PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Prosthesis Design”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources
PubMed1992

Joint replacement components made of hot-forged and surface-treated Ti-6Al-7Nb alloy.

We have developed a titanium-aluminium alloy with the inert alloying element niobium. The optimal composition was found to be Ti-6Al-7Nb (Protasul-100). This custom-made alloy designed for implants shows the same alpha/beta structure as Ti-6Al-4V and exhibits equally good mechanical properties. The corrosion resistance of Ti-6Al-7Nb in sodium chloride solution is equivalent to that of pure titanium and Ti-6Al-4V. This is due to a very dense and stable passive layer. Highly stressed anchorage stems of different hip prosthesis designs have been made from hot-forged Ti-6Al-7Nb. The polished surfaces of hip, knee and wrist joints made of Ti-6Al-7Nb and articulating against polyethylene are surface-treated by means of a very hard and 3-5 microns thick titanium nitride coating (Tribosul-TiN) or by oxygen diffusion hardening (Tribosul-ODH) to a depth of 30 microns.

Humans↗
PubMed1990

Koenig total great toe implant. Preliminary report.

A new first metatarsophalangeal joint implant arthroplasty is described. The two-component, titanium alloy and polyethylene prosthesis designed for weightbearing is noncemented and press-fit. Sixteen cases involving 18 implants were evaluated over 18 months with evidence that good correction and pain free motion can be obtained.

Adult↗
PubMed1990

Stress analysis of the proximo-medial femur after total hip replacement.

Stress-induced bone loss in the proximo-medial femur has been identified as a factor leading to loosening in the artificial hip joint. In an effort to develop a quantitative understanding of the stress distribution that causes bone loss, axial and hoop stresses in the medial calcar of the femur have been determined after total hip replacement, using finite element stress analysis. Stress distributions for a high and a low Young's modulus prosthesis material are compared for both collared and uncollared prosthesis designs. The use of a low-modulus material, and of a collar, are predicted to be advantageous, giving rise to proximo-medial stress patterns similar to those of the normal, intact femur.

Biomechanical Phenomena↗
PubMed1990

Measurement of the mechanical properties of the ovine anterior cruciate ligament bone-ligament-bone complex: a basis for prosthetic evaluation.

The reported ultimate tensile stress of the anterior cruciate ligament varies greatly, ranging from 13 to 147 MPa. This study shows that the orientation and degree of flexion of the bone-ligament-bone complex significantly alter the apparent ultimate tensile properties (ultimate tensile stress ranging from 60 +/- 3 to 123 +/- 15 MPa, ultimate specific extension from 37 +/- 7 to 93 +/- 20%), whilst the method chosen for measuring extension also affects the calculated specific extension of the bone-ligament-bone complex. It is suggested that, for considerations of prosthesis design and evaluation, the mechanical properties of the bone-ligament-bone complex should be measured in anterior draw and extension measured using points as close as possible to the positions of the ligamentous attachment sites.

Animals↗
PubMed1979

Predictive range of motion after total knee replacement.

Evaluation of 145 consecutive total knee arthroplasties pre- and postoperatively revealed that regardless of the preoperative deformity (varus, valgus, and flexion contracture), normal alignment of the knee with full extension was obtainable. The amount of flexion to be achieved postoperatively may be determined by the amount of flexion the patient had preoperatively, especially if the degree of flexion was less than 75 degrees. The prosthesis design, sex, age and diagnosis of rheumatoid arthritis were found not to correlate with postoperative motion and stability. In the osteoarthric knee, however, statistical analyses at 6 and 12 months generally showed less postoperative than preoperative range of motion.

Adult↗
PubMed1991

Reconstructions after resections of tumors involving the proximal femur.

Advances in prosthesis design, the use of allografts, and a systematic approach to the staging and surgical treatment of musculoskeletal tumors have made limb salvage possible in the proximal femoral region. With the use of effective adjuvant therapy, limb salvage is now an option for the majority of patients presenting with locally invasive neoplasms in this area. The increase in functional outcome is sufficient to warrant serious consideration of limb salvage over the corresponding amputation. Preoperative planning is discussed along with surgical techniques.

Arthrodesis↗
PubMed1978

[Biomechanical aspects of arthrosis of the carpometacarpal joint of the thumb and its treatment with a special endoprosthesis].

