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: The purpose of this study is to determine muscle fibre length around the knee before and after anterior cruciate ligament (ACL) transection, and to test its ability to detect instability changes. Material and methods: Pairs of piezoelectric crystals were inserted in four periarticular muscles (vastus lateralis -VL-, vastus medialis -VM-, lateral hamstrings -LH-, medial hamstrings -MH-) around 11 knees from 8 cats. Distance between pairs was measured while performing 10 passive repetitions of anterior tibial displacement at 90 degrees and 30 degrees flexed knee, flexion and extension, and controlled by sagittal plane video recordings. Ultrasound signal between crystals in each pair was analysed to obtain intensity and time-dependent parameters. Data from control and unstable knees were statistically compared. Results: Fibre lengthening was observed in the four studied muscles under anterior tibial traction. Significant increases in fibre length at VL, VM (p< 0,05) and LH (P< 0,01) were seen in unstable knees versus normal knees when anterior tibial traction was performed at 90 degrees knee flexion. Flexion and extension produced passive changes in fibre length (quadriceps lengthening and hamstrings shortening for flexion, the opposite for extension), but no significant variations were measured when the ACL was sectioned. Discussion: Ultrasonomicrometry offers a new approach to comprehend anterior instability of the knee when studying periarticular muscle fibre length. Variations in the response are specific for the anterior tibial displacement in unstable knees. This technique can be used in combination with electromyography for a better understanding of muscle behaviour in ACL deficient knees

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 ± 1947μm² and 3461 ± 1946μm² in men, and 5144 ± 1692μm² and 1945 ± 1039μm² 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.

Aims. Hip arthroplasty aims to accurately recreate joint biomechanics. Considerable attention has been paid to vertical and horizontal offset, but femoral head centre in the anteroposterior (AP) plane has received little attention. This study investigates the accuracy of restoration of joint centre of rotation in the AP plane. Methods. Postoperative CT scans of 40 patients who underwent unilateral uncemented total hip arthroplasty were analyzed. Anteroposterior offset (APO) and femoral anteversion were measured on both the operated and non-operated sides. Sagittal tilt of the femoral stem was also measured. APO measured on axial slices was defined as the perpendicular distance between a line drawn from the anterior most point of the proximal femur (anterior reference line) to the centre of the femoral head. The anterior reference line was made parallel to the posterior condylar axis of the knee to correct for rotation. Results. Overall, 26/40 hips had a centre of rotation displaced posteriorly compared to the contralateral hip, increasing to 33/40 once corrected for sagittal tilt, with a mean posterior displacement of 7 mm. Linear regression analysis indicated that stem anteversion needed to be increased by 10.8° to recreate the head centre in the AP plane. Merely matching the native version would result in a 12 mm posterior displacement. Conclusion. This study demonstrates the significant incidence of posterior displacement of the head centre in uncemented hip arthroplasty. Effects of such displacement include a reduction in impingement free range of motion, potential alterations in muscle force vectors and lever arms, and impaired proprioception due to muscle fibre reorientation. Cite this article: Bone Joint Res 2022;11(3):180–188

Aims

The decrease in the number of satellite cells (SCs), contributing to myofibre formation and reconstitution, and their proliferative capacity, leads to muscle loss, a condition known as sarcopenia. Resistance training can prevent muscle loss; however, the underlying mechanisms of resistance training effects on SCs are not well understood. We therefore conducted a comprehensive transcriptome analysis of SCs in a mouse model.

