Partial Stapedectomy

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Chapter 23 Partial Stapedectomy

Mendell Robinson

Many surgeons prefer a partial stapedectomy technique for the surgical treatment of otosclerosis. A partial stapedectomy should be performed, however, only when the surgeon follows certain basic principles in stapedial footplate surgery. This chapter presents those surgical principles and the manner in which they apply to the partial stapedectomy technique. This chapter also addresses the application of these principles to total stapedectomy and stapedotomy techniques.

HISTORY

In 1958, Shea1 advocated total stapes footplate removal when using the polyethylene strut prosthesis and a vein graft to seal the oval window. Shortly thereafter, Schuknecht2 advocated the use of a wire and fat prosthesis, and House and Greenfield3 later advocated the use of a wire with absorbable gelatin sponge (Gelfoam) prosthesis. The use of the wire/Gelfoam or wire/fat prosthesis necessitated total removal of the footplate for the wire prosthesis to function satisfactorily. Other methods that could be considered a partial stapedectomy technique included the shattered footplate procedure with the use of a polyethylene strut, and the subluxated footplate procedure, both of which necessitated removal of the superstructure of the stapes.4 These two techniques were quickly rejected because of the associated sensorineural hearing loss resulting from either surgical trauma or a perilymphatic fistula.

In 1961, the piston concept was introduced, in which a cup/piston prosthesis was used with a connective tissue graft of vein to seal the oval window.5 The introduction of the piston prosthesis no longer required a total removal of the stapes footplate. The concept evolved of “removing only that part of the footplate which comes out easily.”6 This newly introduced surgical technique consequently produced more successful hearing results and fewer inner ear complications. The same technique could be used for the thin blue footplate with minimal otosclerotic involvement, or for the obliterative footplate, in which only a stapedotomy opening (“drill-out”) could be created. Measurement of the distance between the long process of the incus and stapes footplate was eliminated because a 4-mm prosthesis would protrude into the vestibule 0.2 to 0.3 mm in virtually every case. This slight protrusion would create its self-centering effect. By interposing a vein graft between the prosthesis and vestibule, there was rarely a regrowth of otosclerotic bone, including the obliterative type. Also, because of this protrusion, migration of the piston in subsequent years was virtually unknown.

Because of the unique design of the cup/piston prosthesis, the surgeon was permitted a choice of a total stapedectomy or partial stapedectomy or stapedotomy. The classic cup/piston prosthesis was fabricated of 316L stainless steel, an alloy that is inert in living tissue and is nonmagnetic. Its design enhanced the self-centering effect because of the cup attachment to the lenticular process of the incus (the true physiologic point of attachment), and because of the axially placed stem protruding minimally through the footplate opening. The four holes in the cup and the hole on the distal end of the piston encouraged tissue and vascular ingrowth to secure the prosthesis, and to allow capillaries to vascularize the lenticular process, eliminating the avascular necrosis that so frequently occurred with the polyethylene strut.

The 4 mm length is used in virtually every stapedectomy case whether it is a drill-out stapedotomy, a partial footplate removal, or a total footplate removal. Any connective tissue can be used with this prosthesis, but I prefer a vein graft that outlines the oval window opening and ensures a complete immediate seal of the oval window. Moon7 advocates the cup/piston prosthesis with areolar tissue. The cup/piston prosthesis is radiopaque and easy to localize and identify on routine mastoid radiographic views. Comparison of impedance studies of various stapes prostheses has shown the stainless steel cup/piston to be the closest in compliance to that of a normal mobile stapes.8 Hearing results reported by otologic surgeons who have used this technique have consistently confirmed a 96% air-bone gap closure to within 10 dB.9–11 Similarly, the complete closure (and overclosure) rate has been repeatedly confirmed at 80%, which the wire/tissue prosthesis and wire pistons have yet to attain.

Because the stapes does not increase in size with age, the 4 mm cup/piston prosthesis has been used in children 5 years old, adults, and elderly individuals. All patients who show an air-bone gap and normal results on otologic examination are candidates for stapedectomy surgery if stapedial fixation is found at the time of the middle ear exploration. Approximately 22% of patients with otosclerosis have a diminished cochlear reserve with a Shambaugh preoperative bone conduction classification of D or E. These patients have very severe mixed hearing losses, and in many, only a partial footplate removal can be obtained. These patients also most frequently show complete closure and overclosure of the air-bone gap. For these patients, the extra 10 dB of hearing gain is crucial because of their mixed hearing loss. Approximately 74% of the patients undergoing surgery have partial or total footplate removal that does not necessitate drilling. The remaining 26% require drilling to create a fenestra 0.8 mm in diameter or larger to accept the vein graft and cup/piston prosthesis.6

