Lumbar interbody fusion: recent advances in surgical techniques and bone healing strategies

Biomechanical analysis of posterior, transforaminal, extreme, oblique, and anterior lumbar interbody fusion surgical models: a finite element study

Many lumbar interbody fusion methods have been proposed, but there is a relative scarcity of fundamental biomechanical research on these varied surgical procedures. In this study, a finite element model of an L4-L5 functional spinal unit was created and five interbody fusion methods were evaluated, including posterior lumbar interbody fusion (PLIF), transforaminal lumbar interbody fusion (TLIF), extreme lateral interbody fusion (XLIF), oblique lateral interbody fusion (OLIF) and anterior lumbar interbody fusion (ALIF). Static and harmonic vibration surgery analysis models were developed based on it, investigating the biomechanical properties, as well as the variation of strain energy. Results indicate that while OLIF and XLIF produced similar biomechanical outcomes, 45.8% higher facet joint contact stress in OLIF compared to XLIF. In contrast, TLIF and PLIF exhibit superior performance, with TLIF showing stress concentration on the left-side screw. ALIF outperformed other models in terms of overall stability, but has significantly higher stress peaks and sensitivity to vibration loads. In general, PLIF exhibits no significant shortcomings, TLIF offers excellent dynamic performance, OLIF and XLIF may exert greater pressure on the facet joints, and ALIF provides optimal stability. The integration of these findings into clinical practice can provide a theoretical basis for clinical surgeons when selecting surgical approaches.

Prolonged irrigation time in endoscopic aqueous medium impairs MSC/β-TCP adhesion and osteogenic potential

To evaluate the effects of an endoscopic aqueous environment on the viability and differentiation capacity of autologous bone marrow mesenchymal stem cells (MSCs) enriched with β-tricalcium phosphate (β-TCP). A screening-enrichment-combination circulating system (SECCS) was used to prepare MSCs/β-TCP from a patient. A simulated aqueous flushing environment for spinal endoscopic surgery was established with different flushing times (0-60 min). Scanning electron microscopy (SEM) was employed to determine the adhesion and condition of MSCs/β-TCP. CCK-8 was used to determine the viability of adherent MSCs. The osteogenic, adipogenic, and chondrogenic differentiation potentials of adherent MSCs were assessed with alizarin red, alkaline phosphatase, Oil Red O, and toluidine blue staining. A subcutaneous implantation mouse model was utilized to evaluate the osteogenic capacity of MSCs/β-TCP under different aqueous flushing conditions using micro-CT, haematoxylin-eosin staining, and Von Kossa staining. SEM revealed sustained MSC adhesion on β-TCP across all irrigation durations (0-60 min), with no differences in adhesion density. However, cell viability declined significantly after 30 min(P < 0.05). Differentiation assays demonstrated time-dependent impairments: osteogenic and adipogenic potentials decreased significantly at 30 min (P < 0.05), chondrogenic morphology disorganized after 15 min, while ALP activity declined only at 60 min (P < 0.05). In vivo, irrigation > 15 min markedly reduced bone formation (P < 0.05) and parallel reductions in mineralized matrix(P < 0.05). In summary, prolonged irrigation (> 15 min) in the spinal endoscopic aqueous environment compromises MSC/β-TCP adhesion and osteogenic capacity. Optimizing surgical efficiency and strictly controlling the irrigation time and pressure are critical in preserving graft performance for successful bone fusion.

Adjacent Segment Motion of Stand-Alone ALIF Versus TLIF in the Degenerative Spine: A Biomechanical Study

Study DesignBiomechanical human cadaveric study.ObjectivesTransforaminal lumbar interbody fusion (TLIF) is a well-established procedure for treating degenerative lumbar spine pathologies. However, posterior fixation has been reported to accelerate adjacent segment degeneration (ASD). Posterior fixation can be omitted in screw-anchored stand-alone anterior lumbar interbody fusion (ALIF). The present study aimed to compare the cranial adjacent segment motion of ALIF vs TLIF in specimens with reduced bone mineral density (BMD).MethodsSixteen fresh-frozen lumbosacral spines with reduced BMD (donors' age 71 ± 13years, BMD 95.7 ± 34.5 mg HA/cm3) were used. Range of motion (ROM) and Neutral Zone (NZ) of the cranial adjacent segment were analyzed in flexion-extension, lateral bending, and axial rotation in native state and after TLIF or stand-alone screwed ALIF instrumentation.ResultsNo significant differences between TLIF and stand-alone screwed ALIF were observed for both absolute ROM and NZ of the cranial adjacent segment in instrumented state across all tested motion directions (P  ≥ .267). Decreased relative ROM of the fused segment - normalized to the corresponding segmental ROM in native state - resulted in compensatory increased relative ROM of the cranial adjacent segment after instrumentation. However, the relative adjacent segment ROM did not differ significantly between TLIF and stand-alone screwed ALIF (P ≥ .172).ConclusionsThis study found no clinically significant difference in adjacent segment motion when comparing TLIF with stand-alone screwed ALIF. Hence, both techniques appear to have a negligible impact on adjacent segment motion in poor bone quality. This suggests that neither TLIF nor stand-alone screwed ALIF increase the risk of ASD due to compensatory motion resulting from an operated adjacent segment.

Analyses of proximal adjacent segment degeneration and prognostic factors after lumbar fusion surgery: study based on proximal facet joint angle

OBJECTIVE

Lumbar fusion surgery is a common procedure for treating various degenerative spinal conditions. However, the incidence of proximal adjacent segment degeneration (PASD) remains a concern. This study aimed to investigate the effect of proximal facet joint angle (FJA) on PASD and then identify factors that influence prognosis after lumbar fusion surgery.

METHODS

In this retrospective study, the cases of 192 patients who underwent lumbar fusion surgery between January 2020 and June 2022 were analysed. Patients were classified in accordance with their baseline proximal FJA into the high (≥ 40°) and low (< 40°) FJA groups. Prognosis was evaluated during the last follow-up by using clinical, imaging and functional recovery criteria. PASD was assessed using Weishaupt criteria, and imaging parameters were measured on postoperative computed tomography (CT) reconstructions. Statistical analyses, including univariate and multivariate logistic regression, were performed to identify prognostic factors. Receiver operating characteristic (ROC) curves were used to assess predictive value.

RESULTS

The high FJA group exhibited significantly higher rates of PASD compared with the low FJA group (P < 0.001). No significant differences were observed in sex, age, body mass index (BMI) or follow-up duration between the two groups. Poor prognosis was associated with higher BMI, larger FJA and wider facet joint diameter. Logistic regression analysis identified BMI (odds ratio [OR] = 1.801, P = 0.001), FJA (OR = 6.320, P < 0.001) and facet joint sagittal (OR = 1.888, P < 0.001) and coronal (OR = 1.462, P < 0.001) diameters as independent predictors of poor prognosis. A smaller screw inclination angle was associated with better outcomes (OR = 0.907, P = 0.017). Joint ROC analysis underscored the significant predictive power of these factors (area under the curve = 0.881).

CONCLUSION

This study demonstrates that a larger proximal FJA is associated with increased PASD. It also identifies several prognostic factors that influence outcomes after lumbar fusion surgery. Patients with higher BMI, larger FJA and wider sagittal and coronal diameters are at increased risk for poor prognosis. These findings highlight the importance of comprehensive preoperative assessments to optimise surgical planning and improve outcomes in lumbar fusion surgery.

Incidence rate and risk factors of intraoperative-acquired pressure injury in posterior interbody fusion: A retrospective study of a national inpatient sample database

BACKGROUND

Intraoperative-acquired pressure injuries (IAPIs) are a common complication in posterior intervertebral fusion surgery, leading to adverse outcomes for patients. However, there is a lack of large-scale national database research analyzing the morbidity and associated risk factors of IAPIs in this surgical procedure.

METHODS

This retrospective study analyzed data from the National Inpatient Sample (NIS) database from 2010 to 2019. Demographic, hospital, and patient characteristics were examined, including length of stay (LOS), total costs, in-hospital mortality, preoperative comorbidities, and complications.

RESULT

The overall incidence of IAPIs in posterior intervertebral fusion surgery was 0.2 % from 2010 to 2019. The annual occurrence of interbody fusion demonstrated an M-shaped trend, with rates of 0.2 % in 2010, 0.05 % in 2016, and 0.05 % in 2019. IAPIs were associated with increased preoperative complications, longer LOS, higher total hospitalization costs, and higher in-hospital mortality rates. Risk factors for IAPIs included comorbidities, large hospitals, urban hospitals, deficiency anemia, coagulation disorders, fluid electrolyte disorders, paralysis, and weight loss. Additionally, IAPIs were linked to medical complications such as sepsis, deep vein thrombosis, urinary tract infections, acute renal failure, shock, pneumonia, blood transfusion, and surgical complications such as cerebrospinal fluid leak. Elective admission was found to be a protective factor.

CONCLUSION

Identifying risk factors for IAPIs in posterior intervertebral fusion surgery can help identify high-risk patients and develop preventive measures. By targeting these risk factors, the incidence of IAPIs can be reduced, leading to improved patient outcomes.

Loosening of stand-alone ALIF versus TLIF in degenerated lumbar human spines: an in vitro biomechanical study

PURPOSE

Biomechanical investigation is needed to determine whether stand-alone anterior lumbar interbody fusion with integrated screws (ALIF) is advisable for use in elderly patients. This study aimed to test three null hypotheses: (1) cyclic loading does not cause loosening of ALIF in degenerated lumbar specimens, (2) cyclic loading does not cause loosening in transforaminal lumbar interbody fusion (TLIF) in degenerated lumbar specimens, and (3) Neutral Zone (NZ) and Range of motion (ROM) of ALIF and TLIF do not differ after cyclic loading.

METHODS

Twelve fresh-frozen human cadaveric lumbar motion segments (L1-5, donors' age 76.1 ± 6.7 years; trabecular BMD 97.1 ± 36.9 mgHA/cm3) were utilized. NZ and ROM were assessed after ALIF or TLIF and following cyclic loading for flexion-extension (Flex-Ext), lateral bending (LB), and axial rotation (AR). Axial compression of 0-1150 N was applied over 2000 cycles. Loosening was defined as significant increase in NZ.

RESULTS

Cyclic loading significantly increased NZ of ALIF specimens in Flex-Ext (1.69 ± 1.81°, p =.048) and LB (1.84 ± 1.81°, p =.036), and showed a trend to significance in AR (0.46 ± 0.54°, p =.065). NZ of TLIF specimens did not increase significantly in any motion direction (p ≥.112). ROM and NZ did not differ significantly between ALIF and TLIF in post-cyclic states(p ≥.556).

CONCLUSION

Axial compression loading caused significant loosening of ALIF in Flex-Ext and LB, but not of TLIF in degenerated lumbar human cadaveric specimens. Hence, standalone ALIF cannot be recommended without reservation for the use in elderly patients with degenerative lumbar spines. However, the absolute differences between pre- and post-cyclic states were small, and ROM and NZ of ALIF after cyclic loading were comparable to TLIF.

Quantifying in vitro load-sharing in spinal fusion surgical constructs using strain sensor-equipped fixation rods and force sensor-equipped intervertebral cages

BACKGROUND CONTEXT

Posterior and transforaminal lumbar interbody fusion (PLIF, TLIF) are widely recognized techniques for achieving spinal fusion. However, the biomechanical load-sharing interactions between the intervertebral cage, posterior instrumentation, and anatomical structures in the instrumented lumbar spine-particularly before and after cage subsidence and decompression procedures-remain insufficiently understood.

