Oscillatory work and the step that generates force in single myofibrils from rabbit psoas.

The elementary molecular step that generates force by cross-bridges (CBs) in active muscles has been under intense investigation in the field of muscle biophysics. It is known that an increase in the phosphate (Pi) concentration diminishes isometric force in active fibers, indicating a tight coupling between the force generation step and the Pi release step. The question asked here is whether the force generation occurs before Pi release or after release. We investigated the effect of Pi on oscillatory work production in single myofibrils and found that Pi-attached state(s) to CBs is essential for its production. Oscillatory work is the mechanism that allows an insect to fly by beating its wings, and it also has been observed in skeletal and cardiac muscle fibers, implying that it is an essential feature of all striated muscle types. With our studies, oscillatory work disappears in the absence of Pi in experiments using myofibrils. This suggests that force is generated during a transition between steps of oscillatory work production, and that the states involved in force production must have Pi attached. With sinusoidal analysis, we obtained the kinetic constants around the Pi release steps, established a CB scheme, and evaluated force generated (and supported) by each CB state. Our results demonstrate that force is generated before Pi is released, and the same force is maintained after Pi is released. Stretch activation and/or delayed tension can also be explained with this CB scheme and forms the basis of force generation and oscillatory work production.

Preoperative low muscle mass and early postoperative outcomes in children undergoing living donor liver transplantation: A retrospective study.

Low skeletal muscle mass may develop in children with end-stage liver disease, affecting postoperative outcomes. We retrospectively investigated whether preoperative low muscle mass was associated with early postoperative outcomes in pediatric patients undergoing living donor liver transplantation (LDLT). Electronic medical records of children (age below 12 y) who underwent LDLT between February 1, 2007, and January 31, 2018, were reviewed. The cross-sectional areas of psoas, quadratus lumborum, and erector spinae muscles at the level of fourth-fifth lumbar intervertebral disks were measured using abdominal CT images, divided by the square of the height and were added to obtain the total skeletal muscle index (TSMI). The patients were divided into two groups according to the median TSMI in the second quintile (1859.1 mm 2 /m 2 ). Complications in the early postoperative period (within 30 d after surgery) classified as Clavien-Dindo grade 3 or higher were considered major complications. Logistic regression analyses were performed to determine the association between preoperative low muscle mass and early postoperative outcomes. In the study population of 123 patients (median age, 14 mo; range, 8-38 mo) who underwent LDLT, 29% and 71% were classified in the low (mean TSMI, 1642.5 ± 187.0 mm 2 /m 2 ) and high (mean TSMI 2188.1 ± 273.5 mm 2 /m 2 ) muscle mass groups, respectively. The rates of major complications, mechanical ventilation >96 hours, intensive care unit stay >14 days, hospital stay >30 days, and in-hospital mortality were not significantly different between the 2 groups. Additionally, adverse outcomes according to pediatric end-stage liver disease scores and sex were not significantly different between the 2 groups. In conclusion, preoperative low muscle mass defined by TSMI was not associated with early postoperative outcomes in pediatric patients undergoing LDLT.

Use of 3D-CT-derived psoas major muscle volume in defining sarcopenia in colorectal cancer.

BACKGROUND: Sarcopenia is characterized by reduced skeletal muscle volume and is a condition that is prevalent among elderly patients and associated with poor prognosis as a comorbidity in malignancies. Given the aging population over 80 years old in Japan, an understanding of malignancies, including colorectal cancer (CRC), complicated by sarcopenia is increasingly important. Therefore, the focus of this study is on a novel and practical diagnostic approach of assessment of psoas major muscle volume (PV) using 3-dimensional computed tomography (3D-CT) in diagnosis of sarcopenia in patients with CRC. METHODS: The subjects were 150 patients aged ≥ 80 years with CRC who underwent primary tumor resection at Juntendo University Hospital between 2004 and 2017. 3D-CT measurement of PV and conventional CT measurement of the psoas major muscle cross-sectional area (PA) were used to identify sarcopenia (group S) and non-sarcopenia (group nS) cases. Clinicopathological characteristics, operative results, postoperative complications, and prognosis were compared between these groups. RESULTS: The S:nS ratios were 15:135 for the PV method and 52:98 for the PA method. There was a strong positive correlation (r = 0.66, p < 0.01) between PVI (psoas major muscle volume index) and PAI (psoas major muscle cross-sectional area index), which were calculated by dividing PV or PA by the square of height. Surgical results and postoperative complications did not differ significantly in the S and nS groups defined using each method. Overall survival was worse in group S compared to group nS identified by PV (p < 0.01), but not significantly different in groups S and nS identified by PA (p = 0.77). A Cox proportional hazards model for OS identified group S by PV as an independent predictor of a poor prognosis (p < 0.05), whereas group S by PA was not a predictor of prognosis (p = 0.60). CONCLUSIONS: The PV method for identifying sarcopenia in elderly patients with CRC is more practical and sensitive for prediction of a poor prognosis compared to the conventional method.

