Abstract

Objectives: In this review, we discuss the efficacy of ultrasound (US)-guided versus landmark (LM)-guided median perineurial nerve injections in carpal tunnel syndrome (CTS).

Materials and methods: Initial search of PubMed, Scopus, Web of Science, and Emboss databases using search terms such as “median neuropathy,” “ultrasound-guided,” and “median nerve injection” from October 1966 to May 2023 yielded 4,172 articles to be screened by one reviewer for eligibility and two reviewers for full-text review. The study quality of the resulting 12 articles was assessed using the Newcastle-Ottawa Scale (NOS) and Revised Cochrane Risk of Bias Tool of Randomized Trials (RoB 2).

Results: All 12 articles reviewed evaluated efficacy of US-guided injections relative to LM-guided injections. Nine studies showed improved outcomes in US-guided injections compared to LM-guided, including improvement in the Boston Carpal Tunnel Syndrome Symptom Severity Scale and Functional Status Scale and improvement in procedural pain and injection pain.

Conclusion: Both US-guided and LM-guided median perineurial nerve injections can improve outcomes in patients with CTS. However, further studies are warranted to assess the accuracy of US-guided median perineurial nerve injections compared to LM-guided to effectively conclude whether one technique is superior to the other.

Introduction

Carpal tunnel syndrome (CTS) is a common cause of pain, paresthesia, and weakness in the median nerve distribution that can be debilitating. Options for conservative treatment include resting wrist splints and the placement of injectate surrounding the median nerve inside the carpal tunnel. Types of injectates include glucocorticoids and regenerative agents such as 5% dextrose and platelet-rich plasma.[1] These conservative measures can delay or prevent the need for surgical release of the carpal tunnel. Accurate placement of injectate is necessary to provide the most symptomatic relief and to avoid further injury to the median nerve. Current techniques for carpal tunnel injection include the use of landmark (LM) and ultrasound (US) guidance. Anatomic LMs of the distal wrist crease and palmaris longus tendon are used during the former technique. With US guidance, the median nerve can be directly visualized to bathe the median nerve within the carpal tunnel both superiorly and inferiorly.

In recent years, US-guided procedures have increasingly become more prevalent as evidenced by many studies and systematic reviews demonstrating its utility.[2-10] However, there is still a lack of literature directly comparing the efficacy of US-guided injections versus other modalities of injection such as LM-guided ones. In this review, we discuss the efficacy of US- and LM-guided median perineurial nerve injections in CTS patients in the light of literature data.

Material and Methods

Search strategy

For our initial search, PubMed, Scopus, Web of Science, and Embase databases were utilized with search terms such as “median neuropathy,” “ultrasound-guided,” and “median nerve injection.” A full list of search terms is included in the supplementary materials. (See Supplementary Table 1). These databases were searched from October 1966 to May 2023. The most recent date of the literature search was June 19, 2023. This search generated 6,345 articles with 2,178 duplicates removed, leaving 4,172 to be screened. Those articles were, then, screened by title and abstract to only include human studies written in English with a comparison intervention using the same injectate, leaving 28 studies for full-text review. After full-text review, 12 articles were unanimously chosen by the first and second authors to ultimately be included in the systematic review (Figure 1).

Figure 1. Flow diagram.

Assessment of study quality

Each study was evaluated using either the Newcastle-Ottawa Scale (NOS) or the Revised Cochrane Risk of Bias Tool for Randomized Trials (RoB 2). The NOS assesses cohort and case control studies in terms of selection bias, comparability, and exposure/outcome by assigning points to each criterion with a maximum score of nine points indicating low risk of bias. The RoB 2 assesses randomized trials based on factors involved in the randomization process, study intervention, missing outcome data, measurement of outcome, selection of reported result. A grade of high risk of bias in any category results in an overall high risk of bias.

Results

Overview

All 12 of the studies included in this review compared the efficacy of US-guided injections to LM-guided injections (Table 1). Nine of the studies were randomized clinical trials, two were cohort studies, and one was case control. Injection location varied where one study compared US in-plane and US out-of-plane injections relative to LM.[7] Follow-up time ranged from 12 weeks to one year. Due to the nature of the intervention, most of the studies had difficulty with blinding, thereby resulting in an increased risk of bias (Table 2a). Some of the studies were single-blind, while others were double-blind. Objective measurements to evaluate efficacy included the Boston Carpal Tunnel Syndrome Questionnaire (BCTQ), Visual Analog Scale (VAS), electrodiagnostics, and rate of retreatment following steroid injection. As there was heterogeneity in the studies, designs, and outcomes, A particular caution was exercised regarding the generalizability of our results.

