Endplate volumetric bone mineral density is a predictor for cage subsidence following lateral lumbar interbody fusion: a risk factor analysis

Impact of Lumbar Degenerative Changes on Vertebral Bone Strength: A Finite Element Analysis

Assessing the bone condition in patients with spinal disease is clinically valuable. However, evaluating bone strength in the presence of spine degenerative changes is challenging. Quantitative computed tomography (QCT) and finite element analysis (FEA) have been proposed as methods for more accurate bone quality assessment. This study investigates the relationship between bone strength predicted by FEA and other relevant biological parameters. This retrospective cross-sectional study included 127 patients with spinal disease who underwent preoperative CT scans between 2014 and 2020. Baseline patient characteristics, volumetric bone mineral density (vBMD) measured by QCT, and vertebral bone strength predicted by FEA were collected. The degree of degeneration was evaluated by classifying osteophyte formation, disc height narrowing, vertebral sclerosis, and spondylolisthesis into a grading scale ranging from 0 to 2. Multiple linear regression analysis was conducted to assess the effect of each factor on bone strength predicted by FEA. Of 127 patients, 120 patients (median age was 62 years) were included. The median vBMD and vertebral strength were 114.3 mg/cm3 and 7892.9 N, respectively. After adjusting for age, sex, body mass index, smoking status, diabetes mellitus, vBMD, and degenerative changes, multiple linear regression analysis revealed that sex, vBMD, and degree of degeneration independently increased the vertebral strength measured by FEA. This study suggests that in patients with spinal disease, vertebral bone strength is affected not only by sex and bone mineral density but also by degenerative changes. Thus, bone strength could be predicted more accurately in patients with spinal disease using FEA.

Modeling and construction of nomogram of cage subsidence after single-segment transforaminal lumbar interbody fusions

OBJECTIVE

The purpose of this study is to explore and analyze the risk factors for interbody cage subsidence in patients undergoing single-segment transforaminal lumbar interbody fusion (TLIF) and to construct and validate a visual nomogram risk prediction model.

METHODS

A retrospective analysis was conducted on the clinical data of 159 patients who underwent single-segment TLIF at the Spine Surgery Department of Panyu District Traditional Chinese Medicine Hospital from January 2021 to June 2023. Using the caret package in R, patients were randomly divided into a training set (n = 111) and a validation set (n = 48) in a 7:3 ratio. Multivariable logistic regression was employed for variable selection and the construction of the nomogram model. The predictive model's discrimination, calibration, and clinical utility were evaluated using receiver operating characteristic (ROC) curves, calibration curves, and decision curve analysis (DCA).

RESULTS

There were no statistically significant differences in various indicators between the training set (n = 111) and the validation set (n = 48) (P > 0.05). Univariate analysis in the training set revealed that age, bone density, endplate morphology, anterior vertebral bone spurs, lumbar CT values, and VBQ were statistically significant. Multivariable logistic regression analysis indicated that bone density, anterior vertebral bone spurs, and lumbar CT values were independent predictors of interbody cage subsidence (P < 0.05), and a nomogram model was constructed based on these indicators. The area under the ROC curve (AUC) for the training set and validation set was 0.93 (95% CI 0.89-0.98) and 0.93 (95% CI 0.86-1.00), respectively. The calibration curves showed good fit (training set P = 0.616; validation set P = 0.904). DCA analysis demonstrated that the model has high clinical utility.

CONCLUSION

Bone density, anterior vertebral bone spurs, and lumbar CT values are risk factors for interbody cage subsidence in patients after single-segment transforaminal lumbar interbody fusion. The constructed nomogram model exhibits good predictive value and clinical utility.

Predictive value of vertebral specificity of bone mineral density for cage subsidence among patients undergoing anterior cervical diskectomy and fusion: a retrospective study

PURPOSE

To investigate the predictive value of different vertebral specificity of BMD for cage subsidence among patients undergoing ACDF.

METHODS

BMD at different vertebrae was measured by CT image and MRI image. Cage subsidence was defined as ≥ 3 mm loss of fusion segmental height. Logistic regression analysis was used to identify BMD at specific vertebrae associated with cage subsidence. Receiver operating characteristic curve analysis was used to evaluate the value of BMD of different vertebrae in predicting cage subsidence.

RESULTS

117 patients (182 intervertebral spaces) were included, with a mean age of 54.6 ± 10.9years. The mean follow-up was 12.5 ± 3.8months. Of the 182 intervertebral spaces, subsidence was found in 85 (46.7%) intervertebral spaces. The mean Hounsfield unit (HU) values measured by CT in the subsidence group were significantly lower than those in the non-subsidence group (upper vertebral body: 285.8 vs. 361.8, p < 0.001; lower vertebral body: 262.1 vs. 324.0, p < 0.001; average: 273.9 vs. 342.9, p < 0.001). Similarly, the mean bone quality scores measured by MRI in the subsidence group were higher than those in the non-subsidence group (upper vertebral body: 2.69 vs. 2.19, p < 0.001; lower vertebral body: 2.58 vs. 2.18, p < 0.001; average: 2.63 vs. 2.19, p < 0.001). Logistic regression analysis showed that the HU values were significantly negatively correlated with subsidence (p < 0.001), while the bone quality scores were significantly positively correlated with subsidence (p < 0.001). The results show that the Pre-T1 slope, Post-C2-C7 Cobb angle, and Post-T1 slope in the subsidence group were significantly larger than those in the non-subsidence group, with statistically significant differences (Pre-T1 slope: P = 0.015; Post-C2-C7: P < 0.001; Post-T1 slope: P = 0.006). The results from the multivariate logistic regression analysis indicated that bone density indicators remained statistically significant in predicting fusion device subsidence, while the Post-C2-C7 Cobb angle from the sagittal plane parameters also demonstrated statistical significance.The areas under the curve (AUCs) of BMD in the upper vertebrae were greater than those in the lower vertebrae, whether measured by CT (upper vertebral body: 0.754, lower vertebral body: 0.723; upper endplate: 0.766, lower endplate: 0.712) or MRI (upper vertebral body: 0.755, lower vertebral body: 0.717; upper endplate: 0.702, lower endplate: 0.646). These results indicate that the BMD of the upper vertebrae may be a better predictor of cage subsidence than that of the lower vertebrae.

CONCLUSION

The bone density (HU value and VBQ score) at the surgical site is a strong predictor of cage subsidence in patients undergoing ACDF. For BMD assessment, we recommend that site-specific measurements, particularly those of the upper vertebrae, be given greater consideration rather than relying solely on generalized or averaged values.

Stand-Alone Lateral Lumbar Interbody Fusion and Lateral Lumbar Interbody Fusion With Supplemental Posterior Instrumentation in the Treatment of Lumbar Degenerative Disease: A Meta-Analysis and Systematic Review

STUDY DESIGN

Systematic Review.

OBJECTIVES

Compare the outcomes of stand-alone lateral lumbar interbody fusion (LLIF) and LLIF with supplemental posterior instrumentation in the treatment of lumbar degenerative disease by a Meta-analysis.

METHODS

In this meta-analysis, we searched Pubmed, Embase, and Cochrane databases from inception to Aug 2023. In this study, only study reporting stand-alone LLIF(stand-alone group) and LLIF with supplemental posterior instrumentation (posterior instrumentation group) in the treatment of lumbar degenerative disease and we excluded duplicate publications, research without full text, incomplete information or inability to conduct data extraction, animal experiments, reviews, and systematic reviews. STATA 15.1 software was used to analyze the data.

RESULTS

Among the 15 included articles, the total number of patients was 1177, with 469 patients (638 fused segments) in the standalone group and 708 patients (1046 fused segments) in the posterior instrumentation group. The posterior instrumentation group was better than stand-alone group with significant differences in fusion rate, cage subsidence rate,the restoration of disc height and segmental lordosis, the improvement of ODI, and reoperation rate. While, comparing with posterior instrumentation group,the stand-alone group had less intraoperative blood loss.

CONCLUSIONS

Both stand-alone and instrumented LLIF were effective in improving the clinical outcomes of patients with lumbar degenerative disease. However, the stand-alone LLIF was associated with lower fusion rate, inferior maintenance of indirect decompression, and higher reoperation rate due to high-grade cage subsidence. For patients with risk factors of high-grade cage subsidence, the LLIF with posterior instrumentation may be a better choice.

The risk factors for low back pain following oblique lateral interbody fusion: focus on sarcopenia

BACKGROUND

Sarcopenia had been identified as a factor influencing the postoperative outcomes of lumbar surgery. The effect of sarcopenia on the surgical outcomes in patients who underwent oblique lateral interbody fusion (OLIF) had not yet been examined.

OBJECTIVE

The aim of our study was to investigate the association between sarcopenia and postoperative low back pain (LBP) in patients following OLIF and provide recommendations for surgical strategy.

METHODS

116 patients who underwent OLIF were retrospectively reviewed. Patients were classified into sarcopenia group (Group SP) and non-sarcopenia group (Group NSP). According to whether instruments was performed, Group SP was further divided into OLIF stand-alone group (Group SP-SA) and OLIF with instruments group (Group SP-IN). The patient characteristics, surgical data and questionnaire scores were collected. Oswestry Disability Index (ODI) score was used to evaluate lumbar function and pain intensity. Multivariable logistic regression analysis was used to identify the risk factors for postoperative LBP.

RESULTS

There were 38 patients in Group SP and 78 patients in Group NSP. The incident rare of osteoporosis in Group SP was higher than that in Group NSP (P = 0.012). In Group SP, last follow-up intervertebral height (IH) was lower (P = 0.045) and incident rate of cage subsidence was higher ((P = 0.044). No significant difference (P = 0.229) showed in preoperative ODI scores, however, last follow-up ODI scores in Group SP was significantly higher (P = 0.017) than that in Group NSP. Multivariable logistic regression analysis showed that sarcopenia (P = 0.004), osteoporosis (P = 0.012) and cage subsidence (P = 0.002) were identified as risk factors for postoperative LBP. In Group SP-IN, last follow-up ODI score (P = 0.024) and incident rate of cage subsidence (P = 0.027) were significantly lower Compared to Group SP-SA.

CONCLUSIONS

LBP was a common complication following OLIF with the incidence rate of 18.1%. Sarcopenia, osteoporosis and cage subsidence were risk factors for LBP following OLIF. Instruments effectively reduced the incidence and degree of postoperative LBP in patients with sarcopenia following OLIF. Consequently, we suggest incorporating supplementary instruments for patients with sarcopenia in surgical strategy.

Comparative analysis of MRI-based VBQ and EBQ score for predicting cage subsidence in PILF surgery

BACKGROUND CONTEXT

As lumbar degenerative diseases become more prevalent in an aging population, there is an increasing demand for surgical interventions, such as posterior lumbar interbody fusion (PLIF). However, cage subsidence (CS), observed in 23.9-54% of cases postoperatively, remains a significant complication. Several factors, including age, bone quality, and endplate damage, contribute to the risk of CS, with bone quality being among the most critical determinants. Although DEXA and QCT are widely employed to assess bone density, their routine use in preoperative evaluations is restricted by cost considerations and radiation exposure. Recent studies suggest that MRI-based vertebral body quality (VBQ) and endplate bone quality (EBQ) score offer a viable, non-invasive alternative for evaluating bone quality; however, there is limited research comparing their predictive value for CS.

