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Purpose The purpose of this study was to understand potential baseline transcriptional expression differences in paraspinal skeletal muscle from patients with different underlying lumbar pathologies by comparing multifidus gene expression profiles across individuals with either disc herniation, facet arthropathy, or degenerative spondylolisthesis. Methods Multifidus biopsies were obtained from patients (n = 44) undergoing lumbar surgery for either disc herniation, facet arthropathy, or degenerative spondylolisthesis. Diagnostic categories were based on magnetic resonance images, radiology reports, and intraoperative reports. Gene expression for 42 genes was analysed using qPCR. A one-way analysis of variance was performed for each gene to determine differences in expression across diagnostic groups. Corrections for multiple comparisons across genes (Benjamini–Hochberg) and for between-group post hoc comparisons (Sidak) were applied. Results Adipogenic gene (ADIPOQ) expression was higher in the disc herniation group when compared to the facet arthropathy group (p = 0.032). Adipogenic gene (PPARD) expression was higher in the degenerative spondylolisthesis group when compared to the disc herniation group (p = 0.013), although absolute gene expression levels for all groups was low. Fibrogenic gene (COL3A1) had significantly higher expression in the disc herniation group and facet arthropathy group when compared to the degenerative spondylolisthesis group (p p = 0.038, respectively). When adjusted for multiple comparisons, only COL3A1 remained significant (p = 0.012). Conclusion Individuals with disc herniation and facet arthropathy demonstrate higher COL3A1 gene expression compared to those with degenerative spondylolisthesis. Future research is required to further understand the biological relevance of these transcriptional differences.

Chronic rotator cuff tears can cause severe functional deficits. Addressing the chronic fatty and fibrotic muscle changes is of high clinical interest; however, the architectural and physiological consequences of chronic tear and repair are poorly characterized. We present a detailed architectural and physiological analysis of chronic tear and repair (both over 8 and 16 wk) compared with age-matched control rabbit supraspinatus (SSP) muscles. Using female New Zealand White Rabbits (n = 30, n = 6/group) under 2% isoflurane anesthesia, the SSP was surgically isolated and maximum isometric force was measured at four to six muscle lengths. Architectural analysis was performed, and maximum isometric stress was computed. Whole muscle length-tension curves were generated using architectural measurements to compare experimental physiology to theoretical predictions. Architectural measures are consistent with persistent radial and longitudinal atrophy over time in tenotomy that fails to recover after repair. Maximum isometric force was significantly decreased after 16 wk tenotomy and not significantly improved after repair. Peak isometric force reported here are greater than prior reports of rabbit SSP force after tenotomy. Peak stress was not significantly different between groups and consistent with prior literature of SSP stress. Muscle strain during contraction was significantly decreased after 8 wk of tenotomy and repair, indicating effects of tear and repair on muscle function. The experimental length-tension data were overlaid with predicted curves for each experimental group (generated from structural data), exposing the altered structure-function relationship for tenotomy and repair over time. Data presented here contribute to understanding the physiological implications of disease and repair in the rotator cuff. NEW & NOTEWORTHY We utilize an established method to measure the length-tension relationship for the rabbit supraspinatus in normal, torn, and repaired muscles. We then perform architectural analysis to evaluate structural changes after tear and repair. Although peak isometric force is lower in the tear and repair groups, there are no differences in peak stresses across groups. These findings indicate persistent structural changes (both radial and longitudinal atrophy) and physiological deficiencies (decreased peak force and uncoupling structure-function relationship) after tenotomy that do not significantly recover after repair.

Introduction The potential of regenerative medicine to improve human health has led to the rapid expansion of stem cell clinics throughout the world with varying levels of regulation and oversight. This has led to a market ripe for stem cell tourism, with Tijuana, Mexico, as a major destination. In this study, we characterize the online marketing, intervention details, pricing of services, and assess potential safety risks through web surveillance of regenerative medicine clinics marketing services in Tijuana. Methods We conducted structured online search queries from March to April 2019 using 296 search terms in English and Spanish on two search engines (Google and Bing) to identify websites engaged in direct-to-consumer advertising of regenerative medicine services. We performed content analysis to characterize three categories of interest: online presence, tokens of scientific legitimacy, and intervention details. Results Our structured online searches resulted in 110 unique websites located in Tijuana corresponding to 76 confirmed locations. These clinics’ online presence consisted of direct-to-consumer advertising mainly through a dedicated website (94.5%) or Facebook page (65.5%). The vast majority of these websites (99.1%) did not mention any affiliation to an academic institutions or other overt tokens of scientific legitimacy. Most clinics claimed autologous tissue was the source of treatments (67.3%) and generally did not specify route of administration. Additionally, of the Tijuana clinics identified, 13 claimed licensing, though only 1 matched with available licensing information. Conclusions Regenerative medicine clinics in Tijuana have a significant online presence using direct-to-consumer advertising to attract stem-cell tourism clientele in a bustling border region between Mexico and the USA. This study adds to existing literature evidencing the unregulated nature of online stem cell offerings and provides further evidence of the need for regulatory harmonization, particularly to address stem cell services being offered online across borders.

This study investigated body composition measures in highly trained and untrained individuals using whole-body magnetic resonance imaging (MRI). Additionally, correlations between these measures and skeletal muscle gene expression were performed. Thirty-six individuals were included: endurance-trained males (ME, n = 8) and females (FE, n = 7), strength-trained males (MS, n = 7), and untrained control males (MC, n = 8) and females (FC, n = 6). MRI scans were performed, and resting M. vastus lateralis (VL) biopsies were subjected to RNA sequencing. Liver fat fraction, visceral adipose tissue volume (VAT), total body fat, and total lean tissue were measured from MRI data. Additionally, cross-sectional area (CSA) and fat signal fraction (FSF) were calculated from Mm. pectoralis, M. erector spinae and M. multifidus combined, Mm. quadriceps, and Mm. triceps surae (TS). Liver fat fraction, VAT, and total body fat relative to body weight were lower in ME and FE compared with corresponding controls. MS had a larger CSA across all four muscle groups and lower FSF in all muscles apart from TS compared with MC. ME had a lower FSF across all muscle groups and a larger CSA in all muscles except TS than MC. FE athletes showed a higher CSA in Mm. pectoralis and Mm. quadriceps and a lower CSA in TS than FC with no CSA differences found in the back muscles investigated. Surprisingly, the only difference in FSF between FE and FC was found in Mm. pectoralis. Lastly, correlations between VL gene expression and VL CSA as well as FSF showed that genes positively correlated with CSA revealed an enrichment of the oxidative phosphorylation and thermogenesis pathways, while the genes positively correlated with FSF showed significant enrichment of the spliceosome pathway. Although limited differences were found with training in females, our study suggests that both regular endurance and resistance training are useful in maintaining muscle mass, reducing adipose tissue deposits, and reducing muscle fat content in males.

