Early effect of standalone oblique lateral interbody fusion vs. combined with lateral screw fixation of the vertebral body on single-level lumbar degenerative disc disease: A pilot study

Abstract

BACKGROUND:

For the treatment of single-level lumbar degenerative disc disease (DDD), oblique lateral interbody fusion (OLIF) has clinical advantages. Whether internal fixation needs to be combined for treatment has been the subject of debate.

OBJECTIVE:

To compare the early clinical effects of standalone oblique lateral interbody fusion (S-OLIF) versus OLIF combined with lateral screw fixation of the vertebral body (F-OLIF) on single-level lumbar DDD.

METHODS:

A retrospective analysis was performed on the data of 34 patients for whom the OLIF technique was applied to treat single-level lumbar DDD from August 2018 to May 2021. Patients were divided into the S-OLIF ( $n=$ 18) and F-OLIF groups ( $n=$ 16). Intraoperative blood loss, operative time, and length of hospital stay were recorded. The pain visual analogue scale (VAS) and Oswestry disability index (ODI) before and after the operation were evaluated. The disc height (DH), foraminal height (FH), fused segment lordosis (FSL), lumbar lordosis (LL), cage subsidence, and fusion by CT examination were measured before and after the operation.

RESULTS:

The S-OLIF group experienced a shorter operative time and less intraoperative blood loss than the F-OLIF group, and the differences were statistically significant ( $p<$ 0.05), but the difference in the length of hospital stay was not statistically significant. The postoperative VAS score and ODI of the two groups were significantly lower than those before the operation, but the postoperative differences between the two groups were not statistically significant. Differences were not statistically significant in postoperative FH, DH, FSL and LL of the two groups. Both groups were followed up for no less than 12 months. In the two groups, fusion was achieved at the last follow-up visit.

CONCLUSION:

According to short-term follow-up results, both S-OLIF and F-OLIF can achieve reliable and stable fusion and good clinical effect in the treatment of single-level lumbar DDD.

Keywords

Lumbar spine lumbar degenerative disc oblique lateral interbody fusion minimally invasive clinical effect

1. Introduction

Different lumbar interbody fusion techniques have been widely used to treat chronic lumbar degenerative disc disease (DDD) [1, 2]. After posterior lumbar interbody fusion (PLIF/TLIF) operations, the iatrogenic muscle injury, nerve turbulence, postoperative neurological symptoms, and chronic back pain seriously affect the postoperative effect. Carpener [3] proposed anterior lumbar interbody fusion (ALIF) for patients without spinal stenosis and with neural tube stenosis, which has a 3%–5% risk of retroperitoneal vascular injury. To effectively reduce the risk of retroperitoneal vascular injury, McAfee et al. [4] proposed extreme lateral interbody fusion (XLIF/DLIF), which poses a risk of lumbar plexus and psoas major muscle injury caused by operating through the psoas major muscle [5, 6]. This technique resulted in 62.7% of patients with transient neurological symptoms and 30% of patients with postoperative front thigh numbness and even hip flexor weakness [7].

Oblique lateral interbody fusion (OLIF) was proposed by Mayerr [8] in 1997, by which the lumbar spine can be reached via the space between the retroperitoneal psoas major muscle and the great abdominal vascular sheath, thereby avoiding the lumbar plexus nerve structure between the great vessels and the psoas major muscle. Clinical studies have shown that OLIF poses a much lower risk of nerve injury compared with XLIF/DLIF and a much lower risk of vascular injury and abdominal complications than ALIF. On the treatment of single-level lumbar DDD, OLIF has the clinical advantages of short operative time, little intraoperative blood loss, and fast postoperative recovery [9, 10]. Whether internal fixation needs to be combined for treatment has been the subject of debate. Ohtori et al. [10] reported that, compared with standalone OLIF (S-OLIF), OLIF combined with posterior screw internal fixation was more effective. At present, there is no report of OILF in combination with lateral screw internal fixation of the vertebral body. This study was to confirm whether S-OLIF could achieve the same effect on such patients without combining with lateral screw fixation of the vertebral body. By retrospective analysis of the data of patients adopting OLIF with or without lateral screw fixation of the vertebral body (S-OLIF OR F-OLIF) to treat single-level lumbar DDD from August 2018 to May 2021, recent curative effects were satisfactory.

