CT Evaluation of Prosthetic Ossicular Reconstruction Procedures: What the Otologist Needs to Know1
Jeffrey A. Stone, MD,
Suresh K. Mukherji, MD,
Brian S. Jewett, MD,
Vincent N. Carrasco, MD and
Mauricio Castillo, MD
1 From the Departments of Radiology (J.A.S., S.K.M., M.C.) and Otolaryngology (S.K.M., B.S.J., V.N.C.), University of North Carolina School of Medicine, Chapel Hill. Presented as a scientific exhibit at the 1998 RSNA scientific assembly. Received April 13, 1999; revision requested May 5 and received May 28; accepted June 1. Address reprint requests to J.A.S., Department of Radiology, Medical College of Georgia, 1120 15th St, Augusta, GA 30912-3910 (e-mail: jstone@mail.mcg.edu).
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Figure 1a. Ossicular replacement prostheses. (a) Drawing illustrates a PORP extending from the tympanic membrane (arrowhead) to the capitulum of the stapes (arrow). (b) Drawing illustrates a TORP extending from the tympanic membrane (arrowhead) to the oval window (arrow). The ossicles have been excised in these illustrations.
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Figure 1b. Ossicular replacement prostheses. (a) Drawing illustrates a PORP extending from the tympanic membrane (arrowhead) to the capitulum of the stapes (arrow). (b) Drawing illustrates a TORP extending from the tympanic membrane (arrowhead) to the oval window (arrow). The ossicles have been excised in these illustrations.
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Figure 2. Wire stapes prosthesis. Coronal CT scan shows a thin wire prosthesis (arrowhead) extending from the long process of the incus (white arrow) to the oval window (straight black arrow). The tympanic segment of the facial nerve is seen superior to the prosthesis (curved arrow).
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Figure 3. Piston prosthesis. Axial CT scan shows the distal medial portion of a piston prosthesis (curved arrow) articulating with the oval window (arrowhead). The prosthesis was placed for fenestral otosclerosis as seen at the fissula ante fenestram (straight arrow).
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Figure 4. Prosthetic subluxation. Axial CT scan demonstrates migration of the medial aspect of a Teflon wire stapes prosthesis (arrowhead) anteriorly from the oval window (arrow).
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Figure 5a. Prosthetic subluxation. (a) Coronal CT scan shows subluxation of the medial tip of a stainless steel piston stapes prosthesis (arrowhead) inferior to the oval window (arrow). (b) Axial CT scan reveals that the medial tip of the prosthesis is also anteriorly displaced (arrow). Correlation of axial and coronal CT findings is necessary to determine the exact location of a malfunctioning prosthesis.
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Figure 5b. Prosthetic subluxation. (a) Coronal CT scan shows subluxation of the medial tip of a stainless steel piston stapes prosthesis (arrowhead) inferior to the oval window (arrow). (b) Axial CT scan reveals that the medial tip of the prosthesis is also anteriorly displaced (arrow). Correlation of axial and coronal CT findings is necessary to determine the exact location of a malfunctioning prosthesis.
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Figure 6. Prosthetic extrusion. Coronal CT scan shows a stainless steel piston stapes prosthesis that has migrated from the middle ear cavity (arrowhead). The prosthesis is seen lateral to the tympanic membrane (arrow) in the external auditory canal. Surgery revealed perforation of the tympanic membrane and adherence of the prosthesis to the wall of the external auditory canal.
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> Deformed stapes prosthesis in a patient who experienced sudden conductive hearing loss. Axial CT scan shows a bent stainless steel prosthesis (arrowhead). The medial tip of the prosthesis (arrow) has become detached from the oval window. The prosthesis was replaced at surgery.
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Figure 8a. Vestibular perforation by a stapes prosthesis in a patient with chronic eustachian tube dysfunction and otitis media. (a) Axial CT scan shows a stainless steel prosthesis extending through the oval window (arrowhead) into the vestibule (black arrow). There is a resultant air gap between the incus and the lateral aspect of the prosthesis (white arrow). (b) Coronal CT scan shows that the medial tip of the prosthesis is angled superiorly into the vestibule (arrowhead) and away from the basal turn of the cochlea (arrow).
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Figure 8b. Vestibular perforation by a stapes prosthesis in a patient with chronic eustachian tube dysfunction and otitis media. (a) Axial CT scan shows a stainless steel prosthesis extending through the oval window (arrowhead) into the vestibule (black arrow). There is a resultant air gap between the incus and the lateral aspect of the prosthesis (white arrow). (b) Coronal CT scan shows that the medial tip of the prosthesis is angled superiorly into the vestibule (arrowhead) and away from the basal turn of the cochlea (arrow).
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Figure 9. Incus interposition graft. Coronal CT scan shows a surgically remodeled incus (arrowhead) used as an interposition graft extending from the manubrium of the malleus (curved arrow) to the capitulum of the stapes (straight arrow).
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Figure 10. Normal ossicular anatomy. Coronal CT scan of the ossicular chain shows the relationship between the incus and stapes (cf Fig 9). The long process (open arrow) and lenticular process (solid arrow) of the incus as well as the incudostapedial joint (arrowhead) are also identified.
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Figure 11a. Incus interposition graft dysfunction due to granulation tissue in a patient who presented with progressive conductive hearing loss. (a) Coronal CT scan obtained at the level of the cochlea shows an incus interposition graft encased by granulation tissue (arrow). (b) On a coronal CT scan obtained at the level of the vestibule, the incus interposition graft is seen articulating with the head of the stapes (arrow) despite extensive encasement by granulation tissue.
