SS-31 as a Mitochondrial Protectant in the Treatment of Tendinopathy: Evaluation in a Murine Supraspinatus Tendinopathy Model.

BACKGROUND: Prior studies have demonstrated mitochondrial dysfunction in tendinopathy. The objective of this investigation was to explore the potential of SS-31 (elamipretide), a mitochondrial protectant, to improve mitochondrial function and promote tendon healing in a murine supraspinatus tendinopathy model. METHODS: One hundred and twenty-six mice (252 limbs) were divided into 6 groups (42 limbs/group) that received (I) 4 weeks of impingement; (II) 8 weeks of impingement; (III) 8 weeks of impingement including 4 weeks of SS-31 treatment (5 mg/kg/d) starting after 4 weeks of impingement; (IV) 4 weeks of impingement ending with clip removal, followed by harvesting 4 weeks later; and (V) 4 weeks of impingement ending with clip removal, followed by 4 weeks of SS-31 treatment and harvesting; and a control group. Specimens were prepared for biomechanical testing, histological analysis, transmission electron microscopy, measurement of superoxidative dismutase (SOD) activity, and measurement of gene expression. RESULTS: Failure force decreased after impingement, compared with the intact tendon, and the decrease was partially reversed after clip removal, SS-31 treatment, and the 2 treatments combined. A similar pattern was observed for stiffness. Histological analysis demonstrated higher modified Bonar scores in the impingement groups; however, the changes in tendon morphology were partially reversed following all treatments, especially the combined treatment. Decreased mitochondrial number and altered organization and density of cristae were observed in the impingement groups. Mitochondrial structure and number became more normal, with improvement in morphology of the cristae, after clip removal and/or SS-31 treatment. SOD activity decreased after impingement, compared with the control group, then increased significantly again after treatment, especially in the combined treatment group. Mitochondria-related gene expression decreased in the impingement groups and increased again after treatment. CONCLUSIONS: The mitochondrial protectant SS-31 improved mitochondrial function, promoting tendon healing, especially when combined with removal of subacromial impingement. CLINICAL RELEVANCE: Improving mitochondrial function with agents such as SS-31 may represent an effective treatment to promote healing in the setting of supraspinatus tendinopathy.

Chronic subacromial impingement leads to supraspinatus muscle functional and morphological changes: Evaluation in a murine model.

Muscle atrophy and fatty infiltration have been directly correlated with higher rates of incomplete or failed healing following surgical repair of the rotator cuff. The purpose of this study was to evaluate clinically relevant functional and morphological changes in the supraspinatus muscle at various time points in this model of rotator cuff tendinopathy. Subacromial impingement was induced in 47, male C57BL/6 mice (total 94 limbs) by implantation of a metal clip in the subacromial space. Specimens were evaluated at 4, 6, and 12 weeks postoperatively. Gait analysis was used to measure various kinematic parameters. Supraspinatus muscle wet weight, histology, and quantitative reverse-transcription polymerase chain reaction analysis of genes related to muscle atrophy and adipogenesis were performed to characterize the structural, cellular, and molecular changes. Muscle atrophy and fatty infiltration was evident beginning at 6 weeks, with progression out to 12 weeks. Gait analysis identified significant functional changes in many aspects of gait and abnormal stance tracing as early as 4 weeks, verifying alterations in upper extremity function. We have demonstrated that clinically relevant changes to the supraspinatus muscle are seen starting 6 weeks after induction of subacromial impingement. Furthermore, the gait analysis provides key functional outcome measurements that may be useful for future evaluation of new therapeutic strategies.

Assessment of Mitochondrial Dysfunction in a Murine Model of Supraspinatus Tendinopathy.

