Does right lateral decubitus position change retroperitoneal oblique corridor? A radiographic evaluation from L1 to L5

A cadaveric study showing the OLIF corridor dimensions after retraction of the abdominal great arteries and psoas major

The aim of this study is to assess the oblique lateral interbody fusion (OLIF) corridor dimensions when the abdominal great arteries (the abdominal aorta or common iliac arteries) and psoas major are retracted. Twenty embalmed cadaveric specimens were dissected. The widths of the OLIF operative corridor at L1-2, L2-3, L3-4, and L4-5 were measured with the psoas major and abdominal great arteries in static state, with psoas retraction, and with mild retraction of the abdominal great arteries. The retractable distances of the psoas major and the abdominal great arteries at each lumbar segment were compared. In the static state, the operative corridor gradually narrowed from L1-2 to L4-5, but there was no significant difference in its width between segments (p > 0.05). There was no significant difference in the corridor width between segments after retraction of the psoas major or the abdominal great arteries (p > 0.05). However, retraction of either the psoas major or the abdominal great arteries made the corridor at the L1-5 segments significantly wider than those in the static state (p < 0.05), particularly at L4-5, and the retractable distance of the psoas major was significantly greater (p < 0.05). The cadaveric model demonstrated the use of abdominal great arteries retraction in principle. The OLIF operative corridor could be widened to some extent by retracting the abdominal great arteries, and widened further by retracting the psoas major.

Anterior Column Realignment Using an Anterior-To-Psoas Approach: A Radiographic-Anatomic Feasibility Study at L1-L5

STUDY DESIGN

Cross-sectional radioanatomic study.

OBJECTIVE

To determine the feasibility of performing an anterior column realignment (ACR) using an anterior-to-psoas (ATP) approach at L1-L5.

METHODS

Axial magnetic resonance images (MRI) of the L1-L5 disc levels obtained at a single institution were obtained and analyzed. The feasibility of performing an ACR was assessed using a combination of the size of the left oblique corridor (OC), the psoas morphology using the modified Moro classification, and the anterior disc edge to great vessel distance.

RESULTS

Three hundred MRI studies obtained from 300 patients were included. All patients had a measurable left OC at the L1-L4 levels. Twenty patients (6.7%) had no measurable OC at the L4-L5 level. According to the modified Moro's classification, a high-rising psoas was seen in 4 patients (1.3%) at the L3-L4 level and 57 patients (19.0%) at the L4-L5 level. An ALL release was considered high risk due to no measurable space between the anterior disc edge and the great vessels in 54 patients (18.0%) at the L1-L2 level, 39 patients (13.0%) at the L2-L3 level, 119 patients (39.7%) at the L3-L4 level, and 226 patients (75.3%) at the L4-L5 level.

CONCLUSION

ACR using an ATP approach is the most radioanatomically feasible at L2-L3. The L4-L5 level has the highest risk with regards to both the ATP approach and the ALL release for an ACR due to high rates of unmeasurable left OC and space between the anterior disc edge and the great vessels.

Oblique lateral interbody fusion at L5-S1: feasibility, surgical approach window, incision line, and influencing factors

PURPOSE

The primary aim of this study was to describe the feasibility, surgical approach window (SAW), and incision line (IL) for oblique lateral interbody fusion at L5-S1 (OLIF51) using computed tomography (CT). A secondary aim was to identify associations among approach characteristics and demographic and anthropometric factors.

METHODS

We performed a radiographic study of 50 male and 50 female subjects who received abdominal CT imaging. SAW was measured as the distance from the midline to the medial border of the iliac vessel. IL was measured at the skin surface corresponding to the distance between the center of the disc space and SAW lateral margin. OLIF51 feasibility was defined as the existence of at least a 1-cm SAW without retraction of soft tissues.

RESULTS

For the left side, the OLIF51 SAW and IL were 12.1 ± 4.6 and 175.1 ± 55.3 mm. For the right side, these measures were 10.0 ± 4.3 and 185.0 ± 52.5 mm. Correlations of r = 0.648 (p < 0.001) and r = 0.656 (p < 0.001) were observed between weight and IL on the left and right sides, respectively. OLIF51 was not feasible 23% of the time.

CONCLUSION

To our knowledge, this is the largest CT study to determine the feasibility of performing an OLIF51. Without the use of retraction, OLIF51 is not feasible 23% of the time. Left-sided OLIF51 allows for a larger surgical approach window and smaller incision compared to the right side. Larger incisions are required for adequate surgical exposure in patients with higher weight.

Imaging study of the effect of postural changes on the retroperitoneal oblique corridor in degenerative lumbar scoliosis

PURPOSE

To investigate the effect of postural changes on access for the OLIF of L2 to L5 in patients with degenerative lumbar scoliosis.

METHODS

Twenty-one individuals with degenerative lumbar scoliosis were chosen at random, 11 with left-sided convexity and 10 with left-sided concavity. Axial T2-weighted images were used to measure the following variables: (1) the distance between the left psoas major muscle and the abdominal aorta; (2) the angle of the surgical access; (3) the distance between the psoas major muscle attachment point and the vertebral body's transverse axis; (4) the region of the psoas major muscle above the vertebrae; and (5) the width-to-thickness ratio. A statistical analysis of the measured parameters was done.

RESULTS

The L2-5 segment in the supine position had a significantly longer window distance in the left convex and left concave groups than in the right lateral recumbent posture (P < 0.05). In all segments, the left concave group outperformed the left convex group, which was substantially higher in the right lateral recumbent posture than in the supine position (P < 0.05). After the position change, the spanning area was significantly higher compared to the same segment in the supine position. The psoas major muscle's morphology was stretched.

CONCLUSIONS

The right lateral recumbent position limits access to OLIF for degenerative lumbar scoliosis, and the "safety window" for OLIF operation in the parietal region is smaller in the left convex group compared to the left concave group, posing a higher risk of intraoperative vascular and neurological injury.

