Short-Term Clinical and Radiographic Evaluation of Patients Treated With Expandable and Static Interbody Spacers Following Lumbar Lateral Interbody Fusion

OBJECTIVE

The goal of this study was to evaluate, using computed tomography (CT) and magnetic resonance imaging (MRI), patients who underwent oblique lateral interbody fusion (OLIF) using either expandable or static interbody spacers.

METHODS

Thirty-five patients with degenerative disc disease were surgically treated with one-level OLIF and were followed up for more than 6 months. The Static group consisted of 22 patients, and 13 patients were in the Expandable group. Intraoperative findings included operative time (min), blood loss (ml), and cage size. Low back pain, leg pain, and leg numbness were measured using the Japanese Orthopedic Association score, visual analogue score, and the Roland-Morris Disability Questionnaire. Radiologic evaluation using computed tomography (CT) and magnetic resonance imaging (MRI) allowed measurement of cage subsidence, cross-sectional area (CSA) of the dural sac, disc height, segmental lordosis, foraminal height, and foraminal CSA preoperatively and 6 months postoperatively.

RESULTS

The Expandable group had significantly larger cage height and lordosis than the Static group (P < 0.05). The Expandable group also had greater dural sac area expansion and enlargement of the intervertebral foramen, as well as better correction of vertebral body slip (P < 0.05). Cage subsidence was significantly lower in the Expandable group (P < 0.05). JOA and VAS scores for leg numbness were significantly better in the Expandable group (P < 0.05).

CONCLUSIONS

Compared with static spacers, expandable spacers significantly enlarged the dural sac area, corrected vertebral body slippage, expanded the intervertebral foramen, and achieved good indirect decompression while reducing cage subsidence, resulting in improvement in clinical symptoms.

Posterior Pedicle Screw Fixation With Indirect Decompression Versus Direct Decompression in Treating Thoracolumbar Burst Fracture: A Systematic Review and Meta-Analysis

OBJECTIVE

To compare the safety and efficacy between posterior pedicle screw fixation with direct versus indirect decompression in treating patients with thoracolumbar burst fracture.

METHODS

This study was conducted on the basis of PRISMA statement. We systematically searched the PubMed and Embase databases up to July 3, 2023. Relevant studies comparing indirect decompression and direct decompression were recruited. Weighted mean differences (WMDs), odds ratios (ORs) and 95% confidence intervals (CIs) were analyzed for continuous and dichotomous data, respectively. P < 0.05 was considered statistically significant.

RESULTS

The operation time (WMD: -37.14, 95% CI: [-42.64, 31.64], P < 0.00001, I2 = 0%) and intraoperative blood loss (WMD: -316.82, 95% CI: [-469.80, -163.85], P < 0.0001, I2 = 99%) of indirect decompression group were significantly lower. Percentage of anterior vertebral body height (WMD: 3.98, 95% CI: [2.36, 5.60], P < 0.00001, I2 = 32%) and encroachment rate of the spinal canal (WMD: 1.48, 95% CI: [0.56, 2.40], P = 0.002, I2 = 35%) of indirect decompression group were significantly higher. No statistical difference was identified in grades of neurologic recovery and Cobb angle.

CONCLUSIONS

Posterior pedicle screw fixation with indirect decompression was safe and effective for thoracolumbar burst fracture with or without neurologic deficits when posterior longitudinal ligament was intact.

Is unilateral-approach full-endoscopic lumbar fusion effective for single-level lumbar spondylolisthesis with bilateral symptoms? A preliminary report of 43 CT analysis

PURPOSE

To investigate the clinical results and radiological parameters changes after unilateral-approach endoscopic lumbar interbody fusion (Endo-LIF) for lumbar spondylolisthesis with bilateral symptoms.

METHODS

43 single-level lumbar spondylolisthesis patients with bilateral lower limb symptoms were included from June 2020 to May 2022. All patients underwent unilateral-approach Endo-LIF and postoperative computed tomography. Radiological parameters including disk height (DH), degree of upper vertebral slip (DUVS), and foramen intervertebral parameters including bilateral foraminal height (FH), contralateral foraminal areas (FA) were evaluated. The clinical outcomes including low back pain and bilateral leg pain were evaluated using Visual Analog Scale (VAS) and the Oswestry Disability Index (ODI) before and after surgery.

RESULTS

All cases were successfully completed surgery and followed for average 15.16 ± 5.2 months. DH (44% ± 11%) and DUVS were significantly improvement postoperatively compared with preoperatively (p < 0.05). Statistically significant increases in bilateral FH (25% ± 11% on the surgical side, 17% ± 8% on the contralateral side) and contralateral FA (26% ± 6%) were observed (p < 0.05). The VAS and the ODI scores were significantly decreased in comparison with the preoperative scores (p < 0.05).

CONCLUSION

Unilateral-approach with contralateral indirect decompression in Endo-LIF can acquire satisfactory clinical outcomes. Therefore, unilateral-approach Endo-LIF may be a promising option for lumbar spondylolisthesis with bilateral symptoms.

Effects of indirect foraminal decompression during anterior cervical disc fusion procedure: preliminary results of a prospective study with clinical and radiological outcomes

INTRODUCTION

The respective effects of direct and indirect decompression in the clinical outcome after anterior cervical disc fusion (ACDF) is still debated. The main purpose of this study was to analyze the effects of indirect decompression on foraminal volumes during ACDF performed in patients suffering from cervico-brachial neuralgias due to degenerative foraminal stenosis, i.e. to determine whether implant height was associated with increased postoperative foraminal height and volume.

METHODS

A prospective follow-up of patients who underwent ACDF for cervicobrachial neuralgias due to degenerative foraminal stenosis was conducted. Patient had performed a CT-scan pre and post-operatively. Disc height, foraminal heights and foraminal volumes were measured pre and post operatively.

RESULTS

37 cervical disc fusions were successfully performed in 20 patients, with a total of 148 foramina studied. Foraminal height and volume were measured bilaterally on the pre- and post-operative CT scans (148 foramina studied). After univariate analysis, it was found a significant improvement for every radiological parameter, with a significant increase in disc height, foraminal height and foraminal volume being respectively +3,22 mm (p < 0,001), +2,12 mm (p < 0,001) and +54 mm3 (p < 0,001). Increase in disc height was significantly associated with increase in foraminal height (p < 0,001) and foraminal volume (p < 0,001). At the same time, increase in foraminal height was significantly correlated with foraminal volume (p < 0,001), and seems to be the major component affecting increasing in foraminal volume.

CONCLUSION

Indirect decompression plays an important part in the postoperative foraminal volume increase after ACDF performed for cervicobrachial neuralgias.

Factors affecting successful immediate indirect decompression in oblique lateral interbody fusion in lumbar spinal stenosis patients

Background

Oblique lumbar interbody fusion (OLIF) offers indirect decompression of stenotic lesions of the spinal canal and foramen through immediate disc height restoration. Only a few studies have reported the effect of cage position and associated intraoperatively modifiable factors for successful immediate indirect decompression following OLIF surgery. This study aimed to investigate the intraoperatively modifiable factors for successful radiological outcomes of OLIF.

