Radiofrequency Use in Ankle and Foot Arthroscopy
JAMES P. TASTO
BRENNEN L. LUCAS
This chapter outlines uses of radiofrequency (RF) in foot and ankle surgery, specifically arthroscopy, but will cover some minimally invasive techniques as well. RF has become increasingly popular, and as the science behind it continues to expand, it has become a growing and exciting area in arthroscopy.
In the previous edition of this book, laser technology was discussed in detail in a chapter titled “Future Developments.” Laser is an acronym for Light Amplification by Stimulated Emission of Radiation. The laser, like RF in some ways, can be used to cut, coagulate, and vaporize tissue. The laser utilizes energy in a single beam of light. Both can significantly increase the temperature of the target tissue, but the Coblation technology in RF does not transmit heat directly to the target tissue. As most would agree, the use of laser technology in foot and ankle surgery has fallen out of favor for a multitude of reasons, and therefore, this chapter focuses on RF.1
RF use has gained popularity in many different aspects of surgery including cardiology, otolaryngology, neurosurgery, oncology, general surgery, and orthopedic surgery. In the late 1980s and early 1990s, RF was starting to be discussed in the podiatry literature. These early applications included technique papers for treatment of Morton neuromas percutaneously, treatment of plantar warts, and treating ingrown toenails.2, 3, 4 In the mid to late 1990s, RF started gaining popularity in many arthroscopic procedures.
The popularity has grown in orthopedic surgery since the mid 1990s. Since 1996, adjustable temperature RF probes have been approved for arthroscopic surgery.5 Many different applications have been studied for RF use in orthopedic surgery, some successful and some still in the investigational stages.
Many foot and ankle conditions are successfully treated conservatively. There are a variety of arthroscopic and minimally invasive procedures available when conservative treatment fails. RF is one of the newer technologies available to the arthroscopist.
RF utilizes an alternating current. The patient’s tissue provides the impedance that produces the resistance in the tissues allowing the body to become part of an electrical circuit. RF devices generally have either a monopolar or a bipolar configuration. With monopolar RF, there is a small active electrode that is used by the surgeon and a larger grounding electrode distant to the surgical field. A bipolar probe contains both the active and the return electrodes within the surgical probe making a distant grounding pad unnecessary.6 Coblation technology works by forming a plasma layer using a saline solution. This process produces chemical radicals like OH that can cause volumetric removal of biologic material rather than simply burning it.7 Bipolar RF has become a popular tool in orthopedic surgery with a wide array of applications.
Use of RF devices in arthroscopy is similar to mechanical debridement devices. The device is introduced through a secondary portal and different settings, and modes can be utilized depending on the desired effect. As stated above, various devices may be either monopolar or bipolar and have different settings including Coblation in some cases.
When performing synovectomy, applying pressure through the probe to the tissue is accepted, but when performing chondroplasty, we prefer to employ a “no touch” technique with Coblation while allowing the chondroplasty to be performed at the level of the plasma layer. The Coblation technique creates a charged plasma gas that has sufficient energy to break molecular bonds within tissue at temperatures between 40°C and 70°C. The RF current does not pass directly through the tissue.
When using the different devices, it is absolutely necessary to understand the critical settings for the particular device in use. For example, the temperature created in the tissue being treated is not necessarily higher with a higher setting on the control box (Fig. 18-1). These settings will differ within different devices from the same company and also between companies.
RF can have many uses in orthopedic surgery. The applications in foot and ankle arthroscopy include synovectomy, chondroplasty, resection of impingement lesions, debridement, fusion, and ankle stabilization procedures (Fig. 18-2).
RF treatment of cartilage defects and chondromalacia in all joints has been controversial. Initially, Turner et al. and then Kaplan et al. found favorable results treating chondral pathology with RF.8, 9 Lu et al. studied monopolar RF in 36 adult female sheep with partial-thickness articular cartilage defects. They found that the monopolar RF caused death of almost all chondrocytes in the defect.10 Lu et al. continued to study monopolar and bipolar RF and found significant depth of chondrocyte death up to 1,000 µm.11, 12, 13, 14 These findings were noted to be controversial, and further studies found the depth of penetration much less with chondrocyte viability noted just below the treatment area.15 Amiel et al. stated that the difference in findings was likely multifactorial including only reporting chondrocyte viability with confocal microscopy and previously not studying chondrocyte metabolism with glycosaminoglycan synthesis looking at 35SO4 uptake. Furthermore, and probably most importantly, using an actual surgeon rather than a preset jig, Amiel et al. showed a consistently well-defined zone of ablation with a consistent margin of chondrocyte death 100 to 200 µm.15 Similar depths of chondrocyte injury likely occur with mechanical devices. More recently, it has been shown in animal models that certain RF devices are safe for treating partial chondral defects and/or chondromalacia, but each device has unique effects on the chondral surfaces with different levels of penetration.14, 15
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