Overview of Ossiculoplasty
Ossiculoplasty is a surgical procedure that’s concerned with the tiny bones in your ear that help you to hear. These bones, known as ossicles, can sometimes be broken or misaligned which leads to a loss of hearing. This problem can contribute to around 55% cases of conductive hearing loss, a type of hearing loss where sound can’t pass properly from the outer ear to the inner ear.
Our ability to hear depends on a lot of factors, like our unique body structure. The tiny bones in the ear that make up the ossicular chain are especially important for our hearing. Due to the complex nature of these bones, reconstructing them in a surgery can be rather tricky. The ossicular chain has two important joints that allow flexibility and protect the inner ear. Modern techniques in ossiculoplasty offer ways to replace these two joints with prosthetic bones. However, these techniques come with risks like further loss of hearing and potential movement of the prosthetic bones.
The majority of ossicular chain disorders usually affect one particular bone in the chain called the incus. These disorders can be caused by a variety of factors including diseases of the ear (like Cholesteatoma and Otitis media), physical trauma, birth defects, and sometimes they can simply occur without any known cause.
Doctors first attempted an ossiculoplasty way back in 1901. Over time, doctors have continually updated the classification of ossicular defects, contributing to better treatment options. Still, finding the best middle ear implant for surgery is challenging. A range of materials, both biological and synthetic, are used for the implants. These include materials like ossicles, cartilage, ceramics, and titanium.
Your hearing works by changes in the density of air particles creating sound energy. This sound energy travels into your ear where it meets a substance called ‘perilymph’, a fluid in your inner ear. If the ossicles weren’t there to help the sound energy move from the air to the fluid, most of it would simply bounce back, leading to hearing loss. This is facilitated by a part of your ear called the ‘ossicular chain’. The surface-area ratios within the ear and length differences in the ossicular chain both contribute to helping match this change from air to fluid.
The success of an ossiculoplasty depends on factors like what disease is causing the hearing loss, the materials used in the surgery, and the surgeon’s experience. Though this process has evolved over time, achieving perfect restoration of natural hearing remains a challenge.
Anatomy and Physiology of Ossiculoplasty
The ossicles, which include the malleus, incus, and stapes are tiny bones present in the middle part of our ears. They play a crucial role in helping us hear by converting sound energy into something our brain can understand. These tiny bones are dynamized by the tympanic membrane, also known as our eardrum, which picks up sound energy and sends it through these ossicles and into the cochlea. The cochlea is filled with fluid and its job is to convert these vibrations into electrical signals that our brain can interpret as sounds.
In terms of their development, the malleus and incus originate from the Meckel cartilage of the 1st pharyngeal arch, while the stapes comes from the Reichert cartilage of the 2nd pharyngeal arch. Each of these bones has a specific structure and is held together by a series of ligaments, muscles, and other attachments that keep them in their proper places within the middle ear.
When sound enters our ears, it causes the ossicles to vibrate. These vibrations are then transformed into electrical signals by the cochlea. Contrary to popular belief, the movement of the stapes, which is one of the ossicles, is not always linear like a piston, but shows different vibration patterns and characteristics.
The middle ear also contains muscles, like the tensor tympani and stapedius, which play a role in protecting our ears from harmful loud sounds. These muscles attach to the ossicles and help to stabilize them. If these muscles are damaged or lost due to illness or surgery, their protective function can’t be restored.
Our ability to hear relies on two main aspects: the conversion of sound energy to an electrical format that our brain can understand, and the protection of our physical ear structures from excessive sound energy. The complex interplay of several factors during an ossiculoplasty, a surgery to repair the ossicles, aims to achieve these two aspects. Patient’s pre-existing health conditions, tension of the prosthesis placed, angles, remaining ossicle parts, and the stage of surgery, amongst others, can influence the success of the surgery.
The timing of ossiculoplasty is a controversial topic. Delaying may be considered in cases where the disease is not fully removed yet, or in cases where more aggressive surgical techniques are applied. In any case, preserving the chain of ossicles in our ears is crucial for converting sound energy properly. If this chain is broken, sounds will not effectively reach our inner ear, resulting in a significant decrease in our ability to hear.
