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At least 1,333 records · Page 74Linked to original sources
PubMed1990

Dynamic stress response of the implant/cement interface: an axisymmetric analysis of a knee tibial component.

To determine the adverse effects on the implant/cement interface stresses caused by a dynamic load on the implant, an axisymmetric dynamic finite element analysis was performed for an idealized knee tibial component assuming perfect bonding at the interface. The component, consisting of a metal plate with a central stem, was subjected to a compressive load that varied with time as a terminated ramp function. At first, the reliability of the interface stress predictions was assessed by computing the effects of a number of method-related parameters, viz., the finite element mesh density, the assumed bone properties. Analysis was then performed considering the stem length, cement mantle thickness, and the type of implant metal as design variables. The analysis predicts high-frequency (600 Hz) stress oscillations of significant amplitude at those locations of the interface that are also subjected to high static stresses: near the stem-plate junction and the stem tip for normal stress, and at the stem tip for shear stress. However, the predicted stress amplitude has been found to be particularly sensitive to the assumed rise time of the input load function. With a rise time of 2.0 ms, an input condition considered to be severe enough to represent the most vigorous dynamic activity, the maximum stress augmentation, because of stress oscillations, is predicted to be less than 25%. In general, the design variables have been found to affect the static stresses much more than the dynamic ones. It has been concluded that for the cases studied, dynamic effects are relatively small and a static analysis is sufficient to characterize the interface stress condition.

Aged↗
PubMed1991

[Total prosthesis after ankylosis of the hip joint. Report of 22 cases].

Between 1968 and 1987 we carried out a total replacement arthroplasty on 22 hips which were either ankylosed or had previously undergone arthrodesis. The hips were revised because of pain due to pseudoarthrosis or malposition, pain in the other joints such as the lumbar spine, the ipsilateral knee or the contralateral hip, fractures about the hip, or professional disability. Significant functional and subjective improvement was obtained. The revised hips were painfree, stable and had an average range of flexion of 70 degrees. Pain in other joints was improved if their degenerative changes were moderate, but many required further procedures. Revision of a hip arthrodesis to a replacement arthroplasty is a worthwhile procedure in suitable cases.

Adult↗
PubMed1991

Long-term reaction of the osseous bed around silicone implants.

Between 1970 and 1987, 94 patients received 208 silicone implants at the Department of Orthopaedics, University Hospital, Vienna. Of these, 62.5% were clinically followed up. At follow-up after an average of 116 months, the implant bed was found to be intact in only 41% of cases; in all others we observed lyses around the implant and cysts even in bones at a distance from the operated joint. Histological findings obtained from revision arthroplasty showed a homogeneous picture with foreign-body granulation tissue. These changes were usually clinically inconspicuous and had little effect on patients' subjective well-being. Despite the low discomfort caused, however, the use of such implants in only recommended in critical and severe causes because of the progressive destruction of the osseous bed during the time the implant is in the body.

Adult↗
PubMed2005

[Endoprosthetic replacement of hallux rigidus].

Replacement of the first metatarsophalangeal joint (MTP1) is still controversial when compared with MTP1 fusion in treating hallux rigidus and other disabling conditions of the MTP1 joint. Prospective studies concerning endoprosthetic replacement of the MTP1 joint are not available yet. Nevertheless, better understanding of biomechanics and tribology show favour towards total endoprosthesis. Some currently available models are described (Toefit-Plus, Roto-glide, ReFlexion, Bio-Action, Moje). Furthermore the authors report their results with 30 Toefit-Plus total endoprostheses. Five complications (16.6%) included two dislocations of total prostheses and three bone fissures. In 3 of 14 cases (21%) with a 3-year follow-up, revision surgery was necessary (subluxation, persistent pain, recurrence of hallux rigidus). Of 11 cases (63%) with a 4-year follow-up, 7 revealed secondary loss of range of motion. A more aggressive postoperative treatment with early weight bearing and regular push-off of the first ray is recommended. Based on our results, MTP1 replacement should be indicated restrictively (hallux rigidus, no experiments in cases of important first ray insufficiency).

Arthrodesis↗
PubMed2001

[Endoprosthetic surface replacement of the head of the humerus].

