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C V White

Publications and source records attributed to C V White.

4 recordsLinked to original sources
PubMed1999

Simulation of initial frontside and backside wear rates in a modular acetabular component with multiple screw holes.

A sliding distance-based finite element formulation was implemented to predict initial wear rates at the front and back surfaces of a commercially available modular polyethylene component during in vitro loading conditions. We found that contact area, contact stress, and wear at the back surface were more sensitive to the liner/shell conformity than the presence of multiple screw holes. Furthermore, backside linear and volumetric wear rates were at least three orders of magnitude less than respective wear estimates at the articulating surface. This discrepancy was primarily attributed to the difference in maximum sliding distances at the articulating surfaces (measured in mm) versus the back surface (measured in microm). This is the first study in which backside wear has been quantified and explicitly compared with frontside wear using clinically relevant metrics established for the articulating surface. The results of this study suggest that with a polished metal shell, the presence of screw holes does not substantially increase abrasive backside wear when compared with the effects of backside nonconformity.

Acetabulum↗
PubMed1998

Backside nonconformity and locking restraints affect liner/shell load transfer mechanisms and relative motion in modular acetabular components for total hip replacement.

Nonconformity between the polyethylene liner and the metal shell may exist in modular acetabular components by design, due to manufacturing tolerances, or from locking mechanisms that attach the polyethylene liner to the metal shell. Relative motion at the liner/shell interface has been associated with backside wear, which may contribute to osteolysis which has been clinically observed near screw holes. The purpose of this study was to investigate the effect of nonconformity and locking restraints on the liner/shell relative motion and load transfer mechanisms in a commercially available, metal-backed acetabular component with a polar fenestration. The finite element method was used to explore the hypothesis that backside nonconformity and locking restraints play important roles in long-term surface damage mechanisms that are unique to modular components, such as backside wear and liner extrusion through screw holes. The three-body quasi-static contact problem was solved using a commercially available explicit finite element code, which modeled contact between the femoral head, polyethylene liner, and the metal shell. Four sets of liner boundary conditions were investigated: no restraints, rim restraints, equatorial restraints, and both rim and equatorial restraints. The finite element model with a conforming shell predicted between 8.5 and 12.8 microm of incremental extrusion of the polyethylene through the polar fenestration, consistent with in vitro experiments of the same design under identical loading conditions. Furthermore, idealized rim and/or equatorial liner restraints were found to share up to 71% of the load across the liner/shell interface. Consequently, the results of this study demonstrate that backside nonconformity and locking restraints substantially influence backside relative motion as well as load transfer at the liner/shell interface.

Acetabulum↗
PubMed1991

The use of antidepressants for negative symptoms in a subset of schizophrenic patients.

The authors used a randomized, placebo-controlled design to assess the therapeutic efficacy of adjunctive imipramine, added to fluphenazine decanoate and benztropine, among well-stabilized, negative-symptom schizophrenia and schizoaffective disorder patients who additionally met operationalized criteria for postpsychotic depression. The outcome of the imipramine-treated group was superior in both global ratings and a specific negative-symptom scale. Exacerbation of psychotic symptomatology was not found to be problematic. The implications of this study are discussed in terms of a potential strategy for pharmacotherapy among certain negative-symptom patients and in terms of its relevance to a possible pathophysiological basis for the negative-symptom state.

Adult↗