Korean J Pain 2023; 36(3): 358-368
Published online July 1, 2023 https://doi.org/10.3344/kjp.23092
Copyright © The Korean Pain Society.
Hyun-Jung Kwon1 , Chan-Sik Kim1
, Sungwon Kim1
, Syn Hae Yoon2
, Jungho Koh3
, Young Ki Kim3
, Seong-Soo Choi1
, Jin-Woo Shin1
, Doo-Hwan Kim1
1Department of Anesthesiology and Pain Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
2Department of Anesthesiology and Pain Medicine, El Hospital, Namyangju, Korea
3Department of Anesthesiology and Pain Medicine, Gangneung Asan Hospital, University of Ulsan College of Medicine, Gangneung, Korea
Correspondence to:Doo-Hwan Kim
Department of Anesthesiology and Pain Medicine, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul 05505, Korea
Tel: +82-2-3010-1417, Fax: +82-2-3010-6790, E-mail: dh_kim@amc.seoul.kr
Handling Editor: Woo Seog Sim
Received: March 18, 2023; Revised: May 1, 2023; Accepted: May 11, 2023
This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Background: Recent attention has been directed towards fatty infiltration in the cervical extensor muscles for predicting clinical outcomes in several cervical disorders. This study aimed to investigate the potential association between fatty infiltration in the cervical multifidus and treatment response following cervical interlaminar epidural steroid injection (CIESI) in patients with cervical radicular pain.
Methods: The data of patients with cervical radicular pain who received CIESIs between March 2021 and June 2022 were reviewed. A responder was defined as a patient with a numerical rating scale decrease of ≥ 50% from the baseline to three months after the procedure. The presence of fatty infiltration in the cervical multifidus was assessed, along with patient characteristics, and cervical spine disease severity. To assess cervical sarcopenia, fatty infiltration in the bilateral multifidus muscles was evaluated at the C5–C6 level using the Goutallier classification.
Results: Among 275 included patients, 113 (41.1%) and 162 (58.9%) were classified as non-responders and responders, respectively. The age, severity of disc degeneration, and grade of cervical multifidus fatty degeneration were significantly lower in responders. Multivariate logistic regression analysis revealed that pre-procedural symptoms (radicular pain with neck pain, odd ratio [OR] = 0.527, P = 0.024) and high-grade cervical multifidus fatty degeneration (Goutallier grade 2.5–4, OR = 0.320, P = 0.005) were significantly associated with an unsuccessful response to CIESI.
Conclusions: These results suggest high-grade cervical multifidus fatty infiltration is an independent predictor of poor response to CIESI in patients with cervical radicular pain.
Keywords: Cervical Vertebrae, Injections, Epidural, Neck Pain, Paraspinal Muscles, Radiculopathy, Sarcopenia, Steroids, Treatment Outcome.
Sarcopenia is a medical condition characterized by reduced muscle strength, quantity, or quality, resulting in a decline in physical performance in severe instances [1]. Sarcopenia is linked to unfavorable consequences, such as falls, functional decline, frailty, and mortality [1]. Nowadays, the diagnosis of this condition emphasizes the significance of muscle quality and function instead of solely focusing on muscle mass. Fatty infiltration in skeletal muscle plays a crucial role in reducing both muscle strength and function [2]. Recently, fatty infiltration in cervical extensor muscles was reportedly associated with clinical outcomes in several cervical disorders including cervical radiculopathy [3–6].
Cervical interlaminar epidural steroid injections (CIESIs) have been widely used for symptom relief in cases of cervical radicular pain [7]. Aside from being linked to poor outcomes following lumbar spine surgery, high-grade fatty infiltration of paraspinal muscles in the lumbar region was significantly associated with poor response to epidural steroid injections in elderly patients [8]. To the authors’ knowledge, however, no studies have investigated the relationship between fatty infiltration of the paraspinal muscles and treatment outcomes after CIESI.
