Assessment of fatty infiltration of the hamstring muscles in chronic proximal hamstring ruptures and effect on clinical outcomes after surgical repair: a novel application of the Goutallier classification.

INTRODUCTION: Increased time to surgery has been previously associated with poorer clinical outcomes after surgical treatment of proximal hamstring ruptures, though the etiology remains unclear. The purpose of this study was to evaluate whether degree of muscle atrophy, as assessed using the Goutallier classification system, is associated with worse outcomes following surgical treatment of chronic proximal hamstring ruptures. MATERIALS AND METHODS: This was a retrospective case series of patients who underwent repair of proximal hamstring ruptures from 2012 to 2020 with minimum 2-year follow-up. Patients were included if they underwent primary repair of a proximal hamstring rupture ≥ 6 weeks after the date of injury and had accessible preoperative magnetic resonance imaging (MRI). Exclusion criteria were allograft reconstruction, endoscopic repair, or prior ipsilateral hip surgery. Patients were administered validated surveys: the modified Harris Hip Score (mHHS) and Perth Hamstring Assessment Tool (PHAT). Fatty atrophy on preoperative MRI was independently graded by two musculoskeletal radiologists using the Goutallier classification. Multivariate regression analysis was performed to evaluate associations of preoperative characteristics with muscle atrophy, as well as mHHS and PHAT scores. RESULTS: Complete data sets were obtained for 27 patients. A majority of this cohort was male (63.0%), with a mean age of 51.5 ± 11.8 years and BMI of 26.3 ± 3.8. The mean follow-up time was 62.6 ± 23.1 months, and the mean time from injury-to-surgery was 20.4 ± 15.3 weeks. The Goutallier grading inter-reader weighted kappa coefficient was 0.655. Regression analysis demonstrated that atrophy was not significantly associated with PHAT (p = 0.542) or mHHS (p = 0.574) at latest follow-up. Increased age was significantly predictive of muscle atrophy (ß = 0.62, p = 0.005) and was also found to be a significant predictor of poorer mHHS (ß = - 0.75; p = 0.037). CONCLUSIONS: The degree of atrophy was not found to be an independent predictor of clinical outcomes following repair of chronic proximal hamstring ruptures. Increasing age was significantly predictive of increased atrophy and poorer patient-reported outcomes.

Ultrasound assessment of muscle mass and correlation with clinical outcomes in critically ill patients: a prospective observational study.

PURPOSE: Muscular atrophy implies structural and functional alterations related to muscular force production and movement. This condition has been reported to be the main reason for generalized muscle weakness; it reflects the severity of the disease and can have a profound impact on short- and long-term clinical outcomes. The purpose of this study was to determine whether muscle atrophy ultrasound parameters early predict muscle weakness, morbidity, or 28-days mortality. METHODS: This was a prospective, observational single center cohort study. Ultrasound was used to determine the cross-sectional area and muscle thickness of the rectus femoris on the first and third day of ICU stay. The main outcome was the incidence of significant muscle atrophy (≥ 10%). RESULTS: Ultrasound measurements were made in 31 patients, 58% (18/31) of which showed significant muscle atrophy. The relative loss of muscle mass per day was 1.78 at 5% per day. The presence of muscle atrophy presents increased risk for limb muscle weakness and handgrip weakness. The 28-days mortality rate was similar in both subgroups. CONCLUSION: The presence of muscle atrophy presents an increased clinical risk for the development of limb ICUAW and handgrip, although these observations were not statistically significant. The results could be used to plan future studies on this topic.

A Bioelectrical Impedance Analysis for the Assessment of Muscle Atrophy in Patients with Chronic Inflammatory Demyelinating Polyneuropathy.

Objective Muscle atrophy is observed in a subset of patients with chronic inflammatory demyelinating polyneuropathy (CIDP). Its manifestation is associated with a poor functional prognosis and poor response to immunomodulatory therapies. We evaluated muscle atrophy in patients with CIDP using a bioelectrical impedance analysis (BIA). Methods We enrolled 12 patients with CIDP for a BIA of muscle atrophy. Of these 12 patients, 10 were diagnosed with typical CIDP, 1 with multifocal acquired demyelinating sensory and motor neuropathy, and 1 with distal acquired demyelinating symmetric neuropathy. All 12 patients underwent a series of assessments and evaluations, including a BIA and computed tomography (CT). A correlation was found between the skeletal muscle mass determined by the BIA and that found using CT of the muscles. Results The BIA provided values for each patient's skeletal muscle mass index (SMI) ranging from 4.1 to 8.1 kg/m2. Four of the patients with CIDP had SMI values below the threshold for sarcopenia. CT of the patients' muscles provided scores indicating grades of muscle atrophy in the upper and lower extremities. A comparison of the outcomes from these two measures showed a good correlation between their muscle atrophy ratings (p<0.05). Conclusion We found that a BIA and muscle CT provided muscle atrophy assessments of equivalent accuracy. Therefore, a BIA can be a simple alternative to muscle CT that is suitable for regular use in daily clinical practice as a reliable tool for assessing muscle atrophy in patients with CIDP.