The joint between the trapezium and the first metacarpal is anatomically like a saddle. In function, however, it is used like a ball and socket joint with the following possible movements: 1. Flexion - extension, 2. abduction - adduction, 3. opposition and circumduction. The movements in the two first planes are completely congruent, whereas in the third an incongruent motion of the joint is created by the rotation of the metacarpal on the trapezium. In this situation there is joint contact at one point only, being - biomechanically - a prearthrotic deformity as described by HACKENBROCH. Accordingly, the carpometacarpal joint of the thumb in normal use is exposed to special stress which can end in degeneration. When in arthrosis of the carpometacarpal joint of the thumb conservative measures fail, we replace the deformed joint by prosthesis having the construction of a ball and socket joint. The prosthesis (designed by FRANCOBAL) has a metallic part with body, neck and a sphereshaped head, and a polyethylene socket, which can be coupled to the head by a snap mechanism. Both parts are inserted with polymethylmetacrylate cement into the prepared bone of the trapezium and the first metacarpal. The advantages of this method are: no pain, stability of grip, and motion similar to that of a ball and socket joint. Because this motion is physiological, loosening of the implants and their insertions are avoided. The first 8 patients treated with this method show satisfying functional results. The longer follow-up time is 6 years.

Aged↗
PubMed1991

Catheter balloon valvuloplasty of stenotic porcine bioprosthetic valves: Part II: Mechanisms, complications, and recommendations for clinical use.

During the last several years dilating balloons have been applied in the treatment of stenotic cardiac valves. This interest has been extended to stenotic porcine bioprosthetic valves. Part I of this review discusses the pathologic changes producing stenotic porcine prosthetic valves. Part II of this review describes an in vitro study of porcine prosthetic valve valvuloplasty defining the mechanisms, complications, and clinical applications. Results of this study indicate a limited and cautious role in balloon dilation of stenotic bioprosthetic valves.

Adult↗
PubMed1992

Tissue ingrowth into titanium and hydroxyapatite-coated implants during stable and unstable mechanical conditions.

Lack of initial mechanical stability of cementless prostheses may be responsible for fibrous tissue fixation of prosthetic components to bone. To study the influence of micromovements on bony ingrowth into titanium alloy (Ti) and hydroxyapatite (HA)-coated implants, a loaded unstable device producing movements of 500 microns during each gait cycle was developed. Mechanically stable implants served as controls. The implants were inserted into the weight-bearing regions of all four femoral condyles in each of seven mature dogs. Histological analysis after 4 weeks of implantation showed a fibrous tissue membrane surrounding both Ti and HA-coated implants subjected to micromovements, whereas variable amounts of bony ingrowth were obtained in mechanically stable implants. The pushout test showed that the shear strength of unstable Ti and HA implants was significantly reduced as compared with the corresponding mechanically stable implants (p less than 0.01). However, shear strength values of unstable HA-coated implants were significantly greater than those of unstable Ti implants (p less than 0.01) and comparable to those of stable Ti implants. The greatest shear strength was obtained with stable HA-coated implants, which was threefold stronger as compared with the stable Ti implants (p less than 0.001). Quantitative determination of bony ingrowth agreed with the mechanical test except for the stronger anchorage of unstable HA implants as compared with unstable Ti implants, where no difference in bony ingrowth was found. Unstable HA-coated implants were surrounded by a fibrous membrane containing islands of fibrocartilage with higher collagen concentration, whereas fibrous connective tissue with lower collagen concentration was predominant around unstable Ti implants. In conclusion, micromovements between bone and implant inhibited bony ingrowth and led to the development of a fibrous membrane. The presence of fibrocartilage and a higher collagen concentration in the fibrous membrane may be responsible for the increased shear strength of unstable HA implants. Mechanically stable implants with HA coating had the strongest anchorage and the greatest amount of bony ingrowth.

Analysis of Variance↗
PubMed1992

Migration of porous coated acetabular prostheses fixed with screws: roentgen stereophotogrammetric analysis.

The fixation of screw-fixed, porous-coated acetabular prostheses was studied during 2 years in 21 patients (22 hips) using repeated roentgen stereophotogrammetric measurements. Migration of the center of the prostheses and/or tilting were recorded in five cups after 6 months. Two years after operation, migration was recorded in three, migration and rotation in six, and only rotation in three cups. Bone quality, prosthetic position, and immediate postoperative radiographic appearance of the prosthesis-bone interface did not correlate with the occurrence of migration. Narrow radiolucent zones had developed in half of the patients after 2 years and was associated with proximal migration. Micromovements of screw-fixed, press-fit cups seem to start later compared with previously presented results from cemented acetabular prosthesis.

Acetabulum↗
PubMed1990

The Guildford elbow.

A new unconstrained elbow replacement is described and the results of 44 primary and 5 revision operations assessed. A high incidence of pain relief (82%) and functional improvement (73%) was achieved. However 23% of primary replacements later underwent loosening as assessed radiologically and 12% have undergone revision for pain. Minor complications not affecting the final result occurred in 28%. The causes and significance of the complications are analysed.

Arthritis, Rheumatoid↗
PubMed1991

Evaluation of the healing of precoated vascular dacron prostheses.

