In children with idiopathic pes equinovarus, an investigation of the relationship between changes in achilles tendon length and plantar flexion strength with recurrent metatarsus adductus deformity following ponseti treatment

Aim: To determine factors associated with the recurrent metatarsus adductus deformity, investigating tendon length and muscle strength around the ankle in children with unilateral idiopathic PEV. Patients and Methods: With a recurrent metatarsus adductus deformity identified clinically at the final examination, a total of 20 kids (14 Female, 6 Male) aged between 5 and 10 years who were diagnosed and treated by Ponseti method due to idiopathic PEV were included in the present study. The mean age was 28 days (15-60) at the start of Ponseti treatment, and 7 years (5-9) at the final follow-up. The mean length of the follow-up was 84 months (57-107). All data analyzed in the study were obtained from both involved and uninvolved feet of patients, and then statistical comparisons and correlations were undertaken between both sides. At the final follow-up, ultrasonographic measurement of tendon length and isometric muscle strength around the ankle were assessed. Results: In the assessment of isometric muscle strength, although no difference was observed in terms of dorsiflexion strength (p>0,05), ankle plantar flexion, inversion, and eversion strength were determined to be lower on involved sides than on involved sides (p=0,001; p<0,01). Furthermore, the ratio of plantar flexion/dorsiflexion muscle strength was found to be significantly lower on the uninvolved side than on the involved side (p=0,001; p<0,01). However, no significant difference in terms of the ratio of inversion/eversion muscle strength was detected (p>0,05) between both sides. In the measurement of ultrasonographic tendon length, While Achilles tendon length of the involved side was determined to be significantly longer than that of uninvolved side (p=0,001; p<0,01), peroneal tendon length of the involved side was found to be considerably shorter than that of uninvolved side (p=0,001; p<0,01). Additionally, there was a significant correlation between the ratio of lengthening of Achilles tendon and the ratio of decrease of plantar flexion muscle strength (r:0,530; p=0,016; p<0,05). Similarly, A reverse correlation was observed between involved/uninvolved plantarflexion muscle strength and involved/uninvolved Achilles tendon length (r:-0,524; p=0,018; p<0,05). In the clinical examination of recurrent metatarsus adductus deformity, the deformity was mild in 10% of patients (n=2), moderate in 55% (n=11), and severe 35% (n=7). Conclusion: The length of Achilles tendon following Ponseti treatment can be longer in children with PEV compared to the uninvolved side of those. Furthermore, it can be observed that the ratio of decrease in plantar flexion strength increases with increase in the difference between Achilles tendon length between both sides of this group of patients. The decrease in the plantar flexion strength following Ponseti method can cause a predisposition to a recurrent metatarsus adductus deformity. Furthermore, even if eversion muscle strenght is altered in this group of patients, the muscle balance between inversion and eversion strength may be normal.