Today, modern materials and functional elements enable the orthosis to be specifically adapted to the requirements resulting from the patients gait. Mechanical stance phase control knee joints may secure the knee joint in the early stance phases and release again for knee flexion when the swing phase is initiated. With the help of an orthotic treatment with a stance phase control knee joint, a natural gait pattern can be achieved despite mechanical protection against unwanted knee flexion. In these cases, locked knee joints are often used, which have a good safety function, but do not allow knee flexion when walking during swing phase. With such joints, the knee joint remains mechanically blocked during the swing phase. Patients with locked knee joints must swing the leg forward with the knee extended even during the swing phase. This only works if the patient develops compensatory mechanisms, e.g. by raising the bodys center of gravity in the swing phase (Duchenne limping) or by swinging the orthotic leg to the side (circumduction). Epidemiology
Eradication
Following the widespread use of poliovirus vaccine in the mid-1950s, new cases of poliomyelitis declined dramatically in many industrialized countries. A global effort to eradicate polio - the Global Polio Eradication Initiative - began in 1988, led by the World Health Organization, UNICEF, and The Rotary Foundation. Polio is one of only two diseases currently the subject of a global eradication program, the other being Guinea worm disease.
The Salk vaccine, or inactivated poliovirus vaccine, is based on poliovirus grown in a type of monkey kidney tissue culture (vero cell line), which is chemically inactivated with formalin. After two doses of inactivated poliovirus vaccine (given by injection), 90 percent or more of individuals develop protective antibody to all three serotypes of poliovirus, and at least 99 percent are immune to poliovirus following three doses.Subsequently, Albert Sabin developed another live, oral polio vaccine. It was produced by the repeated passage of the virus through nonhuman cells at subphysiological temperatures. The attenuated poliovirus in the Sabin vaccine replicates very efficiently in the gut, the primary site of wild poliovirus infection and replication, but the vaccine strain is unable to replicate efficiently within nervous system tissue. A single dose of Sabins oral polio vaccine produces immunity to all three poliovirus serotypes in about 50 percent of recipients. Three doses of live-attenuated oral vaccine produce protective antibody to all three poliovirus types in more than 95 percent of recipients. Human trials of Sabins vaccine began in 1957, and in 1958 it was selected, in competition with the live vaccines of Koprowski and other researchers, by the US National Institutes of Health. Licensed in 1962, it rapidly became the only polio vaccine used worldwide. Because the oral polio vaccine is inexpensive, easy to administer, and produces excellent immunity in the intestine (which helps prevent infection with wild virus in areas where it is endemic), it has been the vaccine of choice for controlling poliomyelitis in many countries.