Rapid Improvement in Neck Disability, Mobility, and Sleep Quality with Chronic Neck Pain Treated by Fu's Subcutaneous Needling: A Randomized Control Study

Background Chronic neck pain is a common musculoskeletal disorder caused by overuse of neck and upper back muscles or poor posture, and it is commonly combined with a limited range of motion in the neck and shoulders. Most cases will recover within a few days; however, the symptoms often recur easily. Fu's subcutaneous needling (FSN) is a new therapeutic approach used to treat patients with chronic neck pain. However, there is no solid evidence to support the effectiveness of FSN on chronic neck pain and disability. Methods Participants (n = 60) with chronic neck pain for more than 2 months with pain intensity scored by visual analog scale (VAS) more than five were enrolled in this trial. Participants were equally randomized into the FSN or transcutaneous electrical nerve stimulation (TENS) group who received interventions once a day on day 1, day 2, and day 4. They were assessed by outcome measurements during pre- and post-treatment and followed up for 15 days. Results The VAS was immediately reduced in the FSN and TENS groups and sustained for 15 days of follow-up (all P < 0.001). The immediate effects were also observed as the pressure pain threshold increased in the FSN group on day 2 (P=0.006) and day 4 (P=0.023) after treatment, and tissue hardness decreased by FSN on day 1 and day 2 after treatment (both P < 0.001). FSN and TENS treatment improved neck disability and mobility; moreover, FSN promoted participants to receive better sleep quality, as determined by PSQI assessment (P=0.030). TENS had no benefit on sleep quality. Conclusion FSN was able to relieve pain and relax muscle tightness. Notably, FSN significantly improved neck disability and mobility and enhanced sleep quality. These findings demonstrated that FSN could be an effective alternative treatment option for patients with chronic neck pain. Clinical Trial Registration: ClinicalTrials.gov Identifier: NCT03605576, registered on July 30, 2018.


Introduction
e number of people with neck pain increases daily, and it has become a serious social problem in modern life. Acute neck pain is caused by overuse of the neck and upper back muscles or poor posture or injury, and it is usually combined with a limited range of motion [1]. Symptoms are often resolved without any treatment in a few days. However, most people experience recurrence of symptoms; pain that persists for more than 2 months without improvement is categorized as chronic neck pain that leads not only to upper back pain but also to functional decline that affects daily life, work, and sleep quality [1]. In 2017, more than 280 million cases of neck pain were reported, and the trend of age-standardized point prevalence did not decrease from 1990 [2]. Furthermore, about 10% of the population live with neck disability due to chronic neck pain [1][2][3].
e prevalence is greater in females than in males [4]. e highest prevalence, annual incidences, and years lived with disability from neck pain have been reported in developed regions (such as east Asia, western Europe, North Africa, and the Middle East) and high-income areas (e.g., North America) [2]. ese epidemiological studies showed the urgent need to investigate new strategies for chronic neck pain treatment.
Treatments for chronic neck pain aim to relieve pain and recover functional disability. In general, rest, good posture, and intake of non-steroidal anti-inflammatory drugs are good options for managing neck pain [5]. However, some patients experience recurrent symptoms that persist without improvement. To alleviate these symptoms, some clinical practices are routinely used for chronic neck pain treatment. Transcutaneous electrical nerve stimulation (TENS) is a non-invasive therapy that is widely used in clinics. TENS treatment over the acupuncture points plus infrared irradiation can effectively reduce neck pain [6]. Furthermore, needle therapy is an effective alternative treatment for chronic neck pain. For example, remote acupuncture on TE 5 (Waiguan) and LI 11 (Quchi) has been reported as an effective treatment to manage chronic neck pain caused by myofascial trigger points (MTrPs) on the upper trapezius muscle [7]. Deep dry needling on active MTrPs provides a beneficial effect on pain relief and neck disability on chronic neck pain [8]. Fu's subcutaneous needling (FSN) is an advanced acupuncture that is applied for the treatment of MTrP-induced musculoskeletal disorders [9]. FSN is manipulated by using a disposable needle penetrating the skin of the non-diseased area and targeting the subcutaneous layer rather than the dermis or muscle layer. e swaying and reperfusion approach are the effective features of FSN, distinct from traditional acupuncture or dry needling [9,10]. ese features support FSN as an acceptable and popular needle therapy. Recently, FSN was demonstrated as an effective therapy for lateral epicondylalgia treatment without adverse effects [11]. However, scientific-based evidence to support the effects of remote FSN on chronic neck pain is currently lacking.
In the present study, we evaluated the effectiveness of FSN on chronic neck pain by measuring visual analog scale (VAS), pressure pain threshold (PPT), tissue hardness (TH) meter, neck range of motion (NROM), neck disability index (NDI), and Pittsburgh sleep quality index (PSQI) as outcome measurements. ree treatment sessions were performed on day 1, day 2, and day 4, with assessments before each treatment session and immediately after treatment, as well as on day 8 and day 15 for follow-up. e inclusion criteria were based on (1) adults older than 20 years old; (2) having chronic neck pain for more than 2 months, as defined by the International Association of the Study of Pain, updated in 2011 [12], and VAS greater than 5 points; (3) patients with myofascial pain on the upper back; and (4) pain that was not effective for previous medication or physical therapy. Participants were excluded based on the criteria of (1) contraindications for FSN or TENS treatment, such as serious medical problems, recent trauma, or pregnancy; (2) history of drug abuse (including excess alcohol) that affected pain assessments; (3) received neck, upper back, or upper and lower limb surgery; (4) people with central or peripheral nerve disease; (5) cognitive dysfunction could not be matched with the experimenter; and (6) people with cardiac pacemakers and epilepsy, because electrode patches could not be placed on the skin.

