Maximizing The Effectiveness Of The Evans Calcaneal Osteotomy

Michelle Butterworth, DPM, FACFAS

   One can also utilize a longitudinal lateral incision. Although it parallels the peroneal tendons and sural nerve, and there is less risk for injury to these structures, this incision is against the relaxed skin tension lines. With the lengthening of the lateral column, thick scarring can result.

   Perform blunt dissection through the subcutaneous tissues until you encounter the extensor digitorum brevis muscle belly. Identify the peroneal tendons just inferior to the muscle belly and retract the tendons plantarly. Make an incision along the inferior edge of the extensor digitorum brevis muscle belly and its overlying deep fascia. Take care not to violate the peroneal tendons or their tendon sheath. Then make a vertical incision along the proximal edge of the muscle belly at about the level of the sinus tarsi. Tag the extensor digitorum brevis muscle belly and its overlying deep fascia with sutures, reflect them off the underlying bone and retract them distally to expose the anterior calcaneus.

   Identify the calcaneocuboid joint but avoid aggressive dissection. The ligaments must remain intact so the joint is not destabilized. Identify the calcaneocuboid joint with a Freer elevator and then place an 18 gauge needle into the joint as a reference point. Using a key elevator, proceed to reflect the remaining soft tissues, exposing the anterior lateral calcaneus for osteotomy placement.

Keys To Correct Osteotomy Placement

Correct osteotomy placement is crucial for success of this procedure and I will draw the osteotomy prior to execution to ensure accuracy. Perform the osteotomy 11 to 15 mm proximal to the calcaneocuboid joint. If the osteotomy is too distal or too close to the calcaneocuboid joint, the anterior fragment of the calcaneus will be too small and unstable, and can dislocate dorsally. A small anterior fragment could also become dysvascular, resulting in healing difficulties. Finally, if the osteotomy is too distal, it can violate the anterior facet of the subtalar joint. If it is too proximal, it can violate the middle facet of the subtalar joint and subsequent pain and arthritis could result.

   According to Hyer and colleagues, the majority of calcanei (56 percent) in a study had a conjoined anterior and middle talocalcaneal facet, 3 percent had an absent anterior facet, and 41 percent had separate facets.8 The mean distance from the anterior border of the calcaneus to the proximal edge of the anterior facet was 11.04 mm and the mean separation between the anterior and middle facets, when present, was 3.85 mm. Therefore, the ideal placement of this osteotomy is 11 to 15 mm proximal to the calcaneocuboid joint.

   One should make the osteotomy perpendicular to the lateral wall of the calcaneus and weightbearing surface, and parallel to the calcaneocuboid joint. Make the osteotomy from lateral to medial with a sagittal saw. Then utilize an osteotome to continue the cut through the medial cortex. Do this very carefully to avoid violation of the medial neurovascular bundle and tendons. Proceed to open the osteotomy. I utilize a lamina spreader without teeth but one may use a mini-distractor if desired. If the osteotomy is resistant to distraction, it is probably incomplete. The most common place of osseous continuance is the plantar medial aspect. One can use an osteotome to gingerly transect any points of osseous connection.

   Then open the osteotomy until you have achieved the desired correction. The ideal position of the rearfoot is with the heel in a rectus or slight valgus position.

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