Ultrasound- vs Landmark-Guided Steroid Injection for Carpal Tunnel Syndrome

Is steroid injection guided by ultrasonography (US) superior to landmark-guided injection for carpal tunnel syndrome?

US-guided steroid injection should be considered for carpal tunnel syndrome because statistically significant benefits have been shown in symptom and functional improvement and a reduced rate of complications (number needed to treat [NNT] = 5) compared with landmark-guided injection. (Strength of Recommendation: A, meta-analyses.)

A 2023 Cochrane review of 14 randomized controlled trials (RCTs) and quasi-RCTs (nine with quantifiable data) examined effects of local, landmark-guided corticosteroid injection vs no treatment or placebo injection.¹ Studies included patients 18 years and older diagnosed with carpal tunnel syndrome.

The review found that landmark-guided corticosteroid injection into or near the carpal tunnel likely improved symptoms at 3 months or less (standardized mean difference [SMD] = −0.77; 95% CI, −0.94 to −0.59; eight RCTs; n = 579; moderate-certainty evidence) and at greater than 3 months (SMD = −0.58; 95% CI, −0.89 to −0.28; three RCTs; n = 234; moderate-certainty evidence) compared with no treatment or placebo injection. Functional improvement also was shown at 3 months or less (SMD = −0.62; 95% CI, −0.87 to −0.38; seven RCTs; n = 499; moderate-certainty evidence) compared with no treatment or placebo injection.

Four meta-analyses examined the outcomes of symptom and functional improvement and complications after US- and landmark-guided steroid injections for carpal tunnel syndrome.^2–5 Each meta-analysis reviewed eight or nine studies. All four meta-analyses were RCTs that included adult patients who had carpal tunnel syndrome with at least one US-guided steroid injection group and one landmark-guided steroid injection group. One analysis also included retrospective studies.²

Seven RCTs were analyzed in all four meta-analyses; one meta-analysis included a single retrospective study and, for unclear reasons, excluded an eighth RCT that was found in the other three.² A ninth RCT included in only one meta-analysis was excluded from the others based on the inclusion of vitamin B₁₂ in the injection contents.⁴

Patients in the analyzed studies had carpal tunnel syndrome severity ranging from mild to moderate, moderate to severe, or mild to severe.^2–5 The majority were women. Mean patient age was reported in only one meta-analysis as 53 years (range: 46–59 years) in the US-guided injection group and 52 years (range: 43–62 years) in the landmark-guided injection group.³ Timing of follow-up ranged from 4 to 24 weeks in the RCTs, whereas the retrospective study had a mean follow-up of 7.2 years.

The studies included in these analyses used components of the Boston Carpal Tunnel Questionnaire (BCTQ) to assess symptom and functional improvement. The BCTQ Symptom Severity Scale and BCTQ Functional Status Scale each used a 5-point scale, with a lower score representing milder symptom severity or greater level of function, respectively. The total score for each was an average of the scores for the individual questions.

All four meta-analyses found statistically significant improvement in symptom control at follow-up in the US-guided injection groups vs the landmark-guided injection groups.^2–5 Three of the four meta-analyses identified significant improvement in function in the US-guided injection groups compared with the landmark-guided injection groups^3–5 (Table 1^2–5). Complications assessed included numbness, wrist weakness, pain, and swelling. These were measured in terms of relative risk. Three meta-analyses found a significant decrease in complications in the US-guided injection groups compared with the landmark-guided injection groups.^2–4 One study reported that no serious complications, such as permanent injury, occurred in either group.² One study reported the absolute risk reduction of adverse events as 21%, yielding an NNT of 5.³