Therefore, this study aimed to investigate the potential association between fatty infiltration in the cervical multifidus and successful response following CIESI in patients with cervical radicular pain. This study also aimed to identify other factors associated with a successful response to CIESI.
This study was approved by the institutional review board of Asan Medical Center (protocol number: 2023-0035). The requirement for informed consent was waived because of the retrospective nature of the study. A retrospective review was conducted on the medical records of patients who underwent CIESIs at a pain clinic (Asan Medical Center, Seoul, Korea) between March 2021 and June 2022. The inclusion criteria were as follows: (1) cervical radicular pain, (2) presence of cervical spinal stenosis or cervical disc degeneration on magnetic resonance imaging (MRI), (3) failure to respond to conservative treatment for > 3 months, (4) MRI performed within 1 year preceding the injection. The exclusion criteria were as follows: (1) insufficient medical records with missing numerical rating scale (NRS) scores; (2) patients lost to follow-up within three months after CIESI; (3) axial neck pain without cervical radicular pain; (4) cervical myelopathy; (5) no or insufficient radiologic tests; (6) prior cervical spinal surgery; (7) cervical epidural neuroplasty performed instead of a single injection; and (8) history of CIESI within the last 3 months.
CIESIs were performed as previously reported [9]. All procedures were performed under fluoroscopic guidance. The needle insertion level was determined at C6–C7 or C7–T1, and the paramedian approach was adopted in all procedures. After sterilization, the skin was infiltrated with 1% lidocaine, and a 22G Tuohy needle (Green Medical Supply) was inserted at the target cervical level while guided by an anteroposterior (AP) view. When the needle was advanced until the pedicle level on the vertebral body just inferior to the target interlaminar space on an AP image, fluoroscopy was rotated obliquely in the contralateral side at an angle of 50° ± 5° to visualize the ventral interlaminar line (VILL) between the laminae. Then, the needle was advanced further without loss of resistance (LOR) immediately before the VILL in the contralateral oblique (CLO) view. Subsequently, the needle was cautiously advanced using an LOR-to-air technique to reach the epidural space. When LOR was obtained, 0.5 mL of contrast medium (Omnipaque 300; GE Healthcare) was injected to confirm the epidural space using the CLO and AP views. If the epidural space was confirmed, a 3-mL mixture of 5 mg dexamethasone and 1% lidocaine was administered.
All CIESIs were performed by three attending pain physicians (≥ 4 years of procedural experience), nine fellows (0 to 8 months of experience), and 16 residents (0 to 3 months of experience) according to identical protocols. The trainees performed all the procedures under the supervision of the attending pain physicians.
The pain intensity was evaluated at baseline and 3 months after CIESI using NRSs which ranged from 0 (no pain) to 10 (worst imaginable pain). A responder was defined as a patient with an NRS score decrease of ≥ 50% [10]. The patients were divided into non-responder and responder groups depending on the outcome.
Demographic data, including age, sex, and body mass index (BMI), were collected. Comorbidities (such as diabetes and hypertension), pain duration, last previous procedure, response to last previous procedure, and pre-procedural symptoms (radicular pain with or without neck pain, weakness) were also collected. The cervical curve type (lordosis, straight, or sigmoidal or kyphosis) was assessed using pre-procedural lateral cervical spine X-rays [11].
