Subacromial balloon spacer improves isokinetic performance in patients with massive irreparable rotator cuff tear.

PURPOSE: The aim of this study was to analyse clinical, functional and shoulder kinematics results using subacromial balloon spacer in nonreparable massive rotator cuff tears. Subacromial balloon spacer was hypothesised to improve shoulder kinematics and increases clinical and functional outcomes scores in nonreparable massive rotator cuff tears. METHODS: This is a prospective study in massive rotator cuff tears. From October 2021 to October 2022, a total of 127 shoulders suffering massive rotator cuff tears were initially evaluated. All patients were evaluated preoperatively, at 6 and 12 months. Patients' patient-reported outcome measures (PROM) subjective values using visual analogue scale (VAS) and the Spanish Western Ontario Rotator Cuff Index (WORC) version were analysed. We also evaluated objective outcomes: constant score, range of movement and kinematic shoulder analysis (isokinetic test to evaluate internal and external rotation forces). Statistical analysis was conducted using SPSS software; continuous variables were presented as means and standard deviations (SDs). RESULTS: Seventeen nonrepairable massive rotator cuff tears were finally included. Three patients required reverse shoulder arthroplasty before 6 months postoperative. After 1-year follow-up, objective and subjective (PROM) outcome scores and isokinetic measurements improved in 13 patients. Preoperative VAS improved from 6.5 ± 2.1 to 2 ± 1.9 points on average at 1-year follow-up and WORC index from 1603 ± 217.3 to 699 ± 361.6. Constant score from 42.1 ± 13.1 on average and at 1-year follow-up increased to 60.8 ± 14.7. Range of movement also improved in elevation 122.2 ± 39.3 to 166.9 ± 25.8, abduction 120.3 ± 38.6 to 134.6 ± 21.1, external rotation 30.3 ± 19.7 to 86.1 ± 13.8 and internal rotation L4-T12 on average at 1-year follow-up. Isokinetic evaluation showed functional improvement 1 year after implantation. Both internal and external rotation improved compared with their healthy shoulder. External rotation improved from 30.3° ± 19.7° preoperatively to 86.1° ± 13.8° (43.7% in the isokinetic study) and internal rotation from L4 preoperatively to L1 (49.8% in isokinetic study) on average. CONCLUSION: Among the different alternatives for irreparable rotator cuff injuries surgical treatment, subacromial balloon spacer is an effective alternative in selected patients, both in terms of clinical-functional improvement and short-term isokinetic results. LEVEL OF EVIDENCE: Level II.

Comparison of balance and proprioception of the shoulder joint in girls with and without upper cross syndrome.

INTRODUCTION: Upper cross syndrome is one of the most common disorders of the upper part of body, often associated with abnormalities of forward head, forward shoulders, elevated and protracted of scapula, and increased thoracic kyphosis. Conducting research on upper cross syndrome, especially in girls, is of highly significant, considering this issue and lack of examination of complications and consequences of this syndrome; therefore, this study aims to compare the balance and proprioception of the shoulder joint in girls with and without upper cross syndrome.Method The statistical population included two groups of 10-12-year-old female students, i.e., healthy and those with upper cross syndrome in the city of Khalkhal in Iran in 2022-2023. A total of 60 girl children were included in this study. The subjects were screened using a checker board and after quantitative evaluations of posture, they were assigned into two groups: healthy group (No. 30) and the one suffering from upper cross syndrome (No. 30). Forward head and forward shoulder angle were assessed using photography and kinovea software, kyphosis angle using Goniometer-pro app, static and dynamic balance using BESS and Y tests, also proprioception at angles of 45- and 80-degrees external rotation of the shoulder joint through photography and kinovea software. Data were analyzed through independent t-test in SPSS software version 26 at the significance level of 0.05.Results Healthy girls were in a better position in all variables of static balance (1.14 95% CI: [0.96, 1.70], p = 0.001), dynamic balance (0.81, 95% CI: [0.73,1.24], p = 0.001), proprioception of external rotation of shoulder joint at 45- (0.78, 95% CI: [0.64, 1.14], p = 0.001) and 80-degrees (0.89, 95% CI: [0.59, 1.34], p = 0.001) angles than those with upper cross syndrome.Conclusion It can be concluded that upper cross syndrome causes a decrease in balance and proprioception of the shoulder joint in female students; therefore, along with correcting the abnormalities, special attention should be paid to strengthening and improving these components. It is recommended for rehabilitation professionals to apply exercise training programs to improve the balance and proprioception and correct of the upper cross syndrome: that the strengthening of these components prevents musculoskeletal disorders.Implications for clinical practice• It is recommended for rehabilitation professionals to apply exercise training programs to improve the balance and proprioception of individual with upper cross syndrome.• It is recommended for rehabilitation professionals to apply exercise training programs to correct of the upper cross syndrome in order to prevents musculoskeletal disorders.

