How To Master Talonavicular Fusions
The talonavicular joint arthrodesis has been utilized for a variety of pathologies of the foot. Instability and subluxation of the rearfoot in adult acquired pes valgus is the most common reason for rearfoot fusion. Congenital deformities, neuromuscular diseases and arthritic conditions, whether they are from an inflammatory arthritis, osteoarthritis or posttraumatic causes, are less common pathologies that would require fusion of the talonavicular joint.1
In a rigid rearfoot deformity, such as a multiplanar deformity with heel valgus, forefoot abduction and/or forefoot varus, there is little substitute for a triple arthrodesis. However, when there is a flexible peritalar subluxation and one can manually reduce the deformity, there is the opinion that a single joint fusion of the talonavicular joint can stabilize the foot just as well as a triple arthrodesis.2 Compared to a triple arthrodesis, the talonavicular joint arthrodesis can ultimately reduce morbidity, time in the operating room and lower the incidence of complications. It may also provide some flexibility to the rearfoot.
Adult-Acquired Flatfoot: When Is A Talonavicular Fusion Appropriate?
There are many different surgical approaches for the adult acquired flatfoot. One way is not necessarily better than another as long as one uses sound principles to evaluate and plan the reconstruction.
I analyze flatfoot and divide it into three regions. The first area includes the posterior musculature. Using the Silverskiold test as a guide, one should determine whether to perform a gastrocnemius recession or a tendo-Achilles lengthening. Surgeons should then proceed to address the hindfoot position. If it is rigid, consider either a fusion procedure or a calcaneal osteotomy. If it is flexible, then one can consider subtalar arthroeresis. One would rarely perform a subtalar arthroroesis without doing additional procedures to address the forefoot.
Finally, compare the position of the forefoot to the rearfoot. If there is varus and/or abduction, consider medial column procedures including fusions or osteotomies (i.e. cotton osteotomy). When both rearfoot and forefoot components are flexible, performing a talonavicular joint arthrodesis may be a good option. Certainly, many combinations may occur as all flatfoot deformities are different. Using a systematic approach to evaluate each segment, one can choose appropriate procedures with confidence.
When choosing the talonavicular joint fusion for a completely flexible flatfoot, one can often do it as a solo procedure. I choose not to perform a joint resection with a saw. I prefer to maintain the ball and socket anatomy of the fusion site, using a combination of osteotomes and bone curettes. One can use the curettes to scrape cartilage off the navicular “cup” and employ the osteotomes to chisel cartilage off the talar head. By doing this, one can “dial in” the exact position in the transverse plane (reducing abduction) and frontal plane (reducing forefoot varus). Resecting too much bone with a saw at the fusion site can make it difficult to get a good approximation of bone without a bone graft. Moreover, it is difficult to obtain multiplanar correction with flat surfaces from a saw cut. Ultimately, with more wedging and sculpting, increased bone loss leads to a more difficult approximation.
A Stepwise Approach To Surgical Technique
Prior to surgery, scrub the lower extremity, prep and drape it in the usual sterile fashion. One can perform this procedure under a local with IV sedation without a tourniquet or opt for a general anesthetic with a thigh tourniquet according to your preference
If a posterior lengthening is necessary, surgeons should perform this prior to the fusion. One should map out the anatomic landmarks including the medial malleolus, tibialis anterior tendon and the navicular tuberosity.