PAT is one of the important parts of the Ponseti method. The indication for PAT in third edition of Ponseti management is when ankle dorsiflexion remains less than 10 degrees above neutral after correction of cavus, adductus, and varus. Although Ponseti suggested evaluating infant clubfoot by physical examination, several studies have tried to use radiography and sonography as measurements for evaluating the effect of tenotomy.1,8,16 Zimmerman et al. indicated that the mean differences between pre- and post-tenotomy radiographs were a dorsiflexion increase of 17°, tibio-calcaneal angle increase of 19°, talo-calcaneal angle increase of 9°, and talo-first metatarsal angle increase of 10°.1
The results from Radler et al. showed that only the lateral tibiocalcaneal angle and clinically measured dorsiflexion changed significantly after tenotomy, and the mean improvements were 16.9° and 15.1°, respectively.16 Hisateru et al. used ultrasound to observe the healing process in the gap after tenotomy at two-year follow-up.8 They concluded that only slight irregularity of the internal structure persisted in the affected foot compared to the normal foot.
In our study, we also recorded the amount of improvement of the lateral tibiocalcaneal angle (22.8°), which was similar to the results of Radler et al. and Zimmerman et al. In our opinion, the amount of Achilles lengthening or TCA change under radiography may be used in monitoring the completeness of PAT and the technique of post-PAT casting. If the long-term functional outcome is correlated with intra-operative findings, then the intra-operative findings can be used as a parameter to determine operative decisions. For example, it can be used to predict the necessity of performing an open-ankle and subtalar joint capsular release in the future.
Noncompliance with an abduction orthosis is widely accepted as the primary risk factor for recurrence, but a significant relationship has not yet been established between the compliance and relapse of the deformity.4,6,7,18 Several studies have shown that residual equinus deformity (the extent of ankle dorsiflexion) before and after Achilles tenotomy are related to a higher need for future operative intervention.9,10,12 Kang et al. indicated that lateral TCA measured by radiographs is more objective than physical examination only and is also a predictor for the necessity of performing PAT.10 All our TCAs measured by radiographs after PAT were over 10 degrees and did not receive further intervention. However, a limitation of this study is that the post-casting ankle/foot lateral view was not taken at the same rotation angle as the pre-PAT and post-PAT lateral views due to the external rotation of the long leg cast near 70 degrees in the Ponseti method.
In conclusion, we revealed that the average lengthening of ATL after PAT was 8.5 mm, the average correction of TCA after PAT was 30.8o, and the average dorsiflexion of 8o was lost after casting. A lower pre-PAT TCA correlates with lower post-PAT and post-casting TCA. Furthermore, lower pre-PAT ATL correlates with a lower post-PAT and post-casting ATL. This means that the post-PAT correction effect is negatively correlated with the pre-PAT severity of equinus. The comparison between the post-PAT and post-casting TCA could be used to check the quality of casting in the Ponseti method. TCAs after PAT were all over 10 degrees, and no cases needed further operation in our study. Long-term follow up is necessary to document the final equinus correction.