Quantification of Subtalar Posterior Facet Involvement During Intramedullary Guidance of Total Ankle Arthroplasty:A Cadaveric Study

Total ankle arthroplasty is an evolving treatment of ankle arthritis. One implant uses intramedullary guidance to enhance accuracy by accessing the tibial canal through the inferior aspect of the foot, potentially placing the subtalar joint articulation at risk. The purpose of the present cadaveric anatomic evaluation was to identify posterior subtalar articular facet joint involvement during intramedullary guidance to the tibial canal. Ten below-the-knee cadaveric specimens were used. After drilling into the tibial medullary canal with a 6-mm drill bit and using the standard targeting jig, the specimens were dissected, and the posterior facet was evaluated. We graded posterior facet involvement according to the location of the drill hole and, if within the facet, the percentage of the facet violated by the drill bit, with 100% representing the full circumference of the 6-mm drill bit. Of the 8 specimens in which the drill bit passed through the subtalar posterior articular facet, the encroachment was peripheral in all cases, with no specimen showing circumferential 6-mm drill bit articular penetration (no cases with 100%). Sinus tarsi penetration occurred in 20% of the cases. The dissections with articular involvement included 3 specimens with >50% of the drill bit penetrating and 5 with