Biomechanics of the membranous flexor tendon sheath: the role of Grayson's ligaments.

Background: The biomechanical integrity of the tendon sheath of the fingers has a significant effect on the success of flexor tendon surgery. As nonweightbearing elements, the membranous parts of the sheath have received little attention, and their contribution to sheath movement is still obscure. The authors presumed that Grayson's ligaments, which have been described as force-transmitting elements, might play a role in the biomechanics of the membranous flexor tendon sheath.

Methods: Twenty-two long fingers of cadaver hands were examined. The authors studied the movements of the inner aspect of the tendon sheath and the positions and patterns of the septa of the palmar soft tissues on picrosirius red-enhanced sagittal and transverse sections and hematoxylin and eosin-stained light microscopy specimens.

Results: The movements of the membranous flexor tendon sheath are controlled by subcutaneous structures. The septal patterns of the palmar fat pads indicate the existence of a highly flexible subcutaneous fibrous system in which the deformable fat pad keeps the force-transmitting elements tight. Collagen bundles in the microscopy specimens, which frequently form layers within the septa, are thought to correspond to Grayson's ligaments. The subcutaneous fibrous system adheres predominantly to the membranous parts of the flexor tendon sheath.

Conclusions: Folding of the membranous flexor tendon sheath is guided by the subcutaneous fibrous system, of which the macroscopically dissectible elements are Grayson's ligaments. The current surgical approaches might have a deteriorating effect on the biomechanics of the flexor tendon sheath.