The Effect of Lumbar Spinal Muscle on Spinal Sagittal Alignment: Evaluating Muscle Quantity and Quality

Multifidus atrophy and/or dysfunction following lumbar radiofrequency ablation: A systematic review

BACKGROUND

Lumbar medial branch nerve radiofrequency ablation (LRFA) is an interventional procedure used to treat chronic lumbar facet joint pain. Because the medial branch nerves also innervate the multifidus muscle, it has been proposed that LRFA may pose a risk of multifidus atrophy and/or dysfunction. However, the quality and level of evidence to answer this clinical question have not been established. Therefore, this review aimed to systematically appraise the literature to discern whether the prevailing evidence substantiates the hypothesis in question.

METHODS

A systematic review compliant with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines was performed to evaluate the quality and level of evidence of studies reporting functional and/or structural changes in the multifidus muscle following LRFA.

RESULTS

Only five cohort studies met inclusion criteria. Two studies assessed changes in multifidus function following LRFA with confirmed denervation at electromyography and significant reduction in multifidus shear modulus with ultrasound shear wave elastography. Of the four studies that evaluated changes in multifidus structure with magnetic resonance imaging following LRFA, two demonstrated a decrease in cross-sectional area or an increase in fat infiltration, one demonstrated no change, and one revealed an apparent increase. Given the destructive nature attributed to LRFA, some degree of multifidus atrophy and/or dysfunction may be plausible, albeit with a very low certainty that relies on a restricted body of literature of modest quality and with a presence of high bias.

CONCLUSION

There is a paucity of studies discussing the potential association between LRFA and multifidus atrophy and/or dysfunction. In light of the shortage of high-quality studies and the absence of standardized protocols to assess both changes in the structure and function of the multifidus subsequent to LRFA, there is a pressing need for more prospective studies with a high methodological rigor to comprehensively address and answer this enduring debate in clinical practice.

Paraspinal muscle parameters' predictive value for new vertebral compression fractures post-vertebral augmentation: Nomogram development and validation

Objective

Prior research underscores the significance of paraspinal muscles in maintaining spinal stability. This study aims to investigate the predictive value of paraspinal muscle parameters for the occurrence of new vertebral compression fractures (NVCF) following percutaneous vertebroplasty (PVP) or percutaneous kyphoplasty (PKP) in patients with osteoporotic vertebral compression fractures (OVCF).

Methods

Retrospectively collected data from October 2019 to February 2021 (internal validation, n = 235) and March 2021 to November 2021 (external validation, n = 105) for patients with OVCF treated with PVP/PKP at our institution. They were randomly divided into training (188 cases) and validation groups (47 cases) at an 8:2 ratio. Lasso regression and multivariable logistic regression identified independent risk factors in the training set, and a Nomogram model was developed. Accuracy was assessed using receiver operating characteristic curves (ROC), calibration was evaluated with calibration curves and the Hosmer-Lemeshow test, and clinical utility was analyzed using decision curve analysis (DCA) and clinical impact curve (CIC).

Results

Surgical approach, spinal computed tomography (CT) values, and multifidus skeletal muscle index (SMI) are independent predictors of postoperative NVCF in OVCF patients. A Nomogram model, based on the identified predictors, was developed and uploaded online. Internal validation results showed area under the curve (AUC) values of 0.801, 0.664, and 0.832 for the training set, validation set, and external validation, respectively. Hosmer-Lemeshow goodness-of-fit tests (χ2 = 7.311-14.474, p = 0.070-0.504) and calibration curves indicated good consistency between observed and predicted values. DCA and CIC demonstrated clinical net benefit within risk thresholds of 0.06-0.84, 0.12-0.23, and 0.01-0.27. At specificity 1.00-0.80, the partial AUC (0.106) exceeded that at sensitivity 1.00-0.80 (0.062).

Conclusion

Compared to the spinal CT value, the multifidus SMI has certain potential in predicting the occurrence of NVCF. Additionally, the Nomogram model of this study has a greater negative predictive value.

Can Discharge Radiographs Predict Junctional Complications? A Decision Tree Analysis

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

To determine if standing pre-discharge radiographs can predict the development of junctional complications.

MATERIALS AND METHODS

Adult spinal deformity patients who underwent fusion of the lumbar spine (≥5 levels, LIV pelvis) were included. All patients underwent full-length standing radiographs before hospital discharge. Outcomes of interest included 2-year radiographic PJK and proximal junctional failure (PJF). Patients were stratified into 3 exclusive groups: No PJK, PJK, and PJF. Chi-square automatic interaction detection (CHAID) decision tree analysis was utilized to identify pre-discharge proximal junctional angle (PJA) thresholds associated with increased risk of PJK or PJF.

RESULTS

The 117 study patients had a mean age 65.8 ± 8.5, BMI 27.2 ± 4.9, PI-LL 23.3 ± 17.4, TPA 27.2 ± 11.5. Sample was stratified into 64 (54.7%) No PJK, 39 (33.3%) PJK, 14 (12.0%) PJF. No differences were detected between cohorts in discharge alignment, preop-discharge change, or offset from age-adjusted alignment targets (P > .005). Decision tree analysis showed that the first branch point depended on the UIV, as most patients with an UT UIV did not develop PJK or PJF (no PJK, 67.4%). For patients with an LT UIV, a second branch point occurred based on the ΔPJA. 89.5% of LT patients with a ΔPJA < 4.3° were free of radiographic PJK and PJF. The third branch point occurred based on the PJA at discharge. Thus, the highest risk group was comprised of ΔPJA ≥4.3° and PJA > 15.5°, as 57.1% of developed PJF and 28.6% PJK.

CONCLUSION

Most patients with a lower thoracic UIV, preop-discharge ΔPJA ≥4.3°, and discharge PJA > 15.5° develop PJF.

Fatty Infiltration of Multifidus Muscles: An Easily Overlooked Risk Factor for the Severity of Osteoporotic Vertebral Fractures

OBJECTIVES

Osteoporotic vertebral fractures (OVFs) are a critical public health concern requiring urgent attention, and severe OVFs impose substantial health and economic burdens on patients and society. Analysis of the risk factors for severe OVF is imperative to actively prevent the occurrence of this degenerative disorder. This study aimed to investigate the risk factors associated with the severity of OVF, with a specific focus on changes in the paraspinal muscles.

METHODS

A total of 281 patients with a first-time single-level acute OVF between January 2016 and January 2023 were enrolled in the study. Clinical and radiological data were collected and analyzed. The cross-sectional area (CSA) and degree of fatty infiltration (FI) of the paraspinal muscles, including the multifidus muscles (MFMs), erector spinae muscles (ESMs), and psoas major muscles (PSMs), were measured by magnetic resonance imaging (MRI) of the L4/5 intervertebral discs. According to the classification system of osteoporotic fractures (OF classification) and recommended treatment plan, OVFs were divided into a low-grade OF group and a high-grade OF group. Univariate and multivariate logistic regression analyse s were performed to identify risk factors associated with the severity of OVF.

RESULTS

Ninety-eight patients were included in the low-grade OF group, and 183 patients were included in the high-grade OF group. Univariate analysis revealed a significantly higher incidence of a high degree of FI of MFMs (OR = 1.71, p = 0.002) and ESMs (OR = 1.56, p = 0.021) in the high-grade OF group. Further multivariate logistic regression analysis demonstrated that a high degree of FI of the MFMs (OR = 1.71, p = 0.002) is an independent risk factor for the severity of OVF.

CONCLUSION

A high degree of FI of the MFMs was identified as an independent risk factor for the severity of OVF. Decreasing the degree of FI in the MFMs might lower the incidence of the severity of OVF, potentially reducing the necessity for surgical intervention in OVF patients.

Inter-software and inter-threshold reliability of quantitative paraspinal muscle segmentation

PURPOSE

Changes in the cross-sectional area (CSA) and functional cross-sectional area (FCSA) of the lumbar multifidus (MF) and erector spinae muscles (ES) are factors that can contribute to low back pain. For the assessment of muscle CSA and composition there are various software and threshold methods used for tissue segmentation in quantitative analysis. However, there is currently no gold standard for software as well as muscle segmentation. This study aims to analyze the measurement error between different image processing software and different threshold methods for muscle segmentation.

METHODS

Magnetic resonance images (MRI) of 60 patients were evaluated. Muscle CSA and FCSA measurements were acquired from axial T2-weighted MRI of the MF and ES at L4/L5 and L5/S1. CSA, FCSA, and FCSA/CSA ratio were measured independently by two observers. The MRI images were measured using two different software programs (ImageJ and Amira) and with two threshold methods (Circle/Overlap method) for each software to evaluate FCSA and FCSA/CSA ratio.

RESULTS

Inter-software comparisons revealed high inter-rater reliability. However, poor inter-rater reliability were obtained with different threshold methods. CSA, FCSA, and FCSA/CSA showed excellent inter-software agreement of 0.75-0.99 regardless of the threshold segmentation method. The inter-rater reliability between the two observers ranged between 0.75 and 0.99. Comparison of the two segmentation methods revealed agreement between 0.19 and 0.84. FCSA and FCSA/CSA measured via the Overlap method were significantly higher than those measured via the Circle method (P < 0.01).

CONCLUSION

The present study showed a high degree of reliability with very good agreement between the two software programs. However, study results based on different threshold methods should not be directly compared.

Fusion Length Requiring Spinopelvic Fixation in Lumbosacral Fusion with Anterior Column Support at L5-S1: Assessment of Fusion Status Using Computed Tomography

Background

The lumbosacral (LS) junction has a higher nonunion rate than other lumbar segments, especially in long-level fusion. Nonunion at L5-S1 would result in low back pain, spinal imbalance, and poor surgical outcomes. Although anterior column support at L5-S1 has been recommended to prevent nonunion in long-level LS fusion, fusion length requiring additional spinopelvic fixation (SPF) in LS fusion with anterior column support at L5-S1 has not been evaluated thoroughly. This study aimed to determine the number of fused levels requiring SPF in LS fusion with anterior column support at L5-S1 by assessing the interbody fusion status using computed tomography (CT) depending on the fusion length.

Methods

Patients who underwent instrumented LS fusion with L5-S1 interbody fusion without additional augmentation and CT > 1 year postoperatively were included. The fusion rates were assessed based on the number of fused segments. Patients were divided into two groups depending on the L5-S1 interbody fusion status: those with union vs. those with nonunion. Binary logistic regression analyses were performed to identify risk factors for LS junctional nonunion.

Results

Fusion rates of L5-S1 interbody fusion were 94.9%, 90.3%, 80.0%, 50.0%, 52.6%, and 43.5% for fusion of 1, 2, 3, 4, 5, and ≥ 6 levels, respectively. The number of spinal levels fused ≥ 4 (p < 0.001), low preoperative bone mineral density (BMD; adjusted odds ratio [aOR], 0.667; p = 0.035), and postoperative pelvic incidence (PI) - lumbar lordosis (LL) mismatch (aOR, 1.034; p = 0.040) were identified as significant risk factors for nonunion of L5-S1 interbody fusion according to the multivariate logistic regression analysis.

Conclusions

Exhibiting ≥ 4 fused spinal levels, low preoperative BMD, and large postoperative PI-LL mismatch were identified as independent risk factors for nonunion of anterior column support at L5-S1 in LS fusion without additional fixation. Therefore, SPF should be considered in LS fusion extending to or above L2 to prevent LS junctional nonunion.

