Characteristic of Paraspinal Muscle Change in Coronal Sub-type of Degenerative Lumbar Scoliosis and its Potential Clinical Significance

Abstract

Objective: Clarifying paraspinal muscle (PM) change in degenerative lumbar scoliosis (DLS) is positive to evaluate the progression of scoliosis. This research compares the characteristic of PM change among different coronal sub-types of DLS and explores its potential clinical significance.

Methods: A total of 84 DLS patients between June 2019 to December 2021 were retrospectively analyzed. Patients were classified into three types based on the coronal balance distance (CBD): Type A, CBD <3 cm; Type B: C7 Plumb Line (C7PL) shifted to the concave side of the curve, and CBD >3 cm; Type C: C7PL shifted to the convex side of the curve, and CBD >3 cm. Fat infiltration rates in the multifidus (MS) and erector spinae (ES) at the apex of the main and fractional curves, and spinopelvic parameters were analyzed statistically. Pearson's or Spearman's correlation was applied to analyze the correlation between asymmetric degree of PM change and these parameters in three types.

Results: There were 62 cases with coronal sub-Type A, 6 cases with Type B, and 16 cases with Type C. Patients in Type B and C demonstrated higher fat infiltration in MS on the concave side of both the main and fractional curves when compared to those in Type A. The asymmetric degree of ES change was positively correlated with CBD at the apex of the main curve in Type B and at the apex of the fractional curve in Type C respectively, and that of MS was positively correlated with apical vertebral rotation, while negatively strong-correlated with pelvic incidence and sacral slope in Type C.

Conclusion: PM fatty infiltration presented difference among varied coronal sub-types of DLS patients. The CBD in Type B and C patients was correlated with the asymmetric degree of ES change.

Keywords: Asymmetric degree; Bony structural parameters; Degenerative Lumbar scoliosis; Fat infiltration; Paraspinal muscle.

FIGURE 1

Radiographs showing three sub‐types: Type A (A, D) shows CBD 16.19 mm, AVT 25.91 mm, Cobb Angle 28°, TLK 10°, LL 21°, SVA 65.81 mm, SS 23°, PI 54°. Type B (B, E) shows CBD 31.29 mm, AVT 19.70 mm, Cobb Angle 33°, TLK 23°, LL 42°, SVA −8.13 mm, SS 41°, PI 71°; Type C (C, F) showed CBD 52.95 mm, AVT 49.90 mm, Cobb Angle 33°, TLK 11°, LL 22°, SVA 32.42 mm, SS 19°, PI 41°.

FIGURE 2

Muscle measurements using ImageJ. MS, multifidus; ES, erector spinae; FIA, fat infiltration area. Choosing the 8‐bit image (A). Using the threshold tool of the program, the red area was measured as FIA (B). The regions of interest were outlined with a graphic cursor (C).

FIGURE 3

MRI showing the apex of the primary curve and fractional curve of the three sub‐types. Type A (A, D) shows L1/2, L4/5. Type B (B, E) shows L2/3, L5/S1. Type C (C, F) shows L1/2, L5/S1.

FIGURE 4

Graph showing the correlation between asymmetric degree in ES and AVR at the apex of the fractional curve (A), and that in MS and TLK at the apex of the main curve in Type A (B). ES, erector spinae; AVR, apical vertebral rotation; MS, multifidus; TLK, thoracolumbar kyphosis.

FIGURE 5

Graph showing the correlation between asymmetric degree in ES and CBD at the apex of the main curve in Type B. ES, erector spinae; CBD, coronal balance distance.

FIGURE 6

Graph showing the correlation between asymmetric degree in ES and CBD at the apex of the fractional curve (A), and that in MS and PI, SS, AVT, AVR at the apex of the fractional curve in Type C (B‐E). ES, erector spinae; CBD, coronal balance distance; MS, multifidus; PI, pelvic incidence; SS, sacral slope; AVT, apical vertebral translation; AVR, apical vertebral rotation.