Object: Extensive epidural fibrosis after lumbar spine surgery might be an important underlying cause of failed-back syndrome. Based on previously obtained data, the effect of mitomycin C (MMC) in a concentration of 0.1 mg/ml on spinal epidural fibrosis in a rat laminectomy model was investigated in a large series.
Methods: Eighty adult Wistar rats underwent lumbar laminectomy. In 40 rats, MMC in a concentration of 0.1 mg/ml was locally applied to the laminectomy sites. No similar treatment was performed in the other 40 rats. At intervals from one to 12 weeks after laminectomy, both macroscopic and histological evaluations were performed. For radiological investigation, 10 rats underwent magnetic resonance (MR) imaging at 6 weeks postoperatively. Furthermore, the concentration of MMC in cerebrospinal fluid (CSF) and serum was determined 12 hours postoperatively in seven rats. Due to ease of absorption, high levels of MMC were rapidly detectable in serum, whereas the values obtained from the CSF were markedly lower. In the majority of MMC-treated laminectomy sites, epidural scarring was significantly reduced and dural adhesions were absent, in comparison with control sites (p < 0.001), as confirmed by MR images. Accordingly, the macroscopic dissection of epidural fibrous tissue to reexpose the dura mater was performed more easily and without severe bleeding in these rats. The healing of skin and the lumbar fascia was not affected, and dural leakage was not observed. All control sites showed dense epidural fibrosis with marked dural adherence.
Conclusions: In this experimental model, it was shown that locally applied MMC in a concentration of 0.1 mg/ml effectively reduces epidural fibrosis and dural adherence without side effects in rats that underwent lumbar laminectomy.