The anatomical feasibility of anterior intra- and extra-bifurcation approaches to L5-S1: an anatomic study based on lumbar MRI

BACKGROUND CONTEXT

The anterior approach at L5-S1 has many advantages, however, vascular complications are challenging for spinal surgeons who may not be familiar with the variability of vascular anatomy. There are three different anterior approaches (intra-bifurcation approach and extra-bifurcation: left-, and right-sided prepsoas approaches) described in previous studies to respond to the variability of anterior vascular anatomy for reduction in vascular injury, while no guidance for the choice of approach preoperatively.

PURPOSE

To analyze the anatomical feasibility of three anterior approaches to access the L5-S1 disc space according to a practical framework.

STUDY DESIGN

Retrospective study.

PATIENT SAMPLE

Lumbar magnetic resonance imaging (MRI) from patients who visited our outpatient clinic were reviewed, with 150 cases meeting the inclusion criteria.

OUTCOME MEASURES

The following radiographic parameters were measured on axial T2-weighted MRI at the lower endplate of L5 and the upper endplate of S1: width of the vascular corridor, position of the left and right common iliac vein (CIV), and presence of perivascular adipose tissue (PAT). Moreover, we designed a safe line to evaluate the feasibility of left- and right-sided prepsoas approaches. Cases of lumbosacral transitional vertebrae were identified.

METHODS

The feasibility of the intra-bifurcation approach was determined by the width of the vascular corridor, presence of PAT, and the position of the CIV. The feasibility of the prepsoas approach was determined by the relative position of the CIV to the safe line, presence of PAT, and the intersection point of the CIV and vertebral body.

RESULTS

Sixty-eight percent, 64.7%, and 75.3% cases allowed the intra-bifurcation, left-, and right-sided prepsoas approach to L5-S1, respectively. The cases in this study had at least one of three anterior approaches to access L5-S1 disc space, and 74% of cases had more than one anatomical feasibility of anterior approach. The right-sided prepsoas approach was feasible in the majority of cases because of the vertical course of the right CIV with a significantly higher proportion of presence of PAT. Patients with lumbosacral transitional vertebrae (24 cases) may prefer the prepsoas approaches, and only six cases (25.0%) were determined to be feasible for the intra-bifurcation approach.

CONCLUSIONS

Our study proposes a practical framework to determine whether the three different anterior approaches are feasible access at L5-S1. According to the framework, all cases had the anatomical feasibility of using an anterior approach to access L5-S1, and three-fourths of cases had a replaceable anterior approach when encountering intraoperative difficulties.

Risk factors for postoperative sympathetic chain dysfunction following oblique lateral lumbar interbody fusion: a multivariate analysis

PURPOSE

Postoperative sympathetic chain dysfunction (PSCD) was a relatively common complication after anterior lumbar interbody fusion due to the manipulation adjacent to the lumbar sympathetic chain (LSC). This study aimed to investigate the incidence of PSCD and identify its related independent risk factors after oblique lateral lumbar interbody fusion (OLIF) surgery.

METHODS

PSCD was defined as either of the following in the affected lower limb compared to the contralateral: (1) increase in skin temperature by 1 ºC or more, (2) reduced skin perspiration, (3) limb swelling or skin discoloration. Consecutive patients who underwent OLIF at L4/5 level from February 2018 and May 2022 at a single institution were retrospectively reviewed and divided into two groups: patients with PSCD and patients without PSCD. Binary logistic regression analyses were performed on patients' demographic, comorbidities, radiological datum and perioperative factors to identify independent risk factors for PSCD.

RESULTS

Twelve (5.7%) of 210 patients experienced PSCD following OLIF surgery. Multivariate logistic regression analysis identified the identification of lumbar dextroscoliosis (OR = 7.907, P = 0.012) and the presence of "tear-drop" psoas (OR = 7.216, P = 0.011) as independent risk factors for the PSCD following OLIF.

CONCLUSION

This study identified the lumbar dextroscoliosis and the "tear-drop" psoas as independent risk factors for the development of PSCD after OLIF. Spine alignment examination and the morphological identification of psoas major muscle should be highly noticed for the PSCD prevention following OLIF.

CT-based analysis of oblique lateral interbody fusion from L1 to L5: location of incision, feasibility of safe corridor approach, and influencing factors

PURPOSE

The primary aim was to measure the safe corridor (SC), surgical incision anterior margin (AM), and posterior margin (PM) for OLIF bilaterally from L1 to L5. The secondary aim was to determine the feasibility of approach via the SC. The tertiary aim was to analyze the influence of demographic and anthropometric factors on OLIF parameters.

METHODS

We performed a radiographic analysis of 100 subjects who received an abdominal CT. Measurements of the AM, PM, and SC were obtained as well as patient age, sex, height, weight, and BMI. The intraclass correlation coefficient was used to evaluate interrater reliability. To assess associations among variables, Pearson's correlation tests and multivariate linear regression models were constructed. Sex differences were analyzed using Student's t tests.

RESULTS

At L1-2, L2-3, L3-4, and L4-5, the PM was 6.6, 8.2, 9.4, and 10.2 cm on the left side and 7.2, 7.7, 8.8, and 9.5 cm on the right side in relation to the disk space center. The SC was less than 1 cm 1%, 3%,3%, and 18% of the time on the left side, and 15%, 12%,29%, and 60% on the right side. None of the anthropometric factors demonstrated a strong correlation with incision location. SC was larger on the left side. Interrater ICC was .934.

CONCLUSIONS

This study is the first to provide guidelines on the appropriate location of the incision line during OLIF based on SC from L1 to L5. SC measurements do not vary by sex. OLIF is more feasible via a left-sided approach.

