New Techniques for Treating Chronic Knee and Hip Pain Using Radiofrequency Ablation (RFA) James Sigler, MD Katherine Travnicek, MD

New Techniques Physics of RFA Knee (genicular) RFA Hip RFA Business Development What s next?

Physics of RFA James Sigler, MD Interventional Spine/Pain Medicine KCVA Medical Center Clinical Assistant Professor KUMC PM&R

Physics of RFA Indication for Use Physics of Conventional RF Physics of Cooled RF Lesion Size and Geometry RFA in Pain Management

Indication for Use Radiofrequency Ablation is indicated for use to create RF lesions in nervous tissue Applications include Cervical, Thoracic, Lumbar medial branch nerves Articular nerves to shoulder, hip, knee joints

Conventional RF Ablation Components Active Electrode (Probe within Cannula) Passive Electrode (Grounding Pad) Radiofrequency (RF) Generator Patient (part of the circuit) Active Electrode or Probe Passive Electrode RF Generator or Grounding Pad

Principle of Ionic Heating Charge is alternated (460 khz) Ions in surrounding tissue move creating friction 1 Friction heats surrounding tissue Hot tissue heats probe or electrode by conduction Probe thermocouple located at the tip, reads tissue temperature 1. Organ LW. Appl Neurophysiol 1976;39:69-76.

Factors Responsible for Ionic Heating Electrical Properties Tissue electrical conductivity Local current density Thermal Properties Thermal conductivity Ablative Mechanism Thermally destroys nerve fibers- Coagulation Protein denaturation

Temperature Distribution for Conventional RF Cannula Insulation Cannula Active Tip Temperature drops as radius from tip increases Hottest tissue is at the probe/ tissue interface (limiting factor > 90ºC) Neurodestruction: > 45ºC A small zone of reversible damage surrounds lesion 80 C 65 C 45 C

Lesion Size & Tip Surface Area Electrode Shape: Lesion size depends on the length and gauge of the electrode 2,3 Lesion size increases with the probe s surface area 2. Bogduk N, Macintosh J, Marsland A. Neurosurgery 1987;20:529-35. 3. Alberts WW, Wright EW, Jr., Feinstein B, et al. J Neurosurg 1966;25:421-3. 20 Ga. 10mm 18 Ga. 10mm 20 Ga. 4 mm

Lesion Size & Set Temperature Set Temperature: Lesion volume increases proportionally with set temperature from 50 C to 90 C 3 Modified from Alberts 1966 3. Alberts WW, Wright EW, Jr., Feinstein B, et al. J Neurosurg 1966;25:421-3.

Lesion diameter (mm) Lesion Size & Ablation Duration 10 8 6 4 2 75 C 80 C 85 C 0 50 100 150 200 Time (s) Testing performed in chicken (37 C). Electrode: 18 gauge, 10 mm active tip. Unpublished data. Baylis Medical Company 4. Lord SM, McDonald GJ, Bogduk N. Neurosurgery Quarterly 1998;8:288-308.

Lesion size: Summary: Conventional RF Set temperature: Tissue temps > 90 95 C cause tissue carbonization and vapor formation, limiting lesion size Ablation duration: Tissue temp saturates in secs-to-minutes, limiting lesion size Probe surface area: Adds to interface variability, limiting lesion size

Cooled-RF vs Conventional Cooled-RF increases lesion size by overcoming limitations inherent to conventional RF Cooled-RF lesion shape is more spherical, which can provide advantages for certain indications Cooled-RF requires specialized equipment and supplies which are more costly than conventional RF

Conventional RF Cooled RF Set temp: 60 C Set temp: 60 C

Physics of RFA Modified from 8. Goldberg SN, Gazelle GS, Mueller PR.. AJR Am J Roentgenol 2000;174:323-31.

Lesion Size and Geometry Increasing radius r of a sphere by a factor of 2 increases volume V by a factor of 8 according to:

Lesion Size and Geometry Conventional RF Cooled RF Testing performed in chicken (37 C) for 3:00 at a set temperature of 70 C. Electrode: 18 Gauge, 4mm active tip.

Cooled RF Lesion Properties Size and shape of cooled RF lesions are a function of: - Electrode surface area - Set temperature - Time (Duration) - Coolant Flow Rate - Coolant Temperature Cooled RF- 18Ga, 4mm 40% 10 mm Testing performed in chicken (37 C) for 3:00 at a set temperature of 70 C.

Large Spherical and Forward Projecting Lesion Cooled RF Conventional RF

Cooled-RF System Components Capital Equipment 1. PMG 2. Pain Management Pump Unit 3. Pump Connector Cable 4. Cooled RF Connector Cable Disposable Kit SInergy Kit ThoraCool Kit LumbarCool Kit CerviCool Kit Cooled RF Kit TransDiscal Kit

Advantages CONVENTIONAL Smaller lesion - more precise Cost efficient Time efficient COOLED-RF Larger lesion - better for nerves with anatomic variability Spherical lesion - Distal projection heats in and around difficult anatomy, scar tissue, surgical hardware etc.

RFA in Pain Management Conventional RFA for: Cervical, Thoracic, Lumbar Medial Branches Suprascapular PRFA GRC PRFA Cooled-RFA for: SI Joints Hip Joints Knee Joints