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Biomedical subjects

K Merritt

Publications and source records attributed to K Merritt.

At least 73 records · Page 4Linked to original sources
PubMed1987

Role of internal fixation in infection of open fractures: studies with Staphylococcus aureus and Proteus mirabilis.

Studies of infections in open fractures are described. The hamster was chosen as the experimental model. Osteotomies of the femur were created with an osteotomy saw. Some osteotomies were left to heal and others were fixed with an 0.9 mm K-wire. The infection rates in fixed and unfixed fractures were compared. The first group of hamsters with fixed and unfixed osteotomies was returned to cages with open wounds. There was no difference in the infection rate at 2 weeks. The second group was deliberately contaminated with Staphylococcus aureus and then returned to cages with open wounds. In this group, the infection rate at 2 weeks was lower in the internally-fixed fractures than in the unfixed fractures. The third group was deliberately contaminated with the gram negative organism Proteus mirabilis. In these animals, the infection rate was increased in the presence of the internal fixation device. The fourth group was deliberately contaminated with both Staphylococcus aureus and Proteus mirabilis. The infection rate in these animals was very high; Proteus was recovered from those animals with internal fixation and Staphylococcus was recovered from those animals without internal fixation. These studies in the hamster document the usefulness of this animal as an inexpensive and reproducible model for studying infection of open fractures. The hamsters tolerated the procedure well, and wound and fracture healing progressed satisfactorily.

Animals↗
PubMed1986

The calcar bone graft.

A canine model was developed to investigate the use of an autogeneic iliac bone graft to treat the calcar deficiency commonly found at the time of revision surgery for femoral component loosening. Five large male mixed-breed dogs had bilateral total hip arthroplasty staged at three-month intervals, and were sacrificed at six months. Prior to cementing the femoral component, an experimental calcar defect was made, and a bicortical iliac bone graft was fashioned to fill the defect. Serial roentgenograms showed the grafts had united with no resorption. Technetium-99 bone scans showed more uptake at three months than at six months in the graft region. Disulfine blue injection indicated all grafts were perfused at both three and six months. Thin section histology, fluorochromes, and microradiographs confirmed graft viability in all dogs. Semiquantitative grading of the fluorochromes indicated new bone deposition in 20%-50% of each graft at three months and 50%-80% at six months. Although the calcar bone graft was uniformly successful in this canine study, the clinical application of this technique should be evaluated by long-term results in humans.

Animals↗
PubMed1984

Role of medical materials, both in implant and surface applications, in immune response and in resistance to infection.

The term biocompatibility encompasses many aspects of the behaviour of a material in the body including its effects on the host and the host's effects on it. Two aspects of biocompatibility which are difficult to predict are sensitivity reactions and infections. These reactions are very dependent on the host and other factors beyond the control of the testing laboratory. Much of the information on the problems of sensitivity reactions and infection rates in the actual use of the biomaterials and devices comes from case reports in the literature. This article will focus on review papers and a synthesis of reports and does not contain a thorough citation of the literature.

Administration, Topical↗
PubMed1983

Metal allergy, metal implants and fracture healing.

The rabbit tibia was used as a model to study the effects of metal sensitivity reactions on the healing of fractures. Animals were injected with nickel chloride in Freund's complete adjuvant to cause sensitivity, and fractures were stabilized with 316L stainless steel intramedullary rods and followed for 16 weeks. A control group received no injections. The response was evaluated biomechanically with torsional testing at sacrifice, radiologically by examining the roentgenograms for evidence of loosening, and histologically. The results demonstrated a slight decrease in strength, a moderate increase in resorption and a significant decrease in cellularity and new bone formation in the sensitive animals as compared to control. These results are consistent with a reaction of comparatively short duration.

Animals↗
PubMed1983

The use of the mouse peritoneal cavity for screening for biocompatibility of polymers.

The mouse peritoneal cavity was evaluated as a possible model for the preliminary screening of polymeric implant materials. The phagocytic cells of the cavity were stimulated prior to implant insertion by intraperitoneal injection of thioglycollate, glycogen, or sodium caseinate. Small, cylindrical polymeric implants of polyethylene, polychlorotrifluoroethylene, silicone, nylon-12, ethylene-chlorotrifluoroethylene copolymer, and polyethylene-silicone blend, were inserted and then retrieved at 1, 2, and 3 week intervals. The implants with attached cells were subsequently stained and evaluated as to the amount and type of cellular adherence. Results indicate that cell adherence varies according to the type of material used and therefore the mouse peritoneal cavity is a rapid and inexpensive method to evaluate cellular response to polymeric implant materials.

Animals↗
PubMed1983

XPS analysis of 316 LVM corroded in serum and saline.

