COMPLEX FACIAL RECONSTRUCTION BASED ON 3D MODELS: PRELAMINATION CASES AND LITERATURE REVIEW

INTRODUCTION

The face is one of the most important regions of the human body, which contains complicated and delicate features that help to define the person’s identity¹. The deformities in this region can have multiple etiologies: oral cancer, burns, infections, osteoradionecrosis, vascular lesions, traumatic injuries and congenital anomalies. There are various methods of reconstruction and it is important to perform a morphologic and dynamic evaluation of the patients in order to find the best one².

Advances in 3D technology have given surgeons the answers to complex reconstructive surgery questions. With the introduction of 3D models, it was possible to stop using two-dimensional images or photos for preoperative planning and to start using three-dimensional ones, resulting in a significant decrease of intraoperative time. 3D models can be virtual or physical: the latter ones usually involve the conversion of computerized tomography or magnetic resonance imaging data – 3D printing³ – and can be used in an intraoperative context being a useful reference, since they provide not only visual, but also tactile information. On the other hand, these models have improved the doctor-patient relationship since they enable better understanding of both the craniofacial problem and the desired surgical result, diminishing a lot of anxiety that the patients feel about the possible outcome. The 3D models not only enable a more accurate surgical planning, but also allow a more customized and specific reconstruction for each case. Mandible defects have been successfully fixed with the use of 3D modeling, being its use described in fracture repair surgeries^4-8 and aesthetic surgeries regarding mandibular features^9-14.The processes of orbital reconstruction^15-18, ear reconstruction¹⁹, zygomatic bone repair^20,21, rhinoplasty^22,23 and nose reconstruction^24,25 have also achieved successful aesthetic results due to 3D modeling. To emphasize its wide range of applications, it can also be used in female feminization surgeries, where an individual approach is the key²⁶.

The term prelamination means a process in which a 3D structure – which can be composed of tissues, or tissue engineering products – is engrafted or implanted into a reliable vascular territory without interfering with its blood supply, being transferred to the recipient site 2 to 3 weeks later^27,28. This surgical delay is a period of neovascularization and integration, in which there is an increase in blood flow, an increase in angiogenesis and a reduction of edema so that when the flap is transferred, it is completely vascularized and with defined contours.

The purposes of the present study were to investigate the main applications of 3D modeling used alongside free flaps in facial reconstruction, which free flaps were the most commonly used in these cases, to ascertain if the combined use of 3D models and prelaminated free flaps has already been described and to emphasize the advantages that can come from the use of these last two methods together.

EVALUATION OF THE TOPIC

We conducted a literature review in order to ascertain the current applicability of 3D modeling combined with free flaps in reconstructive surgery.

PubMed and Scopus electronic databases were searched for articles using the following query: (“Reconstructive Surgical Procedures” [Mesh] OR “Surgery, Plastic” [Mesh] OR reconstructive [Text Word] OR reconstruction [Text Word]) AND (“Imaging, Three-Dimensional” [Mesh] OR 3D [Text Word] OR three-dimensional [Text Word]) AND (“Models, Anatomic” [Mesh] OR model [Text Word] OR modeling [Text Word]) AND (“Free Tissue Flaps” [Mesh] OR “free flaps” [Text Word]).

We identified 45 articles from PubMed and 33 from Scopus, amounting to a total of 78 articles (Figure 1). After removing duplicates, we scanned 67 titles and abstracts, selecting 46 for full-analysis. After accessing the full text of the included articles, 17 were excluded. The reasons for exclusion were: reviews (n=6), study not available (n=2), use of grafts and not flaps (n=3) and language issues (n=2). Also, studies with more than 15 years were excluded considering the great technical advances recognized in reconstructive surgery (n=4). Finally, 29 articles were included in the literature review.

We also selected two patients who were treated at our institution who represent suitable examples of innovative prelamination techniques that involved 3D modeling procedures.

CASE 1

A 27-year-old patient with severe sequelae of thermal burns (55 percent total burn surface area), including ectropium, upper and lower lip retraction and partial nasal loss (Figure 2), was a candidate for facial transplantation, but as he did not want this procedure, other options were investigated.

Prelamination was the selected method. The only unburned area in the body of the patient was the left side of the back, where there is a constant pedicle (parascapular artery and vein). In the first stage, an elective surgery was performed to identify and tag the recipient vessels on the neck (Figure 3). The prelamination process was then initiated with a drawing of a facial model on the back of the patient. This was based on a 3D latex model created at the Faculty of Arts as a print of the patient’s face (see Figure 3). At this stage, a partial delay of the flap was performed and the nose and the lips were drawn and open inside the flap, with subsequent placement of biomaterials (porous polyethylene implant) and grafts (Figure 4). After three months was the flap transferred and microvascular anastomosis between the subscapular vessels and the recipient vessels on the neck were created (see Figure 4). Although the perioral reconstruction was achieved successfully, revision surgeries were needed due to the different skin texture and bulk. Reconstruction of the eyelids and correction of the ectropium were performed at the same time through scar release, skin grafting and canthopexy. Later on, due to columellar and alar retraction resulting from a lack of cartilage support and secondary fibrosis of a rather thick flap, and in order to improve nasal shape, a costal cartilage graft was placed. However, this did not provide enough support either and as other local or distant flap options were not available, an anaplastologist fabricated a silicone model for alar rim and columella support to avoid airway collapse and nostril occlusion.

