T2*-Mapping of Knee Cartilage in Response to Mechanical Loading in Alpine Skiing: A Feasibility Study

Abstract

Purpose: This study intends to establish a study protocol for the quantitative magnetic resonance imaging (qMRI) measurement of biochemical changes in knee cartilage induced by mechanical stress during alpine skiing with the implementation of new spring-loaded ski binding. Methods: The MRI-knee-scans (T2*-mapping) of four skiers using a conventional and a spring-loaded ski binding system, alternately, were acquired before and after 1 h/4 h of exposure to alpine skiing. Intrachondral T2* analysis on 60 defined regions of interest in the femorotibial knee joint (FTJ) was conducted. Intra- and interobserver variability and relative changes in the cartilage T2* signal and thickness were calculated. Results: A relevant decrease in the T2* time after 4 h of alpine skiing could be detected at the majority of measurement times. After overnight recovery, the T2* time increased above baseline. Although, the total T2* signal in the superficial cartilage layers was higher than that in the lower ones, no differences between the layers in the T2* changes could be detected. The central and posterior cartilage zones of the FTJ responded with a stronger T2* alteration than the anterior zones. Conclusions: For the first time, a quantitative MRI study setting could be established to detect early knee cartilage reaction due to alpine skiing. Relevant changes in the T2* time and thus in the intrachondral collagen microstructure and the free water content were observed.

Comparing the Effect of Mechanical Loading on Deep and Superficial Cartilage Using Quantitative UTE MRI

“…A previous mechanical loading study detected a relevant decrease in T2* values of knee cartilage after 4 hours of alpine skiing, and T2* values increased above baseline overnight. 5 Behzadi et al also found significantly decreased T2* values in all cartilage segments after 45 minutes of long-distance running. 32 Marathon running seems to have reversed effects on T2* values, with two studies by Zhang and Hesper et al demonstrating increased T2* values after marathon running.…”

“…35 The T2* decrease may be due to collagen fiber deformation and increase of anisotropy and water squeezed out from the cartilage matrix. 5,32 Increased T2* values after marathon running may result from elevated mobility of water, degradation of proteoglycan, and loss of anisotropy of collagen fibers. 5,33,35 In our study, no significant difference was found in thickness and T2* values of deep cartilage after exercise.…”

“…3,4 However, the variation of T2* depends on the duration and type of mechanical loading and the investigated zones. 4,5 The possible mechanisms could include redistribution of free water in cartilage, collagen fiber re-orientation and changes of water protons binding to collagen. 6,7 Furthermore, alerted T2 and T2* values have also been observed in long-term abnormal mechanical environments due to cartilage matrix degradation.…”

Updates on Compositional MRI Mapping of the Cartilage: Emerging Techniques and Applications

“…Recent techniques have shown the feasibility of compositional MRI in assessing cartilage overuse. The feasibility of mapping of the knee cartilage in assessing the response to mechanical loading in skiing was demonstrated 98 . More specific biomechanical measures, such as strain mapping, were evaluated in the knee cartilage, 99 as shown in Fig.…”

“…The feasibility of T * 2 mapping of the knee cartilage in assessing the response to mechanical loading in skiing was demonstrated. 98 More specific biomechanical measures, such as strain mapping, were evaluated in the knee cartilage, 99 as shown in Fig. 11, and intervertebral discs.…”