The process of transmitting sound from the outside world to our inner ear is carefully balanced by the middle ear. It amplifies sound vibrations by about 25 times, incentivizing a pressure gain. This careful balance is achieved through a combination of the size difference between the eardrum and stapes footplate and the lever action of this chain of ossicles.
The ear drum is an important component acting as a bridge between the outer and middle ear, it helps in amplifying sound energy, protects the ear from infections, and ensures smooth communication with the Eustachian tube (a tube connecting the middle ear to the upper part of the throat). If the continuity of the ossicular chain or ear drum are damaged, it can be restored through ossiculoplasty. However, replicating the natural lever effect – that helps to amplify the sounds – is still beyond current medical technology.
Why do People Need Ossiculoplasty
Ossiculoplasty is a type of surgery that aims to restore and improve hearing in people who have conductive hearing loss. Conductive hearing loss happens when the normal process of sound passing through the outer ear to the middle ear and then to the inner ear is blocked or reduced. This surgery can be quite intricate and doesn’t always completely restore normal hearing, but it can significantly improve a patient’s ability to hear, particularly when having a conversation.
Why is this surgery important? Well, when someone has long-term conductive hearing loss, it can lead to other issues such as problems with language development, cognitive abilities, and learning. However, the surgery is most successful when the patient notices an improvement in their hearing that matches the quality of their better-hearing ear. Special factors to consider include if the patient has hearing loss in both ears and whether the patient is a child, as children have smaller ear structures and are more likely to experience certain medical conditions or have accidents that might affect hearing.
Doctors decide whether to perform a ossiculoplasty based on a careful look at a patient’s specific medical condition and how severe the disease is. Sometimes, it might be more critical to focus on removing a cholesteatoma, which is a skin growth that occurs in the middle ear, or achieving a dry, healthy ear before attempting to restore hearing. If a person has had this type of surgery before without success, doctors usually suggest waiting at least 6 months before considering another surgery to give the ear proper time to heal. Alternative options like conventional hearing aids and bone-conduction devices should also be considered.
It’s important to note that conditions like chronic inflammation of the middle ear, complications such as cholesteatomas, and the erosion of the ossicles (the three tiny bones in your ear) account for more than 80% of cases where the ossicular chain has been disrupted. The remaining cases usually result from blunt force or penetrating trauma, or conditions like absence of ossicles and middle ear tumors. Out of all the ossicles, the incus (shaped like an anvil) is most commonly involved, followed by the stapes (the stirrup-shaped bone).
This surgery is best done when the middle ear environment is stable and clean. If there are ongoing problems such as negative middle ear pressure, inadequate growth of air cells in the mastoid bone, build-up of fluid, or Eustachian tube dysfunction, this can interfere with the success of the surgery by negatively impacting the transmission of sound. It’s worth noting that the presence of a recurring cholesteatoma may also undermine the success of the surgery, so it’s crucial that any pre-existing conditions are managed correctly before or during the procedure.
When a Person Should Avoid Ossiculoplasty
One of the biggest reasons doctors might hold off on a certain type of ear surgery, called ossicular chain reconstruction, is if the patient has what’s called acute otitis media. Essentially, this is a fancy term for a really bad ear infection. If a person has this kind of infection, the surgery may be delayed until the infection has cleared up. If not, the infection can lead to complications, like poor healing abilities due to buildup of fluid or pus, damage to the inside lining of the ear, or problems with the Eustachian tube (the tube that connects your ear to the back of your nose). It could also possibly cause the prosthetic used in surgery to be pushed out of the body, which is not ideal.
There are other conditions, like chronic otitis media (which is an ongoing ear infection) or cholesteatoma (an abnormal skin growth in the middle ear), that might mean delaying the surgery, but these are not absolute reasons to not do the surgery. Other factors that might limit the success of the surgery, like not having enough space in the middle ear, past unsuccessful surgeries with similar types of implants, or issues with the small bone in the ear called the stapes, might mean that the surgery would likely not improve hearing as much as hoped.
Another thing to consider is the patient’s overall health and age. If a patient is at high risk for complications from surgery or anesthesia, especially those who are categorized as class III or above by the American Society of Anesthesiologists, the ear surgery might be put on hold. Instead, the doctor might recommend using hearing aids or simply waiting and monitoring the situation.
