Influence of subchondral bone density on intra-articular stresses due to fixation hardware instrumentation and removal: A biomechanical cadaver study.

Abstract

Tibial plateau fractures are often surgically treated to restore native joint congruity and articular alignment. While these injuries portend an increased risk for end stage knee osteoarthritis, it is unknown whether the fixation constructs contribute to the development of osteoarthritis by influencing articular stress distribution following instrumentation. We conducted a cadaver study measuring resultant intra-articular stresses of the native knee due to physiological levels of ex-vivo loading, after instrumentation with plate and screw fixation, and after implant removal. To account for variable subchondral bone density, we used 3D printed bone with osteoporotic and normal cancellous bone volume fraction, and SawBones where there is no appreciable cancellous bone. There was no statistical difference in peak, average, or total contact pressures following implant fixation and removal from the preimplantation articular pressure states in all loads and all models (p > 0.05). There was also no difference between the pressure changes of the cadaveric and Sawbones models. There were statistically significant pressure changes between cadaveric and 3D printed models following fixation, however these changes were within previously described physiologic loads (<10 MPa). Subchondral instrumentation of tibial plateau fractures did not materially alter articular pressures. These findings suggest that the development of end-stage knee osteoarthritis may not be a result of altered biomechancial stresses from the instrumentation. Further, elective removal of implants is not supported by biomechanical reasons alone to reduce future risk. Supplementing cadaveric studies with patient-specific models while tuning variables can enhance the fidelity of these investigations. The findings may guide surgeons in their operative indications and clinical decision making as well as guide future biomechanical research on periarticular implant effects.