The posterior medial blind spot of the distal tibia: implications for surgical fixation

Consideration of medial anatomical structures at risk when placing quadricortical syndesmotic fixation: A cadaveric study

BACKGROUND

Surgical fixation of syndesmotic instability using quadricortical fixation, whether screws or suture-button devices, places structures on the medial side of the tibia at iatrogenic risk. This study aims to radiographically map the anatomic course of structures on the medial aspect of the distal tibia to be able to at-risk zones (ARZs) for syndesmotic fixation.

METHODS

Eighteen fresh-frozen cadaveric ankle specimens were dissected. The saphenous neurovascular bundle (SNVB) and the posterior tibial tendon (PTT) were identified and marked with copper wiring. Standardized and calibrated lateral radiographs of the distal tibia and fibula were analyzed using a grid system consisting of 3 columnar zones from anterior to posterior and five 1-cm rows to chart the anatomic course of the SNVB and the PTT.

RESULTS

The SNVB was located in the more anterior zones (1, 2, or anterior to Zone 1) in 97.3% of specimens. The SNVB traversed from posterior to anterior as it descended proximal to distal. The PTT was found in Zone 3 (most posterior zone) for all specimens. The PTT was noted to pass behind (radiographically overlap) the tibia in 83.3% (15 of 18) of specimens between 1 and 3 cm above the tibiotalar joint.

CONCLUSIONS

Placement of quadricortical syndesmotic fixation places structures on the medial ankle at risk. The SNVB is at considerable risk along the anterior course of the distal tibial while the PTT is only at risk in zone 3 at the distal extent of the tibia.