Analysis of Research Trends in Ultrasound-Guided Acupuncture and Dry-Needling: A Scoping Review

Background: This study aimed to summarize the current status of research on ultrasound-guided acupuncture and dry-needling treatment and the specific treatment methods applied to patients. Methods: A scoping review was conducted, surveying three English databases (PubMed, Embase, and the Cochrane Library) for studies published up to May 2024. All studies related to ultrasound-guided acupuncture and dry-needling treatment were considered. Literature was selected using selection and exclusion criteria, and extracted and organized using EndNote. Results: A total of 107 eligible studies were included. Among the 107 studies, non-comparative studies accounted for the largest proportion (n = 47, 43.9%), followed by randomized controlled trials (RCTs; n = 41, 38.3%). Diseases of the musculoskeletal system or connective tissue (15 diseases of the musculoskeletal system or connective tissue) accounted for most (n = 48, 55.8%) of the 86 diseases studied, followed by symptoms, signs, or clinical conditions not otherwise classified (n = 17, 19.8%). Conclusions: Ultrasound-guided acupuncture and dry-needling have been actively studied and applied for the treatment of various diseases. However, higher-quality studies are needed for further applications in research and clinical practice.


Introduction
Acupuncture originated in Chinese medicine; traditionally, its main purpose is to stimulate specific points called "acupuncture points" along meridians to restore qi flow and activate metabolism.Today, the term has been expanded to include dry-needling, which is applied locally to areas where trigger points (TrPs) exist and myofascial pain.Referred pain, also known as secondary hyperalgesia, is commonly associated with TrPs and occurs when pain is experienced in a different region than its source, a phenomenon frequently observed in nearly all myofascial pain syndromes [1].At medical institutions, patient complaints are followed by a series of tests, and clinician experience is used to diagnose and treat the disease.
However, the commonly used treatment methods of acupuncture and dry-needling are invasive, and the needling process is largely dependent on the practitioner's senses.
Variations in age, sex, body type, and anatomy exist among patients; thus the stability of needle depth and direction and the reproducibility of treatment according to the skill of the practitioner must be studied [2].Ultrasound imaging (ultrasonography) utilizes unique acoustic impedance differences between the internal tissues of the body to transmit a constant pulse wave into the body, and the reflected signal is amplified and converted into a computerized image [3].Ultrasound devices are used as diagnostic and therapeutic aids to improve the accuracy and precision of treatment for non-palpable areas because they can help identify the location of lesions and morbidity [4,5].Therefore, research has been conducted on techniques that combine ultrasound-guided acupuncture and dry-needling to improve the accuracy and precision of existing acupuncture and dry-needling techniques.
Until now, most studies combining acupuncture and dry-needle therapy with ultrasound imaging devices have focused on the treatment of a single disease in patients.Therefore, studies are lacking regarding the overall research status and possibilities of ultrasoundguided acupuncture and dry-needle therapy for researchers and clinical practitioners.
Therefore, in this scoping review, we systematically searched for and analyzed studies related to ultrasound-guided acupuncture (acupuncture, acupotomy, and pharmacopuncture) and dry-needling applications to investigate the current state of research on ultrasound-guided acupuncture and dry-needling.We aimed to identify specific methods of ultrasound-guided acupuncture and dry-needling according to the disease and site, and explore the possibility of further applications to provide reference materials for clinicians.

Materials and Methods
A scoping review was conducted to identify research trends in ultrasound-guided acupuncture and dry-needling.By broadening the scope of the question, the following research questions were set to identify areas where clinical research on ultrasound-guided acupuncture and dry-needling is insufficient.

1.
What are the research trends in ultrasound-guided acupuncture and dry-needling?(Publication year, research design, etc.)

