Presented here is a quantitative, clinical balance assessment method suitable for stroke patients with balance disorders.
In patients with stroke, damage to the central nervous system (CNS) can affect the postural stability and increase the risk of falling. Therefore, accurately assessing the balance is important to understand the type, extent, and causes of balance deficit, and to identify individualized interventions. Clinical assessment methods for balance function can be broadly divided into observation, scale assessment, and balance instrument testing. Here, a clinical protocol is presented for static and dynamic balance assessment in stroke patients, which includes three semiquantitative balance function scale assessments (i.e., Berg Balance Scale, Timed Up and Go Test, and Fugl-Meyer Assessment) and three quantitative instrumental balance evaluation (i.e., Stability Assessment Module, Proprioceptive Assessment Module, and Limit of Stability Module). It is recommended that clinicians consider the use of both classic clinical balance scales and instrumental balance measurements when assessing stroke patients to improve the accuracy of assessments, leading to a better individualized treatment plan.
The human body can maintain posture stability under various conditions, including internal and external disturbances1. Balance relies on sensory input, integration of the central nervous system (CNS), and motor control2. In patients with stroke, damage to the CNS can affect the ability to maintain balance3. Postural instability is an important risk factor for falls4. Approximately 70% of patients experience a fall in the first year after stroke, often with serious consequences, such as hip fracture in elderly patients5,6. Moreover, previous studies have shown that postural sway and increased motor response time to visual stimuli are associated with an increased fall risk7,8. Because strokes have a substantial impact on mobility, accurate qualitative and quantitative balance assessment is important for understanding the type, extent, cause of balance deficit, as well as guidance for individualized interventions and appropriate gait aids9.
Clinical assessment methods for balance can be broadly divided into observation, scale assessment, and balance instrument testing. Observation methods (e.g., the Romberg test10) are only used as a rough screening for patients with balance dysfunction due to their strong subjectivity. Many balance function scales are commonly used in clinical practice because of their ease-of-use, economy, and relative quantification. These include the Tinetti scale11, Berg Balance Scale (BBS)12, Fugl-Meyer Assessment (FMA)13, and Timed Up and Go (TUG) test12. These clinical tests are not suitable for determining the fall risk in patients with significant balance disorders, because they are subjective assessments and often are not able to substantiate the self-reported balance problems experienced by individuals with mild-to-moderate balance problems14. Balance instrument testing, a posturography technique, is a useful tool to quantitatively measure the static and dynamic balance function and require balance evaluation systems, such as a force tilting board with pressure sensors, computers, monitors, balance control panels, and professional balance analysis software. These approaches can assess the degree, type, or cause of the balance damage simultaneously by accurately measuring the center of gravity (COG) and postural sway, thereby precisely and objectively reflecting the patient’s balance function. Balance instrument testing can detect subtle differences or damages that the clinical scales cannot. This can be used to overcome the ceiling effect of the scale assessment. With the increasing application of posturography techniques and popularization of computers, it is necessary to promote objective/quantitative balance assessment into clinical practice.
This article describes a clinical balance assessment method that includes standard clinical balance scales and three-module instrument objective balance assessment for stroke patients with balance disorders. A comparison of the results of the clinical assessment scales versus the instrumental balance assessment, is presented to show the advantages of instrumental balance assessment, especially for stroke patients with mild balance disorders. This protocol can help health professionals achieve accurate evaluation to guide clinical treatments. The representative posturography instrument (see Table of Materials) used in this protocol has been validated for dynamic assessment and statistic assessment in previous studies15,16,17. The system, which is composed of a screen monitor and a tilting board where the patients stand, can be used for evaluating the visual, auditory, and proprioceptive feedback of the patients.
The clinical project was approved by the Medical Ethics Association of the Fifth Affiliated Hospital of Guangzhou Medical University and has been registered at the China Clinical Trial Registration Center (No. ChiCTR1900021291) with the title “The mechanism and effect of Pro-kin system training on static and dynamic balance”.
