Imaging of the postoperative lumbar spine

Abstract

Abstract The failed back surgery syndrome is characterized by intractable pain and varying degrees of disability after spine surgery. The most important task of postoperative imaging is to distinguish conditions that will benefit from surgery from those that will not be improved with another operation. Plain radiographs are important for obtaining a set of basic information about the previously operated levels and overall alignment of the spine. After excluding mechanical instability, bony stenosis, and arachnoiditis, one of the most crucial diagnostic distinctions is that of epidural scar from recurrent or residual herniated disc. Unenhanced CT can make this assessment in 43% to 60% of the cases. The addition of IV contrast to CT increases the diagnostic accuracy to 70% to 83%. Unenhanced MR has a similar accuracy to that of CT with contrast, 76% to 89%. Gadolinium-enhanced MR may further increase the ability to identify scar and disc material noninvasively. With any of these imaging modalities it is essential to distinguish normal postoperative changes from findings that result in persistent or recurrent symptoms. As with preoperative imaging studies, these tests should not be used to screen, but rather to confirm diagnoses based on clinical information. Extreme caution must be exercised to avoid overinterpretation of postoperative imaging abnormalities that do not correspond anatomically to the patient's symptoms.