Based on the pre-procedural MRI, each severity of central stenosis, foraminal stenosis, and disc degeneration at the closest level in correlation with the patient’s symptoms were assessed. For central stenosis, each grade was defined as follows: grade 0, normal; grade 1, obliteration of > 50% of the subarachnoid space without any signs of cord deformity; grade 2, central canal stenosis with spinal cord deformity, or cord deformation with no signal changes in the spinal cord; and grade 3, increased signal intensity of the spinal cord near the compressed level on T2-weighted images [12]. For foraminal stenosis, each grade was defined as follows: grade 0, normal or absence of neural foraminal stenosis with the narrowest neural foraminal width longer than that of the extraforaminal nerve root; grade 1, non-severe cervical neural foraminal stenosis, with the narrowest neural foraminal width the same as or less than (but > 50% of) the extraforaminal nerve root width; and grade 2, severe cervical neural foraminal stenosis, with the narrowest neural foraminal width the same as or less than 50% of the extraforaminal nerve root width [13]. For disc degeneration, each grade was defined as follows: grade 1, low-intensity or structural changes of the nucleus pulposus; grade 2, disc bulge or herniation with annulus fibrosus degeneration; and grade 3, further degeneration with a disc height decrease > 25% [14]. The severity of central stenosis, foraminal stenosis, and disc degeneration in each case was determined by consensus among the three investigators. Additionally, cervical sarcopenia was also assessed using a grading system on fatty infiltration. Fatty infiltration in the bilateral multifidus muscles were evaluated at the C5–C6 level using the Goutallier classification [15,16]. The C5–C6 level is the most commonly involved cervical spine level with degenerative changes, due to its relatively high load-bearing role and flexibility [17,18]. Thus, this level has been frequently selected as a representative for assessing fatty infiltration in the cervical paraspinal muscles. Axial cuts of T2-weighted MRI sequences were utilized by two blinded independent reviewers (Fig. 1). The Goutallier classification is defined as follows: Goutallier 0, no visible fat streaks; Goutallier 1, minimal fatty streaks; Goutallier 2, more muscle present than fat; Goutallier 3, fat and muscle present in equal quantities; Goutallier 4, more fat present than muscle [19]. After the inter-rater reliability between the reviewers was tested, the grades of the two reviewers were averaged and further classified as follows: mild (Goutallier 0–1), moderate (Goutallier 1.5–2), or severe (Goutallier 2.5–4.0) sarcopenia, based on the Fuchs modification of the Goutallier grading system: no fat to minimal fat as mild, more muscles than fat as moderate, and equal/greater fat than muscle as severe [15,16]. All the reviewers were pain physicians who have more than 5 years of experience in diagnosing spine pathologies with spine MRI. Before the study, the reviewers were trained to evaluate fatty infiltration using the Goutallier classification with 30 cases each.
The pre- and post-procedural pain intensities were classified into one of three categories (mild, NRS 1‒3; moderate, NRS 4‒6; and severe, NRS 7‒10).
Categorical variables were presented as absolute numbers with percentages. Continuous variables were compared between non-responders and responders using the Student’s t-test or Mann–Whitney U-test, and were presented as medians with interquartile ranges. Categorical variables were compared using the chi-squared test or Fisher’s exact test. To determine the factors associated with a successful response to CIESI, univariate and multivariate logistic regression analyses were performed. Variables with P values < 0.1 on univariate logistic regression analysis were included in the multivariate logistic regression analyses. P values < 0.05 were considered significant. The odds ratios (ORs) and 95% confidence intervals (CIs) for successful response in the presence of independent predictors of CIESI were calculated by logistic regression analyses. All statistical analyses were performed using IBM SPSS (version 22; IBM Corp.).
A total of 393 patients underwent CIESIs due to cervical radicular pain between March 2021 and June 2022. Among them, 118 were excluded for the following reasons: 21 followed up for less than 3 months, 22 had axial neck pain without cervical radicular pain, 31 had no or insufficient radiologic tests, 9 had history of prior cervical spinal surgery, and 35 underwent cervical epidural neuroplasty. Finally, 275 patients were included. The baseline demographic and clinical characteristics of the patient groups are shown in Table 1.
