Prevalence and associated factors of non-traumatic shoulder pain during spike and serve movements in male high school volleyball players: a cross-sectional study.

BACKGROUND: Nontraumatic shoulder pain is a prevalent issue among male high school volleyball players, but its comprehensive assessment has been lacking in prior research, which often isolated specific aspects of shoulder function. This study aimed to identify contributing factors to shoulder pain in this population. HYPOTHESIS: The hypothesis posited that limited shoulder internal rotation (IR) range of motion (ROM), imbalance in rotator cuff muscle strength, intrinsic sensory disturbance, and joint stability are associated with shoulder pain in male high school volleyball players. Additionally, there was an anticipation that a substantial proportion of players would experience shoulder pain but refrain from reporting it to coaches. METHODS: Forty-nine male volleyball players aged 15-17 years were evaluated between February and June 2023. Questionnaires assessed the prevalence of shoulder pain during spiking and/or serving, as well as the frequency of reporting this pain to coaches. Various factors, including acromio-humeral distance, shoulder ROM, isometric strength, proprioception, joint stability (Upper Quarter Y-Balance Test), joint position sense, and upper extremity power (Seated Medicine Ball Throw Test; SMBT), were quantified. Logistic regression analyses was conducted to explore potential connections between these variables and shoulder pain. RESULTS: Shoulder pain was reported by 39% of participants, but it was rarely communicated to coaches (95%). Jump serves (odds ratio 1.84, p=0.02) and reduced shoulder IR ROM (odds ratio 0.94, p=0.03) were associated with shoulder pain. CONCLUSION: This study provides crucial insights into the prevalence, severity, and associated factors of shoulder pain among male high school volleyball players. The findings underscore the importance of improving athlete-coach communication to facilitate early intervention and preventive measures. Significant associations were observed between the use of jump serves, reduced shoulder internal rotation range of motion, and shoulder pain, highlighting the relevance of specific volleyball techniques in injury prevention. These findings offer valuable guidance to coaches and trainers in developing interventions aimed at mitigating the risk of shoulder pain and enhancing player performance.

Inlay total shoulder arthroplasty in the weight-bearing shoulder of wheelchair-bound patients with paraplegia. A case report.

INTRODUCTION AND IMPORTANCE: Paraplegic patients' activities of daily living (ADLs) involve the use of manual wheelchairs that increase the stress on the shoulder joint. Patients with advanced glenohumeral changes are often resistant to conservative measures and may require surgical interventions. The longevity of a Total Shoulder Arthroplasty is largely unknown in paraplegics due to a lack of studies investigating outcomes in these patients. CASE PRESENTATION: We examined the outcome of two paraplegic patients following inlay total shoulder arthroplasty (iTSA) with a non-spherical humeral head and glenoid inlay replacement. CLINICAL DISCUSSION: Two patients with paraplegia and advanced degenerative joint disease who underwent iTSA were seen at regular follow-up intervals to assess range of motion, strength, and patient-reported outcome measures. Radiographic imaging was utilized to monitor slipping, lateralization, and degradation of the joint space. CONCLUSION: Both patients have shown significant increases in strength, ROM, and PROMs. iTSA proved efficacious in paraplegic patients utilizing a manual wheelchair.

The open Latarjet procedure does not affect scapulohumeral rhythm three months postoperatively.

BACKGROUND: Although it is considered a sensitive indicator of shoulder disabilities, the scapulohumeral rhythm has not been investigated after anterior glenohumeral stabilization with open Latarjet procedure. This study aimed to assess the short-term influence of glenohumeral stabilization on scapulohumeral rhythm in patients who underwent open Latarjet procedure compared to asymptomatic individuals. METHODS: A group of male patients who underwent anterior glenohumeral stabilization by open Latarjet procedure and a healthy group were enrolled in this study. An electromagnetic device was used to record scapulothoracic and glenohumeral joint kinematics during dynamic arm elevation and depression in the scapular plane before and three months after surgery. Then, the three-dimensional dynamic scapulohumeral rhythm was computed bilaterally. SPM ANOVAs were used for statistical analysis. FINDINGS: Twenty-two participants per group were included. The scapulohumeral rhythm of the two groups increased from 1.88 [mean] ± 0.79 [standard deviation] to 2.83 ± 1.52 during the ascending phase, while a decrease followed by a slight increase in the scapulohumeral rhythm were observed during the descending phase. The scapulohumeral rhythm did not significantly differ between the operated and non-operated sides or before and after surgery. When pooling the sides for each group, no significant differences were observed between the groups. INTERPRETATION: The scapulohumeral rhythm in patients who underwent the Latarjet procedure is not modified three months after surgery and is similar to the scapulohumeral rhythm of asymptomatic individuals. These findings suggest that in addition to restoring glenohumeral stability, the open Latarjet procedure preserves shoulder joint coordination three months postoperatively.

