LSS is traditionally treated with open or microscopic laminotomy and foraminotomy via a midline lumbar incision . However, extensive detaching the paraspinal muscles from the spinous processes and lamina may cause increased intraoperative blood loss, postoperative pain and weakness secondary to muscle denervation . Besides, supraspinous and interspinous ligaments injury and extensive facetectomy may cause iatrogenic spinal instability, requiring additional posterior fixation for stabilization [4, 21, 22]. Therefore, various minimally invasive techniques were developed to minimize the surgical trauma [7, 9, 23]. Patients with neurogenic claudication secondary to LSS without degenerative spondylolisthesis or deformity could be treated by both decompression alone and decompression with instrumented fusion [12, 18, 19]. FEV-ULBD and MIS-TLIF are two common minimally invasive procedures to treat LSS, and typical representative of decompression alone technique and decompression plus instrumented fusion technique, respectively. The present retrospective study revealed that both FEV-ULBD and MIS-TLIF are effective to treat one-level LSS without degenerative spondylolisthesis or deformity. As a result, FEV-ULBD is a more minimally invasive option for patients with one-level LSS without degenerative spondylolisthesis or deformity. Moreover, FEV-ULBD is of less economic burden than MIS-TLIF.
During FEV-ULBD, laminotomy and and foraminotomy could be safely performed under excellent endoscopic visualization to guarantee complete decompression, minimize surgical trauma, and prevent spinal instability [8, 10, 11]. However, sufficient decompression without violating the stability of the facet joints may be technically difficult in cases with narrow interlaminar spaces, posterior marginal osteoproliferation of the vertebrae, ossification of the posterior longitudinal ligaments, and recurrences [8, 10]. Excessive facetectomy may be inevitable for sufficient lateral recess decompression and foraminotomy, exacerbating postoperative instability. In the present study, undercutting of the cranial lamina was performed during FEV-ULBD to overcome the difficulty during insertion of the working sheath . Additionally, the excellent endoscopic visualization achieved during FEV-ULBD ensure the undercutting of the cranial lamina, minimized facetectomy, and sufficient decompression of the lateral recess and foramen.
The advantages of FEV-ULBD were to perform bilateral decompression via a unilateral approach with minimize traumatization to the paraspinal musculoligamentous structures; to ensure the sufficient decompression the lateral recess and foramen under excellent endoscopic visualization to minimize neurological injury; and to preserve the stability of the spine with minimized foraminotomy [4, 8, 10, 11]. On the other hand, FEV-ULBD has some disadvantages, such as the steep learning curve. Muscles, facet cysts, and ligaments may be difficult to identify under endoscopic visualization, increasing the risk for iatrogenic injury.
MIS-TLIF has been demonstrated to be a safe option for lumbar fusion with minimized iatrogenic traumatization to the paraspinal musculoligamentous structures [16, 17]. Compared with traditional open TLIF, MIS-TLIF was of similar good clinical outcomes, fusion rates, less postoperative back pain, shorter time to ambulation, and length of hospitalization [16, 17]. MIS-TLIF was performed to achieve the sufficient decompression of LSS, immediate improvement of spinal alignment, and prevention of spinal instability.
While it is controversial about the necessity of instrumented fusion after decompression of LSS [8, 12, 18, 19]. Nowadays, there are growing evidences suggest that decompression alone is better for LSS without degenerative spondylolisthesis or deformity . Försth et al. [19, 25] found that decompression with instrumented fusion did not result in better clinical outcomes than decompression alone for LSS with or without degenerative spondylolisthesis. Compared with decompression alone surgery, the addition of instrumented fusion to decompression surgery significantly increased the hospital costs, including the costs of surgery and the length of hospitalization . In the present study, FEV-ULBD and MIS-TLIF were of similar outcomes, while FEV-ULBD were of lower healthcare cost. As a result, addition of instrumented fusion to decompression surgery may be not necessary.
There are some limitations to the present study. First, it is a retrospective, non-randomized controlled cohort study with a small sample size and short follow-up period. There also may be selection bias, as surgeons determined whether decompression alone or decompress with instrumented fusion should be performed. Further prospective, randomized, controlled studies, with larger sample sizes and longer follow-up periods should be conducted to determine the optimal surgical management for patients with LSS. Second, all the patients included were of one-level LSS without degenerative spondylolisthesis or deformity. As a result, further studies should be conducted to compare the clinical outcomes of FEV-ULBD and MIS-TLIF for LSS with degenerative spondylolisthesis or deformity. Besides, preexisting adjacent level degeneration was not evaluated and compared in the present study.