11 June 2022: Clinical Research
Efficacy of Focused Extracorporeal Shock Wave Therapy in Chronic Low Back Pain: A Prospective Randomized 3-Month Follow-Up StudyKatarzyna Rajfur1ABDEF, Joanna Rajfur1ABDEF, Tomasz Matusz1ABF, Karolina Walewicz1ABD, Robert Dymarek2ABDEFG*, Kuba Ptaszkowski 3ABCD, Jakub Taradaj4ACDEFG
Med Sci Monit 2022; 28:e936614
BACKGROUND: Extracorporeal shock wave therapy (ESWT) is a modern physiotherapeutic method that is useful for treating musculoskeletal conditions. There are still limited data from well-designed studies evaluating the clinical efficiency of ESWT in low back pain (LBP). Therefore, this study aimed to assess the effectiveness of the focused ESWT (fESWT) in reducing pain and improving the functional status of patients with chronic LBP.
MATERIAL AND METHODS: The study involved 40 patients with L5-S1 discopathy with chronic LBP pain who were randomized into 2 groups: group A (n=20, mean age of 42.3±13.1 years) and group B (n=20, mean age of 45.4±14 years). Group A was an experimental group treated with an fESWT at the lumbar and sacral spine (0.15 mJ/mm², 1000 pulses, 4 Hz). Group B was a control group, treated with a sham fESWT. The treatment protocol in both groups included identical stabilization training (45 minutes, once a day, 5 days a week). Study outcomes included subjective pain with a visual analog scale (VAS) and Laitinen Pain Scale (LPS), and functional status using the Oswestry Disability Index (ODI). Measurements were made before and after treatments, as well as follow-up observations at 1 and 3 months following ESWT. The study was prospectively registered at the ISRCTN registry platform (no. ISRCTN13785224).
RESULTS: There was a significant analgesic effect (VAS and LPS) in both groups; however, it was significantly greater in the experimental group compared to the sham group (P<0.05). A more significant decrease in the perceived pain (VAS and LPS) was observed immediately after the active fESWT therapy. In follow-up observations (after 1 and 3 months), there were no significant between-group differences (P>0.05). Also, there was a significant effect in terms of functional state (ODI) for both groups (P<0.05); however, between-group comparisons revealed no statistically significant differences (P>0.05).
CONCLUSIONS: Focused ESWT with an exercise program can be effective in patients with chronic LBP. ESWT allows reducing pain, although it does not seem to significantly improve a patient’s functional state.
Keywords: chronic pain, Extracorporeal Shockwave Therapy, functional status, Low Back Pain, Physical Therapy Modalities, Randomized controlled trial
Extracorporeal shock wave (ESWT) is a modern physiotherapeutic method which is useful for musculoskeletal conditions. Despite some evidence from recent systematic reviews, meta-analyses [1–4], and the Cochrane recommendations , there are still inconclusive results on ESWT. Moreover, the literature on ESWT in low back pain (LBP) treatment in the Web of Science Core Collection, PubMed, and MEDLINE databases is limited. There are only 6 randomized clinical trials (RCTs) showing the effect of ESWT on LBP [6–11] that went through methodological quality analysis using the Physiotherapy Evidence Database (PEDro) score (Table 1). Based on objective data, levels of methodological quality of these randomized clinical trials vary from medium to low. Furthermore, most studies did not meet the essential criteria of Evidence-Based Physiotherapy (no Cochrane recommendation and PEDro indexation), suggesting that this topic still requires in-depth investigation. Therefore, in practice, it is not easy to objectively analyze the clinical effectiveness of such procedures, together with precise recommendations regarding doses, treatment parameters, duration of the procedure, and other relevant aspects of the treatment protocol. For example, it is unclear how to evaluate radial vs focused techniques.
The radial method (rESWT) is based on pneumatic technology, using the principle of accelerated cartridge impact by compressed air under high pressure. In this way, the shock wave penetrates the body with a radiated beam, and its energy decreases with the depth of penetration. The pulse lasts a maximum of 5 ms, and the pressure reached by the wave does not exceed 1 MPa . The focused technique (fESWT) is characterized by a stronger stimulus, having a more intense effect on the tissues. Unlike the radial method, the focused technique uses electroacoustic technology. Under the influence of high voltage, an acoustic shock wave is created in the applicator, forming a focused stimulus using a special lens. This stimulus with special coupling attachments is introduced into the patient’s body at an appropriate depth, at the assumed pressure of up to 100 MPa, and the pulse duration up to 0.2 μs [13,14].
In 2020, our research team published clinical data on radial ESWT in treating patients with chronic LBP  that had the methodologically highest level (9/10 points) according to PEDro score. Our results showed that the ESWT technique might be especially used in maintaining remission of symptoms and preventing recurrence of disease. Therefore, our team has decided to examine an fESWT, which theoretically might have greater technological possibilities than the radial technique. Thus, the study aimed to assess the effectiveness of focused ESWT in reducing pain intensity and improving functional efficiency in patients with chronic LBP.
