Objective: To determine intrarater reliability of clinical examinations and radiographic variables that proposed to identify patients with lumbar segmental instability.

Materials & Methods: In this descriptive and methodological research, 15 patients with chronic non specific low back pain aged 22-43 years with non probability and simple selection (sample of convenience) participated. Clinical examinations included pain intensity, flexion and extension range of motion (ROM) with modified schober method, aberrant movement patterns, ito method of flexion and extension endurance test, sid support test, bilateral straight leg rising (SLR) & sit-up, prone instability test and oswestry index. Radiographic variables included: 1) Quantity of movement (sagital plane transition & rotation) measured with Dupuis and Panjabi method 2) Quality of movement (instability factor, centre of rotation & Centroid). Proposed method from Putto was used for flexion-extension radiography. Five x-rays were taken in neutral, full flexion & extension, mid range of flexion & extension positions from lateral view. We used ICC for reliability of quantitative variables, and Kappa statistic for nominal variables.

Results: Reliability of Pain intensity (ICC=0.89), flexion (ICC=0.93) & extension (ICC=0.74) ROM, Sid support test (ICC=0.85-0.86), extension (ICC=0.86) & flexion (ICC=0.82) endurance were high. Kappa value for aberrant movement patterns (k=0.66), bilateral SLR & sit-up (k=0.65), prone instability test (k=0.66) were substantial. Centre of rotation on X axis (ICC=0.99) & Y axis (ICC=0.96), rotation with Dupuis (ICC=0.83) & Panjabi (ICC=0.88) had very high reliability. Centroid length with 3 (ICC=0.60) & 5 (ICC=0.64) x-rays, instability factor with 3 (ICC=0.61) & 5 (ICC=0.72) x-rays, transition with Dupuis (ICC=0.69) & Panjabi (ICC=0.76) method had moderate to high reliability.

Conclusion: Clinical examinations includig pain intensity, flexion & extension ROM, sid support test, extension & flexion endurance and oswestery index have high to very high reliability. Aberrant movement patterns, bilateral SLR & sit-up and prone instability test have substantial agreement. Radiographic variables have moderate to very high reliability.

Objective: Lumbar segmental instability (LSI) is one subgroup of nonspecific low back pain which its diagnosis has not been clarified. The aim of this study was to present a reliable and novel method for evaluation of lumbar spine kinematics in sagital plane.
Materials & Methods: In this comparative and validity testing study, 15 low back patients suspected to have LSI and 15 matched healthy subjects were recruited. Pulsed digital videofluoroscopy was used to investigate kinematics of lumbar motion segments during flexion and extension movements. Segmental linear transition and angular displacement, and Pathway of Center of Rotation (PICR) were calculated for each lumbar motion segment. Movement pattern of lumbar spine between two groups and during range of motion were compared.Data were analyzed by statistical methods such as:Chi-square,Kolmogroff-Smirnoff, Independent T test avd ANOVA with repeated measurements.
Results: Segmental linear transition was different in patients during both flexion and extension movements at L5-S1 segment (P<0.001). PICR was different in patients for L1 and L5 vertebrae during extension movement (P<0.001). Six patients showed "Delayed-Sequence" movement pattern and were different from others (P<0.001).
Conclusion: Previous studies were unsuccessful to determine differences between LSI patients and healthy subjects. This study determined some differences between two groups during the middle range of lumbar spine. New devices such as digital videofluoroscopy can assist in identifying better criteria to diagnosis of LSI in otherwise nonspecific low back patients in hope of providing more specific treatment.