Low vertebral bone mass is a major risk factor for vertebral compression fractures. While sarcopenia has been shown to be associated with low bone mineral density (BMD), it is not known whether trunk musculature is directly associated with lumbar BMD, and whether exercise modifies this association. Using data from the Multi-Ethnic Study of Atherosclerosis (MESA), we sought to determine the association of muscle density and fat fraction of the psoas, paraspinal, and oblique muscle groups with L3 lumbar volumetric BMD, and whether these associations were modified by exercise. We obtained L3 vBMD measurements, and fat and muscle measurements (in Hounsfield units (HU)) from abdominal CT scans spanning L2-L4 intervertebral disc spaces. Muscle density was defined as the mean HU value for a muscle group area. Fat fraction was calculated as the mean HU value for the muscle group fat area/total muscle group area(sq cm). Exercise data were self-reported (MET-min/wk). We utilized multivariable linear regression to evaluate these associations, stratified by gender, and adjusting for demographics, BMI, smoking status, impaired fasting glucose, and corticosteroid and anti-resorptive medication use. Among 1923 MESA participants, mean age was 62±10, 49% were female, 40% White, 21% Black, 26% Hispanic/Latino and 13% Chinese. In fully adjusted analysis, for every 1 SD higher psoas fat fraction, there was a 3.19 SD lower L3 vBMD in men and 4.3 SD lower SD L3 vBMD in women (p

The rotator cuff (RC) muscles are crucial in moving and stabilizing the glenohumeral joint, and tears can be functionally devastating. Chronic fatty and fibrotic muscle changes, which are nonresponsive to surgical tendon repair, are a focus of contemporary research. The rabbit model recapitulates key biological features of human RC tears, but function and physiology are poorly characterized; limited force and stress data are inconsistent with literature norms in other mammalian species. Here, we present an improved method to assess the physiology of the rabbit supraspinatus muscle (SSP), and we report values for healthy SSP architecture and physiology. Using female New Zealand White Rabbits (

Purpose Evaluate the relationship between muscle microstructure, diffusion time (Δ), and the diffusion tensor (DT) to identify the optimal Δ where changes in muscle fiber size may be detected. Methods The DT was simulated in models with histology informed geometry over a range of Δ with a stimulated echo DT imaging (DTI) sequence using the numerical simulation application DifSim. The difference in the DT at each Δ between healthy and injured skeletal muscle models was calculated, to identify the optimal Δ at which changes in muscle fiber size may be detected. The random permeable barrier model (RPBM) was used to estimate muscle microstructure from the simulated DT measurements, which were compared to the ground truth. Results Across all models, fractional anisotropy provided greater contrast between injured and control models than diffusivity measurements. Compared to control models, in atrophic injury models, the greatest difference in the DT was found between 90 ms and 250 ms. In models with acute edema, the contrast between injured and control muscle increased with increasing diffusion time, although these models had smaller mean fiber areas. RPBM systematically underestimated fiber size but accurately estimated surface area-to-volume ratio of simulated models. Conclusion These findings may better inform pulse sequence parameter selection when performing DTI experiments in vivo. If only a single diffusion experiment can be performed, the selected Δ should be ~170 ms to maximize the ability to discriminate between different injury models. Ideally several diffusion times between 90 ms and 500 ms should be sampled in order to maximize diffusion contrast, particularly when the disease process is unknown.

INTRODUCTION: Intramuscular pressure (IMP) shows promise for estimating individual muscle tension in vivo. However, previous pressure measurements show high variability during isometric contraction and poor correlation with tension during dynamic contraction. METHODS: We hypothesized that enhanced sensor anchoring/orientation would improve tension estimation and thus developed a novel pressure sensor with a barbed housing. Sensors were inserted into the tibialis anterior (TA) of New Zealand White rabbits (N=8) both parallel and perpendicular to the fiber orientation. We measured muscle stress and IMP during both isometric and dynamic contractions. RESULTS: Passive stress showed good agreement for both insertion directions across muscle lengths (ICC>0.8). Active stress and IMP agreement were good (ICC=0.87±0.04) for perpendicular insertions but poor (ICC=0.21±0.22) for parallel insertions across both dynamic contractions and isometric contractions within the muscle’s range of motion. DISCUSSION: These findings support use of IMP measurements to estimate muscle tension across a range of contraction conditions.

BackgroundCryoneurolysis of peripheral nerves uses localised intense cold to induce a prolonged block over multiple weeks that has the promise of providing potent analgesia outlasting the duration of postoperative pain following surgery, as well as treat other acute and chronic pain states. However, it remains unclear whether persistent functional motor deficits remain following cryoneurolysis of mixed sensorimotor peripheral nerves, greatly limiting clinical application of this modality. To help inform future research, we used a rat peroneal nerve injury model to evaluate if cryoneurolysis results in persistent deficits in motor function.MethodsMale Lewis rats (n=30) had their common peroneal nerves exposed bilaterally at the proximal lateral margin of the knee and subsequently underwent cryoneurolysis on one limb and sham treatment on the contralateral limb. Outcomes were evaluated on days 3, 14, 30, 90 and 180. The primary end point was motor function, based on ankle dorsiflexion torque. In addition, sensory function was tested based on von Frey’s filament sensitivity to the peroneal sensory distribution. A subset of animals was sacrificed following functional testing at each time point, and general tissue morphology, connective tissue deposition, and axon counts were evaluated.ResultsMotor deficits in treated limbs were observed at 3 and 14 days but had resolved at time points beyond 1 month. Bilateral sensory deficits were also observed at 3 and 14 days, and also resolved within 1 month. Consistent with motor functional deficits, axon counts trended lower in treated nerves compared with contralateral controls at 3 days; however, axon counts were not significantly different at later time points.ConclusionsWhen applied to a mixed sensorimotor nerve, cryoneurolysis did not result in persistent motor deficits.

