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At least 361 records · Page 20Linked to original sources
PubMed2000

Adsorption control of synovia constituents on artificial joint materials by means of an electric field: evaluation of tribological characteristics.

The supplemental lubrication mechanism by means of an electric field was proposed to reduce friction and wear for the advanced joint prosthesis with the low elastic modulus bearing surface. The possibility of application of this mechanism to the prosthesis was investigated by the fundamental and experimental procedures in simplified sliding conditions. Conductive silicon rubber was used as the low elastic modulus surface. The counterfaces were a titanium alloy and a stainless steel. Protein (gamma-globulin) in lubricant appeared to cause the tribological characteristic to deteriorate in the mixed lubrication regime. High friction seemed to be brought about by the obstruction against the entraining of the fluid flow and the high shear stress due to the microbonding between the asperities of bearing surfaces, which were derived from the adsorbed protein on the hydrophobic surfaces. The repulsive force between the adsorbed film and the bearing materials by means of the d.c. electric field, and the continuous change in polarity on the surface by means of the a.c. electric field appeared to affect the adsorbed film adjacent to the bearing material, so that friction and wear were varied.

Adsorption↗
PubMed1992

Extended indications for functional limb-sparing surgery in extremity sarcoma using complex reconstruction.

From 1980 to 1991, 29 patients underwent complex reconstruction following extremity sarcoma resection. Soft tissue was the site of origin in 15 patients (52%) and bone was the site of origin in 14 patients (48%), with 20 sarcomas (69%) in the lower extremity. Resection consisted of the following procedures: extended anatomical soft-tissue resections (21 patients [72%]), bone resections (18 patients [62%]), and joint resections (14 patients [48%]). Reconstruction involved the following: myocutaneous flaps (20 patients [69%]), joint prosthesis (eight patients [28%]), and bone reconstruction (15 patients [52%]). There was no surgical mortality; one patient required an amputation owing to surgical complications. The site of the first failure was local (four [31%] of 13 patients), lung (five patients [38%]), others (four patients [31%]). At a median follow-up of 23 months, 18 patients (62%) had no evidence of disease, 27 (93%) had no local disease, 21 (72%) had good extremity function, three (10%) had major disabilities, and five (17%) underwent amputations. Local control improved when the margin of resection was larger than 10 mm. Disease-free survival was 67% at 3 years. Overall survival was 51% at 5 years. Tumor size was an independent predictor of overall survival. Local recurrence did not affect overall survival.

Adult↗
PubMed1992

Increased resistance of bacteria after adherence to polymethyl methacrylate. An in vitro study.

The pathobiology of total joint prosthesis infection was investigated in vitro. Discs of polymethylmethacrylate (PMMA) were exposed to a suspension containing cells of 10(8) per mL Staphylococcus epidermidis E-46. After 12 hours, exposed discs were rinsed with phosphate-buffered saline and placed in brain heart infusion broth containing antibiotics (2.5 mg per mL of Cephaloridine). After gentle shaking for 24 hours at 37 degrees C, the bacteria on the PMMA surface were detached and washed with phosphate-buffered saline to remove the antibiotics. Compared with the free bacteria which were detached from the PMMA by sonication immediately after exposure to the antibiotic solution, those allowed to remain adhered to the PMMA surface were more resistant to antibiotics. Scanning electron microscopy showed accumulation of bacteria surrounded by slime on PMMA discs exposed for 12 hours. Our results indicate that resistance of bacteria to antibiotics is increased after adherence to the biomaterial and formation of a slime layer.

Bacterial Adhesion↗
PubMed1982

Osteoarticular and intercalary allograft transplantation in the management of malignant tumors of bone.

Since 1971, the Orthopaedic Service at the Massachusetts General Hospital has treated 106 patients with malignant or aggressive bone tumors by wide resection and replacement with frozen cadaveric allograft. Sixty-one of these patients have been followed for over two years (mean, 4.5 years), allowing a comprehensive end-results analysis. In 45 patients, mostly with giant-cell tumors of chondrosarcomas, the resection involved the articular end of a long bone and the replacement not only included bone, but glycerolized (to prevent freezing injury) and articular cartilage. Ten of the segments were intercalary (bone alone) and six involved a combination of bone and metallic joint prosthesis. Patients were graded as excellent, good, fair, or failure, depending principally on functional capacity. End-results analysis in this group showed that five of the 61 patients had either a local recurrence (2) and/or distant metastases (3); in five additional patients the limb was amputated or the implant removed, primarily because of infection (total failure rate, 16.5%). Forty-five (73.8%) had successful transplants (graded excellent or good) and were able to live essentially normal lives. Six of the patients (10%) required a brace or cane but three of these patients were able to return to preoperative work activities. Although the operations were arduous and difficult, and despite a high infection rate (13%) and occasional pathologic fractures (10%), the results compare favorably with other techniques used to restore the skeleton following massive segmental resection. In long-term follow-up, the data suggest that if no complication ensue in the first two years, the results are generally quite good and the grafts show no evidence of progressive deterioration with time.

