Biomechanical Comparison of Subsidence Between Patient-Specific and Non-Patient-Specific Lumbar Interbody Fusion Cages

STUDY DESIGN

Biomechanical study.

OBJECTIVES

Several strategies to improve the surface of contact between an interbody device and the endplate have been employed to attenuate the risk of cage subsidence. 3D-printed patient-specific cages have been presented as a promising alternative to help mitigate that risk, but there is a lack of biomechanical evidence supporting their use. We aim to evaluate the biomechanical performance of 3D printed patient-specific lumbar interbody fusion cages in relation to commercial cages in preventing subsidence.

METHODS

A cadaveric model is used to investigate the possible advantage of 3D printed patient-specific cages matching the endplate contour using CT-scan imaging in preventing subsidence in relation to commercially available cages (Medtronic Fuse and Capstone). Peak failure force and stiffness were analyzed outcomes for both comparison groups.

RESULTS

PS cages resulted in significantly higher construct stiffness when compared to both commercial cages tested (>59%). PS cage peak failure force was 64% higher when compared to Fuse cage (P < .001) and 18% higher when compared to Capstone cage (P = .086).

CONCLUSIONS

Patient-specific cages required higher compression forces to produce failure and increased the cage-endplate construct' stiffness, decreasing subsidence risk.

Lumbar Disc Replacement Versus Interbody Fusion: Meta-analysis of Complications and Clinical Outcomes

Background

Lumbar spinal fusion is a commonly performed operation with relatively high complication and revision surgery rates. Lumbar disc replacement is less commonly performed but may have some benefits over spinal fusion. This meta-analysis aims to compare the outcomes of lumbar disc replacement (LDR) versus interbody fusion (IBF), assessing their comparative safety and effectiveness in treating lumbar DDD.

Methods

PubMed, Cochrane, and Google Scholar (pages 1-2) were searched up until February 2024. The studied outcomes included operative room (OR) time, estimated blood loss (EBL), length of hospital stay (LOS), complications, reoperations, Oswestry Disability Index (ODI), back pain, and leg pain.

Results

Ten studies were included in this meta-analysis, of which six were randomized controlled trials, three were retrospective studies, and one was a prospective study. A total of 1720 patients were included, with 1034 undergoing LDR and 686 undergoing IBF. No statistically significant differences were observed in OR time, EBL, or LOS between the LDR and IBF groups. The analysis also showed no significant differences in the rates of complications, reoperations, and leg pain between the two groups. However, the LDR group demonstrated a statistically significant reduction in mean back pain (p=0.04) compared to the IBF group.

Conclusion

Both LDR and IBF procedures offer similar results in managing CLBP, considering OR time, EBL, LOS, complication rates, reoperations, and leg pain, with slight superiority of back pain improvement in LDR. This study supports the use of both procedures in managing degenerative spinal disease.

[Effectiveness of injured vertebra fixation with inclined-long pedicle screws combined with interbody fusion for thoracolumbar fracture dislocation with disc injury]

Objective

To investigate the effectiveness of injured vertebra fixation with inclined-long pedicle screws combined with interbody fusion for thoracolumbar fracture dislocation with disc injury.

Methods

Between January 2017 and June 2022, 28 patients with thoracolumbar fracture dislocation with disc injury were underwent posterior depression, the injured vertebra fixation with inclined-long pedicle screws, and interbody fusion. There were 22 males and 6 females, with a mean age of 41.4 years (range, 22-58 years). The causes of injury included falling from height in 18 cases, traffic accident in 5 cases, and bruise in 5 cases. Fracture segment included 1 case of T 11, 7 cases of T 12, 9 cases of L 1, and 11 cases of L 2. According to the American Spinal Injury Association (ASIA) scale, the spinal injuries were graded as grade A in 4 cases, grade B in 2 cases, grade C in 11 cases, and grade D in 11 cases. Preoperative spinal canal encroachment ratio was 17.7%-75.3% (mean, 44.0%); the thoracolumbar injury classification and severity score (TLICS) ranged from 9 to 10 (mean, 9.9). Seventeen patients were associated with other injuries. The time from injury to operation ranged from 1 to 4 days (mean, 2.3 days). The perioperative indicators (operation time, intraoperative blood loss, and the occurrence of complications), clinical evaluation indicators [visual analogue scale (VAS) score and Oswestry Disability Index (ODI)], radiologic evaluation indicators [anterior vertebral height ratio (AVHR), kyphosis Cobb angle (KCA), intervertebral space height (ISH), vertebral wedge angle (VWA), displacement angle (DA), and percent fracture dislocation displacement (PFDD)], neurological function, and interbody fusion were recorded.

Results

The operation time was 110-159 minutes (mean, 130.2 minutes). The intraoperative blood loss was 200-510 mL (mean, 354.3 mL). All incisions healed by first intention, and no surgical complications such as wound infection or hematoma occurred. All patients were followed up 12-15 months (mean, 12.7 months). The chest and lumbar pain significantly relieved, VAS scores and ODI after operation were significantly lower than those before operation, and further decreased with the extension of postoperative time, with significant differences ( P<0.05). At last follow-up, the ASIA classification of neurological function of the patients was grade A in 3 cases, grade B in 1 case, grade C in 1 case, grade D in 10 cases, and grade E in 13 cases, which was significantly different from preoperative one ( Z=-4.772, P<0.001). Imaging review showed that AVHR, KCA, ISH, VWA, DA, and PFDD significantly improved at 1 week, 3 months and last follow-up ( P<0.05). There was no significant difference between different time points after operation ( P>0.05). At last follow-up, according to the modified Brantigan score, all patients achieved good intervertebral bone fusion, including 22 complete fusion and 6 good intervertebral fusion with a few clear lines. No complications such as internal fixation failure or kyphosis occurred during follow-up.

Conclusion

The injured vertebra fixation with inclined-long pedicle screws combined with interbody fusion is an effective treatment for thoracolumbar fracture dislocation with disc injury, which can correct the fracture dislocation, release the nerve compression, restore the injured vertebral height, and reconstruct spinal stabilization.

Early Experience with Prone Lateral Interbody Fusion in Deformity Correction: A Single-Institution Experience

Background/Objectives: Lateral spine surgery offers effective minimally invasive deformity correction, but traditional approaches often involve separate anterior, lateral, and posterior procedures. The prone lateral technique streamlines this process by allowing single-position access for lateral and posterior surgery, potentially benefiting from the lordosing effect of prone positioning. While previous studies have compared prone lateral to direct lateral for adult degenerative diseases, this retrospective review focuses on the outcomes of adult deformity patients undergoing prone lateral interbody fusion. Methods: Ten adult patients underwent single-position prone lateral surgery for spine deformity correction, with a mean follow-up of 18 months. Results: Results showed significant improvements: sagittal vertical axis decreased by 2.4 cm, lumbar lordosis increased by 9.1°, pelvic tilt improved by 3.3°, segmental lordosis across the fusion construct increased by 12.2°, and coronal Cobb angle improved by 6.3°. These benefits remained consistent over the follow-up period. Correlational analysis showed a positive association between improvements in PROs and SVA and SL. When compared to hybrid approaches, prone lateral yielded greater improvements in SVA. Conclusions: Prone lateral surgery demonstrated favorable outcomes with reasonable perioperative risks. However, further research comparing this technique with standard minimally invasive lateral approaches, hybrid, and open approaches is warranted for a comprehensive evaluation.

Biphasic Calcium Phosphate Bone Graft With a Unique Surface Topography: A Single-Center Ambispective Study for Degenerative Disease of the Lumbar Spine

STUDY DESIGN

This study is an ambispective evaluation and analysis of a single-center cohort.

OBJECTIVE

This study aimed to evaluate the performance of a novel biphasic calcium phosphate (BCP) bone graft with submicron-sized needle-shaped surface topography (BCP<µm) in interbody arthrodesis of the lumbar spine.

METHODS

This study was a single-center ambispective assessment of adult patients receiving BCP<µm as part of their lumbar interbody fusion surgery. The primary outcome was a fusion status on computed tomography (CT) 12 months postoperative. The secondary outcomes included postoperative changes in the visual analog scale (VAS), Oswestry Disability Index (ODI), Short Form 12 (SF-12), and length of stay (LOS).

RESULTS

Sixty-three patients with one- to three-level anterior (48, 76%) and lateral (15, 24%) interbody fusions with posterior instrumentation were analyzed. Thirty-one participants (49%) had three or more comorbidities, including heart disease (43 participants, 68%), obesity (31 participants, 49%), and previous lumbar surgery (23 participants, 37%). The mean ODI decreased by 24. The mean SF-12 physical health and SF-12 mental health improved by a mean of 11.5 and 6.3, respectively. The mean VAS for the left leg, right leg, and back improved by a mean of 25.75, 22.07, and 37.87, respectively. Of 101 levels, 91 (90%) demonstrated complete bridging trabecular bone fusion with no evidence of supplemental fixation failure.

CONCLUSION

The data of BCP<µm in interbody fusions for degenerative disease of the lumbar spine provides evidence of fusion in a complicated cohort of patients.

Interim 1-Year Radiographic and Clinical Outcomes Following Anterior Cervical Discectomy and Fusion Using Hydroxyapatite-Infused Polyetheretherketone Interbody Cages

BACKGROUND

This is a multicenter observational registry analysis of 1-year radiographic and clinical outcomes following anterior cervical discectomy and fusion (ACDF) using hydroxyapatite (HA)-infused polyetheretherketone (PEEK) intervertebral cages.

METHODS

Radiographic and clinical outcome data were collected preoperatively and at 6 weeks, 3 months, 6 months, and 12 months postoperatively. To assess fusion, dynamic flexion-extension radiographs were independently evaluated with a validated method. Clinical outcomes were assessed using the following disease-specific measures: Neck Disability Index (NDI) and visual analog scale (VAS) for neck, left arm, and right arm pain. Patient satisfaction was also evaluated.

RESULTS

A total of 789 ACDF patients (men: 51.5%/women: 48.5%; mean body mass index: 29.9 kg/m2) were included at the time of analysis, and 1565 segments have been operated. Successful fusion was confirmed in 91.3% of all operated levels after 6 months and 92.2% after 12 months. Mean NDI scores improved significantly (P < 0.01) preoperatively (46.3, n = 771) to postoperatively (12 months: 25.2, n = 281). Consistently, mean VAS neck (preoperative: 64.2, n = 770; 12 months: 28.6, n = 278), VAS right arm (preoperative: 42.6, n = 766; 12 months: 20.4, n = 277), and VAS left arm (preoperative: 41.1, n = 768; 12 months: 20.8, n = 277) decreased significantly (P < 0.01). Patients reported high satisfaction rates after surgery with no significant changes in postoperative patient satisfaction between 6 weeks and 12 months (95.1%, n = 273).

CONCLUSIONS

ACDF with HA-infused PEEK cages demonstrates promising radiographic and clinical outcomes, supporting the potential benefits of incorporating HA into PEEK cages to enhance fusion rates and improve patient outcomes.

