Effects on pain of percutaneous treatment of cervical disc herniations using DiscoGel: A retrospective analysis

Abstract

Background and purpose

Cervical discogenic pain originates from degenerated intervertebral discs and is a common condition in the middle-aged population. Cervical discs may herniate and give compressions to cervical nerves, with pain and functional limitation of the arms. DiscoGel is a device that can be useful in the treatment of cervical disc herniation, with very short operating time and low radiation dose.

Material and methods

Between March 2018 and April 2019 we performed this procedure on 38 patients with non-fissurated cervical herniation using 0.3–0.4 mL of DiscoGel injected under fluoroscopic guidance. The most common discs affected were C5–C6, C6–C7 and C4–C5. Outcomes were evaluated with Visual Analogue Scale (VAS) and Neuropathic Pain Symptom Inventory (NPSI) scores at 3, 6 and 12 months follow-up. A magnetic resonance imaging (MRI) scan of the cervical spine was performed 3 months after the procedure.

Results

Postoperative examinations showed: VAS 2.15 ± 1.34 and NPSI 2.29 ± 0.71.

Postoperative MRI performed 3 months after the procedure showed a good improvement of cervical disc herniation or bulging or protrusion. The mean dose area product (DAP) was 2803 mGy/cm² with a mean fluoroscopy time of 4 minutes 22 seconds.

Conclusion DiscoGel is a suitable approach for non-fissurated cervical disc herniations, especially in patients that are not suitable for open surgery, with excellent postoperative results, fast recovery and a low radiation dose.

Introduction

Cervical pain in degenerative disc disease is a complex and heterogeneous syndrome that originates from degenerated intervertebral discs^1,2 and is common in the middle-aged population (between 35 and 65 years old). Cervical pain is caused by stress on the discs, which can lead to herniations with concomitant compression of the nerve. Because of its frequency and social impact, this disease is considered a public health problem.¹

Treatment of cervical disc disease involves the use of conservative, pharmacological and rehabilitative therapy options when possible.^3,4

If conservative treatments fail, or if they are not sufficient or appropriate, invasive treatments may be used,^5–13 and micro-discectomy is the most common procedure performed.⁹

To date, minimally invasive treatments, such as laser surgery (percutaneous laser disc decompression, PLDD) or chemodiscolysis with O2-O3, have been shown to have fewer risks than open surgery techniques and allow faster recovery times with very low risk for patients.^10,12,14

Recently, some authors have proposed the use of DiscoGel in degenerative disc pathology of the lumbar spine. This class III intradiscal medical device is made of jellified ethanol associated with tungsten in suspension,^15–19 that according to CIRSE quality assurance guidelines for percutaneous treatments of intervertebral discs²⁰ has the higher success rate and lowest complication rate.

The aim of our study was to analyze and evaluate the feasibility, effectiveness and safety profile of DiscoGel in the treatment of degenerative cervical disease.

Material and methods

Thirty-eight patients (24 males and 12 females) were treated with DiscoGel between March 2018 and April 2019. The average age was 58 ± 17.76 years. Written informed consent was obtained. Institutional Review Board (IRB) was not required for this retrospective analysis.

The inclusion criteria were as follows:

• cervical pain with or without upper limb pain with metameric pain distribution depending on the disc level(s) affected by the disease;

• pain resistant to pain killers and/or physical rehabilitation therapies;

• duration of symptoms of at least 3 months.

The exclusion criteria were as follows:

• clinical or diagnostic features indicating myelopathy;

• severe signs of denervation on electromyography;

• severe radiological stenosis or a reduction in disc height of more than 50%;

• fissuration of the annulus;

• previous surgery of the cervical tract;

• allergies to paramagnetic contrast material.

Each patient was evaluated by objective examination and clinical examination.

For each patient the assessment of pain was performed, using the following:

• Visual Analogue Scale (VAS)²¹

• Neuropathic Pain Symptom Inventory (NPSI)²²

These scales were administered before the procedure (time 0) and 3, 6 and 12 months after the procedure.

No other injections or procedures during the follow-up.

Magnetic resonance imaging (MRI) evaluation of the cervical spine was performed before and 3 months after the procedure by an independent radiologist blinded to the treatment, using sagittal T1-weighted sequences, axial and sagittal T2-weighted sequences and sagittal STIR sequences.

Patients were discharged after an 8-hour observational period following the procedure.

Statistical analysis

Statistical analysis was performed using R (R Core Team (2018), R Foundation for Statistical Computing, Vienna, Austria).

Quantitative variables were compared using the Kruskal–Wallis test and with the Steel–Dwass post hoc test.

