Determinants of lateral fusion in single-level oblique lateral lumbar interbody fusion: a retrospective analysis of fusion patterns and clinical outcomes.

To observe the cage subsidence after oblique lateral interbody fusion (OLIF) for lumbar spondylosis, summarize the characteristics of the cage subsidence, analyze causes, and propose preventive measures. The data of 144 patients of lumbar spine lesions admitted to our hospital from October 2015 to December 2018 were retrospectively analyzed. There were 43 males and 101 females, and the age ranged from 20 to 81 years old, with an average of (60.90±10.06) years old. Disease types:17 patients of lumbar intervertebral disc degenerative disease, 12 patients of giant lumbar disc herniation, 5 patients of discogenic low back pain, 33 patients of lumbar spinal stenosis, 26 patients of lumbar degenerative spondylolisthesis, 28 patients of lumbar spondylolisthesis with spondylolisthesis, 11 patients of adjacent vertebral disease after lumbar internal fixation, 7 patients of primary spondylitis in the inflammatory outcome stage, and 5 patients of lumbar degenerative scoliosis. Preoperative dual-energy X-ray bone mineral density examination showed 57 patients of osteopenia or osteoporosis, and 87 patients of normal bone density. The number of fusion segments:124 patients of single-segment, 11 patients of two-segment, 8 patients of three-segment, four-segment 1 patient. There were 40 patients treated by stand-alone OLIF, and 104 patients by OLIF combined with posterior pedicle screw. Observed the occurrence of fusion cage settlement after operation, conducted monofactor analysis on possible risk factors, and observed the influence of fusion cage settlement on clinical results. All operations were successfully completed, the median operation time was 99 min, and the median intraoperative blood loss was 106 ml. Intraoperative endplate injury occurred in 30 patients and vertebral fracture occurred in 5 patients. The mean follow-up was (14.57±7.14) months from 6 to 30 months. During the follow-up, except for the patients of primary lumbar interstitial inflammation and some patients of lumbar spondylolisthesis with spondylolisthesis, the others all had different degrees of cage subsidence. Cage subsidence classification:119 patients were normal subsidence, and 25 patients were abnormal subsidence (23 patients were gradeⅠ, and 2 patients were gradeⅡ). There was no loosening or rupture of the pedicle screw system. The height of the intervertebral space recovered from the preoperative average (9.48±1.84) mm to the postoperative average (12.65±2.03) mm, and the average (10.51±1.81) mm at the last follow-up. There were statistical differences between postoperative and preoperative, and between the last follow-up and postoperative. The interbody fusion rate was 94.4%. The low back pain VAS decreased from the preoperative average (6.55±2.2 9) to the last follow-up (1.40±0.82), and there was statistically significant different. The leg pain VAS decreased from the preoperative average (4.72±1.49) to the final follow-up (0.60±0.03), and the difference was statistically significant (t=9.13, P<0.000 1). The ODI index recovered from the preoperative average (38.50±6.98)% to the latest follow-up (11.30±3.27)%, and there was statistically significant different. The complication rate was 31.3%(45/144), and the reoperation rate was 9.72%(14/144). Among them, 8 patients were reoperated due to fusion cage subsidence or displacement, accounting for 57.14%(8/14) of reoperation. The fusion cage subsidence in this group had obvious characteristics. The monofactor analysis showed that the number of abnormal subsidence patients in the osteopenia or osteoporosis group, Stand-alone OLIF group, 2 or more segments fusion group, and endplate injury group was higher than that in the normal bone mass group, OLIF combined with pedicle screw fixation group, single segment fusion group, and no endplate injury group, and the comparison had statistical differences. Cage subsidence is a common phenomenon after OLIF surgery. Preoperative osteopenia or osteoporosis, Stand-alone OLIF, 2 or more segments of fusion and intraoperative endplate injury may be important factors for postoperative fusion cage subsidence. Although there is no significant correlation between the degree of cage subsidence and clinical symptoms, there is a risk of cage migration, and prevention needs to be strengthened to reduce serious complications caused by fusion of cage subsidence, including reoperation.

