A longitudinal MRI study of muscle atrophy during lower leg immobilization following ankle fracture

Ultrasound for measurement of skeletal muscle mass quantity and muscle composition/architecture in critically ill patients: A scoping review on studies' aims, methods, and findings

AIMS

This scoping review aimed to identify, explore, and map the objectives, methodological aspects, and results of studies that used ultrasound (US) to assess skeletal muscle (SM) in critically ill patients.

METHODS

A scoping review was conducted according to the Joanna Briggs Institute's methodology. All studies that evaluated SM parameters from the US in patients admitted to the intensive care unit (ICU) were considered eligible. We categorized muscle thickness and cross-sectional area as parameters for assessing SM quantity, while echogenicity, fascicle length, and pennation angle analysis were used to evaluate muscle "quality" (composition/architecture). A literature search was conducted using four databases for articles published until December 2022. Independent reviewers selected the studies and extracted data. Descriptive statistics were calculated to present the results.

RESULTS

A total of 107 studies were included, the majority of which were prospective cohort studies (59.8 %) conducted in general ICUs (49.5 %). The most frequent objective of the studies was to evaluate SM quantity depletion during the ICU stay (25.2 %), followed by determining whether a specific intervention would modify SM (21.5 %). Most studies performed serial SM evaluations (76.1 %). The rectus femoris muscle thickness was evaluated in most studies (67.9 %), followed by the rectus femoris cross-sectional area (54.3 %) and the vastus intermedius muscle thickness (40.2 %). The studies demonstrated the feasibility and reproducibility of US for SM evaluation, especially related to quantitative parameters. Most studies (70.3 %) reported significant SM quantity depletion during hospitalization. However, the accuracy of the US in measuring SM varied across the studies.

CONCLUSIONS

The lack of detailed description and standardization in the protocols adopted by the studies included in this scoping review precludes the translation of the evidence related to US for SM assessment into clinical practice.

The Structural Adaptations That Mediate Disuse-Induced Atrophy of Skeletal Muscle

The maintenance of skeletal muscle mass plays a fundamental role in health and issues associated with quality of life. Mechanical signals are one of the most potent regulators of muscle mass, with a decrease in mechanical loading leading to a decrease in muscle mass. This concept has been supported by a plethora of human- and animal-based studies over the past 100 years and has resulted in the commonly used term of 'disuse atrophy'. These same studies have also provided a great deal of insight into the structural adaptations that mediate disuse-induced atrophy. For instance, disuse results in radial atrophy of fascicles, and this is driven, at least in part, by radial atrophy of the muscle fibers. However, the ultrastructural adaptations that mediate these changes remain far from defined. Indeed, even the most basic questions, such as whether the radial atrophy of muscle fibers is driven by the radial atrophy of myofibrils and/or myofibril hypoplasia, have yet to be answered. In this review, we thoroughly summarize what is known about the macroscopic, microscopic, and ultrastructural adaptations that mediated disuse-induced atrophy and highlight some of the major gaps in knowledge that need to be filled.

Exploring the peripheral mechanisms of lower limb immobilisation on muscle function using novel electrophysiological methods

OBJECTIVE

To explore the effects of short-term immobilisation and subsequent retraining on peripheral nervous system (PNS) measures using two novel electrophysiological methods, muscle velocity recovery cycles (MVRC) and MScanFit motor unit number estimation (MUNE) alongside lower limb muscle strength, muscle imaging and walking capacity.

METHODS

Twelve healthy participants underwent 1-week of ankle immobilisation and 2-weeks of retraining. Assessments before and after immobilisation, and after retraining, included MVRC [muscle membrane properties; muscle relative refractory period (MRRP), early and late supernormality], MScanFit, MRI-scans [muscle contractile cross-sectional area (cCSA)], isokinetic dynamometry [dorsal and plantar flexor muscle strength], and 2-minute maximal walk test [physical function].

RESULTS

After immobilisation, compound muscle action potential (CMAP) amplitude reduced (-1.35[-2.00;-0.69]mV); mean change [95%CI]) alongside reductions in plantar (but not dorsal) flexor muscle cCSA (-124[-246;3]mm2), dorsal flexor muscle strength (isometric -0.06[-0.10;-0.02]Nm/kg, dynamicslow -0.08[-0.11;-0.04]Nm/kg, dynamicfast no changes), plantar flexor muscle strength (isometric -0.20[-0.30;-0.10]Nm/kg, dynamicslow -0.19[-0.28;-0.09]Nm/kg, dynamicfast -0.12[-0.19;-0.05]Nm/kg) and walking capacity (-31[-39;-23]m). After retraining, all immobilisation-affected parameters returned to baseline levels. In contrast, neither MScanFit nor MVRC were affected apart from slightly prolonged MRRP in gastrocnemius.

CONCLUSIONS

PNS do not contribute to the changes observed in muscle strength and walking capacity.

SIGNIFICANCE

Further studies should include both corticospinal and peripheral mechanisms.

Chronic Achilles tendon rupture in elderly treated with a combination of the side-locking loop suture technique and early rehabilitation protocol: two cases report

A chronic Achilles tendon rupture (ATR) is generally defined as a rupture that occurs more than 4-6 weeks after the initial injury. A variety of corrective techniques have been reported, such as direct repair, V-Y plasty, turndown flap, tendon transfer and free tendon grafting. These procedures generally produce good results, but have the disadvantage of requiring prolonged immobilization and weight-bearing restrictions. This may be a risk factor for falls and decreased function in the lower limbs, especially in older patients. Side-locking loop sutures (SLLS) were first introduced in 2010 as a direct repair technique for acute ATR. This technique provides higher tensile strength, which may allow for early rehabilitation protocols such as early range of motion and early weight-bearing of the ankle without postoperative immobilization. In this report, we describe two cases of chronic ATR in elderly patients treated with SLLS and an early rehabilitation protocol.

Gait Analysis to Monitor Fracture Healing of the Lower Leg

Fracture healing is typically monitored by infrequent radiographs. Radiographs come at the cost of radiation exposure and reflect fracture healing with a time lag due to delayed fracture mineralization following increases in stiffness. Since union problems frequently occur after fractures, better and timelier methods to monitor the healing process are required. In this review, we provide an overview of the changes in gait parameters following lower leg fractures to investigate whether gait analysis can be used to monitor fracture healing. Studies assessing gait after lower leg fractures that were treated either surgically or conservatively were included. Spatiotemporal gait parameters, kinematics, kinetics, and pedography showed improvements in the gait pattern throughout the healing process of lower leg fractures. Especially gait speed and asymmetry measures have a high potential to monitor fracture healing. Pedographic measurements showed differences in gait between patients with and without union. No literature was available for other gait measures, but it is expected that further parameters reflect progress in bone healing. In conclusion, gait analysis seems to be a valuable tool for monitoring the healing process and predicting the occurrence of non-union of lower leg fractures.

Elasticity of leg muscles and incidence of falls in older adults: a prospective cohort analysis

PURPOSE

Aging impacts muscle strength and elasticity, which in turn influence dynamic balance, walking speed, and physical performance. We aimed to evaluate the relationship between the elasticity of leg muscles and incidence of falls in older adults.

METHODS

We conducted a prospective cohort analysis with outpatients from a geriatric clinic. Any history of falls in the past year was recorded. Timed up and go test, muscle thickness, and handgrip strength tests were performed. Elasticities of the gastrocnemius medialis (GM) and rectus femoris (RF) muscles were evaluated using shear wave elastography. Patients self-recorded their falls, and additional phone calls were made to them each month for 6 months.

RESULTS

The median age of the patients (n = 55) was 72 years (66-86); and 72% were women. The GM showed significantly lower elasticity in patients with history of falls in the past year than in those without it (8.08 kPa [3.90-16.17] vs. 9.70 kPa [4.99-20.95]; p = 0.028). A similar negative correlation between GM and fall incidence was noted among those with additional falls during the follow-up period (6.96 kPa [3.90-12.41] vs. 9.13 kPa [4.99-20.95]; p = 0.019). GM elasticity was significantly correlated with the timed up and go test score (r = - 0.612, p < 0.001), handgrip strength (r = 0.384, p = 0.015), and muscle thickness (r = 0.232, p = 0.049). No such associations were observed for the RF muscles.

CONCLUSION

GM muscle elasticity is associated with alterations in muscle structure that may lead to falls in older adults. Therefore, muscle elasticity may be a fall predictor in older adults.

Differences in the cross-sectional area along the ankle tendons with both age and sex

Increasing age appears to influence several morphologic changes in major tendons. However, the effects of aging on the cross-sectional area (CSA) of different ankle tendons are much less understood. Furthermore, potential differences in specific tendon regions along the length of the tendons have not been investigated in detail. Sixty healthy adult participants categorized by age as young (n = 20; mean ± SD age = 22.5 ± 4.5 years), middle-age (n = 20; age = 40.6 ± 8. 0 years), or old (n = 20; age = 69.9 ± 9.1 years), from both sexes, were included. The tendon CSA of tibialis anterior (TA), tibialis posterior (TP), fibularis (FT), and Achilles (AT) was measured from T1-weighted 1.5 T MR images in incremental intervals of 10% along its length (from proximal insertion) and compared between different age groups and sexes. The mean CSA of the AT was greater in the middle-age group than both young and old participants (p < 0.01) and large effect sizes were observed for these differences (Cohen's d > 1). Furthermore, there was a significant difference in CSA in all three groups along the length of the different tendons. Region-specific differences between groups were observed in the distal portion (90% and 100% of the length), in which the FT presented greater CSA comparing middle-age to young and old (p < 0.05). In conclusion, (1) great magnitude of morpho-structural differences was discovered in the AT; (2) there are region-specific differences in the CSA of ankle tendons within the three groups and between them; and (3) there were no differences in tendon CSA between sexes.

