
==== Front
Medicine (Baltimore)
Medicine (Baltimore)
MD
Medicine
0025-7974
1536-5964
Lippincott Williams & Wilkins Hagerstown, MD

MD-D-24-03809
00075
10.1097/MD.0000000000039696
3
3800
Research Article
Systematic Review and Meta-Analysis
Effects of acupuncture on shoulder impingement syndrome: A systematic review and meta-analysis
An Sang-Joon KMD dkstkdwns10@naver.com
a
https://orcid.org/0000-0001-8082-7558
Shin Woo-Chul KMD, PhD eddyshin42@naver.com
b
Joo Sungjun KMD sj.joo.kor@gmail.com
a
Cho Jae-Heung KMD, PhD vetkong95@hanmail.net
ab
Chung Won-Seok KMD, PhD omdluke@khu.ac.kr
ab
Song Mi-Yeon KMD, PhD mysong@khu.ac.kr
ab
https://orcid.org/0000-0003-3919-4597
Kim Hyungsuk KMD, PhD ab*
a Department of Clinical Korean Medicine, Graduate School, Kyung Hee University, Seoul, Republic of Korea
b Department of Korean Medicine Rehabilitation, Kyung Hee University College of Korean Medicine, Kyung Hee University Korean Medicine Hospital, Seoul, Republic of Korea.
* Correspondence: Hyungsuk Kim, 23 Kyungheedae-ro, Dongdaemun-gu 02447, Seoul, Republic of Korea (e-mail: kim0874@hanmail.net).
13 9 2024
13 9 2024
103 37 e3969610 4 2024
20 8 2024
23 8 2024
Copyright © 2024 the Author(s). Published by Wolters Kluwer Health, Inc.
2024
https://creativecommons.org/licenses/by-nc/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial License 4.0 (CCBY-NC), where it is permissible to download, share, remix, transform, and buildup the work provided it is properly cited. The work cannot be used commercially without permission from the journal.

Background:

Shoulder impingement syndrome (SIS) is a common condition that causes chronic shoulder pain. The effectiveness of acupuncture in treating chronic shoulder pain has been documented in previous studies; however, existing systematic reviews and meta-analyses have often excluded Chinese databases and combined different types of acupuncture interventions, such as electroacupuncture, warm acupuncture, pharmacopuncture, and acupotomy. Thus, this study specifically examines the exclusive impact of manual acupuncture on SIS.

Methods:

Several databases, including PubMed, Cochrane Central, Embase, 1 Chinese database (China National Knowledge Infrastructure), and 5 Korean databases (ScienceON, Oriental Medicine Advanced Searching Integrated System, KoreaMed, Korean Studies Information Service System, and KMBASE), were systematically searched for relevant studies. The quality of the included studies was evaluated using the Cochrane Assessment Tool for Risk of Bias Version 2. Data collected from the selected studies were synthesized for meta-analysis. The primary outcome was a pain scale score, and the secondary outcomes were shoulder function and disability.

Results:

This study included 5 randomized controlled trials. The primary outcome assessment revealed significantly reduced pain (standardized mean difference [SMD] = −0.50, 95% confidence interval [CI] = −0.74 to −0.27) and improvements in shoulder function and disability (SMD = −0.57, 95% CI = −0.96 to −0.19). A subgroup analysis based on treatment duration indicated that short-term acupuncture treatment (≤4 weeks) exhibited a high level of confidence with low heterogeneity (SMD = −0.37, 95% CI = −0.73 to −0.02).

Conclusion:

Manual acupuncture is effective for relieving pain and improving shoulder function and disability in patients with SIS. However, further research is necessary to validate these findings owing to the limited number of patients and heterogeneity among the studies reviewed.

acupuncture
meta-analysis
shoulder impingement syndrome
systematic review
OPEN-ACCESSTRUE
SDCT
==== Body
pmc1. Introduction

Shoulder pain, which is the third-most common musculoskeletal pain with a prevalence of approximately 7% to 30%, is commonly attributed to issues arising from the subacromial space.[1] Shoulder impingement syndrome (SIS) is characterized by the compression of the tendons forming the rotator cuff within the acromion subcutaneous space which is located between the subcutaneous plane of the acromion and corneal epithelial ligament.[2,3]

