Analysis of Spino-Pelvic Parameters and Segmental Lordosis with L5-S1 Oblique Lateral Interbody Fusion at the Bottom of a Long Construct in Circumferential Minimally Invasive Surgical Correction of Adult Spinal Deformity

A systematic review of pseudarthrosis and reoperation rates in minimally invasive adult spinal deformity correction

Background/objective

The recent development of minimally invasive surgical techniques (MIS) has made possible the correction of adult spinal deformity (ASD) with less blood loss and shorter hospital stays. However, minimally invasive placement of pedicle screws at the proximal level of the construct can increase pseudarthrosis risk, leading to implant failure, kyphosis, and reoperations. We aggregate existing literature to describe pseudarthrosis rates at the proximal thoracic or thoracolumbar junction in MIS and subsequent reoperation rates.

Methods

After a three-tied search strategy in PubMed, we identified 9 articles for study inclusion, describing outcomes from MIS correction of ASD, pseudarthrosis as complication, and surgery on 4+ levels. Baseline patient characteristics and combined rates of pseudarthrosis and reoperation were calculated.

Results

A total of 482 patients were studied with an average [range] age of 65.5 [60.4,72], 6.3 [4.4,11] levels fused per patient, follow-up time of 28.3 [12,39] months, and 64.8% females. Pseudarthrosis was reported in 28 of 482 pooled patients (5.8%) of which 15 of 374 pooled patients (4.0%) ultimately underwent a reoperation for pseudarthrosis. Post-operative characteristics included an estimated blood loss (EBL) of 527.1 [241,1466] mL, operating time of 297.9 [183,475] minutes, and length of stay of 7.7 [5,10] days. Among the papers comparing MIS to open surgery, all reported a significantly lower EBL in patients treated with MIS.

Conclusion

This analysis demonstrate a measurable pseudarthrosis risk when using MIS to treat ASD, overwhelming requiring reoperation. The benefits of MIS must be considered against the drawbacks of pseudarthrosis when determining ASD management.

Clinical and Radiologic Analysis of Minimally Invasive Anterior-Posterior Combined Surgery for Adult Spinal Deformity: Comparison of Oblique Lateral Interbody Fusion at L5/S1 (OLIF51) versus Transforaminal Interbody Fusion

Background and Objectives: Although adult spinal deformity (ASD) surgery brought about improvement in the quality of life of patients, it is accompanied by high invasiveness and several complications. Specifically, mechanical complications of rod fracture, instrumentation failures, and pseudarthrosis are still unsolved issues. To better improve these problems, oblique lateral interbody fusion at L5/S1 (OLIF51) was introduced in 2015 at my institution. The objective of this study was to compare the clinical and radiologic outcomes of anterior-posterior combined surgery for ASD between the use of OLIF51 and transforaminal interbody fusion (TLIF) at L5/S1. Materials and Methods: A total of 117 ASD patients received anterior-posterior correction surgeries either with the use of OLIF51 (35 patients) or L5/S1 TLIF (82 patients). In both groups, L1-5 OLIF and minimally invasive posterior procedures of hybrid or circumferential MIS were employed. The sagittal and coronal spinal alignment and spino-pelvic parameters were recorded preoperatively and at follow-up. The quality-of-life parameters and visual analogue scale were evaluated, as well as surgical complications at follow-up. Results: The average follow-up period was thirty months (13-84). The number of average fused segments was eight (4-12). The operation time and estimated blood loss were significantly lower in OLIF51 than in TLIF. The PI-LL mismatch, LLL, L5/S1 segmental lordosis, and L5 coronal tilt were significantly better in OLIF51 than TLIF. The complication rate was statistically equivalent between the two groups. Conclusions: The introduction of OLIF51 for adult spine deformity surgery led to a decrease in operation time and estimated blood loss, as well as improvement in sagittal and coronal correction compared to TLIF. The circumferential MIS correction and fusion with OLIF51 serve as an effective surgical modality which can be applied to many cases of adult spinal deformity.