BackgroundFor lumbar degenerative diseases, cage subsidence is a serious complication and can result in the failure of indirect decompression in the oblique lumbar interbody fusion (OLIF) procedure. Whether additional lateral plate fixation was effective to improve clinical outcomes and prevent cage subsidence was still unknown. This study aimed to compare the incidence and degree of cage subsidence between stand-alone oblique lumbar interbody fusion (SA-OLIF) and OLIF combined with lateral plate fixation (OLIF + LP) for the treatment of lumbar degenerative diseases and to evaluate the effect of the lateral plate fixation.MethodsThis was a retrospective comparative study. 20 patients with 21 levels underwent SA-OLIF and 21 patients with 26 levels underwent OLIF + LP. We compared clinical and radiographic outcomes between two groups. Clinical evaluation included Visual Analog Scale (VAS) for back pain and leg pain, Japanese Orthopaedic Association (JOA) scores and Oswestry Disability Index (ODI). Radiographical evaluation included disc height (DH), segmental lordosis angle (SL), and subsidence rate on standing lateral radiographs. Cage subsidence was classified using Marchi’s criteria.ResultsThe mean follow-up duration was 6.3 ± 2.4 months. There were no significant differences among perioperative data (operation time, estimated intraoperative blood loss, and complication), clinical outcome (VAS, ODI, and JOA) and radiological outcome (SH and SL). The subsidence rate was 19.0% (4/21) in SA-OLIF group and 19.2% (5/26) in OLIF + LP group. 81.0% in SA-OLIF group and 80.8% in OLIF + LP group had Grade 0 subsidence, 14.3% in SA-OLIF group and 15.4% in OLIF + LP group had Grade I subsidence, and 4.8% in SA-OLIF group and 3.8% in OLIF + LP group had Grade II subsidence (P = 0.984). One patient with severe cage subsidence and lateral plate migration underwent revision surgery.ConclusionsThe additional lateral plate fixation does not appear to be more effective to prevent cage subsidence in the oblique lumbar interbody fusion, compared with stand-alone technique. If severe cage subsidence occurs, it may result in lateral plate migration in OLIF combined with lateral plate fixation.

Study DesignRetrospective cohort study.ObjectiveLimited clinical literature addresses potential differences in fusion features between Oblique lumbar interbody fusion (OLIF) and transforaminal lumbar interbody fusion (TLIF). We observed that in OLIF, there are many cases with the appearance of extra-vertebral bone bridges (EVB), a phenomenon distinct from traditional TLIF fusion. This study aims to compare fusion rates, cage subsidence, and fusion features among OLIF stand-alone (OLIF-SA), OLIF with posterior pedicle screw fixation (OLIF-PS), and TLIF.MethodsWe retrospectively analyzed 198 patients (311 levels) undergoing OLIF-SA, OLIF-PS, or TLIF from July 2017 to June 2021. We assessed patient-reported outcomes, cage subsidence, fusion rate, and fusion features on CT scans.ResultsThe study included 64 OLIF-SA patients (102 levels), 60 OLIF-PS patients (99 levels), and 74 TLIF patients (110 levels). Cage settling rates were 33.3% (OLIF-SA), 17.2% (OLIF-PS), and 32.8% (TLIF), with significant differences between OLIF-PS and TLIF (P < 0.05). Cage subsidence rates showed no significant difference: 11.8% (OLIF-SA), 9.1% (OLIF-PS), and 12.7% (TLIF) (P > 0.05). Fusion rates were 100% (OLIF-SA), 97.0% (OLIF-PS), and 96.4% (TLIF) (P = 0.167). Lateral fusion rates significantly differed: 49.0% (OLIF-SA), 30.3% (OLIF-PS), and 10.9% (TLIF) (P < 0.001). Preoperative osteophytes strongly promote lateral fusion (P < 0.001). VAS and ODI scores improved significantly post-surgery (P < 0.01).ConclusionsOLIF-SA, OLIF-PS, and TLIF surgeries show satisfactory results with comparable fusion rates. Notably, distinctive differences exist in fusion features between OLIF and TLIF surgeries, with lateral fusion more prevalent in OLIF, particularly in OLIF-SA surgeries.

