Biomedical Engineering Reference
In-Depth Information
described. The use of magnetic field therapy in clinical applications dates
back over 500 years. In the fifteenth century, Swiss physician and alche-
mist Philippus von Hohenheim (known as Paracelsus) used lodestones, or
naturally magnetized pieces of the mineral magnetite, to treat conditions
such as epilepsy, diarrhea, and hemorrhage. He believed that the ability of
magnets to attract iron could be replicated by attracting disease away from
t h e b o dy.
As described in Wikipedia (http://en.wikipedia.org/wiki/Pulsed_
electromagnetic_field_therapy; accessed March 2011), pulsed electromag-
netic field therapy is a reparative technique most commonly used in the
field of orthopedics for the treatment of nonunion fractures, failed fusions,
congenital pseudarthrosis, and depression. In the case of bone healing,
PEMF uses electrical energy to direct a series of magnetic pulses through
injured tissue whereby each magnetic pulse induces a tiny electrical signal
that stimulates cellular repair. Many studies have also demonstrated the
effectiveness of PEMF in healing soft-tissue wounds, suppressing inflamma-
tory responses at the cell membrane level to alleviate pain, and increasing
range of motion. The value of pulsed electromagnetic field therapy has been
shown to cover a wide range of conditions, with well-documented trials car-
ried out by hospitals, rheumatologists, physiotherapists, and neurologists.
The emphasis in this section, however, is focused on the developments in
Dallari et al. [56].
8.5.1
Basic Process
Dallari et al. [56] considered a group of 30 subjects who had undergone hip
prosthesis revision. Exclusion criteria were the presence of autoimmune dis-
ease, diabetes mellitus, cancer, infectious disease, and lymphoproliferative
disorder. Subjects were assigned either to the active or to the placebo group
according to a computer-generated schedule: A random number seed was
entered into the computer to generate a list that assigned equal numbers
of active and placebo stimulators (blocks of four: two active and two place-
bos). Subjects and the medical staff were unable to differentiate between the
active and placebo stimulators. The characteristics of the stimulators were
made known only after all clinical and instrumental evaluations had been
completed.
As Dallari et all described, for all subjects the assessment of the mobili-
zation of stems was performed on x-ray films according to the Gustilo-
Pasternak classification, which classifies femoral component loosening into
four types based on the severity of loosening and instability: type I: minimal
endosteal or inner cortical bone loss
type II: proximal canal enlargement with cortical thinning of
50% or more and sometimes a lateral wall defect with an intact
circumferential wall