2. Materials and methods

2.1 Subjects

Inclusion Criteria

1.
Discogenic back pain was diagnosed by discography, and 3 months of conservative therapy failed;
2.
Lumbar spondylolisthesis (first degree, second degree);
3.
Lumbar hyperextension and hyperflexion X-ray radiographs indicated lumbar instability and induced symptoms;
4.
Patients with lesions located in L3–L5 and who received a single-level operation;
5.
Imaging examination and evaluation showed the space between the psoas major muscle and the abdominal vascular sheath was $>$ 1 cm without vascular variation.

Exclusion Criteria

1.
Patients who had no space between the abdominal vascular sheath and the psoas major muscle, blood vessels were variable, and no disc space which was proved by preoperative computed tomography (CT);
2.
Osteoporosis, preoperative bone mineral density with T $<-$ 2.5 standard deviations (SD);
3.
History of anterior lumbar operation or abdominal operation;
4.
Degenerative scoliosis with severe articular process hypertrophy and fusion, severe spinal stenosis, or nerve root compression;
5.
Isthmic spondylolisthesis and adjacent segment disease at the distal end of the original fusion segment, with fusion segments $\geqslant$ 3;
6.
Obesity (body mass index [BMI] $>$ 35 kg/m ${}^{2}$ ).

In accordance with the inclusion and exclusion criteria, data included in this study comprised that of 34 patients for whom the OLIF technique was used to treat single-level lumbar DDD from August 2018 to May 2021, with a postoperative follow-up occurring $\geqslant$ 12 months. This retrospective study was approved by the Ethics Committee of the authors’ affiliated institutions (Approval number no. K2020-12-025). The need for individual consent was waived by the committee because of the retrospective nature of the study.
2.2 Procedure

2.2.1 Preoperative preparation

Patients received radiography of the anteroposterior and lateral position, bilateral oblique, hyperextension and hyperflexion position, lumbar spine CT and magnetic resonance imaging (MRI). The size of the space between the psoas major muscle and the abdominal vascular sheath at the operative segment was evaluated by CT and MRI, the transverse diameter of the target vertebral body and DH were measured, and the model of the interbody fusion cage required was preliminarily estimated. Discogenic back pain patients were diagnosed by preoperative discography.

2.2.2 Operating method

The operation was performed by the same team of doctors. The department personnel structure of our hospital consists of discipline leaders and department directors to formulate the operation plan. There are 4 doctors in the same team (2 doctors in each group of two spinal treatment groups). The patients were in the right lateral decubitus position after induction of general anesthesia. The OLIF operating steps adopted in the S-OLIF group are described in relevant literature [8].

In the F-OLIF group, one pedicle screw and one rod were separately inserted on the center of the lateral edge of the target vertebral body, close to the opening of the upper and low edges of the end plate, screw tap, and vertebral bodies, and later locked and fixed. By C-arm X-ray system fluoroscopy, the positions of fusion cages and screws, adjacent blood vessels, and nerves were checked, the retractor system was carefully removed, and incisions were closed layer by layer. Neural electrophysiology monitoring was not performed during the operation.

2.2.3 Operation and hospitalization situation, follow-up, and efficacy assessment parameters

The operative time, intraoperative blood loss, length of hospital stay, and complications of the two groups were recorded. The preoperative and postoperative pain degree was evaluated by the VAS score. The functional status was evaluated by the ODI. Lateral X-ray imaging before and after the operation was used to measure the following parameters, plus others: (1) the DH (the mean of the heights of the anterior and posterior edges of the disc space); (2) the FH (the maximum distance between the tops of the two vaults that are constituted with the inferior vertebral notch of the upper vertebral body and the superior vertebral notch of the lower vertebral body); (3) the FSL (the included angle between the connection line of the end plates of the upper vertebral body and the connection line of the lower end plates of the lower vertebral body); (4) the LL (the included angle between the connection line of the end plates at L1 and the connection line of the end plates at S1). The location and fusion of the cage were evaluated by CT.

