Relationship Between Paraspinal Muscle Morphology, Function, and Physical Status in Common Spinal Disorders

The deep paraspinal muscles are essential for providing physical support and stability to the spinal column. They play a vital role in maintaining fine postural control of the spine and are responsible for controlling all movements of the vertebral column. These muscles work in coordination to ensure proper alignment and movement of the spine, thereby contributing to overall spinal health and function. Dysfunction or weakness in paraspinal muscles can lead to instability, poor posture, and increased risk of spinal pain disorders. Therefore, understanding the role of deep paraspinal muscles is crucial in maintaining spinal health and preventing musculoskeletal disorders. This summary highlights the significance of assessing both morphology and function of paraspinal muscles in common spinal disorders including chronic low back pain (LBP) and degenerative cervical myelopathy (DCM). While previous studies have focused on either morphology or functional deficits separately, this dissertation aims to comprehensively investigate the structure-function relationship using advanced imaging techniques like magnetic resonance imaging (MRI) and ultrasound. Specifically, chapter three focuses on understanding the relationship between lumbar multifidus muscle (MF) muscle morphology and function in chronic LBP patients, utilizing measures such as fatty infiltration, contraction, stiffness, and elasticity. Similarly, chapter four and five aim to assess cervical muscle morphology as predictors of prognosis and functional recovery in patients with DCM, both pre- and post-operatively. Such comprehensive evaluations are crucial for improving diagnosis, intervention, and therapeutic strategies in spinal disorders, ultimately enhancing patients’ clinical outcomes and quality of life. Finally, chapter six discusses the findings from chapters three, four and five and offers a general conclusion and recommendations for future research

Reliability of Ultrasonography in Measuring Deep Abdominal and Lumbar Multifidus Muscle Dimensions in Patients with Unilateral Lumbar Disc Herniation

Introduction: The purpose of this study was to assess the within-day and between-day reliability of abdominal and lumbar multifidus muscle size in patients with unilateral lumbar disc herniation (LDH) using ultrasonography (US). Materials and methods: In this study, 15 patients with unilateral LDH (20-60 years old) were recruited. To assess within-day and between-day reliability, three images were taken with one hour and one week intervals respectively. The images were taken at rest and during contraction. Results: The within-day and between-day reliability of abdominal muscle thickness measurements using US in patients with unilateral lumbar disc herniation (LDH) in both rest and contraction state was found to be high with ICC=0.87 for within and ICC=0.75 for between-day rates of transverse abdominis (TrA) muscles at rest and ICC=0.78 and 0.75, respectively, in contraction state. For internal oblique muscles, ICC=0.70 at rest and 0.79 in contraction state and ICC=0.73 at rest and 0.77 in contraction state were found for within-day and between-day, respectively. Within-day and between-day reliability at rest with ICC=0.76 and 0.76 and in contraction state with ICC=0.75 and 0.74 were demonstrated for the external oblique muscle. Within-day and between-day reliability rates at rest with ICC=0.88 and 0.84, respectively, and in contraction state with ICC=0.84 and 0.80, respectively were demonstrated for the lumbar multifidus muscle. Conclusion: The results of the present study suggest that US is a reliable method for evaluating the thickness of the abdominal and lumbar multifidus muscles. However, further research is recommended to support the findings of the present study.Keywords: Ultrasonography, disc herniation, abdominal muscles, lumbar multifidus muscle, reliabilit

How inter-rater variability relates to aleatoric and epistemic uncertainty: a case study with deep learning-based paraspinal muscle segmentation

Recent developments in deep learning (DL) techniques have led to great performance improvement in medical image segmentation tasks, especially with the latest Transformer model and its variants. While labels from fusing multi-rater manual segmentations are often employed as ideal ground truths in DL model training, inter-rater variability due to factors such as training bias, image noise, and extreme anatomical variability can still affect the performance and uncertainty of the resulting algorithms. Knowledge regarding how inter-rater variability affects the reliability of the resulting DL algorithms, a key element in clinical deployment, can help inform better training data construction and DL models, but has not been explored extensively. In this paper, we measure aleatoric and epistemic uncertainties using test-time augmentation (TTA), test-time dropout (TTD), and deep ensemble to explore their relationship with inter-rater variability. Furthermore, we compare UNet and TransUNet to study the impacts of Transformers on model uncertainty with two label fusion strategies. We conduct a case study using multi-class paraspinal muscle segmentation from T2w MRIs. Our study reveals the interplay between inter-rater variability and uncertainties, affected by choices of label fusion strategies and DL models.Comment: Accepted in UNSURE MICCAI 202

Cervical muscle morphometry and composition demonstrate prognostic value in degenerative cervical myelopathy outcomes