Fluoroscopy time and dose area product (DAP) data were compared with known mean values (Italian Society of Medical Radiology recommendations) using a single-sample Student t-test.

Technique

The patient was placed in a supine position on the angiographic bed with hyperextension of the neck. Accurate asepsis was performed in the neck, shoulder and upper chest region with ‘Betadine®’. No pre- or intraprocedural anaesthesia was performed.

The angiographic system for fluoroscopy (Philips Allura, Best, the Netherlands) allowed us to evaluate the correct positioning of the cervical spine, aligning the spinous processes on the midline and positioning in parallel the somatic limiters adjacent to the intersomatic space to be treated.

The skin was marked with a sterile marker pen to identify the access site. After the manual manoeuvre of lateral dislocation of carotid-jugular-neurovascular bundle, percutaneous access was performed with a 22G sterile needle 10 cm long (Figure 1). The subsequent fluoroscopy projection was changed from the latero-lateral (LL) projection to the antero-posterior (AP) projection to check the correct positioning of the needle tip close to the centre of the intervertebral disc (Figure 2(a) and (b)). Approximately 0.3–0.5 mL of a gadolinium-based contrast agent at 1 molar concentration (type ‘Gadovist®’) was injected to perform the control discography (Figure 3) to ensure the absence of laceration of the annulus. DiscoGel was inoculated slowly, injecting 0.1 mL every 60 seconds up to a maximum of 0.3–0.4 mL.²³ During the injection, fluoroscopic control scans were performed at the LL and AP positions. Finally, the 22G needle core was inserted, and after approximately 2 minutes the needle can was removed.

Figure 1.

Manual manoeuvre of lateral dislocation of the vascular-nervous neck structures and insertion of a 22G needle with the antero-lateral approach.

Figure 2.

AP (a) and LL (b) projections to check the correct position of the needle tip at the centre of the herniated intervertebral disc.

Figure 3.

Discography was performed using the paramagnetic contrast agent type Gadovist®.

The final control was performed in the LL and AP projections (Figure 4(a) and (b)). The skin surface was disinfected, and a self-medicated patch was placed. The patient was kept in the supine position for about 8 hours. During the procedure an intravenous antibiotic prophylactic therapy (amoxicillin and clavulanic acid) was used. No postoperative home care was prescribed at discharge except a semirigid cervical collar (Zimmer type) was placed on the patient for 48 hours to obtain partial immobilization of the neck and pain killers were given if needed.

Figure 4.

AP (a) and LL (b) projections to control the absence of leakages of DiscoGel.

According to the CIRSE classification, no intra- and postprocedural complications were observed.²⁴

Results

The discs affected were C5–C6 (63,16%), C6–C7(23,68%) and C4–C5 (13,16%) (Table 1). No epidural gadolinium leakage was observed in any patients during discography.

Table 1.

Cervical levels subjected to procedure.

Operated levels	No. (%)
C4–C5	5 (13.16)
C5–C6	24 (63.16)
C6–C7	9 (23.68)

The results are reported in Table 2. At time 0, the VAS scores were 8 ± 0.57. At 3 months, the VAS scores reached an average value of 4.3 ± 1.19; at 6 months, the value was 3.38 ± 1.48, and at 12 months, it was 2.15 ± 1.34 points (Figure 5).

Table 2.

Results at 1, 6 and 12 months follow-up.

	Preoperative score	Postoperative score at 3 months	Postoperative score at 6 months	Postoperative score at 12 months
VAS	8 ± 0.57	4.3 ± 1.19	3.38 ± 1.48	2.15 ± 1.34
NPSI	7.24 ± 1.05	2.61 ± 1.05	2.26 ± 0.69	2.29 ± 0.71

VAS: Visual Analogue Scale; NPSI: Neuropathic Pain Symptom Inventory.

Figure 5.

Kruskal–Wallis test on the VAS scores obtained before and after the procedure: p < 0.05. Post hoc analysis by the Steel–Dwass test, p < 0.05 for all comparisons.

The NPSI scores were 7.24 ±1.05 at time 0, 2.61 ± 1.05 at 3 months, 2.26 ± 0.69 at 6 months and 2.29 ± 0.71 at 12 months (Figure 6).

Figure 6.

Kruskal–Wallis test on the NPSI scores obtained before and after the procedure: p < 0.05. Post hoc analysis showed a statistically significant difference (p < 0.05) between the 12-month follow-up and the preintervention evaluation and between the 3-month follow-up and the 6-month follow-up.

