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Presentation of a cone-beam CT scanning protocol for preprosthetic cranial bone grafting of the atrophic maxilla
Int. J. Oral Maxillofac. Surg. 2012; 41: 863–866 doi:10.1016/j.ijom.2012.03.012, available online at http://www.sciencedirect.com
Technical Note Pre-Implant Surgery
Presentation of a cone-beam CT scanning protocol for preprosthetic cranial bone grafting of the atrophic maxilla
J. De Ceulaer, G. Swennen, J. Abeloos, C. De Clercq Department of Surgery, Division of Maxillofacial Surgery, General Hospital St. John Bruges, Belgium
J. De Ceulaer, G. Swennen, J. Abeloos, C. De Clercq: Presentation of a cone-beam CT scanning protocol for preprosthetic cranial bone grafting of the atrophic maxilla. Int. J. Oral Maxillofac. Surg. 2012; 41: 863–866. # 2012 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved. Abstract. The use of autologous calvarian split thickness bone grafts is a well accepted preprosthetic surgical procedure for reconstruction of the severely atrophied maxilla. Although generally accepted as being a superior bone graft regarding long-term stability, the reported risks in the literature may dissuade the surgeon. A modified cone-beam computed tomography (CBCT) scanning protocol (extended field of view starting from 1 cm below the occlusal plane up to the limit of the cranial vault, 0.4 voxel) is proposed that allows assessment of both the cranial donor site as the maxillary receptor site and the sinus conditions with a single scan. Issues regarding quality of the data, radiation dose and clinical practicability are discussed.
The severely atrophic maxilla (Cawood V and VI), when width and height are insufficient, is a challenge in oral rehabilitation. Several surgical procedures have been described and accepted as useful and reliable techniques including bilateral sinus inlay and onlay1 and Le Fort I downward fracture interpositioning.2 A common site for bone grafting is the iliac crest. In 1982, Tessier introduced the cranial bone graft.3 Although generally accepted as being a superior bone graft regarding long-term stability, the reported risks in the literature (intracerebral, subdural, epidural bleeding) may dissuade the surgeon.3–8 Complications are rare and mostly temporary. In the authors’ experience the only 0901-5027/070863 + 04 $36.00/0
complication was a subcutaneous haematoma that occurred in 3.4%.9 Although complications are rare and usually not severe,3–8 Tessier stated that ‘the use of computed tomographic scanning for evaluation of the thickness of the parietal bones and detection of any abnormalities is necessary’.3 The presurgical diagnostic means to assess the receptor site are: orthopantomography; dentascan (cone-beam computed tomography (CBCT) or multi-slice CT); or a combination of the latter imaging techniques. Often no imaging of the donor site is carried out. Sometimes a lateral cephalogram, revealing little information on the morphology of the cranial bone, is
Accepted for publication 12 March 2012 Available online 16 April 2012
taken. Occasionally multi-slice CT scanning is performed. The purpose of this technical note is to present a new CBCT protocol for simultaneous assessment of the maxillary receptor and cranial donor sites and evaluate its clinical relevance. Image acquisition technique
The scanning protocol is a modification of the first scan of the ‘triple’ CBCT scan protocol that the authors introduced for routine 3D virtual orthognathic surgery planning.10 In order to scan the maxillary receptor and cranial donor sites simultaneously the field of view (FOV) was
# 2012 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.
864
De Ceulaer et al. fistulae, fluid levels, drainage problems, corpora aliena). The thickness of the external cranial cortex can be evaluated by comparing the full thickness of the skull to the thickness of the orientation template (Fig. 4). Case series report
Fig. 1. Left: The FOV and positioning in the orthognathic scanning protocol.1,3 Right: Modification of the FOV and position of the head in the preprosthetic protocol.
modified (scanning starts 1 cm below the occlusional plane and ends above the cranial vault) and the head position adjusted (Fig. 1). CBCT scanning (i-CATTM, Imaging Sciences International, Inc., Hatfield, Pennsylvania, USA) was performed in ‘Extended Field mode (FOV 17 cm diameter, 22 cm height; scan time 2 20 s; voxel size 0.4) at 120 kV (according to DICOM field: 0018,0060 KVP) and 48 mA (according to DICOM field: 0018,1151 XRayTubeCurrent). To be able to better orientate the site of cranial bone harvesting, a radio-opaque orientation template was created and placed on the patient’s head before scanning (Fig. 2). The orientation template was custom-made from an alternative alginate
Fig. 2. Radio-opaque template on skull.