A comparative morphometric analysis of operative windows for performing OLIF among normal and deformity group in lower lumbar spine

PURPOSE

To assess the radiological morphometric parameters of OLIF surgical technique in lower lumbar spine among normal and in patients with adult degenerative spine (levoscoliosis and dextroscoliosis).

METHOD

Standing AP radiographs and MRI in supine position were taken. Patients were divided into 3 groups based on Cobbs' angle into normal, levo and dextro scoliosis. Moros classification was used to calculate bare window (BW), vascular window (VW), Psoas window (PW), psoas major height (pmh) and width (pmw) at lower lumbar levels and measurements were done on PACS.

RESULTS

Seventy five patients (25 in each group) were assessed. BW has trend from L2-L3 > L3-L4 > L4-L5 in dextro and levoscoliosis. PW has trend from L3-L4 > L2-L3 > L4-L5 in levoscoliosis and normal group. VW has trend from L4-L5 > L3-L4 > L2-L3 in dextro and levoscoliosis; pmw has trend from L4-L5 > L3-L4 > L2-L3 in Levo and dextroscoliosis; pmh has trend from L4-L5 > L3-L4 > L2-L3 in levoscoliosis and normal group.

CONCLUSION

BW was noted to be highest at L3-4, lowest at L4-5 in normal group. VW was constant, BW showed a reverse trend with PW across all the levels. Though levoscoliosis group of patients had significantly higher BW, psoas retraction issues are to be kept in mind in view of anatomically taught psoas.

Morphometric Analysis of the Ureter with Respect to Lateral Lumbar Interbody Fusion Using Contrast-Enhanced Computed Tomography

OBJECTIVE

To analyze the anatomical location of the ureter in relation to lateral lumbar interbody fusion and evaluate the potential risk of ureteral injury.

METHODS

One hundred eight patients who performed contrast-enhanced computed tomographic scans were enrolled in this study. The location of the ureter from L2-L3 to L4-L5 was evaluated. The distances between the ureter and psoas muscle, intervertebral disc, and retroperitoneal vessels were also recorded bilaterally.

RESULTS

Over 30% of the ureters were close to the working corridor of extreme lumbar interbody fusion at L2-L3. Most of the ureters were close to working corridor of oblique lumbar interbody fusion, especially at L4-L5. The distance from the ureter to the great vessels on the left side was significantly narrowing from L2-L3 to L4-L5 (28.8±9.5 mm, 22.0±8.0 mm, 15.5±8.4 mm), and it was significantly larger than that on the right side (12.3±6.1 mm, 7.4±5.7 mm, 5.4±4.4 mm).

CONCLUSION

Our findings indicate that the location of the ureter varies widely among individuals. To avoid unexpected damage to the ureter, it is imperative to directly visualize it and verify the ureter is not in the surgical pathway during lateral lumbar interbody fusion.

A modified oblique lumbar interbody fusion: A better way to establish an exposure under direct microscopic vision

Study design

This is a retrospective study.

Objective

To demonstrate a modified oblique lumbar interbody fusion (OILF) technique for L1-L5.

Methods

The modified technique splits anterior portion of psoas belly to access the oblique corridor (OC) anteroinferior to psoas, minimizing psoas manipulation and retraction and avoiding nerve injury while offering excellent microscopic visualization. Psoas weakness and neurovascular complication rates in patients treated with traditional OLIF (T-OLIF) or anteroinferior psoas OLIF (AP-OLIF) were retrospectively reviewed. Clinical outcomes were also reviewed.

Results

A total of 162 cases treated with T-OLIF (n = 73) and AP-OLIF (n = 89) for degenerative lumbar disease were included. The mean operative time and blood loss were less with AP-OLIF (P < 0.01). Approach related complications were 14 (19.1%) with T-OLIF and 4 (4.5%) with AP-OLIF. Postoperative visual analog scale (VAS) and Oswestry Disability Index (ODI) scores improved in both T-OIF and AP-OIF groups (P < 0.01).

Conclusion

The modified OLIF technique (AP-OLIF) is characterized by an easy exposure of the lumbar spine under direct microscopic vision, resulting in less psoas weakness and neurovascular injury.

Characteristics and hotspots of the 50 most cited articles in the field of pre-psoas oblique lumbar interbody fusion

PURPOSE

In the past decade, the field of pre-psoas oblique lumbar interbody fusion (OLIF) has developed rapidly, and with it, the literature on OLIF has grown considerably. This study was designed to analyze the top 50 articles in terms of the number of citations through bibliometric research to demonstrate the research characteristics and hotspots of OLIF.

METHOD

Searching the Web of Science database yielded the 50 most cited publications in the OLIF field as of July 10, 2022. The publications were ranked according to the number of citations. The following sources were evaluated: the year of publications, the number of citations, authors, countries, institutions, journals, research topics, and keyword hotspots.

RESULTS

The most productive period was from 2017 to 2020, with 41 articles. The number of citations varied from 10 to 140, with an average of 35.52, and 1,776 citations were found. World Neurosurgery published the most articles (12), China produced the most articles (16), and the Catholic University of Korea produced the most studies (6). The corresponding author who produced the most articles was J.S. Kim (5), and the first author who produced the most publications was S. Orita (3). The main research topics were anatomical morphology, surgical techniques, indications, outcomes, and complications. The top 10 most cited keywords were "complications," "decompression," "spine," "surgery," "outcomes," "transpsoas approach," "spondylolisthesis," "anterior," "disease," and "injury."

CONCLUSIONS

Certain articles can be distinguished from others using citation analysis as an accurate representation of their impact due to their long-term effectiveness and peer recognition. With these publications, researchers are provided with research priorities and hotspots through influential literature in the field of OLIF.

The Antepsoas (ATP) Surgical Corridor for Lumbar and Lumbosacral Arthrodesis: A Radiographic, Anatomic, and Surgical Investigation

STUDY DESIGN

Retrospective review of prospectively collected data.

