We conducted an ambispective observational study including patients with HS tunnels treated with ultrasound-guided percutaneous galvanic current (GC) or ultrasound-guided intralesional triamcinolone acetonide injection. The safety and efficacy profile of both therapies were evaluated 12 weeks into therapy. The STROBE guidelines were followed for the design of this observational study.

Data corresponding to patients treated with ultrasound-guided intralesional triamcinolone acetonide were collected retrospectively. This treatment is routinely administered in the unit and documented in a structured medical record template with dated clinical examination. Subsequently, the information is anonymized and incorporated into a master database including all patients treated in the unit. This allows identification of the variable of interest and subsequent data collection through medical record review. The tunnels selected for the study were treated with this procedure from February 2019 through February 2022.

Conversely, data from patients treated with percutaneous galvanic current were collected prospectively. Recruitment of patients treated with percutaneous galvanic current took place from October 2022 through May 2023.

The primary endpoint of the study was to compare the safety and efficacy profile of ultrasound-guided percutaneous galvanic current with ultrasound-guided intralesional administration of triamcinolone acetonide in HS tunnels. The secondary endpoint was to analyze the ability of both intralesional therapies to physically eliminate the treated tunnel by replacing it with scar tissue.

Ultrasound-guided percutaneous galvanic current: Local tumescent anesthesia was administered in the area to be treated (100mL of saline solution, 2mL of 2% mepivacaine, 1mL of 0.5% bupivacaine with epinephrine, and 2mL of 1 molar bicarbonate). Subsequently, a 14 G Abbocath needle was inserted into the tunnel under ultrasound guidance and connected to the cathode of the CG Galvani-K® galvanic current generator (Fig. 2). While the patient held a manual anode, 5–10 cycles of GC were delivered at 5mA, continuous, uninterrupted, with constant intensity and duration of 5s. The Abbocath was mobilized within the lesion lumen to ensure contact with the roof, floor, and walls, being withdrawn from distal to proximal 1cm between cycles to achieve homogeneous current administration. A second GC cycle could be administered at week 4 if complete response was not achieved.

Fig. 2.

Galvani-K® device and ultrasound-guided procedure. (A) Galvanic current generator with integrated Abbocath catheter adapter and contact electrode. (B) HS inflammatory tunnel before treatment initiation with inflammatory hyperemia identified by Doppler. (C) Abbocath catheter inserted inside the tunnel under ultrasound guidance. (D) Hyperechogenic sclerosis line after administration of galvanic current and withdrawal of the Abbocath catheter. (E) Week 12 into therapy: disappearance of inflammatory hyperemia on Doppler signal, reduction in longitudinal diameter, and decrease in perilesional edema.

Ultrasound-guided triamcinolone acetonide: A maximum of 1mL of triamcinolone acetonide (TA) at a concentration of 40mg/mL was administered. Injections were performed using 1-mL syringes with 21 G needles. Ultrasound guidance was used to ensure drug administration beneath the tunnel, preventing dilution of the medication within gelatinous material or purulent exudate. The syringe was withdrawn from distal to proximal in 1-cm segments between each pulse of drug administration to ensure homogeneous distribution of the active compound.

In both groups, only 1 lesion per patient was treated. Ultrasound was performed using a 7–15MHz linear probe (myLab25 Esaote Spa, Genoa, Italy) for both interventions. Before treatment administration, the area was disinfected with a 2% chlorhexidine solution.

The inclusion criteria for both treatment groups were: (a) patient older than 18 years; (b) diagnosis of HS; (c) presence of a tunnel amenable to intralesional therapy based on its structural complexity assessed by ultrasound; (d) absence of systemic therapy initiated during the month prior to study inclusion; (e) signed informed consent to participate in the study.

Selection of the lesion to be treated: Lesion assessment was performed through physical and ultrasound examination. The tunnel had to present spontaneous pain, pain on palpation, or active drainage within 1 week prior to inclusion. If the patient presented multiple lesions fulfilling the first criterion, the following criteria were used to select the draining fistula in descending order of priority:

• 1.

  HS tunnel located in a Hurley II area vs Hurley III.

• 2.

  HS tunnel presenting a single tract vs multiple subcutaneous tracts.

• 3.

  HS tunnel without other typical disease lesions (inflammatory nodules, abscesses, other tunnels) in close proximity.

• 4.

  HS tunnel that on B-mode cutaneous ultrasound did NOT show disruption of the inferior wall – findings suggestive of instability, deep extension, and potential associated abscess formation.

• 5.

  HS tunnel considered anatomically more accessible by the investigator for performing study procedures (ultrasound evaluation and follow-up).

The exclusion criteria were: (a) refusal to participate in the study; (b) systemic treatment initiated within the month prior to study inclusion; (c) surgical or intralesional treatment received within the 12 weeks preceding study initiation on the lesion of interest.

This study was approved by the Comité Ético de Investigación Provincial de Granada (internal code 1239-N-22) and was conducted in accordance with the Declaration of Helsinki.

