The concave versus convex approach for minimally invasive lateral lumbar interbody fusion for thoracolumbar degenerative scoliosis

L4-L5 anatomy classification system for lateral lumbar interbody fusion

Lateral lumbar interbody fusion (LLIF), developed by Dr. Luiz Pimenta in 2006, allows access to the spinal column through the psoas major muscle. The technique has many advantages, such as reduced bone and muscular tissue damage, indirect decompression, larger implants, and lordosis correction capabilities. However, this technique also has drawbacks, with the most notorious being the risk of spinal pathologies due to indirect injury of the lumbar plexus, but with low rates of persistent injuries. Therefore, several groups have proposed classifications to help identify patients at a greater risk of presenting with neurological deficits. The present work proposes a classification system that relies on simple observation of easily identifiable key structures to guide lateral L4-L5 LLIF decision-making. Patients aged > 18 years who underwent preoperative magnetic resonance imaging (MRI) between 2022 and 2023 were included until 50 high-quality images were acquired. And excluded as follow Anatomical changes in the vertebral body or major psoas muscles prevent the identification of key structures or poor-quality MRIs. Each anatomy was classified as type I, type II, or type III according to the consensus among the three observers. Fifty anatomical sites were included in this study. 70% of the L4-L5 anatomy were type I, 18% were type II, and 12% were type III. None of the type 3 L4-L5 anatomies were approached using a lateral technique. The proposed classification is an easy and simple method for evaluating the feasibility of a lateral approach to-L4-L5.

Clinical Analysis and Imaging Study of Lateral Lumbar Intervertebral Fusion in the Treatment of Degenerative Lumbar Scoliosis

OBJECTIVE

As the population ages and technology advances, lateral lumbar intervertebral fusion (LLIF) is gaining popularity for the treatment of degenerative lumbar scoliosis (DLS). This study investigated the feasibility, minimally invasive concept, and benefits of LLIF for the treatment of DLS by observing and assessing the clinical efficacy, imaging changes, and complications following the procedure.

METHODS

A retrospective analysis was performed for 52 DLS patients (12 men and 40 women, aged 65.84 ± 9.873 years) who underwent LLIF from January 2019 to January 2023. The operation time, blood loss, complications, clinical efficacy indicators (visual analogue scale [VAS], Oswestry disability index [ODI], and 36-Item Short Form Survey), and imaging indicators (coronal position: Cobb angle and center sacral vertical line-C7 plumbline [CSVL-C7PL]; and sagittal position: sagittal vertical axis [SVA], lumbar lordosis [LL], pelvic incidence angle [PI], and thoracic kyphosis angle [TK] were measured). All patients were followed up. The above clinical evaluation indexes and imaging outcomes of patients postoperatively and at last follow-up were compared to their preoperative results.

RESULTS

Compared to the preoperative values, the Cobb angle and LL angle were significantly improved after surgery (p < 0.001). Meanwhile, CSVL-C7PL, SVA, and TK did not change much after surgery (p > 0.05) but improved significantly at follow-up (p < 0.001). There was no significant change in PI at either the postoperative or follow-up timepoint. The operation took 283.90 ± 81.62 min and resulted in a total blood loss of 257.27 ± 213.44 mL. No significant complications occurred. Patients were followed up for to 21.7 ± 9.8 months. VAS, ODI, and SF-36 scores improved considerably at postoperative and final follow-up compared to preoperative levels (p < 0.001). After surgery, the Cobb angle and LL angle had improved significantly compared to preoperative values (p < 0.001). CSVL-C7PL, SVA, and TK were stable after surgery (p > 0.05) but considerably improved during follow-up (p < 0.001). PI showed no significant change at either the postoperative or follow-up timepoints.

CONCLUSION

Lateral lumbar intervertebral fusion treatment of DLS significantly improved sagittal and coronal balance of the lumbar spine, as well as compensatory thoracic scoliosis, with good clinical and radiological findings. Furthermore, there was less blood, less trauma, and quicker recovery from surgery.

