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

Aims. Sarcopenia is characterized by a generalized progressive loss of skeletal muscle mass, strength, and physical performance. This systematic review primarily evaluated the effects of sarcopenia on postoperative functional recovery and mortality in patients undergoing orthopaedic surgery, and secondarily assessed the methods used to diagnose and define sarcopenia in the orthopaedic literature. Methods. A systematic search was conducted in MEDLINE, EMBASE, and Google Scholar databases according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. Studies involving sarcopenic patients who underwent defined orthopaedic surgery and recorded postoperative outcomes were included. The quality of the criteria by which a diagnosis of sarcopenia was made was evaluated. The quality of the publication was assessed using Newcastle-Ottawa Scale. Results. A total of 365 studies were identified and screened, 26 full-texts were reviewed, and 19 studies were included in the review. A total of 3,009 patients were included, of whom 2,146 (71%) were female and 863 (29%) were male. The mean age of the patients was 75.1 years (SD 7.1). Five studies included patients who underwent spinal surgery, 13 included hip or knee surgery, and one involved patients who underwent fixation of a distal radial fixation. The mean follow-up was 1.9 years (SD 1.9; 5 days to 5.6 years). There was wide heterogeneity in the measurement tools which were used and the parameters for the diagnosis of sarcopenia in the studies. Sarcopenia was associated with at least one deleterious effect on surgical outcomes in all 19 studies. The postoperative rate of mortality was reported in 11 studies (57.9%) and sarcopenia was associated with poorer survival in 73% (8/11) of these. The outcome was most commonly assessed using the Barthel Index (4/19), and sarcopenic patients recorded lower scores in 75% (3/4) of these. Sarcopenia was defined using the gold-standard three parameters (muscle strength, muscle quantity or quality, and muscle function) in four studies (21%), using two parameters in another four (21%) and one in the remaining 11 (58%). The methodological quality of the studies was moderate to high. Conclusion. There is much heterogeneity in the reporting of the parameters which are used for the diagnosis of sarcopenia, and evaluating the outcome of orthopaedic surgery in sarcopenic patients. However, what data exist suggest that sarcopenia impairs recovery and increases postoperative mortality, especially in patients undergoing emergency surgery. Further research is required to develop processes that allow the accurate diagnosis of sarcopenia in orthopaedics, which may facilitate targeted pre- and postoperative interventions that would improve outcomes. Cite this article: Bone Joint J 2022;104-B(3):321–330

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

Aims. Internal hemipelvectomy without reconstruction of the pelvis is a viable treatment for pelvic sarcoma; however, the time it takes to return to excellent function is quite variable. Some patients require greater time and rehabilitation than others. To determine if psoas muscle recovery is associated with changes in ambulatory function, we retrospectively evaluated psoas muscle size and limb-length discrepancy (LLD) before and after treatment and their correlation with objective functional outcomes. Methods. T1-weighted MR images were evaluated at three intervals for 12 pelvic sarcoma patients following interval hemipelvectomy without reconstruction. Correlations between the measured changes and improvements in Timed Up and Go test (TUG) and gait speed outcomes were assessed both independently and using a stepwise multivariate regression model. Results. Increased ipsilesional psoas muscle size from three months postoperatively to latest follow-up was positively correlated with gait speed improvement (r = 0.66). LLD at three months postoperatively was negatively correlated with both TUG (r = -0.71) and gait speed (r = -0.61). Conclusion. This study suggests that psoas muscle strengthening and minimizing initial LLD will achieve the greatest improvements in ambulatory function. LLD and change in hip musculature remain substantial prognostic factors for achieving the best clinical outcomes after internal hemipelvectomy. Changes in psoas size were correlated with the amount of functional improvement. Several patients in this study did not return to their preoperative ipsilateral psoas size, indicating that monitoring changes in psoas size could be a beneficial rehabilitation strategy. Cite this article: Bone Joint J 2023;105-B(3):323–330

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

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

The nervous system is known to be involved in inflammation and repair. We aimed to determine the effect of physical activity on the healing of a muscle injury and to examine the pattern of innervation. Using a drop-ball technique, a contusion was produced in the gastrocnemius in 20 rats. In ten the limb was immobilised in a plaster cast and the remaining ten had mobilisation on a running wheel. The muscle and the corresponding dorsal-root ganglia were studied by histological and immunohistochemical methods. In the mobilisation group, there was a significant reduction in lymphocytes (p = 0.016), macrophages (p = 0.008) and myotubules (p = 0.008) between three and 21 days. The formation of myotubules and the density of nerve fibres was significantly higher (both p = 0.016) compared with those in the immobilisation group at three days, while the density of CGRP-positive fibres was significantly lower (p = 0.016) after 21 days. Mobilisation after contusional injury to the muscle resulted in early and increased formation of myotubules, early nerve regeneration and progressive reduction in inflammation, suggesting that it promoted a better healing response

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

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

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

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

Aims. Dystrophic calcification (DC) is the abnormal appearance of calcified deposits in degenerating tissue, often associated with injury. Extensive DC can lead to heterotopic ossification (HO), a pathological condition of ectopic bone formation. The highest rate of HO was found in combat-related blast injuries, a polytrauma condition with severe muscle injury. It has been noted that the incidence of HO significantly increased in the residual limbs of combat-injured patients if the final amputation was performed within the zone of injury compared to that which was proximal to the zone of injury. While aggressive limb salvage strategies may maximize the function of the residual limb, they may increase the possibility of retaining non-viable muscle tissue inside the body. In this study, we hypothesized that residual dead muscle tissue at the zone of injury could promote HO formation. Methods. We tested the hypothesis by investigating the cellular and molecular consequences of implanting devitalized muscle tissue into mouse muscle pouch in the presence of muscle injury induced by cardiotoxin. Results. Our findings showed that the presence of devitalized muscle tissue could cause a systemic decrease in circulating transforming growth factor-beta 1 (TGF-β1), which promoted DC formation following muscle injury. We further demonstrated that suppression of TGF-β signalling promoted DC in vivo, and potentiated osteogenic differentiation of muscle-derived stromal cells in vitro. Conclusion. Taken together, these findings suggest that TGF-β1 may play a protective role in dead muscle tissue-induced DC, which is relevant to understanding the pathogenesis of post-traumatic HO. Cite this article: Bone Joint Res 2020;9(11):742–750

