This prospective, experimental, randomised, assessor-blinded cadaveric study was undertaken to describe the sono-anatomical features of the radial, ulnar, median and musculocutaneous (RUMM) nerves in rabbits and to develop and evaluate an ultrasound (US)-guided proximal RUMM block technique comparing a medial versus a lateral approach. A total of 13 adult rabbit cadavers were used. In Phase I of the study, four cadavers were used for anatomical dissection and to design and test a lateral and medial single injection point US-guided proximal RUMM block technique, while in Phase II, the medial and lateral approaches were randomly performed on nine cadavers administering 0.1 mL kg