From the archives of the IRCCS Rizzoli Orthopedic Institute, all cases of arthrorrhesis of the subtalar joint with a reabsorbable endorthotic implant in PLLA will be retrieved. An overall electronic database will be created and all medical records of these cases will be reviewed.

The eligibility of each individual patient will be assessed on the basis of the exclusion and inclusion criteria (non-probability convenience sampling).

The study will not present a control group or comparison groups between therapeutic procedures.

Inclusion Criteria:

• Age between 8 and 15 years at the time of surgery
• Arthrorrhosis of the subtalar with reabsorbable endorthotic implant in PLLA
• Minimum follow-up of 5 years

Exclusion Criteria:

• Revisions/explantation of the endorthesis device
• Patients with active acute or chronic infections
• Patients with chronic inflammatory joint diseases
• Patients with previous significant trauma of the lower limbs following surgery
• Patients with pre-existing anomalies of ambulatory kinematics (amputations, neuro-muscular diseases, poliomyelitis, hip dysplasias)
• Patients with cognitive deficits
• - Patients with concomitant neurological pathologies
• Patients suffering from tumor pathology
• Patients with cardiac pacemakers or other prostheses equipped with electronic circuits
• Patients with intracranial metal implants, metal heart valves, vascular clips, ferromagnetic endovascular filters/stents/coils, Swan-Ganz catheters or in any case positioned close to vital anatomical structures
• Patients with orthopedic metal prostheses
• Patients with cochlear implants or fixed hearing aids, lens prostheses with ferromagnetic intra-ocular points, IUD (coil) or splinters made of ferromagnetic material
• Pregnant patients
• Patients with insulin pumps and non-removable contact lenses

pediatric population with subtalar arthrorisis surgery with reabsorbable endorthesis implant in PLLA