MicroRNAs (miRNAs) are a class of small non-coding RNAs that have emerged as potential predictive, prognostic, and therapeutic biomarkers, relevant to many pathophysiological conditions including limb immobilization, osteoarthritis, sarcopenia, and cachexia. Impaired musculoskeletal homeostasis leads to distinct muscle atrophies. Understanding miRNA involvement in the molecular mechanisms underpinning conditions such as muscle wasting may be critical to developing new strategies to improve patient management. MicroRNAs are powerful post-transcriptional regulators of gene expression in muscle and, importantly, are also detectable in the circulation. MicroRNAs are established modulators of muscle satellite stem cell activation, proliferation, and differentiation, however, there have been limited human studies that investigate miRNAs in muscle wasting. This narrative review summarizes the current knowledge as to the role of miRNAs in the skeletal muscle differentiation and atrophy, synthesizing the findings of published data. Cite this article: Bone Joint Res 2020;9(11):798–807

Objectives. The most prevalent disorders of the shoulder are related to the muscles of rotator cuff. In order to develop a mechanical method for the evaluation of the rotator cuff muscles, we created a database of isometric force generation by the rotator cuff muscles in normal adult population. We hypothesised the existence of variations according to age, gender and dominancy of limb. Methods. A total of 400 healthy adult volunteers were tested, classified into groups of 50 men and women for each decade of life. Maximal isometric force was measured at standardised positions for supraspinatus, infraspinatus and subscapularis muscles in both shoulders in every person. Torque of the force was calculated and normalised to lean body mass. The profiles of mean torque-time curves for each age and gender group were compared. Results. Our data showed that men gradually gained maximal strength in the fifth decade, and showed decreased strength in the sixth. In women the maximal strength was gained in the fourth decade with gradual decline to the sixth decade of life. The dominant arm was stronger in most of the tested groups. The torque profiles of the rotator cuff muscles in men at all ages were significantly higher than that in women. Conclusions. We found previously unrecognised variations of rotator cuff muscles’ isometric strength according to age, gender and dominancy in a normal population. The presented data may serve as a basis for the future studies for identification of the abnormal patterns of muscle isometric strength in patients with pathology of the rotator cuff muscles. Cite this article: Bone Joint Res 2013;2:214–19

Objectives. Lower limb muscle power is thought to influence outcome following total knee replacement (TKR). Post-operative deficits in muscle strength are commonly reported, although not explained. We hypothesised that post-operative recovery of lower limb muscle power would be influenced by the number of satellite cells in the quadriceps muscle at time of surgery. . Methods. Biopsies were obtained from 29 patients undergoing TKR. Power output was assessed pre-operatively and at six and 26 weeks post-operatively with a Leg Extensor Power Rig and data were scaled for body weight. Satellite cell content was assessed in two separate analyses, the first cohort (n = 18) using immunohistochemistry and the second (n = 11) by a new quantitative polymerase chain reaction (q-PCR) protocol for Pax-7 (generic satellite cell marker) and Neural Cell Adhesion Molecule (NCAM; marker of activated cells). Results. A significant improvement in power output was observed post-operatively with a mean improvement of 19.7 W (95% confidence interval (CI) 14.43 to 30.07; p < 0.001) in the first cohort and 27.5 W (95% CI 13.2 to 41.9; p = 0.002) in the second. A strong correlation was noted between satellite cell number (immunohistochemistry) and improvement in patient power output (r = 0.64, p = 0.008). Strong correlation was also observed between the expression of Pax-7 and power output (r = 0.79, p = 0.004), and the expression of NCAM and power output (r = 0.84, p = 0.001). The generic marker explained 58% of the variation in power output, and the marker of activated cells 67%. Conclusions. Muscle satellite cell content may determine improvement in lower limb power generation (and thus function) following TKR