CLINICAL RELEVANCE

This study demonstrates a >90% fusion rate by level with reliable improvements in patient reported outcomes, along with a high rate of patient satisfaction, in a large patient cohort undergoing ACDF with HA-infused PEEK cages.

LEVEL OF EVIDENCE

2 .

Preoperative and Postoperative Segmental and Overall Range of Motion in Patients Undergoing Lumbar Spinal Fusion Using HA-Infused PEEK and HA-Treated Titanium Alloy Interbody Cages

STUDY DESIGN

Retrospective observational radiographic analysis.

OBJECTIVE

Determine how single level lumbar interbody fusion (LIF) alters segmental range of motion (ROM) at adjacent levels and decreases overall ROM.

METHODS

This study included 54 patients who underwent single-level anterior (ALIF, 39%), thoraco-LIF (TLIF, 26%), posterior LIF (PLIF, 22%), or lateral LIF (LLIF, 13%) (L2-3/L3-4/L4-5/L5-S1: 4%/13%/35%/48%). Segmental ROM from L1-2 to L5-S1 and the overall lumbar ROM (L1-S1) were assessed from preoperative and postoperative flexion-extension radiographs. K-means cluster analysis was used to identify ROM subgroups.

RESULTS

The overall L1-S1 ROM decreased 14% (25.5 ± 20.4° to 22.0 ± 17.2°, P = .104) postoperatively. ROM at the fusion level decreased 77% (4.8 ± 5.0° to 1.1 ± 1.1°, P < .001). Caudal adjacent segment ROM decreased 12% (5.2 ± 5.7° to 4.6 ± 4.4°, P = .345) and cranially ROM increased 34% (4.3 ± 5.0° to 5.7 ± 5.7°, P = .05). K-cluster analysis identified 3 distinct clusters (P < .05). Cluster 1 lost more ROM and had less improvement in patient-reported outcomes measures (PROMs) than average. Cluster 2 had less ROM loss than average with worse PROMs improvement. Cluster 3 did not have changes in ROM and better improvement in PROMs than average. Successful fusion was verified in 96% of all instrumented segments with >6 months follow-up (ROM <4°).

CONCLUSION

Following single-level L IF, patients should expect a loss of 3.3°, or 14% of overall lumbar motion with increases in ROM of the cranial segment. However, specific clusters of patients exist that experience different relative changes in ROM and PROMs.

Analysis of Personalized Interbody Implants in the Surgical Treatment of Adult Spinal Deformity

STUDY DESIGN

Multicenter cohort.

OBJECTIVES

A report from the International Spine Study Group (ISSG) noted that surgeons failed to achieve alignment goals in nearly two-thirds of 266 complex adult deformity surgery (CADS) cases. We assess whether personalized interbody spacers are associated with improved rates of achieving goal alignment following adult spinal deformity (ASD) surgery.

METHODS

ASD patients were included if their surgery utilized 3D-printed personalized interbody spacer(s) and they met ISSG CADS inclusion criteria. Planned alignment was personalized by the surgeon during interbody planning. Planned vs achieved alignment was assessed and compared with the ISSG CADS series that used stock interbodies.

RESULTS

For 65 patients with personalized interbodies, 62% were women, mean age was 70.3 years (SD = 8.3), mean instrumented levels was 9.9 (SD = 4.1), and the mean number of personalized interbodies per patient was 2.2 (SD = .8). Segmental alignment was achieved close to plan for levels with personalized interbodies, with mean difference between goal and achieved as follows: intervertebral lordosis = .9° (SD = 5.2°), intervertebral coronal angle = .1° (SD = 4.7°), and posterior disc height = -0.1 mm (SD = 2.3 mm). Achieved pelvic incidence-to-lumbar lordosis mismatch (PI-LL) correlated significantly with goal PI-LL (r = .668, P < .001). Compared with the ISSG CADS cohort, utilization of personalized interbodies resulted in significant improvement in achieving PI-LL <5° of plan (P = .046) and showed a significant reduction in cases with PI-LL >15° of plan (P = .012).

CONCLUSIONS

This study supports use of personalized interbodies as a means of better achieving goal segmental sagittal and coronal alignment and significantly improving achievement of goal PI-LL compared with stock devices.

Anterior Fusion and Long-Term Cervical Mobility in Patients With Traumatic Spinal Cord Injury: An Observational Study

Objective This study aims to determine and quantify the impairment of cervical mobility and range of motion in patients with traumatic spinal cord injury (SCI) and subsequent cervical subaxial fusion surgery. Methods A total of 89 patients who underwent interbody fusion of the cervical spine and were admitted to the Spinal Cord Injury Center of the BG Klinikum Hamburg, Germany between 2003 and 2018 were examined after their in-facility rehabilitation was successfully completed. Reclination, inclination, tilt, and rotation of the cervical spine were examined and documented in addition to overall patient characteristics and fusion extent. Results We could identify fusion length and age to be independently negatively correlated with the cervical range of motion in different degrees of movement. We could also show a significant decrease in cervical mobility within our patients when compared to healthy adults. The ability to tilt and rotate the cervical spine was particularly impaired. Conclusions Patients with traumatic SCI and intervertebral fusion suffer from significant impairment of mobility in different degrees of movement. This knowledge can be used to evaluate the rehabilitative challenges and reintegrative needs of individuals after traumatic SCI. Rehabilitation should be adjusted accordingly.

Comparison of Opioid Consumption Patterns of Three Interbody Fusion Surgical Techniques

STUDY DESIGN

Retrospective review.

OBJECTIVES

With increased awareness of the opioid crisis in spine surgery, the focus postoperatively has shifted to managing surgical site pain while minimizing opioid use. Numerous studies have compared outcomes and fusion status of different interbody fusion techniques; however, there is limited literature evaluating opioid consumption postoperatively between techniques. The aim of this study was to assess in-house and postoperative opioid consumption across 3 surgical techniques.

METHODS

Patients were stratified by technique: posterior lumbar interbody fusion (PLIF), minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF), and cortical screw (CS) instrumentation with interbody fusion. Age, ASA, BMI, depression, preoperative opioid use, EBL, and OR time were recorded and compared across surgical groups using Welch's ANOVA and chi-square analysis. Total morphine equivalent dose (MED) was tabulated for both in-house consumption and postoperative prescriptions and was compared across surgical techniques using Welch's ANOVA analysis, Mann Whitney U tests, and linear regression.

RESULTS

Two hundred and thirty nine patients underwent one- or two-level posterior lumbar interbody fusion between 2016 and 2020. One hundred and twenty one patients underwent CS instrumentation, 95 underwent PLIF, and 83 underwent MIS-TLIF. There was a significantly higher percentage of patients who had a history of depression and preoperative opioid consumption in the CS group (P = .001, P = .009). CS instrumentation required significantly less total post-op opioids per kilogram bodyweight compared to MIS-TLIF and PLIF surgeries (P = .029).

CONCLUSIONS

Patients who underwent CS instrumentation required less opioids postoperatively. CS instrumentation may be associated with less postoperative pain due to the less invasive approach, however, patient education and prescriber practice also play a role in postoperative opioid consumption.

Outcomes of 2-Level versus 3- or 4-Level Anterior Cervical Discectomy and Fusion Using a Biomimetic Surface Titanium Cage: Multicenter Experience

OBJECTIVE

Interbody cages for spinal fusions are primarily constructed from polyetheretherketone or titanium compositions. However, these crude macroscopic materials pose limitations for improving the rates of bony fusions. The authors aimed to compare the fusion rates and postoperative complications in patients who underwent 2-level or 3-or 4-level anterior cervical discectomy and fusion (ACDF) performed with the use of a novel biomimetic surface titanium cage.

METHODS

A retrospective, multicenter study was conducted that included all patients who underwent multilevel ACDF with this cage between January 2017 and April 2021. Patient demographics and procedure-related, radiographic, and postoperative complication data were collected.

RESULTS

A total of 124 patients were identified; 69 (55.6%) had a 3-or 4-level fusion and 55 (44.4%) had a 2-level fusion. The demographics of the two groups differed significantly only in terms of age (p=.01). At 3 months, a significantly higher solid fusion rate was found for 2-level fusions than 3-or 4-level fusions (83.7% vs. 56.3%, p=.004); however, significance was lost at 6-months (98.2% vs. 88.4%, respectively; p=.08). No patients required posterior supplemental fixation. Transient dysphagia was the only postoperative complication that was significantly increased in the 3-or 4-level fusion group compared to the 2-level group (27.5% vs. 9.1%, p=.02).

CONCLUSIONS

Radiographic and clinical outcomes were equivalent in 3-or 4-level and 2-level ACDFs in which these biomimetic surface titanium cages were used. Furthermore, the use of this technology led to high fusion rates with no requirement for posterior supplemental fusions.

Transforaminal Interbody Fusion Using the Unilateral Biportal Endoscopic Technique Compared With Transforaminal Lumbar Interbody Fusion for the Treatment of Lumbar Spine Diseases: Analysis of Clinical and Radiological Outcomes

BACKGROUND

There has been a widespread application of minimally invasive spinal surgery techniques in the past few years. Unilateral biportal endoscopic has been successfully used in a variety of lumbar spine diseases, but there are few studies on lumbar fusion assisted by unilateral biportal endoscopy.

OBJECTIVE

To compare the clinical and radiological outcomes of transforaminal interbody fusion using the unilateral biportal endoscopic technique (UBEIF) and transforaminal lumbar interbody fusion (TLIF) in patients with lumbar disease.

METHODS

We studied 128 patients, 58 in the UBEIF group and 70 in the TLIF group. The Oswestry disability index, creatine kinase, visual analog score (VAS) for leg and back pain were used to assess clinical outcomes. Radiographic outcomes were assessed using the fusion rate, internal fixation loosening, and adjacent segment degeneration.

RESULTS

Back and leg pain VAS scores in both groups were significantly lower 3, 6, and 12 months after surgery ( P < .05). A significant reduction in Oswestry disability index in both groups was observed 6 and 12 months after surgery ( P < .05). Compared with the TLIF group at 1 week after surgery, UBEIF patients' VAS score for back pain significantly improved ( P < .05). There was no difference in fusion rate between the 2 groups (98.27% vs 98.57%).

CONCLUSION

UBEIF and TLIF have similar clinical and radiographic outcomes in the treatment of single-segment lumbar disease with lumbar instability, including improved back and leg pain, improved disability, and high fusion rates. Furthermore, with UBEIF, less blood is lost, there is better relief of early back pain, and hospital stays are shorter.

Interbody fusion cage design driven by topology optimization

OBJECTIVE

We used topology optimization technology to explore the new theory and method of interbody fusion cage design and realized an innovative design of interbody cages.

