Minimally invasive techniques in the treatment of chronic spinal pain syndrome

INTRODUCTION

Lower back pain is one of the most common complaints worldwide. According to the World Health Organization (WHO), approximately 80% of people experience lower back pain at least once in their lifetime, with 60% reporting regular or frequent pain [1]. The World Health Organization report also indicates that at any given moment, 4–33% of the global population suffers from lower back pain [2].
Classified into three main types, lower back pain can be acute, lasting from a few hours to several weeks; subacute, occurring periodically and lasting 4–12 weeks; or chronic, persisting for more than 12 weeks. Chronic lower back pain affects 10–15% of the population, while a larger number of individuals regularly experience subacute pain [3]. Chronic lower back pain poses a significant medical, social, and economic burden worldwide and in the United States; it is a leading cause of temporary disability and functional impairment [4–7].
Lower back pain is often associated with conditions such as herniated discs or diseases of the intervertebral discs, leading to compression of nerve roots exiting the spinal canal. Herniated discs occur in 5–20 cases per 1000 adults annually, most commonly between the ages of 30 and 50, with a male-to-female predominance of 2 : 1 [8].
Recent data suggest that degeneration and inflammation of facet joints are the most common causes of lower back pain. Facet joints account for 15–45% of acute and chronic lower back pain cases [9–13]. Pain of atherogenic nature in the spine can also radiate to the buttocks and sometimes even to the back of the thigh, complicating the diagnosis. The characteristic features of atherogenic pain include startup pain and axial loading pain, along with nonspecific radiological findings such as joint swelling, increased joint space, and the presence of excess synovial fluid.
According to clinical guidelines by the National Institute for Health and Care Excellence, London, UK (NICE) for the treatment of lower back pain, first-line therapy involves non-invasive treatment methods such as physical therapy and nonsteroidal anti-inflammatory drugs, which often provide significant relief [14]. In cases of ineffective conservative treatment, invasive methods such as a medial branch block and radiofrequency ablation, laying on the surface of facet joints, are employed.
Radiofrequency ablation (RFA) for treating atherogenic lower back pain was first described by Shealy in 1975 [15]. It was developed as a minimally invasive technique for addressing prolonged and chronic atherogenic pain. The concept involves inducing necrosis of the medial branches of the posterior spinal nerves in patients with facet syndrome, interrupting the pain transmission pathway.
Radiofrequency ablation is an evidence-based treatment method that significantly improves the patient’s condition for 6–18 months, depending on individual characteristics [16–27].
To date, there has been a substantial amount of scientific research, clinical trials, articles, clinical guidelines, and reviews detailing the methodology of this procedure and its remote effects. However, most of them are limited to short-term observations, often up to 1 year or less, and only a small number of publications cover patient follow-ups within a 2-year timeframe [28–31]. Furthermore, most of these studies are limited to small patient series conducted on small samples without any detailed and meticulous description of the applied methodologies, including not only therapeutic but also diagnostic procedures only.
In this literature review, we attempt to delve more deeply into the question of the long-term results of RFA of facet joints, exploring both short-term and remote outcomes of treating patients with prolonged and chronic lower back pain based on the existing scientific research and studies.

MATERIAL AND METHODS

The literature search utilized the following services: Cochrane Database of Systematic Reviews, Cochrane Central Registry of Controlled Trials, PubMed, and Google Scholar. The search spanned used keywords such as “back pain,” “low back pain,” “radiofrequency,” “facet syndrome,” “medial branch,” “RF,” “ablation,” and “denervation,” employing Boolean operators “and” and “or.”
A total of 15 studies were selected.
Among all the analysed articles, those were chosen where the inclusion criteria for patient selection were lower back pain without radiation to the extremities, aggravated in the morning, exhibiting startup pain, worsening with axial loading, and prolonged standing or sitting. Following contemporary recommendations for the treatment of lower back pain, all selected patients had persistent pain (≥ 6 months), previous experience of physiotherapeutic treatment and nonsteroidal anti-inflammatory drugs but had not experienced long-term improvement [2, 14, 32].
In all articles, following actual recommendations and modern scientific approaches to radiofrequency ablation, all patients underwent the preliminary medial branch block using a local anaesthetic (lidocaine, bupivacaine) and corticosteroid (dexamethasone).