Material and Methods
The research was carried out in the Clinical Research Laboratory of the Institute of Health Sciences of the University of Opole. The study was conducted in cooperation with the Department of Physiotherapy of the Wrocław Medical University in Poland. The local and independent Bioethics Committee of the University of Opole approved the study protocol (no. KB/90/FI/2018). The study was prospectively registered at the International Standard Randomized Controlled Trial Number (ISRCTN) registry database (no. ISRCTN13785224). Each participant provided their written informed consent prior to the study. The studies were conducted in accordance with the Helsinki Declaration and Good Clinical Practice guidelines.
RANDOMIZATION AND BLINDING:
Patients were selected for this randomized and single-blinded project by an internist, radiologist, neurologist, neurosurgeon, orthopedist, and physiotherapist. After a positive qualifying procedure, participants were randomly assigned to real or sham ESWT treatments using a computer random number generator (
Patients with L5-S1 discopathy, chronic pain, and no spinal surgical intervention were qualified. The participants were of legal age and had current magnetic resonance imaging (MRI) scans confirming the LBP syndrome – type 3 changes in section L5-S1 according to Modic classification (MC), which describes vertebral endplate lesions.
The exclusion criteria were: discopathy beyond the L5-S1 (MC type 1 and 2), no pain and reduced mobility in the lumbosacral segment, other spinal conditions (fractures, tumors, spondylolisthesis, rheumatic diseases, cauda equina syndrome), pregnancy or ovulation, neurological deficits, implanted cardiac pacemaker, blood coagulation disorders, metal implants within the application site, sensory disturbances, mental disorders, cancer, skin lesions within the treatment site, viral and bacterial infections, painkillers, and anti-inflammatory drugs.
The study involved 40 patients with L5-S1 discopathy of the spine with chronic pain lasting at least 12 weeks. Patients were randomized into 2 groups: group A (n=20) with a mean age of 42.3±13.1 years and group B (n=20) with a mean age of 45.4±14 years. The groups were homogeneous regarding demographic characteristics (Table 2) and initial pain and functional status assessments. Following the Consolidated Standards of Reporting Trials (CONSORT) guidelines for registered randomized clinical trials, the patient flow over the entire period of the study is shown in Figure 1. In both groups, all participants completed treatment. All patients were assessed 1 month later and 3 months after the end of the study. It should be noted that 1 person in group A (business trip at the time of taking the measurements) and 2 people in group B (taking painkillers) were excluded from the statistical analysis.
TREATMENT: Group A was an experimental group treated with an fESWT shockwave using the Duolith SD1 Tower device (Storz Medical, Switzerland; Figures 2, 3). Each procedure was performed using the contact method at the lumbar and sacral spine level in the area of greatest pain indicated by the patient (Figure 4). The following parameters were used for the therapy: energy flux density 0.15 mJ/mm2 (1000 pulses), frequency 4 Hz. An ultrasound gel was used as a coupling substance between the applicator and the patient’s skin to reduce tissue resistance. Treatments were performed twice a week (Monday and Thursday) for 5 weeks (10 treatments in total). The therapy was conducted under ultrasound guidance.
Group B was a control group, treated with a sham fESWT. Stimulation took place using a special polyethylene insert mounted on the top of the applicator, which absorbed energy and limited its spread in the tissue. The treatment procedure was identical to condition A in terms of the audible signals and the technical parameters used in the actual procedure.
The treatment protocol in both groups included identical stabilization training (45 minutes, once a day, 5 days a week, Monday to Friday) with myofascial relaxation of the extensors of the spine, activation of the lumbo-sacro-pelvic complex and deep muscles, stimulation of proper breathing, and dynamic postural exercises.
Therapeutic progress was assessed by analyzing subjective pain sensations using a visual analog scale (VAS), on which the patient-rated the symptoms on a numerical scale from 0 to 10 (0 indicated no pain, 10 indicated the strongest pain).
The Laitinen Pain Scale (LPS) was also used, which measures 4 criteria of pain: its intensity, frequency of its occurrence, use of painkillers, and limitation of motor activity. Patients assigned points from 0 to 4 (0 – no pain, 4 – severe pain) to each of the determined indicators.
Functional fitness was assessed using the Oswestry Disability Index (ODI), which consists of 10 sections, with 8 related to activities of daily living and 2 related to pain concerns; responses are graded from 0 to 5, and the total ODI score is presented on a scoring system of 0–50 or a percentage system of 0–100% indicating the degree of disability.
Tests and questionnaires were administered in both groups at the beginning, after treatment, and during follow-up visits after 1 and 3 months. During this time, the patients were not receiving any other treatment.