Vancomycin Soaking to Reduce Intraoperative Contamination by Cutibacterium acnes During the Latarjet Procedure.

BACKGROUND: Postoperative infection after the Latarjet procedure, ranging from 1% to 6%, can compromise the functional outcome of young athletes. Cutibacterium acnes is a main pathogen as a consequence of an intraoperative contamination. PURPOSE: To evaluate intraoperative contamination with C. acnes and the effectiveness of the local application of vancomycin during the Latarjet procedure. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: This was a single-center study including 75 patients (mean age, 26 years; range, 15-55 years) operated on for anterior shoulder instability with the primary open Latarjet procedure; they underwent the same protocol of skin preparation and preoperative prophylactic antibiotics. Three groups of 25 patients were created and divided sequentially, without the results of each group being known before the end of the study: group A (5 mg/mL of vancomycin), group B (20 mg/mL of vancomycin), and group C (control group with no vancomycin). Swab samples of the coracoid were taken before sectioning the coracoid process (time 1) and after its preparation (time 2). The coracoid was then wrapped in gauze impregnated with different concentrations of vancomycin, except for group C. A final sample (time 3) was taken before screwing the bone block onto the glenoid. All samples were cultured for 21 days, and patients underwent clinical and radiological follow-up for 6 months. RESULTS: The C. acnes contamination rates at times 1, 2, and 3 were 25%, 44%, and 45%, respectively, without significant difference. There was no significant difference between groups A and B with respect to the number of positive cultures at each time point. Of 9 positive cultures at time 1, all were still positive at time 3 in group A, whereas 3 of 5 were negative in group B (P = .027). The rate of C. acnes at time 3 in the control group was higher than that in the 2 other groups (68% vs 44% for group A and 20% for group B; P = .003). Body mass index was the only prognostic factor for a C. acnes-positive culture (26.05 ± 3.39 vs 23.34 ± 2.33; P = .018). No clinical infection was reported at the 6-month postoperative follow-up. CONCLUSION: The rate of C. acnes contamination ranged from 25% to 68% during the open Latarjet procedure in young athletes. Vancomycin reduced the bacterial contamination when it was used at high concentrations in a gauze wrap on the coracoid. The type of C. acnes detected and its clinical implications remain to be studied.

Acute Effects of Handheld Vibration Massage on Posterior Shoulder Soft Tissues.

Background: Interventions using vibration stimulation have been recognized for their potential for increasing range of motion (ROM) without compromising muscle strength. Handheld vibration massagers can efficiently deliver vibration therapy to the shoulder joint and may be a potential treatment. Purpose: To evaluate the effects of vibration massage using a handheld device on the soft tissues of the posterior shoulder joint, particularly on internal rotation (IR) passive ROM and external rotation (ER) muscle strength. Study Design: Crossover study design. Methods: A crossover study with a 5-min vibration massage and passive control condition was conducted in healthy male volunteers (mean age 20.5 ± 1.7 years). Vibration massage was applied to the posterior shoulder soft tissues of the dominant arm, with no intervention under control conditions. IR-ROM (vertebral level and in abduction) and strength of the external rotators (isometric and isokinetic) were measured before and immediately after the intervention. Vertebral levels were calculated as a ratio of lengths (ratio decreases with increased mobility). IR-ROM in abduction, the angle was measured. Statistical analysis was performed with two-way repeated measures ANOVA and paired t-test (Bonferroni correction). Results: Vibration application decreased (improved) vertebral level IR ROM by -4.1% (p < 0.01, d = 0.445) and increased abduction position IR ROM by 11.4° (p < 0.01, d = 0.694). These changes exceeded the 95% confidence interval for the minimum detectable change. By contrast, the control condition produced no changes. IR-ROM (vertebral level and abduction) immediately after the intervention showed significant differences between the control and vibration conditions (p = 0.036, d = 0.273; p = 0.048, d = 0.483, respectively). Muscle strength did not show any interaction, time, or between-condition effects. Conclusions: A massage using a handheld vibration massager applied to the posterior shoulder soft tissues increased IR-ROM without negatively affecting muscle strength, suggesting its potential use as a means of warming up. Level of Evidence: Level 3.

