The effect of lumbar facet joint injection levels on spinopelvic parameters and functional outcome

1. Introduction

Low back pain (LBP) is one of the most frequent symptoms among musculoskeletal pathologies [1]. LBP is a major cause of social and physical disability, and brings a huge financial burden due to the cost of treatment and the loss of labor [2]. Lumbar spine kinematics vary at different levels of the spine [3]. It has been shown that the L4-L5 level has higher mobility during bending motions than more cranial segments, and that the range of flexion-extension is higher at the cranial L2-L3 segment compared to more caudal segments [4, 5].

The primary function of facet joints is to stabilize the motion of the responsible segment during activities [6]. Lumbar facet joints carry approximately 18% of the load that is transferred to the lumbar spine [7]. Degenerative osteoarthritis (OA) can affect facet joints, manifesting as cartilage degeneration, narrowing of the joint space, synovial cyst formation, and osteophyte formation [8]. Lumbar facet joints have rich innervation provided by the medial branches of the dorsal primary rami, and they are susceptible to pain sensation [9]. Facet joint arthritis can cause pain with two mechanisms: degenerative changes in the articular cartilage that can cause pain, and degenerative changes in the joint such as osteophyte formation, can cause nerve root compression [7]. Nearly one-third of reported LBP can be attributed to facet joints [10]. Sagittal spinopelvic parameter changes have been associated with facet joint degeneration [11].

Facet joint injection (FJI) is the second most common spinal intervention after epidural injections and is widely used in the management of back pain. The frequency of FJI continues to increase [12]. Although effects on pain and functional scores have been widely evaluated [13], the effect of FJI on spinopelvic parameters and the relationship between injection levels, and changes in functional outcome scores and the spinopelvic parameter have not been evaluated before.

In this study, we aimed to evaluate the effect of the FJI level on spinopelvic parameters and functional outcome scores, as well as the correlation between functional outcome score and spinopelvic parameters change. Our primary hypothesis was that multilevel FJI is associated with higher improvement in functional outcome score and spinopelvic parameters change. Secondarily, we hypothesized that the changes in the functional outcome score would correlate with the changes in spinopelvic parameters.

2. Materials and methods

The outcomes of 144 patients were evaluated. The mean age of the patients was 60.8 ± 7.6 years. Eighty-four (58.3%) of the patients were female, and 60 (41.7%) were male (Table 1). The mean pre-injection ODI value was 62.6 ± 6.9, and the mean post-injection ODI value was 58.9 ± 8.0 ( P = 0.009). There was perfect intra- and interobserver agreement regarding radiographic measurement parameters (ICC $>$ 0.86 for intraobserver measurements and ICC $>$ 0.82 for interobserver measurements). There was a significant change in pelvic tilt between pre- and post-injection evaluations ( p = 0.032). Pre-injection and post-injection values of ODI and spinopelvic parameters in group 1 and 2 are shown in Table 2. There was a significant improvement in the mean ODI score after injection in group 2 ( p = 0.010). However, there was slight but not significant post-injection improvement in ODI score in group 1 ( p = 0.264). There were significantly higher pre- and post-injection pelvic tilt values in group 2 ( p = 0.001, d = 1.95 and p = 0.007, d = 1.71 respectively). However, pre- to post-injection changes in pelvic tilt were not significant in both groups ( $p>$ 0.05).

The correlation between changes in the ODI and spinopelvic parameters and angles between adjacent vertebrae are shown in Table 3. There was a significant moderate positive correlation (linear relationship) between the change in the ODI value and the change in pelvic tilt ( P = 0.012, r = 0.581). Also, there was a significant low positive correlation (linear relationship) between the change in the ODI value and the change in pelvic tilt ( P = 0.018, r = 0.386). (Table 3).

4. Discussion

This is the first study that evaluates the effect of the FJI level on spinopelvic parameters as well as the correlation between spinopelvic parameters and functional outcome scores. The most important finding of this study was that multiple level injections led to a significant decrease in ODI and pelvic tilt values, while two-level injections did not. In addition, a significantly moderate correlation was found between ODI and pelvic tilt changes. Therefore, multilevel facet joint injection is thought to affect the lumbar lordosis and associated pelvic tilt parameter, resulting in changes in the facet joint orientations and improvement in functional outcome.