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

Study design: To investigate the effects of muscle atrophy on back muscle fatigue:. Objective: To assess fibre type atrophy in patients undergoing surgery for pro-lapsed lumbar intervertebral disc, and to determine its effect upon EMG measures of fatigue. Methods: Intra-operative biopsies were obtained from the erector spinae muscles of patients undergoing microdiscectomy. Mean fibre area of type I and II fibres were determined after myosin ATPase staining. Prior to surgery, EMG activity of the erector spinae muscles was recorded bilaterally at T10 and L3 whilst subjects performed the Biering-Sorensen fatigue test. Power spectral analysis indicated the initial median frequency and its rate of decline (median frequency gradient) at each recording site. Fibre type area was compared with the median frequency measures. Subjects: 34 subjects (20 male) with intervertebral disc prolapse. Results: Mean fibre area of type I and II fibres was 5890 ± 1947μm. 2. and 3461 ± 1946μm. 2. in men, and 5144 ± 1692μm. 2. and 1945 ± 1039μm. 2. in women, indicating marked type II fibre atrophy. Type II MFA was positively correlated with initial median frequency at L3 on the operated side (R=0.445) and negatively correlated with the maximum median frequency gradient of the four recording sites (R= −0.430). Conclusion: Type II fibre atrophy influences EMG measures of fatigue. The decrease in initial median frequency with type II fibre atrophy probably reflects a reduced conduction velocity in these small fibres. The less negative median frequency gradient with decreased type II fibre size indicates a lower rate of fatigue which may be explained by an increased contribution to force generation from type I fibres which occupy a greater proportion of the muscle

Purpose: Several variables related to tourniquet (TQ) inflation contribute to ischemic muscle injury. Among these the duration of ischemia has been identified as a primary factor. The purposes of this study were to investigate the following during and after TQ-induced ischemia during orthopedic trauma surgery:. muscle oxygenation changes measured by near infrared spectroscopy (NIRS);. muscle protein oxidation; and. correlations between muscle oxygenation / hemodynamics and oxidative changes. Method: Consented patients aged 19–69 yrs (n=18) with unilateral ankle fracture requiring surgery at our institution were recruited. A pair of NIRS probes was fixed over the midpoint of the tibialis anterior muscle (TA) on both the injured and healthy legs. A thigh TQ was applied to the injured leg and inflated to 300 mmHg. Using the NIRS apparatus coupled to a laptop with data acquisition software, changes in oxygenated (O2Hb), deoxygenated (HHb), and total hemoglobin (tHb) levels in the TA of both legs were measured before and during TQ inflation, and after release until values returned to baseline. PRE surgical biopsies were collected from the peroneus tertius muscle (PT) immediately after TQ inflation and incision. POST biopsies were collected from the same PT immediately before TQ deflation. Oxidation of PT myosin, actin, and total protein was quantified using Western blot analysis of 4-hydroxynonenal (4-HNE) modified proteins. Data are reported as mean±SD. Results: In PRE biopsies compared to POST biopsies there were large and statistically significant increases in the PT content of 4-NE modified myosin (174.4±128%; P< 1×10-6), actin (223.7±182%; P< 5×10-9), and total protein (567.5±378%; P< 5×10-7). There was a greater increase in PT protein oxidation in male subjects than in female subjects (50.8% difference; P< 0.05). In the TA of the fractured side, there were moderate to strong linear correlations between total protein oxidation and: the relative change in tHb (r=−0.704) and O2Hb (r=−0.415) during the period of TQ inflation and the rate at which the muscle became reoxygenated following TQ release (r=0.502). There was no relationship between muscle protein oxidation and TQ time, nor between muscle protein oxidation and age of patients. Conclusion: TQ-induced muscle ischemia for 21 to 74 min during lower extremity surgery leads to oxidative muscle injury as measured according to myofibrillar contractile protein oxidation. Importantly, we observed that when the TQ was “leaky,” local increases in muscle tHb were associated with a lower magnitude of protein oxidation, however, when local decreases in muscle O2Hb were observed, perhaps due to local blood loss below the TQ, more oxidative changes resulted. Intriguingly, gender appeared to influence the extent of muscle oxidative injury, but age did not. Surprisingly, there was no significant correlation between muscle oxidative injury and the TQ-induced ischemia interval. FUNDING: MSFHR, COF, BCLA

Although interlaminar endoscopic lumbar discectomy (IELD) is considered to be less invasive than microscopic lumbar discectomy (MLD) in treatment of lumbar herniated nucleus pulposus, the radiologic change of multifidus muscles by each surgery has rarely been reported. The aim of the present study was to compare the quantitative and qualitative changes of multifidus muscles between two surgical approaches and to analyze the correlation between various parameters of multifidus muscles and long term surgical outcome. 21 patients who received MLD and 18 patients who received IELD in a single tertiary hospital were enrolled and their preoperative, postoperative (≤15 days), and follow-up (≥6 months) MRIs were analyzed. The cross-sectional area (CSA) and fatty degeneration rate (FD) were quantitatively estimated at the level of surgery. The correlations among CSA, FD, body mass index, follow-up visual analogue scale(VAS) and Oswestry Disability Index(ODI) were assessed. Mean intervals of postoperative MRI and follow-up MRI from surgery were 3.0±3.7 days and 14.5±10.7 months, respectively. During the follow-up period, VAS was improved from 7.1±1.3 to 2.1±1.8 in MLD and from 8.2±1.4 to 2.2±1.8 in IELD. In cases of MLD, comparing with preoperative MRI, ipsilateral CSA was significantly increased in postoperative MRI (795.6mm. 2. vs. 906.5mm. 2. , p<0.01), but it was not significantly different in follow-up MRI (795.6mm. 2. vs. 814.4mm. 2. , p=1.00). However, in case of IELD, the ipsilateral CSAs in preoperative, postoperative, and follow-up periods were 892.0 mm. 2. , 909.3 mm. 2. , and 900.3 mm. 2. , respectively. These changes were not significant over time (p=0.691). The ipsilateral FDs were not significantly changed between preoperative and follow-up periods in both MLD (21.4% vs. 20.9%, p=0.81) and IELD groups (23.5% vs. 21.8%, p=0.19). The increment of ipsilateral CSA had significant correlations with follow-up ODI (r=−0.368, p=0.02). Comparing with IELD, MLD induced more surgical trauma on multifidus muscle in postoperative period, but the muscular damage was recovered in follow-up period. IELD can minimize surgical trauma on multifidus muscle showing similar pain relief as MLD. Favorable surgical outcome in follow-up period may be related to increment of multifidus muscle volume. Figure 1. (A-C) The multifidus muscles in preoperative, postoperative, and follow-up periods, respectively, in patient with MLD. Comparing with preoperative period, the CSA of right multifidus muscle (ipsilateral side) was increased in postoperative period, but recovered in follow-up period. (D-F) The multifidus muscle in preoperative, postoperative, and follow-up periods, respectively, in patient with IELD. The CSA of left multifidus muscles (ipsilateral side) was not significantly changed over time. Comparing preoperative MRIs with follow-up MRIs, the FDs of multifidus muscles were not significantly changed regardless of surgical technique. Figure 2. The CSA was measured by marking region of interest (ROI) and FD was measured by calculating the rate of pixels beyond the threshold in ROI. All measurements were performed using ImageJ software (version 1.52a, National Institutes of Health, Bethesda, Maryland, USA). For any figures or tables, please contact the authors directly

