The comparative effects of spinal and peripheral thrust manipulation and exercise on pain sensitivity and the relation to clinical outcome

The obective of this study was to compare the effects of cervical and shoulder thrust manipulation (TM) and exercise on pain sensitivity, and to explore associations with clinical outcomes in patients with shoulder pain. Experimental studies suggest that spinal TM has an influence on central pain processes, supporting its application for treatment of extremity conditions. Direct comparison of spinal and peripheral TM on pain sensitivity has not been widely examined. Seventy-eight participants with shoulder pain (36 female; mean ± SD age, 39.0 ± 14.5 years) were randomized to receive 3 treatments of cervical TM (n = 26), shoulder TM (n = 27), or shoulder exercise (n = 25) over 2 weeks. Twenty-five healthy participants (13 female; mean ± SD age, 35.2 ± 11.1 years) were assessed to compare pain sensitivity with that in clinical participants at baseline. Primary outcomes were changes in local (eg, shoulder) and remote (eg, tibialis anterior) pressure pain threshold and heat pain threshold occurring over 2 weeks. Secondary outcomes were shoulder pain intensity and patient-rated function at 4, 8, and 12 weeks. Analysis-of-variance models and partial-correlation analyses were conducted to examine comparative effects and the relationship between measures. At baseline, clinical participants exhibited lower local (mean difference, – 1.63 kg; 95% confidence interval [CI]: -2.40, -0.86) and remote pressure pain threshold (mean difference, -1.96 kg; 95% CI: -3.09, -0.82) and heat pain threshold (mean difference, -1.15°C; 95% CI: -2.06, -0.24) compared to controls, suggestive of enhanced pain sensitivity. After the intervention, there were no between-group differences in pain sensitivity or clinical outcome (P>.05). However, improvements were noted, regardless of intervention, for pressure pain threshold (range of mean differences, 0.22-0.32 kg; 95% CI: 0.03, 0.43), heat pain threshold (range of mean differences, 0.30-0.58; 95% CI: 0.06, 0.96), pain intensity (range of mean differences, -1.79 to -1.45; 95% CI: -2.34, -0.94), and function (range of mean differences, 3.15-3.82; 95% CI: 0.69, 6.20) at all time points. No association between pain sensitivity changes and clinical outcome was found (P>.05).

Clinical participants displayed enhanced pain sensitivity, but did not respond differently to cervical or peripheral TM. In fact, in this sample, cervical TM, shoulder TM, and shoulder exercise had similar pain sensitivity and clinical effects. The lack of association between pain sensitivity and clinical pain and function outcomes indicates different (eg, nonspecific) pain pathways for clinical benefit following TM or exercise.