The nineteenth century was a pivotal period for surgery. The introduction of ether anesthesia in 1846 and aseptic wound treatment in 1867 permitted major operations. By the end of the century, radiographs made operative planning and evaluation possible. After two millennia without any substantial alteration to the Hippocratic treatment of humerus fractures, new classifications and treatments emerged based on pathoanatomical findings. The Hippocratic and Galenic influence remained prevalent until the mid-nineteenth century, with bloodletting, diet restrictions, and leeches intertwined with new treatment modalities. These new treatment modalities were responses to findings from postmortem studies in pathological anatomy. A generation of anatomists and surgeons established a pathoanatomical classification accurate by modern standards in the mid-nineteenth century. Although anesthesia permitted open surgery in the mid-nineteenth century, it was used infrequently, mainly for subcutaneous fractures. Mortality and postoperative morbidity rates were high due to a lack of reliable implants, aseptic methods, and antibiotics. By the second half of the century, biomechanical studies in cadaver bones facilitated an etiological understanding of fracture patterns. The pathoanatomical and pathophysiological knowledge acquired by surgeons and anatomists in the nineteenth century and the advent of radiology paved the way for orthopedic procedures developed during the early twentieth century (Chap. 7).