A comparative study of the optimal treatment duration and cumulative effect of transcutaneous electrical nerve stimulation on people with knee osteoarthritis

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A comparative study of the optimal treatment duration and cumulative effect of transcutaneous electrical nerve stimulation on people with knee osteoarthritis

 

Author: Tsui, Ying-yu
Title: A comparative study of the optimal treatment duration and cumulative effect of transcutaneous electrical nerve stimulation on people with knee osteoarthritis
Degree: M.Sc.
Year: 2000
Subject: Knee -- Diseases -- Physical therapy
Osteoarthritis -- Physical therapy
Transcutaneous electrical nerve stimulation
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Dept. of Rehabilitation Sciences
Pages: xv, 99, [4] leaves: ill. ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1523563
URI: http://theses.lib.polyu.edu.hk/handle/200/3422
Abstract: Transcutaneous Electrical Nerve Stimulation (TENS) has been widely used by physiotherapists for managing pain due to knee osteoarthritis (OA). Patients suffering from OA knee usually complain of pain and decrease in mobility. They are in need of an effective means to control the osteoarthritic pain so as to improve exercise tolerance. With an improvement of muscle strength, they can resume a relatively normal mobility level. Recent studies showed that repeated stimulation with TENS produced cumulative analgesic effects on patients with chronic low back pain and OA knee pain (Cheing and Hui-Chan, 1996, 1998). As the treatment duration was 60 min in the above-mentioned studies, it is worth to investigate if shorter treatment duration of 20 min or 40 min will also produce similar cumulative effect. The objective of the study was to examine the optimal treatment duration and the cumulative effect after repeated applications of TENS on patients with OA knee. Thirty-eight patients with a mean age of 65.5 years of age suffered from painful OA knee participated in this study. They were randomly divided into 4 groups receiving TENS at a frequency of 100 Hz and pulse width of 200 us for either (i) 20 min. (TENS20), (ii) 40 min. (TENS40), (iii) 60 min. (TENS60), (iv) 60 min. of placebo TENS (TENSPL). Treatment was given 5 days a week for 2 weeks. A follow-up session was conducted 2 weeks after the cessation of the treatment period. Visual analogue scale (VAS) was used to measure the knee pain during walking at 20-min intervals for 1 hour after stimulation. Thereafter, the VAS scores were re-assessed at a 2-hour interval for 10 hours. Repeated measures ANOVA were employed to evaluate the VAS scores of the 4 groups at various time intervals and across treatment sessions. Linear regression was used to analyse the relationship of the VAS scores and treatment sessions. Besides, the concept of the 'half-life' of the analgesic effect of TENS was also introduced. The time required for the VAS scores to recur at half the intensity level between the pre- and immediately post- stimulation score was defined as time to reach 'half-life'. The time to reach 'half-life' was compared among the 4 groups using the log-rank test, censored data were observed for the patients whose 'half-life' was longer than 10 hours after stimulation. In addition, the outcome measure also included the knee range of motion (ROM) (pain limited ROM and maximum ROM) and the performance of the 'Timed-Up-and-Go' test. Repeated measures ANOVA were employed to analyse the change in the knee ROM (pain limited ROM and maximum ROM) and the 'Timed-Up-and-Go' test among groups and across treatment sessions. After 1 single session of TENS, TENS20, TENS40 and TENS60, but not TENSPL, were equally effective in reducing the VAS scores immediately after treatment (p = 0.003) and even 60 min after the cessation of the TENS treatment (p = 0.009). After 10 sessions of repeated stimulation for 2 weeks, the three active TENS groups but not the placebo stimulation significantly reduce the VAS scores. Alter the cessation of the treatment period, the cumulative analgesic effect can be carryover at least for 2 weeks after treatment. There were significant between-group difference in the VAS scores on Day 5 (p = 0.004), Day 10 (p = 0.000) as well as on the follow-up session (p = 0.000). TEN40 and TENS60 groups were significantly effective in reducing the VAS scores than the TENS20 and TENSPL groups on Day 5 and Day 10. However, the cumulative analgesic effect of TENS seemed to maintain better in the TENS40 groups in the follow-up session. From Day 1 to Day 10, the VAS scores was decreased by 55.05% for the TENS20 group; and 83.40% for the TENS40 group; and 68.37% for the TENS60 group; and only 6.14% for the TENSPL group. By Day 10, the 'half-life' (min.) of the TENS40 and TENS60 groups were significantly longer than those of TENS20 and the TENSPL group (TENS20: 168; TENS40: 256; TENS60: 258; TENSPL: 35; p = 0.000). In addition, there was a higher percentage of patients' experienced a longer duration of pain relief (TENS20: 4%; TENS40: 17%; TENS60: 16%; TENSPL: 6%). Thus, longer stimulation duration (40 min. or 60 min.) produced a more long lasting analgesic effect than 20 min. of TENS or placebo stimulation. After repeated TENS treatment, all the active TENS group but not the placebo group showed significant increase in pain limited knee ROM. In the follow-up session, the pain limited knee ROM of the TENS40 and TENS60 groups were still greater than the TENS20 group. For the maximum knee ROM, there was significant within-group difference across the 10 days of treatment for all active TENS groups, but not the placebo group. However, there was no significant between-groups difference in maximum knee ROM. In the "Timed-Up-and-Go" Test, the patients demonstrated a significant reduction in the time required to perform the "Timed-Up-and-Go" Test after 10 days of repeated active TENS treatment, but not after placebo stimulation. The improvement was still maintained in the follow-up session. However, the between-group difference was insignificant. In conclusion, 40 min and 60 min of TENS treatment were equally effective in decreasing the VAS scores as well as the increase in pain limited knee ROM but not the maximum knee ROM, and reducing the time to perform the "Timed-up-and-Go" test. Besides, the 'half-life' of the analgesic effect was similar for 40 min and 60 min TENS. As the effect of 40 min and 60 min TENS were similar, 40 min TENS seems to be the optimal treatment duration in relieving OA knee pain for cost-effectiveness reason.

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