MRI-based 3-dimensional volumetric assessment of fatty infiltration and muscle atrophy in rotator cuff tears.

BACKGROUND: The Goutallier and Warner Classification systems are useful in determining rotator cuff reparability. Data are limited on how accurately the scapular-Y view used in both systems reflects the 3-dimensional (3-D) changes in fatty infiltration (FI) and muscle atrophy (MA). Tendon retraction in the setting of a cuff tear may also influence the perception of these changes. This study's objectives were to (1) measure the 3-D volume of the supraspinatus muscle in intact rotator cuffs, and with varying magnitudes of retraction; (2) measure the 3-D volume of FI in the supraspinatus muscle in these conditions; and (3) determine the influence of tendon retraction on measured FI and MA using the Goutallier and Warner Classification Systems. METHODS: Between August 2015 and February 2016, all shoulder magnetic resonance images (MRIs) at the Portland VA Medical Center were standardized to include the medial scapular border. MRIs and charts were reviewed for inclusion/exclusion criteria. Included MRIs were categorized into 4 groups based on rotator cuff retraction. Supraspinatus muscle and fossa were traced to create 3-D volumes. FI and MA were measured within the supraspinatus. The supraspinatus muscle was graded among 6 physicians using the Goutallier and Warner classification systems. These grades were compared to 3-D measured FI and MA. The influence of tendon retraction on the measured grades were also evaluated. RESULTS: One hundred nine patients met inclusion/exclusion criteria. Ten MRIs for each group (N = 40) were included for image analysis. Supraspinatus volume tracings were highly reproducible and consistent between tracers. Supraspinatus muscle volumes decreased while global FI and MA increased with greater degrees of tendon retraction. In muscles with less than 10% global fat, fat concentrated in the lateral third of the muscle. In muscle with more than 10% global fat content, it distributed more diffusely throughout the muscle from medial to lateral. In comparing the scapular-Y to a medial cut, there was no consistent trend in FI whereas MA was more accurate at the medial cut. CONCLUSION: Parasagittal imaging location did not significantly influence the Goutallier score; however, assessment of MA using the Warner score leads readers to perceive less MA medially regardless of the magnitude of tendon retraction. The pattern of FI within the supraspinatus muscle changes from a laterally based location around the muscle-tendon junction to a more diffuse, global infiltration pattern when the whole muscle fat content exceeds 10%.

Assessment of myofiber microstructure changes due to atrophy and recovery with time-dependent diffusion MRI.

Current clinical MRI evaluation of musculature largely focuses on nonquantitative assessments (including T1-, T2- and PD-weighted images), which may vary greatly between imaging systems and readers. This work aims to determine the efficacy of a quantitative approach to study the microstructure of muscles at the cellular level with the random permeable barrier model (RPBM) applied to time-dependent diffusion tensor imaging (DTI) for varying diffusion time. Patients (N = 15, eight males and seven females) with atrophied calf muscles due to immobilization of one leg in a nonweight-bearing cast, were enrolled after providing informed consent. Their calf muscles were imaged with stimulated echo diffusion for DTI, T1-mapping and RPBM modeling. Specifically, After cast removal, both calf muscles (atrophied and contralateral control leg) were imaged with MRI for all patients, with follow-up scans to monitor recovery of the atrophied leg for six patients after 4 and 8 weeks. We compare RPBM-derived microstructural metrics: myofiber diameter, a, and sarcolemma permeability, κ, along with macroscopic anatomical parameters (muscle cross-sectional area, fiber orientation, <θ>, and T1 relaxation). ROC analysis was used to compare parameters between control and atrophied muscle, while the Friedman test was used to evaluate the atrophied muscle longitudinally. We found that the RPBM framework enables measurement of microstructural parameters from diffusion time-dependent DTI, of which the myofiber diameter is a stronger predictor of intramuscular morphological changes than either macroscopic (anatomical) measurements or empirical diffusion parameters. This work demonstrates the potential of RPBM to assess pathological changes in musculature that seem undetectable with standard diffusion and anatomical MRI.

