4 Basic Techniques and Decision Making in Middle Ear Cholesteatoma Surgery
4.1 Basic Techniques for Safe Cholesteatoma Surgery
Since cholesteatoma surgery is a “one-man surgery” working in very complicated temporal bone, intensive practice in the temporal bone dissection laboratory is mandatory before performing any procedure to patients. Temporal bone dissection permits acquisition of perfect knowledge of three-dimensional anatomy of the whole temporal bone. Ideally, the same burrs and drill, suction tips, and set of instruments employed during actual surgery should be used so that the otologist perfects his or her manual dexterity.
Removal of bone with a drill plays key role in cholesteatoma surgery. Establishment of a direct clear view is essential. Make maximum effort to obtain appropriate surgical angle, and prepare your surgical field as bloodless as possible. Do not use sharp instruments, especially cutting burrs, if their tips are not in your view. If there is any doubt during surgery, take your time to review the operating field and anatomical landmarks.
Experienced surgeons usually recognize possible danger in particular situations, and can minimize such risks without thinking. On the other hand, it is difficult for beginners to recognize such risks beforehand. Technical tips for safe surgery are described in the following text.
Bony structures are removed with either curettes or burrs.
View the aspect to be drilled as perpendicular as possible. Important structures may not be clearly seen and could be damaged if viewed in shallow angle (▶Fig. 4.1).
The handpiece should be held like a pen without covering the superior aspect of the instrument (▶Fig. 4.2). Straight handpieces are preferred rather than angled ones for better control. Angled handpieces are used only when the straight handpiece obstructs the view in narrow area (see Chapter 3.1.5).
The little and ring fingers should be placed on somewhere stable such as patient’s head. This permits precise manipulation of the burr head without trembling.
The drill should be activated beside the structure to be drilled, and stopped immediately after completing the drilling. Never activate the drill before it is in position and never remove the drill before it stops especially when the burr tip is out of your sight.
No or minimal pressure should be applied to the burr, especially around important structures. Drilling is usually carried out with the side of the burr rather than the tip for faster bone removal under better view.
Use the largest possible burr. It allows gradual exposure of wider area that enhances identification of important structures than small burrs. Use small burrs after identifying three-dimensional anatomy of important structures and the area you drill.
Small burrs, especially cutting, may slip into small bony defect such as exposed fallopian canal (▶Fig. 4.3) and may insult its content, especially when some pressure is applied on the burr head.
Be aware that not only the burr head but also the shaft of the burr can cause severe damage to structures. A fine fiber of connective tissue caught by either the tip or the shaft may suddenly cause catastrophic involvement of entire serial tissue. Such cases are drilling around the meatal skin, the facial nerve, and the chorda tympani (▶Fig. 4.4).
Adjust the length of the burr according to the depth of the area to be drilled. Shorter burrs give better control than longer ones.
Most part of bone work is done using cutting burrs, because they permit faster bone removal. Diamond burrs are reserved for works near delicate structures such as the facial nerve, the dura, the sigmoid sinus, the jugular bulb, and semicircular canals. Cutting burrs may be used in these areas if you do not compress the burr head toward the structures.
Hemostasis on the bone is achieved by using diamond burrs pushed toward the bleeding point without irrigation. This technique is essential for bloodless middle ear surgery. The heat produced by the diamond burr is sufficient to stop bleeding. Use diamond burrs when the cavity starts bleeding. Thereafter, further bone work can be continued with cutting burrs with minimal risk. In the final step of drilling, diamond burrs serve not only for flattening the surface but also for stopping bleeding.
Drilling should be started from dangerous areas and end in safer ones. The starting point of the drill track is much more controllable than its end point (▶Fig. 4.5). For example, drill medial to lateral in the external auditory canal and the attic when working around the ossicular chain.
Burrs should be moved parallel to the important structures such as the facial nerve, the sigmoid sinus and the lateral semicircular canal (▶Fig. 4.6). This will permit gradual skeletonization of these structures, which increases chance for identification and reduces risks of unpleasant damage.
Curettes may be the safer choice to avoid accidental inner ear damage when working around the delicate structures such as ossicular chain.
At the end of surgery, it is very important to wash out bone dust completely from the middle ear by intensive lavage. Remaining bone dust may cause fixation of the ossicular chain to surrounding bony structures.
When working in very deep areas, precise control of the drill becomes more difficult since the point of support of the drill is away from the tip of the burr. Use of large diamond burrs makes such drilling considerably stable, and is appropriate when working around deep dangerous structures such as the internal auditory canal and the horizontal segment of the carotid artery. Copious irrigation is required to avoid thermal injury.