Natural variation of the zygomaticomaxillary complex symmetry in normal individuals

Objective: The study aim was to investigate variations in the symmetry of the zygomaticomaxillary complex (ZMC) in normal individuals.
Method: Computed tomography datasets of 200 individuals without facial fractures were analyzed using a validated three-dimensional analysis technique. The absolute average distance (AD) and 90th percentile distance (NPD) were calculated, representing respectively the overall and maximum symmetry between bilateral ZMCs.
Results: The mean AD and NPD of the total study group was 0.9 ± 0.3 mm (95% CI 0.3–2.3) and 1.7 ± 0.5 mm (95% CI 0.5–3.9), respectively. The mean AD and NPD in males were 1.0 ± 0.3 mm (95% CI 0.28–2.34) and 1.9 ± 0.5 mm (95% CI 0.5–3.9) versus 0.8 ± 0.3 mm (95% CI 0.4–1.7) and 1.6 ± 0.5 mm (95% CI 0.8–2.9), respectively, for females. A statistically significant difference between male and female was found for both AD and NPD (p < 0.01). The male population <40 years had a mean AD and NPD of 1.0 ± 0.3 mm and 1.8 ± 0.5 mm, which was not statistically significant when compared with males >40 years.
Conclusion: The naturally occurring anatomic variation in ZMC symmetry described in this study is proposed as a benchmark for evaluating the amount of preoperative displacement and postoperative reduction of ZMC in trauma cases.