General and Spine-Specific Sarcopenia in Adult Spinal Deformity: a Narrative Overview of Current Strengths and Limitations

Study Design Narrative Review. Objectives Recent studies have separated assessment of sarcopenia into two main categories within spine surgery: (1) general sarcopenia assessing systemic muscle degeneration and (2) spine-specific sarcopenia assessing muscle degeneration within the more localized paraspinal musculature. We sought to highlight challenges in optimizing outcomes for adult spinal deformity (ASD) patients with sarcopenia and evaluate the effectiveness of using general and spine-specific sarcopenia metrics for prognostication. Methods We evaluated the relationship between sarcopenia and surgical outcomes in ASD, explored methods for assessing sarcopenia, and provided recommendations for managing ASD patients with consideration of sarcopenia based on literature review. Global and spine-specific sarcopenia assessment approaches were compared, emphasizing the impact of diagnostic methods, such as MRI and clinical performance tests, on outcome prediction. Results The large variability in sarcopenia measurement methods significantly affected its prognostic utility in ASD treatment. Studies using the psoas muscle to define global sarcopenia revealed mixed results for prediction. Meanwhile, assessments focusing on fatty infiltration of paraspinal muscles showed stronger correlations with complications than general sarcopenia markers. Conclusion Standardizing sarcopenia assessment in ASD is essential to facilitating its integration into clinical practice. Assessments focusing on paraspinal muscle quality demonstrated stronger associations with complications than general sarcopenia markers, underscoring the dissociation between systemic and spine-specific muscle health. Hence, future studies should refine sarcopenia metrics for spine-specific assessment as opposed to global metrics. Research should also be done to optimize interventions specifically targeting spinal sarcopenia to potentially enhance surgical outcomes. Adopting consistent, targeted sarcopenia evaluation can contribute to safer, more effective treatment pathways for ASD patients.