Facet Joint Orientation/Tropism Could Be Associated with Fatty Infiltration in the Lumbar Paraspinal Muscles

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

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

Fatty infiltration of the erector spinae at the upper lumbar spine could be a landmark for low back pain

PURPOSE

Intervertebral disc degeneration (IVDD), Modic changes, and fatty infiltration in the paraspinal muscles are possible causes of low back pain (LBP). Multifidus has been the most commonly blamed paraspinal muscle in the etiology of LBP. However, it contributes to 20% of the extensor moment on the lumbar spine. In the present study, we aimed to identify whether patients with LBP and asymptomatic subjects differed in terms of intervertebral discs, end-plates, and fatty infiltration in their paraspinal muscles.

METHODS

Consecutive women and men, who visited the spine outpatient clinics with chronic LBP and had lumbar spine MRI for their LBP without leg pain were included. Asymptomatic subjects without LBP/leg pain for the last year were recruited. Modic changes, IVDD, and fatty infiltration in the paraspinal muscles were evaluated on lumbar spine magnetic resonance imagings of the patients with LBP and age-, gender- and BMI-matched asymptomatic controls.

RESULTS

Low back pain was closely associated with fatty infiltration in the paraspinal muscles at all lumbar levels whereas it had association with severe IVDD and Modic changes at lower lumbar levels. Multifidus at the lower lumbar levels was the fattiest paraspinal muscle in both asymptomatic subjects and patients with LBP. Patients with LBP had severe fatty infiltration in the erector spinae at the upper lumbar levels.

CONCLUSION

Severe IVDD and Modic changes were more common at lower lumbar levels in patients with LBP. Both asymptomatic subjects and those with LBP had fatty multifidus at lower lumbar levels, whereas those with LBP had fatty infiltration in the erector spinae at upper lumbar levels. We suggest that fatty infiltration could have started in the multifidus. The erector spinae had greater contribution to the lumbar extension compared to the multifidus. Thus, LBP could develop when the quality of the erector spinae at the upper lumbar levels impairs due to fatty infiltration.

Effect of different loads on facet joint motion during lumbar lateral bending in sitting position

OBJECTIVE

To study the effect of weight-bearing on lumbar facet joint during lateral bending in sitting position.

METHODS

Ten normal healthy people (5 males and 5 females) aged 25-39 years (mean 32 ± 4.29 years) were recruited. CT scanning was used to reconstruct the lumbar spine model, and then dual fluoroscopic image system (DFIS) was used to restore the lumbar facet joint movement in sitting position. Finally, the lumbar facet joint translation distance and rotation angle were measured.

RESULTS

In L3-4 level, the displacement of right facet joint in Y-axis was the smallest at 0.05 ± 0.40 mm, the displacement of 0 kg left facet joint in X-axis was the largest at 1.68 ± 0.85 mm, and the rotation angle was - 0.57 ± 1.43° to 5.66 ± 2.70° at 10 kg; in L4-5 level, the displacement of right facet joint in Y-axis was the smallest at 10 kg, - 0.13 ± 0.91 mm, and the displacement of left facet joint in Z-axis was the largest at - 2.11 ± 0.88 mm, and the rotation angle was 0.21 ± 2.14° to 7.89 ± 2.59° at 10 kg; in L5-S1 level, the displacement of right facet joint in Y-axis was the smallest at 10 kg, - 0.17 ± 1.10 mm, and the displacement of 0 kg left facet joint in X-axis was the largest at 2.19 ± 2.28 mm, and the rotation angle was 0.03 ± 2.02° to 3.98 ± 0.37°.

CONCLUSION

In sitting position, weight-bearing has certain influence on the displacement of facet joints during lumbar lateral bending movement, and this influence occurs simultaneously in translation and rotation; the left and right facet joints are not symmetrical during lumbar lateral bending movement.

Risk Factors in Patients with Low Back Pain Under 40 Years Old: Quantitative Analysis Based on Computed Tomography and Magnetic Resonance Imaging mDIXON-Quant

Purpose

While low back pain (LBP) constitutes a global life disorder cause, the contribution of paraspinal muscles to its pathogenicity remains elusive. We characterized the paraspinal muscles of patients with LBP using lumbar three-dimensional computed tomography (CT) and magnetic resonance imaging (MRI) mDIXON-Quant, and evaluated the risk factors combined with clinical data.

Methods

A retrospective study involving 181 patients (10-40 years) who underwent lumbar 3D-CT and MRI mDIXON from January 1, 2021 to December 31, 2022, and divided into normal, non-chronic LBP [non-CLBP], and CLBP groups. Clinical data, paraspinal muscle cross-sectional area, Hounsfield unit for CT values, and fat fraction derived from mDIXON-Quant were compared. Three readers analyzed the images independently; intra- and interobserver agreement was measured. Spearman analysis and multiple logistic regression were used to analyze the correlation between clinical data, radiologic and paraspinal muscle parameters. A nomogram was constructed for individualized prediction.

Results

Correlation analysis revealed that body mass index, visual analog scale score, Pfirrmann grade, annulus fibrosus tear, lumbar lordosis (LL), and Modic changes correlated with LBP (all P<0.05). The Pfirrmann grade and annulus fibrosus tear showed positive correlation (r=0.673, 0.559), whereas LL was negatively correlated (r=-0.469). The multifidus CT values were negatively correlated with LBP at L4-5/L5-S1; the multifidus fat fraction was positively correlated at L4-5/L5-S1 (r=0.734, r=0.584, P<0.001). The multiple logistic regression showed that L4-5 multifidus fat fraction (P=0.046, OR=1.167), Pfirrmann grade (P=0.017, OR=0.063), LL (P=0.002, OR=0.828) and annulus fibrosus tear (P=0.005, OR=0.024) were risk factors for predicting LBP in the non-CLBP group; in the CLBP group, BMI (P=0.048 OR=1.225), L4-5 multifidus fat fraction (P=0.001 OR=1.299), LL (P=0.003, OR=0.841) and Pfirrmann classification (P=0.009, OR=0.046) were risk factors.

Conclusion

BMI, L4-5 multifidus fat fraction, LL, and Pfirrmann grade are risk factors for CLBP in patients under 40; whereas annulus fibrosus tear is an independent risk factor for non-CLBP, nomograms derived from these parameters can help predict LBP and MRI mDIXON-Quant is recommended for quantitatively analyzing paraspinal muscle fat infiltration.