METHODS

In this retrospective study, 165 patients undergoing single-level PLIF surgery were included. MRI-based VBQ and EBQ score were calculated using T1-weighted images, and preoperative QCT was employed as a clinical standard. Cage subsidence was assessed based on postoperative imaging at 12-month follow-up. Statistical analyses, including t-tests, chi-square tests, and ROC curve analyses, were used to evaluate the predictive accuracy of VBQ and EBQ for CS.

RESULTS

The study's findings demonstrated that both VBQ and EBQ scores were significantly correlated with QCT measurements, thereby validating their utility as indicators of bone quality. ROC analysis revealed that VBQ had superior predictive value for CS (AUC = 0.814) compared to EBQ (AUC = 0.719), with both scores demonstrating significant clinical utility in identifying patients at risk for CS. Notably, VBQ exhibited a stronger correlation with preoperative clinical outcomes compared to EBQ, underscoring its greater reliability as a predictor.

CONCLUSIONS

This study highlights the effectiveness of MRI-based VBQ and EBQ score as practical, non-invasive tools for assessing bone quality preoperatively, with VBQ demonstrating superior predictive performance for CS risk. The findings underscore the potential of integrating these MRI-based assessments into routine preoperative planning to improve patient outcomes and minimize complications associated with PLIF surgery.

3D-printed porous titanium versus polyetheretherketone cages in lateral lumbar interbody fusion: a systematic review and meta-analysis of subsidence

Background

Cage subsidence frequently complicates lumbar fusion procedures, including lateral lumbar interbody fusion (LLIF), potentially leading to recurrent pain, impaired fusion, and accelerated degeneration of adjacent segments. A critical factor influencing cage subsidence is the selection of material. Polyetheretherketone (PEEK) and three-dimensional printed titanium (3D-Ti) cages are commonly used in LLIF procedures, each offering distinct advantages. However, these materials possess inherent property differences that may translate into divergent settling rates. To contribute to this discourse and offer insights, this systematic review and meta-analysis aims to compare the rates of cage subsidence between 3D-Ti and PEEK cages in LLIF.

Methods

A meticulous systematic search that employs distinct MeSH terms was conducted in major electronic databases (MEDLINE, PubMed, Embase, Scopus, Web of Science, and Cochrane) up to December 20, 2023. The quality of inclusion was measured using the Newcastle-Ottawa Scale (NOS) for non-randomized trials. The primary outcome measure was cage subsidence, while the secondary outcome involved evaluating subsidence within each treatment segment using the Marchi classification.

Results

The review included 265 patients (441 segments) from three studies. All with NOS ratings exceeding 5 stars. In the analysis, 189 segments (42.9%) underwent LLIF with 3D-Ti cages, while 252 segments (57.1%) participated in LLIF with PEEK cages. Overall, the cage subsidence rate was significantly lower with 3D-Ti compared to PEEK (p < 0.00001, OR = 0.25; 95% CI 0.14 to 0.44). Specifically, the 3D-Ti group exhibited a markedly lower subsidence rate, categorized by grade I, II, and III, compared to the PEEK group (p < 0.05). Furthermore, the incidence of severe subsidence was significantly reduced in the 3D-Ti group compared to the PEEK group (p = 0.0004, OR = 0.17; 95% CI 0.07 to 0.46).

Conclusion

The study concludes that the subsidence rate associated with 3D-Ti cages in LLIF is notably lower than that observed with PEEK cages, underscoring the potential advantages of 3D-Ti cages in mitigating cage subsidence.

Lower Hounsfield Units at the Planned Lowest Instrumented Vertebra Is an Independent Risk Factor for Complications Following Adult Cervical Deformity Surgery

BACKGROUND

The association of Hounsfield units (HU) and junctional pathologies in adult cervical deformity (ACD) surgery has not been elucidated.

OBJECTIVE

Assess if the bone mineral density of the LIV, as assessed by HUs, is prognostic for the risk of complications after ACD surgery.

STUDY DESIGN/SETTING

Retrospective cohort study.

METHODS

HUs were measured on preoperative CT scans. Means comparison test assessed differences in HUs based on the occurrence of complications, linear regression assessed the correlation of HUs with risk factors, and multivariable logistic regression followed by a conditional inference tree derived a threshold for HUs based on the increased likelihood of developing a complication.

RESULTS

In all, 107 ACD patients were included. Thirty-one patients (29.0%) developed a complication (18.7% perioperative), with 20.6% developing DJK and 11.2% developing DJF. There was a significant correlation between lower LIVs and lower HUs ( r =0.351, P =0.01), as well as age and HUs at the LIV. Age did not correlate with change in the DJK angle ( P >0.2). HUs were lower at the LIV for patients who developed a complication and an LIV threshold of 190 HUs was predictive of complications (OR: 4.2, [1.2-7.6]; P =0.009).

CONCLUSIONS

Low bone mineral density at the lowest instrumented vertebra, as assessed by a threshold lower than 190 Hounsfield units, may be a crucial risk factor for the development of complications after cervical deformity surgery. Preoperative CT scans should be routinely considered in at-risk patients to mitigate this modifiable risk factor during surgical planning.

LEVEL OF EVIDENCE

Level-III.

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

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

Perioperative Complications of Oblique Lumbar Interbody Fusion (OLIF): 5 Years of Experience with OLIF

Objective  The objective of this study was to share our early experience with oblique lumbar interbody fusion (OLIF), with emphasis on the perioperative complications and determine clinical outcomes following OLIF. Materials and Methods  It was a retrospective prospective study performed at a single institute from March 2019 to August 2023. A total of 56 consecutive patients who had undergone OLIF for degenerative spine disorders were enrolled in the study. Pre-, intra-, and postoperative data on these patients were collected. All the patients were followed up at regular intervals with an evaluation of Visual Analog Scale (VAS), Oswestry Disability Index (ODI), neurological parameters, and X-rays to look for fusion, screw loosening, pseudoarthrosis, and cage slippage. Statistical analysis was done with the odds ratio, chi-square test, and Student's t -test. A p- value of < 0.05 was considered significant. Results  The overall incidence of complications was 25%, with no mortality. Intraoperative complications were noted in 10.7% of cases. This included endplate fractures ( n  = 3), peritoneal lacerations ( n  = 2), and ureteric injury ( n  = 1). The most common early postoperative complications were postoperative ileus ( n  = 6), followed by anterior thigh or groin numbness ( n  = 3), ipsilateral psoas weakness ( n  = 2), and superficial surgical site infection ( n  = 2). Of the late postoperative complications, cage subsidence was the most common, which occurred in 4 patients, followed by adjacent segment degeneration ( n  = 2) and loss of indirect decompression ( n  = 1). The mean ODI and VAS scores showed significant improvement ( p  < 0.05) at the final follow-up. Conclusion  OLIF is a promising surgical technique with the potential to treat a variety of degenerative conditions of the lumbar spine with a good clinical outcome. Despite its various benefits, OLIF can lead to complications in rare instances, which every spine surgeon should be aware of.

High-Risk Analysis of Vertebral Compression Fractures With Type 2 Diabetes Mellitus: Site-Specific Volumetric Bone Mineral Density

Aims: To explore the distribution of site-specific volumetric bone mineral density (vBMD) and analyze the mechanism of vertebral compression fractures with type 2 diabetes mellitus (T2DM) subjects using quantitative computed tomography (QCT). Materials and Methods: 304 postmenopausal women without T2DM and 274 postmenopausal women with T2DM underwent QCT scan, and all divided into three age subgroups. L1 vertebra was segmented into nine zones based on the corresponding position to the human body. Results: Whether in the T2DM or non-T2DM of each age group, from the ventral to the dorsal side of L1 vertebra, the posterior third zones were the highest, and from the head to the foot of L1 vertebra, the middle third zones were the highest (p < 0.05). Global and most zonal vBMDs of T2DM were higher than those of non-T2DM in the age group of 50-59 years old, vBMD-mp of T2DM was higher in the age group of 60-59 years old, and vBMD-mm of T2DM was higher in the age group of 70-80 years old (p < 0.05). Zonal vBMDs in T2DM were higher than non-T2DM and the difference decreases with age especially in the upper third of L1 vertebra and the lower third of L1 vertebra. Conclusions: Vertebral compression fractures and the confusion between T2DM and vBMD may be all caused by the heterogeneous distribution of vBMDs. The higher risk of T2DM with vertebral compression fractures may be associated with the different loss rate of global and site-specific vBMD, independent of vBMD itself.

Bone Density Correlates With Depth of Subsidence After Expandable Interbody Cage Placement: A Biomechanical Analysis

STUDY DESIGN

Biomechanical analysis.

OBJECTIVE

To evaluate the depth of subsidence resulting from an expandable interbody cage at varying bone foam densities.

SUMMARY OF BACKGROUND DATA

Expandable interbody cages have been shown to be associated with increased rates of subsidence. It is critical to evaluate all variables which may influence a patient's risk of subsidence following the placement of an expandable interbody cage.

METHODS

In the first stage of the study, subsidence depth was measured with 1 Nm of input expansion torque. In the second stage, the depth of subsidence was measured following 150 N output force exerted by an expandable interbody cage. Within each stage, different bone foam densities were analyzed, including 5, 10, 15, and 20 pounds per cubic foot (PCF). Five experimental trials were performed for each PCF material, and the mean subsidence depths were calculated. Trials which failed to reach 150 N output force were considered outliers and were excluded from the analysis.

RESULTS

There was an overall decrease in subsidence depth with increasing bone foam density. The mean subsidence depths at 150 N output force were 2.0±0.3 mm for 5 PCF, 1.8±0.2 mm for 10 PCF, 1.1±0.2 mm for 15 PCF, and 1.1±0.2 mm for 20 PCF bone foam. The mean subsidence depths at 1 Nm of input torque were 2.3±0.5 mm for 5 PCF, 2.3±0.5 mm for 10 PCF, 1.2±0.2 mm for 15 PCF, and 1.1±0.1 mm for 20 PCF bone foam.

CONCLUSIONS

Depth of subsidence was negatively correlated with bone foam density at both constant input torque and constant endplate force. Because tactile feedback of cage expansion into the subsiding bone cannot be reliably distinguished from true expansion of disc space height, surgeons should take bone quality into account when deploying expandable cages.

The influence of proliferative tissue on Hounsfield unit and its correlation with BMD in middle-aged and elderly patients with lumbar degenerative diseases

PURPOSE

The difference of Hounsfield Unit (HU) value in different regions of L3 vertebra in middle-aged and elderly patients with lumbar degeneration diseases (LDD) was analyzed. To investigate the influence of proliferative tissue on HU value of cancellous bone and its correlation with bone mineral density (BMD).

