Effectiveness of Filiform Needle Acupuncture and Long Needle Acupuncture in Managing Periarthritis of the Shoulder: a randomized controlled trial

Abstract

Objectives

Periarthritis of the shoulder (PAS) affects 2-5% of the population and results in significant morbidity. This study evaluates the effectiveness of long needle acupuncture compared to filiform needle acupuncture in managing PAS, with a focus on pain relief and improved range of motion (ROM).

Methods

A randomized controlled trial was conducted with 60 PAS patients who were randomly assigned to receive either long-needle acupuncture (treatment group) or filiform needle acupuncture (control group). Patients in the treatment group received long-needle acupuncture, while those in the control group received filiform needle acupuncture. Both groups underwent 14 treatment sessions over two weeks. The primary outcome was pain reduction measured by the Visual Analogue Scale (VAS). Secondary outcomes included improvements in shoulder abduction, internal rotation, and external rotation.

Results

Post-treatment comparative analysis showed no improvement difference in pain scores between the two groups (p = 0.02) after the Bonferroni adjustment. Specifically, the treatment group exhibited a decrease from 5.9 to 0.9 (p < 0.001), while the control group decreased from 5.5 to 2.2 (p < 0.001). The treatment group experienced more significant improvements in ROM compared to the control group (p < 0.001 for all).

Conclusion

Long-needle acupuncture is as effective as filiform needle acupuncture in managing pain from PAS, but long-needle acupuncture offers better improvements in ROM compared to filiform needle acupuncture. These findings support its integration into PAS treatment regimens, particularly for enhancing functional mobility.

INTRODUCTION

Periarthritis of the shoulder (PAS), commonly referred to as frozen shoulder, is characterized by adhesions and scar tissue formation within the glenohumeral joint, leading to restricted movement and stiffness [1-3]. Clinically, PAS presents with the sudden onset of shoulder pain, followed by a gradual and progressive loss of both active and passive range of motion (ROM) in the affected joint [4]. It affects approximately 2-5% of the population and is associated with significant morbidity and functional impairment [2, 5].

The diagnosis is primarily clinical, based on characteristic physical findings, and may be supported by imaging modalities such as X-rays, ultrasound, or magnetic resonance imaging (MRI), which can reveal thickening of the coracohumeral ligament and other hallmark features [2, 3, 6, 7]. Management strategies include both non-operative and surgical approaches. Non-operative approaches encompass physiotherapy, corticosteroid injections, non-steroidal anti-inflammatory drugs, and, increasingly, acupuncture [3, 8].

Acupuncture, rooted in Traditional Chinese Medicine (TCM), involves the insertion of fine needles at specific body points to alleviate pain and improve function [9, 10]. Several systematic reviews and meta-analyses have demonstrated its efficacy in reducing pain, and improving ROM and shoulder function in patients with PAS [11, 12]. A bibliometric analysis by Chen et al. [13] highlighted a growing body of research and clinical application of acupuncture for shoulder pain over the previous 22 years. This study emphasized the analgesic properties of acupuncture, its role in reducing serum inflammatory markers, and its ability to enhance shoulder joint sensitivity [13].

The filiform needle, one of nine types described in the Neijing, a foundational text of TCM, is widely used in clinical acupuncture [14]. Another type, the long needle, is noted for its ability to regulate Qi and treat various disorders [15]. While long-needle acupuncture has shown significant pain-relieving effects [16, 17], its application in PAS remains underexplored. This study aimed to evaluate the effectiveness of long-needle acupuncture at two acupoints in managing PAS, comparing its outcomes with those of conventional filiform needle acupuncture in terms of pain relief and ROM improvement.