The sample size was based on group differences in primary outcomes (means and standard deviations of pain experience), estimated at 26 participants (13 in each group). A 20% loss to follow-up was allowed for in calculations. The decreasing sample size also applied to historical information from our unit because 45% of patients offered conservative management (physical therapy agents) for LBP opted for ESWT within 6 months.
Statistical analysis was performed using the Statistica 13 program (TIBCO, Inc., USA). Arithmetic means, medians, standard deviations, quartiles, and the range of variability (extreme values) were calculated for measurable variables. For qualitative variables, the frequencies were calculated (the results were given as percentages). Quantitative variables were subjected to the Shapiro-Wilk test to determine the normality of distribution. Comparisons between groups were made using the chi-square test (χ2). Within-group comparisons for measurement conditions 1, 2, 3, and 4 were performed by Friedman’s analysis of variance and a post hoc test (Dunn’s test). Finally, the comparison between the experimental and placebo groups was assessed using the Mann-Whitney U test. The level for statistical significance was α=0.05.
Table 3 presents comparisons of pain (VAS) in both groups. There was a significant effect in both groups (P<0.05). The strongest analgesic effect was observed in the group treated with ESWT – by 5.7 points immediately after therapy, 5.5 points after 1 month, and 5.2 points after 3 months. In the sham ESWT (control) group, a significant decrease of 4.4 points occurred after therapy, then 4.2 points after 1 month, and 4.3 points after 3 months.
Comparing pain between the groups (using the VAS scale showed differences immediately after treatment and 1 month after the end of treatment (Figure 5). For the ESWT group, there was a significantly greater improvement in VAS scores compared to the sham group (P<0.05 for all values), suggesting a clinical superiority of ESWT over the other group. There were no differences in the 3-month follow-up (P>0.05); however, the patients in the experimental ESWT group had greater improvement compared to the control group. The results confirmed the effectiveness of the analgesic effect immediately after treatment and a favorable outcome in long-term follow-up despite the slow recurrence of symptoms.
Table 4 shows the comparisons of perceived pain according to LPS in 4 measurements between the experimental and control groups. The mean pain scores changed significantly in both groups (main effect: P<0.05). A significant decrease in the perceived pain was observed immediately after the therapy by 6.9 points, after 1 month by 6.4 points, after 3 months by 6 points. However, in the control group, there was a significant decrease after the therapy by 4 points, after one month by 3.8 points, after 3 months by 3.4 points.
Patients from the experimental group differed from the control group immediately after treatment, indicating remission of pain (P<0.05). In follow-up observations (after 1 and 3 months), there were no significant differences (P>0.05) (Figure 6), although the trend for therapeutic advantage was still maintained.
Table 5 shows the between-group comparisons of functional assessments taken with the ODI under 4 measurement conditions. There was a significant effect for both groups (significant effect: P<0.05). After the end of treatment in the experimental group, there was a decrease by 15.1 points, after 1 month by 16.1 points, and after 3 months by 15.1 points. The ESWT results suggested a stable clinical effect, taking into account the functional assessment of patients. On the other hand, there was a decrease after therapy by 13 points in the control group and conditions 1 month after, 13.8 points, and 3 months after 12.6 points. However, between-group comparisons revealed no statistically significant differences (Figure 7).
Future research should use other objective measurement methods (eg, stabilometric platform, surface electromyography) and include more participants over a longer period. Also, it is important to establish uniform treatment parameters that can be verified by other researchers. In subsequent studies, the questionnaire assessment of disability should be extended.
Focused ESWT in conjunction with an exercise program can be effective in patients with chronic LBP, both short- and long-term. In addition, focused ESWT allows reducing pain, although it does not seem to improve a patient’s functional state significantly. Thus, ESWT cannot be a key enrichment method for a standard rehabilitation program at this stage. Therefore, further clinical trials should be conducted, especially regarding patient functional evaluation after applying focused ESWT.
FiguresFigure 1. CONSORT flow chart of study participants. fESWT – focused extracorporeal shock wave. Figure 2. Duolith SD1 Tower device for high-energy fESWT. Figure 3. fESWT applicator used in this study. Figure 4. Treatment session using the fESWT applicator. Figure 5. Comparison of VAS scores obtained in 4 measurements between the experimental and control group. fESWT – focused extracorporeal shock wave; M1 – before, M2 – after, M3 – after 1 month, M4 – after 3 months. Figure 6. Comparison of LPS scores obtained in 4 measurements between the experimental and control group. fESWT – focused extracorporeal shock wave; M1 – before, M2 – after, M3 – after 1 month, M4 – after 3 months. Figure 7. Comparison of ODI scores obtained in 4 measurements between the experimental and control group. fESWT – focused extracorporeal shock wave; M1 – before, M2 – after, M3 – after 1 month, M4 – after 3 months.
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