The lower limbs of five cadavers were dissected and the lengths of the muscle fibres and the weights of all the muscles below the knee were measured. From this information the relative strength and excursion of each muscle was determined. We found that the plantarflexors of the ankle were six times as strong as the dorsiflexors. We have therefore discarded the concept of "muscle balance" in tendon transfer surgery and propose that task appropriateness should be the guide. The constant relationship between muscle fibre length and muscle excursion means that contractures are accompanied by decreased excursion. Tendon lengthening improves deformity but does not improve the decreased active range of movement

Aims. Rotational acetabular osteotomy (RAO) is an effective joint-preserving surgical treatment for acetabular dysplasia. The purpose of this study was to investigate changes in muscle strength, gait speed, and clinical outcome in the operated hip after RAO over a one-year period using a standard protocol for rehabilitation. Patients and Methods. A total of 57 patients underwent RAO for acetabular dysplasia. Changes in muscle strength of the operated hip, 10 m gait speed, Japanese Orthopaedic Association (JOA) hip score, and factors correlated with hip muscle strength after RAO were retrospectively analyzed. Results. Three months postoperatively, the strength of the operated hip in flexion and abduction and gait speed had decreased from their preoperative levels. After six months, the strength of flexion and abduction had recovered to their preoperative level, as had gait speed. At one-year follow-up, significant improvements were seen in the strength of hip abduction and gait speed, but muscle strength in hip flexion remained at the preoperative level. The mean JOA score for hip function was 91.4 (51 to 100)) at one-year follow-up. Body mass index (BMI) showed a negative correlation with both strength of hip flexion (r = -0.4203) and abduction (r = -0.4589) one year after RAO. Although weak negative correlations were detected between strength of hip flexion one year after surgery and age (r = -0.2755) and centre-edge (CE) angle (r = -0.2989), no correlation was found between the strength of abduction and age and radiological evaluations of CE angle and acetabular roof obliquity (ARO). Conclusion. Hip muscle strength and gait speed had recovered to their preoperative levels six months after RAO. The clinical outcome at one year was excellent, although the strength of hip flexion did not improve to the same degree as that of hip abduction and gait speed. A higher BMI may result in poorer recovery of hip muscle strength after RAO. Radiologically, acetabular coverage did not affect the recovery of hip muscle strength at one year’s follow-up. A more intensive rehabilitation programme may improve this. Cite this article: Bone Joint J 2019;101-B:1459–1463

Abstract. Background. Progressive muscle ischaemia results in reduced aerobic respiration and increased anaerobic respiration, as cells attempt to survive in a hypoxic environment. Acute compartment syndrome (ACS) is a progressive form of muscle ischaemia that is a surgical emergency resulting in the production of Lactic acid by cells through anaerobic respiration. Our previous research has shown that it is possible to measure H+ ions concentration (pH) as a measure of progressive muscle ischaemia (in vivo) and hypoxia (in vitro). Our aim was to correlate intramuscular pH readings and cell viability techniques with the intramuscular concentration of key metabolic biomarkers [adenosine triphosphate (ATP), Phosphocreatine (PCr), lactate and pyruvate], to assess overall cell health in a hypoxic tissue model. Methods. Nine euthanised Wistar rats were used in a non-circulatory model. A pH catheter was used to measure real-time pH levels from one of the exposed gluteus medius muscles, while muscle biopsies were taken from the contralateral gluteus medius at the start of the experiment and subsequently at every 0.1 of a pH unit decline. The metabolic biomarkers were extracted from the snap frozen muscle biopsies and analyzed with standard fluorimetric method. Another set of biopsies were stained with Hoechst 33342, Ethidium homodimer-1 and Calcein am and imaged with a Zeiss LSM880 confocal microscope. Results. Our study shows that the direct pH electrode readings decrease with time and took an average of 69 minutes to drop to a pH of 6.0. The concentrations of ATP, pyruvate and PCr declined over time, and the concentration of lactate increased over time. At pH 6.0, both ATP and PCr concentrations had decreased by 20% and pyruvate has decreased by 50%, whereas lactate had increased 6-fold. The majority of cells were still viable at a pH of 6.0, suggesting that skeletal muscle cells are remarkably robust to hypoxic insult, although this was a hypoxic model where reperfusion was not possible. Conclusions. Our research suggests that histologically, skeletal muscle cells are remarkably robust to hypoxic insult despite the reduction in the total adenine nucleotide pool, but this may not reflect the full extent of cell injury and quite possibly irreversible injury. The timely restoration of blood flow in theory should halt the hypoxic insult, but late reperfusion results in cellular dysfunction and cell death due to localised free radical formation. Further research investigating the effects of reperfusion in vivo are warranted, as this may identify an optimal time for using pharmacological agents to limit reperfusion injury, around the time of fasciotomy to treat acute compartment syndrome. 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

Aims. Improvements in the evaluation of outcomes following peripheral nerve injury are needed. Recent studies have identified muscle fatigue as an inevitable consequence of muscle reinnervation. This study aimed to quantify and characterize muscle fatigue within a standardized surgical model of muscle reinnervation. Patients and Methods. This retrospective cohort study included 12 patients who underwent Oberlin nerve transfer in an attempt to restore flexion of the elbow following brachial plexus injury. There were ten men and two women with a mean age of 45.5 years (27 to 69). The mean follow-up was 58 months (28 to 100). Repeated and sustained isometric contractions of the elbow flexors were used to assess fatigability of reinnervated muscle. The strength of elbow flexion was measured using a static dynamometer (KgF) and surface electromyography (sEMG). Recordings were used to quantify and characterize fatigability of the reinnervated elbow flexor muscles compared with the uninjured contralateral side. Results. The mean peak force of elbow flexion was 7.88 KgF (. sd. 3.80) compared with 20.65 KgF (. sd . 6.88) on the contralateral side (p < 0.001). Reinnervated elbow flexor muscles (biceps brachialis) showed sEMG evidence of fatigue earlier than normal controls with sustained (60-second) isometric contraction. Reinnervated elbow flexor muscles also showed a trend towards a faster twitch muscle fibre type. Conclusion. The assessment of motor outcomes must involve more than peak force alone. Reinnervated muscle shows a shift towards fast twitch fibres following reinnervation with an earlier onset of fatigue. Our findings suggest that fatigue is a clinically relevant characteristic of reinnervated muscle. Adoption of these metrics into clinical practice and the assessment of outcome could allow a more meaningful comparison to be made between differing forms of treatment and encourage advances in the management of motor recovery following nerve transfer. Cite this article: Bone Joint J 2019;101-B:867–871

