Abstract
BACKGROUND:
Injury to the spinal cord results in standing balance impairment following variable sensorimotor loss. Standing balance training is a realistic goal for the majority of individuals with spinal cord injury (SCI) for which therapists need valid measures to assess standing ability in people with SCI that are relevant to functionality.
Objective:
The objective of the study was to develop an all inclusive Standing Balance Assessment for Individuals with Spinal Cord Injury (SBASCI) measure and to establish its initial psychometric properties.
Methods:
The study was carried out in three phases: Item development, scale development and scale evaluation. Literature review, focus group discussions and evaluation by experts resulted in the development of a 22-item SBASCI scale. The scale was administered on 120 participants with SCI. Exploratory factor analysis and item analysis were used to determine construct validity and internal consistency of the scale.
Results:
Content validity was established qualitatively and quantitatively. The scale shows high internal consistency reliability (Cronbach’s alpha 0.96). The results of the exploratory factor analysis suggested a four factor structure retaining all the 22 items.
Conclusion:
SBASCI is a valid and reliable scale to measure the standing balance of individuals with SCI. Further studies are required to establish other psychometric properties.
Introduction
Injury to the spinal cord resulting in paralysis of muscles of the lower extremity and impairment of standing and walking affects the quality of life to a great extent (Dumont et al., 2001). Often one of the frequently asked questions by an individual after a spinal cord injury (SCI) is “when will I walk again.” Rehabilitation professionals include gait training as one of the major objectives to cater to the patients’ needs but standing might be a more realistic goal than walking for the majority of individuals with SCI (Jaegar et al., 1989). Standing for either functional or therapeutic effects is the first requirement before being able to walk and is a necessary component to achieve many tasks (Jaegar et al., 1989). Standing is commonly thought to confer a number of benefits for the individual. The postulated benefits include prevention of contractures in lower limbs, minimization of osteoporosis, stimulation of circulation, reduction of spasticity and improvement in the renal function (Jaegar et al., 1989).
Balance is the ability to maintain equilibrium by positioning the centre of gravity over base of support and it changes according to the positions and movements of the body segments (Lee et al., 2012). Balance is regulated and integrated by information from the somatosensory, visual and vestibular systems and by the reflexive control of limbs. The spinal cord is a pathway for the somatosensory organs (Lee et al., 2012). The balance of people with spinal cord injuries seems to be affected by the impairment of proprioception and motor function after damage to the central nervous system. Balance is very important to maintain a sitting position and to move from a sitting to standing position. Improving standing balance and weight bearing regulation is vital to improve walking ability (Lee et al., 2012).
Approximately 80% of patients with incomplete SCI can regain ambulatory ability with a well-designed rehabilitation program. However, the majority of patients require a walking device to stand and conduct daily activities, which requires standing balance assessment and training (Poncumhak et al., 2014). To recover this function after SCI, the ability to stand supported or unsupported requires the coordinated use of the whole body, the lower limbs, the trunk, the arms, and the head along with inputs from the sensory systems (Day et al., 2012; Middleton et al., 1999). Therefore, therapists spend a considerable time on balance assessment and eventually design particular balance training programs for the patients with SCI while utilizing walking aids and orthoses dependent on the level of injury (Huxham et al., 2001).
The assessment of standing balance includes a variety of different techniques: functional assessments, posturography and force platforms (Mancini et al., 2010). Standardized tests of balance are available to allow health care professionals to assess an individual’s postural control after SCI such as Romberg Test, Functional Reach Test (FRT), Performance-Oriented Mobility Assessment (POMA), Berg Balance Scale (BBS), and Mini-Balance Evaluation Systems Test (Mini-BESTest) (Di Carlo et al., 2010). BBS and FRT are valid and reliable in the SCI population; however, Mini-BESTest is the most comprehensive measure in the assessment of population with SCI (Arora et al., 2020). Although the BBS is reported to be the most commonly used test in this population, there are a few items which are not suited for subjects of SCI using orthoses such as standing on one leg and picking up an object from the floor. BBS has been widely used and recommended for individuals with AIS C & D and cannot be applied for AIS A & B subjects (Lemay et al., 2010). Also, it shows ceiling effects and does not permit the use of assistive devices. Thus, researchers cautioned that the BBS should be used in conjunction with walking tests when assessing a patient for an appropriate assistive device use (Lemay et al., 2010). Authors recommended Mini-BESTest over BBS as no ceiling effect was observed. But the test has only been assessed in AIS D individuals who have the highest functional level in the SCI population. The authors also stressed the need for further validation (Lemay et al., 2013).
