This was the first prospective cohort study on the clinical effects between lumbar endoscopic fusion surgery and PLIF for the treatment of LSS with degenerative instability at present. Our present results showed that the clinical effects on PE-TLIF for the treatment of LSS with degenerative instability was not inferior than PLIF, and the muscle injury degree in PE-TLIF technique was superior to PLIF operation, and the postoperative drainage volume, postoperative bedridden time, and postoperative VAS-LBP was significantly better for the patients treated by PE-TLIF surgery.
PLIF demonstrated a satisfactory clinical effect for the treatment of lumbar spinal stenosis[4, 13, 14]. Nevertheless, extensive destruction of posterior muscular-ligamentous complex usually leads to muscular atrophy, tremendous postoperative pain, and functional disability[6, 7]. Some researchers found that bilateral stripping of the multifidus on PLIF was related to paraspinal muscle atrophy, and about 20% patients with failed back surgery syndrome was associated with paraspinal muscle atrophy[15, 16]. Kalichman et al found that there was a causal relationship between changes in the paraspinal muscles and low back pain, and a higher density of paraspinal muscles could decrease the symptom of low back pain[17]. In addition, Ranger et al showed that the extent of paraspinal muscle atrophy was associated with postoperative low back pain[18]. In addition, Khan et al described that back-muscle morphometry should be included as a predictor of clinical outcomes in order to improve postoperative functional results and reduce the surgery-related complications[19]. Hence, more and more surgeons believed that decreasing the injury extent of paraspinal muscles was very important to improve the postoperative functional outcomes and reduce the surgical complication rate.
Minimally invasive spine surgeries (MISS) gained popularity to overcome the drawbacks on traditional open surgeries. There are some advantages on MISS, including minimal soft tissue injury, satisfactory clinical effects, reduced the occurrence rate of surgical complication, and better cost-effectiveness[20]. Schwender et al firstly introduced the minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF), and MIS-TLIF technique presented the potential advantages over traditional open techniques[21]. Then, the MIS-TLIF became popular, and obtained satisfactory clinical improvement and fusion rate[22, 23]. Although the MIS-TLIF could minimize the injury to normal anatomic structures, the technique still requires an open incision of the posterior muscular-ligamentous complex for tube placement. Therefore, some surgeons have attempted endoscopic lumbar fusion techniques. Said et al. firstly reported endoscopic fusion techniques for the treatment of lumbar degenerative diseases. The technique could acquire good clinical outcomes, but the complication rate was relative higher[10]. Then Jacquot et al did not recommend the kind of technique because of the 36% complication rate[11]. Hence, decisive technical improvements have been made to reduce the complication rate, including cage improvement, approach modification, and intraoperative visualization enhancement. We also developed our technique named PE-TLIF, and initial clinical results was favorable[12].
In our study, we compared the effectiveness of PE-TLIF and PLIF for the treatment of LSS with degenerative instability. PE-TLIF could obtained similar clinical effects and less muscle injury degree. CK, Max-CSA, and PI were employed to investigate the muscle injury in our study. In the follow-up after operation, these muscle injury related indicators was significantly better in PE-TLIF group than these in PLIF group. The postoperative rehabilitation was significantly improved in PE-TLIF, such as postoperative bedridden time and postoperative VAS-LBP. The compilation rate was low, and only 1 patient suffered temporary knee tendon hyperreflexia. Nerve root injury and cage migration was not included in our study. Our technique made decisive technical improvements, including innovative expandable cage and modified approach. The learning curve on our technique is not very steep, and the technique is easy to be popularized.
The major advantage of our technique is that we innovatively develop some instruments such as guided SAP resection device and parallel expandable cage. We also improved the diameter of working channel to protect the exiting nerve root and the traversing nerve root, and to the benefit of cage insertion via percutaneous surgery. In our clinical experience, the standard operation procedure of guided SAP resection device is very important on our technique, and the SAP device has the ability to ensure the SAP sufficient and safe resection. We also used the innovative hook-shaped front of the cannula to restrict the depth of trepan-cutting SAP to protect the exiting nerve root and dura mater. Endplate preparation played an important role in the fusion aspect, the appearance of hemorrhagic exudation from bone endplate was acceptable under the endoscopic visualization. We also recommend iliac bone autograft and adequate bone graft (≥5mm3 per intervertebral space).
To the best of our knowledge, this is the first prospective cohort study on percutaneous endoscopic transforaminal lumbar interbody fusion for the treatment of LSS with degenerative instability. The muscle injury evaluation between endoscopic lumbar fusion surgery and traditional open surgery was firstly reported in our study. All surgeries were performed by one senior surgeon. A number of data on the characteristics of patients, treatment results and complications were reported in our study. However, certain limitations need be addressed. The number of patients is relatively small. More prospective randomized controlled trials are needed to overcome the limitations of our study.