Methods

This study included 46 patients with 80 surgical levels who underwent OLIF without direct posterior decompression. Preoperative and postoperative radiological parameters were evaluated and intraoperatively modifiable radiologic parameters for successful immediate radiologic decompression on magnetic resonance image (MRI) were determined. Radiologic parameters were preoperative and postoperative radiological parameters including anterior disc height (ADH), posterior disc height (PDH) lumbar lordotic angle (LLA), segmental lordotic angle (SLA), foraminal height (FH), cage position, cross-sectional area (CSA) of the thecal sac, cross-sectional foraminal area (CSF), facet distance (FD).

Results

All radiologic outcomes significantly improved. Comparing preoperative and postoperative values, mean CSA increased from 99.63±40.21 mm2 to 125.02±45.90 mm2 (p<.0001), and mean left CSF increased from 44.54±12.90 mm2 to 69.91±10.80 mm2 (p<.0001). FD also increased from 1.40±0.44 to 1.92±0.71 mm (p<.0001). FH increased from 16.31±3.3 to 18.84±3.47 mm (p<.0001). ADH and PDH also significantly increased (p<.0001). Immediate postoperative CSF and FH improvement rate (%) were significantly correlated with posterior disc height restoration rate (%) (p=.0443, and p=.0234, respectively). In addition, the patients with a cage positioned in the middle of the vertebral body experienced a greater FH improvement rate (%) compared to the patients with a cage positioned anteriorly. Finally, Visual analogue scale (VAS) for leg pain was improved immediately.

Conclusions

OLIF provided satisfactory immediate indirect decompression in central and foraminal spinal stenosis. Moreover, intraoperative surgical technique for successful radiologic CSF and FH improvement included restoration of the PDH and placement of the cage in the middle.

Prone Transpsoas Lateral Interbody Fusion (PTP LIF) with Anterior Docking: Preliminary functional and radiographic outcomes

Background

Disadvantages of lateral interbody fusion (LIF) through a direct, transpsoas approach include difficulties associated with lateral decubitus positioning and limited sagittal correction without anterior longitudinal ligament release or posterior osteotomy. Prior technical descriptions advocate anchoring or docking the retractor into the posterior to middle aspect of the disc space.

Methods

72 patients who underwent 116 total levels of Prone Transpsoas (PTP) LIF with anterior docking with a single surgeon between December 2021 and May 2023 were included. Patient characteristics, perioperative data, as well as postoperative functional and radiographic outcomes were recorded. Subgroup analysis was performed for patients who underwent single-level PTP LIF with single-level percutaneous fixation (SLP). Patients in the SLP subgroup did not undergo direct decompression, release, or osteotomy.

Results

N=41 (56.9%) of cases included the L4-5 level. No vascular, bowel, or other visceral complications occurred. No patients developed a permanent motor deficit. Both the total cohort and the SLP group demonstrated statistically significant improvements in functional outcomes including Oswestry Disability Index (ODI) and Visual Analog Scale (VAS) as well as all radiographic parameters measured. Mean total operative time (incision to completion of closure for lateral and posterior fusion) in the SLP group was 104.3 minutes with a significant downward trend with increasing surgeon experience. The SLP group demonstrated a 9.9° increase in segmental lordosis (SL), a 7.5° increase in lumbar lordosis (LL), 5.3° reduction in pelvic tilt (PT), and a decrease in pelvic incidence - lumbar lordosis mismatch (PI-LL) from 11.0° preoperatively to 3.9°, postoperatively (p<.01).

Conclusions

PTP LIF with anterior docking may address shortcomings associated with traditional lateral interbody fusion by producing safe and reproducible access with improved restoration of segmental lordosis and optimization of spinopelvic parameters.

The Effect of Indirect Decompression Through Extraforaminal Interbody Fusion for Degenerative Lumbar Disease

Purpose

Extraforaminal lumbar interbody fusion as with other methods that involve the mechanism of indirect decompression, the discussion not only focuses on the benefit of minimizing the risk of thecal sac injury and postoperative scarring, but also on the risk of insufficient decompression in the affected neural structures during the reduction of the affected segment.

Methods

Eighty-two patients presenting with degenerative lumbar disease with segmental instability underwent ELIF combined with transpedicular fixation and circumferential fusion. Clinical and radiographic evaluations were performed.

Results

The mean ODI significantly improved from 63.4 preoperatively to 32.3 1 year postoperatively. The mean VAS back pain significantly improved from 5.95 to 2.63 postoperatively and VAS (leg pain) improved from 6.04 to 2.44. The mean CSA increased from 103  mm2 preoperatively to 169  mm2 postoperatively. The median extension ratio of CSA was 33%. Disc height, segmental disc angle, and lumbar lordosis also improved significantly. Only three (3.7%) patients were revised using direct central decompression due to neurologic deterioration.

Conclusion

Spinal stenosis was resolved successfully by indirect decompression through extraforaminal interbody fusion via a transmuscular limited approach.

Minimally Invasive Approach for Degenerative Spondylolisthesis: Lateral Single-Position Surgery with Intraoperative Computed Tomography Navigation and Fluoroscopy: A Technical Note

OBJECTIVE

Degenerative spondylolisthesis (DS) is a prevalent condition that leads to low back pain and neurological symptoms. This technical note presents a novel surgical strategy for treating DS using lateral single-position surgery (SPS) in combination with intraoperative computed tomography navigation and fluoroscopy.

METHODS

Fifteen patients (5 males and 10 females, mean age 70.2 years) diagnosed with DS with a slip of 5 mm or more underwent lateral lumbar interbody fusion (LLIF) with percutaneous pedicle screw (PPS) fixation using this technique. The procedure involved slip reduction using an upside PPS and rod fixation, followed by LLIF performed in the same lateral position. The term "upside PPS" refers to a PPS that is inserted on the ceiling side of the patient's surgical field. Preoperative and postoperative radiographic assessments were conducted to evaluate the effectiveness of the lateral SPS.

RESULTS

The results demonstrated significant improvements in various parameters, including spondylolisthesis reduction, segmental lordosis, disc height, and spinal canal dimensions. The lateral-SPS procedure exhibited several advantages over traditional flip LLIF approaches for slip reduction. Additionally, the technique provided accurate intraoperative navigation guidance through computed tomography imaging, ensuring precise implant placement and slip reduction.

CONCLUSIONS

Combining LLIF and PPS fixation in a single procedure presents a precise, efficient approach for DS treatment, minimizing repositioning needs. This technique enables effective lumbar reconstruction, restoration of spinal stability, and improved patient outcomes. Although further investigation is warranted, lateral SPS surgery may hold promise as an innovative solution for managing DS by reducing surgical invasiveness and optimizing surgical efficiency.

Early Radiological Assessment of Static and Expandable Cages in Lateral Single Position for Indirect Decompression- Lateral Lumbar Interbody Fusion

OBJECTIVE

This study aimed to compare the postoperative alignment of static and expandable cages in lateral single-position (LSP) for indirect decompression in lateral lumbar interbody fusion (LLIF).

