HISTORICAL PERSPECTIVE

Since Matte’s¹ report of a myringostapediopexy in 1901, numerous methods have been attempted to bridge the gap between the tympanic membrane and the inner ear fluids. The modern era of reconstructive middle ear surgery began with reports by Zollner in 1955² and Wullstein in 1956.³ These early attempts focused on creating a sound pressure differential between the oval and round window by adapting the operation to the ossicular problem encountered. If the incus was missing, the graft was placed on the stapes capitulum (type III or columellar tympanoplasty). If the incus and the stapes crura were missing, the graft was laid on the promontory, leaving a mobile footplate exposed (type IV, oval window, or cavum minor tympanoplasty), producing sound protection fort the round window. These techniques usually altered the volume of the middle ear by creating an open mastoid cavity. In 1957, Hall and Rytzner⁴ described the use of an autogenous incus or malleus to reconnect the mobilized footplate to the tympanic membrane in patients with otosclerosis. Hearing results with this technique were very promising, and the importance of a closed mastoid cavity with a normal middle ear space was quickly realized. Soon thereafter, the search for the ideal material to reconstruct the sound conduction mechanism was begun. In the late 1950s and early 1960s, much attention was focused on the use of autogenous and alloplastic materials.

The first reported use of an artificial material to reconstruct the ossicular chain was by Wullstein in 1952,³ when he used a vinyl-acryl plastic known as palavit to connect the tympanic membrane to the stapes footplate. In 1958, Shea⁵ described the use of polyethylene tubing placed on the capitulum of the stapes and wedged under the tympanic membrane. His efforts were soon followed by others using various polyethylene prostheses and other inert materials, such as polytef (Teflon) and silicone elastomer (Silastic). Despite many excellent short-term and long-term hearing results, these early alloplastic materials often resulted in extrusion, significant middle ear reactivity, or, worse, penetration of the inner ear. As a result, many surgeons turned to autogenous prostheses that would be more compatible with the middle ear.

Following the early work of Hall and Rytzner,⁴ several otologists, including Farrior,⁶ Sheehy,⁷ and Guilford,⁸ began reporting on the success of using autografts for ossicular reconstruction. The most commonly used autograft material was the body of the incus; however, cartilage and cortical bone were also used. These natural materials were well tolerated in the middle ear and provided reliable hearing results. The disadvantages that soon became apparent were the prolonged time required to sculpt the prosthesis and the lack of availability in chronically diseased ears. In an effort to circumvent some of these issues, in 1966, House and colleagues⁹ first reported the use of homografts in middle ear reconstruction. Other reports soon followed describing the use of irradiated ossicles, cartilage, and even homograft tympanic membranes with en bloc ossicles.^10,11 Homografts had hearing results and biocompatibility similar to autografts; however, concerns regarding the risk of transmission of human immunodeficiency virus and prions (i.e., Creutzfeldt-Jakob disease) ultimately led to their decline in use.

In a continued effort to find a safe, reliable, and easily available prosthesis, Shea in 1976¹² reported on the use of high-density polyethylene sponge (Plastipore) for middle ear reconstruction. Made of porous polyethylene, this alloplast had nonreactive properties and sufficient porosity to allow ingrowth of tissue. It was readily available commercially and could be easily trimmed with a knife. A similar porous polyethylene that is thermal-fused (Polycel) was developed later and allowed the prosthesis to be coupled to other materials, such as stainless steel. This capability allowed it to be modified to various prosthesis designs. Early reports of porous polyethylene implants revealed a high incidence of extrusion when placed in direct contact with the tympanic membrane. This problem was significantly reduced by placing a disc of cartilage between the head of the prosthesis and the tympanic membrane, as advocated by Coyle Shea and reported by Brackmann and Sheehy.¹³ As a result, Plastipore and Polycel total ossicular replacement prostheses (TORPs) and partial ossicular replacement prostheses (PORPs) continue to be used with good long-term success today.

In an effort to improve extrusion rates associated with porous polyethylene, in 1979 various ceramics were recommended for use in ossicular reconstruction. These alloplastic materials were termed either bioinert or bioactive. Bioinert implants, such as dense aluminum oxide ceramic, did not react with surrounding tissues and were popular in Germany and Japan. Bioactive implants, such as glass ceramic (Ceravital), were biocompatible and reacted with surrounding soft tissue and adjacent bone allowing a coupling between the implant and the ossicle in contact.¹⁴ The advantage of ceramic implants was that they could be placed directly under the tympanic membrane without interposing cartilage; however, they were difficult to handle and shape because of their glass nature.

