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

PURPOSE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Reliability of quality measures of movement in lumbar spine flexion-extension radiography.

BACKGROUND DATA: For center of rotation (COR) and centroid length variables in lumbar flexion-extension radiography, enough reliability information is not available. OBJECTIVE: The objective of this study was to determine the intra-rater reliability of COR and centroid length of lumbar intervertebral movement. METHODS: A methodological research for reliability was designed. Fifteen males with chronic non specific low back pain aged between 22-43 years participated in this study. Study variables included COR of full, flexion and extension arc and centroid length. The proposed method from Putto was used for flexion-extension radiography. Five x-rays were taken in neutral, full flexion and extension, mid-flexion and mid-extension positions. The variables were calculated using Computer Aided Radiographic Analysis of Spine (CARA) software after scanning. The intraclass correlation coefficient (ICC) and standard error of measurement (SEM) were utilized for relative and absolute reliability respectively. RESULTS: The results demonstrated high ICC values on x axis (range: 0.67-0.88) and y axis (range: 0.55-0.90) for full arc COR, high ICC values of flexion arc COR on x axis (range: 0.54-0.97) and y axis (range: 0.48-0.99). ICC values results of extension arc ranged between 0.19-0.60 for x axis and 0.16-0.83 for y axis. ICC values for centroid length ranged between 0.22-0.88. CONCLUSION: Results support previous studies which show very high reliability of full arc COR. In addition, flexion arc COR has desirable reliability and low measurement errors. But, extension arc COR and centroid length have moderate reliability and large measurement errors.