BACKGROUND: The purpose of this study was to assess mitochondrial dysfunction in a murine model of supraspinatus tendinopathy. METHODS: Eighty-four mice (168 limbs) were included in the study. Supraspinatus tendinopathy was induced by inserting a microsurgical clip in the subacromial space of 63 mice bilaterally (126 limbs). Forty-two of these limbs were harvested at 4 weeks postoperatively, 42 underwent clip removal at 4 weeks after the initial procedure and were harvested at 2 weeks, and 42 underwent clip removal at 4 weeks and were harvested at 4 weeks. Forty-two limbs in the remaining 21 mice did not undergo surgical intervention and were utilized as the control group. Outcomes included biomechanical, histological, gene expression, superoxide dismutase (SOD) activity, and transmission electron microscopy (TEM) analyses. RESULTS: Radiographs confirmed stable clip position in the subacromial space at 4 weeks. Biomechanical testing demonstrated a 60% decrease in failure force of the supraspinatus tendons at 4 weeks compared with the control group. The failure force gradually increased at 2 and 4 weeks after clip removal. Histological analysis demonstrated inflammation surrounding the tendon with higher modified Bonar scores at 4 weeks after clip placement followed by gradual improvement following clip removal. The expression of mitochondrial-related genes was decreased at 4 weeks after clip placement and then significantly increased after clip removal. SOD activity decreased significantly at 4 weeks after clip placement but increased following clip removal. TEM images demonstrated alterations in morphology and the number of mitochondria and cristae at 4 weeks after clip placement with improvement after clip removal. CONCLUSIONS: Mitochondrial dysfunction appears to be associated with the development of tendinopathy. CLINICAL RELEVANCE: Mitochondrial protection may offer a potential strategy for delaying the development of tendinopathy and promoting tendon healing.

Increased levels of inflammatory markers in the subscapularis tendon and joint capsule in patients with subacromial impingement.

PURPOSE: To analyze biopsy samples from the subscapularis tendon and from the joint capsule from male patients with subacromial impingement syndrome and compare them with samples from male patients with post-traumatic recurrent shoulder instability, to detect increased inflammatory activity that might be present inside the humeroscapular joint. METHODS: Twenty male patients scheduled for surgery for either subacromial decompression or Bankart reconstruction were included. Four biopsies from each patient were obtained during surgery from the capsule and the subscapularis tendon. Each specimen was analyzed for TNF-α, IL-6, CD-3 and CD-72. Multiplex fluorescence immunohistochemistry was performed on histological samples from the capsule and tendon to demonstrate the level of inflammatory markers. Fluorescence microscope images were acquired using an automated scanning system. On each slide, the number of pixels was registered and used in the analyses. RESULTS: The subacromial impingement syndrome group comprised eight patients, median age 53 (45-74) years, while the instability group 12, median age 27 (22-48) years (p < 0.00001). The amount of IL-6 and TNF-α was significantly higher in the subscapularis tendon of the patients with subacromial impingement syndrome compared with instability patients (p = 0.0015 and p = 0.0008 respectively). In the capsular samples, significantly higher amount of TNF-α and CD-72 was found in patients with subacromial impingement syndrome compared with instability patients (p < 0.0001 for both). On the other hand, the amount of CD-3 was significantly higher in the instability group (p = 0.0013). CONCLUSIONS: This study provides evidence that an extended inflammatory process is present, not only in the subacromial bursa but also in the glenohumeral joint in patients with subacromial impingement syndrome. LEVEL OF EVIDENCE: Level III. CLINICAL RELEVANCE: To develop a treatment targeted towards intra-articular inflammatory cytokines appears appealing.

Seven Key Themes in Physical Therapy Advice for Patients Living With Subacromial Shoulder Pain: A Scoping Review.

OBJECTIVE: To systematically scope the reported advice and education in physical therapy management of patients with subacromial shoulder pain, and to define key themes of the advice and education. DESIGN: Scoping review. LITERATURE SEARCH: We searched MEDLINE, Scopus, Web of Science, and CINAHL, with publication dates from 2007 to September 2019. STUDY SELECTION CRITERIA: We included quantitative and qualitative research that reported on physical therapy interventions for subacromial shoulder pain. DATA SYNTHESIS: We performed a qualitative synthesis that identified items included in patient advice and education. RESULTS: Of 89 original studies included, there were 61 randomized controlled trials; 5 prospective studies; 16 nonrandomized observational intervention studies or case series; and 7 surveys, audits of physical therapy patient records, and focus groups with physical therapists. We identified 7 key themes for advice and education: exercise intensity and pain response, activity modification advice, posture advice, pain self-management advice, pathoanatomical and diagnosis information, behavioral approaches, and pain biology advice. CONCLUSION: While advice focused predominantly on the local tissue pathology model, 10% of studies included information about pain neuroscience education, psychosocial factors, motor imagery, or behavior change. J Orthop Sports Phys Ther 2020;50(6):285-293. doi:10.2519/jospt.2020.9152.

