Asymmetric lip-closing forces in children with repaired unilateral cleft lip and/or palate

The objectives of this study were to estimate the effects of cleft lip and/or palate (CLP) repair on the multidirectional lip-closing forces (LCF) produced during maximum voluntary pursing-like lip-closing movement in children. Thirty Japanese children were divided into the control group and repaired unilateral CLP (RUCL) group, which was subdivided into the unilateral cleft lip and/or alveolus (UCLA) and the unilateral cleft lip and cleft palate (UCLP) groups. The maximum voluntary LCF were recorded in eight directions. No significant differences in any of the directional LCF (DLCF) or total LCF were observed between RUCL and control groups. Symmetrical DLCF were seen in the oblique directions on both sides of the upper lip in the control group, while the oblique DLCF on the non-cleft side was significantly greater than that on the cleft side in RUCL group. Furthermore, symmetrical vertical DLCF were observed in the upper and lower directions in control and UCLA groups, while the vertical DLCF obtained from the lower direction was significantly greater than that obtained from the upper direction in UCLP group. These results indicate that children with repaired CLP display impaired directional specificity, which may cause secondary deformities. These findings aid our understanding of the pathology of secondary deformities in CLP patients after primary surgery for cleft lip or palate. We propose that quantitative assessments of lip-closing function based on the directional specificity of the multidirectional LCF produced during maximum voluntary pursing-like lip-closing movement are useful for assessing the nature of lip-closing dysfunctions.