1. Participant recruitment
2. Clinical scale assessment
3. Static and dynamic balance instrument evaluation
4. Data analysis
Results from nine stroke patients with balance deficits are shown. The average age of the nine patients recruited in our study was 52.7 years; all of them were male. Four suffered from right hemiplegia. The average FIM-LE, TUG, and BBS values were 23.9 points, 31.8 s, and 46.8 points, respectively. The other demographic characteristics (BMI, stroke type, and onset time) are shown in Table 2. Each item score and the total scores of the BBS assessment of each of the nine stroke patients are shown in Table 3. The BBS scores of the nine stroke patients were all above 40 and indicated that they all had mild balance deficits. The results of the instrumental balance evaluation are shown in Table 4. The results for one representative patient for the stability assessment, proprioceptive assessment, and loss of stability tests are shown in Figure 5, Figure 6, and Figure 7, respectively.
In Figure 5C, the results are visually presented over the blue arrow. The values of M-L Standard Deviation (opened eyes and closed eyes), Ellipse Area (opened eyes and closed eyes), and perimeter (opened eyes and closed eyes) show that the patient was in the warning band, based on the manual of the balance system assessment instrument used in this study. The bands were created by examining 1,000 patients. In Figure 6A, the results showed that the average tracking error (ATE) in the left and right feet were both below 100%, whereas in Figure 6B, the results showed poor performance in the S7 section in the right foot (above 100%). In Figure 7A, the results showed that the average Loss of Stability Module (total results) was 42.6% (below 75%), indicating poor performance. Moreover, the results of the Loss of Stability Module in the 1st to 7th objectives were all below 75% and the 5th objective was the lowest at 8.8%.
Paranmeter | Meaning | |
Average COP.X | the average COP on the X-axis/medio-lateral axis (UOM[mm]) | |
Average COP.Y | the average of COP on the Y-axis/ anterior-posterior axis (UOM [mm]) | |
Average F-B Speed | the average speed of forward-backward movements (UOM [mm/sec]) | |
Average M-L Speed | the average speed of medium-lateral movements (UOM ([mm/sec]) | |
Romberg Test-Perimeter Ratio C.E./O.E. | the ratio of perimeter between closed eyes test and opened eyes test. Perimeter represents the math sum of all segments point to point created during the test. The range of the ratio (110–250) in healthy participants as reference based on the manual of manufacture. | |
Romberg Test–Area Ratio C.E./O.E. | the ratio of the perimeter between closed eyes and opened eyes tests. The area represents 95% of the area developed by COP movement. The range of the ratio (110–250) in healthy participants as reference based on the manual of manufacture. | |
Average Track Error, ATE | during the proprioceptive assessment module, the average value of differences between the red line being plotted by the foot and the blue line, which is perfectly round, provides a proprioceptive sensitivity index of the foot being tested. All the ATE index values ranging between zero and 35% are considered as very good regarding subtle proprioceptive control; ATE index values of 35–100% are considered sufficient; and scores above 100% indicate some problem with proprioceptive control, which may need further evaluation and investigation. | |
Average Force Variance | the average of applied loaded in eight fundamental sectors on the tilting board during test. | |
Stability Index | the index is a dispersion index in relation with the waited result (the references axis vertical or horizontal) during the Proprioceptive Assessment test. | |
Reaction time of LOS | the time the patient took to reach their maximal lean-out toward each of the 8 targets in the LOS test. | |
Results of LOS | the values on eight objectives were derived from the amount of on-axis movement of the COG relative to off-axis COG movement and is expressed as a percentage of the total on-axis movement. | |
Average of LOS | the average value of the results on the eight objectives. | |
Notes: COP, center of pressure; UOM, unit of measurment; F-B, forward-backward; M-L, medial-lateral; mm, millimetre; sec, second; C.E, closed eyes; O.E, opened eyes; ATE, average track error; LOS, limits of stability. |
Table 1: The major parameters and their meanings for static and dynamic balance evaluation on the instrument.