To date no comprehensive standing balance measure has been validated for this group, as they have varying levels of standing abilities and balance even though this dimension is crucial for improving quality of life (Jørgensen et al., 2011). There is a need for reliable, valid and cost-effective tests to comprehensively assess standing ability in people with SCI, which encompass a range of tasks that have relevance to ADLs.
The aim of this study was to develop a measure for the assessment of standing balance and to determine its validity and reliability in individuals with SCI.
Methods
This study was approved by the research review committee and the institution’s ethics committee of the Amity University Uttar Pradesh and Indian Spinal Injuries Centre, Delhi, India. We performed the study in multiple phases: Item development, scale development and scale evaluation (Boateng et al., 2018). 120 participants with SCI were included in the present study for assessment and validation of the scale.
Item development phase
The most essential step (step 1) of the item development phase was to elucidate the main objective of the scale as well as the selection of the desired patients for which it is developed and validated. Hence, the new scale was designed and validated to measure standing balance in individuals affected by spinal cord injury. The scale was named Standing Balance Assessment for Spinal Cord Injury (SBASCI) so that it would clearly reflect its purpose.
Step 1 was followed by the generation of items (step 2) through understanding of the review of literature pertaining to various aspects of balance, types of balance control, functional activities requiring good balance control, impairment of balance in SCI, factors affecting balance in normal individuals in SCI, and existing instruments used to measure balance in SCI along with their limitations. Focus groups and discussions with experts (therapists and members of the target population) were carried out. The therapists were rehabilitation professionals with clinical experience of at least two years in training individuals with SCI. The target population was SCI individuals who underwent standing training with various orthoses.
For the item generation, both deductive (literature review) and inductive (focus groups and discussions) approaches were used. As a result, a first draft of the scale was developed containing 16 factors determining standing balance in SCI and were mailed to therapists/SCI experts for review. The participants were asked if they considered the following factors important to assess standing balance: Posture in standing, standing with upper limb position changes such as forwards,, upwards, backwards, sit to stand with appropriate orthoses, stand to sit with appropriate orthoses, pushups in parallel bars, standing with varying positions of the foot such as forwards, backwards,, turning 180 degrees, lower extremity motor score, upper extremity strength, completeness of SCI, neurological level of injury, spasticity in lower limb muscles and any other factors which they considered a significant contributor for standing balance along with the activities/positions/situation that challenges standing balance.
The responses of 18 therapists and seven individuals with SCI were received. The responses were interpreted. All the responses were noted down and laid down in tabular form to interpret the comments from experts.
This led to the development of the second draft of the scale with 26 items generated with instructions. 16 rehabilitation professionals were interviewed (step 3) regarding the clarity of the instructions, appropriateness, possible gradations for each item and rank order of items. Preliminary testing of items (step 4) was done on 10 participants in terms of the clarity of instructions and appropriateness. Based on these responses as well as a literature review, the third draft of the scale was developed.
Scale development phase
The third draft of the scale consisting of 24 items was developed with guidelines and detailed instructions. Performance categories and scoring boundaries were established on the basis of feedback.
Content validity ratio (CVR):
where ne is the number of panellists/experts indicating “essential” and N is the total number of panellists/experts.
The CVR was calculated for each item in the scale and as per Lawsche a minimum of 0.49 was required to satisfy the five percent level of significance, which formed the cutoff for retaining the item. This led to the modification/deletion of three items and the development of the final version of SBASCI containing 22 items.
The developed SBASCI sca;e is a performance-based ordinal scale that includes 22 items. Each item has a score ranging from 0–4 with 0 indicating the lowest level of function and 4 indicating the highest level of function. Each item has a maximum score of four indicating the subject’s ability to perform the activity independently (based either on time constraints, requirement of physical assistance or distance/range required) and a minimum score of zero indicating inability to do the activity. The minimum and maximum score of SBASCI is 0 and 88 respectively. The equipment required for the administration of the SBASCI is one standard chair, parallel bars/walker/crutches/canes, lower limb orthoses used by the individual (KAFO, AFO, gaiters/knee immobilizers), a measuring tape, a stopwatch and a foot stool. These equipments are generally easily available in any clinical setting. The time taken to administer all items of the SBASCI ranged from 15–20 min.