Introduction and Objective. Clinically, it is considered that spastic muscles of patients with cerebral palsy (CP) are shortened, and produce higher force in shorter muscle lengths. Yet, direct quantification of spastic muscles’ forces is rare. Remarkably, previous intraoperative tests in which muscle forces are measured directly as a function of joint angle showed for spastic gracilis (GRA) that its passive forces are low, and only a small percentage of its maximum active force is measured in flexed knee positions. However, the relationship of force characteristics of spastic GRA with its muscle-tendon unit length (l. MTU. ) is unknown. Combining intraoperative experiments with participants’ musculoskeletal models developed based on their gait analyses, we aimed to test if spastic GRA muscle (1) operates at short l. MTU. compared to that of typically developing (TD) children, and exerts higher (2) passive and (3) active forces at shorter lengths, within gait-relevant l. MTU. range. Materials and Methods. Ten limbs of seven children with CP (GMFCS-II) were tested. Pre-surgery, gait analyses were conducted. Intraoperatively, isometric spastic GRA distal forces were measured in ten hip-knee joint angle combinations, in two conditions: (i) passive state and (ii) maximal activation of the GRA exclusively. In OpenSim, gait_2392 model was used for each limb to calculate l. MTU. 's per each hip and knee angle combination and the gait-relevant l. MTU. range, and to analyze gait relevant spastic muscle force - l. MTU. data. l. MTU. values were normalized for the participants’ thigh lengths. Two-way ANOVA was used to compare the patients’ l. MTU. to those of the seven age-matched TD children to test the first hypothesis. In order to test the second and the third hypotheses, Spearman's rank correlation coefficient (ρ) was calculated to seek a correlation between the muscle's operational length (represented by mean l. MTU. within gait cycle) and muscular force characteristics (the percent force at shortest l. MTU. of peak force, either in passive or in active conditions) within gait-relevant l. MTU. range. Results. ANOVA showed that l. MTU. 's of spastic GRA are shorter (on average by 15.4%) compared to those of TD. At the shortest gait-relevant l. MTU. , the GRA passive force was 84.6 (13.7)% of the peak passive force; and the active force was 55.8 (33.9)% of the peak active force. Passive state forces show an increase at longer lengths, whereas active state force characteristics vary in a patient-specific way. Spearman's rank correlation indicated weak correlations between muscle's operational length and muscular force characteristics (ρ= −0.30 P= 0.40, and ρ= −0.27 P= 0.45, for passive and active states, respectively). Therefore, only the first hypothesis was confirmed. Conclusions. Novel muscle force - l. MTU. data for spastic GRA were obtained using intraoperative data and modelling combined. The modelling showed in concert with the clinical considerations that spastic GRA may be a shortened muscle. However, because the model does not distinguish the muscle-belly and tendon lengths, it cannot isolate shorter muscle belly length and how this compares to the data of TD children remains unknown. Moreover, the absence of a strong correlation between shorter operational muscle length and higher force production either in passive or in active conditions highlights the influence of other factors (e.g., muscle structural proteins, and muscle mechanical characteristics including intermuscular interactions etc.) on the pathology rather than ascribing it solely to the length of a spastic muscle itself

Background. Spastic muscles of patients with cerebral palsy (CP) are considered structurally as shortened muscles, that produce high force in short muscle lengths. Yet, previous intraoperative studies in which muscles’ forces are measured directly as a function of joint angle showed consistently that spastic knee flexor muscles produce a low percentage of their maximum force in flexed knee positions. They also showed effects of epimuscular myofascial force transmission (EMFT): simultaneous activation of different muscles elevated target muscle's force. However, quantification of spastic muscle's force - muscle-tendon unit length (l. MTU. ) data during gait is lacking. Aim. Combining intraoperative experiments with participants’ musculoskeletal models developed based on their gait analyses, we aimed to test the following hypotheses: activated spastic semitendinosus (ST) muscle (1) operates at short l. MTU. 's during gait, forces are (2) low at short l. MTU. 's and (3) increase by co-activating other muscles. Methods. Ten limbs of seven children with CP (GMFCS-II) were tested. Pre-surgery, gait analyses were conducted. Intraoperatively, isometric spastic ST distal forces were measured in ten hip-knee joint angle combinations, in two conditions: (i) activation of the ST individually and (ii) simultaneously with the gracilis, biceps femoris, and rectus femoris muscles endorsing EMFT. In OpenSim, gait_2392 model was used for each limb to (a) calculate l. MTU. per each hip and knee angle combination and the gait relevant l. MTU. range, and (b) analyze gait relevant spastic muscle force - l. MTU. data. Two-way ANOVA was used to compare the patients’ l. MTU. to those of the seven age-matched typically developing (TD) children. l. MTU. values were normalized for the participants’ thigh length. (a) was used to test hypothesis (1) and (b) to test hypotheses (2) and (3): in condition (i), the percent of peak force exerted at the shortest l. MTU. calculated per limb was used as a metric for (2). In condition (ii), mean percent change in muscle force calculated within gait-relevant l. MTU. range was used as a metric for (3). Results. Modeling showed that l. MTU. of spastic ST during gait is shorter on average by 14.1% compared to TD. The ST active force at the shortest gait-relevant l. MTU. was 68.6 (20.6)% (39.9–99.2%) of the peak force. Simultaneous activation of other muscles caused substantial increases in force (minimally by 11.1%, up to several folds, with an exception for one limb). Therefore, only the first and third hypotheses were confirmed. Conclusion. The modeling showed in concert with the clinical considerations that spastic ST may be a shortened muscle that produces high force in short muscle lengths. However, this contrasts intraoperative data, which shows only low forces in flexed knee positions. Note that, the model does not distinguish the muscle-belly and tendon lengths. Therefore, it cannot isolate shorter muscle length and how this compares to the data of TD children remains unknown. Yet, the effects of co-activation of other muscles shown intraoperatively to cause an increase of the spastic ST's force are observed also in muscle force - l. MTU. data characterizing gait. Therefore, if indeed spastic ST produces high forces in short muscle-belly lengths alone, elevated forces due to co-activation of other muscles may be considered as a contributor to the patients’ pathological gait. Otherwise, such EMFT effect may be the main determinant of the pathological condition