Existing studies have used both surgical and non-surgical interventions for treating SIS. Surgical approaches include arthroscopic and open subacromial decompression,[4] whereas non-surgical options comprise routine exercise interventions, microwave diathermy therapy, corticosteroid injections, low-level laser therapy, and Kinesio taping.[5]

Acupuncture originated from China and other East Asian countries in the 12th century.[6] In Korea, it remains the most commonly utilized treatment among alternative medicine practices.[7] In Australia, it is widely adopted by the marginalized populations owing to its low health-related burden.[8] Consequently, the clinical application of acupuncture has steadily increased, highlighting the growing necessity for research and policies related to acupuncture treatment.[9] The analgesic effect of acupuncture for various pain conditions such as headache, osteoarthritis, and low back pain, have been documented in numerous studies.[10,11] Acupuncture exerts its analgesic effect through multiple mechanisms, including anti-inflammatory actions, relieving central sensitization, regulating adenosine triphosphate metabolism, managing oxidative stress, and modulating the central pathway.[12,13] In addition, it can modulate innate and adaptive immune responses.[14,15]

Some studies have reported the usefulness of acupuncture for managing SIS.[16,17] Acupuncture effectively manages shoulder pain by reducing pain and enhancing the range of motion (ROM) of the shoulder joints.[18] Moreover, acupuncture is considered an alternative to oral nonsteroidal anti-inflammatory medication to reduce drug dependence.[19]

Several systematic reviews and meta-analyses on this subject have been published.[20–22] However, these studies did not include China’s widely used acupuncture database[20] or randomized controlled trials (RCTs).[22] Additionally, these studies included multiple acupuncture modalities, such as electroacupuncture, warm acupuncture, pharmacopuncture, and acupotomy.[21–24] Therefore, to ascertain the effectiveness of manual acupuncture, the present study incorporated data from a Chinese database and exclusively included studies utilizing manual acupuncture, a technique that is a fundamental form of acupuncture and is historically well-established.

2. Materials and methods

This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020.[25] Obtaining ethical approval was not necessary owing to the study design.

2.1. Criteria for study selection

2.1.1. Study types

This systematic review focused on the analysis of RCTs, excluding quasi-RCTs and crossover studies. RCTs from relevant databases, regardless of language, were included in the analysis.

2.1.2. Participants

This study included patients diagnosed with SIS, without discrimination based on age, race, or sex. SIS was diagnosed based on patient history and imaging tests, such as ultrasound and magnetic resonance imaging,[3] as well as various specialized clinical assessments, including the Hawkins–Kennedy test, Neer test, Jobe test, infraspinatus muscle strength test, and subacromial injection test.[26]

2.1.3. Interventions

Studies that used manual acupuncture, including traditional acupuncture and dry needling, to treat SIS in an experimental group were included. Additionally, studies were considered even if other treatments, such as medication, physical therapy, or exercise therapy, were administered alongside manual acupuncture. For the control group, studies were included if they involved either a sham treatment or non-acupuncture interventions. Meanwhile, studies involving other acupuncture modalities such as warm acupuncture, fire acupuncture, electroacupuncture, pharmacopuncture, or acupotomy, were excluded.

2.1.4. Outcome measures

The primary outcome was pain, assessed using pain scales, such as the visual analog scale (VAS), numeric pain rating scale (NPRS), and pressure pain threshold. Initially, the study protocol included additional measures such as shoulder function, quality of life, and the ROM of the shoulder. However, our search revealed no studies assessing quality of life with a limited number of studies measuring ROM,[27,28] making it challenging to comprehensively synthesize the data. Consequently, we assessed shoulder function-related measures, including the Shoulder Pain and Disability Index (SPADI); synthesis disabilities of the arm, shoulder, and hand; and the Constant–Murley (CM) score, as well as the incidence of adverse reactions.

