A cross-sectional study was designed to compare the static as well as dynamic balance, balance confidence, ankle proprioception, and passive ROM between 2 groups of patients with the high and low levels of ankle plantar flexor spasticity after stroke.

The measurements were be taken at the Biomechanics and Analysis of Human Motion Laboratory, School of Rehabilitation, Tehran University of Medical Sciences in Iran.

The study protocol was approved by the Review Board, School of Rehabilitation, Tehran University of Medical Sciences and the Ethics Committee of Tehran University of Medical Sciences (Reference number: IR.TUMS.FNM.REC.1397.012).

All eligible participants provided a written formal consent after receiving information about the research procedure. We explained the study details to participants before taking the measurements.

Participants with stroke were recruited from the neurology and physiotherapy clinics in Tehran, Iran. Participants were screened for eligibility. The patients were divided into 2 groups based on their level of ankle plantar flexor spasticity according to the Modified Modified Ashworth Scale (MMAS): high spasticity (MMAS score≥2) and low spasticity (MMAS score<2).

The inclusion criteria were as follows: first-ever unilateral stroke (hemorrhagic/ischemic), ankle plantar flexor spasticity≥1 based on the MMAS, walking ability, no fixed contracture in the ankle, independent standing with eyes open/closed, ability to understand and follow the commands, and no pain in the lower limbs. Participants with vision problems or depression as well as those taking antispastic medications or undergoing a rehabilitation program focused on balance and proprioception were excluded.

The physiotherapy and neurology clinics in Tehran were contacted for referring the patients with stroke who were willing to participate in the study. The principal investigator and physiotherapist responsible for assessing the patients and performing the experiments called the heads of these clinics to request cooperation and to describe the eligibility criteria. Moreover, the study aims and eligibility criteria for inclusion of patients were provided in the written form to the heads of the clinics.

Considering the data from the previous study [16], the sample size was estimated to be 28 (n=14 in each group; Z_α=1.96; α=.05; Z_β=.842; standard effect size=1.067).

The patients were interviewed to collect demographic data, including age, gender, height, weight, time since the onset of stroke, etiology (ie, ischemic or hemorrhagic), and the affected side. Patients were assigned to one of the following groups: high spasticity (MMAS score≥2) and low spasticity (MMAS score<2). The severity of ankle plantar flexor spasticity was measured after making the patients rest in bed for 5 minutes in supine position with their shoes taken off [19]. Subsequently, the Activities-Specific Balance Confidence (ABC) questionnaire [20] was administered, followed by the measurements of affected ankle proprioception, passive ROM, posturography, and Timed Up and Go (TUG) test (Figure 1). An experienced physiotherapist performed all the tests.

The primary outcome measures were the MMAS scores, ABC questionnaire, posturography measures in open- and closed-eyes conditions, and TUG test. The secondary outcome measures were the ankle passive ROM and ankle joint proprioception. Table 1 summarizes the outcomes and how they were measured in the study.

The affected ankle plantar flexor spasticity was assessed by an experienced physiotherapist using the reliable and valid MMAS [21,22]. To assess the spasticity severity, the physiotherapist stood on the affected side, stabilized the affected ankle with one hand, and moved it from maximum possible plantar flexion to maximum possible dorsiflexion, counting to 1001 [23]. The definitions of spasticity grades of MMAS are presented in Table 2.

The ABC questionnaire, which is reliable and valid, was used to assess the balance confidence of patients with stroke in performing their daily activities [20,24]. The ABC questionnaire included 16 questions asking the subjects to score their confidence from 0% (no confidence) to 100% (complete confidence). To calculate the total score in percent, the following formula was used: (total score/16)×100.

The static balance of patients was evaluated by posturography. The use of force plate in balance measurement of the patients with stroke has been demonstrated [25]. The physiotherapist asked each patient to stand on the force plate with bare feet, heels apart by 9 cm and at 30° angle, and upper limbs comfortably along the body. The patients were asked to look at a point on the wall at a distance of 2 m during the test with eyes open as well as with eyes closed. Open- or closed-eyes condition was randomly applied with 2-minute rest interval between the conditions. Each condition was repeated 3 times (with a 20-second interval), and the duration of each repetition was 20 seconds. Velocity (in centimeters per second) and the anteroposterior and mediolateral displacements (in centimeters) were recorded 3 times, and an average was calculated [25].

Dynamic balance of patients was measured by TUG Test, which has been proven reliable in patients with stroke [26]. The patient was asked to sit comfortably on the chair with feet resting on the floor. Then the patient was asked to get up from the chair, walk a 3-meter distance, turn around, go back to the same chair, and sit down. The time in seconds was recorded using a stopwatch from the moment the patient got up from the chair to the moment he or she sat back on the chair.

The ankle passive ROM in degree was measured in the supine position with knee extended using a standard goniometer. Axis of the goniometer was located on the lateral malleolus; the stable arm, along the head of the fibula; and the moving arm, along the fifth metatarsal. The physiotherapist stabilized the affected leg by one hand and moved ankle passively to maximum possible dorsiflexion by the other hand [27].

The ankle joint proprioception was measured with the patient sitting on the edge of bed with eyes closed. The electrogoniometer was connected to the longitudinal axis of the tibia and the fifth metatarsal. The physiotherapist slowly and randomly moved the ankle to one of the following angles: 5° plantar flexion, 15° plantar flexion, or 15° dorsiflexion angles. The examiner then held the ankle in that position for 5 seconds and asked the patient to note the ankle position. The ankle was moved passively to the starting position. The ankle was moved again to the desired position, and the patient was asked to report the position. The difference between the starting and the patient-reported position was recorded as an error value. These steps were repeated for 3 times, and the average error (in degree) over those 3 repetitions was considered as a reconstruction error of that angle [28]. The same procedure was performed for all angles with 1-minute rest interval, and the average error was recorded for each angle.

SPSS version 22 (SPSS Inc) was used for the data analysis. The normal distribution was analyzed using the Shapiro-Wilk test. The t test was used to examine the differences between 2 groups. Mixed model univariate analysis of variance (ANOVA) was used to analyze the effect of spasticity level of ankle plantar flexor muscles on the postural sway indicators in open- and closed-eyes conditions. The relationship between the severity of spasticity with the ABC scores, ankle proprioception, passive ROM, and TUG test were analyzed with Spearman rank correlation. The statistical significance was defined at α<.05.