Lumbar ESIs were performed from January 2012 to January 2015. Among the patients, 895 consecutive lumbar ESIs in 492 were reviewed. We received approval from Institutional Review Board. Total 895 lumbar ESIs (285 men, 207 women; mean age, 63.9 years) were used for analysis. There is no significant difference in the two groups' age range. The initial Numeric Rating Scale (NRS) score was assessed in every patient (Table 1), dividing them into no, mild (NRS: 1–3), moderate (NRS: 4–6), and severe pain (NRS: 7–10) categories. We classified the patients into two groups based on the NRS anddefined marked improvement with no pain as a satisfactory result for therapeutic effect. Retrospectively, the therapeutic effect difference in the groups was evaluated: one level transforaminal epidural steroid injection (TFESI) along with caudal epidural injection and two level TFESIs for lumbosacral radiculopathy. The inclusion criteria were presence of low back or leg pain, clear radiculopathy, such as evidenced by computed tomography (CT) or MRI, which was identified by radiologic reports, and the presence of follow-up medical records after caudal ESI. Exclusion criteria were unclear descriptions of symptoms, the absence of evidence of radiculopathy on cross-sectional images or of follow-up data. Injections for two groups were performed for patients with multi-level radiculopathy and contralateral mild radiculopathy or chronic back pain. There was no significant statistical difference in two patient groups' symptoms, who were injected the same steroid dose at each time. Therapeutic effects were analyzed at one, three, and six months after injection in the two comparison groups and assessed by using the NRS.

All therapeutic TFESI were conducted under fluoroscopic guidance by a musculoskeletal radiologist experienced in performing spinal interventions. All the injections were performed as outpatient procedures, after obtaining informed consent. With a patient in susceptible position, the tube was rotated obliquely to ensure the facet joint injection pars interarticularis and a clearly visiblesite for it. Next, the skin and subcutaneous tissues overlying the desired pedicle and nerve root were anesthetized with lidocaine. The needle was then advanced under intermittent fluoroscopy into the neural foramen. If it is not possible to inject in a safe triangle, we had a procedure employing the postero-lateral approach. Serial lateral views were obtained to ensure that the antero-posterior position of the needle tip was appropriate. The needle position was checked through fluoroscopy using injections of contrast materials' small amounts. Postero-anterior and lateral spot radiographs were obtained to document contrast material distribution in epidural space. The steroid was slowly and gently injected (Fig. 1).

Caudal injection was performed in same manner as above, palpating the sacral cornua and localizing the entry point of the needle on A–P view. Sacral cornua were used as landmarks to identify the sacral hiatus, as the sacral hiatus is bounded bilaterally by them. Then, the needle position was confirmed on the oblique, lateral view at the level S2–3. Nonionic contrast materials were injected to the sacral epidural space; then, a mixture of steroid and normal saline was slowly injected (Fig. 2).

Before the injection was performed, the radiologist recorded the duration of symptoms, level, and cause of nerve root impingement on the CT or MR images and the affected dermatomal distribution on the medical charts. Patient outcomes were assessed at one, three, and six month serial follow-up using a NRS that ranged from 0 to 10, subjectively expressed by the patients for the degree of improvement: excellent, good, fair, and poor. An excellent degree represented marked improvement, much improved (> 3-point NRS decreases), good was improvement but with a lesser effect (1–2 point NRS decreases). A fair degree indicated no interval change since the first injection and a poor one meant worsening of pain during the study.

The patients were not informed about the injection method to ensure a blinded protocol for the study. We defined satisfactory results as patients with a reduction of pain as reflected in NRS and no residual pain. After epidural steroid injection, the above-described one, three, and six month serial follow-ups were conducted at a clinical department, as proposed in the literature and based on the duration of therapeutically effective corticosteroids. Follow-up after ESI was scheduled for one month. At follow-up, the outcome was measured on a four-point patient satisfaction scale and recorded on the medical chart. If there was no pain, observations without repeated ESI were considered. If we decided this, the next follow-up was scheduled for three and sixe months later. We advised patients to return to our hospital immediately, even before the routine follow up date, if symptoms recurred.

The Student t-test was used to evaluate age differences between two groups. Statistical analysis was also performed using Fisher's exact test and multiple logistic regression analysis to evaluate differences between the two level TFESIs and one level TFESI subsamples along with caudal epidural injection.

The Fisher's exact test was used to determine differences in sex, therapeutic effects, and the complication rate between the two patient groups. Multiple logistic regression analysis was also performed to assess therapeutic effects. Analyses were performed for both short- and mid-term therapeutic effects. Analyses too place by using the software program SPSS, version 10.0 (SPSS Inc., Chicago, IL, USA). A p value of less than 0.05 was considered to indicate statistical significance.