Surface chemical analysis by x-ray photoelectron spectroscopy (XPS) was undertaken on 316 LVM stainless steel in the attempt to better understand corrosion occurring in vivo. Samples were dipped in saline or in blood serum, corroded in serum or saline by the application of a 5 volt anodic potential, or corroded by fretting. The products produced by fretting corrosion were also examined. XPS analysis revealed rapid protein coating of the stainless steel surfaces exposed to serum, changes in the oxidation state of the surfaces, and changes in the chlorine on the surface. In addition it was demonstrated that the corrosion products generated by fretting in saline had an oxidation state similar to that of chronic chloride whereas the corrosion products generated in serum had an oxidation state similar to that of potassium dichromate. These findings may have important implications since the chromium in dichromate is more biologically active than that in chronic chloride.

Blood↗
PubMed1981

Fretting corrosion in saline and serum.

Fretting corrosion of stainless-steel round hole plates and spherical head screws was studied using a simulator that produced a rocking motion of the heads in the plate holes. Experiments were run for 7 days, with the simulator producing 1 oscillation/s for 16 h/day. Fretting corrosion was studied in 0.9% NaCl and in a 10% solution of fetal calf serum in saline. The results showed a tenfold decrease in fretting corrosion when the serum was added to the saline. Measurements of the weight of the two screws and two-hole plate showed those in saline lost 2.9 mg as compared to 0.3 for those in 10% serum. The concentration of nickel in the saline solutions was 12.4 micrograms/mL compared with 0.85 in serum. Visual examination of the solutions and implants revealed that those in saline had a significant amount of corrosion products while those tested in 10% serum were bright and shiny. Recordings of electrical potentials demonstrated that the addition of serum to saline significantly reduced the change in potential from rest to fretting condition.

Blood↗
PubMed1981

In vivo and in vitro considerations of corrosion testing.

In vitro experiments were conducted in which the fretting corrosion rate of stainless steel plates and screws in 0.9% saline was compared with the rate in solutions of 10% calf serum in saline. The results demonstrated a ten-fold decrease in the fretting corrosion rate with the addition of serum to saline. However, it also demonstrated that the lower concentration of nickel in the serum solutions was more biologically active than the higher concentration in saline when the solutions were used to skin test rabbits made allergic to nickel by injection.

Animals↗
PubMed1980

Metal allergy and the surgical patient.

Allergy to metal implants is under study at the Dartmouth-Hitchcock Medical Center using in vitro examination of white blood cell migration. Retrospective data from 121 patients confirm that allergic responses do occur. Prospective data are being gathered to investigate the incidence, prevalence and relation to morbidity.

Adolescent↗
PubMed1979

Implant site infection rates with porous and dense materials.

The infection rate of implant sites bearing porous and dense implants was studied in mice. In the first model (acute infection) the mice were injected with Staphylococcus aureus subcutaneously at the implant site at the time of implantation. In the second (chronic) model the implants were left in place for four weeks for encapsulation or invasion to occur and then the organisms were inoculated. In the acute model the infection rate with the porous materials was greater. In the chronic model after tissue invasion the infection rate with the dense materials was greater. This supports the hypothesis that microorganisms can evade host defense mechanisms if they enter the pores of the implant before tissue invasion, but that once the implant is invaded with host tissue the bacteria are less apt to establish infection.

Aluminum↗
PubMed1978

Characterization and incidence of pigment production by human clinical group B streptococci.

Pigment was produced in stab cultures by 97% of 297 group B streptococci isolated from human clinical specimens. The pigment, which was associated with a membranous cell fraction, showed a four-banded absorption spectrum similar to that of a carotenoid, with maxima at 435, 566, 485, and 525 nm. Addition of glucose to the growth medium suppressed pigment production in most strains. Only 37% of strains from bovine sources produced pigment.

Anaerobiosis↗
PubMed1978

Analysis of after-hours calls and visits in a family practice.

The after-hours encounter is an important aspect of primary care. This study examined the pattern of patient behavior after hours in a rural Ontario setting serving a mixed white and native population. Of the 83 telephone calls and 59 visits over a six-week period, approximately 60 percent were from females (52 percent of the clinic population), and 70 percnet were for new problems, with acute infection accounting for nearly one third of the contacts. Forty-seven percent of the calls were rated as highly necessary; 56 percent of the calls received visits. The following factors related to the preceding call increased the likelihood of a visit: (1) an early evening call; (2) a high necessity rating; (3) a classification of trauma: (4) caller at the limit of tolerance of symptoms: (5) white caller. The significance of the results and their implications are discussed.

Adolescent↗
PubMed1976

Rapid recognition of group B streptococci by pigment production and counterimmunoelectrophoresis.

Streptococci from clinical isolates were studied for their ability to produce pigment in stab cultures in Columbia agar. Serological grouping of these organisms was done by counterimmunoelectrophoresis using Burroughs-Wellcome antisera. In this group of isolates, 66 of the 68 organisms grouped as B by serological testing produced pigment in the Columbia agar stab cultures. Pigment was not produced by any of the other 36 streptococci studied (11 group A, 9 group C, 4 group D, and 12 nongroupable). The use of the Columbia agar stab culture is recommended as a rapid and simple test for recognition of group B streptococci. The counterimmunoelectrophoresis test is also suggested as a convenient, rapid, and sensitive method for grouping the streptococci.

Adult↗