[Subtalar Arthroereisis]

Subtalar arthroereisis (STA) is an established, minimally invasive, joint-preserving procedure for the treatment of flexible pes planovalgus. Originally used primarily in children, it is increasingly gaining importance as an adjunctive procedure in adults. A distinction is made between endosinotarsal techniques (sinus tarsi spacers) and exosinotarsal procedures (Calcaneo-Stop/SESA screw). The underlying mechanism of action is not based solely on mechanical blockade of pronation, but also on proprioceptive and neuromuscular effects, as well as, in patients with open physes, osseous remodeling. This explains why correction is usually maintained even after implant removal. Comparative studies show largely similar outcomes between the two techniques and implant choice appears to be of secondary importance for clinical success. In adults, endosinotarsal implants are predominantly used, usually combined with FDL transfer, a medializing calcaneal osteotomy, or other flatfoot-correcting procedures. The most common complication is sinus tarsi pain, with reported explantation rates of 7-30%. This article reviews the history, classification, mechanism of action, indications, and surgical technique of both procedures, as well as the current evidence regarding complications and combined interventions. Treatment success depends not on implant type but on correct indication and precise implant positioning. Prospective studies on long-term outcomes remain necessary to further clarify the role of STA within modern reconstructive concepts for adult flexible pes planovalgus.