Sir.—The clinical memorandum "Gowers' Sign in Diskitis" by Kelfer and Haller (Journal 1982;136:555) has an important omission.
Kelfer and Haller hypothesized that the presence of Gowers' sign in a young child with intervertebral disk space infection may be attributed to antalgic inhibition of lumbar spine movement. Perhaps even more important is the mechanical stress produced by the forces that act across the intervertebral disk.
With the patient flexed forward and preparing to "climb up his legs," the center of gravity of the trunk is well forward of the lumbar spine, producing a long lever arm, which would produce very high compressive forces in the lumbar disk in the absence of arm support. Once the patient becomes upright, the center of gravity of the trunk becomes directly above the lumbar spine, thereby producing significantly decreased compressive forces. The significance of such mechanical considerations has been the basis for investigations by