Role of the Paraspinal Muscles in the Sagittal Imbalance Cascade: The Effects of Their Endurance and of Their Morphology on Sagittal Spinopelvic Alignment

BACKGROUND

The role of paraspinal muscle degeneration in the cascade of sagittal imbalance is still unclear. This study aimed to compare paraspinal muscle degeneration in the 4 stages of sagittal imbalance: sagittal balance (SB), compensated sagittal balance (CSB), decompensated sagittal imbalance (DSI), and sagittal imbalance with failure of pelvic compensation (SI-FPC). In addition, it aimed to compare the effects paraspinal muscle endurance and morphology on sagittal spinopelvic alignment in patients with lumbar spinal stenosis.

METHODS

A cross-sectional study of 219 patients hospitalized with lumbar spinal stenosis was performed. The isometric paraspinal extensor endurance test and evaluation of atrophy and fat infiltration of the paraspinal extensor muscles and psoas major on magnetic resonance imaging were performed at baseline. Spinopelvic parameters including lumbar lordosis, pelvic tilt, sacral slope, pelvic incidence, and the sagittal vertical axis were measured.

RESULTS

The patients with lumbar spinal stenosis were divided into 67 with SB, 85 with CSB, 49 with DSI, and 17 with SI-FPC. There were significant differences in paraspinal muscle endurance and morphology among the 4 groups. Furthermore, the SI-FPC group had poorer paraspinal muscle endurance than either the SB or the CSB group. In multiple linear regression analysis, paraspinal muscle endurance and the relative functional cross-sectional area of the paraspinal extensor muscles were the independent predictors of the sagittal vertical axis, and the relative functional cross-sectional area of the psoas major was the independent predictor of relative pelvic version.

CONCLUSIONS

This study indicated that paraspinal muscle degeneration is not only an initiating factor in pelvic retroversion but also a risk factor for progression from a compensated to a decompensated stage. Specifically, the impairment of muscle endurance in the CSB stage may be the reason why patients experience failure of pelvic compensation. In addition, paraspinal muscle endurance and muscle morphology (relative functional cross-sectional area of the paraspinal extensor muscles and psoas major) had different clinical consequences.

LEVEL OF EVIDENCE

Prognostic Level II . See Instructions for Authors for a complete description of levels of evidence.

Evaluation of lumbar paraspinal muscles degeneration and fatty infiltration in dynamic sagittal imbalance based on magnetic resonance imaging

PURPOSE

To explore degeneration and fatty infiltration (FI) of lumbar paraspinal muscles in patients with dynamic sagittal imbalance (DSI) and the relationship between lumbar paraspinal muscles degeneration, fatty infiltration and severity of the disease.

METHODS

We recruited 41 DSI patients and selected 22 lumbar spinal stenosis (LSS) patients without osphyalgia as controls. All patients received magnetic resonance imaging (MRI) scan and DSI patients also received pre-walk and post-walk X-rays. DSI patients were divided into 2 subgroups according to their symptom improvement after conservative treatment. We calculated rmCSA and FI of the lumbar paraspinal muscles. The rmCSA and FI between DSI and control and between DSI subgroups were compared by t test. The regression analysis was used to explore the risk factors influencing disease severity. Receiver operating characteristic (ROC) curves and area under curves (AUCs) were used to evaluate the severity of the disease.

RESULTS

In comparison of rmCSA and FI between DSI and control, there are significant differences of most muscles. In comparison of rmCSA between two subgroups, there are significant differences of most muscles, while in comparison of FI, only muscles in L4 segment have significant different. In logistic regression analysis, total rmCSA and total FI are risk factors influencing disease severity. ROC curves shows that total rmCSA and total FI both achieve an AUC greater than 0.7.

CONCLUSION

Compared with control, DSI patients have degeneration and fatty infiltration of the lumbar paraspinal muscles. The degeneration and fatty infiltration are risk factors influencing disease severity. The total rmCSA and total FI can be used as an indicator to determine whether a patient has severe DSI.

Risk Factors for Distal Junctional Problems Following Long Instrumented Fusion for Degenerative Lumbar Scoliosis: Are they Related to the Paraspinal Muscles

PURPOSE

Although the incidence of distal junctional problems (DJPs) following long construct-based treatment for degenerative lumbar scoliosis (DLS) is lower, affected patients are more likely to require revision surgery when they occur. So the aim of this study is to identify risk factors associated with DJPs to avoid its occurrence by at least 1-year follow-up.

METHODS

A total of 182 DLS patients undergoing long instrumented fusion surgery (≥4 levels) between February 2011 and March 2022 were retrospectively analyzed. Patients were placed into the DJP group if a DJP occurred at the final follow-up; patients without mechanical complications were matched 1:2 according to age, sex and BMI as the control group. Patient characteristics, surgical variables, radiographic parameters, lumbar muscularity and fatty degeneration were analyzed statistically. The statistical differences in the results between the two groups (p values <0.05) and other variables selected by experts were entered into a multivariate logistic regression model, and the forwards likelihood ratio method was used to analyze the independent risk factors for DJPs.

RESULTS

Twenty-four (13.2%) patients suffered a DJP in the postoperative period and the reoperation rate was 8.8%. On univariate analysis, the lowest instrumented vertebra (LIV) CT value (p = 0.042); instrumented levels (p = 0.030); preoperative coronal vertical axis (CVA) (p = 0.046), thoracolumbar kyphosis (TLK) (p = 0.006), L4-S1 lordosis (p = 0.013), sacral slop (SS) (p = 0.030), pelvic tilt (PT) classification (p = 0.004), and sagittal vertical axis (SVA) (p = 0.021); TLK correction (p = 0.049); post-operative CVA (p = 0.029); Overall, There was no significant difference in the paraspinal muscle parameters between the two groups. On multivariate analysis, instrumented levels (OR = 1.595; p = 0.035), preoperative SVA (OR = 1.016; p = 0.022) and preoperative PT (OR = 0.873; p = 0.001) were identified as significant independent risk factors for DJP.

CONCLUSION

Longer instrumented levels, a greater preoperative SVA and a smaller PT were found to be strongly associated with the presence of DJPs in patients treated for DLS. The degeneration of the paraspinal muscles may not be related to the occurrence of DJPs. For DLS patients, the occurrence of DJP can be reduced by selecting reasonable fusion segments and evaluating the patient's sagittal balance and spino-pelvic parameters before operation.

Multifidus dysfunction and restorative neurostimulation: a scoping review

OBJECTIVE

Chronic low back pain (CLBP) is multifactorial in nature, with recent research highlighting the role of multifidus dysfunction in a subset of nonspecific CLBP. This review aimed to provide a foundational reference that elucidates the pathophysiological cascade of multifidus dysfunction, how it contrasts with other CLBP etiologies and the role of restorative neurostimulation.

METHODS

A scoping review of the literature.

RESULTS

In total, 194 articles were included, and findings were presented to highlight emerging principles related to multifidus dysfunction and restorative neurostimulation. Multifidus dysfunction is diagnosed by a history of mechanical, axial, nociceptive CLBP and exam demonstrating functional lumbar instability, which differs from other structural etiologies. Diagnostic images may be used to grade multifidus atrophy and assess other structural pathologies. While various treatments exist for CLBP, restorative neurostimulation distinguishes itself from traditional neurostimulation in a way that treats a different etiology, targets a different anatomical site, and has a distinctive mechanism of action.

CONCLUSIONS

Multifidus dysfunction has been proposed to result from loss of neuromuscular control, which may manifest clinically as muscle inhibition resulting in altered movement patterns. Over time, this cycle may result in potential atrophy, degeneration and CLBP. Restorative neurostimulation, a novel implantable neurostimulator system, stimulates the efferent lumbar medial branch nerve to elicit repetitive multifidus contractions. This intervention aims to interrupt the cycle of dysfunction and normalize multifidus activity incrementally, potentially restoring neuromuscular control. Restorative neurostimulation has been shown to reduce pain and disability in CLBP, improve quality of life and reduce health care expenditures.

Lumbar paraspinal muscle morphology is associated with spinal degeneration in patients with lumbar spinal stenosis

BACKGROUND CONTEXT

Lumbar spinal stenosis (LSS) has been reported to induce changes in paraspinal muscle morphology, but objective physical function and degenerative spine conditions are rarely assessed.

PURPOSE

To identify factors associated with paraspinal muscle morphology using objective physical and degenerative spine assessments in patients with LSS.

STUDY DESIGN/SETTING

Cross-sectional design.

PATIENT SAMPLE

Seventy patients with neurogenic claudication caused by LSS, receiving outpatient physical therapy.

OUTCOME MEASURES

Cross-sectional area (CSA) and functional CSA (FCSA) of the multifidus, erector spinae, and psoas muscles, the severity of stenosis, disc degeneration, and endplate abnormalities were evaluated by magnetic resonance imaging, as well as sagittal spinopelvic alignment by X-ray. Objective physical assessments included pedometry and claudication distance. Patient-reported outcomes included the numerical rating scale of low back pain, leg pain, and leg numbness, and the Zurich Claudication Questionnaire.

METHODS

To assess the impact of LSS on paraspinal muscles, FCSA and FCSA/CSA were compared between the dominant and nondominant sides based on the patients' neurogenic symptoms, and multivariable regression analyses adjusted for age, sex, height, and weight were performed; p<.05 was considered significant.

RESULTS

Seventy patients were analyzed. At one level below the maximum stenotic level, erector spinae FCSA on the dominant side was significantly lower than that on the nondominant side. In the multivariable regression analyses, at one level below the symptomatic level, disc degeneration, endplate abnormalities, and lumbar spinopelvic alignment, such as decreased lumbar lordosis and increased pelvic tilt, were negatively associated with multifidus FCSA and FCSA/CSA ratio. A significant association was observed between dural sac CSA and erector spinae FCSA. Throughout L1/2 to L5/S, disc degeneration, endplate abnormalities, and lumbar spinopelvic alignment were negatively associated with multifidus and erector spinae FCSA or FCSA/CSA.

CONCLUSIONS

Lumbar paraspinal muscle asymmetry caused by LSS was observed only in erector spinae. Disc degeneration, endplate abnormalities, and lumbar spinopelvic alignment, rather than spinal stenosis and LSS symptoms, were more associated with paraspinal muscle atrophy or fat infiltration.

Correlation between Degenerative Thoracolumbar Kyphosis and Lumbar Posterior Muscle

The relationship between spinal alignment, particularly degenerative thoracolumbar kyphosis (DTLK) combined with lumbar spine stenosis (LSS), and paraspinal muscle content remains underexplored. This study aimed to elucidate the characteristics of paraspinal muscle distribution in DTLK patients and its association with lumbar lordosis (LL) and body mass index (BMI).

METHODS

A case-control study was conducted comparing 126 patients with DTLK and LSS against 87 control patients. The lumbar crossing indentation value (LCIV) was introduced as a novel measurement for paraspinal muscle content, and its relationship with thoracolumbar kyphosis (TLK), BMI, and LL was assessed.

RESULTS

LCIV in DTLK patients was found to be lower than in the control group, with a progressive increase from the upper to lower lumbar spine. In the control group, paraspinal muscle content was observed to increase with age and BMI, and LCIV was higher in males. However, the DTLK group showed no gender difference. LCIV in the DTLK group was more pronounced in patients with increased LL. The degree of TLK was not influenced by BMI but was associated with the content of the paravertebral muscle.

