Evaluation of the relationship between paraspinal muscle and subcutaneous fat tissue thickness with lumbar degenerative disc disease by using magnetic resonance imaging

The passive and active components of the axial skeleton of the body provides balance and upright posture during movement. Passive components are vertebrae, intervertebral discs, and ligaments. The active components are the paraspinal and abdominal muscles with neural structures that innervate them. Paraspinal muscles are the unit of the vertebral column that provides active balance and generates power. Low back pain is an important public health problem that can cause chronic pain syndrome and loss of workforce. This condition occurs at least once in more than half of people worldwide. One of the most important causes of low back pain is lumbar degenerative disc disease(LDDD). In this study, we aimed to evaluate the relationship between LDDD and the cross-sectional area calculated using the dimensions of the paraspinal muscle in different planes and the ratio of these dimensions to each other and the subcutaneous fat tissue thickness at the same level. Our study was retrospective and it included control group of 150 patients (78 men, 72 women) MRI results in normal limits and 159 patients(80 men and 79 women) MRI results interpreted as LDDD, all applied to the Radiology Clinic of Adıyaman University Training and Research Hospital for Lumbar MRI with low back pain complaint. All patinets' anteroposterior and lateral diameter and cross-sectional areas ofMusculus multifidus(MM) and Musculus Erector Spinae(MES), cross-sectional area of the L4 vertebra corpus, subcutaneous fat tissue thickness, lumbar lordosis angle, and intervertebral disc heights were measured and compared. In addition to these measurements, fatty infiltration of mentioned muscles, modic degenerative changes of the end plates adjacent to the L4L5 intervertebral disc and discal herniations at this level were also evaluated. In cases with LDDD, the ratio of left and right MM AP diameters tocrosssectional area ofvertebra corpus was found to be lower than the control group (pvalue<0.0001). In addition, in LDDD cases, the ratio of left and right ES AP diameters to cross-sectional area ofvertebra corpus is lower than the control group (left p value: 0.004, right pvalue: 0.007). As the severity of disc degeneration increases from bulging to extrusion, in LDDH, the left and right MM AP diameter / cross-sectional area ratiosignificantly decreases (left pvalue: 0.001; right pvalue: 0.002). Modic type 2 degeneration is the most common degeneration type was found in all grades of lumbar disc herniation. In addition, Modic type 2 degeneration is more common in cases of high grade lumbar disc herniation (p <0.0001). In the light of the data we obtained in our study, we think that the ratio of the AP diameters of posterior paraspinal muscles to cross-sectional area of vertebra corpus may be helpful in evaluating and monitoring the effectiveness of physical exercise and rehabilitation treatments in patients with low back pain and LDDH. In addition, the ratio of musculus mutifidus AP diameters tocross-sectional area of vertebra corpus can give an idea about the severity of LDDH.