[Pelvic coronal inclination change in adolescent flexible flatfoot surgically treated with arthroereisis]

Objective: To evaluate adolescent pelvic coronal inclination angle change after flatfoot treated with arthroereisis. Method: A case-series study. From June 2018 to September 2020, 25 children with flexible flat foot and pelvic obliquity were included in this retrospective study in Peking University Shenzhen Hospital. There were 17 males and 8 females with a mean age of (11.2±2.2) years (9-15 years). There were 5 cases of unilateral flatfoot and 20 cases of bilateral flatfoot. All of the patients were surgically treated with arthroereisis. Regular follow-up was done in 3 months, 1 and 2 years postoperatively. Weightbearing fluoroscopy of entire lower limb and foot were investigated to measure Meary's angle, calcaneal pitch angle, height difference at ankle and pelvic plane, pelvic inclination and sacrum-iliac distance (F value) on coronal plane. Results: The mean Mearys' angle at 3 month postoperatively was improved when compared with that before the operation (3.1°±1.5° vs 25.9°±4.3°, P<0.001), and it remained at the same level 2 years after the operation (compared with that at 1 year after the operation, P=0.748). The calcaneal pitch angle improved significantly at 3-month follow-up when compared with that before the operation (16.6°±2.4° vs 9.9°±1.5°, P<0.001), and there was no significant change between 1 year and 2 years after operation (P=0.542). The height difference at mortise plane were also reduced at the 3-month follow-up(P<0.001), and it remained at the same level at 1 year and 2 years after the operation (P=0.159). Pelvic height difference decreased dramatically from (12.4±1.7) mm (before operation) to (7.1±1.2) mm(3 month after the operation) (P<0.001), it decreased to (3.6±1.8) mm 1 year after the operation (compared with that at 3 months after the operation, P<0.001), and no further reduction was observed 2 years after the surgery (P=0.483). The pelvic inclination angle and sacrum-iliac distance were also improved at 3-month follow-up when compared with those before the operation (both P<0.001), and they declined further 1 year after the operation(both P<0.05), but the decreasing trend disappeared at the 2-year follow-up (both P>0.05). Conclusion: For adolescent flexible flat foot patients with pelvic obliquity, the coronal inclination and pelvic height discrepancy would partially recovered with correction of flatfoot deformity, but it could not be completely corrected in the mean follow-up period of 2 years after the operation.