Materials and Methods
Participants were randomly divided into FSN as the experimental group or TENS as the control group by a raffle system and allocated to the FSN or TENS group (Figure 1). A total of 61 participants were enrolled, but one participant was excluded because of VAS smaller than 5. e participants (60 patients) were divided and allocated into two arms: an experimental group who underwent FSN treatment (30 patients) and a placebo group who underwent TENS treatment (30 patients) via raffle ( Figure 1). Every participant received the intervention of FSN or TENS. ree treatment sessions in this experiment were performed on day 1, day 2, and day 4, with assessments before each treatment session and immediately after treatment, as well as the following day 8 and day 15 for follow-up ( Figure 2). All the treatments were conducted by the same acupuncturist who worked in the medical center in Taiwan for more than 5 years.

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Pain Research and Management

Intervention Procedures.
Participants in the experimental group were treated by using a disposable Fu's subcutaneous needle (Nanjing FSN Medical Co., Ltd., Jiangsu, China) on the radial aspect of the forearm extensors muscle. e needle was inserted into the subcutaneous layer with the whole needle body by holding the inserting device (Figure 3(a)). e insertion point was on the midpoint of the extensor muscle of the affected forearm (the center between the midpoint of cubital crease to elbow tip to the center of transverse crease of the wrist, Figure 3(b)). To ensure that the needle was inserted into the subcutaneous layer rather than the dermis or muscle layers, participants were asked for no pain sensations or soreness during the whole process of insertion. e core needle receded, and the protuberance of the soft tube seat was fixed in the slot of the core seat so that the needle tip was no longer exposed outside, followed by starting a swaying movement (Figures 3(c)-3(e)). e tip of the needle should be maintained at the same horizontal level during swaying by using the thumb and the middle finger to hold the core base, and the index finger and the ring finger were separated on the left and right side of the middle finger to sway in a seesaw-like sector one after the other (Figure 3(f )). Time and frequency of swaying was 50 times within 30 s. After swaying, the participants were asked to shrug their shoulders and raise their head for 10 s and then rest for the same intermission (Figure 4(a)). In this step, the   physician could help participants perform the exercise of contraction of the upper trapezius muscle with resistance ( Figure 4(b)). e cycle was repeated up to three times for 2 min. After finishing the two actions called the "reperfusion approach," with FSN embedded subcutaneously, we removed the needle afterward. Participants in the TENS group were treated with transcutaneous electrical nerve stimulator (Well-Life Healthcare Limited, Taiwan), with the electrodes attached to acupoints TE 5 (Waiguan) and LI 11 (Quchi), according to the guidance of WHO. e treatment parameters were set to pulse width of 200 μs, frequency of 200 Hz, and continuous wave for 20 min.

