Indications and limitations of minimally invasive lateral lumbar interbody fusion without osteotomy for adult spinal deformity.

PURPOSE: The global alignment and proportion (GAP) score was recently developed to consider proportional analysis of spinopelvic alignment and has been indicated for setting surgical goals to decrease the prevalence of mechanical complications. The goal of this study was to clarify the limitations and problems with spinal corrective surgery with minimally invasive lateral lumbar interbody fusion (LLIF) without osteotomy using GAP score, and to establish a preoperative radiographical evaluation to understand the necessity for three-column osteotomy. METHODS: We included data from 57 consecutive patients treated with spinal corrective surgery with LLIF and without Schwab grade 3-6 osteotomy for ASD. To evaluate flexibility of the pelvis and lumbar spine, we examined full-length lateral radiographs with patients standing and prone. Correlations between pre- and postoperative radiographic parameters and GAP score were determined. RESULTS: Most patients achieved a sufficiently ideal lumbar lordosis (87.7%), but ideal sacral slope (SS) was achieved in only 50.8% of patients. Preoperative prone SS showed a significant positive correlation with postoperative SS and a significant negative correlation with GAP score. Patients whose preoperative prone SS was larger than pelvic incidence × 0.59-7.5 tended to achieve proportioned spinopelvic alignment by using LLIF. CONCLUSIONS: The cause of poor outcome of GAP score for ASD corrective surgery with LLIF without osteotomy is a postoperative small SS. Preoperative prone SS is useful for predicting postoperative SS. When preoperative SS in prone patients is relatively small to ideal as calculated using PI, osteotomy or other correctors should be considered to achieve satisfactory spinopelvic parameters. LEVEL OF EVIDENCE: III. These slides can be retrieved under Electronic Supplementary Material.

Does the Access Angle Change the Risk of Approach-Related Complications in Minimally Invasive Lateral Lumbar Interbody Fusion? An MRI Study.

OBJECTIVE: To investigate the potential risk of approach-related complications at different access angles in minimally invasive lateral lumbar interbody fusion. METHODS: Eighty-six axial magnetic resonance images were obtained to analyze the risk of approach-related complications. The access corridor were simulated at different access angles and the potential risk of neurovascular structure injury was evaluated when the access corridor touching or overlapping the corresponding structures at each angle. Furthermore, the safe corridor length was measured when the corridor width was 18 and 22 mm. RESULTS: When access angle was 0°, the potential risk of ipsilateral nerve roots injury was 54.7% at L4-L5. When access angle was 45°, the potential risk of abdominal aorta, contralateral nerve roots or central canal injury at L4-L5 was 79.1%, 74.4%, and 30.2%, respectively. The length of the 18mm-wide access corridor was largest at 0° and it could reach 44.5 mm at L3-L4 and 46.4 mm at L4-L5. While the length of the 22 mm-wide access corridor was 42.3 mm at L3-L4 and 44.1 mm at L4-L5 at 0°. CONCLUSION: Changes in the access angle would not only affect the ipsilateral neurovascular structures, but also might adversely influence the contralateral neural elements. It should be also noted to surgeons that alteration of the access angle changed the corridor length.

Does the Access Angle Change the Risk of Approach-Related Complications in Minimally Invasive Lateral Lumbar Interbody Fusion? An MRI Study

OBJECTIVE: To investigate the potential risk of approach-related complications at different access angles in minimally invasive lateral lumbar interbody fusion. METHODS: Eighty-six axial magnetic resonance images were obtained to analyze the risk of approach-related complications. The access corridor were simulated at different access angles and the potential risk of neurovascular structure injury was evaluated when the access corridor touching or overlapping the corresponding structures at each angle. Furthermore, the safe corridor length was measured when the corridor width was 18 and 22 mm. RESULTS: When access angle was 0°, the potential risk of ipsilateral nerve roots injury was 54.7% at L4–L5. When access angle was 45°, the potential risk of abdominal aorta, contralateral nerve roots or central canal injury at L4–L5 was 79.1%, 74.4%, and 30.2%, respectively. The length of the 18 mm-wide access corridor was largest at 0° and it could reach 44.5 mm at L3–L4 and 46.4 mm at L4–L5. While the length of the 22 mm-wide access corridor was 42.3 mm at L3–L4 and 44.1 mm at L4–L5 at 0°. CONCLUSION: Changes in the access angle would not only affect the ipsilateral neurovascular structures, but also might adversely influence the contralateral neural elements. It should be also noted to surgeons that alteration of the access angle changed the corridor length.

