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BACKGROUND: Continuing advances in cranioplasty have enabled repair of increasingly complicated cranial defects. The development of improved alloplastic materials and employment of free tissue transfer have led to more durable repairs with improved aesthetics. Despite the plethora of reconstructive options, the optimal materials and approaches for particular clinical scenarios remain unclear. This study examines outcomes following cranioplasty for a variety of indications in patients treated with alloplastic material, autogenous tissue, or a combination of both.
METHODS: A retrospective analysis was conducted on patients who had cranioplasty performed at University of Maryland Shock Trauma Center and Johns Hopkins Hospital between 1993 and 2010. A total of 180 patients underwent 195 procedures. Data on patient demographics, reconstructive method, and incidence of complications were obtained. Outcomes studied include infection, wound dehiscence, exposure or resorption of cranioplasty material, flap loss, sinus tract formation, CSF leak, fluid collection, and death. Requirement for reoperation was also noted. Statistical analysis utilized univariate and multivariate logistic regression. In cases where a clinically significant interaction was suspected, Analysis of Covariance was conducted.
RESULTS: Materials used for cranioplasty included alloplastic 42.6% (83/195), autologous 19.0% (37/195), and both combined 38.5% (75/195). Mean defect size was 70.5 cm². A subset of patients had undergone previous irradiation 12.2% (22/180) or had infections 30.6% (55/180) prior to their procedure. The most common complication in this study was post-operative infection 15.9% (31/195). Factors that significantly predisposed to complications included preoperative radiation, previous infection, and frontal location. Preoperative radiation was the strongest predictor of whether patients would develop any complication with an odds ratio (OR) of 7.58 (p < 0.001). These patients were more likely to require repeat operations than their non-irradiated counterparts (OR 5.28, p < 0.005). Patients undergoing frontal cranioplasties were also more likely to require repeat operations (OR 2.03, p < 0.05) than those with cranioplasties in other locations. Preoperative infection predisposed patients to exposure of cranioplasty material almost exclusively in alloplastic reconstructions (OR 4.02, p < 0.005). Preliminary multivariate analysis suggested that in patients with autologous reconstruction, the odds of developing a post-operative infection increased from 0.115 to 0.191 upon exposure to pre-operative radiation. An increase in the odds of post-operative infection was also observed in patients reconstructed with alloplastic material and exposed to radiation, with an increase in this case from 0.193 to 0.312. However, the odds of experiencing any complication did not vary significantly between patients who had alloplastic reconstructions and those who did not.
CONCLUSIONS: Despite the evolution of cranioplasty techniques and materials, complications are not uncommon in these difficult reconstructions. The choice of reconstructive material may modify the risk of developing postoperative complications, but it appears less important than the clinical history in affecting outcome. Attempts to eradicate preexisting infection and minimize exposure to radiation may limit complications in cranioplasty procedures.

Odds Ratios for Factors Influencing Complications - Univariate Analysis

	Post-op Infection	Reoperation	Exposure of Material	Any Complication
Alloplastic vs Autologous	1.70 (p=0.352)	0.38(p<0.05)	2.68 (p=0.196)	2.22 (p=0.077)
Frontal Defect vs All Other	1.07 (p=0.856)	2.03 (p<0.05)	0.60 (p=2.52)	1.05 (p=0.867)
Pre-op Radiation vs No Pre-op Radiation	1.66 (p=0.356)	5.28 (p<0.005)	2.53 (p=0.101)	7.58 (p<0.001)
Pre-op Infection vs No Pre-op Infection	2.09 (p=0.068)	0.82(p=0.540)	4.02 (p<0.005)	2.15 (p<0.05)