METHODS

The medical records of middle-aged and elderly patients with LDD in our hospital from December 2020 to December 2023 were retrospectively analyzed. The patients were divided into osteophyte group and no-osteophyte group according to the presence or absence of osteophyte formation on lumbar spine X-ray. In osteophyte group, cancellous bone HU value, containing cortical bone overall HU value and containing osteophyte overall HU value in L3 vertebra were measured on the lumbar CT cross-section. In no-osteophyte group, only the cancellous bone HU value and the containing cortical bone overall HU value were measured. Differences in HU value in different regions of the L3 vertebral body were compared within and between groups of middle-aged and elderly patients with LDD, respectively. To investigate its effect on cancellous bone HU measurements and to do a correlation analysis with patients' BMD.

RESULTS

A total of 115 patients with LDD were included in this study, including 65 males and 50 females, with an average age of 67.83 ± 6.59 years. The results of the study showed no statistical differences in age (P = 0.15), gender (P = 0.57), smoking (P = 0.88), drinking history (P = 0.76), medical history (P > 0.05) and BMI(P = 0.29) between the two groups. In osteophyte group, the mean cancellous bone HU value was 98.00 ± 25.50 HU, the containing cortical bone overall HU value was 189.02 ± 46.18 HU, and the containing osteophyte overall HU value was 232.69 ± 56.01 HU. The overall HU values containing cortical bone and containing osteophyte were significantly higher than cancellous bone HU value (P < 0.001). In no-osteophyte group, the mean cancellous bone HU value was 102.04 ± 19.64 HU, and the containing cortical bone overall HU value was 175.00 ± 28.97 HU, which was statistically significantly different (P < 0.001). There was no significant difference in cancellous bone HU value and the containing cortical bone overall HU value between the two groups (P > 0.05). The results of the Pearson correlation analysis showed a significant correlation between the cancellous bone HU value of the L3 vertebrae and the QCT BMD value of the patients (r = 0.95, P < 0.001). However, there was no significant correlation between containing cortical bone overall HU value and containing osteophyte overall HU value and the patient's QCT BMD value (P > 0.05).

CONCLUSIONS

Vertebral HU value is an alternative measurement that effectively reflects the patient's BMD. In middle-aged and elderly LDD patients, HU values in different areas of L3 vertebra are significantly different, and hyperplastic tissues such as cortical bone and osteophytes may exponentially lead to higher HU value in patients. Compared with other measurement areas, vertebral cancellous bone HU value have the advantage of accurately assessing patients' BMD.

MRI-based endplate bone quality score predicts cage subsidence following oblique lumbar interbody fusion

BACKGROUND CONTEXT

Cage subsidence is a common complication after lumbar interbody fusion surgery, with low bone mineral density (BMD) being a significant risk factor. Endplate bone quality (EBQ) obtained from clinical MRI scans has been deemed reliable in determining regional BMD. However, the association between EBQ score and cage subsidence following oblique lumbar interbody fusion (OLIF) has not been clearly established.

PURPOSE

This study aims to assess the relationship between EBQ score and cage subsidence in patients who underwent single-level OLIF.

STUDY DESIGN/SETTING

A retrospective study.

PATIENT SAMPLE

The study included adults with degenerative spinal conditions who underwent single-level OLIF at our institution.

OUTCOME MEASURES

Cage subsidence, disc height, EBQ score, fusion rate.

METHODS

This retrospective study analyzed data from patients who underwent single-level OLIF surgery at our institution between October 2017 and August 2022. Postoperative CT scans were used to measure cage subsidence, while the EBQ score was calculated using preoperative noncontrast T1-weighted MRI. To determine the predictive ability of the EBQ score, receiver operating characteristic (ROC) curve analysis was conducted. Additionally, univariable and multivariable logistic regression analyses were performed.

RESULTS

In this study, a total of 88 patients were included and followed up for an average of 15.8 months. It was observed that 32.9% (n=29/88) of the patients experienced cage subsidence. The postsurgery disc height was significantly higher in patients who experienced subsidence compared to those who did not. The mean EBQ scores for patients with nonsubsidence and subsidence were 2.31±0.6 and 3.48±1.2, respectively, and this difference was statistically significant. The ROC curve analysis showed that the AUC for the EBQ score was 0.811 (95% CI: 0.717-0.905). The most suitable threshold for the EBQ score was determined to be 2.318 (sensitivity: 93.1%, specificity: 55.9%). Additionally, the multivariate logistic regression analysis revealed a significant association between a higher EBQ score and an increased risk of subsidence (odds ratio [OR]=6.204, 95% CI=2.520-15.272, p<.001).

CONCLUSIONS

Our findings indicate that higher preoperative EBQ scores are significantly linked to cage subsidence following single-level OLIF. Preoperative measurement of MRI can serve as a valuable tool in predicting cage subsidence.

Defining cage subsidence in anterior, oblique, and lateral lumbar spine fusion approaches: a systematic review of the literature

One of the most common complications of lumbar fusions is cage subsidence, which leads to collapse of disc height and reappearance of the presenting symptomology. However, definitions of cage subsidence are inconsistent, leading to a variety of subsidence calculation methodologies and thresholds. To review previously published literature on cage subsidence in order to present the most common methods for calculating and defining subsidence in the anterior lumbar interbody fusion (ALIF), oblique lateral interbody fusion (OLIF), and lateral lumbar interbody fusion (LLIF) approaches. A search was completed in PubMed and Embase with inclusion criteria focused on identifying any study that provided descriptions of the method, imaging modality, or subsidence threshold used to calculate the presence of cage subsidence. A total of 69 articles were included in the final analysis, of which 18 (26.1%) reported on the ALIF approach, 22 (31.9%) on the OLIF approach, and 31 (44.9%) on the LLIF approach, 2 of which reported on more than one approach. ALIF articles most commonly calculated the loss of disc height over time with a subsidence threshold of > 2 mm. Most OLIF articles calculated the total amount of cage migration into the vertebral bodies, with a threshold of > 2 mm. LLIF was the only approach in which most articles applied the same method for calculation, namely, a grading scale for classifying the loss of disc height over time. We recommend future articles adhere to the most common methodologies presented here to ensure accuracy and generalizability in reporting cage subsidence.

Are the facet joint parameters risk factors for cage subsidence after TLIF in patients with lumbar degenerative spondylolisthesis?

PURPOSE

To assess whether preoperative facet joint parameters in patients with degenerative lumbar spondylolisthesis (DS) are risk factors for cage subsidence (CS) following transforaminal lumbar interbody fusion (TLIF).

METHODS

We enrolled 112 patients with L4-5 DS who underwent TLIF and were followed up for > 1 year. Preoperative demographic characteristics, functional areas of paraspinal muscles and psoas major muscles (PS), total functional area relative to vertebral body area, functional cross-sectional area (FCSA) of PS and lumbar spine extensor muscles, normalized FCSA of PS to the vertebral body area (FCSA/VBA), lumbar indentation value, facet joint orientation, facet joint tropism (FT), cross-sectional area of the superior articular process (SAPA), intervertebral height index, vertebral Hounsfield unit (HU) value, lordosis distribution index, t-scores, sagittal plane parameters, visual analog scale (VAS) for low back pain, VAS for leg pain, Oswestry disability index, global alignment and proportion score and European quality of life-5 dimensions (EQ-5D) were assessed.

RESULTS

Postoperative CS showed significant correlations with preoperative FO(L3-4), FT (L3 and L5), SAPA(L3-5), L5-HU, FCSA/VBA(L3-4), Pre- T-score, post-6-month VAS for back pain and EQ-5D scores among other factors. According to ROC curve analysis, the optimal decision points for FO(L3-4), L3-SAPA, FCSA/VBA(L3-4), L5-HU, and Pre- T-score were 35.88°, 43.76°,114.93, 1.73, 1.55, 136, and - 2.49.

CONCLUSIONS

This study identified preoperative FO, SAPA, preoperative CT, Pre- T-score and the FCSA/VBA as independent risk factors for CS after TLIF for DS. These risk factors should enable spinal surgeons to closely monitor and prevent the occurrence of CS.

The influence of osteoporosis on mechanical complications in lumbar fusion surgery: a systematic review

Background

Adults undergoing spine surgery often have underlying osteoporosis, which may be a risk factor for postoperative complications. Although these associations have been described, osteoporosis remains profoundly underdiagnosed and undertreated in the spine surgery population. A thorough, comprehensive systematic review summarizing the relationships between bone mineral density (BMD) and specific complications of lumbar fusion surgery could be a valuable resource for raising awareness and supporting clinical practice changes.

Methods

PubMed, Embase, and Web of Science databases were searched for original clinical research articles reporting on BMD, or surrogate measure, as a predictor of complications in adults undergoing elective lumbar fusion for degenerative disease or deformity. Endpoints included cage subsidence, screw loosening, pseudarthrosis, vertebral fracture, junctional complications, and reoperation.

Results

A total of 71 studies comprising 12,278 patients were included. Overall, considerable heterogeneity in study populations, methods of bone health assessment, and definition and evaluation of clinical endpoints precluded meta-analysis. Nevertheless, low BMD was associated with higher rates of implant failures like cage subsidence and screw loosening, which were often diagnosed with concomitant pseudarthrosis. Osteoporosis was also a significant risk factor for proximal junctional kyphosis, particularly due to fracture. Many studies found surgical site-specific BMD to best predict focal complications. Functional outcomes were inconsistently addressed.

Conclusions

Our findings suggest osteoporosis is a significant risk factor for mechanical complications of lumbar fusion. These results emphasize the importance of preoperative osteoporosis screening, which allows for medical and surgical optimization of high-risk patients. This review also highlights current practical challenges facing bone health evaluation in patients undergoing elective surgery. Future prospective studies using standardized methods are necessary to strengthen existing evidence, identify optimal predictive thresholds, and establish specialty-specific practice guidelines. In the meantime, an awareness of the surgical implications of osteoporosis and utility of preoperative screening can provide for more informed, effective patient care.

A novel MRI-based Cervical-Endplate Bone Quality score independently predicts cage subsidence after Anterior Cervical Discectomy and Fusion

INTRODUCTION

Postoperative cage subsidence after Anterior Cervical Discectomy and Fusion (ACDF) often has adverse clinical consequences and is closely related to Bone Mineral Density (BMD). Previous studies have shown that cage subsidence can be better predicted by measuring site-specific bone density. MRI-based Endplate Bone Quality (EBQ) scoring effectively predicts cage subsidence after lumbar interbody fusion. However, there is still a lack of studies on the practical application of EBQ scoring in the cervical spine.

PURPOSE

To create a similar MRI-based scoring system for Cervical-EBQ (C-EBQ) and to assess the correlation of the C-EBQ with endplate Computed Tomography (CT)-Hounsfield Units (HU) and the ability of this scoring system to independently predict cage subsidence after ACDF, comparing the predictive ability of the C-EBQ with the Cervical-Vertebral Bone Quality (C-VBQ) score.