The inability to replace human muscle in surgical practice is a significant challenge. An artificial muscle controlled by the nervous system is considered a potential solution for this. We defined it as neuromuscular prosthesis. Muscle loss and dysfunction related to musculoskeletal oncological impairments, neuromuscular diseases, trauma or spinal cord injuries can be treated through artificial muscle implantation. At present, the use of dielectric elastomer actuators working as capacitors appears a promising option. Acrylic or silicone elastomers with carbon nanotubes functioning as the electrode achieve mechanical performances similar to human muscle in vitro. However, mechanical, electrical, and biological issues have prevented clinical application to date. In this study, materials and mechatronic solutions are presented which can tackle current clinical problems associated with implanting an artificial muscle controlled by the nervous system. Progress depends on the improvement of the actuation properties of the elastomer, seamless or wireless integration between the nervous system and the artificial muscle, and on reducing the foreign body response. It is believed that by combining the mechanical, electrical, and biological solutions proposed here, an artificial neuromuscular prosthesis may be a reality in surgical practice in the near future

Summary Statement. Paraspinal muscle contain higher proportion of slow-twich fibers. The fixation of the rat tail induced transition of muscle fiber types in the paravertebral muscles characterised by the decrease in the proportion of the slow type myosin heavy chain. Introduction. Lumbar degenerative kyphosis often accompanies back pain, easy fatigability, fatty degeneration and atrophy of back muscles. There are two types of skeletal muscle fibers according to oxidative activities: slow-twich (Type 1) and fast-twitch (Type 2) fibers. Type 2 fibers were subdivided into three types: Type 2A, 2B and 2D/X. Each fiber type primarily expresses a specific isoform of myosin heavy chain (MHC). It has been known that back muscles contain higher proportion of MHC type 1. However, the impact of kyphosis on the proportion of fiber types in the paravertebral muscles has not been fully understood. The aim of this study is to analyze the transition of muscle fiber types after kyophotic or straight fixation using a rat tail model. Methods. A rat tail was fixed in straight or kyphotic position (straight or kyphosis group) by a custom-made external fixator and wires. A group of animals which underwent only pierced wounds in their tails served as control. The gene expression profiles of isoforms of MHCs in dorsal coccygeal muscles were analyzed by quantitative RT-PCR. The fiber types of muscles were assessed using SDS-PAGE. Band densities of silver-stained gel were quantified. Results. At first, the gene expression profiles of MHCs and protein expression in the dorsal coccygeal muscles were compared with tibilis anterior and gastrocunemius muscles. Higher proportion of MHC type 1 gene and protein expression were confirmed in the dorsal coccygeal muscles than tibialis anterior and gastrocuneimus muscles. MHC type 2B protein expression was not detected in dorsal coccygeal muscles. Next, coccygeal muscles after straight or kyphotic fixation were analyzed and compared with control. Gene expression of MHC type 1 was decreased at 7 and 28 days after fixation in straight and kyphosis group. The significant difference was seen at 28 days in kyphosis group. The band densities of MHC protein type 1 and 2A plus 2D/X were decreased in both straight and kyophosis groups at 28 days after fixation while sample volume was adjusted by wet wight of dissected coccygeal muscles. The mean proportion of MHC protein type 1 separated by SDS-PAGE were decreased in straight and kyphosis group. The difference was significant in straight group. Discussion. Our results demonstrated that the fixation of the rat tail induced transition of muscle fiber types in the paravertebral muscles characterized by the decrease in the proportion of the MHC type 1. Back muscles are required to contract continuously to keep posture. Slow-twitch fibers in back muscle contribute for continuous contraction. Slow-twitch fibers utilise energy efficiently by oxidative process while fast-twitch fibers mainly consume glucose through glycolysis producing lactate acid. Not only decreased amount of MHC but also decreased proportion of MHC type 1 might be the reason of easy fatigability in lumbar degenerative kyphosis. The limitations of this study is the difference between human paravertebral and rat coccygeal muscles and short duration of observation

