Defining Threshold values of Paraspinal Sarcopenia in Patients with Degenerative Lumbar Diseases

Introduction Emerging evidence shows that paraspinal sarcopenia is closely linked to adverse clinical outcomes in degenerative lumbar diseases (DLDs), including degenerative spinal deformity (DSD) and degenerative lumbar stenosis (DLS). However, its definition remains controversial, and precise diagnostic thresholds have yet to be established. Moreover, diagnostic criteria for paraspinal sarcopenia may differ across these DLD subtypes. Methods Patients with DLD were prospectively enrolled. Clinical outcomes included the SRS-22 and visual analog scale scores (VAS) for back pain and leg pain. Fat infiltration rate (FI%) of multifidus muscle was used to assess muscle mass loss. Endurance time (ET) and evaluating muscle maximal exert (MVE) were evaluated to determine paraspinal muscle performance and strength. Threshold values were determined by obtaining the upper or lower quartiles of measured data. Further, distinct and sex-specified threshold values for paraspinal sarcopenia were specifically established for each group. Furthermore, the predictive accuracy of paraspinal sarcopenia measurements for quality of life was assessed by calculating the area under the curve (AUC). Results A total of 342 patients enrolled in this study. The threshold values for paraspinal sarcopenia in DSD were: MF FI%>45%, MVE < 70N, and ET < 7.1s for female; MF FI%>31%, MVE < 86N, and ET < 5.9s for male. The Threshold value for paraspinal sarcopenia in DLS were: MF FI%>19.1%, MVE < 90N, and ET < 15s for females; MF FI%>25%, MVE < 106N, and ET < 17s for males. DSD patients with paraspinal sarcopenia had impaired HRQoL ( P  = 0.004). The thresholds of paraspinal sarcopenia in DSD for worse back pain and SRS-22 scores were good with an AUC of 0.869 and 0.887. Conclusions Threshold values were obtained using paraspinal muscle data from patients with DSD and DLS, respectively. DSD patients with paraspinal sarcopenia exhibited more advanced degenerative spinal changes and poorer quality of life. These findings provide reference values for identifying patients with paraspinal sarcopenia.