Does the Access Angle Change the Risk of Approach-Related Complications in Minimally Invasive Lateral Lumbar Interbody Fusion? An MRI Study

OBJECTIVE: To investigate the potential risk of approach-related complications at different access angles in minimally invasive lateral lumbar interbody fusion.METHODS: Eighty-six axial magnetic resonance images were obtained to analyze the risk of approach-related complications. The access corridor were simulated at different access angles and the potential risk of neurovascular structure injury was evaluated when the access corridor touching or overlapping the corresponding structures at each angle. Furthermore, the safe corridor length was measured when the corridor width was 18 and 22 mm.RESULTS: When access angle was 0°, the potential risk of ipsilateral nerve roots injury was 54.7% at L4–L5. When access angle was 45°, the potential risk of abdominal aorta, contralateral nerve roots or central canal injury at L4–L5 was 79.1%, 74.4%, and 30.2%, respectively. The length of the 18 mm-wide access corridor was largest at 0° and it could reach 44.5 mm at L3–L4 and 46.4 mm at L4–L5. While the length of the 22 mm-wide access corridor was 42.3 mm at L3–L4 and 44.1 mm at L4–L5 at 0°.CONCLUSION: Changes in the access angle would not only affect the ipsilateral neurovascular structures, but also might adversely influence the contralateral neural elements. It should be also noted to surgeons that alteration of the access angle changed the corridor length.

Biomechanical comparison of multilevel lateral interbody fusion with and without supplementary instrumentation: a three-dimensional finite element study.

BACKGROUND: Lateral lumbar interbody fusion (LLIF) is a popular, minimally invasive technique that is used to address challenging multilevel degenerative spinal diseases. It remains controversial whether supplemental instrumentation should be added for multilevel LLIF. In this study, we compared the kinematic stability afforded by stand-alone lateral cages with those supplemented by bilateral pedicle screws and rods (PSR), unilateral PSR, or lateral plate (LP) fixation using a finite-element (FE) model of a multi-level LLIF construct with simulated osteoporosis. Additionally, to evaluate the prospect of cage subsidence, the stress change characteristics were surveyed at cage-endplate interfaces. METHODS: A nonlinear 3-dimensional FE model of the lumbar spine (L2 to sacrum) was used. After validation, four patterns of instrumented 3-level LLIF (L2-L5) were constructed for this analysis: (a) 3 stand-alone lateral cages (SLC), (b) 3 lateral cages with lateral plate and two screws (parallel to endplate) fixated separately (LPC), (c) 3 lateral cages with bilateral pedicle screw and rod fixation (LC + BPSR), and (d) 3 lateral cages with unilateral pedicle and rod fixation (LC + UPSR). The segmental and overall range of motion (ROM) of each implanted condition were investigated and compared with the intact model. The peak von Mises stresses upon each (superior) endplate and the stress distribution were used for analysis. RESULTS: BPSR provided the maximum reduction of ROM among the configurations at every plane of motion (66.7-90.9% of intact spine). UPSR also provided significant segmental ROM reduction (45.0-88.3%). SLC provided a minimal restriction of ROM (10.0-75.1%), and LPC was found to be less stable than both posterior fixation (23.9-86.2%) constructs. The construct with stand-alone lateral cages generated greater endplate stresses than did any of the other multilevel LLIF models. For the L3, L4 and L5 endplates, peak endplate stresses caused by the SLC construct exceeded the BPSR group by 52.7, 63.8, and 54.2% in flexion, 22.3, 40.1, and 31.4% in extension, 170.2, 175.1, and 134.0% in lateral bending, and 90.7, 45.5, and 30.0% in axial rotation, respectively. The stresses tended to be more concentrated at the periphery of the endplates. CONCLUSIONS: SLC and LPC provided inadequate ROM restriction for the multilevel LLIF constructs, whereas lateral cages with BPSR or UPSR fixation provided favorable biomechanical stability. Moreover, SLC generated significantly higher endplate stress compared with supplemental instrumentation, which may have increased the risk of cage subsidence. Further biomechanical and clinical studies are required to validate our FEA findings.

Minimally Invasive Lateral Lumbar Interbody Fusion: Surgical Technique and Review

STUDY DESIGN: Review of the current surgical technique and literature. OBJECTIVES: The aim of this study was to review the surgical technique and the current evidence on minimally invasive lateral lumbar interbody fusion (LLIF). SUMMARY OF LITERATURE REVIEW: Spinal fusion is a useful method in the treatment of various degenerative lumbar diseases. Recently, minimally invasive LLIF has been developed, enabling spine surgeons to perform anterior interbody fusion in a minimally invasive manner. MATERIALS AND METHODS: Review of the surgical technique and the literature. RESULTS: Minimally invasive LLIF may reduce the incidence of complications of anterior lumbar interbody fusion. LLIF may restore disc height more effectively than posterior lumbar interbody fusion and indirectly decompress the neural canal without nerve root or dural retraction or perineural scaring. The current indications for LLIF are almost equivalent to those of anterior and posterior lumbar interbody fusion. Recent studies have reported no differences in the fusion rate or clinical outcomes between LLIF and the conventional anterior or posterior interbody fusion techniques. However, LLIF has nonspecific complications, such as anterior thigh pain and hip flexor weakness. CONCLUSIONS: Minimally invasive LLIF is a promising surgical alternative to the conventional anterior or posterior fusion techniques. LLIF has the advantages of less intraoperative bleeding and soft tissue injury, and a faster return to work. However, postoperative nonspecific complications are problems that need to be addressed.