Abstract
Understanding the tribological behaviour of articular cartilage enables the development of effective replacement biomaterials. This study presents a technique for the investigation of the frictional torque of articular cartilage, for the assessment of replacement biomaterials. A calcium alginate hydrogel was used as the biomaterial for this study. Three different specimen types were examined to include articular cartilage, calcium alginate hydrogel, alone, and in combination with articular cartilage. An axial load, varying from 10 to 100 N, was applied to the specimen and the frictional torque measured whilst an indenter underwent axial rotation from 0° to 2° to 0° for 100 cycles. The resulting frictional torque magnitude was evaluated with a smooth curve fitting function. Linear regression identified a statistically significant relationship between torque magnitude and axial load (p < 0.05) for all specimen variations. From 10 to 100 N of applied load, mean torque magnitude ranged from 0.08±0.010 to 0.11±0.013 N m, 0.08±0.012 to 0.09±0.016 N m and 0.07±0.017 to 0.09±0.020 N m (mean ± standard deviation), for articular cartilage, calcium alginate separately and in combination with articular cartilage, respectively. This study has established a suitable frictional torque testing protocol for potential cartilage replacement biomaterials.
Highlights
Synovial joints consist of articular cartilage and surrounding synovial fluid, including subchondral bone [1]
The articular cartilage conceals the bone ends in synovial joints [2], contributing to a low coefficient of friction reported in the range of 0.002 to 0.02 [3]–[5], aided by a surface roughness of 80 – 170 nm [6]
The mean torque magnitude with respect to axial load across all six specimens is presented in Fig. 5a-c, for cartilage on-bone, and the 2 and 10 mm calcium alginate inserts, respectively
Summary
Synovial joints consist of articular cartilage and surrounding synovial fluid, including subchondral bone [1]. The articular cartilage conceals the bone ends in synovial joints [2], contributing to a low coefficient of friction reported in the range of 0.002 to 0.02 [3]–[5], aided by a surface roughness of 80 – 170 nm [6]. The lubrication mechanisms of articular cartilage contribute to its low friction characteristics [7], [8], minimalising wear [8], [9]. OA contributes to the increased friction of articular cartilage whilst the joint undergoes motion. OA is not solely associated with articular cartilage, as the underlying subchondral bone plays a role. During the earlier stages of OA, increased bone remodelling is observed [12]–[14]
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