Thrust Joint Manipulation to the Cervical Spine in Participants With a Primary Complaint of Temporomandibular Disorder (TMD): A Randomized Clinical Trial

Methods: Research design following CONSORT guidelines. A blinded assessor will measure ROM and PPT. Treating therapists will know group allocation and will receive training to standardize assessments and treatments. Self-report and objective measurements will be taken at baseline, immediately after treatment one, and at one and four week follow-ups.

Data Analysis (primary): Sample size estimations were completed using G-Power, a free online downloadable program. An F-test family with ANOVA: Repeated measures, within-between interaction protocol was selected. While it is optimal to power sample size estimations around a functional outcome measure, the limited use of functional measures in this population created an obstacle. The sample size estimation for this project was powered around maximal mouth opening (MMO) as this most closely relates to function in the TMD population. In order to account for 15% attrition, and maintain equal participants in each arm of this study, the desired sample size is 42 participants.

A 2 x 4 mixed model analysis of variance (ANOVA) will be used with treatment group as the between-subjects factor and time as the within-subjects factor. Separate ANOVAs will be performed for dependent variables and the hypothesis of interest will be group by time interaction for each ANOVA.

To determine if missing data points associated with dropouts were missing at random or missing for systematic reasons, we will perform Little's Missing Completely at Random (MCAR) Test. Intention to treat analysis will be performed by using expectation maximization whereby missing data are computed using regression equations. Planned pair-wise comparisons will examine the difference between baseline and follow-up periods using the Bonferroni equality at an alpha level of 0.05.

Success will be dichotomized using the GROC scale. A cut-off score of +5 or higher on the GROC will be used as a measure of success. Correlations between outcome measures (change scores) and success will be analyzed using an independent t-test to determine if differences between groups exist. Number needed to treat (NNT) will be calculated. Correlations among dependent variables will be analyzed with Pearson/Spearman correlations. Examples include the following: correlation between NDI and jaw functional measures, correlation among PPT at various areas tested, and correlation between change in ROM and change in functional scores. Data analysis will include 95% confidence intervals, and tables, charts, or other figures will be utilized to display findings to enhance reader understanding. Effect size of primary outcome measures including jaw ROM, JFLS, and TMD Disability Index will be calculated and reported. If there is no significant difference between groups noted, a post-hoc power analysis will be performed to determine the risk of Type II error.