RESULTS

According to the data, the positive response to RFA was evaluated based on the following scales: numerical rating scale (NRS) ≥ 2 points, Rolland-Morris scale ≥ 3%, a percentage improvement of pain intensity scale ≥ 50%, medication quantification scale version III (2 points).
According to WHO, evaluating the long-term results of RFA at 12, 12–24, and ≥ 24 months, the results showed that the percentage of patients with an improvement of ≥ 50% was 63.2%, 65.6%, and 44.1%, respectively [2]. Moreover, at 24 months, 70.6% of patients reported improvement on NRS by ≥ 2 points, and 54.1% could not clearly determine the degree of improvement but assessed their condition as “significantly better” [2].
In another study conducted by WHO and involving 70 patients divided into a control and placebo group, the results indicated a significant (8.4%) improvement in the Roland-Morris scale compared to the placebo group (2.2%) [1].
In a study by Wahlgren et al. involving 62 patients, the obtained results demonstrated 58% of patients with a 50% reduction in pain levels, corresponding to 3.4 points on the medication quantification scale third edition (MQS III) [3] (Table 1).

DISCUSSION

Low back pain caused by atherogenic factors (facet syndrome) is a condition that significantly impairs the quality of life for patients and requires thorough examination to adjust/apply adequate treatment. The prevalence of this condition among the population is high, leading to significant socio-economic losses [33–35]. Facet syndrome is primarily characterized by initial pain, increased pain with axial loading, and hyperextension in the lumbar spine. This type of pain tends to be chronic, dull aching, with periodic exacerbations in the form of shooting pain and radiating to the buttocks. Treatment of such pain by rehabilitation specialists and prescription of medications according to the WHO analgesic ladder does not always provide relief. The key to the success of invasive treatment is careful patient selection and baseline diagnostics. Currently, the most common form of alternative treatment is RFA of the medial branch [36].
During the patient examination, detailed collection of medical history with a focus on the nature, type, and strength of pain, as well as questions regarding previous treatment, is essential. If the patient meets all the specified criteria, it is mandatory to perform a preliminary diagnostic block of the medial branches. Diagnostic-therapeutic block of facet joints, the technique of which varies in different sources is a quick and simple procedure (however, it is effective only when the needle is precisely placed at the medial branch passage under fluoroscopic guidance). Under fluoroscopy control, a 22G needle is positioned on the facet joint at the passage of the medial branch. Subsequently, 1 ml of a mixture of local anaesthetic and corticosteroid is administered. After this stage of treatment, the patient is discharged from the hospital with a recommendation to keep a pain diary and attend a follow-up visit in 3–4 weeks. If the effect of the block is satisfactory (50% reduction in pain sensations for 5–10 days), the patient qualifies for RFA [36].
According to Cohen et al., the medial branch block and its outcome are the main prognostic factors for assessing the effectiveness of radiofrequency ablation, although it is not a long-term therapeutic manipulation [37].
Based on the data obtained by Conger et al., approximately 60% of patients who reported improvement in their condition and reduction in pain by ≥ 80% during the 10–30-day period after the block noted sustained pain reduction by ≥ 50% after the second stage of treatment – radiofrequency ablation. Within this same group, during a 2-year observation period, about 29% of individuals reported an 80% reduction in pain, and 13% of respondents noted a 100% reduction.
On the other hand, among patients who assessed the effect of the performed block within a 10–30-day period of ≥ 50% to ≤ 80% reduction in pain sensations, only about 44% reported sustained pain reduction of ≥ 50% during the two-year follow-up [38] (Table 2). The study performed by Cohen et al. aimed at analysing the effectiveness of facet joint block as a predictor of RFA efficiency, 229 patients with a diagnosis of facet syndrome were selected and randomly divided into three separate groups: two control groups that underwent intra-articular block and medial branch block, and a placebo control group that received a physiological solution injection. The distribution of patients was 2 : 2 : 1. The results of the performed block in all three groups were 54%, 55%, and 30%, respectively. After the block, 135 patients underwent radiofrequency thermocoagulation of the medial branches. The improvement scores were 3.0 ±2, 3.2 ±2.5, and 3.5 ±1.9, respectively [37] (Table 3).
Shih et al. compared the results of classic RFA and pulsed radiofrequency (PRF) in patients with lower back pain. After patient selection, both groups underwent medial branch block, followed by PRF and RF. The results showed a significant improvement in the patients’ condition and a reduction in pain sensations. However, researchers identified that the effect of conventional radiofrequency (CRF)lasted longer than that of PRF. The obtained results were as follows: in the PRF group, 25% of patients rated the effect as “fantastic,” 50% as “excellent,” and 15% as “moderate.” In contrast, in the conventional RF group, these indicators were distributed as 65%, 30%, and 5%, respectively. Meanwhile, the control group of patients (only block) was distributed as follows: “fantastic” – 20%, “excellent” – 50%, “moderate” – 25%, “poor” – 5% [39] (Fig. 1).
After one year of observation, the pain assessment on the visual analogue scale was 3.9 ±1.2 in the control group, 3.5 ±1.3 in the PRF group, and 2.4 ±1.1 in the CRF group. Among the patients in the control group, 95% took analgesics one year after the procedure, 75% in the PRF group, and only 40% in the CRF group [39].
These results suggest that even if classical RFA is not possible, the impact of the current on the medial branch yields much better results compared to performing a block alone [32, 40]. However, considering the higher success rates in the group of classical thermocoagulation, it is worth considering additional analgesia options and performing classical lesion.
In addition, this type of intervention is characterized by an extremely low level of complications, provided that the procedures are performed correctly and sequentially, without ignoring diagnostic steps. These include sensory stimulation, aimed at confirming the correct positioning of the electrode at the site of the medial branch passage, through the patient experiencing various sensations related to the action of the current on the nerve (tingling, pain, tingling, vibrations, etc.) (1 V, 50 Hz, 1 ms pulsed), and mandatory stimulation of motor fibres using (3 V, 2 Hz, 1 ms pulsed) to prevent motor function damage during the lesion. Kornick et al. reported that 616 ablation protocols were evaluated in 96 patients (each level of the medial branch exit was considered a separate protocol) [41]. No major complications were detected, and the level of minor complications was 1%, including back pain lasting more than 2 weeks at the thermocoagulation site (3 cases/0.5%) and the occurrence of neuropathic pain lasting 2 weeks in 3 cases (0.5%). All complications in the form of prolonged pain resolved on their own, approximately after 3 weeks. There were also no cases of motor fibre damage, infections, or the emergence of neurological deficits.

