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Long-term Explantation and Complication Rates of Autologous Heterotopic Bone Graft versus Alloplastic Cranioplasties
Michelle K. Oberoi, BA, BS1,2, Sarah Mirzaie, BS1, Kelly X. Huang, HSD1, Vivian J. Hu, BS1, Shaokui Ge PhD2, Miles J. Pfaff, MD, MHS1, Justine C. Lee, MD, PhD1 1 Division of Plastic and Reconstructive Surgery, University of California, Los Angeles, David Geffen School of Medicine, Los Angeles, CA 2 University of California, Riverside School of Medicine, Riverside, CA

Background: Materials for reconstruction of calvarial defects may be classified into two major categories: autologous or alloplastic. In most circumstances, autologous bone is replaced immediately after craniotomy. However, in circumstances when immediate bone replacement is not possible, autologous reconstruction may occur via delayed replacement of banked autologous bone or fresh heterotopic autologous bone retrieved as split grafts from the adjacent calvarium or as flaps from rib or iliac bone. Alternatively, alloplastic materials such as polyetheretherketone (PEEK), polymethylmethacrylate (PMMA), hydroxyapatite (HA), and titanium may be used. While the neurosurgical literature is replete with comparisons of cranioplasty outcomes of banked autologous calvarium versus alloplastic materials, few direct comparisons of fresh, autologous heterotopic bone versus alloplastic materials exist. In this work, we performed a systematic review of the literature to evaluate the long-term cranioplasty outcomes of fresh, heterotopic autologous bone grafting versus alloplastic materials for cranioplasties, specifically focusing on explantation and complication rates.

Methods: A systematic review was performed on PubMed for studies published between March 1971 and December 2020. Inclusion criteria consisted of a mean follow-up ≥ 12 months. Exclusion criteria included publications reporting craniosynostosis cranial vault remodeling, skull recontouring, and compiled outcomes for multiple or mixed materials. Extracted variables included patient demographics, operative details, and explantation and complication rates. Bias was evaluated with the Newcastle-Ottawa instrument. Statistical analyses were performed with independent t, Mann-Whitney U, and Kruskal-Wallis tests (p < 0.05 considered significant).

Results: Thirty articles met the inclusion criteria totaling 109 autologous patients and 1130 alloplastic patients, averaging a follow-up of 31.49 20.70 months, age of 37.33 13.50 years, and defect size of 61.26 33.25 cm2. There were no significant differences in the demographics between the publications reporting outcomes on autologous and alloplastic materials. Compared to alloplastic materials, autologous bone had lower rates of overall explantation (11.95 9.60%, 4.59 4.08%, p = 0.0234), explantation due to infection (6.81 5.83%, 1.83 2.36%, p=0.0118), overall complication (30.18 21.73%, 8.26 10.98%, p = 0.0110), and complication due to infection (7.79 5.23%, 2.75 3.25%, p = 0.0337), Dunn's multiple comparisons test comparing the different materials (autologous bone, PEEK, PMMA, and titanium) revealed that compared to autologous bone, PMMA exhibited greater overall explantation rates (4.59 4.08%, 14.51 10.67%, p = 0.0351), explantation rates due to infection (1.83 2.36%, 8.33 5.67%, p = 0.0093), and complication rates due to infection (2.75 3.25%, 8.33 5.67%, p = 0.0437).

Conclusion: Our findings suggest greater rates of complication and explantation in alloplastic implants compared to autologous heterotopic bone. Specifically, PMMA showed greater rates of overall explantation and of explantation due to infection than did autologous bone.

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