Supraspinatus Research Articles

Three-Dimensional Software- and MR-Imaging-Based Muscle Volumetry Reveals Overestimation of Supraspinatus Muscle Atrophy Using Occupation Ratios in Full-Thickness Tendon Tears.

Supraspinatus muscle atrophy is widely determined from oblique-sagittal MRI by calculating the occupation ratio. This ex vivo and clinical study aimed to validate the accuracy of 3D software- and MR-imaging-based muscle volumetry, as well as to assess the influence of the tear pattern on the occupation ratio. Ten porcine muscle specimens were volumetrized using the physical water displacement volumetry as a standard of reference. A total of 149 individuals with intact supraspinatus tendons, partial tears, and full-thickness tears had 3T MRI. Two radiologists independently determined occupation ratio values. An excellent correlation with a Pearson’s r of 0.95 for the variables physical volumetry using the water displacement method and MR-imaging-based muscle volumetry using the software was found and formed the standard of reference for the patient study. The inter-reader reliability was 0.92 for occupation ratios. The correlation between occupation ratios and software-based muscle volumes was good in patients with intact tendons (0.84) and partial tears (0.93) but considerably lower in patients with full-thickness tears (0.68). Three-dimensional-software- and MR-imaging-based muscle volumetry is reliable and accurate. Compared to 3D muscle volumetry, the occupation ratio method overestimates supraspinatus muscle atrophy in full-thickness tears, which is most likely due to the medial retraction of the myotendinous unit.

Anatomy and clinical application of suprascapular nerve to accessory nerve transfer.

BACKGROUNDLoss of motor function in the trapezius muscle is one complication of radical neck dissection after cutting the accessory nerve (AN) during surgery. Nerve repair is an effective method to restore trapezius muscle function, and includes neurolysis, direct suture, and nerve grafting. The suprascapular nerve (SCN) and AN are next to each other in position. The function of the AN and SCN in shoulder elevation and abduction movement is synergistic. SCN might be considered by surgeons for AN reanimation.AIMTo obtain anatomical and clinical data for partial suprascapular nerve-to-AN transfer.METHODSTen sides of cadavers perfused with formalin were obtained from the Department of Human Anatomy, Histology and Embryology, Peking University Health Science Center. The SCN (n = 10) and AN (n = 10) were carefully dissected in the posterior triangle of the neck, and the trapezius muscle was dissected to fully display the accessory nerve. The length of the SCN from the origin of the brachial plexus (a point) to the scapular notch (b point) and the distance of the SCN from the origin point (a point) to the point (c point) where the AN entered the border of the trapezius muscle were measured. The length and branches of the AN in the trapezius muscle were measured. A female patient aged 55 years underwent surgery for partial SCN to AN transfer at Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology. The patient suffered from recurrent upper gingival cancer. Radical neck dissection was performed on the right side, and the right AN was removed at the intersection between the nerve and the posterior border of the SCM muscle. One-third of the diameter of the SCN was cut off, and combined epineurial and perineurial sutures were applied between the distal end of the cut-off fascicles of the SCN and the proximal end of the AN without tension. Both subjective and objective evaluations were performed before, three months after, and nine months after surgery. For the subjective evaluation, the questionnaire included the Neck Dissection Impairment Index (NDII) and the Constant Shoulder Scale. Electromyography was used for the objective examination. Data were analyzed using t tests with SPSS 19.0 software to determine the relationship between the length of the SCN and the linear distance. A P value of < 0.05 was considered as statistically significant.RESULTSThe whole length of the AN in the trapezius muscle was 16.89 cm. The average numbers of branches distributed in the descending, horizontal and ascending portions were 3.8, 2.6 and 2.2, respectively. The diameter of the AN was 1.94 mm at the anterior border of the trapezius. The length of the suprascapular nerve from the origin of the brachial plexus to the scapular notch was longer than the distance of the suprascapular nerve from the origin point to the point where the accessory nerve entered the upper edge of the trapezius muscle. The amplitude of trapezius muscle electromyography indicated that both the horizontal and ascending portions of the trapezius muscle on the right side had better function than the left side nine months after surgery. The results showed that the right-sided supraspinatus and infraspinatus muscles did not lose more function than the left side.CONCLUSIONBased on anatomical data and clinical application, partial suprascapular nerve-to-AN transfer could be achieved and may improve innervation of the affected trapezius muscle after radical neck dissection.

Influence of Rigor Mortis on Tendon Mobility in an Animal Fresh Cadaver Model.

