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Biomedical subjects

W Rostoker

Publications and source records attributed to W Rostoker.

At least 19 recordsLinked to original sources
PubMed1983

Total surface hip arthroplasty in dogs using a fiber metal composite as a fixation method.

A total hip surface replacement was performed on 13 adult mongrel dogs using a porous fiber metal composite for fixation to bone. Titanium fiber composite rings were molded onto cylindrical acetabular prostheses, and cobalt-chrome fiber inserts were sintered onto the cast cobalt-chrome femoral components. The animals were allowed unrestricted walking. Four dogs were sacrificed between 3 and 5 weeks, five at 7 weeks, one with a femoral neck fracture at 12 weeks, and three at 26 weeks. Bone ingrowth was accomplished in 20 of the 26 prosthetic components. This included 12 femoral components and eight acetabular. The main reason for failure appeared to be inadequate primary fixation, secondary to either poor design or technical difficulties experienced during the surgical procedure.

Animals↗
PubMed1983

Segmental replacement of long bones using titanium fiber metal composite following tumor resection.

A series of 17 long bone defects following tumor resections were reconstructed using titanium fiber metal implants with adequate bone grafts. There were nine diaphyseal segmental arthroplasties and eight arthrodeses of the knee. The results were excellent in 11 and satisfactory in five, and there was one failure. Sixteen patients became fully weight-bearing. Adequate bone grafts, especially from both posterior iliac crests, and good skin coverage are essential to adequate bony reconstruction.

Adult↗
PubMed1983

A canine cementless total hip prosthesis model.

To evaluate a porous fiber titanium composite as a fixation method, total hip arthroplasty was performed in 13 large male mongrel dogs. In seven both acetabular and femoral composites were fixed with a porous titanium fiber composite, and in the other six the acetabulum was fixed with acrylic cement. The animals were killed one, three, and six months following implantation. At autopsy all components were fixed by bony ingrowth. There was progressive remodeling of the ingrown bone and of the bone trabeculae surrounding the prosthesis in the three- and six-month animals, with gradual thickening and development of haversian structures. Cortical osteoporosis, which did not appear to be progressive, was detected in both the one- and six-month specimens.

Acetabulum↗
PubMed1982

Development of a new endosseous dental implant. Part II: Human studies.

The development of an endosseous implant has followed a logical and formal plan. 1. Extensive experiments with animals provided preliminary statistics of successful function, extensive histologic studies, evaluation of biocompatibility, and a preliminary assessment of contraindications. 2. Carefully developed and controlled clinical study of human subjects with frequent examinations and detailed records of both successes and failures again provided new bases for contraindications. The statistics on the clinical study are satisfactory in their results, although they should be regarded as having a somewhat conservative slant. This is because implant failures became a learning base for improved procedures. The program so far has been limited to a single implant design that, with size variants, will serve most applications. However, it is not feasible to modify the design in terms of dimensions for application in the anterior portion of the mouth. A design for this purpose is established on paper and will become a future additional development.

Adult↗
PubMed1982

Segmental replacement of the femur in baboons with fiber metal implants and autologous bone grafts of different particle size.

A study was made of bone ingrowth into fiber metal composite prostheses used to replace large segments of the femur in baboons. Bone grafts of two different types were used to cover the segment: chips of bone with large particle size and ground bone with a smaller particle size. The prosthetic segment was bridged by bone at 3 and 6 months in all cases irrespective of the structure of the transplant. In animals sacrificed at 6 months bone ingrowth occurred, with a marked difference between specimens with the two different grafts. In the ground bone specimens ingrowth occurred over the total surface area, and bone penetrated deep into the composite. With the chip grafts ingrowth was more irregular occurring only in some areas and it was always superficial. The difference is believed to be due to the improved contact between the fiber metal surface and the transplant. The lesser bulk of the ground transplant is advantageous when the soft tissue cover of the bone is thin.

Alloys↗
PubMed1982

The influence of early weight-bearing on experimental total hip arthroplasties in dogs.

The bone-cement interface is an area of concern in the long-term fixation of endoprostheses. The effect of early weight-bearing on the interface has been discussed as an important parameter influencing the characteristics of the interface. In this study, a total hip arthroplasty was performed in two groups of six dogs each. One group was allowed immediate weight-bearing, while in the other, a knee disarticulation amputation was done to prevent weight-bearing. Three animals of each group were killed at three months and three of each group at six months, and a histological study of the interface was done. No morphologic difference was observed between weight-bearing and nonweight-bearing animals in the interface area. Endosteal bone remodeling occurred regardless of weight-bearing stresses. A fibrous membrane was found between the cement and the endosteal surface of the femur, and membrane thickness was similar in all animals. The membrane between the cement and acetabular bone, however, was consistently thicker. Quantitative studies revealed increased femoral cortical bone resorption in the nonweight-bearing animals.