CONCLUSIONS

Paraspinal muscle content, as measured by LCIV, is significantly associated with DTLK and LSS. The study emphasizes the importance of considering paraspinal muscle health in DTLK patients and offers valuable insights for diagnosis and therapeutic interventions.

Spinal‑pelvic sagittal imbalance and paraspinal muscle degeneration in patients with degenerative lumbar spinal stenosis: A monocentric, prospective and observational study

Degenerative lumbar spinal stenosis (DLSS) is a condition in which the body is held in a poor posture for a long period of time, resulting in a change in the stress structure of the lumbar spine that causes degenerative changes in the muscles of the spine. The sagittal balance of the spine and pelvis and the degeneration of the paravertebral muscles have been the focus of recent research. To explore the relationship between paraspinal muscle degeneration and changes in spine-pelvic sagittal parameters in patients with DLSS, 95 patients with DLSS (experimental group) and 70 healthy volunteers (control group) hospitalized in the Ordos Central Hospital between January 2020 and January 2022 were included as study subjects. All patients underwent lumbar magnetic resonance imaging and spinal X-ray using uniform criteria. The correlation between paravertebral muscle parameters and sagittal-pelvic sagittal parameters in patients with DLSS was obtained from two imaging examinations, and the data were organized and grouped in order to explore the correlation between these parameters. There was no significant difference in the general data between the two groups (P>0.05). In the L4-5 DLSS patient group, the ratio of fat infiltration in the right erector spinae (ES) muscle was negatively correlated with thoracic kyphosis (TK) (r=-0.536; P<0.05) but not significantly in the left side. The relative cross-sectional area of the left multifidus muscle (MF RCSA) was positively correlated with TK (r=0.685; r=0.615; P<0.05) but not significantly in the right side. In the L5-S1DLSS patient group, the right MF RCSA and right ES RCSA were significantly positively correlated with TK (r=0.685; r=0.615; P<0.05) but not significant in the left side. Thus, paravertebral muscle parameters were correlated with spinal-pelvic sagittal parameters in patients with DLSS.

Effect of muscle activation on dynamic responses of neck of pilot during emergency ejection: a finite element study

To determine the effect of muscle activation on the dynamic responses of the neck of a pilot during simulated emergency ejections. A complete finite element model of the pilot's head and neck was developed and dynamically validated. Three muscle activation curves were designed to simulate different activation times and levels of muscles during pilot ejection: A is the unconscious activation curve of the neck muscles, B is the pre-activation curve, and C is the continuous activation curve. The acceleration-time curves obtained during ejection were applied to the model, and the influence of the muscles on the dynamic responses of the neck was investigated by analyzing both angles of rotation of the neck segments and disc stresses. Muscle pre-activation reduced fluctuations in the angle of rotation in each phase of the neck. Continuous muscle activation caused a 20% increase in the angle of rotation compared to pre-activation. Moreover, it resulted in a 35% increase in the load on the intervertebral disc. The maximum stress on the disc occurred in the C4-C5 phase. Continuous muscle activation increased both the axial load on the neck and the posterior extension angle of rotation of the neck. Muscle pre-activation during emergency ejection has a protective effect on the neck. However, continuous muscle activation increases the axial load and rotation angle of the neck. A complete finite element model of the pilot's head and neck was established and three neck muscle activation curves were designed to investigate the effects of muscle activation time and level on the dynamic response of the pilot's neck during ejection. This increased insights into the protection mechanism of neck muscles on the axial impact injury of the pilot's head and neck.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Isokinetic strength assessment of trunk muscle and its relationship with spinal-pelvic parameters in patients with degenerative spinal deformity

BACKGROUND

The incidence rate of degenerative spinal deformity (DSD) has gradually increased in the elderly. Currently, the relationship between the functional status of trunk muscle and the spinal-pelvic parameters of DSD patients remains unclear.

OBJECTIVE

This paper aims to explore the relationship between the two factors and provide new clues for exploring the mechanism of the occurrence and development of DSD.

METHODS

A total of 41 DSD patients treated in our hospital (DSD group) and 35 healthy volunteers (control group) were selected. Muscle strength was evaluated using an IsoMed-2000 isokinetic dynamometer, and the trunk flexor and extensor peak torque (PT) of subjects was measured at a low, medium, and high angular velocity of 30∘/s, 60∘/s, and 120∘/s, respectively. Hand grip strength (HGS) was assessed using an electronic grip dynamometer and Surgimap software was used to measure the spinal-pelvic parameters, including the sagittal vertical axis (SVA), thoracic kyphosis (TK), lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT), pelvic incidence rate (PI), and PI-LL, and the relationship between trunk muscle function and various parameters was analyzed.

RESULTS

Under the three angular velocities, the flexor and extensor PT values in the DSD group were lower than those in the control group, and only the extensor PT showed a statistically significant difference (P< 0.05). There was no significant difference in HGS between the two groups (P> 0.05). In the DSD group, the extensor PT at 30∘/s was significantly negatively correlated with SVA (P< 0.05). At 60∘/s and 120∘/s, the extensor PT was significantly negatively correlated with SVA and PT (P< 0.05).

CONCLUSION

Trunk extensor strength is significantly lower in DSD patients than in normal controls. The decline in trunk extensor strength in DSD patients is a type of local muscle dysfunction more closely related to the deformity, which is likely involved in the compensatory mechanism of DSD and may reflect the overall imbalance of the trunk.

The prevalence of locomotive syndrome and its associated factors in patients with Type 2 diabetes mellitus

OBJECTIVES

We investigated the prevalence of locomotive syndrome (LS) and related musculoskeletal diseases [osteoarthritis (OA), lumbar spondylosis, and spinal alignment] in Type 2 diabetes mellitus (DM) patients.

METHODS

Clinical data were collected from 101 patients (55 males; 46 females) admitted to our hospital for diabetes education from October 2018 to April 2021. Patients underwent full-spine and whole-legs standing radiography and physical measurements (10-m walking and grip strength tests and three LS risk tests).

RESULTS

The estimated prevalence of LS was 86.1% (Stage 1: 44.5%, Stage 2: 41.6%), lumbar spondylosis was 11.9%, and hip, knee, and ankle OA were 16.9%, 51.5%, and 12.9%, respectively. Multiple logistic regression analysis identified grip strength [odds ratio (OR) = 0.89, confidence interval (CI) = 0.83-0.94], diabetic retinopathy (OR = 5.85, CI = 1.64-20.78), knee OA (OR = 3.34, CI = 1.11-10.02), and a sagittal vertical axis >40 mm (OR = 3.42, CI = 1.13-10.39) as significantly associated risk factors for worsening LS in Type 2 DM patients.

CONCLUSIONS

This study clarified the epidemiological indicators of LS and associated factors in DM patients. Exercise therapy and DM management are effective strategies to reduce the occurrence and progression of LS.

Are paraspinal muscle quantity, lumbar indentation value, and subcutaneous fat thickness related to disc degeneration? An MRI-based study

INTRODUCTION

The aim of the study was to investigate the relationship between lumbar disc herniation and Goutallier classification (GC), lumbar indentation value, and subcutaneous adipose tissue thickness.

METHODS

102 consecutive patients (59 female and 43 male) with lumbar back pain, numbness, tingling, or pain in the lower extremity indicating radiculopathy who had undergone lumbar magnetic resonance imaging (MRI) and had an intervertebral disc herniation in the L4-5 level, were included in the study. 102 patients who have undergone lumbar MRI in the same time period and have no disc herniation were chosen to be the control group and were selected so as to match the herniated group for sex and age. All these patients' scans were re-interpreted regarding paraspinal muscle atrophy (using the GC), lumbar indentation value, and subcutaneous adipose tissue thickness in the L4-5 level.

RESULTS

The Goutallier score was higher in the herniated group, compared with the non-herniated group (p < 0.001). There was no statistical difference between herniated and non-herniated groups regarding lumbar indentation value (LIV) and subcutaneous adipose tissue thickness (SATT). A Goutallier score of 1.5 provided the highest sensitivity x specificity value to indicate the disc herniation according to the statistical results. The individuals with a Goutallier score of 2, 3, and 4 have 2.87 times more likely to have disc herniation in their MRIs than the ones with a score of 0 and 1.

CONCLUSION

Paraspinal muscle atrophy seems to be related to the presence of disc herniations. The cut-off value of GC to indicate the disc herniation in this study might be useful to predict the risk for disc herniation regarding the Goutallier score. The LIV and SATT measured in magnetic resonance images were randomly distributed between individuals with herniated and non-herniated groups, and statistically, no relationship was observed between these groups regarding these parameters.

IMPLICATIONS FOR PRACTICE

The effect of the parameters studied in this research on disc herniations are expected to be an added value to the literature. The awareness of risk factors for intervertebral disc herniations might be used in preventive medicine to predict the risk and understand the tendency of an individual for disc herniations to occur in the future. Further investigations are needed to establish whether there is a causal relationship or correlation between these parameters and disc herniation.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Morphometry of lumbar muscles in the seated posture with weight-bearing MR scans

Conventional imaging studies of human spine are done in a supine posture in which the axial loading of the spine is not considered. Upright images better reveal the interrelationships between the various internal structures of the spine. The objective of the current study is to determine the cross-sectional areas, radii, and angulations of the psoas, erector spinae, and multifidus muscles of the lumbar spine in the sitting posture. Ten young (mean age 31 ± 4.8 years) asymptomatic female subjects were enrolled. They were seated in an erect posture and weight-bearing T1 and T2 MRIs were obtained. Cross-sectional areas, radii, and angulations of the muscles were measured from L1-L5. Two observers repeated all the measurements for all parameters, and reliability was determined using the inter- and intra-class coefficients. The Pearson product moment correlation was used for association between levels, while level differences were used using a linear regression model. The cross-sectional areas of the psoas and multifidus muscles increased from L1 to L5 (1.9 ± 1.1 to 12.1 ± 2.5 cm2 and 1.8 ± 0.3 to 5.7 ± 1.4 cm2). The cross-sectional area of the erector spinae was greatest at the midlevel (13.9 ± 2.2 cm2) and it decreased in both directions. For the angle, the range for psoas muscles was 75-105°, erector spinae were 39-46° and multifidus was 11-19°. Correlations magnitudes were inconsistent between levels and muscle types. These quantitated data improve our understanding of the geometrical properties in the sitting posture. The weight-bearing MRI-quantified morphometrics of human lumbar spine muscles from this study can be used in biomechanical models for predicting loads on spinal joints under physiological and traumatic situations.

