Journal of Plastic, Reconstructive & Aesthetic Surgery (2014) 67, 336e343

Three-dimensional preoperative virtualplanning and template use for surgicalcorrection of craniosynostosis

Samir Mardini a,*, Saad Alsubaie a, Cenk Cayci a, Harvey Chim a,Nicholas Wetjen b

aDepartment of Plastic Surgery, Mayo Clinic, Rochester, MN, USAbDepartment of Neurological Surgery, Mayo Clinic, Rochester, MN, USA

Received 26 August 2013; accepted 10 November 2013

KEYWORDSCraniosynostosis;Computer-aideddesign;Virtual surgicalplanning;CAD/CAM;Cranial vaultremodelling

* Corresponding author. DepartmentE-mail address: mardini.samir@ma

1748-6815/$-seefrontmatterª2013Brihttp://dx.doi.org/10.1016/j.bjps.2013.1

Summary Background: Surgical correction of craniosynostosis aims to remodel the cranialvault to achieve a morphology approaching that of age-matched norms. However, current sur-gical technique is highly subjective and based largely on the surgeon’s artistic vision in creatinga normal head shape. Here, we present our technique and report our experience with the useof virtual surgery using computer-assisted design (CAD)/computer-assisted manufacturing(CAM) techniques to create a prefabricated template for the planning of osteotomies andthe placement of bone segments, to achieve standardised, objective and precise correctionof craniosynostosis.Methods: Four patients who underwent cranial vault remodelling (CVR; three metopic synos-tosis and one sagittal synostosis) underwent virtual surgical planning (VSP) preoperatively usingCAD/CAM techniques. VSP allows pre-planning of osteotomies to achieve the desired cranialvault shape. Surgical osteotomies and placement of bone segments were performed intra-operatively based on prefabricated templates.Results: All patients demonstrated markedly improved head shape postoperatively. One pa-tient developed a subdural haematoma 6 weeks postoperatively subsequent to a fall wherehe hit his head. The haematoma was drained and a soft spot was present in that location 3months postoperatively.Conclusion: The use of virtual surgery and prefabricated cutting guides allows for a more pre-cise and rapid reconstruction. Surgical osteotomies are pre-planned and rapidly performed us-ing a template, and precise placement of calvarial bone segments is achieved without the needfor subjective assessment of the desired calvarial shape. In addition, patients and familieshave a significantly better understanding of the disease process and anticipated surgery

of Plastic Surgery, Mayo Clinic, 200 1st Street SW, Rochester, MN 55905, USA.yo.edu (S. Mardini).

tishAssociationofPlastic,ReconstructiveandAestheticSurgeons.PublishedbyElsevierLtd.All rightsreserved.1.004

VSP for surgical correction of craniosynostosis 337

preoperatively with the visualisation achieved through virtual surgery. This results in betteralignment of hopes and expectations between the parents and surgeons.ª 2013 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published byElsevier Ltd. All rights reserved.

Craniosynostosis is a congenital disorder that occurs whenthe sutures between the bones of a child’s skull prema-turely fuse leading to the development of an abnormalhead shape and occasionally increased intracranial pres-sure.1e3 The disorder is relatively common and affectsapproximately 1 in every 2500 live births and can contributeto calvarial deformity, increased intracranial pressure andneurodevelopmental impairment.7 A number of surgicalprocedures have been developed to correct deformitiesassociated with craniosynostosis.2,11 There is varied opinionregarding which surgical procedure is optimal and leads tothe best cosmetic outcomes with least risk to the patientand lowest overall cost of care.4,5,6 Regardless of the sur-gical technique used, cranial vault remodelling (CVR) stillrequires a significant degree of subjective assessment bythe surgeon, both preoperatively and intra-operatively, todetermine how to remodel the calvarium to best restorenormal head shape.