From 2012 (the year of the incident) to 2020, the patient has gained better feeding and mouth opening capacity, more effective breathing with more permeable areas and more robust eye protection, which translated into an extremely important functional gain. The aesthetic result has also experienced some improvement (see Figure 2).

CASE 2

A 27-year-old man suffered a motor vehicle accident and presented an almost complete amputation of the left auricle and traumatized temporal skin and fascia (Figure 5)²⁹. He was not a candidate for traditional repair techniques because of an abrasive injury that reached preauricular and retroauricular skin. A porous polyethylene implant was considered, however local flap coverage such as temporoparietal fascia flap was not available due to initial damage to the surrounding tissues. Consequently, a prelaminated radial forearm free flap was selected for reconstruction with prolonged prelamination time and surgical delay (two months). Firstly, a 3D-printed ear made of silicone was created based on the patient’s CT-scan of the contralateral ear and used for intraoperative molding of the polyethylene implant (Medpor^®). The implant consists of two components – extended ear base and helical rim – and both were adjusted into a desirable shape, having the contralateral silicone printed ear as a guide. A subdermal pocket was then dissected on the anterior aspect of the left forearm along the projection of the radial artery for placement of the porous polyethylene implant that was subsequently inserted subdermally (Figure 6). After a two-month period of integration and neovascularization of the added tissue, the prelaminated flap was transferred (Figure 7). Flap reinnervation was performed by direct coaptation of the great auricular nerve to the lateral antebrachial cutaneous nerve. The flap fully survived and there were no complications in the early postoperative period. Revision surgeries were performed. In three to six months, the patient returned to normal state in terms of warmth and cold perception and recovered the discriminative facial sensibility. After one year, the auricular reconstruction was intact and satisfactory aesthetic results were achieved. Four years after the intervention, the patient already wears short hair and is extremely satisfied with his new ear (see Figure 5).

3D MODELING AND FREE FLAPS

The combination of 3D modeling and free flaps has been described in reconstructive surgeries, being more commonly used in maxillary^30-38 and hemimaxillary reconstruction³⁹, orbital defects reconstruction^32,33 and mandibular reconstruction^{35,38,40-47,48-56,40-47}. Moreover, reconstructive surgeries regarding Parry-Romberg syndrome and Treacher Collins syndrome have also made use of this combined tool^57,58. Fibular free flaps were the most commonly used for the correction of bone defects, but the use of a thoracodorsal scapula composite free flap³⁰, vascularized iliac bone combined with a superficial inferior epigastric artery flap³⁷, iliac bone free flap⁴⁸, scapular osteocutaneous free flap⁵⁴, anterolateral thigh dermal adipofascial flap⁵⁷ and temporoparietal galeal flap⁵⁸ were also described (Table 1).

Although the use of 3D modeling for free flap surgery in facial reconstruction is common, the use of 3D modeling to design prelamination for free flaps in facial reconstruction has never been described, being a novel approach. We present two prelaminated free flaps obtained with the use of 3D models: a prelaminated parascapular free flap and a prelaminated radial forearm free flap. They were used in reconstructive surgeries related with burn injuries and ear reconstruction, respectively.

