Extensive Implant Reaction in Failed Subtalar Joint Arthroereisis: Report of Two Cases

Foreign body synovitis with extensive granulomatous giant cell reaction to refractile polyethelene debris is a complication of subtalar arthroereisis not previously reported. We present two cases whereby STA-peg implants were used to treat bilateral painful flexible flatfoot deformities in children. Two boys, presented at 7 and 10 years of age, 2 years after STA-peg procedures and tendo-Achilles lengthening for painful flatfeet. They each had minimal subtalar motion and pain at the sinus tarsi. Radiographs demonstrated surgical defects in the calcaneus with surrounding high signal on the magnetic resonance imaging (MRI) in the subchondral bone of the calcaneus and talus. Both patients failed conservative management and had their implants removed with good relief of their pain. Histology was submitted at the time of implant removal. We present the radiographic and pathologic findings seen in these two patients with failed subtalar arthroereisis due to extensive implant reaction. The pathologic process seen in these patients is a previously unreported complication of this procedure. We do not recommend arthroereisis in the treatment of painful flexible flatfoot in children

Subtalar Joint Arthroereisis in the Management of Pediatric Flexible Flatfoot: A Critical Review of the Literature

Background: Pediatric flexible flatfoot is a common deformity for which a small, but significant number undergo corrective surgery. Arthroereisis is a technique for treating flexible flat-foot by means of inserting a prosthesis into the sinus tarsi. The procedure divides opinion in respect of both its effectiveness and safety. Methods: A database search up until 2010 was used to find articles regarding arthroereisis in pediatric patients. We summarized the findings of this study. Results: Seventy-six studies were identified. Eight of the nine radiographic parameters reported show significant improvement following arthroereisis reflecting both increased static arch height and joint congruency. Calcaneal inclination angle demonstrated the least change with only small increases following arthroereisis. Arthroereisis remains associated with a number of complications including sinus tarsi pain, device extrusion, and under-correction. Complication rates range between 4.8% and 18.6% with unplanned removal rates between 7.1% and 19.3% across all device types. Conclusion: Current evidence is limited to consecutive case series or ad hoc case reports. Limited evidence exists to suggest that devices may have a more complex mode of action than simple motion blocking or axis altering effects. The interplay between osseous alignment and dynamic stability within the foot may contribute to the effectiveness of this procedure. Although literature suggests patient satisfaction rates of between 79% to 100%, qualitative outcome data based on disease specific, validated outcome tools may improve current evidence and permit comparison of future study data.</p