Preliminary radiographic findings and sizing implications on patients undergoing bioabsorbable subtalar arthroereisis

Metallic subtalar arthroereisis implants can require removal. Similarly configured bioabsorbable "interference screws" placed alternatively to metal implants may obviate removal. Radiographic imaging may show the location and sizing of the implant, and evaluate for implant degradation. Patients undergoing subtalar arthroereisis were evaluated with magnetic resonance imaging (computed tomography in one patient) to measure the size of the tarsal canal. The tarsal canal length, along with medial height and lateral height, were assessed. The patient's actual implant size was also noted as well as any signs of implant degradation, bony deformation, granulomas, and so forth. Six patients met the inclusion criteria. The range of implants used was 9 to 12 mm. The radiographic measurements of the tarsal canal were as follows: medial to lateral length, 12.8 +/- 3.4 mm; medial height, 7.3 +/- 2.5 mm; and lateral height, 8.0 +/- 1.7 mm. Two patients underwent implant removal. No cystic or degenerative changes were noted on plain radiographs with bioabsorbable implants. Bioabsorbable interference screws for subtalar arthroereisis placed in the tarsal canal may still require removal, although no detrimental changes were noted radiographically to the surrounding bony structures. The size of the current metallic implants on the market appears larger than the tarsal canal configuration.