What was the aim of the article?
Prolonged loading of the spine during sitting may contribute to back pain and back injury. To date, a direct measurement of spinal load has not been possible. Recently, however, a new spinal implant was developed, that is able to record spinal load during different sitting positions. The aim of this study was to measure spinal load, in the lower part of the spine, during sitting, using an implantable load detector.
What did they do?
Six subjects were recruited to the study. Each subject had suffered some type of fracture in the lower part of their spine (lumbar spine) and had been given a spinal implant, which are designed to replace damaged bone in the spine. The spinal implant had a load detector inside that enabled the experimenters to measure the load being placed on the implant. Each subject was asked to sit on a chair with a backrest positioned at different angles and the researchers measured spinal load in each of these positions.
What were the findings?
The key finding was that as the backrest was inclined backwards there was a reduction in load on the spine. Indeed, just a 10 % backwards inclination reduced spinal load by 19%. In contrast, as the backrest moved forwards from an upright sitting position, there was an increase in load being transmitted through the spine.
What are the implications of this study?
These findings provide more evidence that spinal load can be directly influenced by small changes in backrest position. Since prolonged spinal loading has been associated with an increased risk of back pain, it may be helpful to make full use of the adjustability of your back rest during the day. For example, when you are chatting on the phone, it may be worth moving your back rest to a more reclined position. Regular changes to backrest position may also help reduce loading on one specific part of your back.
When interpreting these findings it is worth remembering that this study was only conducted on a small number of subjects and will need to be repeated in a larger group. In addition, the spinal implant was positioned in one part of the lumbar spine only and so we cannot assume the changes in spinal load reported in this study will generalise to other parts of the lumbar spine.
What is the name of the article?
Rohlmann A et al Measured loads on a vertebral body replacement during sitting. Spine J. 2011 Sep;11(9):870-5.