The Effects of Physical Exercise on Osteocyte Lacunar Morphology and Orientation around Bioresorbable Implants

In this study, we used synchrotron radiation micro-computed tomography (SR-μCT) to investigate the effect of early post-operative physical exercise at 2, 4, and 6 weeks on osteocyte lacunar distribution and morphology in a Sprague Dawley rat femoral defect model after implantation of a bioresorbable pin. Physical exercise has been shown to improve bone remodeling after fracture, but its effects on the lacuno-canalicular network in the presence of bioresorbable implants remain unclear. The structure of lacunae is linked to that of osteocytes, which play an important role in bone remodeling and adaptation to stress. We studied a large number of lacunae (around 670 000 per sample) in terms of their location, morphology, and orientation. We show that in newly formed bone, lacunae are larger and rounder with exercise, while in previously existing bone, lacunae are less oriented along the long bone axis when exercise is performed. In addition, close to the implant, lacunar density is higher with exercise in both newly formed bone and previously existing bone. These findings point to a higher degree of remodeling and a pronounced lacunar response to mechanical stimulation and may thus help clarify bone behavior with exercise around implants to better design post-surgical recovery treatments.