Cath Lab Digest

In order to reduce the risk of potential complications with subtalar joint implants, these authors offer salient tips on the diagnostic workup, an overview of the currently available implants and how to facilitate appropriate procedure selection.

   Subtalar arthroereisis can be an excellent procedure for many patients with varying degrees of pathology. It is a viable option to correct painful flexible flatfoot when other non-surgical treatments have failed. Subtalar arthroereisis is also a great option because it avoids the aggressive bony work one has to do with procedures such as osteotomies and arthrodesis. Subtalar joint (STJ) implants still allow for some rearfoot motion while eliminating excess pronation. The procedure also helps to preserve the soft tissue, resulting in a shorter immobilization period and a quicker recovery period.

   Zaret and Myerson described flexible pes planus as “dorsal and lateral peritalar subluxation of the forefoot, calcaneal eversion, collapse of the medial arch as well as medial uncovering of the talus.”¹ Christensen and colleagues concluded that subtalar joint arthroereisis did not alter the normal closed kinetic chain mechanics and was therefore an effective means of altering subtalar motion.^1,2 However, it is important not to overlook other components of the pes planovalgus deformity, which could require additional procedures.

   When deciding on whether to use a subtalar joint implant, there are many considerations. One must decide what type and size of implant to use. Surgeons must also determine the appropriate procedure selection and if any adjunctive procedures are necessary. By ensuring a thorough physical examination and proper surgical planning, surgeons can minimize the risk of complications with subtalar joint implants.

A Closer Look At The Evolution Of Subtalar Joint Implants

   In 1946, Chambers had described filling the sinus tarsi with bone to prevent eversion and still allow inversion.³ LeLievre first described the term arthroereisis in 1970. He used an accessory bone graft in the sinus tarsi to decrease the motion of the rearfoot and stabilized the bone graft with a staple if necessary.⁴ Since that time, we have seen the evolution of numerous designs of subtalar joint implants.

   Earlier models include the Viladot, which has a stem and umbrella feature to prevent pullout, and the Valenti, a threaded polyethylene plug inserted into the sinus tarsi. The STA-Peg (Wright Medical), which Smith and Millar produced, consists of a stem that inserts into the floor of the sinus tarsi while the lateral process of the talus rests on the top of the platform surface. The Sgarlato device is a mushroom-shaped peg that inserts into the floor of the sinus tarsi and limits forward motion of the lateral process of the talus.⁵ Maxwell and Brancheau introduced the MBA implant.^6,7 It is a threaded titanium implant, which one inserts into the sinus tarsi. It became popular due to its relative ease of insertion, minimal dissection and quick recovery period.

   The Valenti and MBA arthroereisis devices are classified as “self-locking wedges,” which are implants that separate the talus and calcaneus. These implants block eversion while preventing further anterior displacement of the talus.⁵ These types of implants were originally designed for adolescent and adult use because of the minimal disturbance of the sinus tarsi. However, they have become increasingly popular in pediatric use as well.^8,9