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Figure 11b. Incus interposition graft dysfunction due to granulation tissue in a patient who presented with progressive conductive hearing loss. (a) Coronal CT scan obtained at the level of the cochlea shows an incus interposition graft encased by granulation tissue (arrow). (b) On a coronal CT scan obtained at the level of the vestibule, the incus interposition graft is seen articulating with the head of the stapes (arrow) despite extensive encasement by granulation tissue.
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Figure 12. Applebaum prosthesis. Drawing illustrates an Applebaum prosthesis with the characteristic L-shaped configuration. A long notch fits over the end of the partially amputated long process of the incus (arrowhead). The length of the notch can be varied to accommodate residual long processes of different lengths. The capitulum of the stapes inserts into a hole at the other end of the prosthesis (arrow).
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Figure 13a. Applebaum prosthesis. (a) Axial CT scan shows an Applebaum prosthesis with the notch (arrowhead) medial to the long process of the incus (straight arrow), which fits into the notch. The crura of the stapes are also identified (curved arrows). (b) Coronal CT scan shows the medial aspect of the prosthesis (arrowhead) fitted over the capitulum of the stapes (arrow).
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Figure 13b. Applebaum prosthesis. (a) Axial CT scan shows an Applebaum prosthesis with the notch (arrowhead) medial to the long process of the incus (straight arrow), which fits into the notch. The crura of the stapes are also identified (curved arrows). (b) Coronal CT scan shows the medial aspect of the prosthesis (arrowhead) fitted over the capitulum of the stapes (arrow).
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Figure 14. Black oval-top prosthesis. Photograph shows several Black oval-top PORPs (short, thick shafts) and TORPs (long, thin shafts).
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Figure 15. Black TORP. Coronal CT scan shows a Black TORP that has been sectioned through its midportion with the characteristic "horseshoe" appearance (arrow).
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Figure 16. Black PORP. Axial CT scan shows the head (arrowhead) and shaft (arrow) of a Black PORP. The shaft is made of Plasti-Pore (Smith & Nephew) and has significantly lower attenuation than the head. The medial articulation of the prosthesis with the capitulum of the stapes is not seen.
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Figure 17. Black PORP with subluxation. Coronal CT scan obtained at the level of the vestibule and oval window shows the head of a Black PORP (arrowhead) with subluxation inferior to the capitulum of the stapes (arrow).
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Figure 18. Black PORP with subluxation and rotation. Axial CT scan shows the head of a Black PORP (arrowhead) that has become dislocated and has rotated posteriorly to face the tympanic sinus (arrow).
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Figure 19. Black PORP with subluxation due to granulation tissue. Coronal CT scan shows the head of a Black PORP encased in granulation tissue (arrow). The PORP is dislocated and superiorly rotated.
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Figure 20. Black TORP with subluxation due to recurrent cholesteatoma in a patient with a history of mastoidectomy. Axial CT scan shows the head of a Black TORP that has become dislocated and has rotated posteriorly to face the tympanic sinus (arrow). The diagnosis of recurrent cholesteatoma may be difficult in this setting, although new erosion of any residual ossicles or the tegmen tympani may suggest the diagnosis.
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Figure 21. Richards centered prostheses. Photograph shows various Richards PORPs (short, thick shafts) and TORPs (long, thin shafts). A modified Richards PORP (arrowhead) and TORP (arrow) with an off-center head and a groove for the malleus are included.
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Figure 22. Richards PORP. Coronal CT scan shows a Richards PORP. The PORP is encased in granulation tissue but is in normal position with the distal tip in the expected region of the capitulum of the stapes (curved arrow). The hollow shaft is centered on a flat hydroxyapatite head (arrowhead) and manifests as a linear area of low attenuation (straight arrow).
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Figure 23. Goldenberg prosthesis. Photograph shows various Goldenberg PORPs (short, thick shafts) and TORPs (long, thin shafts). The heads of the prostheses are off center relative to the shafts. A prosthesis with a notched head (arrows) is used when the malleus is present. The notch fits over the manubrium of the malleus for added stability.
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Figure 24. Goldenberg TORP. Axial CT scan shows the flat head of a Goldenberg TORP articulating with the tympanic membrane (arrowhead). The shaft (arrow) is off center relative to the head. The articulation of the medial tip of the shaft with the oval window is not seen.
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Figure 25a. Goldenberg TORP with subluxation. (a) Axial CT scan shows the distal shaft of a Goldenberg prosthesis with an attached hydroxyapatite cap (arrowhead). An air gap (arrow) is seen between the cap and the oval window, a finding that indicates subluxation and noncommunication of the TORP with the oval window. On occasion, a hydroxyapatite cap is attached to the end of a TORP to decrease trauma to the oval window. (b) Coronal CT scan shows the Goldenberg TORP in its entirety. The air gap is again seen (arrowhead) (cf a), and slight superior subluxation of the medial shaft relative to the oval window can be identified (arrow).
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Figure 25b. Goldenberg TORP with subluxation. (a) Axial CT scan shows the distal shaft of a Goldenberg prosthesis with an attached hydroxyapatite cap (arrowhead). An air gap (arrow) is seen between the cap and the oval window, a finding that indicates subluxation and noncommunication of the TORP with the oval window. On occasion, a hydroxyapatite cap is attached to the end of a TORP to decrease trauma to the oval window. (b) Coronal CT scan shows the Goldenberg TORP in its entirety. The air gap is again seen (arrowhead) (cf a), and slight superior subluxation of the medial shaft relative to the oval window can be identified (arrow).
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Copyright © 2000 by the Radiological Society of North America.
