Far lateral approaches (XLIF) in adult scoliosis

Enabling Technology with Minimally Invasive Strategies: Robot-Assisted Cortical Bone Trajectory Screw Fixation in Lateral Transpsoas Interbody Fusion

OBJECTIVE

Robot-assisted cortical bone trajectory (CBT) screw placement is safer than the traditional fluoroscopy-assisted approach. This technical note reports a novel technique of robot-assisted CBT screw placement using a subfascial transmuscular approach.

METHODS

This technique involves two stages: first, the positioning of a lumbar interbody cage through a lateral transpsoas approach, and then, the robot-assisted placement of CBT screws. The second step is performed with the patient in prone position with navigation frames (ICT, DRB, and surveillance-marker) registered to the robotic system. A three-dimensional fluoroscopic scan is used to plan the screw trajectory, diameter, and length. The screws are placed with the support of a robotic arm.

RESULTS

The technique allows for accurate and precise placement of CBT screws with minimal soft tissue dissection. Compared to traditional methods, the single-lateral position approach reduces intraoperative time and minimizes postoperative pain and recovery time. The percutaneous transmuscular approach avoids the need for fascial dissection, decreasing the risk of complications such as seroma or hematoma formation.

CONCLUSIONS

To our knowledge, this is the first reported technical note about robot-assisted transmuscular CBT screw placement for posterior fixation in LLIF. The proposed surgical technique aims to combine the advantages of CBT screws and the use of innovative robot-assisted technology.

A Cadaver Study: The Relationship of Vital Organs of the Thoracolumbar Junction During a far Lateral Approach Using a T-12 Corpectomy Model

Study DesignHuman cadaver study.ObjectivesTo provide a qualitative and quantitative evaluation by demonstrating measurements of the proximity of vital structures involved and assessed injuries during a T12-corpectomy and cage implantation via a far lateral approach.Material and MethodsSix fresh-frozen adult cadaveric specimens were dissected according to standardized protocol. A formal left-sided far lateral T12-corpectomy was carried out by trained experienced spine fellows. Upon completion of the procedure, a cage was placed between T11 and L1. We then turned the patient supine and performed a formal celiotomy and sternotomy to allow for an open anterior central inspection of all structures concerned. Vital structures as in vessels, diaphragm, pleural membranes, neural elements, important foramina of the diaphragm (Bochdalek, Morgagni) and the thoracic duct were identified. Any injuries to these structures were recorded and proximity to key relevant structures to this exposure were measured.ResultsWe were able to quantify the actual diaphragm excursions and describe its origins to the spine. There was no actual diaphragm injury in any of the cadavers and there were no injuries to the neurovascular structures. We found expected parietal but no visceral pleural injuries.ConclusionOur cadaver study identified the feasibility of performing a T12-corpectomy through a far lateral approach with no violation of the actual diaphragm and expected limited injuries to the parietal pleura only.

The "20-minute Rule" in Lateral Lumbar Interbody Fusion. Fact or Fiction? A Multi-Center Analysis of 658 Patients

Study DesignRetrospective Cohort Study.ObjectiveLateral lumbar interbody fusion (LLIF) is a treatment option for correcting lumbar degenerative pathologies that uses a retroperitoneal, transpsoas corridor to the disc space. Conventional teaching of the LLIF technique has been to perform the procedure 'as efficiently as possible', with a goal of keeping the total retractor time to less than 20 minutes to prevent injuries. This study aims to examine the sensitivity of the "20-minute" rule for predicting postoperative femoral nerve palsy.MethodsA multicenter, retrospective cohort of patients who underwent an LLIF was established. Retractor time was recorded and compared to postoperative motor exams for its relationship to motor injury.Results658 total patients were included in the study. The most frequently operated level was L4-5 (71.7%). The average retractor time was 17.5 ± 8.0 minutes. The injury rate of the cohort was 1.8% (12/658). There was no difference in average retractor time for non-injured vs injured patients (17.5 ± 8.0 min vs 19.6 ± 11.2 min, P = 0.367). Analysis of the "20-minute" rule for LLIF revealed a sensitivity of 50%, a specificity of 73.8%, and a positive predictive value of 3.4%. There were 174 patients with retractor times >20 minutes and six injuries, yielding a false positive rate of 96.6%.ConclusionPost-operative quadriceps motor palsy after lateral lumbar interbody fusion does not appear to be caused by prolonged retractor time greater than 20 minutes. The authors recommend surgical efficiency without the need to rush through the procedure because the "20-Minute" threshold is approaching. Limiting retractor time to under 20 minutes was a poor predictor of post-operative quadriceps injury.

Indications, complications and outcomes of minimally-invasive lateral lumbar interbody fusion with anterior column realignment vs. standard LLIF using expandable interbody spacers

Background

Anterior column realignment (ACR), using a lateral lumbar or thoracic interbody fusion (LLIF) approach to release the anterior longitudinal ligament (ALL), is a powerful technique to increase segmental lordosis. We here report our experience with the use of expandible LLIF cages for ACR.

Methods

Retrospective, single-center observational cohort study including consecutive patients treated by LLIF using an expandible interbody implant. Patients with ACR were compared to patients without ACR. Our outcomes include adverse events (AEs), radiological (segmental sagittal cobb angle, spinopelvic parameters) and clinical outcomes until 12 months postoperative.

Results

We identified 503 patients, in which we performed LLIF at 732 levels. In 63 patients (12.5%) and 70 levels (9.6%) an expandable cage was used. Of those, in 30 patients (47.6%) and 30 levels, the ALL was released (42.8%). Age (mean 61.4 years), sex (57.1% female), comorbidities and further demographic features were similar, but patients in the ACR group had a higher anesthesiologic risk, were more frequently operated for degenerative deformity and had a more severely dysbalanced spine (all p < 0.05). ACR was most frequently done at L3/4 (36.7%) and L4/5 (23.3%), entailing multilevel fusions in 50% (3-7 levels) and long constructs in 26.7% (>7 levels). Intraoperative AEs occurred in 3.3% (ACR) and 3.0% (no ACR; p = 0.945). In ACR cases, mean segmental lordosis changed from -2.8° (preoperative) to 16.4° (discharge; p < 0.001), 15.0° (3 months; p < 0.001) and 16.9° (12 months; p < 0.001), whereas this change was less in non-ACR cases [4.3° vs. 10.5° (discharge; p < 0.05), 10.9 (3 months; p < 0.05) and 10.4 (12 months; p > 0.05)]. Total lumbar lordosis increased from 27.8° to 45.2° (discharge; p < 0.001), 45.8° (3 months; p < 0.001) and 41.9° (12 months; p < 0.001) in ACR cases and from 37.4° to 46.7° (discharge; p < 0.01), 44.6° (3 months; n.s.) and 44.9° (12 months; n.s.) in non-ACR cases. Rates of AEs and clinical outcomes at 3 and 12 months were similar (all p > 0.05) and no pseudarthrosis at the LLIF level was noted.

Conclusions

ACR using an expandible LLIF interbody implant was safe, promoted solid fusion and restored significantly more segmental lordosis compared to LLIF without ALL release, which was maintained during follow-up.

Lumbar scoliosis and stenosis: What outcomes for which treatment? Analysis of three surgical techniques in 154 patients with minimum two-year follow-up

STUDY DESIGN

Prospective multicentric study.

OBJECTIVE

This study goal was to analyze the clinical and radiographic outcomes of lumbar stenosis and scoliosis (LSS) patients, treated with lumbar decompression (LD), short fusion and decompression (SF) or long fusion with deformity correction (LF).

HYPOTHESIS

Procedures without correction lead to poorer long-term outcomes.

METHODS

Consecutive patients with two-year minimum follow-up, older than 50, with lumbar scoliosis (Cobb angle>15°), and symptomatic lumbar stenosis were included. Age, gender, Lumbar and Radicular Visual Analog Scale, ODI, SF12 and SRS30 were collected. Main and adjacent curves Cobb angles, C7 coronal tilt (C7CT), spinopelvic parameters, and spino-sacral angle (SSA) were measured preoperatively, at one and two years. Patients were sorted into surgery type groups.

RESULTS

In total, 154 patients were included, with respectively 18, 58 and 78 patients in LD, SF and LF groups. Mean age was 69, 85% were women. Clinical scores improved in each group at one year, but only LF group exhibited persistent improvement at 2years. A significant fractional Cobb angle increase was noted in the SF group at 2years (from 12±11° to 18±14°). C7CT significantly increased in the LD group at 2years (from 2.5±1.3° to 5.1±3.5°). LF group presented the highest complication rate (45%, 19% for SF and 0% for LD). The overall revision rate was 14% in SF group and 30% in LF group.

CONCLUSION

LSS is a complex pathology requiring custom-made surgical treatment. LD, SF and LF allow satisfactory clinical outcome, with a better and more sustained clinical improvement for LF despite higher complication and revision rates.

LEVEL OF EVIDENCE

IV.