Acetabulum↗
PubMed1980

Evaluation of sintered titanium fiber composite as a subperiosteal implant.

Seventy-two sintered titanium fiber composite implants were placed subperiosteally and anchored intraosseously on the lateral aspect of 12 dog mandibles. The implants were covered with either Millipore filter, silicone, or left uncovered. Analysis after the animals were killed showed that bone growth into the subperiosteal portion of the implants was maximal at three to six weeks after implantation and remained at a depth of 380 mu through 24 weeks in a majority of the implants. Bone growth into the intraosseous portion also peaked at three to six weeks and remained at 190 to 380 mu through 24 weeks. Covering the implants slowed the rate of osseous ingrowth but did not affect the depth. The implants were well tolerated and the material holds promise for use in oral and maxillofacial surgery.

Animals↗
PubMed1979

Effect of an in vivo environment on the strength of bone cement.

Bar-shaped polymethylmethacrylate test specimens removed from rabbits after implantation for times up to 26 months showed a significant change in fracture stress as determined by three-point bending in the period between 12 and 26 months. There were no adverse findings in the tissue which developed around the bone-cement test bars.

Animals↗
PubMed1979

The influence of grain size on the fatigue behavior of annealed 316 LVM stainless steel.

Experimental tests demonstrate that there is a sharp drop in resistance to fatigue fracture when the grain size is increased from 75 to 150 micrometers. This is at least a partial explanation for fatigue fractures of the stems of total hip-joint prostheses reported in the literature. It is also shown that plastic strains associated with fatigue stressing increase with increasing grain size so that loosening of the bone cement embedment may also be part of the premature failure process.

Hip Joint↗
PubMed1979

Contact pressure dependence of wear rates of ultra high molecular weight polyethylene.

Wear rates of orthopaedic polyethylene in 37 degrees C water are not very contact stress dependent below 1000 psi (6.9 MPa) but above that level they accelerate substantially. The pressure dependence overall follows an exponential function. Creep in the contact pressure range of 3--17 MPa and above is a much larger factor than wear in indentation effects. For accurate measurement of wear rates by depth measurements it is necessary to permit creep to proceed under static load until it ceases before beginning the wear test.

Joint Prosthesis↗
PubMed1978

The appearances of wear on polyethylene--a comparison of in vivo and in vitro wear surfaces.

An examination has been made of the wear surfaces of 21 ultra-high-molecular-weight polyethylene components of hip and knee joint prostheses removed from patients. Both light optics and scanning electron microscope systems of examination have been used. The appearances are compared with specimens subjected to two different in vitro wear tests. Surface appearances related to the wear experience have been classified into seven modes. At least four of these are evidences of what may be four different wear mechanisms. Entrapment of bone-cement particles between articulating surfaces is fundamentally extraneous but is seen to generate the most severe wear. In the absence of bone-cement particles, in vivo, wear seems to be mild. Wear in vitro produces similar surface modes but with different relative emphasis.

Humans↗
PubMed1978

Defects in failed stems of hip prostheses.

A study has been made of the fractures and associated material from 34 prostheses broken in service. All the fractures appear to be of the fatigue type. Search by metallographic analysis for cracklike generating defects in material near the fracture reveals such conditions as abnormally coarse crystals, large nonmetallic inclusions, large inclusion population, undissolved master alloy particles, abnormal carbide segregation, interdendritic segregation, shrinkage, and gas porosity. Recommendations are made for the choice of metallic alloys for femoral stem application.

Chemical Phenomena↗
PubMed1978

Evaluation of couple/crevice corrosion by prosthetic alloys under in vivo conditions.

Alloys of cast Co-Cr-Mo, wrought Co-Cr-W, wrought, Co-Ni-Cr-Mo(MP35N), Ti-60% Al-4% V, and graphite were incorporated in specimens which simulated both a couple and a crevice corrosion condition. These specimens were implanted in a dog for 30 months. Post-sacrifice examination showed no substantial evidence of corrosion activity on the surfaces of the metals except for a tarnish film on the titanium alloy specimens. The presence of the tarnish film is taken as more evidence of corrosion activity and this correlated with a thicker average fibrous membrane, cellular activity in and near the fibrous membrane, and some increased vascularity. These must be regarded as preliminary observations.

Alloys↗