Simple SummaryIn biomechanical research, fresh frozen cadaver material and embalmed specimens are often used to evaluate surgical approaches. Unlike, biomechanical research using fresh cadaver material is rare. There are no reliable data on the point of time when rigor mortis starts to have an impact on results with fresh cadaver material. In this study, the authors have conducted measurements using fresh porcine cadaver tendons of the supraspinatus muscle post mortem to determine the time of onset and the influence of rigor mortis on specimen tissue. 151 min post mortem, a significant decrease in tendon mobility was observed. Therefore, the authors of the presented study concluded that the onset of rigor mortis started 151 min post mortem and decreased the mobility of the tendon. Hence, biomechanical research using fresh cadaver material should ideally be conducted within 150 min post mortem to obtain in vivo-like results without being impacted by rigor mortis.(1) Many biomechanical studies are performed using fresh frozen cadavers or embalmed specimens, although the biomechanical characteristics do not match the characteristics of in vivo tendons. Therefore, a fresh in vivo-like cadaver model has been introduced recently. As a limitation for studies with fresh cadavers, rigor mortis must be considered. The aim of this study was to evaluate the impact of the biomechanical properties and time of occurrence of rigor mortis in a fresh cadaver model. (2) For this study, 15 fresh porcine cadaver shoulders were used in an established biomechanical in vitro model to evaluate the onset of rigor mortis. Measurements took place at ten points of time (t1–t10) beginning 103 min post mortem (pm). The mobility of the supraspinatus tendon was measured in Newton (N) with a modified sensor-enhanced arthroscopic grasper. (3) The mean load measured at the time point t1 was 28.0 ± 11.2 N. The first significant decrease of mobility occurred 151 min post mortem (t4) at a mean load of 30.2 ± 13.7 N. From 227 min pm to 317 min pm, there was no further significant increase. (4) Tendon mobility decreases significantly within the first three hours after the killing. Therefore, reliable results can be obtained within 150 min post mortem before the onset of rigor mortis alters the biomechanical properties.

Muscle-Specific Micro-Ribonucleic Acids miR-1-3p, miR-133a-3p, and miR-133b Reflect Muscle Regeneration After Single-Dose Zoledronic Acid Following Rotator Cuff Repair in a Rodent Chronic Defect Model

Background: Zoledronic acid improves bone microarchitecture and biomechanical properties after chronic rotator cuff repair (RCR) in rats. Besides the positive effects of zoledronic acid on bone mineral density and bone microarchitecture, bisphosphonates have positive effects on skeletal muscle function. Purposes/Hypothesis: The purposes of this study were to (1) longitudinally evaluate circulating bone- and muscle-specific serum micro-ribonucleic acids (miRNAs) and (2) investigate supraspinatus muscle tissue after tenotomy and delayed RCR in a rat model. It was hypothesized that zoledronic acid would improve muscle regeneration after chronic RCR in rats. Study design: Controlled laboratory study. Methods: A total of 34 male Sprague-Dawley rats underwent unilateral (left) supraspinatus tenotomy (time point 1) with delayed transosseous RCR after 3 weeks (time point 2). All rats were sacrificed 8 weeks after RCR (time point 3). Animals were randomly assigned to 2 groups. One day after RCR, the control group was given 1 mL of subcutaneous saline solution, and the intervention group was treated with a subcutaneous single-dose of 100 µg/kg body weight of zoledronic acid. All 34 study animals underwent miRNA analysis at all 3 time points. In 4 animals of each group, histological analyses as well as gene expression analyses were conducted. Results: Circulating miRNAs showed significantly different expressions between both study groups. In the control group, a significant downregulation was observed for muscle-specific miR-1-3p (P = .004), miR-133a-3p (P < .001), and miR-133b (P < .001). Histological analyses showed significantly higher rates of regenerating myofibers on the operated side (left) of both study groups compared with the nonoperated side (right; P = .002). On the nonoperated side, significantly higher rates of regenerating myofibers were observed in the intervention group compared with the control group (P = .031). The myofiber cross-sectional area revealed significantly smaller myofibers on both sides within the intervention group compared with both sides of the control group (P < .001). Within the intervention group, significantly higher expression levels of muscle development/regeneration marker genes embryonal Myosin heavy chain (P = .017) and neonatal Myosin heavy chain (P = .016) were observed on the nonoperated side compared with the operated side. Conclusion: An adjuvant single-dose of zoledronic acid after RCR in a chronic defect model in rats led to significant differences in bone- and muscle-specific miRNA levels. Therefore, miR-1-3p, miR-133a-3p, and miR-133b might be used as biomarkers for muscle regeneration after RCR. Clinical Relevance: Adjuvant treatment with zoledronic acid may improve muscle regeneration after chronic RCR in humans, thus counteracting fatty muscle infiltration and atrophy.