Baseline demographics and clinical characteristics
Variables | Non-responders (n = 113) | Responders (n = 162) | Total (n = 275) | P value |
---|---|---|---|---|
Age (yr) | 57.0 (49.0–66.0) | 54.0 (45.0–64.0) | 56.0 (47.0–65.0) | 0.028 |
Sex, male | 64 (56.6) | 87 (53.7) | 151 (54.9) | 0.720 |
BMI (kg/m2) | 24.3 (22.0–25.8) | 24.7 (22.3–27.0) | 24.5 (22.3–26.5) | 0.096 |
Diabetes | 10 (8.8) | 13 (8.0) | 23 (8.4) | 0.873 |
Hypertension | 28 (24.8) | 28 (17.3) | 56 (20.4) | 0.172 |
Pain duration (mo) | 5.0 (2.0–12.0) | 3.5 (2.0–8.0) | 4.0 (2.0–9.5) | 0.129 |
Last previous procedure | 0.968 | |||
CIESI | 21 (18.6) | 30 (18.5) | ||
Cervical MBB | 7 (6.2) | 7 (4.3) | ||
SGB | 23 (20.4) | 33 (20.4) | ||
TPI | 13 (11.5) | 21 (13.0) | ||
None | 49 (43.4) | 71 (43.8) | ||
Response to last previous procedure | 0.962 | |||
Yes | 35 (54.7) | 52 (57.1) | ||
No | 29 (45.3) | 39 (42.9) | ||
Type of pre-procedural pain | 0.100 | |||
Radicular pain only | 29 (25.7) | 58 (35.8) | 46 (16.7) | |
Radicular pain with neck pain | 84 (74.3) | 104 (64.2) | 188 (68.4) | |
Weakness | 27 (24.1) | 43 (26.5) | 70 (25.5) | 0.754 |
Cervical curve | ||||
Lordosis | 32 (28.3) | 37 (22.8) | 69 (25.1) | 0.324 |
Straight | 62 (54.9) | 103 (63.6) | 165 (60.0) | 0.185 |
Sigmoidal or kyphosis | 19 (16.8) | 22 (13.6) | 41 (14.9) | 0.460 |
Central stenosis | 0.538 | |||
Grade 1 | 4 (9.1) | 14 (9.7) | 9 (10.7) | |
Grade 2 | 40 (90.9) | 130 (89.7) | 72 (85.7) | |
Grade 3 | 0 (0) | 1 (0.7) | 3 (3.6) | |
Foraminal stenosis | 0.747 | |||
Grade 1 | 5 (4.5) | 10 (6.2) | 15 (5.5) | |
Grade 2 | 27 (24.3) | 42 (26.2) | 69 (25.5) | |
Grade 3 | 79 (71.2) | 108 (67.5) | 187 (69.0) | |
Disc degeneration | 0.021 | |||
Grade 1 | 1 (0.9) | 2 (1.2) | 3 (1.1) | |
Grade 2 | 68 (60.7) | 121 (74.7) | 189 (69.0) | |
Grade 3 | 43 (38.4) | 39 (24.1) | 82 (29.9) | |
Diagnosis | 0.322 | |||
Herniated disc | 64 (57.1) | 81 (50.3) | 145 (53.1) | |
Spinal stenosis | 48 (42.9) | 80 (49.7) | 128 (46.9) | |
Cervical sarcopenia, grade | 0.022 | |||
Goutallier 0–1 | 13 (11.5) | 32 (19.8) | 45 (16.4) | |
Goutallier 1.5–2 | 56 (49.6) | 90 (55.6) | 146 (53.1) | |
Goutallier 2.5–4 | 44 (38.9) | 40 (24.7) | 84 (30.5) | |
Pre-procedural NRS | 6.0 (5.0–7.0) | 6.0 (5.0–7.0) | 6.0 (5.0–7.0) | 0.968 |
Pre-procedural pain intensity | 0.378 | |||
Mild | 10 (8.8) | 8 (4.9) | 18 (6.5) | |
Moderate | 69 (61.1) | 108 (66.7) | 177 (64.4) | |
Severe | 34 (30.1) | 46 (28.4) | 80 (29.1) | |
Post-procedural NRS, 1 mo | 4.0 (3.0–6.0) | 2.0 (2.0–3.0) | 3.0 (2.0–4.0) | < 0.001 |
Post-procedural NRS, 3 mo | 5.0 (4.0–6.0) | 2.0 (1.0–2.0) | 3.0 (2.0–4.0) | < 0.001 |
NRS difference, 3 mo | 1.0 (0.0–2.0) | 4.0 (3.0–5.0) | 3.0 (1.0–4.0) | < 0.001 |
Values are expressed as medians (interquartile ranges) or number (%).