METHODS

The lumbar spine of a normal healthy volunteer was scanned to perform reverse modeling. Based on the scan data for the L1-L2 segments of the lumbar spine, a 3D model was reconstructed to obtain the complete simulation model of the L1-L2 segment. The boundary inversion method was used to obtain approximately isotropic material parameters that can effectively characterize the mechanical behavior of vertebrae, thereby reducing the computational complexity. The topology description function was used to model the clinically used traditional fusion cage to obtain Cage A. The moving morphable void-based topology optimization method was used for the integrated design of size, shape, and topology to obtain the optimized fusion cage, Cage B.

RESULTS

The volume fraction of the bone graft window in Cage B was 74.02%, which was 60.67% higher than that (46.07%) in Cage A. Additionally, the structural strain energy in the design domain of Cage B was 1.48 mJ, which was lower than that of Cage A (satisfying the constraints). The maximum stress in the design domain of Cage B was 5.336 Mpa, which was 35.6% lower than that (8.286 Mpa) of Cage A. In addition, the surface stress distribution of Cage B was more uniform than that of Cage A.

CONCLUSION

This study proposed a new innovative design method for interbody fusion cages, which not only provides new insights into the innovative design of interbody fusion cages but may also guide the customized design of interbody fusion cages in different pathological environments.

Which Approach Leads to More Reoperations in Single-Level, Open, Posterior Lumbar Fusion: Transforaminal Lumbar Interbody Fusion or Posterolateral Fusion Alone?

BACKGROUND

Transforaminal lumbar interbody fusion (TLIF) and posterolateral fusion (PLF) without an interbody device are two common approaches for single-level, open posterior fusion. Presently, it is unknown whether one of these operations leads to better outcomes. We sought to compare reoperation, complication, and readmission rates between TLIF and PLF for patients undergoing elective single-level, open, posterior lumbar fusion.

METHODS

A single-center, retrospective cohort study utilizing prospectively collected data was performed. Inclusion criteria were patients undergoing elective single-level, open, posterior lumbar decompression and fusion between October 2010 and April 2021 with at least 1-year follow-up. The two comparison groups were TLIF vs PLF alone without interbody. The primary outcome was need for reoperation at most recent follow-up. Secondary outcomes included 90-day complication and readmission rates. Univariate and multivariable logistic regression analyses were performed.

RESULTS

A total of 850 patients were included, 591 (69.5%) of whom underwent TLIF and 259 (30.5%) of whom underwent PLF. Median follow-up was 6.1 years (interquartile range 3.7-8.9). No significant difference was found in overall reoperation rates (12.4% vs 13.9%, P = 0.534). When stratified by <5-year follow-up (n = 231 TLIF, n = 85 PLF; 37.2%) and ≥5-year follow-up (n = 360 TLIF, n = 174 PLF; 62.8%), no significant differences were seen in either cohort (<5 years: n = 24 TLIF vs n = 9 PLF, P = 0.959; 5+ years: n = 49 TLIF vs n = 27 PLF, P = 0.555). On multivariable logistic regression analysis, the presence of interbody fusion was not associated with reoperation (OR 2.26, 95% CI 0.66-7.74, P = 0.194).

CLINICAL RELEVANCE

For patients undergoing elective single-level, open, posterior lumbar fusion without isthmic spondylolisthesis, no differences were seen in reoperation rates at long-term follow-up. Similar 90-day complication and readmission rates were seen. These results suggest that in degenerative lumbar spine disease without isthmic spondylolisthesis, TLIF and PLF achieved similar outcomes.

LEVEL OF EVIDENCE: 3

How Much Blood Loss Is Too Much for a 1-Level Open Lumbar Fusion?

BACKGROUND

Despite the known association between increased estimated blood loss (EBL) and suboptimal perioperative outcomes, the exact threshold of EBL that impacts outcomes following elective spine surgery remains unknown. In a cohort of patients undergoing elective 1-level open posterior lumbar fusion, we sought to identify EBL thresholds associated with: (1) prolonged length of stay (LOS), (2) postoperative complications, and (3) patient-reported outcomes (PROs).

METHODS

A retrospective, single-center study was performed of patients undergoing elective, 1-level open posterior lumbar fusion with and without interbody fusion between October 2010 and April 2021. The primary exposure variable was EBL. Primary outcomes included: (1) LOS, (2) 30-day complications, and (3) 3-month PROs. Minimum clinically important difference was set at 30% improvement from baseline. For purposes of receiver-operating characteristic curves, LOS was dichotomized as 1 vs ≥2 days.

RESULTS

Of the 2028 patients undergoing posterior lumbar fusion surgery, 1183 underwent 1-level fusions, 763 (64.5%) with interbody fusion and 420 (35.5%) without. With interbody fusion: Median (interquartile range [IQR]) EBL was 350 mL (200-600), and median (IQR) LOS was 2 days (2-3). A positive linear association was found between EBL and LOS (P < 0.001) but not with PROs. EBL above 275 mL was associated with LOS beyond postoperative day 1 (POD1) (area under the curve [AUC] = 0.73, 95% CI 0.68-0.78, P < 0.001), with no significant association with overall complications or PROs. Without interbody fusion: Median EBL (IQR) was 300 mL (150-500), and median (IQR) LOS was 3 days (2-4). A positive linear association was found between EBL and LOS (P < 0.001) but not with PROs. EBL above 238 mL was associated with LOS beyond POD1 (AUC = 0.78, 95% CI 0.71-0.85, P < 0.001), with no impact on overall complications or PROs.

CONCLUSIONS

In patients undergoing 1-level posterior lumbar fusion, EBL volumes greater than 275 and 238 mL in patients with and without interbody fusion, respectively, were associated with increased LOS beyond POD1. No effect was found regarding 30-day complications and 3-month PROs. Although EBL did not directly impact complications or PROs, surgeons may expect longer LOS when higher EBL is reported.

CLINICAL RELEVANCE

EBL above 275 mL with an interbody and 238 mL without an interbody were associated with prolonged LOS beyond POD1 in 1-level open lumbar fusion.

LEVEL OF EVIDENCE: 3

Electroactive Spinal Instrumentation for Targeted Osteogenesis and Spine Fusion: A Computational Study

BACKGROUND

Direct current electrical stimulation may serve as a promising nonpharmacological adjunct promoting osteogenesis and fusion. The aim of this study was to evaluate the utility of electroactive spine instrumentation in the focal delivery of therapeutic electrical stimulation to enhance lumbar bone formation and interbody fusion.

METHODS

A finite element model of adult human lumbar spine (L4-L5) instrumented with single-level electroactive pedicle screws was simulated. Direct current electrical stimulation was routed through anodized electroactive pedicle screws to target regions of fusion. The electrical fields generated by electroactive pedicle screws were evaluated in various tissue compartments including isotropic tissue volumes, cortical, and trabecular bone. Electrical field distributions at various stimulation amplitudes (20-100 µA) and pedicle screw anodization patterns were analyzed in target regions of fusion (eg, intervertebral disc space, vertebral body, and pedicles).

RESULTS

Electrical stimulation with electroactive pedicle screws at various stimulation amplitudes and anodization patterns enabled modulation of spatial distribution and intensity of electric fields within the target regions of lumbar spine. Anodized screws (50%) vs unanodized screws (0%) induced high-amplitude electric fields within the intervertebral disc space and vertebral body but negligible electric fields in spinal canal. Direct current electrical stimulation via anodized screws induced electrical fields, at therapeutic threshold of >1 mV/cm, sufficient for osteoinduction within the target interbody region.

CONCLUSIONS

Selective anodization of electroactive pedicle screws may enable focal delivery of therapeutic electrical stimulation in the target regions in human lumbar spine. This study warrants preclinical and clinical testing of integrated electroactive system in inducing target lumbar fusion in vivo.

CLINICAL RELEVANCE

The findings of this study provide a foundation for clinically investigating electroactive intrumentation to enhance spine fusion.

LEVEL OF EVIDENCE: 5

Biportal endoscopic decompression, debridement, and interbody fusion, combined with percutaneous screw fixation for lumbar brucellosis spondylitis

Objective

This study aims to investigate the effectiveness and feasibility of biportal endoscopic decompression, debridement, and interbody fusion, combined with percutaneous screw fixation for lumbar brucellosis spondylitis (LBS).

Methods

The data of 13 patients with LBS were retrospectively analyzed, who underwent biportal endoscopic decompression, debridement, and interbody fusion, combined with percutaneous screw fixation from May 2020 to June 2022. The patients' clinical data, the duration of operation, the estimated blood loss (including postoperative drainage), and complications were recorded. Clinical outcomes include serum agglutination test (SAT) measures Brucella antibody titer, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), the visual analog scale (VAS) scores of low back and leg, Japanese Orthopaedic Association (JOA) score, Oswestry Disability Index (ODI), American Spinal Injury Association neurological classification, and lordotic angle were analyzed. All patients were assessed using the modified Macnab criteria at the final follow-up. The intervertebral bone graft fusion was assessed using the Bridwell grading criteria.

Results

The mean operation duration was 177.31 ± 19.54 min, and the estimated blood loss was 176.15 ± 43.79 ml (including postoperative drainage was 41.15 ± 10.44 ml). The mean follow-up period was 13.92 ± 1.5 months. SAT showed that the antibody titers of 13 patients were normal 3 months after the operation and at the final follow-up. ESR and CRP levels returned to normal by the end of the 3-month follow-up. VAS scores of low back and leg, JOA score, and ODI significantly improved after the operation throughout the follow-up period (P < 0.05). Based on the modified Macnab criteria, 92.3% showed excellent to good outcomes. One patient had only a percutaneous screw internal fixation on the decompression side due to severe osteoporosis. One case suffered a superficial incision infection postoperatively that healed with dressing change and effective antibiotic treatment. Bony fusion was obtained in all patients at the last follow-up, including 12 cases with grade I and 1 case with grade II, with a fusion rate of 92.31%.

Conclusion

Biportal endoscopic decompression, debridement, and interbody fusion, combined with percutaneous screw fixation is an effective, safe, and viable surgical procedure for the treatment of LBS.

The Significance of Extra-Cage Bridging Bone via Radiographic Lumbar Interbody Fusion Criterion

STUDY DESIGN

Prospective observational study.

OBJECTIVES

We aimed to analysis the distributional patterns of the intra- and extra-cage bridging bone (InCBB and ExCBB) and the significance of ExCBB using suggested lumbar interbody fusion criterion.

METHODS

This study included the patients with planned single-level transforaminal lumbar interbody fusion. We divided bridging bone into InCBB (in void of right or left cage) and ExCBB (outside of cages; anterior, posterior, intermediate, right, or left) and graded bridging scores from 0 to 2 on postoperative 1-year computed tomography. The fusion was defined as at least having one or more graded 2 and the evaluation were conducted twice by 2 raters.

RESULTS

Sixty-five patients were enrolled. All values of intra- and inter-rater reliability in left InCBB, anterior, and posterior ExCBB showed good agreements (≥0.75). Both InCBBs showed similar mean bridging scores (Rt:1.43 vs Lt:1.48), and in ExCBBs, the anterior was the highest (1.43), followed by the posterior (1.14); the right and left were the lowest (0.49 and 0.52 respectively). In subjects determined as fusion (85.4%), complete bridging was observed more in ExCBB (88.8%) than in InCBB (69.9%).