MATERIALS AND METHODS

1. Ethical approval

This trial was approved by the Institutional Ethical Review Board of the Vietnam National Hospital of Acupuncture (IRB-VN01/026-No.594/BB-HDDD) and conducted following the latest guidelines of the Declaration of Helsinki. Written informed consent was obtained from all the participants before enrolment. The trial adhered to the CONSORT guidelines [18]; the acupuncture protocol was designed based on the Standards for Reporting Interventions in Clinical Trials of Acupuncture (STRICTA) [19]. The trial was registered at the Thai Clinical Trials Registry (www.thaiclinicaltrials.org; ID: TCTR20240519006).

2. Trial design

This study constituted a prospective, randomized, controlled trial with blinded outcome assessments and balanced participant allocation. It aimed to test the superiority of long-needle acupuncture over filiform-needle acupuncture in treating PAS. Participants in the intervention group received long-needle acupuncture, while those in the control group underwent filiform-needle acupuncture. The research was conducted from October 2022 to October 2023 at the Senior Specialist Clinic of the Vietnam National Hospital of Acupuncture (Hanoi, Vietnam), with no changes made to the protocol after its initiation.

3. Participants

Eligible participants presented with shoulder pain persisting for over a month, and limited abduction, internal rotation, and external rotation. Exclusion criteria included: age under 18 years, regular use of analgesics, acupuncture within the previous month, history of shoulder fracture, dislocation, or surgery, trauma, cervical radiculopathy, stroke, synovitis, injuries to the rotator cuff or labrum, calcific tendonitis, and rheumatoid or septic arthritis.

4. Sample size calculation

The sample size was estimated using the ‘epi. sscompc’ function in the epiR package of R software (version 4.3.1; R Core Team, Vienna, Austria). An effect size of 0.5, based on unpublished hospital data on acupuncture effectiveness in musculoskeletal conditions and Cohen’s d measure for moderate effects (standard deviation [SD] 0.5), was selected [20]. To detect clinically meaningful differences with 95% power and a 5% significance level, a minimum of 26 patients per group was required. To accommodate a potential 10% dropout rate and ensure statistical robustness, 30 patients were enrolled in each group.

5. Randomization, allocation concealment, and blinding

Eligible participants were randomly assigned to either the treatment or control group using block randomization (block size = 3) at a 1:1 ratio, generated via R software version 4.3.1 (R Core Team, Vienna, Austria). To maintain group indistinguishability and preserve study integrity, participants were assigned codes based on a randomization sequence. Independent researchers at the Vietnam National Hospital of Acupuncture managed the allocation process and ensured confidentiality throughout the study. Outcome evaluators, data managers, and statisticians remained blinded to group assignments for the study’s duration. However, due to the nature of the procedures, acupuncturists could not be blinded to the modality (filiform vs. long-needle acupuncture).

6. Interventions

In the treatment group, a nationally certified acupuncturist with over 20 years of experience administered long-needle acupuncture at aseptically prepared sites. The targeted acupoints on the affected shoulder included Jianyu (LI15), Jianzhen (SI9), Tianquan (PC2), Jiquan (H1), Binao (LI14), Quchi (LI11), Shousanli (LI10), and Hegu (LI4). Sterile disposable stainless steel needles (0.25 × 40 mm) from Wujiang Yunlong Medical Device Co., Ltd. (Jiangsu, China) were inserted from SI9 to H1, PC2 to H1, and LI11 to LI10. At LI4, 0.22 × 25 mm needles were inserted at 45° against the large intestine meridian, penetrating 20 mm. Jiaji (EX-B2) points at C3, C4, and C5, which were needled perpendicularly at a depth of 10-30 mm using the same needle type. Long-needle acupuncture was defined as the use of needles ≥ 75 mm long that traverse two or more acupoints. In this study, a 0.30 × 75 mm needle was used to penetrate from LI15 to LI14, points located approximately 6-9 cm apart along the deltoid region. The needle was inserted obliquely to a typical depth of 60-70 mm, depending on the patient’s body habitus, allowing for a single continuous trajectory between the two points.