METHODS

A total of 161 patients who underwent single-level ACDF for degenerative cervical spondylosis at our institution from 2012 to 2022 were included. Demographics, procedure-related data, and radiological data were collected, and Pearson correlation test was used to determine the correlation between C-EBQ and endplate HU values. Cage subsidence was defined as fusion segment height loss of ≥ 3 mm. Receiver operating characteristic analysis and area-under-the-curve values were used to assess the predictive ability of C-EBQ and C-VBQ. A multivariate logistic regression model was developed to identify potential risk factors associated with subsidence.

RESULTS

Cage subsidence was present in 65 (40.4%) of 161 patients. The mean C-EBQ score was 1.81 ± 0.35 in the group without subsidence and 2.59 ± 0.58 in the group with subsidence (P < 0.001). Multivariate analysis showed that a higher C-EBQ score was significantly associated with subsidence (OR = 5.700; 95%CI = 3.435-8.193; P < 0.001), was the only independent predictor of cage subsidence after ACDF, had a predictive accuracy of 93.7%, which was superior to the C-VBQ score (89.2%), and was significantly negatively correlated with the endplate HU value (r = -0.58, P < 0.001).

CONCLUSIONS

Higher C-EBQ scores were significantly associated with postoperative cage subsidence after ACDF. There was a significant negative correlation between C-EBQ and endplate HU values. The C-EBQ score may be a promising tool for assessing preoperative bone quality and postoperative cage subsidence and is superior to the C-VBQ.

Improved intervertebral fusion in LLIF rabbit model with a novel titanium cage

BACKGROUND CONTEXT

There is no established small animal approach model for the strict simulation of lateral lumbar interbody fusion (LLIF) surgery.

PURPOSE

This study aims to establish a reliable LLIF rabbit model that strictly simulates the procedure and to preliminarily evaluate the differences in fusion outcomes with different graft materials.

STUDY DESIGN

A controlled laboratory.

METHODS

Fifty-four 4-month-old white New Zealand female and male rabbits were selected and divided into five groups: Group A (dissection group) consisted of 9 rabbits, Group B (normal approach group) consisted of 9 rabbits, Group C (autogenous iliac bone group) consisted of 12 rabbits, Group D (BMP-2 carrier material group) consisted of 12 rabbits, and Group E (allograft bone group) consisted of 12 rabbits. Based on data from Group A, a novel titanium metal fusion device was designed. Postoperatively, at the 12-week mark, manual palpation was employed to compare the interbody fusion status among Groups B, C, D, and E. Specimens from Groups C, D, and E were subjected to Micro-CT scanning to compare various parameters such as trabecular bone volume (BV), bone volume fraction (BV/TV, BVF), and bone surface area (BS). Furthermore, a tissue histopathological examination was performed to observe the structure and morphology of newly formed bone within the fusion mass as well as the remodeling of the graft in each group.

RESULTS

Based on the measurements obtained from the dissection group, we designed a U-shaped interbody fusion device with dimensions of 10 mm in length, 2.5 mm in width, and 1.3 mm in height. In Group B, 9 cases exhibited intervertebral mobility. In Group C, 1 case showed nonfusion. In Group D, all cases achieved fusion. In Group E, 4 cases did not achieve fusion. Additionally, the Micro-CT results showed that the interbody fusion index scores were 4.64±0.50 in Group C, 4.33±0.65 in Group D, and 3.36±0.81 in Group E. There was no statistically significant difference in fusion index scores between Groups C and D (p=.853). Notably, Groups C and D had higher scores than Group E (p<.001). The trabecular bone volume (BV) in Groups C and D also showed no significant difference but was significantly higher than in Group E (p<.001). Furthermore, the histopathological results revealed that the specimens from Group E had less newly formed cartilage and bone compared to Groups C and D.

CONCLUSIONS

This study successfully established a strict simulation of the clinical LLIF procedure in a rabbit model. Moreso, we conducted a preliminary validation indicating that the BMP-2 carrier material achieved interbody fusion outcomes similar to autogenous iliac bone.

CLINICAL SIGNIFICANCE

The findings of this investigation from animal models provide a theoretical basis for the clinical use of BMP-2 to promote early spinal fusion in LLIF procedures. Importantly, the study provides a small animal model foundation for research related to LLIF surgery.

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.

Preoperative MRI-based endplate quality: a novel tool for predicting cage subsidence after anterior cervical spine surgery

PURPOSE

The objective of this study was to examine the predictive value of a newly developed MRI-based Endplate Bone Quality (EBQ) in relation to the development of cage subsidence following anterior cervical discectomy and fusion (ACDF).

METHODS

Patients undergoing ACDF for degenerative cervical diseases between January 2017 and June 2022 were included. Correlation between EBQ scores and segmental height loss was analyzed using Pearson's correlation. ROC analyses were employed to ascertain the EBQ cut-off values that predict the occurrence of cage subsidence. Multivariate logistic regression analyses were conducted to identify the risk factors associated with postoperative cage subsidence.

RESULTS

23 individuals (14.56%) exhibited the cage subsidence after ACDF. In the nonsubsidence group, the average EBQ and lowest T-score were determined to be 4.13 ± 1.14 and - 0.84 ± 1.38 g/cm2 respectively. In contrast, the subsidence group exhibited a mean EBQ and lowest T-score of 5.38 ± 0.47 (p < 0.001) and - 1.62 ± 1.34 g/cm2 (p = 0.014), respectively. There was a significant positive correlation (r = 0.798**) between EBQ and the segmental height loss. The EBQ threshold of 4.70 yielded optimal sensitivity (73.9%) and specificity (93.3%) with AUC of 0.806. Furthermore, the lowest T-score (p = 0.045, OR 0.667) and an elevated cervical EBQ score (p < 0.001, OR 8.385) were identified as significant risk factors for cage subsidence after ACDF.

CONCLUSIONS

The EBQ method presents itself as a promising and efficient tool for surgeons to assess patients at risk of cage subsidence and osteoporosis prior to cervical spine surgery, utilizing readily accessible patient data.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Comparison of instrumented and stand-alone lateral lumbar interbody fusion for lumbar degenerative disease: a systematic review and meta-analysis

BACKGROUND

Both instrumented and stand-alone lateral lumbar interbody fusion (LLIF) have been widely used to treat lumbar degenerative disease. However, it remains controversial as whether posterior internal fixation is required when LLIF is performed. This meta-analysis aims to compare the radiographic and clinical results between instrumented and stand-alone LLIF.

METHODS

PubMed, EMBASE and Cochrane Collaboration Library up to March 2023 were searched for studies that compared instrumented and stand-alone LLIF in the treatment of lumbar degenerative disease. The following outcomes were extracted for comparison: interbody fusion rate, cage subsidence rate, reoperation rate, restoration of disc height, segmental lordosis, lumbar lordosis, visual analog scale (VAS) scores of low-back and leg pain and Oswestry Disability Index (ODI) scores.

RESULTS

13 studies involving 1063 patients were included. The pooled results showed that instrumented LLIF had higher fusion rate (OR 2.09; 95% CI 1.16-3.75; P = 0.01), lower cage subsidence (OR 0.50; 95% CI 0.37-0.68; P < 0.001) and reoperation rate (OR 0.28; 95% CI 0.10-0.79; P = 0.02), and more restoration of disc height (MD 0.85; 95% CI 0.18-1.53; P = 0.01) than stand-alone LLIF. The ODI and VAS scores were similar between instrumented and stand-alone LLIF at the last follow-up.

CONCLUSIONS

Based on this meta-analysis, instrumented LLIF is associated with higher rate of fusion, lower rate of cage subsidence and reoperation, and more restoration of disc height than stand-alone LLIF. For patients with high risk factors of cage subsidence, instrumented LLIF should be applied to reduce postoperative complications.

Risk Factors for Subsidence Following Anterior Lumbar Interbody Fusion

STUDY DESIGN

Retrospective cohort.

OBJECTIVE

Anterior lumbar interbody fusion (ALIF) may be complicated by subsidence, which can lead to significant morbidity including pain, disc space collapse, neural compression, segmental kyphosis, instability, and vertebral body fracture. This study sought to identify patient and procedural risk factors for subsidence in patients undergoing ALIF.

METHODS

This study analyzed consecutive patients who underwent ALIF at a single institution with a minimum of 2 years follow-up. Patients were grouped as either Non-Subsidence (NS-ALIF) or Cage Subsidence (CS-ALIF) based on the final postoperative radiograph. Demographic variables, operative characteristics, and radiographic outcomes were evaluated to identify significant predictors on univariate and multivariate statistics.

RESULTS

144 patients (170 levels) were included with an average follow-up of 50.70 ± 28.44 months (4.23 years). The incidence of subsidence was 22.94% (39/170 levels). On univariate statistics, the CS-ALIF group was significantly older (P = .020), had higher BMI (P = .048), worse ASA (P = .001), higher prevalence of comorbid osteoporosis (P < .001), and a more anteriorly placed interbody device (P = .005). On multivariate analysis, anterior cage placement remained the only significant predictor (OR: 1.08, 95% CI: 1.03-1.14; P = .003). There was a significantly higher rate of subsequent adjacent segment surgery among the CS-ALIF group (P = .035).

CONCLUSION

Factors contributing to subsidence in ALIF included older age, higher BMI, severe ASA, and osteoporosis, while anterior cage placement remained the only independent predictor on multivariate analysis. Subsidence was associated with a higher rate of subsequent adjacent segment surgery. Surgical technique should optimize placement of the interbody cage and avoid overstuffing the disc space.

Effects of anti-osteoporosis treatment in elderly patients with osteoporosis and lumbar discectomy and fusion

BACKGROUND

The effect of anti-osteoporosis treatment in elderly patients with osteoporosis and lumbar discectomy and fusion (LIF) for lumbar degenerative diseases is not well known.

OBJECTIVE

This study aimed to evaluate the effect of perioperative anti-osteoporosis treatment in the patients with osteoporosis and LIF.

METHODS

From January to December 2022, patients were divided into three groups according to the inclusive criteria: the normal group (Group A), the osteopenia group (Group B) and the osteoporosis group (Group C). Quantitative computed tomography (QCT), height of the intervertebral space (HIS), segmental sagittal angle (SSA), visual analogue scale (VAS) score and Oswestry Disability Index (ODI) were compared between the groups at the follow-up time. The serum Ca2 + , osteocalcin (OC), propeptide of type I procollagen (PINP) C-terminal cross-linking telopeptide of type I collagen (β-CTX) and 25-OH vitamin D (25-OH VD) levels were compared between the groups at the time of follow-up. Interbody fusion was graded on the X-ray and CT images at the follow-up time.

RESULTS

There were 165 patients in this study. There were significant differences in the mean age, mean score, HIS and SSA between the groups at the different follow-up times. There were significant differences in the concentrations of serum Ca2 + , OC, β-CTX, 25-OH VD and PINP at the sixth month after surgery between the groups. There were significant differences in the concentrations of serum Ca2 + , β-CTX and 25-OH VD between the pre-surgery and at six months after surgery in Group B and β-CTX and 25-OH VD in Group C. There was a significant difference in the degree of fusion between Group B and C (χ2= 5.6243, P< 0.05).