Metabolic profiling of serum and tissue from the rotator interval and anterior capsule in shoulder stiffness: a preliminary study.

BACKGROUND: Using mass spectrometry, we evaluated the metabolic profiles of patients who had rotator cuff tears with shoulder stiffness, or shoulder stiffness only, and compared these with samples from a control group. METHODS: This study enrolled 28 patients, including 10 patients with shoulder stiffness only (group I), nine patients with rotator cuff tear and stiffness (group II), and nine controls selected from patients diagnosed with impingement syndrome or long head of the biceps lesions without evident limitation of joint motion or rotator cuff tears. Serum and tissue from the rotator interval and anterior capsule were collected. In all, 82 samples were analyzed for metabolite profiling using the AbsoluteIDQ™p180 Kit. RESULTS: Comparison of 186 metabolites revealed that groups I and II had significantly higher concentrations of sphingolipids in serum (SM C24:1; group I = 65.16 µm, group II = 68.07 µm) than controls (55.37 µm, p = 0.005 & 0.015, respectively). Higher concentrations of sphingolipids were also present in the rotator interval tissue (SM C22:3) of groups 1 (0.0197 µm) and 2 (0.0144 µm) than controls (0.0081 µm, p = 0.012 & 0.014, respectively). The concentration of glycerophospholipid (PC aa C30:0) was higher in the anterior capsule tissue of groups I (0.850 µm) and II (1.164 µm) than controls (0.572 µm; p = 0.007) Total cholesterol was positively correlated with sphingolipid concentration in serum (SM C24:1, rho = 0.782, p = 0.008) and rotator interval tissue (SM C22:3, rho = 0.750, p = 0.017). There was no significant difference in the metabolites evaluated in groups I and II. CONCLUSION: Metabolic profiling showed that levels of lipid-related metabolites were increased in the anterior capsule tissue and rotator interval tissue of patients with shoulder stiffness. Sphingomyelin (SM C22:3) in the tissue of the rotator interval was positively correlated with the serum level of total cholesterol in patients with shoulder stiffness only. The level of glycerophospholipid (PC30:0) in the anterior capsule was positively correlated with the serum level of total cholesterol in patients who had rotator cuff tear with shoulder stiffness. The results indicate that serum total cholesterol may be related to shoulder stiffness. Future studies are needed to evaluate the role of serum cholesterol in the pathogenesis of shoulder stiffness. TRIAL REGISTRATION: KC12OISI0532. Registered Nov 15, 2012. approval by the Institutional Review Board of Seoul St. Mary's Hospital, the Catholic University of Korea.

Deformation of coracoacromial ligament during overhead movement as an early indicator of subacromial impingement in elite adolescent badminton players.

Objectives: Deformation of the coracoacromial ligament during overhead movement has been linked to shoulder pathologies such as impingement and rotator cuff tear. We, therefore, explored this relationship in a group of elite adolescent badminton players.Method: We performed bilateral shoulder physical and ultrasonographic examination in 35 adolescent asymptomatic badminton players, 13 players with unilateral shoulder pain, and 15 non-athletes of similar age. Coracoacromial ligament deformation, defined as the maximal vertical distance between the ligament apex to a line connecting the acromion and coracoid process, was measured during shoulder abduction and internal rotation and compared within and between groups. Other ultrasonographic measurements and the incidence of shoulder pathologies were also evaluated.Result: Among badminton athletes who reported dominant shoulder pain, coracoacromial ligament deformation was significantly larger in their dominant shoulder than in their non-dominant shoulder (3.5 and 2.0 mm, respectively; p = 0.013); this difference was not present in other groups. Regardless of the presence or absence of pain, athletes displayed more coracoacromial ligament deformation and increased supraspinatus tendon thickness in their dominant shoulder than did the control group. Abnormal ultrasound findings were noted in all groups; however, the incidence was not significantly different.Conclusion: Increased coracoacromial ligament deformation during overhead movement is associated with shoulder pain in elite adolescent badminton players. Our findings may help clinicians identify athletes at risk of subacromial impingement syndrome.