Aims. The aticularis genu (AG) is the least substantial and deepest muscle of the anterior compartment of the thigh and of uncertain significance. The aim of the study was to describe the anatomy of AG in cadaveric specimens, to characterize the relevance of AG in pathological distal femur specimens, and to correlate the anatomy and pathology with preoperative magnetic resonance imaging (MRI) of AG. Methods. In 24 cadaveric specimens, AG was identified, photographed, measured, and dissected including neurovascular supply. In all, 35 resected distal femur specimens were examined. AG was photographed and measured and its utility as a surgical margin examined. Preoperative MRIs of these cases were retrospectively analyzed and assessed and its utility assessed as an anterior soft tissue margin in surgery. In all cadaveric specimens, AG was identified as a substantial structure, deep and separate to vastus itermedius (VI) and separated by a clear fascial plane with a discrete neurovascular supply. Mean length of AG was 16.1 cm ( ± 1.6 cm) origin anterior aspect distal third femur and insertion into suprapatellar bursa. In 32 of 35 pathological specimens, AG was identified (mean length 12.8 cm ( ± 0.6 cm)). Where AG was used as anterior cover in pathological specimens all surgical margins were clear of disease. Of these cases, preoperative MRI identified AG in 34 of 35 cases (mean length 8.8 cm ( ± 0.4 cm)). Results. AG was best visualized with T1-weighted axial images providing sufficient cover in 25 cases confirmed by pathological findings.These results demonstrate AG as a discrete and substantial muscle of the anterior compartment of the thigh, deep to VI and useful in providing anterior soft tissue margin in distal femoral resection in bone tumours. Conclusion. Preoperative assessment of cover by AG may be useful in predicting cases where AG can be dissected, sparing the remaining quadriceps muscle, and therefore function. Cite this article: Bone Joint Open 2020;1-9:585–593

Sarcopenia is an age-related geriatric syndrome which is associated with subsequent disability and morbidity. Currently there is no promising therapy approved for the treatment of sarcopenia. The receptor activator of nuclear factor NF-κB ligand (RANKL) and its receptor (RANK) are expressed in bone and skeletal muscle. Activation of the NF-κB pathway mainly inhibits myogenic differentiation, which leads to skeletal muscle dysfunction and loss. LYVE1 and CD206 positive macrophage has been reported to be associated with progressive impairment of skeletal muscle function with aging. The study aims to investigate the effects of an anti-RANKL treatment on sarcopenic skeletal muscle and explore the related mechanisms on muscle inflammation and the polarization status of macrophages. Sarcopenic senescence-accelerated mouse P8 (SAMP8) mice at month 8 were treated intraperitoneally with 5mg/kg anti-RANKL (IK22/5) or isotype control (2A3; Bio X Cell) antibody every 4 weeks and harvested at month 10. Senescence accelerated mouse resistant-1 (SAMR1) were collected at month 10 as the age-matched non-sarcopenic group. Ex-vivo functional assessment, grip strength and immunostaining of C/EBPa, CD206, F4/80, LYVE1 and PAX7 were performed. Data analysis was done with one-way ANOVA, and the significant level was set at p≤0.05. At month 10, tetanic force/specific tetanic force, twitch force/specific twitch force in anti-RANKL group were significantly higher than control group (all p<0.01). The mice in the anti-RANKL treatment group also showed significantly higher grip strength than Con group (p<0.001). The SAMP8 mice at month 10 expressed significantly more C/EBPa, CD206 and LYVE1 positive area than in SAMR1, while anti-RANKL treatment significantly decreased C/EBPa, CD206 and LYVE1 positive area. The anti-RANKL treatment protected against skeletal muscle dysfunctions through suppressing muscle inflammation and modulating M2 macrophages, which may represent a novel therapeutic approach for sarcopenia. Acknowledgment: Collaborative Research Fund (CRF, Ref: C4032-21GF)

Aim. To assess the relationship between mRNA expression of genetic markers of inflammation (tumour necrosis factor-alpha (TNFα)) and interleukin-6 (IL-6) in the vastus lateralis (VL) of the operated leg, and the strength of the operated leg quadriceps, in patients following THR. Methods. Following ethical approval, 10 patients were recruited prospectively. Distal VL (5cm proximal to lateral supra-patellar pouch) biopsies were obtained intraoperatively and at 6 weeks post-operatively, with maximal voluntary contraction of the operated leg quadriceps (MVCOLQ) in Newtons(N), assessed preoperatively and at 6 weeks post-op. mRNA expression in the biopsies was assessed using the reverse transcriptase polymerase chain reaction (RT-PCR). Relationships were assessed using Spearman's correlation coefficient (data not normally distributed). Results. mRNA RQ (comparison of 6 week VL samples to intraoperative samples) was (mean (SD)) 6.23(12.85) for TNFα and 17.10(47.46) for IL-6. Preoperatively mean MVCOLQ was 188.90(76.84) N and at 6 weeks it was 217.00(53.91) N. There was no significant relationship between TNFα or IL-6 RQ and absolute MVCOLQ at 6 weeks. A trend to significance was noted between TNFα and the improvement (%) in MVCOLQ at 6 weeks (R = −0.552, p=0.098) with no such relationship observed for IL-6 (R = 0.127, p=0.726). Conclusions. In patients with hip osteoarthritis, reduced strength (MVCOLQ) appears to be mediated by muscle inflammation. The trend to correlation that exists for improvement in MVCOLQ with TNFα indicates that muscle inflammation may be one of the causes of pain in patients with severe osteoarthritis

The HIPGEN study funded under EU Horizon 2020 (Grant 7792939) has the aim to investigate the potential of the first regenerative cell therapy for the improvement of recovery after muscle injury in hip fracture patients. For this aim we intramuscularly injected placental derived mesenchymal stromal cells during hip fracture arthroplasty. Despite not having reached the primary endpoint, which was the Short Physical Performance Battery, we could observe an increase in abductor muscle strength and a faster return to balance looking at symmetry in insole measurements during follow up

Massive posterosuperior cuff tears (mRCT) retracted to the glenoid are surgically challenging and often associated with high retear rates. Primary repair is a less-favourable option and other salvage procedures such as SCR and tendon transfers are used. This study presents clinical and radiological outcomes of muscle advancement technique for repair of mRCT. Sixty-one patients (mean age 57±6, 77% males and 23% females) (66 shoulders) underwent all-arthroscopic rotator cuff repair that included supraspinatus and infraspinatus subperiosteal dissection off scapular bony fossae, lateral advancement of tendon laminae, and tension-free double-layer Lasso Loop repair to footprint. Pre-and post-operative range of motion (ROM), cuff strength, VAS, Constant, ASES, and UCLA scores were assessed. Radiologic assessment included modified Patte and Goutallier classifications. All patients had MRI at 6 months to evaluate healing and integrity of repair was assessed using Sugaya classification with Sugaya 4 and 5 considered retears. Advanced fatty degeneration (Goutallier 3-4) was present in 44% and 20% of supraspinatus and infraspinatus. Tendon retraction was to the level of or medial to glenoid in 22%, and just lateral in 66%. 50.8% mRCT extended to teres minor. Subscapularis was partially torn (Lafosse 1-3) in 46% and completely torn (Lafosse 4-5) in 20%. At mean follow-up (52.4 weeks), a significant increase in ROM, Relative Cuff Strength (from 57% to 90% compared to contralateral side), VAS (from 4 ±2.5 to 1±1.7), Constant (50±17.8 to 74 ±13.0), ASES (52 ±17.5 to 87 ±14.9), and UCLA (16± 4.9 to 30 ±4.9) scores were noted. There were six retears (10%), one failure due to P. acnes infection. 93% returned to pre-injury work and 89% of cases returned to pre-injury sport. Satisfaction rate was 96%. Muscle advancement technique for mRCT is a viable option with low retear rates, restoration of ROM, strength, and excellent functional outcomes

