Abstract
We studied changes in articular calcified cartilage (ACC) and subchondral bone (SCB) in the third carpal bones (C3) of Standardbred racehorses with naturally-occurring repetitive loading-induced osteoarthritis (OA). Two osteochondral cores were harvested from dorsal sites from each of 15 post-mortem C3 and classified as control or as showing early or advanced OA changes from visual inspection. We re-examined X-ray micro-computed tomography (µCT) image sets for the presence of high-density mineral infill (HDMI) in ACC cracks and possible high-density mineralized protrusions (HDMP) from the ACC mineralizing (tidemark) front (MF) into hyaline articular cartilage (HAC). We hypothesized and we show that 20-µm µCT resolution in 10-mm diameter samples is sufficient to detect HDMI and HDMP: these are lost upon tissue decalcification for routine paraffin wax histology owing to their predominant mineral content. The findings show that µCT is sufficient to discover HDMI and HDMP, which were seen in 2/10 controls, 6/9 early OA and 8/10 advanced OA cases. This is the first report of HDMI and HDMP in the equine carpus and in the Standardbred breed and the first to rely solely on µCT. HDMP are a candidate cause for mechanical tissue destruction in OA.
Highlights
Articular cartilage comprises two layers mainly distinguished by calcification of the one to make the other: the deep layer of hyaline articular cartilage (HAC) becomes articular calcified cartilage (ACC) [1,2]
high-density mineral infill (HDMI) and high-density mineralized protrusions (HDMP) were found with the greatest incidence in the samples classified as advanced OA, less in the early OA and only one HDMP in a control sample
They held that stresses at the base of the articular cartilage could cause deep horizontal splits in that tissue, whilst, observation shows that such splits are mainly vertical
Summary
Articular cartilage comprises two layers mainly distinguished by calcification of the one to make the other: the deep layer of hyaline articular cartilage (HAC) becomes articular calcified cartilage (ACC) [1,2] This mineralization both stiffens the material and allows it to be resorbed by osteo(chondro)clasts to permit scaffolded bone formation upon the eroded surface, which attaches bone tissue to cartilage, absolutely central to the function of bones and joints. They may be removed by osteoclastic removal in the periodic repair, replacement and refreshment of this junction [2,5] Such cracks repair spontaneously by the formation of a high-density mineralized infill (HDMI) phase. This was first found using backscattered electron scanning electron microscopy (BSE SEM) of flat surfaces of polymethylmethacrylate (PMMA)-embedded blocks in studies of Thoroughbred racehorse distal third metacarpal bones (Mc3: fetlock [6,7]) and hock joints [6]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
