- THIS MATERIAL IS PUBLISHED AND PROTECTED BY U.S. COPYRIGHT LAW - REPRODUCTION PROHIBITED UNLESS FOR PERSONAL USE, EXCEPTING AUTHOR PERMISSION - Peter F. Kelly, D.P.M., F.A.C.F.A.S. Diplomate, American Board of Podiatric Surgery Fellow, American College of Foot and Ankle Surgeons A SYNOPSIS OF GENERAL Nd:YAG LASER APPLICATIONS FOR THE PODIATRIC LASER SURGEON This article briefly overviews the applications in an abbreviated format to summarize the operation of the Nd:YAG to the Podiatric Laser Surgeon. The importance in being familiar with all of these basic apects and techniques when is emphasized here because of the steep learning curve of the instrument. The Nd:YAG Laser is a new technology useful in soft tissue and reconstructive surgery of the foot and ankle. This instrument has been widely received in multidisciplinary medical specialties. Over the past four years, the author has developed the use of the Nd:YAG contact laser for a large number of applications in Podiatric foot and ankle soft tissue dissection component of reconstructive surgery. The Nd:YAG laser is a mid-infrared laser operating in a continuous wave mode at 1064 nm. Because of light characteristics at this frequency, it is convenietly transmitted through a multistranded quartz fiberoptic delivery system. The Nd:YAG laser can be applied in either the free beam mode with a bare fiber, or focused with a sapphire or quartz light scalpel for precise dissection at a powerful localized energy concentration. The former application is useful at high power levels for general destruction of large tumors requiring deep penetration for their eradication. The latter, using the contact-tip, is generally the most applicable for Podiatric surgery and general dissection. The sapphire contact-tip is quite useful for incisional work and dissection. This compares with its bare-fiber application, where the water transmission window effect of the 1064 nm frequency allows deep transmission into tissue to penetrate over 6 mm. The author has found this nonincisional mode only useful to treat dissecting vascular tumors. The author has found the power density selections most appropriate to Podiatric surgery are in the range from 11,500 to 45,000 watts per cm2. For particularly delicate procedures (ie: dorsal nerve decompressions and complex ganglion excision) the P.D. is not recommended to exceed 6,000 W/cm2. By convention, the standard of care in laser surgery has now required power density calculations on operative report for the purpose of documentation and reproducibility by other surgeons. The P.D. is simply calculated by dividing watts by square centimeter of tissue upon which the laser is focused. This may also be specified in joules for total tissue irradiation when this function is multiplied by time. Two types of light scalpels are utilized, frosted and nonfrosted. The frosted scalpel transmits laser energy from its distal 5 mm margin as well as its distal lense, and is appropriate for higher power applications where significant micro-coagulation is desired for dissection. Non- frosted tips are used for more precise thermal laser dissection where energy is focused at the scalpel apex and absolute hemostasis would not be a consideration. The tip best suited for generap Podiatric Surgery is a fronsted 0.6 mm diameter tip. Conventional anesthesia is utilized. A tourniquet use is left to the surgeon's preference. The surgery is initiated with a superficial epidermal inscription using a steel blade. This is carried to the level of the dermis only. The white dermis encountered determines the depth of the cold steel incision. Bleeding should never be encountered. The remainder of the tissue dissection including layer delaminations is performed with the laser scalpel. This is the optimal incision method, and was derived from a variety of incisional techniques. The author has found this technique optimizes the cosmetic result, minimizing fibroblastic stimulation and cell necrosis. While using the frosted contact-tip, perfect hemostasis will be observed. Only a minimal charring or tissue carbonization should be encountered. Delicate neural and vascular structures paralleling the incision will be observed to remain patent, even if separated by a thin membrane of tissue adjacent by only a few microns. Vessels smaller than 1.0 mm can be photocoagulated. The author finds it expedient to ligate larger vessels conventionally. An important principle of technique is that tissue dissection responds from laser light intensity, not by customary mechanical pressure. The tactile feedback of mechanical pressure of the blade is an acquired reflex of the experienced surgeon. This is the most frequent problem with the laser scalpel that surgeons encounter. The tactile feedback from contact- tip is reduced. It cuts like a hot knife through butter. Dissection with the laser scalpel should be continued in linear strokes from proximal to distal margins through the incision. Local tissue temperatures rapidly exceed 100 degrees centigrade so the tip must be kept moving. Tissue carbonization will be minimal and thus smoke evacuation requirements in the operating room are greatly reduced, but still necessary. Minimal smoke plume is produced as compared with the CO2 laser. Thermal hydrolysis of adipose tissue produces water which must be sponged frequently. Water rapidly disseminates the 1064 nm laser frequency and impedes effecient dissection. Because Podiatric incisions are rarely more than several centimeters, the fascial layer integrity is easily maintained and neurovascular structures are readily identified to avoid untoward neural thermal effects. This is important because of the reduced tactile feedback of the more powerful laser ability in dissection. With general bone cases, dissection is continued through to the joint capsule. This capsular incision is carried down through the periosteum with a slight reflection from the bone. Periosteum is to be preserved for future revascularization of the cortex, and any additional dissection off of the bone should be performed with cold steel only. Intense local thermal effects of the laser avascularize small periosteal arteries. Areas where rapid periosteal revascularization would be most appreciated are metaphyseal osteotomy. For nonosseous cases the author routinely allows soft tissues to undergo periods of thermal relaxation by withdrawl of the laser scalpel. This is a good technique to apply when dissecting adjacent to bone so as to minimize adjacent thermally induced periostitis to osseous structures. Closure and dressings for all cases are customary. Sutures remain for an additional several days due to the decreased fibroblastic activity following Nd:YAG interaction with dermal tissue. Margins of laser dissected tissue require a longer period of healing, but there is less scarring. Although reduction in pain, recovery time, and edema will be observed even in initial cases, potential complications exist. These include thermal periostitis, resulting from excessive time exposure form the laser in the proximity of bone capsule and periosteum. Also neural shutdown when infrared energy is radiated into a peripheral nerve causing a reversible protein denaturation affecting conduction velocity, resulting in paresthesia distal to the affected site. It can be expected that the first several laser cases will proceed more slowly and with somewhat more frustration to the surgeon. Sensitizing the surgeon to the decreased tactile feedback of the light scalpel will take only a short time and soon the laser technique will expedite the procedures more rapidly, and personal preferences will develop. The Nd:YAG laser will rapidly become a highly personalized instrument to most surgeons. There is little question that the Neodynium-YAG Contact-Tip Laser has achieved a significant impact to improving the quality of surgical services delivered. Appropriate use of the instrument results in significant decreases in postoperative patient pain, edema, and decreased tissue remodeling time resulting in less patient disability.