Information Statement

Use of Thermal Modalities (Lasers and Radiofrequency Devices) in Orthopaedic Surgery

This Information Statement was developed as an educational tool based on the opinion of the authors. It is not a product of a systematic review. Readers are encouraged to consider the information presented and reach their own conclusions.

Clinical studies reported in orthopaedic literature have not established the significant benefit provided by thermal modalities when compared to other systems now in use. As further clinical research in thermal applications becomes available, the American Academy of Orthopaedic Surgeons (AAOS) encourages investigators to pay special attention to those areas where the techniques can be shown to be effective additions to orthopaedic care.

The AAOS endorses a scientific approach toward the use of thermal modalities in orthopaedic surgery and encourages further clinical and biological study on the potential benefits and hazards of this technology. It is the individual surgeon's responsibility to become familiar with each modality’s US Food and Drug Administration (FDA) clearance status as well as the basic science and biological effects of these techniques if he or she intends to incorporate them into clinical practice. It is also the physician's responsibility to be sensitive to cost containment issues.

The purpose of this statement is to provide information about the use of thermal technology (lasers and radiofrequency devices) in the practice of orthopaedic surgery. This information has been derived from a review of the scientific literature and augmented by the expertise of a group of orthopaedic surgeons and basic scientists experienced in the use of and study of lasers and radiofrequency devices. The literature reports, information presented at meetings by individuals in the group, and experience and knowledge of these individuals were used as reference for the development of this consensus statement. While these modalities have received widespread use, there is still a great deal to learn about their efficacy in orthopaedic surgery.

Evaluation of New Technologies

Any new medical technology should be compared to pre-existing or conventional methods of treatment. Factors such as safety, efficacy, cost effectiveness, clinical advantages and patient outcome should be evaluated before a new technology is accepted. In addition, it is the responsibility of the individual physician to be aware of the U.S. FDA’s device classification status for each medical device he or she uses, and to use the device with appropriate patient consent and in compliance with the law.

Medical Laser Technology and Tissue Interaction

A laser (light amplification by stimulated emission of radiation) produces a beam of photons that is monochromatic, coherent and collimated. Medical lasers extend from the ultraviolet through visible light to the infrared portions of the electromagnetic spectrum. Laser energy can be delivered as a free beam or via a fiber-optic cable. Lasers in the non-visible spectrum require the use of a visible aiming beam for accuracy.

Most lasers have a photothermal effect on tissues that can be used to cut, cauterize, coagulate, vaporize or weld. Heat production can be intense and must be precisely localized by the hand piece tip to avoid damage to surrounding tissue. Heat production is dependent on laser related factors (e.g., wave length, power output, spot size and time of application), tissue related factors (e.g., water content and color) and the surrounding medium (gas vs. fluid). Ultraviolet lasers (e.g., excimer) appear to act primarily through a photochemical action that disrupts molecular bonding, permitting tissue removal with minimal heat buildup.

Radiofrequency (RF) Technology and Tissue Interaction

Radiofrequency (RF) energy is a form of electromagnetic energy in which rapidly oscillating electromagnetic fields cause movement of charged particles. When applied to tissues, the resultant molecular motion generates heat. RF energy can be applied between two points on the tip of a probe (bipolar) or between a single electrode tip and a grounding plate (monopolar). In monopolar devices, the molecular friction created within the tissues adjacent to the probe produces heat. Thus, the actual source of heat is the frictional resistance of the tissue. With bipolar probes, the RF energy follows a much shorter path through a conductive irrigating solution (electrolytes), or through the tissues lying between the tops of the probe.

Similar to laser energy, the thermal effect of RF energy on tissues is dependent on the level of energy, duration of application, and the nature of the tissues. In addition, the electrode type (monopolar vs. bipolar), size, and shape can each have an effect on the tissue.

Although RF devices and lasers differ fundamentally in the way they generate heat within a tissue, both classes of devices are capable of producing temperatures within the rage considered necessary for collagen denaturation and subsequent tissue shrinkage (65°C-75°C). When collagen is heated to 65°C, its heat-labile, intramolecular cross-links are broken, and the protein undergoes a transition from a highly organized crystalline structure to a random, gel-like state (denaturation). Collagen shrinkage occurs through the cumulative effect of the “unwinding” of the triple helix due to the destruction of the heat-labile intramolecular cross-links and the residual tension of the heat-stable intermolecular cross-links. However, it must be remembered that when it comes to cell viability and tissue response, heat is heat. Once critical temperatures are reached, cells will die (45°C) and collagen will become denatured (65°C), no matter what the source of energy.

