Computer reconstruction of human tendon architecture based on NMR images

Abstract

The biomechanical concept of the vertebrate tendon consists of a complex of homogenous fibers oriented parallel to the main axis of the tendon, implying the direction of the fibers corresponds to the lines of forces. However, some observations are inconsistent with this model. 1) In several multimotor musculo-tendinous systems, e.g., the human m., triceps surae complex, the constituents are spirally organized, so that the fiber direction deviates from the ideal axis. 2) High resolution MRI demonstrated that the tendons of the human mm. flexores and extensores digitorum are not homogenous. In the present study MR images of the tendons of the human mm. gastrocnemius and mm. flexores digitorum were used in a 3-D reconstruction of tendon architecture, by smoothing a digitized set of data of the outlines of fascicles and fibers, using a computer program developed by the second author. These parameters were smoothed using bicubic spline technics. transition into visual graphics was accomplished by MATLAB tools application. Most striking in our results is the occurrence of coil in the tendons. In the Achilles tendon spiralization is caused by the fascicles, whereas coiling in the finger flexor tendons originates from the helicoidal arrangement of the fibers. Coil progressively increases peripherally and also in the proximal direction. These findings may throw new light on the visco-elastic properties of tendons.