FJI is a common spinal intervention and several studies have investigated the method of injection, injection agent, and duration of efficacy [22, 23, 24, 25, 26]. Although physical therapy and oral NSAIDs are the first-line treatments for facet joint osteoarthritis, intraarticular injections to the facet joints have been widely used in the management of facet joint osteoarthritis [27].

Successful short-term results have been reported after steroid injection by two randomized studies, but these studies are not up to date [28, 29]. Various studies evaluated the effectiveness of injection treatment, and most of them reported a slight difference after injection over placebo and no difference after a few months. Also, most of them concluded that the evidence was not strong to support FJI [30, 31, 32].

Many studies concluded that patients had pain relief immediately after FJI, and that functional outcomes improve within three-six months [33]. Our results support these findings. Even though we only evaluated pre-injection and three months post-injection parameters, we found a significant improvement in the ODI value after injection when it was performed multilevel.

Different agents can be used in lumbar FJI. Local anesthetics, corticosteroids, hyaluronic acid, or a combination of these agents can be applied into the joint or periarticular area [34]. Wu et al. introduced an autologous platelet-rich plasma (PRP) injection for facet joint pain and reported promising results, but that study did not compare PRP with other treatment options [23]. However, the specific agent used in FJI is a source of controversy. Several studies have evaluated the effect of local anesthetics, steroids, saline (as a placebo), and a combination of these agents [2]. Manchikanti et al. compared different agents for epidural injections and FJIs in a systematic review, and found no difference between local anesthetics and a combination of local anesthetics with steroids for the improvement of facet joint pain [2]. In our study, we used a combination of a long acting corticosteroid (triamcinolone acetonide) and local anesthetic (lidocaine) for therapeutic injections.

There are several different methods to guide FJI, and fluoroscopic guidance has been used for decades [35]. Dietrich et al. compared radiation exposure for patients and physicians during X-ray-guided and CT-guided injections, and found that radiation exposure in fluoroscopy-guided injections was lower for patients, but higher for physicians compared to that in CT-guided injections [35]. A recent meta-analysis reported that ultrasonography-guided FJI are as effective as CT or fluoroscopy-guided FJI [36]. We preferred fluoroscopic guidance as it is easily accessible, inexpensive, and provides adequate guidance, despite radiation exposure.

Low back pain has been associated with increased lumbar lordosis [37]. The pelvis and the lumbar spine are affected by pelvic tilt and lumbar lordosis. Moreover, as the posterior pelvic tilt increases, lumbar lordosis increases [38]. Pelvic tilt, sacral slope, and pelvic incidence are widely used to assess sagittal spinal balance before and after spinal interventions. The relationship between spinopelvic parameter changes and pain, clinical outcomes, and quality of life have been evaluated previously [39]. This is the first study that evaluated the relationship between spinopelvic parameters and clinical results in patients with facet joint osteoarthritis.

A patient’s pelvic incidence does not change, and larger lumbar lordosis with a more sagittal orientation of the lumbar facet joints has been associated with a higher pelvic incidence [40]. An increase in the posterior pelvic tilt is typically a compensatory mechanism in response to a decreased lumbar lordosis to maintain the normal sagittal balance and vice versa [38]. Normal values of spinopelvic parameters can show variation between different races, ages and sexes, but we focused on changes in spinopelvic parameters in patients with facet joint osteoarthritis [41]. Our findings show that clinical improvement after FJI correlates with pelvic tilt changes and related facet joint orientation.

There are some limitations of our study. First, the study population is not large enough to compare each treatment level to one another, so we combined levels and created two groups to make a comparative analysis possible. Second, the treatment response at different times after the injections was not evaluated. Only post-injection three-month parameters were evaluated. Third, we did not take the pain intensity into consideration but we used ODI score in which pain is represented by 10 points. Fourth, different treatment options were not evaluated. We used the same combination (lidocaine and triamcinolone acetonide solution) for all patient injections. The moderate correlation between ODI and pelvic tilt change and weak correlation between ODI and pelvic incidence supports that there is no strong relationship between ODI and spinopelvic parameters change.

5. Conclusion

In conclusion, the ODI score was significantly improved after multi-level injections. Accordingly, multi-level injections are more effective than two-level lower lumbar injections in improving the ODI and decreasing pelvic tilt in patients with lumbar facet joint osteoarthritis. Moreover, the change in the ODI is correlated with the change in the pelvic tilt.