Characteristics of lumbar paravertebral muscle in degenerative sagittal imbalance and the association with the severity of sagittal deformity

English Keywords:Degenerative spinal sagittal imbalance  Senior age  Lumbar paravertebral muscle degeneration

English Abstract:

  【Abstract】 Objectives: To investigate the characteristics of lumbar paravertebral muscles in patients with degenerative spinal sagittal imbalance and the association with the severity of sagittal imbalance. Methods: The clinical data of patients with degenerative spinalsagittal imbalance from January 2017 to September 2020 were retrospectively analyzed. There were 49 males and 71 females with an average age of 70.5±9.2 years. Standing full spine radiographs were used to assess patients′ spinopelvic parameters in the sagittal plane, including C7 sagittal vertical axis(C7-SVA), thoracic kyphosis(TK), lumbar lordosis(LL), pelvic incidence(PI), pelvic tilt(PT) and sacral slope(SS). The total paravertebral muscle area (TCSA) and its relative CSA(RtCSA), the functional cross-sectional area(FCSA) and its relative cross-sectional area(RCSA), and the degree of fat infiltration(FI%) of the muscle at each level were quantified on axial T2-weighted MRI, and the total mean cross-sectional area and degree of fat infiltration were calculated for each patient(aveTCSA, aveRCSA and aveFI%). Differences in paravertebral muscle degeneration were compared between the groups according to age(adult group <65, old group 65-75, senior group >75 years old) and gender grouping respectively. In addition, 120 patients were divided into two groups according to the severity of sagittal imbalance, with 89 patients in the mild imbalance group(MI group)(SVA 5-10cm) and 31 patients in the severe imbalance group(SI group)(SVA>10cm) to analyze the characteristics of paravertebral muscle degeneration. Multiple linear regression analysis was used to analyze the correlation between lumbar paravertebral muscle degeneration and age, gender, body mass index(BMI), and the severity of imbalance. Results: The aveFI% of the paravertebral muscles was significantly higher in female patients than in male patients, but the aveTCSA was significantly higher in male patients(all P<0.05). Among the three groups of patients with spinal sagittal plane imbalance of different age groups, there were significant differences in paraspinal muscle degeneration parameters(FI% and RCSA) from L1/2 to L5/S1 levels(all P<0.05), of which the senior age group was the most significant, while for RtCSA, there was only a significant difference at L1/2 to L3/4 levels. Among patients with different severity of imbalance, the severe imbalance group had smaller PI, LL and TK values and a larger PI-LL for spinopelvic parameters(all P<0.05); for paravertebral muscle parameters, RCSA was statistically different between the two groups at the L2/3 to L5/S1 levels(all P<0.05). There was a significant difference of TCSA between the two groups only at the L4/5 and L5/S1 segments(both P<0.05), and no significant difference in the FI%(both P>0.05). Multiple linear regression analysis showed that, aveTCSA, aveFI%, aveRCSA were associated with age, gender and BMI, while there was no linear correlation with the severity of sagittal imbalance(SVA). Conclusions: Age, gender and BMI were associated with lumbar paravertebral muscle degeneration in patients with spinal degenerative sagittal imbalance. Although there was no significant association between the degree of spinal sagittal imbalance(SVA) and paravertebral degeneration, severe spinal sagittal imbalance suggests more significant paravertebral degeneration.