Computer-assisted procedures are gaining more credi-bility in the field of head and neck surgery16e18. Combinedwith three-dimensional (3D) data (e.g., computed tomog-raphy (CT), cone-beam CT and optical surface scanning),these methods have been used previously for other complexreconstructive procedures such as cranioplasty andcraniofacial reconstruction. Applications range from surgi-cal planning, computer-assisted design (CAD), computed-assisted manufacturing (CAM) of implants to creation ofsurgical templates for bone resection or bone reconstruc-tion, to assist in craniosynostosis surgery, osseous genio-plasty or dental splints in orthognathic surgery.8e10,13,14,19

Burge and colleagues recently12 developed a system thatrelies less on subjective assessment and more on a stand-ardised normal for age shape of the child being operated onby using age-matched templates and CAD/CAM techniquesfor preoperative planning in surgical correction of cranio-synostosis. Here, we report our surgical technique andexperience in the use of preoperative virtual surgery tobetter achieve precise intra-operative goals using a CAD/CAM technique for surgical correction of craniosynostosis.

Preoperative planning and surgical technique

The patient undergoes a CT scan of the cranial structureswith 3D reconstruction. Helical CT scans are obtained and0.755-mm-thick slices are used to generate a 3D model inthe form of uncompressed Digital Imaging and Communi-cations in Medicine (DICOM) data, which is used by thecompany. The radiation dose per scan ranges between 1and 2 mSv. This is much lower than a comparable infantileabdominal CT scan (20 mSv). Once these data are available,the plastic surgeon and the neurological surgeonmeet along with a biomedical engineer to perform virtual

surgery and plan the surgical osteotomies on a computerworkstation. Normative age-appropriate data were used togenerate ideal 3D models to aid the surgical plan based onradiological measurements of normal children.20 In thisnormative study involving measurements of 1464 radio-graphs from 732 children, fronto-occipital diameter,biparietal diameter and cranial length were measured andused to provide mean age- and gender-appropriate mea-surements. These data were used to create precise age-appropriate normative models of calvarial morphologybased on techniques described by Saber et al.,15 with theaid of a company experienced in virtual surgical planning(VSP; Medical Modeling Inc., Golden, CO, USA).

VSP allows planning of surgical osteotomies and reposi-tioning of bone segments based on age-appropriatenormative models to achieve the desired calvarialmorphology. Virtual surgery is performed during Web-basedteam meetings consisting of the paediatric plastic surgeon,neurosurgeon and engineer from the company. Typically,there are two meetings lasting 1.5e2 h. In the firstmeeting, two models are presented by the engineer e thefirst based on the patient’s CT scan data and the secondconstructed from an age-appropriate normative model. Thetwo models are then overlapped, and virtual osteotomiesare performed to reshape the patient’s skull to match itsnormative model. The software allows virtual repositioningof bone segments to best reshape the patient’s skull.Following virtual surgery, planned surgical osteotomies areuploaded into the computer to create templates to be usedin surgery. In the second meeting, details are reviewedbefore generation of customised templates using stereo-lithography. Two templates are created e the first to guidethe location of osteotomies to be made and the second toguide placement and fixation of bone segments. The plan isdiscussed with the patient and the family, with visualisationaided by the CAD/CAM workstation.

The patient is then taken to the operating room, and isprepared and draped in the usual fashion with the 3D modeltemplates within view of the operating field. A coronalincision is made and flaps elevated in a subperiosteal planeto allow exposure of the entire calvarium. Templates areshown for a patient with sagittal synostosis. The first cut-ting template (Figure 1) guides placement of osteotomieson the calvarium. Individual bone segments are labelledwith different alphabets to aid orientation and placementof bone segments in the second template. The cuttingtemplate allows both marking of osteotomies on thecalvarium and labelling of individual bone segments. Cra-niectomy with osteotomy of individual segments is thenperformed. The second shaping template, fabricated basedon age- and gender-appropriate normative measurements,guides placement of individual bone pieces to best achievea normal calvarial morphology. The bone segments are

Figure 1 The first cutting template allows precise placement of osteotomies and labelling of individual bone segments in apatient with sagittal synostosis. Placement of the template on the calvarium after incision and elevation of the flaps in a sub-periosteal plane (left). Marking of planned osteotomies on the calvarium (right).

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placed on the inside of the template (Figure 2(A)) andsecured with resorbable plates. The reconstructedcalvarium is then transferred to the patient and securedfurther with resorbable plates externally where necessaryto provide rigid support (Figure 2(B)). Premoulding ofresorbable plates can be done on a model prior to surgeryto decrease operative time. The incision is then closed inlayers over a drain. The template used is customised to theshape of the skull preoperatively and targeted towardsdesired surgical goals. Intracranial volume can be measuredfollowing the virtual surgical plan to assure that adequatevolume increase is achieved.

