Participants
All participants provided written informed consent before participation. This study was approved by the ethics committee of Mashhad University of Medical Sciences (IR.MUMS.FHMPM.REC.1400.079 dated 28th Jan 2022). The trial was registered with the clinical trials site of www.IRCT.ir (IRCT20210730052024N1) on January 28th 2022..
The inclusion criteria included: Ischemic or hemorrhagic stroke patients in the subacute phase (less than 3 months)(4); diagnosed with hemiplegia(13); patients aged between 18–85 years(14); patients with the ability to walk without the help of others with or without assistive devices (mild to moderate impairment)(3); patients with the ability of understanding the therapist's instructions (MMSE score ≥ 24)(15) and adequate fit of patients within the exoskeleton (height between 160 and 190 cm and weight between 50 and 100 kg)(2). The exclusion criteria included: Significant musculoskeletal or neurological disorders(4); flaccid paralysis(16); stroke caused by tumor or infection(2); bilateral involvement or quadriplegia(2); inability to walk before stroke(2); leg spasticity > 3 on Modified Ashworth Scale(2); uncontrolled cardiovascular or respiratory disorders(17); pusher syndrome (i.e., a clinical disorder that causes active pushing away from the non-hemiparetic side in patients with right or left brain damage)(18) and emergence of each exclusion criteria during the implementation of the study.
Apparatus
Exoskeleton used
The FUM-HEXA-IV robot (briefly HEXA) is a lower-limb wearable robot that features a single active hip joint. It was designed and built at the Center of Advanced Rehabilitation and Robotics Researches at Ferdowsi University of XXX (FUM-CARE). The robot structure and its actuation mechanism are optimized to provide a high torque capacity while minimizing weight, ensuring that patients experience optimal comfort and the robot is as efficient as possible (10). The robot weighs approximately 5.5 kg and can generate a maximum torque of 16 N.M. at each hip joint. This is made possible by the use of a 160-watt Maxon EC90 motor and an AG Harmonic Drive gearbox (Fig. 1). The unique feature of this robot is the ability of interaction with the patient which is provided by force sensors, detecting the amount of force generated by the patient and adapting robots movements based on the demands of the treatment protocol.
Clinical outcome measures
6 Minutes Walking Test (6MWT): In 6MWT, the distance covered in 6 minutes in the unit of meter is used as an indicator of evaluating aerobic capacity. The validity and reliability of this test have been confirmed(19).
Timed Up and Go test (TUG): In TUG, the patient who is sitting stands with the therapist's signal, moves 3 meters forward, then turns around and goes back to the chair and sits and the time of this process in the unit of the second is recorded for assessing the balance in different positions. The validity and reliability of this test have been confirmed(19).
Functional Gait Assessment (FGA): This test is a 10-section tool for measuring walking ability, each section is given from 0 to 3 points (minimum 0 and maximum 30 scores). The Persian version of this tool has been validated(20).
Berg Balance Scale (BBS): This test is a performance-based tool to check functional balance and includes 14 balance sections, each section is given from 0 to 4 points (minimum 0 and maximum 56 scores). The Persian version of this tool has been validated(21).
Stroke Specific-Quality Of Life (SS-QOL): This tool is a patient-centered questionnaire that is especially used to evaluate the quality of life of stroke patients. This tool contains 49 sections in different areas related to the quality of life, each section is given from 1 to 5 points (minimum 49 and maximum 245 scores). The Persian version of this questionnaire has been validated(22).