Anterior Spinal Fusion for Thoraco-Lumbar Idiopathic Scoliosis Comparing Less Invasive Concave versus Traditional Convex Approach: A Pilot Study

Background/Objectives: Anterior spinal fusion for primary thoracolumbar or lumbar (TL/L) adolescent idiopathic scoliosis, AIS, has advantages over posterior fusion, particularly in saving motion segments below the fusion construct. Traditionally, the approach is anterolaterally from the convexity. In adult degenerative scoliosis, the lateral or anterolateral approach may be performed from the traditional or from the concave approach which is less invasive and gives comparable outcomes. The purpose of the present pilot study was to assess the feasibility of the less invasive concave approach for younger AIS patients and compare it to the traditional convex approach over a 5-year follow-up period. Methods: The two cohorts were assessed by comparing pre- to postoperative radiographs, and clinical outcomes for pain, function, self-perception of appearance, and opinion of surgical success were prospectively obtained. Results: Radiographs found that primary TL/L scoliosis significantly improved from 53° to 18° (65%) for both the concave and convex cohorts. Sagittal alignments remained stable and there was no difference between cohorts. Coronal balance improved in both cohorts and sagittal balance was stable for both. Clinically, VAS back pain improved significantly for both cohorts initially and remained improved in the concave group. Leg pain, pain drawing, ODI disability, and VAS appearance scores improved and there was no difference between cohorts. The self-rating of success of the procedure was 100% at early and late follow-up periods. There were no neurological/surgical complications. Conclusions: The concave approach for anterior fusion for TL/L AIS is feasible with comparable radiographic and clinical outcomes to the traditional approach.

Effect of Unintended Tissue Injury on the Development of Thigh Symptoms After Lateral Lumbar Interbody Fusion in Patients With Adult Spinal Deformity: A Retrospective Case Series

STUDY DESIGN

A retrospective case series.

OBJECTIVE

This study aimed to investigate the effects of lateral lumbar interbody fusion (LLIF)-induced unintended tissue damage, including cage subsidence, cage malposition, and hematoma in the psoas major muscle, on the development of thigh symptoms.

SUMMARY OF BACKGROUND DATA

Thigh symptoms are the most frequent complications after LLIF and are assumed to be caused by lumbar plexus compression and/or direct injury to the psoas major muscle. However, the causes and risk factors of thigh symptoms are yet to be fully understood.

MATERIALS AND METHODS

Adult patients with spinal deformity who underwent two-stage surgery using LLIF and a posterior open fusion for the first and second stages, respectively, were included. Computed tomography and magnetic resonance imaging were routinely performed after LLIF before posterior surgery to investigate cage subsidence, cage malposition, and hematoma in the psoas muscle. We evaluated the development of thigh symptoms after LLIF and examined the effects of tissue injury on the occurrence of thigh symptoms. The differences in demographics and surgical and tissue damage parameters were compared between the groups with and without thigh symptoms using unpaired t tests and chi-squared tests. Factors associated with the development of thigh symptoms and muscle weakness were also assessed using logistic regression analysis.

RESULTS

Overall, 130 patients [17 men and 113 women; mean age, 68.7 (range, 47-84)] were included. Thigh symptoms were observed in 52 (40.0%) patients, including muscle weakness and contralateral side symptoms in 20 (15.4%) and 9 (17.3%) patients, respectively. The factors significantly associated with thigh symptoms identified after multiple logistic regression analysis included hematoma (odds ratio: 2.27, 95% CI, 1.03-5.01) and approach from the right side (odds ratio: 2.64, 95% CI, 1.21-5.75). The presence of cage malposition was the only significant factor associated with muscle weakness (odds ratio: 4.12, 95% CI, 1.37-12.4).

CONCLUSIONS

We found unintended tissue injury during LLIF was associated with thigh symptoms. We found that hematoma in the psoas major muscle and cage malposition were the factors associated with thigh symptoms and muscle weakness, respectively.