Conversely, in the control group, the same acupuncturist administered filiform needle acupuncture at equivalent aseptic sites, focusing on LI15, SI9, PC2, LI14, LI11, Yunmen (LU2), and LI4. All insertions used 0.22 × 25 mm needles, identical to those in the treatment group. These were inserted at 45° against the meridian direction or perpendicularly at a depth of 10-30 mm, including at Jiaji (EX-B2) points along C3 to C5. Unlike the treatment group, no long needles were used; all insertions targeted superficial tissue layers using the 0.22 × 25 mm filiform needles exclusively.

In both groups, patients were positioned in the prone position. Upon eliciting the De-qi sensation, acupuncture needles were connected to an M8 electroacupuncture stimulator (Vietnam National Hospital of Acupuncture) via cables with electrode clips attached to the needle handles. Each session lasted 25-30 minutes and was conducted once daily. Electroacupuncture was applied at a frequency of 5-10 Hz, with the amplitude gradually increased from 0 to 150 µA. Patients received a total of 14 sessions, administered daily, including weekends, over two consecutive weeks.

7. Outcome measurements

The primary outcome was shoulder pain, assessed using the Visual Analogue Scale (VAS), a self-reported scale ranging from 0 (no pain) to 10 (worst imaginable pain) [21]. Secondary outcomes included active ROM in shoulder abduction, internal rotation, and external rotation, all measured in a neutral position. Assessments were performed both before the first session and after completing all 14 sessions. These data were used to compare outcomes between the treatment and control groups, and to evaluate within-group changes before and after treatment.

8. Statistical analysis

All data were recorded in Microsoft Excel and analyzed using SPSS software (version 26.0; IBM Corp., Armonk, NY, USA). Continuous variables were reported as means ± standard deviations (SD), and categorical variables as frequencies (n) and percentages. The normality of continuous data was assessed. Normally distributed variables were compared between groups using the Student’s t-test with Bonferroni correction, while non-normally distributed variables were analyzed using the Wilcoxon rank-sum test. Paired t-tests were employed for within-group comparisons. Statistical significance was defined as a two-sided p-value of < 0.05.

RESULTS

A total of 60 patients with shoulder periarthritis received acupuncture treatment at the Vietnam National Hospital of Acupuncture. None withdrew from the study (Fig. 1). Participants were randomly assigned to either a control or treatment group, with 30 patients in each group. The mean age was 52.6 (SD = 9.3) years in the control group and 51.6 (SD = 9.9) years in the treatment group (Table 1), with no significant difference between groups (p = 0.68). Gender distribution was similar, with men comprising 53.3% and 60.0% of the control and treatment groups, respectively (p = 0.79, Table 1). The average duration of symptoms before treatment was approximately three months in both groups, with no significant difference observed (p = 0.92, Table 1).

Figure 1.

Flow chart of the trial procedure.

Table 1.

Patient demographics

Characteristics	Summary statistics		p value
	Control group (n = 30)	Treatment group (n = 30)
Age (years), mean (SD)	52.6 (9.3)	51.6 (9.9)	0.68
Age group, n (%)
30-39	3 (10.0)	5 (16.3)	0.81
40-49	7 (23.3)	5 (16.7)
50-59	13 (43.3)	14 (46.6)
≥ 60	7 (23.3)	6 (20.0)
Gender, n (%)
Male	16 (53.3)	18 (60.0)	0.79
Female	14 (46.7)	12 (40.0)
Mean onset of disease (months), mean (SD)	3.0 (1.9)	3.0 (1.7)	0.92

SD, standard deviation.

Post-treatment analysis revealed no substantial difference in pain reduction between the groups (p = 0.02) (Table 2). However, the treatment group showed significantly greater improvements in abduction, internal rotation, and external rotation (p < 0.001 for abduction and external rotation; p = 0.004 for internal rotation), even after Bonferroni correction.

Table 2.