Phase Angle but Not Psoas Muscle Predicts Nutritional Risk and Prognosis in Males with Hepatocellular Carcinoma.

Despite those with hepatocellular carcinoma (HCC) being at increased risk of malnutrition, there is a notable absence of practical approaches for nutritional assessment in clinical practice. We investigated the usefulness of phase angle (PhA) and Total Psoas Area Index (TPAI) for indicating nutritional risk and HCC prognosis. Weight, height, body mass index (BMI), adductor pollicis muscle thickness (APMT), and handgrip strength (HGS) were assessed. The Nutritional Risk Index (NRI) was calculated. Body composition was assessed using bioimpedance spectroscopy and magnetic resonance imaging. The Child-Turcotte-Pugh (CTP) score and Barcelona-Clinic Liver Cancer (BCLC) classification determined the prognosis. Fifty-one males with HCC were enrolled (CTP C = 11.8%). PhA showed a moderate positive correlation with APMT (r = 0.450; p < 0.001) and HGS (r = 0.418; p = 0.002) and a weak positive correlation with TPAI (r = 0.332; p = 0.021). PhA had a strong positive correlation with NRI (r = 0.614; p < 0.001). Mean PhA values were significantly different according to disease severity (CTP C p = 0.001, and BCLC D p = 0.053). TPAI had no significant correlation with HGS, CTP, or BCLC. PhA was a superior approach for predicting nutritional risk and prognosis in HCC than TPAI. Lower PhA is associated with disease progression, lower muscle mass and function, greater severity of nutritional risk, and increased mortality in HCC.

Quantifying cup overhang after total hip arthroplasty: standardized measurement using reformatted computed tomography and association of overhang distance with iliopsoas impingement.

OBJECTIVES: Currently, there is no standardized measurement method for evaluating cup overhang (CO) in patients undergoing total hip arthroplasty (THA). We propose a novel, standardized method of measuring overhang distance in patients following primary total hip arthroplasty (THA) on computed tomography (CT) images after multiplanar reformation and compare it to a previously proposed measurement method on sagittal CT images. MATERIALS AND METHODS: This retrospective study included patients who underwent primary THA with an anterior approach. Patients with cup overhang (CO) and iliopsoas impingement (IPI) were identified by clinical and imaging data. Uncorrected overhang distance (ODu) was evaluated on orthogonal sagittal CT images while corrected overhang distance (ODc) was evaluated on reformatted sagittal CT images corrected for pelvic rotation and aligned with the plane of the cup face. RESULTS: Out of 220 patients with THA, 23 patients (10.4%) with CO and 16 patients (7.3%) with IPI were identified. CO was significantly associated to IPI (p < 0.001). The inter- and intrareader agreement was almost perfect for ODc (κ = 0.822, κ = 0.850), whereas it was fair and moderate for ODu (κ = 0.391, κ = 0.455), respectively. The discriminative ability of ODc was excellent (area under the curve (AUC) = 0.909 (95% confidence interval (CI) 0.784-1.000)) in the receiver operating characteristic analysis. Conversely, AUC for ODu was poor, measuring 0.677 (95% CI 0.433-0.921). CONCLUSION: We implemented a novel measurement method for CT images reformatted at the plane of the cup face to assess overhang distance in patients with CO following THA. CLINICAL RELEVANCE STATEMENT: While further validation is necessary, the proposed method is characterized by its high reproducibility and might be used to predict the occurrence of iliopsoas impingement in patients with cup overhang following total hip arthroplasty. KEY POINTS: • A novel, standardized method of measuring cup overhang distance in patients following primary total hip arthroplasty on CT images is proposed. • Cup overhang was associated to iliopsoas impingement. The proposed method was reproducible and showed excellent prediction of iliopsoas impingement in patients with cup overhang. • This method can be implemented in clinical practice when assessing CT images of patients with cup overhang for iliopsoas impingement.