Patient No. | Gender | Age | Hauteur | Weight | BMI | Stroke type | Onset time | Affected hemisphere | FIM-LE | TUG | BBS |
(year) | (cm) | (kilogram) | (months) | (second) | |||||||
NO.1 | male | 43 | 173 | 80 | 27 | Infarction | 7 | Right | 27 | 23 | 48 |
NO.2 | male | 62 | 168 | 61 | 22 | Infarction | 34 | Left | 19 | 34 | 45 |
NO.3 | male | 56 | 163 | 57 | 21 | Hemorrhage | 7 | Right | 13 | 60 | 43 |
NO.4 | male | 37 | 173 | 54 | 18 | Hemorrhage | 3 | Left | 23 | 28 | 48 |
NO.5 | male | 41 | 170 | 76 | 26 | Hemorrhage | 17 | Left | 20 | 31 | 45 |
NO.6 | male | 63 | 173 | 76 | 25 | Hemorrhage | 3 | Left | 23 | 45 | 43 |
NO.7 | male | 58 | 177 | 80 | 26 | Hemorrhage | 71 | Left | 34 | 22 | 51 |
NO.8 | male | 47 | 162 | 60 | 23 | Hemorrhage | 1 | Right | 23 | 28 | 48 |
NO.9 | male | 67 | 167 | 63 | 23 | Hemorrhage | 1 | Right | 33 | 15 | 50 |
Mean±SD | 52.7±10..3 | 23.4±2.7 | 16.0±21.9 | 23.9±6.3 | 31.8±12.7 | 46.8±2.7 | |||||
Notes: BMI, body mass index; FIM-LE, lower extremity Fugl-Meyer Assessment; BBS, Berg balance scale. |
Table 2: The demographic characteristics and clinical assessments of the stroke patients tested.
Participant NO. Item |
NO.1 | NO.2 | NO.3 | NO.4 | NO.5 | NO.6 | NO.7 | NO.8 | NO.9 |
Sitting to standing | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 |
Standing unsupported | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 |
Sitting unsupported | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 |
Standing to sitting | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 |
Transfers | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 |
Standing with eyes closed | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 |
Standing with feet together | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 |
Reaching forward with outstretched arm | 4 | 3 | 3 | 3 | 2 | 3 | 4 | 3 | 3 |
Retrieving object from floor | 4 | 4 | 3 | 4 | 4 | 4 | 4 | 4 | 4 |
Turning to look behind | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 |
Turning 360 degrees | 2 | 2 | 2 | 2 | 2 | 2 | 4 | 2 | 4 |
Placing alternate foot on stool | 3 | 1 | 0 | 3 | 2 | 0 | 4 | 4 | 4 |
Standing with one foot in front | 2 | 2 | 2 | 3 | 2 | 1 | 2 | 2 | 2 |
Standing on one foot | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
Total Score (Maximum = 56) | 48 | 45 | 43 | 48 | 45 | 43 | 51 | 48 | 50 |
Notes: Total scores of 0 to 20 indicate high fall risk, 21 to 40 indicate medium fall risk, and 41 to 56 indicate high fall risk. |
Table 3: The Berg balance scale assessment in stroke patients.