The time course of disuse muscle atrophy of the lower limb in health and disease

Short, intermittent episodes of disuse muscle atrophy (DMA) may have negative impact on age related muscle loss. There is evidence of variability in rate of DMA between muscles and over the duration of immobilization. As yet, this is poorly characterized. This review aims to establish and compare the time-course of DMA in immobilized human lower limb muscles in both healthy and critically ill individuals, exploring evidence for an acute phase of DMA and differential rates of atrophy between and muscle groups. MEDLINE, Embase, CINHAL and CENTRAL databases were searched from inception to April 2021 for any study of human lower limb immobilization reporting muscle volume, cross-sectional area (CSA), architecture or lean leg mass over multiple post-immobilization timepoints. Risk of bias was assessed using ROBINS-I. Where possible meta-analysis was performed using a DerSimonian and Laird random effects model with effect sizes reported as mean differences (MD) with 95% confidence intervals (95% CI) at various time-points and a narrative review when meta-analysis was not possible. Twenty-nine studies were included, 12 in healthy volunteers (total n = 140), 18 in patients on an Intensive Therapy Unit (ITU) (total n = 516) and 3 in patients with ankle fracture (total n = 39). The majority of included studies are at moderate risk of bias. Rate of quadriceps atrophy over the first 14 days was significantly greater in the ITU patients (MD -1.01 95% CI -1.32, -0.69), than healthy cohorts (MD -0.12 95% CI -0.49, 0.24) (P < 0.001). Rates of atrophy appeared to vary between muscle groups (greatest in triceps surae (-11.2% day 28), followed by quadriceps (-9.2% day 28), then hamstrings (-6.5% day 28), then foot dorsiflexors (-3.2% day 28)). Rates of atrophy appear to decrease over time in healthy quadriceps (-6.5% day 14 vs. -9.1% day 28) and triceps surae (-7.8% day 14 vs. -11.2% day 28), and ITU quadriceps (-13.2% day 7 vs. -28.2% day 14). There appears to be variability in the rate of DMA between muscle groups, and more rapid atrophy during the earliest period of immobilization, indicating different mechanisms being dominant at different timepoints. Rates of atrophy are greater amongst critically unwell patients. Overall evidence is limited, and existing data has wide variability in the measures reported. Further work is required to fully characterize the time course of DMA in both health and disease.

Progressive exercise versus best practice advice for adults aged 50 years or over after ankle fracture: the AFTER pilot randomised controlled trial

OBJECTIVE

The aim of the Ankle Fracture Treatment: Enhancing Rehabilitation (AFTER) study, a multicentre external pilot parallel-group randomised controlled trial (RCT), was to assess feasibility of a definitive trial comparing rehabilitation approaches after ankle fracture.

SETTING

Five UK National Health Service hospitals.

PARTICIPANTS

Participants were aged 50 years and over with an ankle fracture requiring immobilisation for at least 4 weeks.

INTERVENTIONS

Participants were allocated 1:1 via a central web-based randomisation system to: (1) best practice advice (one session of physiotherapy, up to two optional additional advice sessions) or (2) progressive exercise (up to six sessions of physiotherapy).

PRIMARY OUTCOME MEASURES

Feasibility: (1) participation rate, (2) intervention adherence and (3) retention.

RESULTS

Sixty-one of 112 (54%) eligible participants participated, exceeding progression criteria for participation of 25%. Recruitment progression criteria was 1.5 participants per site per month and 1.4 was observed. At least one intervention session was delivered for 28/30 (93%) of best practice advice and 28/31 (90%) of progressive exercise participants, exceeding the 85% progression criteria. For those providing follow-up data, the proportion of participants reporting performance of home exercises in the best practice advice and the progressive exercise groups at 3 months was 20/23 (87%) and 21/25 (84%), respectively. Mean time from injury to starting physiotherapy was 74.1 days (95% CI 53.9 to 94.1 days) for the best practice advice and 72.7 days (95% CI 54.7 to 88.9) for the progressive exercise group. Follow-up rate (6-month Olerud and Molander Ankle Score) was 28/30 (93%) for the best practice advice group and 26/31 (84%) in the progressive exercise group with an overall follow-up rate of 89%.

CONCLUSIONS

This pilot RCT demonstrated that a definitive trial would be feasible. The main issues to address for a definitive trial are intervention modifications to enable earlier provision of rehabilitation and ensuring similar rates of follow-up in each group.

TRIAL REGISTRATION NUMBER

ISRCTN16612336.

Effects of total knee arthroplasty on skeletal muscle structure and function at the cellular, organellar, and molecular levels

Total knee arthroplasty (TKA) is an important treatment option for knee osteoarthritis (OA) that improves self-reported pain and physical function, but objectively measured physical function typically remains reduced for years after surgery due, in part, to precipitous reductions in lower extremity neuromuscular function early after surgery. The present study examined intrinsic skeletal muscle adaptations during the first 5 weeks post-TKA to identify skeletal muscle attributes that may contribute to functional disability. Patients with advanced stage knee OA were evaluated prior to TKA and 5 weeks after surgery. Biopsies of the vastus lateralis were performed to assess muscle fiber size, contractility, and mitochondrial content, along with assessments of whole muscle size and function. TKA was accompanied by marked reductions in whole muscle size and strength. At the fiber (i.e., cellular) level, TKA caused profound muscle atrophy that was approximately twofold higher than that observed at the whole muscle level. TKA markedly reduced muscle fiber force production, contractile velocity, and power production, with force deficits persisting in myosin heavy chain (MHC) II fibers after expression relative to fiber size. Molecular level assessments suggest reduced strongly bound myosin-actin cross bridges and myofilament lattice stiffness as a mechanism underlying reduced force per unit fiber size. Finally, marked reductions in mitochondrial content were apparent and more prominent in the subsarcolemmal compartment. Our study represents the most comprehensive evaluation of skeletal muscle cellular adaptations to TKA and uncovers novel effects of TKA on muscle fiber size and intrinsic contractility early after surgery that may contribute to functional disability.NEW & NOTEWORTHY We report the first evaluation of the effects of total knee arthroplasty (TKA) on skeletal muscle at the cellular and subcellular levels. We found marked effects of TKA to cause skeletal muscle fiber atrophy and contractile dysfunction in older adults, as well as molecular mechanisms underlying impaired contractility. Our results reveal profound effects of TKA on muscle fiber size and intrinsic contractility early after surgery that may contribute to functional disability.

When is the optimum time for the initiation of early rehabilitative exercise on the postoperative functional recovery of peri-ankle fractures? A network meta-analysis

Objective

The purpose of this study was to explore the safe and most effective initiation time for the functional recovery of patients with peri-ankle fractures after surgery.

Method

We searched electronic databases, including the Cochrane Library, Embase, PubMed and the reference lists of relevant articles published from inception to October 30, 2021. Two researchers independently performed literature screening and data extraction and evaluated the quality of the included literature using the Newcastle–Ottawa Scale. Network meta-analysis, including consistency testing, publication bias, and graphical plotting, was performed using Stata (v16.0).

Results

A total of 25 articles involving 1756 patients were included in this study. The results of the meta-analysis showed that functional exercise within 2 days after surgery may result in lower VAS scores compared to other techniques (P < 0.05). Functional exercise within 12 months may lead to higher AOFAS scores than that of other techniques (P < 0.05). The total postoperative complication rate, including deep vein thrombosis, showed no statistically significant differences between any two interventions (P > 0.05). The results of the surface under the cumulative ranking (SUCRA) showed that functional exercise within two days postoperatively may have the lowest VAS scores (SUCRA = 82.8%), functional exercise within 1 week postoperatively may have the lowest deep vein thrombosis rate (SUCRA = 66.8%), functional exercise within 10 days postoperatively may have the fewest total postoperative complication rate (SUCRA = 73.3%) and functional exercise within 12 months postoperatively may contribute to the highest AOFAS scores (SUCRA = 85.5%).

Conclusion

The results of this study suggest that initiation of rehabilitation within two days after surgery may be the best time to reduce postoperative pain; rehabilitation interventions within 10 days after surgery may be the optimal time for reducing the total postoperative complication rate, including deep vein thrombosis; and continued functional exercise within 12 months after surgery may steadily and ideally improve the function of the ankle joint.

Systematic Review Registration: doi: 10.37766/inplasy2021.12.0030, identifier: INPLASY2021120030

Blood-flow restricted exercise following ankle fractures - A feasibility study

BACKGROUND

The objective was to investigate the feasibility of blood flow restricted exercise (BFRE) as a rehabilitation modality in patients with a unilateral ankle fracture.

METHODS

Feasibility study with a prospective cohort design. Inclusion criteria were above 18 years of age and unilateral ankle fractures.