Quantitative evaluation of correlation between lumbosacral lordosis and pelvic incidence in standing position among asymptomatic Asian adults: a prospective study

The determination of lumbopelvic alignment is essential for planning adult spinal deformity surgery and for ensuring favorable surgical outcomes. This prospective study investigated the correlation between the lumbar section of lumbar spine lordosis and increasing pelvic incidence in 324 Asian adults with a mean age of 55 ± 13 years (range: 20-80 years), comprising 115 male and 209 female volunteers. Participants were divided into three groups based on pelvic incidence (G1, G2, and G3 had pelvic incidence of < 45°, 45-55°, and ≥ 55°, respectively). We determined that distal and proximal lumbar lordosis contributed differentially to the increase in pelvic incidence, whereas the lordosis ratio of the L3-L4 and L4-L5 segments mostly remained constant. The mean contribution ratio of the segmental lordosis from L1 to S1 was as follows: L1-L2, 2.3%; L2-L3, 11.7%; L3-L4, 18.1%; L4-L5, 25.2%; and L5-S1, 42.7%. Pelvic incidence had a stronger correlation with proximal lumbar lordosis than did distal lumbar lordosis. The ratios of proximal lumbar lordosis to distal lumbar lordosis were 37.8% in G1, 45.8% in G2, and 55.9% in G3. These findings serve as a reference for future lumbar spine correction or fusion surgery for Asian adults.

Differences in lumbar paraspinal muscle morphology in patients with sagittal malalignment undergoing posterior lumbar fusion surgery

PURPOSE

To investigate whether (1) there is a difference between patients with normal or sagittal spinal and spinopelvic malalignment in terms of their paraspinal muscle composition and (2) if sagittal malalignment can be predicted using muscle parameters.

METHODS

A retrospective review of patients undergoing posterior lumbar fusion surgery was conducted. A MRI-based muscle measurement technique was used to assess the cross-sectional area, the functional cross-sectional area, the intramuscular fat and fat infiltration (FI) for the psoas and the posterior paraspinal muscles (PPM). Intervertebral disc degeneration was graded for levels L1 to S1. Sagittal vertical axis (SVA; ≥ 50 mm defined as spinal malalignment), pelvic incidence (PI) and lumbar lordosis (LL) were measured, and PI-LL mismatch (PI-LL; ≥ 10° defined as spinopelvic malalignment) was calculated. A receiver operating characteristic (ROC) analysis was conducted to determine the specificity and sensitivity of the FIPPM for predicting sagittal malalignment.

RESULTS

One hundred and fifty patients were analysed. The PI-LL and SVA malalignment groups were found to have a significantly higher FIPPM (PI-LL:47.0 vs. 42.1%; p = 0.019; SVA: 47.7 vs. 41.8%; p = 0.040). ROC analysis predicted sagittal spinal malalignment using FIPPM (cut-off value 42.69%) with a sensitivity of 73.4% and a specificity of 54.1% with an area under the curve of 0.662.

CONCLUSION

Significant differences in the muscle composition between normal and malalignment groups with respect to FIPPM in both sagittal spinal and spinopelvic alignment were found. This work underlines the imminent impact of the paraspinal musculature on the sagittal alignment.

Study on Risk Factors of Primary Non-traumatic OVCF in Chinese Elderly and a Novel Prediction Model

Objective

Prevention of fragility fractures is one of the public health priorities worldwide, whilst the incidence of osteoporotic vertebral compression fractures (OVCF) continues to rise and lacks the corresponding accurate prediction model. This study aimed to screen potential causes and risk factors for primary non‐traumatic osteoporotic vertebral compression fractures (NTOVCF) in the elderly by characterizing a patient population with NTOVCF and comparing it with a population of osteoporotic patients.

Methods

Between January 2013 and January 2022, 208 elderly patients with unequivocal evidence of bone fragility manifested as painful NTOVCF were enrolled, and compared with 220 patients with osteoporosis and no fractures. The demographic data, bone turnover markers, blood routine, serum biochemical values, and radiological findings were investigated. Differences between the fracture and non‐fracture groups were analyzed, and variables significant in univariate analysis and correlation analysis were included in the logistic analysis to build the risk prediction model for osteoporotic vertebral fractures. Univariate analysis using student's t‐tests for continuous variables or a chi‐squared test for categorical variables was conducted to identify risk factors.

Results

No significant differences were revealed regarding age, gender, BMI, smoking, alcohol consumption, blood glucose, propeptide of type I procollagen (P1NP), and N‐terminal middle segment osteocalcin (N‐MID) (P > 0.05). Parathyroid Hormone (PTH), 25(OH)D, serum albumin (ALB), hemoglobin (HB), bone mineral density (BMD), and cross‐sectional area (CSA) of the paraspinal muscle in the fracture group were significantly lower than those in the control group; however, b‐C‐terminal telopeptide of type I collagen (β‐CTX), total cholesterol (TC), high‐density lipoprotein cholesterol (HDL‐C), non‐prostatic acid phosphatase (NACP), and fatty degeneration ratio (FDR) were significantly higher than those in the control group (P < 0.05). Logistic regression analysis showed that ALB, HB, CSA, and BMD were negatively correlated with NTOVCF, while β‐CTX, HDL‐C, NACP, and FDR were positively correlated with NTOVCF.

Conclusion

Decreased physical activity, anemia, hypoproteinemia, imbalances in bone metabolism, abnormal lipid metabolism, and degenerative and decreased muscle mass, were all risk factors for OVCF in the elderly, spontaneous fractures may be the consequence of cumulative declines in multiple physiological systems over the lifespan. Based on this risk model, timely detection of patients with high OVCF risk and implementation of targeted preventive measures is expected to improve the effect of fracture prevention.

Risk Factors for Progressive Spinal Sagittal Imbalance in the Short-Term Course after Total Hip Arthroplasty: A 3 Year Follow-Up Study of Female Patients

Total hip arthroplasty (THA) for patients with hip osteoarthritis improves hip flexion contracture, subsequently improving spinal sagittal balance. However, in some cases, spinal sagittal imbalance develops in the course after THA, and its risk factors remain unknown. We aimed to investigate the risk factors of progressive spinal sagittal imbalance after THA. This retrospective cohort study of a prospectively maintained database included female patients aged ≥50 years who underwent THA. Before performing THA, we obtained each patient’s anthropometric and muscle strength measurements and whole-spine radiographs. Three years postoperatively, patients underwent whole-spine radiography to examine changes in the spinal sagittal balance. Patients were assigned into groups on the basis of their preoperative and 3 year postoperative sagittal vertical axis (SVA) values. Patients with 3 year postoperative SVA values ≥40 mm with an increase ≥30 mm were categorized into the imbalance group; the other patients were categorized into the non-imbalance group. Of 103 patients, 11 (10.7%) were in the imbalance group. In multiple logistic regression analysis, preoperative weak abdominal trunk muscle strength (ATMS) (p = 0.007) and small sacral slope (SS) (p = 0.005) were significant risk factors for progressive spinal sagittal imbalance. In conclusion, risk factors for progressive spinal sagittal imbalance after THA were weak preoperative ATMS and small SS.

Global Alignment and Proportion (GAP) score in asymptomatic individuals: is it universal?

BACKGROUND

The global alignment and proportion (GAP) score was established based on American and European subjects, which might limit its applicability to the Chinese population due to ethnicity-related difference of sagittal alignment.

PURPOSE

To analyze the applicability of GAP score in the Chinese population and to investigate the age- and gender-associated differences of spinopelvic and GAP score parameters.

STUDY DESIGN

A prospective cross-sectional radiographic study.

PATIENTS SAMPLE

Of 692 asymptomatic Chinese volunteers aged between 20 and 79 prospectively recruited between January 2017 and June 2019, 490 subjects were eventually included in this study.

OUTCOME MEASURES

The pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), L1-S1 lordosis, L4-S1 lordosis, sagittal vertical axis (SVA), T1 pelvic angle (TPA) and global tilt (GT) were measured on lateral X-rays. The GAP scores and its parameters including relative pelvic version (RPV), relative lumbar lordosis (RLL), lordosis distribution index (LDI) and relative spinopelvic alignment (RSA) were calculated for each subject.

METHODS

Subjects were divided into four groups: Group 1M: male subjects <60 years old; Group 1F: female subjects <60 years old; Group 2M: male subjects ≥60 years old and Group 2F: female subjects ≥60 years old. The GAP scores and categories were determined and compared between groups. The results of sagittal alignment were compared with the previous studies evaluating the normative sagittal alignment in other populations. Univariate linear regression analysis was carried out between pelvic incidence (PI) and sacral slope (SS), lumbar lordosis (LL) and global tilt (GT) in each group.

RESULTS

The distributions of GAP categories and the updated Roussouly classification were statistically different from other populations. Significantly different distribution of GAP categories was observed between Group 1M and Group 2M, Group 1F and Group 2F, and Group 1M and Group 1F. Radiographic measurements and GAP parameters were significantly different between Group 1M and Group 2M, and Group 1F and Group 2F. Gender-related difference of parameters was more prominent between Group 1M and Group 1F. Linear relationship of PI with SS, LL and GT were different from the regression models of "ideal" sagittal alignment in GAP score.

CONCLUSIONS

The GAP score might be inappropriate in Chinese population due to ethnicity-related alignment difference. Worse feasibility of GAP score was observed in female and old subjects.

Correlation Between Bone Mineral Density (BMD) and Paraspinal Muscle Fat Infiltration Based on QCT: A Cross-Sectional Study

To investigate the correlation between fatty infiltration of the paraspinal muscle and bone mineral density (BMD). In total, 367 subjects (182 men and 185 women) who underwent quantitative computed tomography (QCT) examination were enrolled in this study. A QCT Pro workstation was used to obtain the mean BMD of the lower lumbar spine (L3, L4, L5) and fat fraction (FF) of the paraspinal muscle (psoas and erector spinae) at the corresponding levels. The patient's age, sex, body mass index, number of previous vertebral fractures, physical activity level, and visual analog scale (VAS) score for lower back pain were recorded. For categorical variables, one-way ANOVA and independent-samples t tests were performed. Spearman and Pearson correlation coefficients were used to analyze the correlations among continuous variables. Influential factors were analyzed by multivariate linear regression analysis. Regarding the mean paraspinal muscle FF, there were significant differences between the different vertebral fracture groups (P < 0.05). Age and VAS score showed a positive correlation with the mean paraspinal muscle FF (r = 0.389, 0.454). BMD showed a negative correlation with the mean paraspinal muscle FF (r =  - 0.721). The multiple linear regression analysis showed that vertebral fracture (β = 0.851, P = 0.021) and BMD (β =  - 4.341, P = 0.004) were independent factors of the mean paraspinal muscle FF. This study demonstrated that an advanced age, a greater VAS score, a higher number of vertebral fractures, and a lower BMD may be associated with more severe fatty infiltration of the paraspinal muscle.

Decreased muscle mass and strength affected spinal sagittal malalignment

PURPOSE

Correction surgeries for spinal malalignment showed good clinical outcomes; however, there were concerns including increased invasiveness, complications, and impact on medico-economics. Ideally, an early intervention is needed. To better understand the patho-mechanism and natural course of spinal alignment, the effect of factors such as muscle mass and strength on spinal sagittal imbalance were determined in a multicenter cross-sectional study.

METHODS

After excluding metal implant recipients, 1823 of 2551 patients (mean age: 69.2 ± 13.8 years; men 768, women 1055) were enrolled. Age, sex, past medical history (Charlson comorbidity index), body mass index (BMI), grip strength (GS), and trunk muscle mass (TM) were reviewed. Spinal sagittal imbalance was determined by the SRS-Schwab classification. Multiple comparison analysis among four groups (Normal, Mild, Moderate, Severe) and multinomial logistic regression analysis were performed.

