CT scan-generated frontal sinus templates in osteoplastic flap - PowerPoint by qpv40869

VIEWS: 84 PAGES: 16

									      British Rhinological Society
               May 2008


  CT scan-generated frontal
sinus templates in osteoplastic
         flap surgery


       Mat Daniel, Jason Watson *, Anshul Sama
       Otorhinolaryngology and *Maxillofacial Surgery
       Nottingham University Hospital
          Frontal sinus mapping in
          osteoplastic flap surgery
Crucially important in FS osteoplastic flap surgery

• Caldwell radiograph from 6ft, positioned over FS
• Composite CT image of frontal sinus (Fewins 04)
• Controlled burr holes along proposed osteotomy
  line (or within FS area), connected with
  oscillating drill (Maniglia 91)
• Sinus probing
• Transillumination
• Image Guidance Systems (IGS)
            Frontal sinus mapping

• IGS more accurate than Caldwell, sinus probing,
  or transillumination (Ansari 03, Melroy 06)
• IGS reduces complications (Sindwani 04)
• IGS may not be available, and does not give
  actual 3D representation
• In contrast, most ENT units will have links with a
  maxillofacial laboratory
                  Aim
Develop a 3D template of the frontal sinus
 that can be used intra-operatively as an
       onlay guide to FS mapping
    Model & Template production
  Import CT images,
identify required region
      “Print” 3D sinus model
           layer by layer
          Onlay malleable light-cure
           resin sheet and process
               Drill FS on light-cure sheet
                to form custom template
                           Sterilise for direct
                             use in theatre
                   Clinical use
Close collaboration with prosthetics / maxillofacial
  laboratory
Original model available in theatre
Onlay template sterilised
Template placed onto FS after skin flap
Glabella/ nasion/ supraorbital ridge configuration
  used to anchor template for correct placement
Outline of FS marked with a drill
Computerised 3D reconstruction
Model
Model + template
Template in theatre
FS outlined
FS opened
                  Our experience
8 patients to date
Consistently accurate to within <1mm of actual frontal
  sinus size

Problem: in chronic infection and with multiple previous
  procedures, bone may be difficult to differentiate from
  FS contents on CT, impacting on quality of model and
  thus template
Advantages
Cost<IGS: model £100/£20, template £25
Maxfac lab at most regional hospitals

Better anchoring than X ray           Disadvantages

3D onlay template                          Pre op planning
3D model                           Need specialist facility
                                Construction time (1 week)

                       More expensive than Caldwell X ray

           ?Accuracy comparison with IGS: further research
                  Conclusion
3D models of frontal area generated from CT scans
  can be utilised to create 3D templates of the
  frontal sinus, which are then used intra-op as an
  onlay guide to frontal sinus mapping.
Early experience shows them to be consistently
  accurate to within 1mm, suggesting they would
  be a useful adjunct to current techniques, esp if
  IGS not available.
Comparison with existing techniques is needed.
Thank you

								
To top