Comparative Study of Ultrasound-Guided Corticosteroid Injection with Acupotomy Release Versus Injection Alone in Carpal Tunnel Syndrome: A Randomized Controlled Trial

Abstract

Background

Carpal tunnel syndrome (CTS) arises mainly from median nerve compression and inflammation. This study evaluated the efficacy of ultrasound-guided corticosteroid injection combined with acupotomy release of the transverse carpal ligament vs corticosteroid injection alone in treating CTS.

Material/Methods

In this randomized controlled trial, 68 patients with CTS were enrolled from January 2023 to June 2024 and randomly assigned to receive corticosteroid injection with acupotomy (group A) or corticosteroid injection alone (group B). Symptom severity and function were evaluated using the Boston Carpal Tunnel Questionnaire-Symptom Severity Score (BCTQ-S) and Functional Status Scale (BCTQ-F) at 2 weeks, 1 month, and 3 months after treatment. Ultrasound was used to assess the median nerve’s cross-sectional area (CSA) and flattening ratio before and 3 months after treatment. Complications were monitored.

Results

Both groups exhibited significant improvements in symptoms and function at all follow-up points (P<0.05). At 2 weeks after treatment, no significant differences were observed between the groups in BCTQ-S or BCTQ-F scores. At 1 month, group A had significantly better BCTQ-S (P=0.017) and BCTQ-F (P=0.039) scores than did group B; this superiority remained at 3 months (P<0.01). Ultrasound assessments at 3 months revealed significantly greater improvements in CSA (P=0.009) and flattening ratio (P=0.038) in group A than in group B. No complications were reported in either group.

Conclusions

Ultrasound-guided corticosteroid injection combined with acupotomy release yielded superior symptom relief and functional recovery than injection alone.

Introduction

Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy, affecting approximately 3% to 6% of adults in the general population, with a higher prevalence in women, particularly those aged 40 to 60 years [1,2]. Epidemiological studies show that the female-to-male ratio for CTS is approximately 3: 1 [3]. Clinically, patients with CTS commonly experience pain and paresthesia, and, less commonly, weakness in the median nerve distribution [4].

CTS arises from multiple factors. Mechanical stressors, such as repetitive wrist movements, forceful gripping, and vibration exposure, are key contributors [5]. Metabolic disorders, such as obesity, hypothyroidism, and diabetes, further increase the risk [6]. Elevated intracarpal pressure is central to its pathogenesis. Although the exact cause of increased pressure remains unclear, evidence points to anatomical compression and inflammation as contributing factors [7]. Excessive pressure can directly damage the median nerve, impair axonal transport, and compress perineurial vessels, leading to ischemia, endoneurial edema, and inflammation, all of which exacerbate nerve dysfunction [7].

Corticosteroid injection is a commonly used conservative treatment for CTS [8]. By reducing inflammation within the carpal tunnel, it helps alleviate nerve irritation, offering short-term symptom relief [9]. Clinical studies suggest that corticosteroids are particularly beneficial in patients with mild to moderate CTS, providing rapid pain reduction and functional improvement, typically within 4 to 12 weeks [10]. However, corticosteroids do not address elevated intracarpal pressure and can even exacerbate nerve compression in some cases by causing tissue swelling.

Acupotomy, a minimally invasive technique that combines acupuncture principles with microsurgery, involves using a flat-bladed needle-knife to release tight or fibrotic tissues, aiming to restore function by decompressing structures [11]. Unlike traditional acupuncture, which involves inserting fine needles to stimulate meridian points for pain relief and neuromodulation, acupotomy exerts a mechanical cutting or releasing effect on soft tissues [12]. In CTS, acupotomy targets the transverse carpal ligament to reduce intracarpal pressure and alleviate compression of the median nerve, thereby improving the symptoms of CTS [13]. When performed under ultrasound guidance, acupotomy release ensures precise targeting while minimizing the risk of nerve or vascular injury, thereby offering enhanced safety.

We hypothesize that, by combining corticosteroid injection with acupotomy release, both the inflammatory and mechanical components of CTS can be simultaneously addressed, resulting in more effective symptom relief. Previous studies have demonstrated that this combined approach provides favorable therapeutic outcomes in the management of CTS [14].

In this study, we conducted a clinical observation of the effectiveness of ultrasound-guided intra-carpal corticosteroid injection combined with acupotomy release of the transverse carpal ligament, compared with the effectiveness of corticosteroid injection alone, for the treatment of CTS. The objective was to evaluate the efficacy and safety of the combined treatment approach.

