Application of ultrasound imaging of upper lip orbicularis oris muscle

In this study, we aim to understand the morphology and structure of upper lip orbicularis oris muscle, and to provide clinical evidence for evaluating the effect of repair operation in cleft lip. Subjects included 106 healthy people and 36 postoperative patients of unilateral cleft lip. The upper lip orbicularis oris muscle was scanned using ultrasound in natural closure and pout states. Our results showed that the hierarchical structure of upper lip tissue was demonstrated clearly in ultrasonic images. After reconstruction of unilateral cleft lip, the left and right philtrum columns were still obviously asymmetric, their radian displayed clearly and showed better continuity. In the place of cleft lip side equivalent to philtrum columns, orbicularis oris muscle showed discontinuity and unclear hierarchical structure, which was replaced by hyperechoic scar tissue. The superficial layer would become thicker when pouting. In reconstructed unilateral cleft lip, the superficial layer was thinner than that of healthy controls. In normal upper lip orbicularis oris muscle, the superficial layer thickness was no less than 2.89 mm in philtrum dimple and no less than 3.92 mm in philtrum column, and the deep layer thickness was no less the 1.12 mm. Otherwise, the layer thickness less than above reference values may be considered as diagnostic criteria for dysplasia of upper lip orbicularis oris muscle. In conclusions, ultrasound imaging is able to clearly show the hierarchical structure of upper lip orbicularis oris muscle, and will be beneficial in guiding the upper lip repair and reconstruction surgery.