Tympanoplasty

Anatomy and Physiology

The middle ear cleft, also known as the tympanic cavity, is situated within the petrous temporal bone. The anatomical components of the middle ear include the inner layer of the TM, the Eustachian tube orifice, and the ossicular chain (malleus, incus, stapes). The middle ear cleft communicates posteriorly with the mastoid air cells via the tympanic antrum and the aditus ad antrum; the Eustachian tube connects anteriorly with the nasopharynx, allowing the middle ear to equalize pressure with the ambient environment.

The TM forms the majority of the lateral wall of the middle ear cleft. It is composed of three layers, the stratified squamous epithelial outer layer that is in continuity with the external ear canal, the fibrous stratum (lamina propria) middle layer, which is the most dominant component and provides stability to the TM, and an inner layer that is contiguous with the cuboidal mucosa of the middle ear. Within the fibrous stratum runs solid collagen fibers – it is the limited ability of these fibers to stretch that allows for high compliance with minuscule displacements of acoustic pressures but resistance (low compliance) to additional stretching at higher pressures. The TM diameter is around 10 mm, with a thickness of roughly 0.1 mm; it is usually pearly grey and slightly translucent, allowing for ossicular visibility.[11]

The TM divides anatomically into the pars flaccida superiorly and the pars tensa inferiorly. The pars flaccida is anterior and posterior to the malleolar ligaments; it lacks a central fibrous layer and is, therefore, thinner and more compliant than the pars tensa. The pars tensa forms the majority of the TM, overlying the area below the neck of the malleus.[5] In clinical practice, the TM is further subdivided into four quadrants separated by two imaginary lines, one running horizontally through the umbo and another perpendicular line straight down the malleus handle. For otologic surgeons, familiarity with the complex spatial relations of the components of the middle ear is essential, and surgery is often influenced by both the functional and anatomical characteristics of the middle ear.[5]

Functionally, the TM is the vibrational driver of the middle ear apparatus. Sound energy, in the form of air pressure waves, is transmitted from the TM across the ossicular chain to the fluid-containing inner ear via the oval window, producing a ‘liquid wave.’[12] The role of the TM and ossicular chain is to amplify sound energy and transmit this amplified signal to the cochlea, which converts this mechanical energy into electrical nerve impulses via specialized cells (hair cells) organized tonotopically along the basilar membrane. These impulses are then transmitted to the brainstem via the cochlear nerve.

Indications

The goal of tympanoplasty is to reconstruct the TM with or without reconstruction of the ossicular chain, thereby preventing recurrent infections (otorrhoea) as well as restoring hearing. Indications are primarily CSOM or CSOM with cholesteatoma.[2] Iatrogenic perforation in pediatric patients undergoing ventilation tube insertion for otitis media with effusion has also been documented in the literature as an indication for tympanoplasty.[13] Traumatic TM perforations inflicted by mechanical trauma that do not heal (typically, acute perforations heal without treatment in around 80% of patients) may also warrant repair.[5]

Contraindications

Contraindications for tympanoplasty can be categorized into relative or absolute. Relative contraindications include patient age (extremities of age), a non-functioning Eustachian tube, dead (non-hearing) ear or consideration of tympanoplasty in the patient’s better hearing ear. Absolute contraindications include uncontrolled cholesteatoma, uncontrolled complications or sequelae of otitis media such as intracranial abscess, meningitis or lateral sinus thrombosis, malignancy, or patient-specific anesthetic contraindications.[14]

Equipment

The following equipment may be needed to perform a tympanoplasty:

• Microscope
• Otology instrument tray

If the tympanoplasty is being performed endoscopically, the following may also be required:

• High-resolution camera, light source, monitor
• A rigid endoscope (0, 30, and 45 degrees)[15]

Personnel

The personnel required to carry out a tympanoplasty include:

• An otologist
• An anesthetist
• Scrub team

Preparation

Prior to surgery, a number of investigations assessing middle ear functionality are undertaken – the results can, in turn, influence both the tympanoplasty technique used and also the postoperative outcome.