CONCLUSION

In elderly patients with LIF and osteoporosis, anti-osteoporosis therapy could reduce bone resorption and thus facilitate fusion. Anti-osteoporosis medication tends to enhance radiological, functional, and fusion short-term outcomes.

Comparison of predictive performance for cage subsidence between CT-based Hounsfield units and MRI-based vertebral bone quality score following oblique lumbar interbody fusion

OBJECTIVE

To compare the predictive performance between CT-based Hounsfield units (HU) and MRI-based vertebral bone quality (VBQ) for cage subsidence (CS) following oblique lumbar interbody fusion combined with anterolateral single-rod screw fixation (OLIF-AF).

METHODS

A retrospective study was performed on consecutive patients who underwent OLIF-AF at our institution from 2018 to 2020. CS was determined by CT according to the change in the midpoint intervertebral space height. The VBQ score and HU value were measured from preoperative MRI and CT, respectively. Then, we evaluated the predictive performance of those two parameters by comparing the receiver operating characteristic (ROC) curves.

RESULTS

The mean global and segmental VBQ scores were significantly higher in the CS group, and the mean global and segmental HU values were significantly lower in the CS group. The area under the curve (AUC) of CS prediction was higher in the operative segments' VBQ score and HU value than the measurement in the global lumbar spine. Finally, the combined segmental VBQ score and segmental HU value demonstrated the highest AUC.

CONCLUSION

Both MRI-based VBQ score and CT-based HU value can achieve accurate CS prediction. Moreover, the combination of those two measurements indicated the best predictive performance.

CLINICAL RELEVANCE STATEMENT

Both MRI-based VBQ score and CT-based HU value can be used for cage subsidence prediction, in order to take preventive measures early enough.

KEY POINTS

• Osteoporosis is a risk factor for CS, both MRI-based VBQ score and CT-based HU value are important predictors during vertebral bone quality evaluation. • The VBQ score and HU value measured in the operative segments are better predictors of CS than the measurement in the global lumbar spine. • Combined segmental VBQ score and segmental HU value achieved the best predictive performance for CS.

Comparison of Intraoperative Endplate Injury between Mini-Open Lateral Lumbar Interbody Fusion (LLIF) and Transforaminal Lumbar Interbody Fusion (TLIF) and Analysis of Risk Factors: A Retrospective Study

OBJECTIVE

The study aimed to compare the incidence of intraoperative endplate injury in patients who underwent Transforaminal interbody fusion (TLIF) and mini-open lumbar interbody fusion (LLIF) surgery. The independent risk factors related to endplate injury in LLIF procedure were analyzed.

METHODS

A total of 199 patients who underwent LLIF (n = 106) or TLIF (n = 93) surgery from June 2019 to September 2021 were reviewed. The endplate injury was assessed by postoperative sagittal CT scan. A binary logistic analysis model were used to identify independent risk factors related to LLIF endplate injury based on univariate analysis.

RESULTS

There was an obvious difference in the occurrence of intraoperative endplate injury between LLIF (42/106, 39.6%) and TLIF group (26/93, 28%), although it did not reach the significant level. L1 CT value (OR = 0.985, 95% CI = 0.972-0.998), cage position (OR = 3.881, 95% CI = 1.398-10.771) and height variance (OR = 1.263, 95% CI = 1.013-1.575) were independent risk factors for endplate injury in LLIF procedure. According to the cage settlement patterns, there 5 types of A to E. The severity of the facet joint degeneration was positively related to the occurrence of endplate injury.

CONCLUSIONS

The incidence of intraoperative endplate injury is higher in LLIF than in TLIF procedures. Low bone quantity, cage posterior position and larger height variance are risk factors to induce endplate injury in LLIF surgery. The facet joint degeneration may be related to severe endplate injuries and even fractures.

Cortical Endplate Bone Density Measured by Novel Phantomless Quantitative Computed Tomography May Predict Cage Subsidence more Conveniently and Accurately

OBJECTIVE

Previous studies have shown that bone mineral density (BMD) is a predictor of cage subsidence. Phantom-less quantitative computed tomography (PL-QCT) can measure volumetric bone mineral density (vBMD) of lumbar trabecular and cortical bone. The study of endplate vBMD (EP-vBMD) is important in predicting cage settlement after extreme lateral interbody fusion (XLIF). This study aimed to determine the risk factors for postoperative cage subsidence after XLIF, particularly focusing on the relationship between vBMD measured by automatic PL-QCT and cage subsidence.

METHODS

Patients who underwent XLIF surgery from January 2018 to October 2020 with a minimum of 6 months of follow-up were retrospectively included. Cage subsidence was defined as >2 mm cage sinking on the adjacent endplate in follow-up imaging evaluation. Outcome measures were localized vBMDs included EP-vBMDs with different region of interest (ROI) heights measured by PL-QCT based on a customized muscle-fat algorithm. Shapiro-Wilk test, one-way ANOVA, Mann-Whitney test, Fisher exact test, univariable and multivariable logistic regression and receiver operating characteristic (ROC) curve analysis were executed in this study.

RESULTS

One hundred and thirteen levels of 78 patients were included in the analysis. The mean age was 65 ± 7.9 years for 11 males and 67 females. Cage subsidence occurred on 45 (39.8%) surgical levels. There was no significant difference in demographics, fused levels, or preoperative radiographic parameters. 1.25-mm EP-vBMD (0.991 [0.985,0.997], p = 0.004) and P-TB-vBMD (cage-positioned trabecular volumetric bone mineral density) (0.988 [0.977-0.999], p = 0.026) were cage-subsidence relevant according to univariate analysis. Low 1.25-mm EP-vBMD (0.992 [0.985, 0.999], p = 0.029) was an independent risk factor according to multifactorial analysis.

CONCLUSION

Preoperative low EP-vBMD was an independent risk factor for postoperative cage subsidence after XLIF. EP-vBMD measured by most cortex-occupied ROI may be the optimal vBMD parameter for cage subsidence prediction.

Design and Biomechanical Evaluation of a Bidirectional Expandable Cage for Oblique Lateral Interbody Fusion

OBJECTIVE

Oblique lateral interbody fusion (OLIF) surgery is a minimally invasive spinal surgery technique that has become increasingly popular in recent years. The primary objective of the current study was to design a minimally invasive expandable fusion device that can reduce iatrogenic nerve damage and minimize endplate damage during OLIF surgery, while restoring intervertebral height and alignment. The second objective was to use finite element analysis to evaluate the biomechanical stability of the newly designed expandable fusion device after implantation into the intervertebral space.

METHODS

A new bidirectional expandable cage was designed in this study. A finite element model (FEM) of L3-L5 lumbar segment was modified to simulate decompression and fusion. The modified FEMs were constructed in the following cases: intact model, bidirectional expandable cage (alone, with unilateral pedicle screws [UPSs], and with bilateral pedicle screws [BPSs]) model, conventional OLIF cage (alone, with UPSs, and with BPSs) model. To simulate physiological loadings, the models were subjected to a follower compressive pre-load of 400 N, in addition to 8.0 Nm of flexion, extension, lateral bending, and axial rotation moments.

RESULT

All modified FEMs exhibited a significant reduction in motion at L3-L5 compared to the intact model. Among the fusion models, the bidirectional expandable cage (BEC) with BPS model displayed the highest stiffness and demonstrated a reduced range of motion (48.5%-75.7%). Additionally, the peak stress on the endplate in the conventional OLIF cage (Conv-OLIF) model was generally lower than that in the BEC models. The cage in the BEC ALONE model exhibited the highest stress (93.87-176.3 MPa) on the endplate in most motion modes, while the cage in the Conv-OLIF+BPS model had the lowest stress (16.67-30.58 MPa) on the endplate in most motion modes. The maximum stress on the fixation in the BEC fusion models was generally lower than that in the Conv-OLIF fusion group under the same loading conditions. The OLIF ALONE model had the lowest stress on the adjacent disc, while the stress level in the BEC ALONE model was very close to it.

CONCLUSIONS

The BEC implanted models had higher stiffness, and more proper stress distribution on the posterior fixation was comparable to that of the Conv-OLIF models. However, the endplate stress peaks and cage stress peaks of the BEC models were slightly higher than those of the Conv-OLIF models, though still within a clinically acceptable range. Taking into account both biomechanical and clinical perspectives, BEC-assisted unilateral pedicle screw fixation meet clinical demand and may serve as a viable alternative to Conv-OLIF fusion.

MRI-based Endplate Bone Quality score independently predicts cage subsidence following transforaminal lumbar interbody fusion

BACKGROUND CONTEXT

Cage subsidence following transforaminal lumbar interbody fusion (TLIF) has closely correlated with poor vertebral bone quality. Studies have shown better predictive value for cage subsidence by measuring bone density at specific site. However, few studies have been performed to examine the relationship between site-specific MRI bone assessment and cage subsidence in patients who have undergone lumbar interbody fusion. The association between MRI-based assessment of endplate bone quality and cage subsidence after TLIF remains unclear.

PURPOSE

To study the predictive value of MRI-based endplate bone quality (EBQ) score for cage subsidence following TLIF, using QCT bone densitometry as a reference standard.

STUDY DESIGN/SETTING

A retrospective study.

PATIENT SAMPLE

A total of 280 adult patients undergoing single-segment TLIF for degenerative lumbar spine disease from 2010 to 2020 at our institution who had preoperative T1-weighted MRIs.

OUTCOME MEASURES

Cage subsidence, disc height, endplate bone quality (EBQ) score, bone mineral density, fusion rate.

METHODS

The retrospective study reviewed patients who underwent TLIF at one institution between March 2010 and October 2020. Cage subsidence was measured with postoperative lumbar X-rays based on the cage protrusion through into the superior or inferior end plate or both by more than 2 mm. The EBQ score was measured from preoperative T1-weighted MRI in accordance with the previously reported method.

RESULTS

Cage subsidence was observed in 42 of the 280 patients. Bone densitometry with quantitative computed tomography was visibly reduced in the subsidence group. The mean EBQ scores of the lumbar endplate bone was 4.3±0.9 in nonsubsidence and 5.0±0.6 in subsidence. On multivariate logistic regression, the difference between the two groups was remarkable. Risk of cage subsidence increases significantly with higher EBQ scores (odds ratio [OR]=2.063, 95% confidence interval [CI] 1.365-3.120, p=.001) and was an independent factor in predicting subsidence after TLIF. On receiver operating characteristic curve, the AUC for the EBQ score was 0.820 (95% confidence interval [CI]: 0.755-0.844) and the most suitable threshold for the EBQ score was 4.730 (sensitivity: 76.2%, specificity: 83.2%).

CONCLUSIONS

Higher EBQ scores measured on preoperative MRI correlated significantly with cage subsidence following TLIF. Performing EBQ assessment prior to TLIF may be a valid method of predicting the risk of postoperative subsidence.

Advances in Hounsfield units value for predicting cage subsidence on spinal interbody fusion surgery

PURPOSE

A growing number of studies have demonstrated that Hounsfield units (HU) value can effectively assess bone quality and predict cage subsidence (CS) after spinal surgery. The purpose of this review is to provide an overview of the utility of the HU value for predicting CS after spinal surgery and to raise some of the unresolved questions in this field.

