Citation, DOI & article data
Citation:
Brown N, Hacking C, Foster T, et al. Patellar translation (TT-TG distance). Reference article, Radiopaedia.org (Accessed on 28 Jan 2023) https://doi.org/10.53347/rID-44662
Patellar translation can be measured using the tibial tuberosity to trochlear groove distance (TT-TG distance) by calculating the transverse length between the trochlear groove on the femur and tibial tuberosity on axial images. The measurements are used to quantify patellar instability.
Measurement
Superimpose axial images of:
femoral condyles
tibial tuberosity
Draw a line along the posterior femoral condyles, and then draw the following lines perpendicular to this line:
bisecting the tibial tuberosity (TT)
bisecting the trochlear groove sulcus (TG)
measure the distance between TT and TG = TT-TG distance
Interpretation
normal: <15 mm
borderline: 15-20 mm
abnormal: >20 mm
The distance has been shown to be slightly less when measured on MRI than CT 1.
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- 1. Hinckel B, Gobbi R, Filho E et al. Are the Osseous and Tendinous-Cartilaginous Tibial Tuberosity-Trochlear Groove Distances the Same on CT and MRI? Skeletal Radiol. 2015;44(8):1085-93. doi:10.1007/s00256-015-2118-4 - Pubmed
- 2. Song E, Seon J, Kim M, Seol Y, Lee S. Radiologic Measurement of Tibial Tuberosity-Trochlear Groove (TT-TG) Distance by Lower Extremity Rotational Profile Computed Tomography in Koreans. Clin Orthop Surg. 2016;8(1):45-8. doi:10.4055/cios.2016.8.1.45 - Pubmed
- 3. Dickens A, Morrell N, Doering A, Tandberg D, Treme G. Tibial Tubercle-Trochlear Groove Distance: Defining Normal in a Pediatric Population. J Bone Joint Surg Am. 2014;96(4):318-24. doi:10.2106/JBJS.M.00688 - Pubmed
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