Radiographic and Anatomic Evaluation of Tibial Tubercle to Trochlear Groove Distance

Abstract

Background A lateralized tibial tubercle is an important anatomic predictor of patellar instability and can be used as an indication for a distal realignment procedure. Currently, tibial tubercle to trochlear groove (TT-TG) distance is measured on computed tomography (CT); however, radiographs could be a safer and more efficient modality. The aim of this study is to evaluate and compare TT-TG measurements obtained using CT, anatomical dissections, and a novel radiographic technique. Furthermore, we evaluated the effects of knee flexion and tibial rotation on these measurements.

Methods TT-TG distances were measured on 11 fresh cadaver specimens with CT and compared with anatomic measurements obtained from dissection in full knee extension and 90-degree flexion. Both imaging- and dissection-derived measurements were obtained in neutral, external, and internal tibial rotation. The TT-TG distance was also measured on a modified sunrise X-ray view (knee at 90 degrees).

Results The TT-TG distance obtained on CT was 13.00 ± 1.05 mm and was comparable to measurements derived from anatomic dissections in extension (14.88 ± 1.10 mm) and 90 degrees (12.40 ± 1.93 mm) (p ≥ 0.05). The X-ray measurements of TT-TG distance (5.62 ± 1.16 mm) were significantly different than those measured on CT (p ≤ 0.05). TT-TG distances in neutral tibial position measured on CT and dissection were significantly different than distances measured in full external (19.79 ± 1.33 and 20.92 ± 1.15 mm, respectively) and internal tibia rotation (6.45 ± 1.00 and 10.33 ± 1.19 mm, respectively) (p ≤ 0.05).

Conclusions TT-TG distance measured on CT is comparable to measurements from dissections in both full extension and 90-degree flexion. Tibial rotation has a significant effect on TT-TG measurements. Radiographic measurements did not correlate with CT and anatomic measurements.

Clinical Relevance CT-derived TT-TG measurements are accurate throughout knee range of motion; however, it is important to maintain neutral lower leg rotation to not generate a false-positive or false-negative measurement. Radiographic measurement of TT-TG ration is not currently recommended.

Keywords

patellofemoral instability - TT-TG distance - computed tomography - radiographs

• References

• 1 Colvin AC, West RV. Patellar instability. J Bone Joint Surg Am 2008; 90 (12) 2751-2762
• 2 Amis AA. Current concepts on anatomy and biomechanics of patellar stability. Sports Med Arthrosc Rev 2007; 15 (2) 48-56
• 3 Diks MJ, Wymenga AB, Anderson PG. Patients with lateral tracking patella have better pain relief following CT-guided tuberosity transfer than patients with unstable patella. Knee Surg Sports Traumatol Arthrosc 2003; 11 (6) 384-388
• 4 Brossmann J, Muhle C, Schröder C , et al. Patellar tracking patterns during active and passive knee extension: evaluation with motion-triggered cine MR imaging. Radiology 1993; 187 (1) 205-212
• 5 Powers CM, Shellock FG, Pfaff M. Quantification of patellar tracking using kinematic MRI. J Magn Reson Imaging 1998; 8 (3) 724-732
• 6 van Kampen A, Huiskes R. The three-dimensional tracking pattern of the human patella. J Orthop Res 1990; 8 (3) 372-382
• 7 Muhle C, Brossmann J, Heller M. Kinematic CT and MR imaging of the patellofemoral joint. Eur Radiol 1999; 9 (3) 508-518
• 8 Dejour H, Walch G, Nove-Josserand L, Guier C. Factors of patellar instability: an anatomic radiographic study. Knee Surg Sports Traumatol Arthrosc 1994; 2 (1) 19-26
• 9 Goutallier D, Bernageau J, Lecudonnec B. The measurement of the tibial tuberosity. Patella groove distanced technique and results [author's transl.; in French]. Rev Chir Orthop Repar Appar Mot 1978; 64 (5) 423-428
• 10 Shakespeare D, Fick D. Patellar instability-can the TT-TG distance be measured clinically?. Knee 2005; 12 (3) 201-204
• 11 Kessler MA, Burkart A, Martinek V, Beer A, Imhoff AB. Development of a 3-dimensional method to determine the tibial slope with multislice-CT [in German]. Z Orthop Ihre Grenzgeb 2003; 141 (2) 143-147
• 12 Dejour D, Le Coultre B. Osteotomies in patello-femoral instabilities. Sports Med Arthrosc Rev 2007; 15 (1) 39-46
• 13 Schoettle PB, Zanetti M, Seifert B, Pfirrmann CW, Fucentese SF, Romero J. The tibial tuberosity-trochlear groove distance; a comparative study between CT and MRI scanning. Knee 2006; 13 (1) 26-31
• 14 Pandit S, Frampton C, Stoddart J, Lynskey T. Magnetic resonance imaging assessment of tibial tuberosity-trochlear groove distance: normal values for males and females. Int Orthop 2011; 35 (12) 1799-1803
• 15 Wittstein JR, Bartlett EC, Easterbrook J, Byrd JC. Magnetic resonance imaging evaluation of patellofemoral malalignment. Arthroscopy 2006; 22 (6) 643-649
• 16 Camp CL, Stuart MJ, Krych AJ , et al. CT and MRI measurements of tibial tubercle-trochlear groove distances are not equivalent in patients with patellar instability. Am J Sports Med 2013; 41 (8) 1835-1840