Equipment used for Ossiculoplasty
Ossiculoplasty is a surgery that enhances hearing abilities. It has a success rate of 75% for a procedure referred to as PORP and 68% for another called TORP, within the initial year to year and a half. The success rate at five years for PORP drops to 66%, and for TORP, it drops to 33%. One part of this surgery that has been debated for decades is whether to use natural body materials or man-made synthetic materials for building the prosthesis, which is the artificial part replacing the damaged portion.
For this surgery, the equipment required includes a special microscope used in operations, a specific drill with bits for carving out body tissue grafts, a holder for tiny bones, an instruments tray specifically for ear surgeries, and the prosthesis or artificial part.
Natural body materials, known as autografts, have been used in this type of surgery since 1957. The advantages of autografts include a lower risk of rejection by the body. The most commonly used autograft is a part of a small bone in the ear called the incus, which has the important advantage of being readily available and can be used right away. But, autografts have downsides too. For instance, there might not be enough available bone if the disease has caused significant erosion. Also, the process of carving the graft can eat up more operation time. And, there could be future resorption due to bone inflammation and potential diseased tissue left behind.
Artificial synthetic prostheses have largely replaced natural grafts due to their ready availability, flexibility, and long life. A survey showed that 70% of ear specialists opted for synthetic materials over bone or cartilage. However, there has been no significant difference in hearing improvement observed between using autografts or synthetic prostheses.
Synthetic absolutes can be categorized into three groups:
- PORP – This type connects an intact part of a small bone in the ear called stapes to the malleus (another small bone) or the eardrum.
- TORP – This type connects the base of the stapes to the malleus or the eardrum.
- Incus-interposition or incus-replacement prosthesis:
- Incus-interposition is used when a part of the incus is compromised. This type connects the top of the stapes to the remaining part of the damaged incus.
- An incus-replacement prosthesis is used when the entire incus is missing. The prosthesis is placed between bones in the ear called the manubrium and the stapes.
The first synthetic prostheses were used in 1952, made of vinyl-acryl plastic. In recent times, they have been made from different materials like plastics, metals and other materials also found in nature. But, these materials must stay inactive in the middle of the ear to prevent reactions that can lead to bone damage. Some materials also come with their own disadvantages, like causing inflammation, degradation, and displacement.
The best material perceived so far is hydroxyapatite, the mineral part of bone. It has many benefits, including safety, cost-effectiveness, and easy usage. It is made up of a substance called calcium phosphate ceramic, which is similar to bone mineral and is highly compatible with the body. But hydroxyapatite is also brittle and can be difficult to sculpt and place. Titanium, being lightweight, rigid, and compatible with the body, has recently become popular. Plus, it can be molded to fit different shapes easily.
The material known as bone cement is useful as an additional resource in the surgery. This substance is easy to prepare and apply, with rapid setting times and good body compatibility. Bone cement can be molded to augment the remaining tiny bone, thereby preserving it. Around 90% of patients who underwent reconstruction using bone cement have had their hearing improved to a closure of an air-bone gap by 20dB or more.
Ultimately, the materials used for ossiculoplasty are chosen based on the surgeon’s preference, the specific needs of the patient, and the availability of materials. Surgeons usually opt for the materials that provide the best results and are more readily available.
Who is needed to perform Ossiculoplasty?
An ossiculoplasty is a procedure performed by several healthcare professionals, each playing a crucial role. Here are the key individuals involved:
The otologic surgeon, who is a doctor specializing in diseases and surgery of the ears. Their role is to conduct the procedure itself.
An anesthesiologist, a doctor who administers medicines to keep you asleep and pain-free during the surgery. They also monitor your heart rate, breathing, and other vital signs during the procedure.
A surgical technician or operating room nurse also takes part in the process. They may help prepare for the surgery, assist the surgeon during the procedure, and are also trained to handle any equipment required during the surgery.
Lastly, there’s a circulating or operating room nurse. They help to ensure everything in the operating room runs smoothly. They may not directly take part in the surgery, but they make sure the surgical team has everything they need.
The combined skills and experience of these medical professionals help ensure the ossiculoplasty is safe and successful. They all work together to take care of you throughout the procedure.