PURPOSE

This study aimed to quantify the load-sharing proportions of cages, rods, and anatomical structures in various spinal fusion configurations by comparing the load-sharing behavior of fusion components with intact IVD, after microdiscectomy, midline decompression, and cage instrumentation (uni- and bilateral PLIF, and TLIF) with and without endplate disruption.

STUDY DESIGN

Biomechanical cadaveric study.

METHODS

Sixteen lumbar spinal segments were mechanically tested using strain sensor-equipped rods and force sensor-equipped cages under uniaxial compression ranging from 0 to 1,000 N. The specimens were randomized into 4 groups based on cage configuration: unilateral PLIF (uPLIF), bilateral PLIF (bPLIF), TLIF, and a group with no cage. Each group included specimens from the T12-L1, L2-L3, and L4-L5 spinal segments. Instrumented fixation rods were mounted after applying a 55 N compression on each side to maintain spinal segment lordosis.

RESULTS

Independent of the applied force, anatomical structures, and cages consistently carried the highest force, with median load proportions at 1,000 N being 44.55% for anatomical structures, 36.3% for cages, and 14.44% for rods (n=12). In the absence of a cage, with an intact IVD, fixation rods contributed less to load carriage with a median of 9.0% (n=4). Endplate disruption, serving as a surrogate for cage subsidence, resulted in a 2.5% increase in the absolute load proportion on rods and a 4.4% increase on anatomical structures at 1000 N, while the proportion on the cages decreased by 14.6%. Removing the cage further increased the proportions on rods by 8.3% and on anatomical structures by 32.9%. Among the decompression steps, only small and full nucleotomy increased the load on the rods, with the median load proportions increasing by 1.6% and 4.8% at 1,000 N, respectively.

CONCLUSIONS

This study reveals that regardless of the applied force, anatomical structures and cages consistently carried higher loads compared to the rods. The load taken by the fixation rods was smaller when the IVD was intact and no cage was used, compared to the samples in which cages were inserted. After endplate disruption, cages carried less force whereas rods and anatomical structures took more. Among decompression steps, only small and full nucleotomy increased the load on the rods, consequently decreasing the load on anatomical structures. Anatomical structures contributed more to load carriage than expected, highlighting the importance of their preservation.

CLINICAL SIGNIFICANCE

The findings demonstrate that anatomical structures play a critical role in load-sharing during spinal fusion, consistently carrying more than 40% of the load, while cages contribute synergistically by maintaining intervertebral height and supporting fusion. This highlights the importance of preserving anatomical integrity during surgery.

Unilateral biportal endoscopic lumbar interbody fusion assisted by a Tianji robot for lumbar degenerative disease in elderly patients: a retrospective study

BACKGROUND

Unilateral biportal endoscopic lumbar interbody fusion (UBE-LIF) has been successfully used to treat degenerative lumbar spinal diseases. Nevertheless, the duration of the UBE-LIF procedure notably exceeds that of minimally invasive transforaminal lumbar interbody fusion (Mis-TLIF), increasing the potential for perioperative complications, particularly in elderly patients.

OBJECTIVE

This retrospective study aimed to compare the results of robot assistance (RA) and non-assistance (NA) groups and to explore the benefits of UBE-LIF assisted by a Tianji robot in aged patients.

METHODS

60 patients were divided into two groups: 30 patients in the RA group and 30 in the NA group from January 2022 to June 2023. The surgical duration, estimated intraoperative blood loss, postoperative drainage, length of hospital stays, and radiation exposure were examined and documented. Clinical assessments, including the Oswestry Disability Index (ODI), visual analog scale (VAS), modified MacNab criteria, postoperative complications, and interbody fusion rate, were also evaluated.

RESULTS

No significant differences were observed between the two groups in terms of postoperative drainage, length of postoperative hospital stay, or fusion rate. However, the RA group exhibited lower perioperative complications, estimated intraoperative blood loss, and duration of radiation exposure than the NA group. The average total operation time in the RA group was 105.3 ± 25.8 min, which was significantly shorter than the NA group's average of 130.5 ± 22.5 min (P < 0.001). Furthermore, both groups demonstrated improvements in all clinical outcomes at various postoperative time points, with no significant differences between them (P > 0.05).

CONCLUSIONS

Compared with the NA approach, robot-assisted UBE-LIF technology provides accurate intraoperative guidance and helps spinal surgeons achieve accurate decompression. Furthermore, it can reduce radiation exposure, operation time, blood loss, and surgical complications, thereby improving the surgical efficiency and safety.

An experimental methodology to measure the effects of intervertebral interventions on the facet biomechanics in situ

Whereas facet joints are recognised as being involved in back pain with high prevalence of early degeneration, the biomechanics of facet joints remain understudied and often overlooked in the evaluation of spinal interventions. This study aimed to develop a methodology for investigating the biomechanics of lumbar facet joints and applied it to a mock fusion model with posteriorly centred compressive loads. The proposed methodology involved measuring facet joint biomechanics through synchronized specimen load and displacement measurements, motion capture of the superior facets with 4 K webcams, and pressure mapping through the facet joints. The experimental method was developed using aged ovine lumbar functional units (N = 6). Results showed that the proposed methodology to measure facet joints biomechanics was accurate (displacement errors below 0.2 mm) and able to capture changes in biomechanics following a mock fusion (with significant differences in all measured displacements). Pressure measurement was challenging due to curvature changes in old ovine tissue which was used for method development but translated successfully to human lumbar tissue. It showed that an aged sheep model is not a good model for posterior spinal biomechanics. This work specifies a new, accurate, methodology to evaluate facet joint biomechanics in vitro and, uniquely, how they change following a spinal intervention.

Effectiveness of biportal endoscopic lumbar interbody fusion using the multi-layer bone grafting technique: a retrospective study from Vietnam

STUDY DESIGN

A retrospective cohort study.

PURPOSE

This study aimed to describe the surgical technique of biportal endoscopic (BE) lumbar interbody fusion (LIF) using a multi-layer bone grafting method and to investigate its clinical effectiveness in treating patients with grade I or II lumbar spondylolisthesis (LS).

OVERVIEW OF LITERATURE

Previous studies have described BE-LIF; however, these reports predominantly originate from advanced centers in developed countries, using sophisticated implants such as dual transforaminal LIF (TLIF), oblique LIF, or titanium cages. In contrast, the described method utilizes hydroxyapatite (HA) bone grafts and autologous bone obtained from the preserved inferior articular process (IAP), combined with a single conventional TLIF cage, which provides a cost-effective alternative.

METHODS

This study included 41 patients with single-level grades 1 or 2 LS from February 2023 to February 2024. Clinical outcomes were assessed using the Visual Analog Scale (VAS) for back and leg pain and the Oswestry Disability Index (ODI). Bridwell fusion grades were evaluated via lumbar spine computed tomography performed 6 months postoperatively.

RESULTS

Over a mean follow-up period of 10.6 months (range, 7-18 months), significant improvements were observed in VAS scores for low back pain (from 7.8±0.8 to 2.1±1.4) and leg pain (from 8.1±1.3 to 1.9±1.5) as well as ODI scores (from 50.4±15.4 to 14.8±10.5). The cohort consisted of patients with grades 1 (73.2%) and 2 LS (26.8%) at L4-L5 (58.6%), L5-S1 (34.1%), and L3-L4 (7.3%) levels. The mean operation time was 182.8±36.4 minutes, with a mean intraoperative blood loss of 190.5±81.3 mL and a mean hospital stay of 7.2±3.6 days. Successful fusion (Bridwell grades I/II) was achieved in 82.9% of the cases, with a 4.9% incidence of cage subsidence. Minor complications included durotomies in two patients (4.9%), whereas no major complications, such as nerve root injury, hardware-related issues, or postoperative infections, were reported.

CONCLUSIONS

The described BE-LIF technique, using HA bone grafts, which are an autologous bone from the preserved IAP, and a TLIF cage, is a viable, safe, and effective option for treating low-grade LS. This approach achieves favorable clinical outcomes and high fusion rates, which provides a cost-effective alternative to advanced surgical implants.

Biomechanical Comparison of a Novel Facet Joint Fusion Fixation Device With Conventional Pedicle Screw Fixation Device: A Finite Element Analysis

PURPOSE

The biomechanics of a novel facet joint fusion device is unknown. The objective of this study is to analyze and compare the biomechanical properties of a novel facet joint fusion device integrated with oblique lateral interbody fusion (OLIF) to those of a conventional pedicle screw fixation device, employing finite element analysis.

METHODS

A comprehensive three-dimensional finite element model of the L3-S1 lumbar spine was developed and validated. Based on this model, three surgical groups were created: OLIF combined with the bilateral facet joint fusion fixation (BFJFF + OLIF), unilateral pedicle screw fixation (UPSF + OLIF), and bilateral pedicle screw fixation (BPSF + OLIF), focusing on the L4-L5 level. A torque of 7.5 Nm was applied to simulate vertebral activities under six conditions: flexion, extension, lateral bending (left and right), and axial rotation (left and right). The maximum displacement at the L4-L5 segment was then calculated. The maximum stress values were recorded at the L4-L5 interbody fusion cage and the L3-L4 and L5-S1 segments.

RESULTS

When compared to the other two models, the BFJFF + OLIF model exhibited the smallest maximum displacement value at the L4-L5 segment across all six working conditions. The BFJFF + OLIF model also demonstrated the lowest maximum stress value at the L4-L5 segment interbody fusion cage under flexion, as well as left and right lateral bending and axial rotation conditions when compared with the other models. However, under the extension condition at the L4-L5 interbody fusion cage, the BPSF + OLIF model showed the lowest maximum stress value. At the adjacent L3-L4 segments, the BFJFF + OLIF model registered the lowest maximum stress value during flexion and left lateral bending conditions. At L3-L4, under extension and right lateral bending conditions, the UPSF + OLIF model exhibited the lowest maximum stress value. Under left axial rotation at the L3-L4 segment, both the BFJFF + OLIF and UPSF+OLIF models demonstrated the smallest maximum stress values. Under right axial rotation at the L3-L4 segment, the BPSF + OLIF model recorded the smallest maximum stress value. Concurrently, at the L5-S1 segment, the BFJFF + OLIF model presented the lowest maximum stress value under conditions of flexion, as well as left and right lateral bending and axial rotation. In the L5-S1 segment during the extension condition, the UPSF+OLIF model exhibited the lowest maximum stress value.

CONCLUSIONS

This study demonstrates that the novel device, when combined with OLIF, achieves 360° lumbar fusion by fusing the lumbar facet joints, thereby enhancing spinal stability post-fusion. Concurrently, stress on adjacent segments was diminished. The findings suggest that this device may serve as a novel internal fixation method. It may provide a new option for the surgical treatment of patients with low back pain in the future.

An improved method for measuring the hounsfield units of the vertebral body and pedicles in patients with lumbar degenerative diseases

BACKGROUND

Although measuring vertebral bone density with the use of the computed tomography-based Hounsfield units (HU) is becoming increasingly popular, a much-desired standardized and robust method for measuring HU values accurately, quickly and conveniently was yet to exist.

METHODS

Lumbar CT images of patients with degenerative lumbar diseases were analyzed. The HU values of the vertebral bodies were measured in three planes: mid-axial (including or not including the posterior venous plexus (PVP)), mid-sagittal and mid-frontal; the HU values of the vertebral pedicles were measured in two planes: axial and sagittal. The existing method was improved to measure the HU values of the S1 pedicles. A comparative analysis was performed, the inter- and intra-observer agreements were calculated.

