Distinguishing characteristics of thoracic medial paraspinal structures determined as abnormal by palpation

Abnormal tissue texture and tenderness detected in the paravertebral gutter (PVG) region by manual palpation has been proposed to be an important diagnostic finding in osteopathic medicine. The pathophysiology of tissues at sites detected as abnormal by palpation and reported as tender by the subject (AbPT) is speculative, because evidence of objective characteristics that distinguish abnormal sites from non-tender, normal to palpation (NT) sites is lacking. The first study of this thesis examined the pressure sensitivity of AbPT sites in 32 subjects using a novel pressure algometer. The AbPT regions had a lower mean pressure pain threshold than the three NT regions, and a one-way ANOVA determined these differences to be significant (P < 0.01). This study demonstrated that these sites were significantly more sensitive to manual pressure than adjacent NT sites, above, below, and on the opposite side of the spine, and established that these sites had characteristics different from adjacent NT sites, and were therefore not merely a result of practitioner imagination. Authors in the field of osteopathy have suggested that abnormal tissue texture in the PVG region may be due to either atrophy or hypertrophy of the underlying paraspinal muscle mass. The second study in this thesis compared the thickness of deep paraspinal muscles underlying AbPT and NT sites in the thoracic PVG regions of 40 subjects. The anteroposterior dimension of the deep muscle mass was measured using diagnostic ultrasound by an ultrasonographer who was blinded to the designation of the sites, and found that there was no significant difference (P = 0.61) in the thickness of paraspinal muscles underlying AbPT and NT sites. Early researchers in the field of osteopathy have claimed to provide evidence of paraspinal muscle hyperactivity at sites designated as abnormal using palpation, which has been used to promote the ‘facilitated segment’ aetiology for intervertebral somatic dysfunction. The final study in this thesis examined the electromyographic (EMG) activity of deep paraspinal muscles underlying AbPT and NT sites in the thoracic PVG using fine-wire, intramuscular electrodes in 12 subjects. The normalised EMG activity of muscles underlying AbPT sites was higher than the mean activity at NT sites under all experimental conditions, and analysis with SPANOVA revealed a significant difference between the sites (P = 0.03). The EMG recordings during the prone resting were found to have been contaminated with electromagnetic noise, but, when these were excluded from the analysis, there remained a statistically significant difference between the sites (P = 0.02). Post-hoc analysis revealed the significant difference between sites to occur under the condition of resting seated. The trend for higher EMG activity under other experimental conditions were not significant, most likely due to the large variation between subjects and small sample size, but large and medium effect sizes were calculated for differences between the sites under most conditions. Non-significant trends of decreased EMG responsiveness from baseline resting to more demanding tasks were seen at the AbPT sites relative to the NT sites. Caution must be exercised when interpreting the results of this study because the validity of the method of EMG normalisation requires further investigation. This thesis established that AbPT sites detected by palpation in the thoracic PVG region are more sensitive to pressure, and have differing EMG characteristics from NT sites. This research suggests that increased EMG activity may be a contributing factor to the altered tissue texture detected with palpation