Assess the insertional anatomy of the distal aspect of the triceps brachii muscle using magnetic resonance imaging (MRI) in cadavers with histologic correlation and Play-doh® models of the anatomic findings. Elbows were obtained from twelve cadaveric arm specimens by transverse sectioning through the proximal portion of the humerus and the midportion of the radius and ulna. MRI was performed in all elbows. Two of the elbow specimens were then dissected while ten were studied histologically. Subsequently, Play-doh® models of the anatomic findings of the distal attachment sites of the triceps brachii muscle were prepared. MRI showed a dual partitioned appearance of the distal attachment sites into the olecranon in all specimens. In the deeper tissue planes, the medial head muscle insertion was clearly identified while superficially, the terminal portion of the long and lateral heads appeared as a conjoined tendon. Histologic analysis, however, showed continuous tissue rather than separate structures attaching to the olecranon. Although MRI appeared to reveal separate and distinct attachments of the triceps brachii muscle into the olecranon, histologic analysis delineated complex but continuous tissue related to the attachments of the three heads of this muscle. The Play-doh® models were helpful for the comprehension of this complex anatomy and might serve as a valuable educational tool when applied to the analysis of other musculoskeletal regions.

Background Reversible ε‐amino acetylation of lysine residues regulates transcription as well as metabolic flux; however, roles for specific lysine acetyltransferases in skeletal muscle physiology and function are unknown. In this study, we investigated the role of the related acetyltransferases p300 and cAMP response element‐binding protein‐binding protein (CBP) in skeletal muscle transcriptional homeostasis and physiology in adult mice. Methods Mice with skeletal muscle‐specific and inducible knockout of p300 and CBP (PCKO) were generated by crossing mice with a tamoxifen‐inducible Cre recombinase expressed under the human α‐skeletal actin promoter with mice having LoxP sites flanking exon 9 of the Ep300 and Crebbp genes. Knockout of PCKO was induced at 13–15 weeks of age via oral gavage of tamoxifen for 5 days to both PCKO and littermate control [wildtype (WT)] mice. Body composition, food intake, and muscle function were assessed on day 0 (D0) through 5 (D5). Microarray and tandem mass tag mass spectrometry analyses were performed to assess global RNA and protein levels in skeletal muscle of PCKO and WT mice. Results At D5 after initiating tamoxifen treatment, there was a reduction in body weight (−15%), food intake (−78%), stride length (−46%), and grip strength (−45%) in PCKO compared with WT mice. Additionally, ex vivo contractile function [tetanic tension (kPa)] was severely impaired in PCKO vs. WT mice at D3 (~70–80% lower) and D5 (~80–95% lower) and resulted in lethality within 1 week—a phenotype that is reversed by the presence of a single allele of either p300 or CBP. The impaired muscle function in PCKO mice was paralleled by substantial transcriptional alterations (3310 genes; false discovery rate < 0.1), especially in gene networks central to muscle contraction and structural integrity. This transcriptional uncoupling was accompanied by changes in protein expression patterns indicative of impaired muscle function, albeit to a smaller magnitude (446 proteins; fold‐change > 1.25; false discovery rate < 0.1). Conclusions These data reveal that p300 and CBP are required for the control and maintenance of contractile function and transcriptional homeostasis in skeletal muscle and, ultimately, organism survival. By extension, modulating p300/CBP function may hold promise for the treatment of disorders characterized by impaired contractile function in humans.

The rabbit supraspinatus is a useful translational model for rotator cuff (RC) repair because it recapitulates muscle atrophy and fat accumulation observed in humans after a chronic tear (the “first hit”). However, a timeline of RC tissue response after repair, especially with regard to recent evidence of muscle degeneration and lack of regeneration, is currently unavailable. Thus, the purpose of this study was to characterize the progression of muscle and fat changes over time after the repair of a chronic RC tear in the rabbit model. Two rounds of experiments were conducted in 2017–2018 and 2019–2020 with N = 18 and 16 skeletally mature New Zealand White rabbits, respectively. Animals underwent left supraspinatus tenotomy with repair 8 weeks later. The unoperated right shoulder served as control. The rabbits were sacrificed at 1-, 2-, 4-, and 8-weeks post-repair for histological and biochemical analysis. Atrophy, measured by fiber cross-sectional area and muscle mass, was greatest around 2 weeks after repair. Active muscle degeneration peaked at the same time, involving 8% of slide areas. There was no significant regeneration at any timepoint. Fat accumulation and fibrosis were significantly increased across all time points compared to contralateral. Statement of Clinical Significance: These results demonstrate model reproducibility and a “second hit” phenomenon of repair-induced muscle atrophy and degeneration which partially recovers after a short time, while increased fat and fibrosis persist.

Background Lumbar spine pathology is a common feature of lower back and/or lower extremity pain and is associated with observable degenerative changes in the lumbar paraspinal muscles that are associated with poor clinical prognosis. Despite the commonly observed phenotype of muscle degeneration in this patient population, its underlying molecular mechanisms are not well understood. The aim of this study was to investigate the relationships between groups of genes within the atrophic, myogenic, fibrogenic, adipogenic, and inflammatory pathways and multifidus muscle health in individuals undergoing surgery for lumbar spine pathology. Methods Multifidus muscle biopsies were obtained from patients (n = 59) undergoing surgery for lumbar spine pathology to analyze 42 genes from relevant adipogenic/metabolic, atrophic, fibrogenic, inflammatory, and myogenic gene pathways using quantitative polymerase chain reaction. Multifidus muscle morphology was examined preoperatively in these patients at the level and side of biopsy using T2-weighted magnetic resonance imaging to determine whole muscle compartment area, lean muscle area, fat cross-sectional areas, and proportion of fat within the muscle compartment. These measures were used to investigate the relationships between gene expression patterns and muscle size and quality. Results Relationships between gene expression and imaging revealed significant associations between decreased expression of adipogenic/metabolic gene (PPARD), increased expression of fibrogenic gene (COL3A1), and lower fat fraction on MRI (r = -0.346, p = 0.018, and r = 0.386, p = 0.047 respectively). Decreased expression of myogenic gene (mTOR) was related to greater lean muscle cross-sectional area (r = 0.388, p = 0.045). Conclusion Fibrogenic and adipogenic/metabolic genes were related to pre-operative muscle quality, and myogenic genes were related to pre-operative muscle size. These findings provide insight into molecular pathways associated with muscle health in the presence of lumbar spine pathology, establishing a foundation for future research that addresses how these changes impact outcomes in this patient population.