Participant NO. Parameters |
NO.1 | NO.2 | NO.3 | NO.4 | NO.5 | NO.6 | NO.7 | NO.8 | NO.9 |
STABILITY ASSESSMENT | |||||||||
Average COP.X (E.C/E.O) | -9/-6 | 30/26 | -23/-34 | 15/7 | 29/27 | 11/8 | 13/10 | -33/-27 | 23/18 |
Average COP.Y (E.C/E.O) | -6/-11 | -9/-17 | -5/2 | 12/0 | 11/5 | -20/-21 | -13/19 | -15/-7 | 50/44 |
Average F-B Speed (E.C/E.O) (mm/sec.) | 22/9 | 38/17 | 16/9 | 30/12 | 19/15 | 23/10 | 9/10 | 16/8 | 32/14 |
Average M-L Speed (E.C/E.O) (mm/sec.) | 22/12 | 17/9 | 15/10 | 26/13 | 14/13 | 15/10 | 8/9 | 19/11 | 14/7 |
Romberg Test (Ref. 110-250) | |||||||||
E.C/E.O Perimeter Ratio | 197 | 210 | 155 | 229 | 113 | 189 | 89 | 181 | 210 |
E.C/E.O Area Ratio | 191 | 152 | 194 | 333 | 112 | 406 | 71 | 335 | 152 |
PROPRIOCEPTIVE ASSESSMENT | |||||||||
Average Track Error (Left/Right) (%) | 86/159 | 114/49 | 133/183 | 32/42 | 81/49 | 44/45 | 43/40 | 59/98 | 38/69 |
Average Force Variance (Left/Right) (Kg) | 5.5/5.1 | 0.4/2.8 | 4.8/3.7 | 1.3/1.4 | 3.5/2.4 | 3.7/4.8 | 4.1/3.0 | 3.7/3.9 | 2.0/2.3 |
Stability Index (Left/Right) | 2.98/3.38 | 3.11/1.75 | 3.64/3.91 | 1.3/0.12 | 1.9/1.84 | 1.14/1.58 | 1.36/2.22 | 1.72/2.51 | 1.58/7.5 |
LIMITS OF STABILITY (LOS) | |||||||||
Response Time (sec) | 77 | 84 | 113 | 80 | 78 | 86 | 101 | 83 | 86 |
Average of LOS (%) | 28.7 | 29.7 | 11.3 | 42.6 | 38.2 | 70.9 | 40.3 | 41.9 | 47.1 |
Notes: Average COP.X, average of Center of Pressure (COP) on X-axis; Average COP.Y, average of Center of Pressure (COP) on Y-axis; COP, Center of Pressure; E.C, eye closed; E.O, eye open; Average F-B Speed, average speed of forward-backward; Average M-L Speed, average speed of medium-lateral; Ref., reference; The references 110-250 show which is the range of ratio when the patient is healthy. |
Table 4: Static and dynamic instrumental balance evaluations in stroke patients.
Figure 1: Setup for instrumental balance assessment. Please click here to view a larger version of this figure.
Figure 2: Setup for the Stability Assessment Module. (A) The initial position for the stability assessment. (B) The auxiliary testing equipment and the tilting board. (C) The foot position on the tilting board. (D) The control board for the balance assessment system. Please click here to view a larger version of this figure.
Figure 3: Setup for the Proprioceptive Assessment Module. (A) The initial position for the Proprioceptive Assessment. (B) The right foot moves in clockwise circles. (C) The left foot moves in counterclockwise circles. (D) The foot position on the tilting board. (E) The control board for the balance assessment system. Please click here to view a larger version of this figure.
Figure 4: The setup for the Limits of Stability module. (A) The initial position for the Limits of Stability. (B) The patient is leaning the body away from the midline. (C) The control board for the balance assessment system. Please click here to view a larger version of this figure.
Figure 5: Comparing the stability assessments for patient number 4. Eyes open vs. eyes closed. (A) The basic demographic information and results of the main parameters. (B) The tracing trajectory of COP-eyes open (orange) and COP-eyes closed (green). (C) Comparison of eyes open and eyes closed data: backward-forward standard deviation (BF), medium-lateral standard deviation (ML), and area and perimeter (PER). The patient’s results are over the blue arrow. For every result and both tests (closed eyes, opened eyes) the patient's condition can be determined within the ideal (green), healthy (yellow), or warning (red) band. Please click here to view a larger version of this figure.
Figure 6: Comparing the proprioceptive assessments for patient number 4. (A) The basic demographic information and results of the main parameters. (B) The resulting graph of track errors (%) for the left foot (red bar) and right foot (green bar). (C) The resulting graph of force variance (kg) for the left foot (red bar) and right foot (green bar). (D) The tracing trajectory of the left foot (orange line). (E) The tracing trajectory of the right foot (orange line). Please click here to view a larger version of this figure.
Figure 7: The limits of stability for patient number 4. (A) The basic demographic information and the results of the main parameters. (B) The resulting graph of the A1-A8 loss of stability (LOS) and the tracing trajectory (blue lines) from the COG to the A1-A8 squares in eight directions. Please click here to view a larger version of this figure.