EXCLUSION CRITERIA

history of cardiac or embolic diseases, cancer, diabetes, hypertension and family history of cardio or vascular diseases. The predefined feasibility outcome was based on three criteria regarding patients experience with participating in the BFRE protocol and the absence of any serious adverse events.

RESULTS

Eight patients were included. Median age was 33 years (range: 23-60). All eight patients reported maximum satisfaction on the two questions regarding patient's perception of the overall experience with BFRE training and the feasibility to introduce BFRE as an intervention.

CONCLUSION

Early use of BFRE in patients with unilateral ankle fractures seems feasible in patients without comorbidity.

Acute lateral ankle sprain alters muscle and tendon properties: Case series

BACKGROUND

Acute lateral ankle sprain (LAS) is the most prevalent acute sports trauma. Ankle muscle atrophy and tendon volume decrease have not been analyzed concomitantly with functional impairment and pain following LAS. The objective of the present study was to investigate muscle cross-section area (CSA), tendon CSA and volume, ankle function, and pain in individuals who suffered an acute LAS.

METHODS

A series of cases, cross-sectional study with 20 participants who suffered moderate (grade II) and severe (grade III) acute LAS was undertaken. CSA for muscles (Tibialis Posterior, Fibularis, and Soleus) and tendons (Tibialis Anterior, Tibialis posterior, Fibularis, and Achilles), and volume were measured by magnetic resonance imaging (MRI) less than 48 h (baseline) and 6-weeks after the acute LAS. Ankle function (Cumberland Ankle Instability Tool [CAIT] and Foot and Ankle Outcome Score [FAOS]), ankle mechanical instability (Anterior Drawer Test [ADT]), and pain were also assessed.

RESULTS

All tendons and muscles showed a significant reduction in CSA and volume between baseline and 6-weeks (P < .001). A significant decrease in ankle function was observed 6 weeks after the LAS, along with a reduction in pain and mechanical instability (P = .001). Regarding sprain magnitude, the only difference observed was greater atrophy in muscle CSA in participants with grade III ankle sprain.

CONCLUSION

Patients with acute LAS showed atrophy of ankle muscles and decreased tendon volume and CSA, followed by function impairments at 6-week follow-up.

LEVEL OF EVIDENCE

IV, Case series study.

Early weight bearing and mobilization decrease perioperative complications in patients after ankle fracture; the retrospective multicenter (TRON group) study

BACKGROUND

Open reduction and internal fixation (ORIF) for unstable ankle fractures (AF) are relatively predictable with excellent outcomes. Rehabilitation strategies are still being debated after surgical intervention for AF: non-weight bearing and cast immobilization for six weeks after the surgical repair of unstable AF or early functional treatment with partial weight bearing. This study aimed to compare early weight bearing and functional outcomes and complications.

METHODS

Between April 2014 and March 2019, 1421 patients with AF underwent ORIF at 11 institutions (TRON group). The patients were divided into two groups: Group E started weight bearing within six weeks after surgery, and group L started weightbearing for more than six weeks after. To adjust for baseline difference between groups, a propensity score-matched algorithm was used to match Group E with Group L in a 1:1 ratio of 294 cases each. We compared the American Orthopedic Foot and Ankle Society (AOFAS) score as the functional outcome, the rate of wound dehiscence, superficial and deep infections, blistering, nonunion, neurapraxia, and reoperation at 3, 6, and 12 months after surgery.

RESULTS

The mean period of non-weight bearing was significantly shorter in group E (3.68 ± 1.02 vs. 6.67 ± 1.43; P < 0.001). The mean period of cast immobilization term were shorter in group E (1.84 ± 1.35 vs. 2.65 ± 1.51; P < 0.001). There were no differences in the AOFAS score at any period. The rates of deep infection and reoperation in Group E were significantly lower than those in Group L (1.7% vs. 6.1%; P = 0.009, 2.0% vs. 7.8%; P = 0.002, respectively). There were no significant differences in superficial infection (9 vs. 15; P = 0.297), nonunion (9 vs. 15 P = 0.30), blistering (4 vs. 3; P = 1.00), neurapraxia (2 vs. 1; P = 1.00), and wound dehiscence (15 vs. 18; P = 0.72).

CONCLUSIONS

Although functional outcome was similar depending on whether early weight bearing was allowed, the rates of deep infection and reoperation decreased in patients with early weight bearing. We recommend early postoperative weight bearing in patients with a surgically treated AF.

AKT controls protein synthesis and oxidative metabolism via combined mTORC1 and FOXO1 signalling to govern muscle physiology

BACKGROUND

Skeletomuscular diseases result in significant muscle loss and decreased performance, paralleled by a loss in mitochondrial and oxidative capacity. Insulin and insulin-like growth factor-1 (IGF-1) are two potent anabolic hormones that activate a host of signalling intermediates including the serine/threonine kinase AKT to influence skeletal muscle physiology. Defective AKT signalling is associated with muscle pathology, including cachexia, sarcopenia, and disuse; however, the mechanistic underpinnings remain unresolved.

METHODS

To elucidate the role of AKT signalling in muscle mass and physiology, we generated both congenital and inducible mouse models of skeletal muscle-specific AKT deficiency. To understand the downstream mechanisms mediating AKT's effects on muscle biology, we generated mice lacking AKT1/2 and FOXO1 (M-AKTFOXO1TKO and M-indAKTFOXO1TKO) to inhibit downstream FOXO1 signalling, AKT1/2 and TSC1 (M-AKTTSCTKO and M-indAKTTSCTKO) to activate mTORC1, and AKT1/2, FOXO1, and TSC1 (M-QKO and M-indQKO) to simultaneously activate mTORC1 and inhibit FOXO1 in AKT-deficient skeletal muscle. Muscle proteostasis and physiology were assessed using multiple assays including metabolic labelling, mitochondrial function, fibre typing, ex vivo physiology, and exercise performance.

RESULTS

Here, we show that genetic ablation of skeletal muscle AKT signalling resulted in decreased muscle mass and a loss of oxidative metabolism and muscle performance. Specifically, deletion of muscle AKT activity during development or in adult mice resulted in a significant reduction in muscle growth by 30-40% (P  < 0.0001; n = 12-20) and 15% (P < 0.01 and P < 0.0001; n = 20-30), respectively. Interestingly, this reduction in muscle mass was primarily due to an ~40% reduction in protein synthesis in both M-AKTDKO and M-indAKTDKO muscles (P < 0.05 and P < 0.01; n = 12-20) without significant changes in proteolysis or autophagy. Moreover, a significant reduction in oxidative capacity was observed in both M-AKTDKO (P < 0.05, P < 0.01 and P < 0.001; n = 5-12) and M-indAKTDKO (P < 0.05 and P < 0.01; n = 4). Mechanistically, activation and inhibition of mTORC1/FOXO1, respectively, but neither alone, were sufficient to restore protein synthesis, muscle oxidative capacity, and muscle function in the absence of AKT in vivo. In a mouse model of disuse-induced muscle loss, simultaneous activation of mTORC1 and inhibition of FOXO1 preserved muscle mass following immobilization (~5-10% reduction in casted M-indFOXO1TSCDKO muscles vs. ~30-40% casted M-indControl muscles, P < 0.05 and P < 0.0001; n = 8-16).

CONCLUSIONS

Collectively, this study provides novel insights into the AKT-dependent mechanisms that underlie muscle protein homeostasis, function, and metabolism in both normal physiology and disuse-induced muscle wasting.

Voluntary Forelimbs Exercise Reduces Immobilization-Induced Mechanical Hyperalgesia in the Rat Hind Paw

Voluntary exercise is sufficient to protect against neuropathic pain. However, it is unclear whether voluntary exercise reduces immobilization-induced hyperalgesia. We examined the effect of voluntary forelimb exercise on immobilized-induced hyperalgesia in hind paws of rats. Wistar rats were randomly divided into the (1) both hind limbs immobilized group (IM group), (2) immobilization and exercise with nonimmobilized fore limbs group (EX group), and (3) control group. In the IM and EX groups, the bilateral ankle joints of each rat were immobilized in full plantar flexion with a plaster cast for eight weeks. In the EX group, voluntary exercise using nonimmobilized forelimbs in the running wheel was administered during the immobilization period, while hind limbs were kept immobilized (60 min/day, 5 days/week). Mechanical hyperalgesia in the hind paw was measured using a digital von Frey device every week. To investigate the abnormality of primary sensory neurons and central sensitization, the number of calcitonin gene-related peptide-positive cells in the dorsal root ganglion and the expression level of calcitonin gene-related peptide in the spinal dorsal horn were analyzed by immunohistochemical staining. Immobilization-induced mechanical hyperalgesia was inhibited in the EX group compared to the IM group at three weeks after immobilization. In the EX group, the number of calcitonin gene-related peptide-positive cells in the dorsal root ganglion and the expression level of calcitonin gene-related peptide were significantly decreased compared to those in the IM group. Our results therefore suggest that voluntary forelimb exercise during hind limb immobilization partially reduces immobilization-induced hyperalgesia by suppressing that the plastic changes of the primary sensory nerves that excessively transmit pain and increased responsiveness of nociceptive neurons in the spinal dorsal horn.

