TIBIOTALOCALCANEAL ARTHRODESIS - ANATOMIC AND TECHNICAL CONSIDERATIONS

In the first of this two-part cadaver investigation, we inserted a spe cially designed, pointed device (simulating a 12-mm nail) in an antegr ade fashion in each of eight fresh-frozen cadaver tibial specimens; th e tibial isthmus was used as a centralizing guide. The exit point was noted, and the specimen was dissected to identify the structures at ri sk. In all specimens, we found that the device placed the lateral plan tar artery and nerve at risk (average minimal distance from device to structure, 0 mm) and that damage to the flexor hallucis brevis and pla ntar fascia occurred. In addition, in six of the eight specimens, the device skewered or skived the flexor hallucis longus tendon, We also n oted that in each specimen the exit point was the sustentaculum tall, not the body of the calcaneus as expected, Thus, there was less calcan eal bone-to-rod interface for stability, and distal locking would be l ess effective in the lateral-to-medial direction because of the lack o f medial bone stock. On the basis of the results of the first portion of the study, we investigated an alternative approach to retrograde ti bial nailing to reduce the risk of injury to the plantar and medial st ructures of the foot. We performed a medial malleolar resection, media lly displaced the talus, inserted the device in an antegrade fashion, and dissected the specimens to analyze the structures at risk. We foun d that malleolar resection and medial translation of the distal extrem ity an average of 9.3 mm (range, 7-11 mm) increased the average minima l distance from the tip of the device to the neurovascular bundle to 1 8.4 mm (range, 14-32 mm). We also found that there was no damage to th e flexor hallucis longus and that all eight specimens demonstrated bon y 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 tra nslation of the distal extremity before retrograde nailing of the tibi a may reduce the risk of vital structure injury and enhance the rigidi ty of the fixation.