2.2. Search strategy

Nine databases, including MEDLINE, CENTRAL, Embase, 1 Chinese database (China National Knowledge Infrastructure), and 5 Korean databases (ScienceON, Korean Studies Information Service System, KMBASE, Oriental Medicine Advanced Searching Integrated System, and KoreaMed), were searched from March 15, 2023 to July 7, 2024 to identify RCTs utilizing acupuncture to treat SIS. To refine our search, we combined the keywords “shoulder impingement syndrome” and “acupuncture.” The entire search strategy is shown in Appendix 1, Supplemental Digital Content, http://links.lww.com/MD/N553.

2.3. Data collection and analysis

2.3.1. Study selection

Two researchers (S.A. and W.S.) independently searched the databases and reviewed other sources based on predefined search guidelines. The guidelines included explicit criteria for article selection, outlining both the inclusion and exclusion criteria, along with illustrative examples. Discrepancies between the assessments of the researchers were resolved by a third researcher (H.K.) who evaluated both opinions and made the final decision. Figure 1 illustrates the article selection process.

Figure 1. Study identification process.

2.3.2. Data extraction and management

Two reviewers (S.A. and W.S.) were provided an Excel file for data extraction. The file contained vacant cells, including fields for the title, author, number of participants, arbitration, and results.

2.3.3. Evaluation of the risk of bias and study quality

Both reviewers (S.A. and W.S.) used the revised Cochrane RoB assessment tool (RoB 2.0), to assess the risk of bias in randomized trials.[29] This tool evaluates 5 domains, including bias arising from the randomization process, bias due to deviations from intended interventions, missing outcome data, bias in the measurement of the outcome, and selection of the reported result. The overall risk of bias was determined by integrating the 5 biases.

Each domain was categorized as having a low, unclear, or high risk. Disagreements between the 2 reviewers were resolved by discussion with a third reviewer (H.K.) to reach a consensus regarding the categorization.

2.3.4. Management of missing data

In case of missing or unclear data during the review, the researcher contacted the author of the study to seek clarification and obtain the required information.

2.3.5. Data synthesis and statistical analyses

Continuous data for outcomes are reported as standardized mean differences (SMDs) with 95% confidence intervals (CIs). The study did not include any categorical variables. Odds ratios were used to assess adverse events between the groups.

Differences in outcome measures were assessed using either SMDs or weighted mean differences, depending on the uniformity of the measurement scales across the studies. A random-effects model was employed for meta-analysis, and the Review Manager software (Cochrane Collaboration, Oxford, UK) was utilized.

When the I² value exceeded 50%, indicating substantial heterogeneity, we first performed a multiple-regression analysis to identify moderators of interest. Potential moderators included the duration of treatment, type of intervention other than acupuncture, and follow-up time-point as mentioned in the protocol.[30] Subsequently, subgroup analysis of the significant moderators identified was conducted.

2.3.6. Sensitivity analyses

Sensitivity analyses were conducted as needed to investigate the origins of heterogeneity.

2.3.7. Ethics and dissemination

As previously outlined, the protocol did not involve patient data; therefore, the requirement for ethical approval was waived. The outcomes will be shared through publications in peer-reviewed journals.

3. Results

3.1. Included studies

The PRISMA guidelines were used to investigate and select databases and registers (Fig. 1). A total of 305 studies were initially identified, of which 98 duplicate records were removed before screening. Among the remaining studies, 162 were excluded after screening the titles and abstracts, including 31 studies unrelated to SIS, 61 unrelated to acupuncture, and 70 not designed as an RCT. Full-text studies were assessed after excluding 1 study that could not be retrieved. Additionally, 1 study unrelated to SIS, 5 studies with interventions not involving acupuncture, 28 studies with inadequate study designs, and 5 duplicate studies were excluded. Thus, this systematic review and meta-analysis included 5 RCTs.[18,27,28,31,32] The exclusion criteria and selection process are shown in Figure 1.

3.2. Characteristics of the studies

The specific characteristics of the included studies are outlined in Table 1. The studies involved sample sizes ranging from 66 to 117 patients with SIS and were published between 2017 and 2024. All patients in the experimental groups received manual acupuncture to treat SIS, along with conventional therapies such as physical therapy. In the experimental groups, the treatment duration varied from 4 to 6 weeks.

Table 1 Study characteristics.

