This surgical procedure is performed to treat deafness due to otosclerosis. Otosclerosis is caused by fixation of the foot plate of stapes which prevents efficient sound transmission to the oval window. The deafness caused is conductive in nature.
The surgical procedure is performed under local anesthesia. Advantages of performing this surgery under local anesthesia are:
1. Improvement in hearing can be ascertained on the table.
2. Bleeding is minimal under local anesthesia.
Indications for stapedectomy:
1. Conductive deafness due to fixation of stapes.
2. Air bone gap of at least 40 dB.
3. Presence of Carhart's notch in the audiogram of a patient with conductive deafness.
4. Good cochlear reserve as assessed by the presence of good speech discrimination.
Contraindications for stapedectomy:
1. Poor general condition of the patient.
2. Only hearing ear.
3. Poor cochlear reserve as shown by poor speech discrimination scores
4. Patient with tinnitus and vertigo
5. Presence of active otosclerotic foci (otospongiosis) as evidenced by a positive flemmingo sign.
Since a patient with otosclerosis is also an ideal candidate for hearing aid and surgery, the patient must be properly counselled regarding the advantages and disadvantages of both.
Xylocaine with adrenaline mixed in concentration of 1:1000 is used to infiltrate the external auditory canal. 0.25 ml of the solution is infiltrated using a 27 gauge needle. Infiltration is given as illustrated in the diagram.
A large speculum is used to straighten the external auditory canal. A curved or triangular incision is made in the external canal skin beginning at 2mmaway from the annulus. The incision extends from 11 o clock position to 6 o clock position as viewed in the right ear. The tympano meatal flap is elevated up to the annulus. Using a sharp pick the annulus is slowly lifted from its groove, the middle ear mucosa is exised and the middle ear proper is entered.
In most patients the posterior superior bony overhangmust be curetted using a curette (designed by House). The longprocess comes into view. Curetting is continued till the base ofthe pyramidal process is visualised. Oval window isvisualised. At this point round window reflex is tested by movingthe handle of malleus and looking for movement of roundwindow membrane. In otosclerosis this reflex is absent. Using a hand burr a small fenestra about 0.6mm in diameter is madeover the foot plate. The stability of the incus is left intactbecause the stapedial tendon is not cut at this point. Fromnow on the steps may vary according to the surgeon's viewpoint. Some surgeons would like to insert the piston at this stage withoutdisturbing the stability of the incus. The distance between thelong process of incus and the foot plate is measured using a measuringrod. Appropriate size teflon piston is introduced and humg overthe long process of the incus and is crimped after ascertaining whetherits lower end is inside the fenestra. The stapedial tendonis cut at this point and the supra structure of the stapes isdisarticulated and removed. The Tympanomeatal flap isrepositioned.
Complications of stapedectomy:
1. Facial palsy
2. Vertigo in the immediate post op period
4. Perilymph gush
5. Floating foot plate
6. Tympanic membrane tear
7. Dead labyrinth
8. Perilymph fistula