Table 1. Summary of included studies

Table 1. Continued

Table 1. Continued

Table 1. Continued

Table 1. Continued

Risk of bias assessment

Of the 12 studies, three were observational and assessed using the NOS. All the studies lost at least one point in comparability for lack of blinding of the participants. The study by Omar et al.[9] and Dabees[2] lost a point for inadequate follow up period. The study by Evers et al.[4] lost a point for ascertainment of exposure and imbalance in LM-guided and US-guided groups.[4] The other nine studies were assessed by the RoB 2, and all but one study was found to have high risk of bias. The summary of these evaluations is given in Tables 2a and b.

Table 2a. Quality Assessment using the Revised Cochrane Risk-of-Bias Tool for Randomized Trials

Table 2b. Quality assessment using the Newcastle-Ottawa Quality Assessment scale of included studies

Median perineurial nerve injection efficacy

Of the 12 studies included in this review, nine showed improved outcomes in US-guided injections compared to LM-guided. Dabees,[2] Karaahmet et al.,[6] Lee et al.,[7] and Rayegani et al.[10] found a statistically significant difference in improvement of US-guided relative to LM-guided injections for the BCTQ Symptom Severity Scale (SSS) and Functional Status Scale (FSS). Dabees[2] found US-guided improved BCTQ-SSS and -FSS by 86.66% (p = 0.002) compared to LM-guided 53.33% (p = 0.252). Karaahmet et al.[6] found BCTQ-SSS change after treatment 17.1 for US-guided and 7.9 for LM-guided (p = 0.001) and BCTQ-FSS change after treatment 12.0 for US-guided and 5.0 for LM-guided (p < 0.001). Lee et al.[7] found significant changes for BCTQSSS LM-guided (20.18; p<0.05), US in-plane (12.18; p<0.05), and US out-of-plane (17.41; p < 0.05) and for BCTQ-FSS LM-guided (10.18; p < 0.05), US-in plane (8.76; p < 0.05), and US-out of plane (10.18; p < 0.05). Rayegani et al.[10] observed an improvement in BCTQ-FSS US ulnar in-plane (12.15; p = 0.023), US midline in-plane (12.63; p = 0.019), and LM-guided (14.74; p = 0.000). Dabees[2] found significant improvement of US-guided injections relative to LM-guided in terms of reduction in diameter of median nerve (US 92.31%, LM-guided 40% chi-square 7.304; p = 0.007), normal echogenicity of median nerve (US 100%, LM-guided 57.14% chi-square 6.107; p = 0.013), and return of normal thickness of flexor retinaculum (US-guided 83.33%, LM-guided 37.50% chi-square 3.13; p = 0.044). The retrospective cohort study by Evers et al.[4] found that a higher percentage of LM-guided injections required retreatment and eventual surgery compared to US-guided injections with an odds ratio of retreatment of US-guided compared to LM-guided within one year of 0.45. Makhlouf et al.[8] reported a significant improvement of US-guided relative to LM-guided in pain at two weeks (p = 0.014), reduction in pain from baseline (p = 0.028), pain from baseline at six months (p=0.001), duration of therapeutic effect (p = 0.001), time to next procedure (p = 0.035), needle introduction procedural pain (p = 0.02), and injection pain (p = 0.001).