METHODS

We searched on PubMed, EMBASE, MEDLINE, and Cochrane Library for studies correlating HU value to CS.

RESULTS

Thirty-seven studies were included in this review. We found that HU value can predicted the risk of CS effectively after spinal surgery. Moreover, the HU value of the cancellous vertebral body and the cortical endplate were used for predicting CS, in comparison, the measurement method of HU value in the cancellous vertebral body was more standardized, but which region is more important to CS remains unknown. Different cutoff thresholds of HU value have been established in different surgical procedures for predicting CS. The HU value may be superior to dual-energy X-ray absorptiometry (DEXA) for CS prediction; however, the usage standard of HU value has not been well established.

CONCLUSIONS

The HU value shows great potential for predicting CS and constitutes an advantage over DEXA. However, general consensuses about how CS is defined and HU is measured, which part of HU value is more important, and the appropriate cutoff threshold of the HU value for osteoporosis and CS still require exploration.

Subsidence of Interbody Cage Following Oblique Lateral Interbody Fusion: An Analysis and Potential Risk Factors

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

This study aimed to report the incidence and potential risk factors of polyetheretherketone (PEEK) cage subsidence following oblique lateral interbody fusion (OLIF) for lumbar degenerative diseases. We proposed also an algorithm to minimize subsidence following OLIF surgery.

METHODS

The study included a retrospective cohort of 107 consecutive patients (48 men and 59 women; mean age, 67.4 years) who had received either single- or multi-level OLIF between 2012 and 2019. Patients were classified into subsidence and non-subsidence groups. PEEK cage subsidence was defined as any violation of either endplate from the computed tomography scan in both sagittal and coronal views. Preoperative variables such as age, sex, body mass index, bone mineral density (BMD) measured by preoperative dual-energy X-ray absorptiometry, smoking status, corticosteroid use, diagnosis, operative level, multifidus muscle cross-sectional area, and multifidus muscle fatty degeneration were collected. Age-related variables (height and length) were also documented. Univariate and multivariate logistic regression analyses were used to analyze the risk factors of subsidence.

RESULTS

Of the 107 patients (137 levels), 50 (46.7%) met the subsidence criteria. Higher PEEK cage height had the strongest association with subsidence (OR = 9.59, P < .001). Other factors significantly associated with cage subsistence included age >60 years (OR = 3.15, P = .018), BMD <-2.5 (OR = 2.78, P = .006), and severe multifidus muscle fatty degeneration (OR = 1.97, P = .023).

CONCLUSIONS

Risk factors for subsidence in OLIF were age >60 years, BMD < -2.5, higher cage height, and severe multifidus muscle fatty degeneration. Patients who had subsidence had worse early (3 months) postoperative back and leg pain.

Biomechanical Comparison of Multilevel Stand-Alone Lumbar Lateral Interbody Fusion With Posterior Pedicle Screws: An In Vitro Study

OBJECTIVE

Lumbar lateral interbody fusion (LLIF) allows placement of large interbody cages while preserving ligamentous structures important for stability. Multiple clinical and biomechanical studies have demonstrated the feasibility of stand-alone LLIF in single-level fusion. We sought to compare the stability of 4-level stand-alone LLIF utilizing wide (26 mm) cages with bilateral pedicle screw and rod fixation.

METHODS

Eight human cadaveric specimens of L1-5 were included. Specimens were attached to a universal testing machine (MTS 30/G). Flexion, extension, and lateral bending were attained by applying a 200 N load at a rate of 2 mm/sec. Axial rotation of ± 8° of the specimen was performed at 2°/sec. Three-dimensional specimen motion was recorded using an optical motion-tracking device. Specimens were tested in 4 conditions: (1) intact, (2) bilateral pedicle screws and rods, (3) 26-mm stand-alone LLIF, (4) 26-mm LLIF with bilateral pedicle screws and rods.

RESULTS

Compared to the stand-alone LLIF, bilateral pedicle screws and rods had 47% less range of motion in flexion-extension (p < 0.001), 21% less in lateral bending (p < 0.05), and 20% less in axial rotation (p = 0.1). The addition of bilateral posterior instrumentation to the stand-alone LLIF resulted in decreases of all 3 planes of motion: 61% in flexion-extension ( p < 0.001), 57% in lateral bending (p < 0.001), 22% in axial rotation (p = 0.002).

CONCLUSION

Despite the biomechanical advantages associated with the lateral approach and 26 mm wide cages, stand-alone LLIF for 4-level fusion is not equivalent to pedicle screws and rods.

Increased risks of vertebral fracture and reoperation in primary spinal fusion patients who test positive for osteoporosis by Biomechanical Computed Tomography analysis

BACKGROUND CONTEXT

While osteoporosis is a risk factor for adverse outcomes in spinal fusion patients, diagnosing osteoporosis reliably in this population has been challenging due to degenerative changes and spinal deformities. Addressing that challenge, biomechanical computed tomography analysis (BCT) is a CT-based diagnostic test for osteoporosis that measures both bone mineral density and bone strength (using finite element analysis) at the spine; CT scans taken for spinal evaluation or previous care can be repurposed for the analysis.

PURPOSE

Assess the effectiveness of BCT for preoperatively identifying spinal fusion patients with osteoporosis who are at high risk of reoperation or vertebral fracture.

STUDY DESIGN

Observational cohort study in a multi-center integrated managed care system using existing data from patient medical records and imaging archives.

PATIENT SAMPLE

We studied a randomly sampled subset of all adult patients who had any type of primary thoracic (T4 or below) or lumbar fusion between 2005 and 2018. For inclusion, patients with accessible study data needed a preop CT scan without intravenous contrast that contained images (before any instrumentation) of the upper instrumented vertebral level.

OUTCOME MEASURES

Reoperation for any reason (primary outcome) or a newly documented vertebral fracture (secondary outcome) occurring up to 5 years after the primary surgery.

METHODS

All study data were extracted using available coded information and CT scans from the medical records. BCT was performed at a centralized lab blinded to the clinical outcomes; patients could test positive for osteoporosis based on either low values of bone strength (vertebral strength ≤ 4,500 N women or 6,500 N men) and/or bone mineral density (vertebral trabecular bone mineral density ≤ 80 mg/cm³ both sexes). Cox proportional hazard ratios were adjusted by age, presence of obesity, and whether the fusion was long (four or more levels fused) or short (3 or fewer levels fused); Kaplan-Meier survival was compared by the log rank test. This project was funded by NIH (R44AR064613) and all physician co-authors and author 1 received salary support from their respective departments. Author 6 is employed by, and author 1 has equity in and consults for, the company that provides the BCT test; the other authors declare no conflicts of interest.

RESULTS

For the 469 patients analyzed (298 women, 171 men), median follow-up time was 44.4 months, 11.1% had a reoperation (median time 14.5 months), and 7.7% had a vertebral fracture (median time 2.0 months). Overall, 25.8% of patients tested positive for osteoporosis and no patients under age 50 tested positive. Compared to patients without osteoporosis, those testing positive were at almost five-fold higher risk for vertebral fracture (adjusted hazard ratio 4.7, 95% confidence interval = 2.2-9.7; p<.0001 Kaplan-Meier survival). Of those positive-testing patients, those who tested positive concurrently for low values of both bone strength and bone mineral density (12.6% of patients overall) were at almost four-fold higher risk for reoperation (3.7, 1.9-7.2; Kaplan-Meier survival p<.0001); the remaining positive-testing patients (those who tested positive for low values of either bone strength or bone mineral density but not both) were not at significantly higher risk for reoperation (1.6, 0.7-3.7) but were for vertebral fracture (4.3, 1.9-10.2). For both clinical outcomes, risk remained high for patients who underwent short or long fusion.

CONCLUSION

In a real-world clinical setting, BCT was effective in identifying primary spinal fusion patients aged 50 or older with osteoporosis who were at elevated risks of reoperation and vertebral fracture.

Discordance in lumbar bone mineral density measurements by quantitative computed tomography and dual-energy X-ray absorptiometry in postmenopausal women: a prospective comparative study

BACKGROUND CONTEXT

Level-specific lumbar bone mineral density (BMD) evaluation of a single vertebral body can provide useful surgical planning and osteoporosis management information. Previous comparative studies have primarily focused on detecting spinal osteoporosis but not at specific levels.

PURPOSE

To compare the detection rate of lumbar osteoporosis between quantitative computed tomography (QCT) and dual-energy X-ray absorptiometry (DXA); to explore and analyze the distribution models of QCT-derived BMD and DXA T-score at the specific levels; and to evaluate the diagnostic accuracy of level-specific BMD thresholds for the prediction of osteoporotic vertebral compression fracture (OVCF) in postmenopausal women.

STUDY DESIGN/SETTING

A comparative analysis of prospectively collected data comparing QCT-derived BMD with DXA T-score.

PATIENT SAMPLE

A total of 296 postmenopausal women who were referred to the spine service of a single academic institution were enrolled.

OUTCOME MEASURES

QCT-derived BMD and DXA T-score at specific levels, with or without osteoporotic vertebral compression fracture.

METHODS

Postmenopausal women who underwent QCT and DXA within a week of admission from May 2019 to June 2022 were enrolled. The diagnostic criteria for osteoporosis recommended by the World Health Organization and the American College of Radiology were used for lumbar osteoporotic diagnosis. To evaluate differences in lumbar BMD measurements at specific levels, a threshold of T score=-2.5 and QCT-derived BMD = 80 mg/cm³ were used to categorize level-specific lumbar BMD into low and high BMD. Disagreements in BMD categorization between DXA and QCT were classified as a minor or major discordance based on the definition by Woodson. Data between QCT and DXA were visualized in a stacked bar plot and analyzed. Correlations between DXA and QCT at the specific levels were evaluated using Pearson's linear correlation and scatter plots. Curve fitting of BMD distribution, receiver operating characteristic (ROC) and area under the curve (AUC) for each single vertebral level was performed.

RESULTS

Of the 296 patients, QCT diagnosed 61.1% as osteoporosis, 30.4% as osteopenia and 8.4% as normal. For those screened with DXA, 54.1% of the patients had osteoporosis, 29.4% had osteopenia and 16.6% had normal BMD. Diagnoses were concordant for 194 (65.5%) patients. Of the other 102 discordant patients, 5 (1.7%) were major and 97 (32.8%) were minor. Significant correlations in level-specific BMD between DXA and QCT were observed (p<.001), with Pearson's correlation coefficients ranging from 0.662 to 0.728. The correlation strength was in the order of L1 > L2 > L3 > L4. The low BMD detection rate for QCT was significantly higher than that for DXA at the L3 and L4 levels (65% vs. 47.9% and 68.1% vs 43.7, respectively, p<.001). Patients with OVCF showed significantly lower QCT-derived BMD (47.2 mg/cm³ vs. 83.2 mg/cm³, p<.001) and T-score (-3.39 vs. -1.98, p<.001) than those without OVCF. Among these patients, 82.8% (101/122) were diagnosed with osteoporosis by QCT measurement, while only 74.6% (91/122) were diagnosed by DXA. For discrimination between patients with and without OVCF, QCT-derived BMD showed better diagnosed performance (AUC range from 0.769 to 0.801) than DXA T-score (AUC range from 0.696 to 0.753).

