Communication of Contrast in the Flexor Hallucis Longus Tendon with Other Pedal Tendons at the Master Knot of Henry.

It is important to have a full appreciation of lower-extremity anatomical relationships before undertaking diabetic foot surgery. We sought to evaluate the potential for communication of the flexor hallucis longus (FHL) tendon with other pedal tendons and plantar foot compartments at the master knot of Henry and to provide cadaveric images and computed tomographic (CT) scans of such communications. Computed tomography and subsequent anatomical dissection were performed on embalmed cadaveric limbs. Initially, 5 to 10 mL (1:4 dilution) of iohexol and normal saline was injected into the FHL sheath as it coursed between the two hallux sesamoids. Subsequently, CT scans were obtained in the axial plane using a multidetector CT scanner with sagittal and coronal reformatted images. The limbs were then dissected for specific evaluation of the known variable intertendinous connections between the FHL and flexor digitorum longus (FDL) and quadratus plantae (QP) muscles. One cadaver demonstrated retrograde flow of contrast into the four individual tendons of the FDL, with observation of a large intertendinous slip between the FHL and FDL on dissection. Another cadaver demonstrated contrast filling in the QP with an associated intertendinous slip between the FHL and QP on dissection. These results indicate that the master knot of Henry (the location in the plantar aspect of the midfoot where the FHL and FDL tendons decussate, with the FDL passing superficially over the FHL) has at least the potential to serve as one source of communication in diabetic foot infections from the medial plantar compartment and FHL to the central and lateral compartments via the FDL and to the rearfoot via the QP.