Defining the Structures at Risk and an Anatomical Safe Zone for Percutaneous Antegrade Subtalar Joint Fixation With a Single Screw: A Cadaveric Study.

ABSTRACT

Percutaneous antegrade (anterior to posterior) fixation for subtalar joint (STJ) arthrodesis offers various intraoperative and biomechanical advantages. Currently, the entry point for percutaneous antegrade STJ screw fixation is not clearly described and variable. To our knowledge, there are no publications that evaluate anatomic structures at risk or define an anatomically safe entry point for this fixation. The aim of this investigation was to define an anatomically safe and reproducible entry point for percutaneous antegrade STJ arthrodesis fixation, while also describing anatomic structures at risk when undertaking this method of fixation. We hypothesized that percutaneous single screw antegrade STJ fixation would encroach upon named anatomic structures in more than one cadaveric specimen. Ten cadaver limbs were used in this investigation. A percutaneous guidewire was inserted 5 mm lateral to the tibialis anterior tendon. The midpoint of the talar neck served as the sagittal plane starting point, as seen on the lateral fluoroscopic view. A cannulated 6.5-mm headed screw was inserted antegrade through the STJ into the calcaneus. Each specimen was dissected to assess the distance from the screw to nearby anatomic structures and distance from the tibialis anterior tendon to named structures. Our hypothesis was found to be incorrect, as 0/10 screws invaded neurovascular or tendinous structures. The dorsalis pedis artery and deep peroneal nerve were on average 12.1 ± 2.79 mm and 12.2 ± 2.82 mm lateral to the screw, respectively. These findings are clinically relevant and ultimately allow us to define an anatomic safe starting point for percutaneous antegrade STJ single screw fixation.