Predictors of a Favorable Response to Transforaminal Injection of Steroids in Patients with Lumbar Radicular Pain due to Disc Herniation

Background. Transforaminal injection of steroids (TFIS) is effective for some patients with lumbar radicular pain caused by disc herniation. Factors associated with better outcomes are unknown. Objective. To identify clinical and radiological features predictive of a favorable response to TFIS. Methods. Seventy-one patients with lumbar radicular pain caused by disc herniation were treated with TFIS as part of a previously reported, randomized, clinical trial. The clinical features analyzed were the presence of neurologic symptom, neurologic signs, and the duration of sciatica. Radiological features evaluated using magnetic resonance imaging (MRI) were the segmental level of the pathology, the location and morphological features of the disc herniation, the cross-sectional area of the disc herniation and its ratio to the cross-sectional area of the spinal canal, and the grade of nerve root compression. Results. None of the clinical features was associated with successful outcome from treatment. The only radiological feature associated with successful outcome was the grade of nerve root compression. Of patients with low-grade root compression, 75% responded favorably to TFIS. Only 26% of patients with high-grade nerve root compression responded. Discussion. These results indicate that TFIS is more often successful in patients without significant compression of the nerve root and, therefore, in whom an inflammatory basis for radicular pain is most likely. In such patients, a success rate of 75% renders TFIS an attractive alternative to surgery. In patients with significant compression of the nerve root, the likelihood of benefiting from TFIS is low. The success rate may be no more than that of a placebo effect, and surgery may be a more appropriate consideration.