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ORIGINAL ARTICLE
Year : 2023 | Volume
: 14
| Issue : 1 | Page : 71-75
Location variance of the great vessels while undergoing side-bend positioning changes during lateral interbody fusion
Aaron Joiner1, Gilberto Gomez2, Sohrab K Vatsia2, Tyler Ellett3, Douglas Pahl2
1 Jack Hughston Memorial Hospital Orthopedic Surgery Residency Program, Jack Hughston Memorial Hospital, Phenix City, Alabama; Hughston Clinic, Columbus, Georgia, USA
2 Hughston Clinic, Columbus, USA
3 Edward Via College of Osteopathic Medicine – Auburn Campus, Auburn, Alabama, USA
Correspondence Address:
Sohrab K Vatsia
Hughston Clinic, 6262 Veterans Pkwy Columbus, Columbus 31909, Georgia
USA
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/jcvjs.jcvjs_8_23
Abstract
Background: Minimally invasive lateral lumbar interbody fusion (LLIF) is an increasingly popular surgical technique that facilitates minimally invasive exposure, attenuated blood loss, and potentially improved arthrodesis rates. However, there is a paucity of evidence elucidating the risk of vascular injury associated with LLIF, and no previous studies have evaluated the distance from the lumbar intervertebral space (IVS) to the abdominal vascular structures in a side-bend lateral decubitus position. Therefore, the purpose of this study is to evaluate the average distance, and changes in distance, from the lumbar IVS to the major vessels from supine to side-bend right and left lateral decubitus (RLD and LLD) positions simulating operating room positioning utilizing magnetic resonance imaging (MRI).
Methods: We independently evaluated lumbar MRI scans of 10 adult patients in the supine, RLD, and LLD positions, calculating the distance from each lumbar IVS to adjacent major vascular structures.
Results: At the cephalad lumbar levels (L1-L3), the aorta lies in closer proximity to the IVS in the RLD position, in contrast to the inferior vena cava (IVC), which is further from the IVS in the RLD. At the L3-S1 vertebral levels, the right and left common iliac arteries (CIA) are both further from the IVS in the LLD position, with the notable exception of the right CIA, which lies further from the IVS in the RLD at the L5-S1 level. At both the L4-5 and L5-S1 levels, the right common iliac vein (CIV) is further from the IVS in the RLD. In contrast, the left CIV is further from the IVS at the L4-5 and L5-S1 levels.
Conclusion: Our results suggest that RLD positioning may be safer for LLIF as it affords greater distance away from critical venous structures, however, surgical positioning should be assessed at the discretion of the spine surgeon on a patient-specific basis.
Keywords: Interbody fusion, lumbar spine, minimally invasive, operative positioning, vascular injury
Introduction 
First described in 1944 by Briggs and Milligan, lumbar interbody fusion is widely utilized for an array of diverse spinal pathology and has broad application in trauma, spondylolisthesis, degenerative disc disease, and pseudoarthrosis.[1],[2] Interbody fusion is a surgical procedure that involves the removal of the intervertebral disk and implantation of a graft or bone graft substitute within the confines of surgical exposure. The intervertebral space (IVS) can be accessed through a variety of surgical approaches–including posterior lumbar interbody fusion, transforaminal lumbar interbody fusion, anterior lumbar interbody fusion (ALIF), and direct lateral interbody fusion. Over the past decade, minimally invasive anterolateral approaches have replaced this once predominantly posterior technique.
Minimally invasive lateral lumber interbody fusion (LLIF) is becoming increasingly popular for lumbar fusion as it mitigates surgical approach-related morbidity. Specifically, LLIF has demonstrated reductions in blood loss, operative time, soft-tissue damage, infection rates, and associated hospital costs.[3],[4],[5],[6],[7] LLIF is classically performed with the patient in the right lateral decubitus (RLD) position as the cavus vein is more delicate, and the right iliac vein is positioned laterally to the left, allowing the surgeon to approach from the side opposite these concerns. [Figure 1] demonstrates optimal operative positioning for the LLIF surgical approach. A small incision is made on the patient's side, and a narrow passageway is created through the soft tissues and psoas muscle. An annulotomy followed by a discectomy is performed to allow implantation of the surgeon's choice of implant and the graft material. Complications associated with a direct lateral approach include neurological injuries, muscular injuries (which are typically transient), and vascular injuries.[8],[9],[10],[11] Although major vascular complications are relatively rare–occurring in up to 15.9% of cases–these injuries can have deleterious consequences.[12]
Figure 1: LLIF operative positioning. LLIF - Lateral lumbar interbody fusionOur study sought to determine the specific anatomical distance between the center of each lumbar IVS and associated major vascular structures, as well as the changes in distance from the IVS to the great vessels from a supine to a side-bend lateral operative position.