The templates that are used to position the bone seg-ments in their final place can be produced in two ways.One way allows for the bone segments to be placed on theinside of the template and the other way for bone seg-ments to be placed on the outside. When the bone seg-ments are positioned on the inside of the template, theplates are required to be placed on the inside of the bone.Advantages of plating on the inside of the bone are thatthe plates are not palpable during the initial phasefollowing the reconstruction and during the phase wherethe plates are resorbing. However, there is a theoreticalincrease in risk of injury to the dura while the plates andscrews are present or due to irritation of the dura duringthe resorption phase. Plating on the inside is more chal-lenging when the construct is large as placing, mouldingand fixing the plates on the inside of a ‘bowl’ becomesmore technically challenging. In addition, as there aremany gaps present between the bones, once the finalconstruct is removed from the template, the segmentssometimes require further fixation on the outside tocompletely stabilise the construct. Overall, resorbableplates placed on the inner surface of the skull have been

shown to have excellent functional and cosmetic resultsup to 6 years’ follow-up.22 When the template is producedin a way where the bone segments are placed on theoutside, plating on the outside becomes feasible, whichallows for easy access to the plating and allows for thebone segments to have better contact with the dura. Thedisadvantage of this method would be that the platescould be palpable, particularly in the forehead; and,when the reconstruction involves more than half thecoronal circumference, it becomes difficult to remove theconstruct off the template after fixation of all the bonysegments. Plating both on the inside and on the outsideare reliable methods of providing rigid fixation duringCVR.

Results

Four patients between the ages of 9 and 11 months visitedthe Craniofacial Clinic at Mayo Clinic, Rochester, MN, USA;three with metopic synostosis and one with sagittal synos-tosis. None had elevated intracranial pressures or notabledevelopmental delay. All the patients were otherwisehealthy with an uneventful prenatal and neonatal period.All the patients were male with a mean age of 10.75months. The mean surgical time was 326 min, the meanestimated blood loss was 437.5 ml, the mean blood trans-fusion was 329.25 ml and the mean hospital length of staywas 4.5 days. Demographic and operative details are pre-sented in Table 1. All patients had complete correction ofabnormal calvarial morphology postoperatively. Figure 3shows preoperative and postoperative photographs at 6months’ follow-up of the patient presented in Figures 1and 2 with sagittal synostosis.

Figure 2 The second shaping template guides placement of individual bone segments to best achieve an age and gender matchednormal calvarial morphology in a patient with sagittal synostosis. (A) Bone segments are placed on the internal surface of thetemplate and secured with resorbable plates. (B) The reconstructed calvarium is transferred to the patient and further securedwith resorbable plates on the external aspect. (C) Reconstructed calvarium and template side-by-side.

VSP for surgical correction of craniosynostosis 339

Templates used are shown for another patient withmetopic synostosis, where efforts were targeted towardsremodelling of the anterior cranial vault (Figure 4). Figure 5shows preoperative and postoperative photographs at 2months’ follow-up of this patient.

Table 1 Demographic and operative details of patients.

Number Gender Age(months)

Affectedsuture

Surgicaltime (Min)

1 M 10.5 Metopic 2842 M 11 Metopic 3113 M 11.5 Sagittal 3394 M 10 Metopic 370

One of the patients with metopic synostosis presented tothe emergency room 6 weeks postoperatively with a sub-dural haematoma after a significant fall. He was taken tothe operating room, where a small incision was madethrough the previous coronal scar and the haematoma was

Estimatedblood loss (ml)

Complications Hospital lengthof stay (days)

800 None 4400 None 5200 None 4350 None 5

Figure 3 Preoperative and 6 month postoperative photographs of patient following surgical correction of sagittal synostosis withpreoperative virtual surgery and template guidance. (A) Preoperative frontal view. (B) Preoperative overhead view. (C) Post-operative frontal view. (D) Postoperative overhead view.

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drained. Three months postoperatively, the patient had asoft spot over the area where there was a haematoma.

