title: CT pre-operative planning of a new semi-implantable bone conduction hearing device.
abstract: OBJECTIVE
  Accommodating a novel semi-implantable bone conduction hearing device within the temporal bone presents challenges for surgical planning. This study describes the utility of CT in pre-operative assessment of such an implant.
  
  
  METHODS
  Retrospective review of pre-operative CT, clinical and surgical records of 16 adults considered for device implantation. Radiological suitability was assessed on CT using 3D simulation software. Antero-posterior (AP) dimensions of the mastoid bone and minimum skull thickness were measured. CT planning results were correlated with operative records.
  
  
  RESULTS
  Eight and five candidates were suitable for device placement in the transmastoid and retrosigmoid positions, respectively, and three were radiologically unsuitable. The mean AP diameter of the mastoid cavity was 14.6 mm for the transmastoid group and 4.6 mm for the retrosigmoid group (p < 0.05). Contracted mastoid and/or prior surgery were predisposing factors for unsuitability. Four transmastoid and five retrosigmoid positions required sigmoid sinus/dural depression and/or use of lifts due to insufficient bone capacity.
  
  
  CONCLUSIONS
  A high proportion of patients being considered have contracted or operated mastoids, which reduces the feasibility of the transmastoid approach. This finding combined with the complex temporal bone geometry illustrates the importance of careful CT evaluation using 3D software for precise device simulation.
  
  
  CONCLUSIONS
  • Preoperative temporal bone CT is essential for determining Bonebridge device suitability. • Mastoid under-pneumatisation and prior mastoidectomy predict a retrosigmoid Bonebridge position. • 3D simulation software is recommended for precise device positioning.
authors.affiliation: Department of Imaging & Interventional Radiology, Prince of Wales Hospital, The Chinese University of Hong Kong, 30-32 Ngan Shing Street, Shatin, New Territories, Hong Kong, SAR, China.
authors.forename: Eric K C
authors.initials: EK
authors.lastname: Law
authors.affiliation: Department of Imaging & Interventional Radiology, Prince of Wales Hospital, The Chinese University of Hong Kong, 30-32 Ngan Shing Street, Shatin, New Territories, Hong Kong, SAR, China. drkbhatia@cuhk.edu.hk.
authors.forename: Kunwar S S
authors.initials: KS
authors.lastname: Bhatia
authors.affiliation: Department of Otorhinolaryngology, Head & Neck Surgery, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, SAR, China.
authors.forename: Willis S S
authors.initials: WS
authors.lastname: Tsang
authors.affiliation: Department of Otorhinolaryngology, Head & Neck Surgery, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, SAR, China.
authors.forename: Michael C F
authors.initials: MC
authors.lastname: Tong
authors.affiliation: Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, SAR, China.|Chow Yuk Ho Technology Center for Innovative Medicine, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, SAR, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Shi
mesh_terms: D000293:Adolescent; D000328:Adult; D001844:Bone Conduction / Q000502:physiology*; D003392:Cranial Sinuses / Q000000981:diagnostic imaging; D005260:Female; D006310:Hearing Aids; D006801:Humans; D008297:Male; D008416:Mastoid / Q000000981:diagnostic imaging; D008875:Middle Aged; D010347:Patient Care Planning; D011300:Preoperative Care; D019736:Prostheses and Implants; D011859:Radiography; D012189:Retrospective Studies; D012984:Software; D013701:Temporal Bone / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed / Q000379:methods; D055815:Young Adult
keywords: Bone conduction hearing device; Conducting hearing loss; Retrosigmoid; Temporal bone; Transmastoid