Trident Multi-tined Cannula for Cervical MBRFA Compared to the Conventional Cannula

The Effectiveness and Procedural Characteristics of the Trident Multi-tined Cannula for Cervical Medial Branch Radiofrequency Ablation Compared to the Conventional Cannula; A Multi-site, Single Blinded, Randomized Controlled Trial

Cervical medial branch radiofrequency ablation (CMBRFA) is an effective treatment for cervical facet pain. The efficacy of CMBRFA was proven by studies published in the late 1990's and early 2000's. Patients were selected by a strict, labor-intensive placebo-controlled, diagnostic block protocol and were treated using a conventional monopolar cannula that was positioned parallel to the medial branch, two to three lesions per medial branch nerve and both sagittal and oblique passes. Since the original CMBRFA publications, patient selection for CMBRFA is less strict, and new RFA cannulae have been developed to improve efficiency and safety while maintaining a large ablative lesion.

Current clinical patient selection criteria for CMBRFA tend to be more relaxed than described in early research studies. However, subsequent research has shown that when selection criteria are too relaxed, outcomes are poorer. A recent cross-sectional study reported that when CMBRFA is done in patients selected by >80% pain improvement after dual medial branch blocks, outcomes are similar to patients selected with a stricter selection protocol (100% pain relief) similar to the original CMBRFA studies. Although, the cross-sectional study suggests an appropriate selection criteria, it has not been used in any prospective studies.

The Trident multi-tined cannula is a recent technology that produces a large ablative lesion distal to the triple-tined tip. This design allows a perpendicular/lateral approach to CMBRFA and only requires a single lesion at each medial branch. This differs from the conventional cannula, which produces it's most extensive ablative lesion along the cannula with minimal distal projection. As a result, it requires a parallel approach with multiple burn cycles at the same medial branch. The perpendicular approach with Trident and single lesion cycle at each medial branch are appealing for safety purposes and efficiency however, it's efficacy has not been directly compared to the standard conventional cannula.

Problem: There are no randomized controlled trials comparing novel technologies like Trident cannula to the previously studied conventional cannula in patients selected with a more practical selection criteria.

Purpose: To compared procedural characteristics, pain, and disability outcomes of CMBRFA using either a Trident or conventional cannula in patients with confirmed facet mediated pain (defined by ≥80% symptom reduction after dual medial branch block).

Central Hypothesis: Trident cannula during CMBRFA will result in noninferior improvements in pain and function compared to conventional cannula but will significantly reduce procedural discomfort, time and radiation exposure.

Specific Aims:

1. Determine the proportion of patients with a successful pain response (defined as ≥50% improvement in index pain) to Trident (T-CMBRFA) versus conventional (C-CMBRFA) at 3, 6, and 12 months.
2. Determine the proportion of patients with a successful functional response (defined as ≥10% reduction on neck disability index [NDI]) to T-CMBRFA versus C-CMBRFA at 3, 6, and 12 months.
3. Determine the proportion of patients with a successful perception of improvement (defined as a score ≥6 on the Patient Global Impression of Change [PGIC]) to T-CMBRFA versus C-CMBRFA at 3, 6, and 12 months.

According to the National Center for Health Statistics, neck pain is the third most commonly reported musculoskeletal complaint in the United States. Cervical zygapophysial or "facet" joint pain is responsible for at least 25% of patients with chronic neck pain and is higher in patients with neck pain after a whiplash injury. Individuals with verified facetogenic pain or cervicogenic headaches can be treated with cervical medial branch radiofrequency ablation (CMBRFA). CMBRFA is a minimally invasive percutaneous procedure that utilizes thermal energy to coagulate nerves from the facet joints, and thereby interrupt the nociceptive pain signals. The targeted nociceptive nerves are the medial branches of the cervical dorsal rami and the third occipital nerve.

The gold standard method of facet pain diagnosis is anesthetizing the medial branches that innervate the involved facet joint and subsequently evaluating the significance of symptom improvement; this process is known as a medial branch block (MBB). There is significant practice variability in what is considered a "positive" MBB. A single cervical MBB with 100% symptom improvement has a false positive rate of 27-60%. The false positive rate decreases with stricter selection criteria. The efficacy of CMBRFA was established in the late 1990's and early 2000's when using a strict selection criteria; 100% symptom improvement with concordant dual medial branch block ± placebo-control block.