Surgical outcome of minimal invasive oblique lateral interbody fusion with percutaneous pedicle screw fixation in the treatment of adult degenerative scoliosis

Oblique lateral interbody fusion is performed for lumbar spinal restoration and stabilization, without extensive paraspinal muscle damage or massive bleeding. This study aimed to confirm the radiological and clinical outcomes of minimally invasive oblique lateral interbody fusion (OLIF) with percutaneous pedicle screw fixation (PPSF) as treatment for adult degenerative lumbar scoliosis. Medical records of 40 patients with degenerative lumbar spinal deformities who underwent selective OLIF and PPSF at our hospital between April 2018 and February 2021 were retrospectively reviewed. The study population comprised 7 male and 33 female patients aged 55-79 years. Standing radiography was performed, and the coronal cobb angle, distance between the C7 plumb line and central sacral vertical line, sagittal vertical axis, pelvic tilt, lumbar lordosis (LL), pelvic incidence (PI), and difference between PI and LL (PI-LL) were measured. Coronal scoliosis was defined as a lumbar coronal plane curve of > 15°. All patients achieved statistically significant improvements in coronal and sagittal alignment. The coronal cobb angle was corrected from 18.82° to 11.52°, and the central sacral vertical line was reduced from 18.30 mm to 15.47 mm. The sagittal vertical axis was significantly reduced from 45.95 mm to 32.72 mm. In contrast, the pelvic tilt and LL were minimally changed. For subgroup analyses, patients were divided into the convex and concave groups according to the direction of coronal curve correction. Vertebral body rotation was superior in the convex group than in the concave group. Furthermore, we checked for asymmetric facet degeneration at the upper instrumented vertebra (UIV) level at 1 year postoperatively. Of the 22 patients who underwent more than 3 level fusion surgery, 8 patients were confirmed the postoperative asymmetric facet degeneration in above UIV. Minor complications occurred in 16 patients, who recovered without any problems. Revision surgery was not performed in all cases. Minimally invasive OLIF with PPSF has a lower risk of complications and favorable surgical outcomes in patients with adult degenerative lumbar scoliosis. Access from the convex side is advantageous for the correction of the rotated vertebra. Extending the UIV level to the neutral vertebra can reduce the occurrence of postoperative asymmetric facet degeneration.

Safety of lateral access to the concave side for adult spinal deformity

OBJECTIVE

Minimally invasive surgery (MIS) techniques, particularly lateral lumbar interbody fusion (LLIF), have become increasingly popular for adult spinal deformity (ASD) correction. Much discussion has been had regarding theoretical and clinical advantages to addressing coronal curvature from the convex versus concave side of the curve. In this study, the authors aimed to broadly evaluate the clinical outcomes of addressing ASD with circumferential MIS (cMIS) techniques while accessing the lumbar coronal curvature from the concave side.

METHODS

A multi-institution, retrospective chart and radiographic review was performed for all ASD patients with at least a 10° curvature, as defined by the Scoliosis Research Society, who underwent cMIS correction. The data collected included convex versus concave access to the coronal curve, durable or sensory femoral nerve injury lasting longer than 6 weeks, vascular injury, visceral injury, and any additional major complication, with at least a 2-year follow-up. Neither health-related quality-of-life metrics nor spinopelvic parameters were included within the scope of this study.

RESULTS

A total of 152 patients with ASD treated with cMIS correction via lateral access were identified and analyzed. Of these, 126 (82.9%) were approached from the concave side and 26 (17.1%) were approached from the convex side. In the concave group, 1 (0.8%) motor and 4 (3.2%) sensory deficit cases remained at 6 weeks after the operation. No vascular, visceral, or catastrophic intraoperative injuries were encountered in the concave group. Of the 26 patients in the convex group, 2 (7.7%) experienced motor deficits lasting longer than 6 weeks and 5 (19.2%) had lower-extremity sensory deficits.

CONCLUSIONS

It has been reported that lateral access to the convex side is associated with similar clinical and radiographic outcomes with fewer complications when compared with access to the concave side. Advantages to approaching the lumbar spine from the concave side include using one incision to access multiple levels, breaking the operative table to assist with curvature correction, easier access to the L4-5 disc space, the ability to release the contracted side, and, often, avoidance of the need to access or traverse the thoracic cavity. This study illustrates the largest reported cohort of concave access for cMIS scoliosis correction; few postoperative sensory and motor deficits were found.

