SLR - May 2020 - Collin G. Messerly

Consideration of Medial Anatomical Structures at Risk When Placing Quadricortical Syndesmotic Fixation: A Cadaveric Study

References: Kaiser P, Riedel M, Qudsi R, Watkins I, Ghorbanhoseini M, Nazarian A, Kwon J. Consideration of Medial Anatomical Structures at Risk When Placing Quadricortical Syndesmotic Fixation: A Cadaveric Study. Injury 2020; 51(2) 527-531

Scientific Literature Review 

Reviewed By: Collin G. Messerly, DPM
Residency Program: Regions/HealthPartners Institute – St. Paul, MN 

Podiatric Relevance: Use of quadricortical fixation in the management of syndesmotic instability may be accomplished with either screw or suture-button fixation and careful attention should be provided to the medial structures at risk. It is important when placing syndesmotic fixation to be aware of the saphenous neurovascular bundle (SNVB) and the posterior tibial tendon (PTT) that resides on the medial side of the tibia that are at risk for iatrogenic injury. 

Methods: Eighteen fresh frozen cadaveric specimens were dissected; the SNVB along with its communicating branches and PTT were identified and marked utilizing small gauge copper wiring. The wiring was placed in the saphenous vein and the anterior portion of the PTT. All fascial and tendinous sheath attachments were preserved to not distort normal anatomy. Next lateral radiographs of the distal tibia and fibula were obtained, which were calibrated and standardized. These radiographs were then analyzed utilizing a grid system consisting of three parallel columnar zones from anterior to posterior and five 1 centimeter rows that extend 5 centimeters proximal to the tibiotalar joint. The position of the respective copper wire placed in either the SVNB or PTT was charted according to the location in the grid system.

Results:
The SNVB was located in zone one or two, which was the first two columnar parallel zones 97.3 percent, which correlated to 107/110 grid data points. The SNVB traversed from proximal-posterior to distal-anterior in 16 specimens. The most common crossover point from zone two to zone one was at 3-4 centimeters above the tibiotalar joint which occurred in 43.8 percent. Additionally the SNVB was located anterior to the zone one in three specimens. The PTT was found in zone three in all specimens demonstrating a crossover of columnar zone two at the distal most extent, 0-1 centimeter. The PTT radiographically overlaps with the tibia on a true lateral between 1 and 3 centimeters above the tibiotalar joint in 83.3 percent of the specimens.

Conclusions: Although prior studies have shown potential for injury to medial structures with syndesmotic fixation, the course of these structures has not been previously mapped out. The rate of injury to the SNVB and PTT remains unknown as well. This study demonstrated that the SNVB is at risk along the distal tibia in zones 1 and 2 and a crossover point of 3-4cms proximal to the tibiotalar joint. The PTT was found in zone three in all specimens, meaning a protruding screw in zone three, 0-2 centimeters proximal to the tibiotalar joint could be potentially harmful. An intra-operative grid pattern may be difficult to visualize but knowing the general course of medial neurovascular structures is crucial to prevent iatrogenic injury. The grid system provided clearly shows which structures may be at risk and the general anatomic location of these structures to try and avoid iatrogenic injury when placing quadricortical fixation. 

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