What is the Best Earmold for Narrowed, Curvy, Stiff Canals?

Question

What is the best earmold for narrowed, curvy, stiff canals?

Answer

In my clinical experience a canal style earmold with a short canal made with a "not too soft" material (e.g. Lucite) works the best for these challenging cases. Given the variables associated with skin turgor, however, special materials may also need to be considered. It's best to consult with your preferred earmold lab when making those decisions. In some extreme cases, the canal may be so narrow, that the only coupling option may be a tube fitting.

Since there are no published norms (that I know of) on what constitutes a narrow, curvy or stiff ear canal, I took this question to Chue Yang, the manager of the Unitron manufacturing facility in Plymouth, Minnesota. Chue has more than 20 years of experience making shells and earmolds, which makes him a real expert in building earmolds for unusual ear canals. Here are some considerations Chue shared with me:

• Very Narrow Ear Canal: Usually a collapsed canal that is smaller than the minimum BTE tube diameter of 2.5mm or less in considered "very narrow". For these patients we typically cannot build earmolds, as the tube cannot go beyond the narrowness of the canal. The professional should keep a couple things in mind before ordering an earmold for a very narrow ear canal
  
  
  1. Units that fall into this category are around 1% of total earmolds. Fortunately, they are fairly rare.
     
     
  2. We usually advise customers that we cannot build an earmold for these rare cases, as the remake percentage is pretty high. Therefore, we recommend some type of a tube fitting, perhaps using an open or closed dome.
     
     
  3. If the hearing professional really needs a custom earmold for these cases, see points 3 to 5 below.
  
  
• Narrow Ear Canal: anything that is 2.7mm - 3mm in diameter any where on the canal would be considered a "narrow" ear canal. Here are 5 things to think about when ordering an earmold for a narrow ear canal:
  
  
  1. About 4 to 5% of the impressions we see fall into this category (mainly pediatrics or adults with small ears canals)
     
     
  2. The standard remake rate for earmolds for narrow ear canals is around 5 to 6% within 30 days.
     
     
  3. Use blue silicone ear impression material (less expansion)
     
     
  4. Earmold material: I prefer using a 70 Shore silicone (not too soft as it has to go through the canal at its tightest spot),
     
     
  5. Canal length: This largely depends on where the narrowest point is. I usually like a longer canal on the ear impression to see what the end looks like. If the narrowness does not open up, we usually cannot build the product. If the canal does widen to a outer diameter of 2.7 to 3.0mm we can build an earmold that various lengths. In general, a short canal length is advised.
  
  
• Average Ear Canal: anything 3.0mm and larger - No issues. You can order whatever canal length and material you need.

As you can see from Chue's response, there is a mix of art and science involved in your ordering decisions for narrow, curvy and stiff canals. The bottom line is that you need to carefully examine the ear impression before sending it in. If the canal falls into the narrow or curvy category, you will have to work closely with your preferred earmold lab to get the order right and minimize patient burden.

Brian Taylor, Au.D., is the Director, Practice Development & Clinical Affairs for Unitron. Brian is responsible for all Unitron initiatives related to enhancing our customer's expertise, professionalism, and effectiveness in the areas of hearing aid fitting, product selection, and practice development. He manages the Unitron Unite customer loyalty program. Brian earned his Au.D from Central Michigan University and has over 15 years of clinical and practice management experience.