RESULTS

On multiple comparison analysis, with progressing spinal malalignment, age in both sexes tended to be higher; further, TM in women and GS in both sexes tended to be low. On multinomial logistic regression analysis, age and BMI were positively associated with spinal sagittal malalignment in Mild, Moderate, and Severe groups. TM in Moderate and Severe groups and GS in the Moderate group were negatively associated with spinal sagittal malalignment.

CONCLUSION

Aging, obesity, low TM, and low GS are potential risk factors for spinal sagittal malalignment. Especially, low TM and low GS are potentially associated with more progressed spinal sagittal malalignment. Thus, early intervention for muscles, such as exercise therapy, is needed, while the spinal sagittal alignment is normal or mildly affected.

Risk factors for proximal junctional kyphosis after posterior long-segment internal fixation for chronic symptomatic osteoporotic thoracolumbar fractures with kyphosis

Background

This study aimed to analyze the risk factors for proximal junctional kyphosis (PJK) for patients with chronic symptomatic osteoporotic thoracolumbar fractures (CSOTLF) and kyphosis who underwent long-segment internal fixation.

Methods

We retrospectively reviewed the records of patients with CSOTLF complicated with kyphosis who underwent posterior multilevel internal fixation in our hospital between January 2013 and January 2020. The patients’ age, sex, body mass index (BMI), bone mineral density (BMD), smoking status, cause of injury, comorbidities, injury segments, and American Spinal Injury Association (ASIA) grading non-surgical data; posterior ligament complex (PLC) injury, upper and lower instrumented vertebral position (UIV and LIV, respectively), number of fixed segments surgical data, proximal junctional angle (PJA), sagittal vertebral axis (SVA), pelvic incidence (PI), lumbar lordosis (LL), pelvic incidence-lumbar lordosis mismatch (PI-LL), pelvic tilt (PT), and sacral slope (SS) surgical indicators were collected. Patients were divided into postoperative PJK and non-PJK groups.

Results

This study included 90 patients; among them, 30 (31.58%) developed PJK postoperatively. All patients were followed up for > 24 months (mean 32.5 months). Univariate analysis showed significant differences in age, BMI, BMD, PLC injury, UIV, and LIV fixation position, number of fixation stages, and preoperative PJA, SVA, PI-LL, and SS between the two groups (P < 0.05). Additionally, no significant differences were observed in sex, smoking, cause of injury, complications, injury segment ASIA grade, and preoperative PT between the two groups (P > 0.05). Multifactorial logistic regression analysis showed that age > 70 years (OR = 32.279, P < 0.05), BMI > 28 kg/m² (OR = 7.876, P < 0.05), BMD T value < − 3.5 SD (OR = 20.836, P < 0.05), PLC injury (OR = 13.981, P < 0.05), and preoperative PI-LL > 20° (OR = 13.301, P < 0.05) were risk factors for PJK after posterior long-segment internal fixation in elderly patients with CSOTLF complicated with kyphosis.

Conclusion

CSOTLF patients undergoing posterior long segment internal fixation are prone to PJK, and age > 70 years, BMI > 28 kg/m2, BMD T value < − 3.5 SD, preoperative PI-LL > 20° and PLC injury may increase their risk.

Relationships between Paraspinal Muscle and Spinopelvic Sagittal Balance in Patients with Lumbar Spinal Stenosis

OBJECTIVE

To investigate the relationships between measurements of paraspinal muscle and spinopelvic sagittal parameters and the predictive value of lumbar indentation value (LIV) on sagittal balance in patients with lumbar spinal stenosis.

METHODS

It was a retrospective study. We collected the data of 110 patients, who were diagnosed as lumbar spinal stenosis from December 2018 to May 2019. The total cross-sectional area (tCSA), functional cross-sectional area (fCSA), and fatty infiltration (FI) of paraspinal muscle were measured. The spinopelvic sagittal parameters were also measured, including sagittal vertical axis (SVA), pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), thoracic kyphosis (TK), and PI minus LL (PI-LL). Correlations between measurements of paraspinal muscle and sagittal parameters were investigated by Pearson correlation analysis. The multiple linear regression analysis was used to investigate the LIV, age, gender, and BMI for assessing spinopelvic sagittal balance. Receiver-operating characteristic (ROC) curve was used to find out the most optimum cut-off point of LIV for evaluating SVA.

RESULTS

There were 42 males and 68 females in this study and the mean age was 59.9 ± 10.9 years old. By Pearson correlation analysis, MF tCSA showed significant association with LL (r = 0.455, P < 0.01) and PI-LL (r = -0.286, P < 0.01). MF fCSA had a significant correlation with LL (r = 0.326, P < 0.01) and PI-LL (r = -0.209, P < 0.05). LIV was also significantly correlated to spinopelvic sagittal parameters, including SVA (r = -0.226, P < 0.05), LL (r = 0.576, P < 0.01), TK (r = 0.305, P < 0.01), and PI-LL (r = -0.379, P < 0.01). By multiple linear regression analysis, LIV was independently associated with sagittal parameters, including PI-LL and SVA. The cut-off value of LIV for SVA ≤ 50 mm was 10.5 mm (AUC = 0.641). According to the best cut-off value, patients were divided into two groups. For patients with LIV ≤ 10.5 mm, the percentage of SVA ≤ 50 mm was 54.5% (18/33), while it was 83.1% (64/77) for patients with LIV >10.5 mm.

CONCLUSIONS

As a new index to evaluate paraspinal muscle atrophy, the LIV was independently correlated to spinopelvic sagittal balance. Degeneration of paraspinal muscle was associated with spinopelvic sagittal balance.

Paraspinal myopathy-induced intervertebral disc degeneration and thoracolumbar kyphosis in TSC1mKO mice model-a preliminary study

BACKGROUND

Increasing kyphosis of the spine in a human is a well-recognized clinical phenomenon that has been associated with back pain, poor physical performance and disability. The pathophysiology of age-related kyphosis is complex and has been associated with physiological changes in vertebrae, intervertebral disc (IVD) and paraspinal musculature, which current cross-sectional studies are unable to demonstrate. Creating an in vivo, paraspinal myopathic animal model for longitudinal study of these changes under controlled conditions is thus warranted.

PURPOSE

To confirm the TSC1 gene knockout effect on paraspinal muscle musculature; to analyze the development of spinal kyphosis, IVD degeneration and vertebra structural changes in a longitudinal manner to gain insights into the relationship between these processes.

STUDY DESIGN

A prospective cohort study of 28 female mice, divided into 4 groups-9-month-old TSC1mKO (n=7), 9-month-old control (n=4), 12-month-old TSC1mKO (n=8), and 12-month-old controls (n=9).

METHODS

High resolution micro-computed tomography was used to measure sagittal spinal alignment (Cobb's angle), vertebral height, vertebral body wedging, disc height index (DHI), disc wedge index (DWI), histomorphometry of trabecular bone and erector spinae muscle cross-sectional area. Paraspinal muscle specimens were harvested to assess for myopathic features with H&E stain, muscle fiber size, density of triangular fiber and central nucleus with WGA/DAPI stain, and percentage of fibers with PGC-1α stain. Intervertebral discs were evaluated for disc score using FAST stain.

RESULTS

Compared to controls, paraspinal muscle sections revealed features of myopathy in TSC1mKO mice similar to human sarcopenic paraspinal muscle. While there was significantly greater presence of small triangular fiber and density of central nucleus in 9-and 12-month-old TSC1mKO mice, significantly larger muscle fibers and decreased erector spinae muscle cross-sectional area were only found in 12-month-old TSC1mKO mice compared to controls. TSC1mKO mice developed accelerated thoracolumbar kyphosis, with significantly larger Cobb angles found only at 12 months old. Structural changes to the trabecular bone in terms of higher bone volume fraction and quality, as well as vertebral body wedging were observed only in 12-month-old TSC1mKO mice when compared to controls. Disc degeneration was observed as early as 9 months in TSC1mKO mice and corresponded with disc wedging. However, significant disc height loss was only observed when comparing 12-month-old TSC1mKO mice with controls.

CONCLUSIONS

This study successfully shows the TSC1 gene knockout effect on the development of paraspinal muscle myopathy in a mouse which is characteristic of sarcopenia. The TSC1mKO mice is by far the best model available to study the pathological consequence of sarcopenia on mice spine. With paraspinal muscle myopathy established as early as 9 months, TSC1mKO mice developed disc degeneration and disc wedging. This is followed by kyphosis of the spine at 12 months with concomitant disc height loss and vertebral body wedging due to bone remodeling. Age-related bone loss was not found in our study, suggesting osteoporosis and myopathy-induced vertebral body wedging are likely two independent processes.

CLINICAL SIGNIFICANCE

This is the first study to provide key insights on the early and late consequences of paraspinal myopathy on intervertebral disc degeneration, spinal kyphosis, and vertebral body changes. With this new understanding, future studies evaluating therapies for spinal degeneration may be performed to develop time-sensitive interventions.

Different degeneration patterns of paraspinal muscles in degenerative lumbar diseases: a MRI analysis of 154 patients

STUDY DESIGN

A retrospective study.

OBJECTIVE

To evaluate the different degeneration patterns of paraspinal muscles in degenerative lumbar diseases and their correlation with lumbar spine degeneration severity. The degeneration characteristics of different paraspinal muscles in degenerative lumbar diseases remain unclear.

METHODS

78 patients diagnosed with single-level degenerative lumbar spondylolisthesis (DLS) and 76 patients with degenerative lumbar kyphosis (DLK) were included as DLS and DLK groups. Paraspinal muscle parameters of psoas major (PS), erector spinae (ES) and multifidus muscle (MF) were measured, including fatty infiltration (FI) and relative cross-sectional area (rCSA), namely the ratio of the paraspinal muscle CSA to the CSA of the vertebrae of the same segment. Sagittal parameters including lumbar lordosis (LL) and sagittal vertical axis (SVA) were measured. The paraspinal muscle parameters and ES/MF rCSA ratio were compared between the two groups. Paraspinal muscles parameters including rCSA and FI were also compared between each segments from L1 to L5 in both DLS and DLK groups. In order to determine the influence of sagittal spinal alignment on paraspinal muscle parameters, correlation analysis was conducted between the MF, ES, PS rCSA and FI and the LL in DLS and DLK group.

RESULT

MF atrophy is more significant in DLS patients compared with DLK. Also, MF fatty infiltration in the lower lumbar spine of DLS patients was greater compared to DLK patients. DLK patients showed more significant atrophy of ES and heavier ES fatty infiltration. MF FI was significantly different between all adjacent segments in both DLS and DLK groups. In DLS group, ES FI was significantly different between L2/L3 to L3/L4 and L4/L5 to L5/S1, while in DLK group, the difference of ES FI between all adjacent segments was not significant, and ES FI was found negatively correlated with LL.

CONCLUSIONS

Paraspinal muscles show different degeneration patterns in degenerative lumbar diseases. MF degeneration is segmental in both DLS and DLK patients, while ES degenerated diffusely in DLK patients and correlated with the severity of kyphosis. MF degeneration is more significant in the DLS group, while ES degeneration is more significant in DLK patients. MF is the stabilizer of the lumbar spine segments, while the ES tends to maintain the spinal sagittal balance.

Paraspinal muscle fatty degeneration as a predictor of progressive vertebral collapse in osteoporotic vertebral compression fractures

BACKGROUND CONTEXT

Most osteoporotic vertebral compression fractures (OVCFs) are treated conservatively; however, in some patients, progressive vertebral body collapse leads to spinal deformity and cord compression. These complications are strongly associated with impaired performance activities of daily living and a poor quality of life.

