Three nearly forgotten anatomical triangles of the neck: Triangles of Beclard, Lesser and Pirogoff and their potential applications in surgical dissection of the neck

The neck is an area that lends itself to anatomical geometry, such as triangles. Many triangles of the neck have been described, and some are well known; however, some have been nearly forgotten. The purposes of this study were to review prior literature on the forgotten triangles of the neck, to measure and document the occurrence of these triangles and the structures found within them, and to discuss their surgical significance and relationships to the standard triangles of the neck. This study was carried out on 17 (34 sides) formaldehyde-fixed adult human cadavers (5 males and 12 females), the mean age being 78 years. All triangles were found within the submandibular triangle of the anterior cervical triangle. Beclard's triangle was present on 28 sides and absent on 6 sides because the posterior belly of the digastric muscle did not touch the hyoid bone and because the posterior belly of the digastric muscle was directly over the greater cornu of the hyoid bone. Lesser's triangle was present on 30 sides and absent on 4 sides because the hypoglossal nerve remained inferior to the digastric muscle. Pirogoff's triangle was also present on 30 sides and absent on 4 sides, again because the hypoglossal nerve remained inferior to the digastric muscle. No statistically significant differences were found between the measurements of each leg of any of the three triangles and gender, or between the measurement of each leg of any of the three triangles and right versus left sides. Beclard's triangle, when present, was found to contain both the hypoglossal nerve and the lingual artery. Pirogoff's triangle always contained the lingual artery, and Lesser's triangle contained no major structures, but the lingual artery was deep to its floor. Knowledge of these triangles, their contents, and relationships to other structures of the neck could be important for cranio-facial, oral, general, and neurosurgeons who operate within the neck.