Construct validity of center of rotation in differentiating of lumbar segmental instability patients

Lumbar Segmental Instability (LSI) is a subgroup of nonspecific Low Back Pain (NSLBP) without any accepted diagnostic tool as a gold standard. Some authors emphasize on quality measure such as centre of rotation (COR) but construct validity of this measure had not been approved. Therefore the purpose of the present study was to evaluate Concurrent and Convergent validity of COR in differentiating LSI.

A total of 66 volunteered males participated in three groups named control, NSLBP and LSI groups based on clinical examination. Patients were diagnosed as LSI according to screening criteria adopted by Hicks et al. Study variables included CORs of lumbar segments in sagittal plane. Three x-rays were taken in neutral, flexion and extension positions. The variables were calculated using CARA software. The ANOVA and Tukey test were utilized in statistic analysis.

ANOVA results demonstrated mean differences between three groups for COR of L4 motion segment in y axis (p= 0/008) and L5 motion segment in y axis (p= 0/005) were significant. Tukey test showed significant difference for COR of L4 motion segment in y axis between LSI and healthy groups (p= 0/038) and between LSI and NSLBP groups (p= 0/009). For COR of L5 motion segment in y axis, tukey test demonstrated mean difference between LSI and healthy groups (p= 0/028) and between LSI and NSLBP groups (p= 0/007) were significant. Tukey test did't show any significant difference between NSLBP and healthy groups for COR of L4 (p= 0/852) and L5 (p= 0/871) motion segments in y-axis.

The COR has ability to differentiate patients with signs and symptoms of LSI from other NSLBP and healthy subjects based on the present study results. However, more researches are needed to develop and support results of this study.