Material and Methods

Study Design

This study protocol of this prospective, single-blinded, randomized controlled study was approved by the Ethics Committee of Huzhou Traditional Chinese Medicine Hospital (No. 2023-LW-15). All patients provided written informed consent before being randomly assigned to receive either corticosteroid injection combined with acupotomy release (group A) or corticosteroid injection alone (group B). Randomization was conducted using a computer-generated sequence in blocks of 4, without stratification. To ensure allocation concealment, treatment assignments were placed in sealed envelopes, which were opened only immediately prior to the intervention.

Owing to the clear procedural differences between the 2 interventions, blinding of the patients and treating physicians was not feasible. However, to minimize bias, outcome assessments were performed by an independent investigator who was blinded to group allocation.

Participants

Patients were recruited from outpatient clinics of Huzhou Traditional Chinese Medicine Hospital from January 2023 to June 2024. The inclusion criteria were as follows: (1) patients presented with typical CTS symptoms, such as nocturnal, posture-related, or activity-induced paresthesia in the affected hand lasting for at least 3 months; and (2) electrophysiological testing confirmed mild to moderate CTS, defined as slowed sensory conduction with or without slowed motor conduction, but without evidence of axonal loss. The exclusion criteria were as follows: (1) CTS secondary to trauma, fractures, or space-occupying lesions within the carpal tunnel; (2) a history of prior wrist surgery or a prior corticosteroid injection administered to the affected wrist within the last 6 months; (3) other diseases that could affect hand sensation and function, such as cervical spondylosis, cubital tunnel syndrome, and thoracic outlet syndrome; (4) patients with infectious diseases, immune system diseases, psychiatric diseases, or other contraindications for the treatment; (5) patients with routine oral use of nonsteroidal anti-inflammatory drugs or corticosteroids; and (6) pregnancy or lactation.

Ultrasound-Guided Treatment

Corticosteroid Injection

Patients were seated with the wrist supported on a padded surface, palm up, and fingers relaxed. An ultrasound system (Mindray M9, Shenzhen, China) and a high-frequency linear array ultrasound probe (8–13 MHz) were used. The ultrasound probe was placed parallel to the palmar crease over the proximal carpal tunnel inlet, and a short-axis view was used to examine the transverse carpal ligament and median nerve. Using an in-plane approach, a needle was inserted from the ulnar side, avoiding the ulnar nerve and artery. Under ultrasound guidance, the needle was advanced to the superficial ulnar side of the median nerve, where 2.5 mL of solution (1 mL of 2% lidocaine and 2 mg of compound betamethasone diluted to 5 mL with saline) was injected between the transverse carpal ligament and the median nerve. For hydrodissection, an additional 2.5 mL of the solution was injected deep to the median nerve, between the nerve and the subsynovial connective tissue. After confirmation of correct needle placement and fluid spread around the nerve, the needle was withdrawn, and the injection site was dressed (Figure 1).

Figure 1.

Ultrasound-guided corticosteroid injection (A) above and (B) under the median nerve. MN – median nerve; white arrow – transverse carpal ligament; asterisk – anechoic injectate; red arrow – needle; S – flexor digitorum superficialis tendon; P – flexor digitorum profundus tendon; FPL – flexor pollicis longus tendon.

Acupotomy for Transverse Carpal Ligament Release

With patients in the same position, a longitudinal ultrasound view revealed a thickened transverse carpal ligament and median nerve compression, typically presenting as an hourglass deformity – characterized by nerve flattening at the compression site with proximal and distal swelling [15]. The probe was rotated to a short-axis view to further evaluate the morphology of the ligament and nerve, as well as the target release area – extending from the proximal attachment points of the transverse carpal ligament on the scaphoid tuberosity and pisiform to the distal attachment points on the trapezium and hamate. Further, the depth of the ligament from the skin surface was measured. After standard disinfection, the ultrasound probe, covered in coupling gel and a sterile glove, was used to locate the proximal end of the ligament. The acupotomy (length: 50 mm, diameter: 1.0 mm; Figure 2) entry point was positioned ulnar to the median nerve, approximately 3 mm from the ultrasound probe. After administering local anesthesia (1% lidocaine, 2 mL), the acupotomy was inserted at a 20° angle relative to the skin. Upon reaching the ligament under ultrasound guidance, release was achieved by gently pushing and cutting, while monitoring the acupotomy depth to avoid penetrating beyond the ligament’s base. Long-axis and short-axis ultrasound views were used to observe the procedure in real time, preventing injury to the median nerve and tendons (Figure 3). During the push-cutting process, the practitioner could clearly feel the tissue being incised beneath the acupotomy blade. As the transverse carpal ligament fibers were released, distinct tactile feedback indicating fiber separation was perceived. The acupotomy was then withdrawn, and the puncture site was dressed.

