Quantification of Needle Angles for Traditional Lumbar Medial Branch Radiofrequency Ablation: An Osteological Study

A retrospective single arm cohort study evaluating the efficacy of lumbar medial branch radiofrequency ablation using a multi-tined probe and perpendicular approach

Summary of background data

Lumbar medial branch radiofrequency ablation (LMBRFA) is an effective treatment for facet joint pain. LMBRFA efficacy was originally demonstrated using a parallel technique. Newly developed RFA probes (e.g., Trident) allow a perpendicular approach (P-LMBRFA), which may simplify the RFA technique and lead to superior treatment success rates. However, further investigation is necessary to determine whether these technologies are associated with improved patient outcomes.

Objectives

Evaluate the effectiveness of P-LMBRFA in patients with confirmed facet pain.

Methods

In this retrospective single-arm cohort study, electronic medical records were used to identify consecutive patients with ≥80 % dual medial branch block-confirmed pain relief who underwent first-time P-LMBRFA between 2016 and 2022. Primary outcomes were ≥50 % Numerical Rating Scale (NRS) pain improvement and the minimal clinically important difference (MCID) on the Pain Disability Quality-of-Life Questionnaire (PDQQ) at 3 months post-treatment. Secondary outcomes included the duration and mean retrospective percentage of pain relief after a successful index P-LMBRFA in individuals who reported a return of their index symptoms.

Results

174 participants (60.3 % female, 61.3 ± 14.2 years of age, BMI 29.5 ± 6.7 kg/m2) were analyzed. Success rates for ≥50 % NRS reduction and MCID on the PDQQ at 3 months were 50.6 % (95 % CI = 43.3-57.9 %) and 50.0 % (95 % CI = 42.8-57.2 %), respectively. Of the 88 successful P-LMBRFAs, 60 patients experienced a return of symptoms after 8.7 ± 3.6 months and reported a retrospective mean percentage pain relief of 81.8 % ± 15.8 %.

Discussion/conclusion

Following P-LMBRFA, approximately 50 % of patients reported improvement in pain and disability measures. Extensive, prospective research comparing long-term outcomes of P-LMBRFA and parallel LMRBFA is warranted.

A Novel Fluoroscopic Methodology for Accurate and Precise Lumbar Facet Medial Branch Radiofrequency Ablations: An Educational Report

Although fluoroscopic-guided lumbar facet medial branch radiofrequency ablations (LFMBRFAs) are commonly performed for lumbar spondylosis, literature describing techniques and methods focused on accuracy and precision is scarce. In this case report, we describe an innovative fluoroscopic methodology to help improve LFMBRFA procedural accuracy and precision. A 74-year-old man with a pertinent history of lumbar spondylosis presented with chronic bilateral low axial back pain underwent successful, and uncomplicated bilateral LFMBRFAs. The patient reported 90% to 100% analgesic relief at 6 months follow-up. He did not report any adverse events or complications.

Evaluation of a novel nerve ablation technique to relieve lower back pain: a cadaveric feasibility pilot study

INTRODUCTION

Radiofrequency ablation is a treatment for facetogenic low back pain that targets medial branches of lumbar dorsal rami to denervate facet joints. Clinical outcomes vary; optimizing cannula placement to better capture the medial branch could improve clinical outcomes. A novel parasagittal technique was proposed from an anatomic model; this technique was proposed to optimize capture of the medial branch. The anatomic feasibility of the novel technique has not been evaluated.

OBJECTIVE

To simulate and evaluate the proposed parasagittal technique in its ability to achieve proper cannula placement and proximity of uninsulated cannula tips to the medial branches of the dorsal rami in cadaveric specimens.

METHODS

Under fluoroscopic guidance, the parasagittal technique was used to place 14 cannulae targeting the lumbar medial branches of 2 cadavers. Meticulous dissection was undertaken to assess cannula alignment and measure proximities to target nerves with a digital caliper.

RESULTS

The novel parasagittal technique was successfully performed in a cadaveric model in 12 of 14 attempts. The technique achieved close proximity of cannula tips to medial branches (0.8 ± 1.1 mm). In 2 instances, cannulae were placed unsuccessfully; in one instance, the cannula was too far anterior, and in the other, it was too far retracted.

CONCLUSION

In this cadaveric simulation study, the feasibility of performing the parasagittal technique for lumbar radiofrequency ablation was evaluated. This study suggests that the parasagittal technique is a feasible option for lumbar medial branch radiofrequency ablation.

Optimal caudal needle angulation for lumbar medial branch denervation: A 3D cadaveric and clinical imaging comparison study

Background

Lumbar medial branch (MB) radiofrequency ablation is a common intervention to treat facetogenic low back pain. The consensus among spine pain interventionalists is that capturing a greater length of the MB correlates with a longer duration of pain relief. Therefore, there has been interest in defining optimal needle angles to achieve parallel cannula placement. Presently, there is inconsistency regarding the optimal caudal needle angles.

