The accuracy and reliability of a novel handheld dynamic indentation probefor analysing articular cartilage

This study investigates the accuracy and reliability of a novel handheld in dentation system designed to ascertain the dynamic biomechanical properties of articular cartilage. A series of standard elastomers were assessed with both the handheld indent ation system and a bench-top dynamic indentation system to assess the accur acy of the instrument. Interoperator and intraoperator experiments were und ertaken to investigate the reliability of the system when used by an indivi dual operator and by five different operators. Intraclass coefficients (Rho ) were derived using a random effects model. The system was then used to as certain the topographical variation in the shear moduli and phase lag of ar ticular cartilage across normal ovine tibial plateaux. The system was shown to be highly accurate (R-2 = 0.97), and had excellent reliability when measuring the dynamic shear modulus of articular cartilage (interoperator Rho = 0.75, intraoperator Rho = 0.79). Measurement of stati c shear modulus was less reliable (interoperator Rho = 0.15, intraoperator Rho = 0.52), but may be improved by monitoring the load applied to the inst rument by the operator. The instrument was used to differentiate between di fferent regions of cartilage and generated a topographical map of an ovine tibial plateau. The cartilage located beneath the menisci was 200-500% stif fer than the cartilage that was not covered by the menisci, while the phase lag was almost constant (10 degrees +/- 2 degrees SD) over the entire tibi al plateau. The system was shown to be an accurate and reliable tool for rapidly assess ing the dynamic biomechanical properties of articular cartilage, while bein g small enough to be used arthroscopically.