In 1984, Grote¹⁵ introduced the use of the calcium phosphate ceramic, hydroxyapatite, for tympanoplasty surgery. Subsequently, great interest developed in this material for middle ear prostheses. Hydroxyapatite, which is the mineral matrix of living bone, was known to be a bioactive material achieving integration with surrounding bone and tissue. In 1985, Wehrs¹⁶ developed an incus prosthesis and an incus/stapes prosthesis made of hydroxyapatite and reported successful hearing results with a low extrusion rate 4 years later. Since that time, this material has been adapted to various uses and prosthesis designs. The advantage of this material is that it is quite rigid and has a good sound transfer function.

The disadvantages of hydroxyapatite are that it has a large mass creating a high input impedance, and it is solid, potentially obstructing the surgeon’s view. Because of its brittleness, it is often combined with other materials to create a prosthesis shaft that is more malleable and easier to shape. More recently, hydroxyapatite has been combined with polyethylene (HAPEX) to create an allograft material that approaches the mechanical strength of bone, but is soft enough to cut with a knife.

In an attempt to find a prosthesis that had the rigidity and biocompatibility of hydroxyapatite, but not the mass, titanium prostheses were developed. The specific density of titanium is low, less than 57% that of stainless steel, yet it is extremely rigid. In addition, it is nonmagnetic, has excellent biocompatibility, and lends itself to being manufactured into various shapes and sizes. Most of the titanium prostheses possess an open head, allowing better visualization during placement. First used for ossicular reconstruction in 1993 in Germany,¹⁷ the popularity of titanium prostheses has grown rapidly. Cartilage must still be used, however, between the platform and tympanic membrane to prevent extrusion. Several authors to date have published favorable hearing results with titanium prostheses, and compared with hydroxyapatite, titanium may provide improved hearing responses at higher frequencies because of its low mass.^18–21

Despite the improvements in middle ear prostheses, there remained a need for an adhesive or bone cement to stabilize the prostheses or, in some cases, replace them altogether. In the 1980s, ionomeric cements were used for cranioplasties and ossicular chain reconstruction. Although effective in the middle ear,²² aluminum toxicity issues associated with cranioplasties resulted in ionomeric cements being largely supplanted by hydroxyapatite phosphate cements, which are free of aluminum. Two of these cements currently are being produced for otologic applications—Hydroset (Stryker) and OtoMimix (Gyrus). The cements seem to be well tolerated, and have been particularly useful in reconstructing the long process of the incus and stabilizing prostheses.

Although numerous techniques and materials have been used for ossicular reconstruction, the quest for the ideal prosthesis is ongoing. Today, autogenous and alloplastic prostheses are used with equally good outcomes, and the surgeon should use what is comfortable and provides consistent, favorable results. This chapter primarily focuses on the use of alloplastic material in ossicular chain reconstruction, and principles that improve outcomes in attempts to reconstruct the middle ear sound transformer mechanism.

PATIENT SELECTION AND EVALUATION

The selection of patients undergoing ossicular chain reconstruction largely depends on the problem at hand. Any patient with chronic otitis media may ultimately be a candidate for ossicular chain reconstruction. These patients often present because of the hearing loss associated with their infection or chronic middle ear disease. In other cases, initial hearing may be normal, but become compromised secondary to surgery to remove cholesteatoma. Still other patients present with hearing loss resulting from ossicular problems associated with trauma or congenital ear malformations. Regardless of the cause, the initial evaluation requires a thorough microscopic examination of the ear to identify the problem accurately.

In cases of chronic ear disease, ossicular discontinuity may be diagnosed through a perforation or with severe atelectasis of the tympanic membrane. Most commonly, incus erosion is the cause of conductive hearing loss; however, the presence or absence of all three ossicles should be noted. Cholesteatoma involvement of the ossicles is usually identified on examination. In the event of active infection and drainage, it is important to obtain a dry ear with meticulous cleaning and topical antimicrobial preparations before surgery. If a dry ear cannot be obtained, ossicular reconstruction is often staged after tympanoplasty so that ventilation and the middle ear mucosa can normalize. When there is a conductive hearing loss with an intact eardrum, the history should focus on any head or ear trauma, prior ear surgery, family history of otosclerosis, Tullio phenomenon, or unusual congenital abnormalities. Careful evaluation of the symptoms and findings guides the surgeon in the need for surgery, type of procedure, its urgency, and the anticipated result, based on the type of reconstruction required.