Study	Country	Sample size	Intervention group	Control group	Acupuncture count	De qi sensation	Duration	Number of treatment session	Diagnostic method	Primary outcomes	Secondary outcomes	Adverse events	
Arias-Buría (2017)[31]	Spain	68	Hong DN + exercise therapy	Exercise therapy	Not mentioned	Local twitch response	5 weeks	2 sessions	Hawkins–Kennedy test, Neer test, empty can test, drop arm test, lift-off test	NRPS	DASH	Not reported	
Imani (2021)[32]	Iran	66	Hong DN + PT
DDN + PT	PT	Not mentioned	Local response	4 weeks	3 sessions	Hawkins–Kennedy tests, Neer test, infraspinatus muscle strength test	NPRS	SPADI
ROM	Not reported	
Lewis (2017)[18]	United Kingdom	109	DN + exercise therapy	Exercise therapy	Maximum of 8	Presence	6 weeks	6 sessions
(2 per week for 3 weeks)	Hawkins-Kennedy tests, Neer test	NA	SPADI	Not reported	
Pérez-Palomares (2017)[27]	Spain	117	Hong DN
+
personalized, evidence-based PT	Personalized, evidence-based physical therapy	Not mentioned	Local twitch response	5 weeks	3 sessions	Ultrasound or MRI	VAS	ROM
CM score	Not reported	
Karamanlioglu (2024)[28]	Turkey	71	Acupuncture
+ exercise therapy	Sham acupuncture + Exercise therapy	10	Presence	4 weeks	8 sessions
(2 per week)	physical examination, laboratory tests, radiological evaluation, subacromial injection test	VAS	SPADI
Quick DASH	Not reported	
CM score = Constant–Murley score, DASH = disabilities of the arm, shoulder, and hand, DDN = deep dry needling, DN = dry needling, Hong = Hong dry needling technique (The needles were inserted using a pyramidal technique and removed promptly upon the emergence of local twitch responses), NA = not applicable, NPRS = numeric pain rating scale, PT = physical therapy, ROM = range of motion, SPADI = shoulder pain and disability index, UCLA = UCLA questionnaire, VAS = Visual analog scale.

Three studies[27,28,31] used the VAS as a primary indicator of pain reduction. The NPRS and pressure pain threshold were also employed to assess pain.[27,32] The secondary outcomes were shoulder function and disability.

3.3. Risk of bias

Regarding randomization, 1 study[18] indicated a low risk of bias, whereas 4 studies presented uncertainty (Fig. 2).[27,28,31,32] This uncertainty was attributed to either a lack of information on the allocation sequence or the absence of details regarding whether baseline differences (baseline characteristics) affected the randomization. Regarding bias due to deviations from intended intervention, 2 studies did not specify whether researchers were aware of the interventions assigned to participants, while in the other 2 studies, the lack of blinding may have allowed knowledge of the assigned interventions to influence the outcomes.[18,28,31,32] Additionally, 2 studies demonstrated uncertainty in missing outcome data.[28,32]

Figure 2. Risk of bias graph.

Regarding bias in outcome measurement, the risk of bias was high because the evaluators were the patients themselves, who were aware of the intervention they received. Finally, regarding bias in the selection of reported results, 3 studies[27,31,32] did not present a pre-specified analysis plan, such as a protocol (Appendix 2, Supplemental Digital Content, http://links.lww.com/MD/N554).

3.4. Effects of interventions

3.4.1. Pain

Four studies[27,28,31,32] evaluated the severity of pain using the pain scale. SMD was used to incorporate various pain metrics, including VAS and NPRS. A meta-analysis involving 295 patients revealed that manual acupuncture significantly improved pain reduction in patients with SIS, thus exhibiting low heterogeneity (SMD = −0.50, 95% CI = −0.74 to −0.27, I2 = 0%) (Fig. 3).

Figure 3. Assessment of pain.

3.4.2. Shoulder function and disability

Five studies[18,27,28,31,32] evaluated shoulder joint function and disability. The SMD was used to incorporate various function and disability metrics, including the Shoulder Pain and Disability Index, disabilities of the arm, shoulder, and hand, and the Constant–Murley score. A meta-analysis involving 382 patients indicated a significant enhancement in shoulder function and disability in patients with SIS following manual acupuncture (SMD = −0.57, 95% CI = −0.96 to −0.19, I2 = 67%) (Fig. 4).