Iliopsoas Release in Hip Arthroscopy: Assessment of Muscle Atrophy.

Iliopsoas release is a common procedure for coxa saltans interna of the hip. The possible sequelae from this surgery have not been well studied. The purpose of this study was to determine postoperative atrophy and morphology of the cut tendon. This retrospective review included patients who underwent arthroscopic iliopsoas release and had magnetic resonance imaging of the ipsilateral hip before and after surgical intervention. Cross-sectional area measurements were obtained of the iliopsoas muscle at the level of the distal anterior inferior iliac spine as well as at the L5 vertebral pedicle in patients who had imaging that included the lower lumbar spine. Patient-reported outcomes included the modified Harris Hip Score (mHHS) and the Hip Outcome Score subscales for activities of daily living (HOS ADL) and sport (HOS Sport). A total of 44 patients met inclusion criteria for this study; 26 patients had additional advanced imaging that included the lumbar spine. The cross-sectional area of the iliopsoas at the level of the anterior inferior iliac spine decreased postoperatively by a mean of 191.4 mm2;, this difference was statistically significant (P<.0001). Mean area at the L5 pedicle was 628.9 mm2 on the released side and 1216.2 mm2 on the nonoperative side (P<.05). Mean Goutallier-Fuchs score of the released iliopsoas at the L5 pedicle was 1.3 (SD, 0.7). Mean mHHS, HOS ADL, and HOS Sport scores for patients at least 1 year postoperatively were 51, 56, and 42, respectively. [Orthopedics. 2020;43(3):e171-e176.].

Longitudinal Assessment of Quadriceps Muscle Morphology Before and After Anterior Cruciate Ligament Reconstruction and Its Associations With Patient-Reported Outcomes.

BACKGROUND: Reductions in muscle size are common after anterior cruciate ligament reconstruction (ACLR) and may contribute to suboptimal patient outcomes. However, few studies have quantified postoperative alterations in muscle quality and evaluated its associations with patient-reported function. HYPOTHESES: Rectus femoris cross-sectional area (CSA) will decrease postoperatively but improve at return to activity (RTA), rectus femoris muscle quality (percentage fat [PF]) will increase postoperatively and be greater at RTA compared with preoperative values, and rectus femoris CSA and PF will be associated with International Knee Documentation Committee (IKDC) scores at both postoperative time points. STUDY DESIGN: Case series. LEVEL OF EVIDENCE: Level 4. METHODS: A total of 26 individuals who sustained an ACL injury and underwent reconstructive surgery were evaluated preoperatively (T0), 9 weeks post-ACLR (T1), and at RTA. Rectus femoris CSA and PF were evaluated bilaterally via ultrasound imaging, and patient-reported function was assessed using the IKDC score. RESULTS: Bilateral reductions in rectus femoris CSA were noted from T0 to T1 (P < 0.01). Only the uninvolved limb returned to preoperative CSA (P = 0.80), as the involved limb failed to return to preoperative levels at RTA (P = 0.04). No significant changes in rectus femoris PF were observed across time points (P > 0.05). Lesser PF (P < 0.01) but not CSA (P = 0.75) was associated with higher IKDC score at T1. Lesser PF (P = 0.04) and greater CSA (P = 0.05) was associated with higher IKDC score at RTA. CONCLUSION: Substantial atrophy occurs bilaterally after ACLR, and the involved limb does not return to preoperative muscle size despite the patient completing rehabilitation. Quadriceps muscle morphology is associated with patient-reported function and may be an important rehabilitation target after ACLR. CLINICAL RELEVANCE: Quadriceps atrophy and poor muscle quality may contribute to suboptimal patient functioning and quadriceps dysfunction and may be important in RTA decision making. Assessing muscle morphology using ultrasound may be a feasible and clinically beneficial tool in patients after ACLR.

Automated postoperative muscle assessment of hip arthroplasty patients using multimodal imaging joint segmentation.

