Failed back surgery syndrome (FBSS) was controversial since it was proposed in the 1970s because of its various definitions and diagnostic criteria[13, 14].The definition of ‘dissatisfaction’ and ‘persistent pain’ was equated simplistically and misused. In fact, patients with optimistic expectations for surgery had higher degree of satisfaction in despite of similar postoperative pain scores[15], which highlighted the necessity of our modification. The present study introduced a quantitative satisfaction evaluation in order to standardize the definition of FBSS.
The prevalence of FBSS ranges from 10–40% according to different researches[16, 17]. Persistent pain, frequent hospitalization and the resulting heavy financial burden will not only aggravate the doctor-patient contradicts, but also lead to an excessive occupation of medical resources[18]. Unfortunately, most of the existing studies focused on the psychological factors of patients, while ignoring the inherent characteristics of DLD[8, 9, 14]. This research, on the other hand, based on the comprehensive analysis of disease characteristics and identified a series of independent risk factors of FBSS in order to arouse the vigilance of clinicians and patients, so as to manage high-risk population effectively and promptly.
Studies conducted in different medical centers have proved that hypertension has an adverse effect on chronic pain[19, 20]. What’s more, the intake of antihypertensive agents may increase pain sensitivity[21]. Hypertension is significantly associated with postoperative dissatisfaction for adult spinal deformities according to a multicenter retrospective study [22]. We speculate that this effect may be related to hypertension-mediated sympathetic nervous system dysfunction, which lead to a significant rise in neurological complications following operation[23]. At the same time, chronic pain caused by DLD plays an important role in blood pressure regulation by compromising inhibitory descending pathways and reducing the sensitivity of baroreceptors, which result in the impairment of cardiovascular regulation function with a concomitant increase in blood pressure. A vicious circle of ‘pain-hypertension-pain’ was formed eventually [24–26].
The current study confirms the negative effect of IC on spinal surgery. Based on five-year follow-up, a retrospective study noted that walking distance was significantly correlated with postoperative satisfaction of patients with DLD[27]. Sigmundsson et al.[28] analyzed 5100 patients collected prospectively and found that the rate of satisfaction reported by patients with walking distance > 1000m was 2.4 times higher than that of patients with walking distance < 100m. Similarly, a prospective study [29]reported that the risk of postoperative dissatisfaction could be increased by 10.3 times under the condition of walking difficulty who also showed a significant correlation with symptoms that may bring about FBSS, such as postoperative back pain, leg pain and numbness.
In the context of the rampant pandemic, NRS, whose reliability had been fully corroborated, is favored by clinicians due to its comprehensibility and higher compliance [30]. A retrospective cohort study[11] indicated that preoperative NRS leg pain was the only predictor of patient satisfaction following TLIF, which is analogous to our conclusion : for every 1-point increase in preoperative NRS-leg, the risk of FBSS is reduced by 20%. On the one hand, the operation leads to greater improvement in patients afflicted to more severe limb pain and result in increased satisfaction[31]. On the other hand, patients with lower NRS leg pain have more complicated operation willingness than those with higher NRS because of relatively mild neurologic symptoms. When patients with prolonged illness have to resort to surgery, whom they tended to regard as ‘the final solution’, holding too high or even unrealistic expectations that fully restore to health or return to work immediate postoperatively would finally result in dissatisfaction, even if the operation did improve neurological function to some extent.
HIZ and MCs, the reliable biomarkers of persist pain, play an important role in the course of DLD by inducing inflammatory response[32, 33]. Preoperative MCs suggests poor clinical improvement and slow recovery [34], while HIZ indicates severe disc degeneration/displacement and the resulting severe, prolonged low back pain[35]. In addition, refractory or even aggravated pain/numbness caused by HIZ or MCs outside the surgical segment may be another reason for the dissatisfaction of FBSS patients.
Contrary to a general impression, our result confirms that admission for rehabilitation treatment is a risk factor for FBSS. In this study, only 44 people were hospitalized for rehabilitation postoperatively, accounting for 13.2% of the total. Most of patients said it was out of economic considerations, while others were skeptical of the treatment itself. Despite a lot of research, there is no definite conclusion about mode and timing of postoperative rehabilitation, and even the necessity of hospitalization for it [36, 37]. In fact, a number of RCTs and systematic reviews had pointed out the limited benefits of rehabilitation relative to self-management in terms of improving of pain, walking ability, return to work, working ability, satisfaction and amelioration of poor surgical results [36, 38–40]. A similar effect of rehabilitation and sham treatment suggests that psychologic factors have a substantial effect on efficacy assessment[41]. In this case, the behavior of being hospitalized for further treatment implies the dissatisfaction with the effect of surgery, which can be further deepened with the extension of hospital stay and the increase of cost.
There are several limitations in this study. First, a relatively short follow-up time may mask changes in outcome indicators due to other degeneration in long-term follow-up. From another perspective, it enables us to rule out new symptoms caused by deterioration of the degeneration and use the above risk factors to identify risk groups efficiently. Besides, the conclusions derived from this single-center, retrospective study still need to be verified by high-quality RCTs with a rigorous standard of diagnosis. Even so, we believe these risk factors can provide theoretical support for medical providers and encourage them to pay more attention to the management of high-risk groups.