The effects of exposure of rats with an experimental zygomatic bone fracture to a pulsed 50 Hz magnetic field in combination with other therapeutical treatments on bone healing should be investigated.
Isogeneic (inbred) rats were divided into 9 groups (n=15 rats each): 1) exposure to the sinusoidal magnetic field, 2) exposure to the pulsed magnetic field, 3) treatment with platelet-rich plasma, 4) treatment with bone marrow stromal stem cells, 5) co-exposure to the sinusoidal and pulsed magnetic field, 6) exposure to the pulsed magnetic field and treatment with platelet-rich plasma, 7) exposure to the pulsed magnetic field and treatment with bone marrow stromal stem cells, 8) sham group (no exposure or treatment, only bone fracture) and 9) control group (no exposure, no treatment, no bone fracture).
Except for the control groups, rats in all groups underwent a surgery to induce an experimental non-union fracture of the zygomatic bone. Treatments with platelet-rich plasma or bone marrow stromal stem cells took place directly after creation of the fracture during the same surgery. Exposure to the magnetic fields started on the 7. day after the surgery/treatments.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
50 Hz
Exposure duration:
continuous for 8 hours/day for 1 month
|
|
|
Exposure 2:
50 Hz
Modulation type:
pulsed
Exposure duration:
continuous for 8 hours/day for 1 month
|
|
remark EMF-Portal: as the same exposure device was used for the purpose of obtaining a magnetic field with pulse via intermittent flow of power supply and to obtain a sinusoidal field via constant power flow, it is not evident how a co-exposure to both fields (group 5) was realized
| Frequency | 50 Hz |
|---|---|
| Type | |
| Waveform | |
| Exposure duration | continuous for 8 hours/day for 1 month |
| Exposure source | |
|---|---|
| Chamber | plexiglass and methacrylate cage (43 x 42 x 15 cm3) |
| Setup | Helmholtz coils (70 cm diameter) were placed into a Plexiglas Faraday cage (130 x 65 x 80 cm3); the distance between the 2 coils was adjusted to 47 cm (remark EMF-Portal: Helmholtz configuration?); the magnetic field was created with copper wires, which had 125 loops of 1.5 mm diameter; not clear, where the animal cages were placed |
| Sham exposure | A sham exposure was conducted. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 1.5 mT | - | - | - | - |
| Frequency | 50 Hz |
|---|---|
| Type | |
| Waveform | |
| Exposure duration | continuous for 8 hours/day for 1 month |
| Modulation type | pulsed |
|---|---|
| Pulse width | 25 µs |
| Exposure source |
|
|---|---|
| Setup | intermittent flow of power supply was used for the purpose of obtaining magnetic field with pulse |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 1.5 mT | - | - | - | - |
After 6 months, the bone density showed significant differences between the groups. The highest mean bone density was found in the control group (group 9). Group 6 (pulsed magnetic field and platelet-rich plasma) showed the second highest value followed by group 7 (pulsed magnetic field and bone marrow stromal stem cells).
Regarding the marker levels, significant differences between the groups were found as well. The highest values of hydroxyproline in urine and in bone tissue, alkaline phosphatase and osteocalcin in the blood were found in group 6.
Histopathological comparison of the groups did not point out any differences regarding inflammation. The highest increase in terms of blood vessel formation was observed in group 6, whereas the lowest increase was seen in group 7. The values closest to the control groups in terms of collagen fibrils and osteocyte ratio were found in groups 6 and 7.
The authors conclude that exposure of rats with an experimental zygomatic bone fracture to a pulsed 50 Hz magnetic field in combination with a treatment with platelet-rich plasma might be beneficial for bone healing and useful for clinical applications.
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