In 1996, Lord et al. published in New England Journal of Medicine research showing that when the rigorous diagnostic criteria were adhered to, 63% (CI 95%: 57-69%) and 38% (CI 95%:32-44%) of patients were pain free at 6 and 12 months following CMFRFA. Though comparative dual MBB ± placebo with 100% symptom improvement reduces false positive rates, it is time consuming and expensive, exposes patients to extra radiation and procedural risk, is not required by insurance, and is not the Spine Interventional Society (SIS) recommended gold standard for patient selection for facetogenic pain in the lumbar spine. Currently insurance requires ≥80% symptom improvement with dual facet block. These insurance requirements are consistent with the research supported SIS guidelines for the diagnosis of lumbar facetogenic pain and such practical patient selection criteria are commonly utilized in clinical practice. A recent cross-sectional study reported that when CMBRFA is performed on patients selected by >80% symptom improvement after dual medial branch block, outcomes are similar to patients selected with a stricter selection protocol similar to the original CMBRFA studies however, this needs to be validated in prospective studies.

In early explanatory studies, providers used a conventional monopolar cannulae to ablate targeted medial branch nerves. C-CMBRFA cannula produce the largest lesions along the shaft of the cannula with minimal extension distal to the tip. To increase the likelihood of medial branch ablation the conventional cannula is placed parallel to the targeted medial branch in a posterior to anterior approach with sagittal and oblique passes, and 2-3 lesions per medial branch. Disadvantages to the conventional technique is the procedural time needed for multiple passes and burns and the risk of ventral advancement of the cannula towards vital neurovascular structures. Since the original explanatory C-CMBRFA studies, there have been technologic advances in RFA cannulae in an effort to improve safety and efficiency of CMBRFA.

The Trident multitined cannula was designed to allow a perpendicular/lateral approach to the medial branch nerves. Such approach results in point contact against bone, prevents unintended advancement towards neurovascular structures, and as a result adds to the safety of the procedure. There is also reported efficiency during Trident RFA since only 1 pass and a single lesion at each medial branch is required. A single burn cycle at each site is a possibility because of the unique lesion shape and size. The Trident cannula most commonly used for CMBRFA is 18-gauge and has a 5 mm exposed tip. Once the cannula tip is placed at the target location, 3 tines are deployed anterior and laterally from the cannula tip in an equilateral triangle configuration. Computer simulation calculations predict that a two-minute lesion at 75°C would result in thermal coagulation in an area measuring 7.6 mm wide by 7.6 mm length in the axial plane (at the periosteal surface) and 9.1 mm in height in the sagittal plane (soft tissue lesion) [data provided by Diros Technology Inc.]. These values are comparable to the findings of Finlayson et al who compared thermal lesions morphology of 2 multitined cannulae and a conventional monopolar cannula in an ex vivo model. In the axial plane, with the Trident cannula perpendicular to the periosteum, the mean lesion width and length were 7.3 x 8.8 mm respectively. In the sagittal plane, the mean lesion height was 7.3 mm. Considering that the mean distance between the medial branch nerve at the waist of the articular pillar, and the tip of the superior facet has been documented to be between 7.1-7.4 mm for C3 through C6 and 5.5 mm for C7, a single Trident lesion placed at the waist of the lateral mass should cover approximately one half of the periosteal surface. This should be adequate to accommodate medial branch nerve anatomical variation. Ultimately, the Trident cannula results in an approach that may be technically easier, quicker, safer, more comfortable and as effective as the traditional parallel/posterior approach however, there are no studies comparing Trident to conventional cannula during CMBRFA.

Inclusion Criteria:

1. Adult patient aged ≥18 capable of understanding and providing consent in English and capable of complying with the outcome instruments used.

2. Axial (non-radicular) neck pain for at least 3 months.

3. 7-day average numeric pain rating score (NRS) for neck pain of 4/10 or greater at baseline evaluation.

4. *Positive responses to dual diagnostic MBB blocks using 0.5mL of lidocaine and bupivacaine, on respective encounters on separate days, at each of the appropriate MBBs.

   • Levels selected for diagnostic procedures will be determined by the treating physician based on the overall clinical picture including the location of pain, pain referral patterns, physical examination and imaging findings. The procedural techniques of all MBB blocks will be performed according to Spine Intervention Society guidelines.(14) A pain diary with appropriate diagnostic categories of relief will be provided (100% relief, 80-99% relief, etc.), will be provided. In order to qualify as a positive block, the subject must experience relief lasting at least one hour with lidocaine and two hours with bupivacaine.

Exclusion Criteria:

1. Those receiving remuneration for their pain treatment (e.g. disability, worker's compensation, auto injury in litigation or pending litigation).
2. The patient is incarcerated.
3. Those unable to read English and complete the assessment instruments.
4. Allergy to contrast media or local anesthetics.
5. Chronic widespread pain or somatoform disorder (e.g. fibromyalgia).
6. Prior cervical medial branch radiofrequency neurotomy.
7. Severe clinical depression or psychotic features.
8. Possible pregnancy or other reason that precludes the use of fluoroscopy.
9. Daily chronic opiate use of >50 morphine equivalents.
10. Presence of pacemaker of neurostimulator.
11. Systemic infection at time of procedure.
12. Uncontrolled bleeding diathesis.
13. Requirement of IV procedural sedation.