2.3 Statistical analysis

In this study, serial retrospective cases were analyzed. Measurement data (operative time, intraoperative blood loss, length of hospital stay, follow-up time, VAS score, ODI, DH, FH, FSL, and LL) were expressed by mean $\pm$ SD, and the $t$ -test was used for comparison between the two groups. The enumeration data (gender, lesion segment) were analyzed by continuous calibration chi-squared test or Fisher’s exact test. SPSS Statistics version 24.0 was adopted for statistical analysis of data. $P<$ 0.05 indicated a statistically significant difference.

3. Results

A total of 18 cases were included in the S-OLIF, including 13 females and 5 males, aged 58.39 $\pm$ 5.03 years. The cause of disease comprised 3 cases (17.7%) of discogenic back pain, 5 cases (28.8%) of lumbar instability, and 10 cases (55.5%) of lumbar spondylolisthesis (first degree, second degree). The lesion segment was 4 cases at L3–L4 and 14 cases at L4–L5. The preoperative pain VAS score was 6.83 $\pm$ 1.1. The preoperative Oswestry disability index (ODI) was 45.94% $\pm$ 3.73%. The preoperative imaging indexes were DH of 7.21 $\pm$ 0.24 mm, FH of 11.5 $\pm$ 1.38 mm, FSL of 17.67 ${}^{\circ}$ $\pm$ 1.08 ${}^{\circ}$ , and LL of 51.72 ${}^{\circ}$ $\pm$ 2.32 ${}^{\circ}$ .

A total of 16 cases were included in the F-OLIF group, including 12 females and 4 males, aged 59.00 $\pm$ 4.59 years. The cause of disease comprised 3 cases (18.7%) of discogenic back pain, 4 cases (25%) of lumbar instability, and 9 cases (56.3%) of lumbar spondylolisthesis (first degree, second degree). The lesion segment was 3 cases at L3–L4 and 13 cases at L4–L5. The preoperative VAS score was 7.00 $\pm$ 1.03. The preoperative ODI was 45.5% $\pm$ 3.78%. The preoperative imaging indexes were DH of 7.45 $\pm$ 0.34 mm, FH of 11.13 $\pm$ 1.15 mm, FSL of 18.06 ${}^{\circ}$ $\pm$ 1.18 ${}^{\circ}$ , and LL of 52.56 ${}^{\circ}$ $\pm$ 4.34 ${}^{\circ}$ .

There were no statistically significant differences in general data such as gender, age, lesion type, segment, and in preoperative indexes such as VAS score, ODI index, and imaging indexes (DH, FH, FSL, and LL) (all $P>$ 0.05). The two groups were comparable (Tables 1 and 2).

Table 1
Comparison of general preoperative data between S-OLIF group and F-OLIF group

Group	Gender		Age (year)	Cause of disease			Lesion segment ( $n$ )
	Female	Male		Spondylolisthesis	Instability	Discogenic	L3/4	L4/5
S-OLIF ( $n=$ 18)	13 (72.22)	5 (27.78)	58.39 $\pm$ 5.03	10 (55.56)	5 (27.78)	3 (16.67)	4 (22.22)	14 (77.78)
F-OLIF ( $n=$ 16)	12 (75)	4 (25)	59 $\pm$ 4.59	9 (56.25)	4 (25)	3 (18.75)	3 (18.75)	13 (81.25)
Statistic	0.0336		0.37	0			0.0463
$P$	0.8546		0.7151	1.000			0.9771

Table 2

Comparison of VAS score, Oswestry Disability Index (ODI) and imaging parameters before vs. after operation between S-OLIF group and F-OLIF group