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

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

The kickstand rod technique for correction of coronal malalignment in patients with adult spinal deformity: a systematic review and pooled analysis of 97 cases

Coronal malalignment (CM) has recently gained focus as a key predictor of functional outcomes in patients with adult spinal deformity (ASD). The kickstand rod technique has been described as a novel technique for CM correction using an accessory rod on the convex side of the deformity. This review aimed to evaluate the surgical technique and outcomes of corrective surgery using this technique. The literature search was conducted on three databases (PubMed, EMBASE, and Scopus). After reviewing the search results, six studies were shortlisted for data extraction and pooled analysis. Weighted means for surgical duration, length of stay, amount of coronal correction, and sagittal parameters were calculated. The studies included in the review were published between 2018 and 2023, with a total sample size of 97 patients. The mean age of the study cohort was 61.1 years, with female preponderance. The mean operative time was 333.6 minutes. The mean correction of CM was 5.1 cm (95% confidence interval [CI], 3.6-6.6), the mean sagittal correction was 5.6 cm (95% CI, 4.1-7.1), and the mean change in lumbar lordosis was 17° (95% CI, 10.4-24.1). Preoperative coronal imbalance and mean correction achieved postoperatively were directly related with age. The reoperation rate was 13.2%. The kickstand rod technique compares favorably with conventional techniques such as asymmetric osteotomies in CM management. This technique provides an additional accessory rod that helps increase construct stiffness. Because of limited data, definitive conclusions cannot be drawn from this review; however, this technique is a valuable tool for a surgeon dealing with ASD.

Early outcomes of oblique lateral interbody fusion with posterior fixation versus posterior interbody fusion with fixation for treating adult degenerative scoliosis

OBJECTIVE

To compare the surgical trauma and outcomes between oblique lateral interbody fusion (OLIF) and posterior fixation and posterior lumbar interbody fusion (PLIF) with fixation for adult degenerative scoliosis (ADS).

METHODS

We included ADS patients who underwent OLIF with fixation or PLIF with fixation treatment from June 2020 to December 2022. The preoperative and postoperative spinal pelvic parameters were measured using X-rays. Clinical symptoms were measured using the Oswestry Disability Index and a visual analog scale. We recorded operation time, intraoperative blood loss, blood transfusion, albumin infusion, surgical fixation segment, surgical osteotomy segment, time, and drainage volume.

RESULTS

Forty patients with ADS were included: 20 with OLIF with posterior fixation and 20 with PLIF matched for age, sex, pelvic incidence, and Cobb angle with the OLIF group. There were no significant differences in age, gender, BMI, preoperative spinal parameters, or preoperative clinical symptoms between the groups (p > 0.05). There were no statistical differences in postoperative spinal parameters or clinical symptoms (p > 0.05). Patients in the OLIF group had less intraoperative blood loss (p < 0.01) and fewer intraoperative blood transfusions (p < 0.001) than the posterior surgery group. The number of fixed segments was fewer (p < 0.01), and there were fewer total osteotomy segments (p < 0.001).

CONCLUSION

OLIF with posterior fixation surgery can achieve the same corrective effect and efficacy as a posterior internal fusion with fixation surgery for treating ADS. OLIF with posterior fixation surgery causes less trauma and reduces the number of fixation segments.

A Comparative Clinical Study of Lateral Lumbar Interbody Fusion between Patients with Multiply Operated Back and Patients with First-Time Surgery

Background and Objectives: Patients with multiply operated back (MOB) may suffer from persistent lower-back pain associated with back muscle damage and epidural fibrosis following repeated back surgery (Failed Back Spinal Syndrome). Lateral lumbar interbody fusion (LLIF) is considered to be favorable for MOB patients. However, little scientific research has been carried out for this issue due to variety of the pathogenesis. The purpose of this study was to compare the clinical results of MOB patients and first-time surgery patients who underwent LLIF for lumbar spinal stenosis with degenerative scoliosis and/or degenerative spondylolisthesis (spinal instability). Materials and Methods: LLIF was performed for lumbar spinal stenosis with spinal instability in 55 consecutive cases of single hospital (30 males, 25 females, average age: 69). Clinical outcomes were compared between the MOB patient group (MOB group) and the first surgical patient group (F group). We evaluated the Japanese Orthopaedic Association (JOA) scores and JOA Back Pain Evaluation Questionnaire (JOABPEQ) before and 2 years after surgery. MOB patients were defined as those who have had one or more lumbar surgery on the same intervertebral or adjacent vertebrae in the past. Results: There were 20 cases (12 males, 8 females, average age: 71) in MOB group, and 35 cases (19 males, 16 females, average age: 68) in the F group. There was no significant difference between the two groups in terms of age, sex, number of intervertebral fixations, modic change in fused intervertebral end plate, score of brief scale for evaluation of psychiatric problem, lumbar lordosis, and sagittal vertical axis before and after surgery. The preoperative JOA scores averaged 12.5 points in the MOB group and averaged 11.6 points in the F group. The postoperative JOA scores averaged 23.9 points in the MOB group and averaged 24.7 points in the F group. The preoperative JOABPEQ averaged 36.3 points in the MOB group and averaged 35.4 points in the F group. The postoperative average JOA score was 75.4 in the MOB group and 70.2 in the F group. Conclusions: Based on the results, there was no significant difference in clinical outcomes of the two groups, and there was no new residual lower-back pain. Thus, we considered that LLIF one option for patients with MOB.

The use of electronic conductivity devices can effectively reduce radiation exposure in vertebral body tethering

INTRODUCTION

Vertebral body tethering (VBT) presents new challenges in respect to radiation exposure, as screws cannot be placed free-hand and the lateral positioning of the patients increases scattered radiation. To reduce radiation exposure, we introduced the use of electronic conductivity device (ECD). These are drilling probes send an audio signal when cortical bone is breached. Thus, anterior, bicortical screws can be placed without multiple fluoroscopic controls. ECD has been used for all VBT procedures at our institution starting April 2020. The aim of this study was to test the safety of ECD and its efficacy in radiation reduction in comparison with the current standard, the fluoroscopic guidance.

MATERIALS AND METHODS

All patients who underwent VBT between August 2019 and December 2020 were retrospectively reviewed and divided into two groups according to whether ECD had been used or not. The radiation exposure per procedure and per screw was compared among the two groups, overall and separately for thoracic, lumbar and bilateral procedures. The rate of misplaced screws was calculated.

RESULTS

Data from 62 patients and 825 screws were obtained (397 with ECD). No screw misplacement was observed. Radiation reduction with ECD reached up to 41%. A significant reduction was observed in the radiation per procedure in bilateral instrumentation (from 9.16 to 5.52 mGy*m²), and in the analysis per screw overall (from 9.16 to 5.52 mGy*m²) and for lumbar curves (from 0.54 to 0.32 mGy*m²).

CONCLUSION

ECD can safely and effectively reduce the radiation exposure for VBT procedures.

En-bloc resection of a chordoma in L3 by a combined open posterior and less invasive retroperitoneal approach: technical description and case report

INTRODUCTION

To fulfill oncological criteria, extensive open anterior and posterior approaches are usually performed in the lumbar spine to obtain an appropriate en-bloc spondylectomy. It is commonly accepted that the price of a tumor-free margin includes such extensive incisions and soft-tissue damage, with consequent relevant blood loss and possible postoperative complications as delayed wound healing. In this article, a case of chordoma in L3 is presented, submitted to an oncologically appropriate en-bloc resection performed by an open posterior approach combined with a mini-retroperitoneal approach. The successful oncologic procedure was combined with a short and uneventful postoperative course.

MATERIALS AND METHODS

The authors present the surgical technique and the possible challenges of minimally invasive anterior oncologic surgery as a contribution to a limited literature.

RESULTS

Up to date, palliative care of single metastases has been the main setting in which anterior, minimally invasive surgery has been performed in the lumbar spine. The authors explained how, in selected cases, this approach can be performed in combination with an open posterior access for an oncologically appropriate treatment of a primary malignant tumor.

CONCLUSION

Anterior, minimally invasive surgery can have a role in selected patients with primary malignant tumors of the lumbar spine. The surgical team should have extensive training both in oncologic and minimally invasive surgery.

Lumbar interbody fusion using oblique (OLIF) and lateral (LLIF) approaches for degenerative spine disorders: a meta-analysis of the comparative studies

STUDY DESIGN

Systematic review and meta-analysis.

OBJECTIVE

Historically, posterior approaches to the lumbar spine have allowed surgeons to manage degenerative conditions affecting the lumbar spine. However, spinal muscles injury, post-surgical vertebral instability, cerebrospinal fluid (CSF) leakage, and failed back surgery syndrome (FBSS) represent severe complications that may occur after these surgeries. Lumbar interbody fusion using anterior (ALIF), oblique (OLIF), or lateral (LLIF) approaches may represent valuable surgical alternatives, in case fusion is indicated on single or multiple levels.

METHODS

The present study is a systematic review, conducted according to the PRISMA statement, of comparative studies on OLIF, and LLIF for degenerative spine disorders, and a meta-analysis of their clinical-radiological outcomes and complications.

RESULTS

After screening 1472 papers on PubMed, Scopus, and Cochrane Library, only 3 papers were included in the present study. 318 patients were included for data meta-analysis, 128 in OLIF group, and 190 in LLIF group. There were no significative differences in terms of surgical (intraoperative blood loss and surgical duration) and clinical (VAS-back, VAS-leg, and ODI scores) outcomes, or fusion rates at last follow-up (> 2 years). Significantly higher rates of abdominal complications, system failure, and vascular injuries were recorded in the OLIF group. Conversely, postoperative neurological symptoms and psoas weakness were significatively more common in LLIF group.