Magnetic resonance arthrography with positional manoeuvre for the diagnosis of synovial fold of posterior shoulder joint capsule.

OBJECTIVES: The objective of this study is to prospectively assess the effectiveness of shoulder magnetic resonance (MR) arthrograms with positional manoeuvres in detecting posterior synovial folds. METHODS: Two radiologists independently assessed all axial MR arthrograms in internal rotation, neutral position, and external rotation for the presence of a posterior synovial fold. The diagnostic performances of the MR arthrograms were then compared, with results validated through arthroscopy. RESULTS: Arthroscopy was performed on 81 of the 150 patients included in the study. A posterior synovial fold was identified arthroscopically in eleven of these patients. Measurements of the posterior synovial fold obtained in external rotation and the neutral position of the arm showed a significant correlation with arthroscopic results (p < 0.05). For detecting the posterior synovial fold with arthroscopic correlation, the sensitivity and specificity values for observer 1 and observer 2 were 100-81.4% and 100-88.6%, respectively, for MR arthrograms in the neutral position; 100-52.9% and 100-62.9% for MR arthrograms in external rotation; and 100-95.7% and 81.8-98.6% for MR arthrograms in internal rotation. There was a fair agreement for MR arthrography in external rotation for detecting posterior synovial folds, while MR arthrograms in internal rotation and neutral position showed near-perfect and significant interobserver agreement. CONCLUSION: The rotational positions of the humeral neck during MR arthrographic examination can influence the diagnostic specificity and sensitivity of axial MR arthrograms in detecting the posterior synovial fold. CLINICAL RELEVANCE STATEMENT: The posterior synovial fold can mimic a posterior labral detachment. Therefore, its correct identification is crucial in order to avoid unnecessary surgical procedures. KEY POINTS: Movement of the shoulder may introduce variability in MR arthrography appearance. Rotation of the humeral neck during MR arthrography can affect diagnoses in posterior synovial fold detection. Given that posterior synovial folds can imitate posterior labral detachment, their correct identification is crucial to avoid unnecessary surgical procedures.

Assessment of shoulder joint derangements with magnetic resonance imaging in adult Nigerians.

Objectives: Shoulder pain secondary to various aetiologies is a common musculoskeletal complaint worldwide, and Magnetic Resonance Imaging (MRI) is the most accurate imaging method for evaluating shoulder pain in all age groups. While the patterns of shoulder MRI abnormalities in various demographics have been reported, data on sub-Sahara African populations are still sparse. This study aims to describe the imaging features and spectrum of shoulder joint pathologies on MRI in adult Nigerians. Materials and Methods: This was a retrospective review of the shoulder MRI of 100 adult Nigerians (with and without trauma) from September 2020 to December 2021. Their clinical data and shoulder MRI findings were extracted and analysed. Statistical significance was set at P ≤ 0.05. Results: There were 64 males and 36 females aged 18-82 years. Right shoulder MRI was done in 53 subjects (53%), while the left shoulder was studied in 47 (47%). Supraspinatus tendinopathy (73%), acromioclavicular joint arthropathy (68%), and subacromial-subdeltoid (SASD) bursitis (64%) were the most frequently detected pathologies. Other demonstrated derangements include glenohumeral joint effusion (24%), long head of biceps tendon sheath effusion (18%), labral abnormalities (16%), subcoracoid bursitis (4%), Hill Sach's deformity (3%), anterior glenohumeral dislocation (2%), fatty degeneration of the supraspinatus/infraspinatus muscles (2%), adhesive capsulitis (1%), and other bony abnormalities (contusion, erosion, subchondral cysts). There was no significant difference in the frequency of shoulder abnormalities between the male and female subjects. Conclusion: Acromioclavicular joint arthropathy, SASD bursitis, and rotator cuff disorders were the dominant pathologies in the participants' shoulders.

