Use this link to view the PDF file: NORMAL TENDON VARIATIONS MAY INFLUENCE THE SPREAD OF INFECTION: THE FOOT AND WRIST AS EXAMPLES
Purpose: Our objective was to assess the anatomic variations at the Master Knot of Henry in the midfoot, and how they could potentially affect the spread of infection along the tendon sheaths in the foot. Additionally, we evaluated the previously described anatomic feature of a communicating foramen between the tendon sheaths of the second and third wrist extensor tendons (extensor carpi radialis brevis and extensor pollicis longus), and its ability to facilitate the spread of wrist tendon infection.
Materials and Methods: CT tenography was performed in 10 cadaveric feet, after cannulating the flexor hallucis longus (FHL) tendon sheath at the level of the proximal phalanx and injecting 5-10cc of a 1:4 dilution of Omnipaque 300 and normal saline. Images were obtained in the axial plane using a Siemens Sensation 16 multidetector scanner, with sagittal and coronal reformatted images. Tendons were then exposed from the Master Knot and then distally. Tendinous slip sharing was observed by removing both tendons and observing both the plantar and dorsal aspects. In addition, MRI’s of two confirmed cases of wrist extensor tendon sheath infected tenosynovitis were reviewed, along with a review of MRI’s of twenty cases of non-infective wrist extensor tenosynovitis.
Results: CT tenography was successful in 6 feet. In one case, there was retrograde flow of contrast from the FHL at the Master Knot into the Flexor Digitorum Longus (FDL) tendon sheath and distally into the other four digits. This cadaver demonstrated a large communicating tendinous slip between the FHL and FDL tendons. Another cadaver had a communicating tendinous slip between the FHL and the quadratus plantae (QP), with minimal contrast filling. The other cadaveric feet demonstrated tiny tendinous slips between the FHL and other tendons, without retrograde filling with contrast. In all cases of wrist extensor tenosynovitis (non-infective and infective), extensor compartments two and three were always simultaneously affected, whether or not other compartments were involved.
Conclusion: Anastomotic connections between the FHL tendon and other tendons at the Master Knot are common, and provides a potential pathway for the spread of hallux infection. In the case of the FHL/FDL communication, this would be to the other four digits, and in the case of the FHL/quadratus plantae communication, to the calcaneus. In addition, the naturally occurring synovial sheath foramen between the second and third wrist extensor compartment tendon sheaths resulted in spread of infection to both compartments in the two confirmed cases of infective tenosynovitis, and involvement of both of these compartments in all of the twenty non-infective cases. The extensor pollicis longus and extensor carpi radialis brevis tendon sheaths were always fluid distended together, and never in isolation. Knowledge of common anatomic variations is therefore important in predicting the potential pattern of spread of tendon sheath infection.