Paraspinal muscle, facet joint, and disc problems: risk factors for adjacent segment degeneration after lumbar fusion

Factors and Experiences Associated With Unscheduled Hospital Readmission After Lateral Lumbar Interbody Fusion: A Case-Controlled Study

PURPOSE

Understanding the risk factors associated with unscheduled readmission following lateral lumbar interbody fusion (LLIF) is crucial for mitigating the occurrence of these costly events. This study aims to ascertain the incidence and factors of unscheduled hospital readmission subsequent to LLIF.

METHODS

A retrospective analysis was conducted on patients who underwent LLIF at our institution from March 2016 to February 2023. Instances of unscheduled hospital readmission after LLIF were meticulously recorded, including baseline demographics, characteristics of spine pathology, surgical interventions, duration between two hospitalizations, and hospitalization costs and duration. Reasons for readmission were categorized based on their etiology. A case-control methodology was employed to compare unscheduled hospital readmission patients against planned readmission patients due to staged surgery. Parametric data were analyzed with a two-tailed T-test, nonparametric data with the Wilcoxon rank-sum test, and categorical data with the χ 2 test.

RESULTS

A total of 1521 patients who received LLIF at our institution were included in the study. A total of 59 patients (3.88%) were unscheduled readmitted due to adjacent segment disease (ASD), cage subsidence, the original surgical segments remaining narrow, spondylodiscitis, and pain. 51 patients (3.35%) experienced reoperation, predominantly attributable to ASD. Compared to planned readmission patients, unscheduled readmission patients tended to be younger, had a lower likelihood of having scoliosis, and were more likely to have short-segment surgery and higher initial hospitalization costs. Among unscheduled readmission patients, patients receiving short-segment surgery, as well as those who paid less during the initial hospitalization, demonstrated a higher likelihood of a 90-day readmission rate.

CONCLUSION

Our findings indicated the heightened risks of unscheduled hospital readmission after LLIF. Taking targeted measures against these risk factors is expected to reduce the healthcare burden caused by unplanned readmissions in the future.

Integration of Spinal Musculoskeletal System Parameters for Predicting OVCF in the Elderly: A Comprehensive Predictive Model

Study DesignSystematic literature review.ObjectivesTo develop a predictive model for osteoporotic vertebral compression fractures (OVCF) in the elderly, utilizing current tools that are sensitive to bone and paraspinal muscle changes.MethodsA retrospective analysis of data from 260 patients from October 2020 to December 2022, to form the Model population. This group was split into Training and Testing sets. The Training set aided in creating a nomogram through binary logistic regression. From January 2023 to January 2024, we prospectively collected data from 106 patients to constitute the Validation population. The model's performance was evaluated using concordance index (C-index), calibration curves, and decision curve analysis (DCA) for both internal and external validation.ResultsThe study included 366 patients. The Training and Testing sets were used for nomogram construction and internal validation, while the prospectively collected data was for external validation. Binary logistic regression identified nine independent OVCF risk factors: age, bone mineral density (BMD), quantitative computed tomography (QCT), vertebral bone quality (VBQ), relative functional cross-sectional area of psoas muscles (rFCSAPS), gross and functional muscle fat infiltration of multifidus and psoas muscles (GMFIES+MF and FMFIES+MF), FMFIPS, and mean muscle ratio. The nomogram showed an area under the curve (AUC) of 0.91 for the C-index, with internal and external validation AUCs of 0.90 and 0.92. Calibration curves and DCA indicated a good model fit.ConclusionsThis study identified nine factors as independent predictors of OVCF in the elderly. A nomogram including these factors was developed, proving effective for OVCF prediction.

Multifidus Degeneration: The Key Imaging Predictor of Adjacent Segment Disease

Study DesignRetrospective cohort study.ObjectivesTo identify imaging predictors on pre- and perioperative imaging that are associated with a future revision surgery for adjacent segment disease (ASD) following lumbar fusion.MethodsPatients undergoing open posterior lumbar fusion between 2014-2022 were followed-up for >2-year. The initial MRI was evaluated for disc degeneration by Pfirrmann (grade 1-5); Modic changes (0-3); as well as fatty infiltration and functional cross-sectional area (fCSA) of the multifidus, erector spinae, and psoas. Spinopelvic alignment was measured pre- and postoperatively.ResultsOf 216 patients, 14.8% (n = 32) required revision surgery for ASD in the further course. There were no significant differences in Modic changes or Pfirrmann grades between the ASD group and controls. Fatty infiltration was significantly higher in the ASD group for both the erector spinae (40.5% vs 36.9%, P = 0.043) and multifidus muscles (61.0% vs 53.9%, P = 0.003). Additionally, the multifidus fCSA was smaller in patients who developed ASD (5.7 cm2 vs 6.7 cm2). Pre- and postoperative spinopelvic parameters were not significantly different between groups, and no other MRI measurements showed a significant difference. In a multivariable logistic regression model adjusting for age and sex, multifidus fatty infiltration emerged as the only significant predictor of ASD revision surgery (P = 0.004). Patients with more than 58% multifidus fatty infiltration had over double the risk of developing ASD (OR 2.7, 95% CI: 1.1-6.5, P = 0.032).ConclusionsMultifidus fatty infiltration is the key imaging predictor for the development of ASD requiring surgical revision. Disc degeneration and spinopelvic alignment appear to have less impact.

Sarcopenia Predicts Early Adjacent Segment Disease Development After Anterior and Oblique Lumbar Interbody Fusion

BACKGROUND AND OBJECTIVES

Sarcopenia has recently been shown to increase risk of early adjacent segment disease (ASD) development after transforaminal lumbar interbody fusion. We sought to evaluate whether sarcopenia increases risk of ASD after retroperitoneal approaches for lumbar interbody fusion (eg, anterior lumbar interbody fusion or oblique lateral lumbar interbody fusion).

METHODS

Retrospective data were collected from 104 adult patients aged older than 18 years who underwent short-segment fusion through anterior lumbar interbody fusion or oblique lateral lumbar interbody fusion approach from 2013 to 2023. The primary outcome was development of ASD within 3 years of surgery. Patients who had prior surgery for ASD, underwent long-construct deformity correction, had an ongoing oncological process, or lacked sufficient follow-up were excluded. Psoas and vertebral body volumetric measurements were calculated at the L4 pedicle level using preoperative MRI. Spinopelvic parameters of pelvic tilt, pelvic incidence (PI), lumbar lordosis (LL), and PI-LL mismatch were recorded from standing upright radiographs. Odds ratios were calculated with logistic regression analyses.

RESULTS

Of 104 patients undergoing fusion through retroperitoneal approaches, 25 (24.04%) developed ASD within 3 years. Patient demographics and medical comorbidities did not predict early ASD. Left and right psoas area (cm2) and psoas:vertebral body ratio strongly predicted ASD development (P < .0001). Nineteen patients were categorized as sarcopenic, defined as bilateral psoas:vertebral body ratios >1 SD below the study population gender mean. 16 of the 19 sarcopenic patients developed ASD within 3 years, compared with 9 of the 85 nonsarcopenic patients (84.21% vs 10.59%, P < .0001). Postoperative pelvic tilt and PI-LL mismatch were predictive of ASD on univariate but not multivariate analysis.

CONCLUSION

Sarcopenia significantly predicts ASD development within 3 years after lumbar fusion through retroperitoneal approaches. Irrespective of approach, sarcopenia is a risk factor of ASD formation and should be evaluated preoperatively. Morphometric analysis provides a simple screening tool and can be used to tailor preoperative and postoperative therapies to improve outcomes.

Effect of vertebral rotation on adjacent segment degeneration after the early stage of lumbar fusion surgery

OBJECTIVE

Related studies have shown that the torsional vertebral after fused significantly increase adjacent disc stress and accelerate degeneration. This suggests that vertebral rotation (VR) may accelerate adjacent segment degeneration (ASD). To investigate: (1) the correlation between VR and radiographic adjacent segment degeneration (rASD) after the early stage of lumbar fusion (2), the incidence of rASD with different VR degrees (3), whether the incidence of rASD can be reduced by surgically reducing instrumented vertebrae (IV) rotation.

METHODS

A retrospective analysis was conducted on the cases of 195 patients with lumbar degenerative disease (LDD) who were selected based on inclusion and exclusion criteria. The grade and angle of VR were measured for accurate analysis. The final follow-up evaluated the clinical improvement of the patients and the rASD. The impact of various factors on rASD was observed using univariate and multivariate logistic regression analyses. With different VR grades, Kaplan-Meier survival analysis was used to describe the incidence of rASD at various follow-up intervals.

RESULTS

The results indicate that preoperative adjacent vertebrae (AV) rotation (OR = 1.852, 95% CI = 1.064-3.224, P = 0.029) and IV rotation at final follow-up (OR = 2.748, 95% CI = 1.458-5.177, P = 0.002) are the independent risk factors for rASD. The results of the Kaplan-Meier analysis showed that with different VR grades, the follow-up period was different when the cumulative incidence of rASD reached 50%. The AV rotation decreased in the patients whose IV rotation decreased after the operation (P < 0.001), and the incidence of rASD was also lower (P = 0.004), especial in the fused to S1 group.

CONCLUSIONS

VR is a risk factor for rASD at the early stage of lumbar fusion surgery. Reducing VR during surgery can alleviate the speed of ASD and reduce the incidence of rASD in fused to S1.

Impact of spinal alignment on adjacent segment disease and degeneration after short-segment lumbosacral fusion

BACKGROUND CONTEXT

Adjacent segment disease (ASDis) and degeneration (ASDeg) are common complications following lumbar fusion, ranging from asymptomatic radiographic changes to debilitating symptoms requiring revision surgery. While the impact of spinopelvic alignment (SPA) on postoperative outcomes and ASDis prevention is well-studied in long-construct fusions, its role in short-segment lumbosacral fusions, particularly over the long term, remains unclear.

OBJECTIVE

This study aimed to investigate the association between global and distal lumbar SPA with the development of ASDis and ASDeg in the long-term follow-up of patients undergoing short-segment lumbosacral fusion. Secondary outcomes were patient reported outcome measures (PROMs) in relation to adjacent segment changes.

STUDY DESIGN/SETTING

Retrospective single-center cohort study with minimum follow-up of 5 years.

PATIENT SAMPLE

A total of 86 patients who underwent L4-S1 spinal fusion between 2003 and 2015, with a mean follow-up of 12±4 years.

OUTCOME MEASURES

The primary outcome was the development of adjacent segment changes, classified into 2 groups: (1) surgically-treated ASDis, and (2) ASDeg, defined as radiographic evidence of adjacent segment changes without surgical intervention. Secondary outcomes included PROMs: the Oswestry Disability Index (ODI) and the European Quality of Life 5 Dimensions 5 Level (EQ5D5L).

METHODS

Pre- and postoperative standing radiographs were annotated and the following global lumbar SPA parameters analyzed: Pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT), lumbar lordosis (LL), PI-LL-mismatch, lumbar pelvic angle (LPA). Additionally, the following distal lumbar SPA parameters were analyzed: Distal lordosis (DL) between L4-S1, lordosis distribution index (LDI=DL/LL), PI-DL-difference, DL-PI-ratio, adjacent segment lordosis (ASL). Postoperative ODI and EQ5D5L were assessed via a telephone interview.

