The therapeutic management of symptomatic LDH includes conservative treatment, epidural infiltrations, percutaneous therapeutic techniques, and surgical treatment. Most patients are responded well to physiotherapy, pharmacotherapy, and epidural steroid injection, while some patients still require percutaneous therapeutic techniques or surgery. LDH is most common in middle-aged patients, and early results has showed good outcomes for lumbar discectomy in younger populations[19-21]. In addition, short-term clinical efficacy of PELD has been showed reliable in treating young patients with LDH[22]. Although early study has reported the outcome of lumbar discectomy in elderly patients is as good as in younger patients[23], the surgical options for patients over 65 years with worse general conditions and more comorbidities is challenging and controversial. Both surgeons and patients should balance the surgical risks and benefits of functional improvement and quality of life.
With less trauma, shorter operative time and hospitalization, and local anesthesia, the endoscopic procedures are considered to be an alternative choice for LDH in older population to reduce the occurrence of surgical complications. However, the degenerative changes of all lumbar spine structure gradually occur in normal aging process and mainly cause central spinal stenosis which affects the elderly most[24]. These changes, including disc herniation, ligament flava hypertrophy, and ossification of longitudinal ligament, increased the complexity of surgery in for elderly patients. Conventional PELD is an effective minimally invasive technique to treat LDH in recent years[13,14], but it is still of several limitations. The working cannula of YESS technique and TESSYS technique were established with the aid of intervention technique, which may lead to the neurological injury. In addition, without adequate foraminoplasty, the nerve root could not be fully exposed and intraspinal adequate decompression is difficult to achieve. Due to the obstructive anatomy, foraminoplasty is challenging at L5-S1 level and the nerve root is not possible to achieve adequate decompression via TF approach[25,26]. Hence, conventional PELD can hardly meet the complex surgical requirement for older patients with severe LDH.
As a developed technique of PELD, FELD is performed with full-endoscopic visualized foraminoplasty, which can ensure adequate decompression of nerve root and spinal canal safely. The fluoroscopy is only used to confirm the surgical level and location of intervertebral foramina in the process of FELD, and all the sequent procedures, including foraminoplasty and discectomy, are performed under endoscopic visualization[27]. Thus, compared with conventional PELD, FELD could significantly reduce the fluoroscopy time and the radiation exposure, and ensure adequate and safe decompression. Besides, IL approach is applied in L5-S1 level to avoid the obstacle of iliac crest. In our current study, we were able to directly compare the clinical outcomes and complications of FELD with O-PLIF for stable LDH in patients over 65 years. Chronic diseases, including hypertension, diabetes, and heart disease, accounted for a significant proportion of 2 groups and the distributions were matched. Meanwhile, the degenerative changes were severe in these elderly patients and the distributions of disc degeneration, facet joint degeneration, and lateral recess stenosis between the 2 groups were also similar. The mean ODI, JOA, and VAS postoperative scores were significantly improved over the preoperative scores in both FELD group and O-PLIF group. Besides, no significant difference was found between the 2 groups in postoperative ODI, JOA, VAS scores, and MacNab evaluation. Therefore, the results suggest FELD is as efficacy as conventional O-PLIF in improving function, low-back and leg pain, and quality of life for patients over 65 years.
Compared with open surgery, endoscopic techniques have significant advantages in the following aspects, including local anesthesia, preserving the normal posterior paraspinal structures, less operative time, less blood loss, and short hospital stay. Although annulus fibrosus fenestration and intraoperative nerve root irritation may be painful under local anesthesia, the surgeon could communicate with patient during the operation to confirm that the symptoms have improved, which indicate adequate decompression of the nerve root[12]. Furthermore, with relatively worse cardiopulmonary function, elderly patients have a lower risk of local anesthesia during surgery. In addition, minimal traumatization of FELD reduces the intraoperative blood loss and further shorten hospital stay. In this study, FELD also showed a significantly shorter mean operative time, less mean intraoperative blood loss, and shorter mean hospitalization time than O-PLIF.
Previous studies showed a neurological complication rate of endoscopic techniques of 0%-12.4%[27]. The neurological adverse event rate of FELD in current case series was 1.3% (2/153), which was lower than that of O-PLIF (3.1%, 3/98). Therefore, FELD was relatively safe even for patients over 65 years. As for total adverse event rate of our study, 8(5.2%) patients in FELD group and 16(16.3%) patients in O-PLIF group developed postoperative adverse events during the follow-up period. The total adverse event rate was significantly higher in elderly patients who underwent O-PLIF and the main adverse events were wound infection, pulmonary, and implant related complications. This may be related to open wound of O-PLIF and long-term postoperative bed rest after surgery. Recurrence is another important problem for endoscopic surgery. Early studies have showed a recurrence rate of 3.7%-6.9% during the follow-up period in all patients with LDH[28,14,26]. In current study, 11(7.2%) in 153 patients over 65 years underwent FELD had recurrence. The recurrence was relatively higher in older people than in the general population. Among the 11 patients who were found recurrence in FELD group, 8 patients underwent FELD once again and the other 3 underwent open surgery for further treatment. Adjacent segment degeneration is common after lumbar fusion surgery, with a high rate ranging from 5.2% to 18.5%[29]. In this study, new disc herniation was found in 6(6.1%) elderly patients at the adjacent segment of fusion, which was consistent with previous reports. Therefore, the patients underwent FELD are at risk for recurrence, while the patients underwent O-PLIF are at risk for new disc herniation at the adjacent segment.
Although our study showed some reliable results, there were several limitations. First, since it was a single-centered retrospective study, the generalizability of our findings was limited and a randomized control trail may be more convincing. Second, the follow-up period was relatively short and a long-term follow-up should be required in the future. In addition, some older patients were illiterate and could not complete the clinical assessments by themselves, therefore, their family members were contacted to help them finish these assessments.