In-Situ Cartilage Functionality Assessment Based on Advanced MRI Techniques and Precise Compartmental Knee Joint Loading through Varus and Valgus Stress.

Oliver Said,Philipp Schad,Daniel Benjamin Abrar,Andreas Prescher,Teresa Nolte,Sven Nebelung,Justus Schock,Matthias Knobe,Christiane Kuhl,Daniel Truhn

doi:10.3390/diagnostics11081476

Abstract

Stress MRI brings together mechanical loading and MRI in the functional assessment of cartilage and meniscus, yet lacks basic scientific validation. This study assessed the response-to-loading patterns of cartilage and meniscus incurred by standardized compartmental varus and valgus loading of the human knee joint. Eight human cadaveric knee joints underwent imaging by morphologic (i.e., proton density-weighted fat-saturated and 3D water-selective) and quantitative (i.e., T1ρ and T2 mapping) sequences, both unloaded and loaded to 73.5 N, 147.1 N, and 220.6 N of compartmental pressurization. After manual segmentation of cartilage and meniscus, morphometric measures and T2 and T1ρ relaxation times were quantified. CT-based analysis of joint alignment and histologic and biomechanical tissue measures served as references. Under loading, we observed significant decreases in cartilage thickness (p < 0.001 (repeated measures ANOVA)) and T1ρ relaxation times (p = 0.001; medial meniscus, lateral tibia; (Friedman test)), significant increases in T2 relaxation times (p ≤ 0.004; medial femur, lateral tibia; (Friedman test)), and adaptive joint motion. In conclusion, varus and valgus stress MRI induces meaningful changes in cartilage and meniscus secondary to compartmental loading that may be assessed by cartilage morphometric measures as well as T2 and T1ρ mapping as imaging surrogates of tissue functionality.

Highlights

Magnetic Resonance Imaging (MRI) is considered the most powerful and multifaceted imaging technique of modern medicine and provides the reference standard for joint assessment
Even though clinical MRI techniques are characterized by good-to-excellent diagnostic accuracy in the evaluation of the knee joint [1], early degenerative changes of articular cartilage and the medial and lateral menisci remain difficult to diagnose based on clinical standard MRI techniques [2,3]
Imaging of the knee joint under loading is possible in open low-field MRI scanners (i.e., B0 ≤ 0.5 T) where the patient bears weight [10] or in closed-bore high-field MRI scanners (i.e., B0 ≥ 1.5 T) where the patient is loaded by prototypical devices

Summary

Introduction

Magnetic Resonance Imaging (MRI) is considered the most powerful and multifaceted imaging technique of modern medicine and provides the reference standard for joint assessment. Imaging of the knee joint under loading is possible in open low-field MRI scanners (i.e., B0 ≤ 0.5 T) where the patient bears weight [10] or in closed-bore high-field (clinical) MRI scanners (i.e., B0 ≥ 1.5 T) where the patient is loaded by prototypical devices These devices are positioned in the horizontal bore alongside the patient and make use of optimized signal-to-noise ratio, image resolution, and examination times afforded by higher magnetic field strengths. Such devices most often apply axial loading along the lower extremity’s mechanical axis [7]. The lower extremity must be mechanically immobilized as the joint necessarily undergoes flexion and tibial rotation [14], thereby challenging intra- and inter-patient reproducibility and standardization [11,13]

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Conclusion