Subacromial impingement anatomy and its association with rotator cuff pathology in women: radiograph and MRI correlation, a retrospective evaluation.

OBJECTIVE: To evaluate the relationships between acromial anatomy and developmental alterations with rotator cuff tears in female patients and compare these parameters on radiographs and corresponding MRIs along with inter-reader performance. MATERIALS AND METHODS: Patient demographics, symptoms, and acromial characteristics on radiograph (acromial index, lateral acromion angle, subacromial space on AP and Y- views, acromial anterior and lateral downsloping) and MRI (shape, slope, spur, osteoarthrosis, os acromiale) were recorded. Radiographic and MRI findings were compared and correlated with rotator cuff pathology on MRI. Inter-reader analysis was performed. RESULTS: A total of 140 MRIs from 137 female patients were included. No significant correlation (p > 0.05) existed between acromial parameters and rotator cuff tears, except for a smaller subacromial space on the Y view and spurs correlated with subscapularis tendon tear (p = 0.02, p = 0.04). The presence of lateral downsloping on MRI correlated with a smaller lateral acromion angle (p = 0.0002) and the presence of lateral downsloping on radiography (p = 0.0015). Inter-reader agreements were good to excellent (ICC: 0.65-0.89). CONCLUSION: Subacromial impingement anatomy characteristics have no significant associations with supraspinatus or infraspinatus tears in symptomatic women. Among different measures, supine MRI can be reliably used to identify lateral downsloping of the acromion.

Evaluating the role of subacromial impingement in rotator cuff tendinopathy: Development and analysis of a novel murine model.

Subacromial impingement of the rotator cuff is understood as a contributing factor in the development of rotator cuff tendinopathy. However, changes that occur in the impinged tendon are poorly understood and warrant further study. To enable further study of rotator cuff tendinopathy, we performed a controlled laboratory study to determine feasibility and baseline characteristics of a new murine model for subacromial impingement. This model involves surgically inserting a microvascular clip into the subacromial space in adult C57Bl/6 mice. Along with a sham surgery arm, 90 study animals were distributed among time point groups for sacrifice up to 6 weeks. All animals underwent bilateral surgery (total N = 180). Biomechanical, histologic, and molecular analyses were performed to identify and quantify the progression of changes in the supraspinatus tendon. Decreases in failure force and stiffness were found in impinged tendon specimens compared to sham and no-surgery controls at all study time points. Semi-quantitative scoring of histologic specimens demonstrated significant, persistent tendinopathic changes over 6 weeks. Quantitative real-time polymerase chain reaction analysis of impinged tendon specimens demonstrated persistently increased expression of genes related to matrix remodeling, inflammation, and tendon development. Overall, this novel murine subacromial impingement model creates changes consistent with acute tendonitis, which may mimic the early stages of rotator cuff tendinopathy. A robust, simple, and reproducible animal model of rotator cuff tendinopathy is a valuable research tool to allow further studies of cellular and molecular mechanisms and evaluation of therapeutic interventions in rotator cuff tendinopathy. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2780-2788, 2018.

More histologic and ultrastructural degenerative signs in the subscapularis tendon and the joint capsule in male patients with shoulder impingement.