Knitted and woven Dacron grafts commercially coated with bovine collagen, gelatin and human albumin were implanted end-to-side between the infrarenal aorta and the bifurcation in 35 growing pigs. Grafts were explanted after 4, 8 and 12 weeks and compared to 6 uncoated knitted prostheses preclotted with blood that served as a control. Uncoated grafts rapidly developed a firmly attached neointima lined with endothelium. Compared with coated grafts the thrombus-free area of uncoated grafts was significantly larger (P less than 0.05). The slow resorption of albumin resulted in a delayed and incomplete neointimal healing and failing graft incorporation. Although the bovine collagen was only minimally cross-linked by formaldehyde, healing of the neointima was compromised in a thin woven graft that demonstrated peeling of the inner capsule even after 12 weeks. The identical collagen as well as bovine gelatin were quickly degraded in knitted grafts and both types showed transprosthetic infiltration at 4 weeks. All knitted grafts coated with either collagen or gelatin, however, were occluded after 8 and 12 weeks. Light microscopy revealed hyperplasia of smooth-muscle cells within the thickened distal anastomotic region. These results demonstrate that a timely return of porosity is mandatory for the development and maintenance of an intact neointima. Both the structure of the fabric as well as the method of preparing the coating are crucial variables to determine the rate of biodegradation.

Animals↗
PubMed1992

The influence of metal backing in unicompartmental tibial component fixation. An in vivo roentgen stereophotogrammetric analysis of micromotion.

The fixation of the tibial component in 36 patients with conventionally cemented unicompartmental knee arthroplasties for femorotibial gonarthrosis was studied using roentgen stereophotogrammetric analysis (RSA). Twenty-four tibial components were all-polyethylene while 12 were metal-backed. The follow-up was for 6 years. Significant migration was detected for all cases but two and ranged from 0.3 mm to 5.4 mm. The greater part of the migration occurred during the first 1-2 years, after which two-thirds of the prostheses remained stable. Seven all-polyethylene components were subjected to a stress examination after 1-2 years and displacement, induced by external forces, was found in all seven. A strong correlation was found between the extension of the radiolucent line and the migration. Otherwise, neither demographic, clinical, nor radiographic data correlated with the RSA results. In this study metal backing did not have any influence on prosthetic fixation as measured by RSA.

Aged↗
PubMed1991

Cementless Gustilo-Kyle and BIAS total hip arthroplasty: 2- to 5-year results.

We conducted extensive radiographic and clinical examination of 58 cementless total hip arthroplasties. Forty BIAS femoral stems had heads made of Co-base F 75 alloy and 18 Gustilo-Kyle femoral stems had Ti6A14V alloy heads. The cross-sectional geometry and location of the porous coating pads of the two stem types was identical, the BIAS component being slightly shorter. At the last follow-up, 27.8% of the Gustilo-Kyle femoral components and 2.5% of the BIAS femoral components were unstable. None of the acetabular components in the BIAS group as against 38.9% of the acetabular components in the Gustilo-Kyle group demonstrated wear of more than 1 mm. All unstable components which did not suffer intraoperative fracture had also acetabular wear of more than 1 mm. The only case with endosteal erosion was seen in a patient with an unstable implant displaying the most extensive wear. Nonparametric statistical analysis showed that the patients with Ti6A14V/polyethylene bearing surfaces had a statistically significantly higher extent of wear and a statistically significant higher incidence of femoral component loosening than patients with CrCoMo/polyethylene bearing surfaces.

Adult↗
PubMed1991

Aseptic loosening of straight- and curved-stem Müller femoral prostheses.

Out of 1099 Müller total hip prostheses with straight and curved stems consecutively implanted between 1980 and 1984, those performed in as homogeneous a group as possible of patients under the age of 70 years were selected for the present retrospective study. There were 158 straight femoral stems with cementless RM acetabular cups, 105 straight stems with cemented Müller acetabular cups, and 158 curved stems with cemented Müller acetabular cups, and their results over a mean follow-up period of 5.8 +/- 1.24 years were compared. Six (3.7%) curved and 5 (1.9%) straight-stem prostheses were exchanged due to aseptic loosening; 26 (16.3%) curved and 54 (20.1%) straight-stem prostheses were "at risk" or loose at the time of follow-up. Survival curves show a worse result for straight stems after 6 years; within a follow-up period of 6-8 years there was significantly more radiological loosening in straight stems than in curved. Loosening in straight stems is assumed to develop mainly as a physiological reaction to the presence of bone cement particles.

Aged↗
PubMed1991

Uncoated polyethylene RM acetabular component versus Müller cemented acetabular component. A 4- to 8-year follow-up study.

Comparable patient populations with 160 uncoated RM acetabular cups and 263 cemented Müller standard acetabular cups were submitted to survival-time analysis in a retrospective study with a mean follow-up of 5.3 years for the RM cup and 6.1 years for the Müller cup. After 7-8 years 12% of the RM cups and 4% of the Müller cups had been exchanged, 40% and 15% respectively were loose. The poor performance of the RM cups is ascribed to additional external polyethylene wear, which leads to the formation of granulomas and destroys the weight-bearing osseous structures. Similar granulomas also develop on the proximal stem and thus endanger the same.

Aged↗