Ear Center: Kraus TM Microcut™ Forceps
Kraus TM MicroCut™ Forceps
New Otologic Micro-Rongeurs for Rimming a Tympanic Membrane Perforation During Myringoplasty:
the Kraus TM MicroCut™ Forceps
by Eric M. Kraus, M.D., M.S., F.A.C.S.
Key words: perforation, tympanic membrane, tympanic membrane grafting, tympanic membrane patching, myringoplasty, tympanoplasty, new otologic instrument,rongeurs, micro-rongeurs, forceps, MicroCut™, Kraus TM MicroCut™ Forceps
To initiate healing of a tympanic membrane perforation during myringoplasty, it is necessary to circumferentially excise the epithelial margin of the perforation (rimming) to create a fresh, bleeding edge without over-enlarging the perforation. Because healing varies with the inverse of the area of the rimmed perforation, better healing occurs if the rimmed perforation area remains as small as possible. The principle is important when patching or grafting small perforations after removal of pressure equalization tubes. A fresh, bleeding edge stimulates epithelial migration and is particularly important when revascularization of tissue grafts is required.
The surgical problem was the need to precisely rim small perforations without over-enlargement. Diseased tympanic membranes are more difficult to rim due to atrophy, myringoslcerotic plague, and poor blood supply. Conventional rimming which is performed with otologic sickle and micro-knives, straight picks, cup and alligator forceps, micro-scissors, and perforation rasps, may lead to inadvertent over-enlargement. Imprecise conventional rimming may lead to tearing, inadvertent enlargement, decreased healing, incomplete removal of the epithelial margin, delayed epithelial cyst formation, and residual perforations requiring revision procedures. An otologic micro-rongeur was needed for controlled, efficient, and precise rimming.
The purpose of this report is to introduce the first otologic forceps that has been specifically designed to efficiently and precisely rim tympanic membrane perforations, the Kraus TM MicroCut™ Forceps (MicroCuts™), Medtronic ENT, Jacksonville, FL. (Figure 1, below). Unique design characteristics, recommendations for use, proper cleaning, and additional uses for the MicroCuts™ are discussed.
The Kraus TM MicroCut™ Forceps consists of a stainless steel, finger-thumb handle forceps design with:
- a reverse-action thumb handle
- low profile body
- small diameter, 360 degree rotating barrel with swivel-rotation knob, central cutting rod, side-biting jaw (available in 90 degree, 45 degree forward-biting, and 45 degree backward-biting iterations)
- distal tip tissue basket for capturing excised tissue
- the general configuration is that of a through-cut, micro-rongeur with a universal cutting arc.
The reverse-action handle enhances stability by reducing distal tip motion during cutting. Normal closure motion of the thumb-handle is determined by a preset handle screw that acts as a stop against the non-moving finger-handle. The action permits precise, controlled, perpendicular cutting.
Low Profile Body
The body of the forceps houses the handle action mechanism and cutting rod attachment. The low body profile is level with the barrel swivel-turn wheel, permits unobstructed visualization along the length of the barrel, and facilitates accurate jaw engagement with the tissue margin.
A key feature of the instrument is its small diameter, bidirectional, 360 degree rotating barrel with proximal, low profile, swivel-rotation knob (Figure 2, above). The knurled surface of the knob increases tactile friction to facilitate fine finger adjustment of the arc of rotation and smooth clockwise or counter-clockwise rotation. The 360 degree arc of rotation permits meticulous excision of the epithelial margin by cutting, rotating the barrel a few degrees of arc in either direction, and proceeding with the next adjacent cut. A central cutting rod is housed within the rotating barrel and produces a clean, 1.0 mm. through-cut. When used as recommended, the MicroCuts™ contribute to decreasing surgical time by increasing the "economy of motion" required for the rimming maneuver.
The distal barrel of the MicroCuts™ contains a side-biting jaw for engaging the tissue margin and a distal tip basket for capturing resected tissue. Three models of the MicroCuts™ have been designed, each with a different fixed jaw angle but otherwise identical function:
- 90 degree (standard use)
- 45 degree forward-biting
- 45 degree backward-biting
The jaw angle selected for use is determined by the location and angle of the perforation.
Removable Barrel Sheath
A newly added design feature to the second iteration of the MicroCut™ is a removable barrel sheath. The sheath is removed by loosening a knurled wheel located on the right side of the body and turning a small lever on the left side of the body 20 degrees clockwise. The barrel sheath is then slid forward to remove it from the cutting wire. The cutting wire and barrel may then be thoroughly cleaned. To replace the sheath, the sheath is slid over the cutting wire, the left lever is rotated 20 degrees counterclockwise, and the right wheel is tightened.
After each patient use, and prior to re-sterilization of the Kraus TM Microcut™ Forceps, it is imperative to:
- remove the barrel sheath
- clean the cutting wire thoroughly
- and remove all tissue chips from the distal tip basket (a very fine curved pick under microscopic control works well for removing small tissue chips)
Distal Tip Basket
Incorporated into the design is a distal tip basket which collects resected tissue fragments and prevents tissue from inadvertently entering the middle ear. The volume of the basket is large enough to rim a small perforation without interrupting the procedure to clean the basket. The bottom of the basket contains two small openings to facilitate cleaning.
The Kraus TM MicroCut™ Forceps were designed specifically to assist in preparing tympanic membrane perforations for patching or grafting. The main function of the instrument is to excise the epithelial margin of a perforation without over-enlarging the pre-existing perforation by providing a clean, perpendicular, precise cut. Once rimmed, the perforation may be patched with non-tissue patches (cigarette paper, latex disks, an EpiDisc®, absorbable gelatin film, etc.) or tissue grafts (adipose, fascia, cartilage, perichondrium, areolar tissue, vein, composite grafts, etc.