RESULTS

The HU values of the lumbar vertebrae in the mid-axial planes were the highest (p < 0.001), but showed the most reliable, reproducible and stable values of the intra-class correlation coefficient (ICC) (0.80-0.99 for vertebral bodies and 0.80-0.94 for pedicles). Non-inclusion of the PVP in the ROI did not affect HU values (p > 0.05), and the measurement of the HU values on a slice with the PVP showed high reproducibility (the ICC was 0.93-0.94). Measuring the HU values of the S1 pedicles with the use of the improved method led to an increase in ICC from 0.48 to 0.68.

CONCLUSIONS

Measuring HU values in the L3 alone rather than in the entire lumbar spine or other vertebrae works up to expectations and may be recommended. The ROI should be placed in the mid-axial plane on a slice including the PVP. The most challenging HU measurement is for the S1 pedicles, but the proposed improved method makes it easier to do. These considerations may be particularly relevant to spinal surgeons in their routine practice, including planning the lumbar fusion and screw fixation.

Effect of Approach Based Lumbar Interbody Fusion on Sagittal Spinopelvic Parameters and Functional Outcomes: Comparison between Oblique Lumbar Interbody Fusion (OLIF) and Transforaminal Lumbar Interbody Fusion (TLIF)

PURPOSE

Transforaminal lumbar interbody fusion (TLIF) and oblique lumbar interbody fusion (OLIF) are the most commonly conducted operations for interbody fusions. In addition to fusion, the restoration of proper spinal alignment has become crucial for achieving favorable functional outcomes. There is a lack of agreement on which lumbar interbody fusion technique provides the most effective correction for sagittal spinopelvic parameters (SSPs). This study aims to investigate the functional outcome in terms of SSPs in patients undergoing single level OLIF and TLIF for lumbar degenerative disc disease.

METHODOLOGY

Retrospective analysis of single level OLIF or TLIF was done. The patients' index and follow-up data until 6 months of surgery were collected. Radiographic parameters analysis included disc height (DH), pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), pelvic index, lumbar lordosis (LL), segmental lordosis (SL). Clinical outcomes were recorded using visual analogue scale (VAS) and Oswestry Disability Index (ODI).

RESULTS

In a total of 38 patients (19 in each group) mean age was 51.52 ± 12.67 years in OLIF and 52.17 ± 9.73 years in TLIF. Improvement in DH was more in OLIF but not statistically significant (p = 0.075). Significant improvements were seen in PT, and SL post-TLIF. Change in SSPs among groups shown no significant differences. Both VAS and ODI shown improvements in both the groups but no significant difference was noted while comparing the two groups.

CONCLUSION

The study showed better restoration of SSPs by TLIF in terms of PT and SL although functional outcomes appear similar in both procedures. Increase in DH is the important determinant for resulting good outcome. Patients with maintained spinopelvic balance can be treated satisfactorily with less-invasive OLIF.

The effects of cage on endplate collapse after stand-alone OLIF: based on finite element analysis and in vitro mechanics experiments

Background

Lumbar degenerative diseases are an important factor in disability worldwide, and they are also common among the elderly population. Stand-Alone Oblique Lumbar Interbody Fusion (Stand-Alone OLIF) is a novel surgical approach for treating lumbar degenerative diseases. However, long-term follow-up after surgery has revealed the risk of endplate collapse associated with Stand-Alone OLIF procedures. This study aimed to investigate the effect of the cage factor on endplate collapse after Stand-Alone OLIF.

Methods

Finite element (FE) models and calf lumbar functional units were established separately and used to simulate Stand-Alone OLIF surgery. On the L5 endplate of the FE model and the calf lumbar functional unit, 12 cage positions from anterior to posterior, 16 cage inclination angles from 0° to 15°, and 4 cage heights were selected to simulate surgical models with different cage positions. Compression loads of 400N were applied to the upper surface of the superior vertebral body of the cage, and 10Nm torques in four directions were used to simulate four different physiological movements of the lumbar spine: flexion, extension, lateral curvature and torsion, in order to compare the range of motion of the surgical segment and the endplate stress.

Results

When the cage is placed closer to the anterior and posterior edges of the endplate and when the height of the cage exceeds 12mm, the intervertebral range of motion at the surgical segment is greater and the stress on the endplate is higher during various lumbar spine activities. When the cage is inclined at an angle within 15°, there are no significant differences in the corresponding endplate stress and the range of motion.

Conclusion

For Stand-Alone OLIF surgery, inserting the cage in the central anterior-posterior position of the intervertebral space and selecting a cage with a height not exceeding 12 mm can reduce the stress on the endplate after surgery, which is more conducive to the stability of the lumbar spine postoperatively and reduces the risk of postoperative endplate collapse. The inclination angle of the cage placement does not significantly affect postoperative endplate stress or lumbar stability.

Peptide Hydrogel for Sustained Release of Recombinant Human Bone Morphogenetic Protein-2 In Vitro

This study aimed to investigate the impact of varying the formulation of a specific peptide hydrogel (PepGel) on the release kinetics of rhBMP-2 in vitro. Three PepGel formulations were assessed: (1) 50% v/v (peptides volume/total volume) PepGel, where synthetic peptides were mixed with crosslinking reagents and rhBMP-2 solution; (2) 67% v/v PepGel; (3) 80% v/v PepGel. Each sample was loaded with 12 µg of rhBMP-2 and incubated in PBS. Released rhBMP-2 was quantified by ELISA at 1 h, 6 h, and 1, 2, 4, 7, 10, 14, and 21 days. To explore how PepGel formulations influence rhBMP-2 release, the gel porosities, swelling ratios, and mechanical properties of the three PepGel formulations were quantitatively analyzed. The results showed that rhBMP-2 encapsulated with 50% v/v PepGel exhibited a sustained release over the 21-day experiment, while the 67% and 80% v/v PepGels demonstrated significantly lower rhBMP-2 release rates compared to the 50% formulation after day 7. Higher histological porosity of PepGel was significantly correlated with increased rhBMP-2 release rates. Conversely, the swelling ratio and elastic modulus of the 50% v/v PepGel were significantly lower than that of the 67% and 80% v/v formulations. In conclusion, this study indicates that varying the formulation of crosslinked PepGel can control rhBMP-2 release rates in vitro by modulating gel porosity, swelling ratio, and mechanical properties. Encapsulation with 50% v/v PepGel offers a sustained rhBMP-2 release pattern in vitro; if replicated in vivo, this could mitigate the adverse effects associated with burst release of rhBMP-2 in clinical applications.

The influence of lumbar vertebra and cage related factors on cage-endplate contact after lumbar interbody fusion: An in-vitro experimental study

Lumbar interbody fusion (LIF) using interbody cages is an established treatment for lumbar degenerative disc disease, but fusion results are known to be affected by risk factors such as bone mineral density (BMD), endplate geometry and cage position. At present, direct measurement of endplate-cage contact variables that affect LIF have not been fully identified. The aim of this study was to use cadaveric experiments to investigate the dependency between BMD, endplate geometry, cage parameters like type, orientation, position, and contact variables like stress and area. One vertebral body specimen from each of the five lumbar positions was harvested from five male donors. The lower half of each vertebra was potted and placed in a material testing machine (Instron 8874). A spinal cage was clamped to the machine then lowered to bring it into contact against the superior endplate. A lockable ball-joint was used to rotate the cage such that its inferior surface was congruent with the local endplate surface. A pressure sensor (Tekscan) was placed between the cage and endplate to record contact area and the peak and average contact pressures. Axial compression of 400 N was performed for five positions using a straight cage, and in one anterior position using a curved cage. The linear mixed model was utilised to perform data analyses for experimental results with statistical significance set at p < 0.05. The results indicated two trends toward significance for contact area, one for volumetric BMD (vBMD) of the vertebra (p = 0.081), and another for predicted contact area (p = 0.057). Peak contact pressure correlated significantly with vBMD (p = 0.041), and there was a trend between average contact pressure and lateral position of cage (p = 0.051). In addition, predicted contact area correlated significantly with cage orientation (p < 0.001). These results indicated that high vBMD of vertebra and a medially positioned cage led to higher contact pressures. Logically, low vBMD of vertebra and transverse cage orientation increased the contact area between the cage and endplate. In conclusion, the study identified significant influence of vBMD of vertebra, cage position and orientation on cage-endplate contact which may help to inform cage selection and design for LIF.

Local drug delivery challenges and innovations in spinal neurosurgery

The development of novel therapeutics in the field of spinal neurosurgery faces a litany of translational challenges. Achieving precise drug targeting within the confined spaces associated with the spinal cord, canal and vertebra requires the development of next generation delivery systems and devices. These must be capable of overcoming inherent barriers related to drug diffusion, whilst concurrently ensuring optimal drug distribution and retention. In this review, we provide an overview of the most recent advances in the therapeutic management of diseases and disorders affecting the spine, including systems and devices capable of releasing small molecules and biopharmaceuticals that help eliminate pain and restore the mechanical function and stability of the spine. We highlight material-based approaches and minimally invasive techniques that can be employed to provide control over drug release kinetics and improve retention. We also seek to explore how the newest advancements in nanotechnology, biomaterials, additive manufacturing technologies and imaging modalities can be employed in this translational pursuit. Finally, we discuss the landscape of clinical trials and recently approved products aimed at overcoming the complexities associated with drug delivery to the spine.

Influence of a Lordotic Cage Profile on Global and Segmental Lordosis in the Context of Lumbar TLIF Surgeries: A Retrospective Radiological Analysis

Background/Objectives: Cage implantation decompresses neural elements, stabilizes segments, and promotes fusion, with sagittal balance influenced by cage size, geometry, and position. This retrospective study compared the effects of lumbar interbody cages with 10° and 15° lordotic angles on global and segmental lordosis in patients undergoing transforaminal lumbar interbody fusion (TLIF). Methods: Data from 215 patients who underwent 259 TLIF procedures between 2018 and 2022 were analyzed. All the surgeries were performed by a single senior orthopedic spine surgeon, and cages were selected by the surgeon based on patients' clinical and anatomical factors. Radiographic assessments included measurements of global and segmental lordosis. Results: Patients who received 15° cages demonstrated significantly greater segmental lordosis compared to those who received 10° cages in both bisegmental and monosegmental procedures (p < 0.001). While the global lordosis in the 10°-cage group remained unchanged postoperatively (p = 0.687), bisegmental procedures showed a small but statistically significant increase (p = 0.035). Moreover, global lordosis did not significantly differ between the 10°- and 15°-cage groups. Conclusions: Cage geometry significantly influenced segmental lordosis, with 15° cages achieving overall more superior radiographic results compared to 10° cages. However, global lordosis was unaffected by cage angle, thereby highlighting the multifaceted nature of factors that influence overall spinal alignment. These findings provide valuable insights into lumbar spine surgery, thus emphasizing the need for comprehensive preoperative planning and consideration of individual patient characteristics.

Unique characteristics of bone union at the infected vertebrae after minimally invasive posterior fixation without bone grafting in thoracolumbar pyogenic spondylitis: a retrospective multicenter cohort study

BACKGROUND

The current study aimed to evaluate the bone union rate between infected vertebrae after minimally invasive posterior fixation without bone grafting in thoracolumbar pyogenic spondylitis.