To investigate changes in quadriceps and hamstrings muscle groups during sustained isokinetic knee flexion and extension. 125 paediatric participants (45 males and 80 females, mean age 14.2 years) were divided into two groups: participants with a confirmed ACL tear (ACLi, n = 64), and puberty- and activity-level matched control participants with no prior history of knee injuries (CON, n = 61). Participants completed a series of 44 repetitions of isokinetic knee flexion and extension at 90 deg/ sec using a Biodex dynamometer (Biodex Medical Systems Inc, Shirley, New York). Surface EMG sensors (Delsys Incorporated, Natick, MA) simultaneously recorded the quadriceps and hamstring activations. Muscle function was assessed as the change in quadriceps activation and extension torque were calculated using the percent difference between the mean of the first five trials, and the mean of the last five trials. ACLi participants had significantly higher percent change in quadriceps activation for both healthy and injured legs, in comparison to CON dominant leg. As such, the healthy leg of the ACLi participants is activating significantly more than their health matched controls, while also demonstrating reduced muscular endurance (less torque in later repetitions). Therefore, we conclude that the non-injured limb of the ACLi participant is not performing as a healthy limb. Since return to activity clearance following ACLi implies return to sport against age- and activity matched opponents, clearing young athletes based on the non-injured contralateral limb may put them at greater risk of reinjury

Abstract. Source of Study: London, United Kingdom. This intervention study was conducted to assess two developing protocols for quadriceps and hamstring rehabilitation: Blood Flow Restriction (BFR) and Neuromuscular Electrical Stimulation Training (NMES). BFR involves the application of an external compression cuff to the proximal thigh. In NMES training a portable electrical stimulation unit is connected to the limb via 4 electrodes. In both training modalities, following device application, a standardised set of exercises were performed by all participants. BFR and NMES have been developed to assist with rehabilitation following lower limb trauma and surgery. They offer an alternative for individuals who are unable to tolerate the high mechanical stresses associated with traditional rehabilitation programmes. The use of BFR and NMES in this study was compared across a total of 20 participants. Following allocation into one of the training programmes, the individuals completed training programmes across a 4-week period. Post-intervention outcomes were assessed using Surface Electromyography (EMG) which recorded EMG amplitude values for the following muscles: Vastus Medialis, Vastus Lateralis, Rectus Femoris and Semitendinosus. Increased Semitendinosus muscle activation was observed post intervention in both BFR and NMES training groups. Statistically significant differences between the two groups was not identified. Larger scale randomised-controlled trials are recommended to further assess for possible treatment effects in these promising training modalities

Objectives. Regenerative medicine is an emerging field aimed at the repair and regeneration of various tissues. To this end, cytokines (CKs), growth factors (GFs), and stem/progenitor cells have been applied in this field. However, obtaining and preparing these candidates requires invasive, costly, and time-consuming procedures. We hypothesised that skeletal muscle could be a favorable candidate tissue for the concept of a point-of-care approach. The purpose of this study was to characterize and confirm the biological potential of skeletal muscle supernatant for use in regenerative medicine. Methods. Semitendinosus muscle was used after harvesting tendon from patients who underwent anterior cruciate ligament reconstructions. A total of 500 milligrams of stripped muscle was minced and mixed with 1 mL of saline. The collected supernatant was analysed by enzyme-linked immunosorbent assay (ELISA) and flow cytometry. The biological effects of the supernatant on cell proliferation, osteogenesis, and angiogenesis in vitro were evaluated using human mesenchymal stem cells (hMSCs) and human umbilical cord vein endothelial cells (HUVECs). Results. The supernatant contained several GFs/CKs, with especially high levels of basic fibroblast growth factor, and CD34+ cells as the stem/progenitor cell fraction. With regard to biological potential, we confirmed that cell proliferation, osteoinduction, and angiogenesis in hMSCs and HUVECs were enhanced by the supernatant. Conclusions. The current study demonstrates the potential of a new point-of-care strategy for regenerative medicine using skeletal muscle supernatant. This attractive approach and readily-available material could be a promising option for tissue repair/regeneration in the clinical setting. Cite this article: M. Yoshikawa, T. Nakasa, M. Ishikawa, N. Adachi, M. Ochi. Evaluation of autologous skeletal muscle-derived factors for regenerative medicine applications. Bone Joint Res 2017;6:277–283. DOI: 10.1302/2046-3758.65.BJR-2016-0187.R1

Many patients who undergo a total knee arthroplasty (TKA) wish to return to a more active lifestyle. The implant must be able to restore adequate muscle strength and function. However, this may not be a reality for some patients as quadriceps and hamstrings muscle activity may remain impaired following surgery. The purpose of this study was to compare muscle activity between patients implanted with a medial pivot (MP) or posterior stabilized (PS) implant and controls (CTRL) during ramp walking tasks. Fifteen patients were assigned to either a MP (n=9) or PS (n=6) TKA operated by the same surgeon. Nine months following surgery, the 15 patients along with nine CTRL patients completed motion and EMG analysis during level, ramp ascent & descent walking tasks. Wireless EMG electrodes were placed on six muscles: vastus medialis (VM), vastus lateralis (VL), biceps femoris (BF), semimembranosus (SM) muscles, gastrocnemius medial head (GM), and gastrocnemius lateral head (GL). Participants completed three trials of each condition. EMG data were processed for an entire gait cycle of the operated limb in the TKA groups, and for the dominant limb in the CTRL group. The maximum muscle activity achieved with each muscle during the level trial was used to normalize the ramp trials. The onset and offset of each muscle was determined using the approximated generalized likelihood ratio. Peak muscle activity (PeakLE), total muscle activity (iEMG), and muscle onsets/offsets were determined for each muscle for the ramp ascent and descent trials. Non-parametric Kruskal Wallace tests were used to test for statistical significance between groups with α=0.05. During the ramp up task, both MP and PS groups had significantly greater PeakLE and iEMG for the hamstring muscles compared to the CTRL, whereas the PS group had significantly greater PeakLE compared with the MP group for the SM muscle. During the ramp down task, both MP and PS groups had significantly greater PeakLE and iEMG for the SM and GL muscles compared to the CTRL. The PS group also had significantly greater iEMG for the BF and VM muscles compared to the CTRL. The MP group had a significantly earlier offset for the SM muscle compared to the CTRL. Stability in a cruciate removing TKA is partially controlled by the prosthetic design. During the ramp up task, the TKA groups compensated the tibial anterior translation by activating their hamstrings more and for a longer duration. The MP group required less hamstrings activation than the PS group. During the ramp down task, TKA patients stiffened their knee in order to stabilize the joint. The quadriceps, hamstrings and GL muscle were activated more and for a longer duration than the CTRL group to protect the tibial posterior translation. The PS group required greater BF and VM iEMG than the MP group. Even if surgery reduced pain, differences in muscle activity exist between TKA patients and healthy controls. The prosthetic design provides some stability to the knee, and the MP implant required less muscle activation than the PS implant to stabilize the knee joint

