Background: The monobloc procedure as described by Ortiz-Monasterio has been criticized for tendency for relapse, infection risk, and need for later cranial vault remodelling or cranioplasty due to large areas of incomplete ossification. With distraction techniques, this procedure has increased in popularity, but stability and incomplete ossification remain problematic. We have developed a minimally invasive approach which can take full advantage of this procedure, bringing modern endoscopic and navigational techniques to this formidable operation, thereby minimizing the risks and improving outcomes in the treatment of syndromic craniosynostosis.
Objective: To develop a minimally invasive method for correcting syndromic craniosynostosis using a hybrid regimen of endoscopic craniotomy using piezoelectric osteotomes, minimal dissection and percutaneously distractors.
Methods: Nineteen patients have been treated with novel monobloc osteotomy. The current protocol requires multiple trephines. Then, intracranial endoscopy is used to dissect the frontal lobes from the overlying calvarium, orbital roof and anterior temporal fossa. Using a piezoelectric osteotome with navigation, the calvarial and orbital roof osteotomies are performed from within the cranial vault. The orbital floors are cut transconjunctivally. Pterygomaxillary dysjunction is performed with a coventional osteotome. Limited barrel-stave osteotomies and bony contouring are performed prn. The midface is disimpacted, and custom-designed internal distractors (Osteomed, Dallas, TX) are applied percutaneously. There is no degloving of the midface or calvarium. Distraction is carried out at 1mm/day, with 6 weeks of consolidation.
Results: Mean patient age was 7.33 years. (Crouzon =9, Apert =3, Pfeiffer=1, Saethre-Chotzen =1, 5= provisionally unique syndromes) All osteotomies were able to be completed through limited incisions and trephines. Mean operative time has decreased from the initial 12 hours to a mean of 5.5 hours. Mean midface distraction at infraorbitale is 21 mm. Long term stability of the advancement is superior to conventional osteotomies, with 1 year relapse of 2.5 mm at nasion, 1.8 mm at ANS, and 1.2 mm at point A.
Remarkably, there is radiographic evidence of complete reossification of the entire calvarial and orbital osteotomies in 16/19 patients. Intracranial hypertension has been corrected in all 7 patients with preoperative compromise.
There has been no incidence of dural laceration, visual impairment, significant hemorrhage which required open craniotomy, meningitis, infection, or intracranial hypertension. EBL averaged 760 ml. Hospital stay averaged 6 days, with 3 day ICU stay.
Case Report: A 3year old patient with Crouzon syndrome with intracranial hypertension, nystagmus and threatened blindness underwent the above procedure. Monoblock osteotomy was performed as above. The prototype distractor was placed from the temporal fossa to the lateral orbital wall. During the distraction, the single screw-born malar distractors eventually became dislodged. Nonetheless, the patient satisfactory outcome, advancing 18mm at orbitale. The patient did not experience any late or lasting complications. Vision has normalized in one eye, and improved from light perception to 20/100 in the other. Significant neurological improvements have been documented and the patient has returned to developmental baseline. Acute advancements were 19mm(57 to 76) at ANS, 11mm at nasion (62 to 73) and 8mm at point A(64 to 72). Relapse at these points were -3.1, -2.3 and -1.6 respectively at 10 months.
Conclusion: We have demonstrated the technical feasibility of a minimally invasive approach to monobloc osteotomy. Custom designed distractors, new ultrasonic osteotomes and intracranial osteotomy under endoscopic/navigational control have permitted us to perform this procedure without any calvarial or midface degloving. By limiting dissection, the entire bony fragment remains vascularized, providing profound improvements in callus formation, stability and significantly improved complication rate. With this novel approach, many of the limitations of the original operation can be avoided, and the monobloc can now provide superior results with acceptable morbidity.