The pilot study (step 6) was performed on 10 individuals with SCI (at different spectrum of recovery) to test the feasibility and safety of scale administration.
Scale evaluation phase
This phase comprised of establishing internal consistency reliability and construct validity of the newly developed scale (step 7). The study design used for this phase was a methodological study design with a sample size of 120 subjects (both male and female).
Inclusion criteria
(1) Age 16–60 years; (2) Ability to understand spoken English; (3) C7–L5 level of spinal injury; (4) Traumatic and non-progressive spinal cord injury; (5) Severity of spinal injury (varying degrees of incomplete to complete sensorimotor loss); (6) Ability to stand for at least for 10 seconds with assistive devices (with appropriate orthoses and/or physical assistance).
Exclusion criteria
(1) Inability to follow two step commands; (2) Any neurological, cardiovascular, or orthopedic problem limiting the spinal weight bearing and excursion; (3) Any other concomitant neurological conditions in addition to SCI.
Procedure
SBASCI was administered on 120 participants with SCI. Baseline information regarding name, age, gender, time since injury, neurological level of lesion, AIS grades, assistive devices used, lower limb orthoses and duration of standing training rehabilitation were noted. Written informed consent was taken from all participants prior to participation in the study. The participants were asked to perform the items of the scale, and the score sheet was filled in accordingly.
The following psychometric properties of the scale were tested: (1) Construct Validity; (2) Inter-item correlations and item-scale correlation and analysis of internal consistency reliability.
Results
The results of each phase of the study are summarized separately. All study results were generated using Statistical Analysis System (SAS) software version 9.4. The significance level was set at p≤0.05.
Item development phase
During this phase, a thorough review of the related literature and focus group discussions and interviews as well as preliminary testing on patients led to the development of a pool of appropriate items for the initial draft of the scale.
Scale development phase
To determine the content validity of SBASCI, a minimum CVR of 0.49 was required for the items to satisfy the five percent level of significance, as the number of experts included in the panel was 15. Hence, three items with a CVR less than 0.49 were removed from the initial 26-item scale, resulting in the 22-item scale. The items related to ‘standing with weights’, ‘function mimicking activity with one hand support’, ‘function mimicking activity with both hands support’ were removed in the third draft. The ‘standing with arms raised forward/’ item was split into two separate items as ‘standing with arms raised forwards’ and ‘standing with arms raised ’ based on the comments given by the experts on reviewing the scale qualitatively. CVR values of the 22 items were more than 0.49, and they were thus all retained. The content validity index was computed for the whole scale by calculating the mean of the CVR values of the retained items, which was found to be 0.94 (Lawshe, 1975).
Scale evaluation phase
Descriptive statistics were used to analyze the demographic characteristics of participants (mean, standard deviation (SD) and counts percentage). In Table 1, the associated SBASCI scores (mean, SD) are shown per neurological level of injury, AIS grades, walking aids and orthoses. The overall mean item score is 43.0 for the 120 subjects with a range varying from 2–88. The mean of the score for a sample (N = 120) of 22 items of the scale ranged from 0.5 to 3.7 (Table 2).
Baseline characteristics of the study sample (N = 120)
Baseline characteristics of the study sample (N = 120)
Mean (SD) of scores and median score of items of SBASCI for subjects, N = 120
The analysis was performed in a systematic manner to understand the factors. Kaiser-Meyer-Olkin (KMO) measure of sampling adequacy and Bartlett’s Test value of sphericity were determined and found to be adequate to extract common factors. We achieved a KMO value of 0.887 indicating adequacy of the sample size of 120 as it overcomes more than 70% of cutoff (Raykov et al., 2011). The test of sphericity by the Bartlett test generated a chi-square value of approximately 3643.0058 on a level of statistical significance p < 0.05.
The scree plot (Fig. 1) proceeds to a graphical interpretation of all eigen values and helped us to determine the number of essential factors required for the factorial axes. According to the plot we identified that there are four factors that determined more than 81% of variance as suggested by the proportion of variance on factors components (Fig. 1). Exploratory factor analysis (extracted from principal component analysis) of 22 items yielded four domains with eigenvalue >1 that accounted for more than 81% of variance of the data. After applying maximum likelihood with four domains and orthogonal varimax rotation, all 22 items loaded >0.4 in four domains. These domains were upper body dynamic standing balance, lower body dynamic standing balance, complex standing balance and static standing balance with variance 33%, 35%, 17% and 13%, respectively.
