# Evaluation of HMDs by QFD for Augmented Reality Applications in the Maxillofacial Surgery Domain
## 2 Materials and Methods
### Desk Research on Maxillofacial Practices
#### 2.1.1 Oncological and Reconstructive Surgery  
The maxillofacial region may host different kind of tumours, cancerous or benign, which often require a surgical reconstructive intervention on damaged structures. Bone structures may be damaged directly by a tumour or indirectly by the treatments of the disease: aggressive tumours, such as the squamous cell carcinoma, are treated with radiotherapy app which may cause a necrosis of the bone structures irradiated, called osteoradionecrosis. This is one of the most feared complications after head and neck radiotherapy; in the worst cases, bone re-construction is necessary to restore necrotized tissue. Among head and neck sites, the mandible is the most commonly affected bone [13]. Besides bone structures, cancers may grow in soft tissue such as the odontogenic tissue or the lip, oral cavity, nasopharyngeal, and pharynx tissue. Odontogenic tumours are a heterogeneous group of lesions derived from elements of tooth-forming tissues with a very low frequency of cancerous forms. Although there is a significant variation in the invasiveness of the growth pattern among these tumours, they generally grow slowly, causing the distortion of the bone. However, large tumours may exhibit a much more aggressive behaviour that includes extensive destruction of the bone and proliferation into the soft tissues. The common odontogenic tumours are usually treated conservatively by enucleation or curettage, whereas aggressive or recurrent tumours require radical resection and so a reconstructive intervention.  
Common surgical reconstruction practice harvests a graft from the fibula to repair the mandible. The first reported fibula-free flap mandibular reconstruction was made by [PERSON] [14]. Compared to previous bone flap harvesting sites, the fibula can be harvested as a pure osseous flap or as a hybrid graft with muscle and skin, thereby permitting great flexibility for the reconstruction of virtually any mandibular and soft tissue defects [15]. Flap harvest is relatively straightforward, allowing the ablative and the reconstructive surgeons to work simultaneously.  
Restoring the functional and aesthetic characteristics of the jaw requires accurate preoperative planning to define the position and orientation of the osteotomies and the length of the fibula's segments. Preoperative planning information is used to make tools named cutting guides. Two guides, one to remove the part of the mandible affected by the tumour and one to harvest the fibula flap, are used in the intraoperative phase. Those cutting guides support and orient surgeon's tools during resections. Correct positioning is fundamental in each intraoperative step to obtain a good outcome; however, to have a minimally invasive surgery, surgical accesses must be narrow, meaning that there is a lack of visibility. Giving the surgeon a way to see, anchored to the patient's body, the placement of virtual guides would hasten the fixing and enhance the positioning of the physical guides. Visual assistance could also help the surgeon during the reconstruction phase to place the fibula segments inside the mandible osteotomy site and check the reconstruction compliance with the preoperative planning model. Moreover, the hybrid nature of fibula flaps would require a way to see the proper vascularisation of the soft tissues. Seeing a live view of the blood flux in the operating room could really improve the post-operative procedures.  
To further improve quality and safety of a surgery, the Digital Imaging and COmunuications in Medicine (DICOM) data sets and virtual planning may be used as a useful source of information to keep in check during the surgery.