Structural Health Monitoring of Long Bone Fractures Using Instrumented Intramedullary Nails

Clinical assessment of fracture healing is usually subjective, relying upon the detection of movement (‘feel’) by the surgeon, the patient’s response in terms of pain and confidence, and radiographic evidence of callus and primary bone union. A more quantitative, objective method of measuring the strength of a healing callus would be useful in assessing many aspects, such as the effectiveness of different forms of treatment, the pattern and rate of healing, and the stage at which the patient can return to full weight-bearing activity. The results presented in this paper demonstrate the complexity of monitoring fracture healing in leg stance phase using an instrumented intramedullary (IM) nail equipped with a single sensor. The bone healers exhibited both sigmoidal and linear load responses during fracture healing. Ambulating non-healers demonstrated high nail forces which did not change significantly over time whereas lame non-healers demonstrated a decreasing nail load due to reduced GRF or loosening of fixation.