RESULTS

Among 86 patients with a mean follow-up of 12±4 years the incidence of ASDis was 27.9% (n=24), while 7.0% (n=6) showed ASDeg. No significant differences in pre- and postoperative global lumbar SPA were found in patients who developed ASDis or ASDeg compared to patients who did not. PI (53.6° vs. 59.6°) and preoperative SS (34.9° vs. 40.3°) trended to be lower in the ASDis group compared to controls, although non-significant. Pre- and postoperative distal lumbar SPA parameters did not differ between groups. Patients with adjacent segment changes, regardless of whether they underwent revision surgery, reported worse PROMs. ODI scores were elevated in both the ASDis group (28, IQR 15-42) and the ASDeg group (34, IQR 14-47) compared to controls (10, IQR 2-24; p=.005). EQ5D5L scores were lower in both the ASDis (70, IQR 53-83) and the ASDeg groups (60, IQR 55-85) compared to controls (85, IQR 75-90; p=.025).

CONCLUSION

In this long-term follow-up study of patients undergoing short-segment lumbosacral fusion, neither preoperative nor postoperative SPA was significantly associated with the development of ASDis or ASDeg. These findings suggest that other factors may have a greater influence on ASDis risk. Patients who developed adjacent segment changes, whether or not they required revision surgery, experienced worse long-term postoperative PROMs, indicating the importance of ASDis prevention.

Clinical and Radiologic Outcomes of Single-level Decompression by Unilateral Endoscopic Biportal Technique in Degenerative Spinal Stenosis: Over 5-year Follow-up

STUDY DESIGN

Retrospective.

OBJECTIVE

To report radiologic and clinical outcomes of single-level unilateral biportal endoscopic (UBE) decompression over 5 years for degenerative lumbar spinal stenosis (LSS) without instability.

SUMMARY OF BACKGROUND DATA

UBE decompression has recently been introduced as a surgical treatment for LSS without instability. UBE has been shown in studies to have advantages in the prevention of infection and early rehabilitation. However, there is no long-term follow-up study.

METHODS

One hundred twenty-seven patients who underwent UBE decompression for single-level LSS with at least 5 years of follow-up were analyzed. Clinical outcomes including Oswestry Disability Index (ODI), Visual analog system (VAS), modified MacNab criteria, time to ambulation, operative time, and length of hospital stay were investigated. The radiologic outcome was assessed by dynamic plain radiographs.

RESULTS

ODI improved from 63.2±10.7 before surgery to 18.8±9.2 after 5 years of follow-up (P<0.001). Leg VAS decreased from 7.3±0.7 before surgery to 1.75±0.5 at the last follow-up (P<0.001). Per modified Macnab criteria, only 9.4% (12/127) showed poor clinical results. There were no infections, but there were 4 cases (3%) of dura tear and 1 case (0.07%) of transient palsy. Intervertebral angle showed significant change from preoperative to final follow-up, 6.3 ±3.2-5.2 ±3.5 degrees. (P=0.012). The intervertebral distance also showed a significant difference from 10.5±2.3 mm before surgery to 9.1±2.2 mm after surgery. (P=0.005). No significant changes in dynamic stability occurred. Among 127 patients, revision surgery was performed in 9 cases (7%).

CONCLUSIONS

UBE decompression of LSS without instability demonstrated good clinical outcomes over 5 years and did not show significant segmental instability after surgery. Although revision surgery was performed after UBE decompression, there were no severe complications, and revision rates were similar to other techniques. UBE is considered to be an alternative technique to microscopic and traditional decompression in LSS.

Fatty infiltration in the multifidus predicts screw-loosening following short-segment decompression and fusion: proof of why we should protect and rehabilitate the paraspinal muscles

PURPOSE

Screw-loosening is a common instrumentation-related complication following fusion. Patients who present with pain and neurological symptoms due to screw-loosening require revision. It has been reported that fat-infiltrated and/or atrophied paraspinal muscles were associated with low back pain, disability, radiculopathy, and instrumentation-related failures. However, there is limited and conflicting knowledge regarding the association of paraspinal muscles with screw-loosening. In the present study, we aimed to identify whether fatty infiltration in the paraspinal muscles was associated with screw-loosening.

METHODS

A retrospective analysis of the clinical and radiological data of the patients who underwent short-segment decompression and fusion for lumbar spinal stenosis (LSS) at a tertiary spine clinic between 2013 and 2023. Goutallier's classification system was used for grading fatty infiltration in the paraspinal muscles.

RESULTS

Patients with screw-loosening had fattier multifidus at the upper lumbar spine (particularly L2-L3, cephalad to the upper instrumented level of L3-L4) compared to those without screw-loosening. In univariate analysis fatty multifidus at L2-L3 level, elder age, and male sex had ORs of 1.509 (p = 0.008), 1.116 (p = 0.001) and 4.702 (p = 0.004), respectively. In multivariate analysis fatty multifidus at L2-L3 level, elder age and male sex had ORs 1.428 (p = 0.043), 1.109 (p = 0.003), and 5.911 (p = 0.004), respectively.

CONCLUSION

Fatty infiltration in the multifidus muscle (particularly in the one at the cranial end of the fusion mass) is predictive for screw-loosening following short-segment lumbar decompression and fusion for LSS. Preserving multifidus in subjects is essential to prevent future long-term complications of spine surgery.

Biomechanical effects of screw loosening after lumbar PEEK rod and titanium rod fixation: a finite element analysis

Objective

Screw loosening is a common complication following lumbar spine fixation surgery, yet the biomechanical outcomes after screw loosening remain rarely reported. This study aims to utilize finite element (FE) models to compare the biomechanical performance of PEEK rod dynamic fixation and titanium rod rigid fixation in the postoperative lumbar spine, exploring potential biomechanical mechanisms for re-stabilization of loosened screws.

Methods

A FE model of the lumbar spine from L3 to the sacrum was developed using CT image segmentation. Four L4-S1 fixation models were constructed: PEEK rod dynamic fixation (PEEK model), titanium rod rigid fixation (titanium model), PEEK rod with pedicle screw loosening (PEEK-PSL model), and titanium rod with pedicle screw loosening (titanium -PSL model). A preload of 300 N was applied to the superior surface of L3. Stress distributions in the intervertebral discs, facet joints, pedicle screws, and rods were calculated to evaluate the biomechanical effects of different fixation methods.

Results

Across four physiological loading conditions, the stress differences in intervertebral discs, facet joints, and nucleus pulposus between the PEEK model and titanium model were minimal. However, vertebral body stress was significantly higher in the PEEK model, whereas screw and rod stresses were greater in the titanium model. Screw loosening further increased stress in all models. The S1 screw in the PEEK-PSL model exhibited lower and more uniform stress, while stress was concentrated at the screw-rod junction in the titanium-PSL model.

Conclusion

The PEEK rod fixation system demonstrated superior stress distribution, reducing stress concentration risks and improving stability while minimizing screw loosening rates. In contrast, the titanium rod system offers advantages in scenarios requiring high rigidity, potentially making it more suitable for patients with greater stability needs.

Safety and Utility of Bilateral-contralateral Decompression for Adjacent Segment Stenosis After Lumbar Interbody Fusion Using Unilateral Biportal Endoscopy

STUDY DESIGN

Retrospective case series study.

OBJECTIVE

To evaluate the safety and efficacy of bilateral-contralateral decompression using unilateral biportal endoscopy (UBE) for treating adjacent segment disease (ASD) after lumbar interbody fusion (LIF).

SUMMARY OF BACKGROUND DATA

ASD is a well-documented complication following LIF, often requiring additional surgical interventions. Traditional decompression techniques risk damaging the facet joints, potentially leading to further instability and degeneration. However, our bilateral-contralateral decompression using UBE focuses on minimizing facet joint resection and reducing the risk of postoperative instability.

METHODS

This study included 37 patients who underwent bilateral-contralateral UBE decompression for ASD following LIF at the L4-5 level between September 2020 and March 2022. Radiographic evaluations included measurements of vertebral range of motion (ROM), slip distance, disk height, lumbar lordosis, and facet joint preservation. Clinical assessments were performed using the visual analog scale (VAS) for back and leg pain and the Oswestry disability index (ODI).

RESULTS

The average final follow-up period was 14.5±1.9 mo. The average preoperative ROM was 3.0 degrees, which significantly increased to 4.8° at the final follow-up (P<0.05). Static structure and dynamic stability parameters, including the vertebral slip distance, lumbar lordosis, and disk height, showed no significant differences between the preoperative examination and 1-year postoperative follow-up. The facet joint preservation rate was 97.4±2.1% on average. Significant improvements in VAS scores for leg and back pain and ODI were observed. Despite improvement with conservative treatment in 7 patients with delayed instability, 2 patients required fusion surgery.

CONCLUSIONS

Bilateral-contralateral decompression through UBE has proven to be an effective and safe method for treating ASD following LIF. This technique is particularly suitable for patients requiring spinal stability maintenance. The high rates of facet joint preservation and low incidence of reoperation highlight this technique as a compelling alternative treatment for spinal stenosis.

LEVEL OF EVIDENCE

Level III.

Prediction Model and Risk Factor Analysis of Adjacent Segment Disease After L4-5 Transforaminal Lumbar Interbody Fusion Through Preoperative Radiographic Features

STUDY DESIGN

A retrospective study.

OBJECTIVE

To investigate the risk of adjacent segment disease (ASD) after L4-5 transforaminal lumbar interbody fusion (TLIF) in patients diagnosed with lumbar spinal stenosis (LSS), a prediction model for ASD is established and validated.

METHODS

A retrospective study was carried out on a sample of 290 patients who underwent L4-5 TLIF at Zhongda Hospital, Southeast University, from January 2015 to January 2021. The study collected baseline data and preoperative radiographic features of L3-4 and L5-S1. The determination of the outcome variable was based on X-ray results spanning over 24 months and JOA scores. Multivariate logistic regression was used to identify the risk factors in constructing a nomogram.

RESULTS

Independent risk factors for L3-4 degeneration after TLIF included osteoarthritis of L3-4 facet joints, L3-4 foraminal stenosis, L4 upper endplate osteochondritis, L3-4 local lordosis angle, and L3-4 spinal stenosis. Independent risk factors for L5-S1 degeneration after TLIF included osteoarthritis of L5-S1 facet joints, L5-S1 intervertebral disc degeneration, L5-S1 spinal stenosis, L5-S1 coronal imbalance, and S1 upper endplate osteochondritis. A predictive model was developed. The AUC for the prediction models at L3-4 and L5-S1 were .945 and .956. The calibration curve demonstrated good consistency between the predicted and actual probabilities. The DCA curve indicated the clinical benefit and practical value of this predictive model.

CONCLUSION

This study established nomograms for postoperative degeneration at L3-4 and L5-S1 based on selected preoperative radiographic features. These models provide a valuable auxiliary decision-making system for clinicians and aid in early surgical decisions.

Association between paraspinal muscle quality and surgery for adjacent segment disease

Background

Adjacent segment disease (ASD) is one of the most common complications after spinal fusion. There are several risk factors for ASD, but recently the quality of the paraspinal musculature has been implicated as a potential risk factor. The purpose of this study is to examine the association between paraspinal muscle degeneration and risk of surgery for ASD.