Single position L5-S1 lateral ALIF with simultaneous robotic posterior fixation is safe and improves regional alignment and lordosis distribution index

PURPOSE

Minimally invasive single position lateral ALIF at L5-S1 with simultaneous robot-assisted posterior fixation has technical and anatomic considerations that need further description.

METHODS

This is a retrospective case series of single position lateral ALIF at L5-S1 with robotic assisted fixation. End points included radiographic parameters, lordosis distribution index (LDI), complications, pedicle screw accuracy, and inpatient metrics.

RESULTS

There were 17 patients with mean age of 60.5 years. Eight patients underwent interbody fusion at L5-S1, five patients at L4-S1, two patients at L3-S1, and one patient at L2-S1 in single lateral position. Operative times for 1-level and 2-level cases were 193 min and 278 min, respectively. Mean EBL was 71 cc. Mean improvements in L5-S1 segmental lordosis were 11.7 ± 4.0°, L1-S1 lordosis of 4.8 ± 6.4°, sagittal vertical axis of - 0.1 ± 1.7 cm°, pelvic tilt of - 3.1 ± 5.9°, and pelvic incidence lumbar-lordosis mismatch of - 4.6 ± 6.4°. Six patients corrected into a normal LDI (50-80%) and no patients became imbalanced over a mean follow-up period of 14.4 months. Of 100 screws placed in lateral position with robotic assistance, there were three total breaches (two lateral grade 3, one medial grade 2) for a screw accuracy of 97.0%. There were no neurologic, vascular, bowel, or ureteral injuries, and no implant failure or reoperation.

CONCLUSION

Single position lateral ALIF at L5-S1 with simultaneous robotic placement of pedicle screws by a second surgeon is a safe and effective technique that improves global alignment and lordosis distribution index.

Radiographic comparison of L5-S1 lateral anterior lumbar interbody fusion cage subsidence and displacement by fixation strategy: anterior plate versus integrated screws

OBJECTIVE

The aim of this study was to radiographically compare cage subsidence and displacement between L5-S1 lateral anterior lumbar interbody fusion (ALIF) cages secured with an anterior buttress plate and cages secured with integrated screws.

METHODS

Consecutive patients who underwent L5-S1 lateral ALIF with supplemental posterior fixation by a single surgeon from June 2016 to January 2021 were reviewed. Radiographs were analyzed and compared between the two groups based on the type of fixation used to secure the L5-S1 lateral ALIF cage: 1) anterior buttress plate or 2) integrated screws. The following measurements at L5-S1 were analyzed on radiographs obtained preoperatively, before discharge, and at latest follow-up: 1) anterior disc height, 2) posterior disc height, and 3) segmental lordosis. Cage subsidence and anterior cage displacement were determined radiographically.

RESULTS

One hundred thirty-nine patients (mean age 60.0 ± 14.3 years) were included for analysis. Sixty-eight patients were treated with an anterior buttress plate (mean follow-up 12 ± 5 months), and 71 were treated with integrated screws (mean follow-up 9 ± 3 months). Mean age, sex distribution, preoperative L5-S1 lordosis, preoperative L5-S1 anterior disc height, and preoperative L5-S1 posterior disc height were statistically similar between the two groups. After surgery, the segmental L5-S1 lordosis and L5-S1 anterior disc heights significantly improved for both groups, and each respective measurement was similar between the groups at final follow-up. Posterior disc heights significantly increased after surgery with integrated screws but not with the anterior buttress plate. As such, posterior disc heights were significantly greater at final follow-up for integrated screws. Compared with patients who received integrated screws, significantly more patients who received the anterior buttress plate had cage subsidence cranially through the L5 endplate (20.6% vs 2.8%, p < 0.01), cage subsidence caudally through the S1 endplate (27.9% vs 0%, p < 0.01), and anterior cage displacement (22.1% vs 0%, p < 0.01).

