Effect of osteochondral graft orientation in a biotribological test system

Abstract

Autologous osteochondral transplantation (AOT) utilizing autografts is a widely used technique for the treatment of small‐to‐medium cartilage defects occurring in knee and ankle joints. The application of viable cartilage and bone ensures proper integration, early weight bearing, as well as restoration of biomechanical and biotribological properties. However, alignment of the autografts onto the defect site remains a pivotal aspect of reinstating the properties of the joint toward successful autograft integration. This is the first study to perform tests with different orientations of osteochondral grafts in a cartilage‐on‐cartilage test system. The objective was to estimate if there are differences between aligned and 90°‐rotated grafts concerning molecular biological and biomechanical parameters. Tissue viability, assessed by XTT assay indicated lower metabolic activity in tested osteochondral grafts (aligned, p = 0.0148 and 90°‐rotated, p = 0.0760) in favor of a higher anabolic gene expression (aligned, p = 0.0030 and 90°‐rotated, 0.0027). Tissue structure was evaluated by Safranin O histology and microscopic images of the surface. Aligned and 90°‐rotated grafts revealed no apparent differences between proteoglycan content or cracks and fissures on the cartilage surface. Test medium analyzed after tribological tests for their sulfated glycosaminoglycan content revealed no differences ( p = 0.3282). During the tests, both the friction coefficient and the relative displacement between the two cartilage surfaces were measured, with no significant difference in both parameters (COF, p = 0.2232 and relative displacement, p = 0.3185). From the methods we deployed, this study can infer that there are no differences between aligned and 90°‐rotated osteochondral grafts after tribological tests in the used ex vivo tissue model. © 2019 The Authors. Journal of Orthopaedic Research ® Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res

Effects of Loading Conditions on Articular Cartilage in a Metal‐on‐Cartilage Pairing

“…The osteochondral plugs (8‐mm diameter, 15‐mm length) were harvested from the medial femoral condyle using a cutting tube (OATS; Arthrex Inc., Naples, FL) within 24 h after sacrifice. The anteroposterior orientation was marked to arrange the osteochondral cylinder, as previously described . Each knee yielded nine samples, which were washed with phosphate‐buffered saline (PBS) (Sigma‐Aldrich Chemie GmbH, Steinheim, Germany).…”

“…The metabolic activity of chondrocytes within the cartilage of the osteochondral plugs was measured using an XTT assay kit (Cell Proliferation Kit II (XTT); Roche Diagnostics, Basel, Switzerland), as previously described . In short, cartilage was cut from the osteochondral grafts and bisected longitudinally, with equal distribution of the contact area on both pieces of articular cartilage.…”

Biotribological Tests of Osteochondral Grafts after Treatment with Pro-Inflammatory Cytokines

“…As shown in our previous study, 23 the use of a cartilage-on-cartilage test system reflects native physiological conditions more accurately than testing against a metal or glass counterpart. This test setup is particularly advantageous when imitating inflammatory reactions, as this approach not only depends on the test fluid but also on how the cartilage matrix of both osteochondral grafts changes during treatment.…”

“…A test system with a specially designed sample holder, which was already applied in previous studies, 23 , 24 was used and is shown in Fig. 1 .…”

The dominance of water on lubrication properties of articular joints

“…The process ensures sterile conditions for tests on biological samples that are highly sensitive to the environmental conditions. As the setup is designed for consecutive projects (Bauer et al, 2019) that require possible analysis techniques, such as mass spectroscopy, cell counting with a hemocytometer or microarray methods, it is crucial to inhibit interaction with common ambient conditions that may generate artefacts.…”