Introduction and Aims: With a great progress in bone regeneration, muscle is currently regarded as a largest limiting factor for successful limb lengthening leading to joint contractures and fractures of distraction regenerate. The purpose of this study was to evaluate muscle architectural changes and potential mechanisms of joint contractures during limb lengthening. Method: Nine mature goats underwent 20% unilateral tibial lengthening (0.25 mm x 3/day) and were sacrificed immediately upon completion of distraction. With the stifle (knee) and hock (ankle) joints fixed at similar angles, both limbs were disarticulated at the hip joint and submerged into 10% buffered formalin. Following tissue fixation, all tibial muscles were sequentially dissected and changes in muscle origin-to-incretion length, belly length, tendon length, myofibers length, and sarcomere length were analysed relative to the muscle measurements on the contralateral limb and bone lengthening. Muscle fiber length was assessed under stereoscopic magnification and sarcomere analysis was performed using laser diffraction. Results: Thirteen muscles were identified for each limb. Anterior compartment consisted of two longitudinal and four pennate muscles, whereas posterior compartment had one longitudinal and six pennate muscles. Origin-to-insertion length measurements showed disproportion between the amounts of muscle and bone length increase with muscle-to-bone lengthening ratio ranging from 0.2 to 1.0. When assessed separately, muscle belly stretched more substantially (range, 11–24%) than muscle tendon (range, 3–14%). Longitudinal muscles showed better compliance to limb lengthening than pennate muscles. Origin-to-insertion, muscle belly, and tendon length increase for longitudinal muscles averaged 15%, 21%, and 11%, respectively, whereas for pennate muscles these parameters averaged 10%, 15%, and 6%, respectively. Although anterior pennate muscles showed higher proportion of muscle length increase than posterior pennate muscles, this difference was not significant. Lengthening of muscle fibers varied greatly, ranging from 0% to 88%. Fiber length of posterior muscles increased tremendously (average, 42%). This was associated with comparable increase in sarcomere length (average, 39%). Anterior muscles showed only 10% lengthening of the fibers. However, 12% reduction in sarcomere length indicated addition of new sarcomeres in series to accommodate increase in fiber length. Conclusion: Different response of anterior and posterior muscles to distraction contributed greatly to the development of joint contractures. Posterior tibial muscles were predominantly pennate, larger in volume, and thus showed higher resistance to lengthening. Moreover, posterior muscle fibers incurred lengthening by sarcomere stretching, whereas anterior muscle fibers showed evidence of neosarcomerogenesis

Achilles tendinitis can result, through inflammatory procedures, to tendon degeneration with microtears and nodules. Current conservative or surgical treatment of this lesion proved to be not effective enough. The reason for this is the absence of sufficient oxygenation in the area. In this study we report the results of a novel technique which tries to improve local vascularity. We operated on 15 mature rabbits after they were anasthetized. Soleus fibers were trasplanted in the right achilles tendon. A lesion, 10mm long and 2mm wide was created in the inner band of the tendon simulating tendinitis. In the left achilles tendon the same procedure was done without transplantation. The rabbits were divided in three equal groups and were sacrificed in the first week, the 2nd and 3rd month after the operation. Histopathologic examination was done in both achilles tendons. The following parameters were assessed: transplanted muscle viability, inflammation and neoangiogenesis. We also evaluated the contact between muscle and tendon and the quality of tissue that was formed in the tendinitis simulating area. Inflammatory process was noticed only in the 1st week after surgery. In the other groups viable muscle fibers and tendon tissue was observed. Muscle fibers were in contact with the tendon. The quality of tissue in the tendinitis simulating area was of better quality than in the control group. We conclude that soleus transplanted muscle fibers in the rabbits achilles tendon seem to be oxygen carriers and improve the healing potential of the area. This fact results in tendon reinforcement

Disuse atrophy is the basis for profound physiological changes of the muscles of immobilised limbs. The aim of this study was to use ultrasound to assess the quadriceps musculature and to try and measure atrophy. We monitored the effects of enforced reduction of mobility due to trauma on the intramuscular architecture of the quadriceps using high resolution real-time ultrasonography (HRRTU) in 13 skeletally mature male patients (43.2 years, range 16 to 82 years), with an isolated unilateral diaphyseal fracture of the femur or of the tibia. All patients had undergone interlocked intramedullary nailing (IIN). Using HRRTU, the pennation angles and muscle fibre lengths of vastus lateralis, the cross sectional area (CSA) of the rectus femoris, and the quadriceps muscle layer thickness (MLT) were measured in the injured and the normal contralateral limb. Repeated measurements showed the technique of measurement of the variables used in this study to be highly reproducible. There was a significant difference in the angle of pennation of the vastus lateralis in the nailed (15.4°) and the unnailed limb (21.2°), documenting that muscle atrophy causes a change to muscle architecture that results in a significant decrease in pennation angle (p = 0.0002). The muscle fibre length was significantly different (p=0.002) and there was a significant correlation between pennation angle and muscle fibre length (r=−0.51, p=0.001). There was also a significant difference in the quadriceps MLT (p=0.001) and CSA of the rectus femoris (p=0.0004) implying that the whole of the quadriceps muscle is affected

