Mesoamerican Long Count calendar Mesoamerican Long Count calendar The Mesoamerican Long Count calendar is a non-repeating, vigesimal (base-20) and base-18 calendar used by several pre-Columbian Mesoamerican cultures, most notably the Maya. For this reason, it is often known as the Maya (or Mayan) Long Count calendar. Using a modified vigesimal tally, the Long Count calendar identifies a day by counting the number of days passed since a mythical creation date that corresponds to August 11, 3114 BCE in the Proleptic Gregorian calendar. The Long Count calendar was widely used on monuments. The two most widely used calendars in pre-Columbian Mesoamerica, were the 260-day Tzolk'in
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