BACKGROUND AND OBJECTIVE: In patients treated with hip arthroplasty, the muscular condition and presence of inflammatory reactions are assessed using magnetic resonance imaging (MRI). As MRI lacks contrast for bony structures, computed tomography (CT) is preferred for clinical evaluation of bone tissue and orthopaedic surgical planning. Combining the complementary information of MRI and CT could improve current clinical practice for diagnosis, monitoring and treatment planning. In particular, the different contrast of these modalities could help better quantify the presence of fatty infiltration to characterise muscular condition and assess implant failure. In this work, we combine CT and MRI for joint bone and muscle segmentation and we propose a novel Intramuscular Fat Fraction estimation method for the quantification of muscle atrophy. METHODS: Our multimodal framework is able to segment healthy and pathological musculoskeletal structures as well as implants, and develops into three steps. First, input images are pre-processed to improve the low quality of clinically acquired images and to reduce the noise associated with metal artefact. Subsequently, CT and MRI are non-linearly aligned using a novel approach which imposes rigidity constraints on bony structures to ensure realistic deformation. Finally, taking advantage of a multimodal atlas we created for this task, a multi-atlas based segmentation delineates pelvic bones, abductor muscles and implants on both modalities jointly. From the obtained segmentation, a multimodal estimation of the Intramuscular Fat Fraction can be automatically derived. RESULTS: Evaluation of the segmentation in a leave-one-out cross-validation study on 22 hip sides resulted in an average Dice score of 0.90 for skeletal and 0.84 for muscular structures. Our multimodal Intramuscular Fat Fraction was benchmarked on 27 different cases against a standard radiological score, showing stronger association than a single modality approach in a one-way ANOVA F-test analysis. CONCLUSIONS: The proposed framework represents a promising tool to support image analysis in hip arthroplasty, being robust to the presence of implants and associated image artefacts. By allowing for the automated extraction of a muscle atrophy imaging biomarker, it could quantitatively inform the decision-making process about patient's management.

[Ultrasound Assessment of Ventilator-induced Diaphragmatic Dysfunction in Paediatrics]. / Avaliação Ecográfica da Disfunção Diafragmática Induzida pelo Ventilador em Idade Pediátrica.

INTRODUCTION: Invasive mechanical ventilation contributes to ventilator-induced diaphragmatic dysfunction, delaying extubation and increasing mortality in adults. Despite the possibility of having a higher impact in paediatrics, this dysfunction is not routinely monitored. Diaphragm ultrasound has been proposed as a safe and non-invasive technique for this purpose. The aim of this study was to describe the evolution of diaphragmatic morphology and functional measurements by ultrasound in ventilated children. MATERIAL AND METHODS: Prospective exploratory study. Children admitted to Paediatric Intensive Care Unit requiring mechanical ventilation > 48 hours were included. The diaphragmatic thickness, excursion and the thickening fraction were assessed by ultrasound. RESULTS: Seventeen cases were included, with a median age of 42 months. Ten were male, seven had comorbidities and three in seventeen had malnutrition at admission. The median time under mechanical ventilation was seven days. The median of the initial and minimum diaphragmatic thickness was 2.3 mm and 1.9 mm, respectively, with a median decrease in thickness of 13% under pressure-regulated volume control. Diaphragmatic atrophy was observed in 14/17 cases. Differences in the median thickness variation were found between patients with sepsis and without (0.70 vs 0.25 mm; p = 0.019). During pressure support ventilation there was a tendency to increase diaphragmatic thickness and excursion. Extubation failure occurred for diaphragmatic thickening fraction ≤ 35%. DISCUSSION: Under pressure-regulated volume control there was a tendency for a decrease in diaphragmatic thickness. In the pre-extubation stage under pressure support, there was a tendency for it to increase. These results suggest that, by titrating ventilation using physiological levels of inspiratory effort, we can reduce the diaphragmatic morphological changes associated with ventilation. CONCLUSION: The early recognition of diaphragmatic changes may encourage a targeted approach, namely titration of ventilation, in order to reduce ventilator-induced diaphragmatic dysfunction and its clinical repercussions.

Introdução: A ventilação mecânica invasiva condiciona disfunção diafragmática, atrasando a extubação e aumentando a mortalidade em adultos. Em pediatria, apesar de eventualmente mais relevante, essa disfunção não é sistematicamente avaliada. A ecografia diafragmática tem sido proposta como uma técnica não invasiva e segura para esse fim. O objetivo deste estudo foi descrever a evolução dos índices ecográficos de morfologia e função diafragmáticas em crianças ventiladas. Material e Métodos: Estudo exploratório, prospetivo. Foram incluídas crianças admitidas num Serviço de Cuidados Intensivos Pediátricos sob ventilação mecânica invasiva > 48 horas e realizadas medições ecográficas de espessura, excursão e fração de espessamento diafragmáticas. Resultados: Foram incluídos 17 casos. Mediana de idades: 42 meses. Eram do género masculino 10/17, tinham comorbilidades 7/17 e manifestavam desnutrição na admissão 3/17 casos. Mediana do tempo sob ventilação invasiva: sete dias. Medianas das espessuras diafragmáticas inicial e mínima: 2,3 e 1,9 mm, respetivamente, tendo-se observado uma diminuição mediana da espessura de 13% sob volume controlado regulado por pressão. Observou-se atrofia diafragmática em 14/17 casos. Verificaram-se diferenças na mediana da variação da espessura entre os grupos com e sem sépsis (0,70 vs 0,25 mm; p = 0,019). Durante a ventilação em pressão de suporte, observou-se uma tendência para aumento da espessura e excursão diafragmáticas. Ocorreu falência de extubação parafração de espessamento ≤ 35%. Discussão: Sob volume controlado regulado por pressão verificou-se tendência para diminuição da espessura diafragmática. Sob pressão de suporte, verificou-se uma tendência para o seu aumento. Estes resultados sugerem que, titulando a ventilação, podemos reduzir as alterações morfológicas diafragmáticas associadas à ventilação. Conclusão: O reconhecimento precoce de alterações diafragmáticas poderá fomentar uma abordagem dirigida, de forma a limitar a disfunção diafragmática induzida pelo ventilador e suas repercussões.

