RECORDING TECHNIQUES AND ANALYSIS OF THE ARTICULAR CRACK: A Critical Review of the Literature

Objective: To review the available literature pertaining to the recording and analysis of the joint crack/cavitation sound produced as a result of spinal manipulative therapy. A critical appraisal of the recording and analysis techniques is presented. Data Source: A broad based search of the English language literature was conducted utilising the databases Medline (1966-1996) and Chirolars (1800-1996), using the key words cavitation, noise, sound, audible release, crack/s/ing, vibration, sound recording, acoustic recording and accelerometers, coupled with the terms facet joint, spinal joint and apophyseal joint and chiropractic, osteopathic and spinal manipulation. A manual search was also conducted of non-indexed journals and text books relating to manual therapy of the library at RMIT University, Bundoora, Victoria. Results: There appears to be a paucity of this research relating to spinal manipulative therapy. Research to date has focused on recording the joint crack sounds via microphones or piezoelectric accelerometers both of which appear to have limited applications. Conclusion: Some worthwhile information may be gained by conducting further research into the joint crack phenomenon, particularly with respect to spectral analysis. However, before this research is undertaken a more reliable and accurate means of capturing and processing the joint crack signal needs to be established.