Do Radiographic Results of Transforaminal Lumbar Interbody Fusion Vary with Cage Position in Patients with Degenerative Lumbar Diseases?

Biomechanical effects of cement neck and interspinous process device on locking lumbar interbody cementation

BACKGROUND

Locking lumbar interbody cementation is a surgical option in patients with osteoporosis and low mobility. It can quickly stabilize the spine construct and prevent cage subsidence. However, establishing a stable bridging neck cement between the vertebrae and disc is a key procedure.

METHODS

The validated lumbosacral model analyzed the stress cracking risks for five cement neck diameters under flexion, extension, bending, and twisting. The key indices included disc mobility and neck stress. The biomechanical impact of the interspinous process device was evaluated in high-stress fracture-prone necks.

FINDINGS

The neck diameter has a significant impact on neck stress, especially extension. The maximum neck stress with a 4-mm diameter was very close to the ultimate tensile strength (25.4 MPa) of cement, inducing a high risk of neck fracture. Generally, neck fractures have little effect on disc mobility during flexion, bending, and twisting. However, after the fracture, neck failure led to a 17.1 % increase in disc mobility during extension. If the neck diameter was less than 5 mm on intraoperative radiography, the interspinous process device effectively reduced neck stress by 51.1 % during extension and 31.7 % during bending.

INTERPRETATION

To improve neck strength, the neck diameter should be increased to at least 5 mm during the surgery. If the strength is inadequate, an interspinous process device can be considered to further minimize the risk of fractures, particularly during extension and bending movements.

Risk factors influencing cage retropulsion following lumbar interbody fusion in treating degenerative lumbar diseases: A comprehensive systematic review and meta-analysis

BACKGROUND

Degenerative lumbar diseases (DLDs) often have significant impacts on patients' quality of life, particularly when cage retropulsion (CR) occurs following lumbar interbody fusion (LIF). In this study, we conducted a meta-analysis to assess the risk factors associated with CR after LIF.

METHODS

We retrieved literatures analyzing the risk factors associated with CR following LIF from seven databases. We examined baseline characteristics, diagnosis, comorbidity, fusion level, surgical status, imaging assessment, and cage status to identify potential risk factors.

RESULTS

Sixteen studies involving 8059 patients (251 in the CR group and 7808 in the Non-CR group) were included in the final analysis. The incidence of CR was 3.15 %. Results revealed that older age (mean difference [MD]: 2.35 [0.44, 4.26]), more fusion levels (MD: 0.64 [0.03, 1.25]), comorbidity-osteoarthritis (risk ratio [RR]: 2.02 [1.37, 2.98]), comorbidity-heart disease (RR: 2.95 [1.21, 7.21]), comorbidity-existing vertebral fracture (RR: 5.12 [2.52, 10.39]), endplate injury (RR: 2.93 [1.71, 5.02]), screw loosening (RR: 6.03 [1.90, 19.12]), pear-shaped disc (PSD, RR: 3.14 [1.46, 6.74]), greater mean disc height (MDH, MD: 1.65 [0.58, 2.72]), larger cobb angle (MD: 0.68 [0.10, 1.27] degrees), larger cage height (MD: 0.31 [0.01, 0.61]), and cage type-carbon (RR: 1.62 [1.16, 2.27]) were identified as risk factors for CR following LIF. The incidence of CR decreased with an increase in fusion level.

CONCLUSIONS

Older age, endplate injury, PSD, and nine other factors are identified as risk factors for CR following LIF. Patients with these factors should undergo close monitoring during follow-up to prevent serious complications, such as significant cage displacement.

Comparison of capsule and posterior lumbar interbody fusion in cauda equina syndrome with retention: a 24-month follow-up study

BACKGROUND AND OBJECTIVES

Cauda equina syndrome with retention (CESR) is a severe lumbar condition characterized by painless urine retention due to cauda equina nerve injury. The standard treatment, posterior lumbar interbody fusion (PLIF), often yields suboptimal results. This study aims to compare the clinical safety and efficacy of a novel technique, capsule lumbar interbody fusion (CLIF), with PLIF in CESR patients, hypothesizing that CLIF can enhance neurological recovery by reducing nerve tension.

METHODS

A single-center, retrospective study was conducted on 83 patients with CESR due to lumbar disc herniation, who underwent either PLIF (n = 44) or CLIF (n = 39). Patients were assessed preoperatively and at 3, 12, and 24 months postoperatively using the Oswestry Disability Index (ODI), Visual Analogue Scale (VAS), International Consultation on Incontinence Questionnaire Short Form (ICI-Q-SF), and Rintala score. Urodynamic studies and nerve tension measurements were also performed. Statistical analysis included t tests, Mann-Whitney U tests, and Spearman's correlation.

