The resistivity of epitaxial silver films on mica in vacuum is studied as a function of temperature, thickness, and surface conditions. All samples share a common mica-silver interface. Surface roughness of the other surface is controlled by low-temperature evaporation of very thin silver overlays that anneal below room temperature. The strongly interdependent data are interpreted by rigorous fits to various models of size effects. The fits yield reasonable parameter values, some of which imply temperature-dependent surface scattering. It is shown that resistivity data alone do not suffice to distinguish between different theories of size effects or to identify the detailed aspects of surface scattering.
Osteolysis can occur around loose, as well as well fixed, cemented or cementless acetabular components in total hip arthroplasty. Histologic studies of tissues biopsied from osteolytic regions suggest an adverse foreign body response to polyethylene and other particulate debris from prosthetic materials. Phagocytosis of these particles by macrophages and giant cells stimulate the production of proteolytic enzymes and inflammatory mediators, all leading to tissue destruction. The importance of polyethylene wear debris is now fully appreciated, and it is clear that this is the major contributor to particulate debris. The authors strongly recommend the avoidance of 32 mm femoral heads, thin acetabular component liners, titanium heads, and acetabular screws when absolutely necessary. We strongly advise 26 mm to 28 mm femoral heads, polyethylene thickness of at least 8 mm, precise liner shell contact, rigid fixation of the acetabular metal shell, intimate bone-acetabular shell contact, and circumferential porous coating of femoral components to decrease the amount of and migration potential of polyethylene debris (Table). Based on our current knowledge, these measures will minimize the problem of acetabular osteolysis.
Using a gait mat, we characterized the functional results for thirty-five patients before and after a total knee replacement for the treatment of degenerative arthritis. Preoperatively, we studied three distinct populations of patients. Group I consisted of sixteen patients who were scheduled to have a unilateral total knee replacement and who had no signs or symptoms of arthritis in the contralateral knee. Group II consisted of twelve patients who were scheduled to have a unilateral total knee replacement but who had asymptomatic degenerative arthritis in the contralateral knee. Group III consisted of seven patients who had bilateral arthritis that was to be managed by total knee replacement. The gait mat allowed us to measure stance time, step length, double-support time, swing time, swing-to-stance ratio, and velocity. A knee-rating scale was used to measure pain. The data were compared with those obtained from an age-matched control group of ninety-one subjects. Postoperatively, the gait evaluation revealed marked improvement in all of the patients. However, the patients in Group II did not improve as much as those in Groups I and III did. We concluded that even asymptomatic arthritis can impair gait, that bilateral total knee replacement can yield excellent results, and that patients tend to use the lower limbs in as symmetrical a way as possible. Gait analysis can be an important source of objective information, and it is easily performed by using a gait mat.
The mechanical properties of five synthetic fiberglass casting materials were evaluated and compared with the properties of plaster of Paris. Two of the tests were designed to bear clinical relevance and the third to determine intrinsic material properties. The effect of water on strength degradation was also evaluated. It was found that the synthetics as a group are far superior to plaster of Paris in all methods of testing and that, among the synthetics, KCast Tack Free, Deltalite “S”, and KCast Improved were the stronger materials. Clinically, the most important results are that the synthetics attain their relatively high strength in a much shorter time frame than does plaster of Paris, and retain 70–90% of their strength after being immersed in water and allowed to dry.
Twenty-eight cases of glomus tumor of the hand have been studied from various aspects including a review of the pertinent literature, clinical manifestations, treatment, and the incidence of this lesion in relation to other hand tumors and to glomus tumors occurring extramanually. These interesting and unusual lesions often are not palpable, frequently not visible, and usually not detectable on roentgen examination. Nonetheless, the diagnosis can be readily made if there is awareness of the characteristic triad of symptoms: pain, tenderness, and cold sensitivity. Meticulous complete excision, the only recommended treatment, should result in complete cure.
Conversion of Girdlestone arthroplasty is a demanding procedure dependent on adequate debridement at time of resection and appropriate long-term antibiotic therapy. Patients must be followed closely for persistent sepsis through ESR, aspiration, and physical examination. Pre-reconstruction, existing bone stock should be assessed and revision techniques utilized where appropriate. Our experience is that conversion of Girdlestone pseudoarthrosis to THR can yield good functional results and restore independence.
Computed tomography (CT) scanning is a useful tool in many areas of orthopedics. This prospective study reviews the authors' experience with CT scans in 73 patients studied prior to total hip arthroplasty. The CT scan is valuable in the primary total hip arthroplasty if the radiograph suggests medial, posterior, or superior acetabular wall defects. In some instances, bone grafting or other special procedures are required for the reconstruction of these defects. In the present study, preoperative CT identified an abnormality in 18 cases with deficient acetabular walls, while plain radiographs identified only six of these difficulties. Although important information for planning revision total hip arthroplasties was noted in this series, CT scans are indicated primarily in instances of suspected acetabular wall defects.
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