Procedure
All participants were allocated to two intervention (HEXA) and control groups by randomly blocked allocation method with 6 blocks of 4 subjects. Thus, all 6 permutations of 4 were listed in two groups. The permutations included 1-AABB, 2-ABAB, 3-BAAB, 4-BABA, 5-BBAA, 6-ABBA, and A is the symbol of the intervention group and B is the symbol of the control group. Then, from the table of random numbers with a random starting point, 6 numbers between 1 and 6 were randomly selected by a research assistant, blinded to baseline assessment findings, and according to their order, the patients were assigned to two groups. This study was conducted as a single-blinded pilot RCT, and blinding was done in such a way that one physiotherapist did the evaluation and another physiotherapist did the therapeutic intervention. The duration of treatment in both groups of physiotherapy was 12 sessions, in 3 sessions weekly for 4 consecutive weeks. Before the 1st session and after the 12th session, a physiotherapist other than the therapist (to reduce the bias) evaluated the patients in terms of clinical outcome measures. To reduce the learning and fatigue effects, all the evaluations were done randomly, and in the 1st session, the patient was familiarized with the environment and the tests. Finally, in the statistical software, two study groups were coded as codes 1 and 2, and analysis was done.
In both groups, the treatment time for each session was 60 minutes, including the first 30 minutes of electrotherapy and conventional exercises for stroke patients, and then 30 minutes of gait training on the ground. The time required to don and off the robot in the intervention group was not included at this time. Then, in the control group, the patient walked for 30 minutes with the help of the therapist, and in the HEXA group, the patient placed the robot on the body with the help of a therapist and walked for 30 minutes under the supervision of the therapist(11).
Both groups underwent electrotherapy with Functional Electrical Stimulation current (FES) to contract the ankle dorsiflexor for 15 minutes. Stimulation parameters included 40 Hz frequency and 0.3 millisecond pulse duration. The intensity was increased until the patient's tolerance and the on-and-off ratio was 1:1 and according to the comfort of the patient, the same amount of rest was provided for every 5 to 10 seconds of contraction(23).
As conventional exercises, both groups underwent posture and balance control exercises, weight shifting and active and passive stretching of spastic joints and muscles according to the patient's tolerance. They also underwent progressive strengthening exercises for weak muscles of the involved limbs and trunk, each exercise 10 to 15 repetitions and in 2–3 sets. Manual resistance was applied by the therapist according to the participants' capacity(11).
The distance and time of gait training on the ground in the control group were similar to the intervention group, which was done with the help of a therapist and without the assistance of a robot. The physiotherapist reminded the patient through verbal interaction to try to walk as symmetrical as possible(11). The robot help in the intervention group was as follows: In the first 2 sessions, with 100% power, and from the next sessions, if the conditions and the patient's power were suitable, we had a 10% decrease in the robot's help per session with the aim that the patient gains more independence in walking. Whenever the patient needed to rest, the intervention was temporarily stopped and the therapist regularly asked the patient about any pain or discomfort during the exercise. None of the patients in both groups were given any instructions to use their hands while walking, and the patients were free to do so. In both groups, the therapist encouraged the patients to walk as fast as possible and to the extent that their balance was not disturbed. Therefore, by gradually increasing the walking speed according to the patient's comfort, the intensity of the exercise was proportional to the patient's physical performance level(3).
Statistical analysis
Statistical tests were performed using SPSS version 23 with a significant level of p < 0.05. Shapiro-Wilk test was used to check the distribution. To check the presence of significant differences between the two groups, an independent t-test was used for the Body Mass Index (BMI) variable, and the Mann-Whitney test was used for age and mental state variables. To check the presence of significant differences between the two groups, Pearson's chi-squared test was used for the qualitative variables of gender, lesion type, involved side, and hypertension, and the Likelihood ratio test was used for the variable of diabetes.
To analyze the clinical outcomes, a 2×2 Analysis of Variance (ANOVA) with the within-subject factor of time and the between-subject factor of the group was used. Due to the non-normal distribution, the outcome data of 6MWT were first transformed into a logarithm at base 10 and then analyzed with ANOVA. The results of TUG and BBS, which had normal distribution in one group and non-normal distribution in the other group, were analyzed with both ANOVA without logarithmic transformation and ANOVA after logarithmic transformation. Since the results were the same, for the sake of brevity, only the results of ANOVA without logarithmic transformation were provided (24).