In 1980, Austin12 compared the results of total stapedectomy and partial stapedectomy, tissue seal and no tissue seal, and the small fenestra of Smyth. His statistical analysis, using chi-square tables for success or failure, sensorineural hearing loss, fistula, and complete air-bone gap closure, was computed. He concluded that a tissue seal provides a better success rate, a significantly lower risk of fistula, and a better hearing result in terms of complete closure or overclosure of the air-bone gap. Austin noted that in addition to the increased risk of sensorineural complications and fistulas, the small-diameter pistons used in stapedotomies did not provide as good a hearing result.

SURGICAL TECHNIQUE

Stapedectomy footplate surgery follows a very basic principle—be as atraumatic as possible in removing the footplate of the stapes. This principle is contingent on removal of “only that part of the footplate which comes out easily.”6

Routine stapedectomy is divided into three stages: (1) exposure of the middle ear, incus, stapes, and footplate area; (2) removal of the stapes superstructure; and (3) removal of the stapes footplate. If the opening is 0.8 mm or larger, the piston can function satisfactorily. The new fenestra must be sealed with a tissue graft; a self-centering 4 mm cup/piston bridges the gap from the oval window membrane to the incus (Figs. 23-1 to 23-5).

image

Footplate surgery can be classified as follows:

1. Total footplate removal, in which a blue footplate with all oval window margins is visualized
2. Partial footplate removal, in which absent margins are in part of the circumference of the footplate, but where there is a blue area for perforating
3. Total footplate removal with drilling, in which a thick footplate with margins and without a blue center exists for perforating the footplate (biscuit footplate)
4. Partial footplate removal with drilling, in which absent margins are in part of the circumference of the footplate, and there is no blue area for perforating the footplate
5. Drill-out for obliterative otosclerosis, in which no margins of the oval window and thick-mounding otosclerotic bone exist

The technique used in this method involves the use of the cup/piston stainless steel stapes prosthesis and a vein graft to seal the recreated oval window. The vein graft is usually taken from the dorsum of the opposite hand by an assistant surgeon at the same time the ear is being operated on. After the vein is opened, it is thinned, and as much of the adventitia is removed as possible. It is trimmed to a final size of 4 × 8 mm. The graft is placed in a small bowl of intravenous saline until it is ready for insertion. The vein is folded over the tip of a smooth-jawed microalligator forceps, umbrella style, and is inserted into the middle ear, avoiding contamination by not touching the ear speculum or the wall of the external auditory canal. The vein is placed over the oval window opening with its adventitial surface facing the vestibule. It is indented slightly into the vestibule with a fine, curved needle so that the exact location of the oval window is visualized.

Measurement of the distance between the long process of the incus and the oval window is unnecessary because the 4 mm long prosthesis is used in virtually every case. If there is a drill-out, a 4.5 mm prosthesis optionally may be used to ensure the self-centering effect by protruding 0.7 mm into the vestibule; this also retards formation of new otosclerotic bone. The prosthesis is grasped at its cup end with a small, smooth alligator forceps and targeted into the dimpled portion of the vein graft. It is engaged on the lenticular process of the incus by slightly depressing the socket with the curved needle, and then allowing the prosthesis to rise up and lock onto the lenticular process. The wire loop is rotated over the long process of the incus. The wire is not crimped because the fit is precise. Mucosa grows over the wire loop and secures its position.

Before the middle ear is closed, the malleus is gently palpated to ensure that there is mechanical transmission of vibration from the malleolar handle to the prosthesis. The vein graft is inspected to ensure that the edges of the graft overlap the entire oval window area, and that there is no inversion of any of the edges toward the vestibule; otherwise, this problem may predispose to a perilymphatic fistula. The tympanomeatal flap is replaced, and the ear canal is packed with a strip of silk and an expandable methylcellulose otowick and saturated with neomycin and polymyxin B (Neosporin) solution. The canal packing is removed in 1 week. Prophylactic antibiotics are used preoperatively and postoperatively (tetracycline), and steroid/antibiotic eardrops (Cortisporin otic suspension) are used in the ear canal for 1 week to maintain sterility of the ear canal, and to prevent the otowick from drying out.