METHODS

This retrospective multicenter cohort study evaluated 75 patients of posterior fixation for thoracolumbar pyogenic spondylitis that have been recorded at six relevant institutions from January 2016 to December 2022. Data on age, sex, location of infected vertebrae, number of infected disks, comorbidity, Pola classification, number of vertebrae fixed according to surgery, implant failure requiring revision surgery, and distance according to the type of infected vertebrae after surgery were evaluated. Further, their association with postoperative bone union was investigated > 12 months postoperatively.

RESULTS

Finally, 40 patients were included in the study. In total, 32 (80%) patients achieved bone union at the infected vertebrae after minimally invasive posterior fixation without bone grafting. The mean duration from surgery to union was 10.7 months. Twenty-six (65%) patients initially achieved bone union at the lateral and/or anterior bridging callus. Patients with multiple-level infected disks (33%, 2/6 patients) had a lower bone union rate than those with a single-level infected disk (88%, 30/34 patients) (p = 0.0095).

CONCLUSIONS

In 80% of patients, bone union at the infected vertebrae was achieved after minimally invasive posterior fixation without bone grafting in thoracolumbar pyogenic spondylitis. A total of 65% of the patients achieved initial bone union at the lateral and/or anterior bridging callus. Moreover, patients with multiple-level infected disks had a low bone union rate. Hence, the treatment strategy should be cautiously considered.

TRIAL REGISTRATION

This study was registered retrospectively and all procedures used in this study including the review of patient records were approved by the institutional review board.

Advances in implants and bone graft types for lumbar spinal fusion surgery

The increasing prevalence of spinal disorders worldwide necessitates advanced treatments, particularly interbody fusion for severe cases that are unresponsive to non-surgical interventions. This procedure, especially 360° lumbar interbody fusion, employs an interbody cage, pedicle screw-and-rod instrumentation, and autologous bone graft (ABG) to enhance spinal stability and promote fusion. Despite significant advancements, a persistent 10% incidence of non-union continues to result in compromised patient outcomes and escalated healthcare costs. Innovations in lumbar stabilisation seek to mimic the properties of natural bone, with evolving implant materials like titanium (Ti) and polyetheretherketone (PEEK) and their composites offering new prospects. Additionally, biomimetic cages featuring precisely engineered porosities and interconnectivity have gained traction, as they enhance osteogenic differentiation, support osteogenesis, and alleviate stress-shielding. However, the limitations of ABG, such as harvesting morbidities and limited fusion capacity, have spurred the exploration of sophisticated solutions involving advanced bone graft substitutes. Currently, demineralised bone matrix and ceramics are in clinical use, forming the basis for future investigations into novel bone graft substitutes. Bioglass, a promising newcomer, is under investigation despite its observed rapid absorption and the potential for foreign body reactions in preclinical studies. Its clinical applicability remains under scrutiny, with ongoing research addressing challenges related to burst release and appropriate dosing. Conversely, the well-documented favourable osteogenic potential of growth factors remains encouraging, with current efforts focused on modulating their release dynamics to minimise complications. In this evidence-based narrative review, we provide a comprehensive overview of the evolving landscape of non-degradable spinal implants and bone graft substitutes, emphasising their applications in lumbar spinal fusion surgery. We highlight the necessity for continued research to improve clinical outcomes and enhance patient well-being.

Clinical values of oblique lumbar interbody fusion on the treatment of single-level degenerative lumbar diseases

Objectives

Minimally invasive transforaminal lumbar interbody fusion (Mis-TLIF) and oblique lumbar interbody fusion (OLIF) are increasingly replacing traditional approaches. This study aimed to compare the clinical outcomes of OLIF and Mis-TLIF in treating single-level degenerative lumbar diseases.

Methods

Patients with single-level degenerative lumbar diseases underwent either OLIF (30 patients) or Mis-TLIF (30 patients). Surgical data, including operation time, blood loss, postoperative drainage, and postoperative bed rest duration, were collected. Clinical outcomes were assessed using the Oswestry disability index, the visual analog scale scores for low back pain and leg pain, and Japanese Orthopaedic Association scores for daily ability, along with monitoring of complications.

Results

The OLIF group showed significantly shorter operative times, less blood loss, reduced postoperative drainage, and shorter bed rest durations than the Mis-TLIF group. At the 1-month follow-up, OLIF patients also demonstrated significantly better clinical outcome scores than Mis-TLIF patients. No significant differences were observed between OLIF and Mis-TLIF patients before surgery and after 3 months. Furthermore, lumbar lordosis and disc height were significantly greater in the OLIF group at the final follow-up.

Conclusions

Both OLIF and Mis-TLIF achieved satisfactory and effective long-term clinical outcomes for single-level lumbar degenerative diseases. However, OLIF resulted in less tissue damage, reduced bleeding, better short-term clinical outcomes, and improved recovery of segmental lordosis compared to Mis-TLIF. Therefore, OLIF appears to be the preferable option over Mis-TLIF.

An overview of magnesium-based implants in orthopaedics and a prospect of its application in spine fusion

Due to matching biomechanical properties and significant biological activity, Mg-based implants present great potential in orthopedic applications. In recent years, the biocompatibility and therapeutic effect of magnesium-based implants have been widely investigated in trauma repair. In contrast, the R&D work of Mg-based implants in spinal fusion is still limited. This review firstly introduced the general background for Mg-based implants. Secondly, the mechanical properties and degradation behaviors of Mg and its traditional and novel alloys were reviewed. Then, different surface modification techniques of Mg-based implants were described. Thirdly, this review comprehensively summarized the biological pathways of Mg degradation to promote bone formation in neuro-musculoskeletal circuit, angiogenesis with H-type vessel formation, osteogenesis with osteoblasts activation and chondrocyte ossification as an integrated system. Fourthly, this review followed the translation process of Mg-based implants via updating the preclinical studies in fracture fixation, sports trauma repair and reconstruction, and bone distraction for large bone defect. Furthermore, the pilot clinical studies were involved to demonstrate the reliable clinical safety and satisfactory bioactive effects of Mg-based implants in bone formation. Finally, this review introduced the background of spine fusion surgeryand the challenges of biological matching cage development. At last, this review prospected the translation potential of a hybrid Mg-PEEK spine fusion cage design.

Impact of Gender-Specific Physiological activities on Bone Density and Spinal Alignment Post-Spinal Stabilization Surgery Affecting Quality of Life

Background: The rate of spinal stabilization surgery has increased in recent years among both males and females due to ineffective activities impacting their quality of life, work-disability, and social-disability. Aim: This study aimed to determine the impact of such activities on bone density and spinal alignment after spinal stabilization surgery within the context of Bursa, Turkey. Method: A sample of 450 patients, who had undergone spinal surgery, was included, 210 of which were females and 240 were males. These patients had suffered from different ailments including spinal stenosis, degenerative spondylolisthesis and disc herniation. In order to attain the required outcomes, Core Outcome Measures Index (COMI) was measured before and after (one year) operation. This test measured various positive and negative outcomes post-spinal stabilization surgery including improvement in degree of pain and back function, quality of life, degree of work-disability and social-disability, over a period of 12-months. Patients' satisfaction level with therapy was also measured using a 5-point Likert scale while parametric statistics provided the relationship among variables. Results: The results obtained show that females with all pathologies had worse COMI scores significantly (p < 0.05) as compared to males. However, no significant differences were observed after the operation within the context of gender (p > 0.05). However, 72% of females and 71% of males received minimal clinically important change (MCIC) score of 2.2 for COMI. Hence, gender showed insignificant relationship with MCIC, since females did not show any significant satisfaction level as compared to males concerning their post-operative health outcomes. Conclusion: The study recommends to emphasize on improving therapeutic and surgical measures aiming at attaining significant satisfaction levels after surgery.

Impact of bone density and integrated screw configuration on standalone anterior lumbar interbody construct strength

Background

In anterior lumbar interbody fusion (ALIF), the use of integrated screws is attractive to surgeons because of the ease of implantation and no additional profile. However, the number and length of screws necessary for safe and stable implantation in various bone densities is not yet fully understood. The current study aims to determine how important both length and number of screws are for stability of ALIFs.

Methods

Three bone models with densities of 10, 15, and 20 pounds per cubic foot (PCF) were chosen as surrogates. These were instrumented using the Z-Link lumbar interbody system with either 2, 3, or 4 integrated 4.5 × 20 mm screws or 4.5 × 25 mm screws (Zavation, LLC, Flowood, MS). The bone surrogates were tested with loading conditions resulting in spine extension to measure construct stiffness and peak force.

Results

The failure load of the construct was influenced by the length of screws (p=.01) and density of the bone surrogate (p<.01). There was no difference in failure load between using 2 screws and 3 screws (p=.32) or when using four 20 mm screws versus three 25 mm screws (p=.295).

Conclusion

In our study, both bone density and length of screws significantly affected the construct's load to failure. In certain cases where a greater number of screws are unable to be implanted, the same stability can potentially be conferred with use of longer screws. Future clinical studies should be performed to test these biomechanical results.

Long-term Outcome of Isobar TTL System for the Treatment of Lumbar Degenerative Disc Diseases

OBJECTIVE

The Isobar TTL dynamic fixation system has demonstrated favorable outcomes in the short-term treatment of lumbar degenerative disc diseases (LDDs). However, there is a paucity of extensive research on the long-term effects of this system on LDDs. This study aimed to evaluate the long-term clinical and radiological outcomes of patients with LDDs who underwent treatment utilizing the Isobar TTL dynamic fixation system.

METHODS

The study analyzed the outcomes of 40 patients with LDDs who underwent posterior lumbar decompression and received single-segment Isobar TTL dynamic internal fixation at our hospital between June 2010 and December 2016. The evaluation of clinical therapeutic effect involved assessing postoperative pain levels using the visual analogue scale (VAS) and Oswestry disability index (ODI), both before surgery, 3 months after, and the final follow-up. To determine the preservation of functional motion in dynamically stable segments, we measured the range of motion (ROM) and disc height of stabilized and adjacent segments preoperatively and during the final follow-up. Additionally, we investigated the occurrence of adjacent segment degeneration (ASD).

RESULTS

Forty patients were evaluated, with an average age of 44.65 years and an average follow-up period of 79.37 months. Fourteen patients belonged to the spondylolisthesis group, while the remaining 26 were categorized under the stenosis or herniated disc group. The preoperative ROM of the stabilized segment exhibited a significant reduction from 8.15° ± 2.77° to 5.00° ± 1.82° at the final follow-up (p < 0.001). In contrast, there was a slight elevation in the ROM of the adjacent segment during the final follow-up, increasing from 7.68° ± 2.25° before surgery to 9.36° ± 1.98° (p < 0.001). The intervertebral space height (IH) in the stabilized segment exhibited a significant increase from 10.56 ± 1.99 mm before surgery to 11.39 ± 1.90 mm at the one-week postoperative follow-up (p < 0.001). Conversely, there was a notable decrease in the IH of the adjacent segment from 11.09 ± 1.82 mm preoperatively to 10.86 ± 1.79 mm at the one-week follow-up after surgery (p < 0.001). The incidence of ASD was 15% (6/40) after an average follow-up period of 79.37 months, with a rate of 15.38% (4/26) in the stenosis or herniated disc group and 14.29% (2/14) in the spondylolisthesis group; however, no statistically significant difference was observed in the occurrence of ASD among these groups (p > 0.05).