Figure 4. Assessment of shoulder function and disability.

Owing to heterogeneity exceeding 50%, a subgroup analysis using multiple regression was performed to identify the underlying causes. Among the variables considered, the time-point of follow-up, type of treatments in the intervention and control groups, and the duration of the treatment, the type of treatments in the intervention and control groups was excluded from the analysis because all 4 studies employed physical therapy. Subsequently, the remaining 2 conditions were treated as categorical variables. The multiple-regression analysis yielded significant results for the duration of the treatment, prompting further subgroup analysis based on this factor (P = .0424).

In the subgroup analysis based on the treatment duration, studies were divided and analyzed based on whether the treatment duration was ≤4 weeks or >4 weeks. Studies[28,32] with treatment duration ≤4 weeks exhibited a high level of confidence and low heterogeneity (SMD = −0.37, 95% CI = −0.73 to −0.02, I2 = 0%), whereas studies[18,27,31] with treatment duration >4 weeks showed high heterogeneity (SMD = −0.72, 95% CI = −1.45 to 0.01, I2 = 86%) (Fig. 5).

Figure 5. Assessment of shoulder function and disability (subgroup analyzed based on the duration of treatment).

3.5. Adverse events

No adverse events occurred in all 431 patients who received acupuncture therapy or other treatments.

4. Discussion and conclusions

Although the primary treatment for SIS is conservative and includes exercise therapy, manual therapy, physiotherapy, nonsteroidal anti-inflammatory drugs, and acupuncture, for patients with persistent and recurrent pain, surgical decompression could serve as an alternative option. Few studies have compared the effects of conservative and surgical treatment on SIS. Saltychev et al[33] analyzed 7 RCTs and concluded that surgical treatment is not more effective than exercise. In a study comparing the effectiveness of surgical treatment and conservative interventions on pain and function in patients with SIS, Nazari et al[34] concluded that the effect of surgical intervention alongside physiotherapy is clinically insufficient to demonstrate an advantage over physiotherapy alone. Several studies have indicated the effectiveness of conservative treatment modalities such as acupuncture for SIS. Dong et al have reported that when combined with exercise, acupuncture was effective in relieving pain and improving Constant–Murley scores.[5] Another study which compared the effectiveness of treatment options for subacromial shoulder conditions indicated, with a high probability, that acupuncture was the most effective in relieving short-term pain and improving shoulder function.[35] Given that nonsteroidal anti-inflammatory drugs and corticosteroid injections, which are primarily used as conservative treatments in conventional medicine, have limited evidence supporting their efficacy for SIS and raise concerns regarding their chronic use,[34–36] acupuncture could be an effective, economical, and safe complementary approach for treating SIS.

Various mechanisms have been proposed regarding the analgesic effects of acupuncture. Specifically, acupuncture induces high levels of interleukin-10 and adenosine, which inhibit pro-inflammatory mediators and modulate immune cells to release opioid peptides at local inflammatory sites, thereby exerting peripheral analgesic effects for inflammatory pain.[12] Additionally, acupuncture regulates complex interactions among multiple neuronal pathways and neurotransmitters at the spinal cord and brain levels, alleviating central sensitization by downregulating pain pathways and promoting pain inhibition pathways. Furthermore, acupuncture treatment can significantly improve levels of T cell subsets and immunoglobulins A and M, and it can stimulate and support anti-inflammatory and anti-infectious responses through distinct descending pathways, such as the cholinergic anti-inflammatory pathway and the vagal–adrenal pathway.[14,15]

This systematic review and meta-analysis, which included 5 RCTs, aimed to evaluate the effectiveness of manual acupuncture in treating SIS. In the control groups, only 1 study[28] included sham acupuncture, whereas the remaining studies compared the outcomes of exercise therapy with those of physical therapy alone. Of the 5 studies included, only 3 selected myofascial trigger points for acupuncture, targeting muscles such as the deltoid, supraspinatus, infraspinatus, teres minor, teres major, and subscapularis.[27,31,32] The remaining 2 studies selected traditional acupoints, and the most commonly used acupoints were LI15, LI4, GB21, TE5, TE14, and SI9.[18,28] This study demonstrated that manual acupuncture significantly reduced pain (P < .001) and improved shoulder function and disability (P = .03) in patients with SIS. The subgroup analysis based on treatment duration indicated that short-term treatment (≤4 weeks) exhibited a high level of confidence with low heterogeneity (P = .04, I2 = 0%). Thus, manual acupuncture could be effectively integrated into clinical practice as either an alternative or complementary treatment for the short-term management of SIS, a finding which is consistent with those of previous studies.[35–37] Additionally, no adverse events were reported in the studies, suggesting that manual acupuncture is a relatively safe treatment.