Described is a clinical protocol for static and dynamic balance assessment in stroke patients that includes three semiquantitative balance function scale assessments (BBS, TUG, and FMA-LE) and three models of quantitative instrumental balance evaluation (Stability Assessment, Proprioceptive Assessment, and Limit of Stability). The design of this protocol was based on five main points.
First, the BBS is a 14-function-task on a 5-point scale that semiquantitatively assesses static and dynamic balance and the risk of falls through direct observation of a subject's performance21. The global score of the BBS is 56 points, where scores of 0–20 represent balance impairment, 21–40 represent acceptable balance, and 41–56 represent good balance9. The BBS was originally designed to assess balance in community-dwelling elderly individuals21 and became the most commonly used assessment tool in patients with stroke9 due to its relatively low equipment and space requirements, as well as its reliability and validity22. However, the BBS has floor and ceiling effects, suggesting that the BBS might not detect meaningful changes when used to assess patients at either extreme, who have either severe balance impairment or mild impairment23,24. The nine stroke patients that participated in this study had mild balance deficits based on their BBS scores. The subjects achieved the highest score (4/4) in most of the BBS tests, except for the test that requires reaching forward with an outstretched arm (i.e., one patient with a score of 2/4, six patients with 3/4, and 2 patients with 4/4). It might be still hard to develop a personal treatment strategy for these kinds of patients with high balance function based on the BBS assessment. The TUG and FMA-LE showed similar results. The quantitative balance instrument evaluation is superior to these alternatives. For example, all nine stroke patients had BBS assessment scores of more than 40 points, suggesting that all the patients had relatively good balance performance. All nine patients scored the maximum number of points (4/4) in the standing-with-eye-closed test, whereas the Average COP.X (mediolateral axis) and Average COP.Y (anteroposterior axis) in the Stability Assessment Module of the instrumental balance evaluation presented various values, from -33–30 for the Average COP. X (mediolateral axis) and from -20–50 for the Average COP.Y (anteroposterior axis). The report from one of the nine patients also showed three items in the warning band in Figure 5C. Second, the total score of the BBS assessment could be used to predict the fall risk, in which scores of 0–20 indicate high fall risk, 21–40 indicate medium fall risk, and 41–56 indicate low fall risk19. BBS predicts the fall risk by evaluating the patient’s overall balance performance under different tasks. Moreover, the BBS test that requires reaching forward with an outstretched arm is supposed to evaluate the stability limits of the clinical functional reach, although Wernick-Robinson and collaborators25 suggest that the arm displacement test does not fully reflect dynamic balance. In contrast, based on the manual of the instrument used in this study, the Loss of Stability Module parameter describes the maximum angle at which the body can tilt during standing (the maximum forward-backward angle is 12.5° and the maximum medium-lateral angle is 16°), which is an important indicator of the ability to maintain postural stability under static and dynamic conditions, such as during a quiet stance, in response to postural perturbations, or during postural preparation for movements26. The Loss of Stability Module test could provide measures of COG movements as a patient intentionally leans toward various positions in space27. Ikai et al.28 suggest that decreased postural stability is a common problem associated with stroke. In this protocol, the main parameter of the Loss of Stability Module assessment is reaction time. Brown et al.29 demonstrated increased reaction times among stroke patients during various postural tasks, compared to healthy older adults. Moreover, the Loss of Stability Module module in this protocol evaluates the maximal lean of eight objectives around the COP, whereas the BBS assessment evaluates the forward direction alone.