BMI: body mass index, CIESI: cervical interlaminar epidural steroid injection, MBB: medial branch block, SGB: stellate ganglion block, TPI: trigger point injection, NRS: numerical rating scale.
Of the patients, 162 (58.9%) exhibited a response to treatment. Most patients exhibited none to some degree of fatty infiltration, with the majority classified as Grade 1 (first vs. second investigator; n = 57, 20.7% vs. n = 62, 22.5%) or Grade 2 (n = 136, 49.5% vs. n = 148, 53.8%). The patients with more fatty infiltration were classified as Grade 3 (n = 54, 19.6% vs. n = 35, 12.7%) or Grade 4 (n = 17, 6.2% vs. n = 25, 9.0%). The Goutallier grading results demonstrated excellent inter-rater reliability, with an 83.7% agreement (intraclass correlation coefficient, 0.837 [95% CI, 0.791–0.873]). Cervical multifidus fatty degeneration was significantly less among responders (Goutallier 0–1, 13 [11.5] vs. 32 [19.8]; Goutallier 1.5–2, 56 [49.6] vs. 90 [55.6]; Goutallier 2.5–4, 44 [38.9] vs. 40 [24.7], P = 0.022). The age was significantly lower in responders (57.0 [49.0–66.0] years vs. 54.0 [45.0–64.0] years, P = 0.028). The disc degeneration grade was significantly lower in responders (grade 1, 1 [0.9] vs. 2 [1.2]; grade 2, 68 [60.7] vs. 121 [74.7]; grade 3, 43 [38.4] vs. 39 [24.1], P = 0.021). Although there was no significant difference in pre-procedural NRS between the groups (6.0 [5.0–7.0] vs. 6.0 [5.0–7.0], P = 0.968), NRS were significantly lower in responders at 1 month (4.0 [3.0–6.0] vs. 2.0 [2.0–3.0], P < 0.001) and 3 months (5.0 [4.0–6.0] vs. 2.0 [1.0–2.0], P < 0.001) after the procedure. The NRS difference between baseline and 3 months was significantly greater in responders (1.0 [0.0–2.0] vs. 4.0 [3.0–5.0], P < 0.001, Table 1).
When demographics and clinical characteristics were stratified by the severity of fatty degeneration in the cervical multifidus (Goutallier grade 0–1 vs. 1.5–2 vs. 2.5–4), the 1-month (2.0 [1.0–3.0] vs. 3.0 [2.0–4.0], vs. 4.0 [2.0–5.0], P = 0.001) and 3-month (2.0 [1.0–3.0] vs. 3.0 [2.0–4.0] vs. 3.0 [2.0–5.0], P = 0.009) post-procedural NRS scores were lower in low Goutallier grades. The NRS difference between baseline and 3 months after CIESI was also greater in low Goutallier grades (3.0 [2.0–5.0] vs. 3.0 [2.0–4.0] vs. 2.0 [1.0–3.0], P = 0.001). Similarly, the proportion of responders was also greater in low Goutallier grades (Table 2).
