Available evidence on the safety of cranioplasty materials is limited due to a large diversity in study conduct, patients included and outcomes reported. Autologous bone grafts appear to carry a higher failure risk than allografts. Future publications concerning cranioplasties will benefit by a standardized reporting of surgical procedures, outcomes and graft materials used 1).
It is a simple and cheep alternative to other techniques and is available to any institution that provides autoclaving sterilisation services. 2).
Autologous bone flap cranioplasty remain the gold standard in reconstruction of such cranial defects. However, the morbidity associated with their harvest, additional time required, the need for a second surgical site and the limited supply has led to the search for newer substitutes. Although many materials are available today including biologic and non biologic substitutes, there is still no consensus about the best material.
Although generally accepted concept about timing of cranioplasty using autologous bone is that early cranioplasty has more risk of infection and delayed cranioplasty has risk of non-union or resorption of bone flap.
Shin et al. observed new bone formation on all the frozen autologous bone flaps that was stored within 8 weeks. The timing of cranioplasty may showed no difference of degree of new bone formation. Not only the healing period after cranioplasty but the time interval from craniectomy to cranioplasty could affect the new bone formation 3).
Implantation of autologous cryopreserved bone has been associated with infection rates of up to 33%, resulting in considerable patient morbidity. Predisposing factors for infection and other complications are poorly understood.
A total of 187 patients underwent delayed cranioplasty using autologous bone flaps cryopreserved at -30°C following decompressive craniectomy. Indications for craniectomy were trauma (77.0%), stroke (16.0%), subarachnoid hemorrhage (2.67%), tumor (2.14%), and infection (2.14%). There were 64 complications overall (34.2%), the most common being infection (11.2%) and bone resorption (5.35%). After multivariate analysis, intraoperative cerebrospinal fluid leak was significantly associated with infection, whereas longer duration of surgery and unilateral site were associated with resorption. Cranioplasty using frozen autologous bone is associated with a high rate of infective complications. Intraoperative CSF leak is a potentially modifiable risk factor. Meticulous dissection during cranioplasty surgery to minimize the chance of breaching the dural or pseudodural plane may reduce the chance of bone flap 4)
149 patients who underwent cranioplasty following decompressive craniectomy during the time period January 1998 to December 2012. Autologous bone flaps were sterilised in an autoclave and stored in a refrigerator at a temperature of 8 degrees above zero until cranioplasty was performed. Complications were registered and patient data were analysed in order to identify risk factors for surgical site infection and bone flap resorption after cranioplasty. Only the patients with a follow-up period of >24 months were included in the analysis of bone flap resorption (110 patients).
Surgical side infection occurred in only five patients (3.3%), whereas bone flap resorption developed in 22 patients (20%). The multivariate analysis of the presented data identified the operating time of >120 min (p = 0.0277; OR, 16.877; 95% CI, 1.364-208.906) and the presence of diabetes mellitus (p = 0.0016; OR, 54.261; 95% CI, 4.529-650.083) as independent risk factors of development of infection and the presence of ventriculo-peritoneal (VP) shunt (p < 0.0001; OR, 35.564; 95% CI, 9.962-126.960) as independent risk factor of development of the bone flap resorption.
Reimplantation of the autoclaved autologous bone flap following decompressive craniectomy is a simple and cheep alternative to other techniques and is available to any institution that provides autoclaving sterilisation services. This method is associated with a low rate of surgical site infection, but with a significant rate of the bone flap resorption 5).
In 87 patients. Post-operative complications were recorded in 31 (36 %) patients of whom 22 lost their primary implant. Surgical site infection (SSI) and bone flap resorption (BFR) were the two most common complications, affecting 8 (9.2 %) and 14 (19.7 %) patients, respectively. Only BFR was associated with some of the recorded variables. Using multivariable logistic regression analysis, young age (OR = 0.94, 95 % CI 0.88-1.00, p = 0.04), bone flap fragmentation (OR = 14.3, 95 % CI 2.26-89, p = 0.005), long storage time (OR = 1.03, 95 % CI 1.00-1.04, p = 0.02) and Glasgow Outcome Scale at the time of cranioplasty (OR = 2.55, 95 % CI 1.04-6.23, p = 0.04) were found to be significant risk factors for bone flap resorption.
Cranioplasty after decompressive craniectomy carries a high rate of complications. In this study, SSI and BFR were the two most common complications of which predictive clinical parameters could be identified for BFR only. The results indicate that synthetic implants may be considered in pediatric patients and in cases with fragmented bone flaps or delayed time to cranioplasty. Although the rate of complications was high, 73 % had a successful reinsertion of the autologous graft at a low cost. We feel this result justifies the continued use of cryopreserved bone flaps 6).