Audiometric studies are essential in patients with suspected conductive hearing loss and should include pure tone air and bone conduction with masking, speech discrimination, and tympanometry. Severe eustachian tube dysfunction may necessitate concomitant ventilation tube placement or, in rare cases, preclude ossicular chain reconstruction. Acoustic reflex testing is helpful in distinguishing hearing losses resulting from otosclerosis versus an inner ear conductive hearing loss associated with dehiscence of the superior semicircular canal. In the latter, the reflex is present. Conductive hearing losses greater than 25 dB usually signify an ossicular problem. Audiometric results should always be confirmed with the Weber and Rinne tuning fork examination using 512 Hz and 1024 Hz tuning forks. Before operating on the involved ear, the contralateral ear must be assessed. In cases of a better or only hearing ear, alternatives such as a hearing aid or a canal wall down procedure in the setting of chronic otitis media with cholesteatoma may be more suitable.

Imaging studies are rarely obtained to evaluate the middle ear and ossicles. Thin-section computed tomography (CT) of the temporal bone may provide useful information, however, in cases of extensive cholesteatoma, malleus fixation, incus dislocation, superior canal dehiscence, or suspected congenital ossicular abnormalities.

After a thorough work-up, the physician is prepared to give realistic expectations regarding the chance of hearing restoration and the need for additional surgery. Although ossicular reconstruction may be performed at the time of initial repair or cholesteatoma removal, extensive cases often require reconstruction to be done during a second stage at a later date. In adult patients, 9 to 12 months are allowed to pass before performing a second look procedure to rule out residual cholesteatoma and reconstruct the ossicular chain; in pediatric patients, 6 months is an appropriate time interval. This staging period provides adequate time for small residual cholesteatoma to become apparent, and provides time for diseased mucosa to normalize. Typically, absorbable gelatin film (Gelfilm) is placed over the promontory, and the middle ear is packed with middle ear packing soaked in Merogel a nonototoxic antibiotic solution. Enzymatic type packing in conjunction with the Gelfilm should decrease postoperative middle ear adhesions. Staging in this manner helps to ensure a disease-free ear, and improves hearing outcomes.

The selection of pediatric patients for ossicular reconstruction depends largely on the status of the ear. In the setting of chronic otitis media, the most important goal is to provide a safe, dry ear regardless of age. When a conductive hearing loss is discovered without evidence of chronic ear disease, it is best to wait until the child is 5 to 7 years old to allow time for eustachian tube maturation. If hearing loss is bilateral, hearing aids are a suitable option until that time. When surgery is contemplated, the options, including the use of hearing aids, must be discussed with the parents, who will ultimately make the decision.

When discussing outcomes with patients, it is important to provide a realistic expectation of hearing results. Successful hearing results in ossicular reconstruction are based on the postoperative air-bone gap and stratified as excellent (<10 dB), good (11 to 20 dB), and fair (21 to 30 dB). This success also depends on several factors including the presence or absence of a mobile stapes superstructure, intact canal wall with normal middle ear volume, and adequate eustachian tube function. Although outcomes vary slightly depending on the type of prosthesis used, successful improvement in hearing is generally broken down according to the use of a PORP versus a TORP. In patients undergoing ossicular reconstruction with a PORP, two thirds of patients should achieve hearing outcomes within 15 dB of their bone scores, whereas two thirds of patients with a TORP should achieve hearing outcomes within 25 dB of their bone scores. The disparity in outcomes between PORPs and TORPs is apparent in Brackmann and Sheehy’s review of 1042 cases in which successful hearing with an air-bone gap less than 15 dB was achieved in 63% of PORPs and only 42% of TORPs.²³ Regardless of the technique or type of prosthesis, surgeons should use what they are most comfortable with and provides consistent good hearing results.