CONCLUSIONS

The meta-analysis suggests that OLIF and LLIF are both effective for lumbar degenerative disorders, although each of them presents specific complications and this should represent a relevant element in the surgical planning.

Multisegment transforaminal lumbar interbody fusion (TLIF) combined with Ponte osteotomy in degenerative lumbar scoliosis (DLS) surgery: a minimum of five years' follow-up

PURPOSE

To evaluate the long-term clinical outcomes of degenerative lumbar scoliosis (DLS) with the administration of multisegment transforaminal lumbar interbody fusion (TLIF) combined with Ponte osteotomy long-level fixation fusion, as well as to identify the factors affecting health-related quality of life (HRQOL).

METHODS

This was a retrospective single-centre study involving comprehensive clinical data. The Oswestry Disability Index (ODI), visual analog scale (VAS) outcomes, and Scoliosis Research Society (SRS-22) questionnaire were recorded to assess HRQOL. A correlation analysis was performed to determine the association between HRQOL and radiographic parameters.

RESULTS

A total of 41 consecutive patients (15 males and 26 females) met the inclusion criteria with a follow-up of 8.62 ± 1.20 years. Factors associated with HRQOL were significantly improved post-operation. Global sagittal parameters, including the sagittal vertebral axis (SVA) and T1 pelvic angle (TPA), and local parameters, including apical vertebral translation (AVT) and apical vertebral rotation (AVR), were significantly improved at the last follow-up. Significantly strong correlations between each clinical and radiographic parameter were demonstrated. Moreover, a multiple linear regression analysis demonstrated that the differences in AVT and AVR were significantly correlated with the difference in lumbar lordosis (LL), which was significantly correlated with the differences in SVA and TPA.

CONCLUSION

The surgical treatment of DLS with multisegment TLIF accompanied by Ponte osteotomy and long-level fixations improved the quality of life of patients with a long-term effect. AVR correction is an important factor for LL restoration that significantly correlates with improvements in the sagittal balance parameters SVA and TPA, which are key factors for guaranteeing good HRQOL.

Usefulness of Lateral Lumbar Interbody Fusion Combined with Indirect Decompression for Degenerative Lumbar Spondylolisthesis: A Systematic Review

Background and Objective: The aim of this review was to analyze the existing literature and investigate the outcomes or complications of lateral lumbar interbody fusion (LLIF) combined with indirect decompression for degenerative lumbar spondylolisthesis (DS). Materials and Methods: A database search algorithm was used to query MEDLINE, COCHRANE, and EMBASE to identify the literature reporting LLIF with indirect decompression for DS between January 2010 and December 2021. Improvements in outcome measures and complication rates were pooled and tested for significance. Results: A total of 412 publications were assessed, and 12 studies satisfied the inclusion criteria after full review. The pooled data available in the included studies showed that 438 patients with lumbar spondylolisthesis (mean age 65.2 years; mean body mass index (BMI) 38.1 kg/m²) underwent LLIF. A total of 546 disc spaces were operated on. The most frequently treated levels were L4–L5 and L3–L4. Clinically, the average improvement was 32.5% in ODI, 46.3 mm in low back pain, and 48.3 mm in leg pain estimated from the studies included. SF-36 PCS improved by 51.5% and MCS improved by 19.5%. For radiological outcomes, a reduction in slippage was seen in 6.3%. Disc height increased by 55%, foraminal height increased by 21.1%, the foraminal area on the approach side increased by 21.9%, and on the opposite side it increased by 26.1%. The cross-sectional spinal canal area increased by 20.6% after surgery. Post-operative complications occurred in 5–40% of patients with thigh symptoms, such as anterior thigh numbness, dysesthesia, discomfort, pain, and sensory deficits. Conclusions: Indirect decompression by LLIF for DS is an effective method for improving pain and dysfunction with less surgical invasion. In addition, it has the effect of significantly improving disc height, foraminal height and area, and segmental lordosis on radiological outcomes compared to the posterior approach.

Classification and citation analysis of the 100 top-cited articles on adult spinal deformity since 2011: A bibliometric analysis

BACKGROUND

Studies of the 100 most-cited articles are reported for many subjects. However, none has analyzed the article characteristics associated with high citation frequency. This study aims to (1) graphically depict characteristics of the 100 top-cited articles addressing adult spinal deformity (ASD), (2) diagram the association between articles according to subject and major topic medical subject headings (MeSHs), and (3) investigate whether major topic MeSH correlates with article citation frequency.

METHODS

The 100 top-cited ASD publications since 2011 were retrieved using a PubMed Central search on May 6, 2020. Using titles and abstracts, eight subject categories were identified: surgery, conservative treatment, normal values in spinopelvic alignment, review, cervical alignment, classification, compensatory mechanism, and spine-hip relationship. Sankey diagrams were used to organize the information. Network analysis was performed according to article subject and major topic MeSHs. Pearson's r was used to determine whether the weighted number of citations correlates with major topic MeSHs and the number of citations.

RESULTS

The average number of citations per article was 34.8 (range, 19-156). The most represented country was USA (n = 51). The most productive and highly cited journal was Spine (Phila Pa 1976) (n = 34; average, 38.2 citations per article). The most frequent subject categories and major topic MeSHs were "surgery" (n = 53) and "scoliosis" (weighted count, 9.8), while articles with the subject "compensatory" had the highest average number of citations (64.7). The most highly cited article, by Dr. F. Schwab in 2012, had 156 citations. Network analysis revealed the relationships between these articles according to major topic MeSHs. The weighted number of citations according to major topic MeSHs correlated significantly with article citation frequency (Pearson's r, 0.57; p < 0.001).

CONCLUSION

Multiple characteristics of the 100 top-cited ASD articles are presented in diagrams to guide evidence-based clinical decision-making in ASD.

The Influence of Baseline Clinical Status and Surgical Strategy on Early Good to Excellent Result in Spinal Lumbar Arthrodesis: A Machine Learning Approach

The study aims to create a preoperative model from baseline demographic and health-related quality of life scores (HRQOL) to predict a good to excellent early clinical outcome using a machine learning (ML) approach. A single spine surgery center retrospective review of prospectively collected data from January 2016 to December 2020 from the institutional registry (SpineREG) was performed. The inclusion criteria were age ≥ 18 years, both sexes, lumbar arthrodesis procedure, a complete follow up assessment (Oswestry Disability Index-ODI, SF-36 and COMI back) and the capability to read and understand the Italian language. A delta of improvement of the ODI higher than 12.7/100 was considered a "good early outcome". A combined target model of ODI (Δ ≥ 12.7/100), SF-36 PCS (Δ ≥ 6/100) and COMI back (Δ ≥ 2.2/10) was considered an "excellent early outcome". The performance of the ML models was evaluated in terms of sensitivity, i.e., True Positive Rate (TPR), specificity, i.e., True Negative Rate (TNR), accuracy and area under the receiver operating characteristic curve (AUC ROC). A total of 1243 patients were included in this study. The model for predicting ODI at 6 months' follow up showed a good balance between sensitivity (74.3%) and specificity (79.4%), while providing a good accuracy (75.8%) with ROC AUC = 0.842. The combined target model showed a sensitivity of 74.2% and specificity of 71.8%, with an accuracy of 72.8%, and an ROC AUC = 0.808. The results of our study suggest that a machine learning approach showed high performance in predicting early good to excellent clinical results.

Lateral lumbar interbody fusion in adult spine deformity - A review of literature

INTRODUCTION

Surgery for adult spine deformity presents a challenging issue for spinal surgeons with high morbidity rates reported in the literature. The minimally invasive lateral approach aims at reducing these complications while maintaining similar outcomes as associated with open spinal surgeries. The aim of this paper is to review the literature on the use of lateral lumbar interbody fusion in the cases of adult spinal deformity.

METHODS

A literature review was done using the healthcare database Advanced Research on NICE and NHS website using Medline. Search terms were "XLIF" or "LLIF" or "DLIF" or "lateral lumbar interbody fusion" or "minimal invasive lateral fusion" and "adult spinal deformity" or "spinal deformity".

RESULTS

A total of 417 studies were considered for the review and 44 studies were shortlisted after going through the selection criteria. The data of 1722 patients and 4057 fusion levels were analysed for this review. The mean age of the patients was 65.18 years with L4/5 being the most common level fused in this review. We found significant improvement in the radiological parameters (lordosis, scoliosis, and disk height) in the pooled data. Transient neurological symptoms and cage subsidence were the two most common complications reported.

CONCLUSION

LLIF is a safe and effective approach in managing adult spinal deformity with low morbidity and acceptable complication rates. It can be used alone for lower grades of deformity and as an adjuvant procedure to decrease the magnitude of open surgeries in high-grade deformities.

Peri-Surgical Inflammatory Profile Associated with Mini-Invasive or Standard Open Lumbar Interbody Fusion Approaches

BACKGROUND

Different surgical approaches are available for lumbar interbody fusion (LIF) to treat disc degeneration. However, a quantification of their invasiveness is lacking, and the definition of minimally invasive surgery (MIS) has not been biochemically detailed. We aimed at characterizing the inflammatory, hematological, and clinical peri-surgical responses to different LIF techniques.