Burn injuries demand challenging 3D reconstructions. When it comes to reconstructive options that can be performed in patients with severe burns, skin grafts are often not used because of poor color matching and secondary contracture and local flaps are rarely obtainable in large burns⁵⁹. Therefore, when analyzing reconstructive options in burn patients, it may be necessary to resort to techniques that optimize the resources. Facial transplant surgery is an option to be considered in these cases since it presents better aesthetic results and is usually a one-time surgery. However, the need of lifelong immunosuppressive therapy, which can bring a lot of nefarious complications, such as increased incidence of malignancies, infections and end-organ toxicity⁶⁰, made the patient described in case 1 to refuse this method. Prelamination is one of the most effective mechanisms available for approximating aesthetic reconstructive outcomes using autologous tissue⁶¹, not requiring immunosuppressive therapy, and at the end the patient was scheduled for this technique. When selecting the free-tissue transfer donor site, since the two most commonly ones used to replace facial subunits – the radial forearm and temporoparietal fascia flaps – were compromised, other sites had to be explored⁶². The parascapular tissue on the left dorsal region was intact, and since the parascapular tissue has a constant pedicle, it was the area selected for the prelamination. This optimization of resources was also possible thanks to the 3D model that brought advantages at both the pre- and the intraoperative level. Effectively, the model assumed an important role in the calculation of distances to perform anastomoses, allowing us to obtain tension-free vascular anastomoses. This was particularly important since the parascapular pedicle is relatively short in length. Moreover, the 3D model enabled that, by direct comparison, the design of the lower half of the face (which included the mouth and nose) drawn in the parascapular region had the appropriate proportions and dimensions, therefore enabled programming a more efficient and personalized surgery. Furthermore, in cases like this, where more than half of the surface area is burned and there are few local or distant flaps available, the 3D model is of great importance since it allows surgical planning in order to take the maximum advantage of the little tissue available. Nevertheless, since a rise in facial transplantation cases mortality had been noticed and some apprehension has emerged among transplant candidates, here we have described a method that is also safe in the long-term – in fact, this method offers several advantages when compared to facial transplantation, especially when it comes to long-term risks for the patient (Table 2). Despite the number of revision surgeries required and the modest aesthetic results because of a discrepancy of color and texture between the dorsal and facial skin, the patient still reported a remarkable functional gain. In fact, the improvements in the capacity of feeding and opening the mouth were mainly due to the prelamination technique that was essential in the perioral rehabilitation.

When it comes to ear reconstruction, creating an ear shape from the costal cartilage is the gold standard technique⁶³; however it is quite demanding, it does not have the same elastic properties as ear cartilage and it results in donor site morbidity. Therefore, an alloplastic material – high-density porous polyethylene – which is highly biocompatible, stable, durable and easily moldable was selected. Regarding the importance of the 3D model used here, it is important to note that Medpor^® implants used in auricular reconstruction are often shaped based on a radiographic film with markings of the contralateral ear⁶⁴. However, this method offers only two-dimensional information. The 3D model makes the molding process easier because it provides visual and tactile information and the surgeon manages to make the implant configuration as identical as possible to that of the mold. In addition, using the 3D silicone model as a means of direct comparison in the operating room reduces the intraoperative time. Effectively, a 3D-printed ear mold makes the trimming of the implant an easier and more time-saving procedure, being the final result more similar and symmetrical to the contralateral ear. Finally, the use of this model leads to a reduction in costs: a 3D-printed ear of porous polyethylene may also be ordered from the manufacturer, but it is much more expensive than the conventional universal alloplasts that were used in this case – they are composed of two pieces and are available in three sizes. In fact, here we showed that if a silicone 3D model, based on the contralateral ear, is used as a guide, a more low-cost but yet effective procedure is reachable – ultimately a personalized prelaminated flap was achieved and a symmetrical aesthetic result was obtained.

Nowadays, reconstructive surgery can make use of the techniques that allow us to manage complex cases, achieving very good aesthetic and funcional results. Since the facial anatomy is crucial for the patient’s identity and 3D modeling allows an individual approach, it is easy to understand its extreme importance when it comes to reconstruction of craniofacial defects. 3D modeling has been used for a more efficient planning in surgeries using free flaps and is more often used in mandibular reconstruction with fibular flee flaps. Although its use in the planning of prelamination surgeries hasn’t been described in the literature, we have demonstrated its applicability: the first phase of the prelamination technique was simpler, with achievement of a customized free flap in a significantly decreased intraoperative time, and with both patients, who were complex cases of different etiologies (burn injuries and trauma), achieving good aesthetic and morphologic results.

CONCLUSIONS

The craniofacial region is one of the most complex in the human body and is of great functional and aesthetic importance, making its reconstruction challenging.

3D models allow to obtain a personalized facial reconstruction and this custom-made approach is extremely important for the conservation of the aesthetic appearance and, consequently, individual well-being. On the other hand, prelamination is a complex technique used when we intend to achieve a three-dimensional reconstruction and there are no local grafts or flaps available. This complexity can be reduced with the use of 3D models, which play an important role in the first surgical phase of the technique, allowing achievement of a customized flap designed in the most appropriate way.

Therefore, prelamination and 3D models can be used together as a powerful tool to achieve customized 3D reconstructions in complex cases where the existing reconstructive options are limited.

Role of authors: Francisca Frias acquired, analyzed and interpreted the data and created the manuscript. Ricardo Horta originated the concept of the submission and performed a critical revision of the manuscript.

Declaration: Authors have no conflicts of interest to disclose. We declare that this study has received no financial support. All procedures performed in this study involving human participants were in accordance with ethical standards of the institutional and with the Helsinki declaration and its later amendments or comparable ethical standards. The clinical photographs of the patients presented in this work were obtained with consent.

Corresponding author:

Francisca Frias, MD

Rua Souto de Cima, no 286

4475-671, Castêlo da Maia, Porto, Portugal

E-mail: anaff.cnm@gmail.com