Orthopedic surgeons rely on many different types of imaging to support the diagnosis suspected from your history and physical exam. We asked radiologist Dr. Justin North at OU Medical Center to help explain what each study is for and why your doctor may recommend you need one or several different types of pictures to assist in diagnosing your problem.
According to Dr. North, X-ray, magnetic resonance imaging (MRI), computed tomography (CT), and ultrasound (US) can all be used to help diagnose shoulder problems. X-ray is easy and relatively inexpensive. An X-ray in conjunction with the history and physical exam is vital to appropriately assess a patient, and can tell us the majority of problems with a shoulder. Many orthopedic surgeons will have standing orders for an X-ray to be obtained prior to meeting with a patient, so that they may refer to it during the appointment.
MRI is expensive, but the best comprehensive imaging of the shoulder. It gives very detailed information about soft tissues such as muscles and tendons, and very clearly demonstrates the bone and cartilage structures. It is often utilized to confirm a surgeon’s suspicion of pathology in the shoulder, or to help clarify unclear findings on X-ray or the physical exam.
CT gives us very good bone detail, but soft tissue structures are not as well seen. It is most often used in surgical planning for repair of fractures, or in detecting subtle, non-displaced fractures. Surgeons also use CT for preop planning for shoulder replacements to look at the amount and pattern of wear of the bone, which allows them to choose the best implant and place the implant in the best position.
US can also be used to assess the rotator cuff and soft tissues, but is inadequate for looking at bone. This modality is also very operator-dependent; for it to be effectively utilized, the technologist and radiologist need to be experienced in musculoskeletal applications.
Sometimes, with CT or MRI, we can use contrast material to help visualize pathologic processes. Contrast can be given intravenously (IV) or injected directly into a joint. IV contrast is very helpful in assessing tumors in the bone or soft tissues, and is also very helpful in assessing infections in bones, joints, and soft tissue.
In certain joints, some of the vital structures are very small and difficult to visualize with enough detail to help the surgeon. It is common to place contrast directly into the joint to outline and accentuate these structures. This is most commonly used in the shoulder, hip, and wrist.
No diagnostic test, including imaging, is perfect, and no radiologist is perfect. Sometimes the difference between a severely injured or degenerated structure (like a rotator cuff tendon), versus a frankly torn structure, can be difficult to ascertain on imaging alone. In the cases where we believe a significant injury is present and the structure is found at surgery to be intact, there is usually underlying degeneration or injury and the structure is not totally normal.
Imaging effectiveness is maximized when the radiologist and surgeon have a good working relationship. “When I know what the surgeon really wants to see and know about, I can tailor my imaging and reporting to fit his or her needs. In those cases where the imaging findings are difficult to interpret, it is very helpful to know what the surgeon’s exam findings were, to more properly interpret the images. It is also very helpful when I get feedback after the surgery to know how I am doing, and really dial in on what the imaging looks like versus what is really going on when directly visualized in surgery.”
By Oklahoma Shoulder Center PLLC
March 15, 2020