CONCLUSION

The Isobar TTL dynamic fixation system is an effective treatment for LDDs, improving pain relief, quality of life (QoL) and maintaining stabilized segmental motion. It has demonstrated excellent long-term clinical and radiographic results.

Evaluation of the learning curve and complications in unilateral biportal endoscopic transforaminal lumbar interbody fusion: cumulative sum analysis and risk-adjusted cumulative sum analysis

PURPOSE

To evaluate the learning curve and complications in unilateral biportal endoscopic transforaminal lumbar interbody fusion (ULIF) using the Cumulative Sum (CUSUM) analysis and Risk-adjusted Cumulative Sum (RA-CUSUM) analysis.

METHODS

This study retrospectively analyzed 184 consecutive patients who received ULIF in our hospital, including 104 males and 80 females. CUSUM analysis and RA-CUSUM analysis were used to evaluate the learning curve of ULIF based on the operation time and surgical failure rate, respectively. All postoperative complications were defined as surgical failure. Variables of different phases were compared based on the learning curve.

RESULTS

The CUSUM analysis showed the cutoff point for ULIF was 29 cases, and the RA-CUSUM analysis showed the cutoff point for ULIF was 41 cases. Operating time and hospital stay were significantly decreased as the learning curve progressed (P < 0.05). Visual analogue score (VAS) and Oswestry disability index (ODI) at the last follow-up were significantly lower than preoperatively. At the last follow-up, a total of 171 patients reached intervertebral fusion, with a fusion rate of 92.9% (171/184). A total of eleven complications were observed, and RA-CUSUM analysis showed that the incidence of complications in the early phase was 17.07% and in the late phase was 2.6%, with a significant difference (P < 0.05).

CONCLUSION

ULIF is an effective minimally invasive lumbar fusion surgical technique. But a learning curve of at least 29 cases will be required to master ULIF, while 41 cases will be required to achieve a stable surgical success rate.

Comparing the osteogenesis outcomes of different lumbar interbody fusions (A/O/X/T/PLIF) by evaluating their mechano-driven fusion processes

BACKGROUND

In lumbar interbody fusion (LIF), achieving proper fusion status requires osteogenesis to occur in the disc space. Current LIF techniques, including anterior, oblique, lateral, transforaminal, and posterior LIF (A/O/X/T/PLIF), may result in varying osteogenesis outcomes due to differences in biomechanical characteristics.

METHODS

A mechano-regulation algorithm was developed to predict the fusion processes of A/O/X/T/PLIF based on finite element modeling and iterative evaluations of the mechanobiological activities of mesenchymal stem cells (MSCs) and their differentiated cells (osteoblasts, chondrocytes, and fibroblasts). Fusion occurred in the grafting region, and each differentiated cell type generated the corresponding tissue proportional to its concentration. The corresponding osteogenesis volume was calculated by multiplying the osteoblast concentration by the grafting volume.

RESULTS

TLIF and ALIF achieved markedly greater osteogenesis volumes than did PLIF and O/XLIF (5.46, 5.12, 4.26, and 3.15 cm3, respectively). Grafting volume and cage size were the main factors influencing the osteogenesis outcome in patients treated with LIF. A large grafting volume allowed more osteoblasts (bone tissues) to be accommodated in the disc space. A small cage size reduced the cage/endplate ratio and therefore decreased the stiffness of the LIF. This led to a larger osteogenesis region to promote osteoblastic differentiation of MSCs and osteoblast proliferation (bone regeneration), which subsequently increased the bone fraction in the grafting space.

CONCLUSION

TLIF and ALIF produced more favorable biomechanical environments for osteogenesis than did PLIF and O/XLIF. A small cage and a large grafting volume improve osteogenesis by facilitating osteogenesis-related cell activities driven by mechanical forces.

Comparison of the clinical outcomes of VBE-TLIF versus MIS-TLIF for single-level degenerative lumbar diseases

OBJECTIVE

This research aims to compare the clinical outcomes of VBE-TLIF and MIS-TLIF for the treatment of patients with single-level degenerative lumbar diseases.

METHODS

Ninety patients were enrolled in this study. The estimated blood loss, operation time, postoperative hospitalization days, time to functional exercise, amount of surgical drain and inflammatory index were recorded. The visual analog scale, Oswestry dysfunction index and modified MacNab criteria were used to assessed the patient's back and leg pain, functional status and clinical satisfaction rates.

RESULTS

The average operation time of the VBE-TLIF group was longer than that of the MIS-TLIF group. The time for functional exercise, length of hospital stay, estimated blood loss and amount of surgical drain in the VBE-TLIF group were relative shorter than those in the MIS-TLIF group. Additionally, the levels of CRP, neutrophil, IL-6 and CPK in the VBE-TLIF group were significantly lower than those in the MIS-TLIF group at postoperative days 1 and 3, respectively (P < 0.001). Patients undergoing VBE-TLIF had significantly lower back VAS scores than those in the MIS-TLIF group on postoperative days 1 and 3 (P < 0.001). No significant differences were found in the clinical satisfaction rates (95.83 vs. 95.24%, P = 0.458) or interbody fusion rate (97.92 vs. 95.24%, P = 0.730) between these two surgical procedures.

CONCLUSIONS

Both VBE-TLIF and MIS-TLIF are safe and effective surgical procedures for patients with lumbar diseases, but VBE-TLIF technique is a preferred surgical procedure with merits of reduced surgical trauma and quicker recovery.

Mechano-driven intervertebral bone bridging via oriented mechanical stimulus in a twist metamaterial cage: An in silico study

Stiffer cages provide sufficient mechanical support but fail to promote bone ingrowth due to stress shielding. It remains challenging for fusion cage to satisfy both bone bridging and mechanical stability. Here we designed a fusion cage based on twist metamaterial for improved bone ingrowth, and proved its superiority to the conventional diagonal-based cage in silico. The fusion process was numerically reproduced via an injury-induced osteogenesis model and the mechano-driven bone remodeling algorithm, and the outcomes fusion effects were evaluated by the morphological features of the newly-formed bone and the biomechanical behaviors of the bone-cage composite. The twist-based cages exhibited oriented bone formation in the depth direction, in comparison to the diagonal-based cages. The axial stiffness of the bone-cage composites with twist-based cages was notably higher than that with diagonal-based cages; meanwhile, the ranges of motion of the twist-based fusion segment were lower. It was concluded that the twist metamaterial cages led to oriented bone ingrowth, superior mechanical stability of the bone-cage composite, and less detrimental impacts on the adjacent bones. More generally, metamaterials with a tunable displacement mode of struts might provide more design freedom in implant designs to offer customized mechanical stimulus for osseointegration.

Finite element biomechanical analysis of 3D printed intervertebral fusion cage in osteoporotic population

OBJECTIVE

To study the biomechanical characteristics of each tissue structure when using different 3D printing Cage in osteoporotic patients undergoing interbody fusion.

METHODS

A finite element model of the lumbar spine was reconstructed and validated with regarding a range of motion and intervertebral disc pressure from previous in vitro studies. Cage and pedicle screws were implanted and part of the lamina, spinous process, and facet joints were removed in the L4/5 segment of the validated mode to simulate interbody fusion. A 280 N follower load and 7.5 N·m moment were applied to different postoperative models and intact osteoporotic model to simulate lumbar motion. The biomechanical characteristics of different models were evaluated by calculating and analyzing the range of motion of the fixed and cephalic adjacent segment, the stress of the screw-rod system, the stress at the interface between cage and L5 endplate, and intervertebral disc pressure of the adjacent segment.

RESULTS

After rigid fixation, the range of motion of the fixed segment of model A-C decreased significantly, which was much smaller than that of the osteoporotic model. And with the increase of the axial area of the interbody fusion cages, the fixed segment of model A-C tended to be more stable. The range of motion and intradiscal pressure of the spinal models with different interbody fusion cages were higher than those of the complete osteoporosis model, but there was no significant difference between the postoperative models. On the other hand, the L5 upper endplate stress and screw-rod system stress of model A-C show a decreasing trend in different directions of motion. The stress of the endplate is the highest during flexion, which can reach 40.5 MPa (model A). The difference in endplate stress between models A-C was the largest during lateral bending. The endplate stress of models A and B was 150.5% and 140.9% of that of model C, respectively. The stress of the screw-rod system was the highest during lateral bending (model A, 102.0 MPa), which was 108.4%, 102.4%, 110.4%, 114.2% of model B and 158.5%, 110.1%, 115.8%, 125.4% of model C in flexion, extension, lateral bending, and rotation, respectively.

CONCLUSIONS

For people with osteoporosis, no matter what type of cage is used, good immediate stability can be achieved after surgery. Larger cage sizes provide better fixation without significantly increasing ROM and IDP in adjacent segments, which may contribute to the development of ASD. In addition, larger cage sizes can disperse endplate stress and reduce stress concentration, which is of positive significance in preventing cage subsidence after operation. The cage and screw rod system establish a stress conduction pathway on the spine, and a larger cage greatly enhances the stress-bearing capacity of the front column, which can better distribute the stress of the posterior spine structure and the stress borne by the posterior screw rod system, reduce the stress concentration phenomenon of the nail rod system, and avoid exceeding the yield strength of the material, resulting in the risk of future instrument failure.

Supplementary posterior fusion in patients operated on employing TLIF may decrease the instrumentation failure rate

BACKGROUND

It is supposed that additional posterior fusion may provide additional stability of the pedicle screw; however, the clinical impact of additional posterior fusion in patients treated with TLIF remains uncertain. The objective of this study is to assess the clinical efficacy of circumferential fusion in patients treated with TLIF.

MATERIALS AND METHODS

This is a single-center retrospective evaluation of consecutive 179 patients with degenerative lumbar stenosis and instability of spinal segments. Patients with axial pain and neurogenic claudication or radiculopathy associated with spinal stenosis were enrolled during the period from 2012 to 2018. Transforaminal lumbar interbody fusion (TLIF) with a single cage was used to treat patients. In 118 cases a supplementary posterior fusion was made. The duration of follow-up accounted for 24 months, logistic regression analysis was used to assess factors that influence the complication rate.

RESULTS

The rate of pedicle screw loosening was growing with radiodensity getting decreased and was more frequent in patients with two level fusion. An increase in pedicle screw loosening rate correlated with anterior nonunion Tan 2 and 3 grade while both posterior complete and incomplete fusion resulted in a decline in the complication rate. Lumbosacral fusion, bilateral facet joints` resection and laminectomy turned out to be insignificant factors. The overall goodness of fit of the estimated general multivariate model was χ2 = 87.2230; P < 0.0001. To confirm clinical relevance of those findings, a univariate logistic regression was performed to assess the association between clinically significant pedicle screw instability and posterior fusion in patients operated on employing TLIF. The results of logistic regression analysis demonstrate that additional posterior fusion may decrease the rate of instrumentation failure that requires revision surgery in patients treated with TLIF [B0 = 1.314321; B1 = -3.218279; p = 0.0023; OR = 24.98507; 95% CI (3.209265; 194.5162), the overall goodness of fit of the estimated regression was χ2 = 22.29538, p = <0.0001].

CONCLUSION

Circumferential fusion in patients operated on employing TLIF is associated with a decline in the rate of pedicle screw loosening detected by CT imaging and clinically significant instrumentation failure.

Risk Factors for Cage Migration Following Lateral Lumbar Interbody Fusion Combined With Posterior Instrumentation: A Multicenter Retrospective Study of 983 Cases

STUDY DESIGN

A multicenter retrospective study.