Lateral Lumbar Interbody Fusion: Review of Surgical Technique and Postoperative Multimodality Imaging Findings

The lateral lumbar interbody fusion (LLIF) approach is a minimally invasive surgery that can be used as an alternative to traditional lumbar interbody fusion techniques. LLIF accesses the intervertebral disk through the retroperitoneum and psoas muscle to avoid major vessels and visceral organs. The exposure of retroperitoneal structures during LLIF leads to unique complications compared with other surgical approaches. An understanding of the surgical technique and its associated potential complications is necessary for radiologists who interpret imaging before and after LLIF. Preoperative imaging must carefully assess the location of anatomic structures, including major retroperitoneal vasculature, lumbar nerve roots, lumbosacral plexus, and the genitofemoral nerve, relative to the psoas muscle. Multiple imaging modalities can be used in postoperative assessment including radiographs, CT, CT myelography, and MRI. Of these, CT is the preferred modality, because it can assess a range of complications relating to both the retroperitoneal exposure and the spinal instrumentation, as well as bone integrity and fusion status. This article describes surgical approaches for lumbar interbody fusion, comparing the approaches' indications, contraindications, advantages, and disadvantages; reviews the surgical technique of LLIF and relevant anatomic considerations; and illustrates for interpreting radiologists the normal postoperative findings and potential postsurgical complications of LLIF.

A Systematic Review of Complications Following Minimally Invasive Spine Surgery Including Transforaminal Lumbar Interbody Fusion

PURPOSE OF REVIEW

To assess complications after minimally invasive spinal surgeries including transforaminal lumbar interbody fusion (MI-TLIF) by reviewing the most recent literature.

RECENT FINDINGS

Current literature demonstrates that minimally invasive surgery (MIS) in spine has improved clinical outcomes and reduced complications when compared with open spinal procedures. Recent studies describing MI-TLIF primarily for degenerative disk disease, spondylolisthesis, and vertebral canal stenosis cite over 89 discrete complications, with the most common being radiculitis (ranging from 2.8 to 57.1%), screw malposition (0.3-12.7%), and incidental durotomy (0.3-8.6%). Minimally invasive spine surgery has a distinct set of complications in comparison with other spinal procedures. These complications vary based on the exact MIS procedure and indication. The most frequently documented MI-TLIF complications in current published literature were radiculitis, screw malposition, and incidental durotomy.

Anatomic Considerations in the Lateral Transpsoas Interbody Fusion: The Impact of Age, Sex, BMI, and Scoliosis

STUDY DESIGN

This is a retrospective case series.

OBJECTIVE

Define the anatomic variations and the risk factors for such within the operative corridor of the transpsoas lateral interbody fusion.

SUMMARY OF BACKGROUND DATA

The lateral interbody fusion approach has recently been associated with devastating complications such as injury to the lumbosacral plexus, surrounding vasculature, and bowel. A more comprehensive understanding of anatomic structures in relation to this approach using preoperative imaging would help surgeons identify high-risk patients potentially minimizing these complications.

MATERIALS AND METHODS

Age-sex distributed, naive lumbar spine magnetic resonance imagings (n=180) were used to identify the corridor for the lateral lumbar interbody approach using axial images. Bilateral measurements were taken from L1-S1 to determine the locations of critical vascular, intraperitoneal, and muscular structures. In addition, a subcohort of scoliosis patients (n=39) with a Cobb angle >10 degrees were identified and compared.

RESULTS

Right-sided vascular anatomy was significantly more variant than left (9.9% vs. 5.7%; P=0.001). There were 9 instances of "at-risk" vasculature on the right side compared with 0 on the left (P=0.004). Age increased vascular anatomy variance bilaterally, particularly in the more caudal levels (P≤0.001). A "rising-psoas sign" was observed in 26.1% of patients. Bowel was identified within the corridor in 30.5% of patients and correlated positively with body mass index (P<0.001). Scoliosis increased variant anatomy of left-sided vasculature at L2-3/L3-4. Nearly all variant anatomy in this group was found on the convex side of the curvature (94.2%).