Optimizing rehabilitation outcomes, including preventing pathology and its progression, relies on a comprehensive knowledge of the condition's etiology. Put simply, we cannot optimally prevent or treat what we do not understand. Understanding the etiology of musculoskeletal syndromes and diseases is challenging because these conditions likely result from the interaction between multiple complex factors including time, underlying biology and physiology, and task demands on the system. Furthermore, behavioral and social determinants of health likely play important roles. Research seeking to understand the etiology of a musculoskeletal condition requires a robust and comprehensive conceptual framework that explicitly identifies key variables, relationships, and outcomes measures. The validity of this framework ultimately determines the utility and clinical impact of the research, and therefore deserves frequent and careful scrutiny. In this point of view, we will explore the predominant conceptual framework that has guided research into the etiology of rotator cuff pathology and propose a framework that can help guide future research in an effort to optimally prevent and treat rotator cuff pathology. Although this point of view explores the proposed framework within the context of rotator cuff pathology, it can be generalized and applied across musculoskeletal rehabilitation and research.

Rotator cuff (RC) tears are prevalent in the population above the age of 60. The disease progression leads to muscle atrophy, fibrosis, and fatty infiltration in the chronic state, which is not improved with intervention or surgical repair. This highlights the need to better understand the underlying dysfunction in muscle after RC tendon tear. Contemporary studies aimed at understanding muscle pathobiology after RC tear have considered transcriptional data in mice, rats and sheep models at 2–3 time points (1 to 16 weeks post injury). However, none of these studies observed a transition or resurgence of gene expression after the initial acute time points. In this study, we collected rabbit supraspinatus muscle tissue with high temporal resolution (1, 2, 4, 8, and 16 weeks) post-tenotomy (n = 6/group), to determine if unique, time-dependent transcriptional changes occur. RNA sequencing and analyses were performed to identify a transcriptional timeline of RC muscle changes and related morphological sequelae. At 1-week post-tenotomy, the greatest number of differentially expressed genes was observed (1,069 up/873 down) which decreases through 2 (170/133), 4 (86/41), and 8 weeks (16/18), followed by a resurgence and transition of expression at 16 weeks (1,421/293), a behavior which previously has not been captured or reported. Broadly, 1-week post-tenotomy is an acute time point with expected immune system responses, catabolism, and changes in energy metabolism, which continues into 2 weeks with less intensity and greater contribution from mitochondrial effects. Expression shifts at 4 weeks post-tenotomy to fatty acid oxidation, lipolysis, and general upregulation of adipogenesis related genes. The effects of previous weeks’ transcriptional dysfunction present themselves at 8 weeks post-tenotomy with enriched DNA damage binding, aggresome activity, extracellular matrix-receptor changes, and significant expression of genes known to induce apoptosis. At 16 weeks post-tenotomy, there is a range of enriched pathways including extracellular matrix constituent binding, mitophagy, neuronal activity, immune response, and more, highlighting the chaotic nature of this time point and possibility of a chronic classification. Transcriptional activity correlated significantly with histological changes and were enriched for biologically relevant pathways such as lipid metabolism. These data provide platform for understanding the biological mechanisms of chronic muscle degeneration after RC tears.

Biologically augmented surgical treatments of orthopaedic conditions are increasingly popular. Bone marrow aspirate concentrate is a key orthobiologic tissue source, and the field is moving from the standard iliac crest marrow aspiration toward local aspirations of marrow depots that are accessible during the standard-of-care procedures in an attempt to reduce morbidity, surgery time, and cost. Here, we present the aspiration of the standard iliac marrow depot, but through a novel acetabular approach during total hip arthroplasty. This procedure markedly simplifies biologic augmentation with bone marrow aspirate concentrate in this large patient cohort.

PurposeThe development of ultrashort echo time (UTE) MRI sequences has led to improved imaging of tissues with short T2 relaxation times, such as the deep layer cartilage and meniscus. UTE combined with adiabatic T1ρ preparation (UTE-Adiab-T1ρ) is an MRI measure with low sensitivity to the magic angle effect. This study aimed to investigate the sensitivity of UTE-Adiab-T1ρ to mechanical load-induced deformations in the tibiofemoral cartilage and meniscus of human cadaveric knee joints.MethodsEight knee joints from young (42±12years at death) donors were evaluated on a 3T scanner using the UTE-Adiab-T1ρ sequence under four sequential loading conditions: load=0N (Load0), load=300N (Load1), load=500N (Load2), and load=0N (Unload). UTE-Adiab-T1ρ was measured in the meniscus (M), femoral articular cartilage (FAC), tibial articular cartilage (TAC), articular cartilage regions uncovered by meniscus (AC-UC), and articular cartilage regions covered by meniscus (AC-MC) within region of interests (ROIs) manually selected by an experienced MR scientist. The Kruskal-Wallis test, with corrected significance level for multiple comparisons, was used to examine the UTE-Adiab-T1ρ differences between different loading conditions.ResultsUTE-Adiab-T1ρ decreased in all grouped ROIs under both Load1 and Load2 conditions (-18.7% and-16.9% for M, -18.8% and-12.6% for FAC, -21.4% and-10.7% for TAC, -26.2% and-13.9% for AC-UC, and-16.9% and-10.7% for AC-MC). After unloading, average UTE-Adiab-T1ρ increased across all ROIs and within a lower range compared with the average UTE-Adiab-T1ρ decreases induced by the two previous loading conditions. The loading-induced differences were statistically non-significant.ConclusionsWhile UTE-Adiab-T1ρ reduction by loading is likely an indication of tissue deformation, the increase of UTE-Adiab-T1ρ within a lower range by unloading implies partial tissue restoration. This study highlights the UTE-Adiab-T1ρ technique as an imaging marker of tissue function for detecting deformation patterns under loading.