Assessment of muscle mass depletion in chronic liver disease: Dual-energy x-ray absorptiometry compared with computed tomography.

OBJECTIVES: The aim of this study was to perform intermethod comparisons between the following three measures of muscle mass depletion in patients eligible for liver transplantation: 1) fat-free mass index (FFMI) measured by dual-energy x-ray absorptiometry (DXA), 2) appendicular skeletal muscle mass index (ASMI) measured by DXA, and 3) skeletal muscle index (SMI) measured at the third lumbar level by computed tomography (CT). METHODS: The medical records of patients who received liver transplants between 2009 and 2012 at Karolinska University Hospital were retrospectively reviewed. Adult patients with a chronic liver disease who had both DXA and CT scans performed within a 30-d period during their pretransplant workup were included. RESULTS: Appendicular skeletal muscle mass index measured by DXA (ASMIDXA) and skeletal mass index measured by computed tomography (SMICT) provide similar results when assessing the presence of muscle mass depletion in patients with chronic liver diseases and FFMIDXA can be falsely high in patients with ascites. Both ASMIDXA and SMICT thus appear to be useful methods in the pretransplant evaluation of muscle mass depletion both for patients with and without ascites. CONCLUSIONS: ASMI measured with DXA is a useful alternative method to SMI measured with CT when a CT scan is not clinically indicated or available.

Muscle mass assessment by computed tomography in chronic kidney disease patients: agreement with surrogate methods.

BACKGROUND/OBJECTIVES: Patients with chronic kidney disease (CKD) are subjected to muscle wasting. Therefore, it is important to investigate surrogate methods that enable the assessment of muscle mass loss in the clinical setting. We aimed to analyze the agreement between computed tomography (CT) and surrogate methods for the assessment of muscle mass in non-dialysis CKD patients. SUBJECTS/METHODS: Cross-sectional study including 233 non-dialysis patients on CKD stages 3 to 5 (61 ± 11 years; 64% men; glomerular filtration rate 22 (14-33) mL/min/1.73 m2). The muscle mass was evaluated by CT and bioelectrical impedance, skinfold thicknesses, midarm muscle circumference (MAMC), the predictive equations of Janssen and Baumgartner and the physical examination of muscle atrophy from the subjective global assessment. RESULTS: In males, the MAMC showed the best agreement with CT as indicated by the kappa test (k = 0.57, P < 0.01), sensitivity (S = 68%), specificity (S = 89%) and accuracy (area under the curve-AUC = 0.78), followed by the Baumgartner equation (kappa = 0.46, P < 0.01; sensitivity = 60%; specificity = 87% and AUC = 0.73). In female, the Baumgartner equation showed the best agreement with CT (kappa = 0.43, P < 0.01; sensitivity = 57%; specificity = 86% and AUC = 0.71). CONCLUSIONS: The MAMC and Baumgartner equation showed the best agreement with CT for the assessment of muscle mass in non-dialysis CKD patients.

Comparison of bedside screening methods for frailty assessment in older adult trauma patients in the emergency department.