		S-OLIF ( $n=$ 18)	F-OLIF ( $n=$ 16)	$t$	$p$
VAS	VAS 1	6.83 $\pm$ 1.1	7 $\pm$ 1.03	$-$ 0.45	0.6528
	VAS 2	0.83 $\pm$ 0.71	0.88 $\pm$ 0.72
0.825	$\Delta$ VAS	$-$ 6 $\pm$ 1.46	$-$ 6.13 $\pm$ 1.41	0.25	0.8013
	$t$	$-$ 17.4929	$-$ 17.3968
	$p$	$<$ 0.0001	$<$ 0.0001
ODI	ODI 1	45.94 $\pm$ 3.73	45.5 $\pm$ 3.78	0.34	0.7327
	ODI 2	15.11 $\pm$ 2.14	15.63 $\pm$ 1.96
0.9399	$\Delta$ ODI	$-$ 30.83 $\pm$ 4.4	$-$ 29.88 $\pm$ 3.44	$-$ 0.70	0.4882
	$t$	$-$ 29.7587	$-$ 34.7143
	$p$	$<$ 0.0001	$<$ 0.0001
FH	FH 1	11.5 $\pm$ 1.38	11.13 $\pm$ 1.15	0.85	0.3994
	FH 2	16.08 $\pm$ 1.06	16.32 $\pm$ 0.86
0.59414	$\Delta$ FH	4.58 $\pm$ 1.62	5.19 $\pm$ 1.54	$-$ 1.12	0.2712
	$t$	11.97251	13.4609
	$p$	$<$ 0.0001	$<$ 0.0001
DH	DH 1	7.21 $\pm$ 0.24	7.45 $\pm$ 0.34	$-$ 2.42	0.0215
	DH 2	11.61 $\pm$ 0.46	11.66 $\pm$ 0.34
0.95292	$\Delta$ DH	4.41 $\pm$ 0.56	4.21 $\pm$ 0.47	1.10	0.2779
	$t$	33.60404	35.89172
	$p$	$<$ 0.0001	$<$ 0.0001
SL	SL 1	17.67 $\pm$ 1.08	18.06 $\pm$ 1.18	$-$ 1.02	0.3161
	SL 2	22.61 $\pm$ 1.42	23.19 $\pm$ 1.6
0.78317	$\Delta$ SL	4.94 $\pm$ 1.26	5.13 $\pm$ 1.67	$-$ 0.36	0.7222
	$t$	16.66263	12.28772
	$p$	$<$ 0.0001	$<$ 0.0001
LL	LL 1	51.72 $\pm$ 2.32	52.56 $\pm$ 4.34	$-$ 0.69	0.4960
	LL 2	59.72 $\pm$ 2.78	59.81 $\pm$ 2.64
0.85469	$\Delta$ LL	8 $\pm$ 2.22	7.25 $\pm$ 2.62	0.90	0.3733
	$t$	15.26902	11.06688
	$p$	$<$ 0.0001	$<$ 0.0001

Note. 1: preoperative; 2: postoperative; $\Delta$ : postoperative improvement value compared to preoperative data. The study power for VAS, ODI, FH, DH, FSL, and LL was 0.825, 0.9399, 0.59414, 0.95292, 0.78317 and 0.85469, respectively.

3.1 VAS

After the operation, the lower back pain of the patients in the two groups was significantly relieved, and the VAS scores were improved (S-OLIF group: 6 $\pm$ 1.46) and (F-OLIF group: 6.13 $\pm$ 1.41), with no statistically significant difference ( $P=$ 0.80, Table 2).

3.2 ODI

The functioning of the two groups was improved significantly, the influence on daily activities was decreased, and ODIs were improved (S-OLIF group: 30.83% $\pm$ 4.4%) and (F-OLIF group: 29.88% $\pm$ 3.44%), with no significant difference ( $P=$ 0.48, Table 2).

3.3 Radiological outcomes

CT examinations showed that the sagittal and cross-sectional positions of the fusion cage in the two groups were ideal after the operation, bone grafting was sufficient, X-ray radiographs showed that the DH and FH were recovered, and LL and FSL were improved. In the F-OLIF group, the postoperative placement position of the screw was satisfactory (Fig. 1).

Figure 1.

A and B: Comparison of measurements of preoperative vs. postoperative X-ray radiograph of S-OLIF group; C and D: Comparison of measurements of preoperative vs. postoperative X-ray radiograph of F-OLIF group; E and F: Location and fusion of the cage indicated by CT examination.

(I) DH

In the S-OLIF group, the postoperative DH was 11.61 $\pm$ 0.46 mm, increased by 4.41 $\pm$ 0.56 mm compared with the preoperative data. In the F-OLIF group, the postoperative DH was 11.66 $\pm$ 0.34 mm, increased by 4.21 $\pm$ 0.47 mm compared with the preoperative data. There was no statistically significant difference between the two groups after the operation ( $P=$ 0.28, Table 2).