Objectives To develop a practical step-by-step technique to precisely identify and differentiate tendons and ligaments attaching to the humeral epicondyles, to confirm through gross anatomical study the accurate structure identification provided by this technique and to determine the frequency at which each structure can be identified in healthy volunteers. Materials and methods First, ten fresh frozen cadavers (6 men, age at death = 58–92 years) were examined by two musculoskeletal radiologists and a step-by-step technique for the identification of tendons and ligaments at the level of humeral epicondyles was developed. Second, the accurate identification of structures was confirmed through gross anatomical study including anatomical sections on five specimens and layer-by-layer dissection technique on five others. Finally, 12 healthy volunteers (6 men, average age = 36, range = 28–52) were scanned by two radiologists following the same technique. Results An ultrasonographic technique based on the recognition of bony landmarks and the use of ultrasonographic signs to differentiate overlapping structures was developed and validated through gross anatomical study. In healthy volunteers, most tendons and ligaments were identified and well-defined in ≥ 80% of cases, except for the extensor carpi radialis brevis and extensor digiti minimi tendons on the lateral epicondyle (having common attachments with the extensor digitorum communis) and the palmaris longus tendon on the medial epicondyle (absent, or common attachment with the flexor carpi radialis). Conclusion A step-by-step approach to the ultrasonographic assessment of tendons and ligaments at the humeral epicondyles allowed accurate identification of and differentiation among these structures, in particular those relevant to pathological conditions.

INTRODUCTION After traumatic nerve injury, neuromuscular junction remodeling plays a key role in determining functional outcomes. Immunohistochemical analyses of denervated muscle biopsies may provide valuable prognostic data regarding clinical outcomes to supplement electrodiagnostic studies. METHODS We performed biopsies on nonfunctioning deltoid muscles in two patients after gunshot wounds and visualized the neuromuscular junctions using two-photon microscopy with immunohistochemistry. RESULTS Although the nerves in both patients showed evidence of acute Wallerian degeneration, some of the motor endplates were intact but exhibited significantly decreased surface area and volume. Both patients exhibited substantial recovery of motor function over several weeks postinjury. DISCUSSION Two-photon microscopic assessment of neuromuscular junction integrity and motor endplate morphometry in muscle biopsies provided evidence of partial sparing of muscle innervation. This finding supported the clinical judgment that eventual recovery would occur. With further study, this technique may help to guide operative decisionmaking after traumatic nerve injuries.

Understanding changes in lumbar spine (LS) angles and intervertebral disc (IVD) behavior in end-range positions in healthy subjects can provide a basis for developing more specific LS models and comparing people with spine pathology. The purposes of this study are to quantify 3D LS angles and changes in IVD characteristics with end-range positions in 3 planes of motion using upright MRI in healthy people, and to determine which intervertebral segments contribute most in each plane of movement. Thirteen people (average age = 24.4 years, range 18–51 years; 9 females; BMI = 22.4 ± 1.8 kg/m2) with no history of low back pain were scanned in an upright MRI in standing, sitting flexion, sitting axial rotation (left, right), prone on elbows, prone extension, and standing lateral bending (left, right). Global and local intervertebral LS angles were measured. Anterior-posterior length of the IVD and location of the nucleus pulposus was measured. For the sagittal plane, lower LS segments contribute most to change in position, and the location of the nucleus pulposus migrated from a more posterior position in sitting flexion to a more anterior position in end-range extension. For lateral bending, the upper LS contributes most to end-range positions. Small degrees of intervertebral rotation (1–2°) across all levels were observed for axial plane positions. There were no systematic changes in IVD characteristics for axial or coronal plane positions.

Rotator cuff (RC) tears present a treatment challenge due to muscle atrophy and degeneration, fatty infiltration, and fibrosis. The purpose of this study was to generate a high time-resolution model of RC tear in rabbits and to characterize the progression of architectural and histological changes. Thirty-five female New Zealand White rabbits (age: 6 months) underwent left supraspinatus tenotomy. Five rabbits were used to evaluate immediate muscle architectural changes. The remaining 30 rabbits underwent right shoulder sham surgery and sacrifice at 1, 2, 4, 8, or 16 weeks. Histology was used to quantify muscle fiber cross-sectional area (CSA), muscle degeneration and regeneration, and fat localized to inter- versus intrafascicular regions. Muscle fiber CSA decreased by 26.5% compared to sham at 16 weeks (effect of treatment, p

Background Adolescent idiopathic scoliosis (AIS) is a condition resulting in spinal deformity and tissue adaptation of the paraspinal muscles. Although prior studies have demonstrated asymmetries in fiber type and other energetic features of muscle on the concave side of the curve, muscle morphology, architecture, and composition have not been evaluated. Therefore, the purpose of this study was to compare differences in paraspinal muscle microarchitecture and composition between concave and convex sides of a scoliotic curve in individuals with AIS. Methods Paraspinal muscle biopsies were obtained at the apex of the scoliotic curve in 29 individuals with AIS undergoing surgical deformity correction. Histological assays were performed to quantify fiber size, evidence of muscle degeneration and regeneration, and tissue composition (proportion of muscle, collagen, and fat). Differences between contralateral muscle samples were compared using two‐tailed paired Student's t tests, and relationships between clinical characteristics (age and curve severity) and muscle characteristics were investigated using Pearson correlations. Results Muscle fibers were significantly larger on the convex side of the curve apex (P = .001), but were lower than literature‐based norms for healthy paraspinal muscle. There were no differences in amount of degeneration/regeneration (P = .490) or the proportion of muscle and collagen (P > .350) between the concave and convex sides, but high levels of collagen were observed. There was a trend toward higher fat content on the concave side (P = .074). Larger fiber size asymmetries were associated with greater age (r = .43, P = .046), and trended toward an association with greater curve severity (r = .40, P = .069). Conclusions This study demonstrates that although muscle fibers are larger on the convex side of the scoliotic curve in AIS, muscles on both sides are atrophic compared to non‐scoliotic individuals, and demonstrate levels of collagen similar to severe degenerative spinal pathologies. These findings provide insight into biological maladaptations occurring in paraspinal muscle in the presence of AIS., Muscle adaptations in adolescent idiopathic scoliosis are not well described. Using intraoperative muscle biopsies from both the concave and convex side of the deformity, we found evidence of bilateral atrophy and degeneration as well as side‐specific size and compositional changes.