Methods

We conducted a retrospective review of spinal fusion patients at our institution from 2009 to 2022 who underwent subsequent surgery for ASD. Inclusion criteria included patients aged 18 and older at time of index operation. Control cohort included patients who did not undergo subsequent surgery for adjacent segment disease with a minimum one year follow up. Patients were matched based on age, gender, and BMI. We measured paraspinal fat percentage and circumferential surface area (CSA) at L3 and at the proximal end of their future construct. Paraspinal fat percentage and CSA were measured using ImageJ (National Institutes of Health, Bethesda, Maryland, USA). Student T-test was used to evaluate for statistically significant differences with p-value ≤ .05.

Results

A total of 154 patients were reviewed with 77 patients in each cohort. The average age and BMI in the control group was 61.3 and 30.0 versus 61.2 and 29.6 in patients who underwent subsequent surgery. Overall, patients who underwent surgery for adjacent segment disease had 24% higher paraspinal fat percentage at L3 (13.8 ± 7.7% vs. 11.1 ± 6.5%, p-value = .02) and 22% higher paraspinal fat percentage at the top end of their construct (16.0 ± 9.0% vs. 13.1 ± 7.1%, p-value = .03).

Conclusions

Our study found that patients who undergo surgery for adjacent segment disease have 24% higher fat percentage in their paraspinal musculature at L3 and 22% higher fat percentage at the proximal end of their fusion construct.

Risk factors and treatment strategies for adjacent segment disease following spinal fusion (Review)

Adjacent segment disease (ASD) is a significant clinical complication following cervical and lumbar spinal fusion surgery, characterized by the degeneration of spinal segments adjacent to the fused area. The present literature review aimed to elucidate the risk factors contributing to ASD and to evaluate current and emerging treatment strategies. Epidemiological data indicate that patient‑related factors such as age, pre‑existing spinal degeneration and comorbidities, along with surgical factors including the type of fusion, instrumentation and alignment correction, play pivotal roles in ASD development. Biomechanical alterations post‑fusion further exacerbate the risk. The underlying mechanisms of ASD involve changes in spinal kinematics and disc degeneration, driven by inflammatory and degenerative processes. Diagnostic modalities, such as magnetic resonance imaging and computed tomography scans, are essential for early detection and accurate diagnosis. Preventive strategies emphasize meticulous preoperative planning, advanced surgical techniques and postoperative rehabilitation. Treatment approaches range from conservative methods such as physical therapy and pharmacological interventions to surgical solutions, including revision surgeries and the use of motion‑preserving technologies. Emerging therapies, particularly in regenerative medicine, show promise in mitigating ASD. The present review underscored the necessity of a multidisciplinary approach to optimize patient outcomes and highlighted the need for ongoing research to address gaps in the current understanding of ASD in both cervical and lumbar regions.

Progress in the Application of Hydrogels in Intervertebral Disc Repair: A Comprehensive Review

PURPOSE OF REVIEW

Intervertebral disc degeneration (IVDD) is a common orthopaedic disease and an important cause of lower back pain, which seriously affects the work and life of patients and causes a large economic burden to society. The traditional treatment of IVDD mainly involves early pain relief and late surgical intervention, but it cannot reverse the pathological course of IVDD. Current studies suggest that IVDD is related to the imbalance between the anabolic and catabolic functions of the extracellular matrix (ECM). Anti-inflammatory drugs, bioactive substances, and stem cells have all been shown to improve ECM, but traditional injection methods face short half-life and leakage problems.

RECENT FINDINGS

The good biocompatibility and slow-release function of polymer hydrogels are being noticed and explored to combine with drugs or bioactive substances to treat IVDD. This paper introduces the pathophysiological mechanism of IVDD, and discusses the advantages, disadvantages and development prospects of hydrogels for the treatment of IVDD, so as to provide guidance for future breakthroughs in the treatment of IVDD.

Development and validation of a nomogram to predict the risk of adjacent segment disease after transforaminal lumbar interbody fusion in patients with lumbar degenerative diseases

BACKGROUND

Adjacent segment disease (ASD) is a common and serious complication that can develop in the mid- to long-term after lumbar fusion surgery. However, the underlying mechanisms of ASD are not yet fully understood. This study aimed to develop and validate a risk prediction model for ASD in patients who underwent transforaminal lumbar interbody fusion (TLIF) for lumbar degenerative diseases.

METHODS

Patients with lumbar degenerative disease who underwent TLIF between January 2015 and December 2016 were included in the retrospective study. The participants were divided into two groups: ASD and non-ASD. Univariate and multivariate logistic regression analyses were performed to identify factors influencing ASD after TLIF surgery. The receiver operating characteristic (ROC) curve, calibration curve, and decision curve analysis (DCA) were used to evaluate the model's discrimination, calibration and clinical value, respectively.

RESULTS

A total of 11.5% (59/513) of patients developed ASD. Higher BMI, lower BMD, higher disc grade, and reduced disc height were identified as independent risk factors for ASD after TLIF. The model demonstrated good discrimination in both the training and validation sets, with calibration and Hosmer-Lemeshow tests confirming accuracy, and DCA demonstrating clinical applicability.

CONCLUSIONS

The nomogram model demonstrated promise in predicting ASD in patients who underwent TLIF, aiding clinicians in selecting the most suitable surgical approach and optimizing surgical decisions.

Fatty Infiltration in Paraspinal Muscles: Predicting the Outcome of Lumbar Surgery and Postoperative Complications

Lumbar spine disorders often cause lower back pain, lower limb radiating pain, restricted movement, and neurological dysfunction, which seriously affect the quality of life of middle-aged and older people. It has been found that pathological changes in the spine often cause changes in the morphology and function of the paraspinal muscles (PSMs). Fatty infiltration (FI) in PSMs is closely associated with disc degeneration and Modic changes. And FI causes inflammatory responses that exacerbate the progression of lumbar spine disease and disrupt postoperative recovery. Magnetic resonance imaging can better distinguish between fat and muscle tissue with the threshold technique. Three-dimensional magnetic resonance imaging multi-echo imaging techniques such as water-fat separation and proton density are currently popular for studying FI. Muscle fat content obtained based on these imaging sequences has greater accuracy, visualization, acquisition speed, and utility. The proton density fat fraction calculated from these techniques has been shown to evaluate more subtle changes in PSMs. Magnetic resonance spectroscopy can accurately reflect the relationship between FI and the degeneration of PSMs by measuring intracellular and extracellular lipid values to quantify muscle fat. We have pooled and analyzed published studies and found that patients with spinal disorders often exhibit FI in PSMs. Some studies suggest an association between FI and adverse surgical outcomes, although conflicting results exist. These suggest that clinicians should consider FI when assessing surgical risks and outcomes. Future studies should focus on understanding the biological mechanisms underlying FI and its predictive value in spinal surgery, providing valuable insights for clinical decision-making.

Effectiveness of Interspinous Process Devices in Managing Adjacent Segment Degeneration Following Lumbar Spinal Fusion: A Systematic Review and Meta-Analysis

Background: Adjacent segment degeneration (ASD) is a significant complication following lumbar spinal fusion, often necessitating further surgical interventions and impairing patient outcomes. Interspinous process devices were introduced as an alternative treatment for spinal stenosis and degenerative spondylolisthesis and can potentially reduce the incidence of ASDd. This systematic review and meta-analysis aims to evaluate the effectiveness of interspinous process devices or IPDs in managing ASD following a previous spinal fusion compared to traditional fusion techniques. Methods: Electronic databases, including PubMed, Embase, and the Cochrane Library, were queried for studies assessing IPDs against traditional lumbar fusion methods for managing ASD after previous lumbar fusion, which had been published between January 2014 and the present. Statistical analysis was conducted using Review Manager 5.4. Results: Seven retrospective cohort studies involving 546 patients met the inclusion criteria. The analysis revealed that IPDs were associated with a statistically significant reduction in the incidence of ASD (OR = 0.28, 95% CI: 0.16 to 0.51, p < 0.0001, and I2 = 0% after excluding outliers). The ODI demonstrated a non-significant trend towards improved outcomes with IPDs at the 2-year follow-up (SMD = -3.94; 95% CI: -11.72 to 3.85). Range of motion (ROM) was better preserved with IPDs compared to fusion (SMD = 0.00, 95% CI: -0.41 to 0.41, p = 1.00, I2 = 60%). The visual analogue scale or VAS lower back pain scores were significantly reduced at the 2-year follow-up (SMD = -0.69, 95% CI: -1.18 to -0.19, p = 0.006, and I2 = 74%). VAS leg pain showed consistent improvements (SMD = -0.29; 95% CI: -0.63 to 0.04). Intraoperative blood loss was significantly lower with IPDs (SMD = -2.07; 95% CI: -3.27 to -0.87, p = 0.0007, and I2 = 95%), and operation times were shorter (SMD = -2.22, 95% CI: -3.31 to -1.12, p < 0.0001, and I2 = 94%). Conclusions: The judicious use of IPDs might benefit a subset of patients, particularly those who are not suitable candidates for major corrective surgery.

Establishment of a Rabbit Model of Adjacent Intervertebral Disk Degeneration After Lumbar Fusion and Fixation and Evaluation of Autophagy Factor Expression in Nucleus Pulposus Cells

BACKGROUND

The objectives of this research were to establish an animal model of adjacent segment degeneration (ASD) bordering lumbar fusion and to investigate the expression of autophagy factors in nucleus pulposus cells of adjacent intervertebral disks.

MATERIALS AND METHODS

Twenty-four adult New Zealand white rabbits were enrolled and divided into two groups: group A (n=12) and group B (n=12). Posterolateral fusion and fixation were performed after intervertebral disk degeneration occurred in group A, and the rabbits were monitored for 6 months. Group B was the control group and did not undergo fusion surgery. These rabbits were monitored for 6 months. Real-time quantitative polymerase chain reaction and immunohistochemistry were performed to detect the mRNA and protein expressions of PTEN-induced kinase 1 (PINK1), Parkin, ADAMTS-4, and MMP-3. An external database, the GEO database, was used to examine the expression of these genes and analyze them for differential expression.

RESULTS

After lumbar fusion in rabbits, the animal model of ASD exhibited gradual degeneration of adjacent intervertebral disks over time. Group A displayed significantly higher mRNA and protein expressions of PINK1 and MMP-3 but lower expression of ADAMTS-4 compared with group B (P<.05). The results analyzed in the GEO database showed that the expression of PINK1 was higher in group A than in group B, while the expression of ADAMTS-4 was lower in group A than in group B.

CONCLUSION

After posterolateral lumbar fusion in rabbits, the animal ASD model showed gradual deterioration of adjacent intervertebral disks with prolonged follow-up. The findings indicate the important role of autophagy in the apoptosis of nucleus pulposus cells in adjacent intervertebral disks. [Orthopedics. 2024;47(4):e167-e173.].

Preoperative and follow-up variations of psoas major muscle are related to S1 screw loosening in patients with degenerative lumbar spinal stenosis

BACKGROUND

It was reported the paraspinal muscle played an important role in spinal stability. The preoperative paraspinal muscle was related to S1 screw loosening. But the relationship between preoperative and postoperative change of psoas major muscle (PS) and S1 pedicle screw loosening in degenerative lumbar spinal stenosis (DLSS) patients has not been reported. This study investigated the effects of preoperative and follow-up variations in the psoas major muscle (PS) on the first sacral vertebra (S1) screw loosening in patients with DLSS.

