The Minimum Standards of Reporting Checklist (Additional file 1) contains details of the experimental design, and statistics, and resources used in this study.
This was a randomized, double-blinded, parallel-group experiment conducted at the Centre for Hip Health and Mobility in Vancouver, British Columbia, Canada. This study started in May 2015 and ended in December 2015. All outcome measures which were collected are reported here.
Recruitment and eligibility criteria
Participants were recruited from the general community by advertising in community centres, gyms, tennis facilities, medical clinics and coffee shops in Vancouver, British Columbia. Interested participants contacted the study team either by telephone or email and underwent a telephone interview to screen for the minimal eligibility criteria. A consent form was emailed to those who met the eligibility criteria; and individuals who decided to participate were invited to the Centre for Hip Health and Mobility for further screening and treatment.
Inclusion criteria were: (1) unilateral elbow pain at or around the lateral epicondyle of the humerus for more than 6 weeks, (2) elbow pain provoked by palpation of the lateral humeral epicondyle and by gripping, (3) elbow pain triggered by either resisted wrist extension or resisted middle finger extension , between 19 and 65 years old, and (4) fluent in English.
Exclusion criteria were: (1) any other concurrent neck, shoulder, elbow, or arm disorders, (2) history of any injections for LE (e.g. corticosteroid, autologous whole blood, PRP, or prolotherapy), (3) received acupuncture for LE, (4) pregnant, (5) pacemakers or other electrical device implanted in the body, (6) history of seizures or epilepsy, (7) untreated hemorrhagic disorders, (8) infected tissues, osteomyelitis, or wounds around the elbow, (9) active deep vein thrombosis or thrombophlebitis, (10) impaired sensation at and around the elbow, (11) not able to give accurate and timely feedback due to cognition or communication impairment, (12) cancerous lesions at or around the elbow, (13) radiation therapy around the elbow within the previous 6 months, (14) impaired circulation around the elbow, (15) surgery or bone fracture at or around the elbow previously, (16) needle phobia, (17) inflammatory rheumatic diseases, and (18) opioid medications.
For this pilot study, we actively recruited over an 8-month period. 21 adults with LE participated. All available participants during this period that met all the eligibility criteria were included in this study. To detect a reduction in pain during gripping of 30% (which is a provisional benchmark for a moderately important clinical change ) with a SD of 40 and power of 0.80, a sample size of 16 was required. This calculation was based on a within-group change over time.
Procedures and interventions
After obtaining written informed consent from participants, they were screened for their eligibility for the study by a clinician (JJ).
Before their first visit, participants were asked to: (1) refrain from taking NSAIDs or analgesia for 3 days prior to the study until its completion; (2) avoid any therapy for 3 days prior to the study until its completion; (3) avoid excessive caffeine intake (no more than 2 cups of coffee) 24 h before the study and during the 72 h follow-up; and (4) avoid any activities that aggravate elbow pain for 72 h after treatment.
After the baseline measurements, participants received acupuncture on LI 4, TE 5, LU 5, LI 10, LI 12, SP 6, and GB 34 [36, 42,43,44]. Needling was done only on the affected arm and ipsilateral leg. Only sterile, single-use, disposable stainless steel needles were used (Seirin L-type, 40 mm × 0.25 mm) for both treatment groups. Participants’ skin at the needling sites was cleaned with antiseptic prior to needling. After inserting acupuncture needles into the skin to the required depth (1.5–3.5 cm), the clinician manipulated the acupuncture needles until the patients reported deqi (“arrival of qi”). Deqi is a subjective feeling of a patient at the region where an acupuncture needle is inserted into the acupoint and it is characterized by aching, soreness, numbness, tingling, pressure, or heaviness—this is typically ascribed to stimulation of peripheral sensory nerves .
Participants who were allocated in the EA group received electro-stimulation between two pairs of acupoints: one pair between LI 10 (−ve lead) and LI 12 (+ve lead) and the other pair between LI 4 (−ve lead) and SJ 5 (+ve lead). Electro-stimulation was applied using an electro-acupuncture unit (ES-160) (ITO physiotherapy and rehabilitation, Japan). The frequency was set as alternating between 10 and 30 Hz (alternating between two frequencies every 3 s). The pulse width was set as 400 μs. The intensity was set and maintained at a point at which participants received a sensory stimulus, such as tingling or numbness sensation, without visible muscle contraction. Electro-stimulation was applied for 30 min [46, 47].
Participants in the MA group received sham EA: the wires with metal clips were connected to acupuncture needles the same way as in EA group. However, the intensity dials that were connected to these two wires were not manipulated. Instead, the other intensity dials, which were not connected with wires, were turned on so that the ES-160 would still make stimulus sounds as if participants were receiving electrical stimulation. Participants were told that they may or may not feel a tingling sensation due to the use of micro-currents in the study. The electro-stimulator was placed in an opaque box so that participants were not able to watch how the clinician controlled the machine. In order to find out whether the blinding method was successful or not, participants were asked in the survey “Which group do you think you were belonged to, the EA or MA group?” at the end of the their participation.
