Ear Center: Kraus K-Helix Prostheses

Kraus K-Helix Prostheses for Ossicular Reconstruction

  • Ossicular Prosthesis Having Helical Coil. U.S. Patent #8,057,542 B2.
    Date of patent = November 15, 2011. Int. Cl. A6IF 2/18, H04R 25/00, U.S. Cl. 623/10; 600/25. Field of Classification Search 623/10; 600/39, 25.
  • FDA and CE Mark clearance (approved)
  • The Kraus K-Helix Crown and Kraus K-Helix Piston prostheses received FDA clearance in April 17, 2008,
    510K = # K080070
  • Glass ionomer cement is approved by the FDA for use in the middle ear

Navigate this page. Find hearing results and watch videos of implant technique.

Kraus K-Helix Design
Basic Principles of the Kraus K-Helix Prostheses
Kraus K-Helix Prostheses - implant configurations
Kraus K-Helix Sales Sheet
Hearing Results with Kraus K-Helix Crown
Watch videos of Kraus K-Helix Implant Technique
Grace Medical order reference numbers
Glass ionomer cement - Fuse

Watch videos of how to implant the K-Helix prostheses

Kraus K-Helix PrototypeKraus K-Helix Design

The Kraus K-Helix Prostheses (endohelix prostheses) are novel, titanium middle ear prostheses that have been designed specifically for reconstruction of the human ossicular chain (tiny hearing bones located in the middle ear). When used with middle ear cements, such as glass ionomer cement, endoskeletal ossicular reconstruction is possible. The proximal conic helix design permits cement to "flow" around the coils. The prosthesis serves as a reinforcing "endoskeleton" for the cement similar to steel rods/mesh (rebar) that reinforce concrete. The unique design permits the prostheses to be adjusted in the X-X axis (by expanding the proximal conic helix to increase length or by removing extra coils with a malleus nipper), Y-Y axis (by expanding the cylindrical helix of the K-Helix Piston), and the Z-Z axis (by bending between junction between the conic helix and crown (K-Helix Crown) or between the conic helix and cylindrical helix (K-Helix Piston).


The purpose of the Kraus K-Helix prostheses is to help restore hearing in patients with conductive or mixed conductive-sensorineural hearing loss due to diseased, fractured, or absent middle ear bones (ossicles - the malleus (hammer), incus (anvil), and stapes (stirrup). The K-Helix prostheses serve as "connectors" to connect the middle ear bones to each other, restore anatomy to a more normal anatomic configuration, preserve lever ratios, and avoid conventional PORP/TORP platform contact with the tympanic membrane.

  • Kraus K-Helix Crown: used to connect incus-to-stapes or malleus-to-stapes
  • Kraus K-Helix Piston: used to connect incus-to-footplate or malleus-to-footplate (may be used with a mobile or fixed footplate), also may be used incus-to-neomembrane or malleus-to-neomembrane in revision stapedectomy cases.

In contrast to standard middle ear prostheses called PORP's (partial ossicular replacement prostheses) and TORP's (total ossicular replacement prostheses), the K-Helix prostheses do not require interfacing with the tympanic membrane (eardrum). The prostheses may be used with or without middle ear cements to provide stable connections. Cement use is dependent on anatomic conditions within the middle ear at the time of ossicular reconstruction.

Helix Crown Final Prototype Helix Crown Size Compared to Dime Helix Crown with Cement
K-Helix Design Permits Adjustability Size Compared to U.S. Dime K-Helix Crown with GI Cement


Basic Principles of the Kraus K-Helix Prostheses

  1. reconstruct the ossicular chain by restoring middle ear anatomy as close to normal as possible
  2. provide enhanced stability over that achievable by conventional partial or total ossicular prostheses
  3. achieve maximum ossicular motion without tension or bias
  4. achieve long-term hearing restoration
  5. be used with our without middle ear cements, depending on individual patient anatomy and middle ear status eliminate contact with the tympanic membrane, crimping, and cartilage grafts
  6. provide maximum adjustability and custom fit without the need for specialty instruments such as jigs, crimping forceps, etc.
  7. be MRI compatible
  8. be used with a mobile stapes (K-Helix Crown) or a mobile/immobile footplate (K-Helix Piston)
  9. be used Incus-to-Stapes or Malleus-to-Stapes (K-Helix Crown) or Incus-to-Footplate or Malleus-to-Footplate (K-Helix Piston)
  10. Using the K-Helix prostheses and cement for "endoskeletal reconstruction", the surgeon is able to custom the framework (prosthesis) to the patient's anatomy and "construct" the final prosthesis in the middle ear by coating the prosthesis with cement.

Kraus Endohelix Middle Ear Prostheses - Implant Configurations

Four titanium, middle ear prostheses invented to reconstruct the ossicular chain. Implant procedures begun in July, 2008. Licensed to Grace Medical Corporation, Memphis, TN., the manufacturer of the Kraus K-Helix Prostheses.

  1. Kraus K-Helix Crown: for incus-to-stapes and malleus-to-stapes reconstruction
  2. Kraus K-Helix Piston: for incus-to-footplate and malleus-to-footplate reconstruction (mobile or fixed footplate), may also be used incus-to-neomembrane or malleus-to-neomembrane in cases of revision stapedectomy
  3. Kraus Twister Crown: for TM-to-stapes reconstruction (in development)
  4. Kraus Twister Shoe : for TM-to-footplate reconstruction (in development)


1. Kraus EM, Christopher JY. Endoskeletal Ossicular Reconstruction Using the Kraus K-Helix Crown and Piston Middle Ear Prostheses. ORL Head Neck Nursing 2010;28(4):8-16.
2. Berenholz LP, Burkey JM, Lippy WH. Hearing results in reconstructing the damaged incus with varying lengths of the modified Lippy prosthesis. Otol Neurotol 2011;32 (January):17-20.

Grace Medical Corporation order reference numbers

(Kraus K-Helix Crown and Kraus K-Helix piston available, FDA clearance, CE Mark obtained)
1. Kraus K-Helix Crown: Ref. = order #756-300
2. Kraus K-Helix Piston Ref. = order #757-300
3. Dornhoffer Footplate shoe 0.6mm (to use with Kraus K-Helix Piston): Ref. = order # 636-060

Glass ionomer cement (GIC), call Fuse, is available from Grace Medical Corporation. The cement is packaged in capsules. Capsules are hand activated by removing a protective shield and pushing an activator pin. Once activated, the capsule is placed in a shaker (similar to a paint mixer) and is vibrated for 10 seconds. Once shaken, the capsule is placed in an extruder tool and is expressed from the capsule. All necessary GIC equipment above is available from Grace Medical.

Grace Medical Corporation
8500 Wolf Lake Drive
Memphis, TN  38133
Fax: 901-386-0950
Web: www.gracemedical.com

Kraus K-Helix Prostheses Information Sheet:

Cone Health System, Greensboro, NC, MD Journal K-Helix Article, September 2008:

Reference: MD Journal, The Moses H. Cone Memorial Hospital, MD Journal, K-Helix Article, Sept. 2008, Greensboro, NC, Vol. 6(3), Fall 2008, 6-7. Posted on our web site with the permission of the Moses Cone Health System.1


Last revised September 7, 2020