Subtalar joint arthroereisis is a procedure performed for the correction of a flatfoot deformity. It is most commonly performed in children with a flatfoot deformity that is reducible (meaning that the corrected position can be achieved with manipulation) but may also be used in the adult population for correction of a flexible flatfoot. For very young children, it is frequently performed as an isolated procedure. For older pediatric patients and for adults, it is commonly performed along with adjunct procedures such as an Achilles tendon lengthening, gastrocnemius recession, tendon transfer procedures, arthrodesis of adjacent joints of the foot, or osteotomies that help realign the foot into a more functional position.
Arthroereisis (also known as arthrorisis and arthroerisis) is defined as the limitation or restraint of excessive or abnormal motion across a joint. For those with pes planovalgus, or a painful flatfoot deformity, this excessive motion is corrected at the subtalar joint. The subtalar joint in this foot type is deviated medially, creating a foot that functions with the subtalar joint in its maximally pronated position. This results in a dull, achy, or throbbing pain in the arch of the foot or in the leg, fatigue of the foot and leg, and pain in the lateral foot over the sinus tarsi. In the pediatric patient, who may not necessarily complain of pain, symptoms may include generalized clumsiness, easy fatigue, difficulty in sports and recreation, complaints of leg or foot tiredness or aches, excessive shoe wear, and a refusal to walk long distances or participate in physical activities.
Arthroereisis is a surgical procedure, and should only be attempted after conservative measures have failed to provide relief. Conservative measures may include the use of orthotics, other methods of padding and taping, and possibly the use of cortisone injections in older patients. When conservative therapy has failed, surgical intervention may become an option.
Arthroereisis is performed by placing an implant into the sinus tarsi, which limits the motion of the subtalar joint. Specifically, the motion that is blocked is the anterior displacement and adduction of the talus, which prevents excessive pronation at the joint. This effectively corrects the flatfoot deformity at the subtalar joint, creating a foot the functions closer to normal.
The implants used in arthroereisis procedures were described by Vogler based on his interpretation of how they functioned. These three categories were the stable self-locking wedge implants, the axis-altering implants, and the direct impact implants. This classification has more recently been criticized due to a perceived overlap in function of the various devices used.
The most popular type of implant used is the Maxwell-Brancheau (MBA) implant. The MBA implant is a small, bullet-shaped device that is placed into the sinus tarsi underneath the neck of the talus. It is composed of a titanium alloy, and functions to absorb much of the shock that is placed through the bones during weight-bearing activities. The device prevents the anterior displacement and adduction of the talus, thus reducing pronation at the subtalar joint. The devices are typically left in indefinitely, unless they cause pain or discomfort later. If that is the case, they can be taken out through a relatively simple hardware removal procedure. More recently, absorbable devices have hit the market that are completely resorbed by the body in one year.
Other implants come as alternatives to the MBA implant, such as the STA-peg device. This implant has a small stem that must be inserted into the floor of the sinus tarsi through a small drill hole. The top of the device creates a functional block for the talus, and prevents the anterior displacement and adduction by blocking the lateral process of the talus. Thus, these devices were referred to as the “axis-altering” devices in the past. However, because of the additional drilling of the calcaneus that is necessary for implantation of the device, as well as the necessity of bone cement to hold it in place, the STA-peg has become a less popular option for subtalar joint arthroereisis.
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