Effects of hyperthermia on bone. II. Heating of bonein vivoand stimulation of bone growth

Abstract

Previous studies in vitro have shown that it is possible to achieve comparable temperature distribution in bone and the adjacent soft tissues, under appropriate experimental conditions. The objective of the present work was to determine the effects of hyperthermia on bone in vivo. In order to obtain direct temperature measurements in bone, catheters were surgically installed on top of and inside the medullary cavity of the femur of normal rabbits. The thighs were irradiated with 915 MHz microwaves for 45 min, once or twice a week. The temperatures on and inside the bone were maintained between 42.5 and 44.0 degrees C; the resulting temperatures in the muscle were within 1.0 degrees C at depths equidistant from the applicator. After four to six treatments the femora were excised for histopathological examination. New trabecular bone was deposited around the catheters; most bone components including periosteum, osteoid, and fully calcified matrix could be seen. Large numbers of osteoblasts and osteoclasts lined the trabecular surfaces, and numerous cement lines were visible, running in all directions, indicating extensive bone deposition and remodelling. In contrast, control bones (catheters installed--no hyperthermia) showed much less ossification, with many areas of thin incomplete osteoid. Further, bones treated with hyperthermia only (no surgical trauma) showed no such changes. Thus, it appears that following an initial insult, hyperthermia promotes bone deposition.

Photothermal stress triggered by near-infrared-irradiated carbon nanotubes up-regulates osteogenesis and mineral deposition in tooth-extracted sockets

“…Hyperthermia therapy has been shown to stimulate bone remodelling and the formation of new bone, thus increasing cortical bone density [44][45][46]. The hyperthermal stimulation (1.5-3.0 C above normal) stimulates the longitudinal and concentric growth of the femur and tibia in growing rats and dogs [47].…”

Response of preosteoblasts to thermal stress conditioning and osteoinductive growth factors

“…Furthermore, the use of conditioned culture media acquired from heat-treated osteoblasts (incubator heating at 42°C for 1 h) enhanced OCN secretion and mineralization in bone marrow mesenchymal cells (Ye et al 2007). In addition to water bath or incubator heating, the exposure to elevated temperatures in the range of 42.5-44°C following treatment with 915 MHz microwave for 45 min generated new osseous tissue (Leon et al 1993). Taken together, thermal stress conditioning can potentially serve as a positive cue for bone regeneration, which could be employed in combination with other tissue engineering exogenous stimuli such as GFs.…”

Effects of Low-Dose Microwave on Healing of Fractures with Titanium Alloy Internal Fixation: An Experimental Study in a Rabbit Model

“…However, the use of microwave for extra-corporeal heating of bone seems feasible. Using a dedicated microwave hyperthermia system, Leon et al systematically examined the effect of microwave hyperthermia on bone both in vitro and in vivo [16,17]. They demonstrated that hyperthermia promoted bone deposition.…”

“…They demonstrated that hyperthermia promoted bone deposition. The effect of microwave is mainly induced by the alternating electromagnetic fields, which activates the dipoles in the molecule of the material [16]. The collisions of the molecules cause generation of heat inside the object [53].…”