The aim of the herein presented double-blinded is to compare the effectiveness of the high foot block against placebo infiltration in simple, uni- and bimalleolar ankle fractures.

Included will be all adult patients (>18a) treated surgically at our department. The standard peri-operative procedure at our clinic will no be altered but the additional high ankle block. The intraoperative opioid requirement, the Visual Analogue Scale for Pain (VAS) and the postoperative opioid requirement will be assessed and compared between the two groups

Ankle fractures were among the most common injuries of the lower extremity. Peri-operative, multimodal pain therapy is of great importance in the surgical treatment of those injuries. Whereas simple (uni- and bimalleolar) ankle fractures are covered peri-operatively by oral pain medication and Piritramid-PCA (PCA=Patient-controlled analgesia), complex, trimalleolar fractures usually receive additional regional pain catheters (femoralis blockade and ischiadicus blockade).

Regional pain catheters have the major downside of motor paresis and are therefore critically discussed. Various studies have explored new techniques for perioperative pain therapy. An established procedure in midfoot and forefoot surgery is the foot block. It can be inserted at different heights around the ankle joint. However, the effectiveness of the high foot block has not yet been investigated for ankle fractures. The aim of the herein presented double-blinded is to compare the effectiveness of the high foot block against placebo infiltration in simple, uni- and bimalleolar ankle fractures.

All patients who are operated on in our department due to a uni- or bimalleolar ankle fracture, who are over 18 years of age and have no serious pre-existing conditions or contraindications to local anaesthesia (LA) are eligible for inclusion.

The perioperative procedure does not change to the current treatment standard at the University Hospital Munich - Ludwig Maximilians University (LMU) except for randomization for high foot block or placebo. Both the anesthesia and the postoperative pain therapy correspond to the current treatment standard and are the same for both groups. The intraoperative opioid requirement, the VAS and the postoperative opioid requirement will be assessed.

The data is collected using the RedCap database (#19-177), which has already been reviewed by the ethics committee. The evaluation will be performed using SPSS 25.0 (IBM).

Inclusion Criteria:

• Age >17 years and <71 years
• Glomerular filtration rate (GFR) > 60
• American Society of Anaesthesiologists physical status classification system (ASA) < 4
• Independently mobile without aids before an accident
• Informed consent
• Uni- or bimalleolar (medial and lateral malleolus) ankle fractures requiring surgery

Exclusion Criteria:

• Age <18 years; >70 years
• GFR < 60
• ASA > 3
• Trimalleolar fractures or fractures necessitating open reduction and internal fixation (ORIF) of the posterior malleolus
• Not able to walk without aids (stick, rollator, etc.)
• Allergy to local anesthetics or drugs of the postOP pain regime
• Peripheral polyneuropathy
• Peripheral artery disease (PAD) grade IV°
• Dementia
• Depression, anxiety disorders or sleep disorders 18
• Pregnancy
• Denial of study participation

If requested for a reasonable reason yes

Randomization will be conducted by the Principle Investigator through RedCap. The syringe is prepared under sterile setting in a separate room by a nurse not involved in any further part of the medical treatment. The syringe with unknown content will be handed to the anaesthesiologist performing the anaesthesia. Therefore the anaesthesiologist performing the block as well as the guiding the anaesthesia throughout the surgery does not know what was injected.

The total intraoperative morphine milligram equivalent dose will be automatically drawn from our anaesthesia recording program (NarcoData) and the cumulative morphine milligram equivalent dose use between skin incision and beginning Recovery Room calculated. The patient than receives the Piritramid PCA and the total morphine milligram equivalent dose use will again be drawn automatically from the machine. The VAS Score will be entered by the patient in a tablet.