METHODS

212 patients with DLSS who underwent lumbar surgery were included. The patients were divided into the S1 screw loosening group and the S1 screw non-loosening group. Muscle parameters were measured preoperatively and at last follow-up magnetic resonance imaging. A logistic regression analysis was performed to investigate the risk factors for S1 screw loosening.

RESULTS

The S1 screw loosening rate was 36.32% (77/212). The relative total cross-sectional areas and relative functional cross-sectional areas (rfCSAs) of the PS at L2-S1 were significantly higher after surgery. The increased rfCSA values of the PS at L3-S1 in the S1 screw non-loosening group were significantly higher than those in the S1 screw loosening group. The regression analysis showed male, lower CT value of L1 and longer segment fusion were independent risk factors for S1 screw loosening, and postoperative hypertrophy of the PS was a protective factor for S1 screw loosening.

CONCLUSIONS

Compared to the preoperative muscle, the PS size increased and fatty infiltration decreased after surgery from L2-3 to L5-S1 in patients with DLSS after short-segment lumbar fusion surgery. Postoperative hypertrophy of the PS might be considered as a protective factor for S1 screw loosening. MRI morphometric parameters and postoperative selected exercise of PS for DLSS patients after posterior lumbar fusion surgery might contribute to improvement of surgical outcome.

Systematic Review and Meta-Analysis of the Effect of Osteoporosis on Reoperation Rates and Complications after Surgical Management of Lumbar Degenerative Disease

BACKGROUND

There is considerable heterogeneity in findings and a lack of consensus regarding the interplay between osteoporosis and outcomes in patients with lumbar degenerative spine disease. Therefore, the purpose of this systematic review and meta-analysis was to gather and analyze existing data on the effect of osteoporosis on radiographic, surgical, and clinical outcomes following surgery for lumbar degenerative spinal disease.

METHODS

A systematic review was performed to determine the effect of osteoporosis on the incidence of adverse outcomes after surgical intervention for lumbar degenerative spinal diseases. The approach focused on the radiographic outcomes, reoperation rates, and other medical and surgical complications. Subsequently, a meta-analysis was performed on the eligible studies.

RESULTS

The results of the meta-analysis suggested that osteoporotic patients experienced increased rates of adjacent segment disease (ASD; p=0.015) and cage subsidence (p=0.001) while demonstrating lower reoperation rates than non-osteoporotic patients (7.4% vs. 13.1%; p=0.038). The systematic review also indicated that the length of stay, overall costs, rates of screw loosening, and rates of wound and other medical complications may increase in patients with a lower bone mineral density. Fusion rates, as well as patient-reported and clinical outcomes, did not differ significantly between osteoporotic and non-osteoporotic patients.

CONCLUSIONS

Osteoporosis was associated with an increased risk of ASD, cage migration, and possibly postoperative screw loosening, as well as longer hospital stays, incurring higher costs and an increased likelihood of postoperative complications. However, a link was not established between osteoporosis and poor clinical outcomes.

Risk factors for early-onset adjacent segment degeneration after one-segment posterior lumbar interbody fusion

Adjacent segment degeneration (ASD) is a major postoperative complication associated with posterior lumbar interbody fusion (PLIF). Early-onset ASD may differ pathologically from late-onset ASD. The aim of this study was to identify risk factors for early-onset ASD at the cranial segment occurring within 2 years after surgery. A retrospective study was performed for 170 patients with L4 degenerative spondylolisthesis who underwent one-segment PLIF. Of these patients, 20.6% had early-onset ASD at L3-4. In multivariate logistic regression analysis, preoperative larger % slip, vertebral bone marrow edema at the cranial segment on preoperative MRI (odds ratio 16.8), and surgical disc space distraction (cut-off 4.0 mm) were significant independent risk factors for early-onset ASD. Patients with preoperative imaging findings of bone marrow edema at the cranial segment had a 57.1% rate of early-onset ASD. A vacuum phenomenon and/or concomitant decompression at the cranial segment, the degree of surgical reduction of slippage, and lumbosacral spinal alignment were not risk factors for early-onset ASD. The need for fusion surgery requires careful consideration if vertebral bone marrow edema at the cranial segment adjacent to the fusion segment is detected on preoperative MRI, due to the negative impact of this edema on the incidence of early-onset ASD.

A Propensity Score-Matched Cohort Study Comparing 3 Different Spine Pedicle Screw Fixation Methods: Freehand, Fluoroscopy-Guided, and Robot-Assisted Techniques

OBJECTIVE

This study aimed to compare the accuracy of robotic spine surgery and conventional pedicle screw fixation in lumbar degenerative disease. We evaluated clinical and radiological outcomes to demonstrate the noninferiority of robotic surgery.

METHODS

This study employed propensity score matching and included 3 groups: robot-assisted mini-open posterior lumbar interbody fusion (PLIF) (robotic surgery, RS), c-arm guided minimally invasive surgery transforaminal lumbar interbody fusion (C-arm guidance, CG), and freehand open PLIF (free of guidance, FG) (54 patients each). The mean follow-up period was 2.2 years. The preoperative spine condition was considered. Accuracy was evaluated using the Gertzbein-Robbins scale (GRS score) and Babu classification (Babu score). Radiological outcomes included adjacent segmental disease (ASD) and mechanical failure. Clinical outcomes were assessed based on the visual analogue scale, Oswestry Disability Index, 36-item Short Form health survey, and clinical ASD rate.

RESULTS

Accuracy was higher in the RS group (p < 0.01) than in other groups. The GRS score was lower in the CG group, whereas the Babu score was lower in the FG group compared with the RS group. No significant differences were observed in radiological and clinical outcomes among the 3 groups. Regression analysis identified preoperative facet degeneration, GRS and Babu scores as significant variables for radiological and clinical ASD. Mechanical failure was influenced by the GRS score and patients' age.

CONCLUSION

This study showed the superior accuracy of robotic spine surgery compared with conventional techniques. When combined with minimally invasive surgery, robotic surgery is advantageous with reduced ligament and muscle damage associated with traditional open procedures.

Preoperative Multifidus Muscle Quality is Associated With Patient Reported Outcomes After Lateral Lumbar Interbody Fusion

STUDY DESIGN

Retrospective cohort.

OBJECTIVE

Lateral lumbar interbody fusion (LLIF) commonly involves a transpsoas approach. Despite the association between LLIF, postoperative iliopsoas weakness, and iatrogenic neuropraxia, no study has yet examined the effect of psoas or multifidus muscle quality on patient-reported outcomes (PROs).

METHODS

This study retrospectively reviewed patients who underwent LLIF with 1-year minimum follow-up. Psoas and multifidus muscle qualities were graded on preoperative magnetic resonance imaging using two validated classification systems for muscle atrophy. Average muscle quality was calculated as the mean score from all levels (L1-2 through L5-S1). Univariate and multivariate statistics were utilized to investigate the relationship between psoas/multifidus muscle quality and preoperative, 6-weeks postoperative, and final postoperative PROs.

RESULTS

74 patients (110 levels) with a mean follow-up of 18.71 ± 8.02 months were included for analysis. Greater multifidus atrophy was associated with less improvement on ODI, SF12, and VR12 (P < .05) on univariate analysis. On multivariate analysis, worse multifidus atrophy predicted less improvement on SF12 and VR12 (P < .05).

CONCLUSION

Despite the direct manipulation of the psoas muscle inherent to LLIF, preoperative psoas muscle quality did not affect postoperative outcomes. Rather, the extent of preoperative multifidus fatty infiltration and atrophy was more likely to predict postoperative pain and disability. These findings suggest that multifidus atrophy may be more pertinent than psoas atrophy in its association with patient-reported outcome measures after LLIF.

Impact of osteoporosis and Cement-Augmented fusion on adjacent spinal levels Post-Fusion Surgery: Patient-Specific finite element analysis

Cement-augmentation is a technique commonly used during posterior lumbar instrumented fusion (PLIF) to reinforce compromised osteoporotic vertebral bone, minimize the risk of loosening screws, enhance stability, and improve overall surgical outcomes. In this study, we introduce a novel segmented vertebral body regional modeling approach to investigate the effects of osteoporosis and cement-augmented lumbar fusion on disc biomechanics at spinal levels adjacent to the fused vertebrae. Using our previously validated personalized-poroelastic-osteoligamentous FE model of the spine, fusion was simulated at L4-L5, and the biomechanics of adjacent levels were studied for 30 patients (non-osteoporotic patients (N = 15), osteoporotic patients (N = 15)). PLIF models, with and without cement-augmentation, were developed and compared after an 8 h-rest period (200 N), following a 16 h-cyclic compressive loading of 500-1000 N (40 and 20 min, respectively). Movement in different directions (flexion/ extension/ lateral bending/ axial rotation) was simulated using 10Nm moment before and after cyclic loading. The material mapping algorithm was validated by comparing the results of voxel-based and parametric models. The FE cement-augmented models, subject to daily activity loading, demonstrated significant differences in disc height loss and fluid loss as compared to non-cemented models. The calculated axial stress and fiber strain values were also significantly higher for these models. This work demonstrates that although osteoporosis does not significantly alter the time-dependent characteristics of adjacent IVDs post-surgery, cement-augmentation increases the risk of adjacent segment disease (ASD) incidence. A holistic understanding of the trade-offs and long-term complex interplay between structural reinforcement modalities, including cement augmentation, and altered biomechanics warrants further investigation.

Preoperative Adjacent Facet Joint Osteoarthritis Is Associated with the Incidence of Adjacent Segment Degeneration and Low Back Pain after Lumbar Interbody Fusion

STUDY DESIGN

A retrospective cohort study.

PURPOSE

To analyze the association between preoperative adjacent facet joint osteoarthritis (FJOA) and outcomes of lumbar interbody fusion (LIF).

OVERVIEW OF LITERATURE

Whether preoperative adjacent FJOA is associated with the incidence of radiological adjacent segment degeneration (RASD) and low back pain (LBP) relief after lumbar fusion remains unknown.

METHODS

The study included patients who underwent LIF. The demographic characteristics and radiographic and surgical data were collected and evaluated. The included patients were divided into control group and FJOA group based on the preoperative adjacent facet joint Pathria grade. Preoperative and last follow-up LBP Visual Analog Scale (VAS) score, leg pain (LP) VAS, Oswestry Disability Index (ODI) and RASD were evaluated and compared. The improvement rates in VAS and ODI were calculated and compared between the two groups. Logistic regression was used to analyze the risk factors of LBP relief and incidence of RASD.

RESULTS

In total, 197 patients (control group, 86; FJOA group, 111) were included, and the median follow-up was 46 months. The VAS and ODI in both groups significantly improved after surgery. At the last follow-up, the FJOA group had higher VAS and lower VAS improvement rates of LBP than the control group (p<0.05). However, no significant difference in the LP VAS and ODI was found between the two groups. The incidence of RASD in the FJOA group was significantly higher than that in the control group (48.6% vs. 30.2%, p=0.034). Multivariate logistic regression analysis showed that preoperative adjacent FJOA was significantly associated with LBP relief (odds ratio [OR], 0.691; 95% confidence interval [CI], 0.498-0.958) and the postoperative incidence of RASD (OR, 1.406; 95% CI, 1.020-1.939).