Discussion

The goal of CVR is to correct the cranial shape as muchtowards the normal as possible, for the individual patient.This goal, while laudable, is difficult as there is largesubjectivity in what is ideal or normal. Recent work byNikoo has given us a mathematically averaged skull basedon 103 patients for neonates 8e12 months of age with 3DCT scanning.15 Using these techniques as a basis for gen-eration of age- and gender-appropriate models on a CAD/CAM platform removes the subjectivity from the recon-structive equation.

The evolution of template-assisted reconstruction of thecranial vault has been well documented with surgeons usingmalleable instruments to create templates.21 These tem-plates, however, still had the disadvantage of not using theNikoo skull for the end-reconstructive goal. Burge et al.reported on the first use of the Nikoo skull with templateassistance.12 In those reconstructions, however, what wasused was a bandeau which was based on an idealised skullshape and did not have a true 3D form. Our new model usesage- and gender-matched templates and CAD/CAM tech-niques to achieve a standardised, objective and precisecorrection of craniosynostosis, completely eliminating anyguesswork or subjectivity from the surgery itself.

The application of VSP and template-assisted cranialvault reconstruction is a natural evolution in surgery for

Figure 4 Surgical correction of metopic synostosis using preoperative virtual surgery and templates. (A) Prominent trig-onocephaly is seen after elevation of scalp flaps. (B) Template is placed onto the skull. (C) Markings are made to guide placement ofosteotomies using the template. (D) The reconstructed calvarium and supraorbital bar are placed onto the patient, with immediatecorrection of trigonocephaly.

VSP for surgical correction of craniosynostosis 341

craniosynostosis. The technique allows reproducibleobjective results that improve outcomes regardless of theexpertise of the surgeon. The advantages offered by VSPhave to be balanced against the necessity for radiationexposure in infants during acquisition of the CT scan andcost of the technology. Ultimately, VSP does not obviatethe need for good technical expertise but instead comple-ments it and may be most useful for complex multisuturalcraniosynostosis where freehand osteotomy and shaping ofthe calvarium may result in less predictable results. A po-tential application of VSP would involve calculating volumedifferences of the cranium before and after surgery to moreaccurately quantify results and measure the severity ofdeformity in patients preoperatively.

An additional benefit of preoperative modelling is that itallows a more thorough understanding of the disease pa-thology and surgical process for the parents of affectedpatients through providing a more visual comprehension ofwhat is being undertaken. Patients and families have a

significantly better understanding of the operation due topreoperative counselling before undergoing surgery andpostoperative rehabilitation. This results in better align-ment of hopes and expectations between families andsurgeons. The increased front-end preoperative workloadleads to increased efficiency in the operating room and mayeventually lead to decreased operative times due to elim-ination of any guesswork intra-operatively. At this point,the decrease in time due to the elimination of guesswork isoutweighed by the short learning curve of utilising thedevices.

Conclusion

The use of 3D virtual surgery preoperatively and pre-fabricated templates for cutting guides and placement ofbone segments allows for a precise surgical reconstructionwith restoration of age- and gender-matched normal

Figure 5 Preoperative and 2 month postoperative photographs of patient following surgical correction of metopic synostosis withpreoperative virtual surgery and template guidance. (A) Preoperative frontal view. (B) Preoperative overhead view. (C) Post-operative frontal view. (D) Postoperative overhead view.

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calvarial morphology. Other additional benefits of thesetools are increasing efficiency through premoulding ofplates to fit the calvarium model, with surgical time notexpended in moulding the plates imprecisely, or trying toidentify the best fit of the calvarial grafts to remodel thecranial vault. In addition, patients and family will have asignificantly better understanding of the problem and thechallenges of reconstruction. This results in better align-ment of hopes and expectations between the families andsurgeons.

Statement of financial disclosure

The authors declare that they had no financial interests,conflicts of interest or commercial associations relevant tothis study.

Conflict of interest/funding

None.

References

1. Delashaw JB, Persing JA, Broaddus WC, Jane JA. Cranial vaultgrowth in craniosynostosis. J Neurosurg 1989;70:159e65.

2. Jimenez DF, Barone CM. Endoscopic craniectomy for earlysurgical correction of sagittal craniosynostosis. J Neurosurg1998;88:77e81.

3. Barone CM, Jimenez DF. Endoscopic craniectomy for earlycorrection of craniosynostosis. Plast Reconstr Surg 1999;104:1965e73 [discussion 74e5].

