Is Sonographic Calculation of Talonavicular Angle During Ponseti Correction of Clubfoot a Reliable Prognostic Indicator?

Background: Ultrasonographic evaluation of clubfoot is an objective method of severity assessment. The objective of this article is to assess the reliability of clubfoot severity assessment by sonographic evaluation of talonavicular angle (TNA) and the reliability of assessing change in angle on simulated Ponseti manipulation. Materials and methods: Twenty-six infants with unilateral idiopathic clubfoot, treated by serial manipulation and casting by Ponseti technique, were prospectively evaluated by clinical scoring (Dimeglio and Pirani scores) and sonographic measurements of TNA at the start of treatment, after midfoot correction and after complete correction achieved. The TNA and the change in TNA on simulated Ponseti manipulation were noted. Total number of POP casts required to achieve final correction were noted; and correlated with change in TNA on attempted Ponseti manipulation. Results: Mean TNA in clubfoot (66.46o) in static position was significantly different from that of contralateral normal foot (101.3o). Mean change in TNA on simulated Ponseti manipulation was 22.54o (5-50o) and it showed negative correlation with clinical scores and total number of casts required for final correction (p < 0.05). Linear regression analysis revealed that the change in TNA on simulated Ponseti manipulation was the best predictor of treatment outcome in congenital talips equinovarus (CTEV) (with predictability of 60% compared to 19 and 25% of Dimeglio score and Pirani score respectively). Conclusion: Sonographic evaluation of TNA and change in TNA on simulated Ponseti manipulation can better assess the severity of clubfoot in infants. This objective method of assessment is less expensive, clinically applicable reproducible and it can better predict the treatment outcome.