This prosthesis, because of its unique design, is a “smart” prosthesis—it can be fitted to the incus under many circumstances. It can fit an angled lenticular process; an extra-large lenticular process; an extra-long long process; a short long process; or a fractured, atrophic, or necrotic long process. When a narrow oval window niche or a prolapsed facial nerve is present, the prosthesis easily self-centers into the vein graft. When there is only partial footplate removal or drill-out for obliterative otosclerosis, the vein graft and prosthesis align perfectly because of the self-centering feature.9

MODIFICATIONS OF THE CUP/PISTON STAPES PROSTHESIS

Infrequently, an anatomic variation in the middle ear may result in a prosthesis that performs suboptimally. For these infrequent situations, a cup/piston prosthesis with an offset shaft compensates for a short long process of the incus, a prolapsed facial nerve, and an abnormally high rise of the promontory.

When the lenticular process of the incus is absent, or there is erosion of the long process of the incus, the modified Robinson-Moon-Lippy stapes prosthesis compensates for the absent lenticular process. A cutout is in the cup of the prosthesis to accept the eroded long process of the incus, and the shaft is offset in a way similar to the Moon modification. The length of this prosthesis should be 4.5 mm to compensate for the fact that the long process is in the socket rather than above it.

The standard dimension of the cup is 0.875 mm, inside diameter, and 0.6 mm, stem diameter, with a 4 mm length. The cup/piston prosthesis is available with a large well (1 mm) and a narrow stem (0.4 mm) for a large lenticular process or narrow oval window niche.

INDICATIONS FOR CUP/PISTON PROSTHESIS

The partial or total stapedectomy technique described in this chapter is used for stapes fixation owing to otosclerosis, tympanosclerosis, and osteogenesis imperfecta. It is also used for congenital stapes anomalies and stapedial injuries, including fracture or dislocation of the stapes.

POSTOPERATIVE RESULTS

The postoperative hearing results with this partial-total stapedectomy technique have been consistent and repeatable since first reported in 1961. Subsequent reports by myself and others have repeatedly shown a success rate of 96% for closure to within 10 dB of the air-bone gap. A partial success rate of 3% exists in closure to within 20 dB, leaving only 1% unsuccessful.

Delayed hearing losses have been infrequent. In a 21-year period, the incidence of delayed conductive losses was 1.6%, and incidence of cochlear losses of more than 10 dB was 1.2%. The total continued long-term success rate is 93%. These data were derived from a 20-year study of 4815 stapedectomy cases.13 The causes of a delayed conductive loss and their incidence are as follows: otosclerotic regrowth, 3/1000; tympanofibrosis, 2/1000; malleus fixation, 1/1000; postoperative tympanic membrane perforation, 1/1000; incus necrosis, 1/1000; prosthesis migration, 1/3000; prosthesis extrusion (preoperatively healed perforation), 3/1000; and perilymphatic fistula (first vein graft too small), 1/1000. Delayed cochlear losses resulted primarily from perilymphatic fistula (vein graft too small), 1/2000; cochlear otosclerosis, 1/1000; presbycusis, 4/1000; and viral labyrinthitis, 2/1000.

DISCUSSION

Comparison with Wire/Stapes Prosthesis

With wire prostheses, design, fabrication, and measurement are not standardized. Wires attach to the incus on its long process and not at the physiologic site where the capitulum of the stapes is attached to the incus. Wires are at a disadvantage when there is a short incus, an eroded incus, or a prolapsed facial nerve. Over a long period, there is usually notching of the long process of the incus and occasionally a necrosis of the long process from the notching. Wire/tissue prostheses require total footplate removal, which can be traumatic, and wires are not self-centering and frequently develop a delayed conductive hearing loss because of migration and impingement on the margin of the oval window.

Wire/piston prostheses also exhibit some of the same disadvantages, including the lack of standardization and the incus attachment problems, mentioned earlier. The oval window opening must be precise because an exact fit is mandatory for the stapedotomy technique. The length must be precise: the piston must protrude 0.2 mm into the vestibule. When a stapedotomy opening is created, microfractures of the footplate may occur, increasing the risk of a perilymphatic fistula.

