Investigation into the origin of cavitation sounds during spinal manipulation
Cavitation sounds heard during chiropractic adjustments and manipulations to th extension spine are a common phenomena yet their significance is disputed, the mechanism of their production is a matter of speculation, and their origin has never been localized. (Lewit 1978: 4, Grieve 1989; 525) The purpose of this study was to locate the joints which cavitate during the performance of a L5 spinous hook adjustment and a lower sacroiliac adjustment. It was hypothesised that the cavitation sounds would arise from the L4-L5 and L5-S1facets on the side of contact during the L5 hook adjustment., and from the the sacroiliac joint on the side being adjusted during the lower sacroiliac adjustment. It was also hypothesised that the two adjustments would differ significantly in terms of the cavitation sounds produced. Volunteers were screened for agreement with the inclusion criteria. Of these 30 asymptomatic between the ages of 18 and 30 were selected. This was sample was then randomly divided into two groups of, one of which recieved the L5 hook adjustment and the other the lower sacroiliac adjustment. All of the subjects had eight microphones taped to the skin, over the relevant facets and the sacroiliac joints. Radiographic confirmation was used in order to ensure proper positioning of the microphones. The microphones were then connected to filters, amplifiers and a computer which recorded any sound signals registered during the adjustments.