Outcome Measurements
2.3.1. Visual Analog Scales. VAS is a subjective tool that is commonly used to evaluate pain intensity [13,14]. Participants were subjected to evaluations of the score of pain severity from no pain (score 0) to intolerable pain (score 10) in a 10-cm-long scale. e results were recorded in every pre-treatment (pre-Tx) and post-treatment (post-Tx) on day 1, day 2, and day 4 and followed up to day 8 and day 15 ( Figure 2).

PPT for MTrPs of Upper Trapezius Muscles.
We used a semi-objective tool by Pressure Algometry (OE-220, ITO CO., Ltd., Tokyo, Japan) as Fischer's methods to evaluate PPT [15,16]. First, the physician found the MTrP of upper trapezius muscles and marked the point. e metal probe of pressure algometry was attached vertically to the MTrP, and the press was increased by 1 kg/s. When the participant felt uncomfortable or in pain gradually, this point indicated the threshold of latent MTrP. A point of intolerable pain indicated the threshold of active MTrP. e test was replicated three times at 60 s intervals of the same level of pain by participants. e results of the threshold of active MTrP were recorded, and the mean of the PPT of MTrPs of upper trapezius muscles was calculated.

-45°S
waying movement (f ) Figure 3: Procedure of Fu's subcutaneous needling. FSN was performed with a disposable Fu's subcutaneous needle (bottom) and inserting device (top) (a). e inserting point was on the midpoint between wrist and the elbow of the affected forearm (b). Holding the Fu's subcutaneous needle and receding inserting device (c). Inserting the needle into subcutaneous layer (d) until the whole needle is inserted (e). Swaying the needle in a 30-to-45-degree movement (f ).

Tissue Hardness of Upper Trapezius Muscles.
Soft tissue stiffness was measured by using a tissue hardness meter (OE-220, ITO Co., Ltd., Tokyo, Japan) and applied in clinical studies recently [17][18][19]. e physician placed the metal probe of the tissue hardness meter vertically onto the MTrP of the upper trapezius muscle and pressurized by 1 mm/s. e test was finished when reaching a 10 mm measurement distance. e average of three readings was used for tissue hardness analysis. Every test had a 1 min intermission.

Neck Range of Motion. Cervical Range of Motion
(CROM) instrument (Performance Attainment Associates, 958 Lydia Drive, Roseville, MN 55113) was used to assess NROM [20][21][22]. A gravity inclinometer was used to measure the NROM when participants performed the actions of flexion, extension, left rotation, right rotation, left-side bending, and right-side bending. e three inclinometers on the top, at the front, and at the lateral of the device indicated the 3D angle of neck motion (Figures 5(a)-5(f )).

Neck Disability Index.
Neck disability index (NDI) was modified from the Oswestry Low Back Pain Index [23], and it is the most popular self-rated neck disability instrument due to neck pain [24]. Each of the 10 items was scored from 0 to 5 to achieve a sum of 50 scores. Participants finished the questionnaire before day 1 experiment and on day 8 and day 15 follow-up. e scoring sum below 5 indicated no activity limitation. e sum of 5-14 indicated a mild disability. e sum of 15-24 indicated an intermediate disability. e sum of 25-34 indicated a severe disability. e sum over 34 indicated complete activity limitation.

Pittsburgh Sleep Quality
Index. PSQI is the most effective tool to evaluate sleep quality in adults [25,26]. e questions comprised subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, step disturbance, use of sleeping medication, and daytime dysfunction during the past month. In each item, a score of 0 indicated no difficulty, whereas a score of 3 indicated severe difficulty. e global score of total items yielded a range from 0 to 21. A global score of 5 or more was considered poor sleep quality.