ObjectiveAdequacy of decompression for oblique lateral interbody fusion (OLIF) is a real concern in patients with severe lumbar spinal stenosis (LSS). With this in mind, we combined OLIF with spinal endoscopic technique to achieve a solid fusion and an adequate decompression after one operation.MethodsThis is a technical note. The theoretical basis and operation process of this technique were introduced, and consecutive cases were retrospectively collected. Consecutive patients diagnosed with monosegmental severe LSS (L4/5) and underwent oblique lateral endoscopic decompression and interbody fusion (OLEDIF) from January 2018 to February 2020 were retrospectively collected. Clinical outcomes were assessed by claudication distance, Visual Analog Scale (VAS), and Oswestry Disability Index (ODI) scores. Secondary indicators included operation time, operative blood loss, and postoperative complications.ResultsTen patients were selected for the OLEDIF procedure. They were five women and five men ranging in age from 49 to 75 years (mean age of 63.9 years) and in BMI from 25.4 to 30.2 kg/m2 (mean BMI of 27.5 kg/m2). The preoperative claudication distance was 160.00 ± 68.96 m (range 70–250 m), which was significantly extended on the 3‐month and 1‐year follow‐up (1020.00 ± 407.70 m and 1040.00 ± 416.87 m, respectively). The preoperative VAS score of back pain and radiating leg pain was 5.50 ± 0.97 (range 4–7) and 6.40 ± 0.97 (range 5–8). The score on postoperative month 3 was 1.60 ± 0.52 (range 1–2) and 1.20 ± 0.79 (range 0–2), and the 1‐year follow‐up score was 1.90 ± 0.74 (range 1–3) and 1.60 ± 0.70 (range 1–3), respectively. The preoperative ODI was 72.23 ± 6.30 (range 64.4–82.2), the 3‐month follow‐up ODI was 31.12 ± 4.20 (range 24.4–35.6), and the 1‐year follow‐up ODI was 29.33 ± 5.92 (range 20.0–37.8). Compared with the transforaminal lumbar interbody fusion (TLIF) in the literature, the operation time was not prolonged (189.3 ± 32.5 min vs. 214.9 ± 60.0 min) but the amount of blood loss decreased significantly (113.3 ± 26.7 ml vs. 366.8 ± 298.2 ml). No complications were found except one case presented with dysesthesia of the left leg. Imaging results showed good fusion without cage subsidence during 1‐year follow‐up.ConclusionOLEDIF can achieve complete ventral decompression of the spinal canal and solid fusion of the lumbar spine at one time. It is an effective minimally invasive technique for the treatment of monosegmental severe LSS, which is promising and worthy of further clinical practice.

ABSTRACTObjectiveAlthough endoscopic technologies have been increasingly applied in lumbar fusion surgery in recent years, the advantages and disadvantages of endoscopic posterolateral fusion compared with lateral fusion remain unclear. Six different single‐level lumbar interbody fusion procedures were compared to determine whether indirect decompression fusion could achieve levels of efficacy and safety comparable to those of minimally invasive direct decompression fusion in the treatment of lumbar degenerative disease (LDD).MethodA literature search was conducted in the PubMed, Embase, and Cochrane Library databases, and studies on the treatment of LDD published from 2004 to March 2024 were retrieved. The data of preset clinical outcome measures, including operation time, intraoperative estimated blood loss (EBL), length of hospital stay (LOS), complications, visual analog scale (VAS) score, and the Oswestry Disability Index (ODI), were extracted from the studies.ResultsThirty‐five studies with 3467 patients were included in this review. Network meta‐analysis revealed no significant differences in improvements in pain and disability or adverse events among the procedures, except for uniportal endoscopic lumbar interbody fusion (UELIF), which resulted in a lower degree of improvement in the ODI than oblique lateral interbody fusion (OLIF). Stand‐alone lateral lumbar interbody fusion (SA‐LLIF) exhibited the best performance in terms of indicators of early efficacy, such as surgical time and LOS. OLIF and SA‐LLIF had higher fusion rates than did UELIF and minimally invasive transforaminal lumbar interbody fusion (MIS‐TLIF). MIS‐TLIF resulted in greater EBL than did OLIF, SA‐LLIF, and UELIF.ConclusionMinimally invasive lumbar interbody fusion achieves good therapeutic results in LDD patients regardless of the use of indirect or direct decompression, whereas SA‐LLIF has better early efficacy.