Inferior glenohumeral joint capsule thickness in frozen shoulder via ultrasonography.

Background: The thickening of the inferior glenohumeral joint capsule (IGC) is a characteristic finding in frozen shoulders. However, the relationship between the thickness of the IGC measured using ultrasonography (US) and the range of motion (ROM) remains unclear. This study aimed to investigate a suitable IGC thickness measurement site that can reflect the ROM of frozen shoulders. Methods: The participants were 29 patients with frozen shoulder and 20 healthy shoulders of 10 healthy adult. US measurements of the IGC were performed at 80° elevation in the scapular plane, with thickness was measured at 3 levels in both groups: just above the surgical neck, just above the anatomical neck, and at the parenchymal level. The relationship between thickness and ROM at the 3 levels was also assessed. The thickness of the IGC was evaluated using magnetic resonance imaging and US, as well as the validity of US evaluation. Results: There was a positive correlation (r = 0.72) between magnetic resonance imaging-measured and US-measured IGC thickness. The IGC was thicker in the frozen shoulder group than in the control group at all 3 levels (P < .001). The thickness of the IGC at the parenchymal level showed a significant negative correlation with all ROMs: flexion (r = -0.63), abduction (r = -0.60), external rotation (r = -0.50), and internal rotation (r = -0.52). Conclusion: The thickness of the IGC at the parenchymal level is negatively correlated with the ROM. The evaluation of the IGC in this study will be helpful in selecting treatment options for frozen shoulders.

Occupational mechanical exposures as risk factor for shoulder osteoarthritis: a systematic review.

OBJECTIVES: The aim of this systematic review was to study the association between occupational mechanical exposures and shoulder osteoarthritis (OA). METHODS: A protocol was registered in PROSPERO. Four databases were systematically searched based on PECOS criteria. Outcome was defined as shoulder OA (acromioclavicular (AC) and/or glenohumeral OA) and exposure as occupational mechanical exposures (vibration, upper arm elevation, force, lifting, repetition, and combined mechanical exposures). We included epidemiological studies estimating the prevalence of shoulder OA or the association between occupational mechanical exposures and shoulder OA. Two researchers independently screened articles, performed data extraction, and assessed the risk of bias and level of evidence using GRADE. RESULTS: A total of 1642 articles were screened, of which 7 met the inclusion criteria. Four studies were assessed as having a high risk of bias, 1 with a moderate risk, and 2 with a low risk. Based on job titles, higher prevalence estimates (2.9% to 61.8%) were found in exposed job groups. For all occupational mechanical exposures, exposure-response relations were found in relation to AC OA. For vibration, the odds ratio (OR) ranged between 1.7 and 3.1 in the highest exposure groups, while the ORs for upper arm-elevation, force, lifting, repetition, and combined mechanical exposures ranged between 0.5 to 2.2, 1.3 to 1.8, 7.3 to 10.3, 2.4, and 2.2 to 2.9. Low or very low level of evidence was found for all exposures. CONCLUSIONS: This systematic review found an indication of an association between occupational mechanical exposures and shoulder OA, especially AC OA. However, the level of evidence varied between low and very low. High-quality studies assessing the association and differentiating between the specific shoulder joints are highly warranted.

The effect of humeral tray thickness on glenohumeral loads in a reverse shoulder 'smart' implant.