impression material (AlgiNotTM, Kerr U.S.A., Romulus, USA) and measured 80 mm 60 mm 10 mm. Prior to scanning, the orientation template was positioned on the patient’s head in the parietal region, 3 cm dorsal to the hair line and 3 cm lateral to the midline. After scanning, both the anatomy of the cranial donor and maxillary receptor site can be evaluated with the i-CAT VisionTM viewing software. Absence of diploe, venous lacunae and other anatomical variations of the cranial donor site can be screened for (Fig. 3). The maxillary receptor site can be assessed in height and width but additional clinical relevant information on sinus pathology is available (e.g. evaluation of mucosal lining, oro-antral
Ten patients underwent this new protocol for maxillary bone augmentation by means of cranial bone grafting. Positioning of the template was always performed by the surgeon himself and this appeared to be important because of inter-operator variations in choosing the site for harvesting the grafts. The protocol appeared to be easily applicable and useful in the clinical routine although there were a few problems. One patient’s head was too large for conventional positioning in the CBCT apparatus. This resulted in incomplete visualization of the donor site. This problem could be solved by manipulation of the FOV, but this requires experienced staff. It is expected that this problem will be solved in the near future by developing CBCT equipment with a larger FOV. Major anatomical variations were not detected in any of the patients. In one patient the preoperative scan showed absence of diploe at the harvesting site which implicates greater risk of dura lesions. This radiological finding made the surgeon modify his treatment plan. Instead of a cranial bone graft, anterior iliac crest bone was harvested. Discussion
The modified scanning protocol was applied to 10 consecutive patients scheduled for reconstructive surgery of the severe atrophic maxilla to enable prosthetic dental implant rehabilitation. The protocol was easily applicable in the clinical routine. The clinical relevance for the patient is that a single CBCT scanning protocol allows thorough assessment of the cranial donor and the maxillary receptor site. After scanning, the patient’s data can be evaluated directly using the viewing software of the CBCT apparatus without the need for third party software. Viewing the data with the patient was useful for patient counselling and to explain and illustrate the planned surgical procedure. The scanning resolution of 0.4 voxel revealed good anatomical details of the cranial donor and maxillary receptor sites. Possible concerns might be the radiation dose and cost. The radiation dose in
Cone-beam CT scanning protocol
865
Fig. 3. Assessment of cranial donor and maxillary receptor site in one CBCT scan.
Fig. 4. Comparing the thickness of the template with the thickness of the calvarial bone.
the protocol (50 mSv, unpublished data from Casselman J) described is much lower than that when using the combination of a lateral cephalogram and a multislice CT dentascan, which are often used as preoperative imaging in reconstruction of the severe atrophied maxilla with cranial bone grafts. The radiation dose of the protocol is also less than the combined dose of a lateral cephalogram and a CNCT dentascan (88 mSv, unpublished data Casselman et al.). There are no additional costs compared to a conventional dentascan and no additional software is required. A drawback of the scanning protocol is that patient positioning in the CBCT apparatus is sometimes difficult due to the limited FOV and therefore requires experienced CBCT technical staff, to be
sure that both cranial donor and maxillary receptor site are visualised. Another potential drawback is the surgeon’s learning curve regarding the digital viewing software for interpretation of the images. Overall, the authors conclude that this modified scanning protocol is easily applicable in the clinical routine and provides necessary and additional anatomical information without increasing the radiation dose or cost. Funding
None. Competing interests
None declared.
Ethical approval
Not required.