Results with wire prostheses vary greatly; success rates range from 80% to 95%. With wire/piston stapedotomy procedures, there frequently is a residual, small air-bone gap in the low frequencies. Reports of complete closure are sparse, but the complete closure rate of the wire/fat prosthesis has been reported to be 15% to 20%, and the complete closure rate of the wire/piston stapedotomy procedure has been reported to be 50% or less. The cup/piston complete closure rate has consistently been 80%, however. Impedance studies have shown that wires have a very high compliance, whereas cup/piston prostheses have a compliance similar to that of a normal mobile stapes. This high compliance of wire prostheses reflects the imperfect attachment to the incus because the wire is crimped over the long process and eventually loosens slightly when notching of the incus occurs. Notching and loosening do not occur with the cup/piston prostheses.8

Stainless Steel Prostheses versus Polytef (Teflon) Prostheses

Many materials have been used and advocated for the fabrication of stapes prostheses. Polytef (Teflon) has many advocates because of its inertness and lack of tissue reaction. The stainless steel cup/piston prosthesis, which is fabricated of 316L stainless steel, has also shown a lack of tissue reaction. The main difference between both materials is the weight. A Teflon cup/piston prosthesis weighs 3.3 mg, and a stainless steel cup/piston prosthesis weighs 12.5 mg. An intact stapes freshly removed from the ear weighs 6 mg. Bluestone14 first reported that by loading a polyethylene stapes prosthesis with a steel core, he would obtain a 10 dB increase in hearing at 4000 Hz and 8000 Hz compared with that of the control group.

I reported a study comparing the hearing results in patients with a Robinson stainless-steel cup/piston prosthesis and vein graft in the first ear and a Robinson Teflon cup/piston prosthesis and vein graft in the second ear.15 This study eliminated all variables except the difference in weight of the prostheses. The preoperative hearing level in each ear was the same, as was the footplate pathology in both ears. The design of the prosthesis was exactly the same; only the weight differed. The stainless steel prosthesis weighed almost four times that of the Teflon prosthesis. The results showed that the high-frequency gains in hearing were slightly better for the stainless steel ear (14 dB) than for the Teflon ear (11 dB). The rate of complete closure and overclosure of the air-bone gap was significantly greater in the stainless steel ear (80%) than in the Teflon ear (52%), even though the overall closure of the air-bone gap to within 10 dB was 97% in the stainless steel ear and 96% in the Teflon ear. Impedance studies of this group showed that the compliance of the stainless steel stapes prosthesis most resembled that of the normal mobile stapes, whereas the Teflon prosthesis showed a slightly reduced compliance (high impedance), but as a cup/piston, its compliance curves were more within the range of the mobile stapes than any of the wire prostheses.

This study proved that the heavier prosthesis resulted in a much greater complete closure and overclosure of the air-bone gap, and that there was a small but significant hearing advantage in postoperative results when a metallic prosthesis was used (6 dB). In mixed-type hearing loss, this increased hearing can have a significant effect on the patient’s reaching a serviceable postoperative hearing level.15

Juvenile Otosclerosis

Otosclerosis is usually considered to be a disease of young and middle-aged adults, but juvenile otosclerosis occurs in 15.1% of stapedectomy cases before age 18. I presented an in-depth study of 610 patients (of a total of 4014 patients) who developed clinical otosclerosis before age 18 and underwent stapedectomy.16 Of these 610 patients, 35 underwent surgery before age 18, and 574 underwent surgery after age 18, but their hearing loss had developed during their juvenile years. The youngest patient was 5 years old, and the average age of onset was 11.5 years.

The surgical technique performed on all 610 patients consisted of a partial or total footplate removal, as described in this chapter. All patients younger than 18 received general anesthesia, whereas all patients older than 18 had local anesthesia (lidocaine [Xylocaine] 2% with 1:30,000 epinephrine). The surgical footplate pathology varied considerably between patients younger than 18 and patients older than 18. In the patients younger than 18, 66.7% had a thin blue footplate, which was totally removed, whereas in patients older than 18, only 45.1% had similar pathology. Partial footplate removal was performed in 5.5% of the patients younger than 18 and 9.7% of the patients older than 18. More significantly, drilling of the footplate because of diffuse otosclerotic involvement was necessary in 27.8% of the patients younger than 18 and in 45.2% of patients older than 18. Rate of obliterative otosclerosis, which required drill-outs, was 5.6% in the juvenile group and 12% in their older counterparts. This result is in contrast to 3% prevalence of obliterative otosclerosis for all stapedectomies.

The hearing results were more favorable in patients who underwent surgery before age 18; 100% had an air-bone gap closure of 10 dB or less, and 77.6% had complete closure or overclosure of the air-bone gap. Patients who underwent surgery after age 18 had a very successful closure rate, but only 93.6% had the air-bone gap closed to within 10 dB. Similarly, 77.3% had complete closure or overclosure. A postoperative delayed conductive hearing loss (20 dB) occurred in only one patient 5 years after the initial surgery in the group younger than 18. The postoperative hearing level in all patients younger than 18 (4000 Hz) remained the same or improved.