Intermuscular Coherence Of Rotator Cuff And Deltoid Muscles Varies With Force Output

PURPOSE:To identify intermuscular EMG coherence patterns between the rotator cuff and deltoid muscles at different force levels. METHODS:Surface EMG electrodes were used to record activity from the anterior deltoid (AD), middle deltoid (MD), and infraspinatus (IS) muscles of the dominant shoulder in 7 healthy individuals (mean age ± SD = 19 ± 1, 6 females, 1 male). An intramuscular fine-wire EMG electrode was inserted into supraspinatus (SS). Participants performed 30s contractions of isometric shoulder abduction in the scapular plane at 30° at 25% (low-load), 50% (medium-load) and 75% (high-load) of maximum voluntary contraction with visual feedback of the force output. EMG amplitudes and coherence of each muscle pair in the common drive (0-5 Hz), physiological force tremor (5-12 Hz), beta (15-35 Hz), low-gamma (35-60 Hz) and high-gamma (60-100 Hz) bands were compared across the 3 force levels. RESULTS:EMG amplitudes of all muscles increased as force level increased (all p < 0.05). EMG coherence between IS and deltoid muscles increased as force level increased in the low-gamma band (p < 0.05). SS-IS coherence was also the highest during high-load task in the low-gamma band. These data indicate that additional neural drive with higher force levels stemming from subcortical origin likely mediate the increase in coherence between these muscles. However, SS-IS coherence during the medium and high load tasks were lower than that during the low-load task in the common drive band (p < 0.05), indicating that the increase in drive to these muscles for increasing force output is not targeted at common last-order neurons. Similarly, SS-AD coherence during the high-load task was lower than that during the medium-load task in the beta band (p < 0.05) and SS-AD and SS-MD was lower in the tremor band (p < 0.05) at higher force loads. The reduction in coherence between the SS and deltoid muscles and the SS and IS may serve to protect the humeral head from migrating superiorly at higher force loads. CONCLUSIONS:Increasing force output led to decreased coherence within the rotator cuff muscles and between supraspinatus and the deltoid muscles, but increased coherence between infraspinatus and the deltoid muscles. This likely serves as a protective mechanism against superior humeral head migration.

Validity of Freehand 3-D Ultrasound System in Measurement of the 3-D Surface Shape of Shoulder Muscles.

Freehand 3-D ultrasound (3DUS) system is a promising technique for accurately assessing muscle morphology. However, its accuracy has been validated mainly in terms of volume by examining lower limb muscles. This study was aimed at validating 3DUS in the measurements of 3-D surface shape and volume by comparing them with magnetic resonance imaging (MRI) measurements while ensuring the reproducibility of participant posture by focusing on the shoulder muscles. The supraspinatus, infraspinatus and posterior deltoid muscles of 10 healthy men were scanned using 3DUS and MRI while secured by an immobilization support customized for each participant. A 3-D surface model of each muscle was created from the 3DUS and MRI methods, and the agreement between them was assessed. For the muscle volume, the mean difference between the two models was within -0.51 cm3. For the 3-D surface shape, the distances between the closest points of the two models and the Dice similarity coefficient were calculated. The results indicated that the median surface distance was less than 1.12 mm and the Dice similarity coefficient was larger than 0.85. These results suggest that, given the aforementioned error is permitted, 3DUS can be used as an alternative to MRI in measuring volume and surface shape, even for the shoulder muscles.

EFFECTS OF MYOFASCIAL TRIGGER POINT RELEASE AND THERABAND STRENGTHENING AMONG THE COLLEGIATE VOLLEY BALL PLAYERS WITH GLENOHUMERAL IMPINGEMENT

Background: Volley ball is one of the common sport and most of the college students choose this as a recreational game. Almost 80% of the shoulder injuries are related to spiking movement during the game. This stress the upper arm and the shoulder leading to increased risk of injuries. The common factors that results in shoulder injuries are Glenohumeral internal rotation deficit, Glenohumeral impingement syndrome, scapular dyskinesis and altered biomechanics of ball striking movement. Aim of The Study: The present aim of the study is to identify the effectiveness of Myofascial trigger point release technique and Theraband strengthening on Glenohumeral muscles among the collegiate volley ball players with Glenohumeral impingement syndrome. Methods: There were 30 players taken for the study and pretreatment values were taken. Myofascial trigger point therapy have been applied to supraspinatus muscle. The outcome measures used for the study is Numerical pain rating scale, range of motion and shoulder pain and disability index. The post treatment values were taken. Results: The results of the present study were analyzed using pairedt test and Wilcoxon signed rank test and the test statistics shows statistically significant improvement in the posttest p value &lt; 0.05. Conclusion: The present study concluded that Myofascial trigger point release and Theraband strengthening exercises shows significant improvement in pain reduction, improves range of motion and functional ability among the collegiate volley ball players.