PURPOSE: The purpose of the present study was to analyze biopsy samples from the subscapularis tendon and from the joint capsule from male patients with shoulder impingement syndrome (SAIS) and compare them with samples from male patients with post-traumatic recurrent shoulder instability. The hypothesis of the study was that patients with SAIS would have more histologic and ultrastructural degenerative changes in their subscapularis tendon and joint capsule than patients with post-traumatic recurrent shoulder instability. METHODS: Male patients scheduled for surgery, with either subacromial decompression or Bankart reconstruction, were included. Four biopsies from each patient were obtained from the capsule and four from the subscapularis tendon during arthroscopic surgery. The histologic characteristics and the presence of glycosaminoglycans were assessed using the light microscope, and the ultrastructure was assessed using a transmission electron microscope. RESULTS: Eight patients, median age 53 (45-74) years (p < 0.0001), were included in the impingement group, and 12 patients, median age 27 (22-48) years, were included in the instability group. The histologic assessment revealed significantly higher cellularity and total degeneration score in the capsule (p = 0.016 and p = 0.014 respectively) in patients with subacromial impingement compared with the instability patients. The corresponding finding was not made for the subscapularis tendon. The ultrastructural evaluation revealed that the instability patients had more fibrils with a large diameter (indicating less degeneration) in both the subscapularis tendon and the capsule compared with the impingement patients (p < 0.0001). CONCLUSION: Male patients with subacromial impingement have more histologic and ultrastructural degenerative changes in their shoulder compared with patients with post-traumatic recurrent shoulder instability. CLINICAL RELEVANCE: It appears that in patients with subacromial impingement, the whole shoulder joint is affected and not only the subacromial space. It is the opinion of the authors that intra-articular therapeutic injections could be tried more often in these patients. LEVEL OF EVIDENCE: III.

The role of scapular kinematics in patients with different shoulder musculoskeletal disorders: A systematic review approach.

This study aimed to identify the role of the scapula in shoulder musculoskeletal disorders (SMDs) and provided a systematic review of available studies in the field of scapular three-dimensional kinematics. We systematically searched 5 international databases, including Scopus, EMBASE, PubMed, CINAHL, PEDro, and Cochrane Library from June to September 2015. Twenty studies met the inclusion criteria and were retrieved in full paper. The selected studies were critically appraised independently by two researchers. The patients with shoulder impingement syndrome (SIS) and shoulder instability had an increased protraction, lesser upward rotation (UR), and increased internal rotation (IR) during scapular plane elevation, whereas the patients with frozen shoulders had lesser protraction. Moreover, the patients with SIS had a greater scapular posterior tilt (PT) and external rotation during shoulder abduction. Increased scapular UR and PT with decreased scapular IR was seen in patients with stiffness of Latissimus Dorsi and fibromyalgia without any changes in the scapular IR. The results of this systematic review help the clinicians to have an insight about scapular kinematics as a predictive index for SMDs.

Association of Bicipital Peritendinous Effusion with Subacromial Impingement: A Dynamic Ultrasonographic Study of 337 Shoulders.

Bicipital peritendinous effusion (BPE) is the most common biceps tendon abnormality and can be related to various shoulder ultrasonographic findings. Since the association of BPE with subacromial impingement is unclear, our study aimed to explore its association with the dynamic subacromial impingement test during ultrasound (US) imaging. We included 337 shoulders referred for US examinations and quantified the amount of BPE. Effusion more than 1 mm in thickness was considered a positive finding. A comparison of three grades of subacromial impingement, adjusted by patient demographics, static sonographic shoulder pathology, and physical findings, by using multivariate regression models revealed that the odds ratio of subacromial impingement (with 95% confidence intervals) in the presence of BPE was 6.54 (3.21-13.32) in grade 1, 6.93 (3.05-15.76) in grade 2 and 3.18 (1.48-6.80) in grade 3. An increase in age, subdeltoid bursitis, full-thickness supraspinatus tendon tear, and shoulder stiffness were also associated with BPE. Since our study demonstrated a positive association of BPE with all grades of impingement, a US dynamic subacromial impingement test is suggested when BPE is present. Future prospective studies are needed to identify changes in BPE after treatment.

Tendon Volume Determination on Magnetic Resonance Imaging of Supraspinatus Tendinopathy.