Objectives. Rotator cuff tears are among the most frequent upper extremity injuries. Current treatment strategies do not address the poor quality of the muscle and tendon following chronic rotator cuff tears. Hypoxia-inducible factor-1 alpha (HIF-1α) is a transcription factor that activates many genes that are important in skeletal muscle regeneration. HIF-1α is inhibited under normal physiological conditions by the HIF prolyl 4-hydroxylases (PHDs). In this study, we used a pharmacological PHD inhibitor, GSK1120360A, to enhance the activity of HIF-1α following the repair of a chronic cuff tear, and measured muscle fibre contractility, fibrosis, gene expression, and enthesis mechanics. Methods. Chronic supraspinatus tears were induced in adult rats, and repaired 28 days later. Rats received 0 mg/kg, 3 mg/kg, or 10 mg/kg GSK1120360A daily. Collagen content, contractility, fibre type distribution and size, the expression of genes involved in fibrosis, lipid accumulation, atrophy and inflammation, and the mechanical properties of the enthesis were then assessed two weeks following surgical repair. Results. At two weeks following repair, treatment groups showed increased muscle mass but there was a 15% decrease in force production in the 10 mg/kg group from controls, and no difference between the 0 mg/kg and the 3 mg/kg groups. There was a decrease in the expression of several gene transcripts related to matrix accumulation and fibrosis, and a 50% decrease in collagen content in both treated groups compared with controls. Additionally, the expression of inflammatory genes was reduced in the treated groups compared with controls. Finally, PHD inhibition improved the maximum stress and displacement to failure in repaired tendons. Conclusions. GSK1120360A resulted in improved enthesis mechanics with variable effects on muscle function. PHD inhibition may be beneficial for connective tissue injuries in which muscle atrophy has not occurred. Cite this article: J. P. Gumucio, M. D. Flood, A. Bedi, H. F. Kramer, A. J. Russell, C. L. Mendias. Inhibition of prolyl 4-hydroxylase decreases muscle fibrosis following chronic rotator cuff tear. Bone Joint Res 2017;6:57–65. DOI: 10.1302/2046-3758.61.BJR-2016-0232.R1

Purpose of the study: The aim of this biomechanical study was to assess the performance of the deltoid muscle in the absence of a rotator cuff using different models for shoulder prosthesis. Material and methods: A computer model reproducing the three dimensions of the glenohumeral joint was use to analyze the force of the deltoid muscle during abduction movements in shoulders devoid of a rotator cuff. The three heads of the deltoid were analyzed in order to determine the most effective level of muscle tension. The lever arm of the deltoid was measured from 0–90° abduction. Using this 3D model, we simulated implantation of six different models of reversed prostheses in order to assess the biomechanical situation which would be the most favorable for the deltoid. Performance of the normal deltoid was compared with the performance of the deltoid after implantation of an anatomic prosthesis and after implantation of an reversed prosthesis. Several variables were studied: medial offset of the center of rotation, lateral offset of the humerus, lengthening of the deltoid muscle. Results: Optimal deltoid performance (especially from 60–90° abduction) was observed if the center of rotation was offset medially and the humerus was offset laterally and lowered. A 10% increase in the length of the muscle fibres increased muscle performance 18%. Exaggerated lateral offest of the humerus increased deltoid performance between 30 and 60° abduction but lost its beneficial effect at 90° abduction. From 15° abduction, a scapular notch appeared when the humerus was off set medially. This could be avoided if the humerus was offset laterally with a less medial center of rotation. Beyond 150° abduction, superior impingement appeared irrespective of the type of prosthesis. Discussion and conclusion: This biomechanical study proved the superiority of reversed prostheses compared with anatomic prostheses for massive rotator cuff tears. Medial offset of the center of rotation reduced shear forces on the glenoid. Lateral offset of the humerus increase via a pulley effect the lowering force of the deltoid. Lowering the humerus pulled on the muscle fibers of the deltoid and increased their performance. Dosing these three variables with an appropriate («ideal») design for the reversed prosthesis would optimize deltoid performance in patients with deficient rotator cuffs

