Reliability and validity of the variability model testing procedure for somatic dysfunction assessment: a comparison with gait analysis parameters in healthy subjects

The somatic dysfunction (SD) is a dysfunctional adaptation of musculoskeletal and fascial systems to various endogenous and exogenous stimuli that include pathologies and traumas. According to literature, SD is recognized by four distinct clinical signs: tissue texture abnormalities, positional asymmetry, restricted range of motion and tissue tenderness. However, the present physical examination model did not reach satisfactory results in terms of reliability and validity. Hence, this cross-sectional study investigated the reliability and validity of the new Variability Model (VM) of SD with gait analysis (GA). Three blind examiners tested 27 young healthy subjects for SD on six body regions with a VM examination protocol. According to neutral zone theory, the asymmetry of motion around rest position and the side with the restricted movement (bind), as well as the SD grade were collected and compared with VICON procedure for 3D-GA. The inter-rater reliability for the side with the restricted movement ranged from 0.78 to 0.54, and 0.64 to 0.47 for the SD grade. VM had a sensitivity and specificity of 0.62 and 0.53 in SD detection compared to step length normality. Global SD of the tested regions demonstrated moderate to good correlation with spatial-temporal parameters of GA. The VM showed palpatory reliability and validity with spatial-temporal parameters in GA.