The relationship between the duration and the retraction and atrophy grades in traumatic isolated full-thickness supraspinatus tears in young patients.

BACKGROUND: The study aimed to determine the grade of retraction and atrophy according to the time elapsed in traumatic isolated full-thickness supraspinatus (SS) tears in young patients. METHODS: One thousand twenty-six patients, who underwent arthroscopic shoulder surgery, were retrospectively reviewed. Pre-operative magnetic resonance imaging (MRI) of 69 patients aged 18 to 40 years with isolated traumatic full-thickness SS lesions remaining after exclusion criteria were evaluated for tendon retraction and atrophy grades. SS retraction was determined from a T2-weighted oblique coronal MRI slice, and the atrophy grade was determined from the T1-weighted oblique sagittal MRI slice. The patients were divided into four groups 0-1 month, 1-3 months, 3-6 months, and 6-12 months according to the time between trauma and MRI. The relationship of tendon retraction and muscle atrophy with elapsed time was evaluated, in addition, comparisons between groups were made. RESULTS: Thirty-one (45%) of the patients were female and their mean age was 30 ± 7.3 (18-40) years. The mean age of men was 30.5 ± 6.9 (18-39) years (p = 0.880). The time between rupture and MRI was moderately correlated with retraction and strongly correlated with atrophy grades (r = 0.599, 0.751, respectively). It was observed that there was a statistically significant difference between the 1st (0-1 month) and 2nd (1-3 months) groups (p = 0.003, 0.001, respectively), and between the 2nd and 3rd (3-6 months) groups (p = 0.032, 0.002, respectively), but there was no significant difference between the 3rd and 4th (6-12 months) groups (p = 0.118, 0.057, respectively). In addition, there was a moderate correlation between tendon retraction and atrophy grades (r = 0.668). Power (1- b) in post hoc analysis was calculated as 0.826. CONCLUSIONS: The current study, supported by arthroscopy, showed that there is a moderate and strong positive correlation between the time elapsed after trauma and the level of retraction and degree of atrophy in traumatic full-thickness SS tears, and demonstrated the importance of early surgical intervention in young patients.

Partial Shoulder Arthroplasty Guided by Three-dimensional Prototyping.

Three-dimensional (3D) printing technology is a reality in medicine. In Orthopedics and Traumatology, 3D printing guides a precise and tailored surgical treatment. Understanding and disseminating its applicability, use, and outcomes can foster academicism and improve patient care. This is a report of a rare case of a female young adult patient with osteonecrosis of the humeral head due to avascular necrosis developed in early childhood. The treatment was tailored and optimized with 3D printing, which helped determine the steps for partial humeral arthroplasty.

Effect of electroacupuncture combined with rehabilitation techniques on shoulder function in patients with rotator cuff injuries.

BACKGROUND: The rotator cuff is located below the acromion and deltoid muscles and comprises multiple tendons that wrap around the humeral head, maintaining shoulder joint stability. AIM: To explore the effect of electroacupuncture combined with rehabilitation techniques on shoulder function in patients with rotator cuff injuries. METHODS: We selected 97 patients with rotator cuff injuries treated in the People's Hospital of Yuhuan from February 2020 to May 2023. Patients were grouped using the envelope method. RESULTS: After treatment, the study group's treatment effective rate was 94.90% (46/49 patients), significantly higher than that in the control group (79.17%, 38/48 cases; P < 0.05). Before treatment, there was no difference in Constant Murley Score (CMS) scores, shoulder mobility, or 36-Item Short Form Health Survey (SF-36) scale scores (P > 0.05). Compared with those before treatment, the CMS scores (including pain, daily living ability, shoulder mobility, and muscle strength), all aspects of shoulder mobility (forward flexion, posterior extension, external rotation, internal rotation), and SF-36 scale scores (including physiological, psychological, emotional, physical, vitality, and health status) were higher in both groups after treatment and significantly higher in the study group (P < 0.05). There was no difference in the occurrence of complications between the two treatment groups (P > 0.05). CONCLUSION: Electroacupuncture combined with rehabilitation techniques has a good treatment effect on patients with rotator cuff injuries, helps accelerate the recovery of shoulder function, improves the quality of life, and is highly safe.