Low Hounsfield units on computed tomography are associated with cage subsidence following oblique lumbar interbody fusion (OLIF)

One of the most common complications of lumbar fusions is cage subsidence, which leads to collapse of disc height and reappearance of the presenting symptomology. However, definitions of cage subsidence are inconsistent, leading to a variety of subsidence calculation methodologies and thresholds. To review previously published literature on cage subsidence in order to present the most common methods for calculating and defining subsidence in the anterior lumbar interbody fusion (ALIF), oblique lateral interbody fusion (OLIF), and lateral lumbar interbody fusion (LLIF) approaches. A search was completed in PubMed and Embase with inclusion criteria focused on identifying any study that provided descriptions of the method, imaging modality, or subsidence threshold used to calculate the presence of cage subsidence. A total of 69 articles were included in the final analysis, of which 18 (26.1%) reported on the ALIF approach, 22 (31.9%) on the OLIF approach, and 31 (44.9%) on the LLIF approach, 2 of which reported on more than one approach. ALIF articles most commonly calculated the loss of disc height over time with a subsidence threshold of > 2mm. Most OLIF articles calculated the total amount of cage migration into the vertebral bodies, with a threshold of > 2mm. LLIF was the only approach in which most articles applied the same method for calculation, namely, a grading scale for classifying the loss of disc height over time. We recommend future articles adhere to the most common methodologies presented here to ensure accuracy and generalizability in reporting cage subsidence.

BackgroundTo compare standalone oblique lateral interbody fusion (OLIF) vs. OLIF combined with posterior bilateral percutaneous pedicle screw fixation (OLIF combined) for the treatment of lumbar spondylolisthesis.MethodsThis was a retrospective study of patients who underwent standalone OLIF or combined OLIF between 07/2014 and 08/2017 at two hospitals in China. Direct decompressions were not performed. Visual analog scale (VAS), Oswestry Disability Index (ODI), satisfaction rate, anterior/posterior disc heights (DH), foraminal height (FH), foraminal width (FW), cage subsidence, cage retropulsion, fusion rate, and complications were analyzed. All imaging examinations were read independently by two physicians and the mean measurements were used for analysis.ResultsA total of 73 patients were included: 32 with standalone OLIF and 41 with combined OLIF. The total complication rate was 25.0% with standalone OLIF and 26.8% with combined OLIF. There were no differences in VAS and ODI scores by 2 years of follow-up, but the scores were better with standalone OLIF at 1 week and 3 months (P < 0.05). PDH and FW was smaller in the combined OLIF group compared with the standalone OLIF group before and after surgery (all P < 0.05). There were significant differences in FH before surgery and at 1 week and 3 months between the two groups (all P < 0.05), but the difference disappeared by 2 years (P = 0.111). Cage subsidence occurred in 7.3% (3/41) and 7.3% (3/41) of the patients at 3 and 24 months, respectively, in the combined OLIF group, compared with 6.3% (2/32) and 15.6% (5/32), respectively, in the standalone OLIF group at the same time points (P = 0.287). There was no cage retropulsion in both groups at 2 years. The fusion rate was 85.4%(35/41) in the combined OLIF group and 84.4% (27/32) in the standalone OLIF group at 3 months(P = 0.669). At 24 months, the fusion rate was 100.0% in the combined OLIF group and 93.8% (30/32) in the standalone OLIF group (P = 0.066).ConclusionStandalone OLIF may achieve equivalent clinical and radiological outcomes than OLIF combined with fixation for spondylolisthesis. The rate of complications was similar between the two groups. Patients who are osteoporotic might be better undergoing combined rather than standalone OLIF. The possibilty of proof lies within a future prospective study, preferably an RCT.

