Effects of monopolar radiofrequency heating on intradiscal pressure in sheep

In vivo effects of radiofrequency ablation on long bones and the repair process in swine models

PURPOSE

To investigate in vivo effect of radiofrequency ablation (RFA) on swine long bones and the repair process.

MATERIALS AND METHODS

RFA was performed in six swine at the end and middle part of the tibia or femur. After RFA, radiological examinations were performed, and the swine were killed immediately and at different time points post-RFA for histopathological examination.

RESULTS

All swine had successful RFA. The RFA-induced elliptical necrotic area ranged from 3.81-5.24 cm² (mean 4.08 ± 0.73 cm²) at the bone end but 5.60-8.98 cm² (mean 7.58 ± 1.41) at the middle part immediately after RFA until 10 days, with the necrosis area significantly smaller (P = 0.000) at the end than at the middle. RFA only damaged the cortical bone slightly (0.01 cm thick) with no damage to the soft tissues outside the compact bone at both the end and middle. Surrounding the elliptic pale zone of coagulative necrosis was a narrow brown band of hemorrhage and inflammatory exudate. From day 10 until week 12, tissue proliferation and repair became increasingly apparent, with proliferated granulation, fibrous tissue, and fresh and mature bone trabecula.

CONCLUSION

RFA can quickly and effectively destroy the cancellous bone tissue without affecting the cortical bone and activate bone remodeling.

Cervical intervertebral disc herniation treatment via radiofrequency combined with low-dose collagenase injection into the disc interior using an anterior cervical approach

This study aimed to determine the therapeutic effect of radiofrequency combined with low-dose collagenase injected into the disc interior via an anterior cervical approach for cervical intervertebral disc herniation.Forty-three patients (26-62-year old; male/female ratio: 31/12) with cervical intervertebral disc herniation received radiofrequency combined with 60 to 100 U of collagenase, injected via an anterior cervical approach. The degree of nerve function was assessed using the current Japanese Orthopaedic Association (JOA) scoring system at 3 and 12 months postoperation. A visual analogue scale (VAS) was used to evaluate the degree of pain preoperation and 7 days postoperation. The preoperative and 3 month postoperative protrusion areas were measured and compared via magnetic resonance imaging (MRI) and picture archiving and communication systems (PACS).Compared with the preoperative pain scores, the 7-day postoperative pain was significantly reduced (P <0.01). The excellent and good rates of nerve function amelioration were 93.0% and 90.7% at 3 and 12 months postoperation, respectively, which was not significantly different. Twenty-seven cases exhibited a significantly reduced protrusion area (P <0.01) at 3 months postoperation. No serious side effects were noted.To our knowledge, this is the first study to demonstrate that the use of radiofrequency combined with low-dose collagenase injection into the disc interior via an anterior cervical approach is effective and safe for the treatment of cervical intervertebral disc herniation.

Percutaneous bipolar radiofrequency thermocoagulation for the treatment of lumbar disc herniation

Lumbar disc herniation is usually managed with conservative treatment or surgery. However, conservative therapy seldom yields good results, and surgery is associated with multiple complications. This study aimed to assess bipolar radiofrequency thermocoagulation for the treatment of lumbar disc herniation. A total of 168 patients with lumbar disc herniation suitable for radiofrequency thermocoagulation were enrolled and randomized to monopolar radiofrequency thermocoagulation (control group, n=84) or bipolar radiofrequency thermocoagulation (experimental group, n=84) treatment groups. Ablation sites were targeted under CT scan guidance, and consecutive radiofrequency therapy was used. One and two probes were used for monopolar and bipolar thermocoagulation, respectively. Thermocoagulation was achieved at 50°C, 60°C, and 70°C for 60s each, 80°C for 90s, and 92°C for 100s. Symptoms and complications were evaluated using the modified Macnab criteria and Visual Analog Scale at 7, 30, and 180days postoperatively. At 180days, a significantly higher efficacy rate was obtained in the experimental group compared with control patients (91.6% versus 79.7%, P<0.05). No severe complications were occurred in either group. Targeted ablation via bipolar radiofrequency thermocoagulation is efficient for lumbar disc herniation treatment, and should be further explored for broad clinical application.