PURPOSE: The aim of this study was to observe the effects of changing humeral tray thickness on the resultant of intraoperative glenohumeral joint loads using a load-sensing system (LSS). METHODS: An rTSA was performed on fresh frozen full-body cadaver shoulders by using an internal proprietary LSS on the humeral side. The glenohumeral loads (Newtons) and the direction of the resultant force applied on the implant were recorded during four standard positions (External rotation, Extension, Abduction, Flexion) and three "complex" positions of Activity Daily Life ("behind back", "overhead reach" and "across chest"). For each position, the thickness was increased from 0 to 6 mm in a continuous fashion using the adjustment feature of the humeral system. Each manoeuvre was repeated three times. RESULTS: All shoulder positions showed a high repeatability of the glenohumeral load magnitude measured with an intra-class correlation coefficient of over 0.9. For each position, we observed a strong but no linear correlation between humeral tray thickness and joint loads. It was a cubical correlation (rs = 0,91) with a short ascending phase, then a plateau phase, and finally a phase with an exponential growth of the loads on the humeral implant. In addition, an increase in trail-poly thickness led to a recentering of force application at the interface of the two glenohumeral implants. CONCLUSION: This study provides further insight into the effects of humeral implant thickness on rTSA glenohumeral joint loads during different positions of the arm. Data obtained using this type of device could guide surgeons in finding the proper implant balance during rTSA.

Functional Anatomy and Biomechanics of Shoulder Instability.

The glenohumeral joint is the least congruent and least constrained joint with a complex relationship of static and dynamic stabilizers to balance its native mobility with functional stability. In the young athlete, anterior shoulder instability is multifactorial and can be a challenge to treat, requiring a patient-specific treatment approach. Surgical decision-making must consider patient-specific factors such as age, sport activity and level, underlying ligamentous laxity, and goals for return to activity, in addition to careful scrutiny of the underlying pathology to include humeral and glenoid bone loss and surrounding scapular bone morphology.

Long Head of the Biceps Tendon Plays a Role in Stress Absorption and Humeral Head Restriction during the Late Cocking and Deceleration Phases of Overhead Throwing: A Finite Element Study.

BACKGROUND: Emerging evidence suggests that the long head of the biceps (LHBT) may play a role in stabilizing the glenohumeral joint, and this has led to controversy around the efficacy of biceps tenotomy for superior labral anterior and posterior (SLAP) lesions. Therefore, the aim of this finite element analysis (FEA) study was to determine the stress absorption and humeral head translation restriction effects of the LHBT within the glenohumeral joint during the late cocking and deceleration phases of overhead throwing with a view to resolving the controversy around tenotomy. METHODS: Eight FEA models were created using computed tomography and magnetic resonance imaging data from normal glenohumeral joints. The models represented four LHBT conditions: uninjured, subpectoral tenodesis, tenotomy, and type II SLAP lesions. The late cocking and deceleration phases of the overhead throwing were simulated for each model. The impacts of the four LHBT conditions on glenohumeral joint stress absorption and humeral head displacement restriction were studied based on 1) stress and related distributions on the cartilage, labrum, capsule, and LHBT and 2) humeral head translation variation. RESULTS: The FEA analysis showed that the magnitude of the contact stress on the articular cartilage, labrum, and capsule was the lowest in the uninjured models, followed by the subpectoral tenodesis, tenotomy, and type II SLAP lesion models. Humeral head translation was the most restricted in the subpectoral tenodesis models, followed by the tenotomy and type II SLAP lesion models. CONCLUSION: Finite element analysis demonstrated that the LHBT plays a significant role in stress absorption and displacement restriction in the late cocking and deceleration phases of overhead throwing. Subpectoral tenodesis of the LHBT exhibited lesser amount of stress and humeral head translation than those of tenotomy, thereby making it a better option for patients who engage in overhead throwing.

Clinical and Surgical Outcomes of Shoulder Arthrodesis.

Introduction: Shoulder arthrodesis is typically seen as a salvage procedure with limited functional objectives. In appropriately selected patients, it may effectively alleviate pain, provide stable motion, and offer patient function satisfaction. However, there have been few reports on the outcomes following shoulder arthrodesis. Methods: A multicenter, retrospective chart review of patients undergoing shoulder arthrodesis between 2001 and 2023 in Western Australia was conducted. Clinical records and imaging were then reviewed to determine patient demographics. A cross-sectional analysis of Visual Analogue (VAS), Oxford Shoulder (OSS), and American Shoulder and Elbow Surgeons Shoulder (ASES) Scores, satisfaction and complication rates was conducted. Results: In total, 14 patients with a mean age of 39.5 years (range 22-52 years, 71% male) with a mean follow-up of 7.4 years (range 3 months-18 years) were identified. The most common indications for arthrodesis included osteoarthritis (8, 57%) and instability (6, 43%). Major contributory factors were recurrent seizures (5, 36%) and multiple surgeries (4, 29%). Radiographic union was observed in 13 (93%) patients. The mean VAS was 2.8 (range 0-7), mean OSS was 33.0 (range 23-42) and ASES score was 55.4 (range 37-82). In total, 11 patients (79%) reported being satisfied. Five (36%) patients returned to theatre for complications. Conclusions: In this patient series, shoulder arthrodesis demonstrates a notable efficacy in pain reduction, high satisfaction, acceptable function, and complication rates.

