Epidural fibrosis (EF) is a natural consequence of lumbar disc surgery. However, it contributes to significant unsatisfactory relief of symptoms and failed-back syndrome (FBS). EF, by tethering the dura matter, can adversely affect the outcome and make the nerve roots vulnerable to injury, with dural tears occurring during a reoperation along with an increased incidence of arachnoiditis. EF around the nerve root can be more refractory to treatment than the original disc herniation itself. This is in addition to the fact that a reoperation on the scar can produce more scarring [12].

There is no absolutely effective technique that we currently have to reduce EF formation after lumbar disc surgery. Many considerable efforts have been tried to reduce postoperative EF, but none have been found to be ideal. EF still forms even in minimally invasive interventions [3]. Theoretically speaking, decreasing the amount of postoperative hematoma and, hence, its transformation into fibrous tissue, are the main targets to minimize the risk of EF. So, suction drains (SD) used for removal of collections at the operation site may have an important role in this aspect. Other theoretical approaches include providing a barrier between the exposed dura and the healing tissues. Autogenous barriers are practically the best available. Free fat grafting is recognized by some to be the standard treatment for prevention of postoperative EF [456]. Lastly, applying a drug locally, which is supposed to decrease scar tissue formation, may be accepted, provided that it will not add any harm to the patient [78]. The questions of whether SD, epidural fat placement, and local steroids application reduce EF and whether the reduction of EF improves outcomes have not been answered.

There were no clinically significant differences between the groups as measured by neurological tests, occurrence, and clinical signs and symptoms of adverse events or wound healing characteristics. Patients were nearly equally distributed among both groups (57% of the patients are in group I, and 43% are in group II). Demographic factors, such as age, sex, and side of surgery, did not differ significantly between patients with discrete subgroups (Table 1).

Surgical approach was performed at the levels L4-5 (n=155) and L5-S1 (n=135). No complication was reported, and no new neurological deficits occurred. Neither periprocedural surgical complications, wound infection, nor discitis was observed in our patient groups. No adverse events were directly attributable to SD, fat grafts, or steroid local application. Mean length of hospital stay was 3 days. In group I, mean amount of drainage was 35.00±10.0 mL.

In the following sections, the outcome of the statistical analysis concerning sort-term and late pain relief, functional outcome, SLR test, and MRI findings will be discussed in details.

EF prevention has been a subject of concern for decades. In the early 1900s, Lexer [9] first reported the use of free fat grafts for prevention of scar formation. In 1948, Key and Ford [10], described scar-entrapped nerve root after lumbar surgery. In 1974, LaRocca and Macnab [2] described EF as the "post laminectomy membrane" in a canine model. In 1980, Mayfield [11] documented that fat grafts could prevent "constricting cicatrix", as he described. He also noted the possibility of fat grafts acting as a space occupying lesion and causing neural compression.

Lumbar EF around the dura and nerve roots at and near the operative sites proved to be an important cause of FBS, which is reported to occur in 15%, up to 60%, of operated cases [1213141516171819]. Of these FBS cases, EF was reported to be the cause in 10% to 24% of these cases. The postoperative recurrence of pain after an initial pain-free period was often related to EF [17]. In reoperation, the rate of EF significantly increased to even more than 60% with a consequent worse outcome [1420]. The fibrosis-entrapped nerve root is more susceptible to compression due to the tethering effect of the scar tissue around. Moreover, the presence of EF renders reoperations risky and more difficult. EF increases the risk of dural tear during reoperation [21]. Reoperation in these cases often leads to a poor outcome and further scarring [22]. We do not recommend reoperation when EF is the only cause of FBS [23].

If we consider postoperative lumbar EF occurring as a result of normal wound healing, when the operative bed hematoma is invaded by fibrous tissue from the surrounding tissues, it could then be a preventable disease [1624]. LaRocca and Macnab [2] postulated that fibroblasts, of traumatized muscle origin, infiltrate and replace the epidural hematoma with granulation tissue formation. Granulation tissue then matures into a dense fibrous tissue resulting in dura and nerve root irritation, entrapment, compression, and tethering and being more susceptible to injury [1925]. This results ends with recurrent disc pains and acceleration of osteophyte formation [15].

Smaller incisions, less muscle trauma, and good hemostasis failed to completely solve the problem. Even in minimally invasive procedures, EF still formed [25]. Most synthetic materials that were studied as barriers were not effective, with unsatisfactory results and actually inviting more scarring and more complications compared with control groups. Autogenous barriers had better results, including fascia lata graft, pedicled grafts, and free fat grafts [568181923242627].

To minimize the risk of development of EF, we had to decrease the chance of its formation. Theoretically speaking, the absence of blood in the epidural area post-operatively reduces the possibility of EF formation. Also, preservation of the natural epidural fat is a safe and effective barrier to reduce the occurrence of EF, preventing the invasion of fibrous tissue from the surrounding tissues. So, SD for removal postoperative collections may have an important role. Moreover, providing a natural barrier between the dura and the healing tissues may also play an important role. Lastly, applying a drug locally, which is supposed to decrease scar tissue formation, may be theoretically accepted, provided that it will not add any harm to the patient.