Introduction. Recovery of muscle strength following Total Knee Replacement (TKR) is variable, and can affect the resultant function of the patient. Satellite cells are undifferentiated myogenic precursors considered to be muscle stem cells that lie quiescently around the muscle fibre. These cells repair damaged fibres and have the potential to generate new muscle fibres. Therefore, theoretically, they could be associated with the variation in muscle recovery following surgery. We hypothesised that the recovery of muscle strength following knee replacement in a given patient would be influenced by the underlying number of satellite cells in that patient. Methods. 20 patients undergoing TKR were recruited from the waiting list of a single consultant. A muscle biopsy was taken at the time of surgery from the distal quadriceps. This was fixed in paraffin wax, and sections obtained. Satellite cells were identified with a primary mouse antibody for Pax7 - a cytoplasmic protein marker - and an immunofluorescent goat anti-mouse secondary. Slides were counterstained with DAPI to stain the myonuclei. The positive staining index (PSI) was calculated (number of satellite cells/total number of myonuclei x 100). Recovery of muscle (quadriceps) strength was assessed using the leg extensor power-rig (LegRig) pre-operatively, at 6 and 26 weeks post-operatively. Statistical analysis was performed using the Minitab version 15 software, the level of significance was set as p = 0.05. Results. 3 patients were unable to provide follow-up data. The number of satellite cells amongst individual patients in our cohort varied (PSI 3.07 to 11.35). Improvement in muscle power post-op also varied (0 to 70 W) between the 6 and 26 weeks assessment periods. This improvement in wattage generated between assessments reflected a relative improvement of between 0 and 60% in the strength to bodyweight ratio of these patients. The improvement in muscle power correlated with the satellite cell numbers (determined at the time of surgery). This was true for both absolute improvement in wattage generated (r = 0.54 p= 0.038) and also the improvement in strength to body weight ratio (r = 0.47 p = 0.06). Linear regression analysis demonstrated that the relative satellite cell number accounted for 30% of the improvement in muscle power. Discussion. We have for the first time demonstrated that the magnitude of improvement in muscle strength following TKR may be influenced by the patient's underlying pool of muscle satellite cells, with up to 30% of the variation of improvement in our cohort attributable to the satellite cell population

INTRODUCTION: Chronic experimental rotator cuff tears are associated with muscle retraction, atrophy, fatty infiltration, a pronounced change in the pennation angle of the muscle and consequent shortening of muscle fibres. It was the purpose of this investigation to study whether slow, continuous elongation of the musculotendinous unit can revert the pennation angle and elongate the shortened muscle fibres. MATERIAL AND METHODS: The infraspinatus tendons of twelve sheep were released. After retraction of the tenotomised musculotendinous unit, the infra-spinatus was elongated one mm per day using a new elongation-apparatus. After restoring the approximate original length, the tendon was repaired back. Muscular architecture (retraction and pennation angle), fatty infiltration (in Hounsfield units=HU) and muscular cross sectional area (in % of the mean control side) were analyzed at start, at the time before elongation, at the time of repair and six and eighteen weeks thereafter. RESULTS: In four sheep the elongation failed technically. In the other eight sheep, elongation could be achieved as planned. After retraction of 29mm ± 6 mm after 16 weeks (14% of original length, p=0.008), the mean traction time was 24 days ± 6 days with a mean traction distance of 19 mm ± 4 mm. At sacrifice the mean pennation angle increased in the failed sheep from 30° ± 6° up to 55° ± 14° (p=0.035). In those sheep in which traction was applied, the mean pennation angle was not different to the control side (29.8° ± 7.5° vs. 30° ± 6°, p=0.575). Compared to preoperative, there was a significant increase in fatty infiltration (36 HU, p=0.0001) and decrease of the muscular cross sectional area of 43 % (range 21% to 67%, p=0.0001) at 4 months. In the sheep in which traction could be achieved, fatty infiltration remain unchanged (36 HU ± 6 HU vs 38 HU ± 4 HU, p=0.438) and atrophy decreased by 22% (range 10% to 33%) after 6 weeks of continuous traction (p=0.008). CONCLUSION: Continuous experimental elongation of a retracted musculotendinous unit is technically feasible and might lead to recovery of the muscle architecture, partial reversibility of atrophy and, arrest of progression of fatty infiltration

