In the cases presented here, autologous vertical augmentation with free microvascularised flap has proven to be a reliable approach that allowed lasting esthetic and functional reconstruction. The site healed per primam in all cases. No infection or permanent donor site morbidity was observed. The patients did not report excessive pain, discomfort or any other subjective complaint related to the surgery either in the postoperative or in the follow-up period. The patients’ adherence and compliance was excellent throughout the treatment and also during the follow-up (as indicated by the excellent condition of the dental work and the surrounding hard and soft tissues). The low number of cases can be considered as a weakness of this case series. However, the surgical indication we examined is a relatively rare one, and the long-term outcomes may at least partially make up for that weakness.
Autologous jawbone augmentation methods can be grouped into three main categories, which are as follows: 1) conventional augmentation with intra- or extra-oral autogenous bone grafting; 2) osteodistraction; and 3) free vascularised bone transfer [1, 2]. In our experience, which is in agreement with the literature, the most favorable intraoral donor sites for non-vascularised bone grafting are the mentum and the ramus of the mandible. D1-D2 quality bone can be harvested from both sites [13, 14]. Grafts harvested from these sites are used primarily for lateral augmentation. Bone harvested from the mentum can be used to achieve lateral bone augmentation of 5 mm [15]. Using bone blocks harvested from the ramus region, thinner, 3–4 mm thick D1 quality lateral bone augmentation can be achieved [15, 16]. When it comes to vertical augmentation, though, neither of these methods allow more than 5 mm bone gain [16].
The primary extraoral donor sites are the iliac crest and the calvaria [17]. The main advantage of transplanting bone harvested from the iliac crest is that the site offers a large amount of easily harvestable bone, as well as the simple shaping of the bone blocks [18]. The disadvantage is bone quality: D2-D3 bone is readily resorbed, at rates up to 30–47% [19, 20]. On average, this method yields bone growth of 5–6 mm in both the vertical and horizontal dimensions [21]. The frequency of accompanying donor site morbidity is higher than with other non-vascularised bone grafting modalities. The most common complications are hematoma and seroma, occasionally the paresthesia of the thighs or even the fracture of the iliac spine [21]. For non-vascularised bone transplants, the calvaria is possibly the best donor site for larger vertical augmentation procedures. A large amount of D1 quality bone may be harvested from the calvaria, and the risk of high-degree resorption is low [17, 20, 22]. The thickness of the monocortical bone is 2–3 mm on average, often necessitating the use of a layering technique [20]. On average, this method yields bone growth of 6–7 mm in both the vertical and the horizontal dimensions [23]. Donor site morbidity is low, hematoma and seroma are rare, and post-surgical discomfort is minimal [17, 24].
An entirely different method is osteodistraction, during which the bone is cut and gradually separated, which induces osteogenesis in the resulting gap. This method is used primarily in the reconstruction of vertical deficits. Obvious disadvantages include the discomfort of the patient, the higher risk of infection and that the procedure is time-consuming [25]. However, the results are more reliable, than those obtained using non-vascularised bone transplants: less bone is reabsorbed and higher elevation is possible [15]. It must be noted that the success of this procedure requires an intact bone height of at least 5 mm for the distraction to ensure that the bone is not resorbed or fractured [26]. Free vascularised bone flaps are used primarily in reconstructive surgery, chiefly in the reconstruction of mandibular continuity [5, 27–31]. The procedure is recommended in cases where the mesiodistal extent of the bone defect is more than 5 cm [32]. The native vasculature ensures the survival of the large piece of transplanted bone, which can thus be inserted even into irradiated areas [5]. The transplants used in the reconstruction of major bone defects may also be used in the reconstruction of soft tissue defects when combined with skin paddle relying on septo- or musculocutaneous perforators. The fibula, the iliac crest, the scapula and the radius are the preferred donor sites for the reconstruction of composite maxillofacial defects [30]. The most frequently used donor site is the fibula [5, 27–29], where D1 bone can be harvested. The bone harvested from this site can be 22–25 cm in length and may be used for vertical augmentation of 1-1.5 cm height, which makes fibula graft extremely suitable for the reconstruction of mandibular defects [28, 33]. As for the free vascular flaps, the iliac crest is also suitable for grafting as it is easy to shape and model and can be used to achieve significant vertical augmentation on segments up to 7–9 cm in length. However, the density of the bone is significantly lower D2-3 and donor site morbidity is higher compared to fibular harvest [34]. The radial free flap can be used for vertical bone augmentation of 5–7 mm on segments 8–12 cm in length [33]. Considering the risk of donor site fracture, prophylactic plating of the radius is recommended. The scapular flap is suitable for the reconstruction of bone defects up to 10–15 cm in length, but it offers less bone in the vertical dimension than the free iliac [35] or fibula [36] flap.
The disadvantages of microsurgical reconstructive methods include the necessity of special training and equipment, the risk of donor site morbidity and that these procedures are time-consuming [32]. In the presented cases, mandibular continuity was maintained with a vertical bone defect of at least 1 cm over a segment of at least 5 cm, and the distance between the inferior alveolar nerve or the base of the mandible and the alveolar ridge was smaller than 5 mm. Taking this into consideration, we opted for microsurgical mandibular reconstruction in all cases. According to the literature, such procedures have excellent success rates [5, 27–31]. However, there are two noteworthy disadvantages. First, the microsurgical operation is lengthy, which means that the patient is exposed to prolonged general anesthesia. Second, while the chance of morbidity is low indeed, it may be more severe as compared to other method. Donor site complications may include sensory loss, ankle instability, or contracture of the great toe [37]. Still, we argue that the advantages outweigh the disadvantages. As demonstrated in the presented cases, this method makes it possible to reconstruct large defects, even in irradiated areas. When combined with a skin paddle, the fibula free flap may be used for the reconstruction of soft tissue defects, and it allows optimal gingival coverage for implant and prosthetic procedures. Finally, it leads to immediate aesthetic results, as shown by our cases and by other published cases [5, 27–31]. Therefore, we recommend the described approach for the treatment of large mandibular defects with maintained continuity.