CONCLUSIONS

Given the higher bridging scores in both InCBBs and Ant. ExCBB, bone grafting is important promoting factor to increase the interbody bridging bone regardless of outside or in void of cages. Based on our suggested criterion, ExCBB has a greater proportion compared to InCBBs for determining the fusion and extra-cage bone grafting should be considered as important procedures for interbody fusion.

Role of Surgery in Brucella Spondylodiscitis: An Evaluation of 28 Patients

Background A limited number of studies are available in the literature on the surgical treatment of brucellosis-related spondylodiscitis. This study aimed to define and discuss the role of surgery in brucellosis-related spondylodiscitis. Methodology A total of 28 patients who underwent surgical treatment due to brucellosis-related spondylodiscitis between February 2021 and August 2022 were included in this study. Medical records, radiological images, and laboratory data were collected. Surgical results were evaluated according to the Visual Analog Scale (VAS) and Oswestry Disability Index (ODI). C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) levels, clinical findings, postoperative radiological imaging findings, and complications were evaluated. Results In total, 16 of the patients included in the study were male and 12 were female, with a mean age of 56.4 ± 7.2 years. The mean follow-up duration was 11.8 ± 5.4 months. Brucellosis involvement was in the lumbosacral region in all patients. Overall, 21 patients had a neurological deficit in the preoperative period. Posterior stabilization and fusion were done in 20 (71.4%) patients, while simple laminectomy (decompression) and debridement were done in eight (28.6%) patients. There was a decrease in the pain in the lower back and leg in all patients in the postoperative period. Neurological recovery was achieved in 18 patients with a neurological deficit. Two patients underwent wound drainage in the postoperative period. The patient who had morbid obesity and comorbidities died in the postoperative period. ESR and CRP levels returned to normal at the end of the six-month follow-up. There was a significant recovery in VAS and ODI scores (p < 0.05). In total, 24 (85.4%) patients were considered fully recovered both radiologically and clinically at the end of the follow-up. Conclusions Although long-term and specific antibiotic treatment constitute the main treatment in brucellosis-related spondylodiscitis, debridement, decompression, and stabilization (when required) of infection with a focus on neurological deficits and instability formation and non-stop severe pain are effective and safe treatment options.

Comparisons of oblique lumbar interbody fusion and transforaminal lumbar interbody fusion for degenerative spondylolisthesis: a prospective cohort study with a 2-year follow-up

Objective

This study aimed to compare the clinical outcomes between oblique (OLIF) and transforaminal lumbar interbody fusion (TLIF) for patients with degenerative spondylolisthesis during a 2-year follow-up.

Methods

Patients with symptomatic degenerative spondylolisthesis who underwent OLIF (OLIF group) or TLIF (TLIF group) were prospectively enrolled in the authors' hospital and followed up for 2 years. The primary outcomes were treatment effects [changes in visual analog score (VAS) and Oswestry disability index (ODI) from baseline] at 2 years after surgery; these were compared between two groups. Patient characteristics, radiographic parameters, fusion status, and complication rates were also compared.

Results

In total, 45 patients were eligible for the OLIF group and 47 patients for the TLIF group. The rates of follow-up were 89% and 87% at 2 years, respectively. The comparisons of primary outcomes demonstrated no different changes in VAS-leg (OLIF, 3.4 vs. TLIF, 2.7), VAS-back (OLIF, 2.5 vs. TLIF, 2.1), and ODI (OLIF, 26.8 vs. TLIF, 30). The fusion rates were 86.1% in the TLIF group and 92.5% in the OLIF group at 2 years (P = 0.365). The OLIF group had less estimated blood loss (median, 200 ml) than the TLIF group (median, 300 ml) (P < 0.001). Greater restoration of disc height was obtained by OLIF (mean, 4.6 mm) than the TLIF group (mean, 1.3 mm) in the early postoperative period (P < 0.001). The subsidence rate was lower in the OLIF group than that in the TLIF group (17.5% vs. 38.9%, P = 0.037). The rates of total problematic complications were not different between the two groups (OLIF, 14.6% vs. TLIF, 26.2%, P = 0.192).

Conclusion

OLIF did not show better clinical outcomes than TLIF for degenerative spondylolisthesis, except for lesser blood loss, greater disc height restoration, and lower subsidence rate.

Pedicle Screw-Associated Violation of the Adjacent Unfused Facet Joint: Clinical Outcomes and Fusion Rates

STUDY DESIGN

Retrospective review of a prospective randomized trial.

OBJECTIVES

To compare outcome scores and fusion rates in patients with and without pedicle screw-associated facet joint violation (FJV) after a single-level lumbar fusion.

METHODS

Clinical outcomes data and computed tomography (CT) imaging were reviewed for 157 patients participating in a multicenter prospective trial. Post-operative CT scans at 12-months follow-up were examined for fusion status and FJV. Patient-reported outcomes (PROs) included Oswestry Disability Index (ODI) and Visual Analog Scale (VAS) for leg and low back pain. Chi-square test of independence was used to compare proportions between groups on categorical measures. Two-sample t-test was used to identify differences in mean patient outcome scores. Logistic regression models were performed to determine association between FJV and fusion rates.

RESULTS

Of the 157 patients included, there were 18 (11.5%) with FJV (Group A) and 139 (88.5%) without FJV (Group B). Patients with FJV experienced less improvement in ODI (P = .004) and VAS back pain scores (P = .04) vs patients without FJV. There was no difference in mean VAS leg pain (P = .4997). The rate of fusion at 12-months for patients with FJV (27.8%) was lower compared to those without FJV (71.2%) (P = .0002). Patients with FJV were 76% less likely to have a successful fusion at 12-months.

CONCLUSION

Pedicle screw-associated violation of the adjacent unfused facet joint during single-level lumbar fusion is associated with less improvement in back pain, back pain-associated disability, and a lower fusion rate at 1-year after surgery.

Endplate volumetric bone mineral density biomechanically matched interbody cage

Disc degenerative problems affect the aging population, globally, and interbody fusion is a crucial surgical treatment. The interbody cage is the critical implant in interbody fusion surgery; however, its subsidence risk becomes a remarkable clinical complication. Cage subsidence is caused due to a mismatch of material properties between the bone and implant, specifically, the higher elastic modulus of the cage relative to that of the spinal segments, inducing subsidence. Our recent observation has demonstrated that endplate volumetric bone mineral density (EP-vBMD) measured through the greatest cortex-occupied 1.25-mm height region of interest, using automatic phantomless quantitative computed tomography scanning, could be an independent cage subsidence predictor and a tool for cage selection instruction. Porous design on the metallic cage is a trend in interbody fusion devices as it provides a solution to the subsidence problem. Moreover, the superior osseointegration effect of the metallic cage, like the titanium alloy cage, is retained. Patient-specific customization of porous metallic cages based on the greatest subsidence-related EP-vBMD may be a good modification for the cage design as it can achieve biomechanical matching with the contacting bone tissue. We proposed a novel perspective on porous metallic cages by customizing the elastic modulus of porous metallic cages by modifying its porosity according to endplate elastic modulus calculated from EP-vBMD. A three-grade porosity customization strategy was introduced, and direct porosity-modulus customization was also available depending on the patient's or doctor's discretion.

融合器高度对腰椎椎间融合术后结局影响的研究进展

OBJECTIVE

To summarize the effect of cage height on outcomes of lumbar interbody fusion surgery and the importance of the cage height selection.

METHODS

The related literature was widely reviewed to summarize the research progress on the complications caused by inappropriate height of the cage and the methods of selecting cage height.

RESULTS

Inappropriate height of the cage can lead to endplate injury, cage subsidence, internal fixation failure, adjacent segmental degeneration, over-distraction related pain, insufficient indirect decompression, instability of operation segment, poor interbody fusion, poor sequence of spine, and cage displacement. At present, the selection of the cage height is based on the results of the intraoperative model test, which is reliable but high requirements for surgical experience and hard to standardize.

CONCLUSION

The inappropriate height of the cage may have an adverse impact on the postoperative outcome of patients. It is important to develop a selection standard of the cage height by screening the related influential factors.

Characteristics of interbody bone graft fusion after transforaminal lumbar interbody fusion according to intervertebral space division

BACKGROUND

According to intervertebral space division, the characteristics of interbody bone graft fusion after transforaminal lumbar interbody fusion (TLIF) were assessed via computed tomography (CT) scan to provide a theoretical basis for selecting the bone grafting site of interbody fusion.

METHODS

The medical records of 57 patients with lumbar spinal stenosis and disc herniation treated with TLIF were analysed retrospectively. In total, 57 segments received lumbar interbody fusion. A thin-layer CT scan was performed to evaluate fusion in each zone of the fusion space.

RESULTS

The fusion rates were 57.89% (n = 33) in the anterior cage zone, 73.68% (n = 42) in the posterior cage zone, 66.67% (n = 38) in the decompression zone, 26.32% (n = 15) in the contralateral decompression zone and 94.74% (n = 54) in the inner cage zone. There were significant differences among the fusion rates of the five zones (P < 0.001). Further pairwise comparison revealed that the fusion rates in the inner cage significantly differed from the anterior and posterior cages and decompression and contralateral decompression zones (P = 0.001, 0.002, 0.001 and 0.001, respectively).

CONCLUSION

We think the central cage zone (i.e., inner cage) should be the focus of bone grafting. Although there is small volume of bone graft on the posterior cage zone, the fusion rate is relatively high, only secondary to the inner cage zone. The fusion rate is of the contralateral decompression zone is lower although there is a bone graft.

Oblique Lateral Endoscopic Decompression and Interbody Fusion for Severe Lumbar Spinal Stenosis: Technical Note and Preliminary Results

OBJECTIVE

Adequacy of decompression for oblique lateral interbody fusion (OLIF) is a real concern in patients with severe lumbar spinal stenosis (LSS). With this in mind, we combined OLIF with spinal endoscopic technique to achieve a solid fusion and an adequate decompression after one operation.

METHODS

This is a technical note. The theoretical basis and operation process of this technique were introduced, and consecutive cases were retrospectively collected. Consecutive patients diagnosed with monosegmental severe LSS (L4/5) and underwent oblique lateral endoscopic decompression and interbody fusion (OLEDIF) from January 2018 to February 2020 were retrospectively collected. Clinical outcomes were assessed by claudication distance, Visual Analog Scale (VAS), and Oswestry Disability Index (ODI) scores. Secondary indicators included operation time, operative blood loss, and postoperative complications.

