Mesoamerican calendars was of ritual significance to a number of Mesoamerican cultures. A third major calendar form known as the Long Count is found in the inscriptions of several Mesoamerican cultures, most famously those of the Maya civilization who developed it to its fullest extent during the Classic period (ca. 200–900 CE). The Long Count provided the ability to uniquely identify days over a much longer period of time, by combining a sequence of day-counts or cycles of increasing length, calculated or set from a particular date in the mythical past. Most commonly, five such higher-order cycles in a modified vigesimal (base-20)
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