The geometric features of tibiofemoral joint associated with anterior cruciate ligament injury: Reliability of measurements on conventional MRI

Abstract

Purpose: To evaluate the measurement reliability of the geometric features of tibiofemoral joint on conventional knee MRI and also identify the features associated with increased risk of ACL injury.

Methods: This retrospective case-control study included knee MRIs of 60 patients with ACL injury (34 men, 26 women; mean age 34 ± 13.6 SD) and 60 normal individuals (31 men, 29 women; mean age 36 ± 11.4 SD). Geometric features of distal femur (intercondylar notch width, transcondylar width, and intercondylar notch angle) and tibial plateau (medial tibial plateau slope, lateral tibial plateau slope, and medial tibial plateau depth) were independently measured by two radiologists for each of the patients. Intraclass correlation coefficient (ICC) values were calculated to assess the reliability of the measurements. Variables with acceptable ICC values were included in the final logistic regression model, but the remaining were only reported descriptively.

Results: There was good to excellent agreement between the radiologist in the measurement of ICNW and TCW. However, the agreement between the radiologists was not acceptable for the rest of the variables. The univariate logistic regression model showed as ICNW decreases, the risk of ACL injury increases (OR = 0.12, 95% CI [0.02, 0.60], p = 0.01).

Conclusions: Our results suggest that ICNW and TCW are the only geometric features of the tibiofemoral joint that can be reliably measured on conventional knee MRI. Moreover, decreased ICNW is associated with an increased risk of ACL injury.

Keywords: Anterior cruciate ligament injuries; Femur; Intercondylar notch; Reliability of results; Risk factor; Tibia; Tibial plateau.

Fig. 1

Measurement of the medial and lateral tibial plateau slopes (MTPS, LTPS) and medial tibial plateau depth (MTPD). Using the most proximal axial image of the tibia as a scout image (white boxes), sagittal cuts running through (a) center of the tibial plateau, (b) center of the lateral and (c, d) medial articulation surfaces of tibial plateau were identified. (a) On the sagittal cut running through the center of the tibial plateau, two circles were drawn, which were connecting the anterior and posterior cortices of the proximal tibia and centers of which were at least 4 cm apart. The line connecting the centers of these two circles was drawn and called longitudinal axis (LA) of proximal tibia. Then line P was drawn perpendicular to the longitudinal axis of the tibia. Line P was reproduced on the (b) lateral and (c, d) medial sagittal cuts. On each of these sagittal cuts, anterior and posterior peak pints of tibial plateau were connected using a line. The angles formed between these lines and line P were called (b) LTPS and (c) MTPS. On the medial sagittal cut (d) a new line which was touching the floor of the concavity of the medial tibial plateau and was parallel to the line connecting the anterior and posterior peak points was drawn. The distance between these two parallel lines was measured and recorded as medial tibial plateau depth.

Fig. 2

Measurement of the intercondylar notch angle (INA). The sagittal image of the femur in which the roof of the intercondylar notch was entirely depicted was chosen. The longitudinal axis (LA) of femur was identified by connecting the centers of the two circles, which were connecting the anterior and posterior cortices of the femur and were at least 4 cm apart. The line passing parallel to the roof of the intercondylar notch (line B) was drawn. The angle formed between line A and line B was recorded as intercondylar notch angle.

Fig. 3

Measurement of the transcondylar width (TCW) and Intercondylar notch width (ICNW). The transverse cut of the femur in which the popliteal groove was fully depicted was chosen. On this transverse cut, the line that connected the anterior peak points of the femur condyles was drawn (line A). Another line (line B), which was parallel to line A and was passing through the center of the popliteal groove was drawn. The total length of line B was recorded as transcondylar width (TCW). The intercondylar notch width (ICNW) was also measured on line B.