Comparison of Oblique Lateral Interbody Fusion (OLIF) and Minimally Invasive Transforaminal Lumbar Interbody Fusion (MI-TLIF) for Treatment of Lumbar Degeneration Disease

A Prospective Cohort Study

Hai-Feng Zhu, MM; Xiang-Qian Fang, MD; Feng-Dong Zhao, MD; Jian-Feng Zhang, MD; Xing Zhao, MD; Zhi-Jun Hu, MD; Shun-Wu Fan, MD


Spine. 2022;47(6):E233-E242. 

In This Article

Materials and Methods

Sample Size Estimation

Based on data described by Li et al,[7] we estimated that enrollment of 132 patients (66 patients per arm) would provide the study with 80% power to detect a 20% difference in the complication rate (30% vs.10%), at an alpha significance level of 0.05 (two-tailed) and a 10% loss to follow-up. PASS, version 15 (PASS, NCSS, LLC, 2017), was used for the sample size calculation.

Patient Population and Grouping

Study approval was obtained from the hospital ethics committee. From August 3, 2019 to February 3, 2020, 137 consecutive patients with huge lumbar disc herniation, degenerative spondylolisthesis (DS) of Meyerding grade[14] less than or equal to II degrees, segmental instability,[15,16] or lumbar spinal stenosis of Schiza classification A–C grades[17] were enrolled in this study based on the inclusion and exclusion criteria (detailed in Figure 1). After rigorous screening, all the patients suitable for OLIF and MI-TLIF approaches were included. Preoperatively, demographic and clinical characteristics (Table 1) were documented and all patients were informed about the study protocols. After signing informed consent, patients were assigned to OLIF or MI-TLIF at their request and the surgeon's discretion (Figure 1). All operations were performed by a single surgical team (one surgeon, and three assistants).

Figure 1.

Flow chart for patient population, grouping, assessment of results, and follow-up method.

Surgical Techniques

The MI-TLIF procedure was a two-step processes: first, a K-wire was used to penetrate the multifidus muscle and a trans-muscular surgical corridor was created with two micro-laminectomy retractors (Figure 2A) docking on the facet joint complex (Figure 2B). Second, TLIF was carefully performed with crescent cages (Crescent spinal system, Medtronic Sofamor Danek, Memphis, TN) filled with autograft from laminectomy under magnification. The contralateral side was handled either by the trans-muscular procedure (when decompression was needed), or an inter-muscular Wiltse procedure[5] with pedicle screw insertion.

Figure 2.

Sketch map of two micro-laminectomy retractors (A), MI-TLIF procedure (B), and OLIF procedure (C). MI-TLIF indicates minimally invasive transforaminal lumbar interbody fusion; OLIF, oblique lateral interbody fusion.

The OLIF procedure was referring to our modified lateral approach described previously[18–20] (Figure 2C and Video 1 [Supplemental Digital Content 1,]), utilizing expandable retractors and PEEK intervertebral cages (Clydesdale Spinal System; Medtronic Sofamor Danek, Minneapolis, MN) filled with artificial bone (Wright, TN). Subsequently, patients were placed in prone position and received posterior fixation through an inter-muscular Wiltse procedure with the help of two micro-laminectomy retractors (Figure 2A).

Postoperative Management and Follow-up Method

All patients were encouraged to perform passive straight leg raising 1 day postoperatively, and moderate off-bed activity with a brace 2 to 3 days postoperatively. Return to daily life was not permitted until successful lumbar fusion was achieved.

All patients were strictly followed up through monthly outpatient visits for 6 months, and semi-annual outpatient visits subsequently, until death or loss to follow-up. The latest follow-up was carried out between August 2020 and February 2021, constituting an average follow-up period of 1 year.

Assessment of Outcomes

Clinical outcomes (primary outcomes), were independently assessed by an experienced clinical research coordinator who had not participated in the study. Radiographic outcomes (secondary outcomes), were evaluated by a blinded radiologist and a superior spine surgeon. Measurements were repeated after 3 weeks. Interobserver and intraobserver repeatability was calculated using the intraclass correlation coefficient (ICC) and formula.[21]

Clinical Outcomes

Perioperative Data. Operation time and estimated blood loss were recorded 1 day postoperatively. Serum CK level was measured preoperatively and 1 and 3 days postoperatively. Length of hospital stay was documented on the day of discharge.

Patient-reported Outcomes. Patient-reported outcomes included the Oswestry Disability Index (ODI) score and visual analog scale (VAS) score of low back and leg assessed at 1, 3, and 12 months postoperatively.

Complications. Complications were collected throughout the perioperative and postoperative follow-up periods and treated appropriately.

Radiographic Outcomes. Radiographic outcomes, including DH, SLA, and LLA restoration, were evaluated at1 day, 1 month, and 12 months postoperatively. Detailed measurement criteria of DH, SLA, and LLA were referenced from Zhu et al.[22] The Restored value of each patient = (value after surgery − value before surgery).

The fusion rate was assessed at 12 months postoperatively. According to the improved Brantigan criteria (0–4 points)[23] more than or equal to three points (Supplemental Digital Content 2, was defined as a successful fusion.

Statistical Analysis

Continuous, discrete, and rating variables are presented as mean ± standard deviation (SD), and categorical variables are expressed as frequency or percentage. Student t test was used for intergroup analysis of normal distributed continuous variables. The Mann–Whitney U test was used for intergroup analysis of discrete variables, rating variables, and continuous variables, which were not normally distributed. The chi-square test was used for categorical variables. All analyses were performed using the Statistical Package for the Social Sciences (SPSS 19.0; IBM Corp., Armonk, NY). P < 0.05 indicated statistical significance.