Analysis of the effects of mandibular reconstruction based on microvascular free flaps after oncological resections in 21 patients, using 3D planning, surgical templates and individual implants

Highlights

• Virtual pre-operative planning.

• Custom implants in maxillofacial surgery.

• Oncological reconstructions of mandible.

• Objective morphological analysis of surgical treatment.

Abstract

Introduction

Post- resection defects in the area of the head and neck frequently result in functional impairment of the masticatory system and unaesthetic outcome in the facial appearance. In pediatric population they exert a devastating effect on speech development, breathing and facial growth leading to secondary deformations which are extremely challenging in reconstruction by means of conventional surgery protocols.

Material and Methods

21 patients (14 males/ 7 females) aged 4–17 years old, treated between 2015 and 2019 due to malignant/benign tumors or congenital deformities requiring mandible resection were enrolled in the study. All patients underwent Virtual Surgical Planning (VSP), mandible tumor resection with use surgery guides and defect reconstruction with microvascular bone graft supported with custom implants. Postoperatively, 3D models used for the planning and postoperative 3D model of the reconstructed mandible were compared using authors method based on easily measurable morphometric measurements (3 angles, 3 linear dimensions), allowing a three-dimensional quantitative assessment of postoperative outcomes of the surgery. Linear regression analysis and one-way analysis of variance were used to evaluate the clinical material. The difference was considered significant if p < 0.05.

Results

Free fibula flap (FFF) was most commonly used type of the reconstruction of the pediatric mandible. The average maximum deviation for the analyzed cases was 7.7 mm, and the average minimum deviation was −6.09 mm, however without significant differences and the postoperative position of the mandible condyle was comparable to the position designed in the 3DVSP preoperatively. Position of the whole reconstructed mandible by means of individually planned grafts and plates provided comparable position of the ramus and mandible body and no chin deviation as the differences between the pre-operative axial and sagittal angles and their post-operative equivalents were insignificant (p > 0,05).

Conclusions

This study confirms applicability of the 3DVSP in pediatric craniomaxillofacial surgery. Preoperative planning of the osteotomies, grafting technique and production of the individualized guides and implants provides precise tumor resection and immediate reconstruction adjusted to the specific anatomy of the pediatric patients.

Introduction

The process of computer-assisted surgery (CAS) in mandibular reconstruction involves planning, modelling, surgical [1], [2], [3], and postoperative evaluation phases [4], [5]; but the evaluation phase is not performed in all studies. In the planning phase (Fig. 1a), a computed tomography (CT) scan of the craniofacial skeleton and a CT (with or without angiography) of the donor site is obtained and saved as Digital Imaging and Communications in Medicine (DICOM) files. These 2-dimensional (2D) DICOM images can be subsequently converted into 3-dimensional (3D) surface models in the Standard Tessellation Language (STL) file format. In the revised/evaluation phase (Fig. 1b), a computed tomography (CT) scan of the craniofacial skeleton of the operative site is obtained and saved as DICOM images. After that, these DICOM images are converted into 3D models in STL file format. The preoperative 3D model and postoperative 3D model are compared. Comparison of the preoperative and postoperative data makes it possible to assess the virtual surgical planning (VSP) for each included study. The evaluation approach consists of both pre- and postoperative CT scans of the patient’s skull, followed by an accuracy analysis comparing the postoperative result with the preoperative virtual plan. Examination pre- and postoperative STL models on volume similarity should rule out volume inaccuracies between the two models as much as possible since they can influence the accuracy measurements. Valid comparisons of postoperative accuracy results in computer-assisted reconstruction of the skeletal structures are difficult due to heterogeneity in the imaging modalities, bone defect classification, and evaluation methodologies between studies. [6], [7], [8]. However, the post-operative evaluation is crucial, because of lack of possibility to predict the final position of prosthesis, that depends on the possibility of the acetabulum fixation at the skull base.

De Maesschalck et al. (2017) pioneered an evaluation method for hard tissue accuracy of mandibular reconstruction using CAS, bypassing the need for osteotomy plane determination, and bypassing the use of a superimposition tool [8]. In 2016, Schepers et al. proposed an excellent postoperative evaluation method for virtually planned dental implants in mandibular reconstruction using CAS by measuring the central point deviation [mm] and angular deviation [°] per dental implant [10]. The main limitation of this method is the quantity of measurements per implant which decreases the feasibility, and results in the loss of an overview of the accuracy of the entire reconstruction.

In this article, we propose a more simplified method for the evaluation of the 3D VSP precision and repeatability, for the purposes of reconstructive surgery of the head and neck in children and adolescents. The proposed method is based on easily measurable morphometric measurements (3 angles, 3 linear dimensions), allowing a three-dimensional quantitative assessment of postoperative outcomes. The method uses correlates with the assessment standard that has applied since 2020. The method is suitable regardless of the type of mandibular reconstruction technique used and provides the opportunity to evaluate the results and compare them.