METHODS

68 healthy subjects affected by single-level discopathy (L3 to S1) were addressed to MIS, anterior (ALIF, n = 21) or lateral (LLIF, n = 23), and conventional approaches, transforaminal (TLIF, n = 24), based on the preoperative clinical assessment. Venous blood samples were taken 24 h before the surgery and 24 and 72 h after surgery to assess a wide panel of inflammatory and hematological markers.

RESULTS

martial (serum iron and transferrin) and pro-angiogenic profiles (MMP-2, TWEAK) were improved in ALIF and LLIF compared to TLIF, while the acute phase response (C-reactive protein, sCD163) was enhanced in LLIF.

CONCLUSIONS

MIS procedures (ALIF and LLIF) associated with a reduced incidence of post-operative anemic status, faster recovery, and enhanced pro-angiogenic stimuli compared with TLIF. LLIF associated with an earlier activation of innate immune mechanisms than ALIF and TLIF. The trend of the inflammation markers confirms that the theoretically defined mini-invasive procedures behave as such.

Coronal Plane Gap Increases Postoperative Pseudoarthrosis after Lateral Interbody Fusion for Adult Spinal Deformity

Study Design

This is a retrospective study.

Purpose

This study aims to evaluate the risk factor associated with pseudoarthrosis after placement of lateral interbody fusion (LIF) cages for adult spinal deformity (ASD) treatment.

Overview of Literature

LIF technique is widely used for ASD correction. Furthermore, pseudoarthrosis is a major complication of fusion surgery required for revision surgery.

Methods

This study included 42 patients with ASD (two men and 40 women; 112 segments; mean, 68.5±8.4 years; and mean follow-up, 31.6±17.0 months) who underwent LIF and posterior correction surgery. The concave slot of the LIF cage was filled with an autologous iliac crest bone graft (IBG), and the convex slot with a porous hydroxyapatite/collagen (HAp/Col) composite was soaked with bone marrow aspirate. Endplate injury, the gap between vertebral endplate and cage in the coronal or sagittal plane, and fusion status were evaluated using computed tomography multiplanar reconstruction at 12 months after surgery. Moreover, the associated risk factors for pseudoarthrosis were analyzed.

Results

Fusion at LIF segments were observed in 71.4% segments at 12 months after surgery. Fusion on the concave slot (autologous IBG side), convex slot (porous HAp/Col composite side), and both concave and convex slots were observed in 66.1%, 37.5%, and 36.6% of patients, respectively. Moreover, pseudoarthrosis was observed in 28.6% at 12 months after surgery. Consequently, logistic regression analysis of the fusion at the LIF segment revealed that the gap between the LIF cage and endplate in the coronal plane (p=0.030; odds ratio, 0.183; 95% confidence interval, 0.030–0.183) was significantly associated with pseudoarthrosis at the LIF segments.

Conclusions

ASD surgery fusion rate using LIF cages was 71.4% at 12 months after surgery. The fusion rate was higher on the concave slot filled with autologous IBG than on the convex slot filled with a porous HAp/Col composite. The gap in the coronal plane was a risk factor for pseudoarthrosis at the LIF segment.

Using an Extreme Lateral Interbody Fusion (XLIF) in Revising Failed Transforaminal Lumbar Interbody Fusion (TLIF) With Exchange of Cage

Minimally invasive techniques have gained popularity in spine surgery in recent years. Extreme lateral interbody fusion (XLIF) is one of these techniques. The rapid increase in the use of this approach in either primary or revision surgeries is related to its several advantages including less operative time, less blood loss and reduced length of hospital stay with fast recovery. We report a case of a failed transforaminal lumbar interbody fusion (TLIF) in L4-L5 level, one year after the primary procedure with persistent pain due to failed fusion. Underwent revision, by using XLIF with the removal of old cage and exchange with new large cage. Revision of failed interbody fusion can be achieved through anterior, posterior or lateral approach. The decision to proceed with either method depends on several factors, including previous surgeries, fibrosis and risk of neurovascular injury and surgeon's preference. XLIF approach should be considered in revision surgeries of failed interbody fusion. As it can provide several advantages compared to anterior or posterior approaches, in terms of better fusion rates and lower risk of neurovascular injuries by avoiding the use of the previous passage.

Major complications in extreme lateral interbody fusion access: multicentric study by Italian S.O.L.A.S. group

PURPOSE

The eXtreme Lateral Interbody Fusion (XLIF) approach has gained increasing importance in the last decade. This multicentric retrospective cohort study aims to assess the incidence of major complications in XLIF procedures performed by experienced surgeons and any relationship between the years of experience in XLIF procedures and the surgeon's rate of severe complications.

METHODS

Nine Italian members of the Society of Lateral Access Surgery (SOLAS) have taken part in this study. Each surgeon has declared how many major complications have been observed during his surgical experience and how they were managed. A major complication was defined as an injury that required reoperation, or as a complication, whose sequelae caused functional limitations to the patient after one year postoperatively. Each surgeon was finally asked about his years of experience in spine surgery and XLIF approach. Pearson correlation test was used to evaluate the association between the surgeon's years of experience in XLIF and the rate of major complications; a p-value of last than 0.05 was considered significant.

RESULTS

We observed 14 major complications in 1813 XLIF procedures, performed in 1526 patients. The major complications rate was 0.7722%. Ten complications out of fourteen needed a second surgery. Neither cardiac nor respiratory nor renal complications were observed. No significant correlation was found between the surgeon's years of experience in the XLIF procedure and the number of major complications observed.

CONCLUSION

XLIF revealed a safe and reliable surgical procedure, with a very low rate of major complications, when performed by an expert spine surgeon.

LLIF IN THE CORRECTION OF DEGENERATIVE SCOLIOSIS IN ELDERLY PATIENTS

ABSTRACT Objective The incidence of adult degenerative scoliosis (ADS) among individuals over 50 years old can be as high as 68%. Surgical interventions aimed at correcting the spinal deformity in elderly patients are accompanied by a high risk of complications. The use of lateral lumbar interbody fusion (LLIF) is associated with lower rates of complications when compared with open anterior or posterior fusions. Methods Ninety-three patients with ADS (23 men, 70 women) were operated at the Federal Neurosurgical Center. The average age was 63 (52 to 73 years). Results Back pain, measured according to the Visual Analogue Scale (VAS), decreased from 5.9/6 (4;8) (format – mean/median (1;3 quartile)) to 2.6/3 (1;3) points (p <0.0001). Leg pain according to the VAS decreased from 4.6/4 (3;7) to 1.4/1 (0;2) points (p < 0.0001). Functional adaptation according to the Oswestry Disability Index (ODI) improved from 47.8±17.4 to 38.5±14.5 (p < 0.0273). Pelvic tilt (PT) before the surgery was 23.9±12.2° whereas at 12 months follow-up it was 16.8±5.9° (p < 0.0001). PI-LL mismatch pre surgery was 12.1/13 (9;16)° whereas 12 months later it was 7.9/8 (6;10)° (p = 0.0002). Conclusions Restoration of local sagittal balance in ADS patients by short-segment fixation using LLIF technology leads to a statistically significant improvement in quality of life and increased functional adaptation. A lower incidence of early and late postoperative complications, less intraoperative blood loss and shorter hospital stay makes LLIF, in combination with minimally invasive transpedicular fixation, the method of choice to correct ADS in elderly patients. Level of evidence IV; Case series.

Contraindication of Minimally Invasive Lateral Interbody Fusion for Percutaneous Reduction of Degenerative Spondylolisthesis: A New Radiographic Indicator of Bony Lateral Recess Stenosis Using I Line

Study Design

Retrospective cohort study.

Purpose

This study aimed to evaluate aggravated lateral recess stenosis and clarify the indirect decompression threshold by combined lateral interbody fusion and percutaneous pedicle screw fixation (LIF/PPS).

Overview of Literature

No previous reports have described an effective radiographic indicator for determining the surgical indication for LIF/PPS.

Methods

A retrospective review of 185 consecutive patients, who underwent 1- or 2-level lumbar fusion surgery for degenerative spondylolisthesis (DS). According to their symptomatic improvement, they were placed into either the “recovery” or “no-recovery” group. Preoperative computed tomography (CT) images were evaluated for the position of the superior articular processes at the slipping level, followed by a graded classification (grades 0–3) using the impingement line (I line), a new radiographic indicator. All 432 superior articular facets in 216 slipped levels were classified, and both groups’ characteristics were compared.

Results

There were 171 patients (92.4%) in the recovery group and 14 patients in the no-recovery group (7.6%). All patients in the no-recovery group were diagnosed with symptoms associated with deteriorated bony lateral recess stenosis. All superior articular processes of the lower vertebral body in affected levels reached and exceeded the I line (I line-; grade 2 and 3) on preoperative sagittal CT images. In the recovery group, most superior articular processes did not reach the I line (I line+; grade 0 and 1; p=0.0233).

Conclusions

In DS cases that are classified as grade 2 or greater, the risk of aggravated bony lateral recess stenosis due to corrective surgery is high; therefore, indirect decompression by LIF/PPS is, in principle, contraindicated.

Psoas Hematoma and Late Femoral Nerve Palsy After Extreme Lateral Interbody Fusion and Posterior Spinal Fusion with Instrumentation: A Case Report

Introduction

Psoas hematoma is an uncommon complication following spinal surgeries. It has been reported in both extreme lateral interbody fusion (XLIF) and posterior spinal fusion with instrumentation. Minimally invasive techniques are gaining popularity in recent years due to the appealing advantages of reduced operative time, blood loss, hospital stay, and faster recovery.