RESULTS

Ten patients were selected for the OLEDIF procedure. They were five women and five men ranging in age from 49 to 75 years (mean age of 63.9 years) and in BMI from 25.4 to 30.2 kg/m² (mean BMI of 27.5 kg/m² ). The preoperative claudication distance was 160.00 ± 68.96 m (range 70-250 m), which was significantly extended on the 3-month and 1-year follow-up (1020.00 ± 407.70 m and 1040.00 ± 416.87 m, respectively). The preoperative VAS score of back pain and radiating leg pain was 5.50 ± 0.97 (range 4-7) and 6.40 ± 0.97 (range 5-8). The score on postoperative month 3 was 1.60 ± 0.52 (range 1-2) and 1.20 ± 0.79 (range 0-2), and the 1-year follow-up score was 1.90 ± 0.74 (range 1-3) and 1.60 ± 0.70 (range 1-3), respectively. The preoperative ODI was 72.23 ± 6.30 (range 64.4-82.2), the 3-month follow-up ODI was 31.12 ± 4.20 (range 24.4-35.6), and the 1-year follow-up ODI was 29.33 ± 5.92 (range 20.0-37.8). Compared with the transforaminal lumbar interbody fusion (TLIF) in the literature, the operation time was not prolonged (189.3 ± 32.5 min vs. 214.9 ± 60.0 min) but the amount of blood loss decreased significantly (113.3 ± 26.7 ml vs. 366.8 ± 298.2 ml). No complications were found except one case presented with dysesthesia of the left leg. Imaging results showed good fusion without cage subsidence during 1-year follow-up.

CONCLUSION

OLEDIF can achieve complete ventral decompression of the spinal canal and solid fusion of the lumbar spine at one time. It is an effective minimally invasive technique for the treatment of monosegmental severe LSS, which is promising and worthy of further clinical practice.

Evaluation of Spinal Fusion in Thoracic and Thoracolumbar Spine on Standard X-Rays: A New Grading System for Spinal Interbody Fusion

STUDY DESIGN

Retrospective evaluation of prospectively collected data.

OBJECTIVE

Analyzing time course and stages of interbody fusion of a uniformly operated cohort, defining a grading system and establishing diagnosis-dependent periods of bone healing.

METHODS

Sequential lateral radiographs of 238 patients (313 levels) with interbody fusion operated thoracoscopically were analyzed.

RESULTS

Evaluation of 1696 radiographs with a mean follow-up of 65.19 months and average numbers of 5.42 (2-18) images per level was performed. Diagnoses were Pyogenic Spondylitis (74), Fracture (96), Ankylosing Spondylitis (38) and Degenerative Disease (105). No case with Grade 2 deteriorated to Grade 5. On average, Grade 4 persisted for 113 days, Grade 3 for 197 days, Grade 2 for 286 days and Grade 1 for 316 days. The first 95% of levels ("Green Zone", ≤ Grade 2) fused at 1 year, the remaining 4% levels fused between 12 and 17 months ("Yellow Zone") and the last 1% ("Red Zone") fused after 510 days.

CONCLUSION

Sequential lateral radiographs permit evaluation of interbody fusion. Grade 2 is the threshold point for fusion; once accomplished, failure is unlikely. If fusion (Grade 2,1 or 0) is not reached within 510 days, it should be regarded as failed. The 510-day-threshold could reduce the necessity of CT scanning for assessing fusion.

Comparison of Fusion Rate and Functional Outcome Between Local Cancellous Bone Plus Demineralized Bone Matrix and Local Bone in 1-Level Posterior Lumbar Interbody Fusion

STUDY DESIGN

Retrospective study with prospectively collected data.

OBJECTIVE

The purpose of this study is to investigate the difference in fusion rate and clinical outcome of patients with local bone as filler for the graft and demineralized bone matrix (DBM) plus only the cancellous bone from local bone as a filler for cage in 1-level posterior lumbar interbody fusion (PLIF) with cage.

SUMMARY OF BACKGROUND DATA

Cancellous bone is more advantageous than cortical bone in the local bone for improving bone formation in spine fusion surgery. There are little studies on the difference in fusion rate and reduction of fusion time using only these cancellous bones.

METHODS

Of the 40 patients who underwent 1-level PLIF using cage, 20 patients in group A used local bone and 20 patients in group B used mixture of cancellous bone extracted separately from local bone and commercially available DBM as filler for cage. Changes in fusion rate and intervertebral spacing were measured using lateral radiography, and fusion was determined as nonunion using the Brantigan-Steffee classification. The clinical outcome was evaluated.

RESULTS

There was no difference in height change over time between the two groups. Regarding union grade, group B showed better union grade than group A. However, no difference in union grade change over time was observed between the 2 groups. In group B, Oswestry Disability Index (ODI), Rolland-Morris Disability Questionnaire (RMDQ), and SF-36 mental component score (MCS) significantly decreased, but there was no difference in change over time.

CONCLUSIONS

In 1-level PLIF for degenerative lumbar disease, better fusion rate was observed in the group that used only cancellous bone from local bone plus DBM than that in the group that used local bone; however, there was no difference in fusion grade change over time in the 2 groups.

显微镜辅助微创前路融合与可动式椎间盘镜下融合治疗腰椎退变性疾病的比较研究

OBJECTIVE

To investigate the effectiveness of microscope assisted anterior lumbar discectomy and fusion (ALDF) and mobile microendoscopic discectomy assisted lumbar interbody fusion (MMED-LIF) for lumbar degenerative diseases.

METHODS

A clinical data of 163 patients with lumbar degenerative diseases who met the criteria between January 2018 and December 2020 was retrospectively analyzed. Fifty-three cases were treated with microscope assisted ALDF (ALDF group) and 110 cases with MMED-LIF (MMED-LIF group). There was no significant difference between the two groups in terms of gender, age, disease type, surgical segments, preoperative visual analogue scale (VAS) scores of low back pain and leg pain, Oswestry disability index (ODI), intervertebral space height, lordosis angle, and spondylolisthesis rate of the patients with lumbar spondylolisthesis ( P>0.05). The operation time, intraoperative blood loss, and hospital stay of the two groups were recorded. The effectiveness was evaluated by VAS scores of low back pain and leg pain and ODI. Postoperative lumbar X-ray films were taken to observe the position of Cage and measure the intervertebral space height, lordosis angle, and spondylolisthesis rate of the patients with lumbar spondylolisthesis.

RESULTS

The operations were successfully completed in both groups. The operation time, intraoperative blood loss, and hospital stay in ALDF group were less than those in MMED-LIF group ( P<0.05). The patients in both groups were followed up 12-36 months, with an average of 24 months. The VAS scores of low back pain and leg pain and ODI after operation were lower than those before operation in the two groups, and showed a continuous downward trend, with significant differences between different time points ( P<0.05). There were significant differences between two groups in VAS score of low back pain and ODI ( P<0.05) and no significant difference in VAS score of leg pain ( P>0.05) at each time point. The improvement rates of VAS score of low back pain and ODI in ALDF group were significantly higher than those in MMED-LIF group ( t=7.187, P=0.000; t=2.716, P=0.007), but there was no significant difference in the improvement rate of VAS score of leg pain ( t=0.556, P=0.579). The postoperative lumbar X-ray films showed the significant recovery of the intervertebral space height, lordosis angle, and spondylolisthesis rate at 2 days after operation when compared with preoperation ( P<0.05), and the improvements were maintained until last follow-up ( P>0.05). The improvement rates of intervertebral space height and lordosis angle in ALDF group were significantly higher than those in MMED-LIF group ( P<0.05). There was no significant difference in the reduction rate of spondylolisthesis between the two groups ( t=1.396, P=0.167). During follow-up, there was no loosening or breakage of the implant and no displacement or sinking of the Cage.

CONCLUSION

Under appropriate indications, microscope assisted ALDF and MMED-LIF both can achieve good results for lumbar degenerative diseases. Microscope assisted ALDF was superior to MMED-LIF in the improvement of low back pain and function and the recovery of intervertebral space height and lordosis angle.

In Vitro and In Vivo Comparison of Bone Growth Characteristics in Additive-Manufactured Porous Titanium, Nonporous Titanium, and Porous Tantalum Interbody Cages

Autogenous bone grafts are the gold standard for interbody fusion implant materials; however, they have several disadvantages. Tantalum (Ta) and titanium (Ti) are ideal materials for interbody cages because of their biocompatibility, particularly when they are incorporated into a three-dimensional (3D) porous structure. We conducted an in vitro investigation of the cell attachment and osteogenic markers of self-fabricated uniform porous Ti (20%, 40%, 60%, and 80%), nonporous Ti, and porous Ta cages (n = 6) in each group. Cell attachment, osteogenic markers, and alkaline phosphatase (ALP) were measured. An in vivo study was performed using a pig-posterior-instrumented anterior interbody fusion model to compare the porous Ti (60%), nonporous Ti, and porous Ta interbody cages in 12 pigs. Implant migration and subsidence, determined using plain radiographs, were recorded before surgery, immediately after surgery, and at 1, 3, and 6 months after surgery. Harvested implants were assessed for bone ingrowth and attachment. Relative to the 20% and 40% porous Ti cages, the 60% and 80% cages achieved superior cellular migration into cage pores. Among the cages, osteogenic marker and ALP activity levels were the highest in the 60% porous Ti cage, osteocalcin expression was the highest in the nonporous Ti cage, and the 60% porous Ti cage exhibited the lowest subsidence. In conclusion, the designed porous Ti cage is biocompatible and suitable for lumbar interbody fusion surgery and exhibits faster fusion with less subsidence compared with porous Ta and nonporous Ti cages.

Treatment of restenosis after lumbar decompression surgery: decompression versus decompression and fusion

OBJECTIVE

The aim of this study was to compare perioperative complications and postoperative outcomes between patients with lumbar recurrent stenosis without lumbar instability and radiculopathy who underwent decompression surgery and those who underwent decompression with fusion surgery.

METHODS

For this retrospective study, the authors identified 2606 consecutive patients who underwent posterior surgery for lumbar spinal canal stenosis at eight affiliated hospitals between April 2017 and June 2019. Among these patients, those with a history of prior decompression surgery and central canal restenosis with cauda equina syndrome were included in the study. Those patients with instability or radiculopathy were excluded. The patients were divided between the decompression group and decompression with fusion group. The demographic characteristics, numerical rating scale score for low-back pain, incidence rates of lower-extremity pain and lower-extremity numbness, Oswestry Disability Index score, 3-level EQ-5D score, and patient satisfaction rate were compared between the two groups using the Fisher's exact probability test for nominal variables and the Student t-test for continuous variables, with p < 0.05 as the level of statistical significance.

RESULTS

Forty-six patients met the inclusion criteria (35 males and 11 females; 19 patients underwent decompression and 27 decompression and fusion; mean ± SD age 72.5 ± 8.8 years; mean ± SD follow-up 18.8 ± 6.0 months). Demographic data and perioperative complication rates were similar. The percentages of patients who achieved the minimal clinically important differences for patient-reported outcomes or satisfaction rate at 1 year were similar.

CONCLUSIONS

Among patients with central canal stenosis who underwent revision, the short-term outcomes of the patients who underwent decompression were comparable to those of the patients who underwent decompression and fusion. Decompression surgery may be effective for patients without instability or radiculopathy.