Background: There is a need to identify and quantify mesenchymal stromal cells (MSCs) in human bone marrow aspirate concentrate (BMAC) source tissues, but current methods to do so were established in cultured cell populations. Given that surface marker and gene expression change in cultured cells, it is doubtful that these strategies are valid to quantify MSCs in fresh BMAC. Purpose: To establish the presence, quantity, and heterogeneity of BMAC-derived MSCs in minimally manipulated BMAC using currently available strategies. Study Design: Descriptive laboratory study. Methods: Five published strategies to identify MSCs were compared for suitability and efficiency to quantify clinical-grade BMAC-MSCs and cultured MSCs at the single cell transcriptome level on BMAC samples being used clinically from 15 orthopaedic patients and on 1 cultured MSC sample. Strategies included (1) the guidelines by the International Society for Cellular Therapy (ISCT), (2) CD271 expression, (3) the Ghazanfari et al transcriptional profile, (4) the Jia et al transcriptional profile, and (5) the Silva et al transcriptional profile. Results: ISCT guidelines did not identify any MSCs in BMAC at the transcriptional level and only 1 in 9 million cells at the protein level. Of 12,850 BMAC cells, 9 expressed the CD271 gene. Only 116 of 396 Ghazanfari genes were detected in BMAC, whereas no cells expressed all of them. No cells expressed all Jia genes, but 25 cells expressed at least 13 of 22. No cells expressed all Silva genes, but 19 cells expressed at least 8 of 23. Most importantly, the liberalized strategies tended to identify different cells and most of them clustered with immune cells. Conclusion: Currently available methods need to be liberalized to identify any MSCs in fresh human BMAC and lack consensus at the single cell transcriptome and protein expression levels. These different cells should be isolated and challenged to establish phenotypic differences. Clinical Relevance: This study demonstrated that improved strategies to quantify MSC concentrations in BMAC for clinical applications are urgently needed. Until then, injected minimally manipulated MSC doses should be reported as rough estimates or as unknown.

BackgroundDue to its unique arrangement, the deep and superficial fibers of the multifidus may have differential roles for maintaining spine stabilization and lumbar posture; the superficial multifidus is responsible for lumbar extension and the deep multifidus for intersegmental stability. In patients with chronic lumbar spine pathology, muscle activation patterns have been shown to be attenuated or delayed in the deep, but not superficial, multifidus. This has been interpreted as pain differentially influencing the deep region. However, it is unclear if degenerative changes affecting the composition and function of the multifidus differs between the superficial and deep regions, an alternative explanation for these electrophysiological changes. Therefore, the goal of this study was to investigate macrostructural and microstructural differences between the superficial and deep regions of the multifidus muscle in patients with lumbar spine pathology.MethodsIn 16 patients undergoing lumbar spinal surgery for degenerative conditions, multifidus biopsies were acquired at two distinct locations: 1) the most superficial portion of muscle adjacent to the spinous process and 2) approximately 1 cm lateral to the spinous process and deeper at the spinolaminar border of the affected vertebral level. Structural features related to muscle function were histologically compared between these superficial and deep regions, including tissue composition, fat fraction, fiber cross sectional area, fiber type, regeneration, degeneration, vascularity and inflammation.ResultsNo significant differences in fat signal fraction, muscle area, fiber cross sectional area, muscle regeneration, muscle degeneration, or vascularization were found between the superficial and deep regions of the multifidus. Total collagen content between the two regions was the same. However, the superficial region of the multifidus was found to have less loose and more dense collagen than the deep region.ConclusionsThe results of our study did not support that the deep region of the multifidus is more degenerated in patients with lumbar spine pathology, as gross degenerative changes in muscle microstructure and macrostructure were the same in the superficial and deep regions of the multifidus. In these patients, the multifidus is not protected in order to maintain mobility and structural stability of the spine.

The development of ultrashort echo time (UTE) MRI sequences has led to improved imaging of tissues with short TEight knee joints from young (42 ± 12 years at death) donors were evaluated on a 3 T scanner using the UTE-Adiab-TUTE-Adiab-TWhile UTE-Adiab-T

Advancement of tissue engineering and regenerative medicine (TERM) strategies to replicate tissue structure and function has led to the need for noninvasive assessment of key outcome measures of a construct's state, biocompatibility, and function. Histology based approaches are traditionally used in pre-clinical animal experiments, but are not always feasible or practical if a TERM construct is going to be tested for human use. In order to transition these therapies from benchtop to bedside, rigorously validated imaging techniques must be utilized that are sensitive to key outcome measures that fulfill the FDA standards for TERM construct evaluation. This review discusses key outcome measures for TERM constructs and various clinical- and research-based imaging techniques that can be used to assess them. Potential applications and limitations of these techniques are discussed, as well as resources for the processing, analysis, and interpretation of biomedical images.

BackgroundPhysical activity (PA) in pre-clinical rheumatoid arthritis (RA) is associated with lower RA risk and disease severity. Yet, PA in RA patients is less than in counterparts without RA, which can be attributed partly to symptoms of inflammatory arthritis. Therefore, we investigated whether joint swelling, stiffness, or pain were associated with PA in first-degree relatives (FDRs) of RA patients, a population at higher risk for future RA.MethodsWe evaluated associations of joint stiffness, joint swelling, and joint pain with PA time in 268 FDRs with ≥2 visits over an average 1.2 years. Clinicians confirmed joint swelling. Participants self-reported joint stiffness and/or pain. PA during a typical 24-hour day was quantified via questionnaire, weighted to reflect metabolic expenditure, where 24 hours was the minimum PA time. Linear mixed models evaluated associations between symptoms and change in PA over time, adjusting for age, sex, race, body mass index, smoking, and RA-related autoantibodies.ResultsAverage weighted PA time was 37±7 hours. In cross-sectional analysis, PA time was 1.3±0.9 hours higher in FDRs reporting joint pain (p=0.15); and 0.8±1.6 and 0.4±1 hours lower in FDRs with joint swelling (p=0.60) and stiffness (p=0.69), respectively. Longitudinally, adjusting for baseline PA time, baseline symptoms were not significantly associated with changes in PA time. However, on average over time, joint stiffness and pain were associated with lower PA time (pinteraction=0.0002, pinteraction=0.002), and joint swelling was associated with higher PA time (pinteractionConclusionBaseline symptoms did not predict future PA time, but on average over time, joint symptoms influenced PA time.