Initially, any patient presenting with otorrhoea and hearing loss should undergo a complete history and examination, including a focused head and neck examination and examination of the ear using an otoscope/microscope. This will yield important information regarding TM perforation size, location (categorized into a quadrant, as mentioned previously), otorrhoea ('wet' or 'dry'), and whether there is active inflammation present. Tuning fork evaluation (Rinne and Weber tests at 512 Hz), pure tone audiometry (PTA) with speech discrimination, and tympanography should be performed before and after surgery for comparative evaluation of the difference between air and bone conduction thresholds (air-bone gap).[16][9]

Imaging is rarely required in simple tympanic membrane perforations, but if required, computed tomography (CT) is the preferred imaging modality.[7] CT scanning of the temporal bone is frequently employed for planning the surgical management of cholesteatoma.[17]

As well as assessing the middle ear clinically, the use of questionnaires measuring health-related quality of life outcomes is increasing for patients undergoing tympanoplasty.[9] Most validated questionnaires measure four dimensions: physiological complaints, psychological health, functional impairment, and impact on day-to-day life and interpersonal relationships. Currently, they do not form a mandatory part of the pre-operative workup for tympanoplasty; however, the continuous developments in psychometric measuring techniques will likely yield scientifically sound and reliable conclusions in the future.[9]

Prior to surgery, patients will consent to tympanoplasty. Risks include pain, bleeding, infection, failure of the graft, recurrence, further surgery, worsening hearing loss or deafness, dizziness, and facial nerve injury resulting in facial palsy or to the chorda tympani nerve resulting in taste disturbances. The procedure is typically performed under general anesthetic, and patients will have an opportunity to speak with an anesthetist prior to surgery.

Technique or Treatment

The majority of middle ear surgery involving the TM is classically performed using a postauricular approach; endaural (through the ear canal) and transcanal approaches are also used. Each technique has advantages as well as limitations and factors that are considered when deciding which approach to use, including the size of the TM perforation, the size of the ear canal, and the preference of the surgeon. As in other surgical fields, a trend towards more minimally invasive techniques has made trans-canal or endoscopic ear surgery increasingly popular.[5][15]

Standard theatre preparations are undertaken regardless of the tympanoplasty technique used. Prophylactic antibiotics are commonly administered (although less so during endoscopic surgery). The patient lies supine on the operating table; a head ring is used to provide stability. If required, the patient’s hair will be shaved in the postauricular region. Local infiltration (lidocaine with adrenaline) is administered, and local hemostasis must be achieved.[15] The ear canal is examined and cleaned as necessary, and the TM perforation and ossicles are assessed under microscopic or endoscopic vision prior to commencing the procedure.

Grafts

Autologous material for grafting is readily available, biocompatible, and inexpensive; hence there is limited rationale for utilizing artificial alternatives. Autologous grafts are usually made from temporal fascia or tragal/conchal perichondrium; however, studies have also reported using fascia lata, canal skin, and periosteum.[2] Advantages of using alloplastic grafts such as acellular dermal matrix and absorbable gelatin sponge primarily include the reduced morbidity associated with harvesting autologous grafts, namely less pain and improved cosmetic outcome with no additional scarring.[18] However, the cost implication of using these grafts and the risk of infectious disease transmission may mitigate the advantages mentioned above. In practice, autologous grafts are the preferred type to use by many otologists.[18]

Most surgeons use the temporalis fascia more commonly used in practice than cartilage, and success rates of using this graft in tympanoplasty range between 93% to 97%. However, in situations calling for increased stability, such as multiply-recurrent perforations or high-risk patients, cartilage and perichondrium can be harvested by making an incision through the medial side of the tragal skin, perichondrium, and cartilage.[18][5] While the use of cartilage has been found to be more successful than temporal fascia, mostly because its high tensile strength makes it more resistant to shrinkage, occasional doubts have been raised regarding sound conduction properties due to its rigid quality (resulting in a potential mild, low-frequency, conductive hearing loss from a mass effect)[19] and potential to be misidentified as cholesteatoma postoperatively.[5][18]

Microscopic Approach

When using a microscope, the postauricular and trans-canal approaches are frequently used for tympanoplasty. The Lempert endaural approach is far less commonly used in modern tympanoplasty but remains a viable option. The procedure starts with the surgeon making a semicircular incision roughly 1cm posterior to the auricle skin fold; the ear is folded anteriorly. This incision is carried down through the musculoperiosteum creating a musculoperiosteal flap, which is elevated towards the membranous ear canal, thereby entering the bony ear canal. The skin along the posterior aspect of the bony canal is elevated until the surgeon reaches the tympanomeatal flap incisions. The tympanomeatal flap can then be raised, and the middle ear can be entered.[16] 

