Poly(3-hydroxybutyrate) (PHB) patches for covering anterior skull base defects - an animal study with minipigs

We conclude that PHB patch material may fulfil the specific requirements that are necessary for a dural substitute, including defect closure, stability and biocompatibility. Our results support the assumed positive influence of PHB on bone regeneration.

Although many experimental and clinical studies have been performed to identify a suitable material to repair defects of the dura mater, no ideal dural substitute is currently available. PHB is a biodegradable and biocompatible polymer that might serve as dural substitute and osteosynthesis material in cranial bone defects.

Different standardized PHB patches were used in six minipigs for covering defined bone defects in the anterior skull base including a dura mater lesion as well as in the frontal sinus front wall. After a defined time of implantation of 3, 6, and 9 months PHB patches were explanted and examined for clinical findings, biodegradation, presence of microorganisms, histological findings, and electron microscopy.

The examinations revealed an increasing closure of bone defect corresponding with time. The anterior skull base bone defect was completely closed after 9 months. The histological findings revealed a connective tissue and callus formation around the PHB patches with fibroblasts and foreign body/giant cell reaction growing through PHB membrane pores. There were no reactions or adhesions between brain and PHB or dura mater and PHB, respectively. Investigations of biodegradation and electron microscopy revealed a continuous breakdown of PHB in the course of time with variations due to different PHB structures. Microbiological investigations could not detect any florid intracranial infection.