OBJECTIVE Current management of traumatic peripheral nerve injuries is variable with operative decisions based on assumptions that irreversible degeneration of the human motor endplate (MEP) follows prolonged denervation and precludes reinnervation. However, the mechanism and time course of MEP changes after human peripheral nerve injury have not been investigated. Consequently, there are no objective measures by which to determine the probability of spontaneous recovery and the optimal timing of surgical intervention. To improve guidance for such decisions, the aim of this study was to characterize morphological changes at the human MEP following traumatic nerve injury. METHODS A prospective cohort (here analyzed retrospectively) of 18 patients with traumatic brachial plexus and axillary nerve injuries underwent biopsy of denervated muscles from the upper extremity from 3 days to 6 years after injury. Muscle specimens were processed for H & E staining and immunohistochemistry, with visualization via confocal and two-photon excitation microscopy. RESULTS Immunohistochemical analysis demonstrated varying degrees of fragmentation and acetylcholine receptor dispersion in denervated muscles. Comparison of denervated muscles at different times postinjury revealed progressively increasing degeneration. Linear regression analysis of 3D reconstructions revealed significant linear decreases in MEP volume (R = −0.92, R2 = 0.85, p = 0.001) and surface area (R = −0.75, R2 = 0.56, p = 0.032) as deltoid muscle denervation time increased. Surprisingly, innervated and structurally intact MEPs persisted in denervated muscle specimens from multiple patients 6 or more months after nerve injury, including 2 patients who had presented > 3 years after nerve injury. CONCLUSIONS This study details novel and critically important data about the morphology and temporal sequence of events involved in human MEP degradation after traumatic nerve injuries. Surprisingly, human MEPs not only persisted, but also retained their structures beyond the assumed 6-month window for therapeutic surgical intervention based on previous clinical studies. Preoperative muscle biopsy in patients being considered for nerve transfer may be a useful prognostic tool to determine MEP viability in denervated muscle, with surviving MEPs also being targets for adjuvant therapy.

Many chronic musculoskeletal conditions are associated with loss of muscle volume and quality, resulting in functional decline. While atrophy has long been implicated as the mechanism of muscle loss in these conditions, recent evidence has emerged demonstrating a degenerative phenotype of muscle loss consisting of disrupted muscle fiber membranes, infiltration of cells into muscle fibers, and as previously describer, possible replacement of muscle fibers by adipose tissue. Here, we use human lumbar spine pathology as a model system to provide a more comprehensive analysis of the morphological features of this mode of muscle loss between early and late stages of disease, including an analysis of the cell populations found in paraspinal muscle biopsies from humans with acute vs chronic lumbar spine pathology. Using longitudinal sections, we show that degeneration of muscle fibers is localized within a fiber (ie, focal), and is characterized by discontinuous or ragged membrane disruption, cellular infiltration, and apparently vacant space containing limited numbers of nuclei and hyper‐contractile cell debris. Samples from patients with acute and chronic pathology demonstrate similar magnitudes of muscle degeneration, however, larger proportions of PDGFRβ‐positive progenitor cells and leukocytes were observed in the acute group, with no differences in myogenic cells, macrophages, or T‐cells. By better understanding the cell population behaviors over the course of disease, therapies can be optimized to address the appropriate targets and timing of administration to minimize the functional consequences of muscle degeneration in lumbar spine pathology., Muscle degeneration is highly prevalent in acute and chronic lumbar spine pathology. Individuals with acute pathology demonstrate larger proportions of fibroadipogenic progenitor cells (FAPS) and leukocytes than those with chronic disease. These cells may contribute to the tissue compositional changes that lead to poor outcomes in lumbar spine pathology

Defining variations in skeletal muscle passive mechanical properties at different size scales ranging from single muscle fibers to whole muscles is required in order to understand passive muscle function. It is also of interest from a muscle structural point-of-view to identify the source(s) of passive tension that function at each scale. Thus, we measured passive mechanical properties of single fibers, fiber bundles, fascicles, and whole muscles in three architecturally diverse muscles from New Zealand White rabbits (n = 6) subjected to linear deformation. Passive modulus was quantified at sarcomere lengths across the muscle’s anatomical range. Titin molecular mass and collagen content were also quantified at each size scale, and whole muscle architectural properties were measured. Passive modulus increased non-linearly from fiber to whole muscle for all three muscles emphasizing extracellular sources of passive tension (p < 0.001), and was different among muscles (p < 0.001), with significant muscle by size-scale interaction, indicating quantitatively different scaling for each muscle (p < 0.001). These findings provide insight into the structural basis of passive tension and suggest that the extracellular matrix (ECM) is the dominant contributor to whole muscle and fascicle passive tension. They also demonstrate that caution should be used when inferring whole muscle properties from reduced muscle size preparations such as muscle biopsies.

Magnetic resonance imaging (MRI) is a diagnostic tool that can be used to noninvasively assess lumbar muscle size and fatty infiltration, important biomarkers of muscle health. Diffusion tensor imaging (DTI) is an MRI technique that is sensitive to muscle microstructural features such as fiber size (an important biomarker of muscle health), which is typically only assessed using invasive biopsy techniques. The goal of this study was to establish normative values of level‐dependent lumbar muscle size, fat signal fraction, and restricted diffusion assessed by MRI in a highly active population. Forty‐two active‐duty Marines were imaged using a (a) high‐resolution anatomical, (b) fat‐water separation, and (c) DT‐MRI scan. The multifidus and erector spinae muscles were compared at each level using two‐way repeated measures ANOVA. Secondary analysis included Three dimensional (3D) reconstructions to qualitatively assess lumbar muscle size, fatty infiltration, and fiber orientation via tractography. The erector spinae was found to be larger than the multifidus above L5, with lower fat signal fraction above L3, and a less restricted diffusion profile than the multifidus above L4, with this pattern reversed in the lower lumbar spine. 3D reconstructions demonstrated accumulations of epimuscular fat in the anterior and posterior regions of the lumbar musculature, with minimal intramuscular fatty infiltration. Tractography images demonstrated different orientations of adjacent lumbar musculature, which cannot be visualized with standard MRI pulse sequences. The level dependent differences found in this study provide a normative baseline, for which to better understand whole muscle and microstructural changes associated with aging, low back pain, and pathology., Magnetic resonance imaging (MRI) is a diagnostic tool that can be used to noninvasively assess lumbar muscle size and fatty infiltration, important biomarkers of muscle health. Diffusion tensor imaging (DTI) is an MRI technique that is sensitive to muscle microstructural features such as fiber size (an important biomarker of muscle health), which is typically only assessed using invasive biopsy techniques. The goal of this study was to establish normative values of level‐dependent lumbar muscle size, fat signal fraction, and restricted diffusion assessed by MRI in a highly active population.

