Bioengineering. Thermoelastic Femoral Stress Imaging for Experimental Evaluation of Hip Prosthesis Design.

Biomechanical stress maps of an artificial femur obtained using a new infrared thermography technique validated by strain gages

“…Oh and Harris and Decking et al both used strain gages to show that human cadaveric femurs loaded quasi-statically in mid-stance primarily experienced longitudinal compressive strains on the medial side and longitudinal tensile strains on the lateral side of the proximal trochanter and shaft, being consistent with current data [51,52]. Regarding IR thermography, few prior studies have used this technology to evaluate surface stresses in biomechanics applications [38][39][40][41]. Bougherara et al subjected their test specimens to mean cyclic loads of 840 N, 1500 N, and 2100 N at 5 Hz and successfully validated their results against strain gages, but they tested a polymer-based composite hip implant alone and obtained poor quality images due to the implant's surface texturing [38].…”

“…Bougherara et al subjected their test specimens to mean cyclic loads of 840 N, 1500 N, and 2100 N at 5 Hz and successfully validated their results against strain gages, but they tested a polymer-based composite hip implant alone and obtained poor quality images due to the implant's surface texturing [38]. Hyodo et al assessed a metal hip implant inserted into an artificial femur, oriented it in 9 • of adduction, and subjected it to 5 Hz of cyclic loads from 300 ±200 N to 1800 ± 1700 N, but they did not validate their results using another experimental method and obtained poor quality images [40]. Harwood and Cummings reported using IR thermography on a metal hip implant alone under dynamic forces and validated it with strain gages, but the investigation is from 1986 and employed a much older thermographic technology [41].…”

“…This equation assumes adiabatic conditions, that is, no significant heat loss. The values inputted by the user into the software for the femur's "cortical bone" were = 1.64 g/cm 3 , C = 1 kJ/(kg K), and ˛ = 1.9 × 10 −5 K −1 based on information from the femur's manufacturer and a prior IR study [40,47].…”

“…The camera generated stress maps while averaging the applied load on the sinusoidal waveform. Similar test setups were used previously to image a metal hip implant inserted into an artificial femur, an artificial femur on its own, and a composite hip implant on its own [38][39][40].…”

“…Thus, researchers who wish to minimize their reliance on strain gages and finite element models for stress analysis require a relatively new nondestructive validated experimental method. Three prior studies used infrared (IR) thermography to investigate surface stresses in orthopaedic biomechanics applications [38][39][40]. However, only one of these reports experimentally validated their thermographic technology using another well-accepted experimental technique, but they studied a composite hip implant on its own.…”