Third, the sensory systems related to balance maintenance (i.e., the proprioceptive, visual, and vestibular systems) play distinct roles. The instrumental balance evaluation also presents advantages for determining the cause of the balance disorder compared to the BBS assessment. In the stability assessment module of this protocol, the eye-closed exam was used to reduce or remove the effects of vision, thereby measuring the other major sensor systems (i.e., proprioception and vestibular systems) related to balance. Moreover, proprioception damage is a common symptom after stroke, and it is also an important factor that restricts the balance of patients with hemiplegia30. The proprioceptive assessment module in this protocol was intended to target this specifically. The purpose of the proprioceptive assessment module is to provide the patient with an objective assessment of the proprioceptive sensitivity of the patient’s foot. This test module not only shows the overall foot sensitivity assessment, but also the sectorial assessment. For example, Figure 6 shows that the ATE of both feet (32% left foot and 42% right foot), whereas the worst performance in the S7 section occurred in the right foot. In addition, stroke affects the coordination of various systems in posture control. The prospective module in this protocol can also be used to indirectly reflect the fine coordination function of lower limbs in stroke patients.
Fourth, the bilateral lower limbs were required for assessment in our instrumental balance assessment protocol for stroke patients, which is different from the BBS assessment. In BBS assessment processing, the choices of which leg to stand on or how far to reach are left to the subject. So, for the patient with hemiplegia after stroke, the BBS assessment score might not accurately present the effect of the hemiplegic side on the balance deficit.
Fifth, the other two clinical balance assessments we used in this protocol are believed to evaluate the clinical general walking ability (TUG) and to assess the motor recovery in stroke patients (FMA-LE)31.
During the instrument balance assessment, two important points about troubleshooting must be pointed out. First, during the tests on the mobile platform the physical therapist should very carefully observe the patient’s perceptual conditions and the movement of the system to avoid accidental injuries. Second, a physical therapist must stand behind the subject to prevent falls during the whole testing process.
This study has some limitations. First, the data represent only nine male stroke patients. However, these nine stroke patients all showed mild balance deficits based on the BBS scales, and this protocol obtained more detailed data, showing the advantages of instrumental balance assessment. More stroke patients with moderate to severe balance deficits must be recruited to investigate the prospects of instrumental balance assessment in future study and therapy. Second, previous studies have shown that both gender and age have effects on balance ability. For example, with age, posture balance decreases, thus increasing the risk of falling down. Furthermore, women are more affected than men32. However, because this study is mainly a methodological demonstration of instrumental balance assessment methods, it only included male subjects and a relatively large age span (37–67 years old). Future research needs to include female subjects and an age hierarchy to expand the clinical application of this assessment. Third, the cost of the balance assessment instrument used in the study is relatively high, which might limit its clinical use, but the study objective is to present the methodology. A large number of less expensive, similar balance assessment instruments based on posturography31 could be obtained for clinical practice.
In conclusion, it is recommended that clinicians consider the use of both classic clinical balance scales and balance instrumental measurement in clinical practice for patients after stroke, which could improve the accuracy of assessment and thereby enhance individualized treatment plans.
The authors have nothing to disclose.
The author thanks graduate student Zhencheng Guan, Wude Chen, Haidong Huang, and Qinyi Li (Guangzhou Medical University) for data collection. This study was supported by the National Natural Science Foundation for Young Scientists of China (Grant No.81902281); General Guidance Project of Guangzhou Health and Family Planning Commission (Grant No.20191A011091 and
No.20201A011108); Science and Technology Innovation Project for College Students in Guangzhou Medical University (Grant No. 2018A053), Guangzhou Key Laboratory Fund (Grant No.201905010004) and Major Industrial Technology Project of Guangzhou Science and Technology Bureau (Grant No.201902020001).
Electric Lifting Bed | Guangzhou Yikang Medical Equipment Industrial Co., Ltd | YK-8000 | Required for Fugl-Meyer assessment |
Percussion hammer | ICARE-MEDICAL Co., Ltd. | CRT-104 | Required for Fugl-Meyer assessment |
Prokin Balance System | Tecnobody .S.r.l, Italy | ProKin 252 | Balance evaluation and training system |
Ruler | M&G Chenguang Stationery Co.,Ltd. | AHT99112 | Required for Berg Balance Scale assessment |
Stopwatch | 95,Shenzhen Junsd Industrial Co., Ltd have been striven all the years de | JS-306 | Required for Berg Balance Scale assessment |
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