Multi-mode Magnetic Resonance Imaging Study On The Change Of Target Core Muscle Group In Patients With Chronic Low Back Pain After Rehabilitation Exercise Training

Objectives:To study the morphological and functional changes of paraspinal muscles and gluteus muscles in patients with sedentary chronic low back pain based on multimodal magnetic resonance imaging(MRI)parameters,and to explore the correlation between the improvement of target core muscle group and clinical evaluation after rehabilitation exercise training in patients with chronic low back pain.The ultimate goal is to provide effective quantitative indicators for the development and adjustment of clinical rehabilitation strategies for chronic low back pain,thereby establishing a foundation for devising and refining rehabilitation exercise plans.Methods:This study prospectively recruited 14 patients with chronic low back pain and 14 healthy volunteers as a control group from November 2021 to March 2022.The case group consisted of 9 women and 5 men,with a mean age of 25.50 ± 1.61 years,while the control group had a mean age of 24.86 ± 1.09 years.At baseline,all subjects underwent conventional lumbar spine MRI,axial IDEAL-IQ,BOLD,T1 WI,and BOLD imaging at the level of the superior margin of the femoral head.The case group received additional MRI scans with identical parameters at 1 month and 6 months after core activation and partial external core intensive training.At the median level of the spine on sagittal T2 WI,the degree of L4/5 disc degeneration was assessed using the Pfirrmann grading system;The Skeletal Muscle Index(SMI),fat fraction(FF),and effective transverse relaxation rate(R2*)were measured at the central level of the L4/5intervertebral disc,along with the SMI and R2* of the gluteus maximus and gluteus medius at the horizontal plane of the superior margin of the femoral head.The Numerical Rating Scale(NRS)and Oswestry Disability Index(ODI)were recorded at baseline and at 1 and 6 months after exercise.The differences of SMI,R2* and FF values in the paraspinal muscle,and SMI and R2* in the gluteus maximus and gluteus medium and small muscles at the level of interest between CLBP patients and control group were evaluated.The degree of intervertebral disc degeneration,SMI,R2*,FF values of paraspinal muscle,and SMI and R2* changes of gluteus maximus and gluteus medius in CLBP patients were analyzed after rehabilitation exercise training.To evaluate the difference of NRS score and ODI score in CLBP patients after rehabilitation exercise training.The relationship between FF of paraspinal muscle,R2*of gluteus maximus,R2* of gluteus minor,NRS of low back pain and ODI score in CLBP patients at the level of interest was analyzed.Results:Compared to the control group,the baseline fat fraction(FF)of bilateral paravertebral muscles at the L4/5 intervertebral disc layer in patients with chronic low back pain was significantly higher than that in healthy subjects(P<0.001);There was no significant difference in L4/5 intervertebral disc degeneration between patients with chronic low back pain(P=0.739).In patients with CLBP,the paraspinal muscle FF decreased by 16.18% at 1 month post-training(P = 0.023)and by 27.15% at 6 months post-training(P< 0.001)compared to pre-training values.The SMI of gluteus medius in patients with chronic low back pain was smaller than that of the control group(P=0.002).No significant differences were observed in the degree of intervertebral disc degeneration and the Skeletal Muscle Index(SMI)of the gluteus maximus and gluteus medius at the superior margin of the femoral head between pre-and post-training measurements at 1 month and 6 months(P>0.05).The R2* value of the gluteus maximus muscle increased by 16.38% and 17.37% at 1 month and 6 months posttraining,respectively,compared to pre-training levels.These differences were significant(P=0.022,P=0.016).The R2* values of the gluteus medius increased by17.68% and 17.91%,with statistically significant differences(P= 0.024,P= 0.023).A moderate positive correlation was found between the paraspinal muscle FF and the Oswestry Dysfunction Index score(r= 0.510,P<0.001).The R2* value of the gluteus medius in CLBP patients showed a moderate negative correlation with the Oswestry Dysfunction Index score(r=-0.462,P=0.002),while the R2* value of the gluteus maximus exhibited a moderate negative correlation with the Oswestry Dysfunction Index score(r=-0.488,P<0.05).Additionally,a moderate negative correlation was found between the R2* of the gluteus medius and the FF of paraspinal muscles at the L4/5 level in CLBP patients(r=-0.643,P<0.001).In CLBP patients,the R2* of the gluteus maximus displayed a moderate negative correlation with the FF of paraspinal muscles at the L4/5 level(r=-0.643,P<0.001).The SMI of the gluteus medius was negatively correlated with the FF of paraspinal muscles at the L4/5 level(r =-0.398,P=0.009).Conclusions : The degree of L4/5 intervertebral disc degeneration in sedentary patients with chronic low back pain is similar to that in sedentary patients without low back pain,but the degree of paraspinal muscle fat infiltration is more serious,accompanied by the decrease of gluteus medius muscle morphology and function.The rehabilitation exercise training program of inner core activation and partial outer core muscle strengthening is helpful to relieve chronic low back pain,and can improve the corresponding negative changes of paraspinal muscles and gluteal muscles.Multimodal magnetic resonance imaging can objectively and quantitatively evaluate the exercise training of target muscles,provide effective quantitative indicators for clinical rehabilitation strategies of chronic low back pain,and provide a basis for formulating and adjusting rehabilitation exercise strategies.