Embedded Machine Learning System for Muscle Patterns Detection in a Patient with Shoulder Disarticulation.

The integration of artificial intelligence (AI) models in the classification of electromyographic (EMG) signals represents a significant advancement in the design of control systems for prostheses. This study explores the development of a portable system that classifies the electrical activity of three shoulder muscles in real time for actuator control, marking a milestone in the autonomy of prosthetic devices. Utilizing low-power microcontrollers, the system ensures continuous EMG signal recording, enhancing user mobility. Focusing on a case study-a 42-year-old man with left shoulder disarticulation-EMG activity was recorded over two days using a specifically designed electronic board. Data processing was performed using the Edge Impulse platform, renowned for its effectiveness in implementing AI on edge devices. The first day was dedicated to a training session with 150 repetitions spread across 30 trials and three different movements. Based on these data, the second day tested the AI model's ability to classify EMG signals in new movement executions in real time. The results demonstrate the potential of portable AI-based systems for prosthetic control, offering accurate and swift EMG signal classification that enhances prosthetic user functionality and experience. This study not only underscores the feasibility of real-time EMG signal classification but also paves the way for future research on practical applications and improvements in the quality of life for prosthetic users.

Glenohumeral Internal Rotation Deficit and Risk of Upper Extremity Injury in Overhead Athletes: Systematic Review.

OBJECTIVE: To systematically review the literature on the efficacy of addressing glenohumeral internal rotation deficit (GIRD) and risk of upper-extremity injury in overhead athletes. DATA SOURCES: A search was conducted for relevant studies published in PubMed, Medline, CINAHL, Cochrane, Embase, Ovid, Google Scholar, and Web of Science. STUDY SELECTION: The review focused on randomized controlled trials (RCTSs) and quasi-experiments conducted in English language that assessed the effectiveness of GIRD and the risk of upper-extremity injury in athletes performing overhead movements. The review included 7 RCTs and 2 quasi-experiments out of 5403, which involved a total of 360 participants. DATA EXTRACTION: Two reviewers independently screened the articles, assessed methodological quality, and extracted data for analysis. The review was conducted and reported according to the Preferred Reporting Items for Systematic Reviews. All studies were assessed in duplicate for risk of bias using the Physiotherapy Evidence Database Scale for RCTs. DATA SYNTHESIS: The efficacy of different types of techniques was evaluated, including joint mobilization, sleeper stretch, cross-body stretch, myofascial release, kinesio taping, and rigid taping. These techniques showed improvement in pain score and range of motion. Furthermore, self-myofascial release tends to improve internal rotation; sleeper stretch and cross-body stretch tend to improve internal rotation with 40 percent decline in pain. However, kinesio taping and rigid taping showed positive results for internal rotation. Acute results determined that the metabolic equivalent (MET) group had significantly more horizontal adduction range of motion posttreatment compared with the control group (P=.04). No significant differences existed between MET and joint mobilizations or between joint mobilizations and the control group for horizontal adduction (P>.16). No significant between-group differences existed acutely for internal rotation (P>.28). There were no significant between-group differences for either horizontal adduction or internal rotation at the 15-minute posttests (P>.70). CONCLUSIONS: The study evaluated the efficacy of various techniques in improving pain score and range of motion in individuals with GIRD. Joint mobilization, sleeper stretch, cross-body stretch, myofascial release, kinesio taping, and rigid taping all showed improvements in pain score and range of motion. However, no significant between-group differences were found for horizontal adduction or internal rotation at the 15-minute posttests. These findings suggest that a combination of these techniques may be effective in treating individuals with GIRD.

