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Introduction

Lower back pain (LBP) is the most common pain syndrome that can cause disability (1,2). Pathologies of the lumbar intervertebral discs, lumbar facet joints (LFJs) and the sacroiliac joint are potential sources of chronic LBP (3,4). Disorders of the facet joints represent a common source of LBP. In previous studies, the prevalence of chronic LBP caused by pathologies of the facet joints was reported to be ~30%, which increased with age as LBP exhibits similar characteristics with arthritis (5–8). Osteoarthritis of the LFJs due to degenerative change(s) is considered to be the main cause of facet joint-origin LBP (9). Degenerative changes in LFJs can lead to abnormal stress and strain, resulting in increased load on the facet joint (10). Additionally, increased mechanical load and subsequent inflammation activate nociceptors within and surrounding the joints, which further exacerbate facet joint-origin LBP (10–12).

To manage facet joint-origin pain in clinical practice, intra-articular (IA) LFJ corticosteroid injections are widely and conventionally used, and the positive effect of this treatment has been reported in a number of previous studies (13–20). The effect of IA LFJ corticosteroid injection may be different according to the degree of LFJ degeneration. The prediction of treatment outcome after IA LFJ corticosteroid injection may therefore enable clinicians to apply a more appropriate therapeutic method to patients with LBP. However, little is known about the treatment outcomes of IA LFJ corticosteroid injections according to the severity of facet joint osteoarthritis (FJOA). Therefore, the present study aimed to evaluate whether the severity of FJOA affects IA LFJ corticosteroid injection treatment.

Patients and methods

Patients

The current retrospective study recruited 50 patients who visited the spinal center of Yeungnam University Hospital between March 2014 and Aug 2018 for the management of LFJ pain and received IA LFJ corticosteroid injection treatment (Table I). Patients were included based on the following criteria: (i) ≥6-month history of axial LBP without radicular symptoms (duration of pain was examined by asking patients directly), (ii) aged between 20 and 79 years, (iii) local paraspinalis tenderness with increased pain upon hyperextension, rotation or lateral bending of the lower lumbar spine (iv) ≥80% temporary pain relief following a diagnostic block with IA injection of 0.5 ml of 1% lidocaine (temporary pain relief, assessed using a numerical rating scale (NRS) (21), was evaluated using a survey that the patients filled out) and (v) failure to respond to medication (meloxicam 15 mg and/or acetaminophen/tramadol hydrochloride 325/37.5 mg) or physical therapy prior to IA LFJ corticosteroid injection (LBP ≥4 on a NRS). Each patient underwent a lumbar spine MRI. Patients with disc herniation, lumbar spinal stenosis, spinal instability, coagulopathy, allergy to iodinated contrast, rheumatic disorders or any uncontrolled medical or psychiatric conditions were excluded from the current study. The present study was approved by the Ethics Committee of Yeungnam University Hospital.

Table I. Demographic characteristics and baseline clinical data of the patients included in the current study. Data regarding age and pain duration are presented as mean ± standard deviation.

Table I.

Demographic characteristics and baseline clinical data of the patients included in the current study. Data regarding age and pain duration are presented as mean ± standard deviation.

	Group
Variable	A (n=10)	B (n=27)	C (n=13)	Total (n=50)	P-value
Age (years)	66.0±11.0	62.4±11.8	68.5±7.8	64.7±10.9	0.229
NRS (pre-treatment)	4.3±0.8	4.4±1.1	4.5±1.2	4.4±1.1	0.874
Pain duration (months)	15.8±10.2	20.6±20.5	18.1±14.4	19.0±17.2	0.740
Sex, n (%)
Male	5 (50.0)	12 (44.4)	6 (46.2)	23 (46.0)	0.956
Female	5 (50.0)	15 (55.6)	7 (53.9)	27 (54.0)
Successful pain relief, n (%)
Failure	4 (40.0)	13 (48.2)	7 (53.9)	24 (48.0)	0.805
Success	6 (60.0)	14 (51.9)	6 (46.2)	26 (52.0)

[i] NRS, numerical rating scale.

The 50 patients recruited into the current study were classified into three subgroups according to the results of routinely performed lumbar axial MRI, and based on the study by Maataoui et al (22) (Fig. 1): Group A, the lumbar MRI revealed narrowing of the LFJ space and the presence of small osteophytes (mean age, 66.0±11.0 years; 5 males, 5 females); Group B, the MRI revealed narrowing of the joint space, moderate osteophytes and/or subchondral erosions (mean age, 62.4±11.8 years; 12 males, 15 females); Group C, the MRI revealed narrowing of the joint space and the presence of large osteophytes and subchondral erosion/cysts (mean age, 68.5±7.7 years; 6 males, 7 females).

Figure 1. Grading of facet joint osteoarthritis in representative T2-weighted axial MRI images of the lumbar spine. Group A, narrowing of the lumbar facet joint space and presence of a small osteophyte; group B, narrowing of the joint space, moderate osteophytes and/or subchondral erosions; and group C, narrowing of the joint space, large osteophytes and subchondral erosion/cysts are apparent. Red arrows indicate the facet joints.