Methods Following Institutional Review Board approval, ten volunteers elected to undergo magnetic resonance imaging (MRI) of their lumbar spines in the supine, right, and left side-bend lateral decubitus positions. Informed consent was obtained from all individuals and the scans were completed from 2019 to 2021. Volunteers were included in this study on the basis of age 18–65 years, acceptable body habitus to accommodate our MRI scanner, willingness to undergo supine and side-bend lateral MRI with a thoracic surgical “bump,” and no history of scoliosis. Exclusion criteria included any prior history of surgery as well as any overall contraindications for MRI. During lateral imaging, a standard thoracic bump was placed to accentuate the operative position for an LLIF procedure. Upon completion of imaging, the resultant MRI findings were independently evaluated by two musculoskeletal fellowship-trained radiologists. The nearest distance from the center of each lumbar IVS to the adjacent major vascular structure for each supine, right, and left lateral decubitus (LLD) position was calculated. The collective measurements were subsequently recorded, and comparisons were drawn between the scans of all 10 volunteers, calculating the average distance to major vascular structures and the change in this distance, moving from supine to right (RLD) and left (LLD) side-bend lateral positioning.
Results Of the 10 volunteers, 50% were male (5 patients) and 50% were female (5 patients), with a mean age of 28.8 (range: 21–34). Our results are summarized in [Table 1], [Table 2], [Table 3], [Table 4], according to the great vessels appreciated at each intervertebral level.
Aorta
The aorta was consistently furthest from the IVS in the LLD at the L1-2, L2-3, and L3-4 levels compared to RLD and supine positioning. It was found in the closest proximity to the L3-4 IVS, at 20.6 mm in the RLD position, and in the furthest proximity from the L1-L2 IVS in the LLD position, at 22.3 mm. The change in the distance at the L1-2 level was found to be significant when shifting from supine to RLD as well as LLD. At the L1-2 level, the aorta was found to translate 0.66 mm further (P < 0.001) from the IVS when patient positioning changed from supine to RLD, and 1.20 mm away (P < 0.001) from the IVS in consideration of the shift from supine to LLD.
Inferior vena cava
The IVC was consistently in closer proximity at all lumbar IVS in the LLD when compared to the RLD, lying in closest proximity at the L4-5 IVS in the LLD position. At the L4-5 space, the IVC was found to be 20.7 mm away from the center of the IVS space. When evaluating the change in distance going from supine to RLD and LLD, significant changes were appreciated in the change in position from supine to RLD at the L1-2 and L2-3 levels, with changes in distance 2.90 mm (P < 0.001) and 1.30 mm (P < 0.001), respectively. Regarding supine to LLD positioning, significant changes were found at the L2-3 and L4-5 IVS. At the L2-3 level, the IVC moved 0.72 mm further (P < 0.001) away from the IVS, and at the L4-5 level, the IVC moved 1.80 mm (P < 0.001) in closer proximity to the IVS when changing from supine to LLD position.
Right common iliac artery
The right common iliac arteries (CIA) were found to be closest to the IVS in the RLD position at the L4-5 level and were found furthest from the IVS at the L5-S1 level in the supine position. At the L5-S1 level, the right CIA moved 2.00 mm closer (P < 0.001) to the IVS. Significant changes were also appreciated in shifting from the supine to LLD position at the L3-4 and L5-S1 levels, with the right CIA moving 2.5 mm further away (P < 0.001) and 3.80 mm closer (P < 0.001) to the IVS, respectively.
Left common iliac artery
The left CIA was closest to the L3-4 IVS at 21.0 mm in the RLD position. Significant changes were found at L4-5 and L5-S1 levels when changing from the supine to the RLD position. Specifically, the Left CIA moved closer to the L4-5 IVS by 1.02 mm (P < 0.001) and 1.71 mm (P < 0.001) at the L5-S1 level, when changing from the supine to RLD position.
Right common iliac vein
The right common iliac vein (CIV) was in closest proximity to the L4-5 IVS in the LLD position at a distance of 23.3 mm. A statistically significant change was elucidated at the L5-S1 level when changing position from supine to RLD, with the Right CIV moving 1.16 mm further (P < 0.001) from the IVS.
