Three-dimensional computation of femoral canine morphological parameters: from the theory to the surgery application

The present research was envisioned as a project defined by multiple studies that are strictly correlated each other. The report of the birth, development and practical application to the diagnostic and surgery fields of a novel 3D approach for the computation of femoral measurements was the first aim. Moreover, in the authors’ purpose the description of the translational value of the proposed procedure enhanced with its plausible utility to the daily practice of orthopaedic surgeons, represented another focal point. In this sense, the research started from the validation of the 3D assessment of femoral morphometric parameters. Veterinary literature reports tons of papers describing several methodologies for obtaining femoral measurements through different diagnostic techniques. Furthermore, bibliography presents lot of angles values that are currently adopted and considered as reference parameters for most of the corrective osteotomies. Additionally, in the recent past an increased emphasis on 3D approach grown but little if any attention was devoted to 3D measurements. This trend represented in the authors’ mind the gap with the current knowledge and, thus, an area to be deeply investigated. Indeed, to the best of author knowledge, there were no papers documenting the assessment of 3D femoral axes and angles in veterinary medicine, with no 3D protocol described. In addition, currently available canine femoral measurements related to frontal, sagittal and transverse deformities have only been computed in bi-planar projections, whether acquired from 2D or 3D imaging models. Therefore, starting from the accepted human methods and from the features definition in veterinary literature, we proposed a new approach. The first study was designed to define a 3D methodology, introducing a consistent and quantitative method for the assessment of femoral morphometric parameters in 3D geometrical models. To validate the proposed approach, accurate geometric data were necessary and, therefore, we opted for meshes obtained by a 3D scanner, instead of CT images. Once the validation of the was stated, our focus was directed towards the evaluation of the precision of the proposed 3D protocol. The validation of a novel diagnostic test requires verification of the repeatability, defined as the strength of agreement between repeated measurements of the same samples performed from one examiner, and the reproducibility as well, that express the same variance but between a group of observers. Furthermore, the accuracy of the measurements indicates how close the measurements took with the investigated technique to a true value (gold standard). Therefore, a second project was designed to test the precision of three diagnostic techniques, two largely diffuse (Rx and TC) one recently introduced in veterinary (3D), for the measurement of femoral angles. The second purpose of this study was the investigation of the potential application of the algorithm implemented in a computer-aided-design (CAD) software, using CT data. Considering that for the first study we worked with 3D scanner data, the main aim at this point of the research was represented by the enhancement of the presented 3D protocol for diagnostic purposes. In the author opinion, changing the source of data was necessary because of the availability of CT and MRI equipment in veterinary practice. Finally, the last goal of this project was the translation of the application of 3D computation to the surgical field. The current research contemplates the fact that the augmented interest on 3D computation is not only relevant for diagnostic reasons, but also for surgery. Thus, the correlation between the diagnostic utility of the 3D approach and its plausible practice for surgery purposes was the object of the final study. The starting point was suggested by veterinary literature that reports in few papers the development and application of surgical devices used to perform assisted-correction of bone deformities. These surgical tools are designed through 3D geometrical models and act both as precise intraoperative localizers of osteotomy corrective landmarks and surgical saw guides. Three-dimensional assessment of a bone conformation may improve the understanding and evaluation of bone deformities and occurring joints malalignment. In this sense, the localization of the CORA as well as the accuracy of the orientation of the osteotomy-cutting plane may be significantly upgraded through a 3D approach.

La tesi di dottorato presentata è stata concepita nell’ambito di un più ampio progetto che comprende molteplici studi tra loro intrinsecamente correlati. L’obiettivo principale del lavoro consiste nella descrizione delle basi teoriche, sviluppo nonchè applicazione pratica nel campo della diagnostica per immagine e chirurgia di un nuovo protocollo 3D utilizzato per la misurazione di angoli nel femore del cane. Lo scopo successivo è stato quello di descrivere il valore traslazionale della procedura analitica qui presentata. Il primo passo dell’intera ricerca è rappresentato dalla validazione della metodologia. Un nuovo algoritmo sviluppato consente, per mezzo di un CAD software di comune utilizzo (Rhinoceros), di eseguire la computazione di angoli in 3D. Il secondo step ha previsto la verifica della ripetibilità e della riproducibilità di tale metodica che è stata comparata con quelle più comuni effettuate con radiografia e Tac. Infine, con l’ultimo studio abbiamo traslato le basi teoriche in applicazione chirurgica andando a creare, per mezzo dell’algoritmo elaborato, delle dime chirurgiche. Questi strumenti intra-operatori sono molto utili durante la chirurgia per le osteotomie correttive in quanto si accoppiano perfettamente nel punto di deformità e consentono di guidare l’osteotomia dell’osso.