2.
For what specific diseases or symptoms are ultrasound-guided acupuncture and dry-needling used? 3.
What are the future research directions for ultrasound-guided acupuncture and dry-needling?
Based on Arksey and O'Malley's five steps [6], the authors drafted this study under the guidance of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) [7] extension of the scoping review checklist and Supplementary Materials.
The bibliographic program Endnote x9 (Clarvate Analytics, Philadelphia, PA, USA) was used to search and organize the data, while Microsoft Excel 2016 (Microsoft, Redmond, WA, USA) was used to record the data.Study selection was based on the inclusion and exclusion criteria established in a meeting of the researchers.Titles were reviewed to exclude irrelevant studies, and abstracts were reviewed for the final selection.The search was not restricted by the country in which the study was conducted or by the age, sex, or language of the participants.Two researchers independently reviewed the literature; if any disagreement arose regarding the process and results of evaluating the literature, a third researcher was consulted to reconcile their opinions.
The researchers determined the data items to be extracted as the main items related to the initial research questions, such as year of publication, author, study type, intervention method, target disease, number of experimental/control groups, treatment site, evaluation indicators, and outcomes.Two researchers independently conducted data extraction, and finally, a third researcher reviewed the data and recorded the agreement after exchanging opinions and discussions.

Data Analysis, Summarization, and Reporting of Results
The overall trends of analytics school research in terms of publication year, academic discipline, and research design were recorded.This study aimed to provide the main information and results related to this research topic, wherein the scope of application of the concept of ultrasound-guided acupuncture and dry-needling treatment was analyzed based on the process of the intervention and the clinical symptoms of the subjects.The main findings are described using PRISMA diagrams and are presented in the tables and figures [9].

Article Search and Selection Results
Of the 4996 articles retrieved from the database, 107 were selected for scoping review (Figure 1).

Year of Publication
To identify trends in the volume and content of research over time, the years of publication of ultrasound-guided acupuncture-related studies were analyzed.Since 1974, 2023 was the most active year, with 20 studies (18.7%), followed by 2022, with 17 studies (15.9%) (Figure 2).

Year of Publication
To identify trends in the volume and content of research over time, the years of publication of ultrasound-guided acupuncture-related studies were analyzed.Since 1974, 2023 was the most active year, with 20 studies (18.7%), followed by 2022, with 17 studies (15.9%) (Figure 2).

Study Design
The study design was based on the clinical research literature classification tool DAMI (version 2.0; Health Insurance Review and Assessment Institute, Seoul, Korea) [10], which involved reviewing the abstracts and full texts.Of the 107 studies, non-comparative studies accounted for the largest proportion (n = 47, 43.9%), followed by randomized controlled trials (RCTs), (n = 41, 38.9%).This was followed by four cross-sectional studies and

Study Design
The study design was based on the clinical research literature classification tool DAMI (version 2.0; Health Insurance Review and Assessment Institute, Seoul, Korea) [10], which involved reviewing the abstracts and full texts.Of the 107 studies, non-comparative studies accounted for the largest proportion (n = 47, 43.9%), followed by randomized controlled trials (RCTs), (n = 41, 38.9%).This was followed by four cross-sectional studies and reviews (3.7%), three meta-analyses and non-randomized controlled trials (nRCTs) (2.8%), two prospective cohort studies (1.9%), and one systematic review, pilot study, and reliability study each (0.9%) (Table 1).

Disease Analysis
The diseases studied were categorized according to the ICD-11 criteria.Four reviews of clinical studies [11][12][13][14], one systematic review [15], and three meta-analyses [16][17][18] were excluded because of possible duplications in the analysis of target diseases.Furthermore, 28 studies that were not disease specific, such as those on the safety of needle depth, anatomical approaches, and needle pain or sensation, were excluded.A total of 71 papers were analyzed, and when more than one disease classification was present within a study, each disease or symptom was counted separately.Of the 86 disease categories, category 15, "Diseases of the musculoskeletal system or connective tissue" was reported in 48 (55.8%) cases, followed by category 21, "Symptoms, signs, or clinical findings not classified elsewhere" being observed in 17 (19.8%)cases.Among diseases of the musculoskeletal system or connective tissue, FA01, "Osteoarthritis of knee", was the most common, with 6 (7.0%) cases For 21, ("Symptoms, signs, or clinical findings not otherwise specified") MG30.01, "Chronic widespread pain", was the most common with 10 (11.6%) cases, followed by MG30.02, "Chronic primary musculoskeletal pain" with 3 (3.5%)cases (Appendix S3).

