New details on the clefted uvular muscle: analyzing its role at histological scale by model-based deformation analyses.

OBJECTIVE: As an initial step to a complex reconstruction model for virtual surgery, the present study was carried out to provide data on the prenatal cleft lip and palate uvular muscle in eight specimens. METHOD: Serial sections of viscerocrania of 18 aborted embryos and fetuses were studied microscopically and segmented manually. Registration, three-dimensional reconstruction, and finite element analyses were conducted. RESULTS: Incompletely clefted uvulae showed anterior fusion and dorsal fission of the bilateral uvular muscle bodies. A complete cleft lip and palate specimen evidenced single bilateral uvular muscle bodies lying medially and orally below the cleft shelf, its central longitudinal fibers running beneath the oral-median mucosa. In incompletely clefted uvulae, 10% to 50% of circular peripheral fibers crossed the midline within the central third of the anterioposterior muscle, behind the levator loop. Of the fibers, 30% to 60% crossed to the ipsilateral palatopharyngeus muscle. Fibers inserted into the uvular basal membrane in a 60% nasal and 40% oral distribution at the middle third of the macroscopically clefted uvula. The macroscopic uvula itself consisted of loose connective tissue and salivary glands. Deformation analysis did disclose local stress, suggesting the uvular muscle contributes to velopharyngeal closure in normal anatomy and extends the cleft edges in cleft palate. CONCLUSION: Cleft lip and palate reconstruction should reasonably use the uvular muscle to augment the velar midline bulk. Uvular muscle deformation calculation was successful, permitting functional insight on the basis of microanatomical specimens, so far a bigger complete velar model can be ventured.

Histology and function: analyzing the uvular muscle.

OBJECTIVE: Virtual surgery and virtual patients necessitate quantitative data on the area of interest. The study was conducted to exactly describe the embryonic and fetal uvular muscle (MU), relevant for clinical as well as virtual surgery and virtual patient generation. METHOD: Serially sectioned viscerocrania of 10 aborted embryos and fetuses underwent three-dimensional reconstruction to obtain detailed anatomic data and perform finite element analyses. RESULTS: The MU was paired in 80% of cases, while 20% allowed no clear-cut distinction. The MU merged with the levator muscle beneath the palatal aponeurosis without a hard palate insertion. Superior longitudinal central fibers ran below the nasal mucosa, and few circular peripheral fibers crossed in the central third to the contralateral side. This was seen in 30% of the paired muscles and in all cases when no differentiation was possible; about 40% to 80% MU fibers crossed to the ipsilateral and contralateral palatopharyngeus muscle behind the levator loop. MU fibers inserted 60% nasal and 40% oral to the basal membrane at the middle third of the macroscopic uvula, made of loose connective tissue and salivary glands. The results of the finite element simulation of the uvula showed no distinct patterns or distributions of local stress. CONCLUSIONS: Detailed anatomical study supported the concept of mediocranial MU repositioning during corrective surgery, although the impact is minor to the levator muscle's action. Future mathematical models describing effects of such a maneuver should integrate surrounding structures.