Abstract
Successful fracture healing is dependent on an optimal mechanical and biological environment at the fracture site. Disturbances in fracture healing (non-union) or even critical size bone defects, where void volume is larger than the self-healing capacity of bone tissue, are great challenges for orthopedic surgeons. To address these challenges, new surgical implant concepts have been recently developed to optimize mechanical conditions. First, this review article discusses the mechanical environment on bone and fracture healing. In this context, a new implant concept, variable fixation technology, is introduced. This implant has the unique ability to change its mechanical properties from “rigid” to “dynamic” over the time of fracture healing. This leads to increased callus formation, a more homogeneous callus distribution and thus improved fracture healing. Second, recent advances in the nano- and micro-topography of bone scaffolds for guiding osteoinduction will be reviewed, particularly emphasizing the mimicry of natural bone. We summarize that an optimal scaffold should comprise micropores of 50–150 µm diameter allowing vascularization and migration of stem cells as well as nanotopographical osteoinductive cues, preferably pores of 30 nm diameter. Next to osteoinduction, such nano- and micro-topographical cues may also reduce inflammation and possess an antibacterial activity to further promote bone regeneration.
Highlights
Bone is a living organ that is subject to a continuous modeling and remodeling process throughout its life [1,2]
We previously reported the presence of nanopores of 31.93 ± 0.97 nm diameter on the surface of collagen type I fibers (Figure 2B), structurally closely related to the 30 nm gap region of single D repeats. We further showed these pores to efficiently induce osteogenic differentiation of adult human mesenchymal (MSCs) and neural crest-derived stem cells (NCSCs) and regeneration of calvarial critical size defects [86,87]
Mirulla and colleagues very recently systematically reviewed the progress in periprosthetic bone remodeling through finite element (FE) simulation [104]
Summary
Bone is a living organ that is subject to a continuous modeling and remodeling process throughout its life [1,2]. According to the current understanding of physiological bone healing, a coordinated interaction of molecular, physical and biomechanical factors in complex pathways is necessary [18] In this process, the sequential stages of embryonic endochondral bone formation are repeated during fracture healing. This phase is characterized by the resorption of non-perfused bone substance in the fracture gap. During the modeling/remodeling phase, the woven bone is replaced by organized lamellar bone and the macroscopic bone shape (including the medullary cavity) is fully restored Both forms of fetal bone formation, the intramembranous and endochondral ossification occur. The prerequisites for secondary healing are the activation of bone-forming cells, a so-called relative stability of the fracture and sufficient blood supply. Decrees in construct stiffness using variable fixation on one side of the fracture gap, while the transition between rigid and dynamic fixation produces a 30% decrees in construct stiffness using variable fixation on both side of the fracture gap (H)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