OBJECTIVE: To determine the supraspinatus tendon volume using magnetic resonance imaging (MRI) in dogs with non-calcified supraspinatus tendinopathy (NCST), in dogs with orthopedic disease other than NCST, and in healthy dogs. STUDY DESIGN: Case series. ANIMALS: Twenty-two dogs (18 client-owned dogs; 4 purpose-bred dogs). METHODS: Dogs undergoing shoulder MRI were categorized as NCST if they were diagnosed with NCST only, had histologic confirmed diagnosis, underwent surgical treatment, and were available for follow-up longer than 4 months. Dogs with MRI performed for a forelimb lameness because of a diagnosis other than NCST were categorized as orthopedic control (OC). Healthy dogs from an unrelated study were categorized as healthy controls (HC). Tendon volume was determined from MRI using public domain software and compared across categories. RESULTS: The study included 9 NCST dogs, 9 OC dogs, and 4 HC dogs. The median tendon volume for NCST was 1,323 mm(3), OC was 630 mm(3), and HC was 512 mm(3). The volume was significantly higher in the NCST than OC (P = .0012) and HC (P = .003). There was no difference between OC and HC (P = .76). CONCLUSION: Dogs diagnosed with NCST had higher supraspinatus tendon volumes compared to dogs with other orthopedic disorders and healthy dogs.

The Coracohumeral Distance in Shoulders With Traumatic and Degenerative Subscapularis Tendon Tears.

BACKGROUND: A reduced coracohumeral distance (CHD) is thought to be responsible for subcoracoid impingement. This only accounts for degenerative tendon tears. In traumatic tears, the subcoracoid space should be normal. HYPOTHESIS: The CHD in patients with traumatic subscapularis tendon tears is larger than that in patients with degenerative tears and does not differ from patients with an intact subscapularis tendon. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: A total of 83 patients with arthroscopically certified subscapularis tendon tears were included in the study. Forty-four patients had degenerative causes (group 1), and 39 had traumatic causes (group 2). The control group consisted of 20 patients with traumatic supraspinatus tendon tears and arthroscopically proven, intact subscapularis tendons (group 3). On preoperative axial magnetic resonance imaging, the distance between the CHD was measured, and the values of the 3 groups were compared using the t test. RESULTS: The mean (±SD) CHD in patients with degenerative subscapularis tendon tears was 8.6 ± 2.0 mm (range, 4.0-13.2 mm) and was significantly (P = .0003) smaller than that in patients with traumatic tears (10.2 ± 2.0 mm; range, 6.6-16.2 mm) or controls (10.4 ± 1.8 mm; range, 6.8-14.0 mm). The CHD of controls and patients with traumatic tears did not differ significantly (P = .7875). A CHD of less than 6 mm only occurred in patients with degenerative subscapularis tendon tears. CONCLUSION: The hypothesis that the CHD in patients with degenerative subscapularis tendon tears is significantly smaller than that in patients with traumatic tears or intact subscapularis tendons was confirmed. The CHD in patients with traumatic tears does not differ from that in controls. A CHD of less than 6 mm only occurs in patients with degenerative subscapularis tendon tears.

The effect of glenoid cavity depth on rotator cuff tendinitis.

INTRODUCTION: Some of the most important causes of shoulder pain are inflammation and degenerative changes in the rotator cuff (RC). Magnetic resonance imaging (MRI) is a noninvasive and safe imaging modality. MRI can be used for the evaluation of cuff tendinopathy. In this study, we evaluated the relationship between glenoid cavity depth and cuff tendinopathy and we investigated glenoid cavity depth on the pathogenesis of cuff tendinopathy. MATERIALS AND METHODS: We retrospectively evaluated 215 patients who underwent MRI. Of these, 60 patients showed cuff tendinopathy (group A) and 54 patients showed no pathology (group B). Glenoid cavity depth was calculated in the coronal and transverse planes. RESULTS: The mean axial depth was 1.7 ± 0.9 and the mean coronal depth 3.8 ± 0.9, for group A. The mean axial depth was 3.5 ± 0.7 and the mean coronal depth 1.5 ± 0.8, for group B. There were significant differences in the axial and coronal depths between the two groups. CONCLUSION: High coronal and low axial depth of the glenoid cavity can be used to diagnose RC tendinitis.

