The authors conducted this study to examine the short-term trajectory of recovery from mechanical neck pain, and predictors of trajectory. They employed a prospective longitudinal cohort study with 5 repeated measurements over 4 weeks at community-based physiotherapy clinics in Canada. Participants comprised convenience sample of adults living in those communities (N=50) with non-complicated mechanical neck disorders of any duration. Their treatments were comprised of typical physiotherapy care. For the main outcome index they referred to the Neck Disability Index (NDI), Numeric Rating Scale of pain intensity (NRS). A total of 50 consecutive subjects provided 5 data points over 4 weeks. Exploratory modeling using latent class growth analysis revealed a linear trend in improvement, at a mean of 1.5 NDI point and 0.5 NRS points per week. Within the NDI trajectory, 3 latent classes were identified each with a unique trend: worsening (14.5%), rapid improvement (19.6%) and slow improvement (65.8%). They identified two unique trends within the NRS trajectory: stable (48.0%) and improving (52.0%). Predictors of trajectory class indicated that it may be possible to predict the trajectory. Results are described in light of the sample size.
The authors concluded that the mean trajectory of improvement in neck pain sufficiently fits a linear model and suggests slow but stable improvement over the short term. However, as many as three separate trajectories have been identified which suggest neck pain, and recovery thereof, is not homogenous. They add that that may be useful in the design of clinical trials.