Previous studies in animal models of limb lengthening have shown a wide spectrum of histopathological changes during distraction phase. Much less is known about the structural response of muscle during the consolidation phase. This study aimed to observe and score changes in morphology, weight, length and maximal perimeter of gastrocnemius during the distraction and consolidation phases. Thirty two immature New Zealand white rabbits were divided into two equal groups: lengthening and sham. In each group, half of the rabbits were killed at the end of lengthening and half 5 weeks later. A bilateral external fixator was applied to tibia and a mid-diaphysis osteotomy performed. The lengthening rate was 0.4 mm twice daily with an initial delay of 7 days. 30% lengthening was achieved in 4 to 5 weeks. After sacrifice, the whole gastrocnemius was taken from its attachments. Its weight, length and maximal perimeter were measured. At the middle of belly, a specimen 0.5cm in length was taken from the medial gastrocnemius for H& E and Masson trichrome staining. A scoring system was used to achieve a semi-quantitative analysis of the histopathological changes in gastrocnemius. No abnormal changes were observed in the sham side. Degeneration, atrophy and endomysial fibrosis were all found in the lengthened side. The scores of histopathological changes between the end of lengthening and 5 weeks later showed a decreasing trend, but no significant difference. The weight and perimeter decreased and length increased in the lengthening side. The weight, perimeter and length of gastrocnemius in both lengthening and control sides increased at 5 weeks after the end of lengthening. Muscular atrophy, as shown by a decrease in weight, perimeter and muscle fibre size, occurred and might be due to the combined effect of continuous muscle stretching and inactivity. Continuous stretching of muscles beyond a certain point produced damage. Some studies reported that damage to muscle fibres, which has been shown as degeneration and fibrosis in this study, can release and activate satellite cells. As myoblast precursors, satellite cells become myoblasts, which proliferate and fuse into the microlesioned areas, regenerating and repairing myofibrils. Also, the immature muscles have more active abilities of proliferation, regeneration, growth and healing. In this study gastrocnemius growth shown by an increase in weight, perimeter and length occurred during the consolidation phase of 5 weeks. The mean scores of histopathological changes in gastrocnemius decreased during consolidation period, indicating some recovery of damage to muscle. It is not clear whether this reflects a normal response, which would have been seen in other studies had samples been taken later or whether it is a unique response of the immature animal