RESULTS

Both groups showed significant postoperative improvements, but the CLIF group had superior outcomes. At 12 months, the CLIF group had lower VAS scores (1.15 ± 0.84 vs. 1.68 ± 0.60, p = 0.001) and ODI scores (23.31 ± 7.51 vs. 28.30 ± 8.26, p = 0.005). At 24 months, the CLIF group continued to show better results with ODI scores (15.97 ± 6.43 vs. 22.11 ± 6.41, p < 0.001) and higher ODI recovery rates (60.41 ± 17.6% vs. 44.71 ± 18.99%, p < 0.001). The CLIF group also had better ICI-Q-SF scores (2.13 ± 1.23 vs. 3.02 ± 1.45, p = 0.004) and Rintala scores (17.97 ± 1.43 vs. 16.59 ± 1.54, p < 0.001). Lower postoperative nerve tension in the CLIF group correlated with these improved outcomes.

CONCLUSIONS

CLIF demonstrated superior efficacy over PLIF in treating CESR, with significant improvements in pain relief, functional recovery, and bladder and bowel function. This study highlights the potential of CLIF as a more effective surgical option for CESR, emphasizing its importance in improving patient outcomes and reducing the burden of CESR on patients and society.

Radiographic and Patient-Reported Outcomes in Anteriorly Placed Transforaminal Lumbar Interbody Fusion Cage Versus Anterior Lumbar Interbody Fusion With Posterior Instrumentation

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

To compare outcomes in anteriorly placed transforaminal lumbar interbody fusions (TLIFs) and anterior lumbar interbody fusions (ALIFs).

SUMMARY OF BACKGROUND DATA

TLIF and ALIF are surgical techniques that have become more prevalent in recent years. Although studies have compared the two, none have considered TLIFs with anteriorly placed cages, which may serve as a better comparison to ALIFs.

PATIENTS AND METHODS

Patients undergoing TLIF or ALIF with posterior instrumentation from 2010 to 2020 at a tertiary care institution were retrospectively identified. TLIF cage position was assessed and those with anterior placement were included. Electronic medical records were reviewed to identify patient characteristics and patient-reported outcomes. Radiographic outcomes included posterior disc height (DH), lumbar lordosis (LL), sacral slope, pelvic incidence, and pelvic tilt. Statistical analysis was performed to compare the two groups.

RESULTS

Of the 351 patients, 108 had ALIF with posterior instrumentation and 207 had a TLIF. Preoperatively, patients undergoing TLIF had less LL (53.7° vs . 60.6°, P < 0.001), sacral slope (38.3° vs . 43.7°, P < 0.001), and pelvic incidence (60.1° vs . 66.1°, P < 0.001), all of which remained significant at 1-year and long-term follow-up ( P < 0.001). The TLIF group had less ∆DH (1.51° vs . 5.43°, P < 0.001), ∆LL (1.8° vs . 2.97°, P = 0.038), and ∆segmental lordosis (0.18° vs . 4.40°, P < 0.001) at 1 year postoperatively. At 2 to 3 years, ∆DH ( P < 0.001) and ∆segmental lordosis ( P = 0.001) remained significant, but ∆LL ( P = 0.695) did not. Patients in the TLIF group had higher Visual Analog Scale-Back scores 1 year postoperatively (3.68 vs . 2.16, P = 0.008) and experienced less improvement in Oswestry Disability Index (-17.1 vs . -28.6, P = 0.012) and Visual Analog Scale-Back (-2.67 vs . -4.50, P = 0.008) compared with patients undergoing ALIF.

CONCLUSIONS

Our findings suggest that ALIF with posterior instrumentation performed superiorly in radiographic outcomes and patient-reported outcomes compared with anteriorly placed TLIFs. Anteriorly placed TLIF cages may not achieve the same results as those of ALIF cages.

Effects of Cage Implantation Depth on Sagittal Parameters and Functional Outcomes in Posterior Lumbar Interbody Fusion for the Treatment of L4-L5 Lumbar Degenerative Spondylolisthesis

OBJECTIVE

In the treatment of lumbar degenerative spondylolisthesis (LDS) with Posterior lumbar interbody fusion (PLIF) surgery, interbody fusion implants play a key role in supporting the vertebral body and facilitating fusion. The objective of this study was to assess the impact of implantation depth on sagittal parameters and functional outcomes in patients undergoing PLIF surgery.

