Approaches to minimize the risk of epidural fibrosis after lumbar disc surgery: [clinical - and MRI-based outcome evaluation]

ABSTRACT

Epidural fibrosis [EF] after lumbar disc surgery is a consequence of normal wound healing. Previous clinical studies have demonstrated a significant association between the presence of extensive post-lumbar discectomy EF formation and the recurrence of low-back and radicular pain with poor surgical outcomes in 5% up to 60%; in the nearly absent curable surgical solutions. Moreover, the presence of fibrosis may lead to nerve root tethering and renders reoperations risky. Theoretical approaches to minimizing the risk of developing EF include decreasing the chance of its development by decreasing the amount of postoperative hematoma by suction drainage [SD] and hence its invasion of by dense fibrous tissue; providing a barrier like autogenous fat between the exposed dura and the healing connective tissues; or applying a drug locally which is supposed to decrease scar tissue formation as steroids. In the present study, we aimed to evaluate the results of these theoretical approaches in the clinical and imaging outcomes of patients after lumbar disc surgery. The present study is a prospective, pragmatic, cohort study conducted and designed to evaluate the clinical outcome and efficacy of SD alone and combined with local application of fat grafts and/or steroids in prevention of post-lumbar discectomy EF. These outcomes were compared with outcomes in patients in whom neither the drain nor the barrier or steroids was implanted. A total of 58 patients [25 women, 33 men] indicated for surgery for a symptomatic, unilateral or bilateral, single-level lumbar disc herniation was included in this study. All patients underwent randomization and surgery. Patients were divided into 2 major groups with 33 patients in Group I [intervention group] and 25 patients in Group II [control group]. Group II served as the control, with decompressive surgery of their symptomatic nerve root alone without SD, local fat or steroid application. Group I was subdivided into 4 subgroups [Ia, Ib. Ic, and Id] according to the procedure done, whether decompressive surgery followed by SD alone or SD combined with local fat and/or steroid application. The barrier tested was autogenous fat graft. Thirty one patients underwent surgery at L4-5, and twenty-seven at L5-S1. Clinical outcome was assessed pre-and postoperatively by evaluating pain intensity, and patients' functional outcome. Pain intensity was evaluated in our study by numeric verbal rating [NVR] scale; and the patients' functional clinical outcome was measured by the range of motion and straight leg raising [SLR] tests. Imaging outcome was assessed on the basis of follow-up magnetic resonance imaging [MRI] findings. We proposed an MRI-based grading system for the extent of EF. No operative or early post operative complications were reported, and no new neurological deficits occurred. A significant proportion of patients in group I showed pain relief compared to the control group, as well as compared to the baseline findings. Analysis of functional outcome showed significant improvements in the intervention group compared to the baseline, as well as the control group at intervals of 3 months, 6 months, and 12 months. The results of pain relief and recovery of the functional status at the end of the study [12m] was best in group Id [SD + fat graft + steroids], followed by group Ib [SD + fat graft], group Ic [SD + steroids], and group Ia [SD alone] respectively. The worst results were obtained in the control group II. Based on the definition that less than 6 months of relief is considered short-term and longer than 6 months of relief is considered long-term, a significant number of patients obtained long-term relief with improvement in pain and functional status. At 1-year follow-up MRI examination, there was a trend toward better outcome in the intervention group. Both suction drainage and fatlsteroid combinations consistently reduced the frequency and the extent of epidural fibrosis on MRI. We conclude that, in patients operated on for unilateral, single-level lumbar disc herniations, implantation of suction drainage into the operation site results in less formation of EF radiologically and yields better clinical outcome. Fat grafts further reduced epidural fibrosis and did not impair normal healing. Local steroid is an effective adjuvant in a significant number of patients without adverse effects. Thus, the use of SD with addition of peridural fat barrier and steroids may improve outcome in these patients