Adolescent↗
PubMed2003

Pose estimation of artificial hip joint using a single radiographic projection.

Total hip joint arthroplasty is commonly used in cases of osteoarthritis and rheumatoid arthritis. A hip joint prosthesis consists of a cup and a stem. The relative pose (position and orientation) of the prosthesis, when the patient is standing naturally, is planned pre-operatively; however, there is no guarantee that the pre-operatively planned pose will be accurate. Prosthesis component malposition, which is inadequate positioning of the acetabular or femoral component, results in limited joint movement and a large prosthetic joint contact area, and this can cause dislocation of the femoral head from the cap. Because the range of motion after total hip joint arthroplasty is determined by the relative pose of the cup and the stem, it is important to know the relative pose after hip arthroplasty. Several pose estimation methods using single-plane fluoroscopy or conventional roentgenography have been proposed. Because a conventional radiograph system is commonly used at small cost, a method using conventional radiograms is desirable for use in a clinical setting. In this study, a pose estimation method using conventional radiography is proposed, and an in vitro experiment is performed to evaluate its accuracy. The rotational errors of the relative pose of the cup with respect to the stem were smaller than 2.3 degrees.

Hip Joint↗
PubMed2005

[Pyrocarbon prosthesis for finger interphalangeal joint replacement. Experience after one year].

The long-term results of finger joint replacement, particularly the proximal interphalangeal (PIP) joint, have mostly been disappointing according to a review of the international literature and our own experiences. The recently developed pyrolytic carbon implants (Ascension Orthopedics, Austin, Texas) for replacing the PIP joint were evaluated retrospectively regarding range of motion, functionality, and relief of pain. In our hospital 17 PIP joints were replaced with pyrolytic carbon implants in 16 patients by an offset stem technique inserted without cement. This study included 13 patients; we excluded three patients because of follow-up <3 months. Prerequisites were adequate collateral ligaments, bone stability, and sufficient or at least reconstructable extensor tendons. The purpose of this study was to evaluate the 1-year outcome (minimum 270, maximum 360 days) regarding range of motion, implant stability based on radiological and clinical parameters, and relief of pain using a pre- and postoperative visual and verbal analogue scale.There was an improved range of motion of the PIP joint from 0-28-51 preoperatively to 0-22-77 postoperatively (average value). On the visual analogue scale (0 no pain, 10 incapacitating pain) we achieved pain relief at rest and in motion of 80%. On the verbal analogue scale there was an improvement of 62%. The results of this study demonstrate that pyrolytic carbon implants reduce pain and are functionally superior to arthrodesis. A precise and individual postoperative protocol is necessary for beneficial results.

Adult↗
PubMed1992

Perspectives on artificial joint design.

Due to poor interdisciplinary communication, many artifical joint designs fail to account for some features that normally allow bones to survive for life. In part, these features concern modeling drifts and remodeling basic multicellular units (BMUs), the microdamage thresholds of bone, its load-grain alignment and shear lock properties, load focusing and defocusing, mechanical usage/strain thresholds for controlling the biological mechanisms, and the regional acceleratory phenomenon. This article reviews briefly some major aspects of these features and suggests how implant design might account for them.

Biocompatible Materials↗
PubMed1979

Total joint arthroplasty. The role of biomechanics.

The role of biomechanics is intricately involved in total joint replacement from its inception to its clinical use. By integrating knowledge of joint function and material properties, the artificial joint is designed and tested. After clinical use, the joint function is again studied and failure modes are defined. Biomechanics is the single most important discipline that can be employed to study the cause of failure in order to improve design and technique. This will increase the reliability of, and decrease the incidence of failure associated with, total joint replacement.

Arthroplasty↗