Page 78 - Clinical relevance of current materials for cranial implants

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Chapter 3
Time interval between decompressive craniectomy and cranioplasty
The time interval between decompressive craniectomy and cranioplasty is often considered as a potential risk factor for complications like flap failure,8,21 which was confirmed in this study. On the other hand, several studies did not find such an association6,22,26. As a consequence, no consensus on the optimal time interval between decompressive craniectomy and cranioplasty exists. Many studies distinguish an ‘early’ and ‘late’ group, with varying thresholds; 2 weeks, 2 months, 3 months, and even 6 months have been reported.16,21,26,28,29,36,40,41 It has been recommended that the cranioplasty be performed at a later stage to avoid operating in a possibly contaminated wound4. In contrast, recent findings suggest the cranioplasty may be better performed at an earlier stage to reduce the burden on the patient. Moreover, it may prevent the syndrome of the trephined, and lead to better neurological improvement.4,21,42
Schuss et al. showed a significantly lower resorption rate when the autologous bone was reinserted within two months after decompressive craniectomy. Bone flap resorption was observed after about three months after cranioplasty36. Brommeland et al. showed a significantly higher resorption rate in delayed cranioplasties30. This phenomenon may suggest that if cranioplasty is considered at a later stage in patients who are neurologically unstable, an alloplastic reconstruction may be preferred. Schoekler and Trummer reported a mean interval of 419 days before resorption was observed. However, the timing between decompressive craniectomy and cranioplasty did not significantly influence bone resorption. Still, they recommended the use of an alloplastic cranioplasty when the cranioplasty was planned within two months after the decompressive craniectomy16.
A possible reason why resorption is dependent on the time interval between decompressive craniectomy and cranioplasty is the cell viability in the bone graft. The literature reports that autologous bone stored in bone banks at -80°C contains viable cells. It is likely that these cells respond differently to cold storage. If osteocytes in some patients are more vulnerable, this may lead to worse outcomes due to increased resorption.43 On the other hand, bone flaps kept frozen for 19 months have been shown to maintain the capacity for revascularization38.