OBJECTIVE

This study aimed to elucidate the incidence and risk factors of lateral cage migration (LCM) after lateral lumbar interbody fusion (LLIF) combined with posterior instrumentation.

SUMMARY OF BACKGROUND DATA

LLIF has recently become a widely accepted procedure for the treatment of lumbar degenerative diseases. Although LLIF complications include vascular, nerve, and abdominal organ injuries, few studies have identified specific risk factors for LCM after LLIF.

MATERIALS AND METHODS

Between January 2015 and December 2020, 983 patients with lumbar degenerative diseases or osteoporotic vertebral fractures underwent LLIF combined with posterior instrumentation. The fusion sites were located within the lumbosacral lesions. LCM was defined as a change of >3 mm in the movement of the radiopaque marker on radiographs. The patients were classified into LCM and non-LCM groups. Medical records and preoperative radiographs were also reviewed. The 1:5 nearest-neighbor propensity score matching technique was used to compare both groups, and radiologic parameters, including preoperative disk height (DH), preoperative sagittal disk angle, disk geometry, height variance (cage height minus DH), and endplate injury, were analyzed to identify the factors influencing LCM incidence.

RESULTS

There were 16 patients (1.6%) with LCM (10 men and 6 women; mean age 70.1 yr). The Cochran-Armitage trend test showed a linear trend toward an increased rating of LCM with an increasing number of fused segments ( P =0.003), and LCM occurred at the terminal cage-inserted disk level in all patients in the LCM group. After propensity-matched analysis, we identified high DH ( P <0.001), large sagittal disk angle ( P =0.009), round-type disk ( P =0.008), and undersized cage selection ( P <0.001) as risk factors for LCM.

CONCLUSION

We identified risk factors for LCM after LLIF combined with posterior instrumentation. To avoid this complication, it is important to select the appropriate cage sizes and enhance posterior fixation for at-risk patients.

Baseline Frailty and Discharge to Advanced Care Facilities in Patients Undergoing Lumbar Interbody Fusion for Lumbar Degenerative Disease: A Multicenter Registry Analysis of 7153 Patient Cases Comparing the Risk Analysis Index to the 5-Factor Modified Frailty Index

OBJECTIVE

To evaluate the impact of frailty, as measured by the 5-factor modified Frailty Index (mFI-5) and the Risk Analysis Index (RAI), on advanced care facility discharge (FD) in patients who underwent lumbar fusion for lumbar degenerative spine disease.

METHODS

The American College of Surgeons National Surgical Quality Improvement Program (2012-2020) was queried for adults (≥18 years) undergoing lumbar fusion for lumbar degenerative disease. Descriptive statistics and univariate crosstabulation were used to assess baseline demographics, preoperative comorbidities, and postoperative outcomes. Receiver operating characteristic curve analysis was used to assess the discriminative threshold of the mFI-5 and RAI on FD within this population.

RESULTS

The median patient age in this study cohort (N = 7153) was 56 years and FD occurred in 7.3% of cases. Receiver operating characteristic curve analysis demonstrated that both the mFI-5 and the RAI accurately predicted FD (C-statistics: mFI-5: 0.627; RAI: 0.746). DeLong's test found that the RAI had superior discrimination when compared to the mFI-5 (P < 0.0001).

CONCLUSIONS

RAI is a reliable predictor of FD in lumbar degenerative disease patients who underwent lumbar interbody fusion and demonstrated superior discrimination compared to the mFI-5. Identification of patients at risk for FD may facilitate more precise risk stratification to enable better preoperative decision-making and help set more realistic expectations of care.

Lateral access minimally invasive spine surgery in adult spinal deformity

Background

Oblique lumbar interbody fusion (OLIF) and percutaneous posterior approach for screw fixation (PPS) is the latest minimal invasive treatment for spinal deformity in adult patients (ASD). This study aims to design and highlight key points for ASD correction.

Materials and methods

We retrospectively analyzed 54 patients who had undergone OLIF with PPS for ASD from October 2019 to January 2022 (average 71.5 ± 6.2 years-old, male 4, female 50) with a mean follow-up period of 29.2 months. Clinical outcomes are expressed by values including the Oswestry disability index (ODI) and visual analogue scale (VAS) for back pain. The imagistic assessment was also performed preoperatively and at 12, and 24 months postoperatively. For OLIF51, CT- MRI fusion images were obtained before surgery.

Results

Postoperative ODI and VAS were 30.5 ± 18.9% and 31.2 ± 6.9 mm, respectively. The average operating time and blood loss during the surgical exposure was 490.9 ± 85.4 min and 1195.2 ± 653.8 ml. Preoperative SVA, PI-LL, and PT were 96.5 ± 55.9 mm, 39.3 ± 22.1°, 34.5 ± 11.0°, respectively. Postoperatively, SVA and PT became normal (24.1 ± 39.0 mm, 17.1 ± 10.3°) and PI-LL was ideal (2.4 ± 12.6°). Postoperative ODI and VAS were 30.5 ± 18.9% and 31.2 ± 6.9 mm. For OLIF51, the results revealed gain in L5-S1 lordosis and intervertebral disc height 9.4° and 4.2 mm respectively. The complications consisted of PJK in 21 cases (38.9%), rod breakage in 5 cases (9.3%), deep or superficial wound infection in 2 cases (3.7%).

Conclusion

Clinical and imagistic results of OLIF and PPS for ASD were excellent. The radiographic measurements revealed that OLIF51 created good L5-S1 lordosis and significant L5-S1 disc height. CT-MRI fusion images were very useful for evaluating vascular anatomy for OLIF51.

Short-term clinical efficacy and safety of unilateral biportal endoscopic transforaminal lumbar interbody fusion versus minimally invasive transforaminal lumbar interbody fusion in the treatment of lumbar degenerative diseases: a systematic review and meta-analysis

BACKGROUND

The aim of this study was to comprehensively evaluate the short-term clinical efficacy and safety of unilateral biportal endoscopic transforaminal lumbar interbody fusion (UBE-TLIF) versus minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) for the treatment of lumbar degenerative diseases by meta-analysis.

METHODS

A computer-based search of PubMed, Embase, Web of Science, Cochrane Database, China National Knowledge Infrastructure (CNKI), Wanfang Database, and Chinese Science and Technology Journal Database (VIP) was conducted from the inception of the each database to April 2023. The searched literature was then screened according to strict inclusion and exclusion criteria. The critical data were extracted and analyzed using Review Manager software5.4.1. Pooled effects were calculated on the basis of data attributes by mean difference (MD) or odds ratio (OR) with 95% confidence interval (CI). The Newcastle-Ottawa Scale was used to assess the quality of the studies.

RESULTS

A total of 13 studies and 949 patients met the inclusion criteria for this meta-analysis, 445 in the UBE-LIF group and 504 in the MIS-TLIF group. UBE-TLIF was superior to MIS-TLIF in terms of intraoperative blood flow, postoperative drainage flow, duration of hospital stay, VAS score for low back pain and ODI score, but the operative time was longer than MIS-TLIF group. There were no significant differences between the two groups in terms of total complication rate, modified Macnab grading criteria, fusion rate, VAS score of leg pain, lumbar lordosis, intervertebral disk height.

CONCLUSION

Both UBE-TLIF and MIS-TLIF are effective surgical modalities for the treatment of degenerative lumbar spine diseases. They have similar treatment outcomes, but UBE-TLIF has the advantages of less intraoperative blood loss, shorter postoperative hospital stay, and faster recovery.

TRIAL REGISTRATION

This study has been registered at INPLASY.COM (No. INPLASY202320087).

Biomechanical properties of lumbar vertebral ring apophysis cage under endplate injury: a finite element analysis

OBJECTIVE

This study aimed to compare the biomechanical properties of lumbar interbody fusion involving two types of cages. The study evaluated the effectiveness of the cage spanning the ring apophysis, regardless of the endplate's integrity.

METHODS

A finite element model of the normal spine was established and validated in this study. The validated model was then utilized to simulate Lateral Lumbar Interbody Fusion (LLIF) with posterior pedicle screw fixation without posterior osteotomy. Two models of interbody fusion cage were placed at the L4/5 level, and the destruction of the bony endplate caused by curetting the cartilaginous endplate during surgery was simulated. Four models were established, including Model 1 with an intact endplate and long cage spanning the ring apophysis, Model 2 with endplate decortication and long cage spanning the ring apophysis, Model 3 with an intact endplate and short cage, and Model 4 with endplate decortication and short cage. Analyzed were the ROM of the fixed and adjacent segments, screw rod system stress, interface stress between cage and L5 endplate, trabecular bone stress on the upper surface of L5, and intervertebral disc pressure (IDP) of adjacent segments.

RESULTS

There were no significant differences in ROM and IDP between adjacent segments in each postoperative model. In the short cage model, the range of motion (ROM), contact pressure between the cage and endplate, stress in L5 cancellous bone, and stress in the screw-rod system all exhibited an increase ranging from 0.4% to 79.9%, 252.9% to 526.9%, 27.3% to 133.3%, and 11.4% to 107%, respectively. This trend was further amplified when the endplate was damaged, resulting in a maximum increase of 88.6%, 676.1%, 516.6%, and 109.3%, respectively. Regardless of the integrity of the endplate, the long cage provided greater support strength compared to the short cage.

CONCLUSIONS

Caution should be exercised during endplate preparation and cage placement to maintain the endplate's integrity. Based on preoperative X-ray evaluation, the selection of a cage that exceeds the width of the pedicle by at least 5 mm (ensuring complete coverage of the vertebral ring) has demonstrated remarkable biomechanical performance in lateral lumbar interbody fusion procedures. By opting for such a cage, we expect a reduced occurrence of complications, including cage subsidence, internal fixation system failure, and rod fracture.

Evaluating the Efficacy of Water-Soluble Bone Wax (Tableau Wax) in Reducing Blood Loss in Spinal Fusion Surgery: A Randomized, Controlled, Pilot Study

Background and Objectives: Lumbar decompression with fusion surgery is an effective treatment for spinal stenosis, but critical postoperative hematoma is a concern. Bone wax has been widely used to control bone bleeding but it has some drawbacks. This study aimed to evaluate the efficacy of Tableau wax, a bioabsorbable hemostatic material, in patients undergoing spinal fusion surgery through a pilot study design. Materials and Methods: A total of 31 patients were enrolled in this single-surgeon, single-institution study. The participants underwent transforaminal lumbar interbody fusion surgery and were randomly assigned to the control group (Bone wax) or test group (Tableau wax). Demographic data, pre- and post-operative hemoglobin levels, blood loss volume, surgical time, Oswestry Disability Index, and EQ-5D scores were recorded. Results: The study showed no significant difference in preoperative and postoperative hemoglobin levels, Oswestry Disability Index, and EQ-5D scores between the groups. However, the Tableau wax group had a significantly lower reduction in hemoglobin levels (1.3 ± 1.0 g/dL) and blood loss (438.2 mL) compared to the Bone wax group (2.2 ± 0.9 g/dL and 663.1 mL, respectively; p = 0.018 and p = 0.022).

Biportal endoscopic paraspinal decompressive foraminotomy for lumbar foraminal stenosis: clinical outcomes and factors influencing unsatisfactory outcomes

BACKGROUND

Lumbar foraminal stenosis (LFS) is an important pathologic entity that causes lumbar radiculopathies. Unrecognized LFS may be associated with surgical failure, and LFS remains challenging to treat surgically. This retrospective cohort study aimed to evaluate the clinical outcomes and prognostic factors of decompressive foraminotomy performed using the biportal endoscopic paraspinal approach for LFS.