A dynamical system for the IGF1-AKT signaling pathway in skeletal muscle adaptation

Physical activity produces a change in skeletal-muscle size by activating synthesis or degradation of protein, which are outcomes of stimulating the IGF1-AKT signaling pathway. In this work, we propose a mathematical model that predicts the variation in muscle size under different activity conditions. The IGF1-AKT pathway was modeled using its 4 main molecules as variables in a dynamical system. We checked the stability of the system; we defined exercise training as a function of intensity, duration, and frequency; and we tested the model under four scenarios: first, we considered the daily low-intensity activity that should not promote atrophy nor hypertrophy (steady state); second, we simulated the effects of physical therapy in spinal cord injury patients (atrophy); third, we simulated exercise training in healthy subjects (hypertrophy); and fourth, we considered the effects of suspending a training program in healthy subjects (recovery after hypertrophy). Results showed that: protein synthesis and degradation are inactive, thus the size of the muscle stays stable in the first scenario; the muscle decreases only 10% of its initial size after 84 days of therapy every two days in the second scenario; training frequency produces rapid hypertrophy (11% after 25 days) when training every day, to no hypertrophy when training every 5 days in the third scenario; and a reduction of 50% the gain of the training program in the fourth scenario. By comparing our results to experimental reports, we found a remarkable agreement; therefore, our model is suitable for the development of training and therapeutic protocols.

Rate of Delayed Union With Early Weightbearing Following Intramedullary Screw Fixation of Jones Fractures

BACKGROUND

Jones fractures of the proximal fifth metatarsal are predisposed to delayed union and nonunion due to a tenuous blood supply. Solid intramedullary (IM) screw fixation is recommended to improve healing, traditionally followed by delayed weightbearing (DWB). However, early weightbearing (EWB) postoperatively may facilitate functional recovery. The purpose of this study was to compare union rates and time to union after solid IM screw fixation of Jones fractures in patients treated with an EWB protocol to those treated with a DWB protocol, as well as to identify any factors that may be predictive of delayed or nonunion.

METHODS

True Jones (zone 2 fifth metatarsal base) fractures treated from April 2012 through January 2018 with IM screw fixation and 6 months follow-up were identified (41 fractures in 40 patients; mean ± SD age, 45.3 ± 17.9 years). Patients were divided into EWB and DWB cohorts (within or beyond 2 weeks, respectively). Delayed union (12.5 weeks) was statistically derived from established literature. Union times were compared between cohorts. Regression analyses were conducted to investigate possible confounders contributing to delayed union. There were 20 fractures in the EWB cohort and 21 fractures in the DWB cohort.

RESULTS

There was no significant difference in healing times (EWB: 25% by 6th week, 55% by the 12th week, 20% delayed; DWB: 33% by 6th week, 43% by 12th week, 24% delayed; P = .819) or delayed unions (EWB, 20% vs DWB, 24%; P > .999). There were no nonunions. No significant confounding risk factors were identified.

CONCLUSION

Postoperative protocols using early weightbearing following solid IM screw fixation of Jones fractures appear to be safe and do not delay fracture healing or increase the risk of delayed union. Older age may be a risk for delayed union, but larger studies are needed to evaluate this with appropriate power in light of possible confounders. EWB protocols may allow better functional recovery without compromising outcomes by increasing the risk of delayed union.

LEVEL OF EVIDENCE

Therapeutic level III, retrospective comparative study.

The effect of sitting position changes from pedaling rehabilitation on muscle activity

Sports injuries or traffic accidents make the individuals bedridden for a long duration, easily causing the disuse of lower limb muscles. Exercise rehabilitation is an effective method to improve muscle activity; however, currently, exercise therapy mainly relies on the experience of rehabilitation physicians for determining the rehabilitation parameters. In this paper, we establish a human-machine coupling system model for disuse atrophy of lower limb muscles. We analyze the influence of sitting position on pedaling rehabilitation. The relationship between the sitting position and muscle effect of lower limb muscle is calculated. We optimized the parameters to analyze muscle force and activity distribution in the muscle group during different sitting positions, and the rehabilitation risk area and the invalid area were identified from the distribution map, which helps quantify the maximal exercise of muscles without causing secondary muscle damage. The mapping relationship between sitting position and muscle force was established in this study. Further, muscle activity mapping is performed for overall assessment. Muscle activity assessment considered the training intensity of small muscles and avoids secondary injury of small muscle. The corresponding designated sitting posture improved the intensity of muscle training and shortened the rehabilitation cycle. Systematic distribution areas for different rehabilitation effects in pedal exercises are presented and provide the sitting position distribution areas for patients in the early, middle, and late stages. The proposed model provides theoretical guidance for rehabilitation physicians.

A Systematic Review and Meta-Analysis on Neural Adaptations Following Blood Flow Restriction Training: What We Know and What We Don't Know

Objective: To summarize the existing evidence on the long-term effects of low-load (LL) blood flow restricted (BFR) exercise on neural markers including both central and peripheral adaptations. Methods: A systematic review and meta-analysis was conducted according to the PRISMA guidelines. The literature search was performed independently by two reviewers in the following electronic databases: PubMed, Web of Science, Scopus and CENTRAL. The systematic review included long-term trials investigating the effects of LL-BFR training in healthy subjects and compared theses effects to either LL or high-load (HL) training without blood flow restriction. Results: From a total of N = 4499 studies, N = 10 studies were included in the qualitative synthesis and N = 4 studies in a meta-analysis. The findings indicated that LL-BFR resulted in enhanced levels of muscle excitation compared to LL training with pooled effect sizes of 0.87 (95% CI: 0.38-1.36). Compared to HL training, muscle excitation following LL-BFR was reported as either similar or slightly lower. Differences between central activation between LL-BFR and LL or HL are less clear. Conclusion: The summarized effects in this systematic review and meta-analysis highlight that BFR training facilitates neural adaptations following LL training, although differences to conventional HL training are less evident. Future research is urgently needed to identify neural alterations following long-term blood flow restricted exercise.

The effect of a 12-week custom foot orthotic intervention on muscle size and muscle activity of the intrinsic foot muscle of young adults during gait termination

BACKGROUND

The tissue stress theory is commonly used to prescribe foot orthoses, however the mechanisms of foot orthoses are not understood well. The effect foot orthotics have on the plantar intrinsic muscles remains unclear. The study was designed to assess changes in muscle size and activity of the intrinsic muscles of individuals with pes planus after wearing custom-made foot orthotics for 12-weeks.

METHODS

Eighteen young adults with pes planus were allocated by stratified sampling into the orthotic group (n = 9) or control group (n = 9). Ultrasonography measured the cross-sectional area of the flexor digitorum brevis, abductor digiti minimi, and abductor hallucis at baseline, 6 and 12-weeks. Subsequently, participants completed an unexpected gait termination protocol (12 of 50 trials unexpected) and average electromyography magnitude was recorded.

FINDINGS

After 12-weeks the orthotic group cross-sectional area significantly decreased by 9.6% (P < .001) for the flexor digitorum brevis, 17.1% for abductor digiti minimi (P < .001) and 17.4% for abductor hallucis (P < .001). There were no significant differences of muscle activity magnitude for the intrinsic muscles.

INTERPRETATION

The short-term use of custom-made foot orthoses created a decrease in muscle size of the flexor digitorium brevis, abductor digiti minimi and abductor hallucis plantar intrinsic muscles but had no effect on muscle activity. Clinically, these results help to understand the adaptations that are created when foot orthoses are supporting a pes planus foot structure when reducing plantar pressures. These findings may help enhance the prescription of foot orthoses by adding a strength program to prevent disuse atrophy of these muscles.

Factors influencing treatment recommendations for base of 5th metatarsal fractures in orthopaedic residency programs

BACKGROUND

Management of proximal 5th metatarsal fractures remains a controversial topic in orthopaedic surgery. Both operative and non-operative approaches have been described in the clinical setting. This confusion has led to non-standardized treatment recommendations for proximal 5th metatarsal fractures. This study was designed to analyze concordance rate of treatment recommendations between orthopaedic trainees and orthopaedic foot and ankle experts.

METHODS

An online survey containing 14 cases of proximal 5th metatarsal fractures were distributed to 92 orthopaedic residents in two ACGME-accredited programs. Relevant weight-bearing radiographs, patient's age and gender were provided, and two questions regarding treatment recommendations were surveyed. Resident's recommended treatment was then matched against ultimate treatment by orthopaedic foot and ankle experts. ANOVA and T-test are used for associations between the rate of concordant treatment with PGY and trainee foot and ankle experience. Fleiss' kappa was used to assess the inter-observer agreement.

RESULTS

Seventy-two residents returned the survey. The overall concordance rate was 43.98% with no correlation between agreement rate and PGY-years. No difference in agreement rate was observed between residents who had completed their foot and ankle rotation versus those who had not. There was a slight inter-observer agreement in recommending treatment among all residents (κ=0.117, 95% CI: 0.071-0.184).

CONCLUSIONS

Our data demonstrated no significant concordance between resident level in training regarding proximal 5th metatarsal fracture treatment decisions, nor between residents and subspecialty-trained foot and ankle surgeons. Increased rotations with foot and ankle fellowship-trained surgeons throughout residency may be desirable to improve the quality of residency training.

LEVEL OF EVIDENCE

III.

