Dry Needling at the Thoracolumbar Junction on Measures of Sympathetic Outflow and Flexibility

Overview

Dry needling (DN) is becoming more frequently performed by physical therapists around the world to treat musculoskeletal pain. Dry needling is a form of trigger point therapy that evolved from using injections of local anesthetics. Although dry needling is becoming more commonly used, there is little agreement on how it works. Researchers have focused their efforts investigating other forms of manual therapy until very recently. To date, no studies have looked at how dry needling effects muscles distant from the area being treated. Most of the body's sympathetic nervous system (fight or flight response) is located in the thoracic spine, it may be a "silent" contributor to musculoskeletal problems in the arms and legs. The purpose of this study is to determine how dry needling the thoracolumbar junction affects pain, flexibility, and other non-invasive measures of nervous system output in people who have low back pain and tightness of their hamstring muscles. Standard dry needling treatment will be compared with a placebo. The investigators hypothesize that dry needling will have a greater sympathetic nervous system response, as measured by changes in heart rate, skin temperature and skin conductance, when compared with the placebo. The investigators also hypothesize that dry needling will have a greater positive effect on flexibility of the low back and hamstring muscles when compared to the placebo.

Although DN is being used more often in treatment of musculoskeletal disorders, there continues to be little agreement about the pathways on which it works. Research on the neurophysiological effects of DN has increased in the past 10 years, however much about the treatment is still poorly understood. A better understanding of the neurophysiological mechanisms on which DN acts, and how it influences structures distant from the site of treatment, can lead to improved choices of therapeutic activities, and potentially superior outcomes. Many studies have investigated the effects of joint mobilization or manipulation on the sympathetic nervous system (SNS), but fewer studies have investigated the effects of DN. Of the studies on joint mobilization, a large percentage examined treatment to the cervical spine, specifically C5, and tested SNS-related outcomes in the cervical spine, upper thoracic spine, and upper extremities (UEs). The sympathetic nerve fibers that supply the lower extremities (LEs) originate from T10-L2, and future research should investigate the effects on the LE when its direct sympathetic connection is treated. At this time, there is minimal research on manual therapy treatment to the thoracolumbar (TL) spine and its effect on the LEs. The thoracic spine is the origin of nearly all SNS outflow to the extremities, and should therefore not be overlooked as a potentially "silent" contributor to musculoskeletal dysfunction in the extremities. The goals of this study are: 1. To quantify the magnitude of the SNS response to DN at the TL junction in subjects with low back pain and decreased hamstring length, using valid measures of SNS activity. 2. To describe the effect of DN at the TL junction on muscle length both local and remote to the site of treatment. 3. To determine if DN to the TL junction has a significantly greater segmental sympatho-excitatory effect than extrasegmental effect, as measured by pressure-pain threshold (PPT) in the LE and UE. 4. To determine if immediate changes in SNS activity after DN are related to clinically meaningful outcomes at 24-hour follow-up. Research questions for this study are: 1. What are the differences in indicators of SNS activity, such as heart rate variability (HRV), electrodermal activity (EDA), skin temperature (ST) and PPT of the LE, when DN or sham DN is performed at the TL junction in subjects with low back pain and decreased hamstring length? 2. How does DN to the TL junction affect lumbar paraspinal muscle and hamstring length in subjects with low back pain and decreased hamstring length? 3. How far superiorly does the sympatho-excitatory response ascend when DN is performed at the TL junction in subjects with low back pain and decreased hamstring length? 