4. Jimenez DF, Barone CM, McGee ME, Cartwright CC, Baker CL.Endoscopy-assisted wide-vertex craniectomy, barrel stave

VSP for surgical correction of craniosynostosis 343

osteotomies, and postoperative helmet molding therapy in themanagement of sagittal suture craniosynostosis. J Neurosurg2004;100:407e17.

5. Xia JJ, Phillips CV, Gateno J, et al. Cost-effectiveness analysisfor computer-aided surgical simulation in complex cranio-maxillofacial surgery. J Oral Maxillofac Surg 2006;64:1780e4.

6. Jane JA, Edgerton MT, Futrell JW, Park TS. Immediatecorrection of sagittal synostosis, 1978. J Neurosurg 2007;107:427e32.

7. Persing JA. MOC-PS(SM) CME article: management consider-ations in the treatment of craniosynostosis. Plast Reconstr Surg2008;121:1e11.

8. Hirsch DL, Garfein ES, Christensen AM, Weimer KA, Saddeh PB,Levine JP. Use of computer-aided design and computer-aidedmanufacturing to produce orthognathically ideal surgical out-comes: a paradigm shift in head and neck reconstruction. JOral Maxillofac Surg 2009;67:2115e22.

9. Swennen GR, Mollemans W, Schutyser F. Three-dimensionaltreatment planning of orthognathic surgery in the era of virtualimaging. J Oral Maxillofac Surg 2009;67:2080e92.

10. Xia JJ, Gateno J, Teichgraeber JF. New clinical protocol toevaluate craniomaxillofacial deformity and plan surgicalcorrection. J Oral Maxillofac Surg 2009;67:2093e106.

11. Jimenez DF, Barone CM. Endoscopic techniques for craniosy-nostosis. Atlas Oral Maxillofac Surg Clin North Am 2010;18:93e107.

12. Burge J, Saber NR, Looi T, et al. Application of CAD/CAM pre-fabricated age-matched templates in cranio-orbital remodel-ing in craniosynostosis. J Craniofac Surg 2011;22:1810e3.

13. Quevedo LA, Ruiz JV, Quevedo CA. Using a clinical protocol fororthognathic surgery and assessing a 3-dimensional virtualapproach: current therapy. J Oral Maxillofac Surg 2011;69:623e37.

14. Xia JJ, McGrory JK, Gateno J, et al. A new method to orient 3-dimensional computed tomography models to the natural headposition: a clinical feasibility study. J Oral Maxillofac Surg2011;69:584e91.

15. Saber NR, Phillips J, Looi T, et al. Generation of normativepediatric skull models for use in cranial vault remodelingprocedures. Childs Nerv Syst 2012;28:405e10.

16. Yanez-Vico RM, Iglesias-Linares A, Torres-Lagares D, Gutierrez-Perez JL, Solano-Reina E. A new three-dimensional analysis ofasymmetry for patients with craniofacial syndromes. Oral Dis2012;19:755e62.

17. Bly RA, Chang SH, Cudejkova M, Liu JJ, Moe KS. Computer-Guided orbital reconstruction to improve outcomes. JAMAFacial Plast Surg 2013:1e8.

18. Foley BD, Thayer WP, Honeybrook A, McKenna S, Press S.Mandibular reconstruction using computer-aided design andcomputer-aided manufacturing: an analysis of surgical results.J Oral Maxillofac Surg 2013;71:e111e9.

19. Hierl T, Arnold S, Kruber D, Schulze FP, Humpfner-Hierl H. CAD-CAM-assisted esthetic facial surgery. J Oral Maxillofac Surg2013;71:e15e23.

20. Pereira IMR, Filho AAB, Alvares BR, Palomari ET, Nanni L.Radiological determination of cranial size and index by mea-surement of skull diameters in a population of children inBrazil. Radiol Bras 2008;41:229e34.

21. Pappa H, Richardson D, Webb AA, May P. Individualizedtemplate-guided remodeling of the fronto-orbital bandeau incraniosynostosis corrective surgery. J Craniofac Surg 2009;20:178e9.

22. Serlo WS, Ylikontiola LP, Vesala AL, et al. Effective correctionof frontal cranial deformities using biodegradable fixation onthe inner surface of the cranial bones during infancy. ChildsNerv Syst 2007;23:1439e45.