OBJECTIVE

To investigate the size of prepsoas surgical corridors, developed between the iliopsoas and prespinal vessels, at all disk levels between L1 and S1 granted by left and right lateral antepsoas (ATP) approaches. Secondary aims include evaluation of presurgery radiographic prepsoas windows between L1 and S1 with respect to the intraoperative findings.

SUMMARY OF BACKGROUND DATA

The ATP technique is an evolving alternative to the transpsoas and direct anterior exposures for lumbar fusion. However, the vascular morphometric data of the ATP approach remain underexplored, especially at L5-S1.

MATERIALS AND METHODS

Patients indicated for ATP lumbar-lumbosacral fusion between September 2018 and February 2020 were enrolled (n=121). Data were collected prospectively, including the following (in mm): intraoperative manual measurements of the premobilization psoas-vessel (pre-PV) window, the final postmobilization psoas-vessel (post-PV) window, and the preoperative radiographic psoas-to-vessel distance at the respective studied disk levels.

RESULTS

A total of 121 patients (75 female, mean age: 55.3 yr, 81.8% right-sided approach) underwent a total of 279 levels of spinal fusion. Irrespective of the ATP access laterality, we noted ample postmobilization psoas-vessel (post-PV differential) corridors: largest at L4-L5 (36-38 mm) followed by L5-S1 (31-35 mm), L3-L4 (32-33 mm), L2-L3 (28-30 mm), and L1-L2 (20-24 mm). Similarly, the relative increases of the psoas-vessel corridors (post-PV and pre-PV differentials, averaged: 31 mm at L5-S1, 32 mm at L4-L5, 26 mm at L3-L4, 25 mm at L2-L3, and 14 mm at L1-L2) were also significant in both lateral approaches. In right flank approaches, the right vascular structures projected more dorsally compared with left-sided vasculature ( P <0.05).

CONCLUSION

The ATP access offers generous bilateral prepsoas surgical windows to L1-S1 intervertebral disks, allowing for a safe anterior column release, decompression, instrumentation, and fusion.

Anterior column reconstruction of the lumbar spine in the lateral decubitus position: anatomical and patient-related considerations for ALIF, anterior-to-psoas, and transpsoas LLIF approaches

PURPOSE

Circumferential (AP) lumbar fusion surgery is an effective treatment for degenerative and deformity conditions of the spine. The lateral decubitus position allows for simultaneous access to the anterior and posterior aspects of the spine, enabling instrumentation of both columns without the need for patient repositioning. This paper seeks to outline the anatomical and patient-related considerations in anterior column reconstruction of the lumbar spine from L1-S1 in the lateral decubitus position.

METHODS

We detail the anatomic considerations of the lateral ALIF, transpsoas, and anterior-to-psoas surgical approaches from surgeon experience and comprehensive literature review.

RESULTS

Single-position AP surgery allows simultaneous access to the anterior and posterior column and may combine ALIF, LLIF, and minimally invasive posterior instrumentation techniques from L1-S1 without patient repositioning. Careful history, physical examination, and imaging review optimize safety and efficacy of lateral ALIF or LLIF surgery. An excellent understanding of patient spinal and abdominal anatomy is necessary. Each approach has relative advantages and disadvantages according to the disc level, skeletal, vascular, and psoas anatomy.

CONCLUSIONS

A development of a framework to analyze these factors will result in improved patient outcomes and a reduction in complications for lateral ALIF, transpsoas, and anterior-to-psoas surgeries.

COMPARISON OF PSOAS MORPHOLOGY AND LUMBAR LORDOSIS IN DIFFERENT POSTURES

ABSTRACT Objective: To compare the interobserver reliability of measurements of psoas morphology and lumbar lordosis in different positions and to standardize the performance of magnetic resonance imaging in the prone and lateral positions. Methods: This is a cross-sectional study carried out with asymptomatic volunteers of both sexes, aged over 18 years, with no known pathological changes in the lumbar region. Magnetic resonance imaging of the lumbar spine was performed in the supine, right lateral decubitus and prone positions, obtaining images in T2-weighted sequences in the sagittal and axial planes. The distances were measured from the psoas to the vertebral plateau and from the psoas to the lumbar plexus. The exams were assessed by two independent, blinded orthopedists. Results: There was excellent agreement between the measurements of vertebral size (ICC=0.92), low agreement for plexus distance (ICC=0.63) and high agreement for the anterior margin (ICC=0.84). Conclusion: There was good reproducibility of 2 of the 3 measures proposed, suggesting that the technique in the lateral and prone positions is capable of generating quality images. Level of Evidence 3B; Prospective.

Does surgical body position influence the risk for neurovascular injury in total hip arthroplasty? A magnetic resonance imaging study

BACKGROUND

Neurovascular injury is a critical complication in total hip arthroplasty (THA). However, neurovascular geographic variations around the hip joint in different body positions have not been examined. This study investigated the differences in hip neurovascular geography in the supine and lateral positions using magnetic resonance imaging (MRI).

HYPOTHESIS

The neurovascular geography of the hip is influenced by differences in surgical body position.

PATIENTS AND METHODS

This was a single-center prospective study of 15 healthy volunteers enrolled between January 2018 and March 2019. Each subject's bilateral hips were scanned with a 3-T MRI scanner in both the supine and lateral positions. In T1-weighted axial images at the level of the hip center, the anterior and posterior acetabular edges were defined as reference points at which retractors are commonly placed during surgery. We measured the distance between the anterior acetabular edge and the femoral nerve (dFN), femoral artery (dFA), and femoral vein (dFV), as well as that between the posterior acetabular edge and the sciatic nerve (dSN). The primary outcome measures were the distances in both the supine and lateral positions.