Statistical
Analysis. Statistically significant differences (P < 0.05) among the results were calculated by using Statistical Package for Social Science (SPSS 18.0) for Windows. All data were expressed as mean ± standard deviation (SD). Baseline characteristics analysis of age, sex, VAS, PTT, TH, NROM, NDI, and PSQI was conducted via Student's t-test. For inferential statistics, the within-group analysis of all Pain Research and Management variables was conducted by paired sample t-test, whereas the between-group analysis of the variables was conducted by independent two-sample t-test.

Baseline Characteristics of Two Groups of Participants in the Study.
e baseline characteristics and outcome measurements of the two groups are shown in Table 1 ese results provide a well-randomized prospective study for further investigation.

FSN Treatment Reduces Chronic Neck Pain and Tissue
Hardness Immediately. To understand the immediate effect of FSN on chronic neck pain, we evaluated the VAS, PPT, and TH before and after treatment. e data are shown in  After an intermission of 1 day, the day 4 evaluation results showed that FSN still had a significant effect on VAS (pre-Tx: 3.58 ± 2.42, post-Tx: 1.93 ± 2.24, P < 0.001) and PPT (pre-Tx: 34.08 ± 11.95, post-Tx: 36.03 ± 12.16, P � 0.023) but not on TH (P � 0.705). Only a significant effect on VAS (pre-Tx: 5.20 ± 1.58, post-Tx: 3.90 ± 1.44, P < 0.001) was  Pain Research and Management observed in the TENS group. However, the difference between FSN and TENS in VAS, PPT, and TH was not significant.

Short-Term and Long-Term Effects of FSN on Pain Relief.
In VAS test, both FSN and TENS demonstrated a decrease in pain scale on day 8 and day 15 (P < 0.001 in all tests; Table 3 VAS (0-10)

FSN Improved Neck Disability, Mobility, and Sleep
Quality. Chronic neck pain commonly induces limitations of neck range of motion, followed by poor sleep quality. To estimate the effect of FSN on neck mobility, we analyzed the subjective questionnaire of NDI and objective NROM. e data in Table 4 and Figure 8 showed that the score of NDI improved by FSN from 8.43 ± 4.09 on day 1 pre-Tx to 6.83 ± 4.39 on day 8 (P � 0.010), and the effectiveness was sustained to day 15 (4.96 ± 4.23, P < 0.001). e effectiveness of TENS on NDI was from 10.16 ± 5.84 on day 1 pre-Tx to 8.33 ± 5.73 on day 8, P � 0.036; and to 7.36 ± 5.70 on day 15, P � 0.001. e two groups showed significant effects on short-term and long-term NDI assessment.
To understand further the effect of FSN on neck mobility, NROM was measured during pre-and post-treatment. Both FSN and TENS had benefits on neck motion upon treatment at days 1 and 2, except left rotation in the TENS group (Table 5). After an intermission of 1 day, FSN had benefits on the action of extension, right rotation, right rotation and left/right-side bending on day 4 treatment, whereas TENS had benefits on the actions of flexion, extension, left rotation, and right-side bending (

