This study focuses on optimizing the postoperative pain treatment after major foot and ankle surgery by prolonging the duration of the ultrasound-guided saphenous block. The currently used single shot saphenous block only covers half of the pain intensive period from the saphenous territory, which results in a sharp, break-through pain requiring opioids. The hypothesis is that this protracted mixture will keep the patients free of pain without the use of opioids for the entire pain intensive period and thus increase rehabilitation and patients' satisfaction.

Half of the patients will receive a single shot saphenous block with 10 mL bupivacaine-adrenalin and 1 mL of sodium chloride solution, while the other half will receive 10 mL of bupivacaine-adrenalin and 1 mL of dexamethasone.

The block is strictly a sensory block because it is a selective, sub-sartorial saphenous block at mid-thigh level without any anesthetic effect on the femoral nerve.

The adjuvant dexamethasone has increasingly become a subject of interest regarding a protracted effect, which has been shown in several studies. However, the precise mechanism of action remains speculative, and the results are contradictory regarding the discussion whether the effect is systemic or local. The effect may stem from decreased nociceptive C-fibre activity via a direct action on glucocorticoid receptors and inhibitory potassium channels. Another suggestion is a vasoconstrictive effect, which reduces the systemic uptake of local anaesthetics or a systemic anti-inflammatory effect.

Prolonging the effect of the single shot saphenous block by adding dexamethasone will reduce the need for opioids, which will reduce the risk of adverse effects like nausea, vomiting and respiratory depression. Furthermore, newer studies show that inadequate pain alleviation in the early postoperative period is a risk factor in developing chronic persistent pain.

Inclusion Criteria:

• Elective ankle or hind foot surgery either: (1) total ankle arthroplasty, (2) ankle arthrodesis or (3) subtalar arthrodesis
• Age ≥ 18
• American Society of Anaesthesiology Classification I-III
• Informed consent both orally and in writing after the patient has fully understood the protocol and its limitations.

Exclusion Criteria:

• Communication problems or dementia
• Allergies to any medical product used in the study
• Neuropathy of the sciatic or femoral nerve prior to the operation
• Morbus Charcot-Marie-Tooth disease, diabetic neuropathy, peripheral vascular disease
• BMI > 35
• Pregnancy
• Daily use of opioids
• Coagulation disorders
• Infection at the site of injection or systemic infection