A flexible fluid filled actuator has an elastic bladder and a guide
surrounding the bladder. The guide has asymmetrical elastic properties.
When the bladder is inflated the guide directs the bladder to expand
preferentially in a selected direction or directions. The actuator has
utility in the traction and/or unloading of portions of the body. A
fluid-filled traction apparatus is disclosed which has particular
advantages in spinal unloading.