The aim of this retrospective research was to evaluate and compare the outcome of PED and PDL in geriatric patients with TSS. Although no significant difference was found in clinical results between both groups, the PED techniques brought advantages in terms of faster recovery, less trauma, and less complications from our own experience.
It has been reported that the lower thoracic spine is the most frequently affected segment while the upper and mid-thoracic vertebrae are rarely affected within the thoracic spine. This propensity was also seen in this retrospective research.
The traditional surgical methods for TSS are laminotomy with or without fusion[4,11]. The procedures depends on general physical condition of patient and TSS type according to CT and MRI evaluation[12]. Some have recommended laminoplasty for the treatment of TSS. However, laminoplasty, merely expands the volume of the spinal canal and does not remove the posterior longitudinal ligament or ligamentum flavum, and intervertebral disc herniation, is not suitable for severe TSS because the procedure sometimes leads to an insufficient decompression and is technically difficult due to the adherence of the OLF to the dura mater. Furthermore, lamina treated with laminoplasty may return to the preoperative position.
At present, laminectomy with or without fusion is the most popular procedure for TSS[13]. It has been considered an effective method for TSS with myelopathy to undergo PDL with or without fusion[14]. Some authors[15,16] have recommended laminectomy with fusion in the treatment of TSS for that instability of the thoracic spine was caused by excessive removal of the lamina and facet joint[11], and therefore it sometimes required pedicle screw fixation and fusion. Although laminectomy achieves a good spinal cord decompression, it comes at the price of multiple complications such as increased incidence of acute neurological deterioration, dura tear, and kyphosis. Since the patients are particularly geriatric who frequently have comorbidities, to consider the necessity for more extensive surgery associated with fusion is vital. Besides, some authours have concluded that decompression alone has lower costs than fusion.
Microendoscopic decompression(MED) treating TSS also has been reported by Baba[17].
Although with a surgeon-friendly view, it requires partial facet joint resection and general anesthesia, which is similar to the traditional open approach. So an effective and less invasive surgical technique is warranted. PED has been popular in the treatment of lumbar degenerative disease because of development of endoscopic instruments and increased patient demand[18]. PED is less invasive than MED for selected patients with lumbar degenerative disease[19,20] . Jia [8] performed the PED for the treatment of one OLF case at T2/3. Miao[9] also reported successful PED in treating two cases with unilateral OLF at T9/10 and T3/4 using the PED with paramedian approach.
The postoperative outcomes showed that preoperative symptoms were relieved and the decompression was completed without severe complications. The PED requires only a incision of approximately 7.5 mm, with the advantages of causing little damage to the paraspinal muscles, dissecting less tissue, and reducing operative time and blood loss. Little lamina and facet joint was removed, therefore no instability of the spine was caused. Pedicle screw fixation and fusion may be unnecessary, the medical costs may be reduced. Moreover, PED can reduce the length of hospitalization[21]. Besides, it can provide clear visualization with saline solution, which is helpful in improving safety of the elderly patients[22]. The surgeons can receive feedback during the operation to reduce the risks of anesthesia related complications and avoiding acute neurological deterioration when removing the OLF and disc herniation with endoscopic instruments. For developing countries, it is very benefcial to economically disadvantaged patients if general anaesthesia with neuromonitoring is not necessary. Moreover, compared with PDL, PED can shorten patients recovery time markedly.
Therefore, this procedure could be an effective choice for geriatric patients for whom general anesthesia would be harmful. As for patients with OLF, we can use the diamond high-speed drill to thin the OLF with clear and enlarged visualization as called floating method. Some authors suggested that it could be used to avoid dural tears if the floating method were used[23].
Neurological deterioration is a serious complication for TSS[24]. Some authors reported that the incidence of perioperative neurological deterioration was as high as 14.5%. The insertion of even a 1-mm Kerrison rongeur into the thoracic canal may cause catastrophic neurological deterioration. Therefore, it is dangerous to remove the lamina with a Kerrison rongeur in the thoracic spine. So, in the process of thoracic laminectomy and spinal cord decompression, we should be very careful, which may cause more time and bleeding than open lumbar decompression. In PDL group, one case experienced neurological deterioration after recovery from anesthesia. Although with use of methylprednisolone and functional exercises, the patient condition was not satisfied at final follow-up.
One of the most common complications of the traditional open spinal decompression is CSF leakage[25]. Although not repaired, no cerebrospinal fluid leakage occurred after endoscopic decompression for one case who had intraoperative dural tears in the PED group. In the PDL group, two cases had CSF leakage after the operation, one of whom had incision infection, which resolved after debridement and antibiotic therapy. Although the recovery was good, the process was painful.
We do not recommend that beginners perform PED independently for the flat learning curve. However, with proper diagnosis, precise indication, and good training, experienced skilled surgeons can use the PED to treat TSS. The primary limitations of the retrospective study are the relatively small number of patients and following time.
