Imaging features of the postoperative spine: a guide to basic understanding of spine surgical procedures.

Spinal surgical procedures are becoming more common over the years, and imaging studies can be requested in the postoperative setting, such as a baseline study when implants are used, or when there is a new postoperative issue reported by the patient or even as routine surveillance. Therefore, it helps the surgeon in the appropriate management of cases. In this context, there is increasing importance of the radiologist in the adequate interpretation of postoperative images, as well as in the choice of the most appropriate modality for each case, especially among radiographs, computed tomography, magnetic resonance imaging and nuclear medicine. It is essential to be familiar with the main types of surgical techniques and imaging characteristics of each one, including the type and correct positioning of hardware involved, to differentiate normal and abnormal postoperative appearances. The purpose of this pictorial essay is to illustrate and discuss the more frequently used spine surgical interventions and their imaging characteristics, with an emphasis on classical decompression and fusion/stabilization procedures. KEY POINTS: Plain radiographs remain the main modality for baseline, dynamic evaluation, and follow-ups. CT is the method of choice for assessing bone fusion, hardware integrity and loosening. MRI should be used to evaluate bone marrow and soft tissue complications. Radiologists should be familiar with most performed spinal procedures in order to differentiate normal and abnormal. CRITICAL RELEVANCE STATEMENT: This article discusses the main surgical procedures involved in the spine, which can be didactically divided into decompression, stabilization-fusion, and miscellaneous, as well as the role of diagnostic imaging methods and their main findings in this context.