Acute Compartment Syndrome (ACS) is an orthopaedic emergency that can develop after a wide array of etiologies. In this pilot study the MY01 device was used to assess its ease of use and its ability to continuously reflect the intracompartmental pressure (ICP) and transmit this data to a mobile device in real time. This preliminary data is from the lead site which is presently expanding data collection to five other sites as part of a multi-center study. Patients with long bone trauma of the lower or upper extremity posing a possibility of developing compartment syndrome were enrolled in the study. Informed consent was obtained from the patients. A Health Canada licensed continuous compartmental pressure monitor (MY01) was used to measure ICP. The device was inserted in the compartment that was deemed most likely to develop ACS and ICP was continuously measured for up to 18 hours. Fractures were classified according to the AO/OTA classification. Patient clinical signs and pain levels were recorded by healthcare staff during routine in-patient monitoring and were compared to the ICP from the device. Important treatment information was pulled from the patient's chart to help correlate all of the patient's data and symptoms. The study period was conducted from November 2020 through December 2021. Twenty-six patients were enrolled. There were 17 males, and nine females. The mean age was 38 years (range, 17–76). Seventeen patients received the device post-operatively and nine received it pre-operatively. Preliminary results show that post-operative ICPs tend to be significantly higher than pre-operative ICPs but tend to trend downwards very quickly. The trend in this measurement appears to be more significant than absolute numbers which is a real change from the previous literature. One patient pre-operatively illustrated a steep trend upwards with minimal clinical symptoms but required compartment release at the time of surgery that exhibited no muscle necrosis. The trend in this patient was very steep and, as predicted, predated the clinical findings of compartment syndrome. This trend allows an early warning signal of the absolute pressure, to come, in the compartment that is being assessed by the device. Preliminary results suggest that this device is reliable and relatively easy to use within our institutions. In addition it suggests that intracompartmental pressures can be higher immediately post-op but lower rapidly when the patient does not develop ACS. These results are in line with current literature of the difference between pre and post-operative baselines and thresholds of ICP, but are much more striking, as continuous measurements have not been part of the data set in most of past studies. Further elucidation of the pressure thresholds and profiles are currently being studied in the ongoing larger multicenter study and will add to our understanding of the critical values. This data, plus the added value of continuous trends in the pressure, upwards or downwards, will aid in preventing muscle necrosis during our management of these difficult long bone fractures

Musculoskeletal modeling techniques simulate reverse total shoulder arthroplasty (RTSA) shoulders and how implant placement affects muscle moment arms. Yet, studies have not taken into account how muscle-length changes affect force-generating capacity postoperatively. We develop a patient-specific model for RTSA patients to predict muscle activation. Patient-specific muscle parameters were estimated using an optimization scheme calibrating the model to isometric arm abduction data at 0°, 45°, and 90°. We compared predicted muscle activation to experimental electromyography recordings. A twelve-degree of freedom model with experimental measurements created patient-specific data estimating muscle parameters corresponding to strength. Optimization minimized the difference between measured and estimated joint moments and muscle activations, yielding parameters corresponding to subjects' strength that can predict muscle activation and lengths. Model calibration was performed on RTSA patients' arm abduction data. Predicted muscle activation ranged between 3% and 70% of maximum. The maximum joint moment produced was 10 Nm. The model replicated measured moments accurately (R. 2. > 0.99). The optimized muscle parameters produced feasible muscle moments and activations for dynamic arm abduction when using data from isometric force trials. A normalized correlation was found between predicted and experimental muscle activation for dynamic abduction (r > 0.9); the moment generation to lift the arm was tracked (R. 2. = 0.99). Statement of Clinical Significance: We developed a framework to predict patient-specific muscle parameters. Combined with patient-specific models incorporating joint configurations, kinematics, and bone anatomy, they can predict muscle activation in novel tasks and, e.g., predict how RTSA implant and surgical decisions may affect muscle function

Aims. The aim of this study was to analyse human muscle tissue before and after rotator cuff repair to look for evidence of regeneration, and to characterise the changes seen in the type of muscle fibre. Patients and Methods. Patients were assessed pre-operatively and one year post-operatively using the Oxford Shoulder Score (OSS) and MRI. The cross-sectional area and distribution of the type of muscle fibre were assessed on biopsies, which were taken at surgery and one year post-operatively. Paired samples from eight patients were analysed. There were three men and five women with a mean age of 63 years (50 to 73). Results. All but one patient showed improvement in OSS (p = 0.004). The mean increase in the cross-sectional area of the muscle was 1220 μm. 2. (-801 to 3712; p = 0.03). There was a reduction of type 2a fibres (p = 0.02). A clear relationship could not be seen between the MRI findings and the histological appearances. Conclusion. This is the first study to provide evidence that atrophy of the supraspinatus muscle is reversible. Changes in the types of fibre are discussed. MRI assessment of muscle atrophy may not be fully representative of myofibre atrophy. Cite this article: Bone Joint J 2016;98-B:1389–94

Background. Revision total knee arthroplasties (rTKA) are performed with increasing frequency due to the increasing numbers of primary arthroplasties, but very little is known regarding the influence of muscle strength impairments on functional limitations in this population. Objectives. The aim of this study was to assess relationship between muscle strength and functional level in patient with rTKA. Design and Methods. Twenty-three patients (8 males, 15 females) were included in the study with mean age 68.4±10 years. Patients performed 3 performance tests (50-Step Walking Test, 10 Meter Walk Test, 30-Second Chair-Stand Test), and one self-report test (HSS) were preferred to assess patients. The maximum isometric muscle strength of quadriceps femoris and hamstring muscles of all the patients was measured using Hand-Held Dynamometer (HHD). Results. While moderate-to-strong significant correlations was found between quadriceps femoris muscle strength and 30- Second Chair-Stand Test (r=0.390, p=0.049), 50-Step Walking Test (r=−0.530, p=0.005), 10 Meter Walk Test (r=−0.587, p=0.002), there were not significant correlation between HSS knee score and all performance-based tests (p>0.05). Also there were not significant correlation between hamstring muscle strength and all other measurement tests (p>0.05). Conclusion. The moderate-to-strong statistical significant correlation between quadriceps femoris muscle strength and functional performance tests suggests that improved postoperative quadriceps strengthening could be important to enhance the potential benefits of rTKA