To analyze the causes of vertebral fracture during oblique lateral interbody fusion in the treatment of lumbar spondylopathy, summarize the clinical results, and propose preventive measures. Retrospective analysis was made on the data of 8 cases of lumbar spondylopathy and vertebral fracture treated by oblique lateral interbody fusion in three medical centers from October 2014 to December 2018. All were female, aged from 50 to 81 years with an average of 66.4 years. Disease types included 1 case of lumbar degenerative disease, 3 cases of lumbar spinal stenosis, 2 cases of lumbar degenerative spondylolisthesis and 2 cases of lumbar degenerative scoliosis. Preoperative dual energy X-ray bone mineral density test showed that 2 cases had T-value >-1 SD, 2 cases had T-value -1 to -2.5 SD, and 4 cases had T-value <-2.5 SD. Single segment fusion was in 5 cases, two segment fusion in 1 case and three segment fusion in 2 cases. Four cases were treated with OLIF Stand-alone and 4 cases were treated with OLIF combined with posterior pedicle screw fixation. Postoperative imaging examination showed vertebral fracture, and all of them were single vertebral fracture. There were 2 cases of right lower edge fracture of upper vertebral body at fusion segment, 6 cases of lower vertebral body fracture at fusion segment, and 6 cases with endplate injury and fusion cage partially embedded in vertebral body. Three cases of OLIF Stand-alone were treated with pedicle screw fixation via posterior intermuscular approach, while one case of OLIF Stand-alone and four cases of OLIF combined with posterior pedicle screw fixation were not treated specially. The 5 cases of initial operation and 3 cases of reoperation did not show wound skin necrosis or wound infection. The follow-up time was from 12 to 48 months with an average of 22.8 months. Visual analogue scale (VAS) of low back pain was preoperative decreased from 4 to 8 points (averagely 6.3 points) and postoperative 1 to 3 points (averagely 1.7 points) at the final follow-up. Oswestry disability index (ODI) was preoperative 39.7% to 52.4% (averagely 40.2%), and postoperative 7.9% to 11.2% (averagely 9.5%) at the final follow-up. During the follow-up, there was no loosening or fracture of the pedicle screw system, and no lateral displacement of the fusion cage;however, the fusion cage at the vertebral fracture segment had obvious subsidence. The intervertebral space height of vertebral fracture segment was preoperaive 6.7 to 9.2 mm (averagely 8.1 mm), and postoperative 10.5 to 12.8 mm (averagely 11.2 mm). The improvement rate after operation was 37.98% compared to preoperative. The intervertebral space height at final follow-up was 8.4 to 10.9 mm (averagely 9.3 mm), and the loss rate was 16.71% compared with that after operation. At the final follow-up, interbody fusion was achieved in all cases except for one that could not be identified. The incidence of vertebral fracture during oblique lateral interbody fusion in the treatment of lumbar spondylopathy is lower, and there are many reasons for fracture, including preoperative bone loss or osteoporosis, endplate injury, irregular shape of endplate, excessive selection of fusion cage, and osteophyte hyperplasia at the affected segment. As long as vertebral fracture is found in time and handled properly, the prognosis is well. However, it still needs to strengthen prevention.

Indirect decompression via oblique lateral interbody fusion for severe degenerative lumbar spinal stenosis: a comparative study with direct decompression transforaminal/posterior lumbar interbody fusion