At this stage, if required, the ossicular chain can be repaired by performing an ossiculoplasty.[16] The TM perforation edge is freshened with scissors or cup forceps. An underlay technique, whereby the limbus is undermined, the TM is lifted, and the perforation is covered with a graft medially, is used to reconstruct the TM.[2] For optimum chances of success, the autologous graft should cover both the TM defect while also being anchored to the ear canal for stabilization. Care should be taken to avoid damaging the chorda tympani in the posterior region when elevating the limbus from its bony sulcus.[2]

Endoscopic Approach

Endoscopic repair of TM perforations is less invasive than traditional postauricular and endaural approaches. It can provide a wider view of the middle ear anatomy without making external incisions, reducing operative and recovery time.[15] Studies have demonstrated similar perforation closure rates and audiologic recovery compared with microscopic tympanoplasty.[20] Disadvantages of endoscopic middle ear surgery include surgical manipulations being performed with one hand and the potential harm caused by heat production from the endoscope’s light source to surrounding structures.[15]

Endoscopic tympanoplasty is performed using a transcanal approach. As before, the edges of the perforation are de-epithelized as necessary. An incision is made in the ear canal (endaural, lateral circumferential, or swing door), allowing the tympanomeatal flap and annulus to be elevated, creating access to the middle ear. The malleus is peeled off the TM, and at this stage, the ossicular chain is repaired (ossiculoplasty) if required. The prepared graft is placed medially to the TM remnant and lateral to the malleus. Gel foam sponges are inserted into the middle and outer ear canals.[15] More recently, a ‘butterfly cartilage tympanoplasty technique’ has been described in the literature, which does not require a tympanomeatal flap to be raised. After creating cartilaginous pseudo-flanges, a graft is placed into the perforation, with one flange medial to the TM and the other lateral. Once a satisfactory position has been achieved, gel foam sponges are arranged around the border of the graft.

Complications

Studies have shown tympanoplasty to be successful in over 93% of patients (in patients undergoing primary tympanoplasty using temporalis fascia graft).[18] However, like any surgery, complications can occur. The predominant complications of tympanoplasty include recurrence (this includes failure of the graft), conductive hearing loss, TM perforation, and intra-operative or postoperative ventilation tube insertion.[21] 

One large case series analyzing over 1000 patients undergoing cartilage tympanoplasty reported recurrence of TM perforation in 3.6% to 4.2% of patients (patients with cholesteatoma and high-risk perforations respectively) and conductive hearing loss requiring revision in 1.9% (high-risk perforations with/without patients with cholesteatoma) to 11% of patients (patients undergoing TM repair to improve hearing).[21] Aside from the approach and graft choice, key contributing factors that can influence the postoperative outcome include patient comorbidities such as diabetes, smoking, and immunosuppression.[1]

There are important neural structures that cross the middle ear, namely the facial nerve and chorda tympani. The facial nerve runs within the temporal bone and continues along the posterior wall of the tympanic cavity, superior to the oval window. Iatrogenic injury to the facial nerve is fortunately low due to the extensive training of otology surgeons performing tympanoplasty. The chorda tympani will always be confronted during middle ear surgery, and in CSOM with cholesteatoma, it may have to be sacrificed in order to get full disease clearance.[5]

Clinical Significance

Since the 1950s, tympanoplasty has been performed in patients with CSOM with the aim of reducing infection recurrence and refining hearing and, in turn, improving social development and quality of life. Methods of tympanoplasty have evolved over time; however, despite the increase in uptake of endoscopic middle ear surgery, a postauricular approach using an autologous graft is still the predominant surgical method in many centers.

Enhancing Healthcare Team Outcomes

Managing patients with CSOM requires an interprofessional team composed of otologists, audiologists, radiologists, anesthetists, and nurses. Timely diagnosis and meticulous surgical planning are essential for optimal patient outcomes, including reduced infection rates and improved hearing. In pediatric patients, hearing impairment may profoundly impact speech and language development, and coordination with speech therapists may also be warranted pre and post-operatively. Nurses will assist in patient assessment, coordinate activities among the various specialists, assist in surgery, and offer patient counseling. All interprofessional team members must maintain accurate and updated records so that everyone involved in care has access to the same patient data to guide therapy decisions. The interprofessional model will yield the best patient outcomes with the fewest adverse events.