(II) FH

In the S-OLIF group, the postoperative FH was 16.08 $\pm$ 1.06 mm, increased by 4.58 $\pm$ 1.62 mm compared with the preoperative data. In the F-OLIF group, the postoperative FH was 16.32 $\pm$ 0.86 mm, increased by 5.19 $\pm$ 1.54 mm compared with the preoperative data. There was no statistically significant difference between the two groups after the operation ( $P=$ 0.27, Table 2).

(III) FSL

In the S-OLIF group, the postoperative FSL was 22.61 ${}^{\circ}$ $\pm$ 1.42 ${}^{\circ}$ , increased by 4.94 ${}^{\circ}$ $\pm$ 1.26 ${}^{\circ}$ compared with the preoperative data. In the F-OLIF group, the postoperative FSL was 23.19 ${}^{\circ}$ $\pm$ 1.6 ${}^{\circ}$ , increased by 5.13 ${}^{\circ}$ $\pm$ 1.67 ${}^{\circ}$ compared with the preoperative data. There was no statistically significant difference between the two groups after the operation ( $P=$ 0.37, Table 2).

Figure 2.

Case 1: Images of representative patients. A 58-year female was diagnosed as lumbar instability I spondylolisthesis and underwent standalone OLIF. Preoperative anteroposterior and lateral X-ray radiograph (A, B). Preoperative CT scanning and magnetic resonance imaging (C, D). The last postoperative anteroposterior and lateral X-ray radiograph (E, F), CT imaging scanning (G, H).

Figure 3.

Case 2: Images of representative patients. A 62-year female was diagnosed as lumbar I spondylolisthesis and underwent OLIF together with lateral screw fixation. Preoperative anteroposterior and lateral X-ray radiograph (A, B). Preoperative magnetic resonance imaging and CT scanning (C, D). The last postoperative anteroposterior and lateral X-ray radiograph (E, F), CT imaging scanning (G, H).

(IV) LL

In the S-OLIF group, the postoperative LL was 59.72 ${}^{\circ}$ $\pm$ 2.78 ${}^{\circ}$ , increased by 8 ${}^{\circ}$ $\pm$ 2.22 ${}^{\circ}$ compared with the preoperative data. In the F-OLIF group, the postoperative LL was 59.81 ${}^{\circ}$ $\pm$ 2.64 ${}^{\circ}$ , increased by 7.25 ${}^{\circ}$ $\pm$ 2.62 ${}^{\circ}$ compared with the preoperative data. There was no statistically significant difference between the two groups after the operation ( $P=$ 0.72, Table 2).

(V) Fusion and subsidence [11]

For subsidence of the fusion cage, the S-OLIF group was 1/18 (Grade 0) and the F-OLIF group was 0/16. Fusion was achieved in the two groups.

Cage subsidence was assessed at 3 days postoperatively and the last follow-up using the classification presented by Marchi et al., which based on the amount of cage subsidence into the vertebral endplates in standing neutral lateral radiographs (Grade 0, 0%–24%; Grade I, 25%–49%; Grade II, 50%–74%; and Grade III, 75%–100%). The three illustrative cases are shown in Figs 2–4 to evaluate the clinical effect of OLIF alone.

Table 3

Comparison of general postoperative data and postoperative follow-up between S-OLIF group and F-OLIF group

Group	Operative time (min)	Blood loss (ml)	Length of hospital stay (d)	Follow-up time (M)
S-OLIF ( $n=$ 18)	67 $\pm$ 4.86	52.94 $\pm$ 8.69	5.78 $\pm$ 1.06	12.72 $\pm$ 0.75
F-OLIF ( $n=$ 16)	74.81 $\pm$ 5.14	58.75 $\pm$ 7.64	6.19 $\pm$ 1.68	12.75 $\pm$ 0.93
Statistic	4.55	2.06	0.86	0.11
$P$	$<$ 0.0001	0.0479	0.3963	0.91

Figure 4.

