Biomedical subjects

R M Urban

Publications and source records attributed to R M Urban.

40 records · Page 3Linked to original sources

PubMed1986

A comparative study of porous coatings in a weight-bearing total hip-arthroplasty model.

The purposes of this study were to compare ingrowth of bone into three types of porous coating and to determine the effect of the type of porous coating and the degree of coverage of the stem on the remodeling of bone on the femoral side in cementless hip arthroplasty. A left total hip arthroplasty was performed in forty dogs. Thirty of the dogs had a titanium-alloy femoral prosthesis that had had one of three types of commercially pure titanium porous material applied along the length of the anterior and posterior surfaces of the stem: ten with sintered fiber-metal, ten with sintered beads, and ten with plasma flame-spray coating. The remaining ten dogs had a femoral component that was circumferentially coated with commercially pure titanium that was plasma flame-sprayed along the length of the stem. In each group, five animals were killed at one month and five were killed at six months. Ingrowth of bone into all three types of porous coating was observed, indicating secure fixation of all components. By six months, there was more ingrowth of bone and new medullary bone adjacent to the proximal and distal aspects of the stems compared with the middle level of the stems in all groups. No significant difference in ingrowth of bone was observed in the beaded surface (25.2 per cent) and the fiber-metal surface (16.6 per cent) at one month, but at six months there was significantly less ingrowth into the beaded surface (23.3 per cent) than into the fiber-metal surface (37.3 per cent). In all groups, a proximal-to-distal gradient of loss of cortical bone was observed by six months. The group of dogs that had the stem with the circumferential coating experienced more severe loss of bone than did the three groups that had a stem with a partial coating. The magnitude of loss of bone was dependent on the extent rather than the type of porous coating.

Animals↗

PubMed1984

Metal ion release from titanium-based prosthetic segmental replacements of long bones in baboons: a long-term study.

Forty-five baboons that had received titanium-based fiber metal composite segmental bone replacements were studied along with 13 controls without implants. Thirty-eight baboons with implants were sacrificed, and titanium, aluminum, and vanadium levels were assayed in homogenized lung, kidney, spleen, liver, adjacent muscle, and regional lymph nodes. In seven living baboons with implants, blood and urine samples were obtained for trace metal analysis as well as for biochemical and hematological profiles. In the 38 sacrificed baboons with implants, increased titanium levels were noted in the lungs, spleen, adjacent muscle (quadriceps, soleus, and triceps), and regional lymph nodes (inguinal, axillary, and popliteal) in comparison to those of six sacrificed controls without implants. In addition, vanadium was significantly elevated in the lungs of some animals, while aluminum increases were noted in adjacent muscle (quadriceps, soleus, and triceps), lung, and regional lymph nodes (inguinal, axillary, and popliteal). In the seven living baboons with implants, a sixfold increase (p less than 0.0005) in the urine titanium level was noted in comparison to that of seven living controls without implants. Additionally, elevated aluminum levels were found in the serum (p less than 0.0005) of the group with implants. Biochemical and hematological studies did not indicate statistically significant differences in serum electrolytes, in liver and renal function tests, or in complete blood counts between the seven living baboons with implants and their controls.

Aluminum↗

PubMedDate not supplied

Biocompatibility of Delrin 150: a creep-resistant polymer for total joint prostheses.

A thermoplastic polymer, Delrin 150 (polyoxymethylene homopolymer), with creep resistance ten times that of ultrahigh-molecular-weight polyethylene, is used as a material for total joint prostheses. A study was made of the local and systemic host response to this polymer when implanted in three different mammalian species. 316 LC stainless steel was used as a control. The materials were implanted into muscle and bone as solid cylinders. A total of 446 samples were implanted into 74 animals. The duration of implantation ranged from 2 weeks to 2 years. A semi-quantitative evaluation of local tissue reaction was performed. For each implant, 16 histological criteria were graded for severity of host tissue reaction. The liver, spleen, kidneys, pancreas, and lungs from each animal were also studied for evidence of systemic toxicity. The polymer implants exhibited a mild tissue reaction with the same characteristics as the control. Local tumor formation, bone osteolysis, and surrounding muscle necrosis were not seen. No pathological changes compatible with systemic toxicity by Delrin 150 were observed in the study of the organs. Delrin 150 in solid form did not exhibit local or systemic toxicity and is therefore biocompatible by this study. Powder implantation studies should be performed to simulate tissue response to wear particles.

Animals↗

PubMedDate not supplied

[Histological study of the porous coating of the uncemented acetabulum. Apropos of 11 implants removed at autopsy].

Tissue ingrowth in the porous coating of 11 cementless acetabular components has been studied histologically. These cups were retrieved at autopsy from 8 patients who had undergone a primary total hip arthroplasty. Seven cups had a mean implantation period of 5.1 years, the other 4 had been in place for less than one year. This component was made of commercially pure (cp) titanium, with a porous surface of cp titanium fiber metal. The initial fixation of the cup was achieved by screws. The tissues of the porous coating were studied into 1 mm fields at four levels, and were categorized either as bone, marrow, cartilage or fibrous tissue. The fraction of void space within the porous coating occupied by bone was measured by backscattered scanning electron microscopy. The percentage of 1 mm fields with bony tissue was 20.9% and the fraction of void space occupied by bone was 12%. No regional significant difference was found. The number of fields with bone increased from the interface between the porous coating and the substrate of the cup to the interface between the outer surface of the porous coating and the host bone. All the screw threads were covered with lamellar bone. In the longest term cases, fine metallic and polyethylene debris were observed and their amount increased with time. This study showed that, despite the important variability in bone ingrowth, these cementless cups were able to give entire satisfaction to the patients.

Acetabulum↗