References 1. Tatum Jr H. Maxillary and sinus implant reconstructions. Dent Clin North Am 1986;30:207–29. 2. Cawood JI, Stoelinga PJ, Brouns JJ. Reconstruction of the severely resorbed (Class VI) maxilla. A two-step procedure. Int J Oral Maxillofac Surg 1994;23:219–25. 3. Tessier P, Kawamoto H, Posnick J, Raulo Y, Tulasne JF, Wolfe SA. Taking calvarial grafts, either split in situ or splitting of the parietal bone flap ex vivo – tools and techniques: V. A 9650-case experience in craniofacial and maxillofacial surgery. Plast Reconstr Surg 2005;116:54S–71S.
866
De Ceulaer et al.
4. Cannella DM, Hopkins LN. Superior sagittal sinus laceration complicating an autogenous calvarial bone graft harvest: report of a case. J Oral Maxillofac Surg 1990;48:741–3. 5. Frodel Jr JL, Marentette LJ, Quatela VC, Weinstein GS. Calvarial bone graft harvest. Techniques, considerations and morbidity. Arch Otolaryngol Head Neck Surg 1993;119:17–23. 6. Kline RM, Wolfe SA. Complications associated with the harvesting of cranial bone grafts. Plast Reconstr Surg 1995:95. 7. Sammartino G, Marenzi G, Colella G, Califano L, Grivetto F, Mortellaro C. Autogenous calvarial bone graft harvest: intraoperational
complications. J Craniofac Surg 2005;16: 312–9. 8. Young VL, Schuster RH, Harris LW. Intracerebral hematoma complicating split calvarial bone-graft harvesting. Plast Reconstr Surg 1990;86:763–5. 9. Lenssen L, Barbier L, De Clercq C. Immediate functional loading of provisional implants in the reconstructed atrophic maxilla: preliminary results of a prospective study after 6 months of loading with a provisional bridge. Int J Oral Maxillofac Surg 2011;40: 907–15. 10. Swennen GRJ, Mollemans W, De Clercq. Abeloos J, Lamoral P, Lippens F, et al. A cone-beam CT triple scan procedure
to obtain a three-dimensional augmented virtual skull model appropriate for orthognathic surgery planning. J Craniofac Surg 2009;20: 297–307.
Address: Calix De Clercq Department of Surgery Division of Maxillofacial Surgery General Hospital St. John Bruges Ruddershove 10 8000 Bruges Belgium Tel: +32 50452263 Fax: +32 50452279 E-mail: [email protected]
Technical Note Pre-Implant Surgery
Presentation of a cone-beam CT scanning protocol for preprosthetic cranial bone grafting of the atrophic maxilla
J. De Ceulaer, G. Swennen, J. Abeloos, C. De Clercq Department of Surgery, Division of Maxillofacial Surgery, General Hospital St. John Bruges, Belgium
J. De Ceulaer, G. Swennen, J. Abeloos, C. De Clercq: Presentation of a cone-beam CT scanning protocol for preprosthetic cranial bone grafting of the atrophic maxilla. Int. J. Oral Maxillofac. Surg. 2012; 41: 863–866. # 2012 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved. Abstract. The use of autologous calvarian split thickness bone grafts is a well accepted preprosthetic surgical procedure for reconstruction of the severely atrophied maxilla. Although generally accepted as being a superior bone graft regarding long-term stability, the reported risks in the literature may dissuade the surgeon. A modified cone-beam computed tomography (CBCT) scanning protocol (extended field of view starting from 1 cm below the occlusal plane up to the limit of the cranial vault, 0.4 voxel) is proposed that allows assessment of both the cranial donor site as the maxillary receptor site and the sinus conditions with a single scan. Issues regarding quality of the data, radiation dose and clinical practicability are discussed.