BACKGROUND: Frailty is linked to poor outcomes in older patients. We prospectively compared the utility of the picture-based Clinical Frailty Scale (CFS9), clinical assessments, and ultrasound muscle measurements against the reference FRAIL scale in older adult trauma patients in the emergency department (ED). METHODS: We recruited a convenience sample of adults 65 yrs. or older with blunt trauma and injury severity scores <9. We queried subjects (or surrogates) on the FRAIL scale, and compared this to: physician-based and subject/surrogate-based CFS9; mid-upper arm circumference (MUAC) and grip strength; and ultrasound (US) measures of muscle thickness (limbs and abdominal wall). We derived optimal diagnostic thresholds and calculated performance metrics for each comparison using sensitivity, specificity, predictive values, and area under receiver operating characteristic curves (AUROC). RESULTS: Fifteen of 65 patients were frail by FRAIL scale (23%). CFS9 performed well when assessed by subject/surrogate (AUROC 0.91 [95% CI 0.84-0.98] or physician (AUROC 0.77 [95% CI 0.63-0.91]. Optimal thresholds for both physician and subject/surrogate were CFS9 of 4 or greater. If both physician and subject/surrogate provided scores <4, sensitivity and negative predictive value were 90.0% (54.1-99.5%) and 95.0% (73.1-99.7%). Grip strength and MUAC were not predictors. US measures that combined biceps and quadriceps thickness showed an AUROC of 0.75 compared to the reference standard. CONCLUSION: The ED needs rapid, validated tools to screen for frailty. The CFS9 has excellent negative predictive value in ruling out frailty. Ultrasound of combined biceps and quadriceps has modest concordance as an alternative in trauma patients who cannot provide a history.

Sonoelastography for the Assessment of Muscle Changes in Amyotrophic Lateral Sclerosis: Results of a Pilot Study.

The purpose of this study was to assess the sonoelastographic features of four different muscles in patients with amyotrophic lateral sclerosis compared with healthy controls and to evaluate the relationship of these features to muscle strength and other ultrasonographic variables. Fourteen patients with amyotrophic lateral sclerosis and 20 controls were examined using strain sonoelastography scanning. The RGB channel fraction ratio was analyzed with ImageJ software (Version 1.48). Two main sonoelastographic patterns could be distinguished in the controls: a clear predominance of the blue channel (hard areas) and a more heterogeneous pattern with predominance of the green channel (intermediate stiffness). These patterns were also observed in patients, although a higher green channel score was observed in mildly impaired muscles, whereas a higher blue channel score was observed in the most severely impaired muscle. Sonoelastography may be a good complementary biomarker in the detection and monitoring of muscle changes in amyotrophic lateral sclerosis.

Relationships between tissue microstructure and the diffusion tensor in simulated skeletal muscle.

PURPOSE: To establish a series of relationships defining how muscle microstructure and diffusion tensor imaging (DTI) are related. METHODS: The relationship among key microstructural features of skeletal muscle (fiber size, fibrosis, edema, and permeability) and the diffusion tensor were systematically simulated over physiologically relevant dimensions individually, and in combination, using a numerical simulation application. Stepwise multiple regression was used to identify which microstructural features of muscle significantly predict the diffusion tensor using single-echo and multi-echo DTI pulse sequences. Simulations were also performed in models with histology-informed geometry to investigate the relationship between fiber size and the diffusion tensor in models with real muscle geometry. RESULTS: Fiber size is the strongest predictor of λ2, λ3, mean diffusivity, and fractional anisotropy in skeletal muscle, accounting for approximately 40% of the variance in the diffusion model when calculated with single-echo DTI. This increased to approximately 70% when diffusion measures were calculated from the short T2 component of the multi-echo DTI sequence. This nonlinear relationship begins to plateau in fibers with greater than 60-µm diameter. CONCLUSIONS: As the normal fiber size of a human muscle fiber is 40 to 60 µm, this suggests that DTI is a sensitive tool to monitor muscle atrophy, but may be limited in measurements of muscle with larger fibers. Magn Reson Med 80:317-329, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Skeletal Muscle Ultrasonography in Nutrition and Functional Outcome Assessment of Critically Ill Children: Experience and Insights From Pediatric Disease and Adult Critical Care Studies [Formula: see text].

Evidence suggests that critically ill children develop muscle wasting, which could affect outcomes. Muscle ultrasound has been used to track muscle wasting and association with outcomes in critically ill adults but not children. This review aims to summarize methodological considerations of muscle ultrasound, structural findings, and possibilities for its application in the assessment of nutrition and functional outcomes in critically ill children. Medline, Embase, and CINAHL databases were searched up until April 2016. Articles describing skeletal muscle ultrasound in children and critically ill adults were analyzed qualitatively for details on techniques and findings. Thickness and cross-sectional area of various upper and lower body muscles have been studied to quantify muscle mass and detect muscle changes. The quadriceps femoris muscle is one of the most commonly measured muscles due to its relation to mobility and is sensitive to changes over time. However, the margin of error for quadriceps thickness is too wide to reliably detect muscle changes in critically ill children. Muscle size and its correlation with strength and function also have not yet been studied in critically ill children. Echogenicity, used to detect compromised muscle structure in neuromuscular disease, may be another property worth studying in critically ill children. Muscle ultrasound may be useful in detecting muscle wasting in critically ill children but has not been shown to be sufficiently reliable in this population. Further study of the reliability and correlation with functional outcomes and nutrition intake is required before muscle ultrasound is routinely employed in critically ill children.