Pulsed Electromagnetic Fields (PEMFs) promote joint tissue anabolic activities, particularly in cartilage and bone. Here we investigated the effect of selected PEMFs (75Hz, 1.5mT, 1.3msec) in a differentiating model of murine myoblasts (C2C12) in vitro. C2C12 were seeded at 5×10. 3. cells/cm. 2. in 4 well plates and left to adhere for 24h. Subsequently, cells were either maintained in growth medium (GM) or induced towards myogenic differentiation in low-serum conditions, with and without PEMF exposure, for 4 days. Morphological analysis, myotube formation and fusion index (FI) were assessed with fluorescence microscopy techniques. Metabolic activity was determined by MTT; moreover, a multiplex cytokine array (RayBiotech) allowed cell supernatant molecule quantification. Cells exposed to PEMFs in GM acquired a distinctive elongated morphology, with increased bi-nuclear figures (3.2-fold FI increase over PEMF-unexposed cells) and displayed a significantly higher metabolic activity (+31%, p<0.05 over PEMF-unexposed cells). PEMF exposure increased metabolic activity also under myogenic differentiation (+15% over PEMF-unexposed differentiating cells, p<0.05), with the formation of long, thick polynuclear myotubes, suggesting a role of PEMFs in enhancing myogenesis (7.7-fold FI increase over PEMF-unexposed cells). 4-day culture supernatants revealed the presence of several myokines (KC/CXCL1, LIX, MCP-1, TIMP-1). Preliminary analysis showed a 1.16-fold increase (n=2) of LIX and, notably, a 1.91-fold increase (n=2) of TNF-RI, in cell supernatants of PEMF-exposed over PEMF-unexposed cells. Collectively, these results suggest that PEMF may successfully be applied in models of muscle cell trauma to optimise muscle fibre repair, by fine-tuning the release of myokines, promoting myoblast proliferation and myotube formation

Avulsion of the abductor muscles of the hip may cause severe limp and pain. Limited literature is available on treatment approaches for this problem, and each has shortcomings. This study describes a muscle transfer technique to treat complete irreparable avulsion of the hip abductor muscles and tendons. Ten adult cadaver specimens were dissected to determine nerve and blood supply point of entry in the gluteus maximus and tensor fascia lata (TFL) and evaluate the feasibility and safety of transferring these muscles to substitute for the gluteus medius and minimus. In this technique, the anterior portion of the gluteus maximus and the entire TFL are mobilised and transferred to the greater trochanter such that the muscle fiber direction of the transferred muscles closely matches that of the gluteus medius and minimus. Five patients (five hips) were treated for primary irreparable disruption of the hip abductor muscles using this technique between January 2008 and April 2011. All patients had severe or moderate pain, severe abductor limp, and positive Trendelenburg sign. Patients were evaluated for pain and function at a mean of 28 months (range, 18–60 months) after surgery. All patients could actively abduct 3 months post-operatively. At 1 year post-operatively, three patients had no hip pain, two had mild pain that did not limit their activity, three had no limp, and one had mild limp. One patient fell, fractured his greater trochanter, and has persistent limp and abduction weakness. The anterior portion of the gluteus maximus and the TFL can be transferred to the greater trochanter to substitute for abductor deficiency. In this small series, the surgical procedure was reproducible and effective; further studies with more patients and longer follow-up are needed to confirm this

Purposes of the study and background. Characteristics of muscle activity, represented by surface electromyography (EMG), have shown differences between patients with low back pain and healthy adults; how they relate to functional/clinical scales remains unclear. The purpose of the current study was to examine the correlation between frequency characteristics of EMG and patients' self-rated score of disability using continuous wavelet transform (CWT) analysis. Methods and Results. Fifteen patients with chronic mechanical low back pain (LBP) and 10 healthy adults were recruited. Patients completed the Roland-Morris Disability Questionnaire (RMDQ) and bilateral EMG activity was obtained from erector spinae at vertebral level L4 and T12. Subjects performed 3 brief maximal voluntary contractions (MVCs) of the back extensors and the torque was measured using a dynamometer. CWT was applied to the EMG signals of each muscle in a 200ms window centred around the peak torque obtained during the MVCs. The ratio (low/high frequencies) of the energy, the peak energy, and the frequency of the peak energy were calculated for each muscle and then averaged and correlated with the individual's RMDQ score. Patients had significantly lower peak power than the controls (p=0.04). Additionally, RMDQ positively correlated to the average ratio of energy (rho=0.71; p=0.01), meaning higher disability corresponded to a dominant distribution of energy in the lower-frequencies; but negatively correlated to the average frequency of peak energy (rho=-0.61; p=0.035), meaning lower frequency of peak energy corresponded to higher levels of disability. Conclusion. The current findings support anatomical evidence of changes in muscle fibre composition of back muscles in subjects with chronic LBP. Conflicts of interest: No conflicts of interest. Sources of funding: No funding obtained

