Varied influence of the femoral or tibial component on quadriceps angles: Verified by imaging studies

Abstract

Objective: The aim of this study was to evaluate the varied influence of femoral or tibial component on Quadriceps angles (Q-angle) measured with magnetic resonance image (MRI) and full-length standing scanogram (FLSS) techniques.

Methods: Two groups of patients were studied. The first group underwent MRI studies and the second group underwent FLSS studies. Two-step procedures were carried out. Knee MRI in 60 consecutive adult patients simply taken for meniscus or ligament injuries were utilized at the first step. The standardized patellar center (PC) and tibial tubercle (TT) on the frontal plane of MRI were positioned. At the second step, the FLSS in other 100 consecutive young adult patients taken for chronic unilateral lower extremity injuries were used for locating the two landmarks from MRI. The Q-angle was then determined on the anterior superior iliac spine, standardized PC, and TT on the FLSS.

Results: For 60 patients, the standardized PC was at the point 42% from the lateral end of the trans-epicondylar line of the femur. The TT was at the point 2 cm distal to the tibial articular surface and 37% from the lateral end of the tibial width. For 100 patients, the Q-angle was an average of 9.5° and 65.2% of the Q-angle was contributed by the upper arm (the femur). Women had a larger Q-angle (10.1° vs. 8.8°, p = 0.02) and a shorter femur (41.1 vs. 44.7 cm, p < 0.001).

Conclusion: The Q-angle is about 9.5° with 65.2% contributed by the femur. The Q-angle may mainly be influenced by the femoral component.

Level of evidence: Level IV, Diagnostic Study.

Keywords: Femoral component; Full-length standing scanogram; Influence; Magnetic resonance images; Quadriceps angle; Tibial component.

Fig. 1

A standardized patellar center (PC) is determined. (Left) The femur trans-epicondylar line (TEL) is depicted on the frontal plane. (Right) At the same level of the transverse plane, the deepest point of the trochlear groove (TG) is determined. A perpendicular line is drawn to the tangent of posterior femur condyle. A line parallel to the posterior femur condyle tangent with the widest length is depicted. The standardized PC is positioned at the junction of both lines and expressed by the ratio of the distance to the lateral femur wall (dotted line) to the TEL (%).

Fig, 2

The tibial tubercle (TT) is determined. (Left) On the transverse plane, at the level of the patellar tendon inserted on the proximal tibia, a reference line is depicted with parallel to the posterior femur condyle tangent. A line bisecting the patellar tendon is drawn with perpendicular to the reference line. A line parallel to the reference line is depicted with the largest width in the tibia. The TT is positioned at the junction of both lines and expressed by the ratio of the distance to the lateral tibial wall (dotted line) to the largest tibial width (%). (Right) At the same level of the frontal plane, the tibial width line is depicted. The distance from the line to the articular surface is measured.

Fig. 3

Anatomic landmarks are shown: ASIS, anterior superior iliac spine; F, femoral component; fc, femoral center; MCL, midpoint connecting line; PC, patellar center; P-line, parallel line to fc–tc line; T, tibial component; tc, tibial center; TD, tibial diameter; TEL, trans-epicondylar line; TT, tibial tubercle.