Abstract
Subchondral bone alterations are emerging as considerable clinical problems associated with articular cartilage repair. Their analysis exposes a pattern of variable changes, including intra-lesional osteophytes, residual microfracture holes, peri-hole bone resorption, and subchondral bone cysts. A precise distinction between them is becoming increasingly important. Here, we present a tailored algorithm based on continuous data to analyse subchondral bone changes using micro-CT images, allowing for a clear definition of each entity. We evaluated this algorithm using data sets originating from two large animal models of osteochondral repair. Intra-lesional osteophytes were detected in 3 of 10 defects in the minipig and in 4 of 5 defects in the sheep model. Peri-hole bone resorption was found in 22 of 30 microfracture holes in the minipig and in 17 of 30 microfracture holes in the sheep model. Subchondral bone cysts appeared in 1 microfracture hole in the minipig and in 5 microfracture holes in the sheep model (n = 30 holes each). Calculation of inter-rater agreement (90% agreement) and Cohen’s kappa (kappa = 0.874) revealed that the novel algorithm is highly reliable, reproducible, and valid. Comparison analysis with the best existing semi-quantitative evaluation method was also performed, supporting the enhanced precision of this algorithm.
Highlights
The subchondral bone provides a functional support for the articular cartilage, the gliding tissue that covers the articulating ends of bones
A total of 7 articles were identified in the PubMed database that provide analytic methods to examine the major types of subchondral bone alterations following microfracture treatment in preclinical animal models such as the formation of intra-lesional osteophytes (n = 2 articles), residual microfracture holes (n = 3), peri-hole bone resorption (n = 3), and subchondral bone cysts (n = 4) (Supplementary Fig. 1)
Most of these attempts to evaluate such morphological changes were performed by histology and radiography, including plain radiography, magnetic resonance imaging (MRI), and micro-CT (Table 1)
Summary
The subchondral bone provides a functional support for the articular cartilage, the gliding tissue that covers the articulating ends of bones. It is often involved in defects of the articular cartilage that are difficult to treat[1,2,3,4]. Subchondral bone alterations are emerging as a considerable clinical problem associated with different articular cartilage repair techniques[4]. Their analysis reveals a pattern of variable changes such as intra-lesional osteophytes, residual holes originating from marrow stimulation procedures, peri-hole bone resorption, and subchondral bone cysts. A detailed and reproducible algorithm allowing for a www.nature.com/scientificreports/
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