ObjectivesThis study aimed to examine whether preoperative cervical muscle size, composition, and asymmetry from magnetic resonance imaging (MRI) can predict post-operative outcomes in patients with degenerative cervical myelopathy (DCM).MethodsA total of 171 patients with DCM were included. Relative total cross-sectional area (RCSA), functional CSA (fat-free area, FCSA), ratio of FCSA/CSA (fatty infiltration) and asymmetry of the multifidus (MF) and semispinalis cervicis (SCer) together (MF + SCer), and cervical muscle as a group (MF, SCer, semispinalis capitis, and splenius capitis) were obtained from T2-weighted axial MR images at the mid-disk, at the level of maximum cord compression and the level below. Univariate and multivariate linear regression analyses were used to assess the relationship between baseline cervical muscle measurements of interest with the modified Japanese Orthopedic Association (mJOA), Nurick Classification, Neck Disability Index (NDI), and SF-36 health survey at 6-month and 12-month post-surgery.ResultsLower RCSA of MF + SCer, less CSA MF + SCer asymmetry and greater FCSA/CSA for the cervical muscle group (e.g., less fatty infiltration), and younger age were significant predictors of higher mJOA scores (e.g., less disability) at 6-month and 12-month post-surgery (all p < 0.05). Greater CSA asymmetry in MF + SCer and lower FCSA/CSA (e.g., more fatty infiltration) for the cervical muscle group were significant predictors of higher Nurick scores (e.g., more disability) at 6-month and 12-month post-surgery (all p < 0.05). Lower FCSA MF + Scer asymmetry, lower FCSA/CSA asymmetry of the muscle group, and greater RCSA MF + SCer were significant predictors of higher NDI scores at 6-month and 12-month post-surgery. Finally, greater FCSA/CSA asymmetry of the MF + SCer, greater FCSA asymmetry of the muscle group, greater RCSA of the muscle group, and greater CSA asymmetry of MF + SCer were significant predictors of lower post-operative SF-36 scores at 6- and 12-month post-surgery.ConclusionOur result suggested that cervical paraspinal muscle morphology, specifically greater asymmetry, and fatty infiltration may be important predictors of functional recovery and post-surgical outcomes in patients with DCM

The assessment of paraspinal muscle epimuscular fat in participants with and without low back pain: A case-control study

It remains unclear whether paraspinal muscle fatty infiltration in low back pain (LBP) is i) solely intramuscular, ii) is lying outside the epimysium between the muscle and fascial plane (epimuscular) or iii) or combination of both, as imaging studies often use different segmentation protocols that are not thoroughly described. Epimuscular fat possibly disturbs force generation of paraspinal muscles, but is seldomly explored. This project aimed to 1) compare epimuscular fat in participants with and without chronic LBP, and 2) determine whether epimuscular fat is different across lumbar spinal levels and associated with BMI, age, sex and LBP status, duration or intensity. Fat and water lumbosacral MRIs of 50 chronic LBP participants and 41 healthy controls were used. The presence and extent of epimuscular fat for the paraspinal muscle group (erector spinae and multifidus) was assessed using a qualitative score (0–5 scale; 0 = no epimuscular fat and 5 = epimuscular fat present along the entire muscle) and quantitative manual segmentation method. Chi-squared tests evaluated associations between qualitative epimuscular fat ratings and LBP status at each lumbar level. Bivariate and partial spearman’s rho correlation assessed relationships between quantitative and qualitative epimuscular fat with participants’ characteristics. Epimuscular fat was more frequent at the L4-L5 (X2 = 13.781, p = 0.017) and L5-S1 level (X2 = 27.825, p < 0.001) in participants with LBP compared to controls, which was not found for the higher lumbar levels. The total qualitative score (combined from all levels) showed a significant positive correlation with BMI, age, sex (female) and LBP status (r = 0.23–0.55; p < 0.05). Similarly, the total area of epimuscular fat (quantitative measure) was significantly correlated with BMI, age and LBP status (r = 0.26–0.57; p < 0.05). No correlations were found between epimuscular fat and LBP duration or intensity. Paraspinal muscle epimuscular fat is more common in chronic LBP patients. The functional implications of epimuscular fat should be further explored

Lumbar Multifidus Muscle Morphology Changes in Patient with Different Degrees of Lumbar Disc Herniation: An Ultrasonographic Study