Introduction. The exact mechanisms leading to tendinopathies and tendon ruptures remain poorly understood while their occurrence is clearly associated with exercise. Overloading is thought to be a major factor contributing to the development of tendon pathologies. However, as animal studies have shown, heavy loading alone won't cause tendinopathies. It has been speculated, that malfunctioning adaptation or healing processes might be involved, triggering tendon tissue degeneration. By analysing the expression of the entirety of degrading enzymes (degradome) in pathological and non-pathological, strained and non-strained tendon tissue, the aim of this study was to identify common or opposite patterns in gene regulation. This approach may generate new targets for future studies. Materials and Methods. RNA was extracted from different tendon tissues: normal (n=7), tendinopathic (n=4) and ruptured (n=4) Achilles tendon; normal (n=4) and tendinopathic (n=4) posterior tibialis tendon; normal hamstrings tendon with or without subjection to static strain (n=4). The RNA was reverse transcribed, then pooled per group The expression of 538 protease genes was analysed using Taqman low-density array quantitative RT-PCR. To be considered relevant, changes had to be at least 4fold and measurable at a level below 36 Cts. Results. In general, there was little common regulation when exercised was compared with pathological tissue. The expression of PAMR1 and TNFαIP3 was upregulated with exercise (169-fold and 78-fold), Achilles tendinopathy (9724-fold and 7-fold) and Achilles tendon rupture (1809-fold and 10-fold), while DDI1, PSMB11 and PSH2 which were down-regulated with exercise were upregulated with Achilles pathology. Discussion. The newly found targets may deliver insights into the initiation and progression of tendon pathologies: PAMR1, a regeneration associated muscle protease which has been shown to be downregulated in Duchenne muscular dystrophy and upregulated in regenerating muscle fibers, might also be involved in tendon regeneration; TNFαIP3, which negatively regulates the NF-κB/pro-inflammatory pathway, could have anti-inflammatory function in tendon regeneration. PSMB11 and PSH2 are for the first time shown to be expressed in tendon and regulated in tendon pathology. Using this approach we were able to generate new targets and to add information on function, regulation and expression sites of recently identified proteins

Introduction. Regular, repeated stretching increases joint range of movement (RoM), however the physiology underlying this is not well understood. The traditional view is that increased flexibility after stretching is due to an increase in muscle length or stiffness whereas recent research suggests that increased flexibility is due to modification of tolerance to stretching discomfort/pain. If the pain tolerance theory is correct the same degree of micro-damage to muscle fibres should be demonstrable at the end of RoM before and after a period of stretch training. We hypothesise that increased RoM following a 3 weeks hamstrings static stretching exercise programme may partly be due to adaptive changes in the muscle/tendon tissue. Materials and Methods. Knee angle and torque were recorded in healthy male subjects (n=18) during a maximum knee extension to sensation of pain. Muscle soreness (pain, creatine kinase activity, isometric active torque, RoM) was assessed before knee extension, and 24 and 48 hours after maximum stretch. An exercise group (n=10) was given a daily home hamstring stretching programme and reassessed after 3 weeks and compared to a control group (n=8). At reassessment each subject's hamstring muscles were stretched to the same maximum knee extension joint angle as determined on the first testing occasion. After 24 hours, a reassessment of maximum knee extension angle was made. Results. At the start of the study RoM was 71.3 ± 10.0 degrees and there was no significant difference between groups. After 3 weeks stretching RoM increased significantly (p=0.01) by 9 degrees; the control group showed no change. Stiffness did not differ for either group. Pain score and RoM were the most sensitive markers of muscle damage and were significantly changed 24 and 48 hours after the initial stretch to end of range, (p<0.005) and (p=0.004) respectively. Discussion. The results show that a 3 week stretching programme causes muscle adaptation resulting in an increase in the extensibility of the hamstring muscle/tendon unit but no change in stiffness. The lack of evidence of muscle damage suggests that participants in the stretching group are likely to have undergone a physical change/adaptation rather than simply an increase in pain threshold

