tension and pressure distribution on the structural integrity and biomechanics of the prosthesis, as well as the acetabular wear and tear, in order to assess its reliability. The experimentally determined tension and distortion status at the acetabular bone-metal armour interface, lead to the wear and tear phenomenon, which can be explained by three mechanisms and theories incompletely reflecting the overall process. The histopathologic study of the acetabular bone tissue using FEM (finite elements method) on surgically removed specimens will probably lead to the identification of a series of factors that could reduce the rate of the wear and tear process.

Acetabulum↗
PubMed1977

[Secondary intervention after hip prosthesis (author's transl)].

From 1965-1975 in the orthopedical Univ. Clinic Balgrist, Zurich, there were 177 reoperations after total hip prostheses necessary. In 91 replacements the interval between first and second operation was an average of 4.1 years, in 67 prosthesis-removements 2.1 years. The follow-up showed a relationship between bacteriological culture taken before and during operation and clinical results. The decision to change or remove the prostheses should be made on the positive or negative bacteriological results.

Aged↗
PubMed1986

[Computer-assisted design and production of a femoral hip prosthesis].

The authors believe that a better design of prosthetic femoral stem might reduce the incidence of loosening. They have developed a method to make a prosthesis precisely adapted to a patient. Two X-Rays, one antero-posterior and one lateral view are taken. Several bony points are precisely determined. The magnification of the X-Rays is calculated, using a metallic circular collar placed around the thigh. A computer analyses the X-Rays, bony points are numerated and the prostheses have a length, thickness and shape adapted to the patient's hip. A study of the pressures transmitted by the prostheses to the bone was made using geometrical models. Compared to conventional prostheses, a prosthesis made as an exact fit to the hip of the patient reduces the pressure applied on femoral cortex by two thirds. A prosthesis with a collar also allows reduction of pressure on the cortex by a degree of three to one. The personalized prosthesis obtained by the use of a computer appears to be a stage in progress towards a better fitting and more reliable prosthesis. Twenty five patients have been operated on with good short-term results.

Computers↗