SURGICAL CONSIDERATIONS

The surgeon may encounter ossicular abnormalities when intraoperatively examining the middle ear. During second look procedures after cholesteatoma surgery, the surgeon is aware of the ossicular defect before elevating the tympanomeatal flap, and can decide preoperatively what type of ossicular prosthesis is required. In other cases, the surgeon must make an intraoperative assessment and decision. Consequently, an assortment of prostheses must be available to the surgeon at the time of the procedure. The prostheses and ancillary equipment must be able to address the following ossicular abnormalities:

FIGURE 13-1 Partial ossicular replacement prosthesis bridging the gap between the mobile stapes and mobile malleus.

FIGURE 13-2 Reconstruction of the ossicular chain using bone cement to augment the foreshortened incus.

FIGURE 13-3 Use of the incus bridge prosthesis with bone cement to bridge a large gap between the foreshortened incus and capitulum of the stapes.

FIGURE 13-4 Absent stapes superstructure with mobile footplate and mobile incus and malleus.

FIGURE 13-5 Foreshortened incus in ear with prior stapedotomy.

FIGURE 13-6 Head of malleus removed and prosthesis clipped to malleus handle and extending to fenestra in fixed footplate.

FIGURE 13-7 Floating mass transducer situated in round window niche (vibroplasty).

Although it is preferable to have an intact tympanic membrane when reconstructing the ossicular chain, it is usually not essential. If the reconstruction necessitates a stapedotomy or stapedectomy, however, the tympanic membrane must be intact, and the ear must be free of infection.

PROSTHESIS SELECTION

The ideal prosthesis for reconstructing the ossicular chain is one that is biocompatible, easy to place, and stable over the long term with good sound transmission qualities. When selecting a prosthesis, the surgeon should consider not only the anatomic configuration to be repaired, but also a material that is comfortable to work with during surgery. The multitude of prostheses and techniques that continue to be used today is a testament to the fact that no prosthesis is perfect, and the search for the ideal reconstruction method continues. This section describes some common materials used for ossicular reconstruction today.

Autografts, which have been used since the earliest reconstruction efforts, continue to be used by many surgeons with good results. These are usually autologous incus grafts that can be shaped intraoperatively with a notch for the malleus handle and a cup for the stapes capitulum when present (Fig. 13-8), or a straight shaft to be positioned on the footplate when the stapes is absent. Studies have shown good long-term viability of autologous ossicular grafts, although some concern remains about eventual reabsorption if blood supply is not maintained.²⁴ The time required to sculpt these grafts and the unavailability in some cases has prompted many surgeons to turn to alloplastic materials.

FIGURE 13-8 Autologous incus interposition graft.

Since the 1970s, alloplastic prostheses have achieved significant popularity with the introduction of Plastipore. TORPs and PORPs are biocompatible with the middle ear and provide a reliable sound conduction mechanism. Use of PORPs and TORPs requires interposition of a thin disk of cartilage between the platform and the tympanic membrane to prevent extrusion. PORPs are used in the presence of an intact mobile stapes, and TORPs are used in the absence of the stapes superstructure with a mobile footplate. The malleus is not required for successful use of a PORP or TORP. Polycel, a similar material, has the advantage of being malleable and being coupled to other materials such as stainless steel or hydroxyapatite.

Hydroxyapatite has become popular because of its excellent biocompatibility and multiple applications in prosthesis design. Hydroxyapatite is a calcium ceramic that chemically attaches to bone and is osteoconductive. With time, the implant gradually becomes covered with an epithelial layer resembling normal middle ear mucosa. Cartilage does not have to be used with hydroxyapatite, although some authors still recommend it. Early prostheses were made entirely of dense hydroxyapatite and noted to be brittle. More recent innovations have involved attaching a hydroxyapatite-reinforced polyethylene composite (HAPEX) shaft or cuff to a dense hydroxyapatite body. This allows the cuff or shaft to be easily trimmed to length with a knife. Various HAPEX prostheses have been produced and usually possess one or two notches in the hydroxyapatite body for placement under the malleus handle (Fig. 13-9).

FIGURE 13-9 Partial and total ossicular replacement prostheses currently available for implantation.