A preliminary study of contrast-enhanced ultrasound guided capsule-preserving hydrodilatation in shoulder adhesive capsulitis.

Background: Capsule-preserving hydrodilatation is a common treatment for adhesive capsulitis (AC), and ultrasound (US) has recently become the most popular adjuvant tool for image-guided glenohumeral joint injection. However, traditional US is hardly adequate to assess extracapsular fluid leakage, which may decide the treatment outcomes. In this study, we explored the value of contrast-enhanced ultrasound (CEUS) guided capsule-preserving hydrodilatation with steroids and ultrasonic contrast agents for treatment of AC. Methods: A total of 40 consecutive patients with AC were prospectively enrolled and received CEUS-guided capsule-preserving hydrodilatation. The number of injection attempts, injection volume, and fluid leakage were recorded, and the correlations with clinical features were analyzed by Pearson or Spearman correlation coefficients. Outcome measures including visual analog scale (VAS) score, passive range of motion (ROM), and shoulder pain and disability index (SPADI) score were evaluated at baseline and 4 weeks after treatment. Comparisons between patients with good and poor clinical outcomes were performed with independent t-test, Mann-Whitney U test, and chi-square test. Logistic regression was used to identify predictors of good clinical outcomes. A P value <0.05 defined significance. Results: Access to the glenohumeral joint was successful in 87.5% patients on the first attempt. The infused fluid volume was 21.0±3.40 mL. Longer symptom duration (r=-0.676, P<0.001), greater SPADI (r=-0.148, P=0.007), and decreased ROM in abduction (r=0.38, P=0.016) were associated with a decreased volume of infused fluid. CEUS detected massive fluid leakage in 5 (12.5%) patients, with 4 capsule ruptures confirmed by magnetic resonance imaging (MRI). Longer symptom duration (r=0.485, P=0.001), decreased ROM in the direction of abduction (r=-0.33, P=0.037), and external rotation (r=-0.34, P=0.032) were correlated with an increased incidence of massive fluid leakage. Moreover, patients with good outcomes had significantly shorter symptom duration (5.7±2.09 vs. 11.2±3.89 months, P=0.002) and greater initial VAS score (6.9±1.04 vs. 6.3±0.50, P=0.022) than those with poor outcomes. Absence of massive fluid leakage was an independent predictor of clinical good outcomes at 4 weeks after treatment [odd ratio (OR) =0.05, 95% confidential interval (CI): 0.003-0.882, P=0.041]. Conclusions: CEUS-guided capsule-preserving hydrodilatation allows real-time visualization of capsule dilatation, accurate detection of extracapsular fluid leakage, and identification of risks for capsule rupture. It provides an effective treatment for AC, and is useful to predict patients' clinical outcomes.

GIBPS technique-a novel sequential technique of performing shoulder corticosteroid injections.

The introduction of the xxxxxxxx (GIBPS) technique represents a patient-centric novel and innovative method of ultrasound guided corticosteroid injection targeting the Glenohumeral joint (GHJ) and the Subacromial-Subdeltoid (SASD) bursa in a sequential manner, in the same setting. By integrating the two different sites of injection into a single technique, the procedure has the potential of transforming musculoskeletal interventional radiology and maximising patient care in shoulder pathologies. This procedure aims to reduce patient discomfort, optimise procedural efficiency, and enhance treatment precision through ultrasound guidance and improve the overall patient experience.

Changes in Shoulder Rotation Based on Elevation in Children With Brachial Plexus Birth Injury.