4. Do immediate changes in SNS activity correlate with greater clinical improvements at short-term follow-up, as measured by pain rating, global rating of change (GRC), and the Oswestry Disability Index (ODI)? Hypotheses for this study are: H1: DN will cause a greater SNS response than sham DN, as measured by HRV, ST, EDA, and PPT in the LE. H2: Subjects who receive DN to the TL junction will have a greater improvement in fingertip-to-floor (FTF) measurement, straight leg raise (SLR) and knee extension (KE) measurements from baseline than subjects who receive sham DN. H3: DN to the TL junction will create a greater sympatho-excitatory effect in the LE when compared with the UE, as measured by PPT. H4: There is a relationship between immediate changes in sympathetic outflow, as measured by low frequency (LF) to high frequency (HF) ratio of HRV immediately following DN or sham DN, and GRC, ODI, and pain at 24-hour follow-up. A research proposal has been reviewed and approved by the Institutional Review Board (IRB) of Nova Southeastern University. Subjects will be recruited via advertisements placed in outpatient physical therapy clinics throughout Montgomery and Frederick Counties, in Maryland. A power analysis was performed a priori using G Power (Version 3.1.9.3). Sample size calculation was based on the primary outcome of SNS activity, and PPT was chosen as the primary endpoint because there is the most available data pertaining to PPT after DN treatment. Based on the findings for ipsilateral changes in PPT by Salom-Moreno et al when compared with a control group, 27 subjects in each group (total 54 subjects) will be required to detect an effect size of 0.8 in PPT between the two groups with an alpha level of .05 at a power of 0.8. Subjects will be accepted consecutively and data collection will continue until the desired number of subjects has been reached. Upon arrival at the clinic, the research assistant will confirm that one limb has greater than or equal to 15o of hamstring restriction at R1 and R2. If both limbs meet the criteria for participation, the most restricted limb will be used for analysis. Subjects will complete a Participant Data Form, Informed Consent with assistance from the primary investigator as needed, the Numeric Pain Rating Scale (NPRS), and the ODI. The NPRS is frequently used scale for quantifying pain. The NPRS is an 11-point scale with anchors of "no pain" and "worst pain imaginable." The ODI is one of the most commonly used disability scales for patients with low back pain. It has been found as a favorable measure for symptoms ranging from mild to severe.20 Excellent test-retest reliability has been proven at 24-hour (r=0.99) and 4-day (r=0.91) follow-ups, and test-retest reliability decreases as the length of time before follow-up increases. Subjects will be randomly assigned to the treatment group or the sham needling group. Randomization will occur using a simple method of opaque envelopes sealed with index cards indicating the allocated group inside of it. When a subject arrives and is completing the initial paper work, an envelope will be selected and opened by the primary researcher. The research assistant will be blinded to each subject's group, and will take all baseline measurements. These measurements will include PPT, FTF test, KE, and SLR. PPT will be measured by a Wagner digital algometer (Wagner Instruments, Greenwich, CT, USA) and will be measured in kilograms. Each subject will be instructed to say "stop" when the pressure becomes "slightly unpleasant pain." The maximum pressure at the time the subject says "stop" will be recorded. The mean of three trials will be recorded. The FTF test assesses total trunk flexion mobility and will be performed in the same manner as Perret et al in their validity and reliability study. A subject will stand without shoes on a 20 cm platform with feet together. While keeping knees, arms, and fingers fully extended, the subject will bend forward as far as possible and the vertical distance between the tip of the middle finger and the platform will be recorded. The FTF test has been shown to have excellent intrarater reliability (ICC=.99). The mean of 3 trials will be used for analysis. Baseline® digital inclinometers will be used to measure KE and SLR. SLR will be measured in supine with the knee fully extended and the ankle in a resting position. The inclinometer will be placed at the midpoint between the tibial tuberosity and the distal end of the tibia and secured with a Velcro strap. The subjects will be instructed to keep the contralateral limb in contact with the treatment table at all times. The contralateral limb and pelvis will not be stabilized, as research has shown that stabilization does not affect SLR reliability measures. The examiner will record the number of degrees excursion until the first resistance is felt (R1), and then the number of degrees at maximum, pain-free elevation (R2). The mean of three trials will be recorded. KE will be measured in supine similar to Mason et al in their 2016 study. One inclinometer will be used to maintain 90o hip flexion, while a second inclinometer will be anchored at the midpoint between the tibial tuberosity and the distal end of the tibia. Both will be secured with Velcro straps. The subject's lower leg will be passively extended until the first resistance is felt (R1) and then at the maximum