Surgical implications of the anatomic situation of the mandibular canal for mandibular osteotomies: a cone beam computed tomographic study.

PURPOSE: In bilateral sagittal split osteotomy (BSSO), the risk of lesion of the inferior alveolar nerve (IAN) is important. The aim of this study was to investigate the situation of the IAN in the area of the BSSO in preoperative 158 CBCT. METHODS: The situation of the mandibular canal (MC) has been studied in six coronal sections (one section each 4 mm) from the proximal root of the second mandibular molar. The height of the MC related to the height of the mandible, and the horizontal distance between the MC and the lateral cortical plate related to the mandibular width have been determined in each section. The cancellous bone width has been measured allowing to determine a cancellous bone ratio. RESULTS: The variability of the MC was high, depending mainly on the cancellous bone ratio which was higher when the IAN was deep. When a third molar was present, the MC was lower in the area of the third molar. CONCLUSIONS: To decrease the risk of injuring the IAN in BSSO, the evaluation of the cancellous bone ratio by a preoperative CBCT may be proposed to adapt the surgical technique to the anatomy.

Modified technique used for sagittal splitting of the mandible.

Sagittal osteotomy of the mandible is the most common orthognathic surgery procedure. The drawbacks of this technique are: nerve disturbance, the common formations of a pre-angular notch after mandibular advancement, and the impossibility of lowering the mandibular angle bicortically. The goal of the described technique is to maintain the basal mandibular edge and the internal valve in one single piece. This split prevents unsightly notches appearing after mandibular advancement and it moves down the mandibular angle during counterclockwise rotation and does not increase the intergonial distance. It is especially indicated for skeletal class II cases.

[Is it possible to individualize microvillous large-cell lymphoma among sinusoid lymphomas?]. / Faut-il individualiser le lymphome à grandes cellules microvilleuses parmi les lymphomes intrasinusaux?

Microvillous non-hodgkin lymphomas are large cell malignant lymphomas with a sinus growth pattern and the presence of cytoplasmic processes detected by electron microscopy. Microvillous non-hodgkin lymphomas appear to be of B cell lineage. Neoplasms considered in the differential diagnosis include anaplastic large cell Ki-1 lymphomas, malignant histiocytosis and metastatic carcinoma or malignant melanoma. A panel of markers are usually sufficient to recognize all of these neoplasms except microvillous lymphomas. We report a case of microvillous non-hodgkin lymphoma characterized by a histologic pattern mimicking those of anaplastic large cell Ki-1 lymphoma. However, immunohistochemistry study failed to demonstrate presence of activation antigen such as Ki-1, EMA, interleukin 2 receptor. Ultrastructural study showed that neoplastic cells exhibited filliform cytoplasmic processes. This report raise the possibility of an overlap between microvillous non-hodgkin lymphomas and anaplastic large cell Ki-1 lymphomas of B-cell lineage. It must be emphasized that, initially, these two kinds of lymphomas were defined with different morphologic technologies.