To compare the mid-term follow-up clinical efficacy among three treatment approaches for lumbar degenerative diseases (LDD): standalone oblique lumbar interbody fusion (SF), oblique lumbar interbody fusion combined with lateral screw fixation (LF), and oblique lumbar interbody fusion combined with posterior screw fixation (PF). This retrospective study included a total of 71 cases of single level LDD that underwent OLIF in Hospital of Chengdu University of Traditional Chinese Medicine were retrospectively collected between March 2016 and September 2017. Patients were divided into three groups: 24 cases in the SF group, 24 cases in the LF group and 23 cases in the PF group. Various parameters, such as operation time, hospitalization time, and complications, were recorded. The fusion condition was assessed at last follow up. Clinical outcomes were evaluated using the Visual Analogue Scale (VAS) and Oswestry Disability Index (ODI) from pre-operation to 5years post-surgery. Significantly lower mean operation time and hospitalization time were observed in the SF and LF groups compared to the PF group (p < .05). However, no significant difference in fusion rate was found among the three groups. Regarding clinical outcomes, there was no statistically significant difference in VAS scores between the three groups during all follow-up periods. At the 6th month and 1st year after surgery, the SF and LF groups had significantly lower Oswestry Disability Index (ODI) scores compared to the PF group (p < .05). There was no significant difference in perioperative complication rates among the three groups (p > .05). In the LF group, one case of instrument displacement and urethra injury were reported, while in the SF, LF, and PF groups, 10, 9, and 3 cases of cage subsidence were reported, respectively. The study findings suggest that oblique lumbar interbody fusion (OLIF) is a safe and effective treatment for mid-term management of lumbar degenerative diseases (LDD). Compared to the posterior screw fixation (PF) group, both the standalone OLIF (SF) and OLIF combined with lateral screw fixation (LF) groups showed advantages in terms of reduced operation time, shorter hospitalization, and faster symptom alleviation in the short-term. However, OLIF combined with PF demonstrated comparable symptom relief in the mid-term and had the additional benefit of lower cage subsidence rates while improving fusion rates as well.

BackgroundSarcopenia had been identified as a factor influencing the postoperative outcomes of lumbar surgery. The effect of sarcopenia on the surgical outcomes in patients who underwent oblique lateral interbody fusion (OLIF) had not yet been examined.ObjectiveThe aim of our study was to investigate the association between sarcopenia and postoperative low back pain (LBP) in patients following OLIF and provide recommendations for surgical strategy.Methods116 patients who underwent OLIF were retrospectively reviewed. Patients were classified into sarcopenia group (Group SP) and non-sarcopenia group (Group NSP). According to whether instruments was performed, Group SP was further divided into OLIF stand-alone group (Group SP-SA) and OLIF with instruments group (Group SP-IN). The patient characteristics, surgical data and questionnaire scores were collected. Oswestry Disability Index (ODI) score was used to evaluate lumbar function and pain intensity. Multivariable logistic regression analysis was used to identify the risk factors for postoperative LBP.ResultsThere were 38 patients in Group SP and 78 patients in Group NSP. The incident rare of osteoporosis in Group SP was higher than that in Group NSP (P = 0.012). In Group SP, last follow-up intervertebral height (IH) was lower (P = 0.045) and incident rate of cage subsidence was higher ((P = 0.044). No significant difference (P = 0.229) showed in preoperative ODI scores, however, last follow-up ODI scores in Group SP was significantly higher (P = 0.017) than that in Group NSP. Multivariable logistic regression analysis showed that sarcopenia (P = 0.004), osteoporosis (P = 0.012) and cage subsidence (P = 0.002) were identified as risk factors for postoperative LBP. In Group SP-IN, last follow-up ODI score (P = 0.024) and incident rate of cage subsidence (P = 0.027) were significantly lower Compared to Group SP-SA.ConclusionsLBP was a common complication following OLIF with the incidence rate of 18.1%. Sarcopenia, osteoporosis and cage subsidence were risk factors for LBP following OLIF. Instruments effectively reduced the incidence and degree of postoperative LBP in patients with sarcopenia following OLIF. Consequently, we suggest incorporating supplementary instruments for patients with sarcopenia in surgical strategy.