CONCLUSIONS

In this radiographic analysis of 139 patients who underwent lateral L5-S1 ALIF supplemented by posterior fixation, L5-S1 cages secured with an anterior buttress plate demonstrated significantly higher rates of cage subsidence and anterior cage displacement compared with cages secured with integrated screws. While the more durable stability afforded by cages secured with integrated screws suggests that they may be a more viable fixation strategy for L5-S1 lateral ALIFs, there are multiple factors that can contribute to cage subsidence, and, thus, definitive presumption cannot be made that the findings of this study are directly related to the buttress plate.

Lumbar Interbody Fusion and Osteobiologics for Lumbar Fusion

Lumbar interbody fusion (LIF) is an excellent treatment option for a number of lumbar diseases. LIF can be performed through posterior, transforaminal, anterior, and lateral or oblique approaches. Each technique has its own pearls and pitfalls. Through LIF, segmental stabilization, neural decompression, and deformity correction can be achieved. Minimally invasive surgery has recently gained popularity and each LIF procedure can be performed using minimally invasive techniques to reduce surgery-related complications and improve early postoperative recovery. Despite advances in surgical technology, surgery-related complications after LIF, such as pseudoarthrosis, have not yet been overcome. Although autogenous iliac crest bone graft is the gold standard for spinal fusion, other bone substitutes are available to enhance fusion rate and reduce complications associated with bone harvest. This article reviews the surgical procedures and characteristics of each LIF and the osteobiologics utilized in LIF based on the available evidence.

Management of severe adult spinal deformity with circumferential minimally invasive surgical strategies without posterior column osteotomies: a 13-year experience

OBJECTIVE

To evaluate the mid- to long-term clinical outcomes of circumferential minimally invasive surgery (CMIS) without posterior column osteotomies for severe adult spine deformity (ASD) correction.

METHODS

All patients with a minimum of 2-year follow-up undergoing staged CMIS correction of ASD from January 2007 to July 2018 were identified. All included patients had fusion of 3 or more interbody levels that spanned the L5-S1 junction. Only patients with severe deformity, Coronal Cobb > 50° or at least one SRS-Schwab ++ sagittal modifier (SVA > 95 mm, or PI-LL > 20, or PT > 30) were included. All complications were noted.

RESULT

136 patients met inclusion criteria; mean age of patients was 63.6 years (21-85, SD 13.7). The mean follow-up was 82.8 months (24-159, SD 36.6). The mean number of levels fused was 7 (3-16, SD 3). A total of 40 (29.4%) major complications were noted at final follow-ups: 2 (1.4%) intra-operative, 12 (8.9%) peri-operative (≤ 6 weeks from index), 26 (19.1%) post-operative (> 6 weeks from index). There was a total of 53 (40.0%) minor complications. Seven (5.1%) patients who developed radiographic proximal junctional kyphosis. Three patients (2.2%) developed proximal junctional failure. There were 8 (5.9%) cases of pseudarthrosis. Five of these occurred in patients undergoing AxiaLIF. All patients experienced improvements in patient-perceived outcomes (VAS, TIS, ODI, and SRS-22) and radiographic parameters at last follow-up when compared to pre-op (p < 0.05).

CONCLUSION

Rates of complications with CMIS correction of severe ASD are lower than published rates of complications seen with open ASD correction. Specifically, the incidence of catastrophic complications is lower. Furthermore, CMIS is associated with significant improvements in clinical and functional outcomes, low rates of pseudarthrosis and proximal junctional kyphosis. Therefore, in the appropriately selected patient, CMIS may be an excellent alternative approach to addressing severe ASD.

Outcomes of Oblique Lateral Interbody Fusion for Adult Spinal Deformity: A Systematic Review and Meta-Analysis

STUDY DESIGN

A systematic review and meta-analysis.

OBJECTIVES

To evaluate clinical and radiographic outcomes, and perioperative complications of oblique lateral interbody fusion (OLIF) for adult spinal deformity (ASD).