Utilization of non-invasive imaging tools for assessment of peripheral skeletal muscle size and composition in chronic lung disease: A systematic review.

OBJECTIVES: Non-invasive imaging modalities allow for detailed assessment of peripheral skeletal muscle wasting, which is associated with increased morbidity and mortality in chronic lung disease. Given the increased utilization of imaging tools, a systematic review was conducted using PRISMA guidelines to describe the modalities and acquisition techniques used to evaluate skeletal muscle in chronic lung disease and assess the relationships of muscle size and composition with strength, physical performance, structural alterations and clinical outcomes. METHODS: Six electronic databases were searched (inception-May 2017) to identify prospective studies measuring peripheral skeletal muscle size or composition using computed tomography (CT), magnetic resonance imaging/spectroscopy (MRI/MRS), or ultrasound (US) in adult chronic lung disease patients. RESULTS: Fifty-eight articles were included, which utilized: CT (n = 26), MRI/MRS (n = 16) and US (n = 16) in 2254 participants. All studies measured muscle size, predominantly of the lower extremity (n = 53), and only nine assessed muscle composition (i.e. fat infiltration) mainly with CT or MRI/MRS (n = 7). Thigh muscle size had a significant association with strength (r = 0.43-0.83, n = 13/14 studies), 6-min walk distance (r = 0.60-0.62, n = 3/6) and physical activity (r = 0.30-0.82, n = 3). Thigh muscle atrophy was independently associated with increased re-hospitalization (n = 1) and mortality (n = 3). Increased muscle fat infiltration had a moderate association with reduced physical performance partly related to increased anaerobic metabolism, but its prognostic utility was not assessed. CONCLUSION: Imaging modalities are valuable tools for the characterization of skeletal muscle dysfunction in chronic lung disease in clinical and research settings. The use of muscle imaging as a prognostic marker is promising and requires further study.

Quantitative assessment of fatty infiltration and muscle volume of the rotator cuff muscles using 3-dimensional 2-point Dixon magnetic resonance imaging.

BACKGROUND: In patients with rotator cuff tears, muscle degeneration is known to be a predictor of irreparable tears and poor outcomes after surgical repair. Fatty infiltration and volume of the whole muscles constituting the rotator cuff were quantitatively assessed using 3-dimensional 2-point Dixon magnetic resonance imaging. METHODS: Ten shoulders with a partial-thickness tear, 10 shoulders with an isolated supraspinatus tear, and 10 shoulders with a massive tear involving supraspinatus and infraspinatus were compared with 10 control shoulders after matching age and sex. With segmentation of muscle boundaries, the fat fraction value and the volume of the whole rotator cuff muscles were computed. After reliabilities were determined, differences in fat fraction, muscle volume, and fat-free muscle volume were evaluated. RESULTS: Intra-rater and inter-rater reliabilities were regarded as excellent for fat fraction and muscle volume. Tendon rupture adversely increased the fat fraction value of the respective rotator cuff muscle (P < .002). In the massive tear group, muscle volume was significantly decreased in the infraspinatus (P = .035) and increased in the teres minor (P = .039). With subtraction of fat volume, a significant decrease of fat-free volume of the supraspinatus muscle became apparent with a massive tear (P = .003). CONCLUSION: Three-dimensional measurement could evaluate fatty infiltration and muscular volume with excellent reliabilities. The present study showed that chronic rupture of the tendon adversely increases the fat fraction of the respective muscle and indicates that the residual capacity of the rotator cuff muscles might be overestimated in patients with severe fatty infiltration.

The natural history of donor hamstrings unit after anterior cruciate ligament reconstruction: a prospective MRI scan assessment.