Fractional Limb Volume in Spina Bifida Fetuses as an Assessment Tool for Postnatal Ambulation

BACKGROUND

Prenatal fractional limb volume (FLV) can be used to assess muscle atrophy in fetuses with myelomeningocele.

OBJECTIVE

We hypothesize that FLV in fetal myelomeningocele (fMMC) repair is different from postnatal repair (PNR). Assessing intrauterine muscle development can predict ambulation.

METHODS

A prospective observational study was performed from July 2012 to April 2016. Demographics, clinical outcomes, and FLV of the fetal thigh were assessed by ultrasound. Ambulation videos were collected from patients over 30 months of age. FLV was compared between the fMMC and PNR groups and between ambulators and non-ambulators. Two-sample t test, ANOVA, Spearman's rho correlation, and Bland-Altman plots were used for analysis. A p value <0.05 was used for statistical significance.

RESULTS

Fifty-nine patients were included, 24 had fMMC and 35 had PNR. Videos were obtained in 47 cases (73%). There was no difference in baseline demographics between the groups. There was no significant change in the fMMC group between the FLV at initial presentation and the repeat at 34 weeks gestation (54.5 ± 28.2 and 62.2% ± 16.4; p = 0.6). In contrast, the FLV in the PNR decreased between the initial evaluation and the repeat at 34 weeks (54.1 ± 27.7 to 35.8 ± 34.1%; p = 0.04). FLV at 34 weeks gestation was higher in the fMMC group as compared to the PNR group (62.2 ± 16.4 vs. 35.8 ± 34.1%; p = 0.02). There was no difference in FLV between ambulators and non-ambulators either at initial evaluation (p = 0.8) or at 34 weeks gestation (p = 0.6).

CONCLUSION

Lower FLV in the PNR group compared to fMMC may suggest in utero muscle atrophy. No correlation was seen between FLV and subsequent ambulation; however, future larger studies may be needed.

Progressive functional exercise versus best practice advice for adults aged 50 years or over after ankle fracture: protocol for a pilot randomised controlled trial in the UK - the Ankle Fracture Treatment: Enhancing Rehabilitation (AFTER) study

INTRODUCTION

Ankle fractures result in significant morbidity in adults, with prognosis worsening with increasing age. Previous trials have not found evidence supporting supervised physiotherapy sessions, but these studies have not focused on older adults or tailored the exercise interventions to the complex needs of this patient group. The Ankle Fracture Treatment: Enhancing Rehabilitation study is a pilot randomised controlled trial to assess feasibility of a later definitive trial comparing best-practice advice with progressive functional exercise for adults aged 50 years and over after ankle fracture.The main objectives are to assess: (i) patient engagement with the trial, measured by the participation rate of those eligible; (ii) establish whether the interventions are acceptable to participants and therapists, assessed by intervention adherence levels, participant interviews and a therapist focus group; (iii) participant retention in the trial, measured by the proportion of participants providing outcome data at 6 months; (iv) acceptability of measuring outcomes at 3 and 6 month follow-up.

METHODS AND ANALYSIS

A multicentre pilot randomised controlled trial with an embedded qualitative study. At least 48 patients aged 50 years and over with an ankle fracture requiring surgical management, or non-operative management by immobilisation for at least 4 weeks, will be recruited from a minimum of three National Health Service hospitals in the UK. Participants will be allocated 1:1 via a central web-based randomisation system to: (i) best-practice advice (one session of face-to-face self-management advice delivered by a physiotherapist and up to two optional additional sessions) or (ii) progressive functional exercise (up to six sessions of individual face-to-face physiotherapy). An embedded qualitative study will include one-to-one interviews with up to 20 participants and a therapist focus group.

ETHICS AND DISSEMINATION

Hampshire B Research Ethics Committee (18/SC/0281) gave approval on 2^nd July 2018.

TRIAL REGISTRATION NUMBER

ISRCTN16612336.

Impact of disuse muscular atrophy on the compound muscle action potential

BACKGROUND

Disuse atrophy from immobilization is the result of decreased neural activity and muscle unloading.

METHODS

We studied the impact of disuse on hand intrinsic compound muscle action potentials (CMAPs) in a cohort of 39 patients with unilateral 6-week immobilization of the hand in a cast, after distal radius fracture. We excluded patients with nerve injury. We compared side-to-side CMAP characteristics at the time of cast removal and at a subsequent follow-up visit, after a mean interval of 7.8 weeks.

RESULTS

Statistically significant reductions in CMAP amplitude were noted for the abductor pollicis brevis (29.2%), abductor digiti minimi (19.0%), and first dorsal interosseus (24.9%). There was partial repair of the relative CMAP reduction at the follow-up visit (20.1%, 10.7%, and 8.7%, respectively). There was no significant change in CMAP duration.

CONCLUSIONS

These results provide a framework for quantifying the degree of hand intrinsic CMAP amplitude reduction attributed to disuse.

Simultaneous R2, R2' and R2* measurement of skeletal muscle in a rabbit model of unilateral artery embolization

PURPOSE

To demonstrate the feasibility of using a susceptibility-based MRI technique with multi-echo gradient and spin echo (MEGSE) sequence to achieve simultaneous R2, R2' and R2* measurement and assess skeletal muscle oxygenation alternations in a rabbit model of unilateral artery embolization.

MATERIALS AND METHODS

Approved by the local institutional review board for experimental animal studies, nine New Zealand White rabbits were included in this study. The MEGSE sequence consists of embedding a set of gradient echoes around the echo of a single spin-echo sequence using several gradient echoes to collect the magnetization intensity during the formation and attenuation of spin-echo simultaneously after 180° radio frequency pulse. Within-session and between-day tests were conducted to evaluate the reproducibility of this skeletal muscle oxygenation alternations measurement. Furthermore, all the MEGSE scans of skeletal muscle were conducted using a 3-T clinical MRI scanner during resting state (before unilateral artery embolization operation, pre), 1 h after unilateral artery embolization operation (post1) and 2 h after unilateral artery embolization operation (post2) model to verify the feasibility and sensitivity of this method.

RESULTS

The within-session coefficient of variations (CVs) of R2, R2' and R2* measurements were 1.57%, 3.33% and 2.57%, while the between-day CVs of were 1.42%, 5.85% and 2.85%. In all rabbits, the mean R2 decreased significantly from 36.46 ± 1.03 s^-1 (pre) to 30.58 ± 2.11 s^-1 (post1,**P < 0.01, relative to pre) and 28.62 ± 1.53 s^-1 (post2, **P < 0.01, relative to post1), and the mean R2' went up markedly from 9.88 ± 2.14 s^-1 (pre) to 16.10 ± 2.74 s^-1 (post1, **P < 0.01) and 17.33 ± 2.25 s^-1 (post2, **P < 0.05). The mean R2* increased from 43.27 ± 3.75 s^-1 (pre) to 47.90 ± 5.08 s^-1 (post1, *P < 0.05) and to 48.04 ± 4.42 s^-1 (post2, NS, P > 0.05).

CONCLUSION

This study demonstrates the feasibility of simultaneous R2, R2' and R2* measurement method for the evaluation of skeletal muscle ischemia. Besides, this study indicates the sensitivity of the R2 and R2' compared with R2* and especially the necessity of R2 and R2' measurement for the further evaluation of skeletal muscle ischemia which always causes both edema and hypoxia in a rabbit model of unilateral artery embolization.

Influence of age and level of activity on the applicability of a walker orthosis - a prospective study in different cohorts of healthy volunteers

Background

Walker orthosis are frequently prescribed as they are removable to allow wound control, body care and physiotherapy and are adaptable to the soft tissue conditions. The prerequisite for successful treatment with any walker orthosis is a correct use by the patient. Therefore, the aim of this study was to investigate patients’ handling of a commonly used walker.

Methods

Prospective observational study analyzing the applicability of a walker orthosis in different cohorts with varying age and level of activity. Volunteers were recruited from a mountain-biking-team (Sport), a cardiovascular-health-sports-group (Cardio) and a retirement home (Senior). The correct application was assessed following initial training (t0) and one week later (t1). Outcome parameters were an Application Score, strap tightness, vertical heel lift-off and subjective judgement of correct application.

Results

Thirty-three volunteers, 11 Sports group (31 ± 7a), 12 Cardio group (59 ± 11a), 10 Senior group, (82 ± 5a) were enrolled. No differences for any parameter could be observed between t0 and t1. Age showed a moderate correlation for all outcome parameters and the cohort influenced all variables. The Senior group presented significant inferior results to the Sport- and Cardio group for the Application Score (p = 0.002-p < 0.001) and strap tightness (p < 0.001). Heel lift-off was significantly inferior in the Cardio- and Senior- compared to the Sport group (p = 0.003-p < 0.001). 14% in the Sport-, 4% in the Cardio- and 83% in the Senior group achieved less than 9 points in the Application Score – which was considered insufficient. However, out of these 90% believed the application to be correct.

Conclusions

The elderly cohort living in a retirement home demonstrated an impaired handling of the walker orthosis. Further, participants were incapable to self-assess the correct handling. These aspects should be respected when initiating treatment with a walker orthosis.

Trial registration

Retrospectively registered on the 16th of February 2018: #DRKS00013728 on DRKS.

Electronic supplementary material

The online version of this article (10.1186/s12891-018-2366-2) contains supplementary material, which is available to authorized users.

