Clarifying the impact of spine-specific sarcopenia and generalized sarcopenia on clinical features in patients with lumbar degenerative diseases.

Background: The pathogenesis of paraspinal degeneration and sarcopenia, which is characterized by the decrease in generalized muscle quality and quantity, may be different in patients with lumbar degenerative diseases (LDD). In addition, the impact of them on the clinical features of LDD and their interaction are still unclear.

Purpose: To investigate the impact of generalized and spine-specific sarcopenia on the clinical features of patients with LDD and further examine the mediating role of paraspinal muscles STUDY DESIGN: A retrospective analysis of a prospective, nonrandomized cohort dataset.

Patient Sample: A total of 285 patients with LDD aged over 50 years were enrolled.

Outcome Measures: Sarcopenia was defined when low appendicular muscle mass was present in combination with low muscle strength or low physical performance, and spine-specific sarcopenia was designated below the gender median value of the total rfCSA of the MF at the L3/4-L5/S1 levels. Demographic variables and clinical features including reported outcome measures, spine sagittal parameters, paraspinal muscle parameters and imaging grading system.

Methods: Difference analysis was used to compare the differences between groups in demographic variables and clinical features. Linear regression models were used to evaluate the association between spine-specific and generalized sarcopenia and clinical features. Additionally, mediation analysis was employed to explore the role of paraspinal muscles in the pathway through which generalized sarcopenia affects clinical features.

Results: The generalized-sarcopenia patients exhibited significantly higher scores for VAS-back (p=.03), VAS-leg (p=.038), ODI (p<.001), SVA (p=.011) and tPfirrmann (p<.001), while significantly lower scores were observed for JOA (p=.001), TK (p<.001), LL (p=.005), and tDHI (p=.002). In the subsequent analysis, 36 of subjects were in the SSGS (spine-specific and generalized sarcopenia) group, 123 were in the NSSNGS (non-spine-specific and nongeneralized sarcopenia) group, 19 were in the NSSGS group and 107 were in the SSNGS group. Compared to the NSSNGS group, the SSGS group exhibited significantly lower JOA scores (p<.001), higher ODI scores (p=.003), reduced TK (p=.005), reduced LL (p=.005), increased SVA (p<.001), and a significantly higher tPfirrmann grading (p=.002). In Multiple linear regression analysis, the NSSNGS group exhibited significantly higher JOA, TK, LL, and tDHI values, with increases of 4.15 (p<.001), 8.87 (p<.001), 14.14 (p<.001), and 0.11 (p=.012) times than SSGS group, respectively, along with significantly lower ODI (B=-11.44, p=.006), SVA (B =-44.96, p<.001), and tPfirrmann grading (B=-2.29, p=.001). The mediation analysis indicated that paraspinal muscles play an important role in the association between generalized sarcopenia and LL (effect size=-1.330, 95% CI: -2.748, -0.304), as well as tPfirrmann grading (effect size=0.246, 95% CI: 0.458, 0.524).

Conclusions: Sarcopenia has an adverse impact on the clinical characteristics of LDD patients, particularly when both generalized and paraspinal degeneration coexist. It's important to highlight the significant role of paraspinal muscles, as well as the various mechanisms involved, in the relationship between sarcopenia and clinical features.