METHODS

We included sixty-seven patients who underwent LSP-LLIF for lumbar degenerative disease. We performed radiological assessments preoperatively and two weeks postoperatively using computed tomography and magnetic resonance imaging. We divided the patients into the expandable cage group (23 patients) and the static cage group (44 patients). We measured disc height (DH), segmental lordosis (SL), and foraminal area (FA) from computed tomography images and the area of the dural sac from magnetic resonance imaging. We recorded surgical outcomes and complications.

RESULTS

Both static and expandable cages demonstrated improvements in DH, SL, FA, and dural sac expansion. However, we found no statistically significant differences in the average change in DH (4.4 ± 2.1 mm vs. 4.2 ± 1.8 mm, P = 0.685), the average change in SL (1.0 ± 4.4° vs. 1.9 ± 3.6°, P = 0.310), or FA change (32.5 ± 31.7 mm2 vs. 34.9 ± 29.5 mm2, P = 0.966) between the expandable and static cage groups. We also found no statistically significant difference in dural sac enlargement between the two groups. We observed no significant differences in operation time, estimated blood loss, or length of hospital stay between the two groups. No severe adverse events or additional surgeries were reported.

CONCLUSIONS

In LSP-LLIF without facet joint resection or other posterior techniques, static and expandable cages showed comparable effectiveness in achieving increased DH, SL, FA, and indirect decompression.

Small Preoperative Dural Sac Cross-Sectional Area and Anteriorly Placed Fusion Cages Are Risk Factors for Indirect Decompression Failure after Oblique Lateral Interbody Fusion

OBJECTIVE

1) To investigate if implant-related factors such as cage size and cage position are associated with radiologic improvement after indirect decompression with oblique lateral interbody fusion (OLIF). 2) To investigate the risk factors associated with indirect decompression failure (IDF) at the surgical levels after OLIF.

METHODS

From February 2015 to December 2019, 92 consecutive patients (188 levels) with lumbar spinal stenosis who underwent indirect decompression via OLIF with or without posterior instrumentation were studied retrospectively. Radiographic variables were measured preoperatively and postoperatively. The radiographic results were compared for cages with different heights and positions. IDF was defined as revision surgery within 6 months or persistent compressive symptoms 6 months after surgery.

RESULTS

Postoperative improvements were observed in all measured radiographic parameters except for segmental lordosis. Taller cages were associated with more shrinkage of the bulging disc and greater increase in dural sac diameter. Cages placed posteriorly showed larger postoperative subarticular diameters. Twelve patients (16 levels) had IDF. Multivariate logistic regression showed that after adjusting for age, sex, and body mass index, smaller preoperative dural sac cross-sectional area and anterior positioning of cages were both independent risk factors for IDF.

CONCLUSIONS

OLIF is an effective procedure for indirect decompression. To avoid reoperation for lumbar spinal stenosis, surgeons should aim to place the center of the cage at the posterior half of the lower endplate. Surgical levels with a preoperative dural sac cross-sectional area <44 mm² may not be suitable for indirect decompression.

Indirect Decompression Using Oblique Lumbar Interbody Fusion Revision Surgery Following Previous Posterior Decompression: Comparison of Clinical and Radiologic Outcomes Between Direct and Indirect Decompression Revision Surgery

OBJECTIVE

This study compared the radiological and clinical outcomes with transforaminal lumbar interbody fusion (TLIF) to evaluate the effect of indirect decompression through oblique lumbar interbody fusion (OLIF) as revision surgery.

METHODS

We enrolled patients who underwent single-level fusion with revision surgery at the same level as the previous decompression level. We retrospectively reviewed 25 patients who underwent OLIF from 2017 to 2018 and 25 who received TLIF from 2014 to 2018. Radiologic and clinical outcomes were evaluated by cross-sectional area (CSA) of the spinal canal, thickness and area of ligamentum flavum (LF), subsidence, disc height, fusion rate, Oswestry Disability Index (ODI), and visual analogue scale (VAS).

RESULTS

Compared with OLIF, the thickness and area of the LF after surgery were significantly less in TLIF, and the resulting CSA extension was also significantly higher. However, both groups showed improvement in ODI and VAS after surgery, and there was no difference between the groups. Complications related to the posterior approach in TLIF were 4 cases, and in OLIF, there were 2 cases that underwent additional posterior decompression surgery and 6 cases of transient paresthesia.

CONCLUSION

Since complications associated with the posterior approach can be avoided, OLIF is a safer and useful minimally invasive surgery. Therefore, appropriate indications are applied, OLIF is a good alternative to TLIF when revision surgery is considered.

Successful Criteria for Indirect Decompression With Lateral Lumbar Interbody Fusion

OBJECTIVE

No consensus criteria have been established regarding ideal candidates for indirect decompression with lateral lumbar interbody fusion (LLIF), and contributing factors of indirect decompression failure were rarely reported. We aim to investigate the success rate of indirect decompression by LLIF with proposed selection criteria and identify risk factors associated with indirect decompression failure, defined as persistent pain requiring revision with direct decompression.

METHODS

Data from 191 patients undergoing LLIF were retrospectively reviewed. All the following criteria must be fulfilled: (1) dynamic clinical symptoms (pain relief in supine position), (2) presence of reducible disc height (recovered disc height in supine position), (3) no profound weakness, and (4) no static stenosis. The success rate of indirect decompression with LLIF and results after at least 1 year of follow-up were collected. Preoperative, procedure-related, and postoperative factors were assessed for their relationship with failure.

RESULTS

Of 191 patients,13 patients (6.8%) required additional direct decompression due to persistent pain, giving a criteria success rate of 93.2%. Factors associated with indirect decompression failure included low bone mineral density (T-score < 2.1), low reducible disc height (<13%), low postoperative disc height (< 10 mm), high-grade cage subsidence, and use of plate fixation.

CONCLUSION

We proposed patient selection criteria for indirect decompression with LLIF which had a satisfactory success rate and identified factors associated with the need for additional direct decompression. Our proposed criteria may assist selection of patients likely to achieve good results following indirect decompression with LLIF, and optimize selection based on risk factors of failure.

Predictors for second-stage posterior direct decompression after lateral lumbar interbody fusion: a review of five hundred fifty-seven patients in the past five years

PURPOSE

To analyze the predictors for second-stage posterior direct decompression (PDD) after lateral lumbar interbody fusion (LLIF) procedure.

METHODS

We studied patients who underwent LLIF for degenerative lumbar spinal stenosis in the last five years, from July 2016 to June 2021. All surgical levels were grouped according to Schizas' central canal stenosis (CCS) classification, Pathria's facet joint degeneration (FJD) classification, Bartynski's lateral recess stenosis (LRS) classification, and Lee's foraminal stenosis (FS) classification. Second-stage PDD rates of each subgroup and their annual change were analyzed. Evaluation of risk factors associated with PDD was investigated.