Case 3: Postoperative fusion cage subsidence images of representative patients. A 63-year female was diagnosed as lumbar instability and underwent standalone OLIF. Preoperative anteroposterior and lateral X-ray radiograph (A, B). Preoperative magnetic resonance imaging and CT scanning (C, D). After operation, the last anteroposterior and lateral X-ray radiograph (E, F), the last X-ray and CT imaging scans (G, H). Note: Imaging evaluation parameters of preoperative and postoperative lateral position X-ray radiograph of the S-OLIF group and the F-OLIF group: (1) DH, the mean of the heights of the anterior and posterior edges of the disc space (yellow stands for height); (2) foraminal height (FH), the maximum distance between the tops of the two vaults that are constituted with the inferior vertebral notch of the upper vertebral body and the superior vertebral notch of the lower vertebral body (green stands for height); (3) FSL, the included angle between the connection line of the end plates of the upper vertebral body and the connection line of the lower end plates of the lower vertebral body (blue stands for included angle); (4) LL, the included angle between the connection line of the end plates at L1 and the connection line of the end plates at S1 (dark red stands for the included angle).

3.4 Operation conditions

The operative time was 67.00 $\pm$ 4.86 minutes in the S-OLIF group and 74.81 $\pm$ 5.14 minutes in the F-OLIF group, and the difference was statistically significant ( $P<$ 0.05). The intraoperative blood loss was 52.94 $\pm$ 8.69 mL in the S-OLIF group and 58.75 $\pm$ 7.64 mL in the F-OLIF group, and the difference was statistically significant ( $P<$ 0.05). The length of hospital stay was 5.78 $\pm$ 1.06 days in the S-OLIF group and 6.19 $\pm$ 1.68 days in the F-OLIF group, and the difference was not statistically significant ( $P>$ 0.05). Patients were followed up for 12.72 $\pm$ 0.75 months in the S-OLIF group and 12.75 $\pm$ 0.93 months in the F-OLIF group, and the difference was not statistically significant ( $P>$ 0.05) (Table 3).

3.5 Postoperative complications

In the S-OLIF group, one patient reported pain and numbness in the left leg after the operation, and one patient developed a peritoneum injury. In the F-OLIF group, one patient reported a sympathetic nerve injury, one patient had hip flexor weakness after the operation, and one patient developed an end plate injury. All the complications had disappeared at the final follow-up visit. There was no segmental artery injury or ureteral injury during the operation, and no infection or deep venous thrombosis after the operation.

4. Discussion

As a new minimally invasive technique, OLIF avoids the damage to the structure in the back of the vertebrae and injury of tissue in the vertebral canal caused by the traditional posterior approach PLIF/TLIF and avoids the risk of directly injuring the lumbar plexus and the psoas major muscle via the psoas major muscle approach during lateral lumbar interbody fusion (LLIF/DLIF). Related studies showed that, by the OLIF technique, shorter operative time, less intraoperative blood loss, a shorter length of hospital stay, and other clinical effects were achieved. Silvestre et al. [12] reported in a retrospective analysis of 55 cases of single-level lumbar diseases treated with OLIF that the average blood loss was 53.9 $\pm$ 78.3 ml, the average operative time was 42.4 $\pm$ 16.8 minutes, and the average length of hospital stay was 6.5 $\pm$ 2.3 days. Woods et al. [13] reported that the average intraoperative blood loss of 137 patients treated with OLIF was 83.2 ml. Ohtori et al. [14] reported that, for 12 multi-level scoliosis patients treated by OLIF combined with posterior internal fixation, the operative time was 250 $\pm$ 35 minutes and the intraoperative blood loss was 350 $\pm$ 50 ml, which were reduced compared with the traditional posterior operation. In this study, good results were achieved. The operative time was 67 $\pm$ 4.86 minutes in the Standalone OLIF group and 74.81 $\pm$ 5.14 minutes in the F-OLIF group. The intraoperative blood loss was 52.94 $\pm$ 8.69 ml in the S-OLIF group and 58.75 $\pm$ 7.64 ml in the F-OLIF group. The higher intraoperative blood loss in the F-OLIF group may be related to the longer operative time. However, there was no significant difference in the length of hospital stays between the two groups.