RESULTS

dFN, dFA, and dFV in the supine and lateral positions (mm, mean±standard deviation) were 25.8±5.6 and 32.4±6.4 (p<0.0001), 25.7±4.5 and 32.2±5.0 (p<0.0001), and 26.5±4.8 and 32.3±5.1 (p<0.0001), respectively. Most of these elements moved anteromedially in the lateral position compared to the supine position. There was no significant difference in dSN between the supine and lateral positions (23.7±4.9 and 24.5±6.5 (p=0.46).

DISCUSSION

THA in the supine position may be accompanied by a higher risk of femoral neurovascular injury than that in the lateral position. The application of our findings could reduce the risk of femoral neurovascular injury during THA.

LEVEL OF EVIDENCE

III; prospective diagnostic case control study.

Surgical safe zones for oblique lumbar interbody fusion of L1-5: A cadaveric study

To evaluate the operating range and morphology of the surgical safe zone for oblique lumbar interbody fusion (OLIF). Twenty embalmed full-torso cadaveric specimens were dissected. The oblique corridor and the distance between adjacent lumbar arteries were measured in a static state and with psoas major retraction. The morphology and size of the safe zone for OLIF and the location of the lumbar sympathetic trunk were also recorded. The oblique corridor of the L1-L5 segments was significantly greater in the retracted state than in the static state (p < 0.05). With psoas major retraction, the distances between adjacent lumbar arteries at L1-4 were significantly greater (p < 0.05) than those in the static state. The lumbar sympathetic trunk is just located in the safe zone and travels downward adjacent to the psoas major. The shape of the safe zone for OLIF was approximately an oblique upward parallelogram at L1/2 and L2/3, an isosceles trapezoid at L3/4, and an irregular quadrangle or triangle at L4/5. The safe zone for OLIF at L1/2, L2/3, and L3/4 was significantly larger during retraction than in the static state (p < 0.05). On the lateral side of the lumbar spine there is a natural surgical safe zone for OLIF, which can provide a sufficient operating space. The safe zone has a certain morphological pattern in L1-5 segments and psoas major retraction can significantly enlarge it.

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.

MRI-Based Morphometric Study Regarding Operative Windows of Oblique Lumbar Interbody Fusion in Indian Population

BACKGROUND

The novel Oblique lumbar interbody fusion [OLIF] technique has been proposed as a solution to approach related complications of anterior lumbar interbody fusion [ALIF] and lateral lumbar interbody fusion [LLIF]. There exists no study concerning morphological evaluation of retroperitoneal oblique corridor for the Oblique lumbar interbody fusion (OLIF) technique in the Indian population. The aim of our study was (a) to measure magnetic resonance imaging (MRI) based anatomic parameters concerning OLIF operative windows from L2-L3 to L4-L5 level (b) to determine the feasibility of this technique following MRI-based morphometric evaluation in the Indian population.

MATERIAL AND METHODS

We did retrospective MRI analysis of 307 consecutive patients following our exclusion criteria. Bare window, psoas major window and psoas major width were measured from axial T2 MRI image taken at mid disc level from L2-L3 to L4-L5 levels.

RESULTS

The mean bare window size was largest at L2-L3 (1.39 cm) level followed by L3-L4 and L4-L5 level (1.28 and 0.62 cm respectively), and differences between them were statistically significant (P < 0.001). Females had statistically significant larger bare windows at L2-L3 and L3-L4 level than males (P < 0.001). With increasing age, there was a significant increase in bare window size at each level (P < 0.001). The mean psoas major window (PM^O) and mean psoas major width (PM^I) were largest at L4-L5 level (PM^O = 1.27 cm, PM^I = 3.61 cm) followed by L3-L4 and L2-L3 level (L3-L4: PM^O = 1.19 cm, PM^I = 2.36 cm; L2-L3: PM^O = 0.88 cm, PM^I = 1.39 cm), and differences among each level concerning both parameters were statistically significant (P < 0.001). Both parameters (PM^O, PM^I) were significantly larger in males than females at each level (P < 0.001).

CONCLUSION

The OLIF technique is well suited for lumbar interbody fusion at L2 -L3 and L3-L4 level in the Indian population irrespective of age and sex. At L4-L5 level, overall 17.9 percent of the study population were unsuitable for this technique due to inaccessible bare window. In our opinion, this level may be better suited for OLIF approach in the elderly Indian population, especially for surgeons who are beginning to attempt this technique in their surgical practice. Preoperative MRI evaluation for the OLIF is important to assess its feasibility, as there exists significant age and gender differences in the Indian population for anatomic parameters concerning OLIF operative windows from L2-L3 to L4-L5 levels.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s43465-021-00393-7.

Neutral hip position for the oblique lumbar interbody fusion (OLIF) approach increases the retroperitoneal oblique corridor

BACKGROUND

The prepsoas lateral approach for spinal fusion, oblique lateral lumbar interbody fusion (OLIF), is considered one of the minimally invasive spinal fusion methods and is gaining popularity due to improved outcomes with copious supporting evidence. To date, no publication has studied the various positions of the left hip in actual patients which might affect the retroperitoneal oblique corridor (ROC). The study aimed to find the relevancy of the left hip position and the size of ROC.

METHODS

We recruited 40 consecutive patients who needed diagnostic MRI from the out-patient clinic. MRI scan from L2 to L5 was performed in the supine, right lateral decubitus with hip flexion, and right lateral decubitus with hip in a neutral position. The retroperitoneal oblique corridor (ROC) was measured at the intervertebral disc level and compared.

RESULTS

ROC of the hip in neutral position was significantly larger than hip flexion in all levels (p < 0.05); there was no significant difference in the ROC among levels (p = 0.22). ROC seems to be largest at L2/3 followed by L3/4 and L4/5 respectively in all positions.

CONCLUSIONS

The retroperitoneal oblique corridors of L2 to L5 were significantly increased when the hip is in the neutral position, while the psoas cross-sectional area and anterior thickness were minimized in this position. Surgeons might benefit from a neutral position of the left hip in the oblique lateral lumbar interbody fusion (OLIF) procedure. In conclusion, the retroperitoneal oblique corridors of L2 to L5 were significantly increased when the hip is in the neutral position, while the psoas cross-sectional area and anterior thickness were minimized in this position. Surgeons might benefit from a neutral position of the left hip in the oblique lateral lumbar interbody fusion procedure.