Biomechanical analysis of stand-alone lumbar interbody cages versus 360° constructs: an in vitro and finite element investigation

OBJECTIVE

Low fusion rates and cage subsidence are limitations of lumbar fixation with stand-alone interbody cages. Various approaches to interbody cage placement exist, yet the need for supplemental posterior fixation is not clear from clinical studies. Therefore, as prospective clinical studies are lacking, a comparison of segmental kinematics, cage properties, and load sharing on vertebral endplates is needed. This laboratory investigation evaluates the mechanical stability and biomechanical properties of various interbody fixation techniques by performing cadaveric and finite element (FE) modeling studies.

METHODS

An in vitro experiment using 7 fresh-frozen human cadavers was designed to test intact spines with 1) stand-alone lateral interbody cage constructs (lateral interbody fusion, LIF) and 2) LIF supplemented with posterior pedicle screw-rod fixation (360° constructs). FE and kinematic data were used to validate a ligamentous FE model of the lumbopelvic spine. The validated model was then used to evaluate the stability of stand-alone LIF, transforaminal lumbar interbody fusion (TLIF), and anterior lumbar interbody fusion (ALIF) cages with and without supplemental posterior fixation at the L4-5 level. The FE models of intact and instrumented cases were subjected to a 400-N compressive preload followed by an 8-Nm bending moment to simulate physiological flexion, extension, bending, and axial rotation. Segmental kinematics and load sharing at the inferior endplate were compared.

RESULTS

The FE kinematic predictions were consistent with cadaveric data. The range of motion (ROM) in LIF was significantly lower than intact spines for both stand-alone and 360° constructs. The calculated reduction in motion with respect to intact spines for stand-alone constructs ranged from 43% to 66% for TLIF, 67%-82% for LIF, and 69%-86% for ALIF in flexion, extension, lateral bending, and axial rotation. In flexion and extension, the maximum reduction in motion was 70% for ALIF versus 81% in LIF for stand-alone cases. When supplemented with posterior fixation, the corresponding reduction in ROM was 76%-87% for TLIF, 86%-91% for LIF, and 90%-92% for ALIF. The addition of posterior instrumentation resulted in a significant reduction in peak stress at the superior endplate of the inferior segment in all scenarios.

CONCLUSIONS

Stand-alone ALIF and LIF cages are most effective in providing stability in lateral bending and axial rotation and less so in flexion and extension. Supplemental posterior instrumentation improves stability for all interbody techniques. Comparative clinical data are needed to further define the indications for stand-alone cages in lumbar fusion surgery.

Improving the Management of Patients with Osteoporosis Undergoing Spinal Fusion: The Need for a Bone Mineral Density-Matched Interbody Cage

With an increasingly aging population globally, a confluence has emerged between the rising prevalence of degenerative spinal disease and osteoporosis. Fusion of the anterior spinal column remains the mainstay surgical intervention for many spinal degenerative disorders. However, decreased vertebral bone mineral density (BMD), quantitatively measured by dual x-ray absorptiometry (DXA), complicates treatment with surgical interbody fusion as weak underlying bone stock increases the risk of post-operative implant-related adverse events, including cage subsidence. There is a necessity for developing cages with advanced structural designs that incorporate bioengineering and architectural principles to tailor the interbody fusion device directly to the patient’s BMD status. Specifically, lattice-designed cages that mimic the web-like structure of native cancellous bone have demonstrated excellent resistance to post-operative subsidence. This article provides an introductory profile of a spinal interbody implant designed intentionally to simulate the lattice structure of human cancellous bone, with a similar modulus of elasticity, and specialized to match a patient’s bone status across the BMD continuum. The implant incorporates an open pore design where the degree of pore compactness directly corresponds to the patient’s DXA-defined BMD status, including patients with osteoporosis.

[Results of the study of functional recovery of professional athletes after minimally invasive lumbar fusion]

OBJECTIVE

To conduct a comprehensive clinical-neurological assessment and to study the results of functional recovery of professional athletes after minimally invasive lumbar interbody fusion.

MATERIALS AND METHODS

The retrospective study included 27 patients-professional athletes who were operated on using minimally invasive decompression and stabilization techniques in the period 2010 to 2019. Clinical-neurological effectiveness was assessed when returning to previous sports activity was 14 (9; 17) weeks and 4 (3; 5) years after surgery.

RESULTS

The follow-up showed a significant improvement in clinical and neurological parameters: persistent elimination of radicular and muscular-skeletal symptoms, a decrease in the level of pain according to a visual analogue scale in the lumbar spine from 68 (61; 85) mm to 3 (2; 11) mm (p=0.002) and in the lower extremities from 84 (78; 91) mm to 1 (0; 3) mm (p=0.001), change in the physical component of health from 26.18 (23.58; 28.37) to 49.82 (49.03; 53.04) (p=0.002) and the psychological component of health from 27.87 (26.22; 29.29) to 52.18 (49.12; 55.66) (p=0.001), significant improvement in the perception of physical activity according to the Borg RPE Scale from 17 (16; 18) points to 9 (8; 9) (p<0.001). In one case (3.7%), the patient did not return to his previous sports career.

CONCLUSION

The use of minimally invasive rigid stabilization in the overwhelming majority of professional athletes made it possible in the shortest possible time to achieve regression of neurological symptoms, reduce pain, improve the quality of life, restore the functional state and return to previous sports activities.

Efficacy, Cost, and Complications of Demineralized Bone Matrix in Instrumented Lumbar Fusion: Comparison With rhBMP-2

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

To evaluate demineralized bone matrix as an adjunct for instrumented lumbar spine fusion compared with recombinant human bone morphogenetic protein-2 (rhBMP-2).

METHODS

Clinical and radiographic review was performed of 43 patients with degenerative spine disease treated with posterolateral spinal fusion with or without posterior or transforaminal lumbar interbody fusion. Final analysis included sixteen patients treated with demineralized bone matrix (DBM; Accell Evo3, SeaSpine) compared with a retrospective matched group of 21 patients treated with rhBMP-2 (rhBMP-2, Infuse, Medtronic). All patients were followed for 24 months. Fusion was evaluated by computed tomography and/or x-ray. Clinical outcomes included visual analogue scale (VAS), Oswestry Disability Index (ODI), and Short Form 12 (SF-12).

RESULTS

Overall fusion rate, including posterolateral and/or interbody fusion, was 100% for both groups, though the fusion rates in the posterolateral space alone were 93.5% and 100% for the DBM and rhBMP-2 groups, respectively. Clinical outcomes were similar between groups, with the DBM group showing greater improvement in ODI. The rhBMP-2 group showed higher rates of radiographic complications with 7 of 21 patients (33.3%) demonstrating either adjacent level fusion or ectopic bone formation, compared with zero in the DBM group. Average biologic cost per level was $1522 for DBM and $3505 for rhBMP-2.

CONCLUSIONS

DBM and rhBMP-2 demonstrated similar radiographic and clinical outcomes in instrumented lumbar fusions. rhBMP-2 was associated with higher rates of radiographic complications and significantly higher costs.

Comparative Analysis of Unilateral versus Bilateral Instrumentation in TLIF for Lumbar Degenerative Disorder: Single Center Large Series

BACKGROUND

Transforaminal lumbar interbody fusion (TLIF) with bilateral pedicle screw instrumentation is a well-accepted technique in lumbar degenerative disc disorder. Unilateral instrumentation in TLIF has been reported in the literature. This study aims to compare the clinical and radiological outcomes of unilateral and bilateral instrumented TLIF in a selected series of patients.

METHODS

We retrospectively analyzed patients operated with unilateral pedicle screw fixation in TLIF (UPSF TLIF) or with bilateral pedicle screw fixation in TLIF (BPSF TLIF) with a minimum of 2 years of follow-up. Patients were evaluated at regular intervals for functional and radiological outcomes. Functional outcome was assessed using the Oswestry disability index (ODI) and visual analog score (VAS) preoperatively and at 6 months, 1 year, and 2 years after surgery. Fusion rates were assessed using Bridwell interbody fusion grading.

RESULTS

Our study shows that there was a significant improvement in VAS and ODI in both groups at 2 years follow-up, and there was no significant difference in improvements between the groups. The complication rates between the groups were similar. The fusion rate in UPSF TLIF was 97.3% and was 98.34% in BPSF TLIF; this was not statistically significant between groups. There is a significant difference in terms of blood loss, duration of surgery, and average duration of hospital stay between the groups (P < .001), favoring UPSF TLIF.

CONCLUSIONS

Unilateral pedicle screw fixation in open TLIF is comparable with bilateral pedicle screw fixation in terms of patient-reported clinical outcomes, fusion rates, and complication rates with the additional benefits of less operative time, less blood loss, shorter hospitalization, and less cost in selective cases.

LEVEL OF EVIDENCE

4.

Vulnerability of the L5 nerve root during anterior lumbar interbody fusion at L5-S1: case series and review of the literature

OBJECTIVE

Nerve root injuries associated with anterior lumbar interbody fusion (ALIF) are uncommonly reported in the literature. This case series and review aims to describe the etiology of L5 nerve root injury following ALIF at L5-S1.

METHODS

The authors performed a single-center retrospective review of prospectively collected data of patients who underwent surgery between 2017 and 2019 who had postoperative L5 nerve root injuries after stand-alone L5-S1 ALIF. They also reviewed the literature with regard to nerve root injuries after ALIF procedures.

RESULTS

The authors report on 3 patients with postoperative L5 radiculopathy. All 3 patients had pain that improved. Two of the 3 patients had a neurological deficit, one of which improved.

CONCLUSIONS

Stretch neuropraxia from overdistraction is an important cause of postoperative L5 radiculopathy after L5-S1 ALIF. Judicious use of implants and careful preoperative planning to determine optimal implant sizes are paramount.

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.

Transforaminal Lumbar Interbody Fusion (TLIF) versus Oblique Lumbar Interbody Fusion (OLIF) in Interbody Fusion Technique for Degenerative Spondylolisthesis: A Systematic Review and Meta-Analysis

Preoperative pathology requiring fusion surgery has a great impact on postoperative outcomes. However, the previous clinical and meta-analysis studies did not control for the pathology. In this systematic review, the authors aimed to compare oblique lumbar interbody fusion (OLIF) with transforaminal interbody fusion (TLIF) as an interbody fusion technique in lumbar fusion surgery for patients with degenerative spondylolisthesis (DS). We systematically searched for relevant articles in the available databases. Among the 3022 articles, three studies were identified and met the inclusion criteria. In terms of radiological outcome, the amount of disc height restoration was greater in the OLIF group than in the TLIF group, but there was no significant difference between the two surgical techniques (p = 0.18). In the clinical outcomes, the pain improvement was not significantly different between the two surgical techniques. In terms of surgical outcomes, OLIF resulted in a shorter length of hospital stay and less blood loss than TLIF (p < 0.0001 and p = 0.02, respectively). The present meta-analysis indicated no significant difference in clinical, radiological outcomes, and surgical time between TLIF and OLIF for DS, but the lengths of hospital stay and blood loss were better in OLIF than TLIF. Though encouraging, these findings were based on low-quality evidence from a small number of retrospective studies that are prone to bias.

