Anatomy of Middle Ear Relationships

Prior to performing any ossiculoplasty, a clear understanding of the anatomic relationships of the middle ear is necessary. Despite well-accepted landmarks and the overall consistency of prosthesis length in stapes surgery, such consistency has not carried over into ossiculoplasty. Given a few simple and dependable landmarks, however, many of the complications and uncertainties regarding ossiculo-plasty can be avoided.

The most critical of the middle ear landmarks is the proximal portion of the malleus manubrium (Fig. 20-1). Because the tensor tympani and the anterior malleolar ligament provide two-point fixation at this point, it represents a relatively stable location for reconstruction. A perfect example of the utility of this landmark is the case of the medially rotated manubrium, which results in the umbo resting on the promontory. As the axis of rotation is still about the anterior malleolar ligament, this common scenario can be easily managed by running the prosthesis to the neck of the manubrium, which has likely not been appreciably rotated. At times it is necessary to lift the umbo with a 1-mm hook to facilitate placement of the prosthesis under the manubrium after fixation over the superstructure or footplate (Fig. 20-2). The malleus is consistently 2 mm lateral and 3 to 4 mm anterior to the capitulum of the stapes. This standard distance allows a very predictable position for ossicular reconstruction, regardless of the make or model of the prosthesis.

Another critical portion of the anatomy is the stapes. Given that the capitulum is 1 mm in height and the crura is 2 to 3 mm in height, the height of a properly placed TORP should be 4 to 5 mm. With the

FIGURE 20 — 1 Properly placed prosthesis at neck of malleus. Note tilt of prosthesis head relative to shaft.

FIGURE 20—2 Lifting the umbo for prosthesis placement. The neck of the malleus is relatively stable.

additional 3 to 4 mm of anterior distance from the capitulum, this makes prosthesis design and positioning much more reliable in the stapes-absent situation (Fig. 20-3).

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