PURPOSE: The aim of this prospective study was to assess the natural history of the donor hamstrings, compared to the contralateral knee and thigh. METHODS: In 47 patients who had ACL reconstruction (hamstrings technique), bilateral knees and thighs were investigated using MRI scans, up to 2 years post-operatively. RESULTS: Tendon regeneration below the knee joint line of the semitendinosus occurred in 30/47 (64 %) patients and of the gracilis tendon in 17/47 (36 %) patients. Insertion of both tendons at the "pes anserinus", with normal anatomic relations, was observed in 5/47 (11 %) patients. Semitendinosus and gracilis donor muscles were found retracted in 41/47 (87 %) patients. In 25/47 (53 %) patients, there was evidence of fatty infiltration of the semitendinosus muscle. All (47/47) (100 %) patients showed semitendinosus muscle atrophy and 41/47 (87 %) patients showed gracilis muscle atrophy, compared to the contralateral limb. High signal intensity on STIR images was observed in the semitendinosus in 22/47 (46 %) patients and in the gracilis muscle in 30/47 (64 %) patients, on MRI examination performed up to 24 months post-operatively. CONCLUSIONS: The "regenerated" hamstrings tendons most commonly do not regenerate fully anatomically, so they should not be considered as a first choice for re-harvesting in revision ACL reconstruction. The "donor hamstrings muscles" are found to be shorter, contracted, thinner and with a long-term abnormal MRI signal, features which are considered to be related to reduced muscle performance (knee flexion and internal rotation) post-operatively. LEVEL OF EVIDENCE: II.

Validity of Quadriceps Muscle Thickness Measurement in Patients with Subacute Stroke during Hospitalization for Assessment of Muscle Wasting and Physical Function.

BACKGROUND: Many patients with stroke have difficulty performing voluntary muscle contraction; thus, measurement of patients' muscle power or leg strength is challenging. We investigated the validity of quadriceps muscle thickness (QMT) measurement using ultrasonography (US) for the assessment of muscle wasting and physical function in patients with subacute stroke during hospitalization for convalescent rehabilitation. METHODS: Participants included 52 men with ischemic or hemorrhagic stroke (mean age, 69 ± 11 years) who were hospitalized for inpatient convalescent rehabilitation. The QMT of both legs was measured using US, and functional outcome was assessed according to the modified Rankin Scale (mRS) score and the leg motor selectivity score (6 motor stages defined by Brunnstrom). RESULTS: There was a significant correlation between QMT and leg motor selectivity score (paretic limb: r = .60, P < .001; nonparetic limb: r = .54, P < .001). Additionally, there were significant interaction effects between the QMT of the paretic limb (mRS scores = 1 or 2, 3, 4, and 5 = 3.52 ± .84 cm, 3.19 ± .52 cm, 2.50 ± .46 cm, and 2.20 ± .71 cm, respectively; F = 11.2; P < .0001), the QMT of the nonparetic limb (mRS scores = 1 or 2, 3, 4, and 5 = 3.72 ± .82 cm, 3.16 ± .49 cm, 2.91 ± .54 cm, and 2.42 ± .82 cm, respectively; F = 8.3; P < .001), and functional outcome. CONCLUSION: QMT measurement is a valid method to assess muscle wasting and physical function in patients with subacute stroke during hospitalization for convalescent rehabilitation.

Muscle atrophy in chronic inflammatory demyelinating polyneuropathy: a computed tomography assessment.

BACKGROUND AND PURPOSE: Muscle atrophy is generally mild in patients with chronic inflammatory demyelinating polyneuropathy (CIDP) compared with the severity and duration of the muscle weakness. Muscle atrophy was evaluated using computed tomography (CT) in patients with CIDP. METHODS: Thirty-one patients with typical CIDP who satisfied the diagnostic criteria for the definite CIDP classification proposed by the European Federation of Neurological Societies and the Peripheral Nerve Society were assessed. The clinicopathological findings in patients with muscle atrophy were also compared with those in patients without atrophy. RESULTS: Computed tomography evidence was found of marked muscle atrophy with findings suggestive of fatty degeneration in 11 of the 31 patients with CIDP. CT-assessed muscle atrophy was in the lower extremities, particularly in the ankle plantarflexor muscles. Muscle weakness, which reflects the presence of muscle atrophy, tended to be more pronounced in the lower extremities than in the upper extremities in patients with muscle atrophy, whereas the upper and lower limbs tended to be equally affected in patients without muscle atrophy. Nerve conduction examinations revealed significantly greater reductions in compound muscle action potential amplitudes in the tibial nerves of patients with muscle atrophy. Sural nerve biopsy findings were similar in both groups. The functional prognoses after immunomodulatory therapies were significantly poorer amongst patients with muscle atrophy. CONCLUSIONS: Muscle atrophy was present in a subgroup of patients with CIDP, including patients with a typical form of the disease. These patients tended to demonstrate predominant motor impairments of the lower extremities and poorer functional prognoses.