Scapular Notching on Kinematic Simulated Range of Motion After Reverse Shoulder Arthroplasty Is Not the Result of Impingement in Adduction.

Impingement after reverse shoulder arthroplasty (RSA) is believed to occur from repetitive contact in adduction between the humeral component and the inferior scapular pillar. The primary purpose of this biomechanical study was to confirm the presence of different types of impingement and to examine which daily-life movements are responsible for them. A secondary aim was to provide recommendations on the type of components that would best minimize notching and loss of range of motion (ROM). The study included 12 fresh frozen shoulder specimens; each had a computed tomography (CT) image of the entire scapula and humerus in order to acquire topological information of the bones before RSA implantation. Cyclic tests were run postimplantation with 3 shoulders in each modalities. To quantify bone loss due to impingement, 3-dimensional anatomical models of the scapula were reconstructed from the CT scans and compared to their intact states. We found 8 bony impingements in 7 specimens: 2 at the lateral acromion, 1 at the inferior acromion, 4 scapular notching, and 1 with the glenoid resulting to wear at the 3:00 to 6:00 clock-face position. Impingements occurred in all kinds of tested motions, except for the internal/external rotation at 90° of abduction. The 3 specimens tested in abduction/adduction presented bone loss on the acromion side only. Scapular notching was noted in flexion/extension and in internal/external rotation at 0° of abduction. The humeral polyethylene liner was worn in 2 specimens--1 at the 6:00 to 8:00 clock-face position during internal/external rotation at 0° of abduction and 1 at the 4:00 clock-face position during flexion/extension. The present study revealed that 2 types of impingement interactions coexist and correspond to a frank abutment or lead to a scapular notching (friction-type impingement). Scapular notching seems to be caused by more movements or combination of movements than previously considered, and in particular by movements of flexion/extension and internal/external rotation with the arm at the side. Polyethylene cups with a notch between 3 and 9 o'clock and lower neck-shaft angle (145° or 135°) may play an important role in postoperative ROM limiting scapular notching.

Acromiohumeral Distance During Neuromuscular Electrical Stimulation of the Lower Trapezius and Serratus Anterior Muscles in Healthy Participants.

CONTEXT: Compromise to the acromiohumeral distance has been reported in participants with subacromial impingement syndrome compared with healthy participants. In clinical practice, patients with subacromial shoulder impingement are given strengthening programs targeting the lower trapezius (LT) and serratus anterior (SA) muscles to increase scapular posterior tilt and upward rotation. We are the first to use neuromuscular electrical stimulation to stimulate these muscle groups and evaluate how the muscle contraction affects the acromiohumeral distance. OBJECTIVE: To investigate if electrical muscle stimulation of the LT and SA muscles, both separately and simultaneously, increases the acromiohumeral distance and to identify which muscle-group contraction or combination most influences the acromiohumeral distance. DESIGN: Controlled laboratory study. SETTING: Human performance laboratory. PATIENTS OR OTHER PARTICIPANTS: Twenty participants (10 men and 10 women, age = 26.9 ± 8.0 years, body mass index = 23.8) were screened. INTERVENTION(S): Neuromuscular electrical stimulation of the LT and SA. MAIN OUTCOME MEASURE(S): Ultrasound measurement of the acromiohumeral distance. RESULTS: Acromiohumeral distance increased during contraction via neuromuscular electrical stimulation of the LT muscle (t(19) = -3.89, P = .004), SA muscle (t(19) = -7.67, P = .001), and combined LT and SA muscles (t(19) = -5.09, P = .001). We observed no differences in the increased acromiohumeral distance among the 3 procedures (F(2,57) = 3.109, P = .08). CONCLUSIONS: Our results supported the hypothesis that the muscle force couple around the scapula is important in rehabilitation and scapular control and influences acromiohumeral distance.

Acromiohumeral distance measurement in rotator cuff tendinopathy: is there a reliable, clinically applicable method? A systematic review.