Patients demonstrate distinct trajectories of recovery after THA. The purpose of this study was to assess the impact of adjacent muscle quality on postoperative hip kinematics. We hypothesized that patients with better adjacent muscle quality (less fatty infiltration) would have greater early biomechanical improvement. Adults undergoing primary THA were recruited. Preoperative MRI was obtained and evaluated via Scoring Hip Osteoarthritis with MRI Scores (SHOMRI, Lee, 2015). Muscle quality was assessed by measuring fat fraction [FF] from water-fat sequences. Biomechanics were assessed preoperatively and six weeks postoperatively during a staggered stance sit-to-stand using the Kinematic Deviation Index (KDI, Halvorson, 2022). Spearman's rho was used to assess correlations between muscle quality and function. Ten adults (5M, 5F) were recruited (average age: 60.1, BMI: 23.79, SHOMRI: 40.6, KDI: 2.96). Nine underwent a direct anterior approach and one a posterior approach. Preoperatively, better biomechanical function was very strongly correlated with lower medius FF (rho=0.89), strongly correlated with lower FF in the minimus (rho=0.75) and tensor fascia lata (TFL) FF (rho=0.70), and weakly correlated with SHOMRI (rho=0.29). At six weeks, greater biomechanical improvement was strongly correlated with lower minimus FF (rho=0.63), moderately correlated with medius FF (rho=0.59), and weakly correlated with TFL FF (rho=0.26) and SHOMRI (rho=0.39). Lastly, medius FF was moderately correlated with SHOMRI (rho=0.42) with negligible correlations between SHOMRI and FF in the minimus and TFL. These findings suggest adjacent muscle quality may be related to postoperative function following THA, explaining some of the variability and supporting specialized muscle rehabilitation or regeneration therapy to improve outcomes

Introduction. Intra-articular injury has been described as primary cause of pain in hip dysplasia. At this point it is unknown whether external muscle-tendon related pain coexists with intra-articular pathology. The primary aim was to identify muscle-tendon related pain in 100 dysplasia patients. The secondary aim was to test if muscle-tendon related pain is linearly associated to self-reported hip disability and muscle strength in patient with hip dysplasia. Materials and methods. One hundred patients (17 men) with a mean age of 29 years (SD 9) were included. Clinical entity approach was carried out to identify muscle-tendon related pain. Muscle strength was assessed with a handheld dynamometer and self-reported hip disability was recorded with the Copenhagen Hip and Groin Outcome Score (HAGOS). Results. Iliopsoas- and abductor-related pain were most prevalent with prevalences of 56% (CI 46; 66) and 42% (CI 32; 52), respectively. Adductor-, hamstrings- and rectus abdominis-related pain were less common. There was a significant inverse linear association between muscle-tendon related pain and self-reported hip disability ranging from −3.35 to −7.51 points in the adjusted analysis (p<0.05). Likewise an inverse linear association between muscle-tendon related pain and muscle strength was found ranging from −0.11 Nm/kg to −0.12 Nm/kg in the adjusted analysis (p<0.05). Conclusion. Muscle-tendon related pain seem to exist in about half of patients with hip dysplasia with a high prevalence of muscle-tendon related pain in the iliopsoas and the hip abductors and affects patients” self-reported hip disability and muscle strength negatively

Purpose of study and background. Spinal muscle area (SMA) is often employed to assess muscle functionality and is important for understanding the risk individuals may have of developing back pain or the risk of postural instability and falls.. However, handgrip strength (HGS) has also been utilized as a measure of general muscle capacity. This study aimed to examine the relationship between SMA and HGS to assess whether the latter could be used as an accurate indicator of the former. Methods. 150 participants (75 males and 75 females, aged 47–70 years) were selected from the UK Biobank dataset. Handgrip strength values were extracted and averaged over left and right values. Abdominal MRI images were examined and cross-sectional area of the erector spinae and multifidus determined at the L3/4 level and summed to provide a total muscle area. Results. HGS and SMA (mean±sd) were 39.6 ± 7.4 kg and 4664 ± 868 mm. 2. for males and 24.7 ± 5.9 kg, and 3822 ± 579 mm. 2. for females. Pearson correlation between HGS and SMA was r = 0.41 for males (p = <0.001), r = 0.40 for females (p = <0.001), and r = 0.61 for the combined groups (p<0.001). Conclusion. Significant correlations were found between HGS and SMA for individual sexes and combined groups. However, although HGS may be a useful measure for predicting modifications in group responses in spinal muscle function, for example, following an intervention, it does not have the power to confidently predict muscle values at an individual participant level. Conflicts of interest: No conflicts of interest. Sources of funding: Prince Sattam University, KSA, provided a PhD scholarship for Salman Alharthi