CONCLUSION

QCT provided a more accurate evaluation of lumbar osteoporosis than DXA. The QCT-derived BMD measurements at a specific lumbar level have a high diagnostic performance for OVCF.

The predictive value of psoas and paraspinal muscle parameters measured on MRI for severe cage subsidence after standalone lateral lumbar interbody fusion

BACKGROUND CONTEXT

The effect of psoas and paraspinal muscle parameters on cage subsidence after minimally invasive techniques, such as standalone lateral lumbar interbody fusion (SA-LLIF), is unknown.

PURPOSE

This study aimed to determine whether the functional cross-sectional area (FCSA) of psoas and lumbar spine extensor muscles (multifidus and erector spinae), and psoas FCSA normalized to the vertebral body area (FCSA/VBA) differ among levels with severe cage subsidence after SA-LLIF when compared to levels without severe cage subsidence.

STUDY DESIGN

Retrospective single center cohort study.

PATIENT SAMPLE

Patients who underwent SA-LLIF between 2008 and 2020 for degenerative conditions using exclusively polyetheretherketone (PEEK) cages, had a lumbar magnetic resonance imaging (MRI) scan within 12 months, a lumbar computed tomography (CT) scan within 6 months prior to surgery, and a postoperative clinical and radiographic follow-up at a minimum of 6 months were included.

OUTCOME MEASURES

Severe cage subsidence.

METHODS

MRI measurements included psoas and combined multifidus and erector spinae (paraspinal) FCSA and FCSA/VBA at the L3-L5 pedicles. Following manual segmentation of muscles on axial T2-weighted images using ITK-SNAP (version 3.8.0), the FCSA was calculated using a custom written program on Matlab (version R2019a, The MathWorks, Inc.) that used an automated pixel intensity threshold method to differentiate between fat and muscle. Mean volumetric bone mineral density (vBMD) at L1/2 was measured by quantitative CT. The primary endpoint was severe cage subsidence per level according to the classification by Marchi et al. Multivariable logistic regression analysis was performed using generalized linear mixed models. All analyses were stratified by biological sex.

RESULTS

95 patients (45.3% female) with a total of 188 operated levels were included in the analysis. The patient population was 92.6% Caucasian with a median age at surgery of 65 years. Overall subsidence (Grades 0-III) was 49.5% (53/107 levels) in men versus 58.0% (47/81 levels) in women (p=.302), and severe subsidence (Grades II-III) was 22.4% (24/107 levels) in men versus 25.9% (21/81 levels) in women (p=.608). In men, median psoas FCSA and psoas FCSA/VBA at L3 and L4 were significantly greater in the severe subsidence group when compared to the non-severe subsidence group. No such difference was observed in women. Paraspinal muscle parameters did not differ significantly between non-severe and severe subsidence groups for both sexes. In the multivariable logistic regression analysis with adjustments for vBMD and cage length, psoas FCSA at L3 (OR 1.002; p=.020) and psoas FCSA/VBA at L3 (OR 8.655; p=.029) and L4 (OR 4.273; p=.043) were found to be independent risk factors for severe cage subsidence in men.

CONCLUSIONS

Our study demonstrated that greater psoas FCSA at L3 and psoas FCSA/VBA at L3 and L4 were independent risk factors for severe cage subsidence in men after SA-LLIF with PEEK cages. The higher compressive forces the psoas exerts on lumbar segments as a potential stabilizer might explain these findings. Additional pedicle screw fixation might be warranted in these patients to avoid severe cage subsidence.

Endplate volumetric bone mineral density biomechanically matched interbody cage

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

The association between lumbar paraspinal muscle functional cross-sectional area on MRI and regional volumetric bone mineral density measured by quantitative computed tomography

Osteosarcopenia is a common condition among elderly and postmenopausal female patients. Site-specific bone mineral density is more predictive of bone-related complications. Few studies have investigated muscle-bone associations. Our results demonstrated that in women, significant positive associations between paraspinal muscles FCSA and vBMD exist at different lumbosacral levels. These regional differences should be considered when interpreting bone-muscle associations in the lumbar spine.

INTRODUCTION

There is increasing evidence between bone and muscle volume associations. Previous studies have demonstrated comorbidity between osteoporosis and sarcopenia. Recent studies showed that sarcopenic subjects had a fourfold higher risk of concomitant osteoporosis compared to non-sarcopenic individuals. Although site-specific bone mineral density (BMD) assessments were reported to be more predictive of bone-related complications after spinal fusions than BMD assessments in general, there are few studies that have investigated level-specific bone-muscle interactions. The aim of this study is to investigate the associations between muscle functional cross-sectional area (FCSA) on magnetic resonance imaging (MRI) and site-specific quantitative computed tomography (QCT) volumetric bone mineral density (vBMD) in the lumbosacral region among spine surgery patients.

METHODS

We retrospectively reviewed a prospective institutional database of posterior lumbar fusion patients. Patients with available MRI undergoing posterior lumbar fusion were included. Muscle measurements and FCSA were conducted and calculated utilizing a manual segmentation and custom-written program at the superior endplate of the L3-L5 vertebrae level. vBMD measurements were performed and calculated utilizing a QCT pro software at L1-L2 levels and bilateral sacral ala. We stratified by sex for all analyses.

RESULTS

A total of 105 patients (mean age 61.5 years and 52.4% females) were included. We found that female patients had statistically significant lower muscle FCSA than male patients. After adjusting for age and body mass index (BMI), there were statistically significant positive associations between L1-L2 and S1 vBMD with L3 psoas FCSA as well as sacral ala vBMD with L3 posterior paraspinal and L5 psoas FCSA. These associations were not found in males.

CONCLUSIONS

Our results demonstrated that in women, significant positive associations between the psoas and posterior paraspinal muscle FCSA and vBMD exist in different lumbosacral levels, which are independent of age and BMI. These regional differences should be considered when interpreting bone and muscle associations in the lumbar spine.

Clinical evaluation of the efficacy of a new bone cement-injectable cannulated pedicle screw in the treatment of spondylolysis-type lumbar spondylolisthesis with osteoporosis: a retrospective study

Purpose

To investigate the clinical efficacy and safety of a bone cement-injectable cannulated pedicle screw (CICPS) in the treatment of spondylolysis-type lumbar spondylolisthesis with osteoporosis.

Methods

A retrospective study was conducted on 37 patients (Dual-energy X-ray bone density detection showed different degrees of osteoporosis) with spondylolysis-type lumbar spondylolisthesis who underwent lumbar spondylolisthesis reduction and fusion using a new type of injectable bone cement screw from May 2011 to March 2015. Postoperative clinical efficacy was evaluated by the Visual Analogue Scale (VAS) scores and the Oswestry Disability Index (ODI). Imaging indexes were used to evaluate the stability of internal fixation of the devices 1, 3, 6, and 12 months after surgery and annually thereafter. The safety of the CICPS was assessed by the prevalence of intraoperative and postoperative complications.

Results

A total of 124 CICPS were implanted intraoperatively. Bone cement leakage occurred in 3 screws (2.42%), and no clinical discomfort was found in any patients. All 37 patients were followed up with an average follow-up time of 26.6 ± 13.4 months (12–58 months). In the evaluation of the clinical effects of the operation, the average postoperative VAS score of the patients decreased from 4.30 ± 1.58 before surgery to 0.30 ± 0.70 after surgery (P < 0.001), and the ODI decreased from 47.27% ± 16.97% before surgery to 3.36% ± 5.70% after surgery (P < 0.001). No screw was loose, broken or pulled out.

Conclusion

CICPS is safe and effective in the treatment of spondylolysis-type lumbar spondylolisthesis complicated by osteoporosis.

The predictive value of a novel site-specific MRI-based bone quality assessment, endplate bone quality (EBQ), for severe cage subsidence among patients undergoing standalone lateral lumbar interbody fusion

BACKGROUND CONTEXT

Studies have shown that site-specific bone density measurements had more predictive value for complications than standard whole-region measurements. Recently, MRI-based assessments of vertebral bone quality (VBQ) were introduced. However, there have been few studies that investigate the association between site-specific MRI bone assessment and osteoporosis-related complications in patients undergoing lumbar interbody fusion. In this work, we created a novel site-specific MRI-based assessment of the endplate bone quality (EBQ) and assessed its predictive value for severe cage subsidence following standalone lateral lumbar interbody fusion (SA-LLIF).

PURPOSE

To investigate the predictive value of a novel MRI-based bone assessment for severe cage subsidence after SA-LLIF.

STUDY DESIGN/SETTING

Retrospective cohort study.

PATIENT SAMPLE

Patients who underwent SA-LLIF from 2008 to 2019 at a single, academic institution with available preoperative lumbar CT and T1-weighted MRIs.

OUTCOME MEASURES

Association between EBQ and severe subsidence after SA-LLIF.

METHODS

We retrospectively reviewed the records of SA-LLIF patients treated between 2008 and 2019. EBQ was measured using preoperative non-contrast T1-weighted MRIs of the lumbar spine. EBQ was defined as the average value of signal intensity of both endplates divided by that of the cerebrospinal fluid space at the level of L3. Bivariate and multivariable analyses with generalized linear mixed models were performed and set binary severe subsidence as the outcome.

RESULTS

Two hundred five levels in 89 patients were included. Fifty levels (24.4%) demonstrated severe subsidence. Bone mineral density measured by quantitative computed tomography was significantly lower in the subsidence group. Both VBQ and EBQ were significantly higher in the subsidence group. The EBQ plus Modic change (MC) model demonstrated that the effect of EBQ was independent of MC. In multivariate analyses adjusted with QCT-vBMD, EBQ showed a significant association with cage subsidence whereas VBQ only showed a marginal trend. The EBQ-based prediction model for severe subsidence showed better goodness of fit compared to the VBQ-based model.

CONCLUSIONS

High EBQ was an independent factor for severe cage subsidence after SA-LLIF and the EBQ-based model showed better goodness of fit compared to VBQ- or MC-based models. EBQ assessment before SA-LLIF may provide insight into a patient's risk for severe subsidence.

Low cervical vertebral CT value increased early subsidence of titanium mesh cage after anterior cervical corpectomy and fusion

Study design

This study was a retrospective review.

Objective

To study the predictive effect of Hounsfield units (HU) value in the cervical vertebral body derived from computed tomography (CT) on the early titanium mesh cage (TMC) subsidence after anterior cervical corpectomy and fusion (ACCF).

Methods

This retrospective study was conducted on patients who underwent ACCF at one institution between January 2014 and December 2018. We collected date included age, gender, body mass index (BMI), disease type, surgical segment, whether merge ACDF, HU value of the vertebral body and endplate, vertebral body height loss, cervical lordosis angle, and cervical sagittal alignment. VAS, JOA, and NDI were used to assess clinical efficacy. Univariate analysis was performed to screen the influencing factors of TMC subsidence, and then logistic regression was used to find out the independent risk factors. The ROC curve and area under curve (AUC) were used to analyze the HU value to predict the TMC subsidence.

