Experimental Evaluation of Strain Shielding in Distal Femur in Revision TKA

Abstract

Theoretical concerns about the use of cemented and press-fit stems in revision total knee arthroplasty (TKA) include stress shielding with adverse effects on prosthesis fixation. Radiological studies have showed distal femoral bone resorption after revision TKA. The revision with use of stems can place abnormal stresses. These stresses can promote the effect of bone stress shielding and may contribute to bone loss. Experimental quantification of strain shielding in the distal synthetic femur following TKA is the main purpose of the present study. Three different constructs of TKA were assessed. The first construct included a stemless femoral component. The other two included a press-fit and a cemented femoral stem. Cortical bone strains were measured experimentally with tri-axial strain gauges in synthetic femurs before and after in-vitro knee surgery. The difference between principal strains of implanted and intact femur was calculated for each strain gauge position. This study indicates that the use of stems in distal femur changes the distribution and magnitude of bone strains. The press-fit stem provoked relevant bone area (stem length) subjected to strain shielding and also originated the highest reduction of strains in the distal region, which can potentially induce bone resorption. The stemless implanted femur produced minor bone strain changes relatively to the intact femur. The use of distal femur stems increases initial stability in the bone, but the observed reduction of strains in this region, relative to the intact femur, provokes strain shielding that can induce bone resorption and may compromise the long term implant stability.

Strain shielding in distal femur after patellofemoral arthroplasty under different activity conditions

“…The standard deviations of principal strains obtained in this study were in the range of those calculated in the other experimental studies with synthetic femurs (e.g. Completo et al, 2007;Completo et al, 2008;Cristofolini and Viceconti, 1996;Viceconti et al, 2001;Waide et al, 2003).…”

“…Several experimental studies with composite bones were carried out involving the measurement of bone surface strains. The main purpose of these was to respond to a clinical need in order to investigate in vitro implant-bone load transfer mechanisms, monitoring the strain shielding effect and for finite element model validation (Completo et al, 2007(Completo et al, , 2008Cristofolini and Viceconti, 1996;Viceconti et al, 2001;Waide et al, 2003). The standard deviations of principal strains obtained in this study were in the range of those calculated in the other experimental studies with synthetic femurs (e.g.…”

Biomechanical evaluation of pyrocarbon proximal interphalangeal joint arthroplasty: An in-vitro analysis

“…These experimental results shows that the PIP joint is not immune to using a pyrocarbon prosthesis. The FE models developed to analyse cancellous-bone, major support structure for the implant, presented correlation, slope, intercept values of the linear regressions and RMSE values in the range of other previous experimental-numerical studies performed with synthetic bones (Completo et al, 2013;Completo et al, 2008;Heiner, 2008), which reveals a good agreement between FE and measured strains. As observed experimentally at the cortex, cancellous bone strain behaviour in the implanted PIP joint was very different of intact state for all load-cases analysed.…”

The Evolution of the Field of Biomechanics Through the Lens of Experimental Mechanics

“…For example, one work described the properties of a composite femur under vibration [21], which has ramifications for the design and performance of new orthopedic implants. Other recent works have conducted in-depth investigations into the biomechanics of the femur in fracture fixation and into the phenomena of strain shielding [22,23]. The mechanics of trabecular bone, which is of tremendous interest due to its role in osteoporosis, has been investigated using a novel non-destructive method based on micro-computed tomography technology [24] and was also the subject of a nanoscale biomechanical study by Gao et al [25].…”