CONCLUSIONS

Radiofrequency ablation of the medial branch is an effective and efficient, minimally invasive procedure with a low level of complications for the treatment of chronic and prolonged lower back pain when first-line therapies such as physiotherapy, rehabilitation, and the use of nonsteroidal anti-inflammatory drugs do not yield the desired effect.
The key to successful treatment is the careful selection of patients with clear indications and inclusion criteria for invasive cure and the exclusion of other causes of back pain, such as instability, trauma, spondylolisthesis, etc. Studies also show that in patients with a smaller Cobb angle and older age, the results may be slightly better [38].
In patient selection for RFA of medial branches, the diagnostic block with a local anaesthetic and corticosteroid, with an evaluation of the results and the degree of pain/complaint reduction a month after the diagnosis, is also important. Such an approach is necessary for assessing and predicting the effectiveness of RFA in patients of all age groups, with a direct correlation to the level of effectiveness of the performed block: the more pronounced the effect of the block, the better and longer lasting the results of RFA.
However, many controversial questions remain, such as the duration of radiofrequency ablation, the possible frequency of repetition of the procedure, its effect in stable spondylolisthesis, etc., which require further study and investigation.

Disclosures

1. Institutional review board statement: Not applicable.
2. Assistance with the article: None.
3. Financial support and sponsorship: None.
4. Conflicts of interest: None.

REFERENCES