The OLIF technique has obvious advantages in improving clinical symptoms and the postoperative function of patients after the operation. Ohtori et al. [14, 15] reported that for 35 patients having lumbar diseases and 22 patients having kyphosis after being treated with the OLIF technique, the postoperative VAS pain score and ODI function index score of the lower limbs and lower waist were significantly improved. Fujibayashi et al. [16] reported that for 28 patients having lumbar DDD treated by the OLIF technique, the postoperative VAS pain score and ODI function index of the lower waist were significantly improved.

In this study, the VAS score and ODI index of the two groups are significantly improved compared with preoperative data, and there was no significant difference between the two groups at the last postoperative follow-up visit. This clearly shows that the OLIF technique avoids the injury of the paravertebral muscles caused by a traditional posterior operation and significantly improves the symptoms of lower back pain and the living function of patients after the operation.

The OLIF technique can achieve a satisfactory indirect decompression effect, open the anterior disc space to restore the DH, effectively stretch the posterior longitudinal ligament and ligamentum flavum, and indirectly enlarge the intervertebral foramen and spinal canal, thereby improving clinical symptoms. Fujibayashi et al. [16] reported that for 28 patients having single-level lumbar DDD treated by the OLIF technique, the cross-sectional area of the dural sac evaluated by imageology was increased by 30.2% compared with the preoperative data, and the DH was increased by 82.3% compared with the preoperative data. Oliveira et al. [17] reported that 21 patients receiving OLIF achieved indirect nerve decompression by using the cage alone; the DH, foraminal area, and FH were increased significantly after the operation. Sato et al. [18] reported that the DH and the area of spinal canal were increased after the OLIF operation, and the lower back pain and leg pain were significantly improved compared with preoperative data.

In this study, the DH and FH in the two groups were obviously increased compared with preoperative data, and the clinical symptoms were improved significantly. Studies have confirmed that reconstruction of the LL and FSL is very important for the recovery of symptoms and the prevention of adjacent segmental degeneration [19]. The OLIF technique can protect the integrity of the posterior paravertebral muscle tissue and implant a suitably large cage, whose cross-sectional area is several times that of an ordinary fusion cage, between the anterior vertebral bodies, so the cage can contact the upper and lower vertebral bodies sufficiently. This improves the restoration of the force line at the fusion segment and the stability of the anterior and middle columns of the lumbar spine. The same effect cannot be achieved with the posterior operation. In this study, the FSL and LL in the two groups are restored to satisfaction.

OLIF fusion is closely related to cage subsidence. Studies have shown [20, 21] that cage subsidence and displacement are related to osteoporosis and obesity. Obese patients with osteoporosis T $<-$ 2.5 or BMI $\geqslant$ 30 kg/m ${}^{2}$ benefited more from OLIF combined with pedicle screw fixation. Of course, cage subsidence may occur in OLIF combined with pedicle screw fixation regimen. Jink et al. [22] reported that for 29 patients treated by OLIF combined with posterior pedicle screw fixation, the fusion rate evaluated by CT 12 months after the operation was 92.9%. In a retrospective study Zhao et al. [23] reported that 46 patients were treated with OLIF combined with anterolateral screw fixation (OLIF-AF group) and 52 patients in the TLIF group. At 1 year postoperatively, the fusion rate of the OLIF-AF group was 91.3% (42 of 46), which was higher than the TLIF group 82.7% (43 of 52). Studies have shown that the lateral steel plate does not significantly help the cage subsidence [24]. Relevant studies have shown that the lateral steel screw destroys the subchondral bone trabecular, which may lead to the cage subsidence and vertebral fracture; Lateral steel plates may increase the incidence of related complications [25, 26, 27]. We choose pedicle screws. The screw thread is deeper and thicker. It is not easy to pull out the screw in the vertebral body dominated by cancellous bone, which can play a good role in fixation.

In this study, the cage subsided lightly but fused at the last follow-up visit in one patient in the S-OLIF group, and the fusion rate in the two groups was 100.0%. This may be related to the cases selected, as we excluded the patients with severe osteoporosis or obesity. During posterior internal fixation, the patient’s position needs to be changed, which will obviously prolong the operative time. In this study, screw-rod fixation of the anterior vertebral body was used to complete fusion and fixation of discus intervertebralis without changing the surgical position or significantly prolonging the operative time. No complications related to screw implantation and no non-fusion cases were found in this study.

