Spinal manipulative therapy (SMT) has been used for centuries as a treatment for pain associated with the cervical, thoracic, lumbar and sacral regions of the spine. There is a body of literature suggesting efficacy of SMT for mechanical neck pain, chronic low back pain, sciatica, mechanical thoracic pain, and chronic headache. Despite its apparent efficacy in the treatment of these maladies, the mode by which manipulation exerts its effect remains elusive.

This thesis is a collection of cascading experiments directed towards understanding some of the techniques used by spinal manipulators. Chapter 1 of this thesis addressed the assumption that the joints in the spine are symmetrical in shape and hence anatomy should not affect the ability of a clinician to locate a “manipulatable lesion”. The results of this study suggested that facets joints are often asymmetrical in their anatomy, resulting in asymmetrical force-displacement curves when one vertebra is moved on another. These findings then question the validity of spinal palpation as a diagnostic protocol to locate joints that require manipulation.

Chapter 2 of this thesis investigated the questions “Do tender spinal segments exhibit greater stiffness than those that are not and, does manipulation have any effect on stiffness? The results of that study indicated, firstly, that there were no differences in the vibrational characteristics of tender versus non-tender segments. This would suggest that the relationship between vertebral tenderness and, stiffness between segments is not a simple one. One cannot assume from this study, that tender vertebral motion segments are more or less stiff than their non-tender counterparts. The results also indicated that the vibrational characteristics changed following manipulation. However no consistent pattern of change was apparent.

Chapter 3 of this thesis examined the accuracy of spinal manipulation, by locating the source of the cavitation (cracking sound) that results from the procedure. It was found that manipulation is generally not accurate. However, accuracy is better for thoracic segments as compared to lumbar segments. Accuracy can be improved by creating multiple cavitations during a single manipulative procedure. The majority of cavitations will be remote from the target site, but in most cases one cavitation will emanate from the desired spinal level.

Chapter 4 of this thesis looked at the electromyographic response to manipulation, using electromyography. Considerable work has shown that SMT is associated with muscular reflexes. This chapter compared the reflex response associated with SMT, with that associated with a simple impact. The electromyographic response to manipulation, was quite different than that from a simple impact. The theory that some portion of the mechanism of SMT is through muscular reflexes thus remains viable.