Systematic identification of aberrant non-coding RNAs and their mediated modules in rotator cuff tears.

Background: Rotator cuff tears (RCT) is the most common cause of shoulder dysfunction, however, its molecular mechanisms remain unclear. Non-coding RNAs(ncRNAs), such as long ncRNA (lncRNA), microRNA (miRNA) and circular RNA (circRNA), are involved in a variety of diseases, but little is known about their roles in RCT. Therefore, the purpose of this study is to identify dysregulated ncRNAs and understand how they influence RCT. Methods: We performed RNA sequencing and miRNA sequencing on five pairs of torn supraspinatus muscles and matched unharmed subscapularis muscles to identify RNAs dysregulated in RCT patients. To better comprehend the fundamental biological processes, we carried out enrichment analysis of these dysregulated mRNAs or the co-expressed genes of dysregulated ncRNAs. According to the competing endogenous RNA (ceRNA) theory, we finally established ceRNA networks to explore the relationship among dysregulated RNAs in RCT. Results: A total of 151 mRNAs, 38 miRNAs, 20 lncRNAs and 90 circRNAs were differentially expressed between torn supraspinatus muscles and matched unharmed subscapularis muscles, respectively. We found that these dysregulated mRNAs, the target mRNAs of these dysregulated miRNAs or the co-expressed mRNAs of these dysregulated ncRNAs were enriched in muscle structure development, actin-mediated cell contraction and actin binding. Then we constructed and analyzed the ceRNA network and found that the largest module in the ceRNA network was associated with vasculature development. Based on the topological properties of the largest module, we identified several important ncRNAs including hsa_circ_0000722, hsa-miR-129-5p and hsa-miR-30c-5p, whose interacting mRNAs related to muscle diseases, fat and inflammation. Conclusion: This study presented a systematic dissection of the expression profile of mRNAs and ncRNAs in RCT patients and revealed some important ncRNAs which may contribute to the development of RCT. Such results could provide new insights for further research on RCT.

The correlation between types of posterior upper rotator cuff tears and intramuscular fat infiltration based on magnetic resonance imaging: A retrospective observational study.

Objective: This study investigated the correlation between types of posterior upper rotator cuff tears (RCTs) and intramuscular fat infiltration (FI) in magnetic resonance imaging (MRI). Methods: The shoulder joints of 50 adults with a full-thickness posterior upper RCT diagnosed by MRI, from January 2019 to December 2021, were retrospectively analyzed. The patients were divided into three groups according to tear type: 1) an L-shaped tear group; 2) a crescent/U-shaped tear group; 3) a complete tear group. The correlation among age, gender, tear range, trauma history, and the duration of clinical symptoms was analyzed. The MRI images were used by two musculoskeletal imaging physicians to evaluate the type and range of tears, the Goutallier grade of the supraspinatus and infraspinatus, and the correlations and reliability were analyzed. Results: Differences in the tear range (p < 0.001) and the Goutallier grade of the infraspinatus muscle (p = 0.036) among the L-shaped, crescent/U-shaped, and complete tear groups were statistically significant; however, differences in the Goutallier grade of the supraspinatus muscle was not statistically significant (p = 0.356). In the crescent/U-shaped tear group, age was significantly correlated with the Goutallier grade of the supraspinatus muscle (RS = 0.720, p = 0.029) and the infraspinatus muscle (RS = 0.713, p = 0.032). In the complete tear group, tear range was significantly correlated with the Goutallier grade of the supraspinatus muscle (RS = 0.801, p = 0.001) and the infraspinatus muscle (RS = 0.802, p = 0.001). The Goutallier grades of the supraspinatus muscle (kappa, 0.489) and the infraspinatus muscle (kappa, 0.424) presented with interobserver consistency. Conclusion: The type of posterior upper RCT correlates with the degree of FI. There is a positive correlation between the FI of crescent/U-shaped full-thickness RCTs and age. Additionally, the range of complete tears in the posterior upper RC has a positive correlation with FI.

Linguistic tones in MRI reports correlate with severity of pathology for rotator cuff tendinopathy.

