Fracture fixation usually involves mechanical fixation with rods, plates and/or screws which repair slowly and are susceptible to infection. Treatment of large defects use allografts which have failure rates of up to 25%, and complication rates as high as 30-60%. Implant infection and loosening are serious concerns, but can currently only be measured through expensive instrumented implants, biopsy culture, or radiographs. None of these directly quantify implant loading and stability however. There is therefore a need for a simple, cost effective way to quantify implant loading and stability in patients. The purpose of our study is to design and evaluate an optically-based strain measuring orthopaedic screw to quantify strain variation in the implant in-vivo after surgery and monitor the load sharing between the bone and the implant. The screw head incorporates a spectral ruler based on MoirÃ© effect which indicates strain. The screw system developed will be able to quantify clinically-relevant bone healing strains in the range of 10-3000Î¼strains, corresponding to 0.5-150Î¼m change in length for a 5cm gauge. Through this work, we will be able to develop a unique portable tool for physicians to quantify bone healing rather than relying on less quantitative assessments based on pain and radiography.
Ravikumar, N; Rogalski, M M.; Lake, J; Pelham, H; Urban, M; and DesJardins, J, "Optically-Based Strain Measuring Orthopaedic Screw for Fracture Fixation Implants" (2015). Graduate Research and Discovery Symposium (GRADS). 191.