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At least 739 records · Page 41Linked to original sources
PubMed1992

Sequential infection of silicone metacarpophalangeal joint arthroplasties resulting from skin breakdown.

We report a case of late multiple infected metacarpophalangeal silicone implants in a patient who had had replacement arthroplasty for treatment of rheumatoid arthritis. The patient had done well for 10 years after metacarpophalangeal joint arthroplasty when an implant infection developed. Over the next 4 years the remaining three implants on her dominant extremity also became infected necessitating their removal. The origin of the infections is thought to be the result of excessive and improper usage of the hand.

Arthritis, Rheumatoid↗
PubMed2000

Development of artificial articular cartilage.

Attempts have been made to develop an artificial articular cartilage on the basis of a new viewpoint of joint biomechanics in which the lubrication and load-bearing mechanisms of natural and artificial joints are compared. Polyvinyl alcohol hydrogel (PVA-H), 'a rubber-like gel', was investigated as an artificial articular cartilage and the mechanical properties of this gel were improved through a new synthetic process. In this article the biocompatibility and various mechanical properties of the new improved PVA-H is reported from the perspective of its usefulness as an artificial articular cartilage. As regards lubrication, the changes in thickness and fluid pressure of the gap formed between a glass plate and the specimen under loading were measured and it was found that PVA-H had a thicker fluid film under higher pressures than polyethylene (PE) did. The momentary stress transmitted through the specimen revealed that PVA-H had a lower peak stress and a longer duration of sustained stress than PE, suggesting a better damping effect. The wear factor of PVA-H was approximately five times that of PE. Histological studies of the articular cartilage and synovial membranes around PVA-H implanted for 8-52 weeks showed neither inflammation nor degenerative changes. The artificial articular cartilage made from PVA-H could be attached to the underlying bone using a composite osteochondral device made from titanium fibre mesh. In the second phase of this work, the damage to the tibial articular surface after replacement of the femoral surface in dogs was studied. Pairs of implants made of alumina, titanium or PVA-H on titanium fibre mesh were inserted into the femoral condyles. The two hard materials caused marked pathological changes in the articular cartilage and menisci, but the hydrogel composite replacement caused minimal damage. The composite osteochondral device became rapidly attached to host bone by ingrowth into the supporting mesh. The clinical implications of the possible use of this material in articular resurfacing and joint replacement are discussed.

Aluminum Oxide↗
PubMed1996

Mechanistic and morphological origins of ultra-high molecular weight polyethylene wear debris in total joint replacement prostheses.

The mechanistic and morphological origins of microscopic wear debris generated from UHMWPE articular surfaces in total joint replacement prostheses are investigated in this study. It was found experimentally that the molecular chain structure at the articulating surface of UHMWPE undergoes a re-organization process due to strain accumulation caused by surface traction. This molecular re-organization process creates a fibre-like surface texture that exhibits an anisotropic behaviour similar to a unidirectionally reinforced polymer composite. This composite responds to stresses favourably if loaded along the fibre axis but unfavourably if loaded off axis. Due to the very complex multi-axial motion/loading nature at the articular surfaces in total joint replacements, the stress tensors applied to each localized asperity contact area continuously change their directions and magnitudes. These changes in the localized stress field create an off-axis loading situation at each localized contact zone with respect to the orientation of the molecular chains. Depending on the off-axis angle, failure of the molecular structure occurs in three different ways: tensile rupture at very small off-axis angles, shear rupture at intermediate off-axis angles and transverse splitting at large off-axis angles. These failure mechanisms all produce similar fibre-like wear debris. However, the failure stresses differ significantly among the three modes. According to this molecular wear theory, the preferred polymer microstructure for optimal wear resistance would be a three-dimensionally strong network connected by covalent bonds between molecular chains. For UHMWPE, a three-dimensional molecular network can be created by radiation induced cross-linking. Experiments conducted on both gamma irradiated and unirradiated UHMWPE specimens using a linear wear machine and multi-axial joint simulators confirmed the validity of the molecular wear theory.

Biocompatible Materials↗
PubMed2004

Treatment of temporomandibular joint ankylosis by a modified fossa prosthesis.

BACKGROUND AND OBJECTIVE: Treatment of temporomandibular joint ankylosis is a challenge and suffers from a high incidence of recurrence. Although treatment of ankylosis has been tried as early as nearly 200 years ago, no single technique produced satisfactory results. An alternative technique and a modified spacer system are described in this paper. MATERIAL AND METHODS: Fifteen patients, nine of whom had unilateral and the remaining six had bilateral ankylosis were evaluated. Modified fossa implants were used in all cases. RESULTS: The highest incidence of ankylosis was observed in the 11-20 year age group (nine patients). Falls during childhood was the common aetiological factor. Eight patients had been previously operated upon. Postoperative interinsicial opening values were remarkably different from the preoperative ones and the long-term results were satisfactory. CONCLUSION: With continued research and development in the treatment of ankylosis, temporomandibular joint implants will become more predictable and reliable. This specially designed fossa implant seems to be promising in the treatment of TMJ ankylosis.

Acrylic Resins↗
PubMed1993

In vitro stability of an unconstrained total elbow prosthesis. Influence of axial loading and joint flexion angle.

