4. Discussion
anxiety disorder, anxiety, cardiovascular diseases, chronic pain, pain, chronic back pain, depression, maladaptive behavior, NRS
HEAT, CARDIOVASCULAR DISEASES, ADVERSE EVENTS, CHRONIC LOW BACK PAIN, CHRONIC PAIN
The current pilot study shows a statistically significant improvement in the mobility of the lower back in patients with chronic back pain using an easy-handling and time-saving electrotherapeutical device. However, there was no statistically significant amelioration in the pain sensation. Of note, due to the exploratory nature of the study, these findings should be considered to be hypothesis generating. At first sight, this increase in ROM of the lower back appears unspectacular with poor means because subjective pain levels remained unchanged. However, clinical experience has shown that physical integrity is as important as an amelioration of subjective feeling of pain. Poor physical activity can aggravate chronic pain, e.g., by increasing myogelosis or joint stiffening that results from maintaining a protective posture constantly, and functional mobility is in close connection with subjective well-being and quality of life in chronic pain patients, most likely due to its impact on the personal range of activity and resulting positive influence on the patient’s mental state and self-esteem. Moreover, previous literature has described that chronic pain, depression and cardiovascular diseases can co-occur [The significant increase in the lumbar ROM we observed after regular electrotherapy contrasts with the results of Deyo and colleagues who reported no functional amelioration using TENS [As mentioned above, we did not observe any significant difference in the pain sensation nor in the quality of life after electrotherapy in any of the tests performed. Thereby, several technical considerations concerning the weekly therapy sessions are to be noted: The therapy protocol including the duration of electrical stimulation, session interval and total number of therapies could be still inadequate for long-lasting pain relief. Some patients who received electrotherapy stated that, although the stimulation felt adequate in the beginning, it became too strong after some time, and the pain condition became worse afterwards. Other patients reported a short amelioration of the pain state right after the electrotherapy sessions. However, such pain reduction mostly lasted only a few hours and disappeared within the same day. An intra-individual adaptation of the stimulation, or an inter-individual adaptation of the session interval might be possibly beneficial.In addition, a greater improvement in mobility or pain relief could be possibly achieved if electrotherapy is combined with heat application since it is known that a multimodal therapy approach can be more effective concerning pain relief [Furthermore, an optimal skin contact is crucial. In a few cases, it was difficult to find the adequate mat positioning. If the contact of the mat and the spinal cord was insufficient and if a higher simulation threshold was required, cushions were put under the mat or under the knee to optimize the skin contact. However, finding the appropriate position in the cervical region was still difficult with some of the patients.Nevertheless, the electrotherapeutic mat that was utilized in this study is useful in daily clinical practice due to its easy handling. It could even be operated by the patients themselves after a short training, and thus save much time in daily clinics, where time is scarce anyway.The placebo effect is a well-known problem in studies investigating patients with chronic pain [The degree of blinding was assessed by asking the patient which treatment they thought was administered (treatment vs. control vs. control of control). Indefinite answers were not accepted so that patients had to guess if they were uncertain. The proportion of patients who answered correctly was 48%. Considering that the probability of guessing correctly by chance is about 33%, and that in the case of unblinding or failed blinding, the percentage of correct answers would be 100%, our result seems, at first sight, not that unsuccessful. However, this consideration is statistically incorrect, and a calculation such as the blinding index proposed by James and colleagues [It is obvious that the number of the participants is small, and a greater number of patients would improve the statistical power. Initially, sample size was calculated based on a previous TENS study performed in patients with chronic low back pain, where a difference of NRS of 1 between the groups (primary end point) was used. A power of 80% and standard deviation of 1.5 were set based on the study of Pop et al. [Furthermore, insufficient blinding or biasing due to dropouts might falsely produce a negative effect of electrotherapy. Most patients (14/19) who dropped out did so right after the baseline investigation before randomization was performed and the weekly sessions started. The remaining five patients belonged to the group receiving supra-threshold electrotherapy and quit after the performance of one to four therapy sessions (two patients after the first session, one patient after the second session, one patient after the third session, one patient after the fourth session) No adverse events were observed in these patients. Since the patients were not obliged to state a reason for the discontinuation, this could not be further analyzed. In two of the five patients, depression was diagnosed, and one patient had a diagnosis of depression and anxiety disorder before the enrolment. NRS, QoL and ROM were investigated at the very beginning of the study before randomization was performed, and at the end of the study after the completion of the six sessions of intervention; therefore, we cannot determine whether there were any changes in the pain level between these times. A possible reason for discontinuation may have been a perceived inefficacy of the therapy and a mismatch with the patients’ therapeutic beliefs and expectations.Finally, another possible explanation for the unchanged pain sensation could be that, according to the bio–psycho–social model of pain, the existence of psychologic or socioeconomic factors that do not change easily, such as anxiety, maladaptive behavior, stressful circumstances, poverty, or biological factors, such as remodeling in the central nervous system, tend to result in chronic pain states [