Photo: Graphical abstract – “Reference point indentation for the detection of early osteoarthritis”


We congratulate CHEMMAT’s Dr Josh Workman, Dr Thomas Loho and Prof Ashvin Thambyah for having their abstract shortlisted as one of the 34 finalists out of 263 abstracts reviewed for the Outstanding Abstract Award. This will be awarded at The 11th Asian-Pacific Conference on Biomechanics, December 2-5, 2021 in Kyoto, Japan.


Reference point indentation for the detection of early osteoarthritis

1. Motivation and Aim

The early detection of osteoarthritis (OA) in articular joints is a key step towards providing solutions to slow down, or even halt the progress of this debilitating disease. Current clinical diagnosis of OA typically involves imaging techniques such as X-ray and magnetic resonance imaging (MRI) which are able to acquire morphological and biochemical data of the joint, but are not able to detect the microscopic changes associated with early OA. Some recent work has been conducted to detect early changes to the cartilage surface using indentation techniques, but not the early changes in the underlying bone.

This study aimed to utilize a novel indentation technique called Reference Point Indentation (RPI) to bypass the cartilage layer, and perform dynamic indentation tests of the underlying calcified cartilage and subchondral bone. It was hypothesized that early OA pathophysiology affecting the calcified cartilage and sub-chondral bone could be detected using currently available RPI technology that may be clinically relevant.

2. Approach and Key Findings

The established model of early OA found in the bovine patella was used in this study. 36 cartilage on bone samples with varying levels of naturally occurring early degeneration were obtained and sorted into four even test groups according to the Outerbridge scale (G0-G3). RPI characterization was then carried out at 9 locations on the samples using the BioDent reference point indenter (Active Life Scientific, Inc).

Obtained data was able to show four key parameters with statistically significant changes from healthy G0 samples to moderately degenerate G3 samples. Three of the four parameters are inversely correlated to crack growth toughness and show that more degenerate samples have greater resistance to crack propagation, likely due to the advancement of the calcified region and thickening of the subchondral bone plate. The other key parameter showed a decreasing bone matrix modulus as the level of degeneration increased, indicating that the new bone formed is less stiff, further contributing to the increase in crack growth toughness via more elastic deformation.

3. Originality

Many studies attempt to diagnose OA during the early stages, using techniques varying from indentation, to ultrasound and optical coherence tomography. Whilst some of these studies are promising, they are rarely clinically relevant. The use of RPI on bone tissues has also been attempted to detect osteoporosis, but to our knowledge it has not been employed for the detection of early OA in articular joints.

4. Impact

As the BioDent RPI device is compact and able to be handheld, it shows potential for future use in clinical settings for the diagnosis of early OA in situations where it is not yet macroscopically visible, such as post-traumatic sports injury. This early detection may then enable clinical trials of disease altering drug candidates early enough in the disease progression to see viable results.  

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