Comparison of pain and range of motion after treatment between two groups

	Control group (n = 30)	Treatment group (n = 30)	p value
VAS, mean (SD)	2.20 (2.35)	0.90 (1.60)	0.02*
Range of motion (degrees), mean (SD)
Abduction	118.73 (26.08)	141.02 (12.01)	< 0.001*
Internal rotation	63.20 (15.12)	72.77 (8.48)	0.004*
External rotation	52.63 (16.50)	67.60 (13.20)	< 0.001*

VAS, Visual Analogue Scale; SD, standard deviation.

*Statistical significance at p < 0.05.

Within-group analysis revealed significant reductions in pain scores for both groups: 0.9 (SD = 1.6) in the treatment group and 2.2 (SD = 2.4) in the control group (p < 0.001) (Table 3). Both groups showed significant improvements in abduction, internal rotation, and external rotation following treatment.

Table 3.

Pain and range of motions before and after treatment of two groups

	Control group (n = 30)				Treatment group (n = 30)
	Before treatment	After treatment	p value		Before treatment	After treatment	p value
VAS, mean (SD)	5.5 (2.2)	2.2 (2.4)	< 0.001*		5.9 (1.7)	0.9 (1.6)	< 0.001*
Range of motion (degrees), mean (SD)
Abduction	85.5 (20.3)	118.7 (26.1)	< 0.001*		83.8 (19.0)	141.0 (12.0)	< 0.001*
Internal rotation	51.7 (16.1)	63.2 (15.1)	0.006*		50.8 (15.6)	72.8 (8.5)	< 0.001*
External rotation	39.4 (12.4)	52.6 (16.5)	< 0.001*		38.4 (13.1)	67.6 (13.2)	< 0.001*

VAS, Visual Analogue Scale; SD, standard deviation.

*Statistical significance at p < 0.05.

DISCUSSION

In TCM, PAS is classified under the Bi syndrome, a painful locomotor disorder caused by obstruction of Qi flow [22]. This stagnation leads to the accumulation of Qi and blood in the meridians, resulting in pain, aching, and stiffness in the muscles, bones, tendons, and joints [22]. The etiology of PAS includes both internal and external factors. Internally, it is associated with deficiencies in Qi and blood, and dysfunction of the liver and kidneys [23]. Externally, it is triggered by the invasion of wind, cold, and dampness, which worsen the condition [23]. Acupuncture treatment aims to disperse these external factors, unblock meridians, and regulate the circulation of Qi and blood [7, 15].

The acupoints selected in this study were based on previous research and protocols approved by the Ministry of Health in Vietnam [7, 15, 22-24]. Both local and remote acupoints were employed. Local acupoints targeted specific therapeutic goals, while remote acupoints such as LI11, LI10, and LI4 were used to stimulate meridian Qi in the affected limb, promote circulation, and balance yin and yang. This synergistic selection was intended to optimize the treatment efficacy.

Our findings align with previous research demonstrating the therapeutic benefits of acupuncture for shoulder conditions. For instance, Tao et al. [25] reported significant improvements in shoulder function and pain relief with electropuncture, while Cheing et al. [24] found that combining electroacupuncture with interferential electrotherapy significantly improved shoulder pain and ROM. These findings support the effectiveness of acupuncture as a viable option for managing shoulder pain and dysfunction.

Kim [26] documented significant improvements in shoulder pain and mobility in a patient with an acute frozen shoulder following acupuncture treatment, thereby reinforcing the effectiveness of acupuncture in treating shoulder disorders.

Moreover, systematic reviews by Ben-Arie et al. [12] and Wu et al. [27] confirmed the efficacy of acupuncture in managing frozen shoulder, demonstrating substantial short-term pain relief and functional gains. The current study adds to this evidence base by specifically comparing acupuncture techniques, highlighting the enhanced therapeutic efficacy of long-needle acupuncture for PAS.

