2.1

This retrospective comparative study examines a consecutive cohort of patients diagnosed with HV who underwent surgical correction using a Metaphyseal Extra-Articular Transverse and Akin Osteotomies (META) technique, with spinal anesthesia administered as per institutional protocol. This investigation was conducted following the STROBE guidelines for reporting observational studies . Patients were split into two groups depending on whether they received an Ankle Block, or a Mayo Block as part of their routine care and treatment.

2.2

Between November 2023 and July 2024, patients diagnosed with HV underwent correction using the META technique under spinal anesthesia, following institutional protocol, and received either a MB or an AB.

All procedures, including the Mayo or Ankle Block and the surgical intervention, were performed at a single medical center by the same team of experienced Orthopaedic surgeons with expertise in peripheral nerve blocks (M.V.P.F., G.F.F.) based in Sao Paulo, Brazil.

Surgical intervention was pursued only after conservative measures, including footwear modification, physiotherapy, and adherence to specific guidelines, had proven insufficient ( Fig. 1 ).

Preoperative (A) and postoperative (B) radiographs demonstrating successful hallux valgus correction following minimally invasive surgery.

2.3

Inclusion criteria were as follows: (1) Patients aged 18 years or older; (2) Mild, moderate, or severe HV; (3) Patients undergoing surgical correction using a META technique; (4) Patients who received spinal anesthesia (institutional protocol) and either a Mayo Block or Ankle Block for postoperative pain management. Patients who underwent hallux valgus correction with additional procedures on the lateral rays were excluded from the study. Other exclusion criteria included pre-existing degenerative conditions of the foot or ankle, previous surgeries, and residual effects from tibial pilon, ankle, or foot fractures and patients with symptoms of peripheral neuropathy.

2.4

Patients were administered either an Ankle Block or a Mayo Block based on the preference of the performing surgeon: (G.F.F.) exclusively performed all Ankle Blocks, while (M.V.P.F.) conducted all Mayo Blocks. These choices reflected routine clinical practice and were made independently of this retrospective study, with no randomization or prospective allocation involved.

2.5

This study received approval from the local ethics committee (CAAE: 82277624.3.0000.8114) and adhered to the principles of the Declaration of Helsinki and the Guidelines for Good Clinical Practice.

2.6

The primary outcome was pain assessed at two postoperative time points: 12 h and 24 h after surgery. At the 12-h assessment, patients reported pain levels on the Visual Analog Scale, a validated pain scale . Additionally, the presence or absence of anesthesia in the great toe was recorded. Usage of analgesics administered during the hospital stay was also noted.

At the 24-h assessment, patients reported the VAS pain score only for the foot that underwent the regional block. The duration of anesthesia in hours was recorded for the great toe of each foot. At-home use of analgesia and opioids was documented, as well as patients’ overall comfort, specifically whether they experienced a comfortable night’s sleep.

2.7

Using data from Stefani et al. (ankle block) and Roberts et al. (first metatarsal block), we determined the required sample size for this study. To detect a minimum clinically significant difference of 3.0 h in anesthesia duration, the effect size (Cohen’s d) was calculated as 0.77. Based on this effect size, a two-tailed t -test, a significance level of 0.05, and a statistical power of 0.80, the required sample size was estimated at 27 participants per group, or a total of 54 feet. This calculation ensures the study is adequately powered to detect meaningful differences between the two regional block techniques, providing a reliable framework for evaluating their comparative effectiveness.

2.8

Study data were collected and managed using REDCap electronic data capture tools hosted at the Instituto Prevent Senior . REDCap (Research Electronic Data Capture) is a secure, web-based application designed to support data capture for research studies, providing (1) an intuitive interface for validated data entry; (2) audit trails for tracking data manipulation and export procedures; (3) automated export procedures for seamless data downloads to common statistical packages; and (4) procedures for importing data from external sources.

2.9

Patients underwent the surgical procedure in the supine position, without the use of a tourniquet. The surgical procedure was performed as published by Lewis et al. Surgical incisions are irrigated with saline solution, and the skin is closed with 4–0 nylon sutures. A sterile gauze dressing is then applied, followed by an elastic bandage to secure the site.

2.10

Spinal anesthesia with sedation, standardized as a subarachnoid block with 10 mg of isobaric bupivacaine, was administered by the hospital’s anesthesiologists in accordance with the institutional protocol. All patients were admitted and discharged on the same day, following the day-hospital model.

2.11

The Ankle Block was performed using 10.0 mL of ropivacaine (7.5 mg/mL) and 10.0 mL of saline solution, divided into five injections using a Stimuplex® A50 needle- 22 G, without ultrasound, targeting the following five nerves:

• 1.

  Tibial nerve was blocked with 8.0 mL of anesthetic 2.0 cm proximal to the medial malleolus ( Fig. 2 A).

  

  Ankle block (A-E).

• 2.

  Deep peroneal nerve was injected with 2.0 mL of anesthetic between the extensor hallucis longus and extensor digitorum longus tendons, lateral to the dorsalis pedis artery ( Fig. 2 B).

• 3.

  Superficial peroneal nerve received 6.0 mL in a fan-shaped subcutaneous infiltration at the level of the ankle ( Fig. 2 C).

• 4.

  Saphenous nerve was blocked with 2.0 mL subcutaneously at points near the medial malleolus ( Fig. 2 D).

• 5.

  Sural nerve was blocked with 2.0 mL of anesthetic, injected subcutaneously 1–1.5 cm distal to the tip of the fibula ( Fig. 2 E).

The Ankle Block procedure, including detailed injection techniques and anatomical landmarks, can be viewed in Video 1.

The following is the Supplementary material related to this article Video S1 .

2.12

The Mayo Block was administered with 5.0 mL of ropivacaine (7.5 mg/mL) and 5.0 mL of saline solution, divided into four injections using a Stimuplex® A50 needle- 22 G. The procedure was performed as follows:

• 1.

  Begin by palpating dorsally, just distal to the flare at the base of the first metatarsal and create a wheal. Inject from the dorsal to the plantar surface ( Fig. 3 A).

  

  Mayo block (A-D).

• 2.

  Next, palpate dorsally again, slightly distal to the flare of the first metatarsal base. Inject dorsally, moving from medial to lateral, staying within the subcutaneous tissue and carefully avoiding the deep branch of the dorsalis pedis artery ( Fig. 3 B).

• 3.

  For the third injection, palpate proximally at the first interspace. Insert the needle immediately lateral to the extensor hallucis longus tendon and medial to the dorsalis pedis artery and its deep branch. Inject from the dorsal to the plantar surface ( Fig. 3 C).

• 4.

  Finally, palpate the plantar region, slightly distal to the flare at the base of the first metatarsal. Inject from the medial to the lateral direction in the plantar region, staying in the subcutaneous tissue ( Fig. 3 D).

Each injection delivered approximately 2.5 mL of anesthetic, positioned close to the bone to provide effective anesthesia around the base of the first metatarsal. The complete procedure is demonstrated in Video 2.

The following is the Supplementary material related to this article Video S2 .

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