Results

A total of 85 patients who accepted ACCF were included in this study, and early titanium mesh cage subsidence was demonstrated in 29 patients. The subsidence rate was 34.1%. The JOA, VAS, and NDI scores significantly improved in both groups after the operation. Between the subsidence and non-subsidence groups, there were significant differences in age, intervertebral distraction height, and HU value in both upper and lower vertebral body and endplate. The logistic regression analysis proved that the HU value of the lower vertebral body was an independent risk of TMC subsidence, the AUC was 0.866, and the most appropriate threshold of the HU value was 275 (sensitivity: 87.5%, specificity: 79.3%).

Conclusion

Preoperative cervical CT value is an independent correlative factor for early TMC subsidence after ACCF, and patients with a low CT value of the inferior vertebral body of the operative segment have a higher risk of TMC subsidence in the early postoperative period.

Trial registration: This study is undergoing retrospective registration.

Low Hounsfield units on computed tomography are associated with cage subsidence following oblique lumbar interbody fusion (OLIF)

BACKGROUND CONTEXT

Cage subsidence is one of the most common complications following lumbar interbody fusion surgery. Low bone mineral density (BMD) is an important risk factor that contributes to cage subsidence. Hounsfield units (HU) obtained from clinical computed tomography (CT) scans provided a reliable method for determining regional BMD. The association between HU and cage subsidence following oblique lumbar interbody fusion (OLIF) remains unclear.

PURPOSE

The objective of this study is to evaluate the association between vertebral HU value and cage subsidence following OLIF.

STUDY DESIGN/SETTING

A retrospective study.

PATIENT SAMPLE

Adults with degenerative spinal conditions underwent single-level OLIF at our institution from October 2017 and August 2020 OUTCOME MEASURES: Cage subsidence, disc height, vertebral body global HU value, upper and lower instrumented vertebrae HU value, endplate HU value, fusion rate.

METHODS

This retrospective study was conducted on patients who underwent single-level OLIF at one institution between October 2017 and August 2020. Cage subsidence was measured using the CT scan postoperatively based on the cage protrusion through the vertebral endplates. The HU values were measured from preoperative CT according to previously reported methods.

RESULTS

A total of 70 patients with a mean follow-up of 15.4 months were included in the analysis. The subsidence rate was 25.7% (n=18/70). The average cage subsidence was 2.2 mm, with a range of 0-7.7 mm. No significant difference was found in age, sex, or body mass index (BMI) between the two groups. The mean global HU value of the lumbar vertebral body (L1-5) was 142.7±30.1 in nonsubsidence and 103.7±11.5 in subsidence (p=.004). The upper instrumented vertebrae (UIV) HU value was 141.4±29.7 in the nonsubsidence and 101.1±10.2 in subsidence, (p=.005). The lower instrumented vertebrae (LIV) HU value was 147.4±34.9 in nonsubsidence and 108.1±13.7 in subsidence, (p<.001). The AUC of the UIV HU value was 0.917 (95% CI: 0.853-0.981), and the most appropriate threshold of the HU value was 115 (sensitivity: 84.6%, specificity: 100%). The AUC of the LIV HU value was 0.893 (95%CI: 0.819-0.966), and the most appropriate threshold of the HU value was 125 (sensitivity: 76.9%, specificity: 100%). The mean upper endplate HU value was 235.4±50.9, and the mean lower endplate HU value was 193.4±40.3. No significant difference (upper endplate p=.314, lower endplate p=.189) was observed between the two groups.

CONSLUSIONS

Lower preoperative vertebral body HU values were associated with cage subsidence after single-level OLIF. However, the endplate HU values were not associated with cage subsidence. Preoperative HU measurement is useful in the prediction of the cage subsidence.

Influence of the geometric and material properties of lumbar endplate on lumbar interbody fusion failure: a systematic review

Background

Lumbar interbody fusion (LIF) is an established surgical intervention for patients with leg and back pain secondary to disc herniation or degeneration. Interbody fusion involves removal of the herniated or degenerated disc and insertion of interbody devices with bone grafts into the remaining cavity. Extensive research has been conducted on operative complications such as a failure of fusion or non-union of the vertebral bodies. Multiple factors including surgical, implant, and patient factors influencing the rate of complications have been identified. Patient factors include age, sex, osteoporosis, and patient anatomy. Complications can also be influenced by the interbody cage design. The geometry of the bony endplates as well as their corresponding material properties guides the design of interbody cages, which vary considerably across patients with spinal disorders. However, studies on the effects of such variations on the rate of complications are limited. Therefore, this study aimed to perform a systematic review of lumbar endplate geometry and material property factors in LIF failure.

Methods

Search keywords included ‘factor/cause for spinal fusion failure/cage subsidence/cage migration/non-union’, ‘lumbar’, and ‘interbody’ in electronic databases PubMed and Scopus with no limits on year of publication.

Results

In total, 1341 articles were reviewed, and 29 articles were deemed suitable for inclusion. Adverse events after LIF, such as cage subsidence, cage migration, and non-union, resulted in fusion failure; hence, risk factors for adverse events after LIF, notably those associated with lumbar endplate geometry and material properties, were also associated with fusion failure. Those risk factors were associated with shape, concavity, bone mineral density and stiffness of endplate, segmental disc angle, and intervertebral disc height.

Conclusions

This review demonstrated that decreased contact areas between the cage and endplate, thin and weak bony endplate as well as spinal diseases such as spondylolisthesis and osteoporosis are important causes of adverse events after LIF. These findings will facilitate the selection and design of LIF cages, including customised implants based on patient endplate properties.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-022-03091-8.

Comparison of Long-Term Efficacy of MIS-TLIF Intraoperative Implants in Patients with Osteoporosis

Osteoporosis and degenerative spinal disease are still an unsolvable surgical problem. It is still difficult to solve the complications related to postoperative osteoporosis, such as cage subsidence, displacement, and retraction. Expandable interbody cage is a recent innovation and an increasingly popular alternative to standard static cage. However, the clinical efficacy of MIS-TLIF combined with expandable cage for the treatment of osteoporosis has limited reports. The purpose of this paper was to analyze the efficacy of MIS-TLIF with expandable cage in patients with degenerative lumbar disease with osteoporosis. Patients with osteoporosis who received single-level MIS-TLIF and were followed up for at least 1 year were included. The outcome measures are as follows: clinical features, perioperative period, and neurological complications. JOA score and VAS pain score were used to analyze the improvement of patients’ function. Imaging analysis included segmental lordosis (SL), lumbar lordosis (LL), intervertebral disc height (DH), and the ratio of cage height to preoperative DH (RCD). The final data analysis included 284 patients with osteoporosis. 178 patients used static cages, and 106 patients used expandable cages. There was no significant difference in baseline characteristics, surgical indexes, and JOA and VAS scores between the two groups. There was no difference in SL or LL between static group and expandable group. There was no significant difference in preoperative DH between the two groups. The RCD in the expansion group was significantly lower than that in the static group. The intraoperative and postoperative sedimentation rate in the static group was significantly higher than that in the expandable group. The use of expandable cages in MIS-TLIF has shown good results for the treatment of degenerative lumbar diseases with osteoporosis. Through appropriate surgical techniques, the expandable cage can reduce the risk of cage sinking.

Development of a decision-making pathway for utilizing standalone lateral lumbar interbody fusion

PURPOSE

To develop a decision-making pathway for primary SA-LLIF. Furthermore, we analyzed the agreement of this pathway and compared outcomes of patients undergoing either SA-LLIF or 360-LLIF.

METHOD

A decision-making pathway for SA-LLIF was created based on the results of interviews/surveys of senior spine surgeons with over 10 years of experience. Internal validity was retrospectively evaluated using consecutive patients undergoing either SA-LLIF or 360-LLIF between 01/2018 and 07/2020 with 3D-printed Titanium cages. An outcome assessment looking primarily at revision surgery and secondary at cage subsidence, changes in disk and foraminal height, global and segmental lumbar lordosis, duration of surgery, estimated blood loss, and length of stay was carried out.

RESULTS

78 patients with 124 treated levels (37 SA-LLIF, 41 360-LLIF) were retrospectively analyzed. The pathway showed a direct agreement (SA-LLIF) of 100.0% and an indirect agreement (360-LLIF) of 95.1%. Clinical follow-up averaged 13.5 ± 6.5 months including 4 revision surgeries in the 360-LLIF group and none in the SA-LLIF group (p = 0.117). Radiographic follow-up averaged 9.5 ± 4.3 months, with no statistically significant difference in cage subsidence rate between the groups (p = 0.440). Compared to preoperative images, patients in both groups showed statistically significant changes in disk height (p < 0.001), foraminal height (p < 0.001), as well as restoration of segmental lordosis (p < 0.001 and p = 0.018). The SA-LLIF group showed shorter duration of surgery, less estimated blood loss and shorter LOS (p < 0.001).

CONCLUSION

The proposed decision-making pathway provides a guide to adequately select patients for SA-LLIF. Further studies are needed to assess the external applicability and validity.

LEVEL OF EVIDENCE III

Diagnostic: individual cross-sectional studies with consistently applied reference standard and blinding.

Is instrumented lateral lumbar interbody fusion superior to stand-alone lateral lumbar interbody fusion for the treatment of lumbar degenerative disease? A meta-analysis

The purpose of this meta-analysis was to compare the fusion rate and outcomes directly between patients who underwent stand-alone lateral lumbar interbody fusion (LLIF) and LLIF with supplemental posterior instrumentation. A comprehensive literature search was performed for relevant studies using PubMed, EMBASE, Web of Science, and Cochrane Library. The stand-alone and instrumented LLIF were compared by the fusion rate, the radiographic parameters, the cage subsidence rate, the clinical outcomes, the complication rate, and the reoperation rate. A total of 13 studies comprising 1090 patients with lumbar degenerative disease (LDD) were included. There was no significant statistical difference in the complication rate, and there was no significant clinical difference in the improvement of clinical outcomes at the last follow-up between patients who underwent stand-alone and instrumented LLIF. Nevertheless, lower fusion rate (RR, 0.92; 95% CI 0.87 to 0.98, P = 0.006), inferior restoration of disk height (WMD, -0.68; 95% CI -1.04 to -0.32, P < 0.001) and segmental lordosis (WMD, -1.28; 95% CI -2.30 to -0.27, P = 0.013), higher cage subsidence rate (RR, 1.68; 95% CI 1.36 to 2.07, P < 0.001), and higher reoperation rate (RR, 2.12; 95% CI 1.02 to 4.43, P = 0.045) were observed in the stand-alone group. Both stand-alone and instrumented LLIF were effective in improving the clinical outcomes of patients with LDD. However, the stand-alone LLIF was associated with lower fusion rate, inferior maintenance of indirect decompression, and higher reoperation rate due to high-grade cage subsidence. For patients with risk factors of high-grade cage subsidence, the LLIF with posterior instrumentation may be the better choice.