When appropriately executed, subtalar joint arthroereisis has the potential to significantly restore proper hindfoot anatomy in a flexible flatfoot deformity. The proposed advantages of the procedure versus other surgical methods are manifold. It is simple and quick to perform through a small incision, and the hindfoot can be spared arthrodesis or osteotomy. Recovery usually involves a brief period of non–weight bearing or protected weight bearing that is significantly less compared to most osseous procedures. These advantages are appealing to both surgeons and patients, because the procedure is perceived as a reasonably uncomplicated and efficient means of surgically correcting a flatfoot deformity.

When the procedure is applied to the juvenile flatfoot, there is the additional premise that the orthotic effect allows for favorable musculoskeletal adjustment during a child’s physical maturation, which influences the foot in obtaining intrinsic stability, rendering the implant ultimately unnecessary.^6,7

For these reasons, subtalar arthroereisis has become a prominent surgical option for flexible flatfoot correction. Despite its original emphasis on pediatric flatfoot deformities, it seems increasingly used in the adult population. It has been even further extended to treat the rigid flatfoot with talocalcaneal coalition.⁸ This broad application to flatfoot deformities testifies to its perceived efficacy in addition to its simplicity. Subtalar arthroereisis, however, is not applicable to all flatfoot deformities, whether flexible or rigid, or as an isolated or adjunctive procedure. Those deformities that particularly favor transverse plane dominance may not be suited for arthroereisis. Other complex factors in flatfoot deformities, such as primary joint contribution, associated soft tissue adaptation, relative muscle function, and the presence or absence of connective tissue or neuromuscular causes, dictate judicious evaluation and surgical planning, and arthroereisis may be the least applicable or a completely ineffective procedure.

Relative contraindications reported for this procedure include flatfoot associated with angular deformity at the knee, torsional leg deformities, metatarsus adductus deformities, and valgus ankles,^9,10 whereas reported absolute contraindications include subtalar joint arthritis, peroneal muscle spasm, and excessive ligamentous laxity.^7,9,11–13

In spite of its wide use, there is no definitive consensus or guidelines for its use in children and adults. In regards to optimum age of application in children, Koning and colleagues⁷ believe arthroereisis to have little lasting effect on children beyond age 10 and report the ideal age for arthroereisis is 8 years. Fernandez de Retana⁶ and colleagues, however, advocate arthroereisis be performed before age 12, to allow a remodeling period of at least 2 years, assuming that the foot reaches its full maturity at 14 to 15 years.

In adults who already have obtained full skeletal maturity, this proposed long-term effect of subtalar arthroereisis does not pertain. Reports of retained skeletal correction in adults after explantation, however, suggest otherwise. In a prospective study, Needleman¹² proposed that implants in place for 8 months allow stiffening of the soft tissues that are integral to joint alignment and motion. This seems to be extrapolated from the finding that in those patients who required implant removal 8 or more months after the index procedure, no significant difference could be detected for the 3 radiographic parameters evaluated before and after explantation: medial longitudinal arch, uncovering of the talar head, and the difference in standing ankle height. The strength of this claim is questionable, because subtalar arthroereisis was often combined with other soft tissue or osseous procedures (eg, tendo-Achilles lengthening or gastrocnemius recession, Evans osteotomy, and/or Lapidus arthrodesis or Cotton osteotomy), which could serve as confounding variables.

Schon¹³ similarly postulates that when subtalar arthroereisis is used as an adjunct procedure in conjunction with medial soft tissue stabilizing procedures, the implant typically is no longer needed after soft tissue healing and may be removed without risk to the surgical correction. This is premised on arthroereisis protecting and facilitating healing of the medial soft tissue reconstruction while concomitantly allowing progressive introduction of weight bearing without causing excessive strain on the medial ligaments and tendons.

The 2005 clinical practice guidelines for adult flatfoot suggest that arthroereisis should only be used for early stage II posterior tibial tendon dysfunction or non–posterior tibial tendon dysfunction adult flexible flatfoot secondary to equinus.¹⁴ Consistent with other literature, caution is implied in the application of arthroereisis as an isolated procedure. Long-term compensation and adaptive changes to the foot may require ancillary soft tissue or osseous procedures for appropriate medial column stabilization. Invariably, equinus needs to be surgically addressed.

In addition to flexible flatfoot deformities, subtalar joint arthroereisis has been used in the correction of rigid flatfoot deformities due to tarsal coalitions in children. Giannini and colleagues⁸ reported on the outcome of coalition resection with subtalar arthroereisis in the treatment of flatfeet with talocalcaneal coalitions in 12 patients and 14 feet. Median age of the patients was 14 years (9–18 years) and median follow-up was 40 months (30–64 months). Eighty-six percent of the patients had improvement of pain, and 92.8% had improvement of subtalar joint range of motion. Three patients with fair results were the oldest of the patient population, and their outcome worsened with time. The satisfaction outcome in this study still fell within the range reported for those in pediatric flexible flatfoot deformities.^5–7 The investigators noted better results before the age of 14, which supports the assumption that the foot reaches full maturity at the age of 14 or 15 years,⁶ rendering it incapable of positive adaptation and tolerance of the implant. In the context of skeletally mature pediatric population with talocalcaneal coalitions, the posterior subtalar joint is likely too maladapted for any benefit from procedures short of a subtalar joint arthrodesis. Studies that correlate the success of subtalar arthroereisis with the extent of middle facet coalition may further elucidate the utility of this procedure in these rigid disorders. Pediatric rigid flatfoot secondary to a calcaneonavicular bar may also be considered more suitable for a subtalar arthroereisis, because the subtalar joint is theoretically unaffected from this coalition.