CONCLUSIONS

The preoperative FJOA in the adjacent segments was significantly associated with LBP following LIF. Patients with preoperative FJOA were more likely to have RASD following lumbar fusion surgery.

Lumbar adjacent segment degeneration after spinal fusion surgery: a systematic review and meta-analysis

INTRODUCTION

Adjacent segment degeneration is among the most recognized long-term complications of lumbar surgery for degenerative spine pathologies with a relevant impact in spine surgical and clinical practice. It is reported a incidence of clinical adjacent segment disease between 5-30% of patients undergoing spinal fusion. We aimed to evaluate the main clinical and surgical risk factors for developing adjacent segment disease.

EVIDENCE ACQUISITION

A systematic review and meta-analysis of the pertinent literature was performed, according to PRISMA and PICO guidelines, focusing on clinical and radiological adjacent segment disease. We exclusively included studies reporting demographic and clinical data, and surgical details published from 30 September 2015 to 30 September 2020. The effect of considered risk factors on the presence of adjacent segment disease was explored with a random-effects model.

EVIDENCE SYNTHESIS

A total of 15 scientific publications, corresponding to 6253 patients, met the inclusion criteria for the qualitative and quantitative analysis. 720 of the patients developed a clinical and/or radiological adjacent syndrome disease, and 473 have been surgically managed. Ten articles qualified for the comparative geographical analysis. Advanced age and obesity are relevant risk factors for developing lumbar adjacent segment degeneration. Our data also reported a higher prevalence of adjacent segment degeneration in Western populations than in Eastern populations. The interbody fusion has a protective role toward lumbar adjacent segment degeneration.

CONCLUSIONS

This study highlighted multifactorial issues regarding adjacent segment disease: clinical, anatomical, biomechanical, and radiological features. In view of increasing life expectancy and spinal surgery procedures, extensive multicenter studies will be needed to define the correct management of the adjacent segment disease.

Oblique lateral interbody fusion with internal fixations in the treatment for cross-segment degenerative lumbar spine disease (L2-3 and L4-5) finite element analysis

Multi-segmental lumbar degenerative disease, including intersegmental disc degeneration, is found in clinical practice. Controversy still exists regarding the treatment for cross-segment degeneration. Oblique Lateral Interbody Fusion (OLIF) with several internal fixations was used to treat cross-segment lumbar degenerative disease. A whole lumbar spine model was extracted from CT images of the whole lumbar spine of patients with lumbar degeneration. The L2-3 and L4-5 intervertebral spaces were fused with OLIF using modeling software, the Pedicle screws were performed on L2-3 and L4-5, and different internal fixations were performed on L3-4 in Finite Element (FE) software. Among the six 10 Nm moments of different directions, the L3-4 no surgery (NS) group had the relatively largest Range of Motion (ROM) in the whole lumbar spine, while the L2-5 Long segmental fixation (LSF)group had the smallest ROM and the other groups had similar ROM. The ROM in the L1-2 and L5-S1 was relatively close in the six group models, and the articular cartilage stress and disc stress on the L1-2 and L5-S1 were relatively close. In contrast, the L3-4 ROM differed relatively greatly, with the LSF ROM the smallest and the NS ROM the largest, and the L3-4 Coflex (Coflex) group more active than the L3-4 Bacfuse (Bacfuse) group and the L3-4 translaminar facet screw fixation (TFSF) group. The stress on the articular cartilage and disc at L3-4 was relatively greater in the NS disc and articular cartilage, and greater in the Coflex group than in the Bacfuse and TFSF groups, with the greatest stress on the internal fixation in the TFSF group, followed by the Coflex group, and relatively similar stress in the Bacfuse, LSF, and NS groups. In the TFSF group, the stress on the internal fixation was greater than the yield strength among different directional moments of 10 Nm, which means it is unsuitable to be an internal fixation. The LSF group had the greatest overall ROM, which may lead to postoperative low back discomfort. The NS group has the greatest overall ROM, but its increased stress on the L3-4 disc and articular cartilage may lead to accelerated degeneration of the L3-4 disc and articular cartilage. The Coflex and Bacfuse groups had a reduced L3-4 ROM but a greater stress on disc compared to the LSF group, which may lead to disc degeneration in the long term. However, their stress on the articular cartilage was relatively low. Coflex and Bacfuse can still be considered better surgical options.

Biomechanical effects of iatrogenic muscle-ligaments complex damage on adjacent segments following posterior lumbar interbody fusion: A finite element analysis

OBJECTIVE

To analyze the biomechanical effects of proximal iatrogenic muscle-ligaments complex (MLC) damage on adjacent segments following posterior lumbar interbody fusion (PLIF) by finite element (FE) analysis.

METHODS

The multifidus muscle force was loaded in the validated intact lumbosacral finite element model. Based on whether undergoing PLIF or the proximal MLC damage, three models were established. Range of motion (ROM) and the maximum von Mises (VM) stress of adjacent segments were analyzed, as well as the average muscle force and work capacity in four loading directions.

RESULTS

PLIF results in significant changes in ROM and stress. ROM changed significantly in the upper adjacent segment, the PLIF model changed the most in extension, and the largest change in the lower adjacent segment occurred after MLC damage. The VM stress of the upper adjacent segment occurred in extension of the PLIF model, and that of the lower adjacent segment occurred in rotation after MLC damage. In flexion, ROM, and stress of the damaged MLC fusion model were significantly increased compared with the normal and PLIF models, there was a stepwise amplification. The average muscle force comparison of three models was 5.8530, 12.3185, and 13.4670 N, respectively. The total work capacity comparison was close to that of muscle force.

CONCLUSION

PLIF results in increased ROM and the VM stress of adjacent segments, the proximal MLC damage will aggravate this change. This may increase the risk of ASD and chronic low back pain. Preserving the proximal MLC reduces the biomechanical effects on adjacent segments.

A correlation study of preoperative lumbar paraspinal muscle quality and L5-S1 lumbar foraminal stenosis degeneration after L4-5 TLIF

STUDY DESIGN

This was a retrospective study.

OBJECTIVES

Adjacent segment degeneration (ASD) is a major complication associated with spinal fusion. The lumbar paraspinal muscle is an essential factor influencing the occurrence of ASD. This study aimed to investigate the effect of preoperative lumbar paraspinal muscle quality on L5-S1 adjacent lumbar foraminal stenosis degeneration (ASLFSD) after L4-5 transforaminal lumbar interbody fusion (TLIF).

METHODS

A total of 113 patients diagnosed with lumbar spinal stenosis at L4-5 were treated with TLIF. Lumbar paraspinal muscle measurements were obtained preoperatively and bilaterally from axial T2-weighted MR images. The measurements included the total cross-sectional area of psoas (PS-tCSA), of erector spinae (ES-tCSA), and of multifidus (MF-tCSA); and fatty infiltration of psoas (PS-FI), of erector spinae (ES-FI), and of multifidus (MF-FI). Foraminal measurements, including posterior disc height (PDH), disc-to-facet distance (D-F), foraminal height (FH), and foraminal area (FA), were obtained bilaterally using a computed tomography system. The association between lumbar paraspinal muscle quality and changes in foraminal measurements was also studied.

RESULTS

We observed that the FH and FA significantly reduced at 1 year postoperatively at the mean follow-up period of 41.56 ± 8.38 months (range, 43-50 months), and PDH, D-F, FH, and FA all significantly reduced at final follow-up. These changes in foraminal measurements were significantly and negatively correlated with PS-FI, ES-FI, and MF-FI.

CONCLUSION

During the clinical follow-up, we found that patients with a higher degree of paraspinal muscle FI were more likely to develop L5-S1 ASLFSD after L4-5 TLIF.

The association between morphological characteristics of paraspinal muscle and spinal disorders

BACKGROUND

Spinal disorders affect millions of people worldwide, and can cause significant disability and pain. The paraspinal muscles, located on either side of the spinal column, play a crucial role in the movement, support, and stabilization of the spine. Many spinal disorders can affect paraspinal muscles, as evidenced by changes in their morphology, including hypertrophy, atrophy, and degeneration.

OBJECTIVES

The objectives of this review were to examine the current literature on the relationship between the paraspinal muscles and spinal disorders, summarize the methods used in previous studies, and identify areas for future research.

METHODS

We reviewed studies on the morphological characteristics of the paravertebral muscle and discussed their relationship with spinal disorders, as well as the current limitations and future research directions.

RESULTS

The paraspinal muscles play a critical role in spinal disorders and are important targets for the treatment and prevention of spinal disorders. Clinicians should consider the role of the paraspinal muscles in the development and progression of spinal disorders and incorporate assessments of the paraspinal muscle function in clinical practice.

CONCLUSION

The findings of this review highlight the need for further research to better understand the relationship between the paraspinal muscles and spinal disorders, and to develop effective interventions to improve spinal health and reduce the burden of spinal disorders.

High Endplate Hounsfield Units Value Indicate Intervertebral Disc Degeneration Following Transforaminal Lumbar Interbody Fusion Surgery

OBJECTIVE

Lumbar disc degeneration (LDD) is a common cause of low back pain and disability, and its prevalence increases with age. The aim of this study is to investigate whether endplate Hounsfield unit (HU) values have an effect on lumbar disc degeneration (LDD) after transforaminal lumbar interbody fusion (TLIF) surgery in patients with degenerative lumbar stenosis.

METHODS

This study was a retrospective analysis of patients who underwent TLIF surgery in January 2016 to October 2019. One hundred and fifty-seven patients who underwent TLIF surgery for degenerative lumbar stenosis were enrolled in this study. Demographic data was recorded. VAS and ODI values were compared to assess the surgical outcomes in patients with or without process of LDD after TLIF surgery. Correlation analysis was performed to investigate associations between LDD and endplate HU value. Binary logistic regression analysis was carried out to study relationships between the DDD and the multiple risk factors.

RESULTS

There was a statistically significant correlation between LDD, body mass index (BMI), age, paraspinal muscle atrophy, and total endplate scores (TEPS). Also, a strong and independent association between endplate HU value and LDD was found at every lumbar disc level (p < 0.01). After conditioning on matching factors, multivariate logistic regression analysis showed that higher endplate HU (odds ratio [OR]: 1.003, p = 0.003), higher TEPS (OR: 1.264, p = 0.002), higher BMI (odds ratio [OR]: 1.202, p = 0.002), a smaller cross-sectional area (CSA) of the paraspinal muscle preoperatively (OR: 0.096, p < 0.001) were significant predictors of LDD development after TLIF surgery.

CONCLUSIONS

There is a significant association between LDD and endplate HU value after TLIF surgery in patients with degenerative lumbar stenosis. Beyond that, results from this study provide a mechanism by which high endplate HU value predisposes to LDD after TLIF surgery.

Changes of the posterior paraspinal and psoas muscle in patients with low back pain: a 3-year longitudinal study

PURPOSE

This study aimed to investigate the changes of the posterior paraspinal muscles (PPM) and psoas muscle in patients with low back pain (LBP) over time.

METHODS

Patients with LBP who had a repeat lumbar MRI with a minimum of 3-years apart at a tertiary referral center were analyzed. MRI-based quantitative assessments of the PPM and the psoas muscle were conducted for the baseline and follow-up MRI. The cross sectional area (CSA), the functional cross sectional area (fCSA) and the fat area (FAT) were calculated using a dedicated software program. The fatty infiltration (FI,%) of the regions of interest was calculated. Differences between the 1st and 2nd MRI were calculated for all assessed muscular parameters.

