This invention relates to ultrasonic surgical cutting instruments and more particularly to the cutting tip assemblies thereof. It also pertains to ultrasonic cutting tip assemblies whose tools or tubes are removable or separable from their ultrasonic transition horns.
Devices which effectively utilize ultrasonic energy for variety of applications are well known in a number of diverse arts. The application of ultrasonically vibrating surgical devices used to fragment and remove unwanted tissue with significant precision and safety has thus led to the development of a number of valuable surgical procedures. Accordingly, the use of ultrasonic aspirators for the fragmentation and surgical removal of tissue from a body has become well known. Initially, the technique of surgical aspiration was applied for the fragmentation and removal of cataract tissue as shown, for example, in U.S. Pat. Nos. 3,589,363 and 3,693,613. (Each of the patents and other documents mentioned herein is hereby incorporated by reference in its entirety.) Later, such techniques were applied with significant success to neurosurgery and other surgical specialties where the application of ultrasonic technology through a small, handheld device for selectively removing tissue on a layer-by-layer basis with precise control has proven feasible.
Certain devices known in the art characteristically produce continuous vibrations having a substantial constant amplitude at a frequency of about twenty to thirty kHz up to about forty to fifty kHz. U.S. Pat. No. 3,589,363 describes one such device which is especially adapted for use in the removal of cataracts, while U.S. Pat. No. 4,063,557 describes a device suitable for the removal of soft tissue which is particularly adapted for removing highly compliant elastic tissue mixed with blood. Such devices are continuously operative when a surgeon wishes to fragment and remove tissue, and generally operate under the control of a footswitch easily accessible to him.
Another ultrasonic surgical instrument is disclosed in U.S. Pat. No. 3,990,452 to Murry et al. Solid or two piece brazed tips for a conical or exponential type of sectional concentrator are illustrated therein. The flats that are subsequently machined on both sides of the tip nut for wrench tightening are right angle notches, which add additional loading to the handpiece and cause additional cavitation bubbles to form. Further, not only does the brazing thereof add an costly step to the manufacturing process, but the copper and silver content can be harmful to the patient's living tissue. Additionally, the large rigid nut of this instrument makes a good, consistent, low impedance acoustical coupling more difficult.
Certain limitations have emerged, and in particular, the promise of safe, effective emulsification and removal of unhealthy tissue and especially hard tissue, such as cataract, while minimizing damage to adjacent healthy tissue, has not yet been fully and truly realized. Many of the prior art ultrasonic surgical cutting or emulsifying instruments ineffectively utilize the power supplied to vibrate them and also have proven to be expensive to manufacture. Further, designs of some instruments do not allow the surgeon to easily visualize the surgical procedure at the surgical site and to manipulate the vibrating tool accurately and consistently during each of the procedures. Thus, a need has arisen for an improved ultrasonic cutting tip assembly design.