Functional in-situ assessment of human articular cartilage using MRI: An entire-knee joint loading device

Zielsetzung:

The response to loading of human articular cartilage as assessed by Magnetic Resonance Imaging (MRI) remains to be defined in relation to histology and biomechanics. Thus, an MRI-compatible entire-knee joint loading device for the functional in-situ assessment of cartilage was developed and validated.

Material und Methodik:

A formalin-fixed human knee was scanned by CT in its native configuration and digitally processed to create femoral and tibial bone models, which were covered by artificial articular cartilage in its native configuration using cartilage-mimicking polyvinyl-siloxane. At the medial femoral condyle a defect of 8 mm diameter was created within the artificial cartilage layer, into which native cartilage samples of similar dimensions were placed. Displacement-controlled quasi-static uni-axial loading to 2.5 mm (δ2.5) and 5.0 mm (δ5.0) of tibia (mobile) versus femur (immobile)was performed to study the response to loading of macroscopically intact human articular cartilage samples (n = 5) by serial imaging using PDW TSE sequences and T2W multi-spin echo sequences on a clinical 3.0T MRI system (Achieva, Philips). Biomechanics and histology served as the standards-of-reference.

Ergebnisse:

All samples were histologically intact (Mankin score, 1.8 ± 1.3) and biomechanically homogeneous (Young's Modulus, 0.4 ± 0.1MPa). They could be visualized in their entirety and loading-induced significant decreases in sample height (δ0: 2.9 ± 0.3 mm; δ2.5: 2.6 ± 0.3 mm; δ5.0: 2.0 ± 0.2 mm; p < 0.001) and decay of T2 signal intensity indicative of tissue pressurization were found.

Schlussfolgerungen:

The response-to-loading assessment of cartilage by MRI in a close-to-physiological experimental setting and with reference to histology and biomechanics is possible. Articular cartilage may be functionally evaluated beyond mere static analysis in a basic research context.