Radiofrequency ablation near the bone-muscle interface alters soft tissue lesion dimensions

BACKGROUND AND OBJECTIVES

Radiofrequency (RF) lesions are safe and effective in the treatment of spine pain; however, models developed to study factors affecting lesion dimensions have been performed in homogeneous media that may not accurately simulate human anatomy and electrophysiology. We present a novel ex vivo porcine model for performing RF lesion studies and report the influence of bone on projection of RF ablation lesions into soft tissue.

METHODS

Radiofrequency lesions were performed in porcine rib specimens using monopolar 18-gauge, 10-mm straight active tip cannula, with a lesion temperature of 80°C for 150 seconds. Ten lesions were performed in pure porcine muscle tissue and abutting porcine rib bone with surrounding muscle. Lesions were exposed with dissection and measured with digital calipers.

RESULTS

Maximal effective lesion radius approximately doubled against the bone compared with the pure muscle group (mean, 5.65 mm [95% CI, 5.43-5.87 mm] vs 2.68 mm [95% CI, 2.55-2.81 mm], P < .0001), although this was seen only in a vertical direction and not horizontally. In addition, the prelesion and postlesion impedance of the bone-muscle interface was consistently higher than the muscle-only interface (mean, 165.6 Ohm [95% CI, 146.6-184.6 Ohm] vs 137.8 Ohm [95% CI, 135.5-140.1 Ohm], P = 0.004; 144.3 Ohm [95% CI, 134.3-154.3 Ohm] vs 124.3 Ohm [95% CI, 119.3-129.3 Ohm], P = 0.001). Other dimensions and estimated volume were not significantly different.

CONCLUSIONS

Bone adjacent to RF lesions alters the surrounding electrophysiological environment causing RF lesions to project further perpendicularly from the needle axis, vertically to bone, than previously expected. This phenomenon should be considered in the future modeling and clinical practice of RF.

Intradiscal electrothermal therapy treatment for back pain

The intradiscal electrothermal therapy (IDET) procedure is a minimally invasive technique designed to treat discogenic chronic low back pain. The debate surrounding IDET ranges from the concept of the procedure, the technique and patient selection, to its effectiveness. The procedure provides modest improvement; however, it is considered less invasive and destructive than other modalities of treatments available at the present time, and has lower cost. The effectiveness evidence is limited at the present time, but based on the results of six recently published positive single-arm studies, it appears that patients experienced a perceptible clinical benefit from the IDET procedure. Thus, IDET is recommended in patients with moderate functional impairment, relatively well-maintained disc heights and discogenic pain caused by annular tears or protrusions less than 3-4 mm after the failure of less invasive procedures.

Disc volume reduction with percutaneous nucleoplasty in an animal model

Study Design

We assessed volume following nucleoplasty disc decompression in lower lumbar spines from cadaveric pigs using 7.1Tesla magnetic resonance imaging (MRI).

Purpose

To investigate coblation-induced volume reductions as a possible mechanism underlying nucleoplasty.

Methods

We assessed volume following nucleoplastic disc decompression in pig spines using 7.1-Tesla MRI. Volumetry was performed in lumbar discs of 21 postmortem pigs. A preoperative image data set was obtained, volume was determined, and either disc decompression or placebo therapy was performed in a randomized manner. Group 1 (nucleoplasty group) was treated according to the usual nucleoplasty protocol with coblation current applied to 6 channels for 10 seconds each in an application field of 360°; in group 2 (placebo group) the same procedure was performed but without coblation current. After the procedure, a second data set was generated and volumes calculated and matched with the preoperative measurements in a blinded manner. To analyze the effectiveness of nucleoplasty, volumes between treatment and placebo groups were compared.