On the other hand, studies by Chen et al.,[11] Eslamian et al.,[3] Roh et al.,[12] and Vahdatpour et al.[13] did not show significant difference in efficacy between US-guided and LM-guided injections. The study by Chen et al.[11] compared sensation, grip strength, lateral pinch strength, BCTQ-SSS and -FSS VAS, as well as multiple electromyographic (EMG) factors between US- and LM-guided injections in terms of time and interaction between injection group and time. There was not statistically significant improvement with US-guided intervention over time relative to LM-guided in terms of BCTQ-SSS (p=0.893), -FSS (p=0.936), and VAS (p=0.944). That being said, there was statistically significant improvement in all the above variables relative to time suggesting that both US-guided and LM-guided interventions improve symptoms and function related to median nerve injury over time. Similarly, the study by Omar et al.[9] showed an improvement in the BCTQ-SSS and BCTQ-FSS, nerve conduction studies, and cross-sectional area of the median nerve from steroid injections, but did not show statistically significant differences between US-guided and LM-guided injections. Studies including EMG/nerve conduction velocity data had inconsistent results that did not clearly show statistically significant superiority of US-guided relative to LM-guided injections.[3,6,7,10,11,13]

Discussion

The primary objective of this systematic review was to assess the efficacy of US-versus LM-guided injection of the median nerve. The majority of the studies suggest that efficacy of outcomes in US-guided placement of injectate for the median nerve are increased, compared to LM-guided injections for patients with CTS.[2-10] Although many of the studies showed a statistically significant improvement of CTS with LM-guided injections, the magnitude of improvement was greater in the US-guided group.[2,4-10]

Other important variables to consider that affect the outcomes of each intervention type are those related to patient experience and proficiency of the injector. Makhlouf et al.[8] reported that US-guided injections were associated with reduced procedural pain and reduced overall healthcare costs. Such factors are critical for individual patient care and well-being. Furthermore, the study by Evers et al.[4] showed that the specialty and proficiency of the physician performing the intervention was another variable that could ultimately affect patient outcomes. In that patient population, 69% of US-guided injections were performed by physical medicine and rehabilitation physicians, 26% by rheumatologists, 3% by orthopedic surgeons, and 1% by radiologists.[4] This finding indicates that the training of the physician likely influences both their injection technique and overall proficiency. Therefore, more emphasis should be placed on training for physicians performing these interventions given the steep learning curve.

Utilizing US in evaluating and treating CTS and other musculoskeletal injuries can help quickly rule out other dangerous etiologies with similar presentations. Furthermore, it can help the provider performing the intervention to better understand patients’ individual anatomy both to evaluate the etiology of injury and to guide potential intervention. This guidance would also include clinical decision-making as to which injectate needs to be used for that patient/condition. Yet, the spectrum of carpal tunnel injection is quite broad. Overall, US is a tool which can prioritize patient safety and well-being through more proficient use.

Nonetheless, there are certain limitations that should be noted. This review included studies with high risk of bias as assessed by RoB 2. Due to the nature of the procedure, patients were not blind to the intervention being conducted with US- versus LM-guidance. This risk of bias is exacerbated by the measurement of intervention efficacy by questionnaires completed by the patient and small sample sizes. Since we did not perform a meta-analysis, our study relies on qualitative data from studies that carry a high risk of bias.

In conclusion, both US- guided and LM-guided injections can improve symptoms and functional status of patients with CTS. However, further studies are warranted to assess the accuracy of US-guided median perineurial nerve injections compared to LM-guided to effectively conclude whether one technique is superior to the other. Future directions for assessing accuracy should include prospective US-guided versus LM-guided steroid injections.

Citation:
Kim L, Konda C, Jones E, Özçakar L, Jain NB. Efficacy of ultrasound-guided perineural injections of the median nerve: A systematic review. Arch ISPRM 2026;1(1):11-21. https:// doi.org/10.5606/archisprm.2026.32.

N.B.J., L.O.: Idea/concept, design, control/supervision; L.K.: Data collection and/or processing; L.K., C.K., N.B.J., L.O.: Analysis and/or interpretation; L.K., C.K., E.J.: Literature review, writing the article; L.K., C.K., E.J., L.O.: Critical review.

The authors declare that there are no conflicts of interest with respect to the research, authorship, and/or publication of this article.

This research received no specific grant from any funding agency in the public, commercial, or not‑for‑profit sectors.

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

AI Disclosure
The authors declare that artificial intelligence (AI) tools were not used, or were used solely for language editing, and had no role in data analysis, interpretation, or the formulation of conclusions. All scientific content, data interpretation, and conclusions are the sole responsibility of the authors. The authors further confirm that AI tools were not used to generate, fabricate, or ‘hallucinate’ references, and that all references have been carefully verified for accuracy.

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