The microscope and drill have played a major role in refining otologic and neurotologic techniques. In temporal bone surgery, good control of the microscope is very important.

High-technology surgical microscope.

As expected, use of a high-technology microscope improves the surgeons view, which further enhances the surgical result. However, in many instances, the available microscope is not used to its full advantage. The following points should be kept in mind while using a microscope:

• Do not hesitate to use the microscope; the microscope will enhance the success of the surgery.
  
• Learn about the microscope’s settings and practice maneuvering capabilities before using it for an operation.
  
• Use a higher magnification level when you are uncomfortable with your view of the surgical site.
  
• Adjust the microscope light so that it is high enough to see well, yet low enough to avoid reflective glare.
  
• Take care that the surgical microscope cover does not obstruct the path of the light, thus reducing the illumination at the surgical site.
  
• Enlarge the surgical field if required, which not only increases the working space, but also the illumination of the surgical site.

The general surgical procedure carried out by all surgeons, including the otorhinolaryngologist, is soft tissue surgery. However, the main procedure carried out on the temporal bone is delicate bone surgery, which is the privilege of the otorhinolaryngologist. The burr is the “scalpel” of temporal bone surgery, and special training is required to gain the ability to use it accurately. Novice use of this dangerous instrument can easily result in serious complications.

A drill system should be provided; a good system will have the following three main features:

• high-speed revolution (> 40000 rpm)
  
• ability to adjust revolution speed
  
• ability to select clockwise and counterclockwise rotation

An irrigation system should be provided, both for the laboratory and the operating room. One of the main mistakes while drilling is not using continuous irrigation. This results in the following problems:

• The flutes of the burr may get clogged with bone dust.
  
• The bone and other tissues may be damaged by heat (osteitis, paralysis).
  
• The view may be worsened by accumulated bone dust.

All these problems contribute to an increased risk of complications. For example, facial paralysis may occur as a result of direct damage to the nerve because of reduced vision, or simply as a result of overheating of the bone adjacent to the nerve.

Although several types of burr are available on the market, there are two main types:

• the cutting burr
  
• the diamond burr

The cutting burr has the following advantages over the diamond burr:

• It allows quick drilling.
  
• It prevents the area from becoming clogged with bone dust; especially under continuous irrigation and suction, the view of the operative site always remains clear.

The cutting burr is preferable for use in the cortical bone, and away from critical structures in other parts of bone. Every surgeon should be aware of their personal limits, and when they should change to using a diamond burr.

The diamond burr has the following advantages over the cutting burr:

• The risk of encountering critical structures unexpectedly is reduced because of the burrs slower rate of extirpation.
  
• The risk of damage to critical structures, when it comes into contact with them, is reduced because it is blunter than the cutting burr.
  
• It prevents damaging soft tissues such as the tympanomeatal flap, because these tissues do not easily get entangled in it.

Close to the facial nerve and other vital structures, use of the diamond burr is preferred. However, it should be kept in mind that the diamond burr may also cause facial paralysis due to overheating or excessive pressure.

Other points regarding burr usage are summarized below:

• Use the largest suitable burr for the procedure. The large burr, contrary to common belief, poses a lesser danger of sudden uncontrolled penetration.
  
• Ensure that the cutting burr has enough flukes. If the burr has an insufficient number of flukes, the burr can skip over rather than engage the bone because of the large bite pattern.
  
• Never use burrs with a damaged shaft. Distorted burr shafts also result in skipping of the burr because of uncontrolled movements.
  
• Use the burr under continuous, copious irrigation, except in certain specific situations.
  
• Drill along the axes of the critical structures, which will prevent extensive damage in case of direct contact with the structure.
  
• Set the drill to rotate away from the critical structure that is to be protected when drilling along the axis is not possible. In case of any skipping, the burr will not catch on the critical structure and therefore do no damage.
  
• Drill with the side of the burr rather than the tip. This allows faster drilling because of the larger size of the flukes on the side of the burr. Furthermore, this improves vision as the view is not obscured by the burr tip.
  
• Train yourself to be able to see “through” the bone and to notice color and structural changes. Temporal bone surgery is based on seeing the structures through the last remaining shell of bone before actual exposure.
  
• Also train yourself to sense the differences in resistance encountered by the burr tip, as well as the changes in the sound of the drill while in use as the bone gets thinner or its structure changes, with the same intent.
  
• Use different handpiece shafts according to the procedural needs: a short shaft in the cortical bone, a long shaft in the deeper regions, and an angled shaft in the external auditory canal.

The burr also has an important role in controlling bleeding through the bone. For control of bleeding through the bone, the following alternatives may be used:

• a diamond burr
  
• cauterization
  
• bone wax
  
• absorbable compressed sponge (Gelfoam, Spongel, etc.)
  
• absorbable hemostatic products (Surgicel, etc.)

The technique of stopping oozing through the bone by the use of a drill is relatively simple; on a low-speed setting, the largest possible diamond burr should be moved along the surface of the bleeding area without irrigation.