Coracoclavicular Joint Arthrosis - An Uncommon Cause of Shoulder Pain.

The coracoclavicular joint is a diarthrodial synovial joint that is eventually located between the upper surface of the horizontal part of the coracoid process and the conoid tubercle of the clavicle, and is considered an unusual anatomical alteration. The coracoclavicular joint has a low prevalence and can be diagnosed by imaging tests - radiography and computed tomography. Treatment can be performed both conservatively and surgically. We report a case of an 81-year-old female patient presenting of pain in her left shoulder due to coracoclavicular joint arthrosis. A radiograph of the left shoulder was performed, which detected a deformity in the lower portion of the middle third of the clavicle and the upper portion of the coracoid process, corresponding to the coracoclavicular joint, a finding confirmed by computed tomography. The patient was treated conservatively with analgesics (Dipyrone) and anti-inflammatories (Ibuprofen) with improvement in symptoms.

Biomechanical study of 3D-printed titanium alloy pad for repairing glenoid bone defect.

Background: The purpose of this study was to investigate the effect of 3D-printed technology to repair glenoid bone defect on shoulder joint stability. Methods: The shoulder joints of 25 male cadavers were tested. The 3D-printed glenoid pad was designed and fabricated. The specimens were divided into 5 groups. Group A: no bone defect and the structure of the glenoid labrum and joint capsule was intact; Group B: Anterior inferior bone defect of the shoulder glenoid; Group C: a pad with a width of 2 mm was installed; Group D: a pad with a width of 4 mm was installed; Group E: a pad with a width of 6 mm was installed. This study measured the distance the humeral head moved forward at the time of glenohumeral dislocation and the maximum load required to dislocate the shoulder. Results: The shoulder joint stability and humerus displacement was significantly lower in groups B and C compared with group A (p < .05). Compared with group A, the stability of the shoulder joint of group D was significantly improved (p < .05). However, there was no significant difference in humerus displacement between groups D and A (p > .05). In addition, compared with group A, shoulder joint stability was significantly increased and humerus displacement was significantly decreased in group E (p < .05). Conclusion: The 3D-printed technology can be used to make the shoulder glenoid pad to perfectly restore the geometric shape of the shoulder glenoid articular surface. Moreover, the 3D-printed pad is 2 mm larger than the normal glenoid width to restore the initial stability of the shoulder joint.

Shoulder and Knee Arthroscopy Access Point: Prospective Comparison of Sonographic and Palpatory Detection - Which Method is Better for Novices?

Purpose Arthroscopy is one of the most common interventions in orthopedics. Hence it is important to train users early in order to ensure the safest possible identification of access portals (AP). This prospective study aimed to compare a palpatory (PalpMethod) with a sonographic (SonoMethod) method for AP location in the shoulder and knee joints. Materials and Methods The study included trainee doctors (n=68) attending workshops (lasting approx. 90 minutes). In these workshops a teaching video initially demonstrated the PalpMethod and SonoMethod of AP identification. An experienced operator first marked the access portals on the test subject with a UV pen (determined ideal point [DIP]). Adhesive film was then affixed to the puncture regions. Subsequently participants marked on shoulders and knees first the point determined by palpation, then the point determined by sonography. Analysis involved DIP visualization with a UV lamp and employed a coordinate system around the central DIP. In addition, participants completed an evaluation before and after the workshop. Results The analysis included 324 measurements (n=163 shoulders and n= 161 knees). The majority of participants had not previously attended any courses on manual examination (87.9%) or musculoskeletal ultrasound (93.9%). Overall, the markings participants made on the shoulder using the SonoMethod were significantly closer to the DIP than those made by the PalpMethod (Palp 18.8mm ± 14.5mm vs. Sono 11.2mm ± 7.2mm; p<0.001). On the knee, however, the markings made by the PalpMethod were significantly closer to the DIP overall (Palp 8.0mm ± 3.2mm vs. Sono 12.8mm ± 5.2mm; p<0.001). Conclusion The results show that the SonoMethod produces more accurate markings on the shoulder, while the PalpMethod is superior for the knee.