Aims. Rotator cuff (RC) injuries are characterized by tendon rupture, muscle atrophy, retraction, and fatty infiltration, which increase injury severity and jeopardize adequate tendon repair. Epigenetic drugs, such as histone deacetylase inhibitors (HDACis), possess the capacity to redefine the molecular signature of cells, and they may have the potential to inhibit the transformation of the fibro-adipogenic progenitors (FAPs) within the skeletal muscle into adipocyte-like cells, concurrently enhancing the myogenic potential of the satellite cells. Methods. HDACis were added to FAPs and satellite cell cultures isolated from mice. The HDACi vorinostat was additionally administered into a RC injury animal model. Histological analysis was carried out on the isolated supra- and infraspinatus muscles to assess vorinostat anti-muscle degeneration potential. Results. Vorinostat, a HDACi compound, blocked the adipogenic transformation of muscle-associated FAPs in culture, promoting myogenic progression of the satellite cells. Furthermore, it protected muscle from degeneration after acute RC in mice in the earlier muscle degenerative stage after tenotomy. Conclusion. The HDACi vorinostat may be a candidate to prevent early muscular degeneration after RC injury. Cite this article: Bone Joint Res 2024;13(4):169–183

Tenotomy of the iliopsoas tendon has been described as an effective procedure to treat refractive groin pain induced by iliopsoas tendinitis. However, the procedure forces the rectus femoris to act as the primary hip flexor and little is known about the long-term effects of this procedure on the peri-articular muscle envelope (PAME). Studies suggest that iliopsoas tenotomy results in atrophy of the iliopsoas and decreased hip flexion strength with poorer outcomes, increasing the susceptibility for secondary tendinopathy. The aim of this study is to describe changes in the PAME following psoas release. All patients who presented for clinical examination at our hospital between 2016 and 2021 were retrospectively reviewed. Patients who presented after psoas tenotomy with groin pain and who were unable to actively lift the leg against gravity, were included. Pelvic MRI was taken. Qualitative muscle evaluation was done with the Quartile classification system. Quantitative muscle evaluation was done by establishing the cross-sectional area (CSA). Two independent observers evaluated the ipsi- and contralateral PAME twice. The muscles were evaluated on the level: iliacus, psoas, gluteus minimus-medius-maximus, rectus femoris, tensor fasciae lata, piriformis, obturator externus and internus. For the qualitative evaluation, the intra- and inter-observer reliability was calculated by using kappastatistics. A Bland-Altman analysis was used to evaluate the intra- and inter-observer reliability for the quantitative evaluation. The Wilcoxon test was used to evaluate the changes between the ipsi- and contra-lateral side. 17 patients were included in the study. Following psoas tenotomy, CSA reduced in the ipsilateral gluteus maximus, if compared with the contralateral side. Fatty degeneration occurred in the tensor fascia latae. Both CSA reduction and fatty degeneration was seen for psoas, iliacus, gluteus minimus, piriformis, obturator externus and internus. No CSA reduction and fatty degeneration was seen for gluteus medius and rectus femoris. Conclusions/Discussion. Following psoas tenotomy, the PAME of the hip shows atrophy and fatty degeneration. These changes can lead to detrimental functional problems and may be associated with debilitating rectus femoris tendinopathy. In patients with psoas tendinopathy, some caution is advised when considering an iliopsoas tenotomy

Aims. The aim of this study was to describe a quantitative 3D CT method to measure rotator cuff muscle volume, atrophy, and balance in healthy controls and in three pathological shoulder cohorts. Methods. In all, 102 CT scans were included in the analysis: 46 healthy, 21 cuff tear arthropathy (CTA), 18 irreparable rotator cuff tear (IRCT), and 17 primary osteoarthritis (OA). The four rotator cuff muscles were manually segmented and their volume, including intramuscular fat, was calculated. The normalized volume (NV) of each muscle was calculated by dividing muscle volume to the patient’s scapular bone volume. Muscle volume and percentage of muscle atrophy were compared between muscles and between cohorts. Results. Rotator cuff muscle volume was significantly decreased in patients with OA, CTA, and IRCT compared to healthy patients (p < 0.0001). Atrophy was comparable for all muscles between CTA, IRCT, and OA patients, except for the supraspinatus, which was significantly more atrophied in CTA and IRCT (p = 0.002). In healthy shoulders, the anterior cuff represented 45% of the entire cuff, while the posterior cuff represented 40%. A similar partition between anterior and posterior cuff was also found in both CTA and IRCT patients. However, in OA patients, the relative volume of the anterior (42%) and posterior cuff (45%) were similar. Conclusion. This study shows that rotator cuff muscle volume is significantly decreased in patients with OA, CTA, or IRCT compared to healthy patients, but that only minimal differences can be observed between the different pathological groups. This suggests that the influence of rotator cuff muscle volume and atrophy (including intramuscular fat) as an independent factor of outcome may be overestimated. Cite this article: Bone Jt Open 2021;2(7):552–561