Scree plot/variance estimation for construct validity.
Inter-item correlation was calculated for all 22 items (Table 3). The correlation diagonal matrix was generated for all 22 items with Cronbach’s alpha values (Allen et al., 2008). The inter-item correlation is the Pearson’s correlation coefficient (r) computed for a pair of items. The standardized alpha coefficient for 22 items is 0.962, suggesting that the items have relatively high internal consistency. As a result of the internal consistency of the scale, Cronbach’s α statistics for the four factors ranged between 0.78 to 0.98 which demonstrated competent level of the reliability (Table 4).
Inter-item correlation matrix of SBASCI items
Inter-item correlation matrix of SBASCI items
Cronbach’s alpha coefficients of SBASCI and its domains
This study aimed to develop and validate a new scale named the Standing Balance Assessment for Spinal Cord Injury (SBASCI) for the assessment of standing balance in persons with spinal cord injury (SCI). The scale has shown satisfactory psychometric properties of validity and reliability. Content validity was established by a panel of experts. Construct validity was assessed by exploratory factor analysis (EFA) which identified a four factor structure. Also, internal consistency reliability was high with Cronbach’s alpha of 0.96.
There are numerous balance scales recommended by many authors to be utilized for assessment of balance in individuals with SCI (Arora et al., 2020). However, none of these scales mention the use of orthoses, walking frames and severity of spinal cord lesion while assessing balance in this group. The SBASCI scale is the first of its kind which is developed specifically for individuals with a spinal cord injury with varying levels of standing abilities and balance. Standing balance of individuals with spinal cord injuries has been either assessed by force plates and EMG surface electrodes which are very expensive to use in clinical settings or by other clinical scales which do not consider the significance of requirement of orthosis and walking frames to achieve standing. That led to the need and development of a standing balance scale exclusively for the SCI population with varying levels of neurological lesions and severity of injuries.
SBASCI measures a number of components considered to be essential when measuring standing balance. SBASCI includes the components of static, complex, upper body and lower body dynamic standing balance to assess various aspects of standing balance.
According to Sibley et al., out of 66 tests to assess standing balance, only two measures, the Berg Balance Scale (BBS) and Mini-BESTest, reached the consensus to be used to evaluate balance (Sibley et al. 2015). However, as reported in the same paper, BBS does not measure a few components of balance which are important factors to avoid falls. Secondly, the Mini-BESTest measures maximum components of postural control except functional stability limits (Sibley et al. 2015). According to the theoretical framework at present to assess the construct of balance, there are broadly six domains in the systems framework for postural control and each of these domains should be evaluated to comprehensively assess balance (Sibley et al. 2015; Horak et al., 2009). The newly developed SBASCI is a comprehensive instrument which includes all domains of the systems framework:
Furthermore, the scores of SBASCI improve as per the status in AIS grades, neurological level and orthoses use (Table 1). This indicates the application and relevance of SBASCI in the SCI population and changes in scores as per the changes in functional status of the individual. None of the previous scales showed this kind of applicability in this population.
Clinical relevance
As the rehabilitation for a person with SCI progresses from acute to chronic stage, there is a gradual improvement in the sensorimotor function along with the use of orthosis for standing progressing from the O-frame to parallel bars to walker to crutches and canes. But there is no clinical tool which can assess the patient’s abilities on these domains of standing so as to give a clear understanding of the person’s improvement on standing which will ultimately prepare the individual for gait training. However, the SBASCI is a tool in which the score improves with the improvement of sensorimotor function and the use of orthosis thus shows hierarchy as per the level of spinal cord injury.
Future studies
Inter-rater and test-retest reliability need to be assessed, and floor and ceiling effects need to be determined.
Conclusion
The Standing Balance Assessment for Spinal Cord Injury is a newly developed and validated clinical tool exclusively for individuals with SCI that will assess standing balance function of this population in various domains and will also show an improvement in score as per the level of injury and severity of injury.
Conflict of interest
The Standing Balance Assessment for Spinal Cord Injury scale is registered as a copyright work with the Government of India under registration no. L-85102/2019. However, the authors did not receive any compensation for the scale.
Funding
The study was self-funded.
Footnotes
Acknowledgments
The authors are grateful to all participants who volunteered for the study.