More recently, titanium has been favored as an alloplastic material because of its excellent biocompatibility, rigid strength, and light weight. Titanium prostheses are designed as PORPs or TORPs, and require interposition of cartilage between the prosthesis and tympanic membrane to prevent extrusion. The platform of the prosthesis has an open-top design facilitating placement (see Fig. 13-9). The prostheses come as presized implants of variable length that can be sized and adjusted intraoperatively. Hearing results to date with titanium implants are comparable to hydroxyapatite and polyethylene sponge, and may improve hearing at higher frequencies.^17–21

In addition to conventional prostheses, bone cements have been used with success in ossicular reconstruction. These cements are currently hydroxyapatite-based cements that are mixed intraoperatively and harden within 4 to 6 minutes. They are useful in the setting of incus necrosis, when the gap is not too large, to span the incus and stapes. When a significant amount of incus necrosis is found, a titanium incus/bridge prosthesis can be used to set up a framework or carrier for the bone cement to be applied between the incus and stapes (see Fig. 13-3). Care must be taken to place Gelfoam around the oval window before application to decrease the risk of bone cement getting around the footplate and causing fixation. More recent reports of using bone cement in ossicular reconstruction have shown good hearing results (air-bone gap ≤20 dB) in 90% of patients.^22,25,26

A few scenarios encountered during middle ear surgery may prompt the surgeon to use a specific prosthesis design. Three prostheses that warrant mention are the Plester (Kurz GmbH, Dusslingen, Germany) incudostapedial joint prostheses, the incus/bridge prosthesis, and the malleus/oval window prosthesis. The first two prostheses are used in the setting of incus necrosis to span the gap between the incus and stapes. The Plester angular prosthesis, made of titanium, has two clips that attach to the incus long process remnant with a cup portion that rests on the stapes capitulum. The cup of the prosthesis is first placed on the stapes capitulum, and then the clips are crimped onto the incus remnant. The shaft of the prosthesis comes in different lengths to accommodate differing amounts of incus necrosis. The incus/bridge prosthesis is designed to be used in conjunction with a bone cement. The prosthesis is clipped onto the incus remnant and extends to the capitulum of the stapes. Using the prosthesis as a scaffold, the bone cement is applied to bridge the gap between the incus and stapes capitulum. The malleus/oval window prosthesis has a ball joint that allows the shaft of the prosthesis to be rotated into the oval window after the prosthesis is clipped onto the malleus handle.

Occasionally, one may encounter patients with hearing loss not amenable to standard reconstruction of the ossicular chain or who have failed multiple attempts at ossicular reconstruction. More recent attempts at improving hearing in such situations have focused on introducing sound through the round window using a vibratory transducer. The Vibrant Soundbridge (Med-El, Innsbruck, Austria) comprises an implanted receiver module placed behind the ear and is connected via a small cable to a floating mass transducer that is placed in the round window niche. Electric current from the receiver module drives the magnet within the transducer, transmitting vibratory stimulation to the inner ear. Early hearing results with this novel technique are promising.²⁷

SURGICAL TECHNIQUE

Although the specific surgical technique for reconstructing the ossicular chain may vary from surgeon to surgeon, there are common aspects inherent to all ossicular reconstructions. As with stapedectomies, the ossicular chain reconstruction can be performed under a straight local anesthetic, monitored anesthesia care (MAC), or general anesthesia. This decision is based on the age of the patient (i.e., child versus adult), the patient’s “fear factor,” whether a mastoidectomy is being performed in conjunction with the ossicular chain reconstruction, the patient’s other medical conditions (e.g., Parkinson’s disease), and the comfort level of the surgeon.

Advantages of performing ossicular chain reconstruction under local anesthesia include the following: surgeon and patient ability to assess hearing intraoperatively, absence of gases accumulating in the middle ear space, altering the position of the tympanic membrane with respect to the prosthesis, and the cheaper cost compared with general anesthesia. Many patients prefer to be “asleep” during any surgical procedure, however. With the use of general anesthesia, the patient is unaware of any discomfort, the surgeon is not pressured from a time perspective, and the middle ear gas issue is largely circumvented by not using nitrous oxide.

Exposure and Assessment

Regardless of the type of anesthesia, if one is performing an ossicular chain reconstruction without a concomitant mastoidectomy, the procedure usually is performed with a transcanal approach. If the canal is quite narrow, an endaural or postauricular approach can be employed. When using a transcanal approach, the ear canal is injected with 1% lidocaine (Xylocaine) and 1:40,000 epinephrine. If the patient is older than 65 years, a 1:60,000 solution is used. Using a 3 mL glass syringe, the solution is injected just inside the meatus, and not at the bony-cartilaginous junction where the skin is more adherent (Fig. 13-10). The ear canal is dilated with specula gradually increasing in size; this forces the local anesthetic solution medially. The vascular strip is injected last (Fig. 13-11); this is probably the most important injection.