RESULTS

A total of 353 patients (54.4%female) with a median age of 60.1 years and BMI of 25.8 kg/m2 at baseline were analyzed. The mean time between the 1st and 2nd MRI was 3.6 years. The fCSAPPM declined in both sexes significantly from the 1st to the 2nd MRI, whereas the FATPPM increased. In line with this result, the FIPPM increased in both males (29.9%) and females (19.4%). Females had a higher FIPPM and FIPsoas than males in both MRIs. In females, no significant changes were found for the psoas muscle. The CSAPsoas and fCSAPsoas in males were significantly smaller in the 2nd MRI. With increasing age, a significant trend in a decrease in ∆FIPPM was observed for both sexes.

CONCLUSION

The study revealed significant quantitatively muscular changes in males and females, especially in the posterior paraspinal muscles in only three years' time.

Unilateral Bi/Multi-Portal Endoscopy for the Treatment of Complicated Lumbar Degenerative Diseases with Utilization of Uniaxial Spinal Endoscope, Instead of Arthroscope: Technique Note and Clinical Results

Objective

This article aims to discuss a novel surgical strategy, referred to as unilateral bi/multi-portal endoscopy (UME), which used a uniaxial spinal endoscope instead of an arthroscope in the traditional unilateral biportal endoscopy (UBE) surgical procedure in our study of the treatment of complicated lumbar degenerative diseases.

Methods

This retrospective study included 42 patients diagnosed with high-migrated lumbar disc herniation and bilateral spinal stenosis who underwent UME surgery from January 2021 to December 2021. Patients included 20 men and 22 women, with an average age of 55.97±14.92 years. The average follow-up period was 13.19 months. The demographic data, operation time (min), and complications were recorded and analyzed. The visual analogue scale (VAS), Oswestry Disability Index (ODI) scores were used to evaluate the surgical outcomes. Three-dimensional CT scans and MRI were conducted to evaluate the radiographic improvement.

Results

A total of 26 patients were diagnosed with lumbar disc herniation and 16 with lumbar spinal stenosis. All 42 patients underwent UME surgery and achieved satisfactory outcomes. The operation time was 154.46±46.09 min. The average follow-up time was 13.19±1.33 months. The preoperative back pain (VAS-Back) and the last follow-up VAS-Back were 3.84±1.00 and 0.70±0.46, respectively (P < 0.05). The preoperative leg pain (VAS-Leg) and the last follow-up VAS-Leg were 6.46±1.08 and 1.03±0.64, respectively (P <0.05). Significant differences existed between preoperative ODI scores (58.70±11.22%) and the last follow-up ODI scores (9.24±3.04%; P<0.05). All patients achieved significant pain relief and functional improvement after the surgery. No severe complications occurred, except for two cases of postoperative dysesthesia and one case suffered from vertebral compression fractures induced by a postoperative accidental injury. Symptoms of numbness disappeared within one week with treatment using dexamethasone and neurotrophic drugs. The vertebral fracture case recovered with percutaneous kyphoplasty treatment.

Conclusion

This study suggests that UME is a promising treatment strategy for high-migrated disc herniation and bilateral spinal stenosis.

Biomechanical effect of proximal multifidus injury on adjacent segments during posterior lumbar interbody fusion: a finite element study

BACKGROUND

Adjacent segment degeneration (ASD) is a common complication of lumbar interbody fusion; the paraspinal muscles significantly maintain spinal biomechanical stability. This study aims to investigate the biomechanical effects of proximal multifidus injury on adjacent segments during posterior lumbar interbody fusion (PLIF).

METHODS

Data from a lumbosacral vertebral computed tomography scan of a healthy adult male volunteer were used to establish a normal lumbosacral vertebral finite element model and load the muscle force of the multifidus. A normal model, an L4/5 PLIF model (PFM) based on a preserved proximal multifidus, a total laminectomy PLIF model (TLPFM), and a hemi-laminectomy PLIF model based on a severed proximal multifidus were established, respectively. The range of motion (ROM) and maximum von Mises stress of the upper and lower adjacent segments were analyzed along with the total work of the multifidus muscle force.

RESULTS

This model verified that the ROMs of all segments with four degrees of freedom were similar to those obtained in previous research data, which validated the model. PLIF resulted in an increased ROM and maximum von Mises stress in the upper and lower adjacent segments. The ROM and maximum von Mises stress in the TLPFM were most evident in the upper adjacent segment, except for lateral bending. The ROM of the lower adjacent segment increased most significantly in the PFM in flexion and extension and increased most significantly in the TLPFM in lateral bending and axial rotation, whereas the maximum von Mises stress of the lower adjacent segment increased the most in the TLPFM, except in flexion. The muscle force and work of the multifidus were the greatest in the TLPFM.

CONCLUSIONS

PLIF increased the ROM and maximum von Mises stress in adjacent cranial segments. The preservation of the proximal multifidus muscle contributes to the maintenance of the physiological mechanical behavior of adjacent segments, thus preventing the occurrence and development of ASD.

Biomechanical effect of endplate defects on the intermediate vertebral bone in consecutive two-level anterior cervical discectomy and fusion: a finite element analysis

BACKGROUND

Intermediate vertebral collapse is a newly discovered complication of consecutive two-level anterior cervical discectomy and fusion (ACDF). There have been no analytical studies related to the effects of endplate defects on the biomechanics of the intermediate vertebral bone after ACDF. This study aimed to compare the effects of endplate defects on the intermediate vertebral bone biomechanics in the zero-profile (ZP) and cage-and-plate (CP) methods of consecutive 2-level ACDF and to determine whether collapse of the intermediate vertebra is more likely to occur using ZP.

METHODS

A three-dimensional finite element (FE) model of the intact cervical spine (C2-T1) was constructed and validated. The intact FE model was then modified to build ACDF models and imitate the situation of endplate injury, establishing two groups of models (ZP, IM-ZP and CP, IM-ZP). We simulated cervical motion, such as flexion, extension, lateral bending and axial rotation, and compared the range of motion (ROM), upper and lower endplate stress, fusion fixation device stress, C5 vertebral body stress, intervertebral disc internal pressure (intradiscal pressure, or IDP) and the ROM of adjacent segments in the models.

RESULTS

There was no significant difference between the IM-CP model and the CP model in the ROM of the surgical segment, upper and lower endplate stress, fusion fixation device stress, C5 vertebral body stress, IDP, or ROM of the adjacent segments. Compared with the CP model, the endplate stress of the ZP model is significantly higher in the flexion, extension, lateral bending and axial rotation conditions. Compared with the ZP model, endplate stress, screw stress, C5 vertebral stress and IDP in IM-ZP were significantly increased under flexion, extension, lateral bending and axial rotation conditions.

CONCLUSIONS

Compared to consecutive 2-level ACDF using CP, collapse of the intermediate vertebra is more likely to occur using ZP due to its mechanical characteristics. Intraoperative endplate defects of the anterior lower margin of the middle vertebra are a risk factor leading to collapse of the middle vertebra after consecutive 2-level ACDF using ZP.

Effect of Muscularity and Fatty Infiltration of Paraspinal Muscles on Outcome of Lumbar Interbody Fusion

BACKGROUND

Lumbar paraspinal muscles play an important role in maintaining global spinal alignment and are associated with lower back pain; however, only a few studies on the effect of the paraspinal muscles on the surgical outcome exist. Therefore, this study aimed to analyze the association of preoperative muscularity and fatty infiltration (FI) of paraspinal muscles with the outcome of lumbar interbody fusion.

METHODS

Postoperative clinical and radiographic outcomes were analyzed in 206 patients who underwent surgery for a degenerative lumbar disease. The preoperative diagnosis was spinal stenosis or low-grade spondylolisthesis, and the surgery performed was posterior lumbar interbody fusion or minimally invasive transforaminal lumbar interbody fusion. Indications for surgery were a complaint of severe radiating pain that did not improve with conservative treatment and neurological symptoms accompanied by lower extremity motor weakness. Patients with fractures, infections, tumors, or a history of lumbar surgery were excluded from this study. Clinical outcome measures included functional status, measured using the Oswestry disability index (ODI) and visual analog scale (VAS) score for lower back and leg pain. Other radiographic parameters included measures of spinal alignment, including lumbar lordosis, pelvic tilt, sacral slope, pelvic incidence, C7 sagittal vertical axis, and pelvic incidence-lumbar lordosis mismatch. Lumbar muscularity (LM) and FI were measured preoperatively using a lumbar magnetic resonance image (MRI).

RESULTS

The high LM group showed more significant improvement in VAS score for lower back pain than the low LM group. In contrast, the VAS score for leg pain demonstrated no statistical significance. The high LM group showed more significant improvement in ODI postoperatively than the medium group. The severe FI group showed more significant improvement in ODI postoperatively, whereas the less severe FI group showed more significant improvement in the sagittal balance postoperatively.

CONCLUSION

Patients with high LM and mild FI ratio observed on preoperative MRI demonstrated more favorable clinical and radiographic outcomes after lumbar interbody fusion. Therefore, preoperative paraspinal muscle condition should be considered when planning lumbar interbody fusion.

Relationship between lumbar lordosis, pelvic parameters, PI-LL mismatch and outcome after short fusion surgery for lumbar degenerative disease. Literature review, rational and presentation of public study protocol: RELApSE study (registry for evaluation of lumbar artrodesis sagittal alignEment)

Background

Vertebral arthrodesis for degenerative pathology of the lumbar spine still remains burdened by clinical problems with significant negative results. The introduction of the sagittal balance assessment with the evaluation of the meaning of pelvic parameters and spinopelvic (PI-LL) mismatch offered new evaluation criteria for this widespread pathology, but there is a lack of consistent evidence on long-term outcome.

Methods

The authors performed an extensive systematic review of literature, with the aim to identify all potentially relevant studies about the role and usefulness of the restoration or the assessment of Sagittal balance in lumbar degenerative disease. They present the study protocol RELApSE (NCT05448092 ID) and discuss the rationale through a comprehensive literature review.

Results

From the 237 papers on this topic, a total of 176 articles were selected in this review. The analysis of these literature data shows sparse and variable evidence. There are no observations or guidelines about the value of lordosis restoration or PI-LL mismatch. Most of the works in the literature are retrospective, monocentric, based on small populations, and often address the topic evaluation partially.

Conclusions

The RELApSE study is based on the possibility of comparing a heterogeneous population by pathology and different surgical technical options on some homogeneous clinical and anatomic-radiological measures aiming to understanding the value that global lumbar and segmental lordosis, distribution of lordosis, pelvic tilt, and PI-LL mismatch may have on clinical outcome in lumbar degenerative pathology and on the occurrence of adjacent segment disease.

MRI-based vertebral bone quality score for the assessment of osteoporosis in patients undergoing surgery for lumbar degenerative diseases

PURPOSE

To explore the value of vertebral bone quality (VBQ) scores in diagnosing osteoporosis in patients with lumbar degeneration.