Psoas muscle area is associated with prognosis in elderly patients with hip fracture.

INTRODUCTION: Sarcopenia is a key predictor of prognosis in patients with hip fractures. This study utilized computed tomography (CT) scan (1) to determine the association between psoas muscle cross-sectional area (CSA) and mortality, along with other muscles, and (2) to confirm the correlation between muscle CSA and appendicular lean mass (ALM) measured using DXA in elderly patients with hip fracture. MATERIALS AND METHODS: Patients who were aged ≥ 50 years and underwent surgical treatment for hip fracture were eligible for this study. After a series of exclusion criteria, 217 female patients were included. Patient data, including clinical characteristics, such as body mass index (BMI), CSA, and ALM, were retrospectively collected. The Kaplan-Meier survival method and Cox proportional hazards regression analysis were used for the statistical analyses. The correlation between CSA/BMI and ALM was also assessed. RESULTS: Patients in the lowest quartile of psoas muscle CSA/BMI had shorter survival times than those in the other quartiles. When the Cox proportional hazards regression analysis was adjusted for multiple variables, the lowest quartile of the CSA/BMI of the psoas was a risk factor for mortality. The CSA/BMI of the psoas showed the highest correlation coefficient. The CSA/BMI ratio of the other muscles showed a moderately positive correlation with ALM. CONCLUSION: The CSA of the psoas is associated with prognosis in elderly patients with hip fractures and shows a moderately positive correlation with ALM. Hence, the CSA of psoas is useful for predicting survival and muscle mass in elderly patients with hip fractures.

Comparison of different 2D muscle indexes measured at the level of the 3rd lumbar vertebra in survival prediction in patients with renal cell carcinoma.

BACKGROUND: Low computed tomography (CT)-determined muscle mass, commonly determined with height-adjusted muscle indexes (MIs), predicts worse survival in several cancers and has been suggested as a prognostic assessment tool. Although several MIs measured at the level of the 3rd lumbar vertebra (L3) are commonly used, it remains unestablished how different L3-determined MIs perform in survival prognostication compared to each other. The objective of this study was to investigate the performance of different MIs for survival prognostication in renal cell carcinoma (RCC). METHODS: We retrospectively enrolled 214 consecutive patients with RCC. We determined three L3-MIs (psoas muscle index (PMI), psoas muscle index and erector spinae index (PMI+ESI), and whole skeletal muscle index (SMI)) from preoperative CT scans. Categorization of those with low and normal muscle mass was based on the Youden Index sex-specific MI cut-offs. We determined sensitivity, specificity, and accuracy metrics for predicting 1-year, 5-year, and overall survival (OS) using Cox regression models. RESULTS: Low PMI, PMI+ESI, and SMI significantly predicted decreased 1-year, 5-year, and OS in uni- and multivariate models. PMI+ESI and SMI were more accurate than PMI in males, and PMI and PMI+ESI were more accurate than SMI in females in the prediction of 1-year survival. However, there were no differences in accuracies between MIs in 5-year and OS prediction. INTERPRETATION: PMI+ESI performed well overall in short-term prognostication, but there were no differences between the MIs in long-term prognostication. We recommend the use of PMI+ESI for muscle evaluation, particularly when SMI cannot be evaluated.

Changes in skeletal muscle function during chemotherapy and related factors in patients with acute leukemia.