PURPOSE

To identify the role of the paraspinal muscle as a risk factor for progressive vertebral body collapse in patients with OVCF.

STUDY DESIGN

This was a retrospective observational study.

PATIENT SAMPLE

Fifty-five consecutive patients with OVCF who were treated conservatively from January 2018 to June 2020 in a single spine center and had a minimum follow-up of 6 months.

OUTCOME MEASURES

A lateral plain radiograph in a neutral posture was taken when the patient was first diagnosed and at 1, 3, and 6 months after the first diagnosis. Vertebral height was measured at the point of maximal collapse of the affected vertebral body; vertebral collapse (%) was also measured. The cross-sectional area (CSA) and fatty degeneration of the paraspinal muscle were measured using the open-source software Image J. The visual analogue scale (VAS) scores were collected at the time of initial fracture diagnosis and at 1, 3, and 6 months.

METHODS

The clinical and radiological data were analyzed. In the L4-5 intervertebral disc level, axial T2-weighted magnetic resonance imaging was used to measure the CSA and fatty degeneration of the paraspinal muscles. Correlation and multiple regression analyses were performed to analyze the risk factors associated with progressive vertebral body collapse.

RESULTS

The vertebral collapse difference was strongly associated with paraspinal muscle fatty degeneration (r=0.684, p=.000) and body mass index (r=0.300, p=.026). Multiple linear regression analysis demonstrated that the risk factor for progression of vertebral collapse was paraspinal muscle fatty degeneration (β=0.724, p=.000). There was a statistically significant correlation between the progression in vertebral collapse and VAS score at 3 (r=0.402, p=.002) and 6 months (r=0.604, p=.000).

CONCLUSIONS

In patients with OVCF, fatty degeneration of the paraspinal muscle was a predictive factor for progressive vertebral body collapse. This study suggests that more attention should be paid to patients with paraspinal sarcopenia among those with OVCFs.

Identification of differentially expressed genes in mouse paraspinal muscle in response to microgravity

Lower back pain (LBP) is the primary reason leading to dyskinesia in patients, which can be experienced by people of all ages. Increasing evidence have revealed that paraspinal muscle (PSM) degeneration (PSMD) is a causative contributor to LBP. Current research revealed that fatty infiltration, tissue fibrosis, and muscle atrophy are the characteristic pathological alterations of PSMD, and muscle atrophy is associated with abnormally elevated oxidative stress, reactive oxygen species (ROS) and inflammation. Interestingly, microgravity can induce PSMD and LBP. However, studies on the molecular mechanism of microgravity in the induction of PSMD are strongly limited. This study identified 23 differentially expressed genes (DEGs) in the PSM (longissimus dorsi) of mice which were flown aboard the Bion M1 biosatellite in microgravity by bioinformatics analysis. Then, we performed protein-protein interaction, Gene Ontology function, and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis for the DEGs. We found that Il6ra, Tnfaip2, Myo5a, Sesn1, Lcn2, Lrg1, and Pik3r1 were inflammatory genes; Fbox32, Cdkn1a, Sesn1, and Mafb were associated with muscle atrophy; Cdkn1a, Sesn1, Lcn2, and Net1 were associated with ROS; and Sesn1 and Net1 were linked to oxidative stress. Furthermore, Lcn2, Fbxo32, Cdkn1a, Pik3r1, Sesn1, Net1, Il6ra, Myo5a, Lrg1, and Pfkfb3 were remarkably upregulated, whereas Tnfaip2 and Mafb were remarkably downregulated in PSMD, suggesting that they might play a significant role in regulating the occurrence and development of PSMD. These findings provide theoretical basis and therapeutic targets for the treatment of PSMD.

Lumbar posterior group muscle degeneration: Influencing factors of adjacent vertebral body re-fracture after percutaneous vertebroplasty

Objective

The purpose of the study was to explore the influencing factors of adjacent vertebral re-fracture after percutaneous vertebroplasty (PVP) for osteoporosis vertebral compression fractures (OVCFs).

Methods

We retrospectively analyzed the clinical data of 55 patients with adjacent vertebral re-fracture after PVP operation for OVCFs in our hospital from January 2016 to June 2019, they were followed up for 1 year and included in the fracture group. According to the same inclusion and exclusion criteria, we collected the clinical data of 55 patients with OVCFs without adjacent vertebral re-fracture after PVP in the same period and included them in the non-fracture group. We performed univariate and multivariate logistic regression analysis on the influencing factors of adjacent vertebral re-fracture in patients with OVCFs after PVP.

Results

There were significant differences in body mass index (BMI), bone mineral density (BMD) T-value, amount of bone cement injected, bone cement leakage, history of glucocorticoid use, cross-sectional area (CSA), cross-sectional area asymmetry (CSAA), fat infiltration rate (FIR), and fat infiltration rate asymmetry (FIRA) of lumbar posterior group muscles [multifidus (MF) and erector spinae (ES)] between the two groups (p < 0.05). There was no significant difference in sex, age, or time from the first fracture to operation, the CAS, CSAA, FIR, and FIRA of psoas major (PS) between the two groups (p > 0.05). Multivariate logistic regression showed that a higher dose of bone cement, greater CSAA and FIR of multifidus, and higher CSAA of erector spinae were independent risk factors for recurrent fractures of adjacent vertebrae after PVP.

Conclusion

There are many risk factors for recurrent vertebral fracture after PVP in patients with OVCFs, and degeneration of paraspinal muscles (especially posterior lumbar muscles) may be one of the risks.

The effect of posterior lumbar dynamic fixation and intervertebral fusion on paraspinal muscles

BACKGROUND

The aim of this study was to analyze the effect of unilateral K-rod dynamic internal fixation on paraspinal muscles for lumbar degenerative diseases.

METHODS

This study retrospectively collected 52 patients who underwent lumbar surgery with the K-rod group or PLIF. The operation time, intraoperative blood loss, postoperative drainage volume, postoperative exercise time were compared in the two groups. The visual analog scale (VAS) score and the oswestry dysfunction index (ODI) were employed to evaluate the clinical outcomes. The functional cross-sectional area (FCSA) of the paraspinal muscles and paraspinal muscles fat infiltration were measured to assess on the paraspinal muscles.

RESULTS

As compared with the PLIF group, the operation time, the postoperative time in the field, and the average postoperative hospital stay in the K-rod internal fixation group were significantly shortened. At the last follow-up, both the groups showed significant improvement in the VAS score and ODI. The FCSA atrophy of the upper and lower adjacent segments (UAS and LAS) of the K-rod internal group was significantly less than that of the PLIF group. The extent of increase in the fatty infiltration of the paraspinal muscles in the K-rod group was significantly lesser than that in the PLIF group. The postoperative low back pain of the two groups of patients was significantly positively correlated with the FCSA atrophy.

CONCLUSIONS

As compared to PLIF, the posterior lumbar unilateral K-rod dynamic internal fixation showed significantly lesser paraspinal muscle atrophy and fatty infiltration, which were significantly positively correlated with postoperative low back pain.

Does Unilateral Lumbosacral Radiculopathy Affect the Association between Lumbar Spinal Muscle Morphometry and Bone Mineral Density?

Age-related degenerative changes lead to a gradual decrease in bone mineral density (BMD) and muscle mass. We aimed to assess the effects of decreased BMD and lumbar denervation on lumbar spinal muscle morphometry and the relationship between BMD and lumbar spinal muscular morphometry, respectively. Eighty-one patients, aged 50–85 years, diagnosed with unilateral lumbosacral radiculopathy based on electrodiagnostic studies between January 2016 and April 2021 were enrolled. BMD T scores in the lumbar spine and hip were measured using dual-energy X-ray absorptiometry. The cross-sectional area (CSA) of the psoas, multifidus, and erector spinae located in the middle of the lumbar spine, between the L3 and L4 and between the L4 and L5 levels, respectively, was measured using axial MRI. Functional CSA (FCSA) was defined as the CSA of lean muscle mass. Pearson correlation analyses were performed to evaluate the association between BMD T scores and the CSA, FCSA, and the ratio of the FCSA to the CSA (functional ratio) for each side. The CSA of lumbar spinal muscles showed no significant correlation with lumbar BMD. The FCSA and functional ratio of lumbar spinal muscles were significantly correlated with lumbar BMD. There was no correlation between femur BMD and lumbar spinal muscle morphometry.

Association of frailty with regional sagittal spinal alignment in the elderly

The degenerative changes in the spine of the frail elderly gradually exacerbate the alignment of the spine as the degeneration progresses. This study was conducted to assess the relationship between frailty and spine sagittal alignment measured in terms of global, cervical, thoracic, and lumbo-pelvic parameters. In total, 101 patients aged 75 years and older hospitalized for spine surgery were prospectively enrolled. We evaluated spinal sagittal parameters by dividing them into global (C7 sagittal vertical axis [SVA] and T1 pelvic angle [T1PA]), cervical (the C2-7 Cobb angle, Jackson line, and C2-7 plumb line), thoracic (thoracic kyphosis [TK]), and lumbo-pelvic (pelvic tilt [PT] and pelvic incidence minus lumbar lordosis value [PI-LL]). Patient characteristics; the Fatigue, Resistance, Ambulation, Illness, Loss of Weight (FRAIL) scale; and sagittal spinal parameters were included in the analysis. Multiple regression analysis was performed to identify associations between the FRAIL scale and sagittal spinal parameters. The FRAIL scale showed correlations with global sagittal parameters (C7 SVA [β = 0.225, p = 0.029] and T1PA [β = 0.273, p = 0.008]) and lumbo-pelvic parameters (PT [β = 0.294, p = 0.004] and PI-LL [β = 0.323, p = 0.001). Cervical and thoracic parameters were not directly associated with the FRAIL scale. LL and PI-LL were associated with TK, and TK was associated with cervical parameters (the C2-7 Cobb angle, Jackson line and C2-7 plumb line). In conclusion, frailty status could be an important factor that influences sagittal spinal alignment in the elderly. In this study, it was found that frailty mainly affected the balance of lumbo-pelvic alignment, and consequently affected the balance of the whole spine.

The Quantity and Quality of Lumbar Muscles and Lumbopelvic Parameters in Patients With Degenerative Spondylolisthesis

Introduction

Lumbar degenerative spondylolisthesis (DS) is one of the most common causes of low back pain. The lumbar muscles, such as the psoas major (PM), erector spinae (ES), and multifidus (MF) muscles, play an important role in the stability and functional movement of the lumbar spine. The quantities and qualities of these muscles may be related to the occurrence of DS and lumbopelvic parameters, such as lumbar lordosis (LL) and sacral slope (SS). However,the influence of lumbar muscles on DS and lumbopelvic alignment is not well understood.

Methods

Patients with L4 DS (DS group, n=25) and without DS (non-DS group, n=25) were included. Using sagittal reconstructed CT images of patients who visited our hospital for reasons other than low back disorders, LL, upper lumbar lordosis ([ULL] L1-L4), lower lumbar lordosis ([LLL] L4-S1), and SS were examined. To evaluate the quantity and quality of lumbar muscles, the gross cross-sectional area (GCSA), functional cross-sectional area (FCSA), and fat infiltration (FI) of the PM, ES, and MF muscles were measured by CT images. The lumbopelvic parameters, FCSA, GCSA, and FI of lumbar muscles were compared between the two groups. Then, each lumbar muscle parameter was analyzed for correlation with DS and lumbopelvic parameters.