Correlation study of radiographic characteristics and operative difficulty in lateral-anterior lumbar interbody fusion (LaLIF) at the L4-5 level: a novel classification for case selection

PURPOSE

To analyze correlations between the realistic surgical difficulty of LaLIF and anatomic characteristics in radiographic images, in order to develop a simple classification to provide guiding information for case selection and evaluate the potential risks of the technique.

METHODS

Ninety-six consecutive cases who underwent LaLIF surgeries at the L4-5 level with MR T2-weighted images were analyzed. A novel classification based on the anatomic relationships among the disk, great vessels, and psoas muscle was used for grouping. Clinical outcomes and realistic surgical difficulty parameters were recorded, and comparisons were made among different types of classifications.

RESULTS

Of the 96 analyzed cases, the time of surgical exposure was significantly longer for type C than for type B, and both of these were longer than that of type A. The VAS and ODI were significantly improved at a 1-year follow-up. There was no statistically significant difference among the three types. Type C had the highest incidence of complications, while Type A had the lowest. Analyses of another 304 MRI cases obtained in outpatient clinics showed that the distribution of the three types among these cases was consistent with that of the surgical cohort.

CONCLUSION

Our novel and simple classification provides useful information for case selection. Type A provided the best indication and is most appropriate for a beginner in this technique. Type C includes the most challenging situations, which may have a high incidence of complications and require sophisticated surgical skills to achieve satisfactory outcomes and avoid approach-related complications.

Assessment of Great Vessels for Anterior Access of L5/S1 Using Patient Positioning

STUDY DESIGN

This was a prospective cross-sectional study.

PURPOSE

The aim was to describe the effect of patient positioning, from supine to lateral decubitus position, on the width of the L5/S1 anterior disk space defined by the great vessels.

OVERVIEW OF LITERATURE

The application of the lateral decubitus position interbody fusion has been rapidly increasing; however, there are concerns regarding the access to the lumbosacral region due to the great vessels, which necessitates further morphometric data.

METHODS

A total of 20 consecutive live patients awaiting lumbar surgery were subjected to two magnetic resonance imaging scans on the same day in both supine and lateral decubitus positions at a single center to investigate the anterior L5/S1 disk space.

RESULTS

The bare anterior L5/S1 disk window was present in all patients of this study population, and the mean width was 27 mm in the supine and 22 mm in the lateral decubitus position, with a mean reduction of 5.2 mm between the positions. The oblique corridor angle was measured at a mean of 33°.

CONCLUSIONS

The bare window of L5/S1 disk space was present within this population group, and it was found to be mobile and changed significantly with patient positioning. Therefore, the spine surgeon or the access surgeon must consider the increased potential vascular risk during disk access in lateral decubitus anterior lumbar interbody spinal fusion surgery.

Changes in the Operative Corridor in Oblique Lumbar Interbody Fusion Between Preoperative Magnetic Resonance Imaging and Intraoperative Cone-Beam Computed Tomography Using Morphometric Analysis

Background

The oblique lumbar interbody fusion or anterior-to-psoas (OLIF/ATP) technique relies on a corridor anterior to the psoas and posterior to the vasculature for lumbar interbody fusion. This is evaluated preoperatively with CT and/or MRI. To date, there have been no studies examining how intraoperative, lateral decubitus positioning may change the dimensions of this corridor when compared to preoperative imaging.

Objective

Our objective was to evaluate changes in the intraoperative corridor in the supine and lateral positions utilizing preoperative and intraoperative imaging.

Methods

We performed a retrospective analysis among patients who have undergone an OLIF/ATP approach at two tertiary care centers from 2016 to 2018 by measuring the distance between the left lateral border of the aorta or iliac vessels and anteromedial border of the psoas muscle from L1-L2 through L4-5 disc spaces. We compared this corridor between supine, preoperative MRI axial and intraoperative CT acquired in the right lateral decubitus position.

Results

Thirty-three patients, 15 of whom were female, were included in our study. The average age of the patients was 65.4 years and the average BMI was 31 kg/m². The results revealed a statistically significant increase (p<.05) in the intraoperative corridor from supine to lateral decubitus positioning at all levels. However, age, BMI, and gender had no statistically significant impact on the preoperative versus intraoperative corridor.

Conclusion

This is the first study to provide objective evidence that lateral decubitus positioning increases the intraoperative corridor for OLIF/ATP. Our study demonstrates that lateral decubitus positioning provides a more favorable corridor for the OLIF/ATP technique from L1-L5 disc levels.

The OLIF working corridor based on magnetic resonance imaging: a retrospective research

OBJECTIVE

To provide an anatomical basis for the development of oblique lumbar interbody fusion (OLIF) in Chinese patients.

METHODS

Between November 2018 and June 2019, 300 patients' lumbar MRI data were reviewed. According to the Moro system and zone method described by us, the axial view was vertically divided into 6 zones (A, I II, III, IV, P) and was horizontally divided into 4 zones (R, a, b, c, L). The locations of left psoas muscle and the major artery at L2/3, L3/4, and L4/5 levels were evaluated by the grid system. The aortic bifurcation segments will also be evaluated at the level of the vertebral body or the disc.

RESULTS

At the L2/3 level, left psoas muscle and the major artery in zone Ib were found in 28.0% of subjects, in zone IIb in 20.3%, and in zone Ic in 20.0%; at the L3/4 level, in zone Ab in 20.7% of subjects, in zone Ac in 26.0%, and in zone Ic in 11.0%; and at the L4/5 level, areas in zone Ab in 31.0% of subjects, in zone Ac in 26.0%, and in zone Ib in 11.7%. The aortic bifurcation segments were mainly at the L4 level. The zone of the left psoas muscle at all levels, the zone of the major artery at L4/5 level, and the zone of the aortic bifurcation segments had significant correlation with gender difference (P < 0.05).