This study also revealed a very high incidence of bilateral otosclerosis (92%) when the hearing loss occurred before age 18. Of patients younger than 18 with otosclerosis, 80% had excellent cochlear reserve and did not show a deterioration of sensorineural function after stapedectomy. The longer the hearing loss existed, the greater the degree of footplate pathology that occurred. The probability of requiring a drill-out for obliterative otosclerosis increased fourfold when surgery was deferred to after age 18. Deferring a stapedectomy procedure in a child may not be in the best interest of the patient because of the progressive nature of the footplate pathology and the increased necessity of drilling the footplate.16

SUMMARY

Stapedectomy and stapedotomy for the correction of hearing loss resulting from otosclerotic bony fixation of the stapes are surgical procedures that have evolved almost entirely in the “golden era” of otologic surgery (1955-1985). This era has passed, and even the most popular of the nationally known surgeons who perform stapedectomy have experienced a dramatic decrease in the caseload for stapedectomy. This decrease, in addition to the dispersion of patients to a larger number of trained otolaryngologists, has to some degree compromised the position of the otologic surgeon not only in developing skills and judgment, but also in maintaining the acquired skill necessary to perform the more complicated and precise techniques.

General otolaryngologists and otologists should adopt a technique that is uncomplicated, easy to perform, predictable, and safe for the patient. This technique should be standardized so that it can be performed in the same way for all stapedectomies. Reducing the variables and making one technique work for all cases of stapes fixation would allow the general otolaryngologist gradually to develop the high degree of skill necessary for this procedure. The technique adopted should have minimal risks and immediate or delayed complications, and, if possible, should have the lowest incidence of revision because revisions demand more skill, judgment, and knowledge than primary stapedectomies.

More than 200,000 stapedectomies have been performed in the United States with the technique and prostheses described in this chapter. Despite the overall decrease in the number of stapedectomy procedures performed annually, the number of Robinson cup/piston stapes prostheses used each year continues to increase, indicating the popularity of this simpler and safer technique.

REFERENCES

1. Shea J.J.Jr. Fenestration of the oval window. Ann Otol Rhinol Laryngol. 1958;57:932.

2. Schuknecht H. Stapedectomy and graft prosthesis operation. Acta Otolaryngol (Stockh). 1960;51:241-243.

3. House H.P., Greenfield E.C. Five-year study of wire-loop absorbable gelatin sponge technique. Arch Otolaryngol Head Neck Surg. 1969;89:420-421.

4. Goodhill V. Stapes Surgery for Otosclerosis. St Louis: Paul B Hoeber; 1961. p 136

5. Robinson M. The stainless-steel stapedial prosthesis: One year’s experience. Laryngoscope. 1962;73:514.

6. Robinson M. A four-year study of the stainless-steel stapes. Arch Otolaryngol Head Neck Surg. 1965;82:217-235.

7. Moon C. Stapedectomy connective tissue graft and the stainless-steel prosthesis. Laryngoscope. 1968;78:798-807.

8. Feldman A. Acoustic impedance measurement of post-stapedectomized ears. Laryngoscope. 1969;79:1132-1155.

9. Schondorf J., Pilorget J., Graber S. [The influence of the stapes prosthesis on the long-term results of stapedectomy.]. Head Neck Otolaryngol. 1980;28:153-157.

10. Elonka D., Derlacki E., Harrison W. Stapes prosthesis comparison. Otolaryngol Head Neck Surg. 1982;90:263-265.

11. Girgis T: Stapedectomy: Robinson stapes prosthesis versus wire prosthesis. Presented at American Society of Otology, Rhinology, and Laryngology, Middle Section Meeting, Chicago, January 1985.

12. Austin D.F. Stapedectomy with tissue seal. In: Snow J.B.Jr., editor. Controversy in Otolaryngology. Philadelphia: Saunders, 1980.

13. Robinson M. Total footplate extraction in stapedectomy. Ann Otol Rhinol Laryngol. 1981;90:630-632.

14. Bluestone C.D. Polyethylene stainless-steel core in middle ear surgery. Arch Otolaryngol Head Neck Surg. 1962;76:303.

15. Robinson M. Stapes prosthesis: Stainless steel versus Teflon. Laryngoscope. 1974;84:1982-1995.

16. Robinson M. Juvenile otosclerosis. Ann Otol Rhinol Laryngol. 1983;92:561-565.

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