Figure 2.

Ultrasound-guided acupotomy release of the transverse carpal ligament for the treatment of carpal tunnel syndrome, with (A, B) long-axis and (C, D) short-axis ultrasound images. MN – median nerve; white arrow – transverse carpal ligament; asterisk – anechoic injectate; red arrow – acupotomy; S – flexor digitorum superficialis tendon; P – flexor digitorum profundus tendon; FPL – flexor pollicis longus tendon.

Figure 3.

Images show (A) the frontal view of the acupotomy tool; and (B) lateral view of the acupotomy tool.

All treatments and ultrasound evaluations were performed by a single physician with over 5 years of experience in musculoskeletal ultrasound, to ensure consistency and accuracy.

Outcome Measurement

Patients’ baseline assessment data were collected during routine outpatient visits, and patients were required to return for follow-up visits at 2 weeks, 1 month, and 3 months after treatment, to provide additional assessment information. Symptom severity was evaluated using the Boston Carpal Tunnel Questionnaire–Symptom Severity Score (BCTQ-S), consisting of 11 questions on the frequency, intensity, and duration of hand numbness and pain. Functional status was measured with the Boston Carpal Tunnel Questionnaire-Function Scale (BCTQ-F), which consists of 8 questions on daily hand activities, such as writing and household tasks. Scores range from 1 to 5, with lower scores indicating better function. Ultrasound was used to assess the cross-sectional area (CSA) of the median nerve at the carpal tunnel inlet and its flattening ratio (long axis/short axis) within the carpal tunnel, before treatment and 3 months after treatment (Figure 4). Additionally, complications were monitored. All ultrasound examinations were performed by a single experienced sonographer blinded to group allocation, and all clinical evaluations were conducted by an independent, blinded assessor to ensure consistency and objectivity.

Figure 4.

(A) The median nerve cross-sectional area was measured at the carpal tunnel inlet. (B) The median nerve flattening ratio was measured in the carpal tunnel. MN – median nerve; white arrow – transverse carpal ligament.

Statistical Analysis

Statistical analyses were performed using SPSS 23.0 (IBM Corp, Armonk, NY, USA). Continuous data were presented as means with standard deviations, while categorical data were expressed as counts and proportions. The Shapiro-Wilk test was used to assess the normality of data distribution. Continuous variables were conducted using 2-sample t tests for normally distributed data and Wilcoxon rank-sum tests for non-normally distributed data. Categorical variables were analyzed using the chi-square test or Fisher exact test, depending on data distribution. P values <0.05 indicated statistical significance.

Results

Study Participants

A total of 78 patients who met the preliminary eligibility criteria were invited to participate in the trial. Of these, 68 provided informed consent and were randomly assigned into 2 groups: group A, receiving corticosteroid injection combined with acupotomy release (n=34), and group B, receiving corticosteroid injection alone (n=34). No patients were lost to follow-up throughout the study (Figure 5). Baseline characteristics, including age, sex distribution, body mass index, disease duration, BCTQ scores, and the median nerve’s CSA and flattening ratio were well-balanced across the groups, with no significant differences observed (Table 1).

Figure 5.

Study flow diagram for the group receiving acupotomy release with corticosteroid injection and group receiving corticosteroid injection only.

Table 1.

Baseline characteristics of the patients.

Parameter	Group A (n=34)	Group B (n=34)	P value
Sex (F/M)	26/8	29/5	0.355
Age (years)	55.29±8.45	53.71±10.07	0.483
Dominant side (R/L)	23/11	19/15	0.318
BMI (kg/m2)	22.76±3.13	23.67±3.17	0.235
Disease course (month)	5.12±3.77	4.41±2.95	0.393
BCTQ-S	25.76±4.17	24.50±4.50	0.234
BCTQ-F	12.26±3.67	11.91±3.37	0.681
CSA (mm2)	15.31±2.96	14.33±2.41	0.139
Flattening ratio	3.57±0.54	3.49±0.45	0.493

BMI – body mass index; CSA – cross-sectional area; BCTQ-S – Boston Carpal Tunnel Questionnaire-Symptom Severity Score; BCTQ-F – Boston Carpal Tunnel Questionnaire-Functional Status Scale.

