Anatomic Structures at Risk During Posterior to Anterior Percutaneous Screw Fixation of Posterior Malleolar Fractures: A Cadaveric Study.

Background. There are no established guidelines for fixation of posterior malleolus fractures (PMFs). However, fixation of PMFs appears to be increasing with growing evidence demonstrating benefits for stability, alignment, and early functional outcomes. The purpose of this study was to determine the risk to anatomic structures utilizing a percutaneous technique for posterior to anterior (PA) screw fixation of PMFs. Methods. Percutaneous PA screw placement was carried out on 10 fresh frozen cadaveric ankles followed by dissection to identify soft tissue and neurovascular structures at risk. The distance from the guidewire to each anatomic structure of interest was measured. The correlation between the mean distances from the guidewire to each structure was calculated. Results. The sural nerve was directly transected in 1/10 specimens (10%) and in contact with the wire in a second specimen (10%). There was a significant correlation between the proximity of the guidewire to the apex of Volkmann's tubercle and its proximity to the sural nerve. The flexor hallucis longus (FHL) muscle belly was perforated by the guidewire 40% of the time but was not tethered or entrapped by the screw. Conclusions. Percutaneous PA screw placement is a safe technique which can be improved with several modifications. A mini-open technique is recommended to protect the sural nerve. There may be potential for tethering of the FHL with use of a washer or large screw head. Risk to the anterior and posterior neurovascular bundles is minimal.Levels of Evidence: Level V.