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PURPOSE: To evaluate outcomes after alloplastic cranioplasty in previously infected sites.
METHODS: Medical records were collected from all patients who underwent a cranioplasty at UCSF Medical Center between 1999 and 2007. Patients were stratified by the cranioplasty material used and the presence of a previous infection. The following risk factors were then examined to determine whether they influenced cranioplasty outcome: age, gender, diabetes, hypertension, vascular disease, smoking history, history of radiation, cranioplasty material, and time between surgical site infection and cranioplasty. Microbial analysis was performed to determine the most common causes of initial and recurring infections.
RESULTS: In total, 399 patients were collected. Of these, 109 patients had an occipital encephaloceole repair, a craniosynsostosis repair, or were inaccurately coded. 109 underwent repair with delayed placement of the primary calvarial graft and 181 were repaired with alloplastic materials: titanium mesh, polymethylmethacrylate, or hydroxyapatite. There were 48 alloplastic repairs performed in previously infected sites. 19 had recurrent infections requiring graft removal, resulting in a 40% re-infection rate. This is significantly higher than the 15% infection rate seen with the alloplastic cranioplasties performed in sterile surgical sites. (p<0.001) Neither the cranioplasty material nor the variables examined correlated with increased rates of infection in either sterile or previously infected sites. Microbial analysis showed that MSSA and MRSA are the major sources of infection and are the most likely to recur. (See Table 1)
CONCLUSION: The rate of re-infection in previously infected cranioplasty sites is significantly higher than in sterile sites. The reason for this is likely multifactorial. MSSA and MRSA are the most significant offenders.

Microbial Analysis

Table 1	Sterile Site	Previously Infected Site
Micro	Infection- total(%)	Re-infection- total(%)	Re-infection with same organism- total(%)
MSSA	9(43%)	7(39%)	5(71%)
MRSA	4(19%)	3(17%)	2(29%)
Other*	5(24%)	5(28%)	0(0%)
no growth	3(14%)	3(17%)	~
no record	1	1	~
*includes propionibacterium acnes, staph epi, strep viridans, pseudomonas, c. difficile, fusobacterium nucleatum, enterobacter cloaca, serratia marscesans, enterococcus faecium, staph lugdunensis, stenotrophomonas, streptococcus anginosus, corynebacterium, scedosporium angiospermum, multimicrobial anaerobes