METHODS

A total of 102 consecutive patients with single-level unilateral LFS who underwent biportal endoscopic paraspinal decompressive foraminotomy were included. We evaluated the Visual Analogue Scale (VAS) score and the Oswestry Disability Index (ODI) before and after surgery. Demographic, preoperative data, and radiologic parameters, including the coronal root angle (CRA), were investigated. The patients were divided into Group A (satisfaction group) and Group B (unsatisfaction group). Parameters were compared between these two groups to identify the factors influencing unsatisfactory outcomes.

RESULTS

In Group A (78.8% of patients), VAS and ODI scores significantly improved after biportal endoscopic paraspinal decompressive foraminotomy (p < 0.001). However, Group B (21.2% of patients) showed higher incidences of stenosis at the lower lumbar level (p = 0.009), wide segmental lordosis (p = 0.021), and narrow ipsilateral CRA (p = 0.009). In the logistic regression analysis, lower lumbar level (OR = 13.82, 95% CI: 1.33-143.48, p = 0.028) and narrow ipsilateral CRA (OR = 0.92, 95% CI: 0.86-1.00, p = 0.047) were associated with unsatisfactory outcomes.

CONCLUSIONS

Significant improvement in clinical outcomes was observed for a year after biportal endoscopic paraspinal decompressive foraminotomy. However, clinical outcomes were unsatisfactory in 21.2% of patients, and lower lumbar level and narrow ipsilateral CRA were independent risk factors for unsatisfactory outcomes.

Evaluation of instrumentation and pedicle screw design for posterior lumbar fixation: A pre-clinical in vivo/ex vivo ovine model

Background

Stabilization procedures of the lumbar spine are routinely performed for various conditions, such as spondylolisthesis and scoliosis. Spine surgery has become even more common, with the incidence rates increasing ~30% between 2004 and 2015. Various solutions to increase the success of lumbar stabilization procedures have been proposed, ranging from the device's geometrical configuration to bone quality enhancement via grafting and, recently, through modified drilling instrumentation. Conventional (manual) instrumentation renders the excavated bony fragments ineffective, whereas the "additive" osseodensification rotary drilling compacts the bone fragments into the osteotomy walls, creating nucleating sites for regeneration.

Methods

This study aimed to compare both manual versus rotary Osseodensification (OD) instrumentation as well as two different pedicle screw thread designs in a controlled split animal model in posterior lumbar stabilization to determine the feasibility and potential advantages of each variable with respect to mechanical stability and histomorphology. A total of 164 single thread (82 per thread configuration), pedicle screws (4.5 × 35 mm) were used for the study. Each animal received eight pedicles (four per thread design) screws, which were placed in the lumbar spine of 21 adult sheep. One side of the lumbar spine underwent rotary osseodensification instrumentation, while the contralateral underwent conventional, hand, instrumentation. The animals were euthanized after 6- and 24-weeks of healing, and the vertebrae were removed for biomechanical and histomorphometric analyses. Pullout strength and histologic analysis were performed on all harvested samples.

Results

The rotary instrumentation yielded statistically (p = 0.026) greater pullout strength (1060.6 N ± 181) relative to hand instrumentation (769.3 N ± 181) at the 24-week healing time point. Histomorphometric analysis exhibited significantly higher degrees of bone to implant contact for the rotary instrumentation only at the early healing time point (6 weeks), whereas bone area fraction occupancy was statistically higher for rotary instrumentation at both healing times. The levels of soft tissue infiltration were lower for pedicle screws placed in osteotomies prepared using OD instrumentation relative to hand instrumentation, independent of healing time.

Conclusion

The rotary instrumentation yielded enhanced mechanical and histologic results relative to the conventional hand instrumentation in this lumbar spine stabilization model.

Comparison of C-Arm-Free Oblique Lumbar Interbody Fusion L5-S1 (OLIF51) with Transforaminal Lumbar Interbody Fusion L5-S1 (TLIF51) for Adult Spinal Deformity

Background and Objectives: Adult spinal deformity (ASD) surgery, L5-S1 lordosis is very important factor. The main objective of the research is to retrospectively compare symptomatic presentation and radiological presentation in the sequelae of oblique lumbar inter-body spinal fusion at L5-S1 (OLIF51) and transforaminal lumbar interbody fusion (TLIF) for ASD. Materials and Methods: We retrospectively evaluated 54 patients who underwent corrective spinal fusion for ASD between October 2019 and January 2021. Thirteen patients underwent OLIF51 (average 74.6 years old, group O) and 41 patients underwent TLIF51 (average 70.5 years old, group T). Mean follow-up period was 23.9 months for group O and 28.9 months for group T, ranging from 12 to 43 months. Clinical and radiographic outcomes are assessed using values including visual analogue scale (VAS) for back pain and Oswestry disability index (ODI). Radiographic evaluation was also collected preoperatively and at 6, 12, and 24 months postoperatively. Results: Surgical time in group O was less than that in group T (356 min vs. 492 min, p = 0.003). However, intraoperative blood loss of both groups were not significantly different (1016 mL vs. 1252 mL, p = 0.274). Changes in VAS and ODI were similar in both groups. L5-S1 angle gain and L5-S1 height gain in group O were significantly better than those of group T (9.4° vs. 1.6°, p = 0.0001, 4.2 mm vs. 0.8 mm, p = 0.0002). Conclusions: Clinical outcomes were not significantly different in both groups, but surgical time in OLIF51 was significantly less than that in TLIF51. The radiographic outcomes showed that OLIF51 created more L5-S1 lordosis and L5-S1 disc height compared with TLIF 51.

The efficacy of thoracolumbar interfascial plane block for lumbar spinal surgeries: a systematic review and meta-analysis

BACKGROUND

The intent of this meta-analysis was to examine the efficacy of thoracolumbar interfascial plane block (TLIP) for pain control after lumbar spinal surgery.

METHODS

Randomized controlled trials (RCTs) published on PubMed, CENTRAL, Scopus, Embase, and Web of Science databases up to February 10, 2023, comparing TLIP with no or sham block or wound infiltration for lumbar spinal surgeries were included. Pain scores, total analgesic consumption, and postoperative nausea and vomiting (PONV) were analyzed.

RESULTS

Seventeen RCTs were eligible. Comparing TLIP with no block or sham block, the meta-analysis showed a significant decrease of pain scores at rest and movement at 2 h, 8 h, 12 h, and 24 h. Pooled analysis of four studies showed a significant difference in pain scores at rest between TLIP and wound infiltration group at 8 h but not at 2 h, 12 h, and 24 h. Total analgesic consumption was significantly reduced with TLIP block as compared to no block/sham block and wound infiltration. TLIP block also significantly reduced PONV. GRADE assessment of the evidence was moderate.

CONCLUSION

Moderate quality evidence indicates that TLIP blocks are effective in pain control after lumbar spinal surgeries. TLIP reduces pain scores at rest and movement for up to 24 h, reduces total analgesic consumption, and the incidence of PONV. However, evidence of its efficacy as compared to wound infiltration of local anesthetics is scarce. Results should be interpreted with caution owing low to moderate quality of the primary studies and marked heterogeneity.

Biportal Endoscopic Transforaminal Lumbar Interbody Fusion Using Double Cages: Surgical Techniques and Treatment Outcomes

Objective: To describe the surgical techniques and the treatment outcomes of biportal endoscopic transforaminal lumbar interbody fusion (BETLIF) using double cages.Methods: This study included 89 patients with 114 fusion segments between July 2019 and May 2021. One pure polyetheretherketone (PEEK) cage and 1 composite titanium-PEEK cage were used for interbody fusion. Clinical outcomes measures included visual analogue scale (VAS) scores for lower back pain and leg pain, Oswestry Disability Index (ODI), and Japanese Orthopedic Association (JOA) scores. Computed tomography (CT) of the lumbar spine 1 year postoperatively was used to evaluate the Bridwell interbody fusion grades.Results: There were significant improvement in VAS for lower back pain from 5.2 ± 3.1 to 1.7 ± 2.1, VAS for leg pain from 6.3 ± 2.5 to 1.7 ± 2.0, ODI from 46.7 ± 17.0 to 12.7 ± 16.1, and JOA score from 15.6 ± 6.3 to 26.4 ± 3.2. The p-values were all < 0.001. The average hospital stay was 5.7 ± 1.1 days. The CT studies available for 60 fusion segments showed successful fusion (Bridwell grade I or grade II) in 56 segments (93.3%). Significant cage subsidence of more than 2 mm was only noted in 3 segments (5.0%). Complications included 1 dural tear, 2 pedicle screws malposition, and 2 epidural hematomas, in which 2 patients required reoperations.Conclusion: BETLIF with double cages provided good neural decompression and a sound environment for interbody fusion with a big cage footprint, a large amount of bone graft, endplate preservation, and segmental stability.

Residual motion of different posterior instrumentation and interbody fusion constructs

PURPOSE

To elucidate residual motion of cortical screw (CS) and pedicle screw (PS) constructs with unilateral posterior lumbar interbody fusion (ul-PLIF), bilateral PLIF (bl-PLIF), facet-sparing transforaminal lumbar interbody fusion (fs-TLIF), and facet-resecting TLIF (fr-TLIF).

METHODS

A total of 35 human cadaver lumbar segments were instrumented with PS (n = 18) and CS (n = 17). Range of motion (ROM) and relative ROM changes were recorded in flexion/extension (FE), lateral bending (LB), axial rotation (AR), lateral shear (LS), anterior shear (AS), and axial compression (AC) in five instrumentational states: without interbody fusion (wo-IF), ul-PLIF, bl-PLIF, fs-TLIF, and fr-TLIF.

RESULTS

Whereas FE, LB, AR, and AC noticeably differed between the instrumentational states, AS and LS were less prominently affected. Compared to wo-IF, ul-PLIF caused a significant increase in ROM with PS (FE + 42%, LB + 24%, AR + 34%, and AC + 77%), however, such changes were non-significant with CS. ROM was similar between wo-IF and all other interbody fusion techniques. Insertion of a second PLIF (bl-PLIF) significantly decreased ROM with CS (FE -17%, LB -26%, AR -20%, AC -51%) and PS (FE - 23%, LB - 14%, AR - 20%, AC - 45%,). Facet removal in TLIF significantly increased ROM with CS (FE + 6%, LB + 9%, AR + 17%, AC of + 23%) and PS (FE + 7%, AR + 12%, AC + 13%).

CONCLUSION

bl-PLIF and TLIF show similarly low residual motion in both PS and CS constructs, but ul-PLIF results in increased motion. The fs-TLIF technique is able to further decrease motion compared to fr-TLIF in both the CS and PS constructs.

Is unilateral pedicle screw fixation as effective as bilateral pedicle screw fixation in transforaminal lumbar interbody fusion: a meta-analysis of randomized controlled trials

PURPOSE

This meta-analysis aimed to investigate whether unilateral pedicle screw fixation (UPSF) is comparable to bilateral pedicle screw fixation (BPSF) in transforaminal lumbar interbody fusion (TLIF) for lumbar degenerative diseases.

