Comparison of Postural Balance between Subgroups of Nonspecific Low-back Pain Patients Based on O'Sullivan Classification System and Normal Subjects during Lifting

Balance disorder is one of the most-studied fields in low-back pain patients (LBP). However, there is insufficient information regarding the effect of LBP subgrouping on postural control. The purpose of the present study was to compare postural control between subgroups of chronic nonspecific LBP and healthy subjects during lifting. A total of 35 men with chronic LBP (19 active extension pattern [AEP] and 16 flexion pattern [FP]) and 15 healthy controls were enrolled in this cross-sectional study. Pooled LBP was subdivided based on the O'Sullivan's classification system (OCS). The participants were asked to lift a box from the ground to the waist level and hold it for 20 seconds. The load was 10% of the subject's weight. Force plate system was used to record balance parameters, including standard deviations (SDs) of center of pressure (COP) amplitude and COP velocity in anterior-posterior and medial-lateral directions and mean total velocity. The test was divided into two static and dynamic phases. Data were analyzed using one-way analysis of variance and independent t-test. There were no significant differences between pooled LBP and control groups in any of the variables, except for the SD of the anterior-posterior direction velocity in the X-plane in the static phase ( ). After classifying LBP, the results showed that the healthy and AEP groups were significantly different in SD of COP velocity in the frontal plane ( ), mean total velocity ( ), and SD of COP velocity in the sagittal plane ( ). The present study showed that postural control was not different between the pooled LBP and normal groups. After classifying pooled LBP based on OCS, we found that the AEP showed different postural control as compared to healthy controls in the dynamic phase. The FP and AEP exhibited different postural control relative to the healthy controls in the static phase, and COP velocity was lower in those groups compared to the control group. The results of this study support the concept of LBP classification.