METHODS

We performed a systematic review and meta-analysis of related studies reporting outcomes of OLIF for ASD. The clinical outcomes were assessed by visual analogue scale (VAS) and Oswestry Disability Index (ODI). The radiographic parameters were evaluated by sagittal vertical axis (SVA), pelvic tilt (PT), sacral slope (SS), thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence-lumbar lordosis (PI-LL), Cobb angle and fusion rate. A random effects model and 95% confidence intervals (CI) were performed to investigate the results.

RESULTS

A total of 16 studies involving 519 patients were included in the present study. The mean difference of VAS-back score, VAS-leg score and ODI score before and after surgery was 5.1, 5.0 and 32.3 respectively. The mean correction of LL was 20.6°, with an average of 6.9° per level and the mean correction of Cobb was 16.4°, with an average of 4.7° per level. The mean correction of SVA, PT, SS, TK and PI-LL was 59.3 mm, 11.7°, 6.9°, 9.4° and 20.6° respectively. The mean fusion rate was 94.1%. The incidence of intraoperative and postoperative complications was 4.9% and 29.6% respectively.

CONCLUSIONS

OLIF is an effective and safe surgery method in the treatment of mild or moderate ASD and it has advantages in less intraoperative blood loss and lower perioperative complications.

A Crucial But Neglected Anatomical Factor Underneath Psoas Muscle and Its Clinical Value in Lateral Lumbar Interbody Fusion-The Cleft of Psoas Major (CPM)

Objective

To describe the anatomical feature positioned beneath the psoas muscle at the lateral aspect of the lower lumbar, and to create a new location system to identify the risk factors of lateral lumbar interbody fusion.

Methods

Six cadavers were dissected and analyzed. The anatomy and neurovascular distribution beneath the psoas major from L₃ to S₁ was observed and recorded, with particular focus on the L_4/5 disc and below. The psoas major surface was divided homogeneously into four parts, from the anterior border of psoas major to the transverse process. The cranial‐to‐caudal division was from the lower edge of the psoas muscle attachment on the L₄ vertebrae to the upper part of the S₁ vertebrae, and was divided into five segments. Then a grid system was used to create 20 grids on the psoas major surface, from the anterior border of the muscle to the transverse process and from L₄ to superior S₁, which was used to determine the anatomical structures' distribution and relationship beneath the psoas major.

Results

A cleft was identified beneath the psoas major, from the level of L_4/5 downwards. It was filled with loose connective tissue and neurovascular structures. We termed it the cleft of psoas major (CPM). The sympathetic trunk, ascending lumbar vein, iliolumbar vessels, obturator nerve, femoral nerve and occasionally the great vessels are contained within the CPM, although there is significant interpersonal variation. The grid system on the psoas major surface helped to identify the anatomical structures in CPM. There was a considerably lower frequency of occurrence of neurovascular structures in the grids of I/II at the L_4/5 level where can be considered the “safe zones” for the lateral lumbar interbody fusion. In contrast, the distribution of neurovascular structures at the L₅S₁ level is dense, where the operation risk is high.

Conclusion

The CPM exists lateral to the vertebral surface from L₄ and below. Although the occurrence and distribution of neurovascular structures within the CPM is complex and varies greatly, it can provide a potential cavity for visualization during lateral lumbar interbody fusion. Using psoas major as a reference, this novel grid system can be used to identify the risk factors in CPM and thus identify a safe entry point for surgery.

