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STUDY DESIGN: Secondary analysis of a randomized clinical trial (RCT).

OBJECTIVES: To perform a secondary analysis on the treatment arm of a larger RCT to determine differences in treatment outcomes, adverse reactions, and effect sizes between patients who received cervical thrust manipulation and those who received only nonthrust manipulation as part of an impairment-based, multimodal treatment program of manual physical therapy (MPT) and exercise for patients with mechanical neck pain.

BACKGROUND: A treatment regimen of MPT and exercise has been effective in patients with mechanical neck pain. Limited research has compared the effectiveness of cervical thrust manipulations and nonthrust mobilizations for this patient population, and no studies have investigated the added benefit of cervical thrust manipulations as part of an overall MPT treatment plan.

METHODS: Treatment outcomes from 47 patients in the treatment arm of a larger RCT, with a primary complaint of mechanical neck pain, were analyzed. Twenty-three patients (49%) received cervical thrust manipulations as part of their MPT treatment, and 24 patients (51%) received only cervical nonthrust mobilizations. All patients received up to 6 clinic sessions, twice weekly for 3 weeks, and a home exercise program. Primary outcome measures were the Neck Disability Index (NDI), 2 visual analog scales for cervical and upper extremity pain, and a 15-point global rating of change scale. Blinded outcome measurements were collected at baseline and at 3-, 6- and 52-week follow-ups.

RESULTS:  Consistent with the larger RCT, both subgroups in this secondary analysis demonstrated improvement in short- and long-term pain and disability scores. Low statistical power (β≤.28) and the resultant small effect size indices (–0.21 to 0.17) preclude the identification of any between-group differences. No serious adverse reactions were reported by patients in either subgroup.

CONCLUSIONS: Clinically meaningful and statistically significant improvements in both subgroups of patients over time suggest that cervical thrust manipulation, as part of the MPT treatment plan, did not influence the results of the treatment arm of the larger RCT from which this study was drawn. Although no between-group differences can be identified, the small observed effect sizes in this study may benefit future studies with sample size estimation for larger RCTs and indicate the need to incorporate clinical prediction rule criteria as a means to improve statistical power.

LEVEL OF EVIDENCE: Therapy, level 4.