PURPOSE: Lack of shoulder external rotation is common in children with brachial plexus birth injuries. Development of glenohumeral (GH) dysplasia is associated with progressive loss of passive external rotation. Some authors recommend measuring external rotation with the arm adducted, whereas others recommend measurement with the arm in 90° of abduction. The purpose of this study was to compare active and passive external rotation and internal rotation measured in adduction versus abduction. METHODS: Fifteen children with brachial plexus birth injuries held their affected arms in maximal external and internal rotation with the arm adducted and the arm at approximately 90° of abduction. Active and passive rotations were measured with three-dimensional motion capture. Scapulothoracic (ST) internal/external rotation and GH internal/external rotation joint angles were calculated and compared using multivariable, one-way repeated measures analyses of variance. RESULTS: There were no significant differences for active or passive ST rotation in external rotation in adduction versus abduction. Glenohumeral external rotation was significantly increased with the arm in abduction compared with adduction both actively and passively. There were no differences in ST rotation in active versus passive conditions, but all GH rotations were significantly greater passively. CONCLUSIONS: Shoulder internal/external rotation in abduction and adduction is not interchangeable. Comprehensive assessment of shoulder external and internal rotation should include both adduction and abduction. CLINICAL RELEVANCE: For children with brachial plexus birth injuries, both active and passive GH external rotations were greater in abduction. Therefore, early GH joint dysplasia may be missed if GH external rotation is measured in abduction. Additionally, consistency in arm position is important for comparison over time. The entire ST rotation capacity was used to perform maximal internal and external rotation, but the entire passive GH range of motion was not actively used. This highlights an area for potential surgical intervention to improve motion.

Effects of bench press technique variations on musculoskeletal shoulder loads and potential injury risk.

While shoulder injuries resulting from the bench press exercise are commonly reported, no biomechanical evidence for lowering injury risk is currently available. Therefore, the aim of the present study was to compare musculoskeletal shoulder loads and potential injury risk during several bench press variations. Ten experienced strength athletes performed 21 technical variations of the barbell bench press, including variations in grip width of 1,1.5 and 2 bi-acromial widths (BAW), shoulder abduction angles of 45°, 70° and 90°, and scapula poses including neutral, retracted, and released conditions. Motions and forces were recorded by an opto-electronic measurement system and an instrumented barbell. An OpenSim musculoskeletal shoulder model was employed to estimate joint reaction forces in the glenohumeral and acromioclavicular joints. Time-series of joint reaction forces were compared between techniques by statistical non-parametric mapping. Results showed that narrower grip widths of < 1.5 BAW decreased acromioclavicular compression (p < 0.05), which may decrease the risk for distal clavicular osteolysis. Moreover, scapula retraction, as well as a grip width of < 1.5 BAW (p < 0.05), decreased glenohumeral posterior shear force components and rotator cuff activity and may decrease the risk for glenohumeral instability and rotator cuff injuries. Furthermore, results showed that mediolaterally exerted barbell force components varied considerably between athletes and largely affected shoulder reaction forces. It can be concluded that the grip width, scapula pose and mediolateral exerted barbell forces during the bench press influence musculoskeletal shoulder loads and the potential injury risk. Results of this study can contribute to safer bench press training guidelines.

Muscle and joint function in the rotator cuff deficient shoulder.

Full-thickness rotator cuff tears can lead to poor coaptation of the humeral head to the glenoid, disrupting muscle forces required for glenohumeral joint stability, ultimately leading to joint subluxation. The aim of this study was to evaluate muscle forces and glenohumeral joint translations during elevation in the presence of isolated and combined full-thickness rotator cuff tears. Eight fresh-frozen upper limbs were mounted to a computer-controlled testing apparatus that simulated joint motion by simulated muscle force application. Scapular-plane abduction was performed, and glenohumeral joint translations were measured using an optoelectronic system. Testing was performed in the native shoulder, a following an isolated tear to the supraspinatus, as well as combined tears involving the supraspinatus and subscapularis, as well as supraspinatus, infraspinatus, and teres minor. Rotator cuff tears significantly increased middle deltoid force at 30°, 60°, and 90° of abduction relative to that in the native shoulder (p < 0.05). Significantly greater superior translations were observed relative to the intact shoulder due to combined tears to the supraspinatus and infraspinatus at 30° of abduction (mean increase: 1.6 mm, p = 0.020) and 60° of abduction (mean increase: 4.8 mm, p = 0.040). This study illustrates the infraspinatus-teres minor complex as a major humeral head depressor and contributor to glenohumeral joint stability. An increase in deltoid force during abduction occurs in the presence of rotator cuff tears, which exacerbates superior migration of the humeral head. The findings may help in the development of clinical tests in rotator cuff tear diagnostics, in surgical planning of rotator cuff repair, and in planning of targeted rehabilitation.

