Knees with straight Blumensaat's line have small volume of femoral intercondylar notch.

ABSTRACT

PURPOSE: Smaller femoral intercondylar notch volume has been identified as a risk factor for anterior cruciate ligament injury. The present study aims to investigate differences in the intercondylar notch volume based on differences in the morphology of Blumensaat's line. METHODS: Eighty-eight (88) subjects (42 male and 46 female median age 27 range 15-49), were included in this study. Using 3-dimensional computed tomography (3D-CT), the volume of the intercondylar notch was calculated using a truncated-pyramid shape simulation with the formula [Formula see text]. Femoral condyle height (h) was measured in the sagittal plane of the knee in 3D-CT. The area of the intercondylar notch was measured in the axial slice containing the most proximal level (S1) and most distal level (S2) of Blumensaat's line. In the sagittal view of the knee, Blumensaat's line morphology was classified into either straight or hill type. Statistical analysis was performed to compare h, S1, S2, and notch volume between the straight and hill type groups. RESULTS: Thirty-six subjects were classified as having straight type morphology and 52 subjects were classified as having hill type morphology. The measured h, S1, and S2, of the straight and hill types were 29 ± 4 and 31 ± 4 mm, 213 ± 72 and 205 ± 51 mm2, 375 ± 114 and 430 ± 94 mm2, respectively. The calculated femoral intercondylar notch volume of the straight and hill types was 8.1 ± 2 and 9.5 ± 2 cm3, respectively. Straight type knees showed significantly smaller S2 (p = 0.04), and notch volume (p = 0.01) when compared with hill type knees. CONCLUSION: Intercondylar notch volume was significantly smaller in knees with straight type Blumensaat's line morphology. Considering that Blumensaat's line represents the roof of the femoral notch, morphological variations in Blumensaat's line are likely to reflect variation in notch volume. For clinical relevance, as a smaller notch volume is a risk factor for ACL injury, straight type Blumensaat's line may also be considered a potential risk factor for ACL injury. LEVEL OF EVIDENCE Level III.