CONCLUSION

The left-sided OLIF at L2-L5 disc levels can be a feasible type of surgery for lumbar interbody fusion in the majority of Chinese patients. Before the operation, in order to screen out the appropriate surgical approach, routine lumbar magnetic resonance imaging is recommended to analyze the patient's local anatomical features.

Magnetic Resonance Imaging Study of Oblique Corridor and Trajectory to L1-L5 Intervertebral Disks in Lateral Position

OBJECTIVE

This study investigated the retroperitoneal oblique corridor and trajectory of L1-L5 as the lateral surgical access to the intervertebral disks in the Chinese population and detected the potential relationship between the corridor or trajectory and vertebral parameters, including disk axis, psoas muscle, and retroperitoneal vessel.

METHODS

Seventy magnetic resonance imaging studies performed from January 2017 to January 2019 were investigated. The oblique corridor was defined as the distance between the left lateral border of the retroperitoneal vessel and the anterior border of psoas. The trajectory was defined as the distance between the retroperitoneal vessel and lumbar plexus.

RESULTS

The oblique corridor analysis to L1-L5 disks have the following mean distances: L1-2 13.36 mm, L2-3 13.36 mm, L3-4 12.37 mm, and L4-5 10.36 mm. There was no difference in the L1-L5 corridor between genders. And the position of retroperitoneal vessel was negatively correlated with the corridor width. The trajectory measurements to L1-L5 disks have the following mean distances: L1-2 27.44 mm, L2-3 30.86 mm, L3-4 30.73 mm, and L4-5 24.36 mm. Moreover, the vertebral parameters, including the disk axis and psoas muscle, were positively correlated with the trajectory width. Otherwise, the position of retroperitoneal vessel was negatively correlated with the trajectory width.

CONCLUSIONS

Compared with previous studies, the safe surgical area of the Chinese is generally smaller than that of Caucasian. The position of the retroperitoneal vessel is the vital potential to limit the corridor and trajectory. Preoperative assessment of vertebral parameters, especially vascular structure, is essential for planning surgical process.

The Anatomic Characteristics of the Retroperitoneal Oblique Corridor to the L1-S1 Intervertebral Disc Spaces

STUDY DESIGN

This is a cross-sectional study.

OBJECTIVE

To investigate the oblique corridor to the L1-S1 intervertebral disc space between the psoas muscle and the great vessels in cadaveric specimens bilaterally and the location of genitofemoral nerve and the diaphragmatic crura relative to the oblique corridor.

SUMMARY OF BACKGROUND DATA

Although use of oblique lumbar interbody fusion is rapidly expanding, the morphometric data related to the procedure are limited.

METHODS

Twelve fresh-frozen full-torso cadaveric specimens were dissected to examine the oblique corridor to access the L1-S1 space in a static state and with mild retraction of the psoas. The level at which the genitofemoral nerve pierces from the psoas major and the diaphragmatic crura originate from the lumbar vertebral body was also investigated.

RESULTS

The mean width of oblique corridor in the static state and with mild psoas retraction, respectively, were as follows: on the right side: (L1-2) 13.33 and 16.75 mm; (L2-3) 15.42 and 21.42 mm; (L3-4) 16.58 and 22.67 mm; (L4-5) 12.75 and 21.17 mm; (L5-S1) 5.92 and 12.00 mm; on the left side: (L1-2) 16.75 and 19.67 mm; (L2-3) 18.50 and 25.33 mm; (L3-4) 20.58 and 28.00 mm; (L4-5) 18.17 and 26.08 mm; and (L5-S1) 5.83 and 12.00 mm. The level at which the genitofemoral nerve pierces from the psoas major was between L2 and L4. The diaphragmatic crura originates from L1 to L3.

CONCLUSION

The oblique corridor allows access to the L1-L5 discs from both sides, but it is larger on the left side. The corridor between the iliac vessels and the psoas for L5-S1 is difficult to be applied clinically. Mild psoas retraction can moderately enlarge the oblique corridor. The genitofemoral nerve and diaphragmatic crura may be encountered in this approach and should be carefully observed.

LEVEL OF EVIDENCE

5.

Relation of lumbar sympathetic chain to the open corridor of retroperitoneal oblique approach to lumbar spine: an MRI study

BACKGROUND

Retroperitoneal oblique approach to lumbar spine used surgical corridor between psoas muscle and aorta for exposure to anterior part of lumbar spine. Lumbar sympathetic chain (LSC) runs in the corridor to make it a structure at risk of injury.

RESEARCH QUESTION

Does LSC relationship with surgical corridor for minimally invasive retroperitoneal anterolateral oblique approach change in different intervertebral disc level?

METHODS

Left LSC was identified in axial magnetic resonance imaging images at L2-3, L3-4 and L4-5 intervertebral disc levels of 144 patients. Distances between LSC and left psoas muscle and aorta were recorded.

RESULTS

Mean age of the patients was 62.3 years. LSC was identifiable in 90.9% of levels. Distance between LSC and psoas muscle at L2-3, L3-4 and L4-5 was 4.0 mm, 4.7 mm and 5.2 mm. Statistical difference was found between L2-3 and L4-5 level (p = 0.006). Distance between LSC and aorta at each level was 12.4 mm, 12.3 mm and 10.6 mm without statistical difference. In non-scoliosis group distance between LSC and psoas muscle at each level was 3.1 mm, 3.3 mm and 4.0 mm. Statistical difference was found between L2-3 and L4-5 level (p = 0.012) and between L3-4 and L4-5 level (p = 0.041). Distance between LSC and aorta at each level was 11.9 mm, 11.4 mm and 10.2 mm. Statistical difference was found between L2-3 and L4-5 disc level (p = 0.039).