Systematic Review and Meta-Analysis
One systematic review was retrieved which included a total of 12 RCTs and 481 participants [15].The experimental group received percutaneous ultrasound-guided tendonectomy, and the control group received an alternative treatment (surgical tendonectomy, platelet-rich plasma injection, steroid injection).Percutaneous ultrasound-guided needle tenotomy was effective in maintaining improvement after treatment of chronic tendinopathy compared to other alternative treatments.
A total of 3 meta-analyses were retrieved, which included a total of 3205 participants [16][17][18].In study of ultrasound-guided acupotomy for osteoarthritis, the experimental group that received ultrasound-guided acupotomy showed a reduction in VAS, improvement in knee function on the Lysholm knee score, and a relatively better clinical effectiveness rate compared to the control group.Ultrasound-guided acupotomy was also associated with a lower incidence of adverse events compared to conventional acupuncture (odds ratio = 0.27).In study of ultrasound-guided acupotomy for trigger finger, overall clinical effectiveness (OR = 4.83; 95% CI 2.49-9.37;I2 = 73.1%;p < 0.001) in the experimental group was significantly better than that of the control group (Appendix S4).

Non-Comparative Study
A total of 47 non-comparative studies were retrieved, including 14 case reports of ultrasound-guided acupuncture and dry-needling treatments in one patient and 9 case series with multiple patients.Further, 24 clinical trials existed that were not studies on patient treatment with ultrasound-guided acupuncture or dry-needling but on pain sensation or needle sensation, anatomical studies, and others.

Prospective Cohort Study
Two cohort studies were included in the scoping review (Appendix S6).In a study of ultrasound-guided tendon needling combined with autologous blood injections in 47 cases of patellar tendinopathy in 44 patients [110], patients' Victoria Institute of Sport Assessment scores (VISA) improved significantly when pre-and post-treatment outcomes were followed up for a mean of 14.8 months.In a study of ultrasound-guided dry-needling and percutaneous high-dose stripping for Achilles tendinopathy in 64 patients, significant improvements in pain scales and high patient satisfaction were observed [111].