Systematic Review of Shoulder Imaging Abnormalities in Asymptomatic Adult Shoulders (SCRUTINY): Abnormalities of the glenohumeral joint.

OBJECTIVE: The primary objective was to determine the population prevalence of glenohumeral joint imaging abnormalities in asymptomatic adults. METHOD: We systematically reviewed studies reporting the prevalence of X-ray, ultrasound (US), computed tomography, and magnetic resonance imaging (MRI) abnormalities in adults without shoulder symptoms (PROSPERO registration number CRD42018090041). This report presents the glenohumeral joint imaging findings. We searched Ovid MEDLINE, Embase, CINAHL and Web of Science from inception to June 2023 and assessed risk of bias using a tool designed for prevalence studies. The primary analysis was planned for the general population. The certainty of evidence was assessed using a modified Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) for prognostic studies. RESULTS: Thirty-five studies (4 X-ray, 10 US, 20 MRI, 1 X-ray and MRI) reported useable prevalence data. Two studies were population-based (846 shoulders), 15 studies included miscellaneous study populations (1715 shoulders) and 18 included athletes (727 shoulders). All were judged to be at high risk of bias. Clinical diversity precluded pooling. Population prevalence of glenohumeral osteoarthritis ranged from 15% to 75% (2 studies, 846 shoulders, 1 X-ray, 1 X-ray and MRI; low certainty evidence). Prevalence of labral abnormalities, humeral head cysts and long head of biceps tendon abnormalities were 20%, 5%, 30% respectively (1 study, 20 shoulders, X-ray and MRI; very low certainty evidence). CONCLUSION: The population-based prevalence of glenohumeral joint imaging abnormalities in asymptomatic individuals remains uncertain, but may range between 30% and 75%. Better estimates are needed to inform best evidence-based management of people with shoulder pain.

Maximum in-vivo joint contact forces double during active compared to assisted motion in the glenohumeral joint and decline long-term due to rotator cuff pathologies.

Rehabilitation programs advocate early passive and assisted motion after rotator cuff repair to induce healing und maintaining range of motion while avoiding excessive strain on the repaired tendons. In-vivo glenohumeral joint contact forces reflect the compressive forces generated by the rotator muscles. In the present study, maximum in-vivo joint contact forces (FresMax) were determined to compare active and assisted execution of a single movement and the long-term development of joint compression forces. FresMax were measured in six patients who received instrumented, telemetric modified anatomical hemi endoprostheses of the shoulder joint between 2006 and 2008. Data were gathered 23 months postoperatively (2006-2010), were analysed and compared with measurements 133 months postoperatively. Additional imaging was obtained as x-rays and ultrasound examination. Data analysis was conducted by synchronizing video tapes and measured force curves. New imaging showed a rupture of the M. supraspinatus and progressive joint degeneration. FresMax nearly doubled during active compared to assisted execution of each of the four chosen movements. Over the course of 133 months post-surgery, the studied movements showed a decrease of active compression force, probably due to a ruptured supraspinatus, resulting in a lower active/assisted ratio. A long term follow up after eleven years, eight out of ten measured movements showed a decrease of FresMax. These results support current rehabilitation protocols recommending early passive and assisted motion to limit activation of the rotator muscles generating compressive forces. Following degeneration of the rotator cuff, active joint contact forces decrease over time.Level of evidence: III.

Investigation of the limiting factors of shoulder joint complex motion in college baseball players: motion analysis of the humeral head and rotator cuff using ultrasound.

Background: The relationship between lower mobility, as measured by the elbow forward translation motion (T-motion) test, a new indicator of shoulder joint complex movement that measures elbow position when both dorsal hands are placed on the iliac crest while in a sitting position, and the parameters calculated by ultrasonography is unknown. The purpose of this study was to investigate the limiting factors of T-motion through motion analysis of the humeral head and rotator cuff muscles using ultrasonography in college baseball players. Methods: Thirteen college baseball players participated in this cross-sectional study. The shortest distance from the posterior edge of the glenoid to the humeral head was measured in the static and T-motion positions, and the difference was calculated as the humeral head translation. The velocity of the infraspinatus was calculated during shoulder internal/external rotation using the particle image velocimetry method. These parameters were compared between the throwing and nonthrowing sides to examine the limiting factors of T-motion. Results: This study indicated moderate-to-good reliability for the parameters calculated by ultrasonography. The mean anterior translation distance was significantly greater on the throwing side than on the nonthrowing side (r = 0.56, P = .015). The mean velocity of infraspinatus during internal rotation was significantly lower on the throwing side than on the nonthrowing side (r = 0.51, P = .028). Conclusion: Increased anterior translation of the humeral head and decreased the velocity of infraspinatus are likely correlated with reduced T-motion mobility in college baseball players. These methods showed potential for physical therapy assessment and intervention to prevent shoulder dysfunction.