Botulinum Neurotoxin A (BoNT-A) is a potent neurotoxin with several clinical applications. The goal of this study was to utilize co-expression network theory to analyze temporal transcriptional data from skeletal muscle after BoNT-A treatment. Expression data for 2000 genes (extracted using a ranking heuristic) served as the basis for this analysis. Using weighted gene co-expression network analysis (WGCNA), we identified 19 co-expressed modules, further hierarchically clustered into five groups. Quantifying average expression and co-expression patterns across these groups revealed temporal aspects of muscle's response to BoNT-A. Functional analysis revealed enrichment of group 1 with metabolism; group 5 with contradictory functions of atrophy and cellular recovery; and groups 2 and 3 with extracellular matrix (ECM) and non-fast fiber isoforms. Topological positioning of two highly ranked, significantly expressed genes— Dclk1 and Ostalpha —within group 5 suggested possible mechanistic roles in recovery from BoNT-A induced atrophy. Phenotypic correlations of groups with titin and myosin protein content further emphasized the effect of BoNT-A on the sarcomeric contraction machinery in early phase of chemodenervation. In summary, our approach revealed a hierarchical functional response to BoNT-A induced paralysis with early metabolic and later ECM responses and identified putative biomarkers associated with chemodenervation. Additionally, our results provide an unbiased validation of the response documented in our previous work.

Introduction: Neurotoxin injection is used to treat a wide variety of neuromuscular disorders. The purpose of this study was to measure the functional and structural properties of Botulinum toxin-injected adult rat skeletal muscle over nearly the entire rat lifespan. Methods: Ten groups of animals were subjected to either neurotoxin injection (Botox®, Type A, Allergan, Irvine, CA, USA; BT-A) or saline solution injection. Neurotoxin-injected animals (n=90) were analyzed at different time points: 1 week, 1 month, 3 months, 6 months, 12 months, or 18 months. Results: In spite of the recovery of structural features such as muscle mass and fiber area by 12-months after neurotoxin injection, dorsiflexion torque production remained significantly depressed by 25% even at this time point. Discussion: These data demonstrate that, after a single BT-A injection, while gross muscle morphology recovers over a 12-month time period, loss of contractile function does not. This article is protected by copyright. All rights reserved.

Histological and cell-level changes in the lumbar musculature in individuals with chronic lumbar spine degenerative conditions are not well characterized. Although prior literature supports evidence of changes in fiber type and size, little information exists describing the tissue quality and biology of pathological features of muscle in this population. The purpose of this study was to quantify multifidus tissue composition and structure, inflammation, vascularity, and degeneration in individuals with chronic degenerative lumbar spine pathology. Human multifidus biopsies were acquired from 22 consecutive patients undergoing surgery for chronic degenerative lumbar spine pathology. Relative fractions of muscle, adipose, and extracellular matrix were quantified along with muscle fiber type and cross-sectional area (CSA) and markers of inflammation, vascularity, satellite cell density, and muscle degeneration. On average, multifidus biopsies contained 48.5% muscle, 11.7% adipose tissue, and 26.1% collagen tissue. Elevated inflammatory cell counts (48.5 ± 30.0 macrophages/mm2) and decreased vascularity (275.6 ± 69.4 vessels/mm2) were also observed compared to normative values. Satellite cell densities were on average 13 ± 9 cells per every 100 muscle fibers. Large fiber CSA (3,996.0 ± 1,909.2 um2) and a predominance of type I fibers (61.8 ± 18.0%) were observed in addition to evidence of pathological degeneration-regeneration cycling (18.8 ± 9.4% centrally nucleated fibers, and 55.2 ± 24.2% of muscle regions containing degeneration). High levels of muscle degeneration, inflammation, and decreased vascularity were commonly seen in human multifidus biopsies of individuals with lumbar spine pathology in comparison to normative data. Evidence of active muscle degeneration suggests that changes in muscle tissue are more complex than simple atrophy. This article is protected by copyright. All rights reserved

Author(s): Shahidi, Bahar; Parra, Callan L; Berry, David B; Hubbard, James C; Gombatto, Sara; Zlomislic, Vinko; Allen, R Todd; Hughes-Austin, Jan; Garfin, Steven; Ward, Samuel R | Abstract: Study designRetrospective chart analysis of 199 individuals aged 18 to 80 years scheduled for lumbar spine surgery.ObjectiveThe purpose of this study was to quantify changes in muscle cross-sectional area (CSA) and fat signal fraction (FSF) with age in men and women with lumbar spine pathology and compare them to published normative data.Summary of background dataPathological changes in lumbar paraspinal muscle are often confounded by age-related decline in muscle size (CSA) and quality (fatty infiltration). Individuals with pathology have been shown to have decreased CSA and fatty infiltration of both the multifidus and erector spinae muscles, but the magnitude of these changes in the context of normal aging is unknown.MethodsIndividuals aged 18 to 80 years who were scheduled for lumbar surgery for diagnoses associated with lumbar spine pain or pathology were included. Muscle CSA and FSF of the multifidus and erector spinae were measured from preoperative T2-weighted magnetic resonance images at the L4 level. Univariate and multiple linear regression analyses were performed for each outcome using age and sex as predictor variables. Statistical comparisons of univariate regression parameters (slope and intercept) to published normative data were also performed.ResultsThere was no change in CSA with age in either sex (P g 0.05), but women had lower CSAs than men in both muscles (P l 0.0001). There was an increase in FSF with age in erector spinae and multifidus muscles in both sexes (P l 0.0001). Multifidus FSF values were higher in women with lumbar spine pathology than published values for healthy controls (P = 0.03), and slopes tended to be steeper with pathology for both muscles in women (P l 0.08) but not in men (P g 0.31).ConclusionLumbar muscle fat content, but not CSA, changes with age in individuals with pathology. In women, this increase is more profound than age-related increases in healthy individuals.Level of evidence3.