Results

DS patients displayed significantly greater ULL and lower FI of the PM and ES muscles than non-DS patients (p=0.0078, 0.031, and 0.010, respectively). The FI of the ES muscle was significantly correlated with the presence of DS (p=0.010). The FCSA of the ES and MF muscles and the GCSA of the MF muscle showed a significant correlation with LL and SS in the non-DS group (p<0.05), but not in the DS group..

Conclusion

ULL was greater in L4 DS patients, possibly related to the better quality of the ES muscle. All DS patients showed mild (grade I) spondylolisthesis, suggesting the possibility that lumbar muscle quality is better in patients with mild DS than in those without DS. The ES and MF muscles may play an important role in maintaining the lumbar lordotic angle in non-DS patients but not in DS patients.

Long-Term Influence of Paraspinal Muscle Quantity in Adolescent Idiopathic Scoliosis Following Deformity Correction by Posterior Approach

Pedicle screw instrumentation (PSI) through posterior approach has been the mainstay of deformity correction for adolescent idiopathic scoliosis (AIS). However, changes in the quantity of paraspinal muscles after AIS surgery has remained largely unknown. The aim of this study was to investigate long-term follow-up changes in paraspinal muscle volume in AIS surgery via a posterior approach. Forty-two AIS patients who underwent deformity correction by posterior approach were analyzed through a longitudinal assessment of a cross-sectional area (CSA) in paraspinal muscles with a minimum five-year follow-up. The CSA were measured using axial computed tomography images at the level of the upper endplate L4 by manual tracing. The last follow-up CSA ratio of the psoas major muscle (124.5%) was significantly increased compared to the preoperative CSA ratio (122.0%) (p < 0.005). The last follow-up CSA ratio of the multifidus and erector spine muscles significantly decreased compared to the preoperative CSA ratio (all p < 0.005). The CSA ratio of the erector spine muscle was correlated with the CSA ratio of the psoas major (correlation coefficient = 0.546, p < 0.001). Therefore, minimizing the injury to the erector spine muscle is imperative to maintaining psoas major muscle development in AIS surgery by posterior approach.

Assessing Fatty Infiltration of Paraspinal Muscles in Patients With Lumbar Spinal Stenosis: Goutallier Classification and Quantitative MRI Measurements

Objective: Fatty infiltration of paraspinal muscle is associated with spinal disorders. It can be assessed qualitatively (i.e., Goutallier classification) and quantitatively using image processing software. The aims of this study were to compare paraspinal muscle fatty infiltration as assessed using the Goutallier classification vs. quantitative magnetic resonance images (MRI) measurements and to investigate the association between anthropometric parameters and paraspinal muscle morphology and fatty infiltration in patients with symptomatic lumbar spinal stenosis (LSS).

Methods: Patients affected by symptomatic LSS scheduled for surgery with available MRI of the lumbar spine were included in this retrospective cross-sectional study. Fatty infiltration at each lumbar level was rated qualitatively according to the Goutallier classification and quantified based on the cross-sectional area (CSA) of the paraspinal muscle, of its lean fraction (LeanCSA), and the ratio between LeanCSA and CSA and the CSA relative to the CSA of vertebral body (RCSA). Considering the muscle as a single unit, overall fatty infiltration according to Goutallier, overall CSA, LeanCSA, LeanCSA/CSA, and RCSA were computed as averages (aGoutallier, aCSA, aLeanCSA, aLeanCSA/aCSA, and aRCSA). Associations among parameters were assessed using Spearman's respective Pearson's correlation coefficients.

Results: Eighteen patients, with a mean age of 71.3 years, were included. aGoutallier correlated strongly with aLeanCSA and aLeanCSA/aCSA (R = −0.673 and R = −0.754, both P < 0.001). There was a very strong correlation between values of the left and right sides for CSA (R = 0.956, P < 0.001), LeanCSA (R = 0.900, P < 0.001), and LeanCSA/CSA (R = 0.827, P < 0.001) at all levels. Among all anthropometric measurements, paraspinal muscle CSA correlated the most with height (left: R = 0.737, P < 0.001; right: R = 0.700, P < 0.001), while there was a moderate correlation between vertebral body CSA and paraspinal muscle CSA (left: R = 0.448, P < 0.001; right: R = 0.454, P < 0.001). Paraspinal muscle CSA correlated moderately with body mass index (BMI; left: R = 0.423, P < 0.001; right: R = 0.436, P < 0.001), and there was no significant correlation between aLeanCSA or aLeanCSA/CSA and BMI.

Conclusions: The Goutallier classification is a reliable yet efficient tool for assessing fatty infiltration of paraspinal muscles in patients with symptomatic LSS. We suggest taking body height as a reference for normalization in future studies assessing paraspinal muscle atrophy and fatty infiltration.

The Effect of Cervical Paravertebral Extensor Degeneration on Sagittal Alignment and Functional Status of Cervical Spine in Patients With Cervical Spondylotic Myelopathy

STUDY DESIGN

This was a cross-sectional study.

OBJECTIVE

The objective of this study was to assess cervical paravertebral extensor degeneration in patients with cervical spondylotic myelopathy (CSM) and its impact on the sagittal parameters and functional status of the cervical spine.

SUMMARY OF BACKGROUND DATA

Paravertebral extensor degeneration is well-studied in CSM; however, the effect of extensor degeneration on the sagittal balance and functional status of the cervical spine is unclear.

MATERIALS AND METHODS

We enrolled 52 CSM patients (CSM group) and 52 age-matched and sex-matched healthy adults (control group). The C2-C7 and C0-C2 Cobb angles (CAs), C7 slope, T1 slope, cervical arc cord distance, cervical tilt (CERT), cranial tilt (CRAT), and C2-C7 sagittal vertical axis (SVA) were measured. The cross-sectional areas of the deep extensors (DEA), superficial extensors (SEA), and cervical vertebral body (VBA) of C4-C7 were measured. DEA/VBA and SEA/VBA were used to quantify the extensor volume. We analyzed the fatty infiltration ratio of the deep (DFIR) and superficial extensors (SFIR). The Visual Analog Scale, Neck Disability Index, and modified Japanese Orthopaedic Association Scale scores of the CSM group were calculated.

RESULTS

The DEA/VBA was significantly lower and the DFIR and SFIR were significantly higher in the CSM group. The C4 DEA/VBA correlated with the C2-C7 SVA, C2-C7 CA, CERT, and the Neck Disability Index and modified Japanese Orthopaedic Association Scale scores (r=-0.608, 0.291, 0.335,-0.649, and 0.409, respectively). The DEA/VBA of C5 correlated with the cervical arc cord distance and CRAT (r=-0.350 and -0.356, respectively). The C4 DFIR correlated with the C2-C7 SVA, C2-C7 CA, and the Visual Analog Scale (r=0.286, -0.297, and 0.429, respectively). The SFIR of C7 correlated with the T1 slope and C7 slope (r=0.368 and 0.319, respectively).

CONCLUSIONS

Paravertebral extensor degeneration negatively impacts the sagittal sequence and functional status of the cervical spine in CSM patients. Our study provides an insight into understanding the significance of cervical muscular degeneration in CSM patients.

LEVEL OF EVIDENCE

Level III.

3D analysis of fatty infiltration of the paravertebral lumbar muscles using T2 images-a new approach

PURPOSE

Factors influencing paraspinal muscle degeneration are still not well understood. Fatty infiltration is known to be one main feature of the degeneration cascade. The aim of this cross-sectional study was to illustrate the 3D cluster of paraspinal lumbar muscle degeneration on T2-weighted MRI images using our newly developed software application 'iSix'.

METHODS

Mono- (Mm. rotatores), multi- (Mm. multifidus) and pluri-segmental (M. erector spinae) lumbar muscles groups were segmented on T2-weighted MR sequences using a novel computer-assisted technique for quantitative muscle/fat discrimination. The degree of fatty infiltration of the three predefined muscle groups was compared on a 3-dimensional basis, with regard to segment involvement and age. General linear models were utilized for statistical comparison.

RESULTS

N = 120 segments (age: 52.7; range 16-87 years) could be included. The overall relative fatty infiltration of the mono-segmental muscles was higher (21.1 14.5%) compared to the multi-segmental (16.0 8.8% p = 0.049) and pluri-segmental muscles (8.5 8.0%; p = 0.03). Mono-segmental muscles on the levels L4/5 (22.9 ± 10.2 [CI 17.6-28.2] %) and L5/S1 (27.01 ± 15.1 [CI 21.4-32.7] %) showed a significant higher amount of fat compared to the levels L2/3 (8.2 ± 6.8 [CI 2.2-14.2] %; L4/5 vs. L2/3, p = 0.03; L5/S1 vs. L2/3, p = 0.02) and L3/4 (13.2 ± 5.4 [CI 8.6-17.7]%; L4/5 vs. L3/4, p = 0.02; L5/S1 vs. L3/4, p < 0.01). Multivariate linear regression analyses revealed age and Pfirrmann grade as independent factors for fatty muscle degeneration.

CONCLUSIONS

3D analysis of fatty infiltration is an innovative tool to study lumbar muscle degeneration. Mono-segmental muscles are more severely affected by degeneration compared to multi-/pluri-segmental muscles, especially at the L4/5 and L5/S1 level. Age and disc degeneration independently correlate with muscle degeneration.

Association between fatty infiltration of paraspinal muscle, sagittal spinopelvic alignment and stenosis grade in patients with degenerative lumbar spinal stenosis

Introduction

Sagittal balance and fatty infiltration of paraspinal muscle are important factors in patients with lumbar spinal stenosis (LSS) that may affect patients’ quality of life. Sagittal spinopelvic parameters and fatty infiltration may be associated with the severity of LSS. The purpose of this study was to test the hypothesis that severity of fatty infiltration correlates with severity of LSS and with sagittal pelvic alignment independent of age.

Methods

Age and body mass index (BMI) were extracted. Fatty infiltration was rated according to Goutallier classification and the severity of LSS was graded according to Schizas at five intervertebral disc levels. Overall fatty infiltration was computed as average fatty infiltration (aFI) and severity of LSS was defined as the highest severity of LSS of all segments. The sagittal spinopelvic parameters pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL) and PI-LL were measured. Associations among parameters were assessed using Spearman correlation coefficients adjusted for age (α = 0.05).

Results

165 LSS patients with a median age of 69 years were included. All parameters correlated with age (R>0.162, P<0.05) except BMI and LL (R<0.007, P>0.05). aFI correlated with PI, PT and PI-LL before (R>0.371, P<0.05) and after (R>0.180, P<0.05) adjusting for age. Severity of LSS correlated with PI, PT and PI-LL before (R>0.187, P<0.05) but not after (R<0.130, P>0.05) adjusting for age. aFI correlated with severity of LSS before (R=0.349, P<0.05) but not (R=0.114, P>0.05) after adjusting for age.

Conclusions

The correlation of aFI with sagittal spinopelvic parameters indicates that there might be a relationship between muscle characteristics and the sagittal alignment. Sagittal spinopelvic parameters and fatty infiltration of paraspinal muscles are not associated with radiological severity of LSS. Whether they are associated with clinical manifestation of LSS remains to be investigated.