Case Presentation

We are presenting a case of a 77-year-old male with chronic low back pain, diagnosed to have multilevel degenerative disc disease with central and foraminal disc protrusion at L2-L3, L3-L4, L4-L5 with secondary spinal stenosis, underwent XLIF at L3-L4, L4-L5 and then 2nd stage with posterior L3-L5 fusion with pedicle screws. On the fourth day post-operatively, the patient had flank pain and dropping hemoglobin with femoral nerve palsy symptoms, a CT scan revealed a large psoas hematoma. Conservative management was decided on; a follow-up CT scan and examination showed complete resolution of the hematoma and femoral nerve recovery.

Discussion

The approach to iliopsoas hematoma post spinal surgeries remains controversial. Iliopsoas hematoma should be suspected in any patients post spinal surgeries even with delayed presentations. The decision to proceed with either surgical intervention or conservative management depends on multiple factors, including patient hemodynamic status, progression of collection and femoral nerve palsy.

Conclusion

The exact cause of iliopsoas hematoma post different spinal surgery approaches remains vague. In our opinion, other causes including pre- and post-operative anticoagulants should be investigated. Rushing to drain iliopsoas hematomas in case of femoral nerve palsy might not be the ideal option. Instead, monitoring patient responses to resuscitation and taking a watch and wait approach for femoral nerve palsy might be the proper approach.

Radiological evaluation of fusion patterns after lateral lumbar interbody fusion: institutional case series

INTRODUCTION

There is no consensus on how to evaluate segmental fusion after lateral lumbar interbody fusion (LLIF). Bone bridges (BB) between two contiguous vertebra are reported as pathognomonic criteria for anterior fusion. However, to the best of our knowledge, there are no radiological investigations on zygapophyseal joints (ZJ) status after LLIF. The aim of this radiological study was to investigate the different fusion patterns after LLIF.

MATERIALS AND METHODS

This is a retrospective single-centre radiological study. Patients who underwent LLIF and posterior percutaneous screw fixation for degenerative spondylolisthesis, on a single lumbar level, were considered for eligibility. Complete radiological data and a minimum follow-up of 1 year were the inclusion criteria. Intervertebral BB were investigated for evaluating anterior fusion and ZJ ankylotic degeneration was evaluated according Pathria et al., as a matter of proof of posterior fusion and segmental immobilization.

RESULTS

Seventy-four patients were finally included in the present study. Twelve months after surgery, intervertebral BB were recognized in 58 segments (78.3%), whereas ZJ Pathria grade was I in 8 (10.8%) patients, II in 15 (20.3%) and III in 51 (68.9%) that were considered posteriorly fused. The overlapping rate between anteriorly and posteriorly fused segments was 72.4% (42 segments), whereas 10 (13.5%) did not achieve any fusion, anterior or posterior, and 6 (8.1%) were posteriorly fused only.

CONCLUSIONS

Our results seem to suggest that anterior fusion is not sufficient to achieve segmental immobilization. Further properly designed investigations are needed to investigate eventual clinical-radiological correlations.

Lateral Lumbar Interbody Fusion: What Is the Evidence of Indirect Neural Decompression? A Systematic Review of the Literature

BACKGROUND

In the past decade, lateral lumbar interbody fusion (LLIF) has gained in popularity. A proposed advantage is the achievement of indirect neural decompression. However, evidence of the effectiveness of LLIF in neural decompression in lumbar degenerative conditions remains unclear.

QUESTIONS/PURPOSES

We sought to extrapolate clinical and radiological results and consequently the potential benefits and limitations of LLIF in indirect neural decompression in degenerative lumbar diseases.

METHODS

We conducted a systematic review of the literature in English using the 2009 Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and checklist. Scores on the Oswestry Disability Index (ODI) and visual analog scale (VAS) for back and leg pain were extracted, as were data on the following radiological measurements: disc height (DH), foraminal height (FH), foraminal area (FA), central canal area (CA).

RESULTS

In the 42 articles included, data on 2445 patients (3779 levels treated) with a mean follow-up of 14.8 ± 5.9 months were analyzed. Mean improvements in VAS back, VAS leg, and ODI scale scores were 4.1 ± 2.5, 3.9 ± 2.2, and 21.9 ± 7.2, respectively. Post-operative DH, FH, FA, and CA measurements increased by 68.6%, 21.9%, 37.7%, and 29.3%, respectively.

CONCLUSION

Clinical results indicate LLIF as an efficient technique in indirect neural decompression. Analysis of radiological data demonstrates the effectiveness of symmetrical foraminal decompression. Data regarding indirect decompression of central canal and lateral recess are inconclusive and contradictory. Bony stenosis appears as an absolute contraindication. The role of facet joint degeneration is unclear. This systematic review provides a reference for surgeons to define the potential and limitations of LLIF in indirect neural elements decompression.

Overview of Minimally Invasive Spine Surgery

Minimally invasive spine surgery (MISS) has continued to evolve over the past few decades, with significant advancements in technology and technical skills. From endonasal cervical approaches to extreme lateral lumbar interbody fusions, MISS has showcased its usefulness across all practice areas of the spine, with unique points of access to avoid pertinent neurovascular structures. Adult spine deformity has also recognized the importance of minimally invasive techniques in its ability to limit complications and to provide adequate sagittal alignment correction and improvements in patients' functional status. Although MISS has continued to make significant progress clinically, consideration must also be given to its economic impact and the learning curve surgeons experience in adding these procedures to their armamentarium. This review examines current innovations in MISS, as well as the economic impact and future directions of the field.

Incidence of scoliosis among junior high school students in Zhongshan city, Guangdong and the possible importance of decreased miR-30e expression

OBJECTIVE

We investigated scoliosis incidence among junior high school students in Zhongshan city, Guangdong, China and the expression of miR-30e among those with scoliosis.

METHODS

A total 41,258 students were included. From July 2015 to December 2017, all students underwent screening including routine observation of the standing and sitting posture, Adam's forward bend test, dorsal tilt angle measurement, and X-ray examination. Age, sex, height, weight, and body mass index (BMI) were recorded. Reverse transcription-quantitative polymerase chain reaction was used to assess miR-30e expression among students with scoliosis and 200 healthy students.

RESULTS

Overall, 743 students were diagnosed with scoliosis, with an incidence rate of 1.80%. A total 646 (86.9%) students were diagnosed with idiopathic scoliosis, 38 (5.1%) with congenital scoliosis, and 59 (7.9%) with other scoliosis types. Compared with healthy students, height was significantly greater whereas weight and BMI were significantly lower among students with scoliosis, and expression of miR-30e was significantly lower. However, no significant difference was found in height, weight, BMI, and mean Cobb angle between high/low miR-30e groups.

CONCLUSION

The incidence rate for scoliosis was 1.80%, Compared with healthy students, those with scoliosis were taller, had lower weight and BMI, and miR-30e expression was significantly downregulated.

Useful and innovative methods for the treatment of postoperative coronal malalignment in adult scoliosis: the "kickstand rod" and "tie rod" procedures

STUDY DESIGN

Surgical technique description and case series.

OBJECTIVE

To describe the use of two techniques for the correction of postoperative coronal imbalance after surgical treatment for adult spine deformity (ASD). Sagittal and coronal spinal malalignments are often present in patients with ASD or in patients who have undergone spine surgery. Surgical correction of coronal imbalance is insufficiently investigated, and the literature provides a limited spectrum of surgical options when compared to sagittal imbalance. Nevertheless, this deformity can compromise the surgical outcome and can increase the risk of hardware failure.

METHODS

The kickstand (KR) and tie rod (TR) techniques utilize an accessory rod, linking the previous instrumentation to an independent iliac screw. After a proper release of the lumbar spine with anterior release or posterior osteotomies, the KR technique pushes with distraction on the concave side, whereas the TR technique pulls with compression on the convex side. Four patients (mean age, 64 years; SD 5.7) affected by severe postoperative coronal imbalance were treated. C7-PL ranges from 39 to 76 mm. The mean preoperative ODI was 70/100 (range from 55 to 82). All patients had previous spinopelvic fixation as a consequence of corrective surgery for adult spine deformity. The patients were surgically treated with the addition of supplementary rods connected to the ilium. The rods were used in the concavity or convexity of the deformity functioning as "kickstand" or "tie" or a combination of both.

RESULTS

The mean surgical correction of C7-PL was 35 mm (range from 20 to 52 mm). In particular, the mean correction for kickstand rod technique was 26 mm and for tie rod technique was 43 mm. All of the patients improved their preoperative disability, and mean ODI was 30/100 (range from 10 to 60) at median 19-month follow-up. All postoperative imaging showed implants were in proper position without hardware failure. All of the patients treated demonstrated an immediate postoperative improvement in terms of coronal displacement of the spine. No complications were observed. At 1-year follow-up, all of the patients remained satisfactory in terms of clinical outcomes.

CONCLUSION

The kickstand and tie rod techniques are effective in the treatment of postoperative coronal malalignment. Further studies are needed to confirm these findings.

LEVEL OF EVIDENCE

V: Case report. These slides can be retrieved under Electronic Supplementary Material.

Scoliosis surgery in adulthood: what challenges for what outcome?