Two Handed Technique
For optimal performance, MicroCuts™ are employed using a two handed technique and may be grasped with either the right or left hand. The instrument is held in the dominant hand with the tip of the dominant thumb inserted into the reverse-action handle thumb hole and the tip of the fourth finger inserted into the lower fixed finger hole. The index finger is placed along the inferior aspect of the body to provide maximum stability. Intuitively, the third and fifth fingers rest on the respective superior and inferior surfaces of the lower fixed finger hole. The index finger and thumb of the non-dominant hand are used to grasp the knurled barrel knob and rotate the barrel appropriately prior to making the next cut. The cutting action is performed by the dominant thumb using the full range of motion of the reverse-action handle for each cut. With practice, torque motion of the distal tip can be controlled during cutting.
To cleanly excise tissue, the tip of the MicroCuts™ is positioned in the perforation, the cutting rod is retracted into the barrel, the edge of the perforation is engaged into the side biting jaw, the cutting rod is advanced through the tissue using the full travel of the reverse-action handle, and the MicroCuts™ are gently advanced medially toward the middle ear (away from the surgeon). (Figure 2.) To complete rimming, the barrel is methodically rotated around the circumference of the perforation and sequential through-cuts are made without the need to change instruments.
For most perforations, the 90 degree MicroCut™ is the forceps of choice. For perforations angled toward or away from the surgeon, the 45 degree forward-biting and 45 degree backward-biting models are used. The 45 degree forward-biting jaw is particularly suited for removing the superior and posterior margins of an anterior perforation. The 45 degree backward-biting jaw is helpful when rimming along the fibrous annulus and the anterior malleus handle.
Basket Tip Cleaning
The distal tip basket is effective in capturing all resected tissue. Perforations smaller than 10 percent in size may be rimmed completely without cleaning the basket. When rimming larger perforations, it is necessary to periodically clean the collected tissue fragments. Otologic suctions, such as a #18 Rosen suction or #5 Barron, are effective in evacuating captured tissue. A straight otologic pick or small instrument brush may be used. Prior to sterilization, all tissue must be meticulously removed from the tip basket in order to properly clean and decontaminate the instrument. Incomplete removal of tissue will result in hardened residual tissue, increased proximal cutting rod stress, and potential cutting rod failure.
MicroCuts™ have been designed to excise soft tissue but will resect thin myringosclerotic plaque. Plaque thicker than the side jaw opening cannot be excised. MicroCuts™ were not designed for cutting bone and should not be used for that purpose.
MicroCuts™ may be used in an office or operating room setting. Additional otologic uses include:
- soft tissue/tumor biopsies
- removal of cholesteatoma from delicate structures when cutting rather than pulling is advantageous
- tissue trimming in tight areas not amenable to micro-scissors
- trimming of fibrous tissue attached to the distal handle of the malleus.
- MicroCuts™ may be used for non-otologic procedures such as mucosal biopsies of the inferior turbinate for electron microscopic mucociliary analysis and for procedures that demand precise through-cut excision of a small volume of soft tissue.
A new set of high quality, stainless steel otologic instruments, the Kraus TM MicroCut™ Forceps, are presented. MicroCuts™ are the first otologic instruments specifically designed to cleanly and precisely excise the epithelial margin of a tympanic membrane perforation without over-enlarging the existing perforation. The forceps function as through-cut, otologic micro-rongeurs with a universal cutting arc and are available in three iterations: standard 90 degree , 45 degree forward-biting, and 45 degree backward biting models to accommodate various perforation locations and angles.
- permit controlled, perpendicular through-cut rimming to help ensure complete epithelial resection
- promote healing and perforation closure rates by helping to minimize rimmed perforation diameter
- decrease operating time by utilizing the principle of economy of motion
Incorporated design features include:
- a thumb activated, reverse-action handle mechanism for controlled movement and reduced distal tip motion
- a low profile body to enhance surgical visualization
- a bidirectional, 360 degree rotating barrel with proximal knurled swivel-rotation knob
- distal side biting jaw
- internal 1.0 mm cutting rod,
- a distal tip basket to capture excised tissue.
MicroCuts™ are used for rimming of perforations, controlled micro-biopsies, and any other micro-surgical procedure that requires precision cutting and trimming of soft tissue.
(1) Kraus TM Microcut™, Model MC0270 - 90 degree Forceps
(2) Kraus TM Microcut™, Model MC 0271 - Forward-biting Forceps
(3) Kraus TM Microcut™, Model MC0272 - Backward-biting Forceps
Dr. Kraus would like to thank Ms. Donna Kosmis of Medtronic ENT, MicroFrance®, and Medtronic Xomed, Inc. for their expertise and technical assistance during the development and production of the Kraus TM MicroCut™ Forceps.
Kraus TM MicroCut™ Forceps are identified as follows:
- Kraus TM MicroCut™ Forceps, 90 degree, MCO270
- Kraus TM MicroCut™ Forceps, Forward-Biting MCO271
- Kraus TM MicroCut™ Forceps, Backward-Biting MCO272
For further information, consult www.MedtronicEnt.com or Medtronic Xomed, 6743 Southpoint Drive North, Jacksonville, FL USA 32216-0980.
MicroCut™ is a registered trademark of Medtronic Xomed, Inc. EpiDisc® is a registered mark of Medtronic Xomed, Inc.
Last updated: January 1, 2010