Maya calendar Maya calendar The Maya calendar is a system of calendars used in pre-Columbian Mesoamerica and in many modern communities in the Guatemalan highlands, Veracruz, Oaxaca and Chiapas, Mexico. The essentials of the Maya calendar are based upon a system which had been in common use throughout the region, dating back to at least the 5th century BCE. It shares many aspects with calendars employed by other earlier Mesoamerican civilizations, such as the Zapotec and Olmec and contemporary or later ones such as the Mixtec and Aztec calendars. By the Maya mythological tradition, as documented in Colonial Yucatec accounts and reconstructed
Vertebral fixation Vertebral fixation Vertebral fixation (also known as "spinal fixation") is a orthopedic surgical procedure in which two or more vertebrae are anchored to each other through a synthetic "vertebral fixation device", with the aim of reducing vertebral mobility and thus avoiding possible damage to the spinal cord and/or spinal roots. A vertebral fixation procedure may be indicated in cases of vertebral fracture, vertebral deformity, or degenerative vertebral disorders (such as spondylolisthesis). The device used to achieve vertebral fixation is usually a permanent rigid or semi-rigid prosthesis made of titanium; examples include rods, plates, screws, and various combinations thereof. A less