BACKGROUND: Narrowing of the subacromial space has been noted as a common feature of rotator cuff (RC) tendinopathy. It has been implicated in the development of symptoms and forms the basis for some surgical and rehabilitation approaches. Various radiological methods have been used to measure the subacromial space, which is represented by a two-dimensional measurement of acromiohumeral distance (AHD). A reliable method of measurement could be used to assess the impact of rehabilitation or surgical interventions for RC tendinopathy; however, there are no published reviews assessing the reliability of AHD measurement. OBJECTIVES: The aim of this review was to systematically assess the evidence for the intrarater and inter-rater reliability of radiological methods of measuring AHD, in order to identify the most reliable method for use in RC tendinopathy. STUDY APPRAISAL AND SYNTHESIS: An electronic literature search was carried out and studies describing the reliability of any radiological method of measuring AHD in either healthy or RC tendinopathy groups were included. Eighteen studies met the inclusion criteria and were appraised by two reviewers using the Quality Appraisal for reliability Studies checklist. RESULTS: Eight studies were deemed to be of high methodological quality. Study weaknesses included lack of tester blinding, inadequate description of tester experience, lack of inclusion of symptomatic populations, poor reporting of statistical methods and unclear diagnosis. There was strong evidence for the reliability of ultrasound for measuring AHD, with moderate evidence for MRI and CT measures and conflicting evidence for radiographic methods. Overall, there was lack of research in RC tendinopathy populations, with only six studies including participants with shoulder pain. CONCLUSIONS: The results support the reliability of ultrasound and CT or MRI for the measurement of AHD; however, more studies in symptomatic populations are required. The reliability of AHD measurement using radiographs has not been supported by the studies reviewed.

Posterosuperior glenoid internal impingement of the shoulder in the overhead athlete: pathogenesis, clinical features and MR imaging findings.

Posterosuperior glenoid internal impingement (PGII) is an impingement syndrome of the shoulder that is most commonly seen in the throwing or overhead athlete. The supraspinatus can be normally compressed or impinged between the greater tuberosity and the posterosuperior labrum in the abduction and external rotation position. However, repetitive throwing and biomechanical abnormalities may lead to the intensification of this contact and to the clinical and pathological picture of PGII. The injured athlete usually complains of poor throwing performance and pain located in the posterosuperior aspect of the shoulder. Two main theories regarding the aetiology of PGII have been postulated with differing initial mechanisms. The MRI features of PGII have been described and include supraspinatus and anterior infraspinatus partial undersurface tears, bony changes at the humeral head and labral pathology, including a variation of the type II superior labrum from anterior to posterior lesion. This pictorial essay aims to present cases illustrating the pathophysiology, clinical features and recently described MRI findings, and discuss some of the MR protocol considerations.

MRI analysis of coracohumeral interval width and its relation to rotator cuff tear.

OBJECTIVE: Coracoid impingement is an uncommon cause of the shoulder pain. It is stimulated by adduction, internal rotation and forward flexion. These positions decrease the width of the coracohumeral interval. Owing to restriction of movement, rotator cuff tendons may be overloaded. Thus, in this study, we aimed to determine whether coracoid impingement increase the tendency of rotator cuff tears. MATERIALS AND METHODS: Routine clinical MRI sequences of 117 shoulders were reviewed, and axial coracohumeral interval measurements were taken. Rotator cuff tendon integrity was evaluated. Relation between rotator cuff tear and coracohumeral interval width was commented statically. RESULTS: Seventy-nine of the patients were women, 38 of them men. The average age was 44.8 ± 14.2 (14-75). The mean age of patients with rotator cuff tear was significantly higher than patients without tear (p = 0.001). The mean value of coracohumeral interval width was 8.853 ± 2.491 mm (min: 2.9-max: 15.8). There were no significant differences between coracohumeral interval width of women and men (p = 0.139). The mean value of coracohumeral interval width with rotator cuff tear was 8.362 ± 2.382, and without tear was 9.351 ± 2.520. There was a significant differences between them (p = 0.031). CONCLUSION: According to our study, there was a relationship between coracohumeral interval width and rotator cuff tear, so decreasing coracohumeral interval width may increase tendency of rotator cuff tear.