The Oblique Corridor at L4-L5: A Radiographic-Anatomical Study Into the Feasibility for Lateral Interbody Fusion

Should a Narrow Corridor Be a Contraindication for Performing Oblique Lateral Interbody Fusion Procedure or Not?

STUDY DESIGN

Retrospective study.

OBJECTIVES

We investigated the effect of corridor width on the postoperative outcomes of patients who underwent the OLIF procedure.

METHODS

Patients who underwent OLIF surgery, which included L4-5, between 2015 and 2021 were retrospectively studied. The patients were divided into three groups by the width of the corridor: not more than 10 mm, between 10 and 20 mm, and 20 mm or more. We compared clinical and radiographic outcomes and complications between these groups.

RESULTS

A total of 81 patients were included. There were no significant differences in VAS leg and back pain scores, ODI scores, or complications between each group. The radiographic findings, including cage position, anterior and posterior disc height, segmental Cobb angle, and foraminal height, also showed no significant differences between each group. The only radiographic finding that showed a significant difference between each group was the angle of the cage. We found significantly less degree of angle in the wider than 20 mm group when compared to the other two groups. (P-value = .01). There was no recorded incidence of major vascular complications.

CONCLUSIONS

The width of oblique corridor does not affect clinical outcomes, complications, or radiographic findings, including position of the cage, anterior and posterior disc height, segmental angle, and foraminal height after OLIF procedure, including L4-5 level. Thus, the OLIF procedure can be performed safely even in patients with limited oblique corridors, especially at L4-5.

Antepsoas Approaches to the Lumbar Spine

Lumbar interbody fusion (LIF) is a well-established approach in treating spinal deformity and degenerative conditions of the spine. Since its inception in the 20th century, LIF has continued to evolve, allowing for minimally invasive approaches, high fusion rates, and improving disability scores with favorable complication rates. The anterior to the psoas (ATP) approach utilizes a retroperitoneal pathway medial to the psoas muscle to access the L1-S1intervertebral disc spaces. In contrast to the transpsoas arppoach, its primary advantage is avoiding transgressing the psoas muscle and the contained lumbar plexus, which potentially decreases the risk of injury to the lumbar plexus. Avoiding transgression of the psoas may minimize the risk of transient or permanent neurological deficits secondary to lumbar plexus injury. Indications for ATP approaches may expand as it is shown to be a safe and effective method of achieving spinal arthrodesis.

Psoas Major Swelling Grade Affects the Clinical Outcomes after OLIF: A Retrospective Study of 89 Patients

OBJECTS

Oblique lumbar interbody fusion (OLIF) has gained increasing popularity recently. However, complications resulting from intraoperative retraction of psoas major (PM) sometimes occur. The aim of this study is to evaluate the degree of PM swelling by developing a scoring system called the Psoas Major Swelling Grade (PMSG), and to investigate the correlation between the PMSG and clinical outcomes after OLIF.

METHODS

Patients who underwent L4-5 OLIF at our hospital from May 2019 to May 2021 were reviewed and all data were recorded. The extent of postoperative PM swelling was determined by calculating the percentage of change in the PM area before and after surgery on MRI and divided into three grades subsequently. Swelling within the range of 0% to 25% was defined as grade I, 25%-50% was grade II, and more than 50% was grade III. All patients were grouped into the new grade system and followed up for at least 1 year, during which the visual analog scale (VAS) and Oswestry disability index (ODI) scores were recorded. Categorical data were analyzed using chi-square and Fisher's exact tests, while continuous variables were assessed with one-way ANOVA and paired t-tests.

