The circular arc internal fixation for tibio-talo-calcaneal arthrodesis

Abstract

Introduction: Stabilizing a tibio-talo-calcaneal arthrodesis in anatomical alignment allowing for weight bearing is a technical challenge. Normal anatomy demonstrates alignment of the heel, the posterior subtalar facet, the talus, the ankle joint and the distal tibia on a circular arc. This arc lies on a vertical plane which is slightly angulated inwards in relation to the sagittal plane. Today's hindfoot nails do not respect this alignment. Complications include malalignment, primary instability, plantar neuropraxia. Purpose of the study is to optimize the technique to stabilize the hindfoot in anatomical alignment. Method(s): An instrumentation was designed to create a circular arc bore hole crossing the heel, the posterior subtalar facet, the tibio-talar joint and the distal tibia metaphysis. At the operation, the desired definitive position of the hindfoot is fixed temporarily with Kirschner wires. A guiding frame is fixed to three critical spots of the hindfoot to drill the central hole. Using an image amplifier the hole is bored using a motor driven end cutting flexible reamer which is seated within a rigid curved hull. The nail has the same shape than the hull and is impacted up to the distal tibia. The nail allows for eventual secondary impaction without losing full contact with the surrounding bone. 18 patients have been treated so far using this technique. Result(s): The pathology of the operated patients include posttraumatic, congenital and metabolic (diabetes) conditions. The mean follow-up is 12 months. We did observe 3 ruptures of the tibial locking screw which allowed for more spontaneous impaction. All cases went to consolidation without malunion or other complications. One diabetic patient developed a stable pseudar throsis at the midfoot joints. The patients were treated for 2 weeks post-op with a closed circular cast allowing heel contact to the floor. After 2 weeks our patients did practise partial to full weight bearing using a cam walker for other 6 weeks. Conclusion(s): The tibio-talo-calcaneal arthrodesis can be successfully treated using a central circular arc shaped nail allowing for full form fit between implant and bone. The anatomical bony alignment of the hindfoot is corrected or preserved. Due to the safe and limited approaches, the technique prevents complications such as neurological complications and non-unions. We expect a shorter period of time between surgical fixation and full weight bearing.