Preparing for Ossiculoplasty
Before having a procedure known as an ossiculoplasty, which helps restore the function of damaged middle ear bones, doctors take into consideration your medical history, results of physical exams, and tests related to your hearing and head scans. Generally, you won’t need any lab tests or tissue samples taken. The doctor pays special attention to risk factors, especially when dealing with patients who can only hear from one ear or might experience complications with balance, brain or facial nerve issues, or have other health problems.
Every patient should go through a hearing test known as pure-tone audiometry. This examination helps to determine:
– The types of sounds you can hear without any instruments (air conduction) and with instruments that transmit sounds directly to your inner ear (bone conduction).
– The softest speech you can hear half of the time (speech reception threshold).
– How well you can understand speech when it’s loud enough to hear (speech discrimination).
– A test that measures the functioning of the middle ear (tympanometry).
– A test that measures your inner ear’s automatic response to sound (acoustic reflexes).
Doctors nowadays often use imaging in preparing for ear surgeries. A specific type of CT scan of the tiny bone on the side of the head (temporal bone) can help see bone imperfections and give a clear image of the chain of ear bones (ossicular chain). It can also highlight any disease of the eardrum or the bone behind the ear (tympanomastoid disease), which can affect the surgical plan. The downside is that these images can sometimes fail to tell the difference between different types of tissue changes.
In some cases, doctors use MRI to get a better view of the middle ear space, especially the chain of ear bones and the tube connecting the middle ear and throat (Eustachian tube). Combining this with a CT scan can provide additional valuable information.
Remember that you need to give your approval after being fully informed about the surgery. The process carries risks, such as bleeding, infection, displacement of the implanted ear prostheses, hearing loss, dizziness, changes in taste, facial paralysis, damage to the stability of an ear bone (stapes) leading to deafness, leaks in the inner ear (perilymphatic fistula), and the chance of needing more surgery in the future. There are also other ways to improve hearing, like conventional hearing aids or bone conduction devices, that don’t involve surgery.
How is Ossiculoplasty performed
Ossiculoplasty is a surgical procedure conducted to fix the bones in your middle ear, known as the ossicles. This type of surgery can be carried out under general anesthesia or intravenous sedation (medication given through a vein to help you relax) combined with local anesthesia depending on any additional procedures required during surgery.
If there’s a need to rid the middle ear or the mastoid (bone located behind your ear) of any disease, like conducting a tympanomastoidectomy surgery, then general anesthesia is used. There can also be continuous monitoring of your facial nerves during the operation. However, if the purpose of surgery is to restore the connection among the ossicles in a disease-free ear, then surgery can be performed using local anesthesia combined with intravenous sedation.
The ear is cleaned and draped in a germ-free way before the surgery begins. The middle ear can be reached either through the ear canal (transcanal approach) or behind the ear (postauricular approach). The latter method is mostly used if the patient has a narrow ear canal or significant bony outgrowths. It is also a preferred technique when there’s a need to perform a mastoidectomy surgery together with the ossiculoplasty.
In both methods, a local anesthetic is injected into the ear canal to numb the area and control bleeding. The exact location is picked out under an operating microscope to make sure the medication is delivered accurately.
The ossiculoplasty surgery involves elevating the tympanomeatal flap, which is a portion of tissue in the ear, to access the ossicles. This could be done using either of the aforementioned approaches: the transcanal or postauricular. If the ear canal is found to be too narrow during the surgery, a surgical drill is used to make it suitable for access to the middle ear.
The ossicles of the ear are properly evaluated for any defects and palpated to check their mobility. The most suitable artificial bone for replacing any damaged ossicle is then chosen. It’s important to accurately measure the size of the replacement bone so it fits better in the ossicle chain. A cartilage (tough but flexible tissue) can be acquired from the person’s ear to place over the prosthesis (artificial bone).
After the ossicular replacement (prosthesis) is placed, the tympanomeatal flap is put back to its original position. Cushioning around the artificial bone is also done using a gelatin sponge soaked in topical antibiotic drops to further stabilize it. Packing materials may be used in the ear canal to control bleeding and widen the canal which may have to be taken out after the procedure.