Baseline demographics and clinical characteristics stratified by Goutallier grade
Variables | Goutallier 0–1 (n = 45) | Goutallier 1.5–2 (n = 146) | Goutallier 2.5–4 (n = 84) | P value |
---|---|---|---|---|
Age (yr) | 50.0 (43.0–61.0) | 53.0 (46.0–64.0) | 63.0 (54.0–68.0) | < 0.001 |
Sex, male | 22 (48.9) | 86 (58.9) | 43 (51.2) | 0.355 |
BMI (kg/m2) | 24.7 (22.9–26.2) | 24.6 (22.4–26.9) | 24.3 (22.0–26.0) | 0.318 |
Diabetes | 3 (6.7) | 9 (6.2) | 11 (13.1) | 0.206 |
Hypertension | 8 (17.8) | 32 (21.9) | 16 (19.0) | 0.782 |
Type of pre-procedural pain | 0.087 | |||
Radicular pain only | 8 (17.8) | 49 (33.6) | 30 (35.7) | |
Radicular pain with neck pain | 37 (82.2) | 97 (66.4) | 54 (64.3) | |
Weakness | 12 (26.7) | 40 (27.6) | 18 (21.4) | 0.578 |
Pain duration (mo) | 4.0 (2.0–7.0) | 4.0 (2.0–11.0) | 4.0 (2.0–10.5) | 0.517 |
Cervical curve | ||||
Lordosis | 12 (26.7) | 35 (23.9) | 22 (26.2) | 0.911 |
Straight | 24 (53.3) | 88 (60.3) | 53 (63.1) | 0.556 |
Sigmoidal or kyphosis | 9 (20.0) | 23 (15.8) | 9 (10.7) | 0.338 |
Central stenosis | 0.538 | |||
Grade 1 | 4 (9.1) | 14 (9.7) | 9 (10.7) | |
Grade 2 | 40 (90.9) | 130 (89.7) | 72 (85.7) | |
Grade 3 | 0 (0.0) | 1 (0.7) | 3 (3.6) | |
Foraminal stenosis | 0.828 | |||
Grade 1 | 3 (6.8) | 9 (6.2) | 3 (3.7) | |
Grade 2 | 13 (29.5) | 35 (24.1) | 21 (25.6) | |
Grade 3 | 28 (63.6) | 101 (69.7) | 58 (70.7) | |
Disc degeneration | 0.287 | |||
Grade 1 | 1 (2.2) | 2 (1.4) | 0 (0) | |
Grade 2 | 29 (64.4) | 106 (73.1) | 54 (64.3) | |
Grade 3 | 15 (33.3) | 37 (25.5) | 30 (35.7) | |
Diagnosis | 0.321 | |||
Herniated disc | 27 (60.0) | 71 (49.0) | 47 (56.6) | |
Spinal stenosis | 18 (40.0) | 74 (51.0) | 36 (43.4) | |
Pre-procedural NRS | 6.0 (4.0–7.0) | 6.0 (5.0–7.0) | 6.0 (4.0–6.5) | 0.678 |
Pre-procedural pain intensity | 0.331 | |||
Mild | 5 (11.1) | 7 (4.8) | 6 (7.1) | |
Moderate | 24 (53.3) | 96 (65.8) | 57 (67.9) | |
Severe | 16 (35.6) | 43 (29.5) | 21 (25.0) | |
Post-procedural NRS, 1 mo | 2.0 (1.0–3.0) | 3.0 (2.0–4.0) | 4.0 (2.0–5.0) | 0.001 |
Post-procedural NRS, 3 mo | 2.0 (1.0–3.0) | 3.0 (2.0–4.0) | 3.0 (2.0–5.0) | 0.009 |
NRS difference, 3 mo | 3.0 (2.0–5.0) | 3.0 (2.0–4.0) | 2.0 (1.0–3.0) | 0.001 |
Successful responders | 32 (71.1) | 90 (61.6) | 40 (47.6) | 0.022 |
Values are expressed as medians (interquartile ranges) or number (%).
BMI: body mass index, NRS: numerical rating scale.