RESULTS

Eighty-nine consecutive patients were enrolled in this study, with a mean follow-up duration of 16.9 months. The proportion of female patients in the PMSG I, II, and III groups was 57.1%, 58.3%, and 84.1%, respectively (p = 0.024).  Furthermore, the total complication rate was 43.2% in the PMSG III group, significantly higher than 9.5% and 20.8% in the PMSG I and II groups (p = 0.012). The incidence of thigh paraesthesia was also considerably higher in the PMSG III group at 34.1% (p = 0.015), compared to 9.5% and 8.3% in the PMSG I and II groups. Among the patients, 12.4% exhibited a teardrop-shaped PM, with the majority (90.9%) belonging to the PMSG III group (p = 0.012). Additionally, the PMSG III group demonstrated a higher estimated blood loss (p = 0.007) and significantly worse clinical scores at the 1-week follow-up assessment (p < 0.001).

CONCLUSION

PM swelling adversely affects the OLIF prognosis. Female patients with teardrop-shaped PM are more likely to develop swelling after OLIF. A higher PMSG is associated with a higher complication rate of thigh pain or numbness and worse short-term clinical outcomes.

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.

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.

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.

Different Moro Zones of Psoas Major Affect the Clinical Outcomes after Oblique Lumbar Interbody Fusion: A Retrospective Study of 94 Patients

Oblique lumbar interbody fusion (OLIF) has been driven to the maturity stage in recent years. However, postoperative symptoms such as thigh paresthesia resulting from intraoperative retraction of the psoas major (PM) have sometimes occurred. The aim of this study was to assess the different positions and morphology of PM muscles and their relationship with clinical outcomes after OLIF by introducing the Moro zones. Patients who underwent L4-5 OLIF at our institution between April 2019 and June 2021 were reviewed and all data were recorded. All patients were grouped by Moro zones into a Moro A cohort and a Moro I and II cohort based on the front edges of their left PM muscles. A total of 94 patients were recruited, including 57 in the Moro A group and 37 in the Moro I and II group. Postoperative thigh pain or numbness occurred in 12 (21.1%) and 2 (5.4%) patients in the Moro A group and the Moro I and II group, respectively. There was no difference in the psoas major transverse diameter (PMTD) between groups preoperatively, while longer PMTD was revealed postoperatively in the Moro A group. The operating window (OW) and psoas major sagittal diameter (PMSD) showed significant differences within and between groups. Thirteen patients had teardrop-shaped PM muscles, with 92.3% in the Moro A group showing significantly worse clinical scores at 1-week follow-up. The Moro zones of the PM affected the short-term outcomes after OLIF. Preoperative measurements and analysis of OW, PMSD and PM morphology should be performed as necessary to predict short-term outcomes.

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.

Equipoise for Lateral Access Surgery

OBJECTIVE

To investigate the use of lateral access surgery among surgeons from the Asia-Pacific region to determine equipoise for areas of contentious use.

METHODS

A questionnaire was distributed to members of the Asia Pacific Spine Society. Surgeons were asked about their past experiences with lateral access surgery, including their advantages and disadvantages, specific surgical strategies, choices in implant-related factors, order of levels to operate on in multilevel reconstruction surgery, and postoperative complications.

RESULTS

A total of 69 of 102 surgeons (67.6%) had performed lateral access surgery previously. In total, 56 participating surgeons (54.9%) agreed that anterior column reconstruction via lateral access is most of time superior to transforaminal lumbar interbody fusion and other techniques. Surgeons would consider laminectomy instead of indirect decompression in the presence of severe central or lateral recess stenosis, thickened ligamentum flavum, and facet joint hypertrophy. For the order of levels to operate on in multiple level reconstruction for deformity, where 1 stands for L3-L4 or higher, 2 stands for L4-L5, and 3 stands for L5-S1, 2-1-3 (28/95, 29.5%) was most common, followed by 1-2-3 (26/95, 27.4%), and 3-2-1 (21/95, 22.1%).

CONCLUSIONS

Lateral access surgery is seeing greater use in the Asia-Pacific region, especially in upper middle- to high-income countries, whereas keenness of surgeons who practice in lower middle- to low-income countries can be improved by more training, resources, and reasonable cost. A high percentage of surgeons do not consider indirect decompression for spinal stenosis. There was no consensus on the order of levels in multiple level reconstruction for deformity.