CONCLUSIONS

Given the risks and complications associated with this approach, careful planning must be taken with an understanding of vulnerable anatomic structures. Our analysis suggests that approaching the intervertebral space from the patient's left may reduce the risk of encountering critical vascular structures. Similarly, in the setting of scoliosis, an approach toward the concave side may have a more predictable course for surrounding anatomy.

LEVEL OF EVIDENCE

Level 3-study.

Curve Laterality for Lateral Lumbar Interbody Fusion in Adult Scoliosis Surgery: The Concave Versus Convex Controversy

BACKGROUND

Minimally invasive lateral lumbar interbody fusion (LLIF) is an effective adjunct in adult degenerative scoliosis (ADS) surgery. LLIF approaches performed from the concavity or convexity have inherent approach-related risks and benefits.

OBJECTIVE

To analyze LLIF approach-related complications and radiographic and clinical outcomes in patients with ADS.

METHODS

A multicenter retrospective review of a minimally invasive adult spinal deformity database was queried with a minimum of 2-yr follow-up. Patients were divided into 2 groups as determined by the side of the curve from which the LLIF was performed: concave or convex.

RESULTS

No differences between groups were noted in demographic, and preoperative or postoperative radiographic parameters (all P > .05). There were 8 total complications in the convex group (34.8%) and 21 complications in the concave group (52.5%; P = .17). A subgroup analysis was performed in 49 patients in whom L4-5 was in the primary curve and not in the fractional curve. In this subset of patients, there were 6 complications in the convex group (31.6%) compared to 19 in the concave group (63.3%; P < .05) and both groups experienced significant improvements in coronal Cobb angle, Oswestry Disability Index, and Visual Analog Scale score with no difference between groups.

CONCLUSION

Patients undergoing LLIF for ADS had no statistically significant clinical or operative complication rates regardless of a concave or convex approach to the curve. Clinical outcomes and coronal plane deformity improved regardless of approach side. However, in cases wherein L4-5 is in the primary curve, approaching the fractional curve at L4-5 from the concavity may be associated with a higher complication rate compared to a convex approach.

Minimally Invasive Spinal Surgery for Adult Spinal Deformity

The purpose of this review is to present the current techniques and outcomes of adult spine deformity (ASD) surgery using the minimally invasive spine surgery (MISS) approach. We performed a systemic search of PubMed for literature published through January 2018 with the following terms: "minimally invasive spine surgery," "adult spinal deformity," and "degenerative scoliosis." Of the 138 items that were found through this search, 57 English-language articles were selected for full-text review. According to the severity of the deformity and the symptoms, various types of MISS have been utilized, such as MISS decompression, circumferential MISS, and hybrid surgery. With proper indications, the MISS approach achieved satisfactory clinical and radiological outcomes for ASD, with reduced complication rates. Future studies should aim to define clear indications for the application of various surgical options.

Minimally invasive techniques for lumbar decompressions and fusions

PURPOSE OF REVIEW

The purpose of this study is to summarize the recent literature investigating the use of minimally invasive (MIS) techniques in the treatment of lumbar degenerative stenosis, spondylolisthesis, and scoliosis.

RECENT FINDINGS

MIS lumbar decompression and fusion techniques for degenerative pathology are associated with reduced operative morbidity, shortened length of hospital stay, and reduced postoperative pain and narcotics utilization. Recent studies with long-term clinical follow-up have demonstrated equivalence in clinical outcomes between open and MIS surgical procedures. Radiographically, MIS procedures provide adequate postoperative correction of coronal alignment. Correction of sagittal alignment, however, is more variable based on current reports. MIS techniques are both safe and effective in the treatment of lumbar degenerative pathologies. While some studies have reported on long-term outcomes and costs associated with MIS procedures, more investigation into these topics is still necessary. Additionally, further work is required to analyze the training requirements and learning curves of MIS procedures to better promote adoption amongst surgeons.