Colchicine Therapy for Glenohumeral Osteoarthritis: A Case Report.

Osteoarthritis management primarily focuses on targeting pain. Conventional modalities for pain management include acetaminophen, non-steroidal anti-inflammatory drugs (NSAIDs), and intra-articular corticosteroid injections. However, these approaches may provide minimal pain relief and can be contraindicated for some patients, highlighting the ongoing need for alternative pain management. Colchicine, commonly used in the management of gout, has emerged as a potential option for pain management in osteoarthritis. There are implications of colchicine use for knee and hand osteoarthritis but remains inconclusive. In this context, we present a case of a 68-year-old diabetic woman with glenohumeral osteoarthritis and associated right shoulder pain. Due to minimal pain relief from previous treatments, the patient was given a combination trial of colchicine and acetaminophen for three months. After completion of this treatment, the patient experienced significant pain relief and improved functionality. The aim of this case is to highlight the efficacy of colchicine as a possible treatment option for managing shoulder pain in osteoarthritis.

Development of a musculoskeletal shoulder model considering anatomic joint structures and soft-tissue deformation for dynamic simulation.

The shoulder joint has a high degree of freedom and an extremely complex and unstable kinematic mechanism. Coordinated contraction of the rotator cuff muscles that stop around the humeral head and the deltoid muscles and the extensibility of soft tissues, such as the joint capsule, labrum, and ligaments, contribute to shoulder-joint stability. Understanding the mechanics of shoulder-joint movement, including soft-tissue characteristics, is important for disease prevention and the development of a device for disease treatment. This study aimed to create a musculoskeletal shoulder model to represent the realistic behavior of joint movement and soft-tissue deformation as a dynamic simulation using a rigid-body model for bones and a soft-body model for soft tissues via a spring-damper-mass system. To reproduce the muscle-contraction properties of organisms, we used a muscle-expansion representation and Hill's mechanical muscle model. Shoulder motion, including the movement of the center of rotation in joints, was reproduced, and the strain in the joint capsule during dynamic shoulder movement was quantified. Furthermore, we investigated narrowing of the acromiohumeral distance in several situations to induce tissue damage due to rotator cuff impingement at the anterior-subacromial border during shoulder abduction. Given that the model can analyze exercises under disease conditions, such as muscle and tendon injuries and impingement syndrome, the proposed model is expected to help elucidate disease mechanisms and develop treatment guidelines.

Thoracic outlet syndrome in overhead athletes.

Background: We aimed to retrospectively compare the clinical outcomes of endoscopy-assisted first-rib resection for thoracic outlet syndrome (TOS) between overhead athletes and nonathletes and investigate the return to same-level sports rate in overhead athletes. Methods: We retrospectively reviewed 181 cases with TOS (75 women, 106 men; mean age, 28.4 years; range, 12-57 years) who underwent endoscopy-assisted first-rib resection. We divided into two groups: 79 overhead athletes and 102 nonathletes groups. A transaxillary approach for first-rib resection and neurovascular decompression was performed under magnified visualization. Endoscopic findings related to the neurovascular bundle, interscalene distance, and scalene muscle were evaluated intraoperatively. We assessed the Roos and Disability of the Arm, Shoulder, and Hand scores, return to same-level sports rate, and ball velocity. Results: Overhead athletes were significantly more likely to be men, younger, used the dominant side more frequently, and have a larger physique, more shoulder and elbow pain, and shorter symptom duration. The outcomes of the Roos score revealed significant differences in excellent or good results between overhead athletes (91.1%) and nonathletes (62.8%). The two groups significantly differed in preoperative and postoperative Disability of the Arm, Shoulder, and Hand and recovery rate scores (P = .007, < .001, < .001). Conclusion: Overhead athletes with TOS were more likely to be men, younger, dominant side more frequently, and have more shoulder and elbow pain, and a shorter symptom duration. Endoscopy-assisted transaxillary first-rib resection and neurolysis provided superior clinical outcomes in overhead athletes with TOS compared with nonathletes and a high return-to-same-level-play rate in sports.