Tai Chi and vestibular rehabilitation improve vestibulopathic gait via different neuromuscular mechanisms: Preliminary report

BACKGROUND: Vestibular rehabilitation (VR) is a well-accepted exercise program intended to remedy balance impairment caused by damage to the peripheral vestibular system. Alternative therapies, such as Tai Chi (TC), have recently gained popularity as a treatment for balance impairment. Although VR and TC can benefit people with vestibulopathy, the degree to which gait improvements may be related to neuromuscular adaptations of the lower extremities for the two different therapies are unknown. METHODS: We examined the relationship between lower extremity neuromuscular function and trunk control in 36 older adults with vestibulopathy, randomized to 10 weeks of either VR or TC exercise. Time-distance measures (gait speed, step length, stance duration and step width), lower extremity sagittal plane mechanical energy expenditures (MEE), and trunk sagittal and frontal plane kinematics (peak and range of linear and angular velocity), were measured. RESULTS: Although gait time-distance measures were improved in both groups following treatment, no significant between-groups differences were observed for the MEE and trunk kinematic measures. Significant within groups changes, however, were observed. The TC group significantly increased ankle MEE contribution and decreased hip MEE contribution to total leg MEE, while no significant changes were found within the VR group. The TC group exhibited a positive relationship between change in leg MEE and change in trunk velocity peak and range, while the VR group exhibited a negative relationship. CONCLUSION: Gait function improved in both groups consistent with expectations of the interventions. Differences in each group's response to therapy appear to suggest that improved gait function may be due to different neuromuscular adaptations resulting from the different interventions. The TC group's improvements were associated with reorganized lower extremity neuromuscular patterns, which appear to promote a faster gait and reduced excessive hip compensation. The VR group's improvements, however, were not the result of lower extremity neuromuscular pattern changes. Lower-extremity MEE increases corresponded to attenuated forward trunk linear and angular movement in the VR group, suggesting better control of upper body motion to minimize loss of balance. These data support a growing body of evidence that Tai Chi may be a valuable complementary treatment for vestibular disorders

Estimating polyethylene wear in total hip arthroplasty by using computed tomography and alternative RSA techniques [Elektronisk resurs]

Introduction: Traditionally Total Hip Arthroplasty (THA) components performance, and in particular the performance of the polyethylene liner, is evaluated in 2D by examining plain radiographs or in 3D using Radio Stereo-metric Analysis (RSA). While 2D techniques require only a plain radiograph, they are less accurate. RSA systems, on the other hand, are more accurate but are more complicated to set up and require dedicated equipment. CT scanners are widely available and can measure THA performance in 3D. These techniques fail to estimate wear when tantalum cups are implanted, and alternative methods are needed. Specific Aims: Validate a Computerized Tomography (CT) technique for evaluating THA wear, develop and test algorithms to estimate wear in THA when tantalum cups are implanted. Methods: To validate the 3D CT data and software, a supine hip phantom fitted with a 3-axis micrometer tower was scanned, first (as a feasibilty study) in an experimental ultra-high resolution flat panel CT scanner and then in a multi-detector CT scanner. The micrometers were displaced in the x, y, and z axes, displacement of the micrometers (femoral head) was estimated and then compared to the actual micrometer readings (studies I and II). Wear was also estimated from clinical CT data of patients that had their THA revised: images were analyzed and compared to a coordinate measurement machine (CMM) and a micrometer (study III). For the analysis of liner wear when tantalum cups are used, four methods were tested: standard RSA, Model Based RSA, RSA-Helical axis, and RSA Center of Rotation. To test these methods a supine hip phantom was used and the femur was abducted. The center of the femoral head was calculated using these four methods (Study IV). Results: Study I - Measuring femoral head displacement using a phantom in the high resolution flat panel CT scanner, the mean difference between the actual micrometer displacement and the CT readings was found to be -0.14±0.12 mm (-0.06 to -0.21 mm 95% CI). In study II, similar to study I, a hip phantom was placed in a multi-detector CT and the femoral head displacement was compared between readings from CT data and the actual micrometers displacement. The mean accuracy and precision for the individual axis x, y, and z was 0.159±0.056 mm, 0.113±0.029 mm, and 0.209±0.036 mm respectively, with combined accuracy of 0.285 mm. In study III, we compared CT wear measurement to the actual wear of the same retrieved implant. Ex-planted liners were measured using CMM and micrometer, the average differences and standard deviations were: CMM-CT 0.09±0.29mm, CMM-Micrometer 0.01±0.32, and micrometer-CT 0.11±0.44. In study IV, comparing alternative techniques of calculating femoral head center when tantalum cups are used, the 2D average head-cup distance was calculated by: standard RSA 0.41mm, Model Based RSA 0.38mm, RSA RSA-HAT 0.96mm, and RSA-COR 1.41mm. Conclusion: Under ideal conditions, with no soft tissue or motion artifacts, and with a high resolution flat panel scanner it is possible to record femoral head penetration to a clinically acceptable level.When considering the clinical application of current CT technology and measurement techniques, the expected wear measurement accuracy should be 0.3 mm. In cases where CT technology does not provide an adequate solution for wear measurement (when tantalum cups are implanted), model based RSA provides the closest agreement to gold standard RSA and should be considered as a viable solution for wear measurement

Is Base of Support Greater in Unsteady Gait?

Abstract Background and Purpose. We investigated dynamic interfoot distance (IFD) throughout the gait cycle in people with unsteady gait caused by vestibulopathy and in people without known neuromuscular pathology. We expected that the subjects with unsteady gait would use a greater IFD than subjects without neuromuscular pathology and that this IFD would be correlated with other measures of locomotor stability. Subjects and Methods. Simultaneous whole-body (11-segment) dynamic kinematic data were collected from 22 subjects with vestibulopathy and 22 subjects without known neuromuscular pathology who were matched for age, height, weight, and body mass index. Two trials each of the participants' gait at preferred speed and paced gait at 120 steps/min were analyzed with a repeated-measures design with multiple dependent variables. Quantitative data were analyzed descriptively and with inferential statistics. Results. Interfoot distance at preferred gait speed did not differentiate unsteady subjects with vestibulopathy from the comparison subjects. Paced gait IFD total range and IFD in single-limb support differed between groups, but IFD at heel-strike did not. However, IFD at heel-strike, the traditional measure of “base-of-support width,” was correlated with measurements of whole-body center-of-gravity stability (r=.32–.55). Discussion and Conclusion. Gait at preferred speed permitted the unsteady subjects and the comparison subjects to select similar IFD values, but at the cost of slower gait in the unsteady subjects. When required to walk at a “normal” pace of 120 steps/min, subjects with vestibulopathy increased their IFD. These data suggest that wide-based gait alone cannot differentiate between subjects with and without balance impairments. Base of support and other whole-body kinematic variables are mechanical compensations of vestibulopathic instability. Further studies are needed to determine whether development of active control of these whole-body control variables can occur after vestibular rehabilitation.</jats:p