Changes in the bony alignment of the foot after tendo-Achilles lengthening in patients with planovalgus deformity

BACKGROUND: This study was performed to investigate the change in the bony alignment of the foot after tendo-Achilles lengthening (TAL) and the factors that affect these changes in patients with planovalgus foot deformity. METHODS: Consecutive 97 patients (150 feet; mean age 10 years; range 5.1–35.7) with Achilles tendon contracture (ATC) and planovalgus foot deformity who underwent TAL were included. All patients underwent preoperative and postoperative weight-bearing anteroposterior (AP) or lateral (LAT) foot radiographics. Changes in AP talo-1st metatarsal angle, AP talo-2nd metatarsal angle, LAT talo-1st metatarsal angle, and calcaneal pitch angle and the factors affecting such changes after TAL were analyzed using lineal mixed model. RESULTS: There were no significant change in AP talo-1st metatarsal angle and AP talo-2nd metatarsal angle after TAL in patients with cerebral palsy (CP) (p = 0.236 and 0.212). However, LAT talo-1st metatarsal angle and calcaneal pitch angle were significantly improved after TAL (13.0°, p < 0.001 and 4.5°, p < 0.001). Age was significantly associated with the change in LAT talo-1st metatarsal angle after TAL (p = 0.028). The changes in AP talo-1st metatarsal angle, AP talo-2nd metatarsal angle, and calcaneal pitch angle after TAL were not significantly associated with the diagnosis (p = 0.879, 0.903, and 0.056). However, patients with CP showed more improvement in LAT talo-1st metatarsal angle (− 5.0°, p = 0.034) than those with idiopathic cause. CONCLUSION: This study showed that TAL can improve the bony alignment of the foot in patients with planovalgus and ATC. We recommend that physicians should consider this study’s findings when planning operative treatment for such patients.