FIGURE 13-10 Injection of lateral external auditory canal.

FIGURE 13-11 Vascular strip injection.

Vertical incisions are made at 6 o’clock and 12 o’clock positions, beginning 1 mm lateral to the annulus, and connected by a horizontal incision 10 to 12 mm lateral to the annulus (Fig. 13-12). Although adequate surgical exposure is important, less exposure may facilitate obtaining the proper tension on the prosthesis because the tympanic membrane is stabilized at the bony annulus.

FIGURE 13-12 Canal incisions for tympanomeatal flap.

Although the canal incisions are the same in patients with prior intact canal wall mastoidectomies, the technique is altered in patients with canal wall down mastoidectomies. The 6 o’clock position is shifted anteriorly to 4 o’clock, and the incision at the 12 o’clock position is avoided altogether. The horizontal incision begins anteriorly and extends toward the mastoid cavity. Using this technique, the exposure is more limited, but two point fixation is maintained. This facilitates slight tension on the prosthesis with respect to the tympanic membrane. Particular care should be taken with dissection in the area of the facial ridge, where the vertical segment of the facial nerve may not be protected by a bony coverage.

When adequate exposure is achieved, the status of the middle ear is assessed. In performing a second look procedure, it is essential to check carefully for any residual or recurrent cholesteatoma before considering ossicular chain reconstruction. In addition, the presence of serous fluid may necessitate concomitant placement of a ventilation tube, whereas a dehiscent facial nerve obscuring the oval window may preclude ossicular chain reconstruction using conventional techniques. Vibroplasty techniques may be useful in such cases and in cases with mixed hearing loss, allowing the surgeon to address the conductive and the sensorineural components.²⁷ Although the surgeon’s options may be limited in most situations to a PORP or a TORP, with the advent of bone cements the surgeon must consider alternative techniques.

Before indiscriminately removing a foreshortened incus, the surgeon should consider ways to conserve the middle ear transformer mechanism. In addition, it is particularly important to assess accurately the malleus and the stapes for fixation. Left undetected, fixation of either ossicle would compromise the postoperative hearing results.

Placement of Prosthesis

Regardless of whether the surgeon is placing a PORP or a TORP, it is essential that the prosthesis be under slight tension and at a favorable angle. Various measuring devices are available to assist the surgeon in making the determination. In measuring, one must consider the additional length caused by the cartilage placed between the prosthesis and the overlying tympanic membrane. The prosthesis should fit perfectly without tension before placement of the cartilage. If the prosthesis is slightly short, the length may be corrected later by adding an additional piece of cartilage.

Before placing the prosthesis, the middle ear is partially filled with a middle ear packing material that has been soaked in an antibiotic solution. The sponge facilitates placement of the prosthesis and cartilage, stabilizes them temporarily, and acts as counterpacking for the packing that is to be placed in the canal after replacement of the tympanomeatal flap.

Despite perfect alignment of the PORP or TORP intraoperatively, the prosthesis can shift during the healing process. Adequate middle ear packing may minimize this; a small amount of bone cement placed at the junction of the PORP with the capitulum of the stapes gives the best stability. Bone cement cannot be used on the footplate, however. Instead, a cartilage punch (Kurz) is used to create a “cartilage shoe” that stabilizes the shaft of the TORP and minimizes slippage on the flat footplate surface (Fig. 13-13). A small piece of perichondrium placed on the footplate may limit further slippage on the footplate.

FIGURE 13-13 Cartilage shoe in oval window niche with prosthesis in position on mobile footplate.

Bone cements are increasingly being used not only to stabilize the prosthesis, but also to augment the incus. If the gap between the incus remnant and the stapes capitulum is quite small, the cement can be used alone. If the gap is more substantial, however, a prosthesis such as the incus/bridge prosthesis is placed and secured with bone cement. When using the cement, it is important that packing is placed over the footplate, to protect it from the cement. In addition, the mucosa should be carefully stripped off the portion of the incus and stapes where the cement is being applied. This facilitates a firm bond between the bone and the cement. If one is attaching a stapes prosthesis to a reconstructed incus, a self-crimping type of stapes prosthesis may be preferable.