INTRODUCTION: Skeletal muscle function is an important prognostically relevant indicator in patients with acute leukemia (AL), but skeletal dysfunction during chemotherapy is not well understood. This study aimed to investigate the factors that influence changes in skeletal muscle function from before the start of chemotherapy to before allogeneic hematopoietic stem cell transplantation (allo-HSCT). METHODS: This was a retrospective cohort study that included 90 patients with AL who underwent chemotherapy before transplantation to perform allo-HSCT (men, 67.3%; median age, 53 years). The outcome measure was defined as changes in skeletal muscle function from before chemotherapy to before allo-HSCT, and was assessed by measuring the psoas muscle index (PMI) as skeletal muscle quantity and computed tomography values (CTV) as skeletal muscle quality using a computed tomography scanner. We examined the differences in PMI and CTV before chemotherapy and allo-HSCT, and the factors associated with changes in PMI. RESULT: The mean PMI for before chemotherapy and allo-HSCT were 4.6 ± 1.4 cm2/m2 and 4.0 ± 1.3 cm2/m2 and significant differences were observed (p < 0.001). However, the mean CTV before chemotherapy and allo-HSCT were 47.3 ± 4.5 HU and 47.4 ± 5.0 HU, respectively, and no significant differences were found (p = 0.798). In stepwise multiple regression analysis, age and sex were identified as factors related to changes in PMI (age, p = 0.019; sex, p = 0.001). CONCLUSION: We found that skeletal muscle quantity decreased during chemotherapy in patients with AL and was influenced by male sex and older age. TRIAL REGISTRATION NUMBER:   TRIAL REGISTRATION NUMBER: 34-096(11,243). Date of registration: September 11, 2023.

Three-dimensional numerical schemes for the segmentation of the psoas muscle in X-ray computed tomography images.

The analysis of the psoas muscle in morphological and functional imaging has proved to be an accurate approach to assess sarcopenia, i.e. a systemic loss of skeletal muscle mass and function that may be correlated to multifactorial etiological aspects. The inclusion of sarcopenia assessment into a radiological workflow would need the implementation of computational pipelines for image processing that guarantee segmentation reliability and a significant degree of automation. The present study utilizes three-dimensional numerical schemes for psoas segmentation in low-dose X-ray computed tomography images. Specifically, here we focused on the level set methodology and compared the performances of two standard approaches, a classical evolution model and a three-dimension geodesic model, with the performances of an original first-order modification of this latter one. The results of this analysis show that these gradient-based schemes guarantee reliability with respect to manual segmentation and that the first-order scheme requires a computational burden that is significantly smaller than the one needed by the second-order approach.

Psoas mass index at the level of the third lumbar vertebra on computed tomography is a prognostic predictor for metastatic castration-sensitive prostate cancer.

BACKGROUND: Computed tomography-defined low skeletal muscle mass is associated with oncological outcomes in patients with prostate cancer. However, its association with the outcomes of hormone-treated metastatic castration-sensitive prostate cancer remains unclear. We aimed to determine the association between metastatic castration-sensitive prostate cancer and psoas muscle parameters. METHODS: We retrospectively reviewed 121 patients with N1 and/or M1 metastatic castration-sensitive prostate cancer who underwent primary androgen deprivation therapy between 2005 and 2021, either by administration of luteinizing hormone-releasing hormone agonist/antagonist or by surgical castration accompanied by bicalutamide, a first-generation antiandrogen. Before treatment administration, the psoas muscle index at the level of the third lumbar vertebra (psoas muscle area [cm2]/height2 [m2]) and the mean Hounsfield units of the psoas muscle were evaluated using non-contrast computed tomography and in relation to oncological outcomes. RESULTS: The median follow-up was 56.9 months. Furthermore, during follow-up, 82 (67.7%) and 53 (43.8%) patients progressed to castration-resistant prostate cancer and died, respectively. Multivariate analysis of castration-resistant prostate cancer-free survival and overall survival showed significant differences in the Gleason score, clinical N-stage, and psoas muscle index (median cutoff: 3.044 cm2/m2). CONCLUSIONS: Pretreatment psoas muscle index is an independent predictor of poor castration-resistant prostate cancer-free survival and overall survival in patients with N1 and/or M1 metastatic castration-sensitive prostate cancer.

The role of sarcopenia in fragility fractures of the pelvis - is sarcopenia an underestimated risk factor?

