Dispelling The Misconceptions About Subtalar Arthroereisis
Subtalar arthroereisis has a long evolutionary history since its first conception in the 1940s. Since then, researchers have created and abandoned many different methods, materials and devices. The promise of the next great device to stabilize the subtalar joint complex without osteotomy or arthrodesis usually diminished with long-term usage.
The need to stabilize the talus on the calcaneus without arthrodesis has been a quest for many foot and ankle innovators. However, the scientific literature on this subject has led to many misconceptions as to the true power of the subtalar arthroereisis. Accordingly, let us provide some clarification on this controversial subject.
One of the first misconceptions is that arthroereisis is a “joint blocking” procedure. A joint blocking procedure would imply a limitation of the normal range of motion of that joint. The purpose of an arthroereisis procedure is to limit the excessive motion of the joint in order to restore that joint complex back to normal.
Many have called the devices inserted into the sinus tarsi “subtalar joint implant(s).” This leads one to believe that the device actually inserts into a joint. The reality is that these devices are completely extra-articular. The subtalar joint complex consists of two or three joints: posterior, middle and anterior joints. Sometimes the middle and anterior joints join together to form one continuous joint. In between the posterior portion of the complex and anterior portion is the area of the sinus tarsi, which has no cartilage, no interaction between two or more bones and, finally, is not a joint.
This is important as a “joint implant” has a negative connotation. It usually means that the joint is arthritic and not properly functioning. Therefore, in order to insert this device, one must resect the joint and the implant will replace the function of at least one-half of the joint. Furthermore, most joint implants do not last long and usually need to be replaced after so many years. The term joint implant also indicates not only a more aggressive surgery but also a long recovery usually involving physical therapy.
A better term is sinus tarsi implant or stent. Presently, we can define a stent as any medical device that supports tissue in order to help prevent the abnormal closure or obliteration of that tissue. For example, when one inserts a stent into the sinus of the tarsal bones, it prevents the abnormal closure of that space.
When Should Patients Undergo Subtalar Arthroereisis?
Myth: Surgeons should only perform the subtalar arthroereisis procedure in children. Researchers first developed this procedure with children in mind, primarily because they thought the materials were not durable enough for adults. Furthermore, the thought was that as a child grew, arthroereisis would help to prevent the secondary symptoms of the excessive hindfoot motion. Another reason why children underwent this procedure more than adults had to do with the activity levels of adults.
The initial materials were bone grafts and then medical grade plastics were in use. The problem with bone grafts was they eventually became absorbed or simply lost correction with time. The high-grade medical plastics and silicone devices usually fragmented after the repeated forces from the talus grinding on the calcaneus. Furthermore, once the materials broke down, this led to a possible foreign body reaction. Overall, these materials were less than ideal as a long-term solution.
Maxwell and Brancheau were the first to design a titanium version of a sinus tarsi device modeled after the Valenti design. Initially, this device was mainly in use for pediatric patients and due to the improved material, geriatric patients received the device. The use of titanium created a new level of excitement into the possibility of stabilizing the talus on the calcaneus in adult patients. This opened the door to expand the age range. Even though there was still a gap between the pediatric and geriatric patients’ usage, more patients were able to have this option.