Osteolysis after rigid fixation. The possible role of periosteal neural mechanoreceptors in bone remodeling.

Rigid intramedullary fixation in the rat tibiofibular bone of a tibial fracture caused the development of nonunion in the associated fibular fracture, with marked osteolytic resorption of the fibular fragments. In contrast, with flexible fixation, the associated fibular fracture healed normally. The tibial fractures healed uneventfully in both cases. Histologic examinations showed that there exists a plexus of encapsulated nerve endings (Pacinian corpuscles) in the periosteum of the fibula, at the distal tibiofibular junction. The rat fibula forms a bony contact with the lower midshaft of the anteriorly curved tibia, acting as a supporting shaft. The periosteal neural mechanoreceptors probably sense the fibular loading when the tibia is bent during weight-bearing. Fibular resorption in rigid fixation could be attributed to the rigid intramedullary nail preventing tibial bending and loading of the receptor area. In other words the neural elements could detect the stress protection due to rigid fixation and coordinate the adverse remodeling process.