Design
This study was performed as a double blind controlled clinical trial with parallel groups on patients admitted to the ICUs of academic-healthcare hospitals affiliated to the Kermanshah University of Medical Sciences in 2016. This study was approved by the ethics committee of this university and registered in the Iranian Clinical Trial Center with the code IRCT2017010814333N64.
Participants
The inclusion criteria included hospitalization in the ICU ward for more than 1 week, age between 18 and 60 years, patients who were not able to move their legs voluntarily (unconscious patients and those who were not able to move their lower limbs due to paralysis), agreement to sign the written consent form by the patient or his or her guardian (in case of unconsciousness), lack of disease or musculoskeletal disorder according to a physical examination, lack of damage inside or around the ankle, no history of treatment by electrical stimulation in the ankle zone, no skin disease hindering placement of electrodes or causing sensitivity to electrical stimulation, absence of electrical implant devices (such as pacemaker), and lack of sever spasticity that prevented joint movement. However, the exclusion criteria included skin sensitivity to stimulating electrodes, TENS intolerance and acquiring the ability to move the lower limbs voluntarily during the interventions.
The patients were chosen using the convenience sampling method. Thereafter, they were assigned into two groups (experimental and control groups) with a block size of two through a permuted block random sampling method by a statistical expert not involved in data collection (allocation concealment). The sample size was estimated to be at least 18 patents in each group according to a study by Oo [15] considering the mean ± SD for composite spasticity score as the key variable, confidence interval of 95% and power of 80%. At the beginning of the study, the objective and method of study implementation were explained to the patients or their companions. Also, written consent was taken from them and then the demographic information (age and gender) questionnaire was completed with the help of information from the patients’ file.
Outcome measures
The first outcome measurement in this study was passive ankle range of motion along the plantar flexion and dorsiflexion directions. The ankle’s range of motions was measured using an international manual goniometer device. Compared to radiography, the measurement of a joint angle with the goniometer has a high level of accuracy [16]. It has been claimed that measuring a joint angle with a universal goniometer has moderate to excellent reliability [17]. Therefore, it can be used as a repeatable instrument for measuring the range of motion of human joints.
To measure the range of motions, the patient was placed in a supine position, with absolutely no deviation to right or left in the hip joint (Fig. 1). The measurement technique is described in similar studies [18].
Ankle joint ROM measurement was done bilaterally and the mean value was considered for calculation. One independent assessor who was not the person who applied the stretches, travelled to all three sites and did all ankle measurements.
Interventions
In the control group, when the patient was in supine position with a straight knee, the therapist dorsiflexed the patient’s ankle by applying gentle pressure. Keeping the exertion of the same force but with two degrees less of dorsiflexion, he/she maintained the stretching (Fig. 2) [19]. The stretch was performed for 10 min in each session. For this purpose, there were five 2-min stretches with 1 min of rest between every two stretches. A therapist who had been trained by an experienced physiotherapist applied the ankle stretches for all patients. He tried to keep the applying force equal for different joints.
In the experimental group (TENS along with stretch), before performing the stretching, TENS was used. First, the skin of the ankle region was cleaned using cotton smeared with 70% alcohol to decrease the skin resistance. Next, two electrodes (4*4 cm) were placed on both sides of the ankles. Finally, the TENS stimulations were applied for 30 min at a frequency of 100 Hz, duration of 0.2 ms, and intensity of 15 mA [15, 20, 21]. The electrical stimulation was applied using the ES-320 stimulator (ITO, Japan). Among the TENS mechanism is the activation of nerve impulse in a large number of alpha afferent nerve roots, resulting in the excitation of inhibitory neurons of the dorsal horn or the release of endorphin or both [14]. Further, TENS enhances blood circulation close to the electrodes, which indirectly contributes to regeneration, reduction of spasm and contracture, and relaxation of muscles [14]. The TENS mechanism in mitigating spasticity and contracture of ankle can be due to the excitation of afferent fibers in the peroneal nerve [15].
Increased blood circulation close to the electrodes is also effective in reducing ankle contracture. As there is no need for active participation by the patient in TENS application, it can be used by people who have not been able to perform physical activity for a long time. They can benefit from TENS thanks to its safety and low complications as well as convenience [22].
The interventions of both groups were done three times a week for 2 weeks. The therapist who performed the interventions were not informed about the participants groups. In the first session, the interventions (ankle stretching or TENS stimulation) were explained for patients (or their relatives in case of unawareness).
Data analysis
Data analyses were conducted by SPSS 21.0 (SPSS Inc., Chicago, IL) and P values of < 0.05 were set at level of significance. Frequency (percent) and mean (standard deviation) were used to summarize the accumulated data. The comparisons of background variables including demographic variables and clinical parameters were investigated between the experimental and control groups using the t-test and the chi-squared test.
Normality was confirmed for all ankle range of motion parameters by the Kolmogorov–Smirnov one-sample test. The within-group differences in time trend for each group was assessed by repeated measures analysis of variance. For this test, assumption of the sphericity (consistency of correlations) was not confirmed by Mauchly’s test. Therefore, P values were stated based on the Greenhouse–Geisser test in both groups.
Additionally, the basic measurements of the ankle range of motion parameters were adjusted as covariate and differences between groups from baseline to weeks 1 and 2 were assessed by analysis of covariance (ANCOVA).