Outcome Measurements

As shown in Table 2, both groups exhibited reductions in BCTQ-S and BCTQ-F scores at all follow-up points after treatment, compared with baseline scores. In group A, BCTQ-S scores at 1 and 3 months did not differ significantly, but both were significantly lower than at 2 weeks after treatment. BCTQ-F scores continuously declined over time, with statistically significant improvements at each follow-up. In group B, there was no significant difference in BCTQ-S scores between 2 weeks and 1 month, but scores at 3 months were significantly higher than those at earlier time points. BCTQ-F scores in group B showed no significant differences across all follow-up points.

Table 2.

Clinical outcomes at baseline and 2 weeks, 1 month, and 3 months after treatment.

Parameter	Group A (n=34)	Difference from baseline	Group B (n=34)	Difference from baseline	Inter-group P value
BCTQ-S
Baseline	25.76±4.17abc		24.50±4.50abc
2 wk after tx	18.82±3.57ade	−6.94±3.03	18.12±3.09ae	−6.38±5.59	0.610
1 mo after tx	17.26±3.45bd	−8.50±4.83	19.00±4.01bf	−5.50±5.24	0.017
3 mo after tx	17.47±3.31ce	−8.29±4.83	20.85±3.99cef	−3.65±4.45	0.000
BCTQ-F
Baseline	12.26±3.67abc		11.91±3.37abc
2 wk after tx	11.50±3.42ade	−0.76±1.07	11.12±2.85a	−0.79±0.98	0.906
1 mo after tx	10.91±3.44bdf	−1.35±1.35	11.15±2.96b	−0.76±0.92	0.039
3 mo after tx	10.35±3.21cef	−1.91±1.52	11.24±2.84c	−0.68±1.12	0.000
CSA (mm 2 )
Baseline	15.31±2.96a		14.33±2.41a
3 mo after tx	11.63±2.80a	−3.68±3.22	12.58±2.16a	−1.75±2.68	0.009
Flattening ratio
Baseline	3.57±0.54a		3.49±0.45
3 mo after tx	3.30±0.45a	−0.27±0.37	3.42±0.39	−0.06±0.43	0.038

BCTQ-S – Boston Carpal Tunnel Questionnaire-Symptom Severity Score; BCTQ-F – Boston Carpal Tunnel Questionnaire-Functional Status Scale; CSA – cross-sectional area; tx – treatment; wk – week; mo – month. Significant differences within the same group:

^abetween baseline and 2-week post-tx scores;

^bbetween baseline and 1-month post-tx scores;

^cbetween baseline and 3-month post-tx scores;

^dbetween 2-week and 1-month post-tx scores;

^ebetween 2-week and 3-month post-tx scores;

^Fbetween 1-month and 3-month post-tx scores.

Intergroup comparisons revealed that at 2 weeks, the reductions in BCTQ-S and BCTQ-F scores from baseline were comparable between the 2 groups. However, at 1 month and 3 months after treatment, group A demonstrated significantly greater improvements in both scores, compared with group B.

Ultrasound evaluations showed improvements in the median nerve’s CSA in both groups, compared with baseline, while the flattening ratio improved significantly only in group A. The extent of improvement in both ultrasound parameters was significantly greater in group A than in group B after treatment.

No complications, including nerve injury or infection, were observed in either group throughout the follow-up period.

Discussion

For patients with a clinical diagnosis of mild CTS, conservative treatment is recommended as the initial management strategy. Similarly, for patients with moderate to severe symptoms but electrodiagnostic findings indicating mild or moderate CTS (without axonal loss), conservative approaches can also be appropriate [16]. In this study, we compared 2 conservative treatments for CTS. The results demonstrated that ultrasound-guided corticosteroid injection combined with acupotomy release of the transverse carpal ligament was superior to corticosteroid injection alone. This combined approach showed greater improvements in hand symptoms, functional outcomes, and ultrasound-assessed morphological parameters of the median nerve.

Corticosteroid injection into the carpal tunnel is widely used as a first-line therapy to reduce inflammation and promote recovery. A 2023 systematic review encompassing 14 trials demonstrated that corticosteroid injections provided greater improvement in symptoms and hand function at 3 months, compared with placebo [10]. One trial involving 81 patients with splint-refractory CTS randomized patients to a corticosteroid injection group or a sham treatment group. At 2 weeks after injection, symptom relief was reported in 70% of patients in the corticosteroid group, compared with 34% in the sham group. Among sham-treated patients subsequently receiving betamethasone injections, 73% reported symptom improvement [17]. Our study yielded similar findings, demonstrating that corticosteroid injection into the carpal tunnel significantly improved BCTQ scores and the CSA of the median nerve within the 3-month follow-up period.