number of degrees of pain-free knee extension (R2). After all baseline measurements are completed, subjects will be connected to a BIOPAC® data acquisition unit, which will monitor HRV, ST, and EDA. HRV refers to changes in heart rate as well as interbeat intervals, and will be used in this study to determine changes in heart rate secondary to autonomic nervous system (ANS) activation. HRV will be measured by the peak-to-peak intervals when using photoplethysmography (PPG). ST is a measure of cutaneous circulation, which is mediated by the sympathetic vasoconstrictor and vasodilator nerves. SNS stimulation leads to superficial vasoconstriction, which would lead to a decrease in ST. A ST thermistor transducer will be taped to the dorsal aspect of the foot of the LE that has the greatest hamstring restriction, which will be determine in the baseline testing. Skin thermistor measurements show excellent test-retest reliability, with the typical error \<0.1 degree Celcius. EDA refers to changes in skin conductance when the ANS is stimulated and the sweat glands become more active. They are most concentrated in the palms and plantar surfaces of the feet, so these would be ideal locations for EDA data collection. It is a sensitive and easy method to measure sympathetic arousal, and it is arguably one of the best measures of sympathetic arousal because it does not receive input from the parasympathetic nervous system (PNS). Electrodes with isotonic gel will be placed on the LE that has the greatest hamstring restriction. The active electrode will be on the plantar surface of the foot and the ground electrode will be placed on the dorsal surface of the foot. An 8-minute acclimation period will occur followed by a 5-minute baseline recording. The primary investigator will perform the treatment condition that was randomly assigned. Proper clean technique will be followed for all subjects, including the subjects receiving the placebo. This will decrease the likelihood that the subject will know which treatment he/she is receiving. The PT administering treatment will wear gloves, and 70% isopropyl alcohol will be used to prepare the skin over the muscles to be treated. Subjects will be treated on the right and left sides at both segments. All materials will be handled according to Occupational Safety and Health Administration Blood Borne Pathogens standards. Subjects will continue to have SNS output monitored for 5 minutes after treatment has been completed. After the 5-minute period, subjects will be disconnected from the equipment, and the research assistant will complete all follow-up measurements in the exact manner stated earlier in this chapter. All subjects will attend one follow-up visit approximately 24 hours after their initial visit. The research assistant will gather measurements of FTF, KE, SLR, and PPT of the UE and LE. Subjects will also complete an ODI and a GRC during this visit. GRC is a simple and convenient scale that is used in research and in the clinic to quantify a summation of a patient's improvements in pain, disability, and quality of life. Subjects will be reconnected to the BIOPAC® MP36R data acquisition unit as previously described. They will undergo an 8-minute acclimation period followed by a 5-minute data collection period. The same limb will be monitored as in the subject's initial visit. After data collection is complete, subjects in the sham DN group will be offered DN in the same manner as the DN group. For H1 two-way ANCOVAs will be used for each dependent variable of SNS activity. Covariates will include pre-intervention measurement scores and level of needle anxiety. For H2 flexibility measurements will be separated into "local" and "remote" tests. The FTF test will quantify local flexibility, and the SLR and KE tests will quantify remote flexibility. A two-way ANCOVA will be use for analysis of local flexibility. The covariate will be the pre-intervention scores. For the remote flexibility analysis, a two-way MANCOVA will be used. The covariate will be the pre-intervention measurements. Post-hoc testing will be performed for H1 and H2 to determine between which factors differences occurred, if applicable. For H3 the data will be analyzed using a t test. Change scores in PPT in the LE will be compared to change scores in the UE, and only the DN group will be included. Prior to conducting the tests, data will be analyzed to be sure they meet the assumptions for each statistical test. For H4 a Pearson's r will be used to determine if there is a statistically significant relationship between SNS output immediately after receiving the treatment condition and the outcomes measures of GRC, change in ODI, and change in NPRS. 17 A 2-point change has been found to be the minimum clinically important difference in patients with low back pain and shoulder pain.