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Interpretation of postoperative orthopedic radiographs comprises a significant portion of the practice of not only subspecialized musculoskeletal radiologists but also general radiologists. A good foundation and understanding of the most common performed orthopedic procedures is essential for accurate interpretation of postoperative radiographs. This chapter reviews the basic concepts of joint replacement, spinal fusion, and fracture fixation, which are some of the most common procedures performed by orthopedic surgeons. In addition, the postoperative evaluation of various orthopedic hardware including the imaging findings for common complications will be discussed.
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Joint replacement is one of the most common orthopedic procedures performed. Generalized indications for joint replacement include severe osteoarthritis, avascular necrosis, post-traumatic osteoarthritis, and inflammatory arthropathies such as rheumatoid arthritis. Absolute contraindications for joint replacement include active local or systemic infection. Relative contraindications include obesity, remote infection, unrepaired ligamentous injuries, and neurologic impairment. Prior to the advent of joint replacement, surgical management of a painful or nonfunctional joint included joint arthrodesis (eg, joint fusion), osteotomy, nerve division, and joint debridement. Patients were afforded significant improvement in quality of life with the development of joint replacement techniques; however, earlier joint replacement components often suffered from premature wear. Recent advances in biomaterials and joint replacement technology have led to marked improvements in the longevity of joint prostheses. Orthopedic surgeons can now choose between a vast array of prosthetic devices, many based on preference and familiarity. Though it is impossible for the radiologist to become familiar with all the different devices in the market, the structural material and complications are shared among the variety of different prostheses.
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For knee replacements, the main components of any modern total knee arthroplasty typically include two metallic prosthetic alloy components, one to resurface the femoral side and one to resurface tibial side (Figure 10-1); a plastic polyethylene liner sandwiched in between; and a polyethylene patellar component. The low coefficient of friction between the metal femoral alloy component and the polyethylene component attempts to simulate normal joint movement. Alloys represent the metallic component of the prostheses. On the femoral side, they are combinations of different metals such as chromium–cobalt, chromium–cobalt–titanium, or chromium–cobalt–molybdenum.1 In patients who have metal allergies, newer ceramic femoral components have been developed that are coated with alumina or zirconia. On the tibial side, the baseplate is typically made of titanium; however, some prostheses dispense with a metallic baseplate altogether, instead using an “all-polyethylene” tibial component. These different materials all have individual biomechanical properties based on their composition, and differ in terms of their resistance to stress, strain, and tension. The different biomechanical properties of each material confer different resistance to component fracture and wear of the polyethylene liner that sits in between the tibial and femoral components. Polyethylene liners are radiolucent; in other words, they are not seen on the radiograph. In order to secure the ...