Can the Apex of Tibial Tubercle Represent the Insertion of Patellar Tendon in Measurement of Quadriceps Angles? Imaging Verification

Abstract

Background Clinical measurement of a quadriceps angle (Q-angle) has yet achieved consensus. The patellar stability is generally low despite that the tibial tubercle (TT) is fixed. The aim of this retrospective study was to verify whether the lower arm of a Q-angle (i.e. the patellar tendon [PT]) can be represented by the localization of TT. Methods The locations of the apex of TT and the center of PT in magnetic resonance imaging (MRI) were investigated in 100 consecutive young adult patients (50 men and 50 women; average, 27 years). The tibial width (TW), the distance from the apex of TT and the center of PT to the lateral edge of TW, and the PT width were measured. The ratios of the TT and PT to TW were compared statistically. Results The TW was 64 mm (62-66 mm). The apex of TT was 38% (37-39%) from the lateral edge of TW. The center of PT was 37% (36-38%) from the lateral edge of TW. Except the TW and PT width (both, p < 0.001), there was no statistical significance in all other comparisons between sexes ( p > 0.05). The correlation between the TT and PT in 100 patients was 0.84. There was statistical difference between the two parameters ( p = 0.02). Conclusion Although the center of PT is lateral to the apex of TT, the discrepancy is minimal (1% of TW, about 0.6 mm; or 3% of PT width). Clinically, using the TT to represent the insertion of PT may be reasonable.