A comparison of long-term efficacy of K-rod-assisted non-fusion operation and posterior lumbar interbody fusion for single-segmental lumbar disc herniation

K-rod-assisted non-fusion surgery for the treatment of lumbar disc herniation has been proven to have short-term clinical efficacy. Meanwhile, its long-term effects have not been examined. To observed the long-term clinical efficacy of K-rod-assisted non-fusion operation, this study retrospectively analyzed 22 patients with lumbar disc (L4/5) herniation who underwent K-rod-assisted non-fusion operation (n = 13) or PLIF (n = 9). They were followed-up for more than 5 years. The operation times and blood loss were significantly reduced in the K-rod group compared to the PLIF group. At the last follow-up, the clinical outcomes of the K-rod group were improved compared to those of the PLIF group as observed by the VAS score, JOABPEQ, and ODI. Imaging outcomes at the last follow-up indicated that the loss of height in the L3/4 and L5/S1 intervertebral space, the ROM of L3/4 and L5/S1, and the incidence of adjacent segment degeneration in the PLIF group were significantly higher than those in the K-rod group. According to Pfirrmann grading, Modic changes, and UCLA grading, the incidence of adjacent segment degeneration was 55.6% in the PLIF group and 15.4% in the K-rod group. Changes in spino-pelvic parameters between the two groups were as follows: pelvic index remained unchanged, pelvic tilt angle increased, and lumbar lordosis and sacral slope decreased. Therefore, compared to PLIF, single-segment lumbar disc herniation using K-rod-assisted non-fusion surgery resulted in better long-term clinical efficacy. Our results demonstrate that this procedure can delay adjacent segment degeneration after lumbar surgery.

Factors affecting disc angle restoration in oblique lateral interbody fusion at L5-S1

BACKGROUND CONTEXT

Optimal restoration of the L5-S1 disc angle (DA) is an important surgical goal in spinal reconstructive surgery. Anterior approach is beneficial for L5-S1 DA reconstruction and fusion. However, factors associated with a greater DA restoration in oblique lateral interbody fusion (OLIF) at L5-S1 have not been studied.

PURPOSE

This study aimed to identify factors that aid in achieving a greater DA in OLIF at L5-S1.

STUDY DESIGN/SETTING

A retrospective analysis.

PATIENT SAMPLE

This study involved 61 consecutive patients who underwent OLIF at L5-S1 for lumbar degenerative disease and were followed for more than 1 year. Patients with incomplete data or posterior column osteotomy at L5-S1 were excluded.

OUTCOME MEASURES

The L5-S1 DA was measured preoperatively, postoperatively, and at the last follow-up on standing lateral lumbar radiographs. The associations between demographics and/or surgical and/or radiological factors and the L5-S1 DA at the last follow-up were analyzed using multiple regression analysis.

METHODS

Demographics and surgical factors were reviewed from the medical records with respect to age, sex, body mass index, bone mineral density, diagnosis, surgery level, cage parameters (cage lordotic angle and height), laminectomy performed and/or not performed, estimated blood loss, operative time, configuration of the left common iliac vein. Radiological factors were measured with respect to sagittal parameters, the L5-S1 disc parameters, and the postoperative cage parameters.

RESULTS

The mean preoperative DA at L5-S1 was 5.4±5.0°, which increased to 18.9±5.6° postoperatively (p<.001) and was maintained as 16.5±5.9° at the last follow-up (p<.001). The preoperative DA, end plate lesions, anterior spur, facet joint osteoarthritis, or cage position at L5-S1 did not affect the DA at the last follow-up (all p>.05). Multiple regression analysis showed four independent variables, including increased age, increased cage lordotic angle, laminectomy performed, and absence of cage subsidence as the factors associated with the greater DA at L5-S1.

CONCLUSIONS

OLIF at L5-S1 showed favorable DA restoration regardless of the preoperative conditions. To achieve a greater DA, surgeons should try to distract the anterior disc space for insertion of a larger lordotic cage. Laminectomy during posterior fixation is recommended for achieving additional DA restoration.