Introduction. The direct anterior approach (DAA) and the posterior approach (PA) are 2 common total hip arthroplasty (THA) exposures. This prospective study quantitatively compared changes in periarticular muscle volume after DAA and PA THA. Materials. Nineteen patients undergoing THA were recruited from the practices of 3 fellowship-trained hip surgeons. Each surgeon performed a single approach, DAA or PA. Enrolled patients underwent a preoperative MRI of the affected hip and two subsequent postoperative MRIs, averaging 9.6 and 24.3 weeks after surgery. Clinical evaluations were done by Harris Hip Score at each follow-up interval. Results. MRIs for 10 DAA and 9 PA patients were analyzed. Groups did not differ significantly with regard to BMI, age, or pre-operative muscle volume. 1 DAA patient suffered a periprosthetic fracture and was excluded from the study. DAA hips showed significant atrophy in the obturator internus (−37.3%) muscle at early follow-up, with persistent atrophy of this muscle at the final follow-up. PA hips showed significant atrophy in the obturator internus (−46.8%) and externus (−16.0%), piriformis (−8.12%), and quadratus femoris muscles (−13.1%) at early follow-up, with persistent atrophy of these muscles at final follow-up. Loss of anterior capsular integrity was present at final follow-up in 2/10 DAA hips while loss of posterior capsular integrity was present in 5/9 PA hips. There was no difference in clinical outcomes. Discussion. This study provides objective evidence that, regardless of surgical approach, a muscle whose tendon is detached from its insertion is likely to demonstrate persistent atrophy 6 months following THA. Although the study was not powered to compare clinical outcomes, it should be noted that no significant difference in patient outcomes were observed. For any tables or figures, please contact the authors directly

Cam-type femoroacetabular impingement (FAI) is a common cause for athletic hip injury and early hip osteoarthritis. Although corrective cam FAI surgery can improve patient reported outcome measures (PROMs), it is not clear how surgery affects muscle forces and hip joint loading. Surgery for FAI may redistribute muscle forces and contact forces at the hip joint during routine activities. The purpose of this study was to examine the muscle contributions and hip contact forces during gait in patients prior and after two years of undergoing surgery for cam FAI. Kinematics and kinetics were recorded in 11 patients with symptomatic cam FAI as they completed a gait task. Muscle and hip contact forces during the stance phase were estimated using musculoskeletal modelling and static optimization in OpenSim. All patients reported improvements in PROMs. Post-operatively, patients showed reduced forces in the long head of the biceps femoris at ipsilateral foot-strike and in the rectus femoris at the contralateral foot-strike. The reduced muscle forces decreased sagittal hip moment but did not change hip contact forces. This was the first study to evaluate hip muscle and contact forces in FAI patients post-operatively. Although hip contact forces are not altered following surgery, muscle forces are decreased even after two years. These findings can provide guidance in optimizing recovery protocols after FAI surgery to improve hip flexor and extensor muscle forces

Introduction. Current modeling techniques have been used to model the Reverse Total Shoulder Arthroplasty (RTSA) to account for the geometric changes implemented after RTSA [2,3]. Though these models have provided insight into the effects of geometric changes from RTSA these is still a limitation of understanding muscle function after RTSA on a patient-specific basis. The goal of this study sought to overcome this limitation by developing an approach to calibrate patient-specific muscle strength for an RTSA subject. Methods. The approach was performed for both isometric 0° abduction and dynamic abduction. A 12 degree of freedom (DOF) model developed in our previous work was used in conjunction with our clinical data to create a set of patient-specific data (3 dimensional kinematics, muscle activations (), muscle moment arms, joint moments, muscle length, muscle velocity, tendon slack length (), optimal fiber length, peak isometric force)) that was used in a novel optimization scheme to estimate muscle parameters that correspond to the patient's muscle strength[4]. The optimization varied to minimize the difference between measured (“in vivo”) and predicted joint moments and measured (“in vivo”) and predicted muscle activations (). The predicted joint moments were constructed as a summation of muscle moments. The nested optimization was implemented within matlab (Mathworks). The optimization yields a set of muscle parameters that correspond to the subject's muscle strength. The abduction activity was optimized [4,5]. To validate the model we predicted dynamic joint moment and activation for the abduction activity (Figure 1). Results. The muscle activation for the lateral deltoid had a normalized correlation of value of .91(Figure 1 left). The maximum joint moment produced was 18 newton-meters. The joint moments were reproduced to an value of 1 (Figure 1 Right). Muscle parameters were calculated for both isometric and dynamic abduction. The muscle parameters produced provided a feasible solution to reproduce the muscle activation and joint moments seen “in vivo” (Figure 1). Discussion. Current modeling techniques of the upper extremity focus primarily on geometric changes and their effects on shoulder muscle moment arms. In efforts to create patient-specific models we have developed a framework to predict subject-specific strength characteristics. In order to fully understand muscle function we need muscle parameters that correspond to the subject's strength. This effort in conjunction with patient-specific models that incorporate the patient's joint configurations, kinematics and bone anatomy provide a framework to gain insight into muscle tensioning effects after RTSA. This framework describes the relationship between muscle lengthening and muscle performance (recruitment and force generation). With this framework improvements can be made to the surgical implementation and design of RTSA to improve surgical outcomes. Significance. This abstract is the first of its kind to use patient-specific fluoroscopy kinematics, muscle activation and joint moments to create a framework to predict a patients muscle function (activation, force) for RTSA groups. This now allows us to understand how differences in implant design and surgical technique affect each muscle's ability to generate force and function. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Objectives. Although many clinical and experimental investigations have shed light on muscle atrophy and intramuscular accumulation of fat after rotator cuff disruption, none have reported on their onset in the absence of muscle retraction. Methods. In 30 rabbits, we detached one supraspinatus (SSP) tendon and repaired it immediately, thus preventing muscle retraction. The animals were killed in groups of 10 at one, two and six weeks. Both shoulders of 15 non-operated rabbits served as controls. We measured the weight and volume of SSP muscles and quantified the cross-sectional area of intramuscular fat (i-fat) histologically. Results. There was significant loss of muscle weight and volume after one week (p = 0.004 and 0.003, respectively), and two weeks (both p < 0.001) in the experimental group; which recovered to control values after six weeks. I-fat accumulated one week after immediate repair, greater than in the control group and statistically significant at the mid-part of the muscle (mean 2.7% vs 1.5%, p = 0.008). I-fat continued to accumulate up to six weeks at all sites of the SSP muscle (all 3, p < 0.001). More fat accumulated closer to the musculotendinous junction than at the mid-part after two and six weeks (p = 0.012 and 0.019, respectively). Conclusion. Muscle atrophy and i-fat accumulation occur early after SSP tendon tear and immediate repair. While early repair benefitted muscle recovery, it did not prevent fat accumulation. SSP muscle retraction was not essential to the muscle alterations. The divergent evolution of muscle and fat points to different pathophysiologies. Cite this article: Bone Joint Res 2014;3:117–22