METHODS

A retrospective analysis was conducted of 235 patients treated with lumbar fusion surgery at the age of ≥ 50; they were divided into a degenerative group and a control group according to the severity of degenerative changes on three-dimensional computed tomography. The L1-4 vertebral body and L3 cerebrospinal fluid signal intensities in the T1-weighted lumbar magnetic resonance imaging (MRI) image were recorded, and the VBQ score was calculated. Demographics, clinical data, and dual-energy X-ray absorptiometry (DXA) indicators were recorded, and the VBQ value was compared with bone density and T-score using the Pearson correlation coefficient. The VBQ threshold was obtained according to the control group and compared with the efficacy of osteoporosis diagnosis based on DXA.

RESULTS

A total of 235 patients were included in the study, and the age of the degenerative group was older than that of the control group (61.8 vs. 59.4, P = 0.026). The VBQ score of the control group suggested a higher correlation with the bone mineral density (BMD) value and T-score (r = - 0.611 and - 0.62, respectively). The BMD value and T-score in the degenerative group were higher than those in the control group (P < 0.05). Receiver-operating characteristic curve analysis showed that the VBQ score had a good predictive ability for osteoporosis (AUC = 0.818), with a sensitivity of 93% and a specificity of 65.4%. Among the undiagnosed osteoporosis patients with T-score, the VBQ score after adjusting the threshold was higher in the degenerative group (46.9% vs. 30.8%).

CONCLUSIONS

Emerging VBQ scores can reduce the interference caused by degenerative changes compared to traditional DXA measures. Screening for osteoporosis in patients undergoing lumbar spine surgery provides new ideas.

Comparison of Oblique Lumbar Interbody Fusion Combined with Posterior Decompression (OLIF-PD) and Posterior Lumbar Interbody Fusion (PLIF) in the Treatment of Adjacent Segmental Disease(ASD)

BACKGROUND

An unintended consequence following lumbar fusion is the development of adjacent segment disease (ASD). Oblique lumbar interbody fusion combined with posterior decompression (OLIF-PD) is another feasible option for ASD, and there is no literature report on this combined surgical strategy.

METHODS

A retrospective analysis was performed on 18 ASD patients requiring direct decompression in our hospital between September 2017 and January 2022. Among them, eight patients underwent OLIF-PD revision and ten underwent PLIF revision. There were no significant differences in the baseline data between the two groups. The clinical outcomes and complications were compared between the two groups.

RESULTS

The operation time, operative blood loss and postoperative hospital stay in the OLIF-PD group were significantly lower than those in the PLIF group. The VAS of low back pain in the OLIF-PD group was significantly better than that in the PLIF group during the postoperative follow-up. The ODI at the last follow-up in the OLIF-PD group and the PLIF group were significantly relieved compared with those before operation. The excellent and good rate of the modified MacNab standard at the last follow-up was 87.5% in the OLIF-PD group and 70% in the PLIF group. There was a statistically significant difference in the incidence of complications between the two groups.

CONCLUSION

For ASD requiring direct decompression after posterior lumbar fusion, compared with traditional PLIF revision surgery, OLIF-PD has a similar clinical effect, but has a reduced operation time, blood loss, hospital stay and complications. OLIF-PD may be an alternative revision strategy for ASD.

Anatomical parameters alter the biomechanical responses of adjacent segments following lumbar fusion surgery: Personalized poroelastic finite element modelling investigations

Introduction: While the short-term post-operative outcome of lumbar fusion is satisfying for most patients, adjacent segment disease (ASD) can be prevalent in long-term clinical observations. It might be valuable to investigate if inherent geometrical differences among patients can significantly alter the biomechanics of adjacent levels post-surgery. This study aimed to utilize a validated geometrically personalized poroelastic finite element (FE) modeling technique to evaluate the alteration of biomechanical response in adjacent segments post-fusion. Methods: Thirty patients were categorized for evaluation in this study into two distinct groups [i.e., 1) non-ASD and 2) ASD patients] based on other long-term clinical follow-up investigations. To evaluate the time-dependent responses of the models subjected to cyclic loading, a daily cyclic loading scenario was applied to the FE models. Different rotational movements in different planes were superimposed using a 10 Nm moment after daily loading to compare the rotational motions with those at the beginning of cyclic loading. The biomechanical responses of the lumbosacral FE spine models in both groups were analyzed and compared before and after daily loading. Results: The achieved comparative errors between the FE results and clinical images were on average below 20% and 25% for pre-op and post-op models, respectively, which confirms the applicability of this predictive algorithm for rough pre-planning estimations. The results showed that the disc height loss and fluid loss were increased for the adjacent discs in post-op models after 16 h of cyclic loading. In addition, significant differences in disc height loss and fluid loss were observed between the patients who were in the non-ASD and ASD groups. Similarly, the increased stress and fiber strain in the annulus fibrosus (AF) was higher in the adjacent level of post-op models. However, the calculated stress and fiber strain values were significantly higher for patients with ASD. Discussion: Evaluating the biomechanical response of pre-op and post-op modeling in the non-ASD and ASD groups showed that the inherent geometric differences among patients cause significant variations in the estimated mechanical response. In conclusion, the results of the current study highlighted the effect of geometrical parameters (which may refer to the anatomical conditions or the induced modifications regarding surgical techniques) on time-dependent responses of lumbar spine biomechanics.

ADDISC lumbar disc prosthesis: Analytical and FEA testing of novel implants

The intact intervertebral disc is a six-freedom degree elastic deformation structure with shock absorption. "Ball-and-socket" TDR do not reproduce these properties inducing zygapophyseal joint overload. Elastomeric TDRs reproduce better normal disc kinematics, but repeated core deformation causes its degeneration. We aimed to create a new TDR (ADDISC) reproducing healthy disc features. We designed TDR, analyzed (Finite Element Analysis), and measured every 500,000 cycles for 10 million cycles of the flexion-extension, lateral bending, and axial rotation cyclic compression bench-testing. In the inlay case, we weighted it and measured its deformation. ADDISC has two semi-spherical articular surfaces, one rotation centre for flexion, another for extension, the third for lateral bending, and a polycarbonate urethane inlay providing shock absorption. The first contact is between PCU and metal surfaces. There is no metal-metal contact up to 2000 N, and CoCr28Mo6 absorbs the load. After 10 million cycles at 1.2-2.0 kN loads, wear 140.96 mg (35.50 mm³), but no implant failures. Our TDR has a physiological motion range due to its articular surfaces' shape and the PCU inlay bumpers, minimizing the facet joint overload. ADDISC mimics healthy disc biomechanics and Instantaneous Rotation Center, absorbs shock, reduces wear, and has excellent long-term endurance.

Incidence and Characteristics of Clinical L5-S1 Adjacent Segment Degeneration after L5 Floating Lumbar Fusion: A Multicenter Study

STUDY DESIGN

Retrospective study.

PURPOSE

This study aimed to evaluate the incidence, characteristics, and risk factors for clinical L5-S1 adjacent segment degeneration (ASD) after L5 floating lumbar fusion.

OVERVIEW OF LITERATURE

ASD is known to occur after lumbar spine fusion at a certain frequency. Several studies on radiological L5- S1 ASD have been reported. However, there are only a few studies on L5-S1 ASD with clinical symptoms, including back pain and/or radiculopathy.

METHODS

In total, 306 patients who received L5 floating lumbar fusion were included in this study. Clinical L5-S1 ASD was defined as newly developed radiculopathy in relation to the L5-S1 segment. Patients' medical records and imaging data were retrospectively analyzed. The risk factors for clinical ASD were assessed by an inverse probability of treatment weighting-adjusted logistic regression analysis.

RESULTS

Clinical L5-S1 ASD occurred in 17 patients (5.6%). The mean onset time of L5-S1 ASD was 12.9±7.5 months after the primary surgery. Among these patients, 10 (58.8%) presented with clinical L5-S1 ASD within 12 months. Reoperation was performed in three patients (1.0%). The severity of L5-S1 disk degeneration did not affect the occurrence of L5-S1 ASD. Logistic regression analysis showed that the number of fusion levels was a significant risk factor for clinical L5-S1 ASD.

CONCLUSIONS

The incidence and characteristics of clinical L5-S1 ASD after L5 floating lumbar fusion were retrospectively investigated. This study established that the number of fusion levels was a significant candidate factor for clinical L5-S1 ASD. Careful clinical follow-up is deemed necessary after L5 floating lumbar fusion surgery, especially for patients who received multiple-level fusions.

Correlation between surgical segment mobility and paravertebral muscle fatty infiltration of upper adjacent segment in single-segment LDD patients: retrospective study at a minimum 2 years' follow-up

OBJECTIVE

The purpose of this study was to investigate the relationship between surgical segment mobility and fatty infiltration of the adjacent segment paravertebral muscles in patients with single-segment lumbar degenerative disease (LDD) who underwent decompression with fusion or dynamic stabilization.

METHODS

Retrospective analysis of patients who underwent lumbar decompression combined with titanium rod fixation intertransverse fusion (PITF group), Isobar TTL dynamic stabilization (TTL group) or Isobar EVO dynamic stabilization (EVO group) for single-segment lumbar degenerative disease, from March 2012 to July 2018. The preoperative and final follow-up clinical indexes C-LDSI and the measured imaging indexes (range of motion of the surgical segment and the upper adjacent segment, and Goutallier grade of the upper adjacent segment) were counted, and the differences between the preoperative and final follow-up indexes were compared.

RESULTS

According to the inclusion and exclusion criteria, 68 patients were included in this study, 21 in the PITF group, 24 in the TTL group, and 23 in the EVO group. At the final follow-up, the C-LSDI score had significantly higher in the PITF group than the TTL and EVO groups, and the C-LSDI score was a very strongly negatively correlated with ROM of surgical segment (r=-0.7968, p < 0.001). There was a strong negative correlation between surgical segment and upper adjacent segment mobility (r = -0.6959, p < 0.001). And there was a very strong negative correlation between ROM of surgical segment and upper adjacent segment paravertebral muscle Goutallier classification (r = -0.8092, p < 0.001), whereas the ROM of the upper adjacent segment was strong positive correlated with the Goutallier classification (r = 0.6703, P < 0.001).

CONCLUSION

Compared with decompression combined with rigid fusion, decompression combined with dynamic fixation for single-segment lumbar degenerative disease can significantly reduce postoperative low back stiffness. And a certain range of increased mobility of the dynamic stabilization device can effectively reduce the compensatory mobility of the upper adjacent segment and slow down the fatty infiltration of the paravertebral muscle in the adjacent segment.

Identification of preoperative radiological risk factors for reoperation following percutaneous endoscopic lumbar decompression to treat degenerative lumbar spinal stenosis

Background

This study aimed to identify radiological risk factors associated with reoperation after percutaneous transforaminal endoscopic decompression (PTED) for degenerative lumbar spinal stenosis (DLSS).

Methods

The preoperative clinical data of 527 consecutive patients with DLSS who underwent PTED were retrospectively reviewed. Overall, 44 patients who underwent reoperation were matched for age, sex, body mass index, and surgical segment to 132 control patients with excellent or good clinical outcomes. Radiological characteristics were compared between the groups using independent sample t-tests and Pearson's chi-square tests. A predictive model was established based on multivariate logistic regression analysis.