Discussion
Acupuncture is a therapeutic technique with proven applicability and effectiveness in various diseases, and several studies have been conducted worldwide.Currently, acupuncture is practiced in various ways-including needle knife, pharmacopuncture, and embedding needles-depending on the patient's symptoms and location.However, given its invasive nature, the reproducibility and safety of the treatment has been questioned since the basic process relies on the practitioner's facilitation.Although most acupuncture treatments are highly effective and have minimal or no side effects, differences exist in the amount of stimulation to the patient depending on the depth of needling [112,113].Setting and entering the correct needle point without displacing the needle is essential for quality treatment.As such, studies combining needling techniques with various imaging devices have been actively conducted in foreign countries.However, no study has systematically summarized these techniques or presented them specifically to researchers and clinical practitioners.Therefore, the present study conducted a scoping review to analyze the research trends in ultrasound-guided acupuncture treatment, main applied diseases, specific application methods, and research results, and to suggest future research directions and applications in medical institutions.Three databases were searched for studies on ultrasound-guided acupuncture and dryneedling.For ultrasound-related terms, we used "ultrasound" and "ultrasound-guided."For acupuncture and dry-needling-related terms, we used a combination of "acupuncture", "acupotomy", "dry-needling", "needle knife", "miniscalpel needle [8]", and "pharmacopuncture" to identify the research status of acupuncture treatments in as many fields as possible.Of the 4996 articles retrieved from the database, 107 were selected for scoping review.Studies have been published every year since 1974, and as of May, 7 studies have already been published in 2024, indicating that research remains active.The study design was categorized based on the DAMI version 2.0, which was developed by the Health Insurance Portability and Accountability Institute in 2013.Of the 107 studies, 47 were categorized as non-comparative studies (43.9%), including 24 clinical trials, 14 single-case reports, and 9 case series.RCTs accounted for 41 studies (38.3%).The high proportion of non-comparative studies and RCTs may be because ultrasound-guided acupuncture and dry-needling are new treatment modalities that have not been widely used; therefore, further research on this technique is needed.Six articles that did not specify the sample size of the clinical study were excluded.
In terms of disease classification, 48 studies (55.8%) focused on diseases of the musculoskeletal system or connective tissues.In terms of site classification, most studies focused on joints such as the shoulders and knees.This may be due not only to the fact that acupuncture and dry-needling are gaining attention as nonpharmacologic treatments for pain management, especially in the musculoskeletal system, but also because their effectiveness has been demonstrated, leading to further research in this area.In addition, studies have been conducted on patients treated with ultrasound-guided acupuncture and dry-needling for a variety of conditions, including certain infectious or parasitic diseases, neoplasms, endocrine disorders, nutritional metabolic disorders, neurological disorders, respiratory disorders, genitourinary disorders, and the consequences of trauma or poisoning, with excellent results.These findings suggest that ultrasound-guided acupuncture and dry-needling are not merely limited to musculoskeletal disorders and pain, but can also be applied to a wide range of other conditions.
As for RCTs, 13 studies were conducted wherein the experimental group was treated with ultrasound-guided acupuncture and dry-needling and the control group was treated with modalities other than acupuncture and dry-needling.The next most common experimental and control group design was found in 11 studies, in which the experimental group was treated with ultrasound-guided acupuncture and dry-needling, and the control group was treated with the same acupuncture and dry-needling modalities but without ultrasound guidance.These research trends are primarily driven by studies aimed at confirming the inherent safety of ultrasound-guided acupuncture and dry-needling techniques, as well as exploring the efficacy of adding ultrasound guidance to existing techniques.The results of the RCTs showed that the ultrasound-guided acupuncture and dry-needling treatment groups were relatively more effective than the control group in terms of cure rate, pain reduction, and functional improvement in the between-group comparison.This enhanced efficacy highlights the advantage of ultrasound-guided treatment, which allows for more precise targeting of invisible areas within the body and concentrated treatment directly at the lesion site, compared to traditional acupuncture techniques.
Case reports and case series have reported no adverse effects of ultrasound-guided acupuncture, thus confirming the safety and efficacy of ultrasound-guided acupuncture and dry-needling.Additionally, these techniques have been shown to be effective in improving symptoms and the function of the affected area.
In addition, clinical trials have compared the differences in patient perception of needle depth using ultrasound-guided acupuncture and dry-needling [86,87] and have analyzed the anatomical characteristics of the treatment area [88][89][90][91][92], the changes that occur inside the body after acupuncture treatment [93,94], needle displacement in typical acupuncture cases [95], the usefulness of ultrasound in acupuncture [96,97], the methodological aspects of the treatment technique [98], the efficacy of ultrasound-guided acupuncture and dry-needling [99][100][101][102], the safety and efficacy of conventional acupuncture procedures [103][104][105][106], disease mechanisms [107], and new treatment techniques [108].This indicates that ultrasound-guided acupuncture and dry-needling are not only valuable as treatment modalities but also, in addition to enhancing conventional methods, serve as a foundation for developing new clinical procedures based on existing practices that can be applied to patients.
In these studies, ultrasound-guided acupuncture, dry-needling, acupotomy, pharmacopuncture, and embedding needling were performed alone and in combination with various modalities, such as high-energy shock wave therapy [20,32], physical therapy [45,46], joint mobilization therapy [25], and Chinese herbal prescriptions [51], with good therapeutic effects.These findings demonstrate that existing procedures in medical institutions can be expanded in multiple directions, highlighting the potential for these techniques to offer diverse treatment options for clinicians and be applied effectively to patients.