Safety Considerations

Ocular Hazards

Laser energy can be dangerous to eyes and other tissues. Eye protection such as wavelength-specific goggles for all operating personnel as well as the patient, is suggested to prevent ocular damage. Physicians should follow individual hospital standards and American National Standards Institute (ANSI) standards concerning the use of goggles.

Toxic Smoke Production

As with the use of electrocautery devices, vaporization of tissue with lasers or radiofrequency devices produces a plume of steam or smoke that may generate safety concerns. The most significant of these is the possible spread of viral infections. Products of tissue vaporization must be safely evacuated from the room environment.

Very few laser-specific side effects have been seen in clinical experience. Char, debris, and carbonization that are produced by thermal modalities should be lavaged from the joint.

Fire Hazard

Exposure of flammable material to thermal modalities poses a potential fire hazard.

Other Hazards

Energy dissipation may affect tissues adjacent to the immediate target.

At present, the research is limited, but there is no evidence of mutagenesis occurring as a result of the use of thermal modalities. However, there remains a theoretical concern that excimer lasers in the ultraviolet range might exert mutagenic effects on tissue.

Positive pressure gas insufflation may be required for certain procedures using CO2 lasers. This may cause tissue emphysema or gas embolus, with possible fatal results. The risk of this hazard can be reduced with careful "gas bubble" or "ambient air" technique. Holmium, contact Nd:YAG and excimer lasers can be used under a standard fluid medium and produce essentially no char or carbonization.

The orthopaedic surgeon should be aware of the safety principles and biologic tissue effects of the specific laser wavelength chosen for use in surgery.

Current Use of Thermal Modalities in Orthopaedics

Arthroscopy

Thermal modalities are increasingly used as an adjunctive tool in arthroscopy surgery, especially in the shoulder and the knee, although their use is also increasing in the hip and small joints. Ablative use of thermal energy is indicated in subacromial decompression for coracoacromial ligament release, and for assisting in ablating hypertrophic synovium in the subacromial bursa. It also can be used to resect and contour a torn labrum in the shoulder. In the knee, resection and contouring of torn menisci, resection of hypertrophic synovium, and debridement of soft tissue in the notch may be helpful in ACL reconstruction. The small sizes and different shapes of both monopolar and bipolar probes allow for access to “tight” joints.

Although research is ongoing, the use of thermal modalities for “shrinkage,” or tissue modification in the shoulder, in the treatment of instability is still controversial as is the use of the thermal modification of articular cartilage in the knee. In the shoulder, there are many potential complications including capsular necrosis, axillary nerve neuritis, and capsulitis. The use of thermal energy for tissue modification in any joint still requires further study to determine the indications for future use.

Lumbar Spine

Several centers in the United States have used lasers for the removal of intervertebral disc material in the lumbar spine. This treatment is restricted to patients with contained disc herniations. Large extruded or sequestered fragments of disc cannot be safely removed by lasers, thus conferring the same limitations to those of enzymatic and percutaneous mechanical intradiscal therapy. Flexible spinal endoscopy through small catheters containing onboard lasers has seen limited preliminary use for excision of herniated fragments in the spinal canal.

Intradiscal electrothermal annuloplasty (IDET) has recently been popularized for the treatment of chronic discogenic low back pain. IDET is the application of thermal energy via a small intradiscal catheter to effect structural change in the collagen of the annulus and nucleus.

Although early anecdotal reports suggested promising results with low complication rates, there are no controlled studies showing efficacy beyond or equivalent to placebo effect. IDET’s precise mechanism of action is unknown. Further clinical and basic science studies are necessary to validate future clinical efficacy.

Thermal probes have been used for “shrinkage” of degenerated of herniated disc material. This has been suggested as a minimally invasive treatment for degenerative disc disease, low back pain, and disc herniations.

Credentialing

The AAOS, through its educational endeavors, attempts to educate orthopaedic surgeons and other practitioners about new and existing technology. However, the AAOS does not certify the competence of an individual for clinical use of a new technology or provide any credentials. Credentialing is verified at the facility where the individual has privileges. This includes training in the use of lasers.

© May 1992. Revised June 2003 American Academy of Orthopaedic Surgeons

This material may not be modified without the express written permission of the American Academy of Orthopaedic Surgeons^®.

Information Statement 1010

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