BACKGROUND: Fragility fractures of the pelvis (FFPs) represent a significant health burden, particularly for the elderly. The role of sarcopenia, an age-related loss of muscle mass and function, in the development and impact of these fractures is not well understood. This study aims to investigate the prevalence and impact of osteoporosis and sarcopenia in patients presenting with FFPs. METHODS: This retrospective study evaluated 140 elderly patients with FFPs. The diagnosis of sarcopenia was assessed by psoas muscle area (PMA) and the height-adjusted psoas muscle index (PMI) measured on computed tomography (CT) scans. Clinical data, radiological findings and functional outcomes were recorded and compared with the presence or absence of sarcopenia and osteoporosis. RESULTS: Our study cohort comprised 119 female (85.0%) and 21 (15.0%) male patients. The mean age at the time of injury or onset of symptoms was 82.26 ± 8.50 years. Sarcopenia was diagnosed in 68.6% (n = 96) patients using PMA and 68.8% (n = 88) using PMI. 73.6% (n = 103) of our study population had osteoporosis and 20.0% (n = 28) presented with osteopenia. Patients with sarcopenia and osteoporosis had longer hospital stays (p < 0.04), a higher rate of complications (p < 0.048) and functional recovery was significantly impaired, as evidenced by a greater need for assistance in daily living (p < 0.03). However, they were less likely to undergo surgery (p < 0.03) and the type of FFP differed significantly (p < 0.04). There was no significant difference in mortality rate, pre-hospital health status, age or gender. CONCLUSION: Our study highlights the important role of sarcopenia in FFPs in terms of the serious impact on health and quality of life in elderly patients especially when osteoporosis and sarcopenia occur together. Identifying and targeting sarcopenia in older patients may be an important strategy to reduce pelvic fractures and improve recovery. Further research is needed to develop effective prevention and treatment approaches that target muscle health in the elderly.

Quantification of muscle recovery in post-ICU patients admitted for acute pancreatitis: a longitudinal single-center study.

OBJECTIVES: Critically ill patients with severe pancreatitis exhibit substantial muscle wasting, which limits in-hospital and post-hospital outcomes. Survivors of critical illness undergo extensive recovery processes. Previous studies have explored pancreatic function, quality of life, and costs post-hospitalization for AP patients, but none have comprehensively quantified muscle loss and recovery post-discharge. By applying an AI-based automated segmentation tool, we aimed to quantify muscle mass recovery in ICU patients after discharge. MATERIALS: Muscle segmentation was performed on 22 patients, with a minimum of three measurements taken during hospitalization and one clinically indicated examination after hospital discharge. Changes in psoas muscle area (PMA) between admission, discharge and follow up were calculated. T-Test was performed to identify significant differences between patients able and not able to recover their muscle mass. RESULTS: Monitoring PMA shows muscle loss during and gain after hospitalization: The mean PMA at the first scan before or at ICU admission (TP1) was 17.08 cm², at the last scan before discharge (TP2), mean PMA was 9.61 cm². The percentage change in PMA between TP1 and TP2 ranged from - 85.42% to -2.89%, with a mean change of -40.18%. The maximum muscle decay observed during the stay was - 50.61%. After a mean follow-up period of 438.73 days most patients (81%) were able to increase their muscle mass. Compared to muscle status at TP1, only 27% of patients exhibited full recovery, with the majority still presenting a deficit of 31.96%. CONCLUSION: Muscle recovery in ICU patients suffering from severe AP is highly variable, with only about one third of patients recovering to their initial physical status. Opportunistic screening of post-ICU patient recovery using clinically indicated imaging and AI-based segmentation tools enables precise quantification of patients' muscle status and can be employed to identify individuals who fail to recover and would benefit from secondary rehabilitation. Understanding the dynamics of muscle atrophy may improve prognosis and support personalized patient care.

Survey of major complications after prone transpsoas surgery: an analysis of early adopters' practice.