Results

The analyses revealed significant differences in the presence of lumbosacral transitional vertebra (LSTV, 43.2% vs. 17.4%, p = 0.001), the number of levels with senior-grade disc degeneration (2.57 vs. 1.96, p = 0.018) and facet degeneration (1.91 vs. 1.25 p = 0.002), and the skeletal muscle index (SMI, 849.7 mm²/m² vs. 1008.7 mm²/m², p < 0.001) between patients in the reoperation and control groups. The results of the logistic analysis demonstrated that LSTV (odds ratio [OR] = 2.734, 95% confidence interval [CI]:1.222-6.117, p < 0.014), number of levels with senior-grade facet degeneration (OR = 1.622, 95% CI:1.137-2.315, p = 0.008), and SMI (OR = 0.997, 95% CI:0.995-0.999, p = 0.001) were associated with reoperation after PTED. The application of the nomogram based on these three factors showed good discrimination (area under the receiver operating characteristic curve 0.754, 95% CI 0.670-0.837) and good calibration.

Conclusion

LSTV, more levels with senior-grade facet degeneration, and severe paraspinal muscle atrophy are independent risk factors for reoperation after PTED. These factors can thus be used to predict reoperation risk and to help tailor treatment plans for patients with DLSS.

Evaluation of long-term clinical outcomes and the incidence of adjacent proximal segment degenerative disease with algorithmic transforaminal interbody fusion: A multicenter prospective study

Study Design

This was a prospective multicenter study.

Background

Adjacent segment degenerative disease (ASDd) is a common complication of open transforaminal lumbar interbody fusion (O-TLIF), the leading cause of which is initial adjacent segment degeneration (ASD). To date, various surgical techniques for the prevention of ASDd have been developed, such as, simultaneous use of interspinous stabilization (IS) and preventive rigid stabilization of the adjacent segment. The use of these technologies is often based on the subjective opinion of the operating surgeon, or on the assessment of one of the predictors of ASDd. Only sporadic studies are devoted to a comprehensive study of risk factors of ASDd development and personalized performance of O-TLIF.

Purpose

The purpose of this study was to evaluate long-term clinical outcomes and the incidence of degenerative disease of the adjacent proximal segment using clinical-instrumental algorithm for preoperative planning to O-TLIF.

Materials and Methods

The prospective, nonrandomized, multicenter cohort study included 351 patients who underwent primary O-TLIF, and the adjacent proximal segment had initial ASD. Two cohorts were identified. The prospective cohort included 186 patients who were operated by using the algorithm of personalized O-TLIF performance. The control retrospective cohort consisted of patients (n = 165), from our own database who had been operated on previously without the algorithmized approach. Treatment outcomes were analyzed by Visual Analog Scale (VAS) assessment of pain syndrome, Oswestry Disability Index (ODI) scores, physical component score (PCS) and mental component score (MCS) scores of the Short Form 36 questionnaire, frequency of ASDd was compared between studied cohorts.

Results

Thirty-six months after follow-up, the prospective cohort had better SF36 MCS/PCS outcomes, less disability according to ODI, and lower pain level according to VAS (P < 0.05). The incidence of ASDd in the prospective cohort was 4.9%, which was significantly lower than in the retrospective cohort (9%).

Conclusions

The prospective use of a clinical-instrumental algorithm for preoperative planning of rigid stabilization, depending on the biometric parameters of the proximal adjacent segment, significantly reduced the incidence of ASDd and improved long-term clinical outcomes compared with the retrospective group.

Lyophilized bovine acellular tendon linear fiber material for the reconstruction of attachment structure of paraspinous muscles: an animal in vivo study

Low back pain is common after lumbar spine surgery and the injury from extensive detachment of paraspinal muscles during the surgery may play a vital role. Previously, we prepared a bovine acellular tendon fiber (ATF) material through lyophilization and proved that it could retain its original fibrillar structure and mechanical properties. The objective of this study is to evaluate the effectiveness of this new fiber material used for attachment structure reconstruction of paraspinal muscle. Defect of spinous process, interspinous and supraspinous ligament was established on lumbar spine in rabbit and rat and ATF linear material was implanted to reconstruct the attachment structure. Ultrasound showed the cross-sectional area of the paraspinal muscle in ATF group was larger than that of control group in rats. MRI showed the irregular shape and high signal changes in control group, but regular shape and uniform signal in the ATF group in rabbit. For Electromyogram, the frequency of evoked potential in control group was lower than ATF group and normal rats. HE and Masson staining showed good tissue healing, and immunohistochemical results showed the immune rejection of ATF is significantly lower than that of suture. Reconstruction of the attachment structure of paraspinous muscles with ATF linear material could maintain the morphology, volume and function of paraspinal muscle. ATF material has the potential to be used to manufacture personalized ligaments and other tissue engineering scaffolds. Graphical abstract.

GAP score potential in predicting post-operative spinal mechanical complications: a systematic review of the literature

PURPOSE

In 2017, the GAP score was proposed as a tool to reduce mechanical complications (MC) in adult spinal deformity (ASD) surgery: the reported MC rate for the GAP proportioned category was only 6%, which is clearly lower to the MC rate reported in the literature. The aim of this study is to analyse if the most recent literature confirms the promising results of the original article.

MATERIALS AND METHODS

Using the PRISMA flow chart, we reviewed the literature to analyse GAP score capacity in predicting MC occurrence. We included articles clearly reporting ASD surgery MC stratified by GAP categories and the score's overall capacity to predict MC using the area under the curve (AUC). The quality of the included studies was evaluated using GRADE and MINORS systems.

RESULTS

Eleven retrospective articles (1,517 patients in total) were included. The MC distribution per GAP category was as follows: GAP-P, 32.8%; GAP-MD, 42.3%; GAP-SD, 55.4%. No statistically significant difference was observed between the different categories using the Kruskal-Wallis test (p = 0.08) and the two-by-two Pearson-Chi square test (P Vs MD, p = 0.300; P Vs SD, p = 0.275; MD Vs SD, p = 0.137). The global AUC was 0.68 ± 0.2 (moderate accuracy). The included studies were of poor quality according to the GRADE system and had a high risk of bias based on the MINORS criteria.

CONCLUSION

The actual literature does not corroborate the excellent results reported by the original GAP score article. Further prospective studies, possibly stratified by type of MC and type of surgery, are necessary to validate this score.

Low lumbar multifidus muscle status and bone mineral density are important risk factors for adjacent segment disease after lumbar fusion: a case–control study

Background

The quantity and quality of the paraspinal muscles are important factors that lead to spinal diseases. However, the role of paraspinal muscles in the pathogenesis of adjacent segment disease (ASD) after lumbar fusion surgery is rarely studied. The purpose of the research is to investigate the relationship between paraspinal muscles and ASD.

Methods

Thirty-three patients with ASD were included, and 33 controls without ASD were matched according to the basic demographic information. Cross-sectional images of the paraspinal muscles at each intervertebral disk level (L1–S1) before the first operation were analyzed, and the cross-sectional area (CSA) and degree of fat infiltration (FI) of the multifidus (MF) muscle and the erector spinae muscle were compared.

Results

There was no significant difference in demographic characteristics (P > 0.05) except for the bone mineral density (BMD) (P = 0.037) between the two groups. There were significant differences in the CSA and FI of the lower lumbar multifidus (P < 0.05). The CSA of the MF muscle at L3–L4, FI of the MF muscle at L4–L5 and L5–S1 and BMD were important risk factors for ASD. Among patients who received two-segment fusion for the first time, significant difference was observed in the degree of FI of the MF muscle in the lower lumbar segment (P < 0.05).

Conclusions

The CSA, FI and BMD of the lower lumbar MF muscle were closely related to the occurrence of ASD. The CSA of the MF muscle at L3–L4, the degree of FI of the MF muscle at L4–L5 and L5–S1 and BMD were important risk factors for ASD. The number of fusion segments in the first operation has a certain impact on the above-mentioned conclusions.

Adjacent segment disease after minimally invasive transforaminal lumbar interbody fusion for degenerative lumbar diseases: incidence and risk factors

Study design

Retrospective study.

Objectives

To explore the incidence and risk factors for symptomatic adjacent segment disease (ASD) in patients enveloped in degenerative lumbar diseases after minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF).

Methods

Data were retrospectively analyzed on 744 patients who underwent MIS-TLIF for degenerative lumbar diseases in our hospital from October 2012 to December 2018. The patients were divided into the ASD group and non-ASD (N-ASD) group on the basis of developing ASD at follow-up, and then the incidence of ASD was calculated. Clinical and radiological risk factors were assessed over time to determine their association with ASD by excluding less important factors.

Results

Data were missing for 26 patients, while a total of 718 patients were successfully monitored after MIS-TLIF. Of the 718 individuals participated in the study, 34 (4.7%) patients plagued by ASD required surgical intervention. The average onset time of ASD was 62.7 ± 15.1 months. Univariate analysis results shows that age, bone mineral density (BMD), body mass index (BMI), preoperative adjacent intervertebral disc height and preoperative adjacent segment disc degeneration were significantly different between the ASD and N-ASD groups (p < 0.05). The logistic regression analysis results demonstrated that BMD (p = 0.039, OR = 0.986, 95% CI 0.899–1.115), BMI (p = 0.041, OR = 1.119, 95% CI 1.103–2.397), and preoperative adjacent intervertebral disc degeneration (p = 0.023, OR = 1.215, 95% CI 1.015–1.986) may be seen as risk factors for ASD after MIS-TLIF.

Conclusions

The incidence of ASD was about 4.7% in patients suffer from degenerative lumbar diseases after MIS-TLIF. BMD, BMI and preoperative adjacent intervertebral disc degeneration might be the risk factors for the occurrence of ASD after MIS-TLIF. Our research also suggested that patients with lower BMD, higher BMI and disc preoperative adjacent segment disc degeneration were more likely to develop ASD after MIS-TLIF.

Radiographic adjacent segment degeneration and risk factors for osteoporotic vertebral compression fractures treated with percutaneous kyphoplasty

PURPOSE

In this study, we aimed to clarify whether osteoporotic vertebral compression fracture (OVCF) following percutaneous kyphoplasty (PKP) was associated with a high risk for radiographic adjacent segment degeneration (ASD) and to identify the risk factors for radiographic ASD in these individuals.

METHODS

We retrospectively reviewed consecutive patients with OVCFs who underwent PKP at our institution between November 2015 and January 2021. The incidence of radiographic ASD was calculated and specific subgroups of ASD were identified. Univariate and multivariate analyses of demographic, clinical baseline, and radiologic data were performed to identify risk factors associated with radiographic ASD.

RESULTS

With a mean follow-up time of 27.3 months, a total of 95 eligible patients were enrolled. The incidence of radiographic ASD distinguished from natural degeneration was 52.6%. Patients with OVCFs who underwent PKP had a high risk of developing radiographic ASD, particularly disc degeneration. Intradiscal cement leakage (odds ratio [OR], 5.706; 95% confidence interval [CI], 2.039-15.970; P = 0.001) and preoperative disc height (OR, 0.681; 95% CI, 0.518-0.895; P = 0.006) were identified as independent risk factors.

CONCLUSION

Patients with OVCFs who underwent PKP were more likely to develop radiographic ASD, and their progression was distinguished from natural degeneration. Disc degeneration was the most common type of degeneration. Intradiscal cement leakage and preoperative disc height were identified as independent risk factors for developing radiographic ASD in these patients. Further validation through prospective multicenter studies is required.