Methods: This study will be conducted as an observational quasi-experimental multicenter trial at St. Joseph's Health Care (SJHC), London, ON and the Nova Scotia Health Authority (NSHA) Halifax Infirmary (HI) site, Halifax NS. There will be 250 patients taking part in this study. One hundred and fifty patients have already completed the study in Ontario. The duration of the study at the Halifax Infirmary is 10 months. Healthy patients (aged 18-75 years) scheduled to undergo elbow/ forearm/ or hand surgery will be invited to volunteer in this observational study. A study investigator or resident under direction supervision of a study investigator will perform the ABP block. There is NO experimental drug or treatment in this study. Patient demographics including age, sex, arm circumference, height, weight and Body Mass Index will be recorded. Nerve blocks will be performed in a designated area near operating rooms called the block room. US will be used for identification of the nerves supplying the arm and an ABP block will be performed with a total volume of 30 mL of 0.5% ropivacaine according to a standardized procedure. Measurements of sensory and motor blockage will be recorded every 5 minutes for 30 minutes following the ABP block. Block success will be measured and is defined as a score of ≥ 14 on the Composite Score (CS) within 30 minutes of ABP block completion. According to routine care, all patients will receive a phone call from the investigators 24-48 hours after surgery to inquire about complications. The study follows non-inferiority design to show that the success rate in the obese group is not worse than the non-obese when anesthetized. In non-inferiority trials, both intention to treat and per-protocol analysis are recommended; both approaches should support non-inferiority The student's t-test (unpaired, two tailed) will be used for comparison of the means of continuous, normally distributed data or Mann-Whitney U test as appropriate. Categorical data (success rate, complication rate) are to be analyzed using χ2 test or Fisher's exact test, as appropriate. An interim analysis will not be conducted and set at 0.05 for significance and 95% confidence intervals.