Altered Trunk Position Sense and Its Relation to Balance

Altered Trunk Position Sense and Its Relation to Balance
Functions in People Post-Stroke
Susan Ryerson, PT, DSc, Nancy N. Byl, PT, PhD, David A. Brown, PT, PhD, Rita A. Wong, PT, EdD, and Joseph M. Hidler, PhD
Objective:
To determine whether trunk position sense is impaired in people with poststroke hemiparesis.
Background:
Good trunk stability is essential for balance and extremity use during daily functional activities and higher level tasks. Dynamic stability of the trunk requires adequate flexibility, muscle strength, neural control, and proprioception. While deficits of trunk muscle strength have been identified in people post-stroke, it is not clear whether they have adequate postural control and proprioception to ensure a stable foundation of balance to enable skilled extremity use. Trunk position sense is an essential element of trunk postural control. Even a small impairment in trunk position sense may contribute to trunk instability. However, a specific impairment of trunk position sense has not been reported in people post-stroke.
Subjects:
Twenty subjects with chronic stroke and 21 nonneurologically impaired subjects participated in the study.
Protocol:
TRE was measured using an electromagnetic movement analysis system, the Flock of Birds (Ascension Technology Corporation, Burlington, VT). The Flock of Birds has been found to be an accurate, reliable, and valid measure of angular position in a reconstructed mechanical model of the spine Within-day and day-to-day reliability in subjects with low back pain and ankylosing spondylitis is good with infraclass correlation coefficients ranging from 0.88 to 0.91 this system, the gold standard in TRE testing with an accuracy to 0.1 degree, measures the simultaneous three dimensional angular orientation of a sensor in space relative to an electromagnetic source. The protocol for measuring TRE in this study replicated those used in previously published studies. The principal investigator conducted the TRE testing, but was blinded to the scores until the conclusion of the study.
RESULTS:
The mean of absolute TRE value was significantly greater in both the sagittal and transverse planes in subjects post-stroke compared to non neurologically impaired subjects, as shown in Table 2 (t _ 4.67, P _ 0.0001 and t _ 3.63, P _ 0.0012, respectively). In the frontal plane, mean absolute TRE value was not statistically different between groups.
For subjects post-stroke, the absolute mean sagittal TRE at T1 expressed as a percentage of full active forward flexion range was 11% (range, 2%–18%) compared to 4% (range,
2%–9%) for the control group. To ensure that spine height did not affect TRE, a covariate analysis of spine height on TRE was performed. The results indicated that spine height did not play a role in differences in TRE (P _ 0.992).
DISCUSSION:
Between-Group Differences
The findings of this study suggest that trunk position sense, as defined by TRE, is impaired in individuals in the chronic phase of recovery post-stroke compared to non neurologically impaired people.
Relationship with Clinical Measures
We found that sagittal and transverse TREs were negatively correlated with BBS scores. Since upright trunk control allows safe walking, one might reasonably expect that performance on the BBS, a predictor of safe independent walking, would have a relationship with trunk position sense impairments.
Reliability and Validity:
We were unable to compare our TREs with other values in the literature because this is the first reported study conducted on people post-stroke. However, our mean absolute TRE value of 3.2 degrees for the control group was similar to previously published reports.24–27 In addition, we reported control group sagittal TRE mean values being approximately 4% of full active trunk forward flexion range, which agrees with the findings of Swinkles and Dolan.34 While Swinkles and Dolan reported a tendency for overshooting in subjects with orthopedic spinal pathology, in this study, both groups demonstrated a relatively equal number of subjects overshooting and undershooting. Intraclass correlation coefficient values for within-day and day-to-day test-retest reliability in each plane of movement (ranging from 0.73 to 0.94) agree with previously published reliability values for electromagnetic RE testing. The strong reliability values along with the high degree of accuracy of the Flock of Birds adds strength to the technique used in this study.
CONCLUSION:
For the first time, impairment in trunk position sense as measured by TRE has been identified in people in the chronic phase of recovery post-stroke. This impairment in trunk position sense appears to be related to clinical measures of balance and posture. The findings of this study provide a platform for continuing research in TRE and its relationship to balance and functional performance. In clinical practice, therapists should keep in mind that trunk position sense training may become an important intervention strategy to improve trunk stability as a precursor to balance and functional activities for patients post-stroke.