How common are side effects of spinal manipulation and can these side effects be predicted?

Little scientific support is available concerning usual and unusual reactions after spinal manipulation although such reactions are very common in clinical practice. Fifty-nine manipulative therapists were requested to enroll 15 consecutive patients attending for their first visit to receive spinal manipulation. These patients were asked to complete a questionnaire after this first visit that asked for possible risk factors for spinal manipulation and asked about any side effects after the manipulation. The participating practitioners were asked to note medical diagnosis, manipulated spinal region, number of treated areas and type of additional treatment. Four hundred and sixty five valuable responses were analysed. Two hundred and eighty three patients (60.9%) reported at least one post-manipulative reaction. The most common were headache (19.8%), stiffness (19.5%), local discomfort (15.2%), radiating discomfort (12.1%) and fatigue (12.1%). Most of these reactions began within 4 h and generally disappeared within the next 24 h. Women were more likely to report adverse effects than men (P < 0.001). Multivariate analysis showed that upper cervical manipulation (OR: 3.20; 95%CI: 1.89-7.77), use of medication (OR: 2.20; 95%CI: 1.31-3.69), gender (OR: 1.66; 95%CI: 1.01-2.75) and age (OR: 1.02; 95%CI: 1.00-1.05) were independent predictors of headache after spinal manipulation. The results of this study indicate that reactions to spinal manipulation may be relatively common but are benign in nature and of short duration. Although it is difficult to label side effects as a risk, it is important to differentiate those patients who are susceptible to side effects in order to inform them correctly.