Piezoelectric BoneScalpel osteotomies in osteocutaneous free flaps

The use of ultrasonic technology is not a novel concept amidst surgical specialties. Dentistry was at the foreground of early ultrasonic adaptation with reports in the late 1950s that highlighted its selective ability to cut dento-osseous structures during root canals. Since then, considerable advancements have been made in ultrasonic technology, and many other surgical specialties have incorporated the use of ultrasonic bone scalpels into their practice. The scientific literature has abundant reports demonstrating the versatile use of ultrasonic technology in oral-maxillo-facial surgery, plastic surgery, neurosurgery, and otolaryngology-head and neck surgery. Ultrasound is a cyclic sound pressure with a frequency greater than the upper limit of human hearing, typically 20,000 Hz and above. Using an ultrasonic frequency, these devices transfer their mechanical energy to the molecules in tissue causing them to deform. This process is termed piezoelectric effect, with piezooriginating from Greek, meaning ‘‘to squeeze or press.’’ Along the ultrasonic spectrum, low-frequencies have a selectivity for densely packed, mineralized tissue while higherfrequencies (i.e., Harmonic scalpel) have a propensity for separating soft-tissue. The widespread adaptation of the low-frequency ultrasonic technology is secondary to its minimal learning curve, improved tactile control compared to oscillating saws or rotating burrs, and the preservation of adjacent soft tissue. The harvesting of osteocutaneous free flaps presents a unique challenge to the reconstructive surgeon, specifically the creation of a precise osteotomy often adjacent to a flap’s vital vascular pedicle. Traditional osteotomy instruments are the oscillating saw and rotational burr, which produce considerable vibration and torque respectively. Case reports do exist of flap complications secondary to soft tissue damage, while dissecting the flap’s pedicle and creating osteotomies. Although rare and likely underreported, involuntary injury to critical perforators among all free flap types has been reported at 1.5%. In addition to tactile control and soft tissue protection, surgical reports indicate that low-frequency ultrasonic technology has reduced osteotomy blood loss and bone necrosis compared to traditional osteotomy methods. There have been very few reports of this technology being used for osteocutaneous free flaps, in which the above features would provide a distinct advantage. The Misonix BoneScalpel Ultrasonic Osteotome is a piezoelectric device that offers a low-frequency ultrasonic energy selective to mineralized tissue. Working at 22.5 kHz (22,500 strokes per second), it has disposable blades that can produce a precise linear osteotomy as thin as 0.5 mm, and with an insertion depth up to 20 mm. With these factors in mind, we sought to characterize how the BoneScalpel Ultrasonic Osteotome may benefit the harvesting of different osteocutaneous free flaps used to reconstruct bony defects. The goal of this preliminary report is to describe a future role of piezoelectric technology in the setting of osteocutaneous free-flap osteotomies.