The results of the univariate logistic regression analysis are shown in Table 3. Age (OR, 0.976; 95% CI, 0.956–0.997; P = 0.022) and fatty degeneration in the cervical multifidus (Goutallier grade 1.5–2, 0.653 [0.316–1.349], P = 0.250; Goutallier grade 2.5–4, 0.369 [0.170–0.801], P = 0.012) were associated with successful response to CIESIs. Multivariate logistic regression analysis revealed that pre-procedural symptoms (radicular pain with neck pain, 0.527 [0.302–0.920], P = 0.024) and cervical multifidus fatty degeneration (Goutallier grade 2.5–4; 0.320 [0.144–0.713], P = 0.005) were independent factors significantly associated with an unsuccessful response to CIESIs (Table 3).
Univariate and multivariate logistic regression analyses for predictive factors associated with successful response after cervical interlaminar epidural steroid injection
Variables | Univariate | Multivariate | |||
---|---|---|---|---|---|
Odds ratio (95% CI) | P value | Odds ratio (95% CI) | P value | ||
Age | 0.976 (0.956–0.997) | 0.022 | 0.985 (0.961–1.010) | 0.230 | |
BMI | 1.075 (0.997–1.160) | 0.060 | 1.076 (0.992–1.167) | 0.076 | |
Hypertension | 0.634 (0.352–1.144) | 0.131 | |||
Type of pre-procedural pain | |||||
Radicular pain only | 1 | 1 | |||
Radicular pain with neck pain | 0.619 (0.364–1.052) | 0.076 | 0.527 (0.302–0.920) | 0.024 | |
Pain duration (mo) | 0.995 (0.983–1.006) | 0.363 | |||
Cervical curve, straight | 1.436 (0.880–2.343) | 0.147 | |||
Disc degeneration | |||||
Grade 1 | 1 | 1 | |||
Grade 2 | 0.890 (0.079–9.993) | 0.925 | 1.136 (0.093–13.801) | 0.921 | |
Grade 3 | 0.453 (0.040–5.199) | 0.525 | 0.574 (0.046–7.141) | 0.666 | |
Cervical sarcopenia, grade | |||||
Goutallier 0–1 | 1 | 1 | |||
Goutallier 1.5–2 | 0.653 (0.316–1.349) | 0.250 | 0.562 (0.266–1.187) | 0.131 | |
Goutallier 2.5–4 | 0.369 (0.170–0.801) | 0.012 | 0.320 (0.144–0.713) | 0.005 |
OR: odds ratio, CI: confidence interval, BMI: body mass index.
In this study, successful response at 3 months after CIESI was obtained in about 60% of patients with cervical radicular pain. Additionally, radicular pain combined with neck pain and high-grade multifidus fatty degeneration (Goutallier grade 2.5–4) were independently associated with unsuccessful response after CIESI. To the best of the authors’ knowledge, this is the first study to elicit the association between fatty degeneration in the cervical multifidus and the effect of CIESI.
Patients with accompanying neck pain showed poorer responses after CIESI in this study. CIESI is reportedly the most effective method in reducing radicular pain caused by a herniated disc [20–22]. Overall, the effect of CIESI has been more evident in radicular pain than axial neck pain; it can be explained by the substantial inflammation reduction from CIESI on cervical nerve roots, and complex pathologies of neck pain [21,23,24]. The results of this study were in agreement with this context.
As paraspinal muscle degeneration has been extensively investigated in low back pain and lumbar radiculopathy, it has been also recently explored in neck pain and cervical radiculopathy [6,25,26]. Fatty infiltration is considered a late stage of muscle degeneration, and it is clinically the most important sign of muscle degeneration correlated with clinical outcomes, rather than cross sectional area or volume [27]. In addition, fatty infiltration in the cervical extensor muscles is reportedly associated with clinical symptoms, such as neck pain, cervical functional disability, and postural instability, in several cervical disorders (e.g., whiplash associated disorder, cervical myelopathy) as well as cervical radiculopathy [3–6,28,29]. In patients with cervical radiculopathy, paraspinal muscle degeneration and various spinal pathologies, such as disc degeneration, severe facet joint degeneration, and ossification of the posterior longitudinal ligament, may interact with each other [30–32].
