Three-Dimensional Musculoaponeurotic Architecture of the Human Lower Limb and its Functional Implications

The musculoaponeurotic architecture of the human lower limb has not been previously investigated in three-dimension (3D) at the fiber bundle (FB) level. As musculoaponeurotic architecture is a primary determinant of muscle function, the lack of architectural data has limited our understanding of functional characteristics of lower limb musculature and the development of high-fidelity simulation and biomechanical models. The overall objective of this thesis is to capture the 3D musculoaponeurotic architecture of all of the lower limb muscles, and to use this data to elucidate functional capabilities of muscle groups, individual muscles, and/or intramuscular partitions. In the first study, 48,000 FBs and all of the tendinous/aponeurotic components of 59 lower limb muscles were digitized and modelled, as in situ, to construct an architecturally comprehensive 3D lower limb muscle model. A detailed architectural analysis of three lower limb muscles demonstrated that each had unique spatial arrangement and morphology of the musculoaponeurotic elements resulting in functionally relevant intramuscular partitioning. The second study captured the 3D musculoaponeurotic architecture of vastus medialis obliquus (VMO) and longus (VML) in 12 specimens. The comparison of architectural parameters of VMO and VML indicated that the two partitions have distinct functional characteristics. The more vertical line of action (LoA), greater excursion and force-generating capability of VML suggested that it contributes primarily to knee extension, whereas, VMO’s more horizontal LoA, suggested a role in medial patellar stabilization. The third study investigated and quantified the 3D musculoaponeurotic architecture of the great toe muscles, in 10 specimens, at the FB/aponeurosis level. Functional differences were elucidated through the comparison of the architectural parameters of the medial and lateral great toe muscles and their intramuscular partitions. The medial musculature was found to have similar force generating capability as the lateral musculature, suggesting that medial and lateral forces are balanced. In conclusion, the 3 studies captured high-resolution 3D architectural data, which enabled detailed morphologic and architectural analysis of the lower limb musculature not possible to date. This volumetric data can be used for the development of finite element models capable of higher fidelity lower limb muscle simulation than presently available.Ph.D