Tibiotalocalcaneal arthrodesis: anatomic and technical considerations.

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In the first of this two-part cadaver investigation, we inserted a specially designed, pointed device (simulating a 12-mm nail) in an antegrade fashion in each of eight fresh-frozen cadaver tibial specimens; the tibial isthmus was used as a centralizing guide. The exit point was noted, and the specimen was dissected to identify the structures at risk. In all specimens, we found that the device placed the lateral plantar artery and nerve at risk (average minimal distance from device to structure, 0 mm) and that damage to the flexor hallucis brevis and plantar fascia occurred. In addition, in six of the eight specimens, the device skewered or skived the flexor hallucis longus tendon. We also noted that in each specimen the exit point was the sustentaculum tali, not the body of the calcaneus as expected. Thus, there was less calcaneal bone-to-rod interface for stability, and distal locking would be less effective in the lateral-to-medial direction because of the lack of medial bone stock. On the basis of the results of the first portion of the study, we investigated an alternative approach to retrograde tibial nailing to reduce the risk of injury to the plantar and medial structures of the foot. We performed a medial malleolar resection, medially displaced the talus, inserted the device in an antegrade fashion, and dissected the specimens to analyze the structures at risk. We found that malleolar resection and medial translation of the distal extremity an average of 9.3 mm (range, 7-11 mm) increased the average minimal distance from the tip of the device to the neurovascular bundle to 18.4 mm (range, 14-32 mm). We also found that there was no damage to the flexor hallucis longus and that all eight specimens demonstrated bony contact completely surrounding the nail device within the tuberosity portion of the calcaneus (assessed by postoperative radiographs). The results of this study suggest that malleolar resection and medial translation of the distal extremity before retrograde nailing of the tibia may reduce the risk of vital structure injury and enhance the rigidity of the fixation.