RESULTS

A total of 901 segments from 557 patients were included. The overall PDD rate was 29.97%. An overall PDD rate of 75.21% for grade D CCS, 29.74% for grade C CCS, 41.67% for grade 3 FJD, 37.61% for grade 3 LRS, and 40.70% for grade 3 FS was shown. While there was a continuous decline in annual PDD rate in the past four years, the annual PDD rate for grade D remained at very high levels. Logistic regression analysis had shown grade D CCS as the utmost risk factor for PDD (OR = 17.77). And grade 3 LRS (OR = 4.63), grade 3 FS (OR = 2.42), grade C CCS (OR = 2.41), and grade 3 FJD (OR = 2.04) were also moderately correlated with PDD, which meant they only moderately increased the risk of PDD.

CONCLUSION

Extreme severe lumbar CCS (grade D) is the greatest determinant to perform the second-stage PDD procedure after LLIF.

Radiological Assessment of the Effects of Anterior Cervical Discectomy and Fusion on Distraction of the Posterior Ligamentum Flavum in Patients with Degenerative Cervical Spines

Background

This study aimed to assess the effects of anterior cervical discectomy and fusion (ACDF) on distraction of the posterior ligamentum flavum (LF) by increasing the intervertebral disc height and positioning a graft in patients with degenerative cervical spine disease.

Methods

Sixty-eight patients with degenerative cervical diseases who underwent single-level ACDF were included in the analysis. The intervertebral disc height, Cobb angle, and transverse thickness of the LF were measured, and magnetic resonance imaging was performed both preoperatively and 6 weeks postoperatively on each patient. Correlation analyses were performed to evaluate the relationships between age, sex, change in intervertebral disc height, Cobb angle, and position of the intervertebral implant according to the postoperative change in LF thickness. The position of the intervertebral implant was categorized as anterior, middle, or posterior. We also evaluated radiological effects according to the implant position.

Results

The mean intervertebral disc height increased from 5.88 mm preoperatively to 7.49 mm postoperatively. The Cobb angle was 0.88° preoperatively and 1.43° postoperatively. Age (p = 0.551), sex (p = 0.348), position of cage (p = 0.312), pre- and postoperative intervertebral disc height (p = 0.850, p = 0.900), Cobb angle (p = 0.977, p = 0.460), and LF thickness (p = 0.060, p = 1.00) were not related to changes in postoperative LF thickness. Postoperative increase in disc height was related to Cobb angle (r = 0.351, p = 0.038). No other factors were significantly related. The position of the cage was not related with the change of Cobb angle (p = 0.91), LF thickness (p = 0.31), or disc height (p = 0.54).

Conclusions

Change in the intervertebral disc height and the position of the intervertebral implant after ACDF did not affect the thickness of the LF after surgery in patients with degenerative cervical spine disease.

Clinical and radiographic performance of indirect foraminal decompression with anterior retroperitoneal lumbar approach for interbody fusion (ALIF)

STUDY DESIGN

Retrospective study BACKGROUND: Indirect decompression with ALIF allows the restoration of the disk and foraminal height with limited soft tissue damage. However, it does not offer a direct view of the neural structure and a direct intraoperative assessment of the results of the decompression is not possible. For this reason, ALIF is often accompanied by posterior, direct decompression. So far, there is no consensus on the effects of indirect decompression alone for L5-S1 foraminal stenosis.

OBJECTIVE

Evaluation of the clinical and mechanical performance of indirect decompression with anterior lumbar interbody fusion (ALIF) in L5-S1 foraminal stenosis.

METHODS

All patients who underwent ALIF at our institution and had a minimum follow-up of six months were assessed for inclusion. Radiographic parameters (anterior and posterior disc height, foraminal height and surface, L5-S1 angle, pelvic incidence, pelvic tilt and lumbar lordosis) and clinical data (Oswestry Disability Index - ODI and Numeric Rating Scale - NRS) before ALIF and at the last follow-up were compared. A regression analysis was performed to investigate the correlation between radiographic and clinical outcomes.

RESULTS

Thirty-four patients were available for the study (55.9% female, mean age 53.4±11.5 years), mean follow-up was 26.4±11.1 months. At the last follow-up, a significant increase in foraminal height (14.6±4.0 vs. 17.9±3.9 mm, p<0.001), posterior disc height (6.5±2 vs. 9.1±2 mm, p<0.001) was observed. ODI and NRS back and leg improved significantly. The NRS leg correlated with foraminal height (r=-0.45), foraminal surface (r=-0.36) and anterior (r=-0.41) and posterior disc height (r=-0.43).

CONCLUSION

ALIF provided significant indirect foraminal decompression and improvement of radicular pain. The increase of foraminal height, surface, and posterior disc height is directly associated with radicular pain improvement.

LEVEL OF EVIDENCE

IV AVAILABILITY OF DATA AND MATERIAL: The datasets used and/or analyzed in the present study are available from the corresponding author on reasonable request.

Can Indirect Decompression Reduce Adjacent Segment Degeneration and the Associated Reoperation Rate After Lumbar Interbody Fusion? A Systemic Review and Meta-analysis

OBJECTIVE

We sought to assess and compare the rate of adjacent segment degeneration (ASDeg), adjacent segment disease, and related reoperations between patients who underwent lumbar interbody fusion surgery using indirect or direct decompression.

METHODS

On the basis of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, a systematic review and meta-analysis was performed to identify and analyze studies that compared the rate of ASDeg, adjacent segment disease, and related reoperations between indirect and direct decompression techniques. Indirect decompression included anterior lumbar interbody fusion, lateral lumbar interbody fusion, and oblique lateral interbody fusion, whereas direct decompression included posterior or transforaminal lumbar interbody fusion.

RESULTS

Seven studies including a total of 576 patients (indirect: 314; direct: 262) were identified. The pooled rates of ASDeg were 19.4% (45/232) and 34.9% (66/189) for indirect and direct decompression, respectively. A fixed-effects model showed 0.34 times lower odds of developing ASDeg in the indirect decompression group (odds ratio = 0.34, 95% confidence interval [CI] = 0.20, 0.57). The pooled incidence of reoperation was 2.5% (8/314) and 6.1% (16/262) for indirect and direct decompression, respectively. A fixed-effects model showed 0.40 times lower odds of reoperation from ASDeg in the indirect decompression group (odds ratio = 0.40, 95% CI = 0.18, 0.89). The pooled mean difference for the segmental lordosis angle was 1.80 degrees (95% CI = 0.74, 2.86) and 7.11 degrees (95% CI = 4.47, 9.74) for total lumbar lordosis angle, favoring indirect decompression.

CONCLUSIONS

Indirect decompression showed lower odds of developing ASDeg and undergoing reoperation for ASDeg after lumbar interbody fusion surgery in this meta-analysis. However, the limited number and quality of the included studies should be considered when interpreting the results.

