Letter to the Editor Regarding "Predictors of Surgical Site Infection in Autologous Cranioplasty: A Retrospective Analysis of Subcutaneously Preserved Bone Flaps in Abdominal Pockets"

We read with great interest the article by Alkhaibary et al.1 This study revealed that high blood glucose levels and large skull defect size are significant predictive factors of infection in patients requiring cranioplasty. This study provides important insights to prevent site infections in cranioplasty, and the interpretation of these findings may be enhanced by the following considerations. Uncontrollable high intracranial pressure is the main cause of death after severe traumatic brain injury, and decompressive craniectomy has been proposed as life-saving treatment. Bone flap repositioning is the final step of this treatment, but many complications are troublesome. The literature reports that decompressive craniectomy is associated with increased rate of survival in a vegetative state,2 and the presence of an acute subdural hematoma is associated with an increased risk of hemorrhagic contusions, hydrocephalus, postoperative brain herniation, and poor clinical results.3,4 Furthermore, decompressive craniectomy and cranial reconstruction are procedures often performed in frail patients in poor general condition with a strong predisposition to pulmonary or urinary infections. Many causes may contribute to the onset of infections or postoperative complications. It is well known that elevated blood glucose levels are related to many complications in several diseases and surgical procedures.5,6 Wang et al.7 demonstrated that strict glycemic survey after surgery improves neurologic outcome in neurosurgical patients.7 In contrast, dexamethasone administration may delay wound healing in the general surgical population, especially in diabetic patients.8 At the present time, the best protocol for bone flap conservation in patients who undergo decompressive craniectomy is under debate. Storing the bone flap both in the abdominal subcutaneous tissue and at low freezing temperature are valid and cost-effective solutions, but some problems still exist that may cause bacterial contamination. Nowadays in many countries, including Italy, cryopreservation of the bone flap is the procedure of choice with very low risks of contamination. This procedure is expensive, but it best suits the sterility and the biologic features of the bone flap. Infections may develop owing to other causes: a large defect size of the cranial bone after decompressive craniectomy may facilitate a postoperative infection because of the long operative time necessary for the reconstruction and high skin tension.8 Furthermore, a large bone flap may have insufficient revascularization when repositioned. Other causes of infection or reabsorption of the bone flap were investigated in recent articles, including very young age9 and a large dead space between the cranial bone and the autologous bone flap.10 Another cause of bone flap infection is the long operative time; this is well documented in the literature as a general risk for all surgical procedures.11-13 Finally, if cranioplasty is delayed after decompressive craniectomy, the risk of an unfavorable outcome is very high.14 This could be explained by the decay of the biologic structure of the bone flap when stored for a long time. Recent literature reports that the best time for bone flap repositioning is 3e6 months after decompressive craniectomy.15 In conclusion, the best management of cranioplasty has not been clearly defined, and further efforts are necessary to identify some predictive factors concerning bone flap infection and reabsorption. Other results and future protocols will be useful to perform cranial reconstruction with fewer postoperative complications.