Stimuli and sensors that initiate skeletal muscle hypertrophy following resistance exercise

One of the most striking adaptations to exercise is the skeletal muscle hypertrophy that occurs in response to resistance exercise. A large body of work shows that a mammalian target of rapamycin complex 1 (mTORC1)-mediated increase of muscle protein synthesis is the key, but not sole, mechanism by which resistance exercise causes muscle hypertrophy. While much of the hypertrophy signaling cascade has been identified, the initiating, resistance exercise-induced and hypertrophy-stimulating stimuli have remained elusive. For the purpose of this review, we define an initiating, resistance exercise-induced and hypertrophy-stimulating signal as "hypertrophy stimulus," and the sensor of such a signal as "hypertrophy sensor." In this review we discuss our current knowledge of specific mechanical stimuli, damage/injury-associated and metabolic stress-associated triggers, as potential hypertrophy stimuli. Mechanical signals are the prime hypertrophy stimuli candidates, and a filamin-C-BAG3-dependent regulation of mTORC1, Hippo, and autophagy signaling is a plausible albeit still incompletely characterized hypertrophy sensor. Other candidate mechanosensing mechanisms are nuclear deformation-initiated signaling or several mechanisms related to costameres, which are the functional equivalents of focal adhesions in other cells. While exercise-induced muscle damage is probably not essential for hypertrophy, it is still unclear whether and how such muscle damage could augment a hypertrophic response. Interventions that combine blood flow restriction and especially low load resistance exercise suggest that resistance exercise-regulated metabolites could be hypertrophy stimuli, but this is based on indirect evidence and metabolite candidates are poorly characterized.

Topical thermal therapy with hot packs suppresses physical inactivity-induced mechanical hyperalgesia and up-regulation of NGF

We focused on the analgesic effect of hot packs for mechanical hyperalgesia in physically inactive rats. Male Wistar rats were randomly divided into four groups: control, physical inactivity (PI), PI + sham treatment (PI + sham), and PI + hot pack treatment (PI + hot pack) groups. Physical inactivity rats wore casts on both hind limbs in full plantar flexed position for 4 weeks. Hot pack treatment was performed for 20 min a day, 5 days a week. Although mechanical hyperalgesia and the up-regulation of NGF in the plantar skin and gastrocnemius muscle were observed in the PI and the PI + sham groups, these changes were significantly suppressed in the PI + hot pack group. The present results clearly demonstrated that hot pack treatment was effective in reducing physical inactivity-induced mechanical hyperalgesia and up-regulation of NGF in plantar skin and gastrocnemius muscle.

What Is Important Besides Getting the Bone to Heal? Impact on Tissue Injury Other Than the Fracture

Fracture surgeons do a great job of managing bone issues, but they may overlook the associated soft tissue injuries that play a significant role in the final outcome after musculoskeletal injury. The soft tissue reconstruction ladder can help guide reconstructive procedures based on the least complex procedure that allows the best chance of fracture healing. Muscle injury, volume loss, and deconditioning occur with traumatic injury and during the recovery phase. Neuromuscular stimulation, nutrition, and strength training are potential ways to aid in recovery. Complex periarticular knee injuries have a high rate of associated soft tissue injuries that may affect outcome if associated with knee instability. Identifying and addressing these injuries can increase the likelihood of a good outcome. Articular cartilage loss can make articular reconstruction impossible. Large fresh osteoarticular allografts can be a reconstructive option. Addressing all the damaged structures involved with a fracture may be the next step in improving patient outcomes.

Effect of Eukarion-134 on Akt-mTOR signalling in the rat soleus during 7 days of mechanical unloading

NEW FINDINGS

What is the central question of this study? Translocation of nNOSμ initiates catabolic signalling via FoxO3a and skeletal muscle atrophy during mechanical unloading. Recent evidence suggests that unloading-induced muscle atrophy and FoxO3a activation are redox sensitive. Will a mimetic of superoxide dismutase and catalase (i.e. Eukarion-134) also mitigate suppression of the Akt-mTOR pathway? What is the main finding and its importance? Eukarion-134 rescued Akt-mTOR signalling and sarcolemmal nNOSμ, which were linked to protection against the unloading phenotype, muscle fibre atrophy and partial fibre-type shift from slow to fast twitch. The loss of nNOSμ from the sarcolemma appears crucial to Akt phosphorylation and is redox sensitive, although the mechanisms remain unresolved.

ABSTRACT

Mechanical unloading stimulates rapid changes in skeletal muscle morphology, characterized by atrophy of muscle fibre cross-sectional area and a partial fibre-type shift from slow to fast twitch. Recent studies revealed that oxidative stress contributes to activation of forkhead box O3a (FoxO3a), proteolytic signalling and unloading-induced muscle atrophy via translocation of the μ-splice variant of neuronal nitric oxide synthase (nNOSμ) and activation of FoxO3a. There is limited understanding of the role of reactive oxygen species in the Akt-mammalian target of rapamycin (mTOR) pathway signalling during unloading. We hypothesized that Eukarion-134 (EUK-134), a mimetic of the antioxidant enzymes superoxide dismutase and catalase, would protect Akt-mTOR signalling in the unloaded rat soleus. Male Fischer 344 rats were separated into the following three study groups: ambulatory control (n = 11); 7 days of hindlimb unloading + saline injections (HU, n = 11); or 7 days of HU + EUK-134; (HU + EUK-134, n = 9). EUK-134 mitigated unloading-induced dephosphorylation of Akt, as well as FoxO3a, in the soleus. Phosphorylation of mTOR in the EUK-treated HU rats was not different from that in control animals. However, EUK-134 did not significantly rescue p70S6K phosphorylation. EUK-134 attenuated translocation of nNOSμ from the membrane to the cytosol, reduced nitration of tyrosine residues and suppressed upregulation of caveolin-3 and dysferlin. EUK-134 ameliorated HU-induced remodelling, atrophy of muscle fibres and the 12% increase in type II myosin heavy chain-positive fibres. Attenuation of the unloaded muscle phenotype was associated with decreased reactive oxygen species, as assessed by ethidium-positive nuclei. We conclude that oxidative stress affects Akt-mTOR signalling in unloaded skeletal muscle. Direct linkage of abrogation of nNOSμ translocation with Akt-mTOR signalling during unloading is the subject of future investigation.

The Ankle Injury Management (AIM) trial: a pragmatic, multicentre, equivalence randomised controlled trial and economic evaluation comparing close contact casting with open surgical reduction and internal fixation in the treatment of unstable ankle fractures in patients aged over 60 years

BACKGROUND

Close contact casting (CCC) may offer an alternative to open reduction and internal fixation (ORIF) surgery for unstable ankle fractures in older adults.

OBJECTIVES

We aimed to (1) determine if CCC for unstable ankle fractures in adults aged over 60 years resulted in equivalent clinical outcome compared with ORIF, (2) estimate cost-effectiveness to the NHS and society and (3) explore participant experiences.

DESIGN

A pragmatic, multicentre, equivalence randomised controlled trial incorporating health economic evaluation and qualitative study.

SETTING

Trauma and orthopaedic departments of 24 NHS hospitals.

PARTICIPANTS

Adults aged over 60 years with unstable ankle fracture. Those with serious limb or concomitant disease or substantial cognitive impairment were excluded.

INTERVENTIONS

CCC was conducted under anaesthetic in theatre by surgeons who attended training. ORIF was as per local practice. Participants were randomised in 1 : 1 allocation via remote telephone randomisation. Sequence generation was by random block size, with stratification by centre and fracture pattern.

MAIN OUTCOME MEASURES

Follow-up was conducted at 6 weeks and, by blinded outcome assessors, at 6 months after randomisation. The primary outcome was the Olerud-Molander Ankle Score (OMAS), a patient-reported assessment of ankle function, at 6 months. Secondary outcomes were quality of life (as measured by the European Quality of Life 5-Dimensions, Short Form questionnaire-12 items), pain, ankle range of motion and mobility (as measured by the timed up and go test), patient satisfaction and radiological measures. In accordance with equivalence trial US Food and Drug Administration guidance, primary analysis was per protocol.

RESULTS

We recruited 620 participants, 95 from the pilot and 525 from the multicentre phase, between June 2010 and November 2013. The majority of participants, 579 out of 620 (93%), received the allocated treatment; 52 out of 275 (19%) who received CCC later converted to ORIF because of loss of fracture reduction. CCC resulted in equivalent ankle function compared with ORIF at 6 months {OMAS 64.5 points [standard deviation (SD) 22.4 points] vs. OMAS 66.0 points (SD 21.1 points); mean difference -0.65 points, 95% confidence interval (CI) -3.98 to 2.68 points; standardised effect size -0.04, 95% CI -0.23 to 0.15}. There were no differences in quality of life, ankle motion, pain, mobility and patient satisfaction. Infection and/or wound problems were more common with ORIF [29/298 (10%) vs. 4/275 (1%)], as were additional operating theatre procedures [17/298 (6%) vs. 3/275 (1%)]. Malunion was more common with CCC [38/249 (15%) vs. 8/274 (3%); p < 0.001]. Malleolar non-union was lower in the ORIF group [lateral: 0/274 (0%) vs. 8/248 (3%); p = 0.002; medial: 3/274 (1%) vs. 18/248 (7%); p < 0.001]. During the trial, CCC showed modest mean cost savings [NHS mean difference -£644 (95% CI -£1390 to £76); society mean difference -£683 (95% CI -£1851 to £536)]. Estimates showed some imprecision. Incremental quality-adjusted life-years following CCC were no different from ORIF. Over common willingness-to-pay thresholds, the probability that CCC was cost-effective was very high (> 95% from NHS perspective and 85% from societal perspective). Experiences of treatments were similar; both groups endured the impact of fracture, uncertainty regarding future function and the need for further interventions.