Adolescent idiopathic scoliosis that has progressed over time, de novo scoliosis, and degenerative scoliosis represent different types of adult spinal deformity (ASD). Functional impairment and muscular fatigue are due to sagittal and coronal imbalance of the trunk. Surgical treatment can provide a significant improvement of three-dimensional (3D) thoracolumbar alignment, function, and health-related quality of life (QoL). A patient-specific benefit-risk assessment, including clinical expectations, comorbidities, and the spinal deformity itself, has to be done preoperatively since the risk for mechanical complications is relatively high. Minimal invasive techniques combine posterior percutaneous instrumentation and lateral interbody fusion cages which enables vertebral realignment and indirect foraminal stenosis decompression. This strategy seems appropriate in mild and moderate ASD with a limited number of degenerated segments in the lumbar spine and remaining curve flexibility. Severe ASD needs to be addressed by open surgery, which combines posterior instrumentation, interbody fusion, and osteotomies in stiff deformities. Longer posterior instrumentation of the thoracolumbar spine, the sacrum, and the pelvis carries a risk for mechanical complications such as non-union and proximal junctional kyphosis (PJK). Modern surgical techniques including circumferential lumbosacral fusion and double rods might lower the risk for non-union. Accurate sagittal alignment planning, setting the lumbar sagittal apex according to pelvic incidence, and segmental lordosis distribution, are mandatory for minimizing the risk of PJK.

SURGERY FOR ADULT SPINAL SCOLIOSIS: DO THE BENEFITS OUTWEIGH THE RISKS?

ABSTRACT Around 6% of the elderly population over 65 years of age are affected by adult spinal deformity (ASD). The increasing prevalence of ASD with aging has prompted discussion regarding the use of various techniques for its treatment, such as surgery and conservative treatment. The objective of this study is to investigate whether surgical treatment demonstrates significant benefits as compared to conservative treatment. A literature review was conducted, focusing on the most relevant papers on the topic published in the last five years. Surgical treatment, which costs an average of US$ 99,114 per procedure, enables almost instant improvement of the pain and disability of ASD. The rate of perioperative complications in ASD is approximately 7.5%, and the average improvement in back pain is 6.2 times higher in the surgical approach than in conservative treatment. In addition, the use of modern operative techniques, such as minimally invasive surgery (MIS), reduces the complications and greatly improves patients’ quality of life, compared to open surgery. Therefore, the expected benefits of surgical treatment meets the patient’s expectations by eliminating the pain caused by ASD. Although surgical treatment has a higher cost and a greater risk of complications, the use of minimally invasive techniques give the ASD patient a better quality of life. Level of evidence III; Non-Systematic Review.

Factors Affecting Postoperative Sagittal Alignment after Lateral Lumbar Interbody Fusion in Adult Spinal Deformity: Posterior Osteotomy, Anterior Longitudinal Ligament Rupture, and Endplate Injury

Study Design

Prospective cohort study.

Purpose

To identify factors that affect sagittal alignment correction in lateral lumbar interbody fusion (LIF) surgery for adult spinal deformity (ASD) and to investigate the degree of correction in each condition.

Overview of Literature

LIF is a useful procedure for ASD, but the degree of correction can be affected by posterior osteotomy, intraoperative endplate injury, or anterior longitudinal ligament (ALL) rupture.

Methods

Radiographical data for 30 patients who underwent LIF for ASD were examined prospectively. All underwent two-stage surgery (LIF followed by posterior fixation). Radiographical parameters were measured preoperatively, after LIF, and after posterior fixation; these included the segmental lordotic angle, lumbar lordosis (LL), and other sagittal alignment factors.

Results

LL was corrected from 16.5°±16.7° preoperatively to 33.4°±13.8° after LIF (p <0.001) and then to 52.1°±7.9° following posterior fixation (p <0.001). At levels where Schwab grade 2 osteotomy was performed, the acquired segmental lordotic angles from the preoperative value to after posterior fixation and from after LIF to after posterior fixation were 19.5°±9.2° and 9.9°±3.9°, respectively. On average, 12.4° more was added than in cases without osteotomy. Endplate injury was identified at 21 levels (19.4%) after LIF, with a mean loss of 3.4° in the acquired segmental lordotic angle (5.3°±8.4° and 1.9°±5.9° without and with endplate injury, respectively). ALL rupture was identified at seven levels (6.5%), and on average 19.3° more was added in these cases between the preoperative and postoperative values than in cases without ALL rupture.

Conclusions

LIF provides adequate sagittal alignment restoration for ASD, but the degree of correction is affected by grade 2 osteotomy, intraoperative endplate injury, and ALL rupture.

Comparative Radiographic Outcomes of Lateral and Posterior Lumbar Interbody Fusion in the Treatment of Degenerative Lumbar Kyphosis

STUDY DESIGN

Retrospective case-control study.

PURPOSE

To compare surgical invasiveness and radiological outcomes between posterior lumbar interbody fusion (PLIF) and lateral lumbar interbody fusion (LLIF) for degenerative lumbar kyphosis.

OVERVIEW OF LITERATURE

LLIF is a minimally invasive interbody fusion technique; however, few reports compared the clinical outcomes of conventional PLIF and LLIF for degenerative lumbar kyphosis.

METHODS

Radiographic data for patients who have undergone lumbar interbody fusion (≥3 levels) using PLIF or LLIF for degenerative lumbar kyphosis (lumbar lordosis [LL] <20°) were retrospectively examined. The following radiographic parameters were retrospectively evaluated preoperatively and 2 years postoperatively: segmental lordotic angle, LL, pelvic tilt (PT), pelvic incidence (PI), C7 sagittal vertical axis, and T1 pelvic angle.

RESULTS

Nineteen consecutive cases with PLIF and 27 cases with LLIF were included. There were no significant differences in patients' backgrounds or preoperative radiographic parameters between the PLIF and the LLIF groups. The mean fusion level was 5.5±2.5 levels and 5.8±2.5 levels in the PLIF and LLIF groups, respectively (p=0.69). Although there was no significant difference in surgical times (p=0.58), the estimated blood loss was significantly greater in the PLIF group (p<0.001). Two years postoperatively, comparing the PLIF and LLIF groups, the segmental lordotic angle achieved (7.4°±7.6° and 10.6°±9.4°, respectively; p=0.03), LL (27.8°±13.9° and 39.2°±12.7°, respectively; p=0.006), PI-LL (19.8°±14.8° and 3.1°±17.5°, respectively; p=0.002), and PT (22.6°±7.1° and 14.2°±13.9°, respectively; p=0.02) were significantly better in the LLIF group.

CONCLUSIONS

LLIF provided significantly better sagittal alignment restoration in the context of degenerative lumbar kyphosis, with less blood loss.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Classification of coronal imbalance in adult scoliosis and spine deformity: a treatment-oriented guideline

INTRODUCTION

In adult spinal deformity (ASD), sagittal imbalance and sagittal malalignment have been extensively described in the literature during the past decade, whereas coronal imbalance and coronal malalignment (CM) have been given little attention. CM can cause severe impairment in adult scoliosis and ASD patients, as compensatory mechanisms are limited. The aim of this paper is to develop a comprehensive classification of coronal spinopelvic malalignment and to suggest a treatment algorithm for this condition.

METHODS

This is an expert's opinion consensus based on a retrospective review of CM cases where different patterns of CM were identified, in addition to treatment modifiers. After the identification of the subgroups for each category, surgical planning for each subgroup could be specified.

RESULTS

Two main CM patterns were defined: concave CM (type 1) and convex CM (type 2), and the following modifiers were identified as potentially influencing the choice of surgical strategy: stiffness of the main coronal curve, coronal mobility of the lumbosacral junction and degeneration of the lumbosacral junction. A surgical algorithm was proposed to deal with each situation combining the different patterns and their modifiers.

CONCLUSION

Coronal malalignment is a frequent condition, usually associated to sagittal malalignment, but it is often misunderstood. Its classification should help the spine surgeon to better understand the full spinal alignment of ASD patients. In concave CM, the correction should be obtained at the apex of the main curve. In convex CM, the correction should be obtained at the lumbosacral junction. These slides can be retrieved under Electronic Supplementary Material.

Contribution of Lateral Interbody Fusion in Staged Correction of Adult Degenerative Scoliosis

Objective

Lateral interbody fusion (LIF) is attractive as a less invasive technique to address anterior spinal pathology in the treatment of adult spinal deformity. Its own uses and benefits in treatment of adult degenerative scoliosis are undefined. To investigate the radiographic and clinical outcomes of LIF, and staged LIF and posterior spinal fusion (PSF) for the treatment of adult degenerative scoliosis patients, we analyzed radiographic and clinical outcomes of adult degenerative scoliosis patients who underwent LIF and posterior spinal fusion.

Methods

Forty consecutive adult degenerative scoliosis patients who underwent LIF followed by staged PSF at a single institution were retrospectively reviewed. Long-standing 36” anterior-posterior and lateral radiographs were taken preoperatively, at inter-stage, 3 months, 1 year, and 2 years after surgery were reviewed. Outcomes were assessed through the visual analogue scale (VAS), 36-Item Short Form Health Survey (SF-36), and Oswestry Disability Index (ODI).

