Truncated-pyramid shape simulation for the measurement of femoral intercondylar notch volume can detect the volume difference between ACL-injured and intact subjects.

The purpose of this study was to measure the femoral intercondylar notch volume using a truncated-pyramid shape simulation and compare this volume between anterior cruciate ligament (ACL) injured and intact subjects. Forty-seven subjects diagnosed with ACL tear by MRI (22 male and 25 female: median age 26: range 15–49), and 41 subjects in which knee MRI was performed and no ACL injury detected (20 males and 21 females: median age 27: range 16–49), were included in this study. Using three-dimensional computed tomography (3D-CT), the axial femoral intercondylar notch area was measured in the slice containing the most proximal (S1) and most distal (S2) level of Blumensaat’s line. Femoral condyle height (h) was measured using a sagittal view of knees in 3D-CT. The truncated-pyramid shape simulation was calculated as: Volume = $$\mathrm{h}(\mathrm{S}1+\mathrm{S}2+\sqrt{{s}_{1}{s}_{2}} )/3$$ . Statistical analysis was performed to compare S1, S2, notch height, and notch volume between the ACL-injured and intact groups. The measured S1, S2, and the notch height of the ACL-injured and intact groups were 201 ± 64 and 214 ± 50mm2, 370 ± 91 and 461 ± 94mm2, and 31 ± 3 and 30 ± 4mm, respectively. The calculated femoral intercondylar notch volume of the ACL-injured and intact groups was 8.6 ± 2.2 and 9.9 ± 2.6cm3, respectively. The ACL intact group showed significantly larger S2 and notch volume when compared with the ACL-injured group. For clinical relevance, notch volume and most distal axial notch area parameters were significantly larger in ACL intact subjects. The truncated-pyramid shape simulation is an easy and cost-effective method to evaluate intercondylar notch volume. In knees with small femoral intercondylar notch volume, attention is needed to prevent ACL injury. Level III.