Computer-assisted surgical planning congenital differences and anomalies—nonsyndromic craniosynostosis: A practical workflow

Evaluation

On initial evaluation, all children should undergo a history and physical exam with an emphasis on ruling out nonoperative conditions such as positional plagiocephaly. Virchow’s landmark contribution describes the characteristic compensatory changes in skull growth perpendicular to prematurely fused sutures. These compensatory changes serve as the hallmarks for clinical diagnosis of single-suture craniosynostosis. Several studies have shown that clinical features alone can allow for reliable diagnosis in almost all cases, rendering imaging unnecessary on this basis alone. Imaging does, however, provide the foundation for computer-assisted design and computer-assisted manufacturing (CAD/CAM), as reviewed in this chapter. Imaging should include noncontrast craniomaxillofacial computed tomography (CT) with three-dimensional (3D) reconstruction. When operative intervention is decided upon, a family discussion should be initiated that explains the collaboration between plastic surgery and neurosurgery intraoperatively. The question of whether surgery is indicated in mild phenotypic cases is beyond the scope of the present chapter. In such instances, multidisciplinary discussion becomes paramount, and may include input from the specialties of ophthalmology, genetics, and developmental neuropsychology in addition to plastic surgery and neurosurgery.

Timing of surgery

Although the optimal timing for surgical intervention has yet to be established, certain principles are well understood. Earlier intervention—defined as earlier than 1 year of age—has been shown to reduce the risks for subsequent elevations in intracranial pressure and cognitive deficits. Taking advantage of the time period shortly after the infant hematopoietic nadir, between 3 to 6 months, has also been described. This time frame also capitalizes on the rapid expansion of the cranium and dural osteoinductive capacity for optimal open remodeling outcomes. Beyond 1 year of age, open remodeling can prove more difficult due to the stiffer quality and thickness of the cranial bone. Moreover, beyond this age, bony gaps may be less likely to completely heal. ^, The benefits of early intervention for open cranial vault remodeling surgery must be balanced by the risks, including significant blood loss. The excellent vascular perfusion of the craniofacial region makes this concern especially pertinent in young children with relatively less reserve due to size. With the above considerations, it has been become common practice to proceed with open surgery in the age range of 6 to 12 months. While open surgery is infrequently performed prior to this time point, more minimally invasive strip craniectomy surgery is, by contrast, performed earlier than 4 months of age. Because the latter procedures rarely involve the use of CAD/CAM approaches, particularly in patients with nonsyndromic craniosynostosis, they are not discussed in this chapter.

Computer-assisted design and computer-assisted manufacturing

The benefits of CAD/CAM in craniofacial surgery have been well-described. Given the complexity of calvarial remodeling, the ability to virtually plan, assess, and modify operative approaches with infinite variation can be an invaluable resource. Advantages have been cited for more atypical cases of craniosynostosis with multiple-suture involvement, older patients with significantly thickened bone not amenable to manual bending, and for craniofacial surgeons with less experience in performing complex on-table manipulations. A recent study showed that less experienced craniofacial surgeons using CAD/CAM may achieve noninferior results when compared with more experienced surgeons using traditional methods. Outcomes such as estimated blood loss, inpatient length of stay, and postoperative complications were not significantly different between the two groups, though less experienced surgeons using CAD/CAM did have longer operative times.

Indications for CAD/CAM in craniofacial surgery includes complex reconstructive procedures such as multi-suture reconstruction, cranial vault revisions, facial bipartitions, box osteotomies, and distraction osteogenesis cases. Although the utility of CAD/CAM in these cases has been demonstrated, the role of these technologies in nonsyndromic, single-suture open craniosynostosis surgery is certainly less clear. It has been argued that, for these cases, the financial cost is too great to justify the optimization of more straightforward reconstructive needs, such as patients with single suture fusion that present early enough to plan intervention well before 1 year of age.

In our experience at a large academic medical center, a key consideration favoring CAD/CAM in nonsyndromic craniosynostosis open surgery is late presentation, particularly after 1 year of age when the cranial bone is less amenable to traditional bending and remodeling techniques. As in many tertiary centers, our experience includes a disproportionately large number of patients with such delayed presentations. The reasons for this may be multiple, and include recent immigration to the US from a country without expertise in surgical management of craniosynostosis, previous absence of a diagnosis, and the presence of other intercurrent medical issues that preclude the timely scheduling of open cranial vault remodeling surgery. Because late presenters may frequently exhibit a more severe, abnormal phenotype and an even greater need for complex manipulation of bony segments to establish an aesthetic outcome, CAD/CAM can be particularly advantageous. The innate osteoinductive capacity of the calvarial skeleton is also diminished with age, as previously noted. This translates into a more precise need for bony segment realignment and contact, without relying on secondary healing processes for open bone fill. CAD/CAM can aid in this aspect as well, and bone gaps can be minimized.