Background Chronic spinal disc disease leads to disorders in postural movement coordination and deteriorates postural stability.¹ Recent studies suggest that subjects with lumbar disc herniation (LDH) develop visual compensation mechanisms for underlying sensory–motor deficits. In subjects with unilateral disease, using two separate force plates, enable the balance evaluation of each limb. The aim of this study was to assess postural stability in LDH subjects on both the affected and the unaffected limbs.

Methods The experimental group consisted of ten (6 males, 4 females) LDH subjects (L4/L5 or L5/S1 level) with an age of 41±8 years, weight 79±15 kg and height 177±6 cm. The treatment was only conservative (with no surgical intervention). The control group was composed of eleven healthy subjects (6 males, 5 female) with an age 40±9 years, weight 73±12 kg and height 174±9 cm. Postural sways (center of pressure movement) were evaluated using two force plates Kistler (Kistler Instrumente AG, Switzerland). All participants carried out three 30 s balance tasks: stance with opened eyes (EO), stance with closed eyes (EC) and stance with narrow base of support (NBS). In each test mean loading, medial lateral (ML) and anterior posterior sways (standard deviations of COP coordinates) were evaluated. Statistical analyses were performed by two-way ANOVA with Tukey's post hoc test (Statistica 9.0, independent variables: limb, group).

Results There was no significant difference in limb loading for both the experimental and the control group and total ML sway and AP sway. In the EO and EC conditions, there was no significant difference between postural sway of limbs of LDH subjects and limbs of controls. In the NBS conditions, the ML sway was greater in affected limb compared to dominant (p<0.01) and non-dominant (p<0.05) limbs of controls.

Discussion/Conclusions The results suggest that the balance evaluation of each limb independently can be useful in assessment of groups of subjects with unilateral disease. The LDH subjects showed increased ML postural sway on the affected limb during NBS conditions. Similar findings reported Mientjes and Frank² for chronic low back pain patients. They found an increase in the ML postural sway of these patients compared to healthy controls when the task involved increased complexity and removal of visual information.