Background and Objective: Previous studies demonstrated that the prevalence of lumbar disc herniation (LDH) is relatively high. This investigation aimed to evaluate the size of lumbar multifidus (LM) muscle in patients with different degrees of LDH compared to healthy group, during rest and contraction, using ultrasonography. Materials and Methods: In this non-experimental, analytic, and case control study, ultrasound imaging was used to assess cross-sectional area (CSA) and thickness of the LM muscle in 15 healthy subjects and 60 patients with different stages of LDH (bulging group = 15, protrusion group = 15, extrusion group = 15, sequestration group = 15). Measurements were taken bilaterally at the L4–L5 level, during rest and contraction and results were compared between groups. Results: There was a significant difference between healthy subjects and the extrusion and sequestration groups during rest and contraction for LM muscle CSA and thickness (p = 0.001), as LM muscle CSA and thickness were significantly smaller in extrusion and sequestration patient groups compared to healthy subjects. LM atrophy was greater in patients with extrusion and sequestration groups than in patients with bulging and protrusion, both at rest and during contraction. Significant correlations were also observed between functional disability and intensity of pain with LM CSA and thickness measurements. Conclusions: Patients with extrusion and sequestration LDH had smaller LM muscle at rest and during contraction compared to healthy subjects. Larger LDH lesions were associated with decreased LM muscle size. Patient with more pain, disability, and extrusion and sequestration LDH had greater LM size changes. LM muscle size was not correlated with symptom duration. Further investigation with greater sample size is warranted

Comparison of paraspinal muscle composition measurements using IDEAL fat–water and T2-weighted MR images

PurposeThe purpose of this study was to evaluate the agreement between paraspinal muscle composition measurements obtained from fat-water images using % fat-signal fraction (%FSF) in comparison to those obtained from T2-weighted magnetic resonance images (MRI) using a thresholding method.MethodsA sample of 35 subjects (19 females, 16 males; 40.26 ± 11.3&nbsp;years old) was selected from a cohort of patients with chronic low back pain (LBP). Axial T2-weighted and IDEAL (Lava-Flex, 2 echo sequence) fat and water MR images were obtained using a 3.0 Tesla GE scanner. Multifidus, erector spinae, and psoas major muscle composition measurements were acquired bilaterally at L4-L5 and L5-S1 using both imaging sequences and related measurement methods. All measurements were obtained by the same rater, with a minimum of 7&nbsp;days between each method. Intra-class correlation coefficients (ICCs) were calculated to assess intra-rater reliability. Pearson Correlation and Bland-Altman 95% limits of agreement were used to assess the agreement between both measurement methods.ResultsThe intra-rater reliability was excellent for all measurements with ICCs varying between 0.851 and 0.997. Strong positive correlations indicating a strong relationship between composition measurements were obtained from fat-water and T2-weighted images for bilateral multifidus and erector spinae muscles at both spinal levels and the right psoas major muscle at L4-L5, with correlation coefficient r ranging between 0.67 and 0.92. Bland-Altman plots for bilateral multifidus and erector spinae muscles at both levels revealed excellent agreement between the two methods, however, systematic differences between both methods were evident for psoas major fat measurements.ConclusionOur findings suggest that utilizing fat-water and T2-weighted MR images are comparable for quantifying multifidus and erector spinae muscle composition but not of the psoas major. While this suggests that both methods could be used interchangeably for the multifidus and erector spinae, further evaluation is required to expand and confirm our findings to other spinal levels

The Effects of Combined Motor Control and Isolated Extensor Strengthening versus General Exercise on Paraspinal Muscle Morphology, Composition, and Function in Patients with Chronic Low Back Pain: A Randomized Controlled Trial

Low back pain (LBP), a globally widespread and persistent musculoskeletal disorder, benefits from exercise therapy. However, it remains unclear which type leads to greater changes in paraspinal muscle health. This study aimed to (1) compare the effects of a combined motor control and isolated lumbar extension exercise (MC+ILEX) versus a general exercise (GE) intervention on paraspinal muscle morphology, composition, and function, and (2) examine whether alterations in paraspinal muscle health were correlated with improvements in pain, function, and quality of life. Fifty participants with chronic LBP were randomly assigned to each group and underwent a 12-week supervised intervention program. Magnetic resonance imaging and ultrasound assessments were acquired at baseline, 6 and 12 weeks to examine the impact of each intervention on erector spinae (ES) and multifidus (MF) muscle size (cross-sectional area, CSA), composition, and function at L4-L5 and L5-S1. Self-reported questionnaires were also acquired to assess participant-oriented outcomes. Our findings indicated that the MC+ILEX group demonstrated greater improvements in MF and ES CSA, along with MF thickness at both levels (all p < 0.01). Both groups significantly improved in pain, function, and quality of life. This study provided preliminary results suggesting that an MC+ILEX intervention may improve paraspinal morphology while decreasing pain and disability