Written communication can convey one's emotions, personality, and sentiments. Radiology reports employ medical jargon and serve to document a patients' condition. Patients might misinterpret this medical jargon in a way that increases their anxiety and makes them feel unwell. We were interested whether linguistic tones in MRI reports vary between radiologists and correlate with the severity of pathology. (1) Is there variation in linguistic tones among different radiologists reporting MRI results for rotator cuff tendinopathy? (2) Is the retraction of the supraspinatus tendon in millimeters associated with linguistic tones? Two hundred twenty consecutive MRI reports of patients with full-thickness rotator cuff defects were collected. Supraspinatus retraction was measured on the MRI using viewer tools. Using Kruskal-Wallis H tests, we measured variation between 11 radiologists for the following tones: positive emotion, negative emotion, analytical thinking, cause, insight, tentativeness, certainty, and informal speech. We also measured the correlation of tones and the degree of tendon retraction. Multilevel mixed-effects linear regression models were constructed, seeking factors associated with the tone, accounting for retraction, the presence of prior imaging, and for the effects of each radiologist (nesting). There were statistically significant differences for all of the tones by radiologist. In bivariate analysis, greater retraction of the supraspinatus muscle in millimeters was associated with more negative emotion and certainty, and with less tentativeness. In multilevel mixed-effects linear regression, more negative tones were associated with greater retraction and absence of prior imaging. Greater tentativeness was associated with the absence of prior imaging, but not with retraction. Radiology reports have emotional content that is relatively negative, varies by radiologist and is affected by pathology. Strategies for more hopeful, positive, optimistic descriptions of pathology have the potential to help patients feel better without introducing inaccuracies even if unlikely. Level III, Diagnostic.

Biomechanical investigation of arm position on deforming muscular forces in proximal humerus fractures.

Muscular forces drive proximal humeral fracture deformity, yet it is unknown if arm position can help mitigate such forces. Our hypothesis was that glenohumeral abduction and humeral internal rotation decrease the pull of the supraspinatus and subscapularis muscles, minimizing varus fracture deformity. A medial wedge osteotomy was performed in eight cadaveric shoulders to simulate a two-part fracture. The specimens were tested on a custom shoulder testing system. Humeral head varus was measured following physiologic muscle loading at neutral and 20° humeral internal rotation at both 0° and 20° glenohumeral abduction. There was a significant decrease in varus deformity caused by the subscapularis (p<0.05) at 20° abduction. Significantly increasing humeral internal rotation decreased varus deformity caused by the subscapularis (p<0.05) at both abduction angles and that caused by the supraspinatus (p<0.05) and infraspinatus (p<0.05) at 0° abduction only. Postoperative shoulder abduction and internal rotation can be protective against varus failure following proximal humeral fracture fixation as these positions decrease tension on the supraspinatus and subscapularis muscles. Use of a resting sling that places the shoulder in this position should be considered.

Muscle degeneration in chronic massive rotator cuff tears of the shoulder: Addressing the real problem using a graphene matrix

Massive rotator cuff tears (MRCTs) of the shoulder cause disability and pain among the adult population. In chronic injuries, the tendon retraction and subsequently the loss of mechanical load lead to muscle atrophy, fat accumulation, and fibrosis formation over time. The intrinsic repair mechanism of muscle and the successful repair of the torn tendon cannot reverse the muscle degeneration following MRCTs. To address these limitations, we developed an electroconductive matrix by incorporating graphene nanoplatelets (GnPs) into aligned poly(l-lactic acid) (PLLA) nanofibers. This study aimed to understand 1) the effects of GnP matrices on muscle regeneration and inhibition of fat formation invitro and 2) the ability of GnP matrices to reverse muscle degenerative changes invivo following an MRCT. The GnP matrix significantly increased myotube formation, which can be attributed to enhanced intracellular calcium ions in myoblasts. Moreover, the GnP matrix suppressed adipogenesis in adipose-derived stem cells. These results supported the clinical effects of the GnP matrix on reducing fat accumulation and muscle atrophy. The histological evaluation showed the potential of the GnP matrix to reverse muscle atrophy, fat accumulation, and fibrosis in both supraspinatus and infraspinatus muscles at 24 and 32 wk after the chronic MRCTs of the rat shoulder. The pathological evaluation of internal organs confirmed the long-term biocompatibility of the GnP matrix. We found that reversing muscle degenerative changes improved the morphology and tensile properties of the tendon compared with current surgical techniques. The long-term biocompatibility and the ability of the GnP matrix to treat muscle degeneration are promising for the realization of MRCT healing and regeneration.

A Combination of Long-Duration Electrical Stimulation with External Shoulder Support during Routine Daily Activities in Patients with Post-Hemiplegic Shoulder Subluxation: A Randomized Controlled Study.

