Surgery: kinesitherapy – Kinesitherapy – Ultrasonic
Reexamination Certificate
1998-12-22
2002-02-26
Smith, Ruth S. (Department: 3737)
Surgery: kinesitherapy
Kinesitherapy
Ultrasonic
C601S004000
Reexamination Certificate
active
06350245
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to surgical instruments, and, more particularly, to a surgical device for fragmentation or emulsification of soft tissues of a patient with focused delivery of ultrasonic energy.
Liposuction is a surgical procedure for altering the human form, specifically by removal of localized deposits of fat tissues that are unresponsive to diet or exercise. The procedure is also known as suction lipectomy, lipolysis, and more recently as body contour surgery, body sculpting surgery, or suction-assisted liposuction. It is most often performed by plastic surgeons, although dermatologists, gynecologists, and other surgical specialties also perform the procedure.
The liposuction procedure is typically accomplished by inserting a small liposuction cannula through an incision in the skin, applying a suction source to the end of the liposuction cannula that remains outside of the body, and forcing the working end of the liposuction cannula forward and backward in the layer of fatty tissue. The fatty tissue is torn, crushed, or avulsed, and is then aspirated through small openings along the sides of the liposuction cannula near the tip and then through a central lumen in the liposuction cannula to a tissue canister placed in-line with the liposuction cannula and the suction source. The procedure may involve multiple incisions and many passes of the liposuction cannula in each incision to achieve the desired cosmetic effect for the patient.
The liposuction procedure can be traumatic for the patient. The liposuction cannula does not discriminate between adipose tissue and other tissues such as nerves, blood vessels, or lymph tissues. The mechanical disruption of the above-named tissues by the liposuction cannula may result in, among other things, bleeding, bruising, temporary numbness, or swelling. Further, the final cosmetic result achieved for the patient is a function of the skill of the surgeon, the patient, and the type of surgical instrumentation used in the surgery. Liposuction cannulae used in the liposuction procedure may remove more adipose tissue from one area than another area in the patient, resulting in skin contour irregularities and a final cosmetic result for the patient that is not smooth or uniform.
Therefore, there is a need to improve the surgical instrumentation for the liposuction procedure to help the surgeon to better discriminate between adipose tissue and other tissues such as nerves, blood vessels, and lymph tissues, so that the adipose tissues can be fragmented and removed while the remaining tissues are damaged as little as possible or not at all. Further, there is a need to improve the surgical instrumentation for the liposuction procedure so that adipose tissue is removed in a more uniform and predictable manner so that an improved cosmetic result is achieved for the patient.
Recently, several instruments have combined ultrasonic vibrations and the liposuction cannula to improve upon the tissue discrimination capability of the liposuction cannula and to provide an instrument that removes adipose tissue more uniformly than current liposuction cannulae. This procedure is commonly referred to as ultrasound-assisted lipoplasty. In a typical ultrasound-assisted lipoplasty procedure, an ultrasonically vibrating cannula is inserted through an incision in the patient's skin and passed forward and backward through the adipose tissue layer, directly contacting the tissues to be treated. The ultrasonically vibrating cannula fragments or emulsifies the adipose tissues, which are then usually aspirated through a central lumen in the ultrasonically vibrating cannula.
Initial experiences with the ultrasound-assisted lipoplasty procedure have been mixed. A comparison of the suction-assisted liposuction and ultrasound-assisted lipoplasty approaches with currently available surgical instruments for both procedures was recently given in Ultrasound-Assisted Assisted Lipoplasty Resource Guide, published in PlasticSurgery News, a publication of The American Society of Plastic and Reconstructive Surgeons, 1997. In the article the author cites the disadvantages of the current ultrasound-assisted lipoplasty procedure compared to the suction-assisted liposuction procedure as: 1) burns of the skin are possible, 2) longer incisions are needed, 3) seromas are more common, 4) longer operating times are required, and 5) greater expenses are incurred. Thus, current ultrasound-assisted lipoplasty surgical systems that use an ultrasonically vibrating cannula for fragmentation and aspiration of adipose tissues are more costly and slower than the suction-assisted liposuction procedure and have the potential to damage tissues beyond that of suction-assisted liposuction, including burns of the skin and seroma formation. There is, therefore, a need to increase the speed of the ultrasound-assisted lipoplasty procedure and to minimize the potential for burns or seroma formation.
The use of focused ultrasound has long been known, specifically for diagnostic imaging purposes where the ability to focus the ultrasonic beam determines the imaging resolution of the system. Diagnostic imaging systems operate at frequencies between 1 MHz and 20 MHz to achieve the desired imaging resolution. The ultrasonic power coupled to the tissue of the patient is kept to a minimum to prevent damage to the skin layer and the deeper tissues.
The ability to focus an ultrasonic beam is related to the wavelength of the selected frequency in tissue. At 20 kHz the wavelength in tissue is approximately 7.5 centimeters, fundamentally limiting the ability to focus the beam to a minimum diameter of about 7.5 centimeters, generally too large for a surgical application of ultrasonic energy where the intent is to destroy or fragment a much smaller and precisely controlled volume of tissue in a patient. At 1 MHz the wavelength in tissue is approximately 0.15 centimeters, representing about the limit of resolution at this frequency. While it is possible to achieve sufficient focusing capability at the higher ultrasonic frequencies, such as 1 MHz, the majority of ultrasonic power at the higher frequencies is absorbed in the tissue in the form of heat, creating unsatisfactory thermal injury to tissues if the power density is large enough. Thus, there is a need to provide an instrument that can focus ultrasonic energy at the lower ultrasonic frequencies while supplying sufficient ultrasonic power so that the desired tissue fragmentation is obtained without significant heating of the tissues of the patient.
The most common method of generating ultrasonic energy for surgical or diagnostic applications is with piezoelectric ceramic materials formed to make a piezoelectric transducer that converts electrical energy to vibratory motion. In most applications the piezoelectric transducer is bonded to a flat applicator or an acoustic lens and is driven at the resonant vibratory frequency of the piezoelectric transducer that is determined primarily by the thickness of the piezoelectric transducer. The thickness of a piezoelectric transducer may range from a few tenths of a millimeter to several millimeters. The fundamental equation relating the resonant vibratory frequency and the transducer thickness for a ½ wave free resonance is f=c/2l where f is the frequency in Hz, c is the wave speed of the piezoelectric ceramic material in centimeters per second, and l is the thickness of the piezoelectric transducer in centimeters. A 0.35 centimeter thick piezoelectric transducer vibrating in the thickness mode has a ½ wave free resonance of approximately 417 kHz. At 25 kHz the thickness becomes approximately 5.8 centimeters. Thus, it is difficult to create low frequency transducers using this approach because the thickness of the piezoelectric transducer becomes prohibitive.
Piezoelectric ceramic materials have physical properties that fundamentally limit their ability to convert electrical energy to vibratory motion. There are limitations for voltage, current, temperature, an
Merchant & Gould P.C.
Smith Ruth S.
Young Thomas H.
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