PubMed Health⌕ Search

Biomedical subjects

J S Nyman

Publications and source records attributed to J S Nyman.

8 recordsLinked to original sources
PubMed2001

Total knee replacement with interlocking stems: a preliminary report.

Revision total knee replacements or primary total knee replacements with large amounts of bone loss frequently require long-stemmed prostheses to stabilize the components. The hypothesis of the current study was that long-stemmed prostheses can be fixed with interlocking screws, provide a successful outcome, avoid extensive stress-shielding, and allow easy revision in the future. Ten patients with a minimum 2-year followup were studied. Outcomes were studied preoperatively and postoperatively using the Short Form-12 questionnaires, physical examinations, and radiographs. Complications were recorded. Ability to do activities of daily living, strenuous work, and sedentary work were recorded on a 10-point analog scale. Results indicated that 80% of stems well-fixed as shown on serial radiographs, functional outcome scores postoperatively improved significantly from preoperatively, pain was improved significantly, and positive bone remodeling without stress-shielding was seen in 80% of patients, but 20% had significant stress-shielding in the metaphysis. Complications included two periprosthetic fractures for which the patients did not require revision surgery, and one infection. Long-stemmed total knee components with interlocking fixation seem to be a reasonable alternative when large bone defects exist in the femur or tibia.

Adult↗
PubMed2000

Toward standardization of methods of determination of fracture properties of acrylic bone cement and statistical analysis of test results.

A succinct critical review of the literature on the fatigue, fatigue crack propagation, and fracture toughness (herein collectively termed "fracture properties") of acrylic bone cement is presented, whereby it is pointed out that a plethora of test conditions have been used. This situation precludes meaningful interstudy comparisons and mitigates against a definitive delineation of the effect of a named variable on a specified fracture property. A case for standardization of test conditions is thus made, culminating in the presentation of a recommended set of such conditions. In addition, it is shown that many literature parametric studies employed inappropriate statistical methods for performing pairwise comparisons, and all these studies have not addressed the issue of possible interactions between the parameters being investigated. A methodology for addressing these deficiencies is presented in the present report, and its use is illustrated with a set of notional fatigue test results.

Acrylates↗
PubMed1999

A new method of determining the J-integral fracture toughness of very tough polymers: application to ultra high molecular weight polyethylene.

The thrust of the present work was the development of a new modification to the ASTM E813-89 method for determining the J-integral fracture toughness, JIc, of ductile polymers. The advantages and limitations of the modification, vis a vis the ASTM E813-89 and the hysteresis methods, are presented. The modification was then applied to investigate the effect of sterilization method on the JIc of ultra-high-molecular-weight polyethylene (UHMWPE) specimens that were subsequently aged (heated, in a cylindrical pressure vessel, in oxygen gas at 507 kPa and 70 degrees C for 14 d). Relative to the unsterilized material, it was found that gamma-irradiating the polymer leads to a significant drop in its JIc, while sterilization using either ethylene oxide or gas plasma produced no effect on its JIc. The clinical implications of the present results for the in vivo performance of UHMWPE counterfaces, and, hence, hip and knee arthroplasties, are fully discussed.

Hardness Tests↗
PubMed1998

A methodology for examining the plausibility of accelerated aging protocols for UHMWPE components.

In light of the time-intensive nature of using real-time shelf-aged specimens in research into property changes of ultra-high-molecular-weight polyethylene (UHMWPE), accelerated thermal diffusion oxidative aging (usually referred to as accelerated aging) is frequently resorted to. A number of such aging protocols have been reported in the literature, with various claims for their producing changes in the properties of the polymer being the same as or similar to those seen in real-time shelf-aged samples. The thrust of the present work is the presentation of a methodology for examining such claims. The methodology is applied to six properties (% crystallinity, melting temperature, oxidation index, ultimate tensile strength, ultimate tensile elongation, and tensile toughness) of 4150HP UHMWPE grade, sterilized using six different methods, prior to and following the use of a specific accelerated aging protocol (oxygen gas at 70 degrees C and 507 kPa pressure; 14 d.). These six properties have been identified in the literature as being strongly correlated with the clinical wear of UHMWPE articular components. It is shown that the claim for the protocol used in the present work (in terms of the simulated equivalent shelf aging time) is plausible. It needs to be emphasized, however, that this conclusion is tentative given the paucity of the relevant literature results that are currently available and which are vital to the application of the methodology.

Biocompatible Materials↗
PubMed1997

Effect of mixing method on selected properties of acrylic bone cement.

The present study was an investigation of the effect of the method of mixing the constituents of CMW3 bone cement on selected physical and mechanical properties of the fully polymerized cement. Five such methods were used: hand mixing; "active" vacuum mixing; mixing in a machine that allowed simultaneous mechanical mixing and centrifugation; mixing using this machine followed by application of a "passive" vacuum; and application of a passive vacuum followed by mixing in the machine. It was found that the best overall results were obtained from cement that had been mixed using the second and fifth methods and the values of the properties were: density, 1220 to 1246 kg/m3; areal porosity, 0.02 to 7.04%; ultimate compressive strength, 84 to 112 MPa; ultimate compressive strain, 5.1 to 6.4%; and compressive modulus of elasticity, 2249 to 2877 MPa.

Acrylates↗
PubMed1984

Electric cataract: a rare clinical entity.

Bilateral crystalline lens opacities developed in a 39-year-old black male who had been involved in an electrical accident approximately 1 yr before our examination. The anterior subcapsular opacities had feathered edges and a slightly raised center. The typical appearance and progressive course of the opacities, as well as the history, led to the diagnosis of electric cataract.

Adult↗
PubMed1977

Pupillary examination.

Examination of the pupils is an essential part of the evaluation of patients in optometric practice. In this article, the normal pupil and pupillary reflexes are reviewed, along with a discussion of anisocoria and specific anomalies of the pupils. Explanation of step by step office examination techniques is presented, as well as a discussion of the pathophysiology of abnormal pupils.

Adie Syndrome↗