Radiographs assessment of changes in the psoas muscle at L4-L5 level after single-level lateral lumbar interbody fusion in patients with postoperative motor weakness

The purposes of this study were (1) to investigate postoperative changes in cross-sectional area (CSA) and signal intensity (SI) of the psoas muscle (PS) using magnetic resonance imaging (MRI) and (2) to compare the CSA and SI of the PS between patients with and without motor weakness after single-level lateral lumbar interbody fusion (LLIF) at level L4-L5. Sixty patients were divided into two groups-those with postoperative motor weakness and those without-and the two groups were compared. Baseline demographics and clinical characteristics, such as operation time and blood loss, length of hospital stay, and postoperative complications, were recorded. The CSA and SI of the PS were obtained from the MRI regions of interest defined by manual tracing. Patients who developed motor weakness after surgery were significantly older (p = 0.040). The operation time (p = 0.868), LLIF operative time (p = 0.476), and estimated bleeding loss (p = 0.168) did not differ significantly between groups. In both groups, the CSA and SI of the left and right PS increased after surgery. The change in the CSA of the left PS was significantly higher in patients with weakness (247.6 ± 155.2 mm²) than without weakness (152.2 ± 133.1 mm²) (p = 0.036). The change in SI of the left PS did not differ between the two groups (p = 0.530). To prevent postoperative motor weakness regardless of the operation time, surgeons should be aware of the potential for surgical invasive of the PS during LLIF in older people.

Indirect decompression via oblique lateral interbody fusion for severe degenerative lumbar spinal stenosis: a comparative study with direct decompression transforaminal/posterior lumbar interbody fusion

BACKGROUND CONTEXT

Previous studies have shown that oblique lateral interbody fusion (OLIF) can improve neurological symptoms via "indirect decompression." However, data are lacking in terms of its benefits when compared with conventional transforaminal lumbar interbody fusion (TLIF) and/or posterior lumbar interbody fusion (PLIF) approach, especially in patients with severe central canal stenosis.

PURPOSE

To investigate the clinical outcome of OLIF without posterior decompression versus conventional TLIF and/or PLIF in severe lumbar stenosis diagnosed on preoperative magnetic resonance imaging.

STUDY DESIGN

Retrospective comparative study.

PATIENT SAMPLE

Fifty-one patients who underwent OLIF and 41 patients who underwent conventional TLIF and/or PLIF.

OUTCOME MEASURES

Clinical outcome score by Japanese Orthopedic Association (JOA) score and radiographic outcomes (disc height and fusion rate on computed tomography scan).

MATERIALS/METHODS

We retrospectively reviewed 51 patients who underwent OLIF with supplemental percutaneous pedicle screws (55 levels; OLIF group) and 41 patients who underwent conventional TLIF and/or PLIF (47 levels; TPLIF group). The cross-sectional area of the thecal sac was measured preoperatively in OLIF and TPLIF groups, but postoperatively only in the OLIF group. All patients were diagnosed with severe stenosis based on Schizas classification (Grade C or D) on magnetic resonance imaging. We compared radiographic and clinical outcome scores (JOA score) between the 2 groups at 1 year of follow-up. The radiographic evaluation included the fusion status and disc height on computed tomography scan. Surgical data and perioperative complications were also investigated.

RESULTS

The baseline demographic data of the 2 groups were equivalent in preoperative diagnosis, JOA score, and disc height and/or angle. The cross-sectional area significantly increased postoperatively, which confirmed indirect decompressive effect in the OLIF group. The JOA score improved in both groups at the 1-year follow up (76.6% vs. 73.5% improvement rate in the OLIF and TPLIF groups, respectively). The fusion rate at the 1-year follow-up was higher in the OLIF group than in the TPLIF group (87.2% vs. 57.4%). The disc height restoration was also better in the OLIF group. The operative data demonstrated less estimated blood loss and operative time in the OLIF group.

CONCLUSIONS

OLIF and conventional TLIF and/or PLIF demonstrated comparable short-term clinical outcomes in the treatment of severe degenerative lumbar stenosis. However, the surgical and radiographic outcomes were better in the OLIF group. Surgeons should choose an appropriate approach on a case by case basis, recognizing the perioperative complications specific to each fusion procedure.

Usefulness of Oblique Lumbar Interbody Fusion as Revision Surgery: Comparison of Clinical and Radiological Outcomes Between Primary and Revision Surgery

OBJECTIVE

Oblique lumbar interbody fusion (OLIF) is useful as surgical treatment of degenerative lumbar disease. However, revision surgery has often resulted in worse surgical outcomes than primary surgery. Thus, we compared the usefulness of OLIF as primary surgery (PS) versus revision surgery (RS).

METHODS

We retrospectively investigated 173 patients who had undergone single-level OLIF from 2016 to 2018. The radiological and clinical outcomes were compared between PS (n = 152) and RS (n = 21). The effects of RS on the clinical outcomes (Oswestry Disability Index [ODI] cutoff, 12) after surgery were investigated.

RESULTS

The ODI and visual analog scale score at 6 and 12 months after surgery was worse in the RS group than in the PS group (P < 0.05). In the RS group, the visual analog scale score for leg pain of the previous laminectomy side was worse than that of the virgin side at 6 and 12 months after surgery (P < 0.05). The disc height, ligamentum flavum, and subsidence did not differ between the 2 groups. However, the cross-sectional area enlargement differed between the 2 groups (P < 0.05). Multivariate logistic regression analysis showed that RS and severe subsidence were risk factors for differences in the ODI (P = 0.006 and P = 0.017, respectively).

CONCLUSIONS

Most radiological outcomes were similar between the RS and PS groups, with no differences in complications or the requirement for additional posterior decompression. However, OLIF resulted in relatively poor clinical outcomes when used as RS. Thus, revision spine surgery tends to result in poor outcomes compared with those of primary spine surgery; however, OLIF can be a tolerable option for revision spine surgery.

Effect of manual reduction and indirect decompression on thoracolumbar burst fracture: a comparison study

OBJECTIVE

To evaluate the effect of manual reduction and indirect decompression on thoracolumbar burst fracture.

METHODS

Sixty patients with thoracolumbar burst fracture who were hospitalized from January 2018 to October 2019 were selected and divided into an experimental group (33 cases) and control group (27 cases) according to different treatment methods. The experimental group was treated with manual reduction and indirect decompression, while the control group was not treated with manual reduction. The operation time and intraoperative blood loss were recorded. VAS score was used to evaluate the improvement of pain. The anterior height of the injured vertebra, wedge angle of the injured vertebral body, and encroachment ratio of the injured vertebral canal were used to evaluate the spinal canal decompression and fracture reduction. JOA score was used to evaluate the improvement of spinal function.

RESULTS

There was no significant difference in operation time and intraoperative blood loss between the two groups. Compared with the control group, the VAS score and the wedge angle of the injured vertebral body of the experimental group 3 days after the operation and the last follow-up were significantly lower than that of the control group, and the difference was statistically significant. The ratio of the anterior height of the injured vertebra of the experimental group 3 days after the operation and the last follow-up was significantly higher than that of the control group, and the difference was statistically significant. The difference of the encroachment ratio of the injured vertebral canal between preoperation and 3 days after operation was significantly higher than that of the control group, and the difference was statistically significant. The bladder function of JOA 3 days after the operation of the experimental group was significantly higher than that of the control group, and the difference was statistically significant. And the rest aspect of JOA on 3 days after the operation and last follow-up of the experimental group has no significant difference compared with the control group.

CONCLUSION

Manipulative reduction and indirect decompression can obtain a better clinical effect in the treatment of thoracolumbar burst fractures.