Objective To investigate the preliminary clinical and radiographic outcomes of percutaneous endoscopic lumbar discectomy (PELD) combined with oblique lateral interbody fusion (OLIF) for the degenerative lumbar spondylolisthesis, lumbar spine instability or lumbar spinal stenosis with ruptured disc herniation. Methods Data of 11 patients with degenerative lumbar spondylolisthesis, lumbar spine instability or lumbar spinal stenosis with ruptured disc herniation who had undergone PELD combined with OLIF between March 2017 to July 2018 in our spine surgery center were retrospectively analyzed. There were 5 males and 6 females with an average age of 61.2±6.8 years old. All the patients were diagnosed with degenerative lumbar diseases including lumbar spondylolisthesis (7 cases), lumbar spinal stenosis (3 cases) and segmental instability (1 case). The patients were treated with PELD combined with OLIF. The visual analogue scale (VAS) scores of low back pain and lower limb pain and the Oswestry disability index (ODI) of lumbar function, spinal canal anteroposterior diameter, intervertebral disc height, vertical diameter of intervertebral foramen, segmental angle and the whole lumbar lordotic angle were collected. Results All patients received PELD with local anesthesia before OLIF with general anesthesia. The mean operation time was 52.3±13.2 min and the mean blood loss was 10.9±4.7 ml for PELD. The mean operation time was 56.8±18.0 min and the mean blood loss was 65.5±24.6 ml for OLIF. All patients were followed up for an average of 11.2 months. At the latest follow-up, the mean VAS score for back pain was 1.3±0.8, the mean VAS score for leg pain 1.1±0.5, the mean ODI 14.6%±5.3%, thus all of those were improved significantly compared to those of pre-operation (t=10.37, 16.49, 8.73; P< 0.05). The radiographic results showed the mean pre-operative intervertebral disc height, vertical diameter of intervertebral foramen, spinal canal anteroposterior diameter, segmental angle, and lumbar lordosis angle was 7.1±1.2 mm, 15.3±2.2 mm, 6.2±1.3 mm, 10.2°±3.5°, 16.2°±6.2°, and thus all of those were increased significantly to the latest follow-up 11.5±1.8 mm, 19.2±2.6 mm, 10.4±2.5 mm, 19.3°±7.8°, 27.4°±8.3°, respectively (t=5.83, 4.21, 6.59, 10.32, 7.65; P< 0.05). One of the patients had weakness of flexor hip strength and one had a transient paresthesia immediately post-operation. All symptoms were relieved within 1 month. Another one case had cage subsidence and encountered serious back pain after 1 month, and alleviated after percutaneous pedicle screw fixation. Conclusion PELD combined with OLIF can overcome the limitations of OLIF with indirect decompression effects, resulting in successful direct neural decompression without posterior decompressive procedures and providing a satisfactory outcome for the patients with degenerative lumbar diseases with ruptured disc herniation. Key words: Lumbar vertebrae; Intervertebral disc degeneration; Endoscopy; Spinal fusion; Surgical procedures, minimally invasive