Results

Forty patients with a mean age of 66.3 (range, 49–79) met inclusion criteria. A mean of 3.8 levels (range, 2–5) were fused using LIF, while a mean of 9.0 levels (range, 3–16) were fused during the posterior approach. The mean time between stages was 1.4 days (range, 1–6). The mean follow-up was 19.6 months. Lumbar lordosis was significantly restored from 36.4º preoperatively up to 48.9º (71.4% of total correction) after LIF and 53.9º after PSF. Lumbar coronal Cobb was prominently improved from 38.6º preoperatively to 24.1º (55.8% of total correction) after LIF, 12.6º after PSF respectively. The mean pelvic incidence-lumbar lordosis mismatch was markedly improved from 22.2º preoperatively to 8.1º (86.5% of total correction) after LIF, 5.9º after PSF. Correction of coronal imbalance and sagittal vertebral axis did not reach significance. The rate of perioperative complication was 37.5%. Five patients underwent revision surgery due to wound infection. No major perioperative medical complications occurred. At last follow-up, there were significant improvements in VAS, SF-36 Physical Component Summary and ODI scores.

Conclusion

LIF provides significant corrections in the coronal and sagittal plane in the patients with adult degenerative scoliosis. However, LIF combined with staged PSF provides more excellent radiographic and clinical outcomes, with reduced perioperative risk in the treatment of adult degenerative scoliosis.

Robot-assisted multi-level anterior lumbar interbody fusion: an anatomical study

BACKGROUND

Minimally invasive surgical approaches still provide limited exposure. Access to the L2-L5 intervertebral discs during a single procedure is challenging and often requires repositioning of the patient and adopting an alternative approach.

OBJECTIVES

Investigate the windows to the L2-L5 intervertebral discs to assess the dimensions of the interbody implants suitable for the procedure and evaluate the feasibility of multi-level lumbar intervertebral disc surgery in robot-assisted surgery (RAS) METHODS: Sixteen fresh-frozen cadaveric specimens underwent a retroperitoneal approach to access the L2-L5 intervertebral discs. The L2-L3 to L4-L5 windows were defined as the distance between the left lateral border of the aorta (or nearest common iliac vessel) and the medial border of the psoas, measured in a static state and after gentle medial retraction of the vascular structures. Two living porcine specimens and one cadaveric specimen underwent da Vinci robot-assisted transperitoneal approach to expose the L2-L3 to L4-L5 intervertebral discs and perform multi-level discectomy and interbody implant placement.

RESULTS

The L2-L3 to L4-L5 intervertebral disc windows significantly increased from a static to a retracted state (p < 0.05). The mean L2-L3, L3-L4, and L4-L5 windows measured respectively 20.1, 21.6, and 19.6 mm in the static state, and 27.2, 30.9, and 30.3 mm after gentle vascular retraction. The intervertebral windows from L2-L3 to L4-L5 were successfully exposed through an anterior transperitoneal approach with the da Vinci robot on the cadaveric and living porcine specimens, and interbody implants were inserted.

CONCLUSION

RAS appears to be feasible for a mini-invasive multi-level lumbar intervertebral disc surgery. The RAS procedure, longer and more expensive than conventional MIS approaches, should be reserved for elective patients.

Extreme lateral lumbar interbody fusion (XLIF) in the management of degenerative scoliosis: a retrospective case series

Background

Surgical treatment of adult degenerative scoliosis (DS) always remains a challenge and often necessitates complex multilevel surgery via traditional open approaches. However, the severity of the procedure, in association with the fact that many of these patients are at an advanced age with several comorbidities, results in high rate of complications. Therefore, during the last decade, minimally invasive procedures have gained a place in the treatment of this pathology. Our aim is to determine the safety and efficacy of extra lateral lumbar interbody fusion (XLIF) with or without supplemented instrumentation in the treatment of DS.

Methods

In a retrospective case series study, we reviewed the files of patients who underwent XLIF in our Hospital between 2008 and 2017. We recorded the patients' demographic characteristics, clinical parameters such as back-pain [visual analogue scale (VAS)] and back-related disability [Oswestry Disability Index (ODI)], as well as radiological parameters including the Cobb angle. Comparison of the before and after results were performed with the t-test and Chi-square test, where appropriate.

Results

Twelve patients fulfilled the eligibility criteria of our study. All patients were female, with a mean age of 64.5 years (SD =7.8 years) and 28 months (SD =13 months) follow-up. The XLIF decreased the pain intensity by 4.66 cm (SD =1.23 cm), and improved the back-related disability by 26% (SD =8.35%) in the ODI scale at the 6-month follow-up. Similarly, scoliosis improved by an average of 11.5° (SD =7°) and lordosis changed by an average of 13.5° (SD =10.86°). All changes were statistically significant. There were three complications, two patients presented meralgia paresthetica, which resolved spontaneously in 3 months, and in one patient occurred an intraoperative bowel perforation treated with bowel anastomosis.

Conclusions

XLIF is a feasible and efficient alternative in the treatment of DS. It can be the treatment of choice in elderly patients in whom comorbidities increase the perioperative risk of complications.

Patient Care During Minimally Invasive Lateral Spine Surgery: 1.7 www.aornjournal.org/content/cme

Perioperative nurses care for patients undergoing a wide range of surgical procedures. One fast-growing surgical specialty is spine surgery performed using minimally invasive techniques. Patients may be candidates for minimally invasive spine surgery based on their presenting signs and symptoms and medical imaging test results. Open anterior and posterior surgical approaches to spine surgery are how surgeons traditionally have performed these procedures. However, new technology has enabled a minimally invasive lateral approach to the spine. This approach minimizes many of the risks and challenges associated with both the anterior and posterior approaches. Minimally invasive lateral interbody fusion requires the perioperative nurse to have a thorough understanding of the necessary patient positioning, spinal anatomy, and OR suite setup to ensure a safe and successful surgical experience for the patient.

Incidence and impact of implant subsidence after stand-alone lateral lumbar interbody fusion

BACKGROUND

Few data are available on the occurrence after stand-alone lateral lumbar interbody fusion (LLIF) of implant subsidence, whose definition and incidence vary across studies. The primary objective of this work was to determine the incidence of subsidence 1 year postoperatively, using an original measurement method, whose validity was first assessed. The secondary objective was to assess the clinical impact of subsidence.

HYPOTHESIS

Implant subsidence after stand-alone LLIF is a common complication that can adversely affect clinical outcomes.

MATERIAL AND METHODS

Of 69 included patients who underwent stand-alone LLIF, 67 (97%) were re-evaluated at least 1 year later. Furthermore, 63 (91%) patients had two available computed tomography (CT) scans for assessing subsidence, one performed immediately after surgery and the other 1 year later. Reproducibility of the original measurement method was assessed in a preliminary study. Subsidence was defined as at least 4mm loss of fused space height.

RESULTS

The incidence of subsidence was 32% (20 patients). Subsidence was global in 7 (11%) patients and partial in 13 (21%) patients. Mean loss of height was 5.5±1.5mm. Subsidence predominated anteriorly in 50% of cases. The lordotic curvature of the fused segment was altered in 50% of patients, by a mean of 8°±3°. Fusion was achieved in 67/69 (97%) patients. The Oswestry score and visual analogue scale scores for low-back and nerve-root pain were significantly improved after 1 year in the overall population and in the groups with and without subsidence.

DISCUSSION

Reproducibility of our measurement method was found to be excellent. Subsidence was common but without significant clinical effects after 1 year. Nevertheless, subsidence can be associated with pain and can result in loss of lumbar lordosis, which is a potential risk factor for degenerative disease of the adjacent segments. A score for predicting the risk of subsidence will now be developed by our group as a tool for improving patient selection to stand-alone LLIF.

LEVEL OF EVIDENCE

IV, retrospective cohort study.

MINIMALLY INVASIVE EXTREME LATERAL APPROACH IN SPINAL LUMBAR METASTASIS

INTRODUCTION

The extreme lateral approach has been widely used for the treatment of degenerative diseases. The objective of this study is to present a minimally invasive extreme lateral approach for the treatment of metastatic lesions in the lumbar spine without the use of the evoked potential exam (MEP).

METHODS

Two patients with spinal metastases and indication for surgery via the anterior approach were treated in a cancer referral center in Brazil. They were placed in right lateral decubitus, and an oblique incision was made, exposing the psoas muscle. The anterior approach permitted the release of the psoas muscle from vertebral body and disc, without the need for MEP.

CONCLUSIONS

When cancer cure is no longer possible, a minimally invasive extreme lateral approach to treat tumor metastases in the lumbar spine is a viable option, with short hospitalization time and low morbidity. The dislocation of the psoas muscle avoids the use of the transpsoas approach, which requires MEP equipment and a trained physician. Clinical studies are needed to extend these benefits to oncological patients who have treatment options for their primary disease. Level of Evidence IV; Case series.

Anatomical Modifications during the Lateral Transpsoas Approach to the Lumbar Spine. The Impact of Vertebral Rotation

Background

We investigated impact of vertebral axial rotation on neurovascular anatomy in adult spinal deformity (ASD) patients and provided recommendations on the approach based on degree of axial rotation. In order to isolate vertebral rotation (VR) impact from the superimposed degenerative cascade observed in adulthood, adolescent idiopathic scoliosis (AIS) patients were analyzed.