Discussion
To our knowledge, this study was the first to uncover and demonstrate the effectiveness of FSN in chronic neck pain treatment. We examined the improvement in VAS, PPT, TH, NROM, and outcome measurement of NDI and PSQI after treatment in patients with chronic neck pain. e results of this clinical trial showed that FSN had significant benefits on VAS, NDI, and sleep quality at 15 days follow-up compared with TENS treatment.
TENS is a widely used modality in clinical practice for chronic neck pain with advantages of non-invasive, safe, and immediate effects on pain relief [27]. It is based on electrodes attached to the pain area or acupoints for current transmission. is action stimulates non-nociceptive neuron fibers to block pain transmission in accordance with gate control theory [28]. However, its effectiveness is controversial [29,30]. A meta-analysis of clinical studies showed insufficient evidence regarding treatment with TENS in patients with chronic neck pain [30]. Nevertheless, we observed immediate pain reduction after TENS treatment on day 1, day 2, and day 4 ( Table 2), and TENS-reduced pain effect was sustained to day 8 and day 15 follow-up (Table 3).
Purpose-based acupoints are used for the treatment of various symptoms in ancient acupuncture theories. Needling on different acupoints produces distinct effects. For example, acupuncture at SI 3 (Houxi) and TE 3 (Zhongzhu) is effective for acute neck pain caused by stiff neck or cervical spondylosis [31,32]. In chronic neck pain treatments, TE 5 (Waiguan) and LI 11 (Quchi) are commonly used in acupuncture and TENS [7]. However, the needling points of FSN are on the midpoint of the extensor muscle of forearm, not on the acupoints or MTrPs, different from conventional acupuncture in our study. A treatment strategy focusing on the upper trapezius muscle may be the key to eliminating the condition. For example, muscle energy technique and ischemic compression technique on upper trapezius active MTrPs have a short-term effect on pain relief in patients with nonspecific neck pain [33,34]. In this study, we observed the remote effect of FSN; needling the distal location from the MTrP area led to pain relief and a sustained effect on neck motion and sleep quality (Tables 2, 3, and 5-7). e mechanism may be that needling the myofascial layer triggered the signal transduction of connective tissue to relax the tightened muscles, that is, upper trapezius muscle for chronic neck pain. By combining the swaying and reperfusion approach, FSN effectively relieved neck pain and promoted the remission of the limitation of NROM. Swaying movement of the FSN in the subcutaneous layer released the muscular tension of affected muscles, resulting in pain relief and decreased tissue hardness immediately. e reperfusion approach rapidly restored blood flow, and re-congestion in damaged muscle resulted in accelerated tissue repair. e resistance action of contraction of the upper trapezius muscle helped with the recovery of the disorder.
Tissue hardness or stiffness is the ability of muscle to resist deformation when doing activities. Increase in tissue hardness implies that someone requires more power and energy to respond to the activity of the agonist and antagonistic muscle. e difference between the affected side and the normal side of neck and shoulders can break the coordination. Our data supported the improvement effect of FSN on TH in the first 2 days of treatment. With improvement in neck pain and tissue hardness, FSN could improve neck disability (Table 5). Most people have a problem of poor posture due to looking downward to work or using their cellphone or personal computer for a long period. Immense stress makes people have an involuntary shrug that can cause neck pain. Exercises can improve one's posture to correct positions that prevent neck pain or intervertebral disc herniation [35]. Self-training of the neck muscle is recommended for patients with chronic neck pain and effectively reduces neck pain [36]. If patients are treated with FSN and combine exercise practice, they may stop the disease process of neck pain and the symptoms. e efficacy of combination treatments needs more investigation.
Needle therapy, including dry needling, for chronic neck pain is usually used with more than one filament needle to needle into the MTrPs directly or nearby areas; however, the effectiveness of dry needling on chronic neck pain is equivocal, recently reported by a long-term follow-up trial [37] and a meta-analysis study [38]. Furthermore, given that most people are high responders to needle pain [39], remote therapy and needle-less methods are the better options for  health care. Remote injection with anesthetics has been demonstrated to be an effective treatment for chronic neck pain [40]. e analgesic effects of intramuscular lidocaine injection act on voltage-gated sodium channels to block nerve conduction and sensation in the peripheral nervous system [41]. In our study, we observed that remote FSN on chronic neck pain benefitted pain relief. FSN is suitable for patients who fear needle pain by using the disposable needle insertion away from MTrPs, and this method involves minimal pain. e FSN needle is inserted into the subcutaneous layer, which contains adipose tissue, connective tissues, and numerous vascular and neural networks. Half a century ago, Boguslaw Lipinski reported that the potential mechanism of acupuncture relies on the piezoelectric effect from connective tissues [42]. Furthermore, the neural pathway is the mechanism involved in acupuncture [43], which is applied to nervous system diseases [44]. e effect of acupuncture was blocked by local anesthetic injection in a rat model [45], indicating that peripheral sensory nerves are involved in the action of acupuncture. e mechanical connective tissue reaction instead of neural mechanism in FSN treatment was first investigated in a rabbit model in 2012 [46]. Monitoring the endplate noise from rabbit myofascial trigger spots (MTrSs) with FSN intervention demonstrated that FSN to MTrSs of distal ipsilateral gastrocnemius muscle can initially increase the irritability of MTrS in proximal biceps femoris muscle, followed by a suppression effect after cessation of needling, but these observations were not found in the contralateral side [46]. is hypothesis was also supported in the study of Langevin and her colleagues [47], who hypothesized that mechanical coupling between the needle and connective tissue with winding of tissue around the needle during needle rotation transmits a mechanical signal to connective tissue cells that may explain local and remote, as well as long-term, effects of acupuncture. Unlike Hsieh and her colleagues' animal study of dry needling [48], the mechanism for the effectiveness of dry needling and acupuncture to MTrP-induced disorders was related to an intact neural network. e effectiveness of remote FSN may go through the piezoelectricity and mechanical connective tissue reaction instead of neural mechanism.