To investigate the correlation between CT value and Cage subsidence in patients with lumbar degenerative disease treated with stand-alone oblique lumbar interbody fusion (OLIF). The clinical data of 35 patients with lumbar degenerative diseases treated with stand-alone OLIF between February 2016 and October 2018 were retrospectively analyzed. There were 15 males and 20 females; the age ranged from 29 to 81 years, with an average of 58.4 years. There were 39 operative segments, including 32 cases of single-segment, 2 cases of double-segment, and 1 case of three-segment. Preoperative lumbar CT was used to measure the CT values of the axial position of L 1 vertebral body, the axial and sagittal positions of L 1-4 vertebral body, surgical segment, and the axial position of upper and lower vertebral bodies as the bone mineral density index, and the lowest T value was recorded by dual-energy X-ray absorptiometry. The visual analogue scale (VAS) and Oswestry disability index (ODI) scores were recorded before operation and at last follow-up. At last follow-up, the lumbar interbody fusion was evaluated by X-ray films of the lumbar spine and dynamic position; the lumbar lateral X-ray film was used to measure the subsidence of the Cage, and the patients were divided into subsidence group and nonsubsidence group. The univariate analysis on age, gender, body mass index, lowest T value, CT value of vertebral body, disease type, and surgical segment was performed to initially screen the influencing factors of Cage subsidence; further the logistic regression for multi-factor analysis was used to screen fusion independent risk factors for Cage subsidence. The receiver operating characteristic (ROC) curve and area under curve (AUC) were used to analyze the CT value and the lowest T value to predict the Cage subsidence. Spearman correlation analysis was used to determine the correlation between Cage subsidence and clinical results. All the 35 patients were followed up 27-58 months, with an average of 38.7 months. At last follow-up, the VAS and ODI scores were significantly decreased when compared with preoperative scores ( t=32.850, P=0.000; t=31.731, P=0.000). No recurrent lower extremity radiculopathy occurred and no patient required revision surgery. Twenty-seven cases (77.1%) had no Cage subsidence (nonsubsidence group); 8 cases (22.9%) had at least radiographic evidence of Cage subsidence, the average distance of Cage subsidence was 2.2 mm (range, 1.1-4.2 mm) (subsidence group). At last follow-up, there was 1 case of fusion failure both in the subsidence group and the nonsubsidence group, there was no significant difference in the interbody fusion rate (96.3% vs. 87.5%) between two groups ( P=0.410). Univariate analysis showed that the CT value of vertebral body (L 1 axial position, L 1-4 axial and sagittal positions, surgical segment, and upper and lower vertebral bodies axial positions) and the lowest T value were the influencing factors of Cage subsidence ( P<0.05). According to ROC curve analysis, compared with AUC of the lowest T value [0.738, 95% CI (0.540, 0.936)], the AUC of the L 1-4 axis CT value was 0.850 [95% CI (0.715, 0.984)], which could more effectively predict Cage subsidence. Multivariate analysis showed that the CT value of L 1-4 axis was an independent risk factor for Cage subsidence ( P<0.05). The CT value measurement of the vertebral body based on lumbar spine CT before stand-alone OLIF can predict the Cage subsidence. Patients with low CT values of the lumbar spine have a higher risk of Cage subsidence. However, the Cage subsidence do not lead to adverse clinical results.

Objective To assess the risk of sympathetic nerve injury in oblique lumbar interbody fusion (OLIF) in different lumbar spine segments based on anatomical study. Methods Twenty-four healthy adult volunteers (12 male and female) were selected and routine lumbar spine scanning was performed with MAG MAGOMOM Verio 3.0 T. The anatomical structures of left lumbar sympathetic trunk, abdominal aorta and left psoas muscle were identified on T2 images of L2, 3, L3, 4, L4, 5 intervertebral space. And the anatomical parameters of the OLIF operation approach and the anatomical parameters of the left sympathetic trunk and adjacent structures were measured. The t-test was used to compare the parameters between the different sexes. The comparison of the data between the different segments was performed by the least significant difference (LSD) single factor analysis of variance. Results From the L2, 3 to L4, 5 segments, the anatomical parameters of the OLIF operation approach and the anatomical parameters of the left sympathetic trunk and the adjacent structures showed regular changes. The distances between the anterior margin of the left psoas muscle and the abdominal aorta from L2, 3 to L4, 5 were 13.65±4.10 mm to 9.42 ± 4.00 mm in adult healthy male individuals, and 13.89±3.18 mm to 8.38 ± 3.33 mm in female individuals, showing a significant downward trend. The distances between the left sympathetic trunk and the abdominal aorta from L2, 3 to L4, 5 were 10.76±3.89 mm to 6.68±3.39 mm in adult healthy male individuals, and 11.52±3.02 mm to 6.12±2.95 mm in female individuals, also showing a significant downward trend. There were significant differences in the operation area of OLIF surgery between different segments. The operation area of OLIF surgery was relatively large in L2, 3 segment, and the risk of sympathetic nerve injury was relatively small. The left lumbar sympathetic trunk in the L3, 4 intervertebral space was walking front and inside, and there was a greater risk of injury in the OLIF surgery. Conclusion The left lumbar sympathetic trunk located in or close to OLIF surgery operation field in L2-L5 segments. There was a certain risk of sympathetic nerve injury in OLIF surgery, and the risk of sympathetic nerve injury was different in L2, 3, L3, 4, L4, 5 segments. Key words: Lumbar vertebrae; Spinal fusion; Sympathetic Nervous System; Anatomy, regional