The severely atrophic maxilla (Cawood V and VI), when width and height are insufficient, is a challenge in oral rehabilitation. Several surgical procedures have been described and accepted as useful and reliable techniques including bilateral sinus inlay and onlay1 and Le Fort I downward fracture interpositioning.2 A common site for bone grafting is the iliac crest. In 1982, Tessier introduced the cranial bone graft.3 Although generally accepted as being a superior bone graft regarding long-term stability, the reported risks in the literature (intracerebral, subdural, epidural bleeding) may dissuade the surgeon.3–8 Complications are rare and mostly temporary. In the authors’ experience the only 0901-5027/070863 + 04 $36.00/0
complication was a subcutaneous haematoma that occurred in 3.4%.9 Although complications are rare and usually not severe,3–8 Tessier stated that ‘the use of computed tomographic scanning for evaluation of the thickness of the parietal bones and detection of any abnormalities is necessary’.3 The presurgical diagnostic means to assess the receptor site are: orthopantomography; dentascan (cone-beam computed tomography (CBCT) or multi-slice CT); or a combination of the latter imaging techniques. Often no imaging of the donor site is carried out. Sometimes a lateral cephalogram, revealing little information on the morphology of the cranial bone, is
Accepted for publication 12 March 2012 Available online 16 April 2012
taken. Occasionally multi-slice CT scanning is performed. The purpose of this technical note is to present a new CBCT protocol for simultaneous assessment of the maxillary receptor and cranial donor sites and evaluate its clinical relevance. Image acquisition technique
The scanning protocol is a modification of the first scan of the ‘triple’ CBCT scan protocol that the authors introduced for routine 3D virtual orthognathic surgery planning.10 In order to scan the maxillary receptor and cranial donor sites simultaneously the field of view (FOV) was
# 2012 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.
864
De Ceulaer et al. fistulae, fluid levels, drainage problems, corpora aliena). The thickness of the external cranial cortex can be evaluated by comparing the full thickness of the skull to the thickness of the orientation template (Fig. 4). Case series report
Fig. 1. Left: The FOV and positioning in the orthognathic scanning protocol.1,3 Right: Modification of the FOV and position of the head in the preprosthetic protocol.
modified (scanning starts 1 cm below the occlusional plane and ends above the cranial vault) and the head position adjusted (Fig. 1). CBCT scanning (i-CATTM, Imaging Sciences International, Inc., Hatfield, Pennsylvania, USA) was performed in ‘Extended Field mode (FOV 17 cm diameter, 22 cm height; scan time 2 20 s; voxel size 0.4) at 120 kV (according to DICOM field: 0018,0060 KVP) and 48 mA (according to DICOM field: 0018,1151 XRayTubeCurrent). To be able to better orientate the site of cranial bone harvesting, a radio-opaque orientation template was created and placed on the patient’s head before scanning (Fig. 2). The orientation template was custom-made from an alternative alginate
Fig. 2. Radio-opaque template on skull.
impression material (AlgiNotTM, Kerr U.S.A., Romulus, USA) and measured 80 mm 60 mm 10 mm. Prior to scanning, the orientation template was positioned on the patient’s head in the parietal region, 3 cm dorsal to the hair line and 3 cm lateral to the midline. After scanning, both the anatomy of the cranial donor and maxillary receptor site can be evaluated with the i-CAT VisionTM viewing software. Absence of diploe, venous lacunae and other anatomical variations of the cranial donor site can be screened for (Fig. 3). The maxillary receptor site can be assessed in height and width but additional clinical relevant information on sinus pathology is available (e.g. evaluation of mucosal lining, oro-antral
Ten patients underwent this new protocol for maxillary bone augmentation by means of cranial bone grafting. Positioning of the template was always performed by the surgeon himself and this appeared to be important because of inter-operator variations in choosing the site for harvesting the grafts. The protocol appeared to be easily applicable and useful in the clinical routine although there were a few problems. One patient’s head was too large for conventional positioning in the CBCT apparatus. This resulted in incomplete visualization of the donor site. This problem could be solved by manipulation of the FOV, but this requires experienced staff. It is expected that this problem will be solved in the near future by developing CBCT equipment with a larger FOV. Major anatomical variations were not detected in any of the patients. In one patient the preoperative scan showed absence of diploe at the harvesting site which implicates greater risk of dura lesions. This radiological finding made the surgeon modify his treatment plan. Instead of a cranial bone graft, anterior iliac crest bone was harvested. Discussion
The modified scanning protocol was applied to 10 consecutive patients scheduled for reconstructive surgery of the severe atrophic maxilla to enable prosthetic dental implant rehabilitation. The protocol was easily applicable in the clinical routine. The clinical relevance for the patient is that a single CBCT scanning protocol allows thorough assessment of the cranial donor and the maxillary receptor site. After scanning, the patient’s data can be evaluated directly using the viewing software of the CBCT apparatus without the need for third party software. Viewing the data with the patient was useful for patient counselling and to explain and illustrate the planned surgical procedure. The scanning resolution of 0.4 voxel revealed good anatomical details of the cranial donor and maxillary receptor sites. Possible concerns might be the radiation dose and cost. The radiation dose in
Cone-beam CT scanning protocol
865
Fig. 3. Assessment of cranial donor and maxillary receptor site in one CBCT scan.