Incidence of major and minor vascular injuries during lateral access lumbar interbody fusion procedures: a retrospective comparative study and systematic literature review

During lateral lumbar fusion, the trajectory of implant insertion approaches the great vessels anteriorly and the segmental arteries posteriorly, which carries the risk of vascular complications. We aimed to analyze vascular injuries for potential differences between oblique lateral interbody fusion (OLIF) and lateral lumbar interbody fusion (LLIF) procedures at our institution. This was coupled with a systematic literature review of vascular complications associated with lateral lumbar fusions. A retrospective chart review was completed to identify consecutive patients who underwent lateral access fusions. The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines were used for the systematic review with the search terms "vascular injury" and "lateral lumbar surgery." Of 260 procedures performed at our institution, 211 (81.2%) patients underwent an LLIF and 49 (18.8%) underwent an OLIF. There were no major vascular complications in either group in this comparative study, but there were four (1.5%) minor vascular injuries (2 LLIF, 0.95%; 2 OLIF, 4.1%). Patients who experienced vascular injury experienced a greater amount of blood loss than those who did not (227.5 ± 147.28 vs. 59.32 ± 68.30 ml) (p = 0.11). In our systematic review of 63 articles, major vascular injury occurred in 0-15.4% and minor vascular injury occurred in 0-6% of lateral lumbar fusions. The systematic review and comparative study demonstrate an increased rate of vascular injury in OLIF when compared to LLIF. However, vascular injuries in either procedure are rare, and this study aids previous literature to support the safety of both approaches.

Assessment of 3D Lumbosacral Vascular Anatomy for OLIF51 by Non-Enhanced MRI and CT Medical Image Fusion Technique

Study design: Prospective study. Objective: Medical image fusion can provide information from multiple modalities in a single image. The present study aimed to determine whether three-dimensional (3D) lumbosacral vascular anatomy could be adequately portrayed using a non-enhanced CT–MRI medical image fusion technique. Summary of Background Data: Lateral lumbar interbody fusion has gained popularity for the surgical treatment of adult spinal deformity (ASD). Oblique lumbar interbody fusion at L5–S1 (OLIF51) is receiving considerable attention as a method of creating good L5–S1 lordosis. Access in OLIF51 requires evaluation of the vascular anatomy in the lumbosacral region. Conventional imaging modalities need a contrast medium to describe the vascular anatomy. Methods: Participants comprised 15 patients with ASD or degenerative lumbar disease who underwent corrective surgery at our hospital between January 2020 and June 2021. A 3D vascular image with bony structures was obtained by fusing results from MRI and CT. We processed the merged image and measured the distance between left and right common iliac arteries and veins at two levels: the lower end of the L5 vertebral body (Window A) and the upper end of the S1 vertebral body (Window B). Results: The mean sizes of Window A and Window B were 29.7 ± 10.7 mm and 36.9 ± 10.3 mm, respectively. The mean distance from the bifurcation to the lower end of the L5 vertebra was 23.7 ± 10.9 mm. Coronal deviation of the bifurcation was, from center to left, 12.6 ± 12.3 mm, and the distance from the center of the L5 vertebral body to the bifurcation was 0.79 ± 7.3 mm. Only one case showed a median sacral vein (6.7%). Clinically, we performed OLIF51 in 12 of the 15 cases (80%). Conclusion: Evaluating 3D lumbosacral vascular anatomy using a non-enhanced MRI and CT medical image fusion technique is very useful for OLIF51, particularly for patients in whom the use of contrast medium is contraindicated.

Minimally invasive transforaminal lumbar interbody fusion versus oblique lateral interbody fusion for lumbar degenerative disease: a meta-analysis

BACKGROUND

Minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) and oblique lateral interbody fusion (OLIF) are widely used in the treatment of lumbar degenerative diseases. In the present study, a meta-analysis was conducted to compare the clinical and radiographic efficacy of these two procedures.

METHODS

A systematic literature review was performed, and the quality of retrieved studies was evaluated with the Newcastle-Ottawa Scale (NOS). Clinical outcomes, including operation time, intraoperative blood loss, improvement in Visual Analogue Scale (VAS), improvement in Oswestry Disability Index (ODI), Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ) effectiveness rate and complications, in addition to radiographic outcomes, including restoration of disc height, disc angle, overall lumbar lordosis, fusion rate and subsidence, were extracted and input into a fixed or random effect model to compare the efficacy of MIS-TLIF and OLIF.

