One important concern in orthognathic surgery for patients with FD is the long-term stability of the osteotomized segments as FD-involved bones are affected by a dysplastic process and are typically soft and friable [12]. Therefore, it is difficult to tightly fix the screws and miniplates to the fibrodysplastic bone. However, long-term stability of the osteotomized segments and occlusion was achieved in both our cases and the previously presented reports.
Notably, in cases of lower extremity fracture involved with FD, screw fixation is strongly discouraged. When screws are inserted into the FD-involved bone, the procedure is recommended to be used carefully, and only in patients with adequate strength of cortical bone [2]. However, our experience and those of others have noted that the dense residual bone does not usually remain at the FD-involved bones, such as zygomaticomaxillary buttresses, where conventional rigid fixation cannot be achieved [6,7,8]. Even under these unfavorable conditions, the successful long-term stability after plate/screw fixation of FD-involved osseous segments can be explained. Yeow and Chen [8] suggested that FD of the craniofacial region tends to be more osseous in nature than FD of long bones. Another histological study showed that the dysplastic bone typically healed favorably around the biocompatible titanium screws. Osteointegration was observed between the screws and dysplastic bone [7]. CT imaging of patient no. 1 (Fig. 2) also showed that the interface of the osteotomized bone was healed with dysplastic bone, and the maxillary sinus was obliterated again with a fibrodysplastic lesion. Since the miniplates were covered by the newly formed dysplastic bone, these findings suggest that the dysplastic bone can contribute to the stability of the osseous segments. Because of poor bone quality, it can be challenging, but it is not impossible to achieve adequate fixation on the dysplastic bone intraoperatively, and long-term stability can be expected after the orthognathic surgery. In addition, since FD is not usually bilateral, the normal contralateral side can provide adequate stability if the previous lesion can be healed with softer bone.
Another major concern after FD treatment is recurrence. Depending on the site and extent of involvement, the rate of growth, clinical behavior of the lesion, esthetic disturbance, functional disruption, general health of the patient, and type of surgical intervention can be considered [8, 13]. The prognosis of the monostotic form is reported to be good, whereas prognosis of the polyostotic form is considered to be proportional to the extent of the disease [1]. There is a report that showed that the surgical manipulation can accelerate the re-growth of the remaining FD lesion [14].
In the previously reported 13 cases of orthognathic surgery for FD, no recurrence was reported (Table 1) regardless of monostotic or polyostotic FD. Boyce et al. [15] reported that in patients with craniofacial FD, re-growth and reoperation are more frequent, particularly after debulking procedures, than aggressive reconstructive measures. It has also been suggested that growth hormone excess should be treated prior to surgery to reduce the rate of recurrence after surgery [2, 15]. In some reports, evaluation of biochemical markers, such as serum osteocalcin, and total and bone-specific alkaline phosphatases, has been advised to follow the disease progression [16, 17]. Therefore, the favorable results of our report and previous findings may be explained by the fact that most patients were not syndromic and did not present with endocrine disorders. Another factor is that FD resection and recontouring were performed at the same time during the orthognathic surgery, which is a more aggressive approach than debulking. Since the definition of suitable predictors of the recurrence of FD remains controversial, close follow-up in the long term is emphasized [17, 18].
It is has also been suggested that (1) surgical treatment after confirmation of skeletal maturity and (2) absence of further growth of the dysplastic bone are the most important factors in the successful management of FD affecting the occlusion [3, 4].
While the previously reported cases showed no recurrence of FD, it is unclear whether all cases were examined with CT or the operated site was directly inspected. Although the amount of newly formed bone did not influence facial appearance, we found that dysplastic bone can grow over the miniplates during the healing process and show mild expansion of the lesion.