Methods

Magnetic resonance imaging (MRI) scans (L1-S1) from 50 right-convex thoracic (left-convex lumbar) AIS patients were analyzed. At each intervertebral level, VR, lumbar plexus depth (LPD), and vascular structure depth (VSD) were evaluated. Paired t test analyses were used to describe anatomic differences between the concave and convex aspect of our patients' curves. Correlation analysis was used to investigate relationships with soft tissue modifications and VR.

Results

Fifty AIS patients (17M, 33F) with mean thoracic Cobb of 50.6° ± 17.0° and mean lumbar Cobb of 41.9° ± 13.0° were included. Mean VR at each level was L1-2 = -6.6°, L2-3 = -7.7°, L3-4 = -6.5°, L4-5 = -4.7°, L5-S1 = -2.6° (negative value denotes clockwise rotation). We found significant differences (P < .05) between concave-convex (right-left) LPD at each level (L1-2 = 3.7 mm, L2-3 = 5.1 mm, L3-4 = 4.2 mm, L4-5 = 2.2 mm, L5-S1 = 2.2 mm). Vascular structure depth was significantly different at L1-L2 (3.2 mm) and L5-S1 (3 mm). Significant correlation was found between increasing VR and concave-convex LPD difference (r = 0.68, P < .001).

Conclusions

This study demonstrates that displacement of the lumbar plexus is tied to the magnitude of VR in patients with AIS. When approaching the lumbar spine, this displacement widens the safe surgical corridor on the convex side and narrows the corridor on the concave side.

Level of Evidence

IV.

Clinical Relevance

Preoperative review of MRI scans should occur to assess the patient's safe surgical corridor for lateral lumbar interbody fusion (LLIF). Adult spinal deformity surgeons who approach a degenerated spine in patients with progressive AIS in adulthood must carefully plan for patient positioning, neurovascular anatomy, and realignment objectives prior to the day of surgical intervention.

Minimally Invasive Spinal Surgery for Adult Spinal Deformity

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

A Posterior Oblique Approach to the Lumbar Disk Spaces, Vertebral Bodies, and Lumbar Plexus: A Cadaveric Feasibility Study

STUDY DESIGN

A laboratory cadaveric study.

OBJECTIVE

We aimed to demonstrate the feasibility of a posterior oblique approach, sharing the same advantages as the transpsoas technique while minimizing the risk of lumbar plexus or psoas muscle injuries.

SUMMARY OF BACKGROUND DATA

The transpsoas approach for interbody fusion and corpectomy offers advantages over posterior and anterior approaches. However, possible risks include traumatization of the psoas muscle or lumbar plexus.

METHODS

All lumbar disk spaces and vertebral bodies were exposed by a posterior oblique approach from left and right on a human cadaveric specimen. The exposure obtained and a step-by-step documentation of the procedure is outlined in detail.

RESULTS

We were able to achieve wide exposure of all lumbar disk spaces and vertebral bodies above the L5/S1 disk space. Only the psoas muscle was retracted, and the lumbar plexus nerves were easily visualized and gently retracted. Sharp dissection was only required around the tip of the transverse processes.

CONCLUSIONS

A posterior oblique approach seems to be less invasive than the transpsoas approach. Exposure of the anterior column structures above the iliac crest is comparable. The oblique approach offers direct access to the lumbar plexus and the extraforaminal segments of the nerve roots.

Focal disorders of the spine with compensatory deformities: how to define them

PURPOSE

In this paper, the authors propose classifying the epiphenomenon of spinal deformity in two different categories: structural deformity, when the main driver of the observed deformity is a fixed and stiff alteration of the spinal segments, and compensatory deformity, which includes cases where the observed deformity is due to focal abnormalities. This last category comprises, but is not limited to, spinal stenosis, spondylolisthesis, disc herniation, infection or tumor, hip disease or neurological disease (such as Parkinson's disease).

METHOD

Narrative review article.

RESULTS

We analyzed the focal diseases of the spine that may cause a compensatory deformity inducing adaptation in the unaffected part of the spine.

CONCLUSION

The compensatory mechanisms involved in adaptive deformity represent an attempt to maintain a global alignment, to escape from pain or to control body posture. These slides can be retrieved under Electronic Supplementary material.

Effect of three-dimensional rotational deformity correction in surgery for adult degenerative scoliosis using lumbar lateral interbody fusion and posterior pedicle screw fixation

Introduction

Corrective surgery for adult degenerative scoliosis using lateral interbody fusion (LIF) and additional posterior fixation is an efficient procedure. However, it is unclear how this procedure affects rotational deformity correction. Therefore, the goal of the present study was to use three-dimensional (3D) images, taken during surgery, to investigate rotational deformity correction in the treatment of adult degenerative scoliosis using LIF and posterior fixation using a pedicle screw system.

Methods

The subjects were 12 females who were treated using LIF and posterior fixation for adult degenerative scoliosis. The patients had a mean age of 72 (65-76) years. 3D images were acquired before surgery, after LIF, and after additional posterior fixation. Rotational angles of the upper vertebra with respect to the lower vertebra of each fixed segment were measured in 3 planes. Correction factors for rotational deformity were investigated after LIF and additional posterior fixation.

Results

There were significant improvements in radiographical parameters for global spinal balance. The correction angles per segment were 4.7° for lateral bending, 6.9° for lordosis, and 4.5° for axial rotation. LIF was responsible for correction of four-fifths of lateral bending and axial rotation, and two-thirds of lordotic changes.

Conclusions

Lateral bending, axial rotational deformities, and lordosis were primarily corrected by LIF. Further lordosis correction was achieved using additional posterior fixation. These results indicate that corrective surgery for adult degenerative scoliosis using these procedures is effective for rotational deformity correction and leads to an ideal global spinal alignment.

Graft subsidence as a predictor of revision surgery following stand-alone lateral lumbar interbody fusion

OBJECTIVE

Lateral lumbar interbody fusion (LLIF) is a less invasive surgical option commonly used for a variety of spinal conditions, including in high-risk patient populations. LLIF is often performed as a stand-alone procedure, and may be complicated by graft subsidence, the clinical ramifications of which remain unclear. The aim of this study was to characterize further the sequelae of graft subsidence following stand-alone LLIF.

METHODS

A retrospective review of prospectively collected data was conducted on consecutive patients who underwent stand-alone LLIF between July 2008 and June 2015; 297 patients (623 levels) met inclusion criteria. Imaging studies were examined to grade graft subsidence according to Marchi criteria, and compared between those who required revision surgery and those who did not. Additional variables recorded included levels fused, DEXA (dual-energy x-ray absorptiometry) T-score, body mass index, and routine demographic information. The data were analyzed using the Student t-test, chi-square analysis, and logistic regression analysis to identify potential confounding factors.

RESULTS

Of 297 patients, 34 (11.4%) had radiographic evidence of subsidence and 18 (6.1%) required revision surgery. The median subsidence grade for patients requiring revision surgery was 2.5, compared with 1 for those who did not. Chi-square analysis revealed a significantly higher incidence of revision surgery in patients with high-grade subsidence compared with those with low-grade subsidence. Seven of 18 patients (38.9%) requiring revision surgery suffered a vertebral body fracture. High-grade subsidence was a significant predictor of the need for revision surgery (p < 0.05; OR 12, 95% CI 1.29–13.6), whereas age, body mass index, T-score, and number of levels fused were not. This relationship remained significant despite adjustment for the other variables (OR 14.4; 95% CI 1.30–15.9).

CONCLUSIONS

In this series, more than half of the patients who developed graft subsidence following stand-alone LLIF required revision surgery. When evaluating patients for LLIF, supplemental instrumentation should be considered during the index surgery in patients with a significant risk of graft subsidence.

Understanding Retroperitoneal Anatomy for Lateral Approach Spine Surgery

Lateral approach spine surgery provides effective interbody stabilization, and correction and indirect neural decompression with minimal-incision and less invasive surgery compared with conventional open anterior lumbar fusion. It may also avoid the trauma to paraspinal muscles or facet joints found with transforaminal lumbar interbody fusion and posterior lumbar interbody fusion. However, because lateral approach surgery is fundamentally retroperitoneal approach surgery, it carries potential risk to intra- and retroperitoneal structures, as seen in a conventional open anterior approach. There is an innovative lateral approach technique that reveals different anatomical views; however, it requires reconsideration of the traditional surgical anatomy in more detail than a traditional open anterior approach. The retroperitoneum is the compartmentalized space bounded anteriorly by the posterior parietal peritoneum and posteriorly by the transversalis fascia. The retroperitoneum is divided into three compartments by fascial planes: anterior and posterior pararenal spaces and the perirenal space. Lateral approach surgery requires mobilization of the peritoneum and its content and accurate exposure to the posterior pararenal space. The posterior pararenal space is confined anteriorly by the posterior renal fascia, anteromedially by the lateroconal fascia, and posteriorly by the transversalis fascia. The posterior renal fascia, the lateroconal fascia or the peritoneum should be detached from the transversalis fascia and the psoas fascia to allow exposure to the posterior pararenal space. The posterior pararenal space, however, does not allow a clear view and identification of these fasciae as this relationship is variable and the medial extent of the posterior pararenal space varies among patients. Correct anatomical recognition of the retroperitoneum is essential to success in lateral approach surgery. Spine surgeons must be aware that the retroperitoneal membrane and fascia is multilayered and more complex than is commonly understood. Preoperative abdominal images would facilitate more efficient surgical considerations of retroperitoneal membrane and fascia in lateral approach surgery.