Special Poster Session 51st International Society for the Study of the Lumbar Spine Annual Meeting 2025

Introduction: Paraspinal muscle (PM) quality is a valuable metric for spine patients, correlating with spinal degeneration, low back pain, and poor surgical outcomes. The novel Paraspinal Muscle Quality (PMQ) score, which normalizes lean muscle T2 intensity to cerebrospinal fluid (CSF) on MRI, offers an assessment of PM quality beyond fatty infiltration and cross-sectional area. While PMQ is associated with age and low back pain, its relationship to patient function remains unclear. This study aims to establish its association with physical performance and frailty in spine patients.

Methods: Patients who underwent lumbar spinal fusion surgery from July 2022 to October 2024 were retrospectively analyzed. Physical performance was measured using the Short Physical Performance Battery (SPPB), which evaluates balance, gait speed, and chair stands, each scoring up to 4 points for a total score range of 0–12. Poor physical performance was defined as SPPB ≤ 7 as per guidelines. Patients were classified as not frail (0–2 components), or frail (3 or more) based on the Fried Frailty Phenotype, assessing frailty through five criteria: unintentional weight loss, grip strength, exhaustion, low activity, and slowness. Erector spinae and multifidus muscles were segmented at the L4 upper endplate on axial T2-weighted MRI, with fat and muscle areas calculated using automated thresholding (Figure 1). A CSF region of interest was set at the same axial level or the closest possible level if stenosis was present. The PMQ score was calculated as the ratio of lean muscle to CSF intensity (range: 0–1). Linear regression analyzed the association between PMQ and SPPB, and logistic regression analyzed the association between PMQ and frailty. All regression analyses were adjusted for age, sex, and BMI.

Results: A total of 171 patients (48.0% female) with a mean age of 61 ± 14 years were included. Mean PMQ scores were 0.26 ± 0.13 for multifidus and 0.22 ± 0.10 for erector spinae. Poor physical performance was detected in 15.2% of patients, while 11.7% were classified as frail per the Fried Frailty Phenotype. Multifidus PMQ was a significant predictor of both poor physical performance and frailty, with odds ratios of 1.04 (95% CI: 1.00–1.08, p = 0.049) and 1.05 (95% CI: 1.01–1.09, p = 0.011) per 0.01 increase, respectively. In contrast, erector spinae PMQ showed no significant association with either outcome, yielding odds ratios of 1.03 (95% CI: 0.98–1.08, p = 0.207) for physical performance and 1.04 (95% CI: 0.99–1.09, p = 0.043) for frailty per 0.01 increase.

Discussion: The significant association between multifidus PMQ and both frailty and physical performance underscores its value as an indicator of musculoskeletal aging in spine patients. This finding highlights PMQ’s applicability in clinical assessments and research, offering a practical tool for identifying at-risk patients. Future studies should explore the predictive value of PMQ for outcomes in spine surgery, as it may offer insights into patient resilience, recovery, and long-term surgical success. Incorporating PMQ could thus aid in tailoring interventions and optimizing care strategies for aging spine patients.