The concept of an endoprosthetic surface replacement of the humeral head differs from that of stemmed endoprostheses. It is the replacement of the destroyed joint surface with reconstruction of the normal anatomy and minimal bone resection. The aim of this prospective study was to evaluate the short-term results of a newly developed cup arthroplasty (Durom-Cup) for the humeral head. In a prospective study, 39 patients with 46 Durom-Cups were evaluated preoperatively and every 3 months postoperatively. The average follow-up was 15 +/- 9 months. The group included 28 shoulders with rheumatoid arthritis, 15 joints with osteoarthritis, and 3 humeral head necroses. The Constant-score and SAS-function score were used. The Constant-score increased from 20.25 +/- 9.06 points preoperatively to 46.62 +/- 14.05 at 3 months, to 48.11 +/- 14.49 at 6 months, and to 55.25 +/- 11.6 at 9 months postoperatively. The Constant-score stayed at this level during further follow-up and was 55.81 +/- 16.31 at 12 months postoperatively. The best results were seen in the group of humeral head necroses with a Constant-score of 71.0 +/- 12.2 compared to 54.66 +/- 13.89 in the group of osteoarthritis and 56.78 +/- 13.33 in patients with rheumatoid arthritis at 12 months postoperatively. The results with the Durom-Cup are encouraging so that cup arthroplasty seems to be a good alternative to stemmed prostheses. The main advantages of the humeral head resurfacing are the bone-preserving fixation and the relatively simple surgical technique.

Aged↗
PubMed1988

Composites for bone replacement.

The application of synthetic materials for bone replacement is now well established, but it is recognized that mechanical compatibility, as well as biocompatibility, of the tissue and implant is required if stress shielding and consequent bone resorption is to be avoided at areas of fixation. The development of materials analogous to the natural tissue for longer term implantation is discussed, with particular reference to hydroxyapatite reinforced polymers.

Biocompatible Materials↗
PubMed1991

Correction of ulnar drift during silastic metacarpo-phalangeal joint arthroplasty.

In previous published accounts of silastic replacement arthroplasty of the M.P. joint of the finger in rheumatoid disease, dynamic splintage has been used for up to six months after operation to ensure correction of ulnar drift. We have investigated two methods of surgical correction in a prospective trial in consecutive patients. No dynamic splintage was used. Both resulted in correction of ulnar drift from an average of 34 degrees (maximum 92 degrees) to 8 degrees (maximum 32 degrees) in 86 fingers. The two methods both corrected ulnar drift well, but crossed intrinsic transfer gave a better range of active movement and is recommended as an alternative to dynamic splintage.

Activities of Daily Living↗
PubMed1993

Long-term follow-up of Swanson's silastic arthroplasty of the metacarpophalangeal joints in rheumatoid arthritis.

77 patients with rheumatoid arthritis, 62 female and 15 male, underwent metacarpophalangeal joint arthroplasty on 375 joints using the Swanson design silicone rubber spacer between 1976 and 1985. Retrospectively, 48 of these patients were evaluated by postal questionnaire and 35 of them also underwent objective assessment at intervals ranging from five to 14 years post-operatively. Objective variables recorded included range of active motion, recurrence of ulnar drift and radiographic appearances. Both in the early and late stages, the vast majority of patients were satisfied with the outcome, with abolition of pain, correction of deformity and improved range of motion. There was some loss of mobility with time. However, functional improvement was maintained in the majority. Complication rates compare favourably with other reported series and no case of silicone synovitis was diagnosed. We agree with previous studies that the procedure is useful for lasting relief of pain and enhancement of a patient's sense of well-being and is associated with few complications.

Arthritis, Rheumatoid↗
PubMed1993

Metacarpophalangeal joint arthroplasty based on the osseointegration concept.

The osseointegration concept has been used for fixation of 68 MP joint endoprostheses in 31 patients operated on at the Department of Hand Surgery, Malmö General Hospital during the period 1988-1992. The indications were rheumatoid arthritis (50 joints), primary osteoarthrosis (three joints), post-traumatic osteoarthrosis (three joints), post-traumatic osteoarthrosis (five joints), post-infectious osteoarthrosis (seven joints) and joint deformities secondary to spastic conditions (three joints). The average follow-up time was 2.5 years (6-54 months). The surgical procedure included resection of the joint followed by introduction of screw-shaped titanium fixtures into the bone marrow cavities of the metacarpal and the phalangeal base. Rheumatoid cases usually required grafting of cancellous bone and marrow from the iliac crest. At the same time a flexible constrained silicone spacer was connected to the titanium fixtures in such a way as to allow later replacement of the spacer if accessory. The average active range of motion (ROM) was 57 degrees in the rheumatoid cases and 50 degrees in all cases. Radiological and clinical osseointegration occurred in every case, and there were no clinical signs of loosening. In four cases (6%) there was a fracture of the joint mechanism. Patient satisfaction was high, with pain relief, increased range of motion, improved hand function and good cosmetic appearance.

Adult↗
PubMed1990

Free vascularised toe joint transfer for reconstruction of the metacarpo-phalangeal joint.

Two single and two double free vascularised joint transfers from the foot to hand have been undertaken in four patients over a period of four years. All were to replace metacarpo-phalangeal joints in young patients in whom the use of prosthetic devices was considered unsuitable. All the transfers were successfully completed, but one failed late in the second post-operative week due to sepsis. The results of the remaining three transfers compare favourably with prosthetic arthroplasty and continue to improve. Donor site morbidity in the foot has been minimal and is reviewed.

Adolescent↗