Both intrinsic and extrinsic hand muscles contribute to finger flexion; however there are different ways in which individuals can flex their fingers. Due to different muscle insertions, it is possible to distinguish the mechanical effect of intrinsic muscles from extrinsic muscles. The aim of this observational study was to investigate the degree to which individuals in the population rely on either their intrinsic or extrinsic hand muscles. A high frequency camera was used to record the hands of 31 healthy participants, aged between 18 to 40, while they made a fist repeatedly. The hands were placed on a horizontal plane and the video was taken from the ulnar side, aligned horizontally with the hand. The maximum vertical distance between the fingertip and the distal palmer creases (XY) was recorded using WIN analyze 3D software. Three examiners independently analysed the videos and classified them into intrinsic dominant, extrinsic dominant or a mixed pattern. A t-test was performed on the XY values for the three different categories. The XY height difference between the intrinsic and extrinsic groups were statistically significant (P=0.001). The XY of mixed and intrinsic was also statistically significant (p=0.012) but not for mixed and extrinsic (p=0.46). Assessment of time when movement starts at each individual joint showed significant difference with intrinsic predominant moving the MCPJ before IPJ and extrinsic dominant individual moving their IPJ before MCPJ. This study shows that there is a difference in hand muscle dominance between individuals. More importantly it shows that there are individuals who rely on their intrinsic hand muscles more than their extrinsic muscles

Falls in adults are a major problem and can lead to injuries and death. In order to better understand falls and successful recoveries, identifying kinematics, kinetics, and muscle forces during recovery from loss of balance is crucial. To obtain reactive gait patterns, participants must be subjected to unexpected perturbations such as trips and slips. Previous researchers have reported kinetics recovery data following stumbling; however, the muscle force recovery patterns remain unknown. To better target exercises to reduce the risk of falls, we must first understand which muscles, their magnitude, and their coordination patterns, play a role in a successful recovery from a trip and a slip. Additionally, knowing the successful patterns of lower limb function can help with the diagnosis of faulty movements. A total of 20 healthy adults in their twenties with similar athletic backgrounds were perturbed on a split-belt treadmill using Computer-Assisted Rehabilitation Environment (Motkforce Link) at a preset speed of 1.1m/s. Two kinds of perturbations were administered: slip and trip. Slips were simulated by accelerating one belt, whereas trips were simulated by decelerating one belt. Both perturbations had similar intensity and only differed in the direction. Computational modeling was used to obtain lower-limb function during the compensatory step. SPM paired t-test was used to compare differences in recovery strategies between slip and trip through magnitude and patterns of joints. There were no significant differences in joint angles post tripping vs post-slipping. Results of net joint moments showed that compensating for the loss of balance due to tripping required a higher ankle plantarflexion moment than slipping (at 22-52%; 1.2± 0.3vs0.4±0.2, p<0.001). Additionally, larger gluteus maximus (at 40-50%;8.7±3.8vs2.7±1.1N/kg, p=0.001), gluteus medius (at23~33%; 22.6±5.7vs6.8±3.6N/kg, p<0.001) were generated than post-slipping, respectively. These findings suggested that greater GMAX and GMED forces are required post-trip recovery than slip. Future analysis of trip recovery showed the importance of ankle joint in recovering from forward and backward fall. These results can be used as references in remote diagnosis of joint and muscle weakness and assessment of the risk of falls with the use of accelerometers