Effect of patient-specific scapular morphology on the glenohumeral joint force and shoulder muscle force equilibrium: a study of rotator cuff tear and osteoarthritis patients.

Introduction: Osteoarthritis (OA) and rotator cuff tear (RCT) pathologies have distinct scapular morphologies that impact disease progression. Previous studies examined the correlation between scapular morphology and glenohumeral joint biomechanics through critical shoulder angle (CSA) variations. In abduction, higher CSAs, common in RCT patients, increase vertical shear force and rotator cuff activation, while lower CSAs, common in OA patients, are associated with higher compressive force. However, the impact of the complete patient-specific scapular morphology remains unexplored due to challenges in establishing personalized models. Methods: CT data of 48 OA patients and 55 RCT patients were collected. An automated pipeline customized the AnyBody™ model with patient-specific scapular morphology and glenohumeral joint geometry. Biomechanical simulations calculated glenohumeral joint forces and instability ratios (shear-to-compressive forces). Moment arms and torques of rotator cuff and deltoid muscles were analyzed for each patient-specific geometry. Results and discussion: This study confirms the increased instability ratio on the glenohumeral joint in RCT patients during abduction (mean maximum is 32.80% higher than that in OA), while OA patients exhibit a higher vertical instability ratio in flexion (mean maximum is 24.53% higher than that in RCT) due to the increased inferior vertical shear force. This study further shows lower total joint force in OA patients than that in RCT patients (mean maximum total force for the RCT group is 11.86% greater than that for the OA group), attributed to mechanically advantageous muscle moment arms. The findings highlight the significant impact of the glenohumeral joint center positioning on muscle moment arms and the total force generated. We propose that the RCT pathomechanism is related to force magnitude, while the OA pathomechanism is associated with the shear-to-compressive loading ratio. Overall, this research contributes to the understanding of the impact of the complete 3D scapular morphology of the individual on shoulder biomechanics.

Shoulder external rotation contracture following neonatal brachial plexus injury.

BACKGROUND: Glenohumeral posterior external rotation contractures and scapular winging are frequently overlooked problems in residual neonatal brachial plexus injury (NBPI). Recent attention has emphasized their impact on vital functions such as feeding and hygiene. This study aims to present the epidemiology of posterior glenohumeral contractures in a significant pediatric NBPI population and explore contributing factors. METHODS: We conducted a retrospective analysis of data collected from January 2019 to November 2022, involving a case series of 262 children with residual NBPI. The data included demographics, palsy level, prior surgical history, and the modified Mallet scale. Glenohumeral passive internal rotation in abduction and cross-body adduction angles were measured bilaterally. Subjects were categorized into "Belly-" (Mallet hand-to-belly <3) and "Belly+" (Mallet hand-to-belly ≥3) groups. RESULTS: The median participant age was 7.9 years (range: 3.5-21 years). Extension injury patterns included Erb's palsy (56.5%), extended Erb's palsy (28.6%), and global palsy (14.9%). Contractures exceeding 10°, 20°, and 30° were prevalent in both internal rotation in abduction and cross-body adduction angles. The "Belly-" group (9.5%) demonstrated a significant reduction in both angles compared to the "Belly+" group. Weak correlations were found between internal rotation in abduction (r = 0.390, P < .0001) or cross-body adduction (r = 0.163, P = .0083) angles and Mallet hand-to-abdomen item. Glenohumeral reduction and Hoffer procedures led to a notable decrease in cross-body adduction angle, without affecting "Belly-" prevalence. Global injuries exhibited decreased angles compared to Erb's group. CONCLUSIONS: External rotation glenohumeral contractures are prevalent in residual NBPI, impacting midline access. Surprisingly, the history of glenohumeral procedures or extensive injuries did not increase the likelihood of losing the ability to reach the belly. Receiver operating characteristic analysis suggests specific thresholds for maintaining this ability.