Current Insights On Internal Fixation Of Subtalar Fusions

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Author(s): 
Ryan T. Scott, DPM, AACFAS, and Christopher F. Hyer, DPM, MS, FACFAS

   In contrast to those findings, tapping reduced pullout strength by 8 percent in compasrison to non-tapped guide holes.18 Pullout forces utilizing the anterior to posterior screw orientation had a larger mean failure load in comparison to the pullout forces using the posterior to anterior approach. Specifically, mean failure load for the anterior to posterior approach was 1782 N whereas the mean failure load for the posterior to anterior screw orientation was 1245 N.12 Chapman and colleagues proved that the best screw placement is at the entrance point where the cortex is the thickest.18 Thick cortical bone has been critical in assisting with stabilization of internal fixation. Indeed, the thick cortical bone of the talus is another advantage for the anterior to posterior approach.

   One can inadequately assess deviations medially or laterally from the central aspect of the calcaneus when utilizing only the intraoperative lateral radiographic view. Accordingly, the calcaneal axial view is required to confirm appropriate placement of the guide wire into the central aspect of the calcaneus prior to screw placement. This tip is critically important in the posterior to anterior screw placement as the landing zone is small. Though our cadaver study demonstrated the “top down” screw to be reproducible and generally central into the calcaneus, we still recommend the additional imaging view.

   Dr. Scott is a Fellow of the Orthopedic Foot and Ankle Center in Westerville, Ohio. He is an Associate of the American College of Foot and Ankle Surgeons.

   Dr. Hyer is the Fellowship Director of Orthopedic Foot and Ankle Center in Westerville, Ohio. He is a Fellow of the American College of Foot and Ankle Surgeons.

References

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13. Gable SJ, Bohay DR, Manoli A. Technique tip: aiming guide for accurate placement of subtalar joint screws. Foot Ankle Int. 1995; 16(4):238-39.

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