RESULTS

Seven qualified studies were included. Clinically, OLIF resulted in less intraoperative blood loss and shorter operation time than MIS-TLIF. Improvement of VAS for leg pain was more obvious in the OLIF group (P < 0.0001), whereas improvement of VAS for back pain (P = 0.08) and ODI (P = 0.98) as well as JOABPEQ effectiveness rate (P = 0.18) were similar in the two groups. Radiographically, OLIF was more effective in restoring disc height (P = 0.01) and equivalent in improving the disc angle (P = 0.18) and lumbar lordosis (P = 0.48) compared with MIS-TLIF. The fusion rate (P = 0.11) was similar in both groups, while the subsidence was more severe in the MIS-TLIF group (P < 0.00001).

CONCLUSIONS

The above evidence suggests that OLIF is associated with a shorter operation time (with supplementary fixation in the prone position) and less intraoperative blood loss than MIS-TLIF and can lead to better leg pain alleviation, disc height restoration and subsidence resistance. No differences regarding back pain relief, functional recovery, complications, disc angle restoration, lumbar lordosis restoration and fusion rate were found. However, due to the limited number of studies, our results should be confirmed with high-level studies to fully compare the therapeutic efficacy of MIS-TLIF and OLIF.

TRIAL REGISTRATION

PROSPERO ID:  CRD42020201903 .

Introducing V-Line as a New Strategy to Choose Surgical Corridor in Oblique Lumbar Interbody Fusion at the L5-S1 Segment

Purpose

A retrospective imaging study assessing the availability of oblique lumbar interbody fusion at the level of L5-S1 (OLIF51) and to choose ideal surgical corridor in OLIF51 by introducing V-line.

Methods

The axial views through the center of L5-S1 disc were reviewed. We adopt 18 mm as the width of the simulated surgical corridor. The midline of the surgical corridor is at the center of L5-S1 disc. According to the traction distance of the left iliac vein (LCIV) and psoas major (PM), we defined all the subjects as V (+) (traction-difficultly LCIV), V (-) (traction-friendly LCIV), P (+) (traction-difficultly PM), and P (-) (traction-friendly PM). V-line was defined as a straight line dividing equally the simulated surgical corridor. All cases were divided into 2 groups: The V-line (+) group, more than half of the LCIV region, is located in the ventral part of V-line; the V-line (-) group, more than half of the LCIV region, is located in the dorsal part of V-line. Multiple variables regressive analysis was conducted to analyze the independent risk factors of V-line (+).

Results

V-line (+) was found in 36 (38.7%) patients and V-line (-) in 57 (61.3%). Incidence of V (+) and P (+) was 35.4% (33/93) and 30.1% (28/93), respectively. 16.1% (15/93) subjects processed V (+) and P (+) at the same time. The independent risk factor of V-line (+) were gender of male (P = 0.034, OR: 12.152) and medial position of LCIV (P < 0.001, OR: 265.085). High iliac crest was a significant independent protective factor (P = 0.001, OR: 0.750).

Conclusions

Most patients were suitable for OLIF51. V-line could assess the injury risk of LCIV. For patients who are V-line (+), mainly among males having the LCIV near the midline or the iliac crest relatively low, a surgical corridor external to the LCIV should be taken into consideration.

Inclusion of L5-S1 in oblique lumbar interbody fusion-techniques and early complications-a single center experience

BACKGROUND CONTEXT

The oblique prepsoas retroperitoneal approach to the lumbar spine for interbody fusion or oblique lumbar interbody fusion (OLIF) provides safe access to nearly all lumbar levels. A wide interval between the psoas and aorta allows for a safe and straightforward left-sided oblique approach to the discs above L5. Inclusion of L5-S1 in this approach, however, requires modifications in the technique to navigate the complex and variable vascular anatomy distal to the bifurcation of the great vessels. While different oblique approaches to L5-S1 have been described in the literature, to our knowledge, no previous study has provided guidance for the choice of technique.