Limitations
This scoping study was limited by the fact that the types of studies included were mainly non-comparative, and there was a lack of systematic reviews and meta-analyses.By May 2024, one systematic review [15] and three meta-analyses [16][17][18] had been published, while three protocols for studies had been published, which is not a large number in absolute terms.Larger, more formal studies are needed, but few have been conducted in Korean medical centers, where acupuncture is commonly used.In addition, international studies may differ in terminology [8] or technique, and the interventions in these studies may differ from commonly used acupuncture and dry-needle treatments.Therefore, more high-quality multicenter clinical trials with larger sample sizes are needed to examine the efficacy and safety of ultrasound-guided acupuncture more closely.Second, this study did not include studies wherein ultrasound was only used to diagnose disease; therefore, the results may represent only a small portion of the quality of treatment with ultrasound devices used in real-world clinical practice, which may not represent the full range of applications of ultrasound devices in TCM clinics.Third, the researchers in the included studies did not have the same level of experience, and the ultrasound devices used in the studies were not uniform; therefore, the over or understatement of the results of the preand post-treatment processes cannot be excluded.
Nevertheless, this study is significant, since it is the first scoping review to extensively examine the entire spectrum of ultrasound-guided acupuncture treatments.It also provides a baseline for future researchers and clinical practitioners who wish to implement ultrasound-guided acupuncture in healthcare settings, by presenting the clinical conditions and symptoms for which ultrasound-guided acupuncture can be applied, specific methods of application, their effects, and various numerical outcome indicators that can be used to evaluate them.In particular, this study suggests practical applications of various techniques such as acupotomy, pharmacopuncture, and embedding needle.

Suggestions for Further Research
As such, this study provides two suggestions for future research on the clinical application of ultrasound-guided acupuncture.The first is to conduct research on various topics that can be applied to ultrasound in acupuncture and dry-needle therapy.This study was a scoping review only of articles that used ultrasound guidance for acupuncture and dry-needling, but a search of the database revealed various studies that used ultrasound guidance for acupuncture and dry-needling, including the diagnosis of diseases, evaluation, and comparison of treatment processes.Further research on this topic will expand the possibilities of combining ultrasound with acupuncture and dry-needling in healthcare organizations.Second, ultrasound-guided acupuncture treatments should be standardized.Currently, in the specific method of acupuncture treatment, the terminology is confusing, and the application of acupuncture varies depending on the discretion of the practitioner.Therefore, it would be beneficial for clinical researchers and practitioners to conduct standardized studies on the various aspects of ultrasound-guided acupuncture, such as the use of ultrasound devices.

Conclusions
Using a scoping review, this study analyzed 107 studies of ultrasound-guided acupuncture published through May 2024 and arrived at the following conclusions.

1.
Research on ultrasound-guided acupuncture and dry-needling has been the subject of increasing interest.Various types of studies were conducted, and non-comparative studies were the most common with a total count of 47 (43.9%) comprised of 24 clinical trials, 14 case reports, and 9 case series; RCTs were the most common, with 41 (38.3%) as a single study design.

2.
After categorizing diseases based on ICD-11, ultrasound-guided acupuncture and dry-needling is a reliable and effective treatment technique that can be applied to a variety of diseases.Among the total disease classifications of the papers included in

Figure 1 .
Figure 1.Flowchart of the study selection process.

Figure 1 .
Figure 1.Flowchart of the study selection process.

Figure 2 .
Figure 2. The number of studies published in each year.

Figure 2 .
Figure 2. The number of studies published in each year.

Figure 3 .
Figure 3. Disease sites studied in RCTs and non-RCT.

Table 1 .
Study design of selected studies.

Table 2 .
The Information of included RCT and nRCT.

Table 3 .
Information regarding included case reports and case series.