title: New total ossicular replacement prostheses with a resilient joint:  experimental data from human temporal bones.
abstract: OBJECTIVE
  New flexible total ossicular prostheses with an integrated microjoint can compensate for large static displacements in the reconstructed ossicular chain. When properly designed, they can mimic the function of the joints of the intact chain and ensure good vibration transfer in both straight and bent conditions.
  
  
  BACKGROUND
  Prosthesis dislocations and extrusions are frequently observed after middle ear surgery. They are mainly related to the altered distance between the coupling points because of large static eardrum displacements.
  
  
  METHODS
  The new prostheses consist of 2 titanium shafts, which are incorporated into a silicone body. The sound transfer function and stapes footplate displacement at static loads were evaluated in human temporal bones after ossicular reconstruction using prostheses with 2 different silicones with different hardness values. The stiffness and bending characteristics of the prostheses were investigated with a quasi-static load.
  
  
  RESULTS
  The sound transfer properties of the middle ears with the prostheses inserted under uncompressed conditions were comparable with those of ears with intact ossicular chains. The implant with the soft silicone had improved acoustic transfer characteristics over the implant with the hard silicone in a compressed state. In the quasi-static experiments, the minimum medial footplate displacement was found with the same implant. The bending characteristics depended on the silicone stiffness and correlated closely with the point and angle of the load incidence.
  
  
  CONCLUSIONS
  The titanium prostheses with a resilient joint that were investigated in this study had good sound transfer characteristics under optimal conditions as well as in a compressed state. As a result of joint bending, the implants compensate for the small changes in length of the ossicular chain that occur under varying middle ear pressure. The implants require a stable support at the stapes footplate to function properly.
authors.affiliation: Department of Ear, Nose and Throat Diseases, Vilnius University Emergency Hospital, Vilnius, Lithuania. arechvo@gmail.com
authors.forename: Irina
authors.initials: I
authors.lastname: Arechvo
authors.forename: Matthias
authors.initials: M
authors.lastname: Bornitz
authors.forename: Nikoloz
authors.initials: N
authors.lastname: Lasurashvili
authors.forename: Thomas
authors.initials: T
authors.lastname: Zahnert
authors.forename: Thomas
authors.initials: T
authors.lastname: Beleites
mesh_terms: D001672:Biocompatible Materials; D003054:Cochlear Implants; D004429:Ear Ossicles / Q000601:surgery*; D006801:Humans; D011474:Prosthesis Design; D019919:Prosthesis Implantation; D012828:Silicones; D013016:Sound; D013701:Temporal Bone / Q000000981:diagnostic imaging / Q000601:surgery*; D014025:Titanium; D014463:Ultrasonography; D014732:Vibration
chemical_list: D001672:Biocompatible Materials; D012828:Silicones; D014025:Titanium