INTRODUCTION: The prone transpsoas technique (PTP) is a modification of the traditional lateral lumbar interbody fusion approach, which was first published in the literature in 2020. The technique provides several advantages, such as lordosis correction and redistribution, single-position surgery framework, and ease of performing posterior techniques when needed. However, the prone position also leads to the movement of some retroperitoneal, vascular, and neurological structures, which could impact the complication profile. Therefore, this study aimed to investigate the occurrence of major complications in the practice of early adopters of the PTP approach. METHODS: A questionnaire containing 8 questions was sent to 50 participants and events involving early adopters of the prone transpsoas technique. Of the 50 surgeons, 32 completed the questionnaire, which totaled 1963 cases of PTP surgeries. RESULTS: Nine of the 32 surgeons experienced a major complication (28%), with persistent neurological deficit being the most frequent (7/9). Of the total number of cases, the occurrence of permanent neurological deficits was approximately 0,6%, and the rate of vascular and visceral injuries were both 0,05% (1/1963 for each case). CONCLUSION: Based on the analysis of the questionnaire responses, it can be concluded that PTP is a safe technique with a very low rate of serious complications. However, future studies with a more heterogeneous group of surgeons and a more rigorous linkage between answers and patient data are needed to support the findings of this study.

Pre-operative psoas muscle index, a surrogate for sarcopenia; as a predictor of post-esophagectomy complications.

BACKGROUND: Esophagectomy is the standard of care for curative esophageal cancer. However, it is associated with significant morbidity and mortality. Esophageal cancer is known to negatively affect the nutritional status of patients and many manifest cancer sarcopenia. At present, measures of sarcopenia involve complex and often subjective measurements. We assess whether the Psoas Muscle Index (PMI); an inexpensive, simple, validated method used to diagnose sarcopenia, can be used to predict adverse outcomes in patients after curative esophagectomy. METHODS: Multi-centre, retrospective cohort between 2010-2020, involving all consecutive patients undergoing curative esophagectomy for esophageal cancer in University Malaya Medical Centre, Sungai Buloh Hospital, and Sultanah Aminah Hospital. The cut-off value differentiating low and normal PMI is defined as 443mm2/m2 in males and 326326 mm2/m2 in females. Complications were recorded using the Clavien-Dindo Scale. RESULTS: There was no statistical correlation between PMI and major post-esophagectomy complications (p-value: 0.495). However, complication profile was different, and patients with low PMIs had higher 30-day mortality (21.7%) when compared with patients with normal PMI (8.1%) (p-value: 0.048). CONCLUSIONS: Although PMI did not significantly predict post-esophagectomy complications, low PMI correlates with higher 30-day mortality, reflecting a lower tolerance for complications among these patients. PMI is a useful, inexpensive tool to identify sarcopenia and aids the patient selection process. This alerts healthcare professionals to institute intensive physiotherapy and nutritional optimization prior to esophagectomy.

Clinical and radiographic outcomes following 120 consecutive patients undergoing prone transpsoas lateral lumbar interbody fusion.

PURPOSE: The prone transpsoas approach is a single-position alternative to traditional lateral lumbar interbody fusion (LLIF). Earlier prone LLIF studies have focused on technique, feasibility, perioperative efficiencies, and immediate postoperative radiographic alignment. This study was undertaken to report longer-term clinical and radiographic outcomes, and to identify learnings from experiential evolution of the prone LLIF procedure. METHODS: All consecutive patients undergoing prone LLIF for any indication at one institution were included (n = 120). Demographic, diagnostic, treatment, and outcomes data were captured via prospective institutional registry. Retrospective analysis identified 31 'pre-proceduralization' and 89 'post-proceduralization' prone LLIF approaches, enabling comparison across early and later cohorts. RESULTS: 187 instrumented LLIF levels were performed. Operative time, retraction time, LLIF blood loss, and hospital stay averaged 150 min, 17 min, 50 ml, and 2.2 days, respectively. 79% of cases were without complication. Postoperative hip flexion weakness was identified in 14%, transient lower extremity weakness in 12%, and sensory deficits in 10%. At last follow-up, back pain, worst-leg pain, Oswestry, and EQ-5D health state improved by 55%, 46%, 48%, and 51%, respectively. 99% improved or maintained sagittal alignment with an average 6.5° segmental lordosis gain at LLIF levels. Only intra-psoas retraction time differed between pre- and post-proceduralization; proceduralization saved an average 3.4 min/level (p = 0.0371). CONCLUSIONS: The largest single-center prone LLIF experience with the longest follow-up to-date shows that it results in few complications, quick recovery, improvements in pain and function, high patient satisfaction, and improved sagittal alignment at an average one year and up to four years postoperatively.

Cross-sectional area and fat infiltration of the lumbar spine muscles in patients with back disorders: a deep learning-based big data analysis.

