Surgery – Instruments – Electrical application
Reexamination Certificate
2002-05-08
2004-02-10
Dvorak, Linda C. M. (Department: 3739)
Surgery
Instruments
Electrical application
C606S047000, C606S050000, C607S101000
Reexamination Certificate
active
06689129
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to RF (radiofrequency) devices and methods for delivering RF energy to tissue in a patient's body, and more particularly to an electrode array that allows for controlled low-power RF energy delivery in orthopedic applications, for example in capsular shift procedures.
BACKGROUND OF THE INVENTION
Joint instability in adults is caused by ligaments and cartridge in a joint becoming lax or stretched, due either to the aging process or to acute trauma. Joint instability is a widespread disease and is estimated to affect up to 10 percent of the male population in the U.S. A patient's shoulder joints, knees, ankles and elbows all may become unstable due to lax ligaments. As a specific example, a patient's shoulder joint (or glenohumeral joint capsule) is maintained in a stable condition by a capsular ligament complex, subscapular tendons, rotator cuff and teres minor muscles, among others.
Joint instability is caused by laxity in the fibrous ligament complex within the joint capsule. An increase in ligament laxity may be due to an acute-event type of trauma or recurrent minor trauma (i.e., wear-and-tear). Often, acute-event trauma results in a unidirectional type of instability, whereas normal wear-and-tear results in multidirectional joint instability. In terms of pathology, unidirectional joint instability may be defined as an excess capsular volume (space between the humeral head and synovial surface of the capsule) in a particular location, region or path across the capsule. Multi-directional joint instability generally may be considered to be excessive volume within the entire joint capsule around the humeral head.
Surgeons have developed open surgical treatments for reducing the volume of unstable joint capsules, generally termed “capsular shift procedures”. In such surgery, over-stretched or lax capsular ligaments are tightened and secured around the perimeter of the joint capsule. Such procedures frequently result in post-operative pain, loss of motion, nerve injury and even osteoarthritis. Further, capsular shift patients require lengthy post-operative rehabilitation and often do not achieve pre-injury levels of joint stability.
Surgeons also have developed minimally invasive arthroscopic techniques for performing capsular shift procedures which, for the most part, replicate the open procedures. An arthroscopic approach typically results in less post-operative pain and reduced rehabilitation time. However, arthroscopic capsular shift techniques require high levels of technical expertise. Also, it is not clear whether arthroscopic ligament fixation devices and methods are equal to those available in an open surgical approach.
More recently, to avoid surgical reconstruction of a joint capsule, arthroscopic surgeons have investigated the use of thermal energy to tighten or shrink the ligaments within a joint capsule. A capsular ligament complex includes various types of collagen, which is one of the most abundant proteins in the human body. It is well-known that collagen fibrils will shrink in length when subjected to temperatures ranging above about 60° C. Interstitial collagen consists of a continuous helical molecule made up of three polypeptide coil chains. Each of the three chains is approximately equal in longitudinal dimension with the molecule, being about 1.4 nm in diameter and 300 nm in length along its longitudinal axis in the helical domain portion.
Collagen molecules polymerize into chains in a head-to-tail arrangement generally with each adjacent chain overlapping another by about one-fourth the length of the helical domain. The spatial arrangement of the three peptide chains is unique to collagen, with each chain existing as a right-handed helical coil. The superstructure of the molecule is represented by the three chains that are twisted into a left-handed superhelix. The helical structure of each collagen molecule is bonded together by heat labile cross-links between the three peptide chains providing the molecule with unique physical properties, including high tensile strength and limited longitudinal elasticity.
The heat labile cross-links may be broken by thermal effects, thus causing the helical structure of the molecule to be destroyed (or denatured) with the peptide chains separating into individually randomly coiled structures of significantly lesser length. The thermal cleaving of such cross-links may result in contraction or shrinkage of the collagen molecule along its longitudinal axis by as much as one-third of its original dimension. It is such thermal shrinkage of collagenous ligament tissue that can stabilize a joint capsule.
Collagen shrinks within a specific temperature range, (e.g., 60° C. to 70° C. depending on its type), which range has been variously defined as: the temperature at which a helical structure collagen molecule is denatured; the temperature at which ½ of the helical superstructure is lost; or the temperature at which the collagen shrinkage is greatest. In fact, the concept of a single collagen shrinkage temperature is less than meaningful, because shrinkage or denaturation of collagen depends not only on an actual peak temperature but on a temperature increase profile (increase in temperature at a particular rate and maintenance at a particular temperature over a period of time).
Thus, collagen shrinkage can be attained through high-energy exposure (energy density) for a very short period of time to attain “instantaneous” collagen shrinkage—the method used by all previously known devices (both laser and high-energy RF waves) for joint capsule shrinkage. These previously known treatments shrink collagenous tissue in a matter of seconds (e.g., 1-2 seconds).
Previously known methods of “instantaneous” capsular collagen shrinkage with a high energy (40 to 60 watts) mono-polar RF probe (or similar high-energy laser) suffer from several significant drawbacks. In such an RF treatment (or laser treatment), the surgeon “paints” the tip of the RF probe across a section of a joint capsule targeted for collagen shrinkage. Because the collagen targeted for shrinkage generally lies well under the capsular surface, high RF energy levels are needed to cause shrinkage, typically 40 to 60 watts. These power levels, however, pose a substantial risk of ablating or perforating the synovial surface, which is highly undesirable.
Also, as depicted in
FIG. 1A
, it is difficult to “paint” the RF probe tip (even though only 3-5 mm in diameter) across the targeted portion of the joint capsule due to the limited working space between humeral head H and capsule C, while still maintaining an adequate endoscopic view of the damaged or lax tissue indicated at D in FIG.
1
A. At times, it may be necessary to use an lever-type instrument to pry (or retract) the humeral head away from the joint capsule to provide a larger working space, thus posing a risk of damaging the labrum (the fibrous cartilage surrounding glenoid capsule G).
Further, the previously known methods of creating “instantaneous” collagen shrinkage cause the working space between the humeral head and capsular surface to shrink and disappear practically instantaneously, thus making it necessary to work from a first position treatment location L
1
toward a second location L
2
. Thus, it is generally not possible to return toward the first location L
1
for additional treatment or diagnosis (see FIG.
1
A).
Previously known methods of “painting” tissue with high-energy RF waves with a hand-held probe to achieve rapid collagen shrinkage are not well suited for collagenous tissues of different thicknesses and/or for tissue in which collagen content varies. For example, the capsular regions carrying the medial and inferior glenohumeral ligaments have significant collagen content (e.g., >85%) and are quite thick. Areas between the ligaments and around the axillary recess are quite thin. Other areas of the joint capsule contain much less collagen (e.g., <40%).
Thus, “painting” the synovial surface with RF waves—even if the probe
Dvorak Linda C. M.
Ryan Kromholz & Manion S.C.
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