The post hoc analysis of the VAS score showed a statistically significant difference (p < 0.05) in all comparisons between the scores obtained before and after the procedure. The post hoc analysis of NPSI scores showed a statistically significant difference (p < 0.05) between the 12-month control and the preintervention evaluation and between the 3-month follow-up and the 6-month follow-up (Table 3).

Table 3.

p-value comparison between pre-procedure, 3, 6 and 12 months of VAS and NPSI score.

	p-value VAS	p-value NPSI
12m : PRE	<0.001	<0.001
12m : 3m	<0.001	<0.001
12m : 6m	<0.001	<0.001
3m : 6m	<0.001	= 0.060
3m : PRE	<0.001	= 0.079
6m : PRE	<0.001	= 0.099

VAS: Visual Analogue Scale; NPSI: Neuropathic Pain Symptom Inventory.

The average fluoroscopy time was 4 minutes 42 seconds and the average DAP was 2804 mGy/cm².

A qualitative and systematic MRI evaluation and comparison of pre-procedure (Figure 7(a) and (b)) and post-procedure MRIs at 3 months (Figure 7(c) and (d)), performed by an independent radiologist, showed that in 29 out of 38 cases, the herniation completely disappeared. In the other cases a volumetric reduction of hernias was observed, with no compression on the adjacent nerve structures.

Figure 7.

T2-weighted magnetic resonance imaging (MRI) sagittal (a) and axial (b) images performed before the procedure; T2-weighted MRI sagittal (c) and axial (d) images performed 3 months after the procedure.

Discussion

Discogel is a medical device based on gelled ethanol, a derivative of cellulose and tungsten. This device has a double mechanism of action on the intervertebral disc: ethyl alcohol causes dehydration of the herniation, while the hydrophilic property causes migration of fluid from the periphery of the disc to the nucleus pulposus.

Riquelme et al. have shown the advantages of chemonucleolysis with pure ethanol over chemonucleolysis with chymopapain. The benefits include the lack of allergic reactions, absence of local septic complications, reduced pain after treatment, the absence of aseptic inflammatory complications and a shorter recovery period for patients.

However, pure alcohol also has disadvantages²⁵ such as radiotransparency. Moreover, ethanol can also damage the fibrous annulus, cartilage, vascular walls, nerve structures and dura, with cytotoxic effects, vascular wall sclerosis and thrombosis as well as consequent severe pain and massive necrosis.

DiscoGel has two additional features that are highly advantageous in clinical practice^17,23,26: ethyl-cellulose, which makes the alcohol solution more viscous, transforming it into a gel that is much easier to control, and tungsten, which is radiopaque and allows the monitoring of the injection under fluoroscopic guidance.

Several authors, such as Guarnieri et al., described the absence of complications related to the leakage of ethanol outside the disc during the use of DiscoGel, with a high safety profile.^17,27

The use of DiscoGel at the cervical tract level has been studied by multiple authors in small patient samples.^17–19,26 Stagni et al. showed a success rate of approximately 74%, comparable to that of other minimally invasive techniques, such as chemonucleolysis O2/O3. Our data show a progressive and significant reduction in pain during the follow-up.

In all patients, we had a very good response to treatment in terms of pain reduction at the 3-, 6- and 12-month follow-ups, while neuropathic pain reduction was achieved later after the procedure (NPSI scores showed a statistically significant difference (p < 0.05) between the 12-month follow-up and the preintervention evaluation and between the 3-month follow-up and the 6-month follow-up). This result is probably related to the nerve regeneration and intraneural revascularization that usually are achieved after at least 3–4 months post-injury.^28,29

The use of discography by radiopaque contrast agents is not unanimously agreed upon in the literature.^17–19,25 However, we believe that in the cervical tract, this might be a good practice in order to preserve the spinal cord, as well as the nerve roots, which are located in smaller anatomical space compared to the lumbar region.

To minimize the possibility of adverse events, such as allergic reactions to iodinated contrast material (usually used during fluoroscopic procedures), we considered the use of gadolinium contrast agent (Gadovist® 1 M), which is radiopaque during fluoroscopic visualization.

Our average DAP was 2803 mGy/cm².³⁰

Conclusion

DiscoGel can be an effective, safe and reliable therapeutic solution for the treatment of painful symptoms following disc degeneration in the cervical tract. In particular it can be considered to have a high success rate, as demonstrated by Eloqayli,³¹ and a minimally invasive option in place of open surgical treatment for cervical discogenic pain caused by non-fissurated cervical disc herniation.

We believe that this device can be an excellent solution with the aim of improving quality of life and reducing neuropathic pain.