A special bandage is applied on the behind of your ear for pressure for about 24 to 48 hours. The doctor will usually give you ear drops containing antibiotics, and sometimes steroids, for several weeks postoperatively. Patients are also advised on specific care instructions for their ear. Regular follow-up visits are recommended to carefully clean the ear, only once it has healed adequately to prevent any infection or misplacement of the prosthesis.
Possible Complications of Ossiculoplasty
Ossiculoplasty is a type of ear surgery that can be carefully adapted to each patient’s unique needs. The surgery’s success can be difficult to define as it doesn’t always lead to improved hearing. Although medical technology has advanced considerably, the overall results of the procedure haven’t significantly improved. A successful surgery is generally considered as one where the difference between the loudest level of sound that can pass through the air and the loudness level that can pass through the bones – known as the air-bone gap – is less than 20 decibels.
This surgery may come with some risks, which include:
- Loss of or worsening of hearing
- Taste changes on the same side as the surgery
- Facial nerve paralysis
- Dizziness
- Holes in the eardrum
- Infections
- Ringing in the ears
- No improvement in hearing
It can be challenging to determine whether or not the surgery was successful, especially when the patient’s hearing does not improve. In some cases, patients may initially experience improvements, but later find that their hearing declines due to a variety of factors. These might include tissue death, shift or movement of an artificial ear bone (prosthesis), breakage of an inner ear bone, or a tear in the oval window of the inner ear, which can lead to complete hearing loss and dizziness.
Several factors can influence whether or not the surgery is successful, such as existing ear infections, type of artificial ear bone used, the condition of the natural middle ear bones at the time of surgery, the surgical technique, and the patient’s overall health. Problems like ear infections or the artificial ear bone shifting out of place can result in severe conductive hearing loss.
Issues like fluid buildup in the middle ear or problems with the artificial ear bone happen most often soon after the surgery. However, loss of hearing after an initial improvement might happen due to the recurrence of certain ear conditions, structure of the ear, or scarring around the artificial bone.
In 2001, a tool called the Ossiculoplasty Outcome Parameter Staging (OOPS) index was developed to predict the outcome of patient’s hearing after this surgery. This tool considers factors before and during surgery, such as existing ear drainage, condition of the middle ear lining, presence of a key middle ear bone, type of surgery performed, and whether it’s a new or recurring problem.
Using this index, doctors can predict the success of the surgery, identify patients at risk of complications, and even track improvement in surgical skills. It is also crucial for predicting both short-term and long-term hearing results. There are also other associated risk factors, including poor initial hearing results after surgery, absence of a key middle ear bone, the existence of diseases in the middle ear, smoking, and inability to equalize pressure in one’s ear.
To improve the success rate of ossiculoplasty, it might be more effective to delay the reconstruction of the middle ear’s bone structure in patients with severe diseases that might require more comprehensive ear and mastoid surgery. After surgery, patients are recommended to check their hearing using a hearing test at least once a year and undergo a detailed ear examination at the office to check for any recurrence of middle ear diseases.
If the patient continues to have poor hearing results after the surgery, the doctor will help identify the reason behind it, especially focusing on factors that can be corrected. In some cases, CT and MRI scans can further assist surgeons in evaluating the position of the artificial bone and investigate whether there are any ongoing diseases in the ear that could affect the surgery’s results. Depending on the situation, the patient might need to consider revision surgery.
What Else Should I Know About Ossiculoplasty?
Ossiculoplasty is a surgery that has been around since the 1950s, done to help people who have trouble hearing because something is wrong in the part of the ear called ossicular chain. This surgery has greatly improved people’s ability to speak, interact with others, and generally enjoy life. However, results vary – some people see a big improvement in their hearing tests, while others may not, and some people maintain these improvements long term while others don’t.
Doctors and scientists have invented a lot of different tools and techniques to use in this type of surgery over the years, but there isn’t one that everyone agrees is the best. One reason for this is that typically in this surgery, two joints are replaced with a type of artificial joint (prosthesis). This process is complex and can be particularly tricky with patients who have a disease called cholesteatoma – an abnormal skin growth in the middle ear.
Because of this complexity, more research is needed to find even better ways to fix the middle ear. And in order to give patients the best care possible, all healthcare professionals involved need a deep understanding of the ear’s structure and function, as well as the causes and treatment options for diseases, growths, and injuries in the middle ear.