Total elbow arthroplasty is often used to replace elbow joints that have been severely damaged by arthritis or trauma. A great disparity of designs exists, however, in currently available elbow prostheses. This study evaluated the intrinsic stability of one popular resurfacing implant, the Capitellocondylar (Johnson and Johnson Orthopaedics, Inc., New Brunswick, NJ) total elbow. The in vitro response of this unconstrained prosthesis to valgus-varus and supination-pronation loading was investigated using a materials testing machine. The influence of compressive loading and flexion angle on the intrinsic stability of the prosthesis was studied. The Capitellocondylar prosthesis was found to have little intrinsic constraint, relying on external forces for component stabilization. Dislocations were common at 111 N of compressive loading, while larger loads progressively stabilized the prosthesis. Joint flexion angle had little influence on the intrinsic constraint of the implant except to increase varus stability at lower flexion angles. The Capitellocondylar total elbow prosthesis, as designed by F. C. Ewald, behaves as an unconstrained implant. Adequate soft tissue supports, which are properly balanced to provide controlled loading, are essential to prevent instability of this arthroplasty.

Biomechanical Phenomena↗
PubMed1989

Replacement of the trapeziometacarpal joint with a cemented (Caffinière) prosthesis.

Between 1978 and 1985, 31 Caffinière prostheses were implanted in the first carpometacarpal joints of 28 patients for treatment of degenerative osteoarthritis (26 patients) or rheumatoid arthritis (2 patients). At follow-up an average of 48 (13 to 77) months after operation, four hands had reoperation, with the replacement of six components, five cups and one metacarpal component. In addition, there were x-ray signs of component loosening in three other cases. Of the 29 thumbs that could be evaluated with regard to pain, 27 had no pain at all or only slight pain, and two patients had moderate pain. No patient suffered from severely disabling pain. Mobility and strength were satisfactory.

Adult↗
PubMed1976

Chemotherapy, en bloc resection, and prosthetic bone replacement in the treatment of osteogenic sarcoma.

In an attempt to shrink primary osteogenic sarcoma and allow complete surgical removal of the primary tumor, without amputating the involved limb, intensive preoperative chemotherapy with high dose methotrexate (HDMTX) with citrovorum factor rescue (CFR) and adriamycin (ADR) was initiated in 20 patients with biopsy-proven primary osteogenic sarcoma of the distal femur (15 patients) and proximal tibia (five patients). Following intensive chemotherapy, en bloc resection of the primary tumor with prosthetic replacement of the involved bone was planned. After surgery, adjuvant chemotherapy, consisting of HDMTX with CFR, ADR, and high dose cyclophosphamide was given sequentially for 1 year. Of 20 patients with primary osteogenic sarcoma (two with evidence of pulmonary metastases), 18 had primary tumors that could be clinically measured. Of these 18, 17 demonstrated a decrease in the size of primary tumor prior to surgery, while on chemotherapy. To date, 12 of these patients with osteogenic sarcoma of the distal femur have had total femur and knee joint replacement, and three patients with osteogenic sarcoma of the proximal tibia have had total knee replacement. In all 15 patients, surgical margins were grossly and microscopically free of tumor. There has been no evidence of soft tissue recurrence in any of the 15 patients who have undergone surgery for from 2 to 15 months postoperatively. These preliminary results indicate that with the use of aggressive chemotherapy, it is possible to demonstrate objective tumor regression in primary osteogenic sarcoma, allowing the surgeon to perform en bloc resection of tumor and prosthetic replacement of the involved bone. Although the limb is preserved, it is important to stress that extensive surgery yielding tumor-free margins is performed. The ultimate evaluation of this approach to the treatment of primary osteogenic sarcoma awaits longer observation, to determine limb function and the continued disease-free status, once adjuvant chemotherapy is discontinued.

Adolescent↗
PubMed1976

Preparation and characterization of wear debris of orthopedic materials for biocompatibility studies.

In order to test the biocompatibility of wear debris of orthopedic materials, a method has been developed to produce artificial debris of stainless steel, cobalt-chromium alloy, and high-density polyethylene. In this process, called the accelerated rubbing process, two cylindrical blocks of the same alloy were held under normal pressure in triply distilled water. One block remained stationary while the other rotated at approximately 4000 rpm. The water with the metal debris was recirculated between the rubbing surfaces. To prepare debris from polyethylene, a stainless steel block was rubbed over a polyethylene block submersed in liquid nitrogen. The shape of the metal debris was granular, whereas the polyethylene debris had a shred-like shape. The size distributions were determined from scanning electron micrographs, and it was found that the particles of the metal debris (stainless steel or cobalt-chrome alloy) ranged in sizes from 0.1-10 mu with 75% of all particles less than 2 mu in diameter. The size of polyethylene debris, expressed as the volume of an ellipsoid, ranged from 10-20,000 mu3 with 45% of all particles in the range of 400-2500 mu3. The x-ray diffraction pattern revealed that the debris of stainless steel consisted primarily of the face-centered cubic (fcc) alloy with small amounts of body-centered cubic (bcc) alloy and Fe3O4, whereas the cobalt-chrome debris consisted of the fcc alloy with a small amount of Cr2O3. The structure of the polyethylene debris was quite similar to that of the solid sample used in its preparation. The percent crystallinity Pc and the size of the crystalline regions D were slightly smaller in the debris than in the solid sample, i.e., Pc = 52 and 55%, D = 90 and 130 A, in the debris and the solid, respectively. To test the suitability of the artificial debris for biocompatibility studies, stainless steel debris was implanted into knees of adult female New Zealand rabbits. Bacterial challenge studies indicated prolongation, but not increased susceptibility to infection.

Animals↗