Biophysical regulation of osteotomy healing: An animal study

Background Osteotomies have been performed for centuries yet there remains a remarkable lack of consensus on optimal methods for cutting bone. There is universal agreement, however, that preserving cell viability is critical. Purpose To identify mechanobiological parameters influencing bone formation after osteotomy site preparation. Materials and methods A murine maxillary osteotomy model was used to evaluate healing. Computational modeling characterized stress and strain distributions in the osteotomy, as well as the magnitude and distribution of heat generated by drilling. The impact of osteocyte death and bone composition were assessed using molecular and cellular assays. Results The phases of osteotomy healing in mice align closely with results in large animals; in addition, molecular analyses extended our understanding of osteoprogenitor cell proliferation, differentiation, and mineralization. Computational analyses provided insights into temperature changes caused by drilling and the mechanobiological state in the healing osteotomies, while concomitant cellular assays correlate drill speed with osteocyte apoptosis and bone resorption. Even when drilling was controlled, trabeculated, spongy (Type III) bone healed faster than densely lamellar (Type I) bone because of the abundance of Wnt responsive osteoprogenitor cells in the former. Conclusions These data provide a mechanobiological framework for evaluating tools and technologies designed to improve osteotomy site preparation.