Maximizing The Effectiveness Of The Evans Calcaneal Osteotomy

Author(s): 
Michelle Butterworth, DPM, FACFAS

Pertinent Insights On Utilizing Bone Grafts

One would then measure the gap at the osteotomy site and fashion a bone graft. The correction in most pediatric patients averages 10 mm and typically ranges from 8 to 12 mm. In an adult, the maximum graft size to utilize is 8 mm. I typically do not use grafts over these dimensions because it can cause increased pressure and secondary pain and arthritis at the calcaneocuboid joint. If further correction is needed and the graft has reached its maximum size, I will typically perform a posterior calcaneal displacement osteotomy in addition to the Evans osteotomy instead of utilizing a larger graft.

   I utilize allogeneic bone graft. Many authors have shown that due to the increased vascularity of the calcaneus, allogeneic bone graft incorporates very well and this procedure does not warrant an autogenous graft.9-11 Also, a combined corticocancellous graft is the most advantageous graft for this procedure. The cancellous bone allows increased vascularity and aids in graft incorporation and healing. The cortical bone adds strength to the graft to combat the compressive forces within the osteotomy. I prefer to use an allogeneic tricortical iliac crest bone graft, 15 to 18 mm in width. This width will typically allow enough bone graft for the Evans osteotomy and a Cotton osteotomy if this procedure is also needed for further correction of the medial arch.

   Then fashion the bone graft into a trapezoidal shape. The cortical bone is going to be on the dorsal, lateral and plantar aspects, and the cancellous bone will be on the distal and proximal aspects of the osteotomy. The most lateral aspect of the graft is the widest and it tapers down to about 3 to 4 mm as it goes medially.

   Precut allogeneic bone wedges are also available. I have utilized some of these grafts with success but these grafts are only bicortical. These grafts are also sometimes longer than desired, from lateral to medial, especially in pediatric patients, and one needs to cut and shorten the grafts to fit properly. If you are using precut grafts, I recommend minimal tamping and manipulation of these grafts to maintain their strength and integrity. I do not have experience utilizing other types of grafting/wedge material at the osteotomy site. My preferred choice, based on experience, success and reproducible outcomes, is allogeneic, tricortical iliac crest bone graft, cut and fashioned individually.

   After fashioning the graft, open the osteotomy site, insert the bone graft and tamp it into place so the lateral edge lines up evenly with the lateral wall of the calcaneus and there is no prominence. Place the bone graft in the central part of the osteotomy. The surgeon needs to ensure the graft is not too dorsal entering the subtalar joint. The bone graft usually does not fill the entire space of the osteotomy. However, the graft typically incorporates very well and these spaces are not cause for concern. One can add additional bone graft if desired but this is not standard for me.

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