There are also complications with the OLIF technique; for example, injury of abdominal great vessels and lumbar segmental vessels, lumbar plexus injury, sympathetic chain injury, ureteral injury, and peritoneal injury [28, 29]. Anatomical research on the nerve at the retroperitoneal space by Uribe et al. [30] states: “The genitofemoral nerve at L4–L5 level is located in front of the discus intervertebralis, nervi ilioinguinalis and nervi iliohypogastricus are located at the middle level of discus intervertebralis, and nervus cutaneus femoris lateralis is located behind the discus intervertebralis. Therefore, when placing the safe passage, pay attention to moving forward. Studies have shown that intraoperative electrophysiological examination cannot reduce the risk of nerve injury because real-time electromyography cannot monitor sensory nerves [31]. OLIF can technically reduce the risk of the above nerve injuries. Intraoperative electrophysiological examination was not performed in the two groups. Complications in this group had disappeared during the last follow-up visit without ureteral injury, sympathetic injury, and vascular injury. To reduce the occurrence of complications, we recommend measuring the distance between the anterior edge of the psoas major muscle and the lumbar blood vessels by MRI and CT examination, and not using this technique when it is $<$ 1 cm or blood vessels are variable [13, 32].

There are some limitations in this study: (1) The sample size is small. We will continue to collect data to analyze and summarize large samples in the future; (2) Retrospective study and screening of cases lead to selection bias; the choice of operation is not random, which affects the results; (3) In this study, X-rays was used to determine the subsidence, CT need to be applied to further confirm the findings in this study. (4) Only the early effect of the two operating methods was studied. Long-term follow-up and comparison of long-term curative effects will be carried out in the future.

5. Conclusions

The results of this study show that after such relevant contraindications as osteoporosis and obesity are excluded, in treatment of single-level lumbar DDD, neither OLIF alone nor OLIF combined with lateral screw fixation of the vertebral body will interfere with the posterior paravertebral muscles. During recent follow-up, clinical and radiological results were satisfactory.

Ethics statement

This study was conducted with approval from the Ethics Committee of Fujian Provincial Hospital (K2020-12-025). The study was conducted in accordance with the Declaration of Helsinki.

Funding

No external funding was received to conduct this study.

Informed consent

Written informed consent was obtained from all participants.

Availability of data and materials

The materials described in the manuscript, including all relevant raw data, are freely available from the corresponding author to any scientist wishing to use them for non-commercial purposes, without breaching participant confidentiality.

Author contributions

Conception and design of the research: MGQ; Acquisition of data: ZH; Analysis and interpretation of the data: MGQ, CL; Statistical analysis: KFL, SSL; Obtaining financing: SGZ; Writing of the manuscript: MGQ; Critical revision of the manuscript for intellectual content: MGQ, SGZ; All authors read and approved the final manuscript.

Footnotes

Acknowledgments

The authors would like to acknowledge the hard and dedicated work of all staff that implemented the intervention and evaluation components of the study.

Conflict of interest

The authors declare that they have no competing interests.

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Early effect of standalone oblique lateral interbody fusion vs. combined with lateral screw fixation of the vertebral body on single-level lumbar degenerative disc disease: A pilot study

Abstract

BACKGROUND:

OBJECTIVE:

METHODS:

RESULTS:

CONCLUSION:

Keywords

1. Introduction

2. Materials and methods

2.1 Subjects

2.2.1 Preoperative preparation

2.2.2 Operating method

2.2.3 Operation and hospitalization situation, follow-up, and efficacy assessment parameters

2.3 Statistical analysis

3. Results

Table 1 Comparison of general preoperative data between S-OLIF group and F-OLIF group

3.2 ODI

3.3 Radiological outcomes

(I) DH

(II) FH

(III) FSL

(IV) LL

(V) Fusion and subsidence [11]

3.5 Postoperative complications

4. Discussion

5. Conclusions

Ethics statement

Funding

Informed consent

Availability of data and materials

Author contributions

Footnotes

Acknowledgments

Conflict of interest

References

Table 1
Comparison of general preoperative data between S-OLIF group and F-OLIF group