PURPOSE: Validated deep learning models represent a valuable option to perform large-scale research studies aiming to evaluate muscle quality and quantity of paravertebral lumbar muscles at the population level. This study aimed to assess lumbar spine muscle cross-sectional area (CSA) and fat infiltration (FI) in a large cohort of subjects with back disorders through a validated deep learning model. METHODS: T2 axial MRI images of 4434 patients (n = 2609 females, n = 1825 males; mean age: 56.7 ± 16.8) with back disorders, such as fracture, spine surgery or herniation, were retrospectively collected from a clinical database and automatically segmented. CSA, expressed as the ratio between total muscle area (TMA) and the vertebral body area (VBA), and FI, in percentages, of psoas major, quadratus lumborum, erector spinae, and multifidus were analyzed as primary outcomes. RESULTS: Male subjects had significantly higher CSA (6.8 ± 1.7 vs. 5.9 ± 1.5 TMA/VBA; p < 0.001) and lower FI (21.9 ± 8.3% vs. 15.0 ± 7.3%; p < 0.001) than females. Multifidus had more FI (27.2 ± 10.6%; p < 0.001) than erector spinae (22.2 ± 9.7%), quadratus lumborum (17.5 ± 7.0%) and psoas (13.7 ± 5.8%) whereas CSA was higher in erector spinae than other lumbar muscles. A high positive correlation between age and total FI was detected (rs = 0.73; p < 0.001) whereas a negligible negative correlation between total CSA and age was observed (rs = - 0.24; p < 0.001). Subjects with fractures had lower CSA and higher FI compared to those with herniations, surgery and with no clear pathological conditions. CONCLUSION: CSA and FI values of paravertebral muscles vary a lot in accordance with subjects' sex, age and clinical conditions. Given also the large inter-muscle differences in CSA and FI, the choice of muscles needs to be considered with attention by spine surgeons or physiotherapists when investigating changes in lumbar muscle morphology in clinical practice.

The cross-sectional area of gluteal muscle on multiaxial CT scan as a predictor for diagnosing sarcopenia in patients with degenerative lumbar disease.

PURPOSE: This study examined the predictive value of the gluteal muscle index (GMI) for diagnosing sarcopenia in patients with degenerative lumbar disease (DLD), highlighting the need for effective diagnostic markers in this population. METHODS: This prospective observational study included 202 elderly patients scheduled for lumbar spine surgery. Muscle indices for psoas, paraspinal, and gluteal muscles were measured using multiaxial computed tomography. Sarcopenia was diagnosed per the 2019 Asian Working Group for Sarcopenia (AWGS) criteria. Statistical analysis comprised univariate and multivariate logistic regression to identify predictors of sarcopenia. RESULTS: Of patients, 77% were diagnosed with sarcopenia. The GMI and psoas muscle index (PMI) were identified as significant predictors of sarcopenia in the univariate analysis. Multivariate analysis confirmed their predictive value, with higher indices correlating with a reduced risk of sarcopenia (GMI odds ratio [OR] = 0.95, 95% confidence interval [CI] = 0.92-0.97; PMI OR = 0.95, 95% CI = 0.92-0.98, both P < .001). CONCLUSION: The GMI serves as a reliable predictor of sarcopenia in elderly patients undergoing lumbar spine surgery for DLD, suggesting a significant role of gluteal muscles in diagnosing sarcopenia. Incorporating GMI into clinical assessments is critical to better manage and diagnose sarcopenia in this population.

Preoperative and follow-up variations of psoas major muscle are related to S1 screw loosening in patients with degenerative lumbar spinal stenosis.