The most challenging ossicular chain reconstruction is when the incus is absent, and the footplate is fixed. One can use a TORP, but great care is needed to ensure that the prosthesis does not sublux into the vestibule. Several prostheses attach to the malleus handle to limit the incursion of the prosthesis into the vestibule. A slit is made in the periosteum of the malleus, and the prosthesis is secured laterally; the shaft of the prosthesis is then rotated into the fenestra created in the footplate (see Fig. 13-6).

If performing a vibroplasty, the floating mass transducer can be placed in various locations. It is most frequently placed on the footplate or on the round window. When placed in the round window niche, the transducer should be reinforced with a piece of cartilage to prevent displacement of the transducer away from the round window during activation (see Fig. 13-7).

POSTOPERATIVE CARE

In patients undergoing ossicular chain reconstruction using either a transcanal or a postauricular approach, perioperative systemic antibiotics have been administered and a mastoid dressing has been placed. This dressing is removed on the patient’s first postoperative day. The patient is instructed to keep the ear dry. If a postauricular incision has been made, the patient is seen 7 to 10 days postoperatively for suture or Steri-Strip removal. The patient’s middle ear and external ear have typically been packed with Merogel and Gelfoam, respectively. The patient continues to take water precautions with respect to the external ear canal, but is allowed to get water behind the ear. Four weeks postoperatively, the patient is instructed to instill antibiotic ear drops in the external auditory canal, 3 drops three times daily for 2 weeks. The patient returns 3 months postoperatively to have the ear examined and the hearing assessed.

FACTORS THAT MAKE A DIFFERENCE

To achieve optimal hearing outcomes on a consistent basis, and to minimize the potential for extrusion, the surgeon must take into consideration various factors. First, the surgeon and patient must have realistic expectations of hearing outcomes. A patient with poor eustachian tube function or a patient with a very limited middle ear space after a canal wall down mastoidectomy is not as likely to have the same hearing results as a patient with a post-traumatic incudostapedial discontinuity in an otherwise normal middle ear. In patients with poor eustachian tube function, the surgeon should use a slightly shorter prosthesis, anticipating some retraction medially; this optimizes hearing without risking extrusion. In some patients with severe eustachian tube dysfunction, a concomitant ventilation tube may be required. Despite careful prosthesis selection and placement, extrusion continues to be a cause of failure in ossicular reconstruction. Extrusion rates have ranged from 5% to 39% in the literature, and current rates of extrusion have been reported to be 1% for titanium prostheses and 3.3% for hydroxyapatite.

Whether the middle ear space is narrowed or not, the prosthesis should always be under slight tension. This tension is achieved by minimally elevating the tympanomeatal flap and accurately sizing the prosthesis and cartilage. The cartilage should completely cover the platform of the prosthesis without touching the side walls. The middle ear is packed with a packing that breaks down adhesions and yet stabilizes the prosthesis. The ear canal is packed as well to stabilize the tympanic membrane and prosthesis further.

Although PORPs are less likely to slip than TORPs, a small amount of bone cement placed on the interface between the prosthesis and the capitulum of the stapes alleviates the problem altogether. To minimize slippage of a TORP, the cartilage shoe prosthesis is placed on the footplate, and the shaft of the prosthesis extends through the fenestra created in the cartilage. If one attempts to place a TORP in a patient without a footplate, it is essential that a large piece of connective tissue be placed over the oval window and downward pressure on the prosthesis minimized. Otherwise, the prosthesis may extend into the vestibule, risking a sensorineural hearing loss.

Staging the operation in patients with concomitant tympanic membrane perforations or in patients undergoing cholesteatoma surgery may make the difference between success and failure when reconstructing the ossicular chain. Although Silastic was previously used to cover the denuded promontory and maintain a middle ear space, Gelfilm works equally well, and does not create the thick mucosal sac that occasionally envelops the Silastic sheeting. In addition, the Gelfilm resorbs over time and does not obscure the middle ear structures during the second stage procedure.

SUMMARY

Since the 1950s, much progress has been made in reconstructing the middle ear sound transformer mechanism. Improvements in technique and materials have been seen. In the future, further developments are anticipated in “powered prostheses,” which would allow the surgeon to address the conductive and the sensorineural components in a patient with a mixed hearing loss. Even with these innovations, however, the surgeon must continue to assess each patient on an individual basis, alter the surgical technique based on those findings, and adhere to the basic principles of chronic ear surgery.