From February 2016 to January 2018, a total of 93 consecutive patients of degenerative spondylolisthesis (grade I-II) were had ELIF and TLIF because of back and leg pain. Ninety-three patients initially fulfilled the study criteria, and seven patients were lost to follow-up. Of the remaining 86 patients available for analysis, 42 cases had ELIF (group ELIF, included 20 men and 22 women with an average age of 51.73 ± 5.48 years), and 44 patients had TLIF (group TLIF, included 23 men and 21 women with an average age of 52.16 ± 5.39 years). The inclusion criteria were adult degenerative spondylolisthesis (grades I–II) which only one or two level fusion (L3/4, L4/5, or couple levels). Exclusion criteria included pathologic conditions of the lumbar spine (trauma, tumor, or infection). The two groups had similar age and sex distribution, level of pain, and the pain history (Table 1).
Table 1 Patients general data (Means ± SD)
|
Group
|
Gender
|
Older
|
Level
|
History
|
|
Male
|
Female
|
(years)
|
L3/4
|
L4/5
|
L3/4,4/5
|
(years)
|
ELIF(42)
|
20
|
22
|
51.73 ± 5.48
|
11
|
19
|
12
|
3.16 ± 1.52
|
TLIF(44)
|
23
|
21
|
52.16 ± 5.39
|
10
|
21
|
13
|
3.28 ± 1.37
|
There was no significant difference between two groups (P > 0.05)
|
Surgical procedures
Under general anesthesia, all patients had nerve decompression, disc removed, bone graft and cage which packed with bone graft were inserted in the interbody space, and pedicle screw instrumentation was used. The TLIF procedure was performed in the standard fashion as reported in previous studies, and the ELIF procedures was performed under C-arm image step by step.[13,20,19] The endoscopic discectomy and nerve decompression was performed at first. After nerve decompression accomplished, the working tube for cage insertion was placed in the disc space, and rechecked by the endoscopic to ensure nerve and dual was safe and working tube was on the good position for subtotal discectomy and endplate preparation. Then, subtotal discectomy and endplate preparation was accomplished using a combination of straight and angled curettes and rasps. Then bone graft and expandable cage which packed with bone graft were inserted in the disc space. The expandable cage are inserted at a contracted height to allow safer entry into the disc space with less chance for impingement of the traversing and exiting nerve roots. The cage is then expanded in the interbody space to restore disc height and obtain interbody cage purchase. Maintaining the pars protects the exiting nerve root and dorsal root ganglion during cage insertion. Third, percutaneous pedicle screw were placement and compression be performed. Thorough release of the disc space and restoration of disc height aids in reduction of spondylolisthesis. If reduction of a spondylolisthesis is still desired, the rods can be fixed into the caudal vertebrae, and the pedicle screws from the cranial vertebra can be reduced to the rod. Fluoroscopic guidance should be used to ensure thorough discectomy and endplate preparation, bone graft and cage insertion, and percutaneous pedicle screw placement (Figure 1,2). Brace support was recommended for 4–6 weeks after surgery.
Figure 1 Male patients of 42 years old had the procedures of ELIF for the spondylolisthesis of L3/4 and L4/5. The figures show the cage position and pedicle screws was good position. The patients had good clinical outcomes and bone fusion at 12 months after operation. A1-A4 shows the endoscopic discectomy and cage insertion in L4/5 disc space. B1-B5 shows the endoscopic discectomy and cage insertion in L3/4 disc space. A5 and B5 shows the lumbar back skin of patient on pre- and post-operation. C1-C4 shows the patient pre-opertion images of x-ray and MRI. C5 and C6 shows the post-operation radiographs of lumbar spine.
Critical of clinical outcomes
Before surgery and at the one year follow-up, operation times, blood loss, hospital stays, pain (Visual Analog Scale, VAS), functional disability (Oswestry Disability Index, ODI), and Mac Nab criteria were quantified in follow-up. All patients had preoperative and post-operative plain radiographs, computed tomography (CT) scans, and magnetic resonance (MR) images. The focus was to evaluate five radiographic characteristics at follow-up: (1) percentage of slip and percentage of reduction, (2) height of disk space and intervertebral foramen, (3) cage position, and (4) fusion rate. Bone fusion was determined on the criteria of continuity of trabecular pattern, and the fusion rate assessed using CT-scan reconstruction.
Figure 2 Female patients of 39 years old had the procedures of ELIF for the spondylolisthesis of L4/5. The figures show the cage position and pedicle screws was good position (A, C ,D), nerve had better decompression (B), and the skin incision was small (E).
Statistical analysis
All measurements were performed by a single observer and are expressed as means ± SD. Using the SPSS 17.0 statistics software, classic t-test and chi-square test were performed.