Current modeling techniques have been used to model the Reverse Total Shoulder Arthroplasty (RTSA) to account for the geometric changes implemented after RTSA. Though these models have provided insight into the effects of geometric changes from RTSA these is still a limitation of understanding muscle function after RTSA on a patient-specific basis. The goal of this study sought to overcome this limitation by developing an approach to calibrate patient-specific muscle strength for an RTSA subject. The approach was performed for both isometric 0° abduction and dynamic abduction. A 12 degree of freedom (DOF) model developed in our previous work was used in conjunction with our clinical data to create a set of patient-specific data (3 dimensional kinematics, muscle activations, muscle moment arms, joint moments, muscle length, muscle velocity, tendon slack length, optimal fiber length, peak isometric force)) that was used in a novel optimization scheme to estimate muscle parameters that correspond to the patient's muscle strength[4]. The optimization varied to minimize the difference between measured(“in vivo”) and predicted joint moments and measured (“in vivo”) and predicted muscle activations. The predicted joint moments were constructed as a summation of muscle moments. The nested optimization was implemented within matlab (Mathworks). The optimization yields a set of muscle parameters that correspond to the subject's muscle strength. The abduction activity was optimized. The maximum activation for the muscles within the model ranged between .03–2.4 (Figure 1). The maximum joint moment produced was 11 newton-meters. The joint moments were reproduced to an value of 1. Muscle parameters were calculated for both isometric and dynamic abduction (Figure 2). The muscle parameters produced provided a feasible solution to reproduce the joint moments seen “in vivo” (Figure 3). Current modeling techniques of the upper extremity focus primarily on geometry. In efforts to create patient-specific models we have developed a framework to predict subject-specific strength characteristics. In order to fully understand muscle function we need muscle parameters that correspond to the subject's strength. This effort in conjunction with patient-specific models that incorporate the patient's joint configurations, kinematics and bone anatomy hopes to provide a framework to gain insight into muscle tensioning effects after RTSA. With this framework improvements can be made to the surgical implementation and design of RTSA to improve surgical outcomes

Modern musculoskeletal modeling techniques have been used to simulate shoulders with reverse total shoulder arthroplasty and study how geometric changes resulting from implant placement affect shoulder muscle moment arms. These studies do not, however, take into account how changes in muscle length will affect the force generating capacity of muscles in their post-operative state. The goal of this study was to develop and calibrate a patient-specific shoulder model for subjects with RTSA in order to predict muscle activation during dynamic activities. Patient-specific muscle parameters were estimated using a nested optimization scheme calibrating the model to isometric arm abduction data at 0°, 45° and 90°. The model was validated by comparing predicted muscle activation for dynamic abduction to experimental electromyography recordings. A twelve-degree of freedom model was used with experimental measurements to create a set of patient-specific data (three-dimensional kinematics, muscle activations, muscle moment arms, joint moments, muscle lengths, muscle velocities, tendon slack lengths, optimal fiber lengths and peak isometric forces) estimating muscle parameters corresponding to each patient's measured strength. The optimization varied muscle parameters to minimize the difference between measured and estimated joint moments and muscle activations for isometric abduction trials. This optimization yields a set of patient-specific muscle parameters corresponding to the subject's own muscle strength that can be used to predict muscle activation and muscle lengths for a range of dynamic activities. The model calibration/optimization procedure was performed on arm abduction data for a subject with reverse total shoulder arthroplasty. Muscle activation predicted by the model ranged between 3% and 90% of maximum. The maximum joint moment produced was 20 Nm. The model replicated measured joint moments accurately (R2 > 0.99). The optimized muscle parameter set produced feasible muscle moments and muscle activations for dynamic arm abduction, when calibrated using data from isometric force trials. Current modeling techniques for the upper extremity focus primarily on geometric changes and their effects on shoulder muscle moment arms. In an effort to create patient-specific models, we have developed a framework to predict subject-specific muscle parameters. These estimated muscle parameters, in combination with patient-specific models that incorporate the patient's joint configurations, kinematics and bone anatomy, provide a framework to predict dynamic muscle activation in novel tasks and, for example, predict how joint center changes with reverse total shoulder arthroplasty may affect muscle function

The iliocapsularis muscle is a little known muscle that originates in part from the inferior border of the anterior-inferior iliac spine, but the main origin arises from an elongated attachment of the anteromedial hip capsule and inserts just distal to the lesser trochanter. Nevertheless, this muscle is an important landmark for exposure of the anteromedial hip capsule and psoas tendon interval during performance of the Bernese periacetabular osteotomy. Speculations about the function of this muscle as a tightener of the hip capsule and femoral head stabilisator have grown when an apparent hypertrophy of this muscle was encountered in patients with dysplasia of the hip. The aim of this study was to compare the morphology of the iliocapsularis muscle between patients with decreased (developmental dysplasia of the hip) and increased acetabular coverage (pincer-type of femoroac-etabular impingement) using Arthro-MRIs. Dysplasia of the hip (Group I) was defined as an LCE angle of less than 25° with a minimal acetabular index of 14° and pincer type of FAI (Group II) was defined as and LCE angle exceeding 39° on conventional radiographs. This resulted in 37 hips in Group I and 45 hips in Group II. The morphology of the iliocapsularis muscle was measured on axial slices of Arthro-MRIs. The parameters were muscle thickness, width and cross section at 4cm distal of the spina iliaca anterior inferior and also distal of the femoral head. Additionally, the volume of the muscle from its origins to the cross section distal of the femoral head was computed. All parameters were significantly increased in Group I compared to Group II (p< 0.05). In Group I the mean thickness was 20 ± 4.5 (range, 12 – 29) mm, width 25 ± 5.2 (range, 17 – 37), and cross section 281 ± 10.7 (range, 139 – 591) mm2 compared to Group II with a mean thickness of 17 ± 4.4 (range, 10 – 27) mm, width 22 ± 5.0 (range, 11 – 31), and cross section 235 ± 10.3 (range, 90 – 535) mm2. The muscle volume in Group I was 6.8 ± 2.9 (range, 2.2 – 13.0) cm3 compared to Group II with 8.7 ± 3.7 (range, 3.4 – 18.1) cm3. The results differed more when corrected for gender with the largest differences found for women. In hip dysplasia the anterior acetabular coverage is decreased. Because of the iliocapsularis muscle’s origination on the hip capsule, contrition of the muscle theoretically can tighten the anterior hip capsule, thus helping to stabilized the femoral head within the dysplastic acetabular. Although the true function of the iliocapsularis muscle remains unknown, constant use of this muscle in attempting to stabilize the femoral head in hip dysplasia theoretically would explain the apparent hypertrophy of this muscle