In the US, the tendency is to use a lower register. For example, "heart disease" is far more commonly used than "cardiopathy," especailly when addressing patients. Likewise, "eye specialist" is preferred to "ophthalmologist." Patient education departments at big hospitals hire specially trained educators to edit patient education material to make sure the language does not go above a certain reading competency level (usually 8th grade).

Some terms seem to resist the attempt to simplify. For instance, the public seems to prefer "pediatrician" to "childhood specialist" and "gynecologist" to "women specialist." Two years ago, M.D. Anderson Cancer Center in Houston, Texas, changed the official name of the pediatric oncology clinic to "Child and Adolescent Center." Until today, however, parents still call it the "pediatiric clinic."

Some terms are used in specific contexts, but not in others. For example, abdominal cramps are not called "colic" unless the reference is to an infant. There is no rational explanation for this preference. I remember one situation when an Egyptian medical interpreter (who was a physician by training) was assisting a stomach cancer patient from the UAE. The patient used the word مغص, so the interpreter translated it as "colic," whereupon the clinician admonished the interpreter, "I know you are a physician, but please I want to know exactly what the patient said, not how you would say it as a physician." The interpreter could not understand the admonishment. The explanation is that in the US, the typical patient would usually say, "I have some abdominal cramps," while the typical parent would say, "we switched to this formula because the other one, while cheaper, made my baby colicky."

Americans love abbreviations, especially acronyms and intialisms. ENT is definitely more commonly used than otorhinolaringology.

As to your specific question, Orthopedics is very commonly used in the US.