METHODS

This study reviewed 128 patients with L4-L5 LDS between January 2016 and August 2019. All patients underwent an open PLIF surgery that included intravertebral decompression, implantation of pedicle screws and cage. We grouped according to the position of the center of the cage relative to the L5 vertebral endplate. Patients with the center of the cage located at the anterior 1/2 of the upper end plate of the L5 vertebral body were divided into Anterior group, and located at the posterior 1/2 of the upper end plate of the L5 vertebral body were divided into Posterior group. The lumbar lordosis (LL), segmental lordosis (SL), sacral slope (SS), pelvic incidence (PI), pelvic tilt (PT) and slope degree (SD) was measured for radiographic outcomes. We used the visual analog scale (VAS) and the oswestry disability index (ODI) score to assess functional outcomes. Paired t-test was used to compare imaging and bedside data before and after surgery between the two groups, and independent sample t-test, χ2 test and Fisher exact test were used to compare the data between the two groups.

RESULT

The mean follow-up of Anterior group was 44.13 ± 9.23 months, and Posterior group was 45.62 ± 10.29 months (P > 0.05). The LL, SL, PT, SS, SD and PI-LL after operation showed great improvements, relative to the corresponding preoperative values in both groups (P < 0.05). Compared to Posterior group, Anterior group exhibited far enhanced SL (15.49 ± 3.28 vs. 13.67 ± 2.53, P < 0.05), LL (53.47 ± 3.21 vs. 52.08 ± 3.15, P < 0.05) outcomes and showed depressed PI-LL (8.87 ± 5.05 vs. 10.73 ± 5.39, P < 0.05) outcomes at the final follow-up. Meanwhile, the SL in Anterior group (16.18 ± 3.99) 1 months after operation were also higher than in Posterior group (14.12 ± 3.57) (P < 0.05). We found that VAS and ODI at the final follow-up in Anterior group (3.62 ± 0.96, 25.19 ± 5.25) were significantly lower than those in Posterior group (4.12 ± 0.98, 27.68 ± 5.13) (P < 0.05).

CONCLUSIONS

For patients with LDS, the anteriorly placed cage may provide better improvement of SL after PLIF surgery. Meanwhile, the anteriorly placed cage may achieve better sagittal parameters of LL and PI-LL and functional outcomes at the final follow-up.

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

The impact of cage positioning on lumbar lordosis and disc space restoration following minimally invasive lateral lumbar interbody fusion

OBJECTIVE

The objective of this study was to evaluate patient and surgical factors that predict increased overall lumbar lordosis (LL) and segmental lordosis correction following a minimally invasive lateral lumbar interbody fusion (LLIF) procedure.

METHODS

A retrospective review was conducted of all patients who underwent one- or two-level LLIF. Preoperative, initial postoperative, and 6-month postoperative measurements of LL, segmental lordosis, anterior disc height, and posterior disc height were collected from standing lateral radiographs for each patient. Cage placement was measured utilizing the center point ratio (CPR) on immediate postoperative radiographs. Spearman correlations were used to assess associations between cage lordosis and radiographic parameters. Multivariate linear regression was performed to assess independent predictors of outcomes.

RESULTS

A total of 106 levels in 78 unique patients were included. Most procedures involved fusion of one level (n = 50, 64.1%), most commonly L3-4 (46.2%). Despite no differences in baseline segmental lordosis, patients with anteriorly or centrally placed cages experienced the greatest segmental lordosis correction immediately (mean anterior 4.81° and central 4.46° vs posterior 2.47°, p = 0.0315) and at 6 months postoperatively, and patients with anteriorly placed cages had greater overall lordosis correction postoperatively (mean 6.30°, p = 0.0338). At the 6-month follow-up, patients with anteriorly placed cages experienced the greatest increase in anterior disc height (mean anterior 6.24 mm vs posterior 3.69 mm, p = 0.0122). Cages placed more posteriorly increased the change in posterior disc height postoperatively (mean posterior 4.91 mm vs anterior 1.80 mm, p = 0.0001) and at 6 months (mean posterior 4.18 mm vs anterior 2.06 mm, p = 0.0255). There were no correlations between cage lordotic angle and outcomes. On multivariate regression, anterior cage placement predicted greater 6-month improvement in segmental lordosis, while posterior placement predicted greater 6-month improvement in posterior disc height. Percutaneous screw placement, cage lordotic angle, and cage height did not independently predict any radiographic outcomes.

CONCLUSIONS

LLIF procedures reliably improve LL and increase intervertebral disc space. Anterior cage placement improves the lordosis angle greater than posterior placement, which better corrects sagittal alignment, but there is still a significant improvement in lordosis even with a posteriorly placed cage. Posterior cage placement provides greater restoration in posterior disc space height, maximizing indirect decompression, but even the anteriorly placed cages provided indirect decompression. Cage parameters including cage height, lordosis angle, and material do not impact radiographic improvement.