Adaptation of computerized posturography to assess seated balance in persons with spinal cord injury

Abstract

Background: The ability to retain or improve seated balance function after spinal cord injury (SCI) may mean the difference between independence and requiring assistance for basic activities of daily living. Compared with assessments of standing and walking balance, seated balance assessments remain relatively underemphasized and under-utilized.

Objective: To optimize tools for assessing seated balance deficits and recovery in SCI.

Design: Cross-sectional observational study of different methods for assessing seated balance function.

Setting: Veterans Affairs Center of Excellence for the Medical Consequences of Spinal Cord Injury.

Participants: Seven able-bodied volunteers, seven participants with chronic motor-complete thoracic SCI.

Interventions: A computerized pressure-plate apparatus designed for testing standing balance was adapted into a seated balance assessment system.

Outcome measures: Seated section of Berg Balance Scale; modified functional reach test; and two posturography tests: limits of stability and clinical test of sensory integration on balance.

Results: Seated posturography demonstrated improved correlation with neurological level of lesion compared to that of routinely applied subjective clinical tests.

Conclusion: Seated posturography represents an appealing outcome measure that may be applied toward the measurement of functional changes in response to various rehabilitation interventions in individuals with paralysis.

Figures

Figure 1

Seated balance testing setup. (A) Arms across chest starting position for Berg Scale and LOS. (B) MFRT – the position of the ulnar styloid process is tracked as the subject leans forward as far as possible without falling. (C) Limits of stability testing – the subject leans toward on-screen targets in eight cardinal directions. (D) Clinical test of sensory interaction on balance – arms-extended/eyes-open position.

Figure 2

Example of computerized posturography output. LOS testing for one subject with T8 AIS A SCI as he leaned toward eight targets. The points on the lean trajectory of “endpoint excursion” (EPE) and “maximal excursion” (MXE) are indicated for the right-front and the right targets. EPE and MXE are calculated as percent of target distance attained. DCL is the percent of total movement that is toward the target.

Figure 3

Dynamic seated balance testing is more sensitive to SCI. Able-bodied volunteers (black bars) and subjects with chronic motor-complete thoracic SCI (gray bars) were tested on static and dynamic measures of seated balance. SCI subjects were more impaired on dynamic (average score: 31.9%) than static (average score: 77.6%) balance outcomes. BBS, seated portion of Berg Balance Scale; Chest-EO, postural sway velocity during stationary sitting as in Fig 1A; Stretch-EO, sway during sitting as in Fig 1D; Chest-EC, sway while seated as in 1A with eyes closed; Stretch-EC, sway while seated as in 1D with eyes closed; MFRT, modified functional reach test; EPE, endpoint excursion; MXE, maximal endpoint excursion; DCL, directional control. **P < 0.001; *P < 0.01. Error bars, SEM.

Figure 4

Computerized posturography is more sensitive to SCI lesion level. Seven subjects with chronic motor-complete SCI at varying thoracic levels were tested on static and dynamic measures of seated balance. Individual SCI subject scores were plotted against lesion level. The plot shows results for a subjective static balance test (BBS, gray circles), a subjective dynamic balance test (MFRT, black triangles), and a computerized dynamic balance test (DCL, black squares). Note the prominent ceiling effect for BBS, and the floor effect for MFRT. Linear regression R2 values confirm that DCL correlated better with level of lesion than subjective scores did. See Fig. 3 legend for abbreviations.