In a randomized, double-anonymized, placebo-controlled trial, Schröder et al. [28] evaluated the immediate analgesic effect of acupuncture in patients with adhesive capsulitis. Their study demonstrated that press tack needles significantly improved pain scores compared to a placebo. Follow-up clinical observations with classical acupuncture confirmed that these immediate benefits could be maintained and translated into long-term outcomes when combined with standard conservative therapy [28]. This study highlights the importance of acupuncture as an adjunct treatment, capable of expediting recovery and enhancing pain management in PAS.

Long-needle acupuncture is characterized by the use of needles ≥ 75 mm in length, allowing for slower, deeper insertion into structures such as tendons, joint capsules, and muscle layers. A key advantage of this technique is its ability to penetrate multiple acupoints along the same meridian, facilitating a more potent regulation of Qi flow across the median pathway. This approach promotes the balance of yin and yang, and triggers more profound therapeutic responses. It is particularly suitable for chronic musculoskeletal disorders, such as PAS. Although long-needle acupuncture offers broader stimulation and potentially faster improvement in ROM, it requires greater practitioner expertise. It may involve a higher risk of discomfort or minor adverse events compared to superficial needling.

Long-needle acupuncture demonstrated superior efficacy in improving shoulder function, particularly in enhancing ROM. While both groups showed considerable reductions in pain (as indicated by VAS scores), the difference between them was insignificant after Bonferroni adjustment (p = 0.02). However, the treatment group, which received long-needle acupuncture, exhibited significantly greater improvements in shoulder abduction, internal rotation, and external rotation compared to the control group (p < 0.001 for abduction and external rotation, p = 0.004 for internal rotation). These findings suggest that although long-needle acupuncture may not significantly outperform filiform acupuncture in pain relief, it offers greater benefits in restoring functional mobility in patients with PAS.

The superior efficacy of long-needle acupuncture in improving ROM may stem from its ability to stimulate deeper tissues and meridians, eliciting more profound physiological responses [15]. In TCM, the long needle is one of the nine classical types of acupuncture needles described in the “Huangdi Neijing,” a foundational text. Each needle type serves specific therapeutic functions [15]. The long needle, characterized by a sharp point and thin, elongated body, is designed for deep insertion, allowing access to structures such as muscles, tendons, and joint capsules that are less reachable with shorter needles. This design enables more extensive and intensive regulation of Qi along the affected meridians.

By simultaneously activating multiple acupoints along a single meridian, long-needle acupuncture more effectively harmonizes yin and yang compared to filiform needling, which typically targets more superficial areas. This deeper stimulation is beneficial for treating chronic musculoskeletal conditions, such as PAS, as it promotes anti-inflammatory effects and alleviates pain more effectively [15]. Wang et al. [16] supported these findings, reporting that long-needle acupuncture achieved superior pain relief by targeting deeper anatomical layers, resulting in improved therapeutic outcomes compared to superficial techniques, such as filiform acupuncture.

This study has several limitations, including its single-center design and relatively small sample size. Moreover, the absence of long-term follow-up limits the evaluation of the sustained effects of long-needle acupuncture. Another limitation is the exclusion of the Shoulder Pain and Disability Index (SPADI) as a functional outcome measure, which could have provided a more comprehensive evaluation of the treatment impact on shoulder-related pain and disability. Future research should incorporate SPADI alongside larger, multi-center trials with extended follow-up to confirm these findings and better understand the long-term efficacy of long-needle acupuncture. Further studies investigating the underlying mechanisms of long-needle acupuncture are also warranted to elucidate its therapeutic potential and inform the development of optimized treatment protocols.

CONCLUSION

This study demonstrated that long-needle acupuncture is more effective than filiform-needle acupuncture in improving shoulder ROM in patients with PAS. While both approaches significantly reduced pain, the difference between groups was insignificant. However, long-needle acupuncture offered superior improvements in shoulder mobility, particularly in abduction, internal rotation, and external rotation. These findings support the inclusion of long-needle acupuncture as a valuable component of PAS treatment, particularly for enhancing functional mobility. Further research is needed to validate these results, evaluate long-term effects, and assess broader functional effects using tools such as the SPADI.