Correlation of T2* relaxation times of the retropatellar cartilage with tibial tuberosity-trochlea groove distance in professional soccer players

Abstract

The tibial tuberosity-trochlear groove (TT-TG) distance is a radiographic measurement that is used to quantify malalignment of the patellofemoral joint (PFJ) in cross-sectional imaging. There is an ongoing debate about the impact of the TT-TG-distance on lateral patellar instability and the initiating of cartilage degeneration. In this prospective study, the association of T2* relaxation times and TT-TG distances in professional soccer players was analyzed. 36 knees of 18 professional soccer players (age: 21 ± 2.8 years) were evaluated. Participants underwent knee MRI at 3 T. For qualitative image analysis, fat-saturated 2D PD-weighted Fast Spin Echo (FSE) and T1-weighted FSE sequences were used. For quantitative analysis, T2* measurements in 3D data acquisitions were performed. In a qualitative analysis there was no structural cartilage damage and no abnormalities of the patellar and trochlea shape. The highest T2* values (26.7 ± 5.9 ms) were observed in the central compartment of the patella. The mean TT-TG distance was 10 ± 4 mm (range 3-20 mm). There was no significant correlation between TT-TG distance and T2* relaxation times in all three compartments of the retropatellar cartilage. Our study shows that so long as patellar and trochlear morphology is normal, TT-TG distance alone does not affect the tissue structure of the retropatellar cartilage in professional soccer players.

Figure 1

T2* relaxation times for the three predefined compartments in the deep (red) and superficial layers (blue) of the cartilage in the PFJ compartment.

Figure 2

Color maps of the lateral (a, d), central (b, e), and medial (c, f) compartment of the retropatellar cartilage in a patient with low TT–TG-distance (3 mm, a–c) and a patient with a high TT–TG-distance (20 mm, d–f).

Figure 3

Correlation analysis between T2* relaxation times of retropatellar cartilage and TT–TG distances.

Figure 4

Determination of the TT–TG distance using fat suppressed PD-weighted images in transversal orientation. First, the most proximal MR image slice with full cartilage coverage of the trochlear groove is chosen to assess the trochlear groove, and the posterior condylar line is drawn tangential to the chondral border of the posterior condyles of the femur. Further, the TL is drawn perpendicular to posterior condylar line (a). Secondly, TL will be transferred to most cephalad image in which the patellar tendon is fully in contact with the tibial tubercle. The center of the tibial tubercle is marked at the midpoint of the patellar tendon on this image. The final TT–TG distance will be taken as the perpendicular distance from the center of the tibial tubercle to the transferred TL (b).

Figure 5

The predefined areas of the retropatellar cartilage for T2* measurements with the corresponding PD weighted images for morphological orientation (a–c). T2* measurements were performed on sagittal images in the deep (region of interest in green) and superficial (region of interest in yellow) layer of the retropatellar cartilage. Measurement were performed in the lateral (d), central (e) and the medial (f) compartment of the joint space.