Distraction osteogenesis in the management of mandibular hypoplasia secondary to temporomandibular joint ankylosis. Long term follow up.

PURPOSE

The aim of this retrospective study was to evaluate the short-term and long-term skeletal and soft-tissue stability after MDO with or without genioplasty, as well as the stability of the achieved maximum inter-incisal opening (MIO) in patients with mandibular hypoplasia secondary to TMJ ankylosis.

PATIENTS AND METHODS

Twenty patients with mandibular hypoplasia secondary to TMJ ankylosis were managed by a two-stage surgical protocol, gap arthroplasty as the first stage, followed by MDO. The patients were analyzed for skeletal and soft-tissue stability as well as the maintenance of the achieved MIO. Lateral cephalograms were evaluated at four time intervals: pre-distraction (T1), after a consolidation period with or without genioplasty (T2), after one year following consolidation (T3), and at the longest follow-up (T4). Statistical analyses compared the skeletal and soft-tissue changes at different intervals in every group.

RESULTS

All the ankylosed joints except three were treated with gap arthroplasty without costochondral graft. The MIO was increased from 8.2 ± 2.1 mm preoperatively to 40.2 ± 1.7 mm postoperatively. After the consolidation period, MIO decreased to 23 ± 6.5 mm. The patients were instructed to restart active physiotherapy after removal of the distractors to regain the pre-distraction MIO, which was maintained during the short-term follow-up. The mean follow-up period was 8.5 ± 1.5 years. At the end of the follow-up, two patients showed recurrence of ankylosis. Cephalometric analysis revealed great improvements in the hard- and soft-tissue structures after MDO with or without genioplasty. Several significant long-term relapses could be observed in all groups; however, they did not reach their pre-operative values.

CONCLUSION

TMJ ankylosis leads to severe, multidirectional mandibular hypoplasia, which is significantly corrected with the MDO. The MDO provides a stable short-term improvement in the facial esthetics at the first postoperative year, but a significant relapse occurs during the long term follow-up. Nevertheless, a satisfied facial esthetic is maintained for up to seven to 12 years postoperatively. During the activation period, the MDO minimizes the gained MIO after release of ankylosis, but the MIO is successfully restored with physiotherapy.