Protecting Medial Soft Tissue Structures In Hindfoot Arthrodesis With The Medial Displacement Calcaneal Osteotomy

Hindfoot arthrodesis has grown into a powerful tool for foot and ankle surgeons with applications in multiple pathologies. Since Ryerson’s original description of hindfoot arthrodesis, much has changed, including a variety of incision approaches as well as a growing number of fixation techniques.¹ The number of joints included in the hindfoot arthrodesis for many surgeons has also evolved to include only subtalar and talonavicular joints, or the “double” arthrodesis.

More recently, adjunct procedures have received further emphasis as well. These include procedures for addressing the posterior muscle group and procedures to control valgus moments that stress medial structures, leading to a less desirable result.

Unfortunately, after some well-done hindfoot arthrodeses, certain patients on subsequent follow-up have developed ankle valgus. Authors have noted that the single incision medial approach dissection itself may cause damage to or weaken the deltoid ligament, leading to the same valgus failure issues.²

However, researchers have also described the development of ankle valgus after traditional triple arthrodesis with Hyer and colleagues finding ankle valgus occurring after both traditional two-incision triple arthrodesis as well as medial approach double arthrodesis at rates of 54.8 percent and 25 percent respectively.³ This could possibly be attributed to deltoid ligament insufficiency that surgeons may not have recognized preoperatively.

Consider those patients with longstanding deformities, obesity and other comorbidities that have intensified compromise on medial soft tissues. These patients begin with a weakened deltoid complex, which after traditional hindfoot fusion and under the stress of a new arthrodesis, can progress a weak deltoid to actual failure, and cause subsequent valgus to the ankle and foot. Increased deltoid pathology has been visible on magnetic resonance imaging (MRI) of individuals with posterior tibial tendon insufficiency.⁴ Song and coworkers have also demonstrated increased force through the deltoid after triple arthrodesis, leading the authors to consider medializing calcaneal osteotomies as a way of protecting the deltoid area prophylactically.⁵ One must be sure to have weightbearing radiographs of the ankle preoperatively but also remember the “at-risk” patient with longstanding deformity, obesity, etc.

What You Should Know About The Medial Displacement Calcaneal Osteotomy

Surgeons often use the medial displacement calcaneal osteotomy as described by Koutsgiannis as part of flatfoot reconstruction.⁶ The purpose of the procedure is to medialize the weightbearing axis of the hindfoot and have the Achilles pull in a more varus trajectory. With these biomechanics in mind, one can realize the benefits of the procedure in helping protect medial soft tissue repairs and augmentations including flexor digitorum longus transfers, spring ligament reconstructions, and deltoid ligament repairs and augmentations.

In our experience, the latter has become a significant consideration when performing flatfoot reconstructions in the setting of severe or longstanding deformities that do not yet show radiographic valgus changes to the ankle joint itself. The medial displacement calcaneal osteotomy has shown good outcomes and low complication rates.⁷

A Closer Look At The Surgical Technique

With this in mind, our technique for multiple hindfoot arthrodesis is most commonly arthrodesis of subtalar and talonavicular joints, medial displacement calcaneal osteotomy, a Cotton osteotomy, and posterior muscle group lengthening with the patient supine with an ipsilateral hip bump.

After positioning the patient, complete the posterior muscle group lengthening if it is indicated. Then plan incisions for the double arthrodesis and medial displacement calcaneal osteotomy. The subtalar incision is a traditional distal incision to the tip of the fibula with the surgeon carrying the incision distally toward the fourth metatarsal base. Make the talonavicular incision on the dorsal aspect of the joint at an interval between the anterior tibial and extensor hallucis longus tendons. Prepare the joints appropriately and utilize two large cannulated, partially threaded screws for final fixation of the subtalar joint. Place one screw from the dorsal aspect of the talar neck into the body of the calcaneus and place the other from the plantar calcaneus into the body of the talus. Fixate the talonavicular joint with one large cannulated, partially threaded screw and a dorsal plate.

For patients considered “at risk” for deltoid insufficiency, after joint preparation, place the initial guidewire from dorsal to plantar across the subtalar joint. Drive the guidewire across the angle of the calcaneus and then stop advancing the guidewire, allowing room for the traditional medial displacement calcaneal osteotomy bone cut in the tuberosity. While placing this guidewire, hold the forefoot supinated with one hand and maintain the rearfoot correction. Drive the guide pin with the other hand. Measure and place the screw. Then reduce the talonavicular joint, correcting the midfoot varus and abduction, and place the guide pin for a cannulated screw across the talonavicular joint. Providing this fixation prior to performing the medial displacement calcaneal osteotomy allows for a more stable calcaneus and rearfoot. This provisional fixation permits easier medialization of the tuberosity and placement of fixation.

