Effect of bioabsorbable osseous fixation materials on dura mater and brain tissue.

Bioabsorbable materials are frequently used in pediatric cranial surgery, but the effects of these materials on neural tissue are not known. The authors assessed the histologic alterations to dura mater and brain tissue associated with bioabsorbable plates. Fifteen Sprague-Dawley rats were given sham cranial surgery; an additional 30 underwent placement of 8 x 8-mm polylactic acid/poly-glycolic acid plates. The rats were assessed weekly for neurologic or behavioral changes suggesting neural damage. A portion of each group was killed at 3, 6, and 12 months for histologic analysis of cranium, dura mater, and brain tissue by standard hematoxylin and eosin stain. None of the animals showed any behavioral changes or neurologic deficits. The plates were gradually hydrolyzed over the study period, and all had disappeared by 12 months. The histologic examination showed fibrous encapsulation around the plates, accompanied by foreign body giant cell reaction and calcification. Focal gliosis, where evident, was mild and confined primarily to the superficial cortex of the brain beneath the plate. The infiltration of the dura mater and underlying brain parenchyma was negligible. In conclusion, the neurologic and histologic effect of bioabsorbable plates on neural tissue may be considered negligible in the early postoperative period.