The importance of Blumensaat’s line morphology for accurate femoral ACL footprint evaluation using the quadrant method

The importance of Blumensaat’s line morphology for accurate femoral ACL footprint evaluation using the quadrant method, by Yahagi, Iriuchishima,, Horaguchi, et al. KSSTA (2018) 26(2):455–461.

Morphological variation of the Blumensaat’s line
Following Iriuchishima’s classification*, the morphology of the Blumensaat’s line was classified into straight, small hill, and large hill types.

Straight type
The Blumensaat’s line (intercondylar roof) appeared more or less straight, and the transition from the Blumensaat’s line to the posterior cortex was clearly defined.

Small hill type
A protrusion spanning less than half of the line was observed at the posterior (proximal) part of the Blumensaat’s line.

Large hill type
A protrusion spanning more than half of the line was observed at the proximal part of the the Blumensaat’s line.

*Iriuchishima T, Ryu K, Aizawa S, Fu FH (2016) Blumensaat’s line is not always straight: morphological variations of the lateral wall of the femoral intercondylar notch. Knee Surg Sports Traumatol Arthrosc 24:2752–2757

iriuchishima-blumensaat-line-morphology
Morphological variations of the Blumensaat’s line. In Iriuchishima’s classification, the morphology of the Blumensaat’s line has three types of variations: straight type, small hill type, and large hill type

Grid placement in the quadrant method
In the same images used for the morphological evaluation of the Blumensaat’s line, four types of quadrant grid placement were evaluated according to the morphological variations of the Blumensaat’s line and the chondral lesion

  • Grid (1) Without consideration of hill existence and not including the chondral lesion. The baseline of the quadrant grid was matched to the anterior part of the Blumensaat’s line. The lower and side line of the grid were tangential to the medial wall of the lateral femoral condyle.
  • Grid (2) Without consideration of hill existence and including the chondral lesion. The base line of the grid was determined as in Grid 1. The lower and side line were tangential to the articular surface.
  • Grid (3) With consideration of hill existence and not including the chondral lesion. The baseline of the grid was the line connecting the anterior edge of the Blumensaat’s line and the top of the hill. The lower and side line of the grid were tangential to the medial wall of the lateral femoral condyle.
  • Grid (4) With consideration of hill existence and including the chondral lesion. The baseline of the grid was determined as in Grid 3. The lower and side line were tangential to the articular surface. The measurement accuracy of the Image J software were, 0.1 mm and 0.1 mm2.
yahagi2017-quadrant-grid-placement
Quadrant grid placement according to the morphological variations of the Blumensaat’s line and the chondral lesion. According to the morphological variations of the Blumensaat’s line and the chondral lesion, quadrant grids were placed as: Grid (1) without consideration of hill existence and not including the chondral lesion. Grid (2) without consideration of hill existence and including the chondral lesion. Grid (3) with consideration of hill existence and not including the chondral lesion. Grid (4) with consideration of hill existence and including the chondral lesion