Biomedical subjects
Publications and source records attributed to H Stalder.
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The stiffness of the AO external pedicular fixator was analysed in an experimental laboratory study using three different sets of pedicle screws and different configurations of the implant. The experiments were performed with a wooden model as well as with bi-segmental human lumbar spine specimens with disc and ligaments intact. The capacity of the AO external pedicular fixator to compensate axial load, transversal- and torsion forces was compared to physiological requirements. Of particular interest was the effect of preload on the axial stiffness. It is demonstrated that the axial stiffness of the AO external pedicular fixator is so low that the axial load on the lumbar spine level in humans cannot be influenced by the fixator even when preloaded. However the resistance against torsion and transversal slipping is probably higher than required in vivo. No significant differences were found between the three types of pedicular screws. The effect of the triangular counter nuts of the AO external pedicular fixator on the transversal- and torsion stability was important. The presented results suggest that the AO external pedicular fixator can be of significant value in segmental rotation- and translocation pathologies of the lumbar spine and that the effect of isolated segmental distraction has probably been overestimated.
The current status of antiviral therapy is reviewed, including discussion of older approaches together with more recently developed chemotherapy. Following the introduction dealing with pathophysiological aspects of virus disease, the different approaches to antiviral therapy are presented. The reasons for the slow progress in antiviral therapy are discussed. These include: 1. the necessity of intracellular penetration of drugs acting on viral replication; 2. the severe toxicity of most antiviral drugs; 3. the narrow antiviral spectrum of most of these agents; 4. the difficulty of making a rapid etiological diagnosis in view of the necessity of starting (specific?) treatment early in the course of the disease; 5. the difficult evaluation of beneficial as compared with deleterious effects of antiviral therapy. After a detailed review of clinically tested substances, including immunoglobulins, synthetic antiviral drugs (amantadine, nucleoside analogs, thiosemicarbazones and photodynamic dyes) and interferon, a guide concerning indications and application of specific antiviral therapy is presented. Although at present there are few indications, clinicians should be aware of the (present and future) possibilities of antiviral therapy.