Acupuncture needles were left in place for 30 min in both treatment groups. Acupuncture points located on the leg (GB 34, SP 6) were re-stimulated with a twirling method, in both treatment groups, once during the middle of treatment. Manipulation of the needles during the treatment was to stimulate acupuncture points, which in turn stimulates peripheral sensory nerves to create pain relief. All acupuncture was performed by a clinician (JJ) who was a registered acupuncturist in British Columbia with over 10 years of experience in clinical practice and teaching acupuncture.
A randomization list of 20 equally weighted, unblocked allocations was uploaded to clinical data management software (REDCAP) prior to the start of the study. The randomization sequence was concealed from the clinician and assessor, and the randomization was stratified by sex. To avoid clinician bias, the participants’ treatment group allocation was assigned after all the treatment steps were completed, including insertion of the acupuncture needles, with the exception of the final step of applying the electro-stimulation current. After placement of the acupuncture needles by the clinician (JJ), a third person who was not involved in this study was called to the treatment room to witness the completion of needling and the randomization process by pressing a button on a computer using the REDCAP software.
Baseline and outcome measurements
Prior to receiving treatment, participants’ demographic information, the level of pain and functional disability (PRTEE questionnaire), and the level of pain-related fear of movement (TSK-11 questionnaire), were recorded independently by the participants.
PFGS of unaffected and affected arms with LE were taken by a third, blinded investigator (EB) at baseline, immediately after treatment, and 24 and 72 h after the treatment. For PGFS (and the other outcome measures), 72 h was selected based on the expected duration of analgesia as observed by Molsberger and Hille . Each measurement was repeated three times at 30-s intervals starting with the unaffected arm. Effort to get three consistent readings with less than 10% discrepancy between measurements was made by measuring PFGS more than three times if needed. To avoid bias, encouragement was not given at any time during PFGS measurements and participants were blinded to their PFGS readings. PFGS was measured with an electronic digital grip dynamometer (MIE Medical research, UK). Participants were in the supine position with the arm at the side (slight abduction), elbow extended, forearm pronated, and wrist extended. When testing PFGS, we ensured that the dynamometer and forearm were fully supported on the table top. For measurements in the affected arm, participants were instructed to apply force gradually on the grip and stop squeezing as soon as pain was felt; if participants had pain at rest, they were asked to squeeze until the point where their pain first increased; and for measurement of the unaffected arm, they were asked to squeeze the grip maximally.
Perceived pain level was recorded on an 11-point numeric rating scale (NRS) by a third investigator (EB). Participants were instructed to squeeze their fist as tightly as possible, and rate their resulting pain from 0 to 10, with 10 being the worst imaginable pain. This method of rating pain during a provocative maneuver was selected because (a) many people with LE do not have any resting pain, (b) the method avoids any manipulation or palpation of the elbow by an assessor, and (c) the method avoids any recall bias associated with rating average or worst pain during the previous week. The NRS has shown to a reliable tool for measuring pain in patients with musculoskeletal disorders of upper limb .
Acupuncture treatment, measurement of PFGS, and numeric rating of pain were all conducted in the same (supine) position. Before and after acupuncture treatment, PFGS was evaluated followed by pain rating.
Participants were provided with pain diaries to fill out after leaving the research centre, and asked to rate their pain 3 times a day (morning immediately on waking, midday, bedtime) for 72 h following treatment. For self-measurement, participants were instructed to stand straight and position their arms hanging at the side of their body, with their elbow extended, forearm pronated, and wrist extended, make a fist as tightly as possible, then rate their pain. Verbal instructions were given with demonstrations to participants onsite, and the written and visual instructions were listed on the first page of their pain diary.
The GROC scale is a reliable and valid measure of patient’s perceived level of change in their condition over a period of time, commonly used in clinical research and practice . Although we considered it unlikely that there would be any significant clinical improvement over the brief course of our experiments, at the 24 h time point participants were asked “Over the past 24 h since you received acupuncture treatment, how has your condition changed with respect to your elbow pain?” and were asked to rate their condition on a seven-point Likert type scale—much better, moderately better, slightly better, unchanged, slightly worse, moderately worse, and much worse.
At the conclusion of the study, participants were asked to guess their group allocation and report their confidence level with the answer. They had choices of ‘Not confident at all’, ‘Somewhat confident’, ‘Neutral’, ‘Confident’ and ‘Very confident’. In addition, they were questioned: (1) whether they needed to take NSAIDS or any other pain killers for pain control; (2) whether they avoided receiving any therapy; and (3) whether they avoided any activities that aggravate their elbow pain during their participation period.
Linear mixed-effects models (repeat measures ANOVA) were used to determine whether there were changes in pain-free grip strength and perceived pain level over a 72-h period after one treatment of either EA or MA, and whether this change differed between the two treatment groups. Pain levels measured on site and at home (via diaries) were considered as separate outcomes (due to the variation in testing position necessitated by the experimental design), and were therefore analyzed in separate models. The independent variables were time (within-participants) and treatment (between-participants). Although this was not the primary goal of the study, the impact of potential covariates (hand dominance, age, sex, duration of LE, TSK score, PRTEE total score and subscores) were included in the statistical model to determine their potential influence on the change in pain or change in PFGS. P values were adjusted using the Bonferroni method, and P values of less than 0.05 were considered statistically significant. Analysis was performed by an independent statistician at UBC.