STUDY OF THE DIAMETER OF THE OBLIQUE CORRIDOR IN LATERAL DECUBITUS AND DORSAL DECUBITUS: RADIOLOGICAL STUDY

ABSTRACT Introduction: Degenerative intervertebral disc disease and its impact on quality of life when associated with sagittal misalignmentis a current topic in the literature. The technique known as OLIF derives from the need to use anterior cage stop romote stabilization of the affected segment, indirect decompression, restoration of segmental lordosis, and sagittal balance. Methods: Single-center, non-randomized, comparative, observational study. The following variables were measured using magnetic resonance imaging of the lumbar spine in dorsal and lateral decubitus, establishing a comparison between the size of the OLIF corridor in the L3L4 and L4L5 segments, as well as a comparison of corridor size between the different positions. Results: There was no difference incorridor size in the comparison between decubitus. However, when the L3L4 and L4L5 levels were compared, there was a significant difference in the size of the corridor in both the lateral and dorsal positions. Conclusion: The present study did not show any difference between the size of the OLIF corridor in L3L4 and L4L5 in the different decubitus, suggesting that thee valuation of the corridor in convention al magnetic resonance images appearstobe safe andreflects the actual size when positio ned for performing the OLIF technique. Level of evidence III; Retrospective study.

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.

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.

Reliability of the new modified Moro's classification and oblique corridor grading to assess the feasibility of oblique lumbar interbody fusion

Introduction

The modified Moro's classification (MMC) of psoas morphology and oblique corridor (OC) grading were recently proposed. Their reliability needs to be tested.

Methods

T2 weighted lumbar disc level axial-cut MRI images of patients with degenerative spondylosis were distributed to five spine surgeons. The inter and intra-rater reliability of MMC and OC grading were calculated based on their ratings.

Results

Based on kappa statistics, we inferred that both MMC and OC grading are reliable measures.

Conclusion

Both MMC and OC grading, in combination, can be used to predict the feasibility of oblique lumbar interbody fusion and aid in patient selection.

Factors Influencing Early Disc Height Loss Following Lateral Lumbar Interbody Fusion

Study Design

Retrospective radiological analysis.

Purpose

To analyze the factors influencing early disc height loss following lateral lumbar interbody fusion (LLIF).

Overview of Literature

Postoperative disc height loss can occur naturally as a result of mechanical loading. This phenomenon is enabled by the yielding of the polyaxial screw heads and settling of the cage to the endplates. When coupled with cage subsidence, there can be significant reduction in the foraminal space which ultimately compromises the indirect decompression achieved by LLIF.

Methods

Seventy-two cage levels in 37 patients aged 62±10.2 years who underwent single or multilevel LLIF for degenerative spinal conditions were selected. Their preoperative and postoperative follow-up radiographs were used to measure the anterior disc height (ADH), posterior disc height (PDH), mean disc height (MDH), disc space angle (DSA), and segmental angle. Correlations between the loss of disc height and several factors, including age, construct length, preoperative lordosis, postoperative lordosis, disc height, cage dimensions, and cage position, were analyzed.

Results

We found that the lateral interbody cages significantly increased ADH, PDH, MDH, and DSA after surgery (p <0.0001). However, there was a loss of disc height over time. All postoperative disc height parameters, especially the amount of increase in MDH (r =0.413, p <0.0001) after surgery, showed a significant positive association with early disc height loss. The levels demonstrating a significant (≥25%) height loss were those that exhibited a substantial height increase (128.3%, 4.6±3.0 to 10.5±5.6 mm) postoperatively. However, the levels that showed less than 25% height loss were those that exhibited, on average, only a 57.4% height increase post-operatively.

Conclusions

The greater the postoperative increase in disc height, the greater the disc height loss throughout early follow-up. Therefore, achieving an optimal disc height rather than overcorrection is an important surgical strategy to adopt when performing LLIF.