Left common iliac vein
The left CIV was in the closest proximity to the RLD position at the L4-5 IVS space at 21.1 mm. The left CIV was also determined to be closer to the IVS at both the L4-5 and L5-S1 levels in the RLD compared to the LLD. Statistically significant changes were appreciated in changes from supine to RLD at both the L4-5 and L5-S1 levels with the Left CIV moving 0.70 mm closer (P < 0.001) to the IVS and 0.64 mm away (P < 0.001) from the IVS, respectively. Regarding supine to LLD position changes, at the L5-S1 level, the left CIV moved 1.12 mm away (P < 0.001) from the IVS.
Right internal iliac artery
The right IIA was closest to the IVS in the supine position at the L5-S1 level. When comparing the RLD and LLD positions, the IVS was in closer proximity to the LLD position at 32.3 mm at the L5-S1 level. Changes from supine to both RLD and LLD were found to be significant, with the movement of 3.59 mm away (P < 0.001) from the IVS and 3.40 mm away (P < 0.001) from the IVS, respectively.
Left internal iliac artery
The left IIA was furthest in the LLD position at the L5-S1 level and was equidistant in the RLD and supine positions. A statistically significant difference was appreciated at the L5-S1 level when positioning was shifted from supine to LLD with a change in distance of 1.94 mm away (P < 0.001) from the IVS.
Discussion To the best of our knowledge, this is the first study evaluating the change in major vascular structures when adjusting from a supine to right or LLD position simulating operative side-bend positioning during lateral lumbar interbody fusion procedures. This study provides context for anatomic “safe zones,” and expected changes in major vascular structures when re-positioning from the preoperative supine position to a side-bend lateral position in the operating room.
When evaluating whether the RLD or LLD is a safer approach for LLIF procedures, our results suggest that an RLD position may in fact be safer for patients. Specifically, at the proximal lumbar levels (L1-L3), our results demonstrate that the aorta is closer to the IVS in the RLD position, which lies in contrast to the IVC. Evaluating the lower lumbar levels (L3-S1), the Right and Left CIA are both further from the IVS in the LLD compared to RLD, with the only exception occurring at the L5-S1 level, where the Right CIA is further from the IVS in the RLD. At both the L4-5 and L5-S1 levels, the Right CIV is further from the IVS in the RLD. This contrasts with the Left CIV, which is further from the IVS of the L4-5 and L5-S1 levels. Anatomically, the arterial vessels are more durable to potential retraction compared to venous structures. With this notion in mind, it can be a discriminator against the use of RLD versus LLD – our results support the fact that RLD, or “left side up,” positioning offers safer surgical access during LLIF as the IVC and right CIV are furthest away from the IVS in this position.
A previous study by Choi et al. assessed the risk of vascular injury during lateral ALIF at the L5/S1 anterior disc space–with results demonstrating that, in the RLD position, the accessibility of the surgical bare window validates the RLD as a practical approach for ALIF.[13] In addition, in a related study by Deukmedjian et al., positional changes of the major intraabdominal vessels were examined in lumbar interbody fusion, although side-bend positioning was not evaluated. Their group measured distance changes from supine to lateral decubitus positioning without the use of an operative “bump,” concluding that, at the proximal lumbar level (L1-L3), the aorta and IVC move away from the surgical corridor when the patient is placed in the lateral position, allowing for surgeon preference at these levels. Moreover, in contrast to our findings, their results at the lower lumbar levels demonstrate that an LLD, or “right side up” position may be preferable.[14]
Our study has several limitations. Primarily, we acknowledge the small sample size of 10 volunteers within our study. In addition, within this cohort, the mean age of volunteers was 28.8 years, which is considerably lower than the age of the average patient undergoing an LLIF. A younger patient cohort may also differ from an older one with respect to mobility, as younger patients may be easier to position, thus increasing access to optimal side-bend lateral positioning. Moreover, there is also a presumption of less cardiovascular disease in younger patients. The presence of significant cardiovascular disease in the typically older LLIF surgical population could inhibit arteriovascular movement/collapsibility during position changes.
Conclusion This study provides spine surgeons with an expected amount of movement in major vascular structures when adjusting from a supine to side-bend lateral position in the operating room. Our results also suggest that an RLD position may be generally safer for LLIF as it allows for a greater distance away from the venous structures, but surgical positioning should be assessed by the surgeon on a patient-specific basis.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
References 
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