23 - Variation in Human Meniscal Root Orientation

Poster Board Number: 23
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Abstract Body : The menisci play a fundamental role in the effective transmission and distribution of loads in the knee during locomotion. The meniscal roots are critical for both the positioning and function of the menisci. Compressive forces during loading are transformed into tensile stresses in the circumferential fibers of the meniscal body periphery; the circumferential fibers of the meniscal body continue into the insertional ligaments which transmit this tensile load to the bone. Despite the crucial function of meniscal roots in the knee, variation in the orientation of these insertional ligaments is not well understood. Here I quantify three-dimensional variation in the orientation of the meniscotibial roots of the menisci in modern humans.

The knees of 61 cadaveric individuals (34 female, 27 male) were dissected to expose the menisci and their insertions. Photogrammetry and blue light scanning were used to generate surface models for each knee. Meniscal models were created by merging scans of each the menisci and with scans of the tibial plateau. Proximal cross-sections were taken where each of the four meniscotibial roots crosses the condyle border; distal cross-sections were taken close to each root’s attachment site. The centroids of each cross-section were collected as landmarks; all individuals were then Procrustes aligned relative to the proximal cross-section centroids. Unit vectors were determined from the proximal point to distal point of each aligned root. Mean orientation, concentration, and ovalness for each root were calculated using spherical statistics.

Three-dimensional variation in orientation was found to differ significantly for all meniscotibial roots in the human knee (p< 0.001.) While the orientation distributions of the posteromedial (PM) and posterolateral (PL) roots were roughly rotationally symmetric about their means, the orientation distributions of the anteromedial (AM) and anterolateral (AL) roots were more elliptical. The PM root was found to have the highest degree of variation in its orientation, and the AM root was found to have the least variation. In addition to showing the least scatter in its orientation overall, the AM root also has the most elliptical orientation distribution. No significant differences were found in the mean orientation or concentration parameter for any root when analyzed by biological sex.

These results indicate that there is three-dimensional variation in the orientation of the meniscal roots and that the degree of meniscal orientation variation differs for each root. These findings have implications for the prevention and treatment of knee injury as training and surgical methodologies develop to incorporate a more thorough understanding of individual variation in human knee anatomy.