LIMITATIONS

Assessors at 6 weeks were necessarily not blinded. The learning-effect analysis was inconclusive because of limited CCC applications per surgeon.

CONCLUSIONS

CCC provides a clinically equivalent outcome to ORIF at reduced cost to the NHS and to society at 6 months.

FUTURE WORK

Longer-term follow-up of trial participants is under way to address concerns over potential later complications or additional procedures and their potential to impact on ankle function. Further study of the patient factors, radiological fracture patterns and outcomes, treatment responses and prognosis would also contribute to understanding the treatment pathway.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN04180738.

FUNDING

The National Institute for Health Research Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 20, No. 75. See the NIHR Journals Library website for further project information. This report was developed in association with the National Institute for Health Research Oxford Biomedical Research Unit funding scheme. The pilot phase was funded by the AO Research Foundation.

Ultrasound assessment of rectus femoris and anterior tibialis muscles in young trauma patients

Purpose

Quantitative and qualitative changes of skeletal muscle are typical and early findings in trauma patients, being possibly associated with functional impairment. Early assessment of muscle changes—as evaluated by muscle ultrasonography—could yield important information about patient’s outcome.

Methods

In this prospective observational study, we used ultrasonography to evaluate the morphological changes of rectus femoris (RF) and anterior tibialis (AT) muscles in a group of young, previously healthy trauma patients on enteral feeding.

Results

We studied 38 severely injured patients (median Injury Severity Score = 34; median age = 40 y.o.) over the course of the ICU stay up to 3 weeks after trauma. We found a progressive loss of muscle mass from day 0 to day 20, that was more relevant for the RF (45%) than for the AT (22%); this was accompanied by an increase in echogenicity (up to 2.5 by the Heckmatt Scale, where normal echogenicity = 1), which is an indicator of myofibers depletion.

Conclusions

Ultrasound evaluation of skeletal muscles is inexpensive, noninvasive, simple and easily repeatable. By this method, we were able to quantify the morphological changes of skeletal muscle in trauma patients. Further studies may rely on this technicque to evaluate the impact of different therapeutic strategies on muscle wasting.

Interventional strategies to combat muscle disuse atrophy in humans: focus on neuromuscular electrical stimulation and dietary protein

Numerous situations, such as the recovery from illness or rehabilitation after injury, necessitate a period of muscle disuse in otherwise healthy individuals. Even a few days of immobilization or bed rest can lead to substantial loss of skeletal muscle tissue and compromise metabolic health. The decline in muscle mass is attributed largely to a decline in postabsorptive and postprandial muscle protein synthesis rates. Reintroduction of some level of muscle contraction by the application of neuromuscular electrical stimulation (NMES) can augment both postabsorptive and postprandial muscle protein synthesis rates and, as such, prevent or attenuate muscle loss during short-term disuse in various clinical populations. Whereas maintenance of habitual dietary protein consumption is a prerequisite for muscle mass maintenance, supplementing dietary protein above habitual intake levels does not prevent muscle loss during disuse in otherwise healthy humans. Combining the anabolic properties of physical activity (or surrogates) with appropriate nutritional support likely further increases the capacity to preserve skeletal muscle mass during a period of disuse. Therefore, effective interventional strategies to prevent or alleviate muscle disuse atrophy should include both exercise (mimetics) and appropriate nutritional support.

Age-related changes in the effects of strength training on lower leg muscles in healthy individuals measured using MRI

Background

We previously measured the rate of regaining muscle strength during rehabilitation of lower leg muscles in patients following lower leg casting. Our primary aim in this study was to measure the rate of gain of strength in healthy individuals undergoing a similar training regime. Our secondary aim was to test the ability of MRI to provide a biomarker for muscle function.

Methods

Men and women were recruited in three age groups: 20–30, 50–65 and over 70 years. Their response to resistance training of the right lower leg twice a week for 8 weeks was monitored using a dynamometer and MRI of tibialis anterior, soleus and gastrocnemius muscles at 2 weekly intervals to measure muscle size (anatomical cross-sectional area (ACSA)) and quality (T₂ relaxation). Forty-four volunteers completed the study.

Results

Baseline strength declined with age. Training had no effect in middle-aged females or in elderly men in dorsiflexion. Other groups significantly increased both plantarflexion and dorsiflexion strength at rates up to 5.5 N m week^-1 in young females in plantarflexion and 1.25 N m week^-1 in young males in dorsiflexion. No changes were observed in ACSA or T₂ in any age group in any muscle.

Conclusion

Exercise training improves muscle strength in males at all ages except the elderly in dorsiflexion. Responses in females were less clear with variation across age and muscle groups. These results were not reflected in simple MRI measures that do not, therefore, provide a good biomarker for muscle atrophy or the efficacy of rehabilitation.

Shorter recovery can be achieved from using walking boot after operative treatment of an ankle fracture

Background/Objective

Ankle fractures, even if treated surgically, usually take a long time to heal. For all patients with ankle fracture, immobilisation is a critical part of treatment. Short-leg walking boots (WBs) have been reported to be an effective alternative to plaster casts (PCs) that could shorten this postoperative recuperative period. The aim of this study was to compare the functional recovery of a conventional PC with that of a WB after surgery for ankle fractures.

Methods

Forty-seven patients (mean age, 53.9 ± 12 years) who had undergone surgical operation for an unstable ankle fracture from January 2008 to October 2014 were reviewed retrospectively. Either a PC or a WB was prescribed postoperatively, with 25 patients and 22 patients, respectively. The time that it took the patient to stand unipedal on the affected side after allowing full-weight bear and to walk without crutches were used for assessment of functional recovery. The prevalence of postoperative loss of reduction and nonunion was also reviewed.

Results

Both the time of being able to stand unipedal on the injured side and to walk without crutches were significantly shorter in patients using WBs (WB, 2.6 weeks; PC, 4.5 weeks, p = 0.01; WB, 1.4 weeks; PC, 3.1 weeks, p = 0.03). There were no patients with loss of reduction or nonunion.

Conclusion

Patients who used WBs showed a significantly faster recovery. WBs have an adjustable heel lift that allows users to change the ankle position slightly plantarflexed that helps walking in a postoperative swollen ankle. WBs are easy to slip on, and it is easy to adjust the ankle position in conformity with swelling so that the least painful position could be maintained during walking. WBs have good fixity to allow immediate weight-bearing postoperatively, and there were no cases with loss of reduction postoperatively. The Rocker bottom design minimises the sagittal plane motion in the specific joint of the foot, which also facilitates the course of recuperation. An ankle fracture fixed appropriately endures loading when a WB is used. The WB treatment results in faster functional recovery, allowing the patients to return to normal activity at a faster rate.

Near-Infrared Optical Imaging Noninvasively Detects Acutely Damaged Muscle

Muscle damage is currently assessed through methods such as muscle biopsy, serum biomarkers, functional testing, and imaging procedures, each with its own inherent limitations, and a pressing need for a safe, repeatable, inexpensive, and noninvasive modality to assess the state of muscle health remains. Our aim was to develop and assess near-infrared (NIR) optical imaging as a novel noninvasive method of detecting and quantifying muscle damage. An immobilization-reambulation model was used for inducing muscle damage and recovery in the lower hindlimbs in mice. Confirmation of muscle damage was obtained using in vivo indocyanine green-enhanced NIR optical imaging, magnetic resonance imaging, and ex vivo tissue analysis. The soleus of the immobilized-reambulated hindlimb was found to have a greater amount of muscle damage compared to that in the contralateral nonimmobilized limb, confirmed by in vivo indocyanine green-enhanced NIR optical imaging (3.86-fold increase in radiant efficiency), magnetic resonance imaging (1.41-fold increase in T2), and an ex vivo spectrophotometric assay of indocyanine green uptake (1.87-fold increase in normalized absorbance). Contrast-enhanced NIR optical imaging provides a sensitive, rapid, and noninvasive screening method that can be used for imaging and quantifying muscle damage and recovery in vivo.