In patients treated with TA, general consent was obtained for the collection of routine clinical practice data, including authorization for the use of anonymized clinical data in subsequent studies.

In patients treated with GC, specific informed consent was obtained due to its experimental nature as a physical therapy. This consent included a section authorizing the use of anonymized clinical information in subsequent studies.

Primary efficacy variables: Complete response: A complete treatment response was defined as the absence of spontaneous suppuration or suppuration upon vigorous digital pressure during physical examination, together with the absence of Doppler signal suggestive of inflammatory activity on ultrasound, both assessed 12 weeks after treatment.

Secondary efficacy variables: Physical disappearance of the treated tunnel: This was defined as the absence of a draining opening or signs of active inflammation on physical examination along with the absence of ultrasound structures consistent with an inflammatory HS tunnel and soft tissue edema suggestive of inflammatory activity in the treated area. Additionally, changes in clinical variables, inflammatory activity, or disease severity (such as pain, IHS4, IHS4-55,5 and Hurley stage) 12 weeks into therapy were evaluated and considered secondary efficacy variables.

Primary safety variables: Possible adverse effects related to the intervention were recorded and evaluated by an investigator independent of the clinician performing the therapy. The following adverse effects were predefined and coded: syncope, organ damage, nerve damage, infection of the treated area, bleeding from the treated area, development of seroma, hyperglycemia, and cutaneous atrophy. Any other event potentially associated with the intervention was additionally recorded.

Other variables: Sociodemographic and clinical variables were recorded for each patient, including age, sex, non-biologic systemic treatment, biologic systemic treatment, and ultrasound-measured length of the lesion to be treated. Pain was evaluated using a numerical rating scale (NRS), while overall disease severity was assessed using the Hurley staging system and the IHS4 (International Hidradenitis Suppurativa Severity Score System) formula. The IHS4-55 version was used as a secondary efficacy variable.

Descriptive statistics were used to evaluate the characteristics of the sample. Normality of variables was assessed using the Shapiro–Wilk test. Continuous variables are presented as mean and standard deviation (SD), and categorical variables as relative and absolute frequency distributions. The chi-square test or Fisher's exact test, as appropriate, was used to compare nominal variables, while the Student's t test or the Wilcoxon–Mann–Whitney test was applied to compare continuous data between two nominal groups. To explore associated factors, simple linear regression was used for continuous variables. The β coefficient and SD were used to predict the logarithmic probabilities of the dependent variable. Pairwise interactions between model covariates were evaluated, and potential confounding covariates were identified through changes in model parameters or a 30% variation in their value. Repeated-measures ANOVA was used to analyze differences in repeated measurements of continuous variables. Statistical significance was defined as P<.05. Statistical analyses were performed using JMP version 14.1.0 (SAS Institute).

A total of 66 patients were included, 26 treated with GC and 40 with TA. No differences were identified between groups in terms of sex, age, ultrasound lesion length, percentage of patients receiving biologic therapy, treated body areas, or baseline IHS4. The percentage of patients receiving systemic therapy with non-biologic drugs was higher in the TA group, as were baseline pain and Hurley stage (Table 1).

At 12 weeks, complete clinical response (absence of suppuration+absence of Doppler inflammation) was achieved in 77.6% (20/26) of patients treated with GC and in 55% (22/40) of patients treated with TA (P=.07). After adjustment using a multivariable model, complete response remained associated with the type of therapy applied, independently of systemic treatment, baseline IHS4, or Hurley stage.

Patients treated with GC experienced a 52.3% reduction in IHS4, whereas those treated with TA showed a 41% reduction, with no differences between groups (P=.38). In this regard, 61.5% (16/26) of patients from the GC group and 35% (26/40) of patients treated with TA achieved IHS4-55 (P=.03). Regarding symptomatic control, a greater reduction in pain – assessed using a visual analog scale – was observed in patients treated with GC (80.4% reduction with GC vs 22% with TA; P<.01) (Table 2).

Lesions were evaluated by ultrasound to analyze structural changes at 12 weeks. In the GC group, 38.46% (10/26) of treated tunnels were physically eliminated, meaning that the typical ultrasound image of an HS tunnel had been completely replaced by cicatricial changes (Table 2). Patients treated with TA did not experience physical disappearance of the treated tunnel at 12 weeks (P<.01).

Two patients treated with GC (7.7%) developed adverse effects: one episode of bleeding and one episode of blister formation immediately after the intervention. Of note, 5 patients treated with GC (19.2%) reported a self-limited episode of tunnel inflammation within the first week after treatment, which was expected given that the mechanism of action of the therapy is based on reactivation of the NLRP3 inflammasome. Among the 5 patients who developed a post-treatment flare, 4 achieved complete clinical response.

In the TA group, 4 of 40 patients (10%) experienced adverse effects: 3 (7.5%) developed cutaneous atrophy and 1 (2.5%), hyperglycemia (Fig. 3).

Fig. 3.

Adverse effects observed with each therapy from 48h to 12 weeks into therapy.