The incidence of degenerative lumbar disease is continuously increasing due to the ageing of the population. The most common levels of degenerative lesions in the lumbar spine are L4-5 and L5-S1 levels, which include: DDD, HNP, lumbar spinal stenosis, and unstable spinal disorders with chronic and sustained clinical symptoms 21. Due to increasing demand for minimally invasive surgery, spine surgeons have a tendency of preferring MIS-TLIF 22–24, ALIF, LLIF, and OLIF. Although these have pros and cons in terms of surgical approaches and corridor, these techniques have given high fusion rate and satisfactory clinical results. ALIF and LLIF have strong advantages of restoration of sagittal and coronal alignment as well as high fusion rate. However, even though the incidence is low, ALIF has serious complications such as retrograde ejaculation and visceral or vascular injury 25–27. According to the literature 28, LLIF has frequent complications related to the approach such as lumbar plexopathy and others. Nevertheless, this approach may decrease vascular complications if compared to ALIF. In addition, it may not only yield a wide intervertebral endplate for spinal fusion but also result in excellent radiologic restoration of sagittal and coronal alignment. A previous cadaver study 29 reported that the incidence of LLIF approach-related lumbar plexus injury at L4-5 level is higher than that of other lumbar levels. To counter approach-related hurdles of ALIF and LLIF, OLIF has been proposed as a solution to access lumbar disc space through the corridor between the left common iliac artery and the anterior belly of the psoas muscle 14,15.
Many spine surgeons are adopting the OLIF technique due to its many potential advantages 14,30,31. Moreover, recent study revealed that OLIF has a lower incidence of lumbar plexopathy when compared to direct lateral transpsoas interbody fusion 32. Although the clinical analyses of OLIF have been investigated in many studies, surgical outcomes and perioperative complications of OLIF technique focused on L4-5 level have rarely been reported. In this study, we investigated surgical outcomes and perioperative complications of OLIF at L4-5 to determine whether OLIF is an acceptable procedure at L4-5 level or not.
Considering the origin of the technique, OLIF is a novel variation of the traditional lumbar interbody fusion technique developed from both ALIF and LLIF techniques. The main advantages of OLIF technique can be summarized as follows: (1) OLIF utilizes the potential space between the lateral border of the abdominal aorta and the anterior border of left psoas muscles. It is minimally invasive, resulting in less bleeding, shorter operative time, and faster postoperative mobilization 14. (2) OLIF allows removal of a large amount of disc and a large volume of bone graft, thus achieving timely and solid fusion through indirect spinal canal decompression. It can effectively restore the disc space and intervertebral foramen height, allowing deformity correction with good results similar to ALIF or LLIF 30,33,34. (3) OLIF uses a corridor that lies in the front of the psoas muscle, thereby enabling surgeons to avoid injury to that particular muscle as well as keeping away from the lumbar plexus. (4) Compared to direct lateral transpsoas interbody fusion, OLIF could be done in the patients with high ilium. Theoretically, this could avoid postoperative thigh weakness or lumbar plexopathy compared to the splitting maneuver of psoas muscle fibers in LLIF 32. Moreover, intraoperative neurophysiological monitoring is not required 35, thus having a benefit in terms of cost-effectiveness. (5) The approach is not performed through the peritoneal cavity, therefore avoiding interference with abdominal organs. In addition, the incision in the abdominal wall is made along muscle fibers. This technique maintains the dominance of rectus abdominis, reduces nerve damage, improves postoperative wound healing, and prevents abdominal hernia 35.
Some previous studies 14,30,33,34,36,37 have reported that OLIF procedure is an acceptable technique in lumbar interbody fusion for degenerative lumbar spine disease. It has been reported to have good surgical results without major complications. Most degenerative lumbar lesions occur at the L4-5 level. Theoretically, OLIF technique may be able to avoid neurologic deficit associated with trans-psoas approach, which was also revealed by a previous study 32. Our results demonstrated that: (1) clinical symptoms of all cases were improved significantly after surgery. ODI and NRS for back and leg significantly (P < 0.05) improved at postoperative 6 months, 1 year, and 2 years compared with preoperative data. Patient satisfaction rate, return to daily activity, and surgical recommendation to others were also evaluated in all patients, showing good to excellent outcomes for all criteria. (2) All patients have had good surgical results without major complications (0%). Although a few patients complained of sympathetic syndrome and lumbar plexopathy, most symptoms were mild and transient. The majority of the symptoms improved within 6 months after surgery. There was no vascular or urinary injury in OLIF at L4-5 level. However, one case of ureter injury occurred in OLIF at L2-3 level 38, which was not enrolled in this study. The mean hospital stay after surgery was 6.4 days, longer than that expressed in other published data. Nonetheless, this criterion is not related to complications but rather with insurance and healthcare system regulations in authors’ country. (3) Radiological data including disc height, segmental lordotic angle, and lumbar lordotic angle showed excellent results, thereby achieving good sagittal alignments. Foramen height was significantly increased postoperatively compared with preoperative data, thereby achieving good indirect decompression. Based on modified Bridwell fusion criteria, fusion rates of L4-5 level at postoperative 6 months, 1 year, 2 years were 85.71%, 96.42%, and 100%, respectively, similar to results of previous studies. The low fusion rate at 6 months and 1 year might be explained by the fact that the autograft from iliac bone was not used routinely because allograft with DBMs were used in all subjects in exception to two.
Lumbar plexus and psoas injury are unlikely in OLIF as dissection is performed anterior to the psoas muscle. However, potential risks associated with OLIF surgery include sympathetic dysfunction and vascular injury 31. Thus, we should pay great attention to individual differences in OLIF regional anatomy, particularly in preoperative analysis. There was no vascular, urinary tract, or bowel injury in the patients enrolled in this study. Sympathetic chain symptoms were the most common approach-related complications (14.2%). During follow-up periods, four patients showed sympathetic chain symptoms (left leg swelling), three of which gradually recovered within 2 to 4 months. For the other remaining patient, mild symptoms persisted beyond 6 months. Lumbar plexopathy was observed in two patients. One patient suffered from left inguinal discomfort, this patient were treated with conservative care and gradually recovered 3 to 6 months after surgery. Another patient had mild paresthesia on inguinal area and subjective weakness, for only 6 months, only when he ran or climbed the stairs.
In cases of severe canal stenosis due to facet hypertrophy and lateral recess stenosis, it is not easy to achieve satisfactory decompression by OLIF alone. For such situations, patients underwent additional laminotomy or laminectomy at the same level (L4-5). In our series, 7 patients underwent additional decompressive laminotomy or laminectomy after OLIF at L4-5 level. Access corridor between the abdominal aorta and the left psoas muscles of less than 10 mm was a contraindication for OLIF procedure in our series.
In this study, the mean age of participant was 63.8 years. Most patients had medical co-morbidities (17/28, 60.7%). Nevertheless, their overall clinical outcome was satisfactory. There was no serious complication reported. Therefore, OLIF may be considered as an acceptable surgical option for degenerative lumbar lesions at L4-5 level.
Even though this study was the first investigation focusing on OLIF at L4-5 level, it had several limitations. First, it had a retrospective study design with a small samples size. A larger number of patients should be enrolled in future studies to confirm our findings. In addition, the duration of follow-up was relatively short. Further follow-up is needed to strengthen these observations. Lastly, a comparative study with other types of fusion surgery is needed. This is also the work we need to do in the future.