Relationship Between Low Back Pain and the Size and Density of the Erector Spinae Muscle and Multifidus Muscle Using CT Imaging in a Selected Community-Based Population

STUDY DESIGN: Case-control study (retrospective comparative study). OBJECTIVES: The purpose of this study was to define the relationship between low back pain (LBP) and the cross-sectional area (CSA) and density of the erector spinae muscle (ESM) and isolated multifidus muscle (IMM) on computed tomography (CT) scans of patients with a chief complaint other than LBP. SUMMARY OF LITERATURE REVIEW: Most previous studies have focused on radiographic data from patients with a chief complaint of LBP, rather than on radiographic data from patients with a chief complaint other than LBP. MATERIALS AND METHODS: This retrospective study included 475 patients who underwent CT scans between January 1, 2010 and December 31, 2010. The CSA and density of the ESM, IMM, and the psoas muscle (PM) were obtained. All measurements were calculated as the ratio of each muscle. The relationships between the CSA of each muscle and both types of LBP were analyzed. RESULTS: The ESM-to-PM ratio in terms of density was 1.227±0.797 in the LBP group and 0.645±0.732 in the non-LBP group (p=0.174). The IMM-to-PM ratio in terms of density was 0.664±0.515 in the LBP group and 0.806±0.518 in the non-LBP group (p=0.007). CONCLUSIONS: The IMM was more relevant to LBP than the ESM of the back, and density was more relevant to LBP than the CSA of regular muscles. The IMM was more useful than the ESM for analyzing LBP.

Comparison of the Extent of Degeneration among the Normal Disc, Immobilized Disc, and Immobilized Disc with an Endplate Fracture

BACKGROUND: This study attempts to prove a cause and effect relationship between spine immobilization following posterior fixation for unstable burst fractures and degeneration observed following hardware removal. METHODS: We enrolled 57 patients (259 intervertebral discs [IVDs]) who underwent only posterior instrumentation without fusion for thoracolumbar and lumbar unstable burst fractures. We arbitrarily named the IVD that has an endplate fracture after immobilization using pedicle screws as the fractured endplate and immobilized disc (FEID), the IVD that has no endplate fracture after immobilization using pedicle screws as the nonfractured endplate and immobilized disc (NFEID), and the IVD that has no endplate fracture and no immobilization instrumentation as the normal disc (ND). At 2 years after implant removal, magnetic resonance imaging (MRI) was performed again for comparison. The extent of disc degeneration was classified using the Pfirrmann classification system. RESULTS: FEIDs were present in 67 levels, NFEIDs in 78 levels, and NDs in 114 levels. According to the Pfirrmann classification, 7.9% of the NDs, 32.1% of the NFEIDs, and 43.3% of the FEIDs were more degenerated at 2 years after implant removal. The FEIDs and NFEIDs were more degenerated than the NDs and the FEIDs were more degenerated than the NFEIDs at statistically significant levels (p < 0.001 for both). CONCLUSIONS: Spine immobilization with transpedicular screws has a significant influence on disc degeneration, and an endplate fracture accelerates the degeneration process.