Human Skeletal Muscle Disuse Atrophy: Effects on Muscle Protein Synthesis, Breakdown, and Insulin Resistance-A Qualitative Review

The ever increasing burden of an aging population and pandemic of metabolic syndrome worldwide demands further understanding of the modifiable risk factors in reducing disability and morbidity associated with these conditions. Disuse skeletal muscle atrophy (sometimes referred to as “simple” atrophy) and insulin resistance are “non-pathological” events resulting from sedentary behavior and periods of enforced immobilization e.g., due to fractures or elective orthopedic surgery. Yet, the processes and drivers regulating disuse atrophy and insulin resistance and the associated molecular events remain unclear—especially in humans. The aim of this review is to present current knowledge of relationships between muscle protein turnover, insulin resistance and muscle atrophy during disuse, principally in humans. Immobilization lowers fasted state muscle protein synthesis (MPS) and induces fed-state “anabolic resistance.” While a lack of dynamic measurements of muscle protein breakdown (MPB) precludes defining a definitive role for MPB in disuse atrophy, some proteolytic “marker” studies (e.g., MPB genes) suggest a potential early elevation. Immobilization also induces muscle insulin resistance (IR). Moreover, the trajectory of muscle atrophy appears to be accelerated in persistent IR states (e.g., Type II diabetes), suggesting IR may contribute to muscle disuse atrophy under these conditions. Nonetheless, the role of differences in insulin sensitivity across distinct muscle groups and its effects on rates of atrophy remains unclear. Multifaceted time-course studies into the collective role of insulin resistance and muscle protein turnover in the setting of disuse muscle atrophy, in humans, are needed to facilitate the development of appropriate countermeasures and efficacious rehabilitation protocols.

Diminished Foot and Ankle Muscle Volumes in Young Adults With Chronic Ankle Instability

Background:

Patients with chronic ankle instability (CAI) have demonstrated altered neuromuscular function and decreased muscle strength when compared with healthy counterparts without a history of ankle sprain. Up to this point, muscle volumes have not been analyzed in patients with CAI to determine whether deficits in muscle size are present following recurrent sprain.

Purpose:

To analyze intrinsic and extrinsic foot and ankle muscle volumes and 4-way ankle strength in young adults with and without CAI.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

Five patients with CAI (mean age, 23.0 ± 4 years; 1 male, 4 females) and 5 healthy controls (mean age, 23.8 ± 4.5 years; 1 male, 4 females) volunteered for this study. Novel fast-acquisition magnetic resonance imaging (MRI) was used to scan from above the femoral condyles through the foot and ankle. The perimeter of each muscle was outlined on each axial slice and then the 2-dimensional area was multiplied by the slice thickness (5 mm) to calculate the muscle volume. Plantar flexion, dorsiflexion, inversion, and eversion isometric strength were measured using a handheld dynamometer. Patients with CAI were compared with healthy controls on all measures of muscle volume and strength. Extrinsic muscle volumes of patients with CAI were also compared with a normative database of healthy controls (n = 24) by calculating z scores for each muscle individually for each CAI subject.

Results:

The CAI group had smaller total shank, superficial posterior compartment, soleus, adductor hallucis obliqus, and flexor hallucis brevis muscle volumes compared with healthy controls as indicated by group means and associated 90% CIs that did not overlap. Cohen d effect sizes for the significant group differences were all large and ranged from 1.46 to 3.52, with 90% CIs that did not cross zero. The CAI group had lower eversion, dorsiflexion, and 4-way composite ankle strength, all with group means and associated 90% CIs that did not overlap. No other significant differences were identified.

Conclusion:

Patients with CAI demonstrate atrophy of intrinsic and extrinsic foot and ankle musculature accompanied by lower ankle strength.

Clinical Relevance:

Clinicians should be aware of the muscle atrophy and strength deficits when prescribing rehabilitation for patients with lateral ankle sprain or CAI.

Treatment of Acute Jones Fractures Without Weightbearing Restriction

Jones fractures are reportedly prone to nonunion and generally treated with a period of non-weightbearing or operative treatment. Extended non-weightbearing can have adverse effects, and operative treatment poses various risks. We report the clinical results of patients treated without weightbearing restriction. All patients treated for metatarsal fractures by a single surgeon from January 1, 2000 to December 31, 2009 were identified through the clinical billing records by International Classification of Diseases, ninth revision, code. Through a radiographic and medical record review, 27 consecutive patients with acute Jones fractures treated without weightbearing restriction were identified. The demographic information and clinical and radiographic results were recorded. Of the 27 patients, 24 (89%) had achieved clinical union at a mean of 8.0 ± 2.6 weeks. Complete radiographic union was noted in 13 (48%) patients, and 13 (48%) others had made significant progress toward radiographic union but had not yet reached it. Two (8.3%) patients were lost to follow-up. One patient (4%) developed nonunion. Patients with acute Jones fractures can be treated without weightbearing restriction. This protocol results in rapid clinical union and a low rate of nonunion.

Acquired Muscle Weakness in the Surgical Intensive Care Unit

Muscle weakness is common in the surgical intensive care unit (ICU). Low muscle mass at ICU admission is a significant predictor of adverse outcomes. The consequences of ICU-acquired muscle weakness depend on the underlying mechanism. Temporary drug-induced weakness when properly managed may not affect outcome. Severe perioperative acquired weakness that is associated with adverse outcomes (prolonged mechanical ventilation, increases in ICU length of stay, and mortality) occurs with persistent (time frame: days) activation of protein degradation pathways, decreases in the drive to the skeletal muscle, and impaired muscular homeostasis. ICU-acquired muscle weakness can be prevented by early treatment of the underlying disease, goal-directed therapy, restrictive use of immobilizing medications, optimal nutrition, activating ventilatory modes, early rehabilitation, and preventive drug therapy. In this article, the authors review the nosology, epidemiology, diagnosis, and prevention of ICU-acquired weakness in surgical ICU patients.

Effects of Vibration Therapy on Immobilization-Induced Hypersensitivity in Rats

BACKGROUND

Cast immobilization induces mechanical hypersensitivity, which disturbs rehabilitation. Although vibration therapy can reduce various types of pain, whether vibration reduces immobilization-induced hypersensitivity remains unclear.

OBJECTIVE

The purpose of this study was to investigate the preventive and therapeutic effects of vibration therapy on immobilization-induced hypersensitivity.

DESIGN

The experimental design of the study involved conducting behavioral, histological, and immunohistochemical studies in model rats.

METHODS

Thirty-five Wistar rats (8 weeks old, all male) were used. The right ankle joints of 30 rats were immobilized by plaster cast for 8 weeks, and 5 rats were used as controls. The immobilized rats were divided randomly into the following 3 groups: (1) immobilization-only group (Im, n=10); (2) vibration therapy group 1, for which vibration therapy was initiated immediately after the onset of immobilization (Im+Vib1, n=10); and (3) vibration therapy group 2, for which vibration therapy was initiated 4 weeks after the onset of immobilization (Im+Vib2, n=10). Vibration was applied to the hind paw. The mechanical hypersensitivity and epidermal thickness of the hind paw skin were measured. To investigate central sensitization, calcitonin gene-related peptide (CGRP) expression in the spinal cord and dorsal root ganglion (DRG) was analyzed.

RESULTS

Immobilization-induced hypersensitivity was inhibited in the Im+Vib1 group but not in the Im+Vib2 group. Central sensitization, which was indicated by increases in CGRP expression in the spinal cord and the size of the area of CGRP-positive neurons in the DRG, was inhibited in only the Im+Vib1 group. Epidermal thickness was not affected by vibration stimulation.

LIMITATIONS

A limitation of this study is that the results were limited to an animal model and cannot be generalized to humans.

CONCLUSIONS

The data suggest that initiation of vibration therapy in the early phase of immobilization may inhibit the development of immobilization-induced hypersensitivity.

Bracing versus casting in ankle fractures

Casting and splinting techniques for treating patients with fractures have been used for centuries. Functional bracing after ankle fracture has recently been utilized in an effort to avoid the atrophy and stiffness sometimes associated with casting; functional bracing allows for early mobilization of the ankle joint during recovery. Our review investigated the published literature comparing bracing with casting after ankle fracture. Studies examining both operatively and nonoperatively treated ankle fractures were included. There is minimal evidence supporting the use of functional bracing over cast immobilization to improve functional outcome, range of motion, swelling, or post-traumatic arthrosis after ankle fracture in the long term. The primary benefits of functional bracing are the potential to return to work earlier and bracing may facilitate activities of daily living, such as bathing and dressing. In addition, there may be a decreased patient risk of developing deep vein thrombosis due to immobilization. However, there is an increased risk of wound infection when using a brace after open reduction and internal fixation of an unstable ankle fracture. Functional bracing can be used for treating stable and postoperative ankle fractures in compliant patients to potentially expedite and facilitate the recovery process.

Use it or lose it: multiscale skeletal muscle adaptation to mechanical stimuli

Skeletal muscle undergoes continuous turnover to adapt to changes in its mechanical environment. Overload increases muscle mass, whereas underload decreases muscle mass. These changes are correlated with, and enabled by, structural alterations across the molecular, subcellular, cellular, tissue, and organ scales. Despite extensive research on muscle adaptation at the individual scales, the interaction of the underlying mechanisms across the scales remains poorly understood. Here, we present a thorough review and a broad classification of multiscale muscle adaptation in response to a variety of mechanical stimuli. From this classification, we suggest that a mathematical model for skeletal muscle adaptation should include the four major stimuli, overstretch, understretch, overload, and underload, and the five key players in skeletal muscle adaptation, myosin heavy chain isoform, serial sarcomere number, parallel sarcomere number, pennation angle, and extracellular matrix composition. Including this information in multiscale computational models of muscle will shape our understanding of the interacting mechanisms of skeletal muscle adaptation across the scales. Ultimately, this will allow us to rationalize the design of exercise and rehabilitation programs, and improve the long-term success of interventional treatment in musculoskeletal disease.