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Biomedical subjects

Gregory W Faris

Publications and source records attributed to Gregory W Faris.

10 recordsLinked to original sources
PubMed2006

Polyethylene sterilization and production affects wear in total hip arthroplasties.

Production and package sterilization techniques for the polyethylene used in acetabular components for total hip arthroplasties are known to affect wear. We considered three combinations of techniques: sterilization by radiation in inert gas with isostatically molded polyethylene, in inert gas and ram-extruded polyethylene, and in air with extruded polyethylene. The intent of this study was to confirm that molded polyethylene and polyethylene radiated in inert environments reduce wear rates in vivo, to determine the combination of methods with the least wear, and to determine how much variance in wear is attributable to these methods. We reviewed 150 consecutive total hip arthroplasties done in 133 patients using 28-mm cobalt-chrome femoral heads and polyethylene-lined, titanium, ring-locked acetabular components. The least wear occurred in gamma inert-molded polyethylene components. The mean volumetric wear rates were 52.12 mm3/year for gamma inert-molded, 62.32 mm3/year for gamma inert-extruded, and 66.09 mm3/year for gamma air-extruded polyethylene components. Relative risk assessment found gamma air-extruded and gamma inert-extruded polyethylene components to wear 16% and 11% more than gamma inert-molded polyethylene components, respectively. Gender, body mass index, and age accounted for the greatest amount of the explained variance in volumetric wear (57.5%, 21.6%, and 14.4, respectively), followed by angle of wear (3.4%), and sterilization and production technique (3.2%).

Acetabulum↗
PubMed2005

Upconversion from aqueous phase lanthanide chelates.

We have prepared and characterized several lanthanide ion complexes of multidentate ligands or chelates in an effort to develop new upconverting luminescent labels that can be immune to autofluorescence and photobleaching. This study has involved the characterization of various chelates of Nd, Er, and Tm with respect to relative luminescent efficiency and excited-state lifetimes and explored various two-photon stepwise excitation mechanisms. Using peak laser powers near 100 kW, the upconversion emissions of Nd in Nd(EDTA)2(5-) at 386 nm, Er in Er(DPA)3(3-) at 550 nm, and Tm in Tm(DPA)3(3-) at 480 nm, at levels of approximately 10(-12) moles can be detected.

Chelating Agents↗
PubMed2005

Optically addressed droplet-based protein assay.

We demonstrate a new method for performing protein assays with very small volumes ( approximately 1.7 muL to 14 pL). Using a laser to modify local surface energy, we manipulate, fuse, and mix droplets containing horseradish peroxidase and its substrates. A detection limit of approximately 30 attomoles of reacting enzyme was measured by optical absorption. We discuss the possibility of extending this lower limit to zeptomoles of enzyme.

Benzothiazoles↗
PubMed2005

P(N) approximation for frequency-domain measurements in scattering media.

Presented here are expressions for the P(N) approximation for light propagation in scattering media in the frequency domain. To elucidate parametric dependencies, the derivation uses normalization of the resulting expressions to either the total interaction coefficient or the reduced total interaction coefficient. For the latter case, a set of reduced phase function coefficients are introduced. Expression of the P(N) approximation as a conventional eigenvalue problem facilitates computation of the eigenvalues or attenuation coefficients. This approach is used to determine the attenuation coefficients in the asymptotic regime over the full values of the scattering albedo and reduced scattering albedo (0 to 1) and all positive values of the asymmetry factor (0 to 1). Frequency-domain measurements yield a sensitivity to turbid media optical properties for reduced scattering albedos as small as 0.2. P(N) calculations are used to assess the magnitude of errors associated with the P1 and P3 approximations over a range of scattering albedo, phase function, and modulation frequency.

Computer Simulation↗
PubMed2004

Total knee arthroplasty in patients with angular varus or valgus deformities of > or = 20 degrees.

Of 8,014 surgeries between January 1986 and August 2000, 82 primary total knee arthroplasties (TKAs) were performed on 75 patients with severe preoperative varus or valgus deformity of greater than or equal to 20 degrees with a minimum 2-year follow-up time and a posterior cruciate retaining prosthesis. This study was designed to determine whether these patients (group A) could be as successful, using a Knee Society score (KSS) and alignment, as a matched control group (group B). There was no statistical difference in knee score, alignment, or revision. One revision was performed among the severely deformed. Knees that had severe angular deformities performed as well as deformity-free TKAs. Patients with excessive deformity should not be excluded from surgical correction solely based on this deformity.

Aged↗
PubMed2004

Tibial component failure mechanisms in total knee arthroplasty.

The purpose of this study was to examine the failure mechanisms and factors associated with failure of a nonmodular metal backed cemented tibial component. Out of 3152 total knee replacements done for osteoarthritis, 41 tibial components had been revised (1.3%). Four distinct failure mechanisms were identified: 20 knees were revised for medial bone collapse, 13 for ligamentous imbalance, 6 for progressive radiolucencies, and 2 for pain. Factors associated with medial bone collapse were varus tibial component alignment more than 3.0 degrees , Body Mass Index higher than 33.7, and overall postoperative varus limb alignment. Ligamentous imbalance was more prevalent in knees with preoperative valgus deformity. There were no knees revised for tibial component polyethylene wear or osteolysis. We conclude that the dominant failure mechanisms for this component design are related to preoperative deformity, technical factors of component alignment, overall limb alignment, and ligamentous imbalance.

Adult↗
PubMed2003

Total joint arthroplasty in the extremely elderly: hip and knee arthroplasty after entering the 89th year of life.

The goal of this study was to evaluate the complications and efficacy of total joint arthroplasty in the extremely elderly and compare the survival with the normal age-matched population. One hundred one joint arthroplasties (45 total knee arthroplasties [TKAs], 56 total hip arthroplasties [THAs]) were performed in 83 patients 89 years old and older. Over an average follow-up period of 2.5 years, 26 (31%) of the patients died. Three patients (3.6%) died within the first 2 months' postoperatively. The perioperative medical complication rate (excluding deaths) was 14%. Significant improvements were noted in pain scores, Harris Hip Scores, and Knee Society Scores. The survival of patients in their nineties who undergo total joint arthroplasty is at least equal to the survival of an age-matched population for 2.5 years following surgery. With careful patient selection and patient care to minimize medical complications, total joint arthroplasty can be an excellent option for patients who are age 89 and older.

Age Factors↗