Lumbar interbody fusion is a prevalent surgical procedure for DLS for which TLIF can achieve slipping reduction, immediate segmental stability, and intervertebral fusion by direct decompression and posterior pedicle screw fixation, which is a prevalent fusion procedure for DLS . Owing to the development of minimally invasive technology, MIS-TLIF utilizes tubular channels to expose the operative field. Compared with traditional TLIF, MIS-TLIF can minimize the injury of soft tissues and muscles which can lesson intraoperative blood loss, perioperative infection rate . OLIF, a new minimally invasive fusion procedure, can expose the intervertebral disc completely and insert the cage as much as necessary. OLIF can correct DS through effective ligament stretching and can achieve reductions in slipping, immediate segmental stability, and intervertebral fusion. Simultaneously, OLIF can cause indirect decompression by providing segmental lordosis, expanding the foraminal area, restoring the spinal canal area, and so forth. Compared with posterior fusion, OLIF avoids damage to the posterior spinal structure and offers the advantages of shortening operation duration and reducing blood loss . OLIF is widely used in clinical practice. For intervertebral instability, endplate injury, osteoporosis, and posterior revision surgery, OLIF should be supplemented with pedicle screw fixation . Takayoshi et al. reported a mean 12-months fusion rate of 51 subjects treated with OLIF combined pedicle screw fixation was 87.2% . In our study, no cage subsidence nor nonfusions were found at the last follow-up, providing further evidence that posterior pedicle screw fixation can descend the incident of cage settlement while increase intervertebral fusion rate.
Traditional OLIF involves inserting a cage in lateral decumbent position and PPS inserted in prone position. This turning of patient prolongs the operation time and increases risks including cage displacement, posterior peritoneal injury, anesthesia accidents, and so on [18–19]. In recent years, a navigation system combined with an O-arm system has been extensively applied in spinal surgery . O-arm and Navigation system integrates three functions of intraoperative three-dimensional imaging: real-time infrared tracking, visual image display, and real-time feedback on the adjacent relationship between the screw and the bony structure. Therefore, the surgeon can track the position of the surgical instrument accurately which helps them to achieve pedicle screw insertion accurately . We have modified the OLIF using the O-arm and navigation system to insert PPS in the lateral position. The advantages of this modified procedure include avoiding cage shifting, conserving medical supplies, and shortening the duration of the operation. In the NASP-OLIF group, 100 screws were implanted. The total screw insertion time was 30.16 ± 5.45 min, the per screw placement time was 7.54 ± 1.36 min, the adequate accuracy of screw placement rate was 96%, and no complications related to screw track dislocation occurred after the operation. Blizzard et al. clarified that the per screw placement time of this technology was 5.9 min and the adequate precision of the screw placement rate was 94.9% . Additionally, it was reported that the adequate precision of the screw placement rate was 98.2% by Ouchida et al. . In this study, the NASP-OLIF group had significantly shortened operation times, reduced intraoperative blood loss, and shortened postoperative first-floor activity duration. These changes may have occurred for the following reasons: (1) NASP-OLIF does not require changing the patient’s surgical position, which helped to reduce operation time; and (2) NASP-OLIF is based on O-arm navigation-assisted screw placement, which can assist with avoiding pedicle screw misplacement and shorten the operation duration. In another study, Wang et al. reported the surgical efficacy in 20 patients who underwent PLIF . The study participants were divided into free-hand and O-arm groups according to different screw placement methods. The results indicated that the total operation time in the free-hand group was 255.19 ± 40.26 min, while that in the O-arm group was 222.55 ± 38 min. In conclusion, NASP-OLIF is a safe and efficient technique.
The study indicated that both NASP-OLIF and MIS-TLIF groups can obtain good surgical effects in the treatment of L4 DLS. IDH and IFA in the NASP-OLIF group were significantly improved on postoperative and the last follow-up, which may be related to the following reasons:
(1) NASP-OLIF can expose intervertebral disc completely, which helps for thorough removal of the intervertebral disc tissue. However, MIS-TLIF can only expose a part of the intervertebral disc; (2) The cage of NASP-OLIF is longer, wider, and more solid, and it is placed across the cortical bone on both sides of the intervertebral space; thus, it coffers intervertebral distraction and maintenance. Many biomechanical studies have shown that the cage of OLIF provides stronger stabilization than the cage of TLIF. Yuan et al. . indicated that lateral cages was stiffer than bullet cages. It was also shown that the average stiffness of NASP-OLIF constructs was stronger than that of MIS-TLIF constructs; (3) Posterior PPS fixation was mainly used to maintain the postoperative vertebral space height, and both groups were treated with posterior PPS fixation. There were no difference in Segmental lordosis between groups on postoperative and last follow-up, which may be related to the following reasons: (1) The bony endplate may be injured during intervertebral decompression in two groups, which may lead to intervertebral subsidence after cage implantation, and the segmental lordosis is easily lost in postoperative follow-up; and (2) The cage of NASP-OLIF provides a specific lordosis (generally 6°). Further, the large cage inserted in anterior position of intervertebral disc can provide a certain segment lordosis; and (3) the correction of segmental lordosis mainly depends on the compression shortening of the structure of posterior pedicle screws and connecting rods. There was no remarkable difference of improvement in CSA between groups. However, the MIS-TLIF procedure could remove posterior bony ligament structures such as facet joints and ligamentum flavum, which can cause direct decompression in the spinal canal. NASP-OLIF was able to remove the intervertebral disc tissue completely and insert a large cage to stretch the ligament structure, which can cause indirect decompression in the spinal canal.
In this study, VAS and ODI of subjects between groups were improved on postoperative follow-up. It was shown that NASP-OLIF and MIS-TLIF can obtain a good surgical effect. However, the NASP-OLIF group had superior improvement in VASB and ODI on postoperative and last follow-up. This was because the NASP-OLIF group had less injury to paraspinal muscles and posterior bony structures.
This study has several limitations. First, the full-length spine radiography was not performed, and the parameters of the spine and pelvis were not evaluated. Second, the overall sample size was tiny and follow-up time was not longer. Multicenter clinical observations with large sample sizes and long-term follow-up are necessary to assess and compare clinical efficiency of NASP-OLIF and MIS-TLIF in the future. Third, as this study is a retrospective analysis, its results require confirmation by higher-level evidence.