Plan the medial displacement calcaneal osteotomy skin incision by identifying the superior and inferior margins of the calcaneus, being parallel and posterior to the peroneal tendons, which one can verify via fluoroscopy. The incision for the medial displacement calcaneal osteotomy should be a sufficient distance from a traditional subtalar joint fusion incision in order to reduce the risk of potential wound issues.
Make the osteotomy in the posterior portion of the body of the calcaneus in standard fashion. The most superior extent of the cut should be anterior enough to avoid the Achilles and its insertion, and the inferior cut should be clear of the plantar fascial insertion and the weightbearing portion of the calcaneus. Additional structures to avoid would be the peroneal tendons more anteriorly as well as the sural nerve, which is located 14 mm distal and 14 mm posterior to the lateral malleolus.⁸ After completing the osteotomy and freeing the soft tissues to allow for translation, plantarflexion of the ankle can help with medialization. This removes Achilles tension and one can move the tuberosity medially more freely. Then dorsiflex the ankle. This subsequently engages the Achilles to create tension and friction, and holds the tuberosity in the desired position.

After translating the tuberosity and confirming position, place a guide pin for a large cannulated screw from the plantar calcaneus and angled to cross the osteotomy. One can also angle this screw to drive it across the posterior facet of the subtalar joint as well to act as the second screw for your subtalar fusion construct. If so desired, one can place an additional large cannulated screw more horizontally across just the medial displacement calcaneal osteotomy itself but this is not typically necessary. Verify the subtalar joint and medial displacement calcaneal osteotomy screw placement on lateral foot, AP ankle and calcaneal axial views. Then complete the talonavicular fixation as desired. We typically use a dorsal plate. Perform any other adjunct procedures and perform closure per your surgical protocol.

In Conclusion

The medial displacement calcaneal osteotomy, from our standpoint, is a very powerful tool when the surgeon combines it with a double or triple arthrodesis in what we would consider a “stage 3.5” or “at-risk” flatfoot. This is a flatfoot in which there are not clear changes to the ankle on weightbearing radiographs but there is nonetheless a severe, longstanding deformity, which may contain attenuated portions of deltoid that can lead to later compromise.

Adding the medial displacement calcaneal osteotomy to hindfoot arthrodesis in these patients should alter the weightbearing axis more medially through the hindfoot and protect the deltoid and medial structures of the ankle. Without additional protection for the medial ankle ligamentous structures, it is a vulnerable location for a valgus moment to occur during weightbearing and could lead to failure of a triple or double arthrodesis in flatfoot correction.

Dr. Burns is an Assistant Professor of Orthopaedic Surgery at the University of Pittsburgh School of Medicine. He is the Director of the University of Pittsburgh Medical Center Podiatric Medicine and Surgery Residency Program and Lower Extremity Reconstruction/Trauma Fellowship. Dr. Burns is the Chief of the Podiatry Section of the University of Pittsburgh Medical Center Mercy Hospital.

Dr. St. John is a Fellow in Lower Extremity Limb Salvage and Trauma at the University of Pittsburgh Medical Center.

References

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2. Anand P, Nunley JA, DeOrio JK. Single-incision medial approach for double arthrodesis of hindfoot in posterior tibialis tendon dysfunction. Foot Ankle Int. 2013;34(3):338-44.
3. Hyer CF, Galli MM, Scott RT, Bussewitz B, Berlet GC. Ankle valgus after hindfoot arthrodesis: a radiographic and chart comparison of the medial double and triple arthrodeses. J Foot Ankle Surg. 2014;53(1):55-8.
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5. Song SJ, Lee S, O’Malley MJ, Otis JC, Sung H, Deland JT. Deltoid ligament strain after correction of acquired flatfoot deformity by triple arthrodesis. Foot Ankle Int. 2000;21(7):573-7.
6. Koutsogiannis E. Treatment of mobile flat foot by displacement osteotomy of the calcaneus. J Bone Joint Surg. 1971;53(1):96-100.
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8. Lawrence SJ, Botte MJ. The sural nerve in the foot and ankle: an anatomic study with clinical and surgical implications. Foot Ankle Int. 1994;15(9):490-4.