Study Design
A retrospective diagnostic accuracy study was conducted using internal training and temporal validation cohorts.
Purpose
This study aimed to develop and validate sex-specific diagnostic nomograms for sarcopenia in patients with degenerative lumbar disease (DLD), based on body mass index (BMI), hand-grip strength (HGS), and computed tomography (CT)–derived lumbar muscle indices. Overview of Literature: The Asian Working Group for Sarcopenia (AWGS) 2019 algorithm requires appendicular skeletal muscle mass (ASM) measurement by dual-energy X-ray absorptiometry or bioimpedance analysis together with HGS and a physical performance test. These measurements are not always feasible in spine clinics, although a preoperative lumbar CT is routinely available.
Methods
A training set of 196 patients scheduled for lumbar surgery and a temporal validation set of 150 patients with DLD were analyzed. Sarcopenia was diagnosed according to the AWGS 2019 criteria. Sex-specific multivariable logistic regression was performed using BMI, HGS, psoas muscle index, paraspinal muscle index (PaMI), and gluteal muscle index (GMI), and the resulting models were translated into nomograms. Discrimination was assessed by the area under the receiver operating characteristic curve (AUC), calibration by calibration plots and mean absolute error (MAE), and the optimal cut-off was identified using the Youden index.
Results
The prevalence of sarcopenia was 62.2% (122/196) in the training set and 58.0% (87/150) in the validation set. In the training set, sarcopenic patients had significantly lower BMI (23.7±3.7 vs. 27.0±3.3 kg/m2), HGS (20.3±8.0 vs. 29.2±30.5 kg), PaMI (8.7±5.4 vs. 13.9±8.0), and GMI (26.1±5.7 vs. 30.9±6.2) than non-sarcopenic patients (all p<0.05). On validation, the male nomogram achieved an AUC of 0.958 with an MAE of 0.040, and the female nomogram achieved an AUC of 0.830 with an MAE of 0.021. The Youden index was 0.78 for males and 0.59 for females.
Conclusion
Sex-specific nomograms based on BMI, HGS, and CT-derived lumbar muscle indices provided accurate diagnosis of sarcopenia in patients with DLD without requiring whole-body ASM measurement or a physical performance test, offering a practical screening tool in the spine clinic.

Objective
To investigate the association of quantitative paraspinal muscle measurements to the Oswestry disability index (ODI) in patients with lumbar spondylolisthesis.
Materials and Methods
Ninety two patients (mean age, 61.6 years; male, mean age, 71.8 years ; female; mean body mass index [BMI], 24.9 kg/m² ) who had undergone lumbar fusion due to spondylolisthesis with available selfcompleted postoperative ODI were included. The total cross-sectional area (CSA) and functional CSA (FCSA; i.e., area containing only lean muscle tissue) of the paraspinal muscle group (multifidus and erector spinae muscles) and the psoas muscles were measured at L2–L3, L3–L4, and L4–L5 disc levels each on preoperative magnetic resonance imaging (MRI) and the sum of areas at each level served as representative values for each muscle. The FCSA/total CSA ratio and the skeletal muscle index (SMI=muscle area [cm² ]/patient height2 [m² ]) were calculated. Pearson’s correlation analyses were performed to evaluate the relationship between preoperative paraspinal muscle measurements and postoperative ODI.
Results
Quantitative values of low paraspinal muscle showed significant correlation with high ODI values. As a result of this study, the preoperative paraspinal muscle was quantified in the group of patients undergoing spinal fusion. Patients with low value in CSA and FCSA of paraspinal muscle could observe the tendency to transition to low clinical outcomes. Therefore, quantitative values of surrounding muscles are factors affecting clinical outcomes of patients undergoing spinal surgery Conclusion: Smaller muscle bulk (total CSA) of psoas muscles and lean muscle mass (FCSA) of paraspinal muscle group and psoas muscles combined on preoperative MRI were associated with significant postoperative disability based on ODI in patients with lumbar spondylolisthesis.