Transfacet Minimally Invasive Transforaminal Lumbar Interbody Fusion With an Expandable Interbody Device-Part I: 2-Dimensional Operative Video and Technical Report

BACKGROUND

Advances in operative techniques and minimally invasive technologies have evolved to maximize patient outcomes and radiographic results, while reducing morbidity and recovery time.

OBJECTIVE

To describe the operative technique for a transfacet minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) as a proposed modification to the standard approach MIS-TLIF.

METHODS

We present the case of a 72-yr-old man with left-sided lumbar radiculopathy. Preoperative imaging demonstrated degenerative lumbar anterolisthesis at L4-5, with associated canal and neuroforaminal stenosis. The patient underwent transfacet MIS-TLIF at L4-L5. We describe the preoperative planning, patient positioning, incision and dissection, pedicle screw insertion, transfacet approach to the working access corridor, discectomy, interbody device placement, fixation, and closure.

RESULTS

The transfacet MIS-TLIF utilizes 3 key techniques to safely maximize surgical correction: (1) a limited bony resection based on the superior articular process, leaving the medial inferior articular process, lateral superior articular process, and rostral pars intact, providing a working bony corridor that protects the traversing and exiting nerve roots; (2) decortication and release of the contralateral facet joint to provide additional capacity for indirect decompression and provide the first point of osseous fusion; and (3) placement of an expandable interbody device that provides additional indirect decompression to the working side and contralateral foramen.

CONCLUSION

The transfacet MIS-TLIF uniquely leverages a bony working corridor to access the disc space for discectomy and interbody placement. Transfacet MIS-TLIF is a feasible solution for lumbar spinal reconstruction to maximize direct and indirect decompression of the neuroforamina and central spinal canal in patients with lumbar degenerative diseases and low-grade spondylolisthesis.

Transfacet Minimally Invasive Transforaminal Lumbar Interbody Fusion With an Expandable Interbody Device-Part II: Consecutive Case Series

BACKGROUND

Advances in operative techniques and instrumentation technology have evolved to maximize patient outcomes following minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF). The transfacet MIS-TLIF is a modified approach to the standard MIS-TLIF that leverages a bony working corridor to access the disc space for discectomy and interbody device placement.

OBJECTIVE

To evaluate clinical and radiographic results following transfacet MIS-TLIF using an expandable interbody device.

METHODS

We performed a retrospective review of consecutive patients who underwent transfacet MIS-TLIF for degenerative lumbar spondylolisthesis. Patient-reported outcome measures for pain and disability were assessed. Sagittal lumbar segmental parameters and regional lumbopelvic parameters were assessed on upright lateral radiographs obtained preoperatively and during follow-up.

RESULTS

A total of 68 patients (61.8% male) underwent transfacet MIS-TLIF at 74 levels. The mean age was 63.4 yr and the mean follow-up 15.2 mo. Patients experienced significant short- and long-term postoperative improvements on the numeric rating scale for low back pain (-2.3/10) and Oswestry Disability Index (-12.0/50). Transfacet MIS-TLIF was associated with an immediate and sustained reduction of spondylolisthesis, and an increase in index-level disc height (+0.71 cm), foraminal height (+0.28 cm), and segmental lordosis (+6.83°). Patients with preoperative hypolordosis (<40°) experienced significant increases in segmental (+9.10°) and overall lumbar lordosis (+8.65°). Pelvic parameters were not significantly changed, regardless of preoperative alignment. Device subsidence was observed in 6/74 (8.1%) levels, and fusion in 50/53 (94.3%) levels after 12 mo.

CONCLUSION

Transfacet MIS-TLIF was associated with clinical improvements and restoration of radiographic sagittal segmental parameters. Regional alignment correction was observed among patients with hypolordosis at baseline.

The correlation of intraoperative distraction of intervertebral disc with the postoperative canal and foramen expansion following oblique lumbar interbody fusion

PURPOSE

To examine the correlation of intraoperative distraction of intervertebral disc with the postoperative central canal and foramen expansion by oblique lumbar interbody fusion (OLIF) with indirect decompression.

METHODS

Patients who underwent OLIF between October 2013 and April 2017 were included. Clinical outcomes included back and leg pain evaluated by visual analog scale (VAS) and Oswestry Disability Index (ODI). Intraoperative radiographic parameters of height ratio [(HR) = disc height/intervertebral body height)] and cage location were evaluated on intraoperative fluoroscopic images. Disc height (DH), foraminal height (FH), cross-sectional area of spinal canal (CSAC), and CSA of the foramen (CSAF) were measured.

RESULTS

A total of 47 patients involving 62 levels were enrolled in this study. Mean follow-up was 43.8 ± 12.0 months. These patients reported an improvement of 61.7% in VAS back, 68.1% in VAS leg, and 46% in ODI (all p < 0.01). Radiographic parameters including HR, DH, FH, CSAC, and CSAF were also significantly increased by 32.6%, 48.2%, 21.4%, 44.0%, and 40.1% (left-side CSAF) or 45.4% (right-side CSAF), respectively (p < 0.05). HR increment was correlated with CSA (canal and foramen) increment. Slightly higher improvements of HR, DH, FH, CSAC, and CSAF (both sides) were noted when cage was located at middle rather than anterior (p > 0.05).

CONCLUSIONS

The ligamentotaxis effect of OLIF is capable of supporting indirect decompression of central canal and neural foramina and clinical improvement. HR is a reliable intraoperative assessment method. In addition, intraoperative HR increment was correlated with postoperative neural elements expansion.

Indirect Decompression Using Lateral Lumbar Interbody Fusion for Restenosis after an Initial Decompression Surgery

Study Design

Retrospective comparative study.

Purpose

We compared clinical and radiographical outcomes after lumbar decompression revision surgery for restenosis by lateral lumbar interbody fusion (LLIF) and posterior lumbar interbody fusion (PLIF).

Overview of Literature

Indirect lumbar decompression with LLIF was used to treat degenerative lumbar diseases requiring neural decompression. However, only a few studies have focused on the effectiveness of this technique for restenosis after lumbar decompression.

Methods

We retrospectively investigated 52 cases involving lumbar interbody fusions for restenosis with spondylolisthesis after lumbar decompressions; these cases consisted of 15 patients who underwent indirect decompression with LLIF and posterior fixation and 37 patients who underwent the same procedure with PLIF. We compared Japanese Orthopaedic Association (JOA) scores and perioperative complications between groups. The cross-sectional areas of the thecal sac on magnetic resonance imaging were measured before, immediately after, and 2 years after surgery. We conducted statistical analyses using unpaired t -test and Fisher’s exact tests, and a p-value <0.05 was considered statistically significant.

Results

The operative time was significantly shorter in the LLIF group than in the PLIF group (115.3±33.6 min vs. 186.2±34.2 min, respectively; p<0.001). In addition, the intraoperative blood loss was significantly lower in the LLIF group than in the PLIF group (58.2±32.7 mL vs. 303.2±140.1 mL, respectively; p<0.001). We found two cases of transient lateral thigh weakness (13.3%) in the LLIF group and five cases of incidental durotomy, one case of deep infection, and one case of neurological deterioration in the PLIF group—resulting in a higher complication incidence (18.9%), although it did not reach (p=0.63). The JOA scores improved significantly in both groups.

