The space available for the anterior cruciate ligament in the intercondylar notch is less in patients with ACL injury

Purpose The aim of this study was to determine if a difference exists in the relationship between the femoral intercondylar notch volume, and the volumes of anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) in ACL injured patients and healthy subjects. Methods Intact knees of 19 healthy subjects and bilateral knees of 18 ipsilateral ACL reconstructed patients were scanned using 3-tesla high-resolution magnetic resonance imaging. The intercondylar notch, ACL, PCL and hamstring graft were segmented using three-dimensional (3D) processing software. The native intercondylar notch, ACL, and PCL volumes were compared between both groups. The volumes of native ACL and graft were compared in ACL injured patients. Results The following volumes showed no significant differences between the ACL injured group and control group; intercondylar notch (9.9 +/- 2.3 vs 9.6 +/- 1.7 cm(3)), ACL (2.4 +/- 0.7 vs 2.4 +/- 0.6 cm(3)) and PCL (3.9 +/- 1.0 vs 3.4 +/- 0.8 cm(3)), and the ratio of the ACL to the intercondylar notch (24.6 +/- 5.0 vs 25.4 +/- 2.9%). There was a significant difference in the ratio of PCL to the intercondylar notch (39.1 +/- 4.3 vs 35.9 +/- 4.9%,p = 0.023). The graft was significantly larger than native ACL volume (3.0 +/- 0.7 vs 2.4 +/- 0.7 cm(3),p = 0.012). Conclusions The ratio of the PCL volume in the femoral intercondylar notch was higher in the ACL injured group compared to the healthy control group, despite the ratio of ACL volume in the femoral intercondylar notch being similar in both groups. A greater awareness of the potentially limited space for the graft alongside the PCL within the femoral intercondylar notch may allow surgeons a more informed choice of graft type and size.