CONCLUSION

LSC moves away from psoas muscle and becomes closer to aorta in L4-5 disc level. These slides can be retrieved under Electronic Supplementary Material.

Radiographic Study of Lumbar Sympathetic Trunk in Oblique Lateral Interbody Fusion Surgery

BACKGROUND

Oblique lateral interbody fusion (OLIF) surgery provides a convenient and minimal access to the lesion disc with few complications; however, the left lumbar sympathetic trunk (LST) lies in the surgical field with a certain incidence of injury. The aim of this study was to describe the anatomic structures of the left LST at risk for injury during OLIF at different lumbar segment levels based on radiologic evaluations.

METHODS

Forty-four healthy young people (22 men and 22 women) were recruited, and routine lumbar magnetic resonance radiograph was performed. The LST, abdominal aorta (AA), and psoas muscle (PM) were observed, and all parameters were acquired using axial T2-weighted turbo spin echo sequence images. Independent-samples t test, 1-way analysis of variance test, and Least significant difference test were used to explore the LST's tract and the anatomic relationship with the adjacent anatomic landmarks at different levels.

RESULTS

The distance from the left lateral border of the AA to the anterior medial border of the left PM was significantly narrowing from the L2-3 to L4-5 segment levels (13.72 ± 3.00, 11.78 ± 2.69, and 9.18 ± 3.43 mm). The distance from the left lateral border of the AA to the left LST was also significantly decreased from the L2-3 to L4-5 segment levels (11.14 ± 2.89, 9.36 ± 2.79, and 6.63 ± 2.94 mm). However, the distance from the leading edge of the left PM to the left LST had no statistical differences among all adjacent segment levels (2.96 ± 0.62, 2.83 ± 0.62, and 3.07 ± 0.86 mm). The location of the left LST is more backward and lateral at level L2-3, whereas it is inside front at levels L3-4 and L4-5.

CONCLUSIONS

The practical risk of LST injury in different segment levels varied with specific anatomic conditions. The segment level L2-3 could provide a safer surgical space for OLIF, and the risk of the left LST injury might be greater during OLIF at level L4-5.

Morphometric MRI Imaging Study of the Corridor for the Oblique Lumbar Interbody Fusion Technique at L1-L5

BACKGROUND

Anterior lumbar interbody fusion and lateral lumbar interbody fusion are associated with approach-related disadvantages. Oblique lumbar interbody fusion (OLIF) is the proposed solution, especially for upper lumbar levels. We analyzed the size and regional anatomy of the corridor used in the OLIF technique between levels L1 and L5.

METHODS

This is a morphometric study of 200 randomly selected magnetic resonance imaging (MRI) studies with features of lumbar degenerative disease. On MRI, the oblique corridor was defined as the smallest distance between the psoas major muscle and aorta or inferior vena cava (or common iliac artery) and measured at the L1/L2, L2/L3, L3/L4, and L4/L5 disc levels on both the left and right on the axial images at the mid-disc level.

RESULTS

Mean distances of the oblique corridor on the left side were L1/L2 = 18.90 mm, L2/L3 = 15.50 mm; L3/L4 = 12.75 mm, and L4/L5 = 8.92 mm; on the right side, they were L1/L2 = 14.80 mm, L2/L3 = 5.50 mm, L3/L4 = 3.00 mm, and L4/L5 = 1.46 mm. For both sides, the corridor size was not significantly affected by sex, and it increased with age and decreased at the inferior lumbar disc levels. The L1/L2 and L2/L3 levels may be obstructed by the ipsilateral kidney and renal vasculature on both sides and the liver on the right side.

CONCLUSIONS

A left-sided OLIF approach is viable for both sexes. Oblique access to the L1/L2 and L2/L3 disc levels is feasible regardless of age, whereas the L3/L4 and L4/L5 levels may be more suitable in older patients, especially for male patients. The right-sided approach is less likely to be performed effectively.

Preoperative evaluation of left common iliac vein in oblique lateral interbody fusion at L5-S1

PURPOSE

Oblique lateral interbody fusion (OLIF) L5-S1 is essentially to perform an anterior lumbar interbody fusion (ALIF) in the lateral position. Because the surgical procedures are performed "obliquely" over the left common iliac vein (LCIV), ensuring that the vein is protected which is particularly important. We aimed to evaluate the configuration of LCIV and its risk of mobilization during anterior approach at L5-S1 segment.

METHODS

This study involved 65 consecutive patients who underwent anterior lumbar fusion (ALIF, n = 39; OLIF, n = 26) at the L5-S1 segment. Three independent examiners evaluated the configuration of the LCIV at the L5-S1 disc on axial magnetic resonance images of the lumbar spine. The LCIV was categorized into three types according to the difficulty of mobilization: type I (no requirement for mobilization; LCIV runs laterally for more than two-thirds of the length of the left side of the L5-S1 disc), type II (easy mobilization; LCIV obstructs the L5-S1 disc space, but the perivascular adipose tissue is present under the LCIV), and type III (potentially difficult mobilization; no perivascular adipose tissue under the LCIV). The patient records were reviewed for vascular complications.

RESULTS

There were 21 men and 44 women in this study, with a mean age of 63.4 years (range 19-83 years). Type I LCIV configuration was found in 32 (49.2%) patients, type II in 18 (27.7%), and type III in 15 (23.1%). There were 7 (10.8%) patients with LCIV injury (type I, n = 0; type II, n = 2; type III, n = 5) (P = 0.003). Intraobserver reliability for the LCIV classification ranged from substantial to excellent, and interobserver reliability ranged from moderate to excellent.

CONCLUSIONS

Preoperative evaluation for anterior approach to the L5-S1 segment should take account of the LCIV position, as well as the difficulty of its mobilization. The type III LCIV configuration showed a high rate of vascular injury.