Computer-Assisted Design and Manufacturing Assists Less Experienced Surgeons in Achieving Equivalent Outcomes in Cranial Vault Reconstruction

The Role of Virtual Surgical Planning in Surgery for Complex Craniosynostosis

Background

Virtual surgical planning (VSP) decreases reliance on intraoperative subjective assessment of aesthetic and functional outcomes in craniofacial surgery. Here, we describe our experience of using VSP for complex craniosynostosis surgery to inform preoperative decision making and optimize postoperative outcomes.

Methods

Chart review was performed for children treated with craniosynostosis at our institution from 2015 to 2021. Eight VSP maneuvers were defined and assigned to each patient when applicable: (1) complex cranioplasty: combined autologous and synthetic; (2) autologous cranioplasty; (3) synthetic cranioplasty; (4) vector analysis and distractor placement; (5) complex osteotomies; (6) multilayered intraoperative plans; (7) volume analysis; and (8) communication with parents. Outcomes between VSP and non-VSP cohorts were compared.

Results

Of 166 total cases, 32 were considered complex, defined by multisutural craniosynostosis, syndromic craniosynostosis, or revision status. Of these complex cases, 20 underwent VSP and 12 did not. There was no difference in mean operative time between the VSP and non-VSP groups (541 versus 532 min, P = 0.82) or in unexpected return to operating room (10.5% versus 8.3%, P = 0.84). VSP was most often used to communicate the surgical plan with parents (90%) and plan complex osteotomies (85%).

Conclusions

In this cohort, VSP was most often used to communicate the surgical plan with families and plan complex osteotomies. Our results indicate that VSP may improve intraoperative efficiency and safety for complex craniosynostosis surgery. This tool can be considered a useful adjunct to plan and guide intraoperative decisions in complex cases, reducing variability and guiding parental expectations.

Accuracy of Surgical Outcome Using Computer-Aided Surgical Simulation in Fronto-Orbital Advancement for Craniosynostosis: A Pilot Study

BACKGROUND AND OBJECTIVE

Computer-aided surgical simulation (CASS) can be used to virtually plan ideal outcomes of craniosynostosis surgery. Our purpose was to create a workflow analyzing the accuracy of surgical outcomes relative to virtually planned fronto-orbital advancement (FOA).

METHODS

Patients who underwent FOA using CASS between October 1, 2017, and February 28, 2022, at our center and had postoperative computed tomography within 6 months of surgery were included. Virtual 3-dimensional (3D) models were created and coregistered using each patient's preoperative and postoperative computed tomography data. Three points on each bony segment were used to define the object in 3D space. Each planned bony segment was manipulated to match the actual postoperative outcome. The change in position of the 3D object was measured in translational (X, Y, Z) and rotational (roll, pitch, yaw) aspects to represent differences between planned and actual postoperative positions. The difference in the translational position of several bony landmarks was also recorded. Wilcoxon signed-rank tests were performed to measure significance of these differences from the ideal value of 0, which would indicate no difference between preoperative plan and postoperative outcome.

RESULTS

Data for 63 bony segments were analyzed from 8 patients who met the inclusion criteria. Median differences between planned and actual outcomes of the segment groups ranged from -0.3 to -1.3 mm in the X plane; 1.4 to 5.6 mm in the Y plane; 0.9 to 2.7 mm in the Z plane; -1.2° to -4.5° in pitch; -0.1° to 1.0° in roll; and -2.8° to 1.0° in yaw. No significant difference from 0 was found in 21 of 24 segment region/side combinations. Translational differences of bony landmarks ranged from -2.7 to 3.6 mm.

CONCLUSION

A high degree of accuracy was observed relative to the CASS plan. Virtual analysis of surgical accuracy in FOA using CASS was feasible.

Composite grafts made of polycaprolactone fiber mats and oil-based calcium phosphate cement pastes for the reconstruction of cranial and maxillofacial defects

OBJECTIVES

Synthetic bone substitutes which can be adapted preoperatively and patient specific may be helpful in various bony defects in the field of oral- and maxillofacial surgery. For this purpose, composite grafts made of self-setting and oil-based calcium phosphate cement (CPC) pastes, which were reinforced with 3D-printed polycaprolactone (PCL) fiber mats were manufactured.

MATERIALS AND METHODS

Bone defect models were acquired using patient data from real defect situations of patients from our clinic. Using a mirror imaging technique, templates of the defect situation were fabricated via a commercially available 3D-printing system. The composite grafts were assembled layer by layer, aligned on top of these templates and fitted into the defect situation. Besides, PCL-reinforced CPC samples were evaluated regarding their structural and mechanical properties via X-ray diffraction (XRD), infrared (IR) spectroscopy, scanning electron microscopy (SEM), and 3-point-bending testing.

RESULTS

The process sequence including data acquisition, template fabrication, and manufacturing of patient specific implants proved to be accurate and uncomplicated. The individual implants consisting mainly of hydroxyapatite and tetracalcium phosphate displayed good processability and a high precision of fit. The mechanical properties of the CPC cements in terms of maximum force and stress load to material fatigue were not negatively affected by the PCL fiber reinforcement, whereas clinical handling properties increased remarkably.

