Biomechanical analysis of Osteoarthritic Infrapatellar Fat Pad (IFP) and Suprapatellar Fat Pad (SFP): mechanical shear tests. [English translation]

The knee is the largest and most complex joint of the human body, both functionally and structurally, and it’s necessary to perform daily human activities. It is also the joint most frequently affected by osteoarthritis, the most common disorder among the global population, but the risk factors are basically still unknown. Recent studies are investigating the role played by adipose tissue in the knee in the onset of the disease, focusing specifically on the infrapatellar and suprapatellar fat pads (IFP and SFP).
The aim of this study is to observe the mechanical behavior of these tissues.
IFP and SFP specimens were obtained from ten different subjects, in order to compare their different biomechanical characteristics.
Experimental shear tests were performed at three different strain rates.
The data obtained from the tests were used to calculate mechanical parameters such as shear stress (τ), shear strain (γ), from which were calculated and represented stress-strain shear curves.
Moreover, shear modulus (G), energy dissipation density (EDI) and peak-to-peak shear stress (ptp) were evaluated.
These values were used to make comparisons between subjects and individuals, who underwent total knee arthroplasty (OA specimens), grouped according to their properties such as gender, age and BMI. Then, the OA specimens together were compared to a healthy specimen of a subject who underwent to amputation due to leg cancer.
The experimental data obtained from the mechanical tests were compared with those found in the literature, although they were largely absent.
The reported results can be considered as a starting point for understanding how the biomechanical characteristics of the tissue influence the progression of the disease, as well as being valuable for the development of models of the knee joint and prosthetic replacement devices.