PURPOSE

Our objectives were to evaluate our early experience with the safety of including L5-S1 in OLIF using 3 different approach techniques, as well as to compare early complications between OLIF with and without L5-S1 inclusion.

STUDY DESIGN

Retrospective cohort study.

PATIENT SAMPLE

Of the 87 patients who underwent lumbar interbody fusion at 167 spinal levels via an OLIF approach, 19 included L5-S1 (group A) and 68 did not (group B).

OUTCOME MEASURES

Demographics, levels fused, indications, operative time (ORT), estimated blood loss (EBL), vascular ligation, intraoperative blood transfusion, length of stay (LOS), discharge to rehabilitation facility, and complications (intraoperative, early ≤90 days, and delayed >90 days) were retrospectively assessed and compared between the groups.

METHODS

A retrospective chart and imaging review of all consecutive patients who underwent OLIF at a single institution was performed. Indications for OLIF included symptomatic lumbar degenerative stenosis, deformity, and spondylolisthesis. The L5-S1 level, when included, was approached via one of the following 3 techniques: (1) a left-sided intrabifurcation approach; (2) left-sided prepsoas approach; and (3) right-sided prepsoas approach. Vascular anatomic variations at the lumbosacral junction were evaluated using the preoperative magnetic resonance imaging (MRI), and a "facet line" was proposed to assess this relationship. A minimum of 6 months of follow-up data were assessed for approach-related morbidities.

RESULTS

Demographics and operative indications were similar between the groups. The mean follow-up was 10.8 (6-36) months. ORT was significantly longer in group A than in group B (322 vs. 256.3 min, respectively; p=.001); however, no difference in ORT between the two groups was found in the subanalyses for 2- and 3-level surgeries. Differences in EBL (260 vs. 207.91 cc, p=.251) and LOS (2.76 vs. 2.48 days, p=.491) did not reach statistical significance. Ligation of the iliolumbar vein, segmental veins, median sacral vessels, or any vascular structure, as needed for adequate exposure, was required in 13 (68.4%) patients from group A and 4 (5.9%) from group B (p<.00001). Two patients suffered minor vascular injuries (1 in each group); however, no major vascular injuries were seen. Complications were not significantly different between groups A and B, or between the three approaches to L5-S1, and trended lower in the latter part of the series as the learning curve progressed.

CONCLUSIONS

Inclusion of L5-S1 in OLIF is safe and feasible through three different approaches but likely involves greater operative complexity. In our early experience, inclusion of L5-S1 showed no increase in early complications. This is the first series that reports the use of 3 different oblique approaches to L5-S1. The proposed "facet line" in the preoperative MRI may guide the choice of approach.

Lumbar Interbody Fusion: Techniques, Pearls and Pitfalls

Lumbar interbody fusion (LIF) is an effective and popular surgical procedure for the management of various spinal pathologies, especially degenerative diseases. Currently, LIF can be performed with posterior, transforaminal, anterior, and lateral approaches by open surgery or minimally invasive surgery (MIS). Each technique has its own advantages and disadvantages. In general, posterior LIF is a well-established procedure with good fusion rates and low complication rates but is limited by the possibility of iatrogenic injury to the neural structures and paraspinal muscles. Transforaminal LIF is frequently performed using an MIS technique and has an advantage of reducing these iatrogenic injuries. Anterior LIF (ALIF) can restore the disk height and sagittal alignment but has inherent approach-related challenges such as visceral and vascular complications. Lateral LIF and oblique LIF are performed using an MIS technique and have shown postoperative outcomes similar to ALIF; however, these approaches carry a risk of injury to psoas, lumbar plexus, and vascular structures. Herein, we provide a detailed description of the surgical procedures of each LIF technique. We shall then consider the pearls and pitfalls, as well as propose surgical indications and contraindications based on the available evidence in the literatures.