BACKGROUND: It was reported the paraspinal muscle played an important role in spinal stability. The preoperative paraspinal muscle was related to S1 screw loosening. But the relationship between preoperative and postoperative change of psoas major muscle (PS) and S1 pedicle screw loosening in degenerative lumbar spinal stenosis (DLSS) patients has not been reported. This study investigated the effects of preoperative and follow-up variations in the psoas major muscle (PS) on the first sacral vertebra (S1) screw loosening in patients with DLSS. METHODS: 212 patients with DLSS who underwent lumbar surgery were included. The patients were divided into the S1 screw loosening group and the S1 screw non-loosening group. Muscle parameters were measured preoperatively and at last follow-up magnetic resonance imaging. A logistic regression analysis was performed to investigate the risk factors for S1 screw loosening. RESULTS: The S1 screw loosening rate was 36.32% (77/212). The relative total cross-sectional areas and relative functional cross-sectional areas (rfCSAs) of the PS at L2-S1 were significantly higher after surgery. The increased rfCSA values of the PS at L3-S1 in the S1 screw non-loosening group were significantly higher than those in the S1 screw loosening group. The regression analysis showed male, lower CT value of L1 and longer segment fusion were independent risk factors for S1 screw loosening, and postoperative hypertrophy of the PS was a protective factor for S1 screw loosening. CONCLUSIONS: Compared to the preoperative muscle, the PS size increased and fatty infiltration decreased after surgery from L2-3 to L5-S1 in patients with DLSS after short-segment lumbar fusion surgery. Postoperative hypertrophy of the PS might be considered as a protective factor for S1 screw loosening. MRI morphometric parameters and postoperative selected exercise of PS for DLSS patients after posterior lumbar fusion surgery might contribute to improvement of surgical outcome.

Psoas attenuation is associated with early postoperative complications in geriatric patients undergoing multilevel lumbar fusion surgery for degenerative lumbar spinal stenosis.

BACKGROUND: Morphometric analysis of the psoas major muscle has shown utility in predicting postoperative morbidity in various surgical fields, but its usefulness in predicting complications in elderly patients undergoing multilevel lumbar fusion surgery has not been studied. The study aimed to investigate if psoas major parameters are independent risk factors of early postoperative complication among elderly patients. METHODS: Patients who underwent multilevel lumbar fusion for degenerative lumbar spinal stenosis (DLSS) were included. The psoas major was measured at the lumbar 3/4 intervertebral disc level in three ways on computed tomography image: psoas muscle mass index, mean muscle attenuation, and morphologic change of the psoas major. Early complications were graded using the Clavien-Dindo classification system and the Comprehensive complication index (CCI). A CCI ≥ 26.2 indicated severe complications. Logistic regression was performed to identify independent risk factors. RESULTS: This retrospective study reviewed 108 patients (mean age 70.9 years, female to male ratio 1.8:1). Complications were observed in 72.2% of patients, with allogeneic blood transfusion being the most frequent (66.7%), followed by wound infection, acute heart failure (2.8% each). Severe complications occurred in 13.9% of patients. After multivariable regression analysis, those in the lowest psoas muscle attenuation tertile had higher odds of experiencing early postoperative complications (OR: 3.327, 95% CI 1.134-9.763, p = 0.029) and severe complications (OR: 6.964, 95% CI 1.928-25.160, p = 0.003). CONCLUSION: The psoas muscle attenuation can be used as a predictor of early postoperative complications in elderly patients undergoing multilevel lumbar fusion surgery for DLSS.

Correlation between preoperative CT scan of the paraspinal, psoas, and gluteus muscles and postoperative ambulatory status in patients with femoral neck fractures.

BACKGROUND: This study aimed to investigate the relationship between femoral neck fractures and sarcopenia. METHODS: This was a retrospective analysis of 92 patients with femoral neck fractures, from September 2017 to March 2020, who were classified into high ambulatory status (HG) and low ambulatory status (LG) groups. Ambulatory status was assessed before surgery, one week after surgery, at discharge, and during the final follow-up. To evaluate sarcopenia, muscle mass and fatty degeneration of the muscles were measured using preoperative CT. An axial slice of the superior end of the L5 vertebra was used to evaluate the paraspinal and psoas muscles, a slice of the superior end of the femoral head for the gluteus maximus muscle, and a slice of the inferior end of the sacroiliac joint for the gluteus medius muscle. The degeneration of the muscles was evaluated according to the Goutallier classification. RESULTS: The cross-sectional area of the gluteus medius and paraspinal muscles was significantly correlated with ambulatory status before the injury, at discharge, and during the final follow-up. CONCLUSIONS: Measurement of the gluteus medius and paraspinal muscles has the potential to evaluate sarcopenia and predict ambulatory status after femoral neck fractures.