Extent of fatty infiltration in lumbar paraspinal muscles in adults with degenerative scoliosis: segmental differences in muscle involvement.

PURPOSE

With increased life expectancy, age-related spinal disorders such as adult degenerative scoliosis (ADS) are becoming more prevalent. However, few studies have comprehensively evaluated the role of lumbar paraspinal muscles in the pathogenesis of ADS. This study aimed to (1) systematically review current literature on the association between paraspinal muscles and ADS and (2) compare lumbar paraspinal muscle fatty infiltration between age- and sex-matched individuals with and without ADS, stratified by treatment type.

METHODS

For the first part of the study, a systematic literature review was conducted using PubMed/MEDLINE databases, following PRISMA guidelines, to identify studies on the role of paraspinal muscles in ADS. For the second part, a total of 145 participants were evaluated: 40% (n = 58) were controls, 32.4% (n = 47) had conservatively managed ADS, and 27.6% (n = 40) had surgically treated ADS. Fatty infiltration of the multifidus, erector spinae, and psoas muscles was assessed via lumbar spine magnetic resonance imaging at three curve locations: apex, above the apex, and below the apex.

RESULTS

Compared with controls, patients with ADS exhibited significantly higher fatty infiltration in the multifidus, erector spinae, and psoas muscles on the concave and convex sides of the curve. Logistic regression analysis revealed that each one-point increase in fatty infiltration score of the concave-sided multifidus and psoas at the apex was associated with a 2.3-fold and 4.1-fold increased likelihood of having ADS, respectively. Additionally, a one-point increase in fatty infiltration in the concave-sided psoas above the apex and the convex-sided psoas below the apex was associated with 6.9-fold and 2.7-fold increased odds of ADS, respectively.

CONCLUSION

Fatty infiltration in the psoas muscle may contribute to the early development of ADS, while increased fatty infiltration in the concave-sided multifidus at the apex may influence surgical decision-making. Comprehensive assessment of lumbar paraspinal muscles is essential for optimizing management strategies in patients with ADS.