Introduction. There is a lack of evidence-based treatments for patients with chronic pain after total knee arthroplasty (TKA). It is well-established that knee extensor and flexor muscle strength are markedly impaired following TKA, but no studies have examined muscle strength and power in patients with chronic pain after TKA. Therefore, the aim was to investigate if neuromuscular exercises and pain neuroscience education (PNE) were superior to PNE alone for improvement of muscle strength and power in patients with chronic pain after TKA. Method. This report presents the exploratory analysis of a randomized controlled trial (NCT03886259). Participants with chronic moderate-to-severe average daily pain intensity and no signs of prosthesis failure at least one year after primary TKA were included. Participants were randomized to receive either supervised neuromuscular exercise and PNE or the same PNE sessions alone. The outcomes were changes from baseline to 12-months for peak leg extension power and maximum muscle strength, measured during maximal voluntary isometric contractions, for the knee extensors and flexors. Result. Sixty-nine participants (age 62.2±7.2, 40 females) were included. No between-group differences were observed for peak leg extension power (difference 13.6 Watts, 95% CI -22.2 to 49.3), maximum knee extensor muscle strength (difference -20.9 Newtons, 95% CI -65.8 to 24.0) or maximum knee flexor muscle strength (difference 8.6 Newtons, 95% CI -11.9 to 29.1). Peak leg extension power (26.3 Watts, 95% CI 4.3 to 48.3) and maximum knee flexor muscle strength (19.7 Newtons, 95% CI 7.6 to 31.9) improved significantly in the neuromuscular exercise and PNE group with no significant improvements observed in the PNE alone group. Conclusion. Neuromuscular exercise and PNE did not improve muscle strength and power compared to PNE alone in patients with chronic pain after TKA. Acknowledgements. This study was funded by the Danish Rheumatism Association, the Svend Andersen Foundation and Lions Club Denmark

The direct anterior approach (DAA) is a popular minimally invasive approach for total hip arthroplasty (THA). It usually involves ligation of the lateral femoral circumflex artery's ascending branch (a-LFCA), which contributes to the perfusion of the tensor fasciae latae (TFL) muscle. Periarticular muscle status and clinical outcome were assessed after DAA-THA after a-LFCA preservation versus ligation. We evaluated surgical records of 161 patients undergoing DAA-THA with tentative preservation of the a-LFCA by the senior author between May and November 2021. Among 92 eligible patients, 33 (35 hips) featured successful preservation, of which 20 (22 hips, 13 female) participated in the study. From 59 patients with ligated a-LFCA, 26 (27 hips, 15 female) were enrolled, constituting the control group. MRI and clinical examinations were performed at 17–26 months to analyze volume and fatty infiltration of the TFL, gluteus medius and gluteus minimus muscles relative to the contralateral non-THA hip (15 preserved, 18 ligated). Clinical and radiographic data was retrospectively extracted from patient files. Patient-reported outcomes (PROMs) were added from the THA registry. There was a relative difference in TFL muscle volume of -6.27 cm. 3. (−9.89%, p=0.018) after a-LFCA preservation versus -8.6 cm. 3. (=11.62%, p=0.002) after ligation, without group differences (p>0.340). a-LFCA preservation showed lower relative TFL fatty infiltration (p=0.10). Gluteal muscle status was similar between sides and groups. Coxa valga morphology was more frequent in a-LFCA preservation (83%) than ligation (17%). Clinical outcomes showed high patient satisfaction in both groups, without difference in PROMs, but less anterolateral soft-tissue swelling after a-LFCA preservation (p<0.001). Despite excellent clinical results in both groups, preservation of the a-LFCA was associated with less TFL fatty infiltration and soft tissue swelling. Provided there is no compromise of intraoperative access we recommend a-LFCA preservation for DAA-THA