Factors associated with using an interbody fusion device for low-grade lumbar degenerative versus isthmic spondylolisthesis: a retrospective cohort study

OBJECTIVE

Many studies have utilized a combined cohort of patients with degenerative spondylolisthesis (DS) and isthmic spondylolisthesis (IS) to evaluate indications and outcomes. Intuitively, these are very different populations, and rates, indications, and outcomes may differ. The goal of this study was to compare specific patient characteristics associated with the utilization of a posterior lumbar interbody device between cohorts of patients with DS and IS, as well as to compare rates of interbody device use and patient-rated outcomes at 1 year after surgical treatment.

METHODS

The authors included patients who underwent posterior lumbar interbody fusion or instrumented posterolateral fusion for grade I or II DS or IS and had been enrolled in the Canadian Spine Outcomes and Research Network registry from 2009 to 2016. The outcome measures were score on the Oswestry Disability Index, scores for back pain and leg pain on the numeric rating scale, and mental component summary (MCS) score and physical component summary score on the 12-Item Short-Form Health Survey. Descriptive statistics were used to compare spondylolisthesis groups, logistic regression was used to compare interbody device use, and the chi-square test was used to compare the proportions of patients who achieved a minimal clinically important difference (MCID) at 1 year after surgery.

RESULTS

In total, 119 patients had IS and 339 had DS. Patients with DS were more commonly women, older, less likely to smoke, and more likely to have neurogenic claudication and comorbidities, whereas patients with IS more commonly had radicular pain, neurological deficits, and worse back pain. Spondylolisthesis was more common at the L4-5 level in patients with DS and at the L5-S1 level in patients with IS. Similar proportions of patients had an interbody device (78.6% of patients with DS vs 82.4% of patients with IS, p = 0.429). Among patients with IS, factors associated with interbody device utilization were BMI ≥ 30 kg/m2 and increased baseline leg pain intensity. Factors associated with interbody device utilization in patients with DS were younger age, increased number of total comorbidities, and lower baseline MCS score. For each outcome measure, similar proportions of patients in the surgical treatment and spondylolisthesis groups achieved the MCID at 1 year after surgery.

CONCLUSIONS

Although the demographic and patient characteristics associated with interbody device utilization differed between cohorts, similar proportions of patients attained clinically meaningful improvement at 1 year after surgery.

Prone transpsoas lumbar corpectomy: simultaneous posterior and lateral lumbar access for difficult clinical scenarios

OBJECTIVE

Lateral lumbar corpectomy with interbody fusion has been well described via a transpsoas approach in the lateral position, as has lumbar interbody fusion with posterior fixation in the prone position. However, no previous report has described the use of both an open posterior approach and a lateral transpsoas approach simultaneously in the prone position. Here, the authors describe their technique of performing transpsoas lumbar corpectomy in the prone position in order to have simultaneous posterior and lateral access for difficult clinical scenarios, and they report their early clinical experience.

METHODS

The surgical technique for simultaneous posterior and lateral transpsoas access to the lumbar spine was reviewed and described in detail. The cases of 2 patients who underwent simultaneous posterior and lateral access in the prone position for complex lumbar pathology were retrospectively reviewed. Clinical presentation, preoperative radiographs, postoperative course, and postoperative radiographs were reviewed.

RESULTS

The first patient presented after previous transforaminal lumbar interbody fusion that was complicated by significant subsidence of the intervertebral cage, vertebral body split fracture, rotational instability, and resulting spinal stenosis. A simultaneous posterior and lateral transpsoas approach in the prone position allowed for removal of the previous cage, lumbar corpectomy, and rigid posterior fixation with direct decompression. The second patient had a significant pathologic burst fracture secondary to a plasmacytoma with retropulsion, resulting in vertebra plana and significant canal stenosis. Simultaneous approaches allowed for complete resection of the plasmacytoma, restoration of lumbar alignment, rigid fixation, and direct posterior decompression. There were no short-term complications, and both patients had resolution of their preoperative symptoms.

CONCLUSIONS

Simultaneous posterior and lateral transpsoas access to the lumbar spine in the prone position is a previously unreported technique that allows a safe surgical approach to difficult clinical scenarios.

One surgeon's learning curve with single position lateral lumbar interbody fusion: perioperative outcomes and complications

BACKGROUND

Single position (SP) lateral transpsoas lumbar interbody fusion (LLIF) with posterior pedicle screw fixation (PPSF) reduces operative time compared to dual positioning. However, the learning curve has not yet been described. The purpose of this study was to define the learning curve SP LLIF with PPSF.

METHODS

This retrospective case series included the first 161 consecutive patients who underwent SP LLIF and PPSF with the senior author. Primary analysis of operative time versus case number included single level cases without adjacent level procedures. Secondary analyses included 1-3 level cases without adjacent level procedures. Operative time for 2 and 3 level procedures was normalized to single-level cases. The learning curve was assessed with linear regression, which was found to fit the data better than logarithmic regression as judged by R² values and data visualization. Perioperative outcomes as a function of case number were analyzed by least squares linear regression and Mann Whitney U-tests.

RESULTS

For single level surgeries without adjacent procedures (n=87), operative time decreased by a total of 28.7 (95% CI, 9.6, 47.9) minutes over the series (P<0.001). For 1-3 level cases with no adjacent procedures (n=131), normalized operative time decreased by 23.1 (7.6, 38.6) minutes (P<0.001). Post-operative change in hematocrit, length of hospital stay, post-operative change in lordosis, 90-day complications, suboptimal screw placement, and 6-week post-operative Oswestry Disability Index (ODI) score did not correlate with case number. Intraoperative fluids decreased 3.7 mL (95% CI, 0.7, 6.7) per case (P=0.015).

CONCLUSIONS

In SP LLIF with PPSF, case number correlated with decreased operative time, but not complications. The surgeon's prior experience with dual position (DP) LLIF likely contributed to the minimal learning curve observed. Surgeons adopting SP LLIF with minimal prior DP LLIF experience may experience a steeper curve.

Percutaneous endoscopic posterior lumbar interbody fusion for the treatment of degenerative lumbar diseases: a technical note and summary of the initial clinical outcomes

BACKGROUND

Percutaneous endoscopic lumbar interbody fusion was a new technique that leads to improved visualization, improved safety and less trauma than does the traditional procedure. The purpose of this study was to introduce the technique of percutaneous endoscopic posterior lumbar interbody fusion (PE-PLIF) and determine its efficacy.

METHODS

35 patients with an average age of 52.3±13.7 years were treated with single-segment PE-PLIF. The perioperative parameters and the radiographic parameters were measured. The visual analog scale (VAS) score for low back pain, VAS score for leg pain and Oswestry disability index (ODI) score were used to assess the levels of pain and function.

RESULTS

The mean estimated volume of blood loss was 68.6±32.3 ml, operative time was 179.6±31.0 minutes. PE-PLIF significantly reduced the VAS score for low back pain, VAS score for leg pain and ODI score, and improved the posterior disc height, lumbar lordosis angle and segmental lordosis angle (p < 0.05). The rate of satisfaction was 94.3%. One patient suffered a dural tear. There was one case of contralateral radiculopathy that was relieved after conservative treatment.

CONCLUSIONS

This research suggests that PE-PLIF is a minimally invasive, safe, and effective treatment for degenerative lumbar diseases requiring interbody fusion.

Minimally invasive injectable lumbar interbody fusion with mineralized collagen-modified PMMA bone cement: A new animal model

This study was to develop a feasible and safe animal model for minimally invasive injectable lumbar interbody fusion using a novel biomaterial, mineralized collagen-polymethylmethacrylate bone cement (MC-PMMA), with unilateral pedicle screw fixation in an in vivo goat model. Eight goats (Capra aegagrus hircus) were divided into three groups: MC-PMMA, unmodified commercial-polymethylmethacrylate bone cement (UC-PMMA), and a control group (titanium cage filled with autogenous bone, TC-AB). Each group of goats was treated with minimally invasive lumbar interbody fusion at the L3/L4 and L5/L6 disc spaces (injected for MC-PMMA and UC-PMMA, implanted for TC-AB). The pedicle screws were inserted at the L3, L4, L5, and L6 vertebrae, respectively, and fixed on the left side. The characteristics of osteogenesis and bone growth were assessed at the third and the sixth month, respectively. The methods of evaluation included the survival of each animal, X-ray imaging, and 256-layer spiral computed tomography (256-CT) scanning, imaged with three-dimensional microfocus computed tomography (micro-CT), and histological analysis. The results showed that PMMA bone cement can be extruded smoothly after doping MC, the MC-PMMA integrates better with bone than the UC-PMMA, and all goats recovered after surgery without nerve damage. After 3 and 6 months, the implants were stable. New trabecular bone was observed in the TC-AB group. In the UC-PMMA group a thick fibrous capsule had formed around the implants. The MC-PMMA was observed to have perfect osteogenesis and bone ingrowth to adjacent bone surface. Minimally invasive injectable lumbar interbody fusion using MC-PMMA bone cement was shown to have profound clinical value, and the MC-PMMA showed potential application prospects.

Simultaneous Combined Major Arterial and Lumbar Plexus Injury During Primary Extra Lateral Interbody Fusion: Case Report and Review of the Literature

Extra lateral interbody fusion (XLIF) has been established in recent years as an effective approach to address degenerative lumbar disc disease (DLDD). Although neurological and vascular complications during XLIF have been reported, to our knowledge, a combination of simultaneous vascular and neurovascular complication during XLIF has not been reported to date. A 72-year-old female patient was admitted to our orthopaedic department because of back pain associated with severe neuropathic radicular pain to her both lower extremities, incomplete paraplegia and low back fistula with serous secretion for several weeks. She had been wheel-chair bound since nine years before her admission in our department when she had her initial XLIF operation in another institution. Intraoperatively, an aorta lesion occurred, which was emergently addressed, along with lumbar plexus injury. Since then, she had an extensive history of subsequent operations that ended with a T10-S1 posterior lumbar fusion, with no improvement of her neurological condition, complicated by hardware-induced infection. She underwent her last operation in our department; removal of the posterior lumbar construct and extensive debridement of the posterior lumbar spine. We present this rare case and we perform an extensive literature review. Although XLIF has been established in recent years, the report of major vascular injuries, although rare, has questioned its safety profile. Spine surgeons should be aware of catastrophic major neurovascular complications associated with this procedure and be prepared to address them.

