Keywords:
Anatomy, Extremities, Musculoskeletal system, MR, Education, Athletic injuries, Hyperplasia / Hypertrophy
Authors:
R. Prada Gonzalez, E. Santos Armentia, M. Costas Álvarez, D. Pereira Barreiro, A. M. Villanueva Campos, C. Jurado Basildo; Vigo/ES
DOI:
10.26044/ecr2019/C-2712
Conclusion
⇒ An association between a high-patella and an increased TT-TG and SHFP impingement exist,
suggesting that SHFP impingement may be an indicator of patellofemoral maltrackig.
⇒ The variability of TT-PCL in different MR studies of the same patient is lower than that of TT-TG,
and could be a very useful parameter in the MRI study to confirm patellofemoral instability.
- TT-TG evaluates the position of the tibial tubercle relative to the femoral trochlea,
but it is difficult to calculate in dysplastic trochlea and it varies if the trochlea is internally rotated (as in increased femoral anteversion) or if the tibial tubercle is lateralized. The gold standard method to evaluate the TT-TG distance is the CT with the knee extended.
Current literature shows that TT-TG is not identical in CT and MRI: it is larger on CT than on MRI because the position of the tibia with respect to the femur changes during flexion.
- However,
TT-PCL is not influenced by the rotation of the knee or the shape of the trochlea,
and is similar in the knee in flexion and extension position.
- Knee flexion grades may vary between the first and second MR exams and may explain the increased variability of TT-TG versus TT-PCL.
- The TT-TG values are higher in SHFP impingement group but the average TT-TG is less than 20 mm.
This result is related to what is published in the literature that the value of TT-TG on MRI is less than that calculated in CT.
⇒ Surprisingly,
the values of TT-PCL in SHFP impingement group were no greater than those of TT-TG.
- This could be explained by the greatest difficulty in calculating this parameter and the least experience in its evaluation.
- More research is needed to assess the reference value of TT-PCL in patients with patellofemoral instability.
⇒ Finally,
the stability and worsening of SHFP edema between the initial and posterior exams of SHFP impingement group demonstrate that the signal alteration is real and must be taken into account by the radiologists,
having to be reflected in the reports of MR,
as a potential factor associated with patellofemoral maltracking.