Superior outcomes following cervical fusion vs. multimodal rehabilitation in a subgroup of randomized Whiplash-Associated-Disorders (WAD) patients indicating somatic pain origin-Comparison of outcome assessments made by four examiners from different disciplines

Abstract

Background and aims: Whiplash-Associated Disorders (WAD) are characterized by great variability in long-term symptoms. Patients with central neck and movement-induced stabbing pain participated in a randomized study comparing cervical fusion and multimodal rehabilitation. As reported in our previous paper, more patients treated by cervical fusion than by rehabilitation experienced pain relief. Although patient reported outcome measures are a core component of outcome evaluation, independent examiner has been recommended. Because of the heterogeneity of WAD complaints the patients in our study were examined at baseline and follow-up by four experts representing neurology, orthopedics, psychology and physical medicine. The aim was to compare the professional assessments of change both regarding the possible impact of the different examiners' perspectives on individual patient's outcome, and also on the analysis of possible outcome differences between the treatment groups.

Methods: WAD patients with long-term neck pain as the predominant symptom after a traffic accident were eligible. The neck pain origin should be in the midline and perceived as dull and aching, with sudden movement inducing midline stabbing pain. Of the 1,052 patients in contact with our team, 49 were eligible. The overall treatment effect was evaluated on a global outcome transitional scale. The criteria for the scale categories were defined by each expert's professional perspective on change in the whiplash complaints. Statistical methods that take account of the non-metric properties of ordered categorical data were used. Observed inter-expert disagreement was evaluated by the Svensson method that identifies and measures systematic group-related disagreement separately from disagreement caused by individual variation. Possible differences in the distributions of assessments on the expert-specific outcome scales between the treatment groups were analyzed by the Kruskal-Wallis test.

Results: The per-protocol evaluation showed that a majority of the 18 patients who underwent fusion surgery were assessed as somewhat or much better, ranging from 67% to 78% depending on the expert. Corresponding proportions of improvement in the 17 patients treated by multimodal rehabilitation ranged from 29% to 53%. The statistical analyses confirmed better outcomes in the patients treated by fusion surgery, with p-values ranging from 0.003 to 0.04. The experts' assessments of intra-patient change disagreed more or less for all patients. The analyses of the paired comparisons confirmed that these disagreements could most probably be explained by the different profession-specific operational definitions of the outcome scales rather than by individual variations in data.

Conclusions: The multi-dimensional complexity of WAD-related complaints was comprehensively demonstrated by the inter-disciplinary disagreements in assessing intra-patient outcomes. The superiority of positive treatment effects in patients who underwent cervical fusion compared with multimodal rehabilitation was evident to all experts.

Implications: The results strengthen our previous opinion that neck pain in this subgroup of WAD patients has a somatic origin. More than one examiner is recommended for multi-dimensional outcome assessments.

Keywords: fusion surgery; global scale of change; inter-rater agreement; ordinal data; randomized study; symptoms of whiplash-associated disorders (WAD).