Safety Profile and Radiographic and Clinical Outcomes of Stand-Alone 2-Level Anterior Lumbar Interbody Fusion: A Case Series of 41 Consecutive Patients

Objective: The use of stand-alone 2-level anterior lumbar interbody fusion (ALIF) for degenerative lumbar disease has been increasing as an alternative to routinely augmenting these constructs with posterior fixation or fusion. Despite the potential benefits of a stand-alone approach (decreased cost and operative time, decreased pain and early mobilization), there is a paucity of information regarding these operations in the literature. This investigation aimed to determine the safety profile, radiographic outcomes including fusion rates, improvement in preoperative pain, and spinopelvic parameter modification, for patients undergoing stand-alone 2-level ALIF.

Methods: This retrospective case series involved a chart review of all patients undergoing 2-level stand-alone ALIF at a single tertiary hospital from 2008 to 2018. Data included patient demographics, hospitalization, complications and radiological studies. Visual analog scale (VAS) back and leg scores were measured via patient-administered surveys preoperatively and up to 18 weeks postoperatively.

Results: Forty-one patients who underwent L4-S1 stand-alone ALIF were included. Sixteen (39%) of patients had undergone previous posterior lumbar surgery. Length of stay averaged 4.2 days. Complication rates were comparable to 1-level ALIF. Two patients required reoperation. Fusion rates were 100% for L4-5 and 94.4% for L5-S1. There was no significant change in lumbar lordosis (LL) or LL-pelvic incidence (PI), but there was improved segmental lordosis (SL) and disc height at L4-S1 on final follow-up imaging. There was also modest but statistically significant improvement in VAS back and leg scores.

Conclusions: Stand-alone 2-level ALIF is an option for a surgeon to perform in the absence of significant instability, even in the setting of prior posterior surgery. These procedures increase SL and disc height, but do not have the same effect on LL or LL-PI.

Expandable Interbody Fusion Cages: An Editorial on the Surgeon's Perspective on Recent Technological Advances and Their Biomechanical Implications

BACKGROUND

Expandable cages have gone through several iterations since they first appeared on the market in the early 2000s. Their development was prompted by some common problems associated with static interbody cages, including migration, expulsion, dural or neural traction injury, and pseudarthrosis.

OBJECTIVE

To summarize current technological advances from earlier expandable lumbar interbody fusion devices to implants with vertical and medial-to-lateral expansion mechanisms.

METHODS

The authors review the currently available expandable cage designs, the incremental technological advances, and how these devices impact minimally invasive surgery interbody procedures and clinical outcomes. The strategic concepts intended to improve the minimally invasive application of expandable interbody fusion implants are reviewed from a surgeon's perspective in a clinical context to discuss how their use may improve patient outcomes.

CONCLUSIONS

The geometrical configuration, effective stiffness of composite multi-material cage designs may impact the bone-implant contact area with the endplates. Hybridization strategies of expandable cage technology with modern minimally invasive and endoscopic spinal surgery techniques are presented by outlining their advantages and disadvantages.

LEVEL OF EVIDENCE

1 CLINICAL RELEVANCE: Systematic review.

Increasing Fusion Rate Between 1 and 2 Years After Instrumented Posterolateral Spinal Fusion and the Role of Bone Grafting

STUDY DESIGN

Two-year clinical and radiographic follow-up of a double-blind, multicenter, randomized, intra-patient controlled, non-inferiority trial comparing a bone graft substitute (AttraX Putty) with autograft in instrumented posterolateral fusion (PLF) surgery.

OBJECTIVES

The aim of this study was to compare PLF rates between 1 and 2 years of follow-up and between graft types, and to explore the role of bone grafting based on the location of the PLF mass.

SUMMARY OF BACKGROUND DATA

There are indications that bony fusion proceeds over time, but it is unknown to what extent this can be related to bone grafting.

METHODS

A total of 100 adult patients underwent a primary, single- or multilevel, thoracolumbar PLF. After instrumentation and preparation for grafting, the randomized allocation side of AttraX Putty was disclosed. The contralateral posterolateral gutters were grafted with autograft. At 1-year follow-up, and in case of no fusion at 2 years, the fusion status of both sides of each segment was blindly assessed on CT scans. Intertransverse and facet fusion were scored separately. Difference in fusion rates after 1 and 2 years and between grafts were analyzed with a Generalized Estimating Equations (GEE) model (P < 0.05).

RESULTS

The 2-year PLF rate (66 patients) was 70% at the AttraX Putty and 68% at the autograft side, compared to 55% and 52% after 1 year (87 patients). GEE analysis demonstrated a significant increase for both conditions (odds ratio 2.0, 95% confidence interval 1.5-2.7, P < 0.001), but no difference between the grafts (P = 0.595). Ongoing bone formation was only observed between the facet joints.

CONCLUSION

This intra-patient controlled trial demonstrated a significant increase in PLF rate between 1 and 2 years after instrumented thoracolumbar fusion, but no difference between AttraX Putty and autograft. Based on the location of the PLF mass, this increase is most likely the result of immobilization instead of grafting.

LEVEL OF EVIDENCE

1.

Advances in Spinal Fusion Strategies in Adult Deformity Surgery

BACKGROUND

As the frequency of adult deformity surgery (ADS) continues to increase, our understanding of techniques that enhance fusion must continue to evolve because pseudarthrosis can be a serious and costly event.

PURPOSES/QUESTIONS

We sought to conduct a review of the literature investigating techniques that can enhance outcomes of ADS.

METHODS

Two databases were searched for keywords such as "advances in spinal fusion," "new technology in adult spinal deformity," "interbody devices for adult spinal deformity," "adult spinal deformity rods," and "screw design in adult spinal deformity" to examine recent literature and trends in ADS.

RESULTS

We identified 45 articles for our review. Topics studied include the use of multiple rods, interbody fusion, distal fixation techniques, and bone morphogenetic protein or iliac crest bone graft.

CONCLUSIONS

Many recent innovations in treatments to enhance fusion in ADS have been studied, some more controversial than others. Further research into the efficacy of these techniques may increase fusion rates in ADS.

Factors affecting approach selection for minimally invasive versus open surgery in the treatment of adult spinal deformity: analysis of a prospective, nonrandomized multicenter study

OBJECTIVE

Surgical decision-making and planning is a key factor in optimizing outcomes in adult spinal deformity (ASD). Minimally invasive spinal (MIS) strategies for ASD have been increasingly used as an option to decrease postoperative morbidity. This study analyzes factors involved in the selection of either a traditional open approach or a minimally invasive approach to treat ASD in a prospective, nonrandomized multicenter trial. All centers had at least 5 years of experience in minimally invasive techniques for ASD.

METHODS

The study enrolled 268 patients, of whom 120 underwent open surgery and 148 underwent MIS surgery. Inclusion criteria included age ≥ 18 years, and at least one of the following criteria: coronal curve (CC) ≥ 20°, sagittal vertical axis (SVA) > 5 cm, pelvic tilt (PT) > 25°, or thoracic kyphosis (TK) > 60°. Surgical approach selection was made at the discretion of the operating surgeon. Preoperative significant differences were included in a multivariate logistic regression analysis to determine odds ratios (ORs) for approach selection.

RESULTS

Significant preoperative differences (p < 0.05) between open and MIS groups were noted for age (61.9 vs 66.7 years), numerical rating scale (NRS) back pain score (7.8 vs 7), CC (36° vs 26.1°), PT (26.4° vs 23°), T1 pelvic angle (TPA; 25.8° vs 21.7°), and pelvic incidence-lumbar lordosis (PI-LL; 19.6° vs 14.9°). No significant differences in BMI (29 vs 28.5 kg/m2), NRS leg pain score (5.2 vs 5.7), Oswestry Disability Index (48.4 vs 47.2), Scoliosis Research Society 22-item questionnaire score (2.7 vs 2.8), PI (58.3° vs 57.1°), LL (38.9° vs 42.3°), or SVA (73.8 mm vs 60.3 mm) were found. Multivariate analysis found that age (OR 1.05, p = 0.002), VAS back pain score (OR 1.21, p = 0.016), CC (OR 1.03, p < 0.001), decompression (OR 4.35, p < 0.001), and TPA (OR 1.09, p = 0.023) were significant factors in approach selection.

CONCLUSIONS

Increasing age was the primary driver for selecting MIS surgery. Conversely, increasingly severe deformities and the need for open decompression were the main factors influencing the selection of traditional open surgery. As experience with MIS surgery continues to accumulate, future longitudinal evaluation will reveal if more experience, use of specialized treatment algorithms, refinement of techniques, and technology will expand surgeon adoption of MIS techniques for adult spinal deformity.

Anterior lumbar compared to oblique lumbar interbody approaches for multilevel fusions to the sacrum in adults with spinal deformity and degeneration

OBJECTIVE

In adult spinal deformity and degenerative conditions of the spine, interbody fusion to the sacrum often is performed to enhance arthrodesis, induce lordosis, and alleviate stenosis. Anterior lumbar interbody fusion (ALIF) has traditionally been performed, but minimally invasive oblique lumbar interbody fusion (OLIF) may or may not cause less morbidity because less retraction of the abdominal viscera is required. The authors evaluated whether there was a difference between the results of ALIF and OLIF in multilevel anterior or lateral interbody fusion to the sacrum.

METHODS

Patients from 2013 to 2018 who underwent multilevel ALIF or OLIF to the sacrum were retrospectively studied. Inclusion criteria were adult spinal deformity or degenerative pathology and multilevel ALIF or OLIF to the sacrum. Demographic, implant, perioperative, and radiographic variables were collected. Statistical calculations were performed for significant differences.

RESULTS

Data from a total of 127 patients were analyzed (66 OLIF patients and 61 ALIF patients). The mean follow-up times were 27.21 (ALIF) and 24.11 (OLIF) months. The mean surgical time was 251.48 minutes for ALIF patients and 234.48 minutes for OLIF patients (p = 0.154). The mean hospital stay was 7.79 days for ALIF patients and 7.02 days for OLIF patients (p = 0.159). The mean time to being able to eat solid food was 4.03 days for ALIF patients and 1.30 days for OLIF patients (p < 0.001). After excluding patients who had undergone L5-S1 posterior column osteotomy, 54 ALIF patients and 41 OLIF patients were analyzed for L5-S1 radiographic changes. The mean cage height was 14.94 mm for ALIF patients and 13.56 mm for OLIF patients (p = 0.001), and the mean cage lordosis was 15.87° in the ALIF group and 16.81° in the OLIF group (p = 0.278). The mean increases in anterior disc height were 7.34 mm and 4.72 mm for the ALIF and OLIF groups, respectively (p = 0.001), and the mean increases in posterior disc height were 3.35 mm and 1.24 mm (p < 0.001), respectively. The mean change in L5-S1 lordosis was 4.33° for ALIF patients and 4.59° for OLIF patients (p = 0.829).

CONCLUSIONS

Patients who underwent multilevel OLIF and ALIF to the sacrum had comparable operative times. OLIF was associated with a quicker ileus recovery and less blood loss. At L5-S1, ALIF allowed larger cages to be placed, resulting in a greater disc height change, but there was no significant difference in L5-S1 segmental lordosis.