Furthermore, the multifidus muscle seemed to be the most susceptible cervical extensor muscle to fatty changes, due to abundant type I collagen [3], thereby making it the most closely related to clinical outcomes [29,33]. Therefore, multifidus sarcopenia was evaluated using the grading system for muscle fatty infiltration [15,16]. As patients with cervical radiculopathy have significantly larger amounts of fatty infiltration in their muscles compared with healthy controls [3], this study revealed that high-grade fatty infiltration in the multifidus muscle might have adverse impacts on the response to CIESI in patients with cervical radicular pain. Similarly, a recent study found that high fatty infiltration of the paraspinal muscles in the lumbar area was independently associated with poor response to lumbar epidural steroid injections in patients with lumbar spondylosis [8]. The underlying mechanisms of multifidus fatty infiltration in spinal disorders are not well-understood. Although severe and extensive atrophy in the multifidus muscle was also associated with radiculopathy [34], it is uncertain whether fatty infiltration is a cause or consequence of cervical radiculopathy. Muscle denervation or disuse from persistent pain and disability can lead to deconditioning and subsequent histologic changes [35,36]. A chronic or recurrent proinflammatory state due to a spinal pathology is also attributable to muscle degeneration with fatty infiltration [30,37–39]. Muscular fatty change, in turn, can lead to a vicious cycle of chronic systemic inflammation and progressive mechanical and metabolic skeletal muscle dysfunction [2,40]. Low levels of chronic inflammation can contribute to the widespread symptoms observed in chronic pain disorders [41]. Further research on plausible mechanisms is required to make better treatment plans and predict clinical outcomes of CIESI.
In the additional analysis stratified by fatty infiltration severity, only age was significantly associated with the severity of multifidus fatty infiltration, which corresponds with the prior study [16]. Although intramuscular adipose tissues compositionally varied in different body locations depending on sex and BMI [42,43], they did not have a significant association with fatty infiltration severity in this study, which was consistent with the results of a prior lumbar-related study [8].
Although disc degeneration was significantly different between the groups, it was not associated with an unsuccessful post-injection response. Other radiologic findings, such as cervical curve, central stenosis, and foraminal stenosis, were not significantly different between the groups, as they were in other studies [44,45].
This study has several limitations. First, the grade of sarcopenia was evaluated only with fatty degeneration of the multifidus muscle at a single C5‒C6 level. Thus, a single axial-cut evaluation could not reflect the entire muscle composition. Furthermore, it is impossible to draw conclusions regarding degeneration of other cervical muscles. Second, only the pre-procedural MRI was evaluated. Therefore, imaging studies may not exactly reflect the condition of the patient at the time of the procedure. Third, successful response was defined using only the NRS difference, which did not reflect any changes in other symptoms, such as sensory disturbance and motor weakness. Finally, the outcomes were only assessed within the 3 months after the procedure; long-term effects were not evaluated due to a lack of data.
In conclusion, high-grade cervical multifidus fatty infiltration may independently predict a poor response to CIESI in patients with cervical radicular pain. Further prospective studies are needed to investigate the relationship between long-term outcomes following CIESI and associated factors.
The authors thank the residents and clinical fellows of the Pain Clinic of Asan Medical Center for their kind support in conducting this research.
The datasets supporting the findings of this study are available from the corresponding author upon reasonable request.
No potential conflict of interest relevant to this article was reported.
No funding to declare.
Hyun-Jung Kwon: Writing/manuscript preparation; Chan-Sik Kim: Investigation; Sungwon Kim: Investigation; Syn Hae Yoon: Investigation; Jungho Koh: Investigation; Young Ki Kim: Investigation; Seong-Soo Choi: Writing/manuscript preparation; Jin-Woo Shin: Writing/manuscript preparation; Doo-Hwan Kim: Supervision.