Impact of SPECT/CT on orthopedic bone scintigraphy

Learning Objectives 1. Illustrate how SPECT/CT improves the accuracy of conventional bone scintigraphy. 2. Provide insight into how bone scintigraphy can solve difficult clinical questions in orthopedics.

In the United States alone, orthopedic surgeons perform over 600,000 hip and knee replacements annually. Despite advances in technology and prosthesis design, 10-25% of patients can experience pain and discomfort within the first 5 years of the procedure due to loosening, infection, fracture, or heterotopic bone formation. Similarly, more than 400,000 spine fusion surgeries are performed annually for back pain, and many patients suffer from post-laminectomy syndrome. Bone scintigraphy can provide an invaluable functional assessment of skeletal pathology that radiographic techniques cannot. Additionally, the anatomic information provided by CT or MRI is often limited due to artifacts caused by metallic prostheses. In many cases, planar images may not be sufficient to correctly localize the findings, which is imperative for accurate diagnoses. It has been reported that the addition of SPECT can increase the sensitivity of planar images; however, it does not provide the anatomic detail necessary for complete characterization of the disease. In SPECT/CT, fusion of the functional SPECT information with the morphologic data from the CT portion, clarifies the equivocal information from each modality alone and significantly improves the diagnostic accuracy of the study. Our example cases display the imaging findings of multiple musculoskeletal cases, with and without prostheses, which demonstrate the value of SPECT/CT in orthopedics; such as localizing pseudarthrosis, differentiating fracture from synovial herniation pit, delineating stress fracture from arthritis, distinguishing compression fracture from degenerative disc disease, or clarifying diskitis from bone metastasis. Due to the definitive diagnoses made by SPECT/CT imaging in these challenging cases, effective clinical management decisions were made without the need for additional imaging.