Procedures

Treatment was administered using a posterior approach, where patients were placed the prone position for C-arm fluoroscopy (Siemens Healthineers; Table II) and a cushion was placed below the lower abdomen to straighten the lumbar spine. The C-arm tube was angled cephalad and rotated until it was at a tangent to the LFJ space. Under C-arm fluoroscopy, after confirming IA access by injecting 0.3 ml of contrast into the LFJ space, 10 mg (0.25 ml) of dexamethasone mixed with 0.25 ml of 0.125% bupivacaine was injected using a 26-gauge and a 90 mm spinal needle (Fig. 2). The IA LFJ corticosteroid injection was administered once for each patient. During the follow-up period, which occurred for a duration of 3 months, all the recruited patients received no additional oral medication or physical therapy.

Figure 2. Intra-articular lumbar facet joint corticosteroid injection. C-arm fluoroscopy-guided intra-articular contrast injection into the left L4-5 facet joint.

Table II. Treated facet joint level of each group.

Table II.

Treated facet joint level of each group.

Lumbar level, n (%)	Group A	Group B	Group C
L3/4	2 (20.0)	3 (11.1)	2 (15.4)
L4/5	5 (50.0)	16 (59.3)	6 (46.2)
L5/S1	3 (30.0)	8 (29.6)	5 (38.4)

[i] L, lumbar spine; S, sacral spine

Outcome measures

Pain intensity was assessed using an NRS, which was administered prior to treatment and at 1, 2 and 3 months after IA LFJ corticosteroid injection. NRS score was measured once for each follow-up. Successful treatment was defined as a >50% reduction in NRS score at 3 months compared with the pre-treatment NRS score. To validate changes in pain reduction, NRS scores were evaluated by assessing the difference between the pretreatment and the 3 month follow-up treatment NRS scores [change in NRS (%) =(pretreatment score-score at 3 months after treatment)/pretreatment score ×100].

Statistical analysis

The demographic characteristics and baseline clinical variables were summarized using descriptive analysis. Values of quantitative variables are presented as the mean ± standard deviation, while qualitative variables are presented as frequencies and percentages. Demographic data and successful pain relief were compared among the three groups using the chi-squared test for qualitative variables and one-way ANOVA for quantitative variables. A multiple comparisons test was performed using the Scheffe method. Analysis of transition aspect for NRS scores in all recruited patients, by time, was performed using a repeated measures ANOVA. The analysis of transition aspect for NRS scores by time, group and interaction effects (time differences by group) was performed using a repeated measure two (time and factor) factor analysis. Multiple comparisons were performed by contrast with Bonferroni's correction. P<0.05 was considered to indicate a statistically significant difference. All tests were two-sided and data were analyzed using SPSS version 22.0 (IBM Corp.).

Results

NRS scores were significantly decreased at the follow-up evaluations of each patient

All patients completed the study and no adverse effects were observed from treatment. No statistically significant differences were observed in demographic data among groups (Table I). Among all patients, mean NRS scores were significantly reduced as follows: Pretreatment NRS, 4.4±1.1; NRS at 1 month, 2.3±1.3; NRS at 2 months, 2.4±1.4 and NRS at 3 months, 2.5±1.4 (Fig. 3A). NRS scores changed significantly over time (P<0.001). Compared with pretreatment, the NRS scores at each evaluation time point were significantly lower (P<0.001). A total of 26 (52%) patients experienced successful pain relief (≥50%) after IA LFJ corticosteroid injection (Table I).

Figure 3. NRS score for lumbar facet joint-origin pain over the assessment period. (A) Mean NRS scores of all recruited patients. The mean NRS scores at 1, 2 and 3 months after intra-articular lumbar facet joint corticosteroid injection. (B) Changes in the mean NRS in each group at 1, 2 and 3 months after intra-articular lumbar facet joint corticosteroid injection. NRS, numerical rating scale. *P<0.001 vs. pre treatment.

All groups exhibited a significant decrease in NRS score at each follow-up evaluation

In group A, the mean NRS score significantly decreased after treatment. The pretreatment NRS score was 4.3±0.8. At 1 month, the mean NRS was 2.2±0.9, at 2 months, 2.2±1.2 and at 3 months, 2.1±1.3 (Fig. 3B). In group B, the mean NRS decreased from 4.4±1.1 before treatment to 2.4±1.6 at 1 month, to 2.5±1.6 at 2 months, and to 2.6±1.6 at 3 months after treatment. In group C, the mean NRS was 4.5±1.2 before treatment, 2.3±1.1 at 1 month, 2.4±1.3 at 2 months, and 2.8±1.1 at 3 months after treatment. Among the three groups, the NRS scores at 1, 2 and 3 months were significantly lower than the pretreatment scores (P<0.001). NRS scores from pretreatment to each evaluation time point were significantly lower in all three groups (P<0.001). However, changes in NRS scores were not significantly different between groups (P=0.889). A period of 3 months after treatment, 6 (60.0%) patients in group A, 14 (51.9%) in group B and 6 (46.2%) in group C reported successful pain relief (≥50%). The rates of successful pain relief at 3 months after treatment were not significantly different among the three groups (P=0.805; Table I).

