Abstract
Category:
Ankle Arthritis
Introduction/Purpose:
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 subtalar facet, the talus, the ankle joint and the distal tibia on a regular curve. This curve lies on a vertical plane which is slightly angulated inwards in relation to the sagittal plane. Today’s hindfoot nails are either straight or bent. The hole which accommodates the implant is always straight and thus does not respect the normal alignment of the hindfoot. This technique may cause a plantar neurapraxia, the nail holds poorly the calcaneus and tends to create a hindfoot varus. Purpose of the study is to optimize the technique to stabilize the hindfoot in anatomical alignment.
Methods:
A preliminary trial using 15 cadaveric feet was performed to find the optimal shape of a central hindfoot nail. 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. A distal locking screw crossing the subtalar joint and a proximal locking screw within the tibia concludes the central fixation. 9 patients have been treated so far using this technique.
Results:
In vitro trials demonstrated an excellent spontaneous stability of the hindfoot after introduction of the nail. The pathology of the operated patients include post-traumatic, 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 pseudarthrosis at the midfoot joints. All patients were treated for 2 weeks post-op with a closed circular cast without weight bearing. After 2 weeks our patients did practise partial weight bearing using a cam walker for other 6 weeks.
Conclusion:
The tibio-talo-calcaneal arthrodesis can be successfully treated using a central circular arc shaped nail respecting form fit function. The anatomical bony alignment of the hindfoot is preserved. Due to the safe approaches, the technique may prevent shortcomings such as neurological complications and non-unions. We expect a shorter period between surgical fixation and full weight bearing.