CONCLUSION

PCL fiber reinforcement of CPC cements enables the production of very freely modelable three-dimensional implants with adequate chemical and mechanical properties for bone replacement applications.

CLINICAL RELEVANCE

The complex bone morphology in the region of the facial skull often poses a great challenge for a sufficient reconstruction of bony defects. A full-fledged bone replacement here often requires the replication of filigree three-dimensional structures partly without support from the surrounding tissue. With regard to this problem, the combination of smooth 3D-printed fiber mats and oil-based CPC pastes represents a promising method for fabricating patient specific degradable implants for the treatment of various craniofacial bone defects.

Patient-specific Composite Anatomic Models: Improving the Foundation for Craniosynostosis Repair

Preoperative surgical planning incorporating computer-aided design and manufacturing is increasingly being utilized today within the fields of craniomaxillofacial, orthopedic, and neurosurgery. Application of these techniques for craniosynostosis reconstruction can include patient-specific anatomic reference models, "normal" reference models or patient-specific cutting/marking guides based on the presurgical plan. The major challenge remains the lack of tangible means to transfer the preoperative plan to the operating table. We propose a simple solution to utilize a digitally designed, 3D-printed "composite model" as a structural template for cranial vault reconstruction. The composite model is generated by merging the abnormal patient cranial anatomy with the "dural surface topography" of an age-matched, sex-matched, and ethnicity-matched normative skull model. We illustrate the applicability of this approach in 2 divergent cases: 22-month-old African American male with sagittal synostosis and 5-month-old White male with metopic synostosis. The aim of this technical report is to describe our application of this computer-aided design and modeling workflow for the creation of practical 3D-printed skulls that can serve as intraoperative frameworks for the correction of craniosynostosis. With success in our first 2 cases, we believe this approach of a composite model is another step in reducing our reliance on subjective guesswork, and the fundamental aspect of the workflow has a wider application within the field of craniofacial surgery for both clinical patient care and education.

Comparison of the Accuracy and Clinical Parameters of Patient-Specific and Conventionally Bended Plates for Mandibular Reconstruction

Objectives

This retrospective study compared two mandibular reconstruction procedures-conventional reconstruction plates (CR) and patient-specific implants (PSI)-and evaluated their accuracy of reconstruction and clinical outcome.

Methods

Overall, 94 patients had undergone mandibular reconstruction with CR (n = 48) and PSI (n = 46). Six detectable and replicable anatomical reference points, identified via computer tomography, were used for defining the mandibular dimensions. The accuracy of reconstruction was assessed using pre- and postoperative differences.

Results

In the CR group, the largest difference was at the lateral point of the condyle mandibulae (D2) -1.56 mm (SD = 3.8). In the PSI group, the largest difference between preoperative and postoperative measurement was shown at the processus coronoid (D5) with +1.86 mm (SD = 6.0). Significant differences within the groups in pre- and postoperative measurements were identified at the gonion (D6) [t(56) = -2.217; p = .031 <.05]. In the CR group, the difference was 1.5 (SD = 3.9) and in the PSI group -1.04 (SD = 4.9). CR did not demonstrate a higher risk of plate fractures and post-operative complications compared to PSI.

Conclusion

For reconstructing mandibular defects, CR and PSI are eligible. In each case, the advantages and disadvantages of these approaches must be assessed. The functional and esthetic outcome of mandibular reconstruction significantly improves with the experience of the surgeon in conducting microvascular grafts and familiarity with computer-assisted surgery. Interoperator variability can be reduced, and training of younger surgeons involved in planning can be reaching better outcomes in the future.

Syndromic Craniosynostosis: Unique Management Considerations

Craniosynostosis involves the premature fusion of 1 or more cranial sutures and commonly presents as an isolated, nonsyndromic diagnosis. A subset of patients have syndromic craniosynostosis. Several unique considerations must be taken into account when managing patients with syndromic craniosynostosis. A multidisciplinary craniofacial team with a central coordinator is particularly useful for coordinating care among various specialists, and close monitoring is mandatory owing to the increased risk of intracranial hypertension. Surgical management varies among centers, but core options include fronto-orbital advancement with cranial vault remodeling, posterior vault expansion, endoscopic-assisted suturectomy with postoperative orthotic therapy, and midface advancement.

"Black bone": the new backbone in CAD/CAM-assisted craniosynostosis surgery?

BACKGROUND

Computer-assisted design and manufacturing (CAD/CAM) techniques have been implemented in craniosynostosis surgery to facilitate cranial remodeling. However, until now, computed tomography (CT) scans with ionizing radiation were necessary to plan the procedure and create guiding templates. The purpose of this study was to present our series using CAD/CAM techniques in planning and conducting fronto-orbital advancement surgery in patients with trigonocephaly with datasets acquired only by "black bone" magnetic resonance imaging (MRI).

