Structural, compositional, and functional effects of blunt and sharp cartilage damage on the joint: A 9‐month equine groove model study

Abstract

This study aimed to quantify the long-term progression of blunt and sharp cartilage defects and their effect on joint homeostasis and function of the equine carpus. In nine adult Shetland ponies, the cartilage in the radiocarpal and middle carpal joint of one front limb was grooved (blunt or sharp randomized). The ponies were subjected to an 8-week exercise protocol and euthanized at 39 weeks. Structural and compositional alterations in joint tissues were evaluated in vivo using serial radiographs, synovial biopsies, and synovial fluid samples. Joint function was monitored by quantitative gait analysis. Macroscopic, microscopic, and biomechanical evaluation of the cartilage and assessment of subchondral bone parameters were performed ex vivo. Grooved cartilage showed higher OARSI microscopy scores than the contralateral sham-operated controls (p < 0.0001). Blunt-grooved cartilage scored higher than sharp-grooved cartilage (p = 0.007) and fixed charge density around these grooves was lower (p = 0.006). Equilibrium and instantaneous moduli trended lower in grooved cartilage than their controls (significant for radiocarpal joints). Changes in other tissues included a threefold to sevenfold change in interleukin-6 expression in synovium from grooved joints at week 23 (p = 0.042) and an increased CPII/C2C ratio in synovial fluid extracted from blunt-grooved joints at week 35 (p = 0.010).Gait analysis outcome revealed mild, gradually increasing lameness. In conclusion, blunt and, to a lesser extent, sharp grooves in combination with a period of moderate exercise, lead to mild degeneration in equine carpal cartilage over a 9-month period, but the effect on overall joint health remains limited.

Site- and Zone-Dependent Changes in Proteoglycan Content and Biomechanical Properties of Bluntly and Sharply Grooved Equine Articular Cartilage

“… 7 , 34 , 36 Briefly, blunt and sharp grooves were made by arthrotomy, performed by a European board‐certified equine surgeon (HB) in one randomly assigned front limb per animal. Three grooves (two in parallel in palmaro-dorsal direction and one in mediolateral direction) were randomly made in the cartilage of the radial facet of the third carpal bone (middle carpal joint) and of the intermediate carpal bone (radiocarpal joint), as described previously 37 (Fig. 1 a, step 1).…”

“…In our previous study, 37 we investigated the structural, compositional, and functional effects of blunt and sharp cartilage damage on the joint. In that study, microscopical analysis (optical density evaluation) was limited to grooved cartilages and measuring the mean value of PG content around the lesions.…”

“…In the present study we aimed to gain further insights into the subtle events taking place at the early stages of cartilage degeneration in bluntly and sharply grooved joints. Also, we aimed to provide novel data that could be combined with the collected data in our previous study 37 for computational modelling, in order to unravel the tissue deterioration mechanisms in grooved joints. Thus, we investigated long-term changes in PG distribution of bluntly and sharply grooved equine carpal cartilage and the opposing contact surfaces as a function of tissue depth and distance-to-groove.…”

Deformation behaviors and mechanical impairments of tissue cracks in immature and mature cartilages

“…Further studies should focus on investigating the long-term effects of cracks in tissues undergoing microscopic degeneration, 68,73,74 either via in vitro method using a bioreactor 26 or using an in vivo approach through live animal testing. 75 Microscopic deformation of tissue and cells near the crack should be quantified to improve our understanding of the effect of crack morphology on cell mechanobiology. 38,76 There are limitations in this study that need to be considered.…”

“…Therefore, the immature cartilage may possess the regenerative ability to “cope” with tissue cracks that are not available in the mature cartilage. Further studies should focus on investigating the long‐term effects of cracks in tissues undergoing microscopic degeneration, 68,73,74 either via in vitro method using a bioreactor 26 or using an in vivo approach through live animal testing 75 . Microscopic deformation of tissue and cells near the crack should be quantified to improve our understanding of the effect of crack morphology on cell mechanobiology 38,76 …”