Selective laser melted titanium implants: a new technique for the reconstruction of extensive zygomatic complex defects

Three-dimensional reconstruction of the zygomatic-orbito-maxillary complex is one of the most challenging procedures in craniofacial surgery. The normal anatomical contour and position of the zygomatic bone are critical for the appearance of the face [10]. Here, we described a successful use of a custom-made SLM titanium implant for the reconstruction of a post-traumatic zygomatic bone defect. Although the bony symmetry was maintained at one-year follow-up (Figure 7), the patient continued to exhibited soft tissue asymmetry. This asymmetry was most likely the result of buccal and zygomatic fat pad atrophy in response to the initial trauma and atrophy of the facial expression muscles secondary to facial nerve palsy.

Because the residual zygomatic bone was deficient in volume and shape, an osteotomy alone would have not properly corrected the projections. The patient rejected the option of free tissue transfer. Thus the only available option was alloplastic implantation. Different materials can be used in cases of post-traumatic zygomatic deficiency, the advantages and drawbacks of each of these materials have been thoroughly documented in the literature [6,8].

The development of CAD/CAM technology has opened new perspectives in the field of alloplastic implant production [11]. After three-dimensional reconstruction of a skull containing the defect, the future implant can be produced by “mirroring” the healthy side. Thus, the projection and symmetry of the zygomatico-maxillary complex can be re-established [7,11]. SLM is one of the CAD/CAM techniques that allows for the production of porous titanium parts that mimic bone structure [12]. Titanium is the most commonly used material in medical implants because it is highly biocompatible and integrates very well into tissues [13]. The mechanical properties of SLM titanium products are also within the ranges of the properties of bone [12]. These similarities are particularly important because implant materials that are much stiffer than the bone can generate stress shielding, which can potentially lead to bone resorption or hinder bone regeneration [14]. Bone resorption caused by stress shielding is believed to contribute to the aseptic loosening of implants [15]. In contrast, the porous surfaces of SLM titanium parts have been demonstrated to be favorable for cell adhesion, migration and ingrowth, and these properties result in strong bone-implant contact. When an implant is populated with osteogenic cells, these cells not only migrate on the surface of the implant but also inside the pores of the implant [13]. Due to advantages of the titanium structures produced by SLM, we designed and produced a patient-specific implant for zygoma recontouring using this technology (Figure 4). The implant fit perfectly into the defect, no corrections being needed at the time of surgery (Figure 5). Similar findings have been reported in the literature [7,9]. The implant was designed in the form of a shell and filled with cortico-cancellous chips from the anterior iliac crest to stimulate its integration. This implant behaved as reported in the literature [13], no complications or side-effects occurred.

The left eye enophthalmos was not corrected because anterior repositioning of the globe would have exposed a larger part of the cornea due to the presence of lagophthalmos. The limitation of the presented reconstructive procedure is that it addressed only the bony deficiency, leaving the soft tissue atrophy to be dealt with later. This atrophy could be corrected with structural fat grafting.

The SLM technique was an expensive procedure. However, the preoperative investment in time and technology was worthwhile due to the proper geometry of the implant, reduced operative time and the lack of donor site morbidity. These characteristics are consistent with those reported in the literature [7,9]. The drawback of the current study is the nature of single-patient case report, lacking sufficient follow-up. To reach definitive conclusions, extensive clinical studies should be conducted.