Nevertheless, the long-term efficacy of corticosteroid injections in symptom relief remains uncertain. Our study showed that while the BCTQ-S scores at 3 months after corticosteroid injection improved compared with baseline, they were higher than the scores recorded at 2 weeks and 1 month after treatment. This suggests a declining trend in symptom improvement over time, even though hydrodissection of the median nerve was performed in addition to the corticosteroid injection. This phenomenon may be associated with the waning therapeutic efficacy of corticosteroids over time [18]. A trial comparing methylprednisolone with placebo found that the effects of methylprednisolone diminished after 1 year [19]. Furthermore, a 5-year follow-up study revealed that symptom severity in the corticosteroid injection group was similar to that of other treatment groups, with most patients (91%) eventually undergoing carpal tunnel release surgery [20].

These findings suggest that corticosteroid injection provides short-term relief for CTS, likely due to its limited effect on reducing intracarpal pressure. While corticosteroid injection effectively alleviates inflammation and temporarily relieves symptoms, it does not address mechanical factors, such as a thickened transverse carpal ligament. As noted, elevated intracarpal pressure is a key factor in CTS pathogenesis, leading to median nerve compression, demyelination, and axonal degeneration. Early decompression of the carpal tunnel is essential for relieving symptoms and restoring damaged nerve function, as it helps improve nerve conduction and prevent further neurological deterioration [21]. The primary goal of using acupotomy in the treatment of CTS is to release the transverse carpal ligament, thereby relieving the compression on the median nerve. Cadaveric studies have demonstrated the feasibility of acupotomy therapy as a viable method for CTS treatment [22]. Although minimally invasive procedures, such as endoscopic release, are effective in relieving compression of the transverse carpal ligament, they typically require an operating room setting and carry certain surgical risks [23]. In contrast, acupotomy release is less invasive, can be performed in an outpatient setting, and offers a more accessible alternative. It is worth noting that conventional acupotomy therapy, relying solely on anatomical landmarks and performed blindly, poses risks of injuring nerves, tendons, and blood vessels. As a result, this technique demands exceptional anatomical knowledge and advanced procedural skills from the practitioner. However, ultrasound-guided treatment for CTS enables visualization, significantly enhancing the precision and safety of the procedure [24]. Meanwhile, ultrasound, as a non-invasive, easily accessible, cost-effective, and patient-friendly imaging modality, is increasingly used in the diagnosis and staging of CTS [25]. It allows for the measurement of the diameter and CSA of the median nerve, providing an objective assessment of nerve compression. In addition, ultrasound allows real-time evaluation of the nerve’s vascularity and mobility and its relationship with surrounding structures, making it an excellent tool for treatment guidance [26]. Our findings indicated that combined treatment using ultrasound-guided acupotomy release and corticosteroid injection provided greater relief of CTS symptoms and functions at all follow-up points, compared with corticosteroid injection alone. However, acupotomy therapy requires a high level of operator skill, particularly in ultrasound anatomy, and has a notable learning curve, limiting its widespread adoption among physicians without specialized training. Moreover, careful patient selection is essential. In individuals with advanced disease, anatomical variations, or comorbidities, such as severe tenosynovitis, this minimally invasive approach can carry increased procedural risks.

This study has several limitations. First, the sample size was determined based on clinical feasibility – such as patient availability and recruitment capacity – without a formal power calculation, which may have reduced statistical power. Second, the single-center design limits generalizability, as outcomes can vary with patient characteristics, operator expertise, and healthcare settings. Third, the short follow-up duration of 3 months may have been insufficient to assess long-term efficacy and symptom recurrence. We recommended an extended follow-up in future studies. In addition, all procedures in this study were performed by a single experienced operator. While this ensured technical consistency, it limits the generalizability of the findings. Future studies should involve multiple operators to better assess the reproducibility and applicability of the results in broader clinical settings. Lastly, the absence of patient blinding and a sham acupotomy control group may have introduced bias. Although sham procedures were not feasible in this exploratory setting, owing to ethical and practical concerns, we acknowledge this as a methodological limitation. Future randomized controlled trials should consider incorporating sham controls to better isolate the effect of acupotomy.

Conclusions

This study highlights the synergistic therapeutic effects of acupotomy release, nerve blockade, and ultrasound imaging. This combined procedure was simple, time-efficient, and suitable for an outpatient setting. It also improved the overall quality of treatment, allowing patients to recover, return to work, and reintegrate into society faster.