The relationship of global sagittal malalignment to fatty infiltration in the aging spine

PURPOSE

To investigate associations between muscle size, fat infiltration (FI), and global sagittal alignment in patients with adult spinal deformity (ASD).

METHODS

Retrospective cohort study was conducted on a single-institution database of ASD patients with preoperative radiographs and CTs. Following multiplanar reconstructions of CTs, images in the plane of each vertebra were generated. The posterior vertebral musculature (PVM) was contoured on axial images at three vertebral levels (T2, T10, L3). FI was calculated by comparing Hounsfield units within muscles to the normative values of fat. Correlation analyses were conducted between demographics, alignment, and muscle characteristics.

RESULTS

107 patients underwent preoperative spine CT (58yo, 79%F, BMI 27 kg/m²). Muscle data were available for 49 pts at T2, 39 pts at T10, and 81 pts at L3. Mean FI was T2 = 33% ± 18, T10 = 28% ± 19, L3_Erector = 39% ± 19, and L3_Psoas = 19% ± 9. FI correlated across levels (T2 vs. T10 r = 0.698; T10 vs L3_Erector r = 0.506; L3_Erector vs Psoas r = 0.419) and with demographics; older pts had greater fat percentages (r = 0.31-0.45) and BMIs (r = 0.24-0.51). Increased FI at T2, T10, and L3 was associated with increased pelvic retroversion (PT: r = 0.25-0.43), global deformity (TPA: r = 0.27-0.45), and anterior malalignment (SVA: r = 0.23-0.41). The degree of FI in the PVM increased with the severity of SRS-Schwab PT and SVA modifiers.

CONCLUSION

In ASD patients, global sagittal malalignment is related to FI of the PVM throughout the lumbar and thoracic spine, as identified through CT. Future research should investigate how FI relates to ASD pathogenesis.

A comparison of the bilateral decompression via unilateral approach versus conventional approach transforaminal lumbar interbody fusion for the treatment of lumbar degenerative disc disease in the elderly

Background

Bilateral decompression via unilateral approach (BDUA) is an effective surgical approach for treating lumbar degenerative diseases. However, no studies of prognosis, especially the recovery of the soft tissue, have reported using BDUA in an elderly population. The aims of these research were to investigate the early efficacy of the bilateral decompression via unilateral approach versus conventional approach transforaminal lumbar interbody fusion (TLIF) for the treatment of lumbar degenerative disc disease in the patients over 65 years of age, especially in the perioperative factors and the recovery of the soft tissue.

Methods

The clinical data from 61 aging patients with lumbar degenerative disease who received surgical treatment were retrospectively analyzed. 31 cases who received the lumbar interbody fusion surgery with bilateral decompression via unilateral approach (BDUA) were compared with 30 cases who received conventional approach transforaminal lumbar interbody fusion. The radiographic parameters were measured using X-ray including lumbar lordosis angle and fusion rate. Japanese Orthopedic Association (JOA), Visual Analogue Scale (VAS) and Oswestry Disability Index (ODI) scores were used to evaluate the clinical outcomes at different time points. Fatty degeneration ratio and area of muscle/vertebral body were used to detect recovery of soft tissue.

Results

The BDUA approach group was found to have significantly less intraoperative blood loss(p < 0.05) and postoperative drainage(p < 0.05) compared to conventional approach transforaminal lumbar interbody fusion group. Symptoms of spinal canal stenosis and nerve compression were significantly relieved postoperatively, as compared with the preoperative state. However, the opposite side had a lower rate of fatty degeneration (9.42 ± 3.17%) comparing to decompression side (11.68 ± 3.08%) (P < 0.05) six months after surgery in the BDUA group. While there were no significant differences (P > 0.05) in two sides of conventional transforaminal lumbar interbody fusion approach group six months after surgery.

Conclusions

Bilateral decompression via unilateral approach (BDUA) is able to reduce the intraoperative and postoperative body fluid loss in the elderly. The opposite side of decompression in BDUA shows less fatty degeneration in 6 months, which indicates better recovery of the soft tissue of the aging patients.

Sarcopenia and Back Muscle Degeneration as Risk Factors for Degenerative Adult Spinal Deformity with Sagittal Imbalance and Degenerative Spinal Disease: A Comparative Study

BACKGROUND

Many factors affect spinal alignment in adult spinal deformity with sagittal imbalance. However, although the importance of the paravertebral muscle and ligamentum complex in proper spinal alignment is well recognized, little information is available regarding the role of the paravertebral muscles in maintaining sagittal spinal alignment.

METHODS

A total of 108 patients who had visited our institution from January 2016 to June 2018 were included in the present study. The patients were categorized as follows: degenerative adult spinal deformity with sagittal imbalance group and degenerative spinal disease group. The appendicular skeletal muscle mass index and handgrip strength of each patient were measured to evaluate for sarcopenia. Computed tomography was used to measure the cross-sectional area (CSA) and fat infiltration rate to evaluate paravertebral muscle morphology. The paravertebral muscle function was assessed by measuring the lumbar flexor strength and lumbar extensor strength using a lumbar isokinetic dynamometer.

RESULTS

The degenerative adult spinal deformity with sagittal imbalance group had a lower CSA index and lumbar extensor strength index and higher fat infiltration rate than the degenerative spinal disease group. No statistically significant differences in the appendicular skeletal muscle mass index and handgrip strength were found between the 2 groups. Only the CSA showed a correlation with the radiological parameters, such as pelvic tilt and lumbar lordosis.

CONCLUSIONS

Degeneration of the paravertebral muscle is a risk factor for degenerative adult spinal deformity with sagittal imbalance but not for sarcopenia. Thus, spinal sagittal imbalance is affected by isolated paravertebral muscle degeneration rather than by systemic muscle degeneration.

Lumbar lordosis morphology correlates to pelvic incidence and erector spinae muscularity

The retrospective study aimed to investigate the relationship between lumbar lordosis morphology, pelvic incidence and paraspinal muscle. It enrolled asymptomatic adult volunteers aged between 18 and 45 years old. Lumbar lordosis morphology, consisting of total lumbar lordosis (LL), proximal lumbar lordosis (PLL), distal lumbar lordosis (DLL), lumbar lordosis apex (LLA) and inflexion point, was evaluated, as well as pelvic incidence (PI) and muscularity of erector spinae (ES) and multifidus. Pearson correlation was performed to analyze the relationship between each other parameter. Cases were stratified according to pelvic incidence (very low < 30°, low 30°–45°, moderate 45°–60°, and high > 60°), comparison between groups was performed by univariance analysis. 87 asymptomatic adult volunteers (33 females and 54 males) were included in the study. PLL revealed a correlation with LLA (r = 0.603, p = 0.002) and inflexion point (r = 0.536, p = 0.004), but did not DLL with LL apex (r = 0.204, p = 0.058) or inflexion point (r = 0.210, p = 0.051). PI revealed a greater correlation with PLL (r = −0.673, p < 0.001) than with DLL (r = −0.237, p = 0.045). Linear stepwise regression analysis also exhibited the correlation between PI and PLL (R² = 0.452, PLL = 16.2–0.61 * PI, p < 0.001). ES muscularity correlated with LL apex (r = −0.279, p = 0.014) and inflexion point (r = −0.227, p = 0.047). Stratification by PI demonstrated PLL increased across groups (p < 0.001), but DLL was comparable between low and moderate PI group (p = 0.329). Lumbar lordosis morphology appears to accommodate to pelvic incidence and erector spinae muscularity. Proximal lumbar lordosis has a bigger correlation with pelvic incidence than the distal lumbar lordosis. The results are helpful for restoring a rational lumbar lordosis shape in long fusion surgery.

Musculature adaption in patients with lumbosacral transitional vertebrae: a matched-pair analysis of 46 patients

OBJECTIVE

Even though lumbosacral transitional vertebrae (LSTV) are one of the most common congenital anomalies of the spine, their effect on surrounding soft tissues is not well-studied. We therefore aimed at analyzing the association between LSTV and changes in volume, mass, symmetry, and degeneration of lumbar and trunk muscles.

MATERIALS AND METHODS

Abdomen-pelvis CT scans were analyzed in patients with LSTV and a matched control group. LSTV were classified according to the Castellvi classification. Muscles were segmented from the remaining soft tissue and their cross-sectional area and volume were examined at five defined levels. Threshold segmentation was used to differentiate between muscle fibers and fat tissue. Matched pairs were compared using Wilcoxon rank sum tests. For comparison of categorical data, chi-squared tests were performed and for associations between the degree of fusion and muscle size and degeneration, Spearman's correlation coefficients were calculated. Inter- and intrarater reliabilities were evaluated by computing intraclass correlation coefficients.

RESULTS

Forty-six patients with LSTV and 46 controls were included. Muscle volume of the paraspinal and trunk muscles was significantly lower (707.0 cm³ vs. 809.7 cm³, p < 0.001) and fatty muscle changes were significantly increased in all but the caudal paravertebral muscles of LSTV patients (M. psoas p < 0.04, M. quadratus lumborum p < 0.001, paravertebral muscles p = 0.011, M. rectus abdominis p < 0.001, M. obliquus abdominis p < 0.001). Correlations between the degree of Castellvi classification and muscle volume were significant (p = 0.001).

CONCLUSION

LSTV are associated with a reduction in muscle volume and an increase in muscle degeneration of both lumbar and trunk muscles.

Degenerative lumbar scoliosis patients with proximal junctional kyphosis have lower muscularity, fatty degeneration at the lumbar area

PURPOSE

To assess the lumbar muscle conditions on the incidence of proximal junctional kyphosis (PJK) after long-level correction and instrumentation surgery for degenerative lumbar scoliosis (DLS) patients with a minimum 2-year follow-up.

METHODS

Eighty-four DLS patients undergoing long instrumented fusion surgery (≥ 5 vertebrae) were retrospectively studied. According to the occurrence of PJK at the final follow-up, patients were divided into the PJK group and the Non-PJK group. Patient characteristics, surgical variables and radiographic parameters were analyzed statistically. The lumbar muscularity (cross-sectional area of muscle-disc ratio × 100) and fatty degeneration (signal intensity of muscle-subcutaneous fat ratio × 100) were evaluated on magnetic resonance imaging .

RESULTS

The prevalence of PJK was 20.24%. Gender, age at surgery, body mass index, uppermost instrumented vertebrae level, fusions extending to the sacrum, and levels fused were not significantly different between the groups. Lower bone mineral density, smaller functional cross-sectional area (FCSA) of paraspinal extensor muscles (PSE), higher lean muscle-fat index and total muscle-fat index of PSE, greater preoperative thoracolumbar kyphosis (TLK), smaller preoperative sacral slope (SS), larger preoperative sagittal vertical axis were identified in PJK group. Logistic regression analysis showed that osteoporosis, preoperative TLK > 15°, SS > 24°, FCSA of PSE > 138.75, and total muscle-fat index of PSE > 4.08 were independently associated with PJK. The final follow-up VAS score for back pain was higher, and SRS-22 subcategories of pain, function, self-image, and total score were significantly lower in the PJK group.

CONCLUSION

Osteoporosis, lower lumbar muscularity and higher fatty degeneration, preoperative greater TLK and smaller SS were found to be strongly associated with the presence of PJK in DLS.