Limitations.
is study had some limitations. First, patients with chronic neck pain usually have an accompanying disability such as limited neck motion and poor sleep quality. e disorder is not restricted to elders only; up to 67% of the young population (aged 18-29 years) have had a 12-month prevalence of chronic neck pain [49]. Young people often recover more quickly than elders. In our study, only four young people were recruited in the TENS group with a smaller VAS score of 5 and 6. is may not influence the effect of FSN or TENS on chronic neck pain in this study. Second, patients with the TENS intervention in this study comprised the control group; however, it was not a real placebo group compared with the FSN group. A sham FSN design is needed to be an ideal placebo group when compared with the FSN group to evaluate the treatment's effectiveness. Sham FSN may be designed by intervention with a swaying or reperfusion approach alone, or without both procedures. As expected, the sham FSN may not provide any improvement on chronic neck pain symptoms, but neck pain decreased while the FSN needle was penetrated into the skin. However, choosing an ineffectual treatment was impossible for subjects in this study. We were obliged to take TENS as the control group to compare the effectiveness of FSN on chronic neck pain. e small sample size was another limitation of this study, which resulted in a small statistical power. Small sample sizes make some results inconclusive. For example, a significant improvement was observed for neck disability in the FSN and TENS groups and sleep quality in the FSN group only (Table 4, Figure 8, and Table 7). However, we could not prove the beneficial effects of FSN compared with TENS treatment via difference analysis on day 8 and day 15 follow-up, even if the difference was greater in the FSN group than in the TENS group (all P > 0.05), Supplementary Table 1 and Supplementary Table 2. Future research is required to establish a large population involving other institutes to amplify the statistical power and reach conclusive results.

Conclusions
is study is the first to investigate FSN treatment of chronic neck pain with scientific evidence by using several objective evaluation tools in a clinical setting. FSN could not only relieve neck pain but also it improved the PPT and TH. Notably, FSN significantly improved neck disability and enhanced sleep quality.
Data Availability e data that support the findings of this study are available from the corresponding author, upon reasonable request.
Ethical Approval e study was conducted according to the guidelines of the Declaration of Helsinki and approved by the Institutional Review Board of China Medical University Hospital (CMUH107-REC2-031) and was registered at Clinical-Trials.gov (Identifier: NCT03605576)

Consent
Informed consent was obtained from all participants involved in the study and was retained and archived by corresponding author.

Conflicts of Interest
e authors declare no conflicts of interest.

Authors' Contributions
Conceptualization was performed by Ching-Hsuan Huang, Mao-Feng Sun, Zhonghua Fu, Jian Sun, and Li-Wei Chou. Data curation was performed by Ching-Hsuan Huang.
Funding acquisition was performed by Li-Wei Chou. Investigation was performed by Ching-Hsuan Huang. Methodology was performed by Ching-Hsuan Huang, Zhonghua Fu, Jian Sun, and Li-Wei Chou. Analysis was performed by Ching-Hsuan Huang and Lung-Hung Tsai. Supervision was performed by Mao-Feng Sun. Original draft was prepared by Ching-Hsuan Huang and Lung-Hung Tsai. Review and editing were done by Ching-Hsuan Huang, Lung-Hung Tsai, and Li-Wei Chou. All authors have read and agreed to the published version of the manuscript. Ching-Hsuan Huang and Lung-Hung Tsai contributed equally to this work.