Results

The average preoperative nucleus volume was 0.994 ml (SD: 0.298 ml). In the nucleoplasty group (n = 21) volume was reduced by an average of 0.087 ml (SD: 0.110 ml) or 7.14%. In the placebo group (n = 21) volume was increased by an average of 0.075 ml (SD: 0.075 ml) or 8.94%. The average nucleoplasty-induced volume reduction was 0.162 ml (SD: 0.124 ml) or 16.08%. Volume reduction in lumbar discs was significant in favor of the nucleoplasty group (p<0.0001).

Conclusions

Our study demonstrates that nucleoplasty has a volume-reducing effect on the lumbar nucleus pulposus in an animal model. Furthermore, we show the volume reduction to be a coblation effect of nucleoplasty in porcine discs.

Percutaneous disc decompression with nucleoplasty-volumetry of the nucleus pulposus using ultrahigh-field MRI

PURPOSE

To evaluate changes in nucleus pulposus volume as a potential parameter for the effects of disc decompression.

METHODS

Fifty-two discs (T8 to L1) were extracted from 26 pigs and separated into thoracic (T8 to T11) and thoracolumbar discs (T12 to L1). The discs were imaged using 7.1 Tesla ultrahigh-field magnetic resonance imaging (MRI) with acquisition of axial T2-weighted turbo spin-echo sequences for determination of baseline and postinterventional nucleus pulposus volumes. Volumes were calculated using OsiriX® (http://www.osirix-viewer.com). After randomization, one group was treated with nucleoplasty, while the placebo group was treated with an identical procedure but without coblation current. The readers analyzing the MR images were blinded to the kind of procedure performed. Baseline and postinterventional volumes were compared between the nucleoplasty and placebo group.

RESULTS

Average preinterventional nucleus volume was 0.799 (SD: 0.212) ml. Postinterventional volume reduction in the nucleoplasty group was significant at 0.052 (SD: 0.035) ml or 6.30% (p<0.0001) (thoracic discs) and 0.082 (SD: 0.042) ml or 7.25% (p = 0.0078) (thoracolumbar discs). Nucleoplasty achieved volume reductions of 0.114 (SD: 0.054) ml or 14.72% (thoracic) and 0.093 (SD: 0.081) ml or 11.61% (thoracolumbar) compared with the placebo group.

CONCLUSIONS

Nucleoplasty significantly reduces thoracic and thoracolumbar nucleus pulposus volumes in porcine discs.

Histological changes and temperature distribution studies of a novel bipolar radiofrequency heating system in degenerated and nondegenerated human cadaver lumbar discs

OBJECTIVE AND STUDY DESIGN

The purpose of this experimentation was to investigate the safety of a novel cooled bipolar radiofrequency system by examining histology and monitoring temperature distribution in the disc, epidural space, and adjacent to the nerve roots. In our study we used two human cadaver lumbar spines, one moderately to severely degenerated and the other mildly degenerated.

SETTING AND INTERVENTIONS

Radiofrequency ablation of the disc posterior annulus is a theoretically plausible technique to ablate the nociceptors and to modify collagen of the annulus fibrosus. A novel cooled bipolar radiofrequency system is used to perform a procedure called intervertebral disc biacuplasty to heat the posterior annulus for the treatment of discogenic pain. Four lumbar intervertebral discs were treated in each spine sample using the bipolar system while two lumbar discs of each spine were used as controls.

RESULTS

Temperatures developed in the posterior annulus of the disc were on average 52.35 +/- 5.07 degrees C, while in the intervertebral foramen and in the spinal canal were 38.84 +/- 1.7 degrees C and 38.29 +/- 2.04 degrees C, respectively. There was no histological evidence of damage to any other structures including vertebral end plates, epidural space, or nerve roots. Additionally, there were no histological changes in the posterior annulus that were consistent with heat-induced changes to collagen structure.

CONCLUSIONS

Temperatures reached in the posterior annulus during transdiscal biacuplasty were greater than required (45 degrees C) for neuroablation. Temperatures reached at the neural foramina and epidural were low enough to avoid neural damage.