Objectives

The objectives of this study were to: 1) use a dissection-based 3D modelling methodology to quantify optimal caudal needle angles from cadaveric models; and 2) compare optimal cadaver-derived caudal needle angles with real-world patient-derived needle angles.

Methods

Eighteen formalin embalmed lumbosacral spine specimens were dissected, digitized, and modelled in 3D. Virtual needles were simulated and placed parallel with the L1-L5 MBs. Cadaver-derived caudal needle angles were measured from the high-fidelity 3D models with optimally placed virtual needles. Lateral fluoroscopic images of patients (n = 200) that received lumbar MB denervation were reviewed to measure patient-derived caudal needle angles (L3-L5 MB levels). Descriptive statistics were used to analyze the cadaver (L1-L5 MB levels) and patient-derived (L3-L5 MB levels) caudal needle angles. The cadaver and patient-derived mean caudal needle angles for L3-L5 MB levels were compared.

Results

There was variability in the cadaver-derived mean caudal needle angles. The lowest mean caudal needle angle was the L1 MB level measured at 41.57 ± 8.56° (range: 27.14° - 53.96°). The highest was the L5 MB level with a mean caudal needle angle of 60.79 ± 8.55° (range: 46.97° - 79.74°). A total of 123 patients were included and 369 caudal needle angles (L3-L5 MB levels) were measured and analyzed. There was variability in the patient-derived mean caudal needle angles. The patient-derived mean caudal needle angles were 29.18 ± 8.77° (range: 11.80° - 61.31°), 33.34 ± 7.23° (range: 16.40° - 54.15°), and 49.08 ± 8.87° (range: 26.45° - 76.95°) for the L3, L4, and L5 MB levels, respectively. There was a significant difference in mean caudal needle angle between cadaver and patient-derived needle angles at the L3, L4, and L5 MB levels.

Conclusions

Analysis of cadaver-derived needle angles versus patient-derived data suggests optimization of lumbar MB denervation requires greater caudal angulation to achieve parallel needle placement. Further research is required to assess the clinical implications.

Parasagittal needle placement approach for lumbar medial branch denervation: a brief technical report

Radiofrequency denervation of lumbar medial branches is a viable treatment option to manage chronic facetogenic low back pain. Traditionally, lumbar medial branch denervation involves placement of the electrode's active tip at a 20-degree angulation away from the parasagittal plane. However, more recent anatomical studies have provided evidence supporting the feasibility of an alternative parasagittal approach targeting the posterior half of the lateral neck of the superior articular process to capture the lumbar medial branches. Currently, there is a lack of clinical data on the effectiveness of the alternative parasagittal needle placement technique. Therefore, in this brief technical report, the parasagittal needle placement technique and the pain relief outcomes in four consecutive patients following treatment with the parasagittal approach are described.

3D nerve proximity mapping of the medial branch of lumbar dorsal ramus: An anatomical study

Objective

Lumbar medial branch (MB) radiofrequency ablation is a common intervention to treat facetogenic low back pain. Consensus among spine pain interventionalists is that the cannula tip should be placed adjacent to the periosteum of the lateral neck of the superior articular process (SAP) to ensure maximum contact with the MB. The spatial relationship of the nerve to the periosteum of the lateral neck of the SAP has not been quantified in 3D. The objectives of the current study were to: 1) use 3D modelling technology to quantify the location along the lateral neck of the SAP where the MB is in direct contact with the periosteum; and 2) identify target site(s) to optimize lumbar MB denervation.

Design

Seventy lumbar dorsal rami in 14 formalin-embalmed specimens were dissected, digitized, and modeled in 3D. The 3D positional data of the MB were used to generate a novel nerve proximity map which provided a method to quantify and visualize the 3D course of the MB in relation to the periosteum of the lateral neck of SAP. The percent of the lateral neck of SAP in contact with the MB was quantified and consistent target site(s) identified.

Results

There was variability in the percentage of the lateral neck of SAP in contact with the MB. The mean percentage of the lateral neck of SAP in contact with the MB for the L1-L5 levels ranged between 57.39 ± 10.72 % (for L1) to 81.54 ± 10.48 % (for L5). The nerve proximity map showed consistent course of the MB along the posterior portion of the lateral neck of SAP and at a novel target site distal to the mamillo-accessory notch (i.e. sub-mammillary landmark).

Conclusion

The percent of the lateral neck that was in contact with the MB was quantified and visualized using a novel nerve proximity mapping methodology which may be used to inform cannula tip depth placement. Further, the nerve proximity maps were used to identify an alternative landmark to extend the length of the MB captured. The proposed sub-mammillary landmark may be a viable target site pending future anatomical and clinical investigations.

High-fidelity 3D modelling of the lumbar dorsal rami

Objective

Lumbar medial branch denervation is commonly used to treat chronic facetogenic low back pain. Controversy exists regarding risk to adjacent neural structures. The objectives of this cadaveric study were to: (1) dissect, digitize, and model in 3D the branches of the first (L1) to fifth (L5) lumbar dorsal rami located near the junction of the transverse process and lateral neck of the superior articular process; and (2) quantify the minimal distance between the lateral/intermediate and medial branches at the anterior quarter and midpoint of the lateral neck of the superior articular process.

