Adult acquired flatfoot is a frequent deformity which appears as a severe and complex osseous derangement. It implies multiple and combined 3D modifications of the foot skeletal architecture. The modern Cone-Beam CT technology can now provide access to foot bone scans in 3D and in weight-bearing (WBCT), allowing to thoroughly characterize also most of the flatfoot deformities. This study aims at measuring these deformities in patients with indication for the Mini Bone Block Distraction Subtalar Arthrodesis (SAMBB), a surgical technique which intends to restore the correct relationship between the talus and the calcaneus by placing bone grafts in the sinus tarsi, i.e. the tunnel between the two bones. The measurements were obtained by means of 3D bone models from a single WBCT scan, two different segmentation tools and a single original geometrical technique. In particular, for the present clinical application, 21 patients underwent WBCT (Carestream, US), while standing in a single leg up-right position. From these CT scans, 3D models of each of the foot bones were reconstructed by means of two software. On the one hand, manual segmentation was performed with a state-of-the-art tool (MIS, Materialise, Belgium); on the other hand, a new automatic software (Bonelogic® Ortho Foot and Ankle, Disior, Finland - DIS) was exploited to obtain corresponding 3D reconstructions from the same scans. From both reconstructions, traditional planar (2D) and novel 3D angles of the foot bones were calculated based on anatomical axes and planes obtained through automatic PCA (Principal Component Analysis) statistical procedure. With the present full 3D technique, sources of errors such as the projection artefacts, foot positioning and subjective identification of landmarks, are removed and objective and comprehensive angular and linear measurements to quantify accurately this pathology can be finally taken. The present investigation shows that MIS-based and DIS-based bone models compare very well, in fact the mean difference between manual and automatic segmentations was within 3 degrees for most of the angular measurements. Moreover, the present thorough 3D measurements demonstrate further the large deformities implied in severe flat feet and, in general, are more consistent than those obtained with planar projections (2D). Finally, a preliminary analysis of 6 feet 8 months post-op (via modified SAMBB) was performed and revealed considerable corrections in 3D at the rear- but also at the fore-foot.
Il piede piatto è una patologia molto frequente che si presenta come una complessa alterazione ossea caratterizzata da molteplici e complesse malformazioni dell’architettura del piede. La moderna tecnologia Cone-Beam CT permette di avere accesso alle ossa del piede in 3D e in carico (WBCT), consentendo di caratterizzare accuratamente la maggior parte delle deformità del piede piatto. Questo studio si pone l’obiettivo di misurare tali deformità in pazienti che dovranno sottoporsi a Mini Bone Block Distraction Subtalar Arhrodesis (SAMBB), una tecnica chirurgica che mira a ripristinare il corretto rapporto tra astragalo e calcagno posizionando innesti ossei nel sinus tarsi, ovvero il tunnel che si trova tra questi due segmenti ossei. Le misure sono state calcolate a partire da modelli 3D del piede ottenuti con due diversi strumenti di segmentazione. In particolare, nel presente studio, 21 pazienti sono stati sottoposti a WBCT (Carestream, US), in posizione eretta monopodalica. Dalle stesse scansioni CT sono stati ricostruiti i modelli 3D delle singole ossa del piede utilizzando due software: Mimics (MIS, Materialise, Belgio) che rappresenta il gold standard e permette una segmentazione manuale e Disior (DIS, Bonelogic® Ortho Foot and Ankle, Finlandia) che invece rende automatica la procedura di segmentazione. Da entrambe le ricostruzioni sono stati calcolati sia gli angoli tradizionali 2D sia quelli 3D delle ossa del piede sulla base di assi e piani anatomici ottenuti attraverso la PCA (Principal Component Analysis), una procedura statistica automatica. La tecnica 3D permette di eliminare qualsiasi fonte di errore, per esempio artefatti da proiezione, posizionamento del piede e identificazione soggettiva dei punti di repere e di ottenere misure angolari e lineari oggettive e accurate per quantificare approfonditamente la patologia in esame. Il presente studio mostra come i modelli ossei 3D ricostruiti con MIS e DIS si confrontino molto bene tra loro, con una differenza media tra segmentazione manuale e automatica entro i 3 gradi per la maggior parte delle misure angolari. Inoltre, le presenti misure 3D dimostrano ulteriormente le grandi deformità dei casi più gravi di piede piatto e, in generale, sono più consistenti rispetto alle proiezioni planari (2D). Infine, un’analisi preliminare eseguita su 6 scansioni a 8 mesi dall’intervento (tramite SAMBB) ha dimostrato correzioni notevoli in 3D sia nel retropiede che nell’avampiede, fornendo un risultato incoraggiante per l’impiego futuro di questa tecnica.
Bone alignments via weight-bearing CT scans and 3D reconstruction tools in flatfoot : development and exploitation of novel techniques
Scicolone, Silvia;PAVANI, CHIARA
2019/2020
Abstract
Adult acquired flatfoot is a frequent deformity which appears as a severe and complex osseous derangement. It implies multiple and combined 3D modifications of the foot skeletal architecture. The modern Cone-Beam CT technology can now provide access to foot bone scans in 3D and in weight-bearing (WBCT), allowing to thoroughly characterize also most of the flatfoot deformities. This study aims at measuring these deformities in patients with indication for the Mini Bone Block Distraction Subtalar Arthrodesis (SAMBB), a surgical technique which intends to restore the correct relationship between the talus and the calcaneus by placing bone grafts in the sinus tarsi, i.e. the tunnel between the two bones. The measurements were obtained by means of 3D bone models from a single WBCT scan, two different segmentation tools and a single original geometrical technique. In particular, for the present clinical application, 21 patients underwent WBCT (Carestream, US), while standing in a single leg up-right position. From these CT scans, 3D models of each of the foot bones were reconstructed by means of two software. On the one hand, manual segmentation was performed with a state-of-the-art tool (MIS, Materialise, Belgium); on the other hand, a new automatic software (Bonelogic® Ortho Foot and Ankle, Disior, Finland - DIS) was exploited to obtain corresponding 3D reconstructions from the same scans. From both reconstructions, traditional planar (2D) and novel 3D angles of the foot bones were calculated based on anatomical axes and planes obtained through automatic PCA (Principal Component Analysis) statistical procedure. With the present full 3D technique, sources of errors such as the projection artefacts, foot positioning and subjective identification of landmarks, are removed and objective and comprehensive angular and linear measurements to quantify accurately this pathology can be finally taken. The present investigation shows that MIS-based and DIS-based bone models compare very well, in fact the mean difference between manual and automatic segmentations was within 3 degrees for most of the angular measurements. Moreover, the present thorough 3D measurements demonstrate further the large deformities implied in severe flat feet and, in general, are more consistent than those obtained with planar projections (2D). Finally, a preliminary analysis of 6 feet 8 months post-op (via modified SAMBB) was performed and revealed considerable corrections in 3D at the rear- but also at the fore-foot.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/173422