Introduction & aims: Quadriceps muscle wasting is common in patients with osteoarthritis (OA) of the hip and knee. Previous studies,using ultrasound and performing biopsies, have demonstrated quadriceps muscle fibre atrophy. Thigh girth measurements are quoted in textbooks as a means of quantitatively assessing muscle bulk. This study has looked at these measurements in patients with hip and knee OA to see if these measurements are useful. Method: 87 patients (mean age 62, range 36–87) with a diagnosis of OA were seen in the pre-assessment clinic. 47 were awaiting total hip replacement (THR) and 40 were awaiting total knee replacement (TKR).All were awaiting primary arthroplasty and had not had previous joint surgery. Thigh girth measurements were taken at 2 points corresponding with one-third and two-thirds of the length between the anterior superior iliac spine and the tibial tuberosity. These measurements were taken for both thighs. The observed differences were analysed with normal probability plots and paired Student’s t-tests. Results: No significant difference in thigh girth could be detected in patients awaiting total knee replacement. Girth was significantly reduced in the thigh on the side of planned THR. This difference was apparent when measured both proximally and distally. Conclusion: Measurements of thigh girth were not useful indicators of quadriceps wasting in patients awaiting TKR. Patients awaiting THR should have thigh girth measured, those with reduced thigh girth on the side of planned arthroplasty may have quadriceps atrophy and can then be referred for physiotherapy prior to surgery

Reverse total shoulder arthroplasty (RTSA) is increasingly used in the United States since approval by the FDA in 2003. RTSA relieves pain and restores mobility in arthritic rotator cuff deficient shoulders. Though many advantages of RTSA have been demonstrated, there still are a variety of complications (implant loosening, shoulder impingement, infection, frozen shoulder) making apparent much still is to be learned how RTSA modifies normal shoulder function. The goal of this study was to assess how RTSA affects deltoid muscle moment generating capacity post-surgery using a subject-specific computational model driven by in vivo kinematic data. A subject-specific 12 degree-of-freedom (DOF) musculoskeletal model was used to analyze the shoulders of 27 subjects (14-RTSA, 12-Normal). The model was modified from the work of Holzbaur et al. to directly input 6 DOF humerus and scapula kinematics obtained using fluoroscopy. Model geometry was scaled according to each subject's skeletal dimensions. In vivo abduction kinematics for each subject were input to their subject-specific model and muscle moment arms for the anterior, lateral and posterior aspects of the deltoid were measured over the arc of motion. Similar patterns of muscle moment arm changes were observed for normal and RTSA shoulders. The moment arm of the anterior deltoid was positive with the arm at the side and decreased monotonically, crossing zero (the point at which the muscle fibers pass across the joint center) between 50°–60° glenohumeral abduction (Figure 1a). The average moment arm of the lateral deltoid was constant and positive in normal shoulders, but showed a decreasing trend with abduction in RTSA shoulders (Figure 1b). The posterior deltoid moment arm was negative with the arm at the side, and increased monotonically to a positive value with increasing glenohumeral abduction (Figure 1c). Subject-specific moment arm values for RTSA shoulders were highly variable compared to normal shoulders. 2-way repeated measures ANOVA showed significant differences between RTSA and normal shoulders for all three aspects of the deltoid moment arm, where the moment arms in RTSA shoulders were smaller in magnitude. Shoulder functional capacity is a product of the moment generating ability of the shoulder muscles which, in turn, are a function of the muscle moment arms and muscle forces. Placement of implant components during RTSA can directly affect the geometric relationship between the humerus and scapula and, therefore, the muscle moment arms in the RTSA shoulder. Our results show RTSA shoulders maintain the same muscle moment arm patterns as healthy shoulders, but they show much greater inter-subject variation and smaller moment arm magnitudes. These observations show directly how RTSA configuration and implant placement affect deltoid moment arms, and provide an objective basis for determining optimal implant configuration and surgical placement to maximize RTSA function in a patient-specific manner