INTRODUCTION: Since its advent by McCarthy et al1 in 1992, mandibular distraction has become the primary choice for the treatment of patients with moderate to severe Robin sequence.2 Based on the Ilizarov principle of bone lengthening,3 mandibular distraction relieves airway obstruction by lengthening the mandible. Despite its effectiveness, a potential yet problematic complication of mandibular distraction is temporomandibular joint (TMJ) ankylosis. Previous studies report TMJ ankylosis rates of up to 10%,4 whereas other studies have shown virtually no incidences of TMJ sequelae.5 A theory on this difference relates to distraction vector; a vertical vector is more likely to lead to TMJ ankylosis because of the cranially directed pressure withstood by the TMJ during activation, as compared to horizontally or obliquely directed vector. Historically, our center has used a vertical distraction vector with a more recent conversion to an obliquely oriented vector. The purpose of this presentation is to discern if there is difference in rates of TMJ ankylosis between vertical and oblique distraction groups.
METHODS: After Institutional Review Board approval, a retrospective chart review was performed of all patients who underwent mandibular distraction at Children’s Mercy Hospital from 1997 to 2015. All operations were performed by 3 surgeons. Ankylosis rates were compared between the 2 groups.
RESULTS: Ninety-four patients were reviewed. The average age of presentation was 103 days. Seventy underwent vertical distraction, whereas 24 underwent oblique distraction. TMJ ankylosis was recorded in 12 cases, all in the vertical vector group, a 17% rate of ankylosis. There were no cases of ankylosis in the oblique vector group. The average age at diagnosis of TMJ ankylosis was 6.5 years. When excluding all syndromic patients in both groups, 48 patients remained. Thirty-four underwent vertical distraction versus 12 for the oblique group. There still was a 12% rate of ankylosis, all in the vertical group.
CONCLUSION: Vertical mandibular distraction carries a significantly increased risk of TMJ ankylosis and should be avoided.
1. McCarthy JG, Schreiber J, Karp N, et al. Lengthening the human mandible by gradual distraction. Plast Reconstr Surg. 1992;89:1–8; discussion 9–10.
2. Zenha H, Azevedo L, Rios L, et al. Bilateral mandibular distraction osteogenesis in neonates with Pierre Robin sequence and airway obstruction: a primary option. Craniomaxillofac Trauma Reconstr. 2012;5:25–30.
3. Ilizarov GA. The tension-stress effect on the genesis and growth of tissues: part I. The influence of stability of fixation and soft-tissue preservation. Clin Orthop Relat Res. 1989:249–281.
4. Andrews BT, Fan KL, Roostaeian J, et al. Incidence of concomitant airway anomalies when using the University of California, Los Angeles, protocol for neonatal mandibular distraction. Plast Reconstr Surg. 2013;131:1116Y1123.
5. Murage K, Costa M, Friel M, et al. Complications associated with neonatal mandibular distraction osteogenesis in the treatment of Robin sequence. J Craniofac Surg. 2014;25:383–387.