Abstract
ObjectiveBeyond static assessment, functional techniques are increasingly applied in magnetic resonance imaging (MRI) studies. Stress MRI techniques bring together MRI and mechanical loading to study knee joint and tissue functionality, yet prototypical axial compressive loading devices are bulky and complex to operate. This study aimed to design and validate an MRI-compatible pressure-controlled varus–valgus loading device that applies loading along the joint line.MethodsFollowing the device’s thorough validation, we demonstrated proof of concept by subjecting a structurally intact human cadaveric knee joint to serial imaging in unloaded and loaded configurations, i.e. to varus and valgus loading at 7.5 kPa (= 73.5 N), 15 kPa (= 147.1 N), and 22.5 kPa (= 220.6 N). Following clinical standard (PDw fs) and high-resolution 3D water-selective cartilage (WATSc) sequences, we performed manual segmentations and computations of morphometric cartilage measures. We used CT and radiography (to quantify joint space widths) and histology and biomechanics (to assess tissue quality) as references.ResultsWe found (sub)regional decreases in cartilage volume, thickness, and mean joint space widths reflective of areal pressurization of the medial and lateral femorotibial compartments.DiscussionOnce substantiated by larger sample sizes, varus–valgus loading may provide a powerful alternative stress MRI technique.
Highlights
Magnetic resonance imaging (MRI) is clearly the most powerful and versatile technique for musculoskeletal imaging
This study was divided into two parts: (1) the development, construction, and validation of an MRI-compatible pressurecontrolled VVL device; and (2) its proof-of-concept application in studying changes within a human cadaveric knee joint based on MR imaging, computed tomography (CT) and radiography and as a function of gradually increased VVL intensities
No significant magnetic field inhomogeneity or image artefacts were associated with the presence of the loading device inside the scanner as indicated by B0 or B1 mapping and the T2*-weighted sequence, respectively
Summary
Magnetic resonance imaging (MRI) is clearly the most powerful and versatile technique for musculoskeletal imaging. Providing the reference standard imaging modality for the non-invasive assessment of intra- and periarticular structures of the human knee joint, current clinical-standard morphological MRI studies are usually performed with the patient in a supine position and their joints in an unloaded and, unphysiological configuration. Open MRI scanners can examine the patient in a standing or seated position, thereby enabling imaging of the lower extremity under weight-bearing [1, 2]. Magnetic Resonance Materials in Physics, Biology and Medicine (2020) 33:839–854 quality secondary to significantly lower field strengths (i.e. B0 ≤ 0.5 T), signal-to-noise ratios, and image resolutions [3]. This in turn challenges the reliable detection of slight changes in the intraarticular soft tissues’ morphological appearance [4]
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