Discussion

In the present study, the clinical effects of IA LFJ corticosteroid injection were evaluated and the effects of injection were compared according to the severity of FJOA. The results demonstrated that pain severity, which was measured via the NRS scoring system, was significantly decreased following IA LFJ corticosteroid injection in all three groups, which were classified according to the severity of FJOA. Furthermore, the pain-reducing effect of IA LFJ corticosteroid injection was not significantly different among the three groups.

FJOA-associated LBP may originate from inflammation within the area surrounding the LFJ (23,24). The anti-inflammatory properties of injected corticosteroids block the production and release of inflammatory mediators, consequently inhibiting processes associated with inflammation (25). Furthermore, corticosteroids inhibit neural transmission within nociceptive C-fibers (26). The significant pain reduction observed in the current study appears to have been induced by the effects of the corticosteroid. Additionally, injection of bupivacaine in patients may block pain transmission in the synovial lining within nociceptive C-fibers and reduce ectopic discharge (27). Therefore, bupivacaine, at least in part, may have contributed to the extensive pain relief reported in the current study. The results of the current study were contrary to the expectation that the effect of IA LFJ injection would be diminished in patients with severe FJOA. Although some patients exhibited severe FJOA, there was no statistically significant difference in the effect of injection between patients with severe FJOA and patients with non-severe FJOA. The corticosteroid can be suggested to exhibit anti-inflammatory and analgesic effects that are sufficient to alleviate all LFJ-origin LBP, regardless of the severity of FJOA (28). Bupivacaine has also been known to block transmissions in nociceptive C-fibers (27). Additionally, structures, including lumbar paraspinalis muscles, paraspinal ligament and intervertebral discs, may prevent or mitigate the severe mechanical loading on the LFJ.

In the current study, the degree of pre-treatment facet joint-origin pain was not significantly different among the three groups. However, the present study included a relatively small number of patients. Additionally, to the best of our knowledge, no previous study has reported the association between the level of pain and structural changes of the facet joint. Suri et al (29) indicated that severe FJOA is more often observed in patients exhibiting back pain than in those without back pain. However, the aforementioned study did not evaluate the degree of pain according to severity of FJOA. Therefore, for this to be confirmed, further studies are required.

To the best of our knowledge, a total of four previous studies have reported the effects of IA LFJ corticosteroid injection in controlling LFJ-origin pain (30–33). In 2011, Kawu et al (30) performed IA LFJ corticosteroid injection treatment in 10 patients, 90% of whom experienced a pain reduction of >50% according to visual analogue scale (VAS) scores 6 months after treatment. In the same year, Celik et al (31) performed IA LFJ corticosteroid injection treatment in 40 patients, with the mean VAS scores being reduced by ~75% of pre-treatment scores 6 months after treatment. In 2013, Ribeiro et al (32) performed IA LFJ corticosteroid injection treatment in 31 patients, who exhibited a ~50% reduction in mean VAS of pre-treatment scores 3 months after treatment. In 2017, Do et al (33) performed IA LFJ corticosteroid injection treatment in 30 patients and reported that the mean NRS score was reduced from 5 at pretreatment to 3.2 at 6 months following injection. In the current study, patients were classified into 3 groups according to lumbar axial MRI results. Consistent with the results of previous studies, a significant decrease was observed in mean NRS scores, in all groups, after IA LFJ corticosteroid injection (13–20). Additionally, the current study is, to the best of our knowledge, the first to evaluate and compare treatment outcomes of IA LFJ corticosteroid injection according to the severity of FJOA.

In conclusion, the results of the current study demonstrated that the IA LFJ corticosteroid injection treatment was effective, regardless of FJOA severity. I IA LFJ corticosteroid injections may be a useful clinical option for the management of FJOA-mediated LBP. However, the present study had certain limitations, including its retrospective design and relatively small sample size. Additionally, the long-term effect of IA LFJ corticosteroid injection were not evaluated. Therefore, further studies are required to overcome these limitations and support the results of the present study.

Acknowledgements

Not applicable.

Funding

The present study was supported by a National Research Foundation of Korea grant funded by the Korean government (grant no. NRF-2019R1F1A1061348).

Availability of data and materials

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Authors' contributions

DGK and MCC performed wrote the manuscript and acquired the data. SGK and AYL designed the current study, analyzed the data and revised manuscript. MCC supervised the study and conducted critical revision of manuscript. All authors read and approved the final manuscript.

Ethics approval and consent to participate

The present study was approved by the Ethics Committee of Yeungnam University Hospital, and written informed consent was obtained from all patients.

Patient consent for publication

All participants provided written informed consent for publication.

Competing interests

The authors declare that they have no competing interests.

Glossary

Abbreviations

Abbreviations:

References