Conclusions

Indirect decompression using LLIF provided acceptable clinical and radiographical outcomes in patients with restenosis with spondylolisthesis after lumbar decompression; no revision-surgery-specific complications were found. Our results suggest that LLIF is a safe and minimally invasive procedure for revision surgery.

OLIF Combined with Anterior Fixation for Lumbar Synovial Cysts with Instability

BACKGROUND

The optimal management of lumbar synovial cysts (LSCs) has always been controversial. Open or minimally invasive partial hemilaminotomy as a direct decompression approach has been widely studied, whereas to our knowledge, there has been no report of an indirect decompression method for LSC.

CASE DESCRIPTION

A 60-year-old male complained of chronic low back pain for 2 years. He reported that the pain had been getting worse and started radiating to the bilateral posterior thighs and right lateral calf for 6 months. An ovoid lesion with a hyperintense center attached to the medial side of the right facet joint at the L4-5 level, as well as L4-5 dynamic instability, were found with magnetic resonance imaging and lumbar x-ray examinations, respectively. L4-5 oblique lumbar interbody fusion combined with anterior fixation was performed. After surgery, the patient felt distinct pain relief and was discharged on the third day postoperatively. Three months later, lumbar magnetic resonance imaging and 3-dimensional computed tomography were performed again. The L4-5 disk height and foraminal height recovered from 7.1-12.3 mm and 14.8-18.5 mm, respectively. No evidence of a cyst was disclosed. The patient did not complain of any low back pain or radicular pain during the 12-month follow-up.

CONCLUSIONS

Indirect decompression surgery may be a new option for the management of LSC, especially in those with lumbar instability and that communicate with the facet joint. Further research with a larger and more comprehensive sample population is required.

Anterior lumbar interbody fusion (ALIF): biometrical results and own experiences

Lumbar fusion is a mainstay in the treatment of low back pain resulting from degenerative disc disease. Anterior lumbar interbody fusion (ALIF) has become a reasonable treatment technique to achieve indirect foraminal decompression with high fusion rates. The aim of the study was to analyse the biometrical parameters of the lumbar spine and the clinical outcome. The medical records of 51 patients treated with ALIF between 2012 and 2016 were retrospectively reviewed. Anterior and posterior disc height (DH), lumbar lordosis (LL), local disc angle (LDA) and foraminal dimensions were obtained on pre- and postoperative plain radiographs and computed tomography scans using ImageJ and Surgimap software according to the pedicle–pedicle technique. To evaluate the interbody fusion status on the last follow-up CT scans, we used Bridwell criteria. Preoperative and 12 months postoperative Oswestry Disability Index (ODI) scores were determined for all patients. The average length of hospitalisation was 4 days. Most of the patients had degenerative disc disease with foraminal stenosis. Five patients had early complications like paresthesia of lower limbs, sympathetic dysfunction or wound infections, but there were no major complications. Statistically significant (P < .01) improvement was observed in foraminal dimensions (area = 49%, height = 33% and width = 19%), anterior DH (49%), posterior DH (69%), LDA (47%) and LL (17.5%). Posterior DH correlated significantly with foramen height improvement. Radiographic evidence of fusion according to the modified Bridwell criteria (grade I and grade II) was observed in 96% (49/51) of the patients in the last CT of the lumbar spine. We also observed significant improvement in functional recovery in 94% of patients. The mini-open ALIF approach is a reasonable alternative to the more extensive posterior approaches. ALIF significantly restores the height of the intervertebral disc, indirectly increases foraminal dimensions, increases lordosis angle with significant short and long-term pain relief and functional recovery.

Cervical Interfacet Spacers to Promote Indirect Decompression and Enhance Fusion in Degenerative Spine: A Review

BACKGROUND

Among the posterior techniques, the use of cervical interfacet spacers (CISs) represents a promising technology whose potentialities are still being studied. The purpose of the present review was to assess the available data on CISs.

METHODS

A search on PubMed was performed. The search terms were "cervical interfacet spacers," "facet spacers," "DTRAX facet system," "Goel facet spacer," "pseudarthrosis," "cervical lordosis," "iatrogenic kyphosis," "cervical foraminal decompression," "cervical biomechanics," "atlantoaxial instability," and "subaxial instability."

RESULTS

Mechanical studies have shown that stand-alone CISs promoted stiffness in all directions, except for extension. Foraminal distraction was recorded in 86% of the cases. Clinical studies have shown that the use of CISs could promote successful arthrodesis, given the large surface area affected by fusion and decreasing the need for autografts. The effectiveness for the treatment of radiculopathy has been confirmed by several clinical studies. In a series of 154 levels of implanted CISs, no evidence of significant loss of cervical lordosis was identified. CISs could help in enhancing fusion in C1-C2 fixation.

CONCLUSIONS

Biomechanical studies on specimens showed a positive trend in increasing stiffness of the cervical spine, despite some controversial results. In clinical studies, facet distraction was shown to be a safe and valid option for clinical indirect decompression, although longer follow-up is required for confirmation. No evidence of the loss of cervical lordosis has been recorded. The long-term effects and CIS use in revision procedures as adjuvant implants to treat pseudarthrosis or atlantoaxial instability are currently under investigation, and further studies are needed.

Unplanned Second-Stage Decompression for Neurological Deterioration Caused by Central Canal Stenosis after Indirect Lumbar Decompression Surgery

Study Design

Prospective cohort study.

Purpose

This study aimed to identify risk factors for unplanned second-stage decompression for postoperative neurological deficit after indirect decompression using lateral lumbar interbody fusion (LLIF) with posterior fixation.

Overview of Literature

Indirect lumbar decompression with LLIF has been used as a minimally invasive alternative to direct decompression to treat degenerative lumbar diseases requiring neural decompression. However, evidence on the prevalence of neurological deficits caused by spinal canal stenosis after indirect decompression is limited.

Methods

This study included 158 patients (mean age, 71.13±7.98 years; male/female ratio, 67/91) who underwent indirect decompression with LLIF and posterior fixation. Indirect decompression was performed at 271 levels (mean level, 1.71±0.97). Logistic regression analysis was used to identify the risk factors for postoperative neurological deficits. The variables included were age, sex, body mass index, presence of primary diseases, diabetes mellitus, preoperative motor deficit, levels operated on, preoperative severity of lumbar stenosis, and preoperative Japanese Orthopedic Association (JOA) score.

Results

Postoperative neurological deficit due to spinal canal stenosis occurred in three patients (1.9%). Spinal stenosis due to hemodialysis (p<0.001), ligament ossification (p<0.001), presence of preoperative motor paralysis (p<0.001), low JOA score (p=0.004), and severe canal stenosis (p=0.02) were significantly more frequent in the paralysis group.

Conclusions

Severe preoperative canal stenosis and neurological deficit were identified as risk factors for postoperative neurological deterioration caused by spinal canal stenosis. Additionally, uncommon diseases, such as spinal stenosis due to hemodialysis and ligament ossification, increased the risk of postoperative neurological deficit; therefore, in such cases, indirect decompression is contraindicated.