Regarding EF and clinical recovery, Jinkins et al. [1] suggested that fibrosis in the epidural space may be less important, and Coskun et al. [13] did not find a relation between EF and pain scores. However, we have found a good correlation between scores for the NVR scale and the grade of EF by MRI. We think that the SD prevents or minimizes postoperative collections, hematoma, or seroma that give rise to EF. In our study, a significant proportion of patients in group I with SD showed pain relief compared to the control group, as well as compared to the baseline findings. Using suction drainage with a combination of fat grafts and steroid local application significantly reduced the frequency and the extent of EF, with a statistically significant difference in short-term and late pain relief between the Intervention group and control group.

Based on our findings, we suggested that fibrosis in the epidural space was important in the pathogenesis of FBS. The good correlation between EF, the MRI findings, and clinical outcomes concluded that using the studied preventive tools significantly reduced the frequency and the extent of EF. This suggested that the EF was not just a radiological entity. Many outcome scales were used to figure out the results of lumbar surgery, making it difficult to compare different studies. Complete or partial relief of pain was achieved in 56% to 86% of the reported series, long-term good to excellent results ranged from 64% to 69%. We achieved clinical and neurological excellent improvement in 63.6% of our patients plus 18.2% of the cases showed fair improvement. We evaluated pain relief, and, most particularly, we evaluated activity-related pain, which is, after all, the most important thing to the patient.

The SD group at 3, 6, and 12 months was clearly superior to the control group. There was a statistically significant difference in short-term and late pain relief between the Intervention group and control group. There was a clear improvement in activity-related pain in SD patients. In the long run, using suction drainage with a combination of fat grafts and steroid local application significantly increased pain relief, significantly improved straight leg raising, and significantly enhanced functional outcome measured by flexion, extension, and lateral flexion angles. We can therefore say that SD and fat graft provide benefits, not only to the patient, but also to the surgeon.

EF formation takes about 6 weeks to 6 months postoperatively, clearly identified on MRI by at least 3 months, stabilized by 6 months, with no further changes at 12 months [12829]. So, in this study, the MRI evaluation follow-up time was 12 months, selected for the effectiveness of analysis. With MRI, EF was clearly identified as a relatively low signal intensity, as compared with the high signal intensity epidural fat, and as the very low signal intensity cerebrospinal fluid on T1-weighted images. EF usually homogeneously enhanced the following contrast administration. So, its identification is possible and makes the differentiation of EF and disc herniation easy [293031].

In this study, we achieved a relatively simple approach for evaluation of EF using axial MR images, with interpretation of its extent. This approach made it possible to study the relation between the extent of EF, patient's symptoms, and surgical outcomes. Precise description of the extent of EF on MRI added clear facts about the causes and pathogenesis of FBS. In contrast to the grading system described by Ross et al. [31], utilizing five levels of the vertebral body and disc level, we only utilized, in this study, three levels evaluation, centered on the level of the neural exit foramina and it was more than enough. The protocol that we used was designed to be easily followed by others.

Cervellini et al. [28], was the first to describe the rate and grade of EF. Cervellini et al. [28] and Sen et al. [6] reported seeing mostly grade II (moderate) EF. Cinotti et al. [29] did not find any correlation between the amount of EF, as seen intraoperatively and on MR, and FBS. In this study, we have evaluated the occurrence rate and EF grades in our patients. At 12 months, 82.2% of the original 290 total cases had a degree or another of EF, with 0% of the intervention group had extensive EF scores, while 40% of the control group had extensive EF scores. We observed that, in patients with SD, formation of EF was prevented or tended to be less extensive, reporting mild and moderate EF in SD-patients and extensive EF in non-SD-patients. This finding supported the idea that the presence of barrier between dura and blood prevented formation of EF. We found that both SD and fat/steroid combinations consistently reduced the frequency and the extent of EF. Combinations were most effective and resulted in up to 100% with minimal or no EF whereas controls exhibited over 64% of the sites with EF. Our results in patients without SD were similar to those in Cervellini's and Sen's series in that the intervention group had less extensive EF and that the control patients had a less degree of nonextensive EF. In addition, our findings demonstrated that fat/steroid combination provided small but apparent additional benefit to those obtained by fat alone, in the SD group. The SD with fat graft and local steroid application patients conversely had not a higher degree of non-extensive scar only, but a trend toward scar prevention.

Ross [30] found that patients with extensive EF were 3.2-fold more likely to experience recurrent radicular pain than those patients with less extensive EF. They reported a significant association between the presence of extensive EF and the recurrence of radicular pain. Our results concerning this correlation conflicted with Cinotti et al. [29] and agreed with the others [223031]. This study demonstrated that, following lumbar disc surgery, with the use of SD, fat grafts, and/or steroids, a significant proportion of patients expected to have chronic, refractory low back and lower extremity pain as part of FBS experienced improvements in NVR scores, compared to the control group. Associated improvements in functional outcomes (range of motion, and SLR tests) were also noted as compared to baseline measurements and results of the control group. Analysis of these results suggested that SD, fat grafts, and/or steroids used after decompressive surgery significantly improved both short and long term outcomes. We considered the amount of EF seen on follow up MRI after lumbar disc surgery an important prognostic factor that should not be bypassed.

This study has clearly demonstrated the fact that the use of suction drainage alone or combined with only fat grafts, fats grafts and local steroids application, or only local steroids application significantly improved patient outcome with respect to short-term and late pain relief, functional outcome, and SLR. In addition, the same tools significantly reduced EF as measured by an MRI. Grading of EF with the mentioned simple MRI grading system showed a good clinical correlation between outcome on one side and the extent of EF on the other side.