Assessment of Stresses About The Cervical Spine: Caused by Posture and Position of the Head

Dr. Kenneth Hansraj, MD. Chief of Spine Surgery New York Spine Surgery & Rehabilitation Medicine. New York, New York

Preamble: Billions of people are using cell phone devices on the planet, essentially in poor posture. The purpose of this study is to assess the forces incrementally seen by the cervical spine as the head is tilted forward, into worsening posture. This data is also necessary for cervical spine surgeons to understand in the reconstruction of the neck.

Materials & Methods: A model of the cervical spine was created with realistic values in Cosmosworks, a finite element assessment package. Calculations were made and then forces were extracted in newtons and then converted into pounds. We made the calculations using neck + head, which gave an average weight of 60 newtons (6kg or 13.2 pounds). The center of mass was located 16cm above C7 or 15cm from the top of the skull.

Results: The weight seen by the spine dramatically increases when flexing the head forward at varying degrees. An adult head weighs 10-12 pounds in the neutral position. As the head tilts forward the forces seen by the neck surges to 27 pounds at 15 degrees, 40 pounds at 30 degrees, 49 pounds at 45 degrees and 60 pounds at 60 degrees. At 90 degrees the model prediction was not reliable.

Discussion: Loss of the natural curve of the cervical spine, leads to incrementally increased stresses about the cervical spine. These stresses may lead to early wear, tear, degeneration and possibly surgeries. Cervical spine surgeons need to pay attention to the alignment and therefore to the stresses about the spine when performing anterior discectomies and fusion along with arthroplasties.