Indirect foraminal decompression after anterior lumbar interbody fusion: a prospective radiographic study using a new pedicle-to-pedicle technique

BACKGROUND CONTEXT

A frequently quoted advantage of anterior lumbar interbody fusion (ALIF) is indirect foraminal decompression, although there are few studies substantiating this statement. Also, there are no clinical studies using a standardized method to measure the foraminal area (FA) and the correlation with disc height (DH) parameters. This study is proposed to measure the degree of indirect foraminal decompression radiologically using a standardized method and correlate with the intervertebral disc parameters.

PURPOSE

To standardize the foramen measurement technique. To measure indirect neural foraminal decompression in surgically operated patients after ALIF using radiographic measurement and elucidate factors affecting foraminal restoration.

STUDY DESIGN

A prospective cohort study.

PATIENT SAMPLE

A continuous cohort of patients undergoing ALIF surgery.

OUTCOME MEASURES

It included FA, foraminal height (FH), and foraminal width.

METHODS

This is a prospective analysis of a single surgeon series of consecutive patients undergoing an ALIF from 2011 to 2013. Pre- and postoperative computed tomography scans were used to obtain a standardized foramen snapshot using the pedicle-to-pedicle (P-P) technique, and measurements were obtained using image j software. Radiologic parameters such as DH, local disc angle (LDA), and lumbar lordosis (LL) were measured using radiographs and Surgimap software.

RESULTS

One-hundred forty patients with 184 levels were operated. Anterior lumbar interbody fusion resulted in a statistically significant (p<.01) improvement in foraminal dimensions (area=67%, height=21%, and width=38%). Other parameters also significantly improved, including anterior DH (90%), posterior DH (77%), LDA, and LL (6%). Posterior DH correlated significantly with FH improvement. Statistically, the P-P technique presented with high intra- and interclass reliabilities.

CONCLUSIONS

Anterior lumbar interbody fusion results in significant indirect foraminal decompression based on the new P-P technique. Posterior DH is a significant factor in the restoration of the FH.

Technical note: Resolution of spontaneous electromyographic discharge following disk-space distraction during lateral transpsoas interbody fusion

Purpose

The lateral transpsoas interbody fusion (LTIF) is an increasingly popular minimally invasive technique for lumbar interbody fusion. Although a posterior approach to the lumbar spine has traditionally been favored for the treatment of canal stenosis and neural foraminal stenosis, a growing body of evidence suggests that indirect decompression of the spinal canal and neural foramen can be achieved using a lateral transpsoas approach to the lumbar spine. We present 2 cases that may suggest a role for spontaneous electromyography (s-EMG) monitoring in assessing the adequacy of decompression during LTIF.

Methods

The 2 cases presented in this technical note illustrate resolution of s-EMG firing during LTIF, following distraction across the disk space. Removal of the distracting device produced the return of s-EMG firing. Both of these cases were operated at the L2-3 level.

Results

In the first case, s-EMG firing was noted in the bilateral tibialis anterior leads. Resolution of EMG firing may suggest indirect decompression of the canal via ligamentotaxis as the L5 root traverses the L2-3 disk space. In the second case, s-EMG firing was noted in the left abductor hallucis and resolved with distraction of the L2-3 disk space. Again, this may be explained by canal decompression via ligamentotaxis as the S1 root traverses the L2-3 disk space.

Conclusion

In both cases, distraction across the disk space resulted in resolution of s-EMG discharges—this correlated with an improvement in symptoms. These findings may suggest a role for s-EMG as a marker for adequacy of decompression in a select subset of patients undergoing LTIF. Further study is needed to determine if resolution of s-EMG is a useful measure of indirect decompression during LTIF.

Effects on inadvertent endplate fracture following lateral cage placement on range of motion and indirect spine decompression in lumbar spine fusion constructs: A cadaveric study

BACKGROUND

The lateral transpsoas approach to interbody fusion is gaining popularity. Existing literature suggests that perioperative vertebra-related complications include endplate breach owing to aggressive enedplate preparation and poor bone quality. The acute effects of cage subsidence on stabilization and indirect decompression at the affected level are unknown. The purpose of this study was to compare the kinematics and radiographic metrics of indirect decompression in lumbar spines instrumented with laterally placed cages in the presence of inadvertent endplate fracture, which was determined radiographically, to specimens instrumented with lateral cages with intact endplates.

METHODS

Five levels in 5 specimens sustained endplate fracture during lateral cage implantation followed by supplementary fixation (pedicle screw/rod [PSR]: n = 1; anterolateral plate [ALP]: n = 4), as part of a larger laboratory-based study. Range of motion (ROM) in these specimens was compared with 13 instrumented specimens with intact endplates. All specimens were scanned using computed tomography (CT) in the intact, noninstrumented condition and after 2-level cage placement with internal fixation under a 400-N follower load. Changes in disc height, foraminal area, and canal area were measured and compared between specimens with intact endplates and fractured endplates.

RESULTS

Subsidence in the single PSR specimen and 4 ALP specimens was 6.5 mm and 4.3 ± 2.7 mm (range: 2.2-8.3 mm), respectively. ROM was increased in the PSR and ALP specimens with endplate fracture when compared with instrumented specimens with intact endplates. In 3 ALP specimens with endplate fracture, ROM in some motion planes increased relative to the intact, noninstrumented spine. These increases in ROM were paralleled by increase in cage translations during cyclic loading (up to 3.3 mm) and an unpredictable radiographic outcome with increases or decreases in posterior disc height, foraminal area, and canal area when compared with instrumented specimens with intact endplates.

CONCLUSIONS

Endplate fracture and cage subsidence noted radiographically intraoperatively or in the early postoperative period may be indicative of biomechanical instability at the affected level concomitant with a lack of neurologic decompression, which may require revision surgery.

A novel computer algorithm allows for volumetric and cross-sectional area analysis of indirect decompression following transpsoas lumbar arthrodesis despite variations in MRI technique

Many patients present for neurosurgical spine evaluation with MRI studies conducted at facilities outside of the treating medical center. These images often vary widely in technique, for example, variation in slice thickness, number of slices, and gantry angle. While these images may be sufficient in conjunction with a physical exam to make surgical evaluations, we have found they are often incapable of being used for objective post-operative volumetric comparisons. In order to overcome this, we created a computer program that compensates for these variations in MRI technique. For this study, we examined patients who had undergone outside MRI pre-operatively and were deemed appropriate for a lateral retroperitoneal transpsoas lumbar interbody arthrodesis procedure. Volumetric analysis was performed on sagittal and axial T2-weighted pre- and post-operative MRI. The percentage change of central canal volume and foraminal area was calculated for each level. The authors identified five levels with MRI sufficient for volumetric analysis and eight levels (16 foramina) sufficient for foraminal cross-sectional analysis. Through use of our computer algorithm, average central canal volume and foraminal cross-sectional area was calculated to increase by 32.8% and 67.6% respectively following the procedure. These results are consistent with previous study findings and support the idea that restoration of the anterior column via a lateral approach can result in significant indirect decompression of the neural elements. Additionally, the novel algorithm created and used for this study suggests that it can achieve quick measurement and comparison of MRI studies despite variations in pre- and post-operative technique.