An age-related computational framework for predicting tibial fracture healing under walking rehabilitation: a comparison between younger and older adults

Mechanical factors regulate tissue differentiation during fracture healing. However, how age-related differences in gait kinematics, muscle forces, and bone microarchitecture modulate local biomechanical microenvironment remains unclear. We developed an age-related computational framework to link musculoskeletal loading during partial weight-bearing (PWB) walking to a mechanoregulation-based tibial fracture healing model. Open-source biomechanical datasets of younger (21 – 30 years) and older adults (61 – 84 years) were conducted to simulate muscle and joint forces by the developed age-related musculoskeletal model PWB walking rehabilitation. These forces were sampled and inserted into an age-related fracture healing model. The healing outcomes were systematically evaluated by computing the probability of success (PoS) of endochondral ossification and vascularization. Results demonstrated that the timing and intensity of peak mechanical stimulation varied by age groups. The linear relationships between age-related joint forces and mechanical stimulation suggest that older adults are more prone to fracture non-union and ruptured blood vessels. To achieve optimal healing, older adults require longer postoperative recovery periods before initiating PWB rehabilitation exercises. However, neovascularisation is highly sensitive to weight-bearing regardless of age. This study provides a transferable framework for testing postoperative protocols in computational simulations, highlighting the need for age-related rehabilitation strategies to optimize fracture healing.