Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Thermal applicators
Reexamination Certificate
2001-08-29
2003-09-09
Gibson, Roy D. (Department: 3739)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Thermal applicators
C606S034000
Reexamination Certificate
active
06618626
ABSTRACT:
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention relates to the field of electrosurgical probes and procedures for performing endoscopic thermal capsullorhaphy. In particular, the invention relates to electrosurgical probes and methods for locating and protecting the axillary nerve while performing arthroscopic thermal capsullorhaphy on the human shoulder.
2. The Prior State of the Art
The joint of the human shoulder provides the greatest range of motion of all the joints in the human body. However, when ligaments of the shoulder become stretched or damaged the shoulder can suffer from a condition known as shoulder instability, which can significantly limit the function of the shoulder. Shoulder instability can result from a violent injury that causes the shoulder to dislocate, or by a repetitive injury that stretches the ligaments of the shoulder over a period of time. Shoulder instability, if not cured, may cause chronic pain, arthritis, and loss of function.
Shoulder instability can sometimes be treated with rehabilitation. However, if rehabilitation is not successful or appropriate then surgery may be required. Surgery generally involves the tightening of lax and over-stretched capsular ligaments. Some surgical techniques, referred to as “capsular shift procedures,” tighten and generally reconstruct the capsular ligaments of the shoulder.
Capsular shift procedures can be performed by open surgery or by arthroscopic surgery. Open surgery often results in greater post-operative pain and requires more extensive rehabilitation than arthroscopic surgery. Accordingly, as arthroscopic techniques continue to develop, they are increasingly chosen as the preferred method in the treatment of shoulder instability.
One recent advance in arthroscopic surgery, which is known as thermal capsullorhaphy, offers distinct advantages over capsular shift procedures and other similar techniques because it does not require the surgical reconstruction of the ligament capsules. This technique, which is also known as “thermal capsulorraphy,” “thermal capsular shrinking,” “radiofrequency thermal shrinking,” and “thermal capsular shift,” involves the non-contact shrinking of the capsular ligaments by heating the collagen fibers within the capsular ligaments with a radiofrequency probe (electrode) operating in either a bipolar or monopolar mode.
One problem associated with thermal capsullorhaphy, however, is that the temperature required to shrink the capsular ligaments can cause severe nerve damage. In particular, nerves have been shown to sustain irreversible injury at temperatures exceeding 55° C., yet the minimum temperature required to shrink collagen and the capsular ligaments is known to be approximately 65° C., with actual procedural temperatures approaching 100° C.
Of particular interest is the axillary nerve, also known as the circumflex nerve, which passes directly beneath the inferior gleno-humeral capsular ligament of the shoulder, placing it at risk for thermal injury during thermal capsullorhaphy. Temporary injury to the axillary nerve, also known as axillary neuropraxia, as well as permanent thermal injury to the axillary nerve, are possible consequences of thermal capsullorhaphy because the intraarticular anatomic landmarks defining the course of the axillary nerve are vague, thereby making it difficult to identify and to avoid applying heat to the regions of tissue where the nerve is proximate the capsular ligaments. Although the temperatures that are applied to the capsular ligaments during thermal capsullorhaphy decrease exponentially with tissue depth, temperatures in excess of 55° C. can easily be achieved at the minimal depths where the axillary nerve is located proximately to the capsular ligaments. Compounding this problem is the fact that the measured distance between the axillary nerve and the capsule ligaments in cadaveric specimens varies widely, suggesting that thermal capsullorhaphy creates a greater risk of axillary nerve injury for certain shoulders than for others.
Axillary neuropraxia and permanent damage to the axillary nerve can be avoided by using nerve stimulating devices to stimulate the axillary nerve and to identify the high-risk regions where the axillary nerve is extremely close to the capsular ligaments. The high-risk regions can then be avoided so that the axillary nerve is not overheated during the procedure. Existing nerve stimulating devices, typically used to identify nerves to be anesthetized, emit direct current (“DC”) pulses that stimulate motor nerves such as the axillary nerve. When a motor nerve is stimulated, it causes the muscles supplied by the nerve to contract. The visual observation of stimulating the axillary nerve, for example, is a physical jump or movement of the deltoid muscle.
Existing nerve stimulating devices, however, are not suitable for arthroscopic procedures. Arthroscopic procedures require the surgical site to be filled with a saline solution, which is highly conductive and which diffuses the DC energy before it can stimulate the axillary nerve, thereby making it difficult to identify and locate the high-risk regions of the capsular ligament that should be avoided during thermal capsullorhaphy.
Some existing RF electrodes are configured with temperature sensors located in the tip of the electrode for controlling the temperatures that are generated by the electrode. The temperature sensor in effect measures existing local surface temperatures and controls the RF energy that is applied by the electrode to the capsular ligaments. The benefit of temperature sensor electrodes in protecting the axillary nerve, however, is extremely limited. In particular, these electrodes are unable to identify the high-risk regions where the axillary nerve passes the capsular ligaments.
Accordingly, there is presently a need in the art for improved methods and devices that are able to locate the high-risk regions of the capsular ligaments during arthroscopic thermal capsullorhaphy in order to reduce the risk of axillary neuropraxia.
SUMMARY OF THE INVENTION
The present invention is directed to improved apparatus and methods for protecting the axillary nerve during thermal capsullorhaphy. In particular, the present invention is directed to systems comprising improved radiofrequency (RF) electrosurgical devices and methods for identifying and avoiding regions of the capsular ligaments that are in extremely close proximity to the axillary nerve, thereby reducing the risk of axillary neuropraxia or permanent damage to the axillary nerve while performing arthroscopic thermal capsullorhaphy. The apparatus and methods of the invention utilize what is known in the art as a coagulation or “coag” RF waveform to stimulate and locate the axillary nerve preparatory to, or during, thermal capsullorhaphy.
The systems of the invention utilize intraoperative electrical stimulation of the axillary nerve as the means of identifying the anatomically “high-risk” regions of the capsular ligaments that should be avoided during the thermal capsullorhaphy procedure. By avoiding the high-risk regions it is possible to minimize the likelihood of causing thermal damage to the axillary nerve.
According to one embodiment, an RF electrosurgical probe is electrically connected to a standard electrosurgical generator that is capable of producing RF energy having a coag waveform. The electrosurgical probe is equipped with a tip for dispensing the RF energy and a power cord that supplies RF energy from the generator. The probe may optionally include different activation switches depending on whether one wishes to shrink ligament tissue or perform nerve stimulation.
The electrosurgical probe can operate in a nerve stimulation mode and a tissue shrinkage mode. In the nerve stimulation mode, a quantity of RF energy is emitted from the electrosurgical probe that at least indirectly causes a nerve within a nerve stimulation zone to be stimulated, but which is insufficient to cause thermal damage to the nerve. The nerve stimulation zone is the area directly
Gentelia John S.
West, Jr. Hugh S.
Gibson Roy D.
HS West Investments LLC
Roane Aaron
Workman Nydegger
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