Combined electric and magnetic field therapy for bone repair and regeneration: an investigation in a 3-mm and an augmented 17-mm tibia osteotomy model in sheep

Abstract
Background
Therapies using electromagnetic field technology show evidence of enhanced bone regeneration at the fracture site, potentially preventing delayed or nonunions.

Methods
Combined electric and magnetic field (CEMF) treatment was evaluated in two standardized sheep tibia osteotomy models: a 3-mm non-critical size gap model and a 17-mm critical size defect model augmented with autologous bone grafts, both stabilized with locking compression plates. CEMF treatment was delivered across the fracture gap twice daily for 90 min, starting 4 days postoperatively (post-OP) until sacrifice (9 or 12 weeks post-OP, respectively). Control groups received no CEMF treatment. Bone healing was evaluated radiographically, morphometrically (micro-CT), biomechanically and histologically.

Results
In the 3-mm gap model, the CEMF group (n‚Äâ=‚Äâ6) exhibited higher callus mineral density compared to the Control group (n‚Äâ=‚Äâ6), two-fold higher biomechanical torsional rigidity and a histologically more advanced callus maturity (no statistically significant differences). In the 17-mm graft model, differences between the Control (n‚Äâ=‚Äâ6) and CEMF group (n‚Äâ=‚Äâ6) were more pronounced. The CEMF group showed a radiologically more advanced callus, a higher callus volume (p‚Äâ=‚Äâ0.003) and a 2.6‚Äâ√ó‚Äâhigher biomechanical torsional rigidity (p‚Äâ=‚Äâ0.024), combined with a histologically more advanced callus maturity and healing.

Conclusions
This study showed that CEMF therapy notably enhanced bone healing resulting in better new bone structure, callus morphology and superior biomechanical properties. This technology could transform a standard inert orthopedic implant into an active device stimulating bone tissue for accelerated healing and regeneration.