Design

Eighteen formalin-embalmed specimens were dissected, digitized and modeled in 3D. The high-fidelity 3D models were used to compare branching patterns and quantify the mean minimal distance between the lateral/intermediate and medial branches of the lumbar dorsal ramus at the anterior quarter and midpoint of the lateral neck of the superior articular process. A Two-way ANOVA was performed to determine if difference of mean distances was significant.

Results

There was variability in the branching pattern of the lumbar dorsal rami. In 46 cases (51.1%) the lumbar dorsal ramus divided into 2 branches, in 41 cases (45.6%) into 3, and in 3 cases (3.3%) 4. The mean minimal distance between the lateral/intermediate and medial branches was significantly greater at the midpoint (3.2 ± 2.5 mm) than the anterior quarter (1.2 ± 1.8 mm) of the lateral neck of superior articular process.

Conclusion

Minimal distance measurements between the branches of the lumbar dorsal rami at the anterior quarter and midpoint of the lateral neck of the superior articular process were computed. When placing the distal end of the needle tip at the anterior quarter of the lateral neck of the superior articular process, the smaller mean minimal distance between the branches suggests there is a greater risk for inadvertent denervation of the lateral/intermediate branches. Further anatomical and clinical investigations are required.

Quantification of needle angles for lumbar medial branch denervation targeting the posterior half of the superior articular process: an osteological study

BACKGROUND

Lumbar medial branch radiofrequency ablation (RFA) is a common intervention to manage chronic axial low back pain originating from the facet joints. A more parasagittal approach targeting the posterior half of the lateral neck of superior articular process (SAP) was previously proposed. However, specific needle angles to achieve parallel placement at this target site have not been investigated.

OBJECTIVE

To quantify and compare the needle angles, on posterior and lateral views, to achieve parallel placement of electrodes along the medial branch at the posterior half of the lateral neck of SAP at each lumbar vertebral level (L1-L5) and sacrum.

DESIGN

Osteological Study.

METHODS

Twelve disarticulated lumbosacral spines (n = 72 individual bones) were used in this study. Needles were placed along the periosteum of the posterior half of the lateral neck of SAP, bilaterally and photographed. Mean needle angles for each vertebral level (L1-L5) and sacrum were quantified, and statistical differences were analyzed.

RESULTS

The posterior view provided the degrees of lateral displacement from the parasagittal plane (abduction angle), while the lateral view provided the degrees of declination (cranial-to-caudal angle) of the needle. Mean needle angles at each level varied, ranging from 5.63 ± 5.76° to 14.50 ± 14.24° (abduction angle, posterior view) and 40.17 ± 7.32° to 64.10 ± 9.73° (cranial-to-caudal angle, lateral view). In posterior view, a < 10-degree needle angle interval was most frequently identified (57.0% of needle placements). In lateral view, the 40-50-degree (L1-L2), 50-60-degree (L3-L5), and 60-70-degree (sacrum) needle angle intervals occurred most frequently (54.2%, 50.0%, and 41.7% of needle placements, respectively).

CONCLUSIONS

Targeting the posterior half of the lateral neck of SAP required <10-degree angulation from parasagittal plane in majority of cases. However, variability of needle angles suggests a standard "one-size-fits-all" approach may not be the optimal technique.

3. Pain originating from the lumbar facet joints

INTRODUCTION

Pain originating from the lumbar facets can be defined as pain that arises from the innervated structures comprising the joint: the subchondral bone, synovium, synovial folds, and joint capsule. Reported prevalence rates range from 4.8% to over 50% among patients with mechanical low back pain, with diagnosis heavily dependent on the criteria employed. In well-designed studies, the prevalence is generally between 10% and 20%, increasing with age.

METHODS

The literature on the diagnosis and treatment of lumbar facet joint pain was retrieved and summarized.

RESULTS

There are no pathognomic signs or symptoms of pain originating from the lumbar facet joints. The most common reported symptom is uni- or bilateral (in more advanced cases) axial low back pain, which often radiates into the upper legs in a non-dermatomal distribution. Most patients report an aching type of pain exacerbated by activity, sometimes with morning stiffness. The diagnostic value of abnormal radiologic findings is poor owing to the low specificity. SPECT can accurately identify joint inflammation and has a predictive value for diagnostic lumbar facet injections. After "red flags" are ruled out, conservatives should be considered. In those unresponsive to conservative therapy with symptoms and physical examination suggesting lumbar facet joint pain, a diagnostic/prognostic medial branch block can be performed which remains the most reliable way to select patients for radiofrequency ablation.

CONCLUSIONS

Well-selected individuals with chronic low back originating from the facet joints may benefit from lumbar medial branch radiofrequency ablation.