Fig. 4. Comparing the thickness of the template with the thickness of the calvarial bone.
the protocol (50 mSv, unpublished data from Casselman J) described is much lower than that when using the combination of a lateral cephalogram and a multislice CT dentascan, which are often used as preoperative imaging in reconstruction of the severe atrophied maxilla with cranial bone grafts. The radiation dose of the protocol is also less than the combined dose of a lateral cephalogram and a CNCT dentascan (88 mSv, unpublished data Casselman et al.). There are no additional costs compared to a conventional dentascan and no additional software is required. A drawback of the scanning protocol is that patient positioning in the CBCT apparatus is sometimes difficult due to the limited FOV and therefore requires experienced CBCT technical staff, to be
sure that both cranial donor and maxillary receptor site are visualised. Another potential drawback is the surgeon’s learning curve regarding the digital viewing software for interpretation of the images. Overall, the authors conclude that this modified scanning protocol is easily applicable in the clinical routine and provides necessary and additional anatomical information without increasing the radiation dose or cost. Funding
None. Competing interests
None declared.
Ethical approval
Not required.
References 1. Tatum Jr H. Maxillary and sinus implant reconstructions. Dent Clin North Am 1986;30:207–29. 2. Cawood JI, Stoelinga PJ, Brouns JJ. Reconstruction of the severely resorbed (Class VI) maxilla. A two-step procedure. Int J Oral Maxillofac Surg 1994;23:219–25. 3. Tessier P, Kawamoto H, Posnick J, Raulo Y, Tulasne JF, Wolfe SA. Taking calvarial grafts, either split in situ or splitting of the parietal bone flap ex vivo – tools and techniques: V. A 9650-case experience in craniofacial and maxillofacial surgery. Plast Reconstr Surg 2005;116:54S–71S.
866
De Ceulaer et al.
4. Cannella DM, Hopkins LN. Superior sagittal sinus laceration complicating an autogenous calvarial bone graft harvest: report of a case. J Oral Maxillofac Surg 1990;48:741–3. 5. Frodel Jr JL, Marentette LJ, Quatela VC, Weinstein GS. Calvarial bone graft harvest. Techniques, considerations and morbidity. Arch Otolaryngol Head Neck Surg 1993;119:17–23. 6. Kline RM, Wolfe SA. Complications associated with the harvesting of cranial bone grafts. Plast Reconstr Surg 1995:95. 7. Sammartino G, Marenzi G, Colella G, Califano L, Grivetto F, Mortellaro C. Autogenous calvarial bone graft harvest: intraoperational
complications. J Craniofac Surg 2005;16: 312–9. 8. Young VL, Schuster RH, Harris LW. Intracerebral hematoma complicating split calvarial bone-graft harvesting. Plast Reconstr Surg 1990;86:763–5. 9. Lenssen L, Barbier L, De Clercq C. Immediate functional loading of provisional implants in the reconstructed atrophic maxilla: preliminary results of a prospective study after 6 months of loading with a provisional bridge. Int J Oral Maxillofac Surg 2011;40: 907–15. 10. Swennen GRJ, Mollemans W, De Clercq. Abeloos J, Lamoral P, Lippens F, et al. A cone-beam CT triple scan procedure
to obtain a three-dimensional augmented virtual skull model appropriate for orthognathic surgery planning. J Craniofac Surg 2009;20: 297–307.
Address: Calix De Clercq Department of Surgery Division of Maxillofacial Surgery General Hospital St. John Bruges Ruddershove 10 8000 Bruges Belgium Tel: +32 50452263 Fax: +32 50452279 E-mail: [email protected]