METHODS

Six consecutively operated cases from 2019 were included in this study. All patients suffered from non-syndromic trigonocephaly with no primary surgeries. All patients underwent cranial MRI including black bone sequences. Preoperative planning and guides were created based on the DICOM datasets. We analyzed demographic data, clinical data, and outcome measured by Whitaker score.

RESULTS

In all cases, precise frontobasal advancement was possible with the CAD/CAM guides created by black bone MRI. The mean operation time and planning time were 222 and 32 min. The time on intensive and intermediate care unit (ICU/IMC) time was 4.5 days, respectively. All but one case were classified as Whitaker I.

CONCLUSION

In trigonocephaly treatment by frontobasal advancement, black bone MRI-based CAD/CAM craniosynostosis surgery is safe and feasible. It offers the major advantage of completely avoiding CT scans and ionizing radiation with superior imaging quality of intracranial structures. Thus, it improves intraoperative safety and-at the same time-has the potential to reduce operating room (OR) time.

The need for overcorrection: evaluation of computer-assisted, virtually planned, fronto-orbital advancement using postoperative 3D photography

OBJECTIVE

The main indication for craniofacial remodeling of craniosynostosis is to correct the deformity, but potential increased intracranial pressure resulting in neurocognitive damage and neuropsychological disadvantages cannot be neglected. The relapse rate after fronto-orbital advancement (FOA) seems to be high; however, to date, objective measurement techniques do not exist. The aim of this study was to quantify the outcome of FOA using computer-assisted design (CAD) and computer-assisted manufacturing (CAM) to create individualized 3D-printed templates for correction of craniosynostosis, using postoperative 3D photographic head and face surface scans during follow-up.

METHODS

The authors included all patients who underwent FOA between 2014 and 2020 with individualized, CAD/CAM-based, 3D-printed templates and received postoperative 3D photographic face and head scans at follow-up. Since 2016, the authors have routinely planned an additional "overcorrection" of 3 mm to the CAD-based FOA correction of the affected side(s). The virtually planned supraorbital angle for FOA correction was compared with the postoperative supraorbital angle measured on postoperative 3D photographic head and face surface scans. The primary outcome was the delta between the planned CAD/CAM FOA correction and that achieved based on 3D photographs. Secondary outcomes included outcomes with and those without "overcorrection," time of surgery, blood loss, and morbidity.

RESULTS

Short-term follow-up (mean 9 months after surgery; 14 patients) showed a delta of 12° between the planned and achieved supraorbital angle. Long-term follow-up (mean 23 months; 8 patients) showed stagnant supraorbital angles without a significant increase in relapse. Postsurgical supraorbital angles after an additionally planned overcorrection (of 3 mm) of the affected side showed a mean delta of 11° versus 14° without overcorrection. The perioperative and postoperative complication rates of the whole cohort (n = 36) were very low, and the mean (SD) intraoperative blood loss was 128 (60) ml with a mean (SD) transfused red blood cell volume of 133 (67) ml.

CONCLUSIONS

Postoperative measurement of the applied FOA on 3D photographs is a feasible and objective method for assessment of surgical results. The delta between the FOA correction planned with CAD/CAM and the achieved correction can be analyzed on postoperative 3D photographs. In the future, calculation of the amount of "overcorrection" needed to avoid relapse of the affected side(s) after FOA may be possible with the aid of these techniques.

Trends in Utilization of Virtual Surgical Planning in Pediatric Craniofacial Surgery

INTRODUCTION

While the use of virtual surgical planning (VSP) has been well described in the adult craniofacial literature, there has been little written about pediatric uses or trends. The purpose of this study is to evaluate the evolving utilization of VSP for pediatric craniofacial procedures.

METHODS

The authors' prospective institutional review board-approved craniofacial registry was queried for index craniofacial procedures from January 2011 through December 2018. Data was collected regarding utilization of traditional surgical planning versus VSP, as well as the extent of VSP's influence on the operative procedure. These data were analyzed for trends over time and compared using appropriate statistics.

RESULTS

During the study period, a total of 1131 index craniofacial cases were performed, of which 160 cases (14.1%) utilized VSP. Utilization of VSP collectively increased over time, from 2.0% in 2011 to 18.6% in 2018 (P < 0.001). Utilization rates of VSP varied across procedures from 0% of craniosynostosis cases and fronto-orbital advancement cases to 67% of osteocutaneous free tissue transfers (P < 0.001). The most profound contributor to increase in VSP utilization was orthognathic surgery, utilized in 0% of orthognathic procedures in 2011 to 68.3% of orthognathic procedures in 2018 (P < 0.001).

CONCLUSIONS

Utilization of virtual surgical planning for pediatric craniofacial procedures is increasing, especially for complex orthognathic procedures and osteocutaneous free tissue transfers. Utilization patterns of individual components of the VSP system demonstrate unique footprints across the spectrum of craniofacial procedures, which reinforces the specific and variable benefits of this workflow for treating pediatric craniofacial disorders.