Use of the Pirani score in monitoring progression of correction and in guiding indications for tenotomy in the Ponseti method: Are we coming to the same decisions?

Purpose: The Pirani score is widely used in the treatment of idiopathic clubfoot. Some authors recommended to base decision for Achilles tenotomy in Ponseti method on this score (hindfoot score [HFS] > 1, once reducibility of lateral head of talus (LHT) is zero) instead of originally described indications (dorsiflexion < -10-15° once complete abduction is achieved). Yet correspondence of these indications has not been evaluated. Aim of this study was to verify whether in a cohort, where decision is based on dorsiflexion, the Pirani score corresponds to the limits suggested. Secondarily, to describe temporal variation in Pirani score along treatment, which has not been previously investigated.

Methods: In a prospective study, 79 idiopathic clubfeet in 47 cases consecutively treated with Ponseti method by a single orthopaedic surgeon were evaluated at each casting session with Pirani system; score progression and scores at time of decision to perform tenotomy were determined.

Results: HFS and its subcomponents showed minimal improvement during subsequent sessions of casting and then rapid correction with tenotomy. Medial crease resolved rapidly. Midfoot score and its remaining subcomponents corrected gradually. Total Pirani score showed initially a progressive correction and then a more abrupt improvement with tenotomy. At the time of decision to perform tenotomy, in 8 (10.1%) of 79 cases, the decision whether or not to perform tenotomy based on dorsiflexion would have been different based on the cut-offs for Pirani score suggested.

Conclusion: Using Pirani score in guiding indication for tenotomy may imply different decisions in a portion of cases, which should be considered when comparing series.