Abstract. Objectives. Acute compartment syndrome (ACS) is a progressive form of muscle ischaemia that is a surgical emergency and can have detrimental outcomes for patients if not treated optimally. The current problem is that there is no clear diagnostic threshold for ACS or guidance as to when fasciotomies should be performed. A new diagnostic method(s) is necessary to provide real-time information about the extent of muscle ischaemia in ACS. Given that lactic acid is produced by cells through anaerobic respiration, it may be possible to measure H+ ion concentration and to use this as a measure of ischaemia within muscle. Although we are familiar with the key biochemical metabolites involved in ischaemia; and the use of viability dyes in cell culture to distinguish between living or dead cells is well recognised; research has not been undertaken to correlate the biochemical and histological findings of ischaemia in skeletal muscle biopsies. Our primary aim was to investigate the potential for viability dyes to be used on live skeletal muscle biopsies (explants). Our secondary aim was to correlate the intramuscular pH readings with muscle biopsy viability. Methods. Nine euthanised Wistar rats were used. A pH catheter was inserted into one exposed gluteus medius muscles to record real-time pH levels and muscle biopsies were taken from the contralateral gluteus medius at the start of experiment and subsequently at every 0.1 of pH unit drop. Prior to muscle biopsy, the surface of the gluteus medius was painted with a layer of 50µmol/l Brilliant blue FCF solution to facilitate biopsy orientation. A 4mm punch biopsy tool was used to take biopsies. Each muscle biopsy was placed in a base mould filled with 4% ultra-low melting point agarose. The agarose embedded tissue block was sectioned to generate 400 micron thick tissue slices with a vibratome. The tissue slices were then placed in the staining solution with Hoechst 33342, Ethidium homodimer-1 and Calcein am. The tissue slices were imaged with Zeiss LSM880 confocal microscope's Z stack function. A dead muscle control was created by adding TritonX-100 to other tissue slices. For quantitative analyses, the images were analysed in Image J using the selection tool. This permitted individual cells to be identified and the mean grey value of each channel to be defined. Using the dead control, we were able to identify the threshold value for living cells using the Calcein AM channel. Results. Viability dyes, used primarily for cell cultures, can be used with skeletal muscle explants. Our study also showed that despite a significant reduction in tissue pH concentration over time, that almost 100% of muscle cells were still viable at pH 6.0, suggesting that skeletal muscle cells are robust to hypoxic insult in the absence of reperfusion. Conclusions. Viability dyes can be used on skeletal muscle biopsies. Further research investigating the likely associations between direct measured pH using a pH catheter, the concentrations of key cellular metabolic markers, and muscle tissue histology using vitality dyes in response to ischaemia, rather than hypoxia, is warranted. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Introduction. A 6cm femoral gain requires 5-Y during normal growth, but only 6–8-W surgically (x30–40 faster). In lengthening surgery, losses of muscle force (MF) and circumferences (MC) are major. Recovery is long, preventing sports till bone fusion. Can we maintain MC and strength throughout the entire lengthening and how?. We monitored for over 30 years patients for muscle force (isokinetic), circumferences, activities (including sports) and food intake, and acted on the 5 principles of the Osteostasis. Materials & Methods. Over 750 femoral lengthening with Full WB Nails (FWBN) got Isokinetic testing (≧1991), circumferences measurements (≧2012; 20-15-10-5-0cm above patella, max-calf, mini/max-ankle), food intake (≧2012), using MyFitnessPal App (≧2016), gradually enforced. Preoperative training along with a daily post-operative training are supervised by our trainers. Recommendations for food intake and activities were provided. Patients noted on a specific App all parameters. Compliance was noted. Results. Instead of a traditional 7–9cm circumference loss for 8–10cm gains using Ex-fix or nails, with FWBN and our protocols, no MC loss could be noted in compliant pre-trained patients, intensive early post-op resistance training, high calory intake (M:>4200, F:>3000; 20–25% Proteins) and supplements (no fat pad increase). Bone fusion could be obtained at the end of lengthening or within short weeks (Healing Index down to 8D/cm). Non-compliant patients (or using morphine), lost weight and MC. Conclusions. Increasing by 8–10cm muscle length, even bilaterally, and maintaining MC during lengthening, is possible, with very fast bone fusion. It requires building up several hundred of grams of muscles. The ‘building up equation’ associating resistance bike from the early post-operative phase with sports, strong food intake with increased protein intake, and added supplements with no morphine medication, proved to boost circumferences and bone fusion. It induced fast recovery, walking and sports capacities

Background. Trunk muscles play an important role in supporting the spinal column. A decline in trunk muscle mass, as measured by bioelectrical impedance analysis (TMM–BIA), is associated with low back pain and poor quality of life. Purpose. The purpose of this study was to determine whether TMM–BIA correlates with quantitative and functional assessments traditionally used for the trunk muscles. Methods. We included 380 participants (aged ≥ 65 years; 152 males, 228 females) from the Shiraniwa Elderly Cohort (Shiraniwa) study, for whom the following data were available: TMM–BIA, lumbar magnetic resonance imaging (MRI), and back muscle strength (BMS). We measured the cross-sectional area (CSA) and fat-free CSA of the paravertebral muscles (PVM), including the erector spinae (ES), multifidus (MF), and psoas major (PM), on an axial lumbar MRI at L3/4. The correlation between TMM–BIA and the CSA of PVM, fat-free CSA of PVM, and BMS was investigated. Results. TMMBIA correlated with the CSA of total PVM and each individual PVM. A stronger correlation between TMM–BIA and fat-free CSA of PVM was observed. The TMM–BIA also strongly correlated with BMS. Conclusion. TMM–BIA is an easy and reliable way to evaluate the trunk muscle mass in a clinical setting. Conflict of interest. None. Sources of funding. None