METHODS

Up to September 2022, established electronic literature databases including PubMed, Web of Science, EMBASE, and the Cochrane Library were systematically searched. Randomized controlled trials (RCTs) published in English that compared the efficacy of UPSF versus BPSF in TLIF were included. The methodological quality was evaluated, relevant data was extracted, and suitable meta-analysis was carried out. Data of fusion rate, complications, cage migration, visual analog scale (VAS), and Oswestry Disability Index (ODI), total blood loss (TBL), operation time, and hospital stay were extracted and analyzed. Pooled mean differences and risk ratio (RR) along with 95% confidence intervals (95% CI) were calculated for the results.

RESULTS

Ten RCTs including 614 patients (UPSF = 294, BPSF = 320) were included in our meta-analysis. There were no significant differences in terms of fusion rate, VAS (VAS-BP and VAS-LP), ODI, complications, or hospital stay between UPSF and BPSF groups (P > 0.05, respectively). The UPSF group clearly had the advantage of less blood loss (SMD = -2.99, 95% CI [-4.54, -1.45], P = 0.0001) and operation time (SMD = -2.05, 95% CI [-3.10, -1.00], P = 0.0001). However, UPSF increased cage migration more than BPSF (10.7% vs 4.8%, RR = 2.23, 95% CI [1.07, 4.65],  P = 0.03).

CONCLUSION

According to the findings of this meta-analysis, UPSF is just as effective as BPSF in TLIF and may reduce blood loss and operation time. Nevertheless, UPSF may result in more cage migration than BPSF.

Biomechanical evaluation of different sizes of 3D printed cage in lumbar interbody fusion-a finite element analysis

OBJECTIVE

To study the biomechanical characteristics of various tissue structures of different sizes of 3D printed Cage in lumbar interbody fusion.

METHODS

A finite element model of normal spine was reconstructed and verified. Pedicle screws and Cage of different sizes were implanted in the L4/5 segment to simulate lumbar interbody fusion. The range of motion of the fixed and cephalic adjacent segment, the stress of the screw-rod system, the stress at the interface between cage and L5 endplate, and intervertebral disc pressure of the adjacent segment were calculated and analyzed.

RESULTS

The range of motion and intervertebral disc pressure of the adjacent segment of each postoperative model were larger than those of the intact model, but there was not much difference between them. The stress of cage-endplate interface was also larger than that of the intact model. However, the difference is that the stress of the endplate and the screw-rod system has a tendency to decrease with the increase of the axial area of cage.

CONCLUSIONS

Cage with larger axial area in lumbar interbody fusion can reduce the stress of internal fixation system and endplate, but will not increase the range of motion and intervertebral disc pressure of adjacent segment. It has a certain effect in preventing the cage subsidence, internal fixation system failure and screw rod fracture.

Computational comparison of anterior lumbar interbody fusion and oblique lumbar interbody fusion with various supplementary fixation systems: a finite element analysis

BACKGROUND AND OBJECTIVE

Anterior lumbar interbody fusion (ALIF) and oblique lumbar interbody fusion (OLIF) have shown a great surgical potential, while it has always been controversial which surgical approach and which type of fixation system should be selected. This study investigated the biomechanical response of ALIF and OLIF with various supplementary fixation systems using the finite element method.

MATERIALS AND METHODS

Lumbar L4-L5 ALIF and OLIF models stabilized by different supplementary fixation systems (stand-alone cage, integrated stand-alone cage, anterior plate, and bilateral pedicle screw) were developed to assess the segmental range of motion (ROM), endplate stress (EPS), and screw-bone interface stress (SBIS).

EXPERIMENTAL RESULTS

ALIF showed lower ROM and EPS than OLIF in all motion planes and less SBIS in the most of motion planes compared with OLIF when the anterior plate or pedicle screw was used. ALIF induced higher ROM, while lower EPS and SBIS than OLIF in the majority of motion planes when integrated stand-alone cage was utilized. Using a stand-alone cage in ALIF and OLIF led to cage migration. Integrated stand-alone cage prevented the cage migration, whereas caused significantly larger ROM, EPS, and SBIS than other fixation systems except for the rotation plane. In the most of motion planes, the pedicle screw had the lowest ROM, EPS, and SBIS. The anterior plate induced a slightly larger ROM, EPS, and SBIS than the pedicle screw, while the differences were not significant.

CONCLUSION

ALIF exhibited a better performance in postoperative segmental stability, endplate stress, and screw-bone interface stress than OLIF when the anterior plate or the pedicle screw was used. The pedicle screw could provide the greatest postoperative segmental stability, less cage subsidence incidence, and lower risk of fixation system loosening in ALIF and OLIF. The anterior plate could also contribute to the stability required and fewer complications, while not as effectively as the pedicle screw. Extreme caution should be regarded when the stand-alone cage is used due to the risk of cage migration. The integrated stand-alone cage may be an alternative method; however, further optimization is needed to reduce complications and improve postoperative segmental stability.

Measuring compressive loads on a 'smart' lumbar interbody fusion cage: Proof of concept

There are several complications associated with lumbar interbody fusion surgery however, pseudarthrosis (non-union) presents a multifaceted challenge in the postoperative management of the patient. Rates of pseudarthrosis range from 3 to 20 % in patients with healthy bone and 20 to 30 % in patients with osteoporosis. The current methods in post-operative follow-up - radiographs and CT, have high false positive rates and poor agreement between them. The aim of this study was to develop and test a proof-of-concept load-sensing interbody cage that may be used to monitor fusion progression. Piezoresistive pressure sensors were calibrated and embedded within a polyether ether ketone (PEEK) interbody cage. Silicone and poly (methyl methacrylate) (PMMA) were inserted in the graft regions to simulate early and solid fusion. The load-sensing cage was subjected to distributed and eccentric compressive loads up to 900 N between synthetic lumbar vertebral bodies. Under maximum load, the anterior sensors recorded a 56-58 % reduction in pressure in the full fusion state compared to early fusion. Lateral regions measured a 36-37 % stress reduction while the central location reduced by 45 %. The two graft states were distinguishable by sensor-recorded pressure at lower loads. The sensors more effectively detected left and right eccentric loads compared to anterior and posterior. Further, the load-sensing cage was able to detect changes in endplate stiffness. The proof-of-concept 'smart' cage could detect differences in fusion state, endplate stiffness, and loading conditions in this in vitro experimental setup.

Application of platelet-rich plasma in spinal surgery

With the aging of the population and changes in lifestyle, the incidence of spine-related diseases is increasing, which has become a major global public health problem; this results in a huge economic burden on the family and society. Spinal diseases and complications can lead to loss of motor, sensory, and autonomic functions. Therefore, it is necessary to identify effective treatment strategies. Currently, the treatment of spine-related diseases includes conservative, surgical, and minimally invasive interventional therapies. However, these treatment methods have several drawbacks such as drug tolerance and dependence, adjacent spondylosis, secondary surgery, infection, nerve injury, dural rupture, nonunion, and pseudoarthrosis. Further, it is more challenging to promote the regeneration of the interstitial disc and restore its biomechanical properties. Therefore, clinicians urgently need to identify methods that can limit disease progression or cure diseases at the etiological level. Platelet-rich plasma (PRP), a platelet-rich form of plasma extracted from venous blood, is a blood-derived product. Alpha granules contain a large number of cytokines, such as platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), epidermal growth factor, platelet factor 4 (PF-4), insulin-like growth factor-1 (IGF-1), and transforming growth factor-β (TGF-β). These growth factors allow stem cell proliferation and angiogenesis, promote bone regeneration, improve the local microenvironment, and enhance tissue regeneration capacity and functional recovery. This review describes the application of PRP in the treatment of spine-related diseases and discusses the clinical application of PRP in spinal surgery.

Effects of the cage height and positioning on clinical and radiographic outcome of lateral lumbar interbody fusion: a retrospective study

BACKGROUND

The proper cage positioning and height in lateral lumbar interbody fusion (LLIF). This study evaluated their effects on clinical and radiographic outcome measures in patients undergoing LLIF.

METHODS

This single-center retrospective study analyzed the characteristics and perioperative data of patients who underwent LLIF between January 2019 and December 2020. Radiographic (lumbar lordosis [LL], foraminal height, disc height [DH], segmental angle [SA], cross-sectional area [CSA] of thecal sac) and clinical (Oswestry Disability Index and Visual Analog Scale) outcomes were assessed preoperatively, postoperatively, and at the last follow-up. The effects of cage height and positioning on these parameters were also investigated.

RESULTS

With a mean follow-up of 12.8 months, 47 patients with 70 operated level were analyzed. Data demonstrated that postsurgical clinical and radiographic outcome measures were significantly better than before surgery(P < 0.05). Cage height and positioning showed no significant difference with regarding to clinical outcome(P > 0.05). Subgroup analysis of the cage positioning showed that DH and SA were better restored by the final follow-up in patients with anteriorly placed cages than those with posteriorly placed cages (P < 0.05). Cages of posterior position showed significantly upgrading cage subsidence (P = 0.047). Cage height subgroup analysis showed that the preoperative forminal height, DH, and SA in the 11-mm cage group were significantly lower than in the 13-mm cage group; however, these parameters were comparable in the two groups postoperatively and at the final follow-up (P > 0.05). Furthermore, the postoperative and final follow-up degrees of DH, SA, and LL have improved in the 11-mm cage group more than the 13-mm cage group. The preoperative, postoperative, and final follow-up LL values in the 11-mm cage group were lower than in the 13-mm cage group(P < 0.01).

CONCLUSIONS

Cage height and positioning did not affect the clinical outcomes in the present study. Cages in anterior position showed better restoration in DH, SA and decreased the incidence of cage subsidence. A comparable radiographic outcome can be achieved by inserting an appropriate cage height based on preoperative radiography.

Efficacy of transforaminal lumbar interbody fusion in the treatment of double-level lumbar spondylolisthesis with sagittal imbalance

OBJECTIVE

To analyze the clinical efficacy of transforaminal lumbar interbody fusion (TLIF) in the treatment of continuous double-level lumbar spondylolisthesis with sagittal imbalance.

METHODS

The clinical data of 36 patients with double-level spondylolisthesis treated with TLIF were included and divided into L3/L4 double spondylolisthesis group and L4/L5 double spondylolisthesis group according to the site of spondylolisthesis. The sagittal parameters of the patients were measured by standing anteroposterior and lateral X-rays of the whole spine, and the visual analogue scale (VAS) for lumbar and lower limb pain, Japanese Orthopaedic Association (JOA), and Oswestry Disability Index (ODI) were recorded. The imaging parameters and clinical parameters of the patients before surgery, after surgery, and at the last follow-up were compared and statistically analyzed.

RESULTS

A total of 36 patients were included in the study and all had sagittal imbalance. Among them, there were 21 cases of L3 and L4 spondylolisthesis, 6 males and 15 females, with an average age of 64.7 ± 9.4 years; there were 15 cases of L4 and L5 spondylolisthesis, 4 males and 11 females, with an average age of 66.5 ± 8.0 years. 36 patients completed the operation, the operation time was 190.28 ± 6.12 min, and intraoperative blood loss was 345 ± 11 ml. Compared with preoperative, there were significant differences in SVA, TPA, T1-SPi, LL, PT, SS, PI-LL, SD, SA, and SP between patients after surgery and at the last follow-up (P < 0.05). Compared with preoperative, VAS score, JOA score, and ODI index of waist and lower limbs were significantly improved after the operation and at the last follow-up, and there was a significant difference (P < 0.05).

CONCLUSION

TLIF can effectively relieve the symptoms of patients with continuous double-level lumbar spondylolisthesis, restore lumbar lordosis and sagittal spinal sequence, and improve the quality of life of patients.