Technical and practical improvements in arthroscopic indentation technique for diagnostics of articular cartilage softening

Indentation measurements have been proposed to serve as sensitive in vivo diagnostics of cartilage degeneration. However, practical difficulties have hindered the use of quantitative indentation techniques during routine arthroscopies. In this study we modified the previously commercial indentation technique by designing software for quality control of manual indentations. With the modifications, our aim was to introduce more rapid and less erroneous measurements, as well as more automatic and objective analyses. The performance of the technique was tested in situ using six bovine medial tibial plateaus. All measurements were conducted by three operators. The intraoperator reproducibility was reasonable (CV% = 7.1) and the interoperator reproducibility was good (intraclass correlation coefficient =0.976). Further, the novel technique was tested by a single operator using 10 bovine medial tibial plateaus. The indentation stiffness values determined with the arthroscopic instrument correlated significantly with the dynamic (r=0.823) and equilibrium (r=0.752) moduli as well as tissue water (r=0.830) and hydroxyproline (r=0.776) contents. To conclude, the novel measurement technique showed good reproducibility and was found to give valuable information on cartilage properties. Most importantly, the measurements and analyses were more straightforward and automatic than those introduced in the original indentation approach.