The strengths of this study include the comprehensive search strategy employed that encompassed multiple databases, including Chinese and Korean databases, which are often excluded in similar reviews. The inclusion criteria was strictly defined, focusing exclusively on manual acupuncture to avoid the confounding effects of other acupuncture modalities. Furthermore, although the number of studies included is limited, the studies encompassed interventions used in various countries in Asia and Europe. Notably, none of these studies were conducted in East Asian countries, such as Korea, China, Japan, and Taiwan, where acupuncture is most widely practiced clinically. This review excluded other forms of acupuncture to exclusively evaluate the effects of manual acupuncture. In East Asian countries, acupuncture treatments typically employ various modalities such as electroacupuncture, warm acupuncture, pharmacopuncture, thread embedding, and acupotomy. Therefore, it is possible that no studies fitting the criteria of this systematic review were available in East Asian countries.

Nevertheless, this study has certain limitations. First, the relatively small sample size limits the generalizability of the results. Second, the heterogeneity in study designs, acupoint usage, and the treatment durations posed challenges in synthesizing the data. Particularly, as mentioned earlier, only 1 of the included studies had a control group that incorporated a sham acupuncture, which poses a high risk of bias. Third, the treatment duration in the included studies was within 6 weeks. Thus, analyzing long-term treatment effects was not possible. Finally, except for 1 study, most studies involved administering acupuncture in only a portion of the sessions throughout the entire treatment period, thus necessitating caution in interpreting the results.

In conclusion, manual acupuncture is a safe and effective treatment for SIS in terms of reducing pain and improving shoulder function. However, owing to the high heterogeneity and low quality of the studies reviewed, the results need to be interpreted with caution. Well-designed controlled trials with longer treatment durations and an appropriate control group, including a sham acupuncture, need to be conducted across various countries to obtain more robust data for future systematic reviews and meta-analyses.

Author contributions

Conceptualization: Sang-Joon An, Hyungsuk Kim.

Data curation: Sang-Joon An.

Formal analysis: Sang-Joon An.

Investigation: Sang-Joon An, Sungjun Joo.

Methodology: Sang-Joon An, Sungjun Joo.

Resources: Woo-Chul Shin.

Software: Sang-Joon An.

Supervision: Woo-Chul Shin, Jae-Heung Cho, Won-Seok Chung, Mi-Yeon Song, Hyungsuk Kim.

Visualization: Sang-Joon An, Woo-Chul Shin.

Writing – original draft: Sang-Joon An.

Writing – review & editing: Woo-Chul Shin, Sang-Joon An, Jae-Heung Cho, Won-Seok Chung, Mi-Yeon Song, Hyungsuk Kim.

Supplementary Material

Abbreviations:

CI confidence interval

NPRS numeric pain rating scale

PRISMA Preferred Reporting Items for Systematic Reviews and Meta-Analyses

RCT randomized controlled trial

ROM range of motion

SIS shoulder impingement syndrome

SMD standardized mean difference

SPADI shoulder pain and disability index

VAS visual analog scale

The authors have no funding and conflicts of interest to disclose.

The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

Supplemental Digital Content is available for this article.

How to cite this article: An S-J, Shin W-C, Joo S, Cho J-H, Chung W-S, Song M-Y, Kim H. Effects of acupuncture on shoulder impingement syndrome: A systematic review and meta-analysis. Medicine 2024;103:37(e39696).

S-JA and W-CS contributed equally to this work.

This protocol was registered in PROSPERO (CRD42023443940). Registration number: CRD42023443940 on PROSPERO (https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42023443940).
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