The study objective was to determine the effect of long-duration neuromuscular electric stimulation (NMES) on shoulder subluxation and upper-extremity function during the acute post-stroke stage. Twenty-eight subjects (mean age ± standard deviation −70.0 ± 14.0 years) were randomly assigned to an experimental or to a control group receiving NMES to the supraspinatus and posterior deltoid muscles or sham treatment for 6 weeks. All the subjects continued standard rehabilitation and external shoulder support (EST). Assessments were conducted pre- and post-intervention and at a 2 week follow-up session by an assessor blind to group allocation. Outcome measures included the degree of shoulder subluxation, Fugl–Meyer assessment-upper extremity (FMA-UE) test, FMA—hand and finger subscales, Functional Independence Measure (FIM), and shoulder pain (using the Numeric Pain Rate Scale). Shoulder subluxation was significantly lower, while the FMA-UE and FMA—hand and finger subscales were significantly improved in the experimental group post-intervention and at follow-up compared to the control group. FIM at follow-up improved more in the experimental group. No change was observed in pain level in both groups. Supplementing NMES to standard rehabilitation and EST is beneficial in reducing shoulder subluxation and improving upper-extremity function. Further research is necessary to determine effect of longer treatment duration and longer follow-up periods.

Suture Augmentation Neutralizes Deforming Muscular Forces in a Simulated 2-Part Osteoporotic Proximal Humeral Fracture Model.

To evaluate the contribution that tension-relieving sutures, placed between a proximal humeral locking plate and the rotator cuff muscles, had on preventing varus malalignment in an osteoporotic 2-part proximal humerus fracture model. A 2-part fracture model was created in 8 cadaveric specimens and then fixed with a lateral locking plate. A custom shoulder testing system was used to increase loading through the supraspinatus (SS) tendon to drive varus deformity. Trials were performed with no suture placement; SS only; SS and subscapularis (SB); and SS, SB, and infraspinatus. The primary outcome was contribution of each point of suture fixation to prevention of varus collapse. Suture augmentation to the SS, SB, and infraspinatus significantly decreased humeral head varus collapse when compared with the plate alone at nearly all loads ( P < 0.05). There were no significant differences in humeral head varus collapse between the 3 suture constructs. In our biomechanical evaluation of a simulated osteoporotic 2-part proximal humerus fracture with incompetent medial calcar, tension-relieving sutures placed between a lateral locked plate and the rotator cuff tendons prevented varus malalignment.

Ultrasound assessment after a subscapularis-sparing approach to total shoulder arthroplasty.

Although anatomic total shoulder arthroplasty (ATSA) has favorable outcomes, nearly all techniques involve subscapularis tendon release for shoulder joint access. Such takedown of the subscapularis may be associated with decreased function, instability, and pain. Subscapularis-sparing approaches have the theoretical benefits of improved function, decreased failure of the tendon reattachment site, and early range of motion and rehabilitation. The primary purpose of this study was to use ultrasound to assess the postoperative integrity of the subscapularis tendon and surrounding soft tissues after ATSA with a subscapularis-sparing technique through an extensile anterosuperior skin incision. Our hypothesis was that this subscapularis-sparing approach would have low rates of subscapularis disruption. A consecutive cohort of patients who underwent subscapularis-sparing ATSA between 2014 and 2017 were included. Ultrasound was used to evaluate the rotator cuff tendons and deltoid postoperatively, and these were classified as intact, disrupted, or unable to be adequately visualized. Clinical outcome scores, range of motion, and strength measurements were also collected at 1-3 years postoperatively. Thirty-seven subscapularis tendons and 40 supraspinatus and infraspinatus muscles were adequately visualized and included for analysis. Of the subscapularis muscles, 32 (86%) were intact; 38 of the visualized supraspinatus muscles (95%) and 39 of the infraspinatus muscles (98%) were intact. No dehiscence or loss of integrity of the deltoid was noted. Clinical comparison between patients with disrupted subscapularis muscles and patients without such disruption demonstrated no difference in clinical outcome scores and postoperative range of motion but showed less strength in forward flexion, abduction, and external rotation. The rate of subscapularis disruption using a subscapularis-sparing approach for ATSA was low (14%), but the potential for tendon disruption was not eradicated. Favorable clinical outcomes support this surgical approach as a potential technique for ATSA.

Evidence-Based Clinical Guidelines from the American Society of Pain and Neuroscience for the Use of Implantable Peripheral Nerve Stimulation in the Treatment of Chronic Pain.

The objective of this peripheral nerve stimulation consensus guideline is to add to the current family of consensus practice guidelines and incorporate a systematic review process. The published literature was searched from relevant electronic databases, including PubMed, Scopus, Cochrane Central Register of Controlled Trials, and Web of Science from database inception to March 29, 2021. Inclusion criteria encompassed studies that described peripheral nerve stimulation in patients in terms of clinical outcomes for various pain conditions, physiological mechanism of action, surgical technique, technique of placement, and adverse events. Twenty randomized controlled trials and 33 prospective observational studies were included in the systematic review process. There is Level I evidence supporting the efficacy of PNS for treatment of chronic migraine headaches via occipital nerve stimulation; chronic hemiplegic shoulder pain via stimulation of nerves innervating the trapezius, supraspinatus, and deltoid muscles; failed back surgery syndrome via subcutaneous peripheral field stimulation; and lower extremity neuropathic and lower extremity post-amputation pain. Evidence from current Level I studies combined with newer technologies facilitating less invasive and easier electrode placement make peripheral nerve stimulation an attractive alternative for managing patients with complex pain disorders. Peripheral nerve stimulation should be used judiciously as an adjunct for chronic and acute postoperative pain following adequate patient screening and positive diagnostic nerve block or stimulation trial.

Early-stage inflammation changes in supraspinatus muscle after rotator cuff tear.

Rotator cuff (RC) tendon tear leads to impaired shoulder function and pain. The supraspinatus (SS) tendon is most often affected, but the biological response of the SS muscle to SS tendon tear is largely unknown. This study aimed to investigate time-dependent muscle inflammation, degeneration, fatty infiltration, and regeneration in experimental SS tear conditions. Forty-five C57BL/6 mice were subjected to SS tendon tear and allowed to recover for 1, 3, 5, 7, 14, or 28 days. The extent of muscle damage was examined using histologic, flow cytometric, proteomic, and chemiluminescence analyses. We found that muscle inflammation peaked around day 5 with increased monocyte infiltration and increased cytokine levels in the ipsilateral compared to the contralateral SS muscle. Bioinformatics analysis of proteomics on mice that survived 5 days after RC tendon tear revealed upregulated proteins involved in "neutrophil activation involved in immune response" and "extracellular matrix organization," whereas "skeletal muscle tissue development and contraction" and "respiratory electron transport chain" were among the most downregulated. Histologic analysis of collagen showed increased collagen accumulation and fatty infiltration of the ipsilateral SS over time. Finally, we observed time- and lesion-dependent changes in satellite cell and fibro-adipogenic progenitor populations. Altogether, we demonstrate that the SS muscle shows severe signs of acute inflammation, early degeneration, and fatty infiltration, as well as reduced regenerative potential following SS tendon tear.

Poster 155: Muscle-Derived Beige Adipose Precursors Secrete Promyogenic Exosomes that Treat Rotator Cuff Muscle Degeneration in Mice and are Identified in Humans by Single-Cell RNA Sequencing

Objectives:Muscle atrophy, fibrosis, and fatty infiltration are common to a variety of sports-related and degenerative conditions and are thought to be irreversible. Fibroadipogenic progenitors (FAPs) are multipotent resident muscle stem cells with the capacity to differentiate into fibrogenic as well as white- and beige adipose tissue (WAT; BAT). FAPs that have assumed a BAT differentiation state (FAP-BAT) have proven efficacious in treating muscle degeneration in a variety of injury models. The purpose of this study was to characterize the subpopulation of murine FAPs with FAP-BAT activity, determine whether their pro-myogenic effect is mediated via exosomes, and analyze human FAPs for an analogous pro-myogenic, exosome-rich subpopulation. Given their non-myogenic differentiation capacity, it was hypothesized that FAP-BAT exerts a pro-myogenic effect on the injured muscle environment through the secretion of exosomes.Methods:FAPs from UCP1-reporter mice were isolated via FACS and sorted according to the differential intensity of the UCP1 signal observed: negative for UCP1 (UCP1-), intermediate intensity (UCP1+), and high intensity (UCP1++). Bulk RNAseq was performed on UCP1-, UCP1+, and UCP1++ FAPs to evaluate distinct characteristics of each population. Exosomes were harvested from UCP1++ (Exo-FB) and UCP1- (Exo-nFB) cells using cushioned-density gradient ultracentrifugation and used to treat C2C12 cells and MEFs in vitro, and the myotube fusion index was assessed. Exo-FB and Exo-nFB were then used to treat WT C57B/L6J mice that had undergone massive rotator cuff tear. At 6 weeks mice were sacrificed and supraspinatus muscles were harvested and analyzed for muscle atrophy, fibrosis, fatty infiltration, and UCP1 expression. Single-cell RNA sequencing (scRNAseq) was then performed on FAPs isolated from human rotator cuff muscle that were treated with mirabegron or standard media to assess for the presence of a parallel promyogenic subpopulation of FAP-BAT cells in humans.Results:Flow cytometry analysis of sorted UCP1-reporter mouse FAPs revealed a trimodal distribution of UCP1 signal intensity, which correlated with three distinct transcriptomic profiles characterized with bulk RNAseq. UCP1++ cells were marked by high mitochondrial gene expression, BAT markers, and exosome surface makers (Table 1). UCP1- cells were marked by fibrogenic markers and UCP1+ cells were characterized differential enrichment of WAT markers (Table 1). Exo-FB treatment of C2C12 cells resulted in robust myotube fusion, with a myotube fusion index of 33.3 ± 6.3% compared to 7.1 ± 3.2% with Exo-nFB (p <0.001) and 8.8 ± 3.3% with exosome-free media (p = 0.0014), while treatment of MEFs resulted in transdifferentiation into myotubes (Fig. 1). Mice that were treated with Exo-FB at the time of rotator cuff injury demonstrated markedly reduced muscle atrophy and FI compared to treatment with Exo-nFB or PBS (Fig. 2). ScRNAseq of human FAPs from the rotator cuff revealed 6 distinct subpopulations of human FAPs, with differential expression of mitochondrial genes, certain BAT markers, and exosome surface markers noted within one of the subpopulations (Fig. 3).Conclusions:FAP-BAT cells comprise a subpopulation of FAPs with upregulated mitochondrial gene expression and exosome production that mediates promyogenic effects in vitro and in vivo, and are present as a transcriptomically similar subpopulation of FAPs in humans.Table 1.Highly Differentially Expressed Genes of UCP1++ FAPsFigure 1.C2C12 cells and MEFs cultured for 14 days with Exo-FB(2 x 109), Exo-nFB(2 x 109), or exosome-free media, and stained for myosin heavy chain (MF20)j scale bar = 50µm (A), Myotube fusion index was calculated as the percentage of nuclei per field contained within an MF20+ myotube. n-3 replicates per condition; ** indicates p<0.005, *** indicates p<0.001.Figure 3.Light microscoay and immunofluorescence of human FAPs grown in standard media (top row) or mirabegron treated media (bottom row); scale bar =50µm; red arrows indicates predominant perilipin expression, green arrow indicates predominant UCP1 expression, yellow arrow indicates expression of both UCP1 and perilipin (A) UMAP plot of human scRNAseq data demonstrating 5 distinct clusters of human FAPs identified with Seurat (B) UMAP plot demonstrating distribution of human FAPs by in vitro treatment conditions: standard media or mirabegron (c). Dot plot of top 20 differentially expressed genes by treatment condition based upon adjusted p-value; “Average Expression” denotes z-score from mean overaal gene expression (D). Dot plot demonstrating unifrom increase in mitochondrial gene expression with mirabegron (E). Dot plot showing 13 genes that are significantly differentially expressed in both murine UCP1++ FAPs and human FAP subpopulations (F). Dot plot demonstrating additional characterstic genes of interest stratified by cluster. Red arrows indicates populations favorted to contain FAP-BAT cells at varying differentiations stages; green arrow highlights Adrb2 receptor expression; blue arrow highlights exosome surface markers CD63 and CD81(G).

Prevalence of shoulder pain amongst Malaysia men's wheelchair basketball players

Introduction: The shoulder is at high risk of injury, particularly in throwing activities such as basketball. Aims: The objective of this study was to determine the prevalence and patterns of shoulder pain amongst Malaysian men's wheelchair basketball (WCBB) players. Furthermore, factors that are associated with shoulder pain were investigated. Materials and Methods: Eleven national WCBB players participated in this study. All players completed the clinical research forms which collected socio-demographic information, WCBB participation and history of shoulder pain. Assessments of shoulders range of motion, isometric muscle strengths and clinical shoulder tests were performed on all players. Results: The prevalence of shoulder pain amongst Malaysian WCBB players was 36.4%. Players with current shoulder pain had significantly higher Performance Corrected Wheelchair User's Shoulder Pain Index (PC-WUSPI) scores (13.8 vs. 3.3, P = 0.02) and a greater number of positive shoulder clinical tests (3.5 vs. 1.0, P = 0.04) than players without pain. Players with shoulder pain are frequently diagnosed with rotator cuff injuries, particularly involving the supraspinatus and subscapularis muscles. A significant moderately strong positive correlation between PC-WUSPI score and number of positive clinical shoulder tests was found (r = 0.71; P = 0.01). Conclusions: Prevalence and patterns of shoulder pain amongst Malaysian men's WCBB players are comparable to previous studies. A strong association between PC-WUSPI score and number of positive clinical shoulder tests suggests a potential